BH3 mimetics and multi-kinase inhibition in AML.
Beauchamp Elspeth M,Platanias Leonidas C
In this issue of Blood, Rahmani et al show in preclinical studies that the combination of the multi-kinase inhibitor sorafenib with the BH3 mimetic obatoclax results in enhanced antileukemic effects compared with the effects of each agent alone. This work has important clinical implications because it describes a novel approach to overcome acute myeloid leukemia (AML) cell resistance by combining agents that are currently being investigated in trials as single agents.
CCL5 mediates target-kinase independent resistance to FLT3 inhibitors in FLT3-ITD-positive AML.
Waldeck Silvia,Rassner Michael,Keye Philip,Follo Marie,Herchenbach Dieter,Endres Cornelia,Charlet Anne,Andrieux Geoffroy,Salzer Ulrich,Boerries Melanie,Duyster Justus,von Bubnoff Nikolas
FLT3-ITD tyrosine kinase inhibitors (TKI) show limited clinical activity in acute myeloid leukemia (AML) due to emerging resistance. TKI resistance is mediated by secondary FLT3-ITD mutations only in a minority of cases. We hypothesize that the cytokine CCL5 protects AML cells from TKI-mediated cell death and contributes to treatment resistance. We generated PKC412- and sorafenib-resistant MOLM-13 cell lines as an in vitro model to study TKI resistance in AML. Increased CCL5 levels were detected in supernatants from PKC412-resistant cell lines compared to TKI-sensitive cells. Moreover, CCL5 treatment of TKI-sensitive cells induced resistance to PKC412. In resistant cell lines with high CCL5 release, we observed a significant downregulation of the CCL5-receptor CCR5 and CXCR4. In these cell lines, TKI resistance could be partly overcome by addition of the CXCR4-receptor antagonist plerixafor. Microarray and intracellular flow cytometry analyses revealed increased p-Akt or p-Stat5 levels in PKC412-resistant cell lines releasing high amounts of CCL5. Treatment with the CXCR4 antagonist plerixafor, αCCL5, or CCR5-targeting siRNA led to a decrease of p-Akt-positive cells. Transient transfection of sensitive MOLM-13 cells with a CCL5-encoding vector mediated resistance against PKC412 and led to an increase in p-Akt-positive and p-Stat5-positive cells. Isolated AML blasts from patients treated with PKC412 revealed that CCL5 transcript levels increase significantly at relapse. Taken together, our findings indicate that CCL5 mediates resistance to FLT3-TKIs in FLT3-ITD-mutated AML and could possibly serve as a biomarker to predict drug resistance.
Synthesis and biological evaluation of 6-phenylpurine linked hydroxamates as novel histone deacetylase inhibitors.
Chen Dizhong,Soh Chang Kai,Goh Wei Huang,Wang Zilong,Wang Haishan
A series of 6-phenylpurine based hydroxamates have been designed, synthesized and evaluated. Compound 3b and its analogs are potent histone deacetylase (HDAC) but weak PI3K/mTOR inhibitors. These compounds demonstrated broad anti-cancer activities against 38 cancer cell lines with leukemia, lymphoma, and the majority of liver cancer cell lines exhibiting the most sensitivity towards these compounds. Compound 3b demonstrated modulation of HDAC targets in vitro in a dose-dependent manner. It has good in vitro ADME profile that translated into a greatly improved pharmacokinetic profile. 3b also demonstrated modulation of HDACs in tumors in a PC-3 xenograft model. It was further evaluated in combination therapies in vitro. It exhibited additive or synergistic growth inhibition effect in HepG2 cells when combined with a number of approved drugs such as sorafenib, sunitinib, and erlotinib. Hence, 3b has the potential to be combined with the above to treat advanced liver cancer. As such, current data warrant further evaluation, optimization, and subsequent in vivo validation of the potential combination therapies.
The role of small molecule Flt3 receptor protein-tyrosine kinase inhibitors in the treatment of Flt3-positive acute myelogenous leukemias.
Flt3 is expressed by early myeloid and lymphoid progenitor cells and it regulates the proliferation and differentiation of hematopoietic cells. Flt3 is activated by the Flt3 ligand, the monomeric form of which is a polypeptide of about 200 amino acid residues. Both membrane-associated and soluble Flt3 ligands, which are a product of the same gene, function as noncovalent dimers. FLT3 mutations occur in about one-third of newly diagnosed acute myelogenous leukemia (AML) patients. This disease is a malignancy of hematopoietic progenitor cells with a variable clinical course; the incidence of this disorder is more than twice that of patients with chronic myelogenous leukemias (20,000 vs. 8500 new patients per year, respectively, in the United States). FLT3 internal tandem duplication (ITD) results from the head-to-tail duplication of from one to more than 100 amino acids within the juxtamembrane domain and such duplication occurs in about 20-25 % of patients with acute myelogenous leukemias. FLT3 tyrosine kinase (FLT3 TK) mutations, usually within the activation segment, occur in 5-10 % of these patients. The mainstay for the care of acute myelogenous leukemias include daunorubicin or idarubicin and cytarabine. Older patients who are not candidates for such traditional therapy are usually given 5-azacitidine, decitabine, or clofarabine. The addition of orally effective small molecule Flt3 inhibitors to these therapies may prolong event-free and overall survival, a subject of ongoing clinical studies. Midostaurin is US FDA-approved in combination with standard cytarabine and daunorubicin for first-line induction chemotherapy and in combination with cytarabine for second-line consolidation chemotherapy in the treatment of acute myelogenous leukemias with FLT3-postive mutations. Moreover, gilteritinib is a Flt3 multikinase inhibitor that is also FDA approved for the care of adult patients with relapsed or refractory acute myelogenous leukemias with FLT3 mutations. Quizartinib is a Flt3 multikinase inhibitor that was approved by the Ministry of Health, Labor and Welfare (MHLW) of Japan for the treatment of adult patients with relapsed/refractory Flt3-positive acute myelogenous leukemias. Gilteritinib and quizartinib bind to Flt3 with the inactive DFG-D structure and are classified as type II inhibitors. Furthermore, ponatinib is a multikinase inhibitor that is approved as therapy for Philadelphia chromosome-positive acute lymphoblastic and chronic myelogenous leukemias; it is used off label for the treatment of patients with acute myelogenous leukemias. Moreover, sorafenib is FDA-approved for the treatment of hepatocellular, renal cell, and differentiated thyroid cancers and it is used off label as maintenance therapy following allogeneic hematopoietic stem cell transplantation in the treatment of acute myelogenous leukemias. Other drugs that are in clinical trials for the treatment of this disorder include sunitinib, crenolanib, FF10101, and lestaurtinib. Unlike chronic myelogenous leukemias, which result solely from the formation of the BCR-Abl chimeric protein kinase, acute myelogenous leukemias result from multi-factorial causes and are prone to be resistant to both cytotoxic and targeted therapies. Consequently, there is a pressing need for better understanding the etiologies of acute myelogenous leukemias and for the development of more effective therapies.
Mitochondrial TXNRD3 confers drug resistance via redox-mediated mechanism and is a potential therapeutic target in vivo.
Liu Xiaoxia,Zhang Yanyu,Lu Wenhua,Han Yi,Yang Jing,Jiang Weiye,You Xin,Luo Yao,Wen Shijun,Hu Yumin,Huang Peng
Alterations in ROS metabolism and redox signaling are often observed in cancer cells and play a significant role in tumor development and drug resistance. However, the mechanisms by which redox alterations impact cellular sensitivity to anticancer drugs remain elusive. Here we have identified the mitochondrial isoform of thioredoxin reductase 3 (mtTXNRD3), through RT-PCR microarray screen, as a key molecule that confers drug resistance to sorafenib and other clinical anticancer agents. High expression of mtTXNRD3 is detected in drug-resistant leukemia and hepatocellular carcinoma cells associated with significant metabolic alterations manifested by low mitochondrial respiration and high glycolysis. Mechanistically, high mtTXNRD3 activity keeps the mitochondrial thioredoxin2 (Trx2) in a reduced stage that in turn stabilizes several key survival molecules including HK2, Bcl-XL, Bcl-2, and MCL-1, leading to increased cell survival and drug resistance. Pharmacological inhibition of thioredoxin reductase by auranofin effectively overcomes such drug resistance in vitro and in vivo, suggesting that targeting this redox mechanism may be a feasible strategy to treat drug-resistant cancer.
FLT3 D835 mutations confer differential resistance to type II FLT3 inhibitors.
Smith C C,Lin K,Stecula A,Sali A,Shah N P
Activating mutations in FLT3 occur in ~30% of adult acute myeloid leukemia, primarily consisting of internal tandem duplication (ITD) mutations (~25%) and point mutations in the tyrosine kinase domain (~5%), commonly at the activation loop residue D835. Secondary kinase domain mutations in FLT3-ITD, particularly at the D835 residue are frequently associated with acquired clinical resistance to effective FLT3 tyrosine kinase inhibitors (TKIs). Molecular docking studies have suggested that D835 mutations primarily confer resistance by stabilizing an active Asp-Phe-Gly in ('DFG-in') kinase conformation unfavorable to the binding of type II FLT3 TKIs, which target a 'DFG-out' inactive conformation. We profiled the activity of active type II FLT3 TKIs against D835 kinase domain mutants that have been clinically detected to date. We found that type II inhibitors (quizartinib, sorafenib, ponatinib and PLX3397) retain activity against specific D835 substitutions. Modeling studies suggest that bulky hydrophobic substitutions (D835Y/V/I/F) at this residue are particularly resistant, whereas mutations that preserve interactions between D835 and S838 are relatively sensitive (D835E/N). All mutants retain sensitivity to the type I inhibitor crenolanib. These results suggest that patients with relatively sensitive D835 mutations should be included in clinical trials of type II FLT3 TKIs.
Role of CYP3A4 in bone marrow microenvironment-mediated protection of FLT3/ITD AML from tyrosine kinase inhibitors.
Chang Yu-Ting,Hernandez Daniela,Alonso Salvador,Gao Minling,Su Meng,Ghiaur Gabriel,Levis Mark J,Jones Richard J
An intriguing aspect of the clinical activity of FMS-like tyrosine kinase 3 inhibitors (FLT3 TKIs) is their apparent higher activity against peripheral blasts from FLT3/internal tandem duplication (ITD) acute myeloid leukemia than marrow disease in the same patients. Accordingly, studies showed that the bone marrow microenvironment plays a role in FLT3 TKI resistance, although the underlying mechanisms are unclear. We recently identified a previously undescribed mechanism by which the bone marrow microenvironment can contribute to drug resistance: expression of cytochrome P450 enzymes (CYPs). In fact, bone marrow stromal cells (BMSCs) expressed most CYPs, including CYP3A4. Because hepatic CYP3A4 plays a role in the inactivation of several FLT3 TKIs, we explored the potential role of CYP3A4 in bone marrow microenvironment-mediated FLT3 TKI resistance. We found that CYP3A4 plays a major role in BMSC-mediated inhibition in the activity of 3 different FLT3 TKIs (sorafenib, quizartinib, and gilteritinib) against FLT3/ITD acute myeloid leukemia (AML). Furthermore, clarithromycin, a clinically active CYP3A4 inhibitor, significantly reversed the protective effects of BMSCs. We show, for the first time, that bone marrow stromal CYP3A4 contributes to FLT3 TKI resistance in the bone marrow. These results suggest that combining FLT3 TKIs with CYP3A4 inhibitors could be a promising strategy toward improving the activity of FLT3 TKIs.
Antileukemic activity of the HSP70 inhibitor pifithrin-μ in acute leukemia.
Kaiser M,Kühnl A,Reins J,Fischer S,Ortiz-Tanchez J,Schlee C,Mochmann L H,Heesch S,Benlasfer O,Hofmann W-K,Thiel E,Baldus C D
Blood cancer journal
Heat shock protein (HSP) 70 is aberrantly expressed in different malignancies and has emerged as a promising new target for anticancer therapy. Here, we analyzed the in vitro antileukemic effects of pifithrin-μ (PFT-μ), an inhibitor of inducible HSP70, in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) cell lines, as well as in primary AML blasts. PFT-μ significantly inhibited cell viability at low micromolar concentrations in all cell lines tested, with IC50 values ranging from 2.5 to 12.7 μ, and was highly active in primary AML blasts with a median IC50 of 8.9 μ (range 5.7-37.2). Importantly, higher IC50 values were seen in normal hematopoietic cells. In AML and ALL, PFT-μ induced apoptosis and cell cycle arrest in a dose-dependent fashion. PFT-μ also led to an increase of the active form of caspase-3 and reduced the intracellular concentrations of AKT and ERK1/2 in NALM-6 cells. Moreover, PFT-μ enhanced cytotoxicity of cytarabine, 17-(allylamino)-17-desmethoxygeldanamycin, suberoylanilide hydroxamic acid, and sorafenib in NALM-6, TOM-1 and KG-1a cells. This is the first study demonstrating significant antileukemic effects of the HSP70 inhibitor PFT-μ, alone and in combination with different antineoplastic drugs in both AML and ALL. Our results suggest a potential therapeutic role for PFT-μ in acute leukemias.
Towards better combination regimens of cytarabine and FLT3 inhibitors in acute myeloid leukemia.
Elmeliegy Mohamed,Den Haese Jason,Talati Chetasi,Wetzler Meir,Jusko William J
Cancer chemotherapy and pharmacology
BACKGROUND:AML patients with FLT3/ITD mutations have poor response to cytarabine-based chemotherapy. FLT3 inhibitors (FLT3i) may resensitize cells to cytarabine (CYT). Improving treatment outcome of this combination may benefit from a mechanistic extrapolation approach from in vitro data. METHODS:The effects of CYT and several FLT3i on cell proliferation and cell cycle kinetics were examined in AML cell lines. The effect of FLT3i (quizartinib, midostaurin, sorafenib) on cell proliferation and cell cycle kinetics was assessed in AML cell lines with differing FLT3 status; HEL (negligible expression of wild-type FLT3), EOL1 (wild-type FLT3), MV4-11 (FLT3-ITD resulting in constitutively active isoform). Semi-mechanistic cell cycle models for CYT and FLT3i were developed. Clinical CYT and quizartinib pharmacokinetic dosage regimens were modeled. Survival of AML patients was described via a hazard model. Simulations exploring different CYT/quizartinib regimens were conducted with the goal of improving treatment outcome. RESULTS:FLT3 status was associated with sensitivity to CYT (HEL cells most sensitive > EOL1 > MV4-11 cells). This order of sensitivity is reversed for FLT3i. Cytarabine induced apoptosis in the S-phase while all FLT3i induced apoptosis and cell cycle arrest at G1 phase. Simulations of candidate clinical regimens predict better cell kill upon adding quizartinib simultaneously with or immediately after CYT exposure. Overall survival was predicted to be significantly better with quizartinib 200 mg administered every 48 h vs every 24 h in patients with FLT3 aberrations. CONCLUSION:Simultaneous administration of quizartinib and CYT every other day is a promising combination regimen for AML patients with FLT3 mutations.
Quizartinib-resistant FLT3-ITD acute myeloid leukemia cells are sensitive to the FLT3-Aurora kinase inhibitor CCT241736.
Moore Andrew S,Faisal Amir,Mak Grace W Y,Miraki-Moud Farideh,Bavetsias Vassilios,Valenti Melanie,Box Gary,Hallsworth Albert,de Haven Brandon Alexis,Xavier Cristina P R,Stronge Randal,Pearson Andrew D J,Blagg Julian,Raynaud Florence I,Chopra Rajesh,Eccles Suzanne A,Taussig David C,Linardopoulos Spiros
Internal tandem duplication of FLT3 (FLT3-ITD) is one of the most common somatic mutations in acute myeloid leukemia (AML); it causes constitutive activation of FLT3 kinase and is associated with high relapse rates and poor survival. Small-molecule inhibition of FLT3 represents an attractive therapeutic strategy for this subtype of AML, although resistance from secondary FLT3 tyrosine kinase domain (FLT3-TKD) mutations is an emerging clinical problem. CCT241736 is an orally bioavailable, selective, and potent dual inhibitor of FLT3 and Aurora kinases. FLT3-ITD+ cells with secondary FLT3-TKD mutations have high in vitro relative resistance to the FLT3 inhibitors quizartinib and sorafenib, but not to CCT241736. The mechanism of action of CCT241736 results in significant in vivo efficacy, with inhibition of tumor growth observed in efficacy studies in FLT3-ITD and FLT3-ITD-TKD human tumor xenograft models. The efficacy of CCT241736 was also confirmed in primary samples from AML patients, including those with quizartinib-resistant disease, which induces apoptosis through inhibition of both FLT3 and Aurora kinases. The unique combination of CCT241736 properties based on robust potency, dual selectivity, and significant in vivo activity indicate that CCT241736 is a bona fide clinical drug candidate for FLT3-ITD and TKD AML patients with resistance to current drugs.
Inhibition of S6K1 enhances glucose deprivation-induced cell death via downregulation of anti-apoptotic proteins in MCF-7 breast cancer cells.
Choi Ha-Na,Jin Hyeon-Ok,Kim Jae-Hee,Hong Sung-Eun,Kim Hyun-Ah,Kim Eun-Kyu,Lee Jin Kyung,Park In-Chul,Noh Woo Chul
Biochemical and biophysical research communications
Nutrient-limiting conditions are frequently encountered by tumor cells in poorly vascularized microenvironments. These stress conditions may facilitate the selection of tumor cells with an inherent ability to decrease apoptotic potential. Therefore, selective targeting of tumor cells under glucose deprivation conditions may provide an effective alternative strategy for cancer therapy. In the present study, we investigated the effects of S6 kinase 1 (S6K1) inhibition on glucose deprivation-induced cell death and the underlying mechanisms in MCF-7 breast cancer cells. PF4708671, a selective inhibitor of S6K1, and knockdown of S6K1 with specific siRNA enhanced cell death induced under glucose deprivation conditions. Moreover, inhibition of S6K1 led to apoptosis in glucose-starved MCF-7 cells via downregulation of the anti-apoptotic proteins, Mcl-1 and survivin. Further experiments revealed that sorafenib, shown to be involved in Mcl-1 and survivin downregulation via mTOR/S6K1 inhibition significantly promotes cell death under glucose deprivation conditions. These findings collectively suggest that S6K1 plays an important role in tumor cell survival under stress conditions, and thus inhibition of S6K1 may be an effective strategy for sensitizing cells to glucose deprivation.
AMG 925 is a dual FLT3/CDK4 inhibitor with the potential to overcome FLT3 inhibitor resistance in acute myeloid leukemia.
Li Cong,Liu Liqin,Liang Lingming,Xia Zhen,Li Zhihong,Wang Xianghong,McGee Lawrence R,Newhall Katie,Sinclair Angus,Kamb Alexander,Wickramasinghe Dineli,Dai Kang
Molecular cancer therapeutics
Resistance to FLT3 inhibitors is a serious clinical issue in treating acute myelogenous leukemia (AML). AMG 925, a dual FLT3/CDK4 inhibitor, has been developed to overcome this resistance. It is hypothesized that the combined inhibition of FLT3 and CDK4 may reduce occurrence of the FLT3 resistance mutations, and thereby prolong clinical responses. To test this hypothesis, we attempted to isolate AML cell clones resistant to AMG 925 or to FLT3 inhibitors. After a selection of over 8 months with AMG 925, we could only isolate partially resistant clones. No new mutations in FLT3 were found, but a 2- to 3-fold increase in total FLT3 protein was detected and believed to contribute to the partial resistance. In contrast, selection with the FLT3 inhibitors sorafenib or AC220 (Quizartinib), led to a resistance and the appearance of a number of mutations in FLT3 kinase domains, including the known hot spot sites D835 and F691. However, when AC220 was combined with the CDK4 inhibitor PD0332991 (palbociclib) at 0.1 μmol/L or higher, no resistance mutations were obtained, indicating that the CDK4-inhibiting activity of AMG 925 contributed to the failure to develop drug resistance. AMG 925 was shown to potently inhibit the FLT3 inhibitor-resistant mutation D835Y/V. This feature of AMG 925 was also considered to contribute to the lack of resistance mutations to the compound. Together, our data suggest that AMG 925 has the potential to reduce resistance mutations in FLT3 and may prolong clinical responses.
Targeting the leukemia microenvironment by CXCR4 inhibition overcomes resistance to kinase inhibitors and chemotherapy in AML.
Zeng Zhihong,Shi Yue Xi,Samudio Ismael J,Wang Rui-Yu,Ling Xiaoyang,Frolova Olga,Levis Mark,Rubin Joshua B,Negrin Robert R,Estey Elihu H,Konoplev Sergej,Andreeff Michael,Konopleva Marina
SDF-1alpha/CXCR4 signaling plays a key role in leukemia/bone marrow microenvironment interactions. We previously reported that bone marrow-derived stromal cells inhibit chemotherapy-induced apoptosis in acute myeloid leukemia (AML). Here we demonstrate that the CXCR4 inhibitor AMD3465 antagonized stromal-derived factor 1alpha (SDF-1alpha)-induced and stroma-induced chemotaxis and inhibited SDF-1alpha-induced activation of prosurvival signaling pathways in leukemic cells. Further, CXCR4 inhibition partially abrogated the protective effects of stromal cells on chemotherapy-induced apoptosis in AML cells. Fetal liver tyrosine kinase-3 (FLT3) gene mutations activate CXCR4 signaling, and coculture with stromal cells significantly diminished antileukemia effects of FLT3 inhibitors in cells with mutated FLT3. Notably, CXCR4 inhibition increased the sensitivity of FLT3-mutated leukemic cells to the apoptogenic effects of the FLT3 inhibitor sorafenib. In vivo studies demonstrated that AMD3465, alone or in combination with granulocyte colony-stimulating factor, induced mobilization of AML cells and progenitor cells into circulation and enhanced antileukemic effects of chemotherapy and sorafenib, resulting in markedly reduced leukemia burden and prolonged survival of the animals. These findings indicate that SDF-1alpha/CXCR4 interactions contribute to the resistance of leukemic cells to signal transduction inhibitor- and chemotherapy-induced apoptosis in systems mimicking the physiologic microenvironment. Disruption of these interactions with CXCR4 inhibitors represents a novel strategy of sensitizing leukemic cells by targeting their protective bone marrow microenvironment.
Emerging treatment paradigms with FLT3 inhibitors in acute myeloid leukemia.
Short Nicholas J,Kantarjian Hagop,Ravandi Farhad,Daver Naval
Therapeutic advances in hematology
Mutations in the fms-like tyrosine kinase 3 () gene are detected in approximately one-third of patients with newly diagnosed acute myeloid leukemia (AML). These consist of the more common -internal tandem duplication (ITD) in approximately 20-25% of AML cases, and point mutations in the tyrosine kinase domain (TKD) in approximately 5-10%. mutations, especially -ITD, are associated with proliferative disease, increased risk of relapse, and inferior overall survival when treated with conventional regimens. However, the recent development of well tolerated and active FLT3 inhibitors has significantly improved the outcomes of this aggressive subtype of AML. The multikinase inhibitor midostaurin was approved by the United States Food and Drug Administration (US FDA) in April 2017 for the frontline treatment of patients with -mutated (either ITD or TKD) AML in combination with induction chemotherapy, representing the first new drug approval in AML in nearly two decades. In November 2018, the US FDA also approved the second-generation FLT3 inhibitor gilteritinib as a single agent for patients with relapsed or refractory -mutated AML. Promising phase I and II efficacy data for quizartinib is likely to lead to a third regulatory approval in relapsed/refractory AML in the near future. However, despite the significant progress made in managing -mutated AML, many questions remain regarding the best approach to integrate these inhibitors into combination regimens, and also the optimal sequencing of different FLT3 inhibitors in various clinical settings. This review comprehensively examines the FLT3 inhibitors currently in clinical development, with an emphasis on their spectra of activity against different mutations and other kinases, clinical safety and efficacy data, and their current and future roles in the management of AML. The mechanisms of resistance to FLT3 inhibitors and potential combination strategies to overcome such resistance pathways are also discussed.
FLT3 ligand impedes the efficacy of FLT3 inhibitors in vitro and in vivo.
Sato Takashi,Yang Xiaochuan,Knapper Steven,White Paul,Smith B Douglas,Galkin Steven,Small Donald,Burnett Alan,Levis Mark
We examined in vivo FLT3 inhibition in acute myeloid leukemia patients treated with chemotherapy followed by the FLT3 inhibitor lestaurtinib, comparing newly diagnosed acute myeloid leukemia patients with relapsed patients. Because we noted that in vivo FLT3 inhibition by lestaurtinib was less effective in the relapsed patients compared with the newly diagnosed patients, we investigated whether plasma FLT3 ligand (FL) levels could influence the efficacy of FLT3 inhibition in these patients. After intensive chemotherapy, FL levels rose to a mean of 488 pg/mL on day 15 of induction therapy for newly diagnosed patients, whereas they rose to a mean of 1148 pg/mL in the relapsed patients. FL levels rose even higher with successive courses of chemotherapy, to a mean of 3251 pg/mL after the fourth course. In vitro, exogenous FL at concentrations similar to those observed in patients mitigated FLT3 inhibition and cytotoxicity for each of 5 different FLT3 inhibitors (lestaurtinib, midostaurin, sorafenib, KW-2449, and AC220). The dramatic increase in FL level after chemotherapy represents a possible obstacle to inhibiting FLT3 in this clinical setting. These findings could have important implications regarding the design and outcome of trials of FLT3 inhibitors and furthermore suggest a rationale for targeting FL as a therapeutic strategy.
Combination of ATO with FLT3 TKIs eliminates FLT3/ITD+ leukemia cells through reduced expression of FLT3.
Nagai Kozo,Hou Lihong,Li Li,Nguyen Bao,Seale Tessa,Shirley Courtney,Ma Hayley,Levis Mark,Ghiaur Gabriel,Duffield Amy,Small Donald
Acute myeloid leukemia (AML) patients with FLT3/ITD mutations have a poor prognosis. Monotherapy with selective FLT3 tyrosine kinase inhibitors (TKIs) have shown transient and limited efficacy due to the development of resistance. Arsenic trioxide (ATO, AsO) has been proven effective in treating acute promyelocytic leukemia (APL) and has shown activity in some cases of refractory and relapsed AML and other hematologic malignances. We explored the feasibility of combining FLT3 TKIs with ATO in the treatment of FLT3/ITD+ leukemias. The combination of FLT3 TKIs with ATO showed synergistic effects in reducing proliferation, viability and colony forming ability, and increased apoptosis in FLT3/ITD+ cells and primary patient samples. In contrast, no cooperativity was observed against wild-type FLT3 leukemia cells. ATO reduced expression of FLT3 RNA and its upstream transcriptional regulators (HOXA9, MEIS1), and induced poly-ubiquitination and degradation of the FLT3 protein, partly through reducing its binding with USP10. ATO also synergizes with FLT3 TKIs to inactivate FLT3 autophosphorylation and phosphorylation of its downstream signaling targets, including STAT5, AKT and ERK. Furthermore, ATO combined with sorafenib, a FLT3 TKI, reduced growth of FLT3/ITD+ leukemia cells in NSG recipients. In conclusion, these results suggest that ATO is a potential candidate to study in clinical trials in combination with FLT3 TKIs to improve the treatment of FLT3/ITD+ leukemia.
Dual FLT3/TOPK inhibitor with activity against FLT3-ITD secondary mutations potently inhibits acute myeloid leukemia cell lines.
Dayal Neetu,Opoku-Temeng Clement,Hernandez Delmis E,Sooreshjani Moloud Aflaki,Carter-Cooper Brandon A,Lapidus Rena G,Sintim Herman O
Future medicinal chemistry
AIM:Approximately 30% of acute myeloid leukemia (AML) patients carry FLT3 tyrosine kinase domain (TKD) mutations or internal tandem duplication (FLT3-ITD). Currently there is a paucity of compounds that are active against drug-resistant FLT3-ITD, which contains secondary mutations in the TKD, mainly at residues D835/F691. RESULTS:HSD1169, a novel compound, is active against FLT3-ITD (D835 or F691). HSD1169 is also active against T-LAK cell-originated protein kinase (TOPK), a collaborating kinase that is highly expressed in AML cell lines. HSD1169 was active against MV4-11 and Molm-14 (FLT3-ITD cell lines) but not NOMO-1 or HL60 (FLT3-WT cell lines). HSD1169 was also active against sorafenib-resistant Molm13-res cell line (containing FLT3-ITD/D835Y). CONCLUSION:HSD1169 or an analog could become a therapeutic agent for AML containing drug-resistant FLT3-ITD.
Mechanisms of apoptosis induction by simultaneous inhibition of PI3K and FLT3-ITD in AML cells in the hypoxic bone marrow microenvironment.
Jin Linhua,Tabe Yoko,Lu Hongbo,Borthakur Gautam,Miida Takashi,Kantarjian Hagop,Andreeff Michael,Konopleva Marina
We investigated the antileukemia effects and molecular mechanisms of apoptosis induction by simultaneous blockade of PI3K and mutant FLT3 in AML cells grown under hypoxia in co-cultures with bone marrow stromal cells. Combined treatment with selective class I PI3K inhibitor GDC-0941 and sorafenib reversed the protective effects of bone marrow stromal cells on FLT3-mutant AML cells in hypoxia, which was associated with downregulation of Pim-1 and Mcl-1 expression levels. These findings suggest that combined inhibition of PI3K and FLT3-ITD may constitute a targeted approach to eradicating chemoresistant AML cells sequestered in hypoxic bone marrow niches.
AC220 is a uniquely potent and selective inhibitor of FLT3 for the treatment of acute myeloid leukemia (AML).
Zarrinkar Patrick P,Gunawardane Ruwanthi N,Cramer Merryl D,Gardner Michael F,Brigham Daniel,Belli Barbara,Karaman Mazen W,Pratz Keith W,Pallares Gabriel,Chao Qi,Sprankle Kelly G,Patel Hitesh K,Levis Mark,Armstrong Robert C,James Joyce,Bhagwat Shripad S
Activating mutations in the receptor tyrosine kinase FLT3 are present in up to approximately 30% of acute myeloid leukemia (AML) patients, implicating FLT3 as a driver of the disease and therefore as a target for therapy. We report the characterization of AC220, a second-generation FLT3 inhibitor, and a comparison of AC220 with the first-generation FLT3 inhibitors CEP-701, MLN-518, PKC-412, sorafenib, and sunitinib. AC220 exhibits low nanomolar potency in biochemical and cellular assays and exceptional kinase selectivity, and in animal models is efficacious at doses as low as 1 mg/kg given orally once daily. The data reveal that the combination of excellent potency, selectivity, and pharmacokinetic properties is unique to AC220, which therefore is the first drug candidate with a profile that matches the characteristics desirable for a clinical FLT3 inhibitor.
Mutations of FLT3/ITD confer resistance to multiple tyrosine kinase inhibitors.
Williams A B,Nguyen B,Li L,Brown P,Levis M,Leahy D,Small D
FMS-like tyrosine kinase 3 (FLT3) normally functions in the survival/proliferation of hematopoietic stem/progenitor cells, but its constitutive activation by internal tandem duplication (ITD) mutations correlates with a poor prognosis in AML. The development of FLT3 tyrosine kinase inhibitors (TKI) is a promising strategy, but resistance that arises during the course of treatment caused by secondary mutations within the mutated gene itself poses a significant challenge. In an effort to predict FLT3 resistance mutations that might develop in patients, we used saturation mutagenesis of FLT3/ITD followed by selection of transfected cells in FLT3 TKI. We identified F621L, A627P, F691L and Y842C mutations in FLT3/ITD that confer varying levels of resistance to FLT3 TKI. Western blotting confirmed that some FLT3 TKI were ineffective at inhibiting FLT3 autophosphorylation and signaling through MAP kinase, STAT5 and AKT in some mutants. Balb/c mice transplanted with the FLT3/ITD Y842C mutation confirmed resistance to sorafenib in vivo but not to lestaurtinib. These results indicate a growing number of FLT3 mutations that are likely to be encountered in patients. Such knowledge, combined with known remaining sensitivity to other FLT3 TKI, will be important to establish as secondary drug treatments that can be substituted when these mutants are encountered.
Downregulation of Mcl-1 through GSK-3β activation contributes to arsenic trioxide-induced apoptosis in acute myeloid leukemia cells.
Wang R,Xia L,Gabrilove J,Waxman S,Jing Y
Arsenic trioxide (ATO) induces disease remission in acute promyelocytic leukemia (APL) patients, but not in non-APL acute myeloid leukemia (AML) patients. ATO at therapeutic concentrations (1-2 μM) induces APL NB4, but not non-APL HL-60, cells to undergo apoptosis through the mitochondrial pathway. The role of antiapoptotic protein Mcl-1 in ATO-induced apoptosis was determined. The levels of Mcl-1 were decreased in NB4, but not in HL-60, cells after ATO treatment through proteasomal degradation. Both glycogen synthase kinase-3β (GSK-3β) inhibitor SB216763 and siRNA blocked ATO-induced Mcl-1 reduction as well as attenuated ATO-induced apoptosis in NB4 cells. Silencing Mcl-1 sensitized HL-60 cells to ATO-induced apoptosis. Both ERK and AKT inhibitors decreased Mcl-1 levels and enhanced ATO-induced apoptosis in HL-60 cells. Sorafenib, an Raf inhibitor, activated GSK-3β by inhibiting its phosphorylation, decreased Mcl-1 levels and decreased intracellular glutathione levels in HL-60 cells. Sorafenib plus ATO augmented reactive oxygen species production and apoptosis induction in HL-60 cells and in primary AML cells. These results indicate that ATO induces Mcl-1 degradation through activation of GSK-3β in APL cells and provide a rationale for utilizing ATO in combination with sorafenib for the treatment of non-APL AML patients.
Comparison of antitumor effects of multitargeted tyrosine kinase inhibitors in acute myelogenous leukemia.
Hu Shuiying,Niu Hongmei,Minkin Patton,Orwick Shelley,Shimada Akira,Inaba Hiroto,Dahl Gary V H,Rubnitz Jeffrey,Baker Sharyn D
Molecular cancer therapeutics
We compared the antitumor activities of the multitargeted tyrosine kinase inhibitors imatinib, sorafenib, and sunitinib to determine which inhibitor is best suited to be used for the treatment of acute myelogenous leukemia (AML). In nine human AML cell lines, sorafenib and sunitinib were more potent inhibitors of cellular proliferation than imatinib (IC50, 0.27 to >40, 0.002-9.1, and 0.007-13 micromol/L for imatinib, sorafenib, and sunitinib, respectively). Sorafenib and sunitinib were potent inhibitors of cells with fms-like tyrosine kinase 3 internal tandem duplication (IC50, 2 and 7 nmol/L) and c-KIT N822K mutations (IC50, 23 and 40 nmol/L). In four cell lines (MV4-11, Kasumi-1, KG-1, and U937) that spanned a range of drug sensitivities, sorafenib and sunitinib had similar activity in apoptosis and cell cycle assays, except that sunitinib did not promote apoptosis in U937 cells. Both drugs inhibited mitogen-activated protein kinase signaling but had no effect on AKT signaling in most of the cell lines tested. Sorafenib was substantially more bound than sunitinib in human plasma (unbound fraction, 0.59% versus 8.4%) and cell culture medium (unbound fraction, 1.3% versus 39%), indicating that sorafenib was more potent than sunitinib and that unbound sorafenib concentrations with activity against most AML cell lines are achievable in vivo. There was more intracellular accumulation of sorafenib than of sunitinib and imatinib in AML cells. Between 1 and 10 micromol/L, sorafenib inhibited the proliferation of six of nine primary AML blast samples by > or =50%. Our results highlight the pharmacologic features of sorafenib that may provide it an advantage in the treatment of AML.
All-trans retinoic acid synergizes with FLT3 inhibition to eliminate FLT3/ITD+ leukemia stem cells in vitro and in vivo.
Ma Hayley S,Greenblatt Sarah M,Shirley Courtney M,Duffield Amy S,Bruner J Kyle,Li Li,Nguyen Bao,Jung Eric,Aplan Peter D,Ghiaur Gabriel,Jones Richard J,Small Donald
FMS-like tyrosine kinase 3 (FLT3)-mutant acute myeloid leukemia (AML) portends a poor prognosis, and ineffective targeting of the leukemic stem cell (LSC) population remains one of several obstacles in treating this disease. All-trans retinoic acid (ATRA) has been used in several clinical trials for the treatment of nonpromyelocytic AML with limited clinical activity observed. FLT3 tyrosine kinase inhibitors (TKIs) used as monotherapy also achieve limited clinical responses and are thus far unable to affect cure rates in AML patients. We explored the efficacy of combining ATRA and FLT3 TKIs to eliminate FLT3/internal tandem duplication (ITD)(+) LSCs. Our studies reveal highly synergistic drug activity, preferentially inducing apoptosis in FLT3/ITD(+) cell lines and patient samples. Colony-forming unit assays further demonstrate decreased clonogenicity of FLT3/ITD(+) cells upon treatment with ATRA and TKI. Most importantly, the drug combination depletes FLT3/ITD(+) LSCs in a genetic mouse model of AML, and prolongs survival of leukemic mice. Furthermore, engraftment of primary FLT3/ITD(+) patient samples is reduced in mice following treatment with FLT3 TKI and ATRA in combination, with evidence of cellular differentiation occurring in vivo. Mechanistically, we provide evidence that the synergism of ATRA and FLT3 TKIs is at least in part due to the observation that FLT3 TKI treatment upregulates the antiapoptotic protein Bcl6, limiting the drug's apoptotic effect. However, cotreatment with ATRA reduces Bcl6 expression to baseline levels through suppression of interleukin-6 receptor signaling. These studies provide evidence of the potential of this drug combination to eliminate FLT3/ITD(+) LSCs and reduce the rate of relapse in AML patients with FLT3 mutations.
Crenolanib is active against models of drug-resistant FLT3-ITD-positive acute myeloid leukemia.
Zimmerman Eric I,Turner David C,Buaboonnam Jassada,Hu Shuiying,Orwick Shelley,Roberts Michael S,Janke Laura J,Ramachandran Abhijit,Stewart Clinton F,Inaba Hiroto,Baker Sharyn D
FLT3 kinase internal tandem duplication (ITD) mutations are common in acute myeloid leukemia (AML) and are associated with poor clinical outcomes. Although initial responses to FLT3 tyrosine kinase inhibitors (TKIs) are observed in FLT3-ITD-positive patients, subsequent relapse often occurs upon acquisition of secondary FLT3 kinase domain (KD) mutations, primarily at residues D835 and F691. Using biochemical assays, we determined that crenolanib, a novel TKI, demonstrates type I properties and is active against FLT3 containing ITD and/or D835- or F691-activating mutations. Potent activity was observed in FLT3-ITD-positive AML cell lines. Crenolanib delayed the outgrowth of MV4-11 cells in a xenograft mouse model, whereas in combination with the type II TKI sorafenib, a significant decrease in leukemic burden (P < .001) and prolonged survival (P < .01) was observed compared with either type I or II TKI alone. Crenolanib was active against Ba/F3 cells harboring FLT3-ITD and secondary KD mutations and sorafenib-resistant MOLM-13 cells containing FLT3-ITD/D835Y both in vitro and in vivo. In addition, crenolanib inhibited drug-resistant AML primary blasts with FLT3-ITD and D835H/Y mutations. These preclinical data demonstrate that crenolanib is effective against FLT3-ITD containing secondary KD mutations, suggesting that crenolanib may be a useful therapeutic agent for TKI-naive and drug-resistant FLT3-ITD-positive AML.
Synergistic antitumor efficacy of sequentially combined paclitaxel with sorafenib in vitro and in vivo NSCLC models harboring KRAS or BRAF mutations.
Zhang Xiang-Hua,Shin Jung-Young,Kim Jeong-Oh,Oh Ji-Eun,Yoon Seong-Ae,Jung Chan-Kwon,Kang Jin-Hyoung
Studies on non-small cell lung cancer (NSCLC) patients with KRAS or BRAF mutations are urgently needed to improve clinical outcomes. We evaluated the cytotoxicities of paclitaxel and sorafenib alone and in combination in NSCLC cell lines with KRAS or BRAF mutations and investigated the mechanism of the interaction between the drugs. We found synergistic antitumor efficacy with paclitaxel followed by sorafenib in in vitro and in vivo models of NSCLC. And, we determined that downregulation of the phosphorylated ERK and Rb, and Mcl-1 plays a critical role in the synergistic activity of the drugs. Further clinical trials are needed to verify the antitumor efficacy of this combination.
Inhibition of extracellular signal-regulated kinase activity by sorafenib increases sensitivity to DNR in K562 cells.
Xiao Ruo-Zhi,He Cheng-Ming,Xiong Mu-Jun,Ruan Xing-Xing,Wang Li-Lin,Chen Yan,Lin Dong-Jun
The mitogen-activated protein kinase (MAPK) pathway has a protective function on the management of hematologic malignancies. The aim of this study was to assess whether the induction of MAPK-mediated effects contributes to the therapeutic value of combination sorafenib and daunorubicin (DNR) treatment. Herein, we found that DNR increased phosphorylation of extracellular signal-regulated kinases (ERK1/2) in K562 cells. ERK1/2 activity was blocked by either the mitogen-induced extracellular kinase (MEK) inhibitor U0126 or a multi-kinase inhibitor sorafenib. Of note, sorafenib sensitized K562 to DNR by inhibiting proliferation and inducing apoptosis in a dose-dependent manner which was through blocking the RAF/MEK/ERK pathway. Moreover, K562 cells transfected with a constitutively active MEK2DD plasmid showed increasing IC50 values following DNR treatment compared with control cells. Combination of DNR with MEK inhibitor U0126 synergistically inhibited K562 cell growth. In conclusion, our results indicated that sorafenib sensitized K562 cells to DNR-induced cytotoxicity by downregulating p-ERK1/2 expression. DNR in combination with sorafenib may represent a new and potential therapeutic strategy in treating acute leukemia with high p-ERK1/2 levels.
Metabolic alterations and drug sensitivity of tyrosine kinase inhibitor resistant leukemia cells with a FLT3/ITD mutation.
Huang Amin,Ju Huai-Qiang,Liu Kaiyan,Zhan Guilian,Liu Daolu,Wen Shijun,Garcia-Manero Guillermo,Huang Peng,Hu Yumin
Internal tandem duplication (ITD) of the juxtamembrane region of FMS-like tyrosine kinase-3 (FLT3) receptor is a common type of mutation in adult acute myeloid leukemia (AML), and patient response to FLT3 inhibitors appears to be transient due to the emergence of drug resistance. We established two sorafenib-resistant cell lines carrying FLT3/ITD mutations, including the murine BaF3/ITD-R and human MV4-11-R cell lines. Gene expression profile analysis of the resistant and parental cells suggests that the highest ranked molecular and cellular functions of the differentially expressed genes are related to mitochondrial dysfunction. Both murine and human resistant cell lines display a longer doubling time, along with a significant inhibition of mitochondrial respiratory chain activity and substantial upregulation of glycolysis. The sorafenib-resistant cells exhibit increased expression of a majority of glycolytic enzymes, including hexokinase 2, which is also highly expressed in the mitochondrial fraction and is associated with resistance to apoptotic cell death. The sorafenib-resistant cells are collaterally sensitive to a number of glycolytic inhibitors including 2-deoxyglucose and 3-bromopyruvate propylester. Our study reveals a metabolic signature of sorafenib-resistant cells and suggests that glycolytic inhibition may override such resistance and warrant further clinical investigation.
Reversal of acquired drug resistance in FLT3-mutated acute myeloid leukemia cells via distinct drug combination strategies.
Zhang Weiguo,Gao Chen,Konopleva Marina,Chen Ye,Jacamo Rodrigo O,Borthakur Gautam,Cortes Jorge E,Ravandi Farhad,Ramachandran Abhijit,Andreeff Michael
Clinical cancer research : an official journal of the American Association for Cancer Research
PURPOSE:FMS-like tyrosine kinase-3 (FLT3) internal tandem duplication (FLT3-ITD) mutations are common in patients with acute myeloid leukemia (AML). These patients regularly develop resistance to FLT3 inhibitors suggesting that targeted combination drug strategies are needed to enhance AML therapy efficacy. EXPERIMENTAL DESIGN:Acquired point mutations of FLT3-ITD gene were screened using cDNA-based sequencing approach in vitro sorafenib-resistant cells, which were developed by long-term exposure of Ba/F3-ITD to increasing doses of sorafenib, and in FLT3-ITD mutated AML patients, who developed relapse following sorafenib therapy. Drug effects (e.g., proliferation inhibition, apoptosis induction, and changes in signal transduction protein expression) were assessed in AML cells harboring the point mutations in vitro and in FLT3-ITD-mutated AML patient samples. RESULTS:We identified several acquired point mutations in the tyrosine kinase domains (TKD) of the FLT3 gene in sorafenib-resistant murine leukemia cell line carrying human FLT3-ITD mutations, which were also detected in two of four sorafenib-resistant patient samples. Engineering these point mutations into Ba/F3-ITD cells generated sublines that demonstrated varying degrees of sorafenib [a type II tyrosine kinase inhibitor (TKI)] resistance. A similar pattern of resistance could be observed by exposing these sublines to the other type II TKIs AC220 and MLN518. However, these sublines retained sensitivity to the type I TKIs PKC412 or crenolanib. The combination of crenolanib with sorafenib demonstrated marked cytotoxic effects in all of the sorafenib-resistant sublines. CONCLUSIONS:These combination strategies could be clinically important in reversing acquired resistance to FLT3 inhibition in AML.
Synergistic interactions between vorinostat and sorafenib in chronic myelogenous leukemia cells involve Mcl-1 and p21CIP1 down-regulation.
Dasmahapatra Girija,Yerram Nitin,Dai Yun,Dent Paul,Grant Steven
Clinical cancer research : an official journal of the American Association for Cancer Research
PURPOSE:Interactions between the multikinase inhibitor sorafenib (Bay 43-9006) and the histone deacetylase inhibitor vorinostat were examined in chronic myelogenous leukemia (CML) cells sensitive and resistant to imatinib mesylate. EXPERIMENTAL DESIGN:K562, LAMA 84, and primary CML patient-derived CD34(+) mononuclear cells were exposed to vorinostat followed by sorafenib, after which effects on cell viability and various survival signaling pathways were monitored by flow cytometry, clonogenic assays, and Western blotting. Real-time reverse transcription-PCR was used to monitor gene expression, and the functional contribution of p21(CIP1) and Mcl-1 down-regulation were determined in cells transfected with corresponding constructs. RESULTS:Pretreatment (24 h) with vorinostat followed by sorafenib optimally induced mitochondrial injury and cell death in Bcr/Abl(+) cells (e.g., K562 and LAMA 84). Similar results were obtained in imatinib mesylate-resistant cells expressing activated Lyn as well as in primary CD34(+) bone marrow cells obtained from CML patients. This regimen also markedly inhibited CML cell colony formation. Combined but not individual treatment of CML cells with vorinostat and sorafenib triggered pronounced mitochondrial dysfunction (i.e., cytochrome c, Smac, and AIF release), caspase activation, poly(ADP-ribose) polymerase cleavage, and down-regulation of Mcl-1. Sorafenib also blocked vorinostat-mediated induction of p21(CIP1). Down-regulation of Mcl-1 was caspase and transcription independent, whereas p21(CIP1) down-regulation was partially caspase and transcription dependent. Enforced expression of p21(CIP1) and particularly Mcl-1 significantly attenuated vorinostat/sorafenib-mediated lethality. CONCLUSIONS:These findings suggest that combined treatment with vorinostat and sorafenib synergistically induces apoptosis in CML cells through a process that involves Mcl-1 down-regulation and inhibition of p21(CIP1) induction.
Chidamide Enhances the Cytotoxicity of Cytarabine and Sorafenib in Acute Myeloid Leukemia Cells by Modulating H3K9me3 and Autophagy Levels.
Huang He,Wenbing Yang,Dong Aishu,He Zhewei,Yao Rongxing,Guo Wenjian
Frontiers in oncology
Previous studies showed that chidamide enhances the cytotoxicity of drugs in acute myeloid leukemia (AML) cells. Therefore, we examined whether chidamide enhanced the cytotoxicity of drugs in AML cells by affecting H3K9me3 and autophagy levels. AML cells (THP-1 and MV4-11 cells) were treated with chidamide, cytarabine (Ara-c), or sorafenib alone or in combination. Cell proliferation and survival rates were analyzed by MTT, flow cytometry, and Western blotting assays. The results showed that a low dose of chidamide enhanced the cytotoxicity of Ara-c or sorafenib in AML cells, decreasing proliferation and increasing apoptosis. H3K9me3 levels as assessed by Western blotting were upregulated by chidamide treatment. Chromatin immunoprecipitation sequencing, which was used to investigate potential signaling pathways, indicated that the autophagy pathway might play a role in the effects of chidamide. The level of autophagy induced in AML cells upon treatment with Ara-c or sorafenib was inhibited by chidamide, and autophagy markers (LC3, P62) were tested by Western blotting. SIRT1 messenger RNA (mRNA) and protein levels were lower in AML cells treated with Ara-c or sorafenib in combination with chidamide than those in cells treated with these drugs alone. Additionally, the Integrative Genomics Viewer results indicate that the H3K9me3 changes were related to SIRT1-binding sites. Together, these results show that chidamide enhances the cytotoxicity of two chemotherapy drugs in AML cells by increasing the H3K9me3 level and inhibiting autophagy via decreasing the expression of SIRT1. Chidamide may be a potential treatment strategy for AML in the future, especially for refractory AML patients.
The multikinase inhibitor sorafenib potentiates TRAIL lethality in human leukemia cells in association with Mcl-1 and cFLIPL down-regulation.
Rosato Roberto R,Almenara Jorge A,Coe Stefanie,Grant Steven
Interactions between the multikinase inhibitor sorafenib and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) were examined in malignant hematopoietic cells. Pretreatment (24 h) of U937 leukemia cells with 7.5 micromol/L sorafenib dramatically increased apoptosis induced by sublethal concentrations of TRAIL/Apo2L (75 ng/mL). Similar interactions were observed in Raji, Jurkat, Karpas, K562, U266 cells, primary acute myelogenous leukemia blasts, but not in normal CD34+ bone marrow cells. Sorafenib/TRAIL-induced cell death was accompanied by mitochondrial injury and release of cytochrome c, Smac, and AIF into the cytosol and caspase-9, caspase-3, caspase-7, and caspase-8 activation. Sorafenib pretreatment down-regulated Bcl-xL and abrogated Mcl-1 expression, whereas addition of TRAIL sharply increased Bid activation, conformational change of Bak (ccBak) and Bax (ccBax), and Bax translocation. Ectopic Mcl-1 expression significantly attenuated sorafenib/TRAIL-mediated lethality and dramatically reduced ccBak while minimally affecting levels of ccBax. Similarly, inhibition of the receptor-mediated apoptotic cascade with a caspase-8 dominant-negative mutant significantly blocked sorafenib/TRAIL-induced lethality but not Mcl-1 down-regulation or Bak/Bax conformational change, indicating that TRAIL-mediated receptor pathway activation is required for maximal lethality. Sorafenib/TRAIL did not increase expression of DR4/DR5, or recruitment of procaspase-8 or FADD to the death-inducing signaling complex (DISC), but strikingly increased DISC-associated procaspase-8 activation. Sorafenib also down-regulated cFLIP(L), most likely through a translational mechanism, in association with diminished eIF4E phosphorylation, whereas ectopic expression of cFLIP(L) significantly reduced sorafenib/TRAIL lethality. Together, these results suggest that in human leukemia cells, sorafenib potentiates TRAIL-induced lethality by down-regulating Mcl-1 and cFLIP(L), events that cooperate to engage the intrinsic and extrinsic apoptotic cascades, culminating in pronounced mitochondrial injury and apoptosis.
The sorafenib plus nutlin-3 combination promotes synergistic cytotoxicity in acute myeloid leukemic cells irrespectively of FLT3 and p53 status.
Zauli Giorgio,Celeghini Claudio,Melloni Elisabetta,Voltan Rebecca,Ongari Manuele,Tiribelli Mario,di Iasio Maria Grazia,Lanza Francesco,Secchiero Paola
BACKGROUND:Both the multi-kinase inhibitor sorafenib and the small molecule inhibitor of the MDM2/p53 interaction, nutlin-3, used alone, have shown promising anti-leukemic activity in acute myeloid leukemia cells. Thus, in this study we investigated the effect of the combination of sorafenib plus nutlin-3 in acute myeloid leukemia. DESIGN AND METHODS:Primary acute myeloid leukemia blasts (n=13) and FLT3(wild-type)/p53(wild-type) (OCI-AML3), FLT3(mutated)/p53(wild-type) (MOLM), FLT3(mutated)/p53(mutated) (MV4-11), FLT3(wild-type)/p53(deleted) (HL60) or FLT3(wild-type)/p53(mutated) (NB4) acute myeloid cell lines were exposed to sorafenib, used alone or in association with nutlin-3 at a 1:1 ratio, in a range of clinically achievable concentrations (1-10 μM). Induction of apoptosis and autophagy was evaluated by transmission electron microscopy and by specific flow cytometry analyses. The levels of Mcl-1, p53 and Bak proteins were analyzed by western blotting. Knock-down of Bax and Bak gene expression was performed in transfection experiments with specific short interfering RNA. RESULTS:The sorafenib+nutlin-3 drug combination exhibits synergistic cytotoxicity in primary acute myeloid leukemia blasts and in acute myeloid leukemia cell lines with maximal cytotoxicity in FLT3(mutated) MV4-11 and MOLM, followed by the FLT3(wild-type) OCI-AML3, HL60 and NB4 cell lines. The cytotoxic activity of sorafenib+nutlin-3 was characterized by an increase of both apoptosis and autophagy. Moreover, Bax and Bak showed prominent roles in mediating the decrease of cell viability in response to the drug combination in p53(wild-type) OCI-AML3 and p53(deleted) HL-60 cells, respectively, as demonstrated in transfection experiments performed with specific short interfering RNA. CONCLUSIONS:Our data demonstrate that acute myeloid leukemia cells show a variable but overall good susceptibility to the innovative therapeutic combination of sorafenib+nutlin-3, which differentially involves the pro-apoptotic Bcl-2 family members Bax and Bak in p53(wild-type) and p53(deleted) cells.
Sorafenib Inhibition of Mcl-1 Accelerates ATRA-Induced Apoptosis in Differentiation-Responsive AML Cells.
Wang Rui,Xia Lijuan,Gabrilove Janice,Waxman Samuel,Jing Yongkui
Clinical cancer research : an official journal of the American Association for Cancer Research
PURPOSE:All trans-retinoic acid (ATRA) is successful in treating acute promyelocytic leukemia (APL) by inducing terminal differentiation-mediated cell death, but it has limited activity in non-APL acute myeloid leukemia (AML). We aim to improve ATRA therapy of AML by enhancing apoptosis through repression of the antiapoptotic proteins Bcl-2 and Mcl-1. EXPERIMENTAL DESIGN:APL and AML cell lines, as well as primary AML samples, were used to explore the mechanisms regulating differentiation and apoptosis during ATRA treatment. Stable transfection and gene silencing with siRNA were used to identify the key factors that inhibit apoptosis during induction of differentiation and drugs that accelerate apoptosis. RESULTS:In differentiation-responsive AML cells, ATRA treatment induces long-lasting repression of Bcl-2 while first upmodulating and then reducing the Mcl-1 level. The Mcl-1 level appears to serve as a gatekeeper between differentiation and apoptosis. During differentiation induction, activation of MEK/ERK and PI3K/Akt pathways by ATRA leads to activation of p90RSK and inactivation of glycogen synthase kinase 3β (GSK3β), which increase Mcl-1 levels by increasing its translation and stability. Sorafenib blocks ATRA-induced Mcl-1 increase by reversing p90RSK activation and GSK3β inactivation, maintains the repressed Bcl-2 level, and enhances ATRA induced apoptosis in non-APL AML cell lines and in primary AML cells. CONCLUSIONS:Inhibition of Mcl-1 is required for apoptosis induction in ATRA differentiation-responsive AML cells. ATRA and sorafenib can be developed as a novel drug combination therapy for AML patients because this drug combination augments apoptosis by inhibiting Bcl-2 and Mcl-1.
Activity of the multikinase inhibitor sorafenib in combination with cytarabine in acute myeloid leukemia.
Hu Shuiying,Niu Hongmei,Inaba Hiroto,Orwick Shelley,Rose Charles,Panetta John C,Yang Shengping,Pounds Stanley,Fan Yiping,Calabrese Christopher,Rehg Jerold E,Campana Dario,Rubnitz Jeffrey E,Baker Sharyn D
Journal of the National Cancer Institute
BACKGROUND:Acute myeloid leukemia (AML) is a genetically heterogeneous cancer that frequently exhibits aberrant kinase signaling. We investigated a treatment strategy combining sorafenib, a multikinase inhibitor with limited single-agent activity in AML, and cytarabine, a key component of AML chemotherapy. METHODS:Using 10 human AML cell lines, we determined the effects of sorafenib (10 μM) on antileukemic activity by measuring cell viability, proliferation, ERK1/2 signaling, and apoptosis. We also investigated the effects of sorafenib treatment on the accumulation of cytarabine and phosphorylated metabolites in vitro. A human equivalent dose of sorafenib in nontumor-bearing NOD-SCID-IL2Rγ(null) mice was determined by pharmacokinetic studies using high performance liquid chromatography with tandem mass spectrometric detection, and steady-state concentrations were estimated by the fit of a one-compartment pharmacokinetic model to concentration-time data. The antitumor activity of sorafenib alone (60 mg/kg) twice daily, cytarabine alone (6.25 mg/kg administered intraperitoneally), or sorafenib once or twice daily plus cytarabine was evaluated in NOD-SCID-IL2Rγ(null) mice bearing AML xenografts. RESULTS:Sorafenib at 10 μM inhibited cell viability, proliferation and ERK1/2 signaling, and induced apoptosis in all cell lines studied. Sorafenib also increased the cellular accumulation of cytarabine and metabolites resulting in additive to synergistic antileukemic activity. A dose of 60 mg/kg in mice produced a human equivalent sorafenib steady-state plasma exposure of 10 μM. The more dose-intensive twice-daily sorafenib plus cytarabine (n = 15) statistically significantly prolonged median survival in an AML xenograft model compared with sorafenib once daily plus cytarabine (n = 12), cytarabine alone (n = 26), or controls (n = 27) (sorafenib twice daily plus cytarabine, median survival = 46 days; sorafenib once daily plus cytarabine, median survival = 40 days; cytarabine alone, median survival = 36 days; control, median survival = 19 days; P < .001 for combination twice daily vs all other treatments listed). CONCLUSIONS:Sorafenib in combination with cytarabine resulted in strong anti-AML activity in vitro and in vivo. These results warrant clinical evaluation of sorafenib with cytarabine-based regimens in molecularly heterogeneous AML.
Inhibition of Bcl-2 antiapoptotic members by obatoclax potently enhances sorafenib-induced apoptosis in human myeloid leukemia cells through a Bim-dependent process.
Rahmani Mohamed,Aust Mandy Mayo,Attkisson Elisa,Williams David C,Ferreira-Gonzalez Andrea,Grant Steven
Interactions between the multikinase inhibitor sorafenib and the BH3-mimetic obatoclax (GX15-070) were examined in human acute myeloid leukemia (AML) cells. Treatment with sorafenib/obatoclax induced pronounced apoptosis in and reduced the clonogenic growth of multiple AML lines and primary AML cells but not normal CD34(+) cells. Sorafenib triggered rapid and pronounced Mcl-1 down-regulation accompanied by enhanced binding of Bim to Bcl-2 and Bcl-xL, effects that were abolished by obatoclax coadministration. Notably, shRNA knockdown of Bim, Bak, or Bax, but not Noxa, significantly attenuated obatoclax/sorafenib lethality, whereas ectopic expression of Mcl-1 exerted a protective effect. Furthermore, exposure of leukemia cells to sorafenib and obatoclax markedly induced autophagy, reflected by rapid and pronounced LC3 processing and LC3-green fluorescent protein (GFP) punctate formation. Multiple autophagy inhibitors or VPS34 knockdown, significantly potentiated sorafenib/obatoclax lethality, indicating a cytoprotective role for autophagy in this setting. Finally, studies in a xenograft mouse model revealed that combined sorafenib/obatoclax treatment markedly reduced tumor growth and significantly prolonged survival in association with Mcl-1 down-regulation and apoptosis induction, whereas agents administered individually had only modest effects. These findings suggest that combining sorafenib with agents that inhibit Mcl-1 and Bcl-2/Bcl-xL such as obatoclax may represent a novel and potentially effective strategy in AML.
Synergistic cytotoxicity of sorafenib with busulfan and nucleoside analogs in human FMS-like tyrosine kinase 3 internal tandem duplications-positive acute myeloid leukemia cells.
Song Guiyun,Valdez Benigno C,Li Yang,Liu Yan,Champlin Richard E,Andersson Borje S
Biology of blood and marrow transplantation : journal of the American Society for Blood and Marrow Transplantation
Clofarabine (Clo), fludarabine (Flu), and busulfan (Bu) are used in pretransplantation conditioning therapy for patients with myeloid leukemia. To further improve their efficacy in FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD)-positive acute myeloid leukemia (AML), we investigated their synergism with sorafenib (Sor). Exposure of FLT3-ITD-positive MV-4-11 and MOLM 13 cells to Bu+Clo+Flu+Sor resulted in synergistic cytotoxicity; no such synergism was observed in the FLT3-wild type THP-1 and KBM3/Bu250(6) cell lines. The drug synergism in MV-4-11 cells could be attributed to activation of DNA damage response, histone 3 modifications, inhibition of prosurvival kinases, and activation of apoptosis. Further, the phosphorylation of kinases, including FLT3, MAPK kinase (MEK), and AKT, was inhibited. The FLT3-ITD substrate STAT5 and its target gene PIM 2 product decreased when cells were exposed to Sor alone, Bu+Clo+Flu, and Bu+Clo+Flu+Sor. The level of the proapoptotic protein p53 upregulated modulator of apoptosis (PUMA) increased, whereas the level of prosurvival protein MCL-1 decreased when cells were exposed to Bu+Clo+Flu+Sor. The interactions of PUMA with MCL-1 and/or BCL-2 were enhanced when cells were exposed to Bu+Clo+Flu or Bu+Clo+Flu+Sor. The changes in the level of these proteins, which are involved in mitochondrial control of apoptosis, correlate with changes in mitochondrial membrane potential. Bu+Clo+Flu+Sor decreased mitochondrial membrane potential by 60% and caused leakage of cytochrome c, second mitochondria-derived activator of caspases (SMAC)/direct IAP Binding protein with low pI (DIABLO), and AIF from the mitochondria to the cytoplasm, caspase activation, and cell death, suggesting the activation of apoptosis. Analogous, synergistic cytotoxicity in response to Bu, Clo, Flu, and Sor was observed in mononuclear cells isolated from FLT3-ITD-positive AML patients. Although our previous studies were aimed at standardizing the conditioning regimen, the new findings suggest that patients with abnormal expression of FLT3 might further benefit from individualizing treatment through the addition of Sor to Bu+Clo+Flu, thereby providing personalized pretransplantation therapy.
Sorafenib induces cell death in chronic lymphocytic leukemia by translational downregulation of Mcl-1.
Huber S,Oelsner M,Decker T,zum Büschenfelde C Meyer,Wagner M,Lutzny G,Kuhnt T,Schmidt B,Oostendorp R A J,Peschel C,Ringshausen I
Chronic lymphocytic leukemia (CLL) has a high prevalence in western countries and remains incurable to date. Here, we provide evidence that the multikinase inhibitor sorafenib induces apoptosis in primary CLL cells. This strong pro-apoptotic effect is not restricted to any subgroup of patients, based on Binet stage and the expression of ZAP70 or CD38. Mechanistically, sorafenib-induced cell death is preceded by a rapid downregulation of Mcl-1 through the inhibition of protein translation. Subsequently, the cell intrinsic apoptotic pathway is activated, indicated by destabilization of the mitochondrial membrane potential and activation of caspase-3 and -9. In contrast to sorafenib, the monoclonal vascular epidermal growth factor (VEGF)-antibody bevacizumab failed to induce apoptosis in CLL cells, suggesting that sorafenib induces cell death irrespectively of VEGF signalling. Notably, although sorafenib inhibits phosphorylation of the Scr-kinase Lck, knock-down of Lck did not induce apoptosis in CLL cells. Of note, the pro-apoptotic effect of sorafenib is not restricted to cell-cycle arrested cells, but is also maintained in proliferating CLL cells. In addition, we provide evidence that sorafenib can overcome drug resistance in CLL cells protected by microenvironmental signals from stromal cells. Conclusively, sorafenib is highly active in CLL and may compose a new therapeutic option for patients who relapse after immunochemotherapy.
Sorafenib induces paradoxical phosphorylation of the extracellular signal-regulated kinase pathway in acute myeloid leukemia cells lacking FLT3-ITD mutation.
Fouladi Fariba,Jehn Lutz B,Metzelder Stephan K,Hub Florian,Henkenius Katharina,Burchert Andreas,Brendel Cornelia,Stiewe Thorsten,Neubauer Andreas
Leukemia & lymphoma
Gain-of-function mutations in the RAS and FLT3 genes are frequently found in cells of acute myeloid leukemia (AML), leading to constitutive activation of signaling pathways that regulate fundamental cellular processes, and are therefore attractive targets for AML therapy. The multi-targeted kinase inhibitor sorafenib is efficacious in AML with FLT3-internal tandem duplication (ITD), but resistance to therapy is an important clinical problem. It is unclear whether AML lacking FLT3-ITD responds to sorafenib. Using AML cell lines, we have shown that a low concentration of sorafenib induces opposing effects depending on the oncogenic background. In FLT3-ITD positive cells sorafenib blocks Erk activity and cell proliferation, and triggers apoptosis. However, in cells lacking FLT3-ITD, sorafenib paradoxically activates Erk2, and stimulates cellular proliferation and metabolic activity. Thus, depending on the genetic context, sorafenib is a beneficial inhibitor or paradoxical activator of mitogenic signaling pathways in AML. These results harbor important consequences in planning clinical trials in AML.
Metformin synergistically sensitizes FLT3-ITD-positive acute myeloid leukemia to sorafenib by promoting mTOR-mediated apoptosis and autophagy.
Wang Fangfang,Liu Zuofeng,Zeng Jisha,Zhu Hongyan,Li Jingjing,Cheng Xiaomin,Jiang Tao,Zhang Li,Zhang Chuanfen,Chen Tie,Liu Ting,Jia Yongqian
Mutations of Fms-like tyrosine kinase 3-internal tandem duplication (FLT3-ITD), accounting for approximately 30% of patients with acute myeloid leukemia (AML), results in poor therapeutic efficacy and short survival. Sorafenib, an oral multikinase inhibitor, can inhibit FLT3 and improve clinical outcome of FLT3 mutated leukemia. Our current studies have shown that, the antidiabetic drug metformin also exerts anti-leukemic effect by activating p-AMPK and synergistically sensitizes FLT3 mutated AML to sorafenib. Both agents suppress cell proliferation in a dose-dependent manner and induce apoptosis via cell cycle arrest, but does not obviously modulate autophagy marker, light chain 3 (LC3). Mechanistically, in the presence of metformin, the anticancer potential of sorafenib, accompanying with increased LC3 levels, is found to be synergistically enhanced with the remarkably reduced protein expression of the mTOR/p70S6K/4EBP1 pathway, while not appreciably altering cell cycle. Overall, these results show metformin in aid of sorafenib may represent a promising and attractive strategy for the treatment of FLT3-ITD mutated AML.
Arsenic Trioxide and Sorafenib Induce Synthetic Lethality of FLT3-ITD Acute Myeloid Leukemia Cells.
Wang Rui,Li Ying,Gong Ping,Gabrilove Janice,Waxman Samuel,Jing Yongkui
Molecular cancer therapeutics
Acute myeloid leukemia (AML) with Fms-related tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation is notoriously hard to treat. We identified two drugs that together form an effective combination therapy against FLT3-ITD AML. One of the drugs, Sorafenib, an inhibitor of FLT3-ITD and other kinase activity, produces an impressive but short-lived remission in FLT3-ITD AML patients. The second, arsenic trioxide (ATO), at therapeutically achievable concentrations, reduces the level of FLT3-ITD and Mcl-1 proteins, and induces apoptosis in leukemic cell lines and in primary cells expressing FLT3-ITD. We linked this relative sensitivity to ATO to low levels of reduced glutathione. While producing proapoptotic effects, ATO treatment also has an unwanted effect whereby it causes the accumulation of the phosphorylated (inactive) form of glycogen synthase kinase 3β (GSK3β), a kinase necessary for apoptosis. When ATO is combined with Sorafenib, GSK3β is activated, Mcl-1 is further reduced, and proapoptotic proteins Bak and Bax are activated. Mice xenografted with FLT3-ITD MOLM13 cell line treated with the Sorafenib/ATO combination have significantly improved survival. This combination has potential to improve the therapeutic outcome of FLT3-ITD-targeted therapy of AML patients. .
Phosphoproteome Analysis Reveals Differential Mode of Action of Sorafenib in Wildtype and Mutated FLT3 Acute Myeloid Leukemia (AML) Cells.
Roolf Catrin,Dybowski Nikolaj,Sekora Anett,Mueller Stefan,Knuebel Gudrun,Tebbe Andreas,Murua Escobar Hugo,Godl Klaus,Junghanss Christian,Schaab Christoph
Molecular & cellular proteomics : MCP
Constitutively activating internal tandem duplication (ITD) alterations of the receptor tyrosine kinase FLT3 (Fms-like tyrosine kinase 3) are common in acute myeloid leukemia (AML) and classifies FLT3 as an attractive therapeutic target. So far, applications of FLT3 small molecule inhibitors have been investigated primarily in FLT3-ITD patients. Only recently, a prolonged event-free survival has been observed in AML patients who were treated with the multikinase inhibitor sorafenib in addition to standard therapy. Here, we studied the sorafenib effect on proliferation in a panel of 13 FLT3-ITD and FLT3-ITD AML cell lines. Sorafenib IC50 values ranged from 0.001 to 5.6 μm, whereas FLT3-ITD cells (MOLM-13, MV4-11) were found to be more sensitive to sorafenib than FLT3-ITD cells. However, we identified two FLT3-ITD cell lines (MONO-MAC-1 and OCI-AML-2) which were also sorafenib sensitive. Phosphoproteome analyses revealed that the affected pathways differed in sorafenib sensitive FLT3-ITD and FLT3-ITD cells. In MV4-11 cells sorafenib suppressed mTOR signaling by direct inhibition of FLT3. In MONO-MAC-1 cells sorafenib inhibited the MEK/ERK pathway. These data suggest that the FLT3 status in AML patients might not be the only factor predicting response to treatment with sorafenib.
Sorafenib promotes graft-versus-leukemia activity in mice and humans through IL-15 production in FLT3-ITD-mutant leukemia cells.
Mathew Nimitha R,Baumgartner Francis,Braun Lukas,O'Sullivan David,Thomas Simone,Waterhouse Miguel,Müller Tony A,Hanke Kathrin,Taromi Sanaz,Apostolova Petya,Illert Anna L,Melchinger Wolfgang,Duquesne Sandra,Schmitt-Graeff Annette,Osswald Lena,Yan Kai-Li,Weber Arnim,Tugues Sonia,Spath Sabine,Pfeifer Dietmar,Follo Marie,Claus Rainer,Lübbert Michael,Rummelt Christoph,Bertz Hartmut,Wäsch Ralph,Haag Johanna,Schmidts Andrea,Schultheiss Michael,Bettinger Dominik,Thimme Robert,Ullrich Evelyn,Tanriver Yakup,Vuong Giang Lam,Arnold Renate,Hemmati Philipp,Wolf Dominik,Ditschkowski Markus,Jilg Cordula,Wilhelm Konrad,Leiber Christian,Gerull Sabine,Halter Jörg,Lengerke Claudia,Pabst Thomas,Schroeder Thomas,Kobbe Guido,Rösler Wolf,Doostkam Soroush,Meckel Stephan,Stabla Kathleen,Metzelder Stephan K,Halbach Sebastian,Brummer Tilman,Hu Zehan,Dengjel Joern,Hackanson Björn,Schmid Christoph,Holtick Udo,Scheid Christof,Spyridonidis Alexandros,Stölzel Friedrich,Ordemann Rainer,Müller Lutz P,Sicre-de-Fontbrune Flore,Ihorst Gabriele,Kuball Jürgen,Ehlert Jan E,Feger Daniel,Wagner Eva-Maria,Cahn Jean-Yves,Schnell Jacqueline,Kuchenbauer Florian,Bunjes Donald,Chakraverty Ronjon,Richardson Simon,Gill Saar,Kröger Nicolaus,Ayuk Francis,Vago Luca,Ciceri Fabio,Müller Antonia M,Kondo Takeshi,Teshima Takanori,Klaeger Susan,Kuster Bernhard,Kim Dennis Dong Hwan,Weisdorf Daniel,van der Velden Walter,Dörfel Daniela,Bethge Wolfgang,Hilgendorf Inken,Hochhaus Andreas,Andrieux Geoffroy,Börries Melanie,Busch Hauke,Magenau John,Reddy Pavan,Labopin Myriam,Antin Joseph H,Henden Andrea S,Hill Geoffrey R,Kennedy Glen A,Bar Merav,Sarma Anita,McLornan Donal,Mufti Ghulam,Oran Betul,Rezvani Katayoun,Shah Omid,Negrin Robert S,Nagler Arnon,Prinz Marco,Burchert Andreas,Neubauer Andreas,Beelen Dietrich,Mackensen Andreas,von Bubnoff Nikolas,Herr Wolfgang,Becher Burkhard,Socié Gerard,Caligiuri Michael A,Ruggiero Eliana,Bonini Chiara,Häcker Georg,Duyster Justus,Finke Jürgen,Pearce Erika,Blazar Bruce R,Zeiser Robert
Individuals with acute myeloid leukemia (AML) harboring an internal tandem duplication (ITD) in the gene encoding Fms-related tyrosine kinase 3 (FLT3) who relapse after allogeneic hematopoietic cell transplantation (allo-HCT) have a 1-year survival rate below 20%. We observed that sorafenib, a multitargeted tyrosine kinase inhibitor, increased IL-15 production by FLT3-ITD leukemia cells. This synergized with the allogeneic CD8 T cell response, leading to long-term survival in six mouse models of FLT3-ITD AML. Sorafenib-related IL-15 production caused an increase in CD8CD107aIFN-γ T cells with features of longevity (high levels of Bcl-2 and reduced PD-1 levels), which eradicated leukemia in secondary recipients. Mechanistically, sorafenib reduced expression of the transcription factor ATF4, thereby blocking negative regulation of interferon regulatory factor 7 (IRF7) activation, which enhanced IL-15 transcription. Both IRF7 knockdown and ATF4 overexpression in leukemia cells antagonized sorafenib-induced IL-15 production in vitro. Human FLT3-ITD AML cells obtained from sorafenib responders following sorafenib therapy showed increased levels of IL-15, phosphorylated IRF7, and a transcriptionally active IRF7 chromatin state. The mitochondrial spare respiratory capacity and glycolytic capacity of CD8 T cells increased upon sorafenib treatment in sorafenib responders but not in nonresponders. Our findings indicate that the synergism of T cells and sorafenib is mediated via reduced ATF4 expression, causing activation of the IRF7-IL-15 axis in leukemia cells and thereby leading to metabolic reprogramming of leukemia-reactive T cells in humans. Therefore, sorafenib treatment has the potential to contribute to an immune-mediated cure of FLT3-ITD-mutant AML relapse, an otherwise fatal complication after allo-HCT.
Melatonin enhances sorafenib-induced cytotoxicity in FLT3-ITD acute myeloid leukemia cells by redox modification.
Tian Tian,Li Jiajun,Li Yizhuo,Lu Yun-Xin,Tang Yan-Lai,Wang Hua,Zheng Fufu,Shi Dingbo,Long Qian,Chen Miao,Garcia-Manero Guillermo,Hu Yumin,Qin Lijun,Deng Wuguo
Acute myeloid leukemia (AML) with an internal tandem duplication in Fms-related tyrosine kinase 3 (FLT3-ITD) is identified as a subgroup with poor outcome and intrinsic resistance to chemotherapy and therefore urgent need for development of novel therapeutic strategies. : The antitumor effects of melatonin alone or combined with sorafenib were evaluated via flow cytometry and immunoblotting assays in FLT-ITD AML cells. Also, the and models were used to test the synergistic effects of melatonin and sorafenib against leukemia with FLT3/ITD mutation. : Our study shows for the first time that melatonin inhibits proliferation and induces apoptosis in FLT3/ITD-positive leukemia cells. Mechanistically, melatonin preferentially causes overproduction of reactive oxygen species (ROS) and ultimately massive cell death in FLT3-ITD AML cells. Moreover, melatonin significantly enhances the cytotoxicity induced by the FLT3 tyrosine kinase inhibitor sorafenib in AML cells with FLT3/ITD through redox modification. Importantly, combination of melatonin and sorafenib exhibited highly synergistic therapeutic activity in MV4-11 xenografts and a murine model bearing FLT3/ITD leukemia. : This study indicates that melatonin, alone or in combination with sorafenib, has potential to improve the therapeutic outcome of AML patients with FLT3-ITD mutation that merits further investigation.