Induction Of Apoptosis By D-limonene Is Mediated By Mitochondrial Death Pathway In Human Leukemia Cells

Objective: To investigate the apoptosis effect induced by d-limonene in human human leukemia cells and its mechanism.Methods: Using K562 and HL-60 cell lines, we investigated the anti-tumor activity of d-limonene. Apoptosis was evaluated by Annexin V/PI binding assay. Flow cytometry and western blot were performed to evaluate expression of some apoptosis-regulating proteins.Results: d-Limonene induced apoptosis in a dose- and time-dependent manner in both tested cells. We found an increase in Bax protein expression, the release of cytochrome c from mitochondria, and an increase in caspase-9 and cleaved caspase-3, but not caspase-8. Broad-spectrum caspase inhibitor and a caspase-3-specific inhibitor were able to prevent activation of d-limonene induced apoptotic cell death.Conclusions: The caspase-dependent mitochondrial death pathway is primarily involved in the development of d-limonene-induced apoptosis in human leukemia cells.