Anticancer activity of different phenols is documented, but underlying mechanisms remain elusive. Recently, we have shown that cannabidiol kills the cells of acute lymphoblastic leukemia (ALL) by a direct interaction with mitochondria, with their consequent dysfunction. In the present study, cytotoxic effects of several phenolic compounds against human the T-ALL cell line Jurkat were tested by means of resazurin-based metabolic assay. To unravel underlying mechanisms, mitochondrial membrane potential (∆Ψm) and [Ca2+]m measurements were undertaken, and reactive oxygen species generation and cell death were evaluated by flow cytometry. Three out of eight tested phenolics, cannabidiol, curcumin and quercetin, which displayed a significant cytotoxic effect, also dissipated the ∆Ψm and induced a significant [Ca2+]m increase, whereas inefficient phenols did not. Dissipation of the ∆Ψm by cannabidiol was prevented by cyclosporine A and reverted by Ru360, inhibitors of the permeation transition pore and mitochondrial Ca2+ uniporter, respectively. Ru360 prevented the phenol-induced [Ca2+]m rise, but neither cyclosporine A nor Ru360 affected the curcumin- and quercetin-induced ∆Ψm depolarization. Ru360 impeded the curcumin- and cannabidiol-induced cell death. Thus, all three phenols exert their antileukemic activity via mitochondrial Ca2+ overload, whereas curcumin and quercetin suppress the metabolism of leukemic cells by direct mitochondrial uncoupling.
Keywords: acute lymphoblastic leukemia; cannabidiol; curcumin; cytotoxicity; mitochondria; quercetin.