trichostatin-a and Triple-Negative-Breast-Neoplasms

Failures to treat triple-negative breast cancer (TNBC) are mainly due to chemoresistance or radioresistance. We and others previously discovered that zinc finger E-box-binding homeobox 1 (ZEB1) is a massive driver causing these resistance. However, how to dynamically modulate the intrinsic expression of ZEB1 during cell cycle progression is elusive. Here integrated affinity purification combined with mass spectrometry and TCGA analysis identify a cell cycle-related E3 ubiquitin ligase, checkpoint with forkhead and ring finger domains (CHFR), as a key negative regulator of ZEB1 in TNBC. Functional studies reveal that CHFR associates with and decreases ZEB1 expression in a ubiquitinating-dependent manner and that CHFR represses fatty acid synthase (FASN) expression through ZEB1, leading to significant cell death of TNBC under chemotherapy. Intriguingly, a small-molecule inhibitor of HDAC under clinical trial, Trichostatin A (TSA), increases the expression of CHFR independent of histone acetylation, thereby destabilizes ZEB1 and sensitizes the resistant TNBC cells to conventional chemotherapy. In patients with basal-like breast cancers, CHFR levels significantly correlates with survival. These findings suggest the therapeutic potential for targeting CHFR-ZEB1 signaling in resistant malignant breast cancers.

Topics: Antineoplastic Agents; Apoptosis; Cell Cycle Proteins; Cell Line, Tumor; Down-Regulation; Doxorubicin; Drug Resistance, Neoplasm; Humans; Hydroxamic Acids; Neoplasm Proteins; Poly-ADP-Ribose Binding Proteins; Protein Stability; Treatment Outcome; Triple Negative Breast Neoplasms; Ubiquitin-Protein Ligases; Zinc Finger E-box-Binding Homeobox 1

Triple negative breast cancer (TNBC) is the most aggressive subtype of breast cancer with poor outcome. Because of lacking therapeutic targets, chemotherapy is the main treatment option for patients with TNBC. Overexpression of HDACs correlates with tumorigenesis, highlighting the potential of HDACs as therapeutic targets for TNBC. Here we demonstrate that trichostatin A (TSA, a HDAC inhibitor) selectively inhibits the proliferation of TNBC cell lines HCC1806 and HCC38 rather than a normal breast cell line MCF10A. The inhibition of TNBC by TSA is via its roles in inducing cell cycle arrest and apoptosis. TSA treatment leads to decreased expression of CYCLIN D1, CDK4, CDK6 and BCL-XL, but increased P21 expression. Moreover, combination of TSA with doxorubicin has synergistic effects on inhibiting proliferation of HCC1806 and HCC38 cells. Our studies identified a promising epigenetic-based therapeutic strategy that may be implemented in the therapy of fatal human breast cancer.

Topics: Apoptosis; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Humans; Hydroxamic Acids; Triple Negative Breast Neoplasms

The present study evaluated the mechanism of apoptosis caused by post-translational modification, hyperacetylation in triple-negative breast cancer (TNBC) cells. We previously showed that trichostatin A (TSA) induced secretion of acetylated apurinic apyrimidinic endonuclease 1/redox factor-1 (Ac-APE1/Ref-1). This is the first report showing that Ac-APE1/Ref-1 initiates apoptosis in TNBC cells by binding to the receptor for advanced glycation end products (RAGE). The functional significance of secreted Ac-APE1/Ref-1 was studied by induction of intracellular hyperacetylation through co-treatment with acetylsalicylic acid and TSA in MDA-MB-231 cells. In response to hyperacetylation, secretion of Ac-APE1/Ref-1 in vesicles was observed, resulting in significantly decreased cell viability and induction of apoptosis with increased expression of RAGE. The hyperacetylation-induced apoptosis was similar in two other TNBC cell lines: BT-459 and MDA-MB-468. Therefore, hyperacetylation may be a therapeutic target for treatment of TNBCs. This study introduces a novel paradigm whereby post-translational modification induces apoptotic cell death in breast cancer cells resistant to standard chemotherapeutic agents through secretion of auto- or paracrine molecules such as Ac-APE1/Ref-1.

Topics: Acetylation; Antigens, Neoplasm; Apoptosis; Aspirin; Breast Neoplasms; Cell Line, Tumor; Cell Membrane; Cell Survival; DNA-(Apurinic or Apyrimidinic Site) Lyase; Female; Gene Expression Regulation, Neoplastic; Humans; Hydroxamic Acids; MCF-7 Cells; Microscopy, Electron, Transmission; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Protein Processing, Post-Translational; Receptor for Advanced Glycation End Products; Triple Negative Breast Neoplasms

Lapatinib, a dual EGFR/HER2 tyrosine kinase inhibitor, has been shown to improve the survival rate of patients with advanced HER2-positive breast cancers. However, the off-target activity of lapatinib in inducing EGFR expression without tyrosine kinase activity was demonstrated to render HER2-negative breast cancer cells more metastatic, suggesting a limitation to the therapeutic effectiveness of this dual inhibitor in HER2-heterogeneous tumors. Therefore, targeting EGFR expression may be a feasible approach to improve the anticancer efficiency of lapatinib-based therapy. Inhibition of HDAC has been previously reported to epigenetically suppress EGFR protein expression. In this study, however, our data indicated that treatment with HDAC inhibitors trichostatin A (TSA), but not suberoylanilide hydroxamic acid (SAHA) or HDAC siRNA, can attenuate both protein and mRNA expressions of EGFR in lapatinib-treated triple-negative breast cancer cells, suggesting that TSA may suppress EGFR expression independently of HDAC inhibition. Nevertheless, TSA reduced EGFR 3'UTR activity and induced the gene expression of microRNA-7, a known EGFR-targeting microRNA. Furthermore, treatment with microRNA-7 inhibitor attenuated TSA-mediated EGFR suppression. These results suggest that TSA induced microRNA-7 expression to downregulate EGFR expression in an HDAC-independent manner.

Topics: Antineoplastic Agents; Cell Line, Tumor; ErbB Receptors; Gene Expression Regulation, Neoplastic; Histone Deacetylases; Humans; Hydroxamic Acids; Lapatinib; MicroRNAs; Protein Kinase Inhibitors; Quinazolines; RNA, Messenger; Triple Negative Breast Neoplasms