Thioridazine Enhances TRAIL Cytotoxicity in Human Myeloid Leukemic Cells By up-Regulating DR5 and Modulating PI3K-AKT-NF-Kb Pathway

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in cancer cells but not in most normal cells, and is identified to be effective in various cancers, include myeloid leukemic cells[1]. Although some leukemia cell lines, K562 and KG-1, are sensitive to TRAIL, many showed certain degrees of resistance to TRAIL-mediated apoptosis[2,3], and the mechanism remains largely unknown, which forced us to find out ways to solve the problem. In this study, we investigated whether thioridazine, a phenothiazine derivative, could overcome the TRAIL resistance in K562 and KG-1 cells. Recently, we showed that Compared to treatment with thioridazine or TRAIL alone, co-treatment with thioridazine and TRAIL-induced apoptosis in K562 and KG-1 cells synergistically. This combination led to activation of caspase-8 and Bid, the cytosolic cumulation of cytochrome c from mitochondria as well as caspase-3 activated downstream. Treatment with thioridazine induced down-regulation of PI3K-AKT-NF-κB pathway. meanwhile, thioridazine dropped the level of NF-κB-dependent Bcl-xL, leading caspase activated and Bid cleaved. the expression of TRAIL-receptors in both K562 and KG-1 cells underwentthe treatment of thioridazine investigated that thioridazine significantly up-regulated DR5 by up to 51.22%, but not other TRAIL-receptors such as DR4, decoy receptor 1, and DcR2. Therefore, our results indicate that the combination of TRAIL with thioridazine overturn TRAIL resistance through Up-regulating the expression of DR5 and down-regulation of AKT protein, and combination treatment with thioridazine and TRAIL may be a novel therapeutic strategy in leukemia. Reference: Srivastava R K. TRAIL/Apo-2L: mechanisms and clinical applications in cancer.[J]. Neoplasia, 2001, 3(6):535-546. Nimmanapalli R, Porosnicu M, Nguyen D, et al. Cotreatment with STI-571 enhances tumor necrosis factor alpha-related apoptosis-inducing ligand (TRAIL or apo-2L)-induced apoptosis of Bcr-Abl-positive human acute leukemia cells.[J]. Clinical Cancer Research An Official Journal of the American Association for Cancer Research, 2001, 7(2):350-357. Yang T, Lan J, Huang Q, et al. Embelin sensitizes acute myeloid leukemia cells to TRAIL through XIAP inhibition and NF-κB inactivation.[J]. Cell Biochemistry & Biophysics, 2015, 71(1):291-297. Disclosures No relevant conflicts of interest to declare.