ALS2CR7 (CDK15) attenuates TRAIL induced apoptosis by inducing phosphorylation of survivin Thr34

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered a promising agent for medical applications because it induces apoptosis selectively in a variety of cancer cells without toxicity to normal human cells. However, its therapeutic potential has been limited by the existence of several cancer cells with TRAIL resistance. TRAIL resistance results from a variety of mechanisms, which occur at various points in the cellular signaling pathways. In this study, we demonstrate that ALS2CR7 (CDK15) can mediate resistance to TRAIL. We also demonstrate that cell viability of TRAIL sensitive HCT116 and MDA-MB-231 cells increased after TRAIL treatment in ALS2CR7 transfected cancer cells compared with vector transfected cancer cells. Furthermore, cell viability was decreased by TRAIL treatment after knockdown with ALS2CR7 siRNA in TRAIL resistant HT29 and MCF-7 cells. We also show that the activated form of apoptotic proteins such as caspase-3, -8 and -9 and PARP increased after TRAIL treatment in the control group, but decreased in the ALS2CR7 transfected group. The expression of survival proteins such as bcl2 and survivin in TRAIL sensitive cancer cells increased in the ALS2CR7 transfected group, but decreased in TRAIL resistant cancer cells treated with ALS2CR7 siRNA. Other survival proteins such as FLIP and XIAP were not affected. ALS2CR7 appears to bind with only survivin, and not bcl2. The phospho-survivin (Thr34) critical in drug resistance was increased by transfection with ALS2CR7, but the expression of death receptors such as DR4 and DR5 was not affected. ALS2CR7 did not bind with any of the death receptors in our study. In summary, our results suggest that ALS2CR7 confers TRAIL resistance to cancer cells via phosphorylation of survivin.