and Determinants of Tumor Grade and mTOR Activation in VHL-Deficient Mouse Models of Renal Cell Carcinoma.
Leung Janet Y,Kim William Y
<b/> Large genome sequencing efforts have identified frequent mutations in the histone-modifying and chromatin-remodeling genes and in clear cell renal cell carcinoma (ccRCC). In this issue of , Gu and colleagues model these genetic events in mice and report that dual inactivation of with either or results in faithful genetically engineered murine models of ccRCC. Moreover, their work establishes that and are determinants of tumor grade and mTORC1 activation and provocatively suggests that the cell of origin of ccRCC may lie in PAX8-expressing Bowman capsule cells. .
BAP1 complex promotes transcription by opposing PRC1-mediated H2A ubiquitylation.
Campagne Antoine,Lee Ming-Kang,Zielinski Dina,Michaud Audrey,Le Corre Stéphanie,Dingli Florent,Chen Hong,Shahidian Lara Z,Vassilev Ivaylo,Servant Nicolas,Loew Damarys,Pasmant Eric,Postel-Vinay Sophie,Wassef Michel,Margueron Raphaël
In Drosophila, a complex consisting of Calypso and ASX catalyzes H2A deubiquitination and has been reported to act as part of the Polycomb machinery in transcriptional silencing. The mammalian homologs of these proteins (BAP1 and ASXL1/2/3, respectively), are frequently mutated in various cancer types, yet their precise functions remain unclear. Using an integrative approach based on isogenic cell lines generated with CRISPR/Cas9, we uncover an unanticipated role for BAP1 in gene activation. This function requires the assembly of an enzymatically active BAP1-associated core complex (BAP1.com) containing one of the redundant ASXL proteins. We investigate the mechanism underlying BAP1.com-mediated transcriptional regulation and show that it does not participate in Polycomb-mediated silencing. Instead, our results establish that the function of BAP1.com is to safeguard transcriptionally active genes against silencing by the Polycomb Repressive Complex 1.
A Subset of Mesotheliomas With Improved Survival Occurring in Carriers of BAP1 and Other Germline Mutations.
Pastorino Sandra,Yoshikawa Yoshie,Pass Harvey I,Emi Mitsuru,Nasu Masaki,Pagano Ian,Takinishi Yasutaka,Yamamoto Ryuji,Minaai Michael,Hashimoto-Tamaoki Tomoko,Ohmuraya Masaki,Goto Keisuke,Goparaju Chandra,Sarin Kavita Y,Tanji Mika,Bononi Angela,Napolitano Andrea,Gaudino Giovanni,Hesdorffer Mary,Yang Haining,Carbone Michele
Journal of clinical oncology : official journal of the American Society of Clinical Oncology
PURPOSE:We hypothesized that four criteria could help identify malignant mesotheliomas (MMs) most likely linked to germline mutations of BAP1 or of other genes: family history of MM, BAP1-associated cancers, or multiple malignancies; or age younger than 50 years. PATIENTS AND METHODS:Over the course of 7 years, 79 patients with MM met the four criteria; 22 of the 79 (28%) reported possible asbestos exposure. They were screened for germline BAP1 mutations by Sanger sequencing and by targeted next-generation sequencing (tNGS) for germline mutations in 55 additional cancer-linked genes. Deleterious mutations detected by tNGS were validated by Sanger sequencing. RESULTS:Of the 79 patients, 43 (16 probands and 27 relatives) had deleterious germline BAP1 mutations. The median age at diagnosis was 54 years and median survival was 5 years. Among the remaining 36 patients with no BAP1 mutation, median age at diagnosis was 45 years, median survival was 9 years, and 12 had deleterious mutations of additional genes linked to cancer. When compared with patients with MMs in the SEER cohort, median age at diagnosis (72 years), median survival for all MM stages (8 months), and stage I (11 months) were significantly different from the 79 patients with MM in the current study ( P < .0001). CONCLUSION:We provide criteria that help identify a subset of patients with MM who had significantly improved survival. Most of these patients were not aware of asbestos exposure and carried either pathogenic germline mutations of BAP1 or of additional genes linked to cancer, some of which may have targeted-therapy options. These patients and their relatives are susceptible to development of additional cancers; therefore, genetic counseling and cancer screening should be considered.
BAP1 mutations define a homogeneous subgroup of hepatocellular carcinoma with fibrolamellar-like features and activated PKA.
Hirsch Théo Z,Negulescu Ana,Gupta Barkha,Caruso Stefano,Noblet Bénédicte,Couchy Gabrielle,Bayard Quentin,Meunier Léa,Morcrette Guillaume,Scoazec Jean-Yves,Blanc Jean-Frédéric,Amaddeo Giuliana,Nault Jean-Charles,Bioulac-Sage Paulette,Ziol Marianne,Beaufrère Aurélie,Paradis Valérie,Calderaro Julien,Imbeaud Sandrine,Zucman-Rossi Jessica
Journal of hepatology
BACKGROUND & AIMS:DNAJB1-PRKACA fusion is a specific driver event in fibrolamellar carcinoma (FLC), a rare subtype of hepatocellular carcinoma (HCC) that occurs in adolescents and young adults. In older patients, molecular determinants of HCC with mixed histological features of HCC and FLC (mixed-FLC/HCC) remain to be discovered. METHODS:A series of 151 liver tumors including 126 HCC, 15 FLC, and 10 mixed-FLC/HCC were analyzed by RNAseq and whole-genome- or whole-exome sequencing. Western blots were performed to validate genomic discoveries. Results were validated using the TCGA database. RESULTS:Most of the mixed-FLC/HCC RNAseq clustered in a robust subgroup of 17 tumors, which all had mutations or translocations inactivating BAP1, the gene encoding BRCA1-associated protein-1. Like FLC, BAP1-HCC were significantly enriched in females, patients with a lack of chronic liver disease, and fibrotic tumors compared to non-BAP1 HCC. However, patients were older and had a poorer prognosis than those with FLC. BAP1 tumors were immune hot, showed progenitor features and did not show DNAJB1-PRKACA fusion, while almost none of these tumors had mutations in CTNNB1, TP53 and TERT promoter. In contrast, 80% of the BAP1 tumors showed a chromosome gain of PRKACA at 19p13, combined with a loss of PRKAR2A (coding for the inhibitory regulatory subunit of PKA) at 3p21, leading to a high PRKACA/PRKAR2A ratio at the mRNA and protein levels. CONCLUSION:We have characterized a subgroup of BAP1-driven HCC with fibrolamellar-like features and a dysregulation of the PKA pathway, which could be at the root of the clinical and histological similarities between BAP1 tumors and DNAJB1-PRKACA FLCs. LAY SUMMARY:Herein, we have defined a homogeneous subgroup of hepatocellular carcinomas in which the BAP1 gene is inactivated. This leads to the development of cancers with features similar to those of fibrolamellar carcinoma. These tumors more frequently develop in females without chronic liver disease or cirrhosis. The presence of PKA activation and T cell infiltrates suggest that these tumors could be treated with PKA inhibitors or immunomodulators.
Prevalence and Preliminary Validation of Screening Criteria to Identify Carriers of Germline BAP1 Mutations.
Zauderer Marjorie G,Jayakumaran Gowtham,DuBoff Mariel,Zhang Liying,Francis Jasmine H,Abramson David H,Cercek Andrea,Nash Garrett M,Shoushtari Alexander,Chapman Paul,D'Angelo Sandra,Arnold Angela G,Siegel Beth,Fleischut Megan Harlan,Ni Andy,Rimner Andreas,Rusch Valerie W,Adusumilli Prasad S,Travis William,Sauter Jennifer L,Zehir Ahmet,Mandelker Diana,Ladanyi Marc,Robson Mark
Journal of thoracic oncology : official publication of the International Association for the Study of Lung Cancer
INTRODUCTION:Inherited mutations are easily detected factors that influence the disease courses and optimal treatment strategies of some cancers. Germline mutations in BRCA1 associated protein 1 (BAP1) are associated with unique disease profiles in mesothelioma, atypical spitz nevi, and uveal melanoma, but the patient characteristics of an unselected population of BAP1 carriers identified by an ascertainment prevalence study are unknown. METHODS:We collected blood samples, cancer histories, and occupational exposures from 183 unselected patients with BAP1-related diseases. Clinical information for each patient was obtained from medical records. Germline DNA was extracted from blood samples and sequenced using a next-generation sequencing assay. We tested screening criteria developed to identify patients with a possible germline BAP1 mutation. RESULTS:Pathogenic or likely pathogenic germline BAP1 mutations were observed in 5 of 180 sequenced specimens and were exclusively found in patients identified by our screening criteria. Several patients with characteristics suspicious for a heritable deleterious mutation did not have a germline BAP1 mutation. The prevalence of pathogenic germline BAP1 mutations in patients with mesothelioma was 4.4% (95% confidence interval 1.1-11.1). CONCLUSIONS:Results from the first unselected prevalence ascertainment study of germline BAP1 alterations suggest that the frequency of this mutation is low among patients with mesothelioma. The proposed screening criteria successfully identified all patients with germline BAP1-mutant mesothelioma. These screening guidelines may assist physicians in selecting patients who would benefit from genetic testing. Future efforts should validate and refine these criteria and search for other germline mutations associated with mesothelioma and related diseases.
An emerging model for BAP1's role in regulating cell cycle progression.
Eletr Ziad M,Wilkinson Keith D
Cell biochemistry and biophysics
BRCA1-associated protein-1 (BAP1) is a 729 residue, nuclear-localized deubiquitinating enzyme (DUB) that displays tumor suppressor properties in the BAP1-null NCI-H226 lung carcinoma cell line. Studies that have altered BAP1 cellular levels or enzymatic activity have reported defects in cell cycle progression, notably at the G1/S transition. Recently BAP1 was shown to associate with the transcriptional regulator host cell factor 1 (HCF-1). The BAP1/HCF-1 interaction is mediated by the HCF-1 Kelch domain and an HCF-1 binding motif (HBM) within BAP1. HCF-1 is modified with ubiquitin in vivo, and ectopic studies suggest BAP1 deubiquitinates HCF-1. HCF-1 is a chromatin-associated protein thought to both activate and repress transcription by linking appropriate histone-modifying enzymes to a subset of transcription factors. One known role of HCF-1 is to promote cell cycle progression at the G1/S boundary by recruiting H3K4 histone methyltransferases to the E2F1 transcription factor so that genes required for S-phase can be transcribed. Given the robust associations between BAP1/HCF-1 and HCF-1/E2Fs, it is reasonable to speculate that BAP1 influences cell proliferation at G1/S by co-regulating transcription from HCF-1/E2F-governed promoters.
BRCA-associated protein 1 mutant cholangiocarcinoma: an aggressive disease subtype.
Al-Shamsi Humaid O,Anand Deepa,Shroff Rachna T,Jain Apurva,Zuo Mingxin,Conrad Claudius,Vauthey Jean-Nicolas,Javle Milind M
Journal of gastrointestinal oncology
BACKGROUND:BRCA-associated protein 1, an enzyme encoded by the BAP1 gene, is commonly mutated in uveal melanoma, mesothelioma, and renal cancers. Tumors with BAP1 mutation follow an aggressive course. BAP1 mutations have also been observed in cholangiocarcinoma (CCA). The clinical phenotype of BAP1 mutant CCA may yield useful prognostic and therapeutic information but has not been defined. METHODS:The records of CCA patients who underwent next-generation sequencing (NGS) were reviewed, and data on clinical, histopathological, genetic, and radiological features; response to therapy; time to progression; and survival were analyzed. RESULTS:Twenty-two cases of BAP1-mutation associated CCA were diagnosed from January 1, 2009, to February 1, 2015, at our center. Twenty patients had intrahepatic CCA and two had extrahepatic CCA. Tumor sizes (largest dimension) ranged from 2 to 16 cm (mean, 8.5 cm). Twelve patients had tumors that were poorly differentiated. Majority of the patients had advanced disease at presentation and 13 had bone metastases. Thirteen patients (59%) experienced rapidly progressive disease following primary therapy (chemotherapy or surgical resection). The mean time to tumor progression was 3.8 months after the first line chemotherapy. CONCLUSIONS:BAP1 mutation in CCA may be associated with aggressive disease and poor response to standard therapies. Therefore, BAP1-targeted therapies need to be investigated.
Synthetic lethality in malignant pleural mesothelioma with PARP1 inhibition.
Srinivasan Gayathri,Sidhu Gurjit Singh,Williamson Elizabeth A,Jaiswal Aruna S,Najmunnisa Nasreen,Wilcoxen Keith,Jones Dennie,George Thomas J,Hromas Robert
Cancer chemotherapy and pharmacology
Malignant pleural mesotheliomas (MPM) are most often surgically unresectable, and they respond poorly to current chemotherapy and radiation therapy. Between 23 and 64% of malignant pleural mesothelioma have somatic inactivating mutations in the BAP1 gene. BAP1 is a homologous recombination (HR) DNA repair component found in the BRCA1/BARD1 complex. Similar to BRCA1/2 deficient cancers, mutation in the BAP1 gene leads to a deficient HR pathway and increases the reliance on other DNA repair pathways. We hypothesized that BAP1-mutant MPM would require PARP1 for survival, similar to the BRCA1/2 mutant breast and ovarian cancers. Therefore, we used the clinical PARP1 inhibitors niraparib and olaparib to assess whether they could induce synthetic lethality in MPM. Surprisingly, we found that all MPM cell lines examined, regardless of BAP1 status, were addicted to PARP1-mediated DNA repair for survival. We found that niraparib and olaparib exposure markedly decreased clonal survival in multiple MPM cell lines, with and without BAP1 mutations. This clonal cell death may be due to the extensive replication fork collapse and genomic instability that PARP1 inhibition induces in MPM cells. The requirement of MPM cells for PARP1 suggests that they may generally arise from defects in HR DNA repair. More importantly, these data demonstrate that the PARP1 inhibitors could be effective in the treatment of MPM, for which little effective therapy exists.
BRCA1-Associated Protein-1 Suppresses Osteosarcoma Cell Proliferation and Migration Through Regulation PI3K/Akt Pathway.
Gao Shuming,Sun Hongjiang,Cheng Cai,Wang Guangya
DNA and cell biology
BRCA1-associated protein-1 (BAP1) is an important nuclear-localized deubiquitinating enzyme. Dysregulation of BAP1 has been reported in many types of cancers. However, there are few articles on the role of BAP1 in osteosarcoma (OS) and the molecular mechanisms of BAP1 in OS remain largely unknown. In this study, we examined the expression of BAP1 in the tissue sample from OS patients and healthy control subjects, and then investigated the biological function and molecular mechanisms of BAP1 in OS. We found that BAP1 was significantly reduced in OS patients and OS cell lines. Then we found that BAP1 has a key role in OS cell proliferation, apoptosis, migration, and invasion. Furthermore, we found that BAP1 exerted its influence on the PI3K/Akt signaling pathway and there was physical association between BAP1 and miR-125. In conclusion, our data highlight the important roles of BAP1 in the survival of OS. It may be a potential therapy for OS.
Analysis of CCDC6 as a novel biomarker for the clinical use of PARP1 inhibitors in malignant pleural mesothelioma.
Morra Francesco,Merolla Francesco,D'Abbiero Debora,Ilardi Gennaro,Campione Severo,Monaco Roberto,Guggino Gianluca,Ambrosio Francesca,Staibano Stefania,Cerrato Aniello,Visconti Roberta,Celetti Angela
Lung cancer (Amsterdam, Netherlands)
OBJECTIVES:CCDC6 (coiled-coil domain containing 6) is a player of the HR response to DNA damage and has been predicted to interact with BAP1, another HR-DNA repair gene highly mutated in Malignant Pleural Mesothelioma (MPM), an aggressive cancer with poor prognosis. CCDC6 levels are modulated by the deubiquitinase USP7, and CCDC6 defects have been reported in several tumors determining PARP-inhibitors sensitivity. Our aim was to investigate the functional role of CCDC6 in MPM carcinogenesis and response to PARP-inhibitors. MATERIALS AND METHODS:The interaction between CCDC6 and BAP1 was confirmed in MPM cells, by co-immunoprecipitation. Upon USP7 inhibition, that induces CCDC6 degradation, the ability to repair the DSBs and the sensitivity to PARP inhibitors, was explored by HR reporter and by cells viability assays, respectively. A TMA including 34 MPM cores was immunostained for CCDC6, USP7 and BAP1 and the results correlated by statistical analysis. RESULTS:MPM cells depleted of CCDC6 showed defects in DSBs repair and sensitivity to PARP inhibitors. The silencing of CCDC6 when combined with the overexpression of BAP1-mutant (Δ221-238) enhanced the HR-DNA repair defects and the PARP inhibitors sensitivity. In the TMA of MPM primary samples, the staining of CCDC6 and of its de-ubiquitinase USP7 showed a significant correlation in the tested primary samples (p = 0.01). CCDC6 was barely detected in 30% of the tumors that also carried BAP1 defects. CONCLUSION:The combination of CCDC6 and BAP1 staining may indicate therapeutic options for DDR targeting, acting in synergism with cisplatinum.
Toward an improved definition of the tumor spectrum associated with BAP1 germline mutations.
Wiesner Thomas,Fried Isabella,Ulz Peter,Stacher Elvira,Popper Helmut,Murali Rajmohan,Kutzner Heinz,Lax Sigurd,Smolle-Jüttner Freya,Geigl Jochen B,Speicher Michael R
Journal of clinical oncology : official journal of the American Society of Clinical Oncology
The Arabidopsis BAP1 and BAP2 genes are general inhibitors of programmed cell death.
Yang Huijun,Yang Shuhua,Li Yongqing,Hua Jian
Here we identify the BAP1 and BAP2 genes of Arabidopsis (Arabidopsis thaliana) as general inhibitors of programmed cell death (PCD) across the kingdoms. These two homologous genes encode small proteins containing a calcium-dependent phospholipid-binding C2 domain. BAP1 and its functional partner BON1 have been shown to negatively regulate defense responses and a disease resistance gene SNC1. Genetic studies here reveal an overlapping function of the BAP1 and BAP2 genes in cell death control. The loss of BAP2 function induces accelerated hypersensitive responses but does not compromise plant growth or confer enhanced resistance to virulent bacterial or oomycete pathogens. The loss of both BAP1 and BAP2 confers seedling lethality mediated by PAD4 and EDS1, two regulators of cell death and defense responses. Overexpression of BAP1 or BAP2 with their partner BON1 inhibits PCD induced by pathogens, the proapoptotic gene BAX, and superoxide-generating paraquat in Arabidopsis or Nicotiana benthamiana. Moreover, expressing BAP1 or BAP2 in yeast (Saccharomyces cerevisiae) alleviates cell death induced by hydrogen peroxide. Thus, the BAP genes function as general negative regulators of PCD induced by biotic and abiotic stimuli including reactive oxygen species. The dual roles of BAP and BON genes in repressing defense responses mediated by disease resistance genes and in inhibiting general PCD has implications in understanding the evolution of plant innate immunity.
Deubiquitinating enzyme BAP1 is involved in the formation and maintenance of the diapause embryos of Artemia.
Yang Fan,Jia Sheng-Nan,Yu Yan-Qin,Ye Xiang,Liu Jun,Qian Ye-Qing,Yang Wei-Jun
Cell stress & chaperones
The modification of proteins by ubiquitination and deubiquitination plays an important role in various cellular processes. BRCA1-associated protein-1 (BAP1) is a deubiquitinating enzyme whose function in the control of the cell cycle requires both its deubiquitinating activity and nuclear localization. In the present study, a ubiquitin carboxyl-terminal hydrolase belonging to the BAP1 family was identified and characterized from Artemia parthenogenetica, a member of a family of brine shrimp that, under certain conditions, produce and release diapause embryos in which cell division and turnover of macromolecules are arrested. Western blot analysis and in vitro enzyme activity assay revealed ArBAP1 to be a cytoplasmic protein with typical ubiquitin hydrolase activity. Northern blot analysis revealed that ArBAP1 was abundant in the abdomen of Artemia producing diapause-destined embryos. Furthermore, by in situ hybridization, ArBAP1 was located exclusively in the embryos. In vivo knockdown of ArBAP1 by RNA interference resulted in the formation of embryos with split shells and abortive nauplii. The present findings suggest that ArBAP1, the first reported cytoplasmic BAP1, participates in the formation of diapause embryos and plays an important role in the control of cell cycle arrest in these encysted embryos.
PBRM1 and BAP1 as novel targets for renal cell carcinoma.
Cancer journal (Sudbury, Mass.)
Technological advances in genome sequencing have led to the identification of novel driver genes mutated in renal cancer. Hitherto, 1 gene was known to be frequently mutated in renal cell carcinoma of clear cell type (ccRCC), the von Hippel-Lindau (VHL) gene. VHL was identified by positional cloning as the gene responsible for a familial syndrome with renal cancer predisposition, von Hippel-Lindau. Subsequently, VHL was found to be inactivated in approximately 90% of sporadic ccRCC. The discovery of VHL, together with the elucidation of its function, transformed the treatment of ccRCC leading to the introduction of 5 new drugs into the clinic. However, no other familial ccRCC predisposing genes are frequently mutated in sporadic ccRCC. With the development of massively parallel sequencing, a plethora of somatically mutated genes has been identified. Most genes are mutated at low frequencies, but 3 genes are mutated in more than 10% of ccRCC, PBRM1 (mutated in ~50%), BAP1 (~15%), and SETD2 (~15%). Like VHL, all 3 genes are 2-hit tumor suppressor genes. Furthermore, these 3 genes are within a 50-Mb region on the short arm of chromosome 3p that encompasses VHL and is deleted in ~90% of ccRCC. We discovered that PBRM1 mutations tend to anticorrelate with BAP1 mutations in ccRCC and that PBRM1- and BAP1-mutated tumors exhibit different biology and are associated with markedly different outcomes. This established the foundation for the first molecular genetic classification of sporadic ccRCC. Herein, I review the evidence that implicated PBRM1 and BAP1 as renal cancer driver genes, provide an update on the function of the gene products, and speculate on how mutations in these genes may be exploited therapeutically.
The ubiquitin carboxyl hydrolase BAP1 forms a ternary complex with YY1 and HCF-1 and is a critical regulator of gene expression.
Yu Helen,Mashtalir Nazar,Daou Salima,Hammond-Martel Ian,Ross Julie,Sui Guangchao,Hart Gerald W,Rauscher Frank J,Drobetsky Elliot,Milot Eric,Shi Yang,Affar El Bachir
Molecular and cellular biology
The candidate tumor suppressor BAP1 is a deubiquitinating enzyme (DUB) involved in the regulation of cell proliferation, although the molecular mechanisms governing its function remain poorly defined. BAP1 was recently shown to interact with and deubiquitinate the transcriptional regulator host cell factor 1 (HCF-1). Here we show that BAP1 assembles multiprotein complexes containing numerous transcription factors and cofactors, including HCF-1 and the transcription factor Yin Yang 1 (YY1). Through its coiled-coil motif, BAP1 directly interacts with the zinc fingers of YY1. Moreover, HCF-1 interacts with the middle region of YY1 encompassing the glycine-lysine-rich domain and is essential for the formation of a ternary complex with YY1 and BAP1 in vivo. BAP1 activates transcription in an enzymatic-activity-dependent manner and regulates the expression of a variety of genes involved in numerous cellular processes. We further show that BAP1 and HCF-1 are recruited by YY1 to the promoter of the cox7c gene, which encodes a mitochondrial protein used here as a model of BAP1-activated gene expression. Our findings (i) establish a direct link between BAP1 and the transcriptional control of genes regulating cell growth and proliferation and (ii) shed light on a novel mechanism of transcription regulation involving ubiquitin signaling.
Loss of BAP1 Leads to More YAPing in Pancreatic Cancer.
Brekken Rolf A
Pancreatic cancer is increasing in incidence and is expected to be the second leading cause of cancer-related mortality by the year 2030. Understanding molecular pathways that contribute to pancreatic cancer initiation and progression provides the opportunity to uncover potential molecular vulnerabilities that can be exploited therapeutically. In this issue of , Lee and colleagues provide compelling evidence that BRCA1-associated protein (BAP1) functions as a tumor suppressor in pancreatic cancer by promoting the activity of the Hippo tumor suppressor pathway, highlighting YAP and TAZ, Hippo effectors, as attractive therapeutic targets in pancreatic ductal adenocarcinoma, especially in BAP1-deficient or low tumors..
Adverse outcomes in clear cell renal cell carcinoma with mutations of 3p21 epigenetic regulators BAP1 and SETD2: a report by MSKCC and the KIRC TCGA research network.
Hakimi A Ari,Ostrovnaya Irina,Reva Boris,Schultz Nikolaus,Chen Ying-Bei,Gonen Mithat,Liu Han,Takeda Shugaku,Voss Martin H,Tickoo Satish K,Reuter Victor E,Russo Paul,Cheng Emily H,Sander Chris,Motzer Robert J,Hsieh James J,
Clinical cancer research : an official journal of the American Association for Cancer Research
PURPOSE:To investigate the impact of newly identified chromosome 3p21 epigenetic tumor suppressors PBRM1, SETD2, and BAP1 on cancer-specific survival (CSS) of 609 patients with clear cell renal cell carcinoma (ccRCC) from 2 distinct cohorts. EXPERIMENTAL DESIGN:Select sequencing on 3p tumor suppressors of 188 patients who underwent resection of primary ccRCC at the Memorial Sloan-Kettering Cancer Center (MSKCC) was conducted to interrogate the genotype-phenotype associations. These findings were compared with analyses of the genomic and clinical dataset from our nonoverlapping The Cancer Genome Atlas (TCGA) cohort of 421 patients with primary ccRCC. RESULTS:3p21 tumor suppressors are frequently mutated in both the MSKCC (PBRM1, 30.3%; SETD2, 7.4%; BAP1, 6.4%) and the TCGA (PBRM1, 33.5%; SETD2, 11.6%; BAP1, 9.7%) cohorts. BAP1 mutations are associated with worse CSS in both cohorts [MSKCC, P = 0.002; HR 7.71; 95% confidence interval (CI)2.08-28.6; TCGA, P = 0.002; HR 2.21; 95% CI 1.35-3.63]. SETD2 are associated with worse CSS in the TCGA cohort (P = 0.036; HR 1.68; 95% CI 1.04-2.73). On the contrary, PBRM1 mutations, the second most common gene mutations of ccRCC, have no impact on CSS. CONCLUSION:The chromosome 3p21 locus harbors 3 frequently mutated ccRCC tumor suppressor genes. BAP1 and SETD2 mutations (6%-12%) are associated with worse CSS, suggesting their roles in disease progression. PBRM1 mutations (30%-34%) do not impact CSS, implicating its principal role in the tumor initiation. Future efforts should focus on therapeutic interventions and further clinical, pathologic, and molecular interrogation of this novel class of tumor suppressors.
Aberrant promoter hypermethylation of PBRM1, BAP1, SETD2, KDM6A and other chromatin-modifying genes is absent or rare in clear cell RCC.
Ibragimova Ilsiya,Maradeo Marie E,Dulaimi Essel,Cairns Paul
Recent sequencing studies of clear cell (conventional) renal cell carcinoma (ccRCC) have identified inactivating point mutations in the chromatin-modifying genes PBRM1, KDM6A/UTX, KDM5C/JARID1C, SETD2, MLL2 and BAP1. To investigate whether aberrant hypermethylation is a mechanism of inactivation of these tumor suppressor genes in ccRCC, we sequenced the promoter region within a bona fide CpG island of PBRM1, KDM6A, SETD2 and BAP1 in bisulfite-modified DNA of a representative series of 50 primary ccRCC, 4 normal renal parenchyma specimens and 5 RCC cell lines. We also interrogated the promoter methylation status of KDM5C and ARID1A in the Cancer Genome Atlas (TCGA) ccRCC Infinium data set. PBRM1, KDM6A, SETD2 and BAP1 were unmethylated in all tumor and normal specimens. KDM5C and ARID1A were unmethylated in the TCGA 219 ccRCC and 119 adjacent normal specimens. Aberrant promoter hypermethylation of PBRM1, BAP1 and the other chromatin-modifying genes examined here is therefore absent or rare in ccRCC.
BAP1/ASXL1 recruitment and activation for H2A deubiquitination.
Sahtoe Danny D,van Dijk Willem J,Ekkebus Reggy,Ovaa Huib,Sixma Titia K
The deubiquitinating enzyme BAP1 is an important tumor suppressor that has drawn attention in the clinic since its loss leads to a variety of cancers. BAP1 is activated by ASXL1 to deubiquitinate mono-ubiquitinated H2A at K119 in Polycomb gene repression, but the mechanism of this reaction remains poorly defined. Here we show that the BAP1 C-terminal extension is important for H2A deubiquitination by auto-recruiting BAP1 to nucleosomes in a process that does not require the nucleosome acidic patch. This initial encounter-like complex is unproductive and needs to be activated by the DEUBAD domains of ASXL1, ASXL2 or ASXL3 to increase BAP1's affinity for ubiquitin on H2A, to drive the deubiquitination reaction. The reaction is specific for Polycomb modifications of H2A as the complex cannot deubiquitinate the DNA damage-dependent ubiquitination at H2A K13/15. Our results contribute to the molecular understanding of this important tumor suppressor.
Loss of the tumor suppressor BAP1 causes myeloid transformation.
Dey Anwesha,Seshasayee Dhaya,Noubade Rajkumar,French Dorothy M,Liu Jinfeng,Chaurushiya Mira S,Kirkpatrick Donald S,Pham Victoria C,Lill Jennie R,Bakalarski Corey E,Wu Jiansheng,Phu Lilian,Katavolos Paula,LaFave Lindsay M,Abdel-Wahab Omar,Modrusan Zora,Seshagiri Somasekar,Dong Ken,Lin Zhonghua,Balazs Mercedesz,Suriben Rowena,Newton Kim,Hymowitz Sarah,Garcia-Manero Guillermo,Martin Flavius,Levine Ross L,Dixit Vishva M
Science (New York, N.Y.)
De-ubiquitinating enzyme BAP1 is mutated in a hereditary cancer syndrome with increased risk of mesothelioma and uveal melanoma. Somatic BAP1 mutations occur in various malignancies. We show that mouse Bap1 gene deletion is lethal during embryogenesis, but systemic or hematopoietic-restricted deletion in adults recapitulates features of human myelodysplastic syndrome (MDS). Knockin mice expressing BAP1 with a 3xFlag tag revealed that BAP1 interacts with host cell factor-1 (HCF-1), O-linked N-acetylglucosamine transferase (OGT), and the polycomb group proteins ASXL1 and ASXL2 in vivo. OGT and HCF-1 levels were decreased by Bap1 deletion, indicating a critical role for BAP1 in stabilizing these epigenetic regulators. Human ASXL1 is mutated frequently in chronic myelomonocytic leukemia (CMML) so an ASXL/BAP1 complex may suppress CMML. A BAP1 catalytic mutation found in a MDS patient implies that BAP1 loss of function has similar consequences in mice and humans.
Loss of BAP1 Is Associated with Upregulation of the NFkB Pathway and Increased HLA Class I Expression in Uveal Melanoma.
Souri Zahra,Wierenga Annemijn P A,van Weeghel Christiaan,van der Velden Pieter A,Kroes Wilma G M,Luyten Gregorius P M,van der Burg Sjoerd H,Jochemsen Aart G,Jager Martine J
One of the characteristics of prognostically infaust uveal melanoma (UM) is an inflammatory phenotype, which is characterized by high numbers of infiltrating T cells and macrophages, and a high HLA Class I expression. We wondered how this inflammation is regulated, and considered that one of the most important regulators of inflammation, the NFkB pathway, might play a role. We analyzed 64 UM samples for expression of HLA Class I, its regulators, and of members of the NFkB transcription family, using an Illumina HT12V4 array. HLA Class I expression and infiltrating immune cells were also determined by immunohistochemical staining. Information was obtained regarding chromosome status by Affymetrix Nsp array. Our analysis shows that expression of NFkB1, NFkB2 and RELB positively correlates with the level of HLA Class I expression and the number of infiltrating T cells and macrophages, while SPP1 and PPARγ are negatively correlated. Increased levels of NFkB1 and NFkB2 and decreased levels of SPP1 and PPARγ are seen in Monosomy 3/BAP1-negative tumors. This is also the case in non-inflammatory UM, indicating that our observation not only involves infiltrating leukocytes but the tumor cells themselves. We report that the NFkB pathway is associated with inflammation and HLA Class I expression in UM, and is upregulated when BAP1 expression is lost.
Retracted: Histone H2B ubquitination regulates retinoic acid signaling through the cooperation of ASXL1 and BAP1.
Lee Sang-Wang,Youn Hyesook,Kim Eun-Joo,Um Soo-Jong
Despite the importance of retinoic acid (RA) signaling and histone monoubiquitination in determining cell fate, the underlying mechanism linking the two processes is poorly explored. We describe that additional sex comb-like 1 (ASXL1) represses RA receptor activity by cooperating with BRCA1-associated protein 1 (BAP1), which contains the ubiquitin C-terminal hydrolase (UCH) domain. Both the UCH- and ASXL1-binding domains of BAP1 were required for cooperation. In contrast to Drosophila BAP1, mammalian BAP1 cleaved ubiquitin from histone H2B. As supported by BAP1 mutants, ASXL1 was critical for BAP1 recruitment to chromatin and its activation therein. ASXL1 requirement was supported using Asxl1 null mice embryonic fibroblasts. Both ASXL1 and BAP1 were downregulated during RA-induced P19 cell differentiation with concomitant increase of ubiquitinated H2B, leading to activation of Hox genes. Our data demonstrate the critical role of ASXL1 cooperation with BAP1 in cell differentiation through the regulation of RA signaling associated with H2B ubiquitination.
Deubiquitination of γ-tubulin by BAP1 prevents chromosome instability in breast cancer cells.
Zarrizi Reihaneh,Menard Julien Albert,Belting Mattias,Massoumi Ramin
Microtubule nucleation requires the γ-tubulin ring complex, and during the M-phase (mitosis) this complex accumulates at the centrosome to support mitotic spindle formation. The posttranslational modification of γ-tubulin through ubiquitination is vital for regulating microtubule nucleation and centrosome duplication. Blocking the BRCA1/BARD1-dependent ubiquitination of γ-tubulin causes centrosome amplification. In the current study, we identified BRCA1-associated protein-1 (BAP1) as a deubiquitination enzyme for γ-tubulin. BAP1 was downregulated in metastatic adenocarcinoma breast cell lines compared with noncancerous human breast epithelial cells. Furthermore, low expression of BAP1 was associated with reduced overall survival of patients with breast cancer. Reduced expression of BAP1 in breast cancer cell lines was associated with mitotic abnormalities. Importantly, rescue experiments including expression of full length but not the catalytic mutant of BAP1 reduced ubiquitination of γ-tubulin and prevented mitotic defects. Our study uncovers a new mechanism for BAP1 involved in deubiquitination of γ-tubulin, which is required to prevent abnormal mitotic spindle formation and genome instability.
Tumor suppressor and deubiquitinase BAP1 promotes DNA double-strand break repair.
Yu Helen,Pak Helen,Hammond-Martel Ian,Ghram Mehdi,Rodrigue Amélie,Daou Salima,Barbour Haithem,Corbeil Luc,Hébert Josée,Drobetsky Elliot,Masson Jean Yves,Di Noia Javier M,Affar El Bachir
Proceedings of the National Academy of Sciences of the United States of America
The cellular response to highly genotoxic DNA double-strand breaks (DSBs) involves the exquisite coordination of multiple signaling and repair factors. Here, we conducted a functional RNAi screen and identified BAP1 as a deubiquitinase required for efficient assembly of the homologous recombination (HR) factors BRCA1 and RAD51 at ionizing radiation (IR) -induced foci. BAP1 is a chromatin-associated protein frequently inactivated in cancers of various tissues. To further investigate the role of BAP1 in DSB repair, we used a gene targeting approach to knockout (KO) this deubiquitinase in chicken DT40 cells. We show that BAP1-deficient cells are (i) sensitive to IR and other agents that induce DSBs, (ii) defective in HR-mediated immunoglobulin gene conversion, and (iii) exhibit an increased frequency of chromosomal breaks after IR treatment. We also show that BAP1 is recruited to chromatin in the proximity of a single site-specific I-SceI-induced DSB. Finally, we identified six IR-induced phosphorylation sites in BAP1 and showed that mutation of these residues inhibits BAP1 recruitment to DSB sites. We also found that both BAP1 catalytic activity and its phosphorylation are critical for promoting DNA repair and cellular recovery from DNA damage. Our data reveal an important role for BAP1 in DSB repair by HR, thereby providing a possible molecular basis for its tumor suppressor function.
BAP1 regulation of the key adaptor protein NCoR1 is critical for γ-globin gene repression.
Yu Lei,Jearawiriyapaisarn Natee,Lee Mary P,Hosoya Tomonori,Wu Qingqing,Myers Greggory,Lim Kim-Chew,Kurita Ryo,Nakamura Yukio,Vojtek Anne B,Rual Jean-François,Engel James Douglas
Genes & development
Human globin gene production transcriptionally "switches" from fetal to adult synthesis shortly after birth and is controlled by macromolecular complexes that enhance or suppress transcription by elements scattered throughout the locus. The DRED (direct repeat erythroid-definitive) repressor is recruited to the ε-globin and γ-globin promoters by the orphan nuclear receptors TR2 (NR2C1) and TR4 (NR2C2) to engender their silencing in adult erythroid cells. Here we found that nuclear receptor corepressor-1 (NCoR1) is a critical component of DRED that acts as a scaffold to unite the DNA-binding and epigenetic enzyme components (e.g., DNA methyltransferase 1 [DNMT1] and lysine-specific demethylase 1 [LSD1]) that elicit DRED function. We also describe a potent new regulator of γ-globin repression: The deubiquitinase BRCA1-associated protein-1 (BAP1) is a component of the repressor complex whose activity maintains NCoR1 at sites in the β-globin locus, and BAP1 inhibition in erythroid cells massively induces γ-globin synthesis. These data provide new mechanistic insights through the discovery of novel epigenetic enzymes that mediate γ-globin gene repression.
Cancer-associated ASXL1 mutations may act as gain-of-function mutations of the ASXL1-BAP1 complex.
Balasubramani Anand,Larjo Antti,Bassein Jed A,Chang Xing,Hastie Ryan B,Togher Susan M,Lähdesmäki Harri,Rao Anjana
ASXL1 is the obligate regulatory subunit of a deubiquitinase complex whose catalytic subunit is BAP1. Heterozygous mutations of ASXL1 that result in premature truncations are frequent in myeloid leukemias and Bohring-Opitz syndrome. Here we demonstrate that ASXL1 truncations confer enhanced activity on the ASXL1-BAP1 complex. Stable expression of truncated, hyperactive ASXL1-BAP1 complexes in a haematopoietic precursor cell line results in global erasure of H2AK119Ub, striking depletion of H3K27me3, selective upregulation of a subset of genes whose promoters are marked by both H2AK119Ub and H3K4me3, and spontaneous differentiation to the mast cell lineage. These outcomes require the catalytic activity of BAP1, indicating that they are downstream consequences of H2AK119Ub erasure. In bone marrow precursors, expression of truncated ASXL1-BAP1 complex cooperates with TET2 loss-of-function to increase differentiation to the myeloid lineage in vivo. Our data raise the possibility that ASXL1 truncation mutations confer gain-of-function on the ASXL-BAP1 complex.
BAP1 is phosphorylated at serine 592 in S-phase following DNA damage.
Eletr Ziad M,Yin Luming,Wilkinson Keith D
The human BAP1 deubiquitinating enzyme is a chromatin-bound transcriptional regulator and tumor suppressor. BAP1 functions in suppressing cell proliferation, yet its role in the DNA damage response pathway is less understood. In this study we characterized DNA damage-induced phosphorylation of BAP1 at serine 592 (pS592) and the cellular outcomes of this modification. In contrast to the majority of BAP1, pS592-BAP1 is predominantly dissociated from chromatin. Our findings support a model whereby stress induced phosphorylation functions to displace BAP1 from specific promoters. We hypothesize that this regulates the transcription of a subset of genes involved in the response to DNA damage.
BRCA1-associated protein 1 (BAP1) deubiquitinase antagonizes the ubiquitin-mediated activation of FoxK2 target genes.
Okino Yuki,Machida Yuka,Frankland-Searby Sarah,Machida Yuichi J
The Journal of biological chemistry
BRCA1-associated protein 1 (BAP1), which is frequently mutated in cancer, functions as a deubiquitinase (DUB) for histone H2A. Although BAP1 interacts with a transcriptional regulator, HCF-1, and transcription factors FoxK1 and FoxK2, how BAP1 controls gene expression remains unclear. This study investigates the importance of BAP1 DUB activity and the interactions with FoxK2 and HCF-1 in the regulation of FoxK2 target genes. We show that FoxK2 recruits BAP1 to the target genes through the forkhead-associated domain, which interacts with Thr(P)-493 on BAP1. BAP1, in turn, recruits HCF-1, thereby forming a ternary complex in which BAP1 bridges FoxK2 and HCF-1. BAP1 represses FoxK2 target genes, and this effect requires BAP1 DUB activity but not interaction with HCF-1. Importantly, BAP1 depletion causes up-regulation of FoxK2 target genes only in the presence of the Ring1B-Bmi1 complex, an E3 ubiquitin ligase for histone H2A, indicating an antagonizing role of BAP1 against Ring1B-Bmi1. Our findings suggest that BAP1 deficiency causes increased expression of target genes in a Ring1B-Bmi1-dependent manner.
Loss of the deubiquitylase BAP1 alters class I histone deacetylase expression and sensitivity of mesothelioma cells to HDAC inhibitors.
Sacco Joseph J,Kenyani Jenna,Butt Zohra,Carter Rachel,Chew Hui Yi,Cheeseman Liam P,Darling Sarah,Denny Michael,Urbé Sylvie,Clague Michael J,Coulson Judy M
Histone deacetylases are important targets for cancer therapeutics, but their regulation is poorly understood. Our data show coordinated transcription of HDAC1 and HDAC2 in lung cancer cell lines, but suggest HDAC2 protein expression is cell-context specific. Through an unbiased siRNA screen we found that BRCA1-associated protein 1 (BAP1) regulates their expression, with HDAC2 reduced and HDAC1 increased in BAP1 depleted cells. BAP1 loss-of-function is increasingly reported in cancers including thoracic malignancies, with frequent mutation in malignant pleural mesothelioma. Endogenous HDAC2 directly correlates with BAP1 across a panel of lung cancer cell lines, and is downregulated in mesothelioma cell lines with genetic BAP1 inactivation. We find that BAP1 regulates HDAC2 by increasing transcript abundance, rather than opposing its ubiquitylation. Importantly, although total cellular HDAC activity is unaffected by transient depletion of HDAC2 or of BAP1 due to HDAC1 compensation, this isoenzyme imbalance sensitizes MSTO-211H cells to HDAC inhibitors. However, other established mesothelioma cell lines with low endogenous HDAC2 have adapted to become more resistant to HDAC inhibition. Our work establishes a mechanism by which BAP1 loss alters sensitivity of cancer cells to HDAC inhibitors. Assessment of BAP1 and HDAC expression may ultimately help identify patients likely to respond to HDAC inhibitors.
Loss of functional BAP1 augments sensitivity to TRAIL in cancer cells.
Kolluri Krishna Kalyan,Alifrangis Constantine,Kumar Neelam,Ishii Yuki,Price Stacey,Michaut Magali,Williams Steven,Barthorpe Syd,Lightfoot Howard,Busacca Sara,Sharkey Annabel,Yuan Zhenqiang,Sage Elizabeth K,Vallath Sabarinath,Le Quesne John,Tice David A,Alrifai Doraid,von Karstedt Sylvia,Montinaro Antonella,Guppy Naomi,Waller David A,Nakas Apostolos,Good Robert,Holmes Alan,Walczak Henning,Fennell Dean A,Garnett Mathew,Iorio Francesco,Wessels Lodewyk,McDermott Ultan,Janes Samuel M
Malignant mesothelioma (MM) is poorly responsive to systemic cytotoxic chemotherapy and invariably fatal. Here we describe a screen of 94 drugs in 15 exome-sequenced MM lines and the discovery of a subset defined by loss of function of the nuclear deubiquitinase BRCA associated protein-1 (BAP1) that demonstrate heightened sensitivity to TRAIL (tumour necrosis factor-related apoptosis-inducing ligand). This association is observed across human early passage MM cultures, mouse xenografts and human tumour explants. We demonstrate that BAP1 deubiquitinase activity and its association with ASXL1 to form the Polycomb repressive deubiquitinase complex (PR-DUB) impacts TRAIL sensitivity implicating transcriptional modulation as an underlying mechanism. Death receptor agonists are well-tolerated anti-cancer agents demonstrating limited therapeutic benefit in trials without a targeting biomarker. We identify loss-of-function mutations, which are frequent in MM, as a potential genomic stratification tool for TRAIL sensitivity with immediate and actionable therapeutic implications.
Bap1 is essential for kidney function and cooperates with Vhl in renal tumorigenesis.
Wang Shan-Shan,Gu Yi-Feng,Wolff Nicholas,Stefanius Karoliina,Christie Alana,Dey Anwesha,Hammer Robert E,Xie Xian-Jin,Rakheja Dinesh,Pedrosa Ivan,Carroll Thomas,McKay Renée M,Kapur Payal,Brugarolas James
Proceedings of the National Academy of Sciences of the United States of America
Why different species are predisposed to different tumor spectra is not well understood. In particular, whether the physical location of tumor suppressor genes relative to one another influences tumor predisposition is unknown. Renal cancer presents a unique opportunity to explore this question. Renal cell carcinoma (RCC) of clear-cell type (ccRCC), the most common type, begins with an intragenic mutation in the von Hippel-Lindau (VHL) gene and loss of 3p (where VHL is located). Chromosome 3p harbors several additional tumor suppressor genes, including BRCA1-associated protein-1 (BAP1). In the mouse, Vhl is on a different chromosome than Bap1. Thus, whereas loss of 3p in humans simultaneously deletes one copy of BAP1, loss of heterozygosity in the corresponding Vhl region in the mouse would not affect Bap1. To test the role of BAP1 in ccRCC development, we generated mice deficient for either Vhl or Vhl together with one allele of Bap1 in nephron progenitor cells. Six2-Cre;Vhl(F/F);Bap1(F/+) mice developed ccRCC, but Six2-Cre;Vhl(F/F) mice did not. Kidneys from Six2-Cre;Vhl(F/F);Bap1(F/+) mice resembled kidneys from humans with VHL syndrome, containing multiple lesions spanning from benign cysts to cystic and solid RCC. Although the tumors were small, they showed nuclear atypia and exhibited features of human ccRCC. These results provide an explanation for why VHL heterozygous humans, but not mice, develop ccRCC. They also explain why a mouse model of ccRCC has been lacking. More broadly, our data suggest that differences in tumor predisposition across species may be explained, at least in part, by differences in the location of two-hit tumor suppressor genes across the genome.
Loss of BAP1 function leads to EZH2-dependent transformation.
LaFave Lindsay M,Béguelin Wendy,Koche Richard,Teater Matt,Spitzer Barbara,Chramiec Alan,Papalexi Efthymia,Keller Matthew D,Hricik Todd,Konstantinoff Katerina,Micol Jean-Baptiste,Durham Benjamin,Knutson Sarah K,Campbell John E,Blum Gil,Shi Xinxu,Doud Emma H,Krivtsov Andrei V,Chung Young Rock,Khodos Inna,de Stanchina Elisa,Ouerfelli Ouathek,Adusumilli Prasad S,Thomas Paul M,Kelleher Neil L,Luo Minkui,Keilhack Heike,Abdel-Wahab Omar,Melnick Ari,Armstrong Scott A,Levine Ross L
The tumor suppressors BAP1 and ASXL1 interact to form a polycomb deubiquitinase complex that removes monoubiquitin from histone H2A lysine 119 (H2AK119Ub). However, BAP1 and ASXL1 are mutated in distinct cancer types, consistent with independent roles in regulating epigenetic state and malignant transformation. Here we demonstrate that Bap1 loss in mice results in increased trimethylated histone H3 lysine 27 (H3K27me3), elevated enhancer of zeste 2 polycomb repressive complex 2 subunit (Ezh2) expression, and enhanced repression of polycomb repressive complex 2 (PRC2) targets. These findings contrast with the reduction in H3K27me3 levels seen with Asxl1 loss. Conditional deletion of Bap1 and Ezh2 in vivo abrogates the myeloid progenitor expansion induced by Bap1 loss alone. Loss of BAP1 results in a marked decrease in H4K20 monomethylation (H4K20me1). Consistent with a role for H4K20me1 in the transcriptional regulation of EZH2, expression of SETD8-the H4K20me1 methyltransferase-reduces EZH2 expression and abrogates the proliferation of BAP1-mutant cells. Furthermore, mesothelioma cells that lack BAP1 are sensitive to EZH2 pharmacologic inhibition, suggesting a novel therapeutic approach for BAP1-mutant malignancies.
BAP1 regulates cell cycle progression through E2F1 target genes and mediates transcriptional silencing via H2A monoubiquitination in uveal melanoma cells.
Pan Hui,Jia Renbing,Zhang Leilei,Xu Shiqiong,Wu Qing,Song Xin,Zhang He,Ge Shengfang,Xu Xiaoliang Leon,Fan Xianqun
The international journal of biochemistry & cell biology
Uveal melanoma (UM) is the most common form of primary intraocular malignancy in adult and has the tendency to metastasize. BAP1 mutations are frequently found in UM and are associated with a poor prognosis. The role of BAP1 in cell cycle regulation is currently a research highlight, but its underlying mechanism is not well understood. Here, we report that BAP1 knockdown can lead to G1 arrest and is accompanied by a decrease in the expression of S phase genes in OCM1 cells. Furthermore, in chromatin immunoprecipitation experiments, BAP1 could bind to E2F1 responsive promoters and the localization of BAP1 to E2F1-responsive promoters is host cell factor-1 dependent. Moreover, BAP1 knockdown leads to increased H2AK119ub1 levels on E2F responsive promoters. Together, these results provide new insight into the mechanisms of BAP1 in cell cycle regulation.
The BAP1/ASXL2 Histone H2A Deubiquitinase Complex Regulates Cell Proliferation and Is Disrupted in Cancer.
Daou Salima,Hammond-Martel Ian,Mashtalir Nazar,Barbour Haithem,Gagnon Jessica,Iannantuono Nicholas V G,Nkwe Nadine Sen,Motorina Alena,Pak Helen,Yu Helen,Wurtele Hugo,Milot Eric,Mallette Frédérick A,Carbone Michele,Affar El Bachir
The Journal of biological chemistry
The deubiquitinase (DUB) and tumor suppressor BAP1 catalyzes ubiquitin removal from histone H2A Lys-119 and coordinates cell proliferation, but how BAP1 partners modulate its function remains poorly understood. Here, we report that BAP1 forms two mutually exclusive complexes with the transcriptional regulators ASXL1 and ASXL2, which are necessary for maintaining proper protein levels of this DUB. Conversely, BAP1 is essential for maintaining ASXL2, but not ASXL1, protein stability. Notably, cancer-associated loss of BAP1 expression results in ASXL2 destabilization and hence loss of its function. ASXL1 and ASXL2 use their ASXM domains to interact with the C-terminal domain (CTD) of BAP1, and these interactions are required for ubiquitin binding and H2A deubiquitination. The deubiquitination-promoting effect of ASXM requires intramolecular interactions between catalytic and non-catalytic domains of BAP1, which generate a composite ubiquitin-binding interface (CUBI). Notably, the CUBI engages multiple interactions with ubiquitin involving (i) the ubiquitin carboxyl hydrolase catalytic domain of BAP1, which interacts with the hydrophobic patch of ubiquitin, and (ii) the CTD domain, which interacts with a charged patch of ubiquitin. Significantly, we identified cancer-associated mutations of BAP1 that disrupt the CUBI and notably an in-frame deletion in the CTD that inhibits its interaction with ASXL1/2 and DUB activity and deregulates cell proliferation. Moreover, we demonstrated that BAP1 interaction with ASXL2 regulates cell senescence and that ASXL2 cancer-associated mutations disrupt BAP1 DUB activity. Thus, inactivation of the BAP1/ASXL2 axis might contribute to cancer development.
Stabilization of MCRS1 by BAP1 prevents chromosome instability in renal cell carcinoma.
Peng Jingtao,Ma Jian,Li Weiguo,Mo Ren,Zhang Pingzhao,Gao Kun,Jin Xiaofeng,Xiao Jiantao,Wang Chenji,Fan Jie
Characterization of the exome and genome of carcinoma (ccRCC) by next-generation sequencing identified numerous genetic alternations. BRCA1-associated protein-1 (BAP1) was identified as one of the most frequently mutated genes in ccRCC, suggesting that BAP1 is a potential key driver for ccRCC cancer initiation and progression. However, how BAP1 mutations contribute to ccRCC remains to be elucidated. BAP1 is a nuclear de-ubiquitinating enzyme and cleaves the ubiquitin chain from the substrates. Here, we identified MCRS1 as a bona fide substrate for BAP1. MCRS1 is a component of the centrosome proteins, and plays an essential role in spindle assembly. BAP1 binds to MCRS1 and stabilizes MCRS1 by de-ubiquitination. BAP1 contributes to chromosome stability partially via MCRS1. A positive correlation was identified between BAP1 and MCRS1 expression in ccRCC tissues. Both BAP1 loss and MCRS1 down-regulation in ccRCC were associated with adverse clinicopathological features. This study revealed a novel mechanism for BAP1 involved in MCRS1 stability regulation, and provided insight in understanding the relationship between BAP1 mutations and chromosome instability in ccRCC.
Genomic profiling of malignant peritoneal mesothelioma reveals recurrent alterations in epigenetic regulatory genes BAP1, SETD2, and DDX3X.
Joseph Nancy M,Chen Yunn-Yi,Nasr Anthony,Yeh Iwei,Talevich Eric,Onodera Courtney,Bastian Boris C,Rabban Joseph T,Garg Karuna,Zaloudek Charles,Solomon David A
Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc
Malignant mesothelioma is a rare cancer that arises from the mesothelial cells that line the pleural cavity and less commonly from the peritoneal lining of the abdomen and pelvis. Most pleural mesotheliomas arise in patients with a history of asbestos exposure, whereas the association of peritoneal mesotheliomas with exposure to asbestos and other potential carcinogens is less clear, suggesting that the genetic alterations that drive malignant peritoneal mesothelioma may be unique from those in pleural mesothelioma. Treatment options for all malignant mesotheliomas are currently limited, with no known targeted therapies available. To better understand the molecular pathogenesis of malignant peritoneal mesothelioma, we sequenced 510 cancer-related genes in 13 patients with malignant mesothelioma arising in the peritoneal cavity. The most frequent genetic alteration was biallelic inactivation of the BAP1 gene, which occurred in 9/13 cases, with an additional two cases demonstrating monoallelic loss of BAP1. All 11 of these cases demonstrated loss of BAP1 nuclear staining by immunohistochemistry, whereas two tumors without BAP1 alteration and all 42 cases of histologic mimics in peritoneum (8 multilocular peritoneal inclusion cyst, 6 well-differentiated papillary mesothelioma of the peritoneum, 16 adenomatoid tumor, and 12 low-grade serous carcinoma of the ovary) demonstrated intact BAP1 nuclear staining. Additional recurrently mutated genes in this cohort of malignant peritoneal mesotheliomas included NF2 (3/13), SETD2 (2/13), and DDX3X (2/13). While these genes are known to be recurrently mutated in pleural mesotheliomas, the frequencies are distinct in peritoneal mesotheliomas, with nearly 85% of peritoneal tumors harboring BAP1 alterations versus only 20-30% of pleural tumors. Together, these findings demonstrate the importance of epigenetic modifiers including BAP1, SETD2, and DDX3X in mesothelial tumorigenesis and suggest opportunities for targeted therapies.
BAP1: role in carcinogenesis and clinical implications.
Kobrinski Daniel A,Yang Haining,Kittaneh Muaiad
Translational lung cancer research
BRCA-1 associated protein 1 () is a tumor suppressor gene that has been implicated in the pathogenesis of several malignancies and is gaining more recognition as a crucial gene that could be amenable to therapeutic manipulation. There is a growing interest in prevention and establishing cancer screening guidelines in patients with germline mutations to aid with early detection and treatment of associated malignancies. We aim to give a concise review of and its role in carcinogenesis, the cancer predisposition syndrome and discuss clinical implications including suggested screening guidelines, and potential targeted therapeutic options.
MiR-125a-5p functions as a tumour suppressor in breast cancer by downregulating BAP1.
Yan Liang,Yu Meng-Chao,Gao Guang-Lei,Liang Hong-Wei,Zhou Xin-Yan,Zhu Zhou-Ting,Zhang Chen-Yu,Wang Ya-Bing,Chen Xi
Journal of cellular biochemistry
MicroRNAs (miRNAs) play an important role in the regulation of human cancers, including breast cancer (BC). In the current study, we examined the expression pattern of the miRNA miR-125a-5p in human BC tissues, tumorigenesis of BC progression. We found that miR-125a-5p was significantly downregulated in human BC tissues. Overexpression of miR-125a-5p in a xenograft mouse model indicated that miR-125a-5p may function as a tumour suppressor during carcinogenesis. To explore the molecular mechanism by which miR-125a-5p contributes to BC progression, we predicted the target genes of miR-125a-5p and identified BC susceptibility gene 1-associated protein 1 (BAP1) as a direct target. Finally, we demonstrated that BAP1 had opposing effects to those of miR-125a-5p on BC cells, suggesting that miR-125a-5p may inhibit cell proliferation and promote cell apoptosis by negatively regulating BAP1. Taken together, our findings provide the first clues regarding the role of miR-125a-5p as a tumour suppressor in BC via the inhibition of BAP1 translation.
BAP1 induces cell death via interaction with 14-3-3 in neuroblastoma.
Sime Wondossen,Niu Qiankun,Abassi Yasmin,Masoumi Katarzyna Chmielarska,Zarrizi Reihaneh,Køhler Julie Bonne,Kjellström Sven,Lasorsa Vito Alessandro,Capasso Mario,Fu Haian,Massoumi Ramin
Cell death & disease
BRCA1-associated protein 1 (BAP1) is a nuclear deubiquitinating enzyme that is associated with multiprotein complexes that regulate key cellular pathways, including cell cycle, cellular differentiation, cell death, and the DNA damage response. In this study, we found that the reduced expression of BAP1 pro6motes the survival of neuroblastoma cells, and restoring the levels of BAP1 in these cells facilitated a delay in S and G2/M phase of the cell cycle, as well as cell apoptosis. The mechanism that BAP1 induces cell death is mediated via an interaction with 14-3-3 protein. The association between BAP1 and 14-3-3 protein releases the apoptotic inducer protein Bax from 14-3-3 and promotes cell death through the intrinsic apoptosis pathway. Xenograft studies confirmed that the expression of BAP1 reduces tumor growth and progression in vivo by lowering the levels of pro-survival factors such as Bcl-2, which in turn diminish the survival potential of the tumor cells. Patient data analyses confirmed the finding that the high-BAP1 mRNA expression correlates with a better clinical outcome. In summary, our study uncovers a new mechanism for BAP1 in the regulation of cell apoptosis in neuroblastoma cells.
Modulating BAP1 expression affects ROS homeostasis, cell motility and mitochondrial function.
Hebert Lucie,Bellanger Dorine,Guillas Chloé,Campagne Antoine,Dingli Florent,Loew Damarys,Fievet Alice,Jacquemin Virginie,Popova Tatiana,Jean Didier,Mechta-Grigoriou Fatima,Margueron Raphaël,Stern Marc-Henri
The tumor suppressor BAP1 associates with ASXL1/2 to form the core Polycomb complex PR-DUB, which catalyzes the removal of mono-ubiquitin from several substrates including histone H2A. This complex also mediates the poly-deubiquitination of HCFC1, OGT and PCG1-α, preventing them from proteasomal degradation. Surprisingly, considering its role in a Polycomb complex, no transcriptional signature was consistently found among -inactivated tumor types. It was hypothesized that BAP1 tumor suppressor activity could reside, at least in part, in stabilizing proteins through its poly-deubiquitinase activity. Quantitative mass spectrometry and gene expression arrays were used to investigate the consequences of expression modulation in the NCI-H226 mesothelioma cell line. Analysis of differentially expressed proteins revealed enrichment in cytoskeleton organization, mitochondrial activity and ROS management, while gene expression analysis revealed enrichment in the epithelial-to-mesenchymal transition pathway. Functional assessments in BAP1 inactivated, BAP1 wild-type and BAP1 catalytically dead-expressing NCI-H226 and QR mesothelioma cell lines confirmed alteration of these pathways and demonstrated that BAP1 deubiquitinase activity was mandatory to maintain these phenotypes. Interestingly, monitoring intracellular ROS levels partly restored the morphology and the mitochondrial activity. Finally, the study suggests new tumorigenic and cellular functions of BAP1 and shows for the first time the interest of studying the proteome as readout of BAP1 inactivation.
The Tumor Suppressor BAP1 Regulates the Hippo Pathway in Pancreatic Ductal Adenocarcinoma.
Lee Ho-June,Pham Trang,Chang Matthew T,Barnes Dwight,Cai Allen G,Noubade Rajkumar,Totpal Klara,Chen Xu,Tran Christopher,Hagenbeek Thijs,Wu Xiumin,Eastham-Anderson Jeff,Tao Janet,Lee Wyne,Bastian Boris C,Carbone Michele,Webster Joshua D,Dey Anwesha
The deubiquitinating enzyme BAP1 is mutated in a hereditary cancer syndrome with a high risk for mesothelioma and melanocytic tumors. Here, we show that pancreatic intraepithelial neoplasia driven by oncogenic mutant KrasG12D progressed to pancreatic adenocarcinoma in the absence of BAP1. The Hippo pathway was deregulated in BAP1-deficient pancreatic tumors, with the tumor suppressor LATS exhibiting enhanced ubiquitin-dependent proteasomal degradation. Therefore, BAP1 may limit tumor progression by stabilizing LATS and thereby promoting activity of the Hippo tumor suppressor pathway. SIGNIFICANCE: BAP1 is mutated in a broad spectrum of tumors. Pancreatic Bap1 deficiency causes acinar atrophy but combines with oncogenic Ras to produce pancreatic tumors. BAP1-deficient tumors exhibit deregulation of the Hippo pathway..
CCR5 blockade inflames antitumor immunity in BAP1-mutant clear cell renal cell carcinoma.
Zhou Quan,Qi Yangyang,Wang Zewei,Zeng Han,Zhang Hongyu,Liu Zhaopei,Huang Qiuren,Xiong Ying,Wang Jiajun,Chang Yuan,Bai Qi,Xia Yu,Wang Yiwei,Liu Li,Xu Le,Dai Bo,Guo Jianming,Zhu Yu,Zhang Weijuan,Xu Jiejie
Journal for immunotherapy of cancer
BACKGROUND:Patients with BRCA1-associated protein 1 (BAP1)-mutant clear cell renal cell carcinoma (ccRCC) have worse prognosis. C-C chemokine receptor 5 (CCR5) plays an important role in ccRCC development and its expression is elevated in BAP1-mutant tumors. METHODS:533 patients with ccRCC from The Cancer Genome Atlas cohort and 797 patients with ccRCC from the Shanghai cohort were enrolled. In vitro and in vivo studies were conducted with human ccRCC tumors and murine tumor models. The association between BAP1 and CCR5 or its ligands was assessed by immunohistochemistry, flow cytometry, real-time PCR and ELISA. Survival was compared between different subpopulations of patients using Kaplan-Meier curve. Therapeutic effect of CCR5 blockade was validated using human ccRCC tumors and murine models. RESULTS:Expression of CCR5 and its ligands were elevated in BAP1-mutant patients with ccRCC. High CCR5 expression was indicative of poor prognosis in BAP1-low group of patients. CCR5 blockade prolonged the survival of tumor-bearing mice, resulting in enhanced cytotoxicity of T cells and antigen presentation of dendritic cells but repressed immune checkpoint expression. CCR5 ligands could recruit CCR5 regulatory T cells to the tumor microenvironment. Additionally, BAP1-mutant ccRCC tumor cells secreted CCR5 ligands, which increased programmed cell death ligand 1 expression. However, both processes could be inhibited by CCR5 blockade. Study limitations include the unclear impact of CCR5 expressed by other cell populations. CONCLUSIONS:CCR5 in BAP1-mutant ccRCC results in an immune-suppressive microenvironment. Targeting CCR5 could provide a potential therapeutic benefit for patients. TRIAL REGISTRATION NUMBER:NCT01358721, CA209-009.
Highly expressed EZH2 in combination with BAP1 and MTAP loss, as detected by immunohistochemistry, is useful for differentiating malignant pleural mesothelioma from reactive mesothelial hyperplasia.
Yoshimura Masayo,Kinoshita Yoshiaki,Hamasaki Makoto,Matsumoto Shinji,Hida Tomoyuki,Oda Yoshinao,Iwasaki Akinori,Nabeshima Kazuki
Lung cancer (Amsterdam, Netherlands)
OBJECTIVE:Malignant pleural mesothelioma (MPM) is an aggressive neoplasm with poor prognosis. Loss of BRCA-associated protein 1 (BAP1) protein expression as detected by immunohistochemistry (IHC) and homozygous deletion (HD) of the 9p21 locus as detected by fluorescence in situ hybridization (FISH) permits differentiation of MPM from reactive mesothelial hyperplasia (RMH). We have previously reported that detecting the loss of methylthioadenosine phosphorylase (MTAP) using IHC is a surrogate assay for 9p21 FISH. Furthermore, enhancer of zeste homolog 2 (EZH2), which encodes a component of polycomb repressor complex 2 (PRC-2), has been overexpressed in various tumors as well as MPM. In the current study, we investigated whether EZH2 IHC assay, alone or in combination with BAP1 and MTAP IHC, is useful for distinguishing MPM from RMH. MATERIALS AND METHODS:We examined IHC expression of EZH2, BAP1, and MTAP, and 9p21 FISH in MPM (n = 38) and RMH (n = 29) and analyzed the sensitivity and specificity of each detection assay for distinguishing MPM from RMH. RESULTS AND CONCLUSION:EZH2, BAP1, and MTAP IHC, and 9p21 FISH were characterized by a 100% specificity each and 44.7%, 52.6%, 47.4%, and 65.8% sensitivities, respectively. A combination of EZH2 and BAP1 IHC, and 9p21 FISH showed the greatest sensitivity (89.5%). Using IHC alone (EZH2, BAP1, and MTAP IHC) also yielded a good sensitivity of 86.9%; this level is high enough for routine diagnostics. There were no statistically significant associations between expression of EZH2 and that of other markers (BAP1 and MTAP IHC) or 9p21 HD. However, a high expression level of EZH2 was significantly associated with short survival (P = 0.025). In conclusion, adding a high expression level of EZH2 to a combination of BAP1 and MTAP loss, all detected by IHC, demonstrated useful for discriminating MPM from RMH.
EZH2 Expression is increased in BAP1-mutant renal clear cell carcinoma and is related to poor prognosis.
Sun Chenmin,Zhao Chunchun,Li Shugen,Wang Jianqing,Zhou Qidong,Sun Jianliang,Ding Qiang,Liu Min,Ding Guanxiong
Journal of Cancer
BAP1 is frequently mutated in clear cell renal cell carcinoma (ccRCC) with a definitive role still unclear. In silico analysis of BAP1-mutant and wild-type gene enrichment and functional annotation in TCGA-KIRC dataset was performed. Target gene was studied based on functional clustering and was knowledge-based. Validation using in-house pathological sections were performed immunohistochemically. and studies on target gene were performed. The TCGA ccRCC dataset included 534 ccRCC samples. BAP1 was frequently mutated and more frequently downregulated in ccRCC compared to normal kidney tissue or benign renal tumors. In the analysis between samples with BAP1 mutation (N = 33) and pan-negative (N = 33), we found that cancers with BAP1 mutation was significantly enriched for 14 pathways, of which 3 were DNA repair pathways, in which EZH2 played a role. CcRCC patients with lower BAP1 expression had poor prognosis and showed higher EZH2 expression, which also conferred worsened survival. Genetic and pharmaceutical inhibition of EZH2 not only inhibited BAP1-mutatn ccRCC cell viability and invasion but also abrogated genetic replenishing of BAP1 expression. Validation cohort encompassing 62 ccRCC samples confirmed the worsened phenotype for cases with higher EZH2 expression and significant positive correlation between expressions of EZH2 and BAP1. EZH2 inhibitor also inhibited tumor growth in xenograft mouse model with BAP1-mutated ccRCC cells with unremarkable toxicity. CcRCC with decreased BAP1 level has poor prognosis and is associated with higher EZH2 expression. Inhibition of EZH2 in BAP1-mutated entity holds promise for further investigation.
Sensitivity to asbestos is increased in patients with mesothelioma and pathogenic germline variants in BAP1 or other DNA repair genes.
Betti Marta,Aspesi Anna,Ferrante Daniela,Sculco Marika,Righi Luisella,Mirabelli Dario,Napoli Francesca,Rondón-Lagos Milena,Casalone Elisabetta,Vignolo Lutati Francesca,Ogliara Paola,Bironzo Paolo,Gironi C Laura,Savoia Paola,Maffè Antonella,Ungari Silvana,Grosso Federica,Libener Roberta,Boldorini Renzo,Valiante Michele,Pasini Barbara,Matullo Giuseppe,Scagliotti Giorgio,Magnani Corrado,Dianzani Irma
Genes, chromosomes & cancer
Pathogenic germline variants in the BAP1 tumor suppressor gene can cause a cancer syndrome called BAP1 tumor predisposition syndrome (BAP1-TPDS), which is characterized by predisposition to mesothelioma, melanoma, renal cell carcinoma, basal cell carcinoma, and other tumors. Other genes that may predispose to mesothelioma are CDKN2A and DNA repair genes. Asbestos exposure has often been reported in patients with malignant pleural mesothelioma (MPM) and germline variants in BAP1, but this exposure has never been quantified. We aimed to search for germline variants in BAP1 among 25 new Italian probands with suspected BAP1-TPDS, summarize the prevalence of these variants in 39 Italian patients with familial MPM and other tumors recruited over a 5-year period, and compare cumulative asbestos exposure in 14 patients with MPM and pathogenic germline variants in BAP1, CDKN2A, or DNA repair genes with that of 67 patients without germline variants in 94 cancer-predisposing genes. We report here a new pathogenic germline variant in BAP1: c.783 + 2 T > C. The prevalence of pathogenic germline variants in BAP1 was 7.7% among patients with familial MPM (3/39). Patients with pathogenic germline variants in BAP1, CDKN2A, or DNA repair genes showed lower cumulative asbestos exposure than patients without germline variants in 94 cancer-predisposing genes (P = .00002). This suggests an interaction between genetic risk factors and asbestos in the development of mesothelioma.
Transposase mapping identifies the genomic targets of BAP1 in uveal melanoma.
Yen Matthew,Qi Zongtai,Chen Xuhua,Cooper John A,Mitra Robi D,Onken Michael D
BMC medical genomics
BACKGROUND:BAP1 is a histone deubiquitinase that acts as a tumor and metastasis suppressor associated with disease progression in human cancer. We have used the "Calling Card System" of transposase-directed transposon insertion mapping to identify the genomic targets of BAP1 in uveal melanoma (UM). This system was developed to identify the genomic loci visited by transcription factors that bind directly to DNA; our study is the first use of the system with a chromatin-remodeling factor that binds to histones but does not interact directly with DNA. METHODS:The transposase piggyBac (PBase) was fused to BAP1 and expressed in OCM-1A UM cells. The insertion of transposons near BAP1 binding sites in UM cells were identified by genomic sequencing. We also examined RNA expression in the same OCM-1A UM cells after BAP1 depletion to identify BAP1 binding sites associated with BAP1-responsive genes. Sets of significant genes were analyzed for common pathways, transcription factor binding sites, and ability to identify molecular tumor classes. RESULTS:We found a strong correlation between multiple calling-card transposon insertions targeted by BAP1-PBase and BAP1-responsive expression of adjacent genes. BAP1-bound genomic loci showed narrow distributions of insertions and were near transcription start sites, consistent with recruitment of BAP1 to these sites by specific DNA-binding proteins. Sequence consensus analysis of BAP1-bound sites showed enrichment of motifs specific for YY1, NRF1 and Ets transcription factors, which have been shown to interact with BAP1 in other cell types. Further, a subset of the BAP1 genomic target genes was able to discriminate aggressive tumors in published gene expression data from primary UM tumors. CONCLUSIONS:The calling card methodology works equally well for chromatin regulatory factors that do not interact directly with DNA as for transcription factors. This technique has generated a new and expanded list of BAP1 targets in UM that provides important insight into metastasis pathways and identifies novel potential therapeutic targets.
Status Determines the Sensitivity of Malignant Mesothelioma Cells to Gemcitabine Treatment.
Guazzelli Alice,Meysami Parisa,Bakker Emyr,Demonacos Constantinos,Giordano Antonio,Krstic-Demonacos Marija,Mutti Luciano
International journal of molecular sciences
Malignant mesothelioma (MMe) is a cancer with poor prognosis and resistance to standard treatments. Recent reports have highlighted the role of the () in the development of MMe. In this study, the chemosensitivity of human mesothelioma cell lines carrying wild-type (WT), mutant and silenced was analysed. The mutant cells were significantly less sensitive than WT cell lines to the clinically relevant drug gemcitabine. Silencing of significantly increased resistance of MMe cells to gemcitabine. Cell cycle analysis suggested that gemcitabine induced Sub-G1 phase accumulation of the WT cells and increased in the S-phase in both WT and mutant cells. Analysis of the role of BAP1 in apoptosis suggested that gemcitabine induced early apoptosis in both WT and mutant cells but with a much higher degree in the WT cells. Effects on the population of cells in late apoptosis, which can mark necrosis and necroptosis, could not be seen in the mutant cells, highlighting the possibility that BAP1 plays a role in several types of cell death. Significantly decreased DNA damage in the form of double-strand breaks was observed in gemcitabine-treated mutant cells, compared to WT cells under the same conditions. After silencing, a significant decrease in DNA damage in the form of double-strand breaks was observed compared to cells transfected with scramble siRNA. Taken together, the results presented in this manuscript shed light on the role of BAP1 in the response of MMe cells to gemcitabine treatment and in particular in the control of the DNA damage response, therefore providing a potential route for more efficient MMe therapy.