RESUMO
BACKGROUND: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) has been perceived as a promising anti-cancer agent because of its unique ability to kill cancer cells while sparing normal cells. However, translation of TRAIL to clinical studies was less successful as a large number of cancer cells acquire resistance to TRAIL-based monotherapies. An ideal strategy to overcome TRAIL resistance is to combine it with potential sensitizing agents. OBJECTIVE: To investigate the TRAIL-sensitizing effect of curcumin in leukemia. METHODS: The mechanism underlying TRAIL sensitization by curcumin was studied by flow cytometric analysis of TRAIL receptors in leukemic cell lines and patient samples, and immunoblot detection of TRAIL-apoptosis signaling proteins. RESULTS: Curcumin augments TRAIL-apoptotic signaling in leukemic cells by upregulating the expression of DR4 and DR5 along with suppression of cFLIP and anti-apoptotic proteins Mcl-1, Bcl-xl, and XIAP. Curcumin pre-treatment significantly (p < 0.01) enhanced the sensitivity of leukemic cell lines to TRAIL recombinant proteins. IL2-TRAIL peptide in the presence of curcumin induced potent apoptosis (p < 0.001) as compared to TRAIL and IL2-TRAIL protein in leukemic cell lines with IC50 < 0.1 µΜ. Additionally, the combination of IL2-TRAIL peptide and curcumin showed significant cytotoxicity in patient peripheral blood mononuclear cells (PBMCs) with an efficacy of 90% in acute myeloid leukemia (AML), but 100% in acute lymphoblastic leukemia (ALL), chronic lymphocytic leukemia (CLL) and chronic myelomonocytic leukemia (CMML). CONCLUSION: Overall, our results suggest that curcumin potentiates TRAIL-induced apoptosis through modulation of death receptors and anti-apoptotic proteins which significantly enhances the therapeutic efficacy.