Our previous studies with siRNA delivery were able to sensitize breast cancer cells by targeting anti-apoptotic proteins survivin (Montazeri Aliabadi et al., 2011) and Mcl-1 (Aliabadi et al., 2013a), so that this class of proteins (rather than cell cycle proteins) might be more suitable to target for chemo-sensitization. This evidence concerns the gene BIRC5 and breast cancer.