The ability to evade apoptosis is one of the defining hallmarks of cancer. It enables the survival of cancer cells under abnormal growth stimulation and mediates their increased resistance to treatment with cytotoxic drugs and radiation. Therefore, antiapoptotic proteins that counteract apoptosis signaling represent promising new therapeutic targets to impair cancer cell growth and enhance treatment response. As soon as RNA interference (RNAi) was demonstrated in mammalian cells, it rapidly became an essential tool for gene knockdown in preclinical models, making it possible to define the role of specific genes in the onset and progression of cancer and explore their potential as therapeutic targets. The present review summarizes the findings from studies relying on the use of RNAi-based approaches to functionally validate two members of the inhibitors of apoptosis protein family, survivin and Apollon/BRUCE, as new cancer therapeutic targets. Results collected thus far indicate that targeting the survivin network efficiently inhibits tumor growth potential and increases spontaneous and treatment-induced apoptosis of cancer cells. Based on these findings, the applicability of survivin-directed strategies for the clinical treatment of human tumors is currently under investigation. As regards Apollon/ BRUCE, although very preliminary, results of RNAi-mediated gene knockdown point to the possibility to significantly impair tumor cell proliferation through the induction of apoptosis.
Keywords: Apollon/BRUCE, apoptosis, chemosensitivity, human tumors, inhibitors of apoptosis proteins, radiosensitivity, survivin, cancer cells, therapeutic targets, clinical treatment of human tumors, mammalian cells, C-terminal Bid fragment (tBID), proapoptotic protein, controlled signaling pathways, inhibitors of apoptosis proteins (IAPs), human leukocyte