Selective TRAIL-triggered apoptosis due to overexpression of TRAIL death receptor 5 (DR5) in P-glycoprotein-bearing multidrug resistant CEM/VBL1000 human leukemia cells.

The death-inducing cytokine, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), holds enormous promise as a cancer therapeutic due to its highly selective apoptosis-inducing action on neoplastic versus normal cells. Our results revealed that TRAIL selectively triggered apoptosis in the P-glycoprotein (P-gp, ABCB1) and DR5 overexpressing CEM/VBL1000 multidrug resistant leukemia cell line, but not in the parental CEM cells. Moreover, TRAIL treatment reduced P-gp expression in these cells. Mechanistic analysis of TRAIL-induced apoptosis revealed that TRAIL hypersensitivity is due to robust upregulation of the TRAIL receptor DR5 at the protein and mRNA levels during development of MDR in the CEM/VBL1000 variant. DR5 upregulation was independent of the level of expression of endoplasmic reticulum stress regulator C/EBP homologous transcription factor (CH0P/GADD153). TRAIL-triggered apoptosis was associated with increased expression of FADD; activation of caspases-3, -8, -9, and -10; and cytochrome c release from mitochondria. Therefore, both the extrinsic and intrinsic apoptosis pathways are involved in this process. These findings for the first time reveal that TRAIL treatment selectively causes apoptosis in P-gp-overexpressing CEM/VBL1000 cells through strong upregulation of DR5. Moreover, this hypersensitivity to TRAIL and its effect on reducing P-gp expression in these cells hold significant clinical implications for using TRAIL to eradicate MDR malignant cells.