Mechanisms of resistance of chemotherapy in early-stage triple negative breast cancer (TNBC).
Wein Lironne,Loi Sherene
Breast (Edinburgh, Scotland)
Triple negative breast cancer (TNBC) a clinically aggressive subtype of breast cancer with poor outcomes. Chromosomal instability is a hallmark of many TNBCs, and likely underlies its ability to adapt and rapidly become resistant to chemotherapy. A study of residual disease after neoadjuvant chemotherapy have identified biological mechanisms driving this resistance to chemotherapy. Copy number amplifications such as MCL1, MYC and JAK2, as well as PTEN deletions or mutations have all been identified at a higher frequency in residual disease, suggesting they may play a role in de novo or acquired chemotherapy resistance. Increased copy number and expression of the PIM1 proto-oncogene in TNBC has also been identified as a new target of chemotherapy resistance. However, given the genomic instability and subclonal nature of driver mutations in TNBC, single agent targeted therapy is unlikely to be effective. Lately immune evasion has also been identified as another key characteristic of poor prognostic and chemo-resistant primary TNBCs. Combinations of checkpoint inhibition with targeted therapy and/or chemotherapy are currently being investigated.
Disruption of the anaphase-promoting complex confers resistance to TTK inhibitors in triple-negative breast cancer.
Thu K L,Silvester J,Elliott M J,Ba-Alawi W,Duncan M H,Elia A C,Mer A S,Smirnov P,Safikhani Z,Haibe-Kains B,Mak T W,Cescon D W
Proceedings of the National Academy of Sciences of the United States of America
TTK protein kinase (TTK), also known as Monopolar spindle 1 (MPS1), is a key regulator of the spindle assembly checkpoint (SAC), which functions to maintain genomic integrity. TTK has emerged as a promising therapeutic target in human cancers, including triple-negative breast cancer (TNBC). Several TTK inhibitors (TTKis) are being evaluated in clinical trials, and an understanding of the mechanisms mediating TTKi sensitivity and resistance could inform the successful development of this class of agents. We evaluated the cellular effects of the potent clinical TTKi CFI-402257 in TNBC models. CFI-402257 induced apoptosis and potentiated aneuploidy in TNBC lines by accelerating progression through mitosis and inducing mitotic segregation errors. We used genome-wide CRISPR/Cas9 screens in multiple TNBC cell lines to identify mechanisms of resistance to CFI-402257. Our functional genomic screens identified members of the anaphase-promoting complex/cyclosome (APC/C) complex, which promotes mitotic progression following inactivation of the SAC. Several screen candidates were validated to confer resistance to CFI-402257 and other TTKis using CRISPR/Cas9 and siRNA methods. These findings extend the observation that impairment of the APC/C enables cells to tolerate genomic instability caused by SAC inactivation, and support the notion that a measure of APC/C function could predict the response to TTK inhibition. Indeed, an APC/C gene expression signature is significantly associated with CFI-402257 response in breast and lung adenocarcinoma cell line panels. This expression signature, along with somatic alterations in genes involved in mitotic progression, represent potential biomarkers that could be evaluated in ongoing clinical trials of CFI-402257 or other TTKis.
RECQL5 plays an essential role in maintaining genome stability and viability of triple-negative breast cancer cells.
Peng Jin,Tang Lichun,Cai Mengjiao,Chen Huan,Wong Jiemin,Zhang Pumin
Triple-negative breast cancer (TNBC) is a malignancy that currently lacks targeted therapies. The majority of TNBCs can be characterized as basal-like and has an expression profile enriched with genes involved in DNA damage repair and checkpoint response. Here, we report that TNBC cells are under replication stress and are constantly generating DNA double-strand breaks, which is not seen in non-TNBC cells. Consequently, we found that RECQL5, which encodes a RecQ family DNA helicase involved in many aspects of DNA metabolism including replication and repair, was essential for TNBC cells to survive and proliferate in vitro and in vivo. Compromising RECQL5 function in TNBC cells results in persistence of DNA damage, G2 arrest, and ultimately, cessation of proliferation. Our results suggest RECQL5 may be a potential therapeutic target for TNBC.
Immunotherapy for triple-negative breast cancer: Existing challenges and exciting prospects.
Jia Hongyan,Truica Cristina I,Wang Bin,Wang Yanhong,Ren Xingcong,Harvey Harold A,Song Jianxun,Yang Jin-Ming
Drug resistance updates : reviews and commentaries in antimicrobial and anticancer chemotherapy
Patients with breast tumors that do not express the estrogen receptor, the progesterone receptor, nor Her-2/neu are hence termed "triple negatives", and generally have a poor prognosis, with high rates of systemic recurrence and refractoriness to conventional therapy regardless of the choice of adjuvant treatment. Thus, more effective therapeutic options are sorely needed for triple-negative breast cancer (TNBC), which occurs in approximately 20% of diagnosed breast cancers. In recent years, exploiting intrinsic mechanisms of the host immune system to eradicate cancer cells has achieved impressive success, and the advances in immunotherapy have yielded potential new therapeutic strategies for the treatment of this devastating subtype of breast cancer. It is anticipated that the responses initiated by immunotherapeutic interventions will explicitly target and annihilate tumor cells, while at the same time spare normal cells. Various immunotherapeutic approaches have been already developed and tested, which include the blockade of immune checkpoints using neutralizing or blocking antibodies, induction of cytotoxic T lymphocytes (CTLs), adoptive cell transfer-based therapy, and modulation of the tumor microenvironment to enhance the activity of CTLs. One of the most important areas of breast cancer research today is understanding the immune features and profiles of TNBC and devising novel immune-modulatory strategies to tackling TNBC, a subtype of breast cancer notorious for its poor prognosis and its imperviousness to conventional treatments. On the optimal side, one can anticipate that novel, effective, and personalized immunotherapy for TNBC will soon achieve more success and impact clinical treatment of this disease which afflicts approximately 20% of patients with breast cancer. In the present review, we highlight the current progress and encouraging developments in cancer immunotherapy, with a goal to discuss the challenges and to provide future perspectives on how to exploit a variety of new immunotherapeutic approaches including checkpoint inhibitors and neoadjuvant immunotherapy for the treatment of patients with TNBC.