4-(4-chloro-2-methylphenoxy)-n-hydroxybutanamide and Breast-Neoplasms

Women with estrogen receptor positive (ER+) breast cancer receive treatment with tamoxifen or aromatase inhibitors as adjuvant hormone therapy, but their tumors frequently exhibit de novo or acquired resistance. Current strategies being developed to overcome resistance involve a combination of growth factor pathway inhibitors in addition to hormone therapy. Unfortunately, prolongation of responses with these new approaches is measured only in months. We reasoned that a pro-apoptotic strategy would be preferable since cell death would abrogate the process of adaptive reprogramming and eliminate the resistant cells rather than inhibiting their growth. Our hypothesis was that combinations of pro-apoptotic agents could be designed that would act synergistically as opposed to a merely additively. We examined two model strategies to determine which would result in the greatest synergy: a vertical approach that involved the targeting of two or more steps in a single pathway and a horizontal one, targeting steps in more than one parallel pathway. We found that combinations involving horizontal activation resulted in greater synergy than vertical. Combination index and isobologram analyses revealed that the horizontal combination of the small molecule 4-(4-chloro-2-methylphenoxy)-N-hydroxybutanamide (CMH) along with T-DM1 displayed the strongest synergy for inducing apoptosis in hormone refractory breast cancer cells. Both the reprogrammed, hormone resistant cells and the wild type responded to certain combinations with synergistic enhancement of apoptosis. These data suggest that combinations using T-DM1 are promising for further in vivo studies both in xenografts and in patients.

Topics: Ado-Trastuzumab Emtansine; Antibodies, Monoclonal, Humanized; Apoptosis; Breast Neoplasms; Cell Line, Tumor; Drug Synergism; Estradiol; Female; Humans; Hydroxamic Acids; Maytansine; Organization and Administration; Trastuzumab

Cellular FLICE (FADD-like IL-1beta-converting enzyme)-inhibitory protein (c-FLIP) is a major resistance factor for the tumor necrosis factor-related apoptosis-inducing ligand TRAIL and in drug resistance in human malignancies. c-FLIP is an antagonist of caspases-8 and -10, which inhibits apoptosis and is expressed as long (c-FLIP(L)) and short (c-FLIP(S)) splice forms. c-FLIP is often overexpressed in various human cancers, including breast cancer. Several studies have shown that silencing c-FLIP by specific siRNAs sensitizes cancer cells to TRAIL and anticancer agents. However, systemic use of siRNA as a therapeutic agent is not practical at present. In order to reduce or inhibit c-FLIP expression, small molecules are needed to allow targeting c-FLIP without inhibiting caspases-8 and -10. We used a small molecule inhibitor of c-FLIP, 4-(4-chloro-2-methylphenoxy)-N-hydroxybutanamide (CMH), and show that CMH, but not its inactive analog, downregulated c-FLIP(L) and c-FLIP(S) mRNA and protein levels, caused poly(ADP-ribose) polymerase (PARP) degradation, reduced cell survival, and induced apoptosis in MCF-7 breast cancer cells. These results revealed that c-FLIP is a critical apoptosis regulator that can serve as a target for small molecule inhibitors that downregulate its expression and serve as effective targeted therapeutics against breast cancer cells.

Topics: Apoptosis; Blotting, Western; Breast Neoplasms; CASP8 and FADD-Like Apoptosis Regulating Protein; Cell Proliferation; Female; Humans; Hydroxamic Acids; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured