Gallic acid induces G₀/G₁ phase arrest and apoptosis in human leukemia HL-60 cells through inhibiting cyclin D and E, and activating mitochondria-dependent pathway.

Gallic acid (GA) induces apoptosis in different types of cancer cell lines. In this study, we investigate the apoptotic effects induced by GA in human promyelocytic leukemia HL-60 cells, and clarify the underlying mechanism. Our results showed that GA reduced the viability of HL-60 cells in a dose- and time-dependent manner. GA led to G(0)/G(1) phase arrest in HL-60 cells through promoting p21 and p27 and inhibiting the levels of cyclin D and cyclin E. GA caused DNA damage and fragmentation in HL-60 cells as assayed using DAPI staining and Comet assay. Flow cytometric analysis revealed that GA increased Ca(2+) levels and reduced the mitochondrial membrane potential (ΔΨ(m)) in HL-60 cells. Apoptotic protein expressions were determined by Western blotting. The results indicated that GA-mediated apoptosis of HL-60 cells mainly depended on mitochondrial pathway, by promoting the release of cytochrome c, apoptosis-inducing factor (AIF) and endonuclease G (Endo G) and by up-regulating the protein expression of Bcl-2-associated X protein (BAX), caspase-4, caspase-9 and caspase-3. In addition, GA also activated the death receptor-dependent pathway by enhancing the protein expressions of fatty acid synthase (FAS), FAS ligand (FASL), caspase-8 and BCL-2 interacting domain (BID). We determined the mRNA expression of the gene levels of these proteins by real-time PCR. The results showed that GA-mediated apoptosis of HL-60 cells mainly depended on up-regulation of the mRNA of caspase-8, caspase-9, caspase-3, AIF and Endo G. In conclusion, GA-induced apoptosis occurs through the death receptor and mitochondria-mediated pathways. The evaluation of GA as a potential therapeutic agent for treatment of leukemia seems warranted.