SMAC Mimetic BV6 Co-Treatment Downregulates the Factors Involved in Resistance and Relapse of Cancer: IAPs and Autophagy

SIMPLE SUMMARY: Breast cancer is the most prominent cancer among women. Therapeutic resistance and reoccurrence of cancer after various therapies, such as chemotherapy, radiotherapy etc., is the major cause of death. In various studies, it has been shown that dysregulation or defect in the cell death mechanisms such as apoptosis and autophagy is the key reason behind the issues. An increase in the level of inhibitors of apoptosis (IAPs) proteins and autophagy is founded in various cancers. Besides, the SMAC proteins that inhibit the action of IAPs are also found to be downregulated. In this study, BV6, a SMAC mimetic compound, not only induces apoptosis via inhibiting the action of IAPs but also downregulates autophagy. In addition, promising anticancer results were obtained after treating the breast cancer cells with BV6 in combination with death ligands such as TNF-related apoptosis-inducing ligand (TRAIL) and Tumor necrosis factor-α (TNF-α). It is an investigational study, and to the best of our knowledge, our study, for the first time, demonstrated the effect of BV6 on autophagy. This study presents the significance of SMAC mimetic compounds in the downregulation of factors responsible for cancer resistance and reoccurrence. The study may well provide a potent therapeutic target for the development of novel anti-cancer therapy using SMAC mimetics. ABSTRACT: Cancer is the utmost common disease-causing death worldwide, characterized by uncontrollable cell division with the potential of metastasis. Overexpression of the Inhibitors of Apoptosis proteins (IAPs) and autophagy correlates with tumorigenesis, therapeutic resistance, and reoccurrence after anticancer therapies. This study illuminates the role and efficacy of smac mimetic compound BV6 alone and in co-treatment with death ligands such as TRAIL and TNFα in the regulation of cell death mechanisms, i.e., apoptosis and autophagy. In this study, MTT assays, wound healing assays, and cellular and nuclear morphological studies were done. DAPI staining, AO/EtBr staining and AnnexinV/PI FACS was done to study the apoptosis. The expression of IAPs and autophagy biomarkers was analyzed using Real time-PCR and western blotting. Meanwhile, TEM demonstrated autophagy and cellular autophagic vacuoles in response to the BV6. The result shows a promising anti-cancer effect of BV6 alone as well as in combinational treatment with TRAIL and TNFα, compared to the lone treatment of TRAIL and TNFα in both breast cancer cell lines. The smac mimetic compound might provide an alternative combinational therapy with conventional anticancer therapies to tackle their inefficiency at the advanced stage of cancer, cancer resistance, and reoccurrence. Also, IAPs and autophagic proteins could act as potent target molecules for the development of novel anti-cancer drugs in pathogenesis and the betterment of regimens for cancer.