6-[(1-naphthylmethyl)sulfanyl]-9H-purine induces G2/M phase arrest and apoptosis in human hepatocellular carcinoma HepG2 cells

Due to the increasing incidence of cancer, a leading cause of death worldwide, discovery of new therapeutic drugs is urgently needed. By screening for agents with low toxicity that selectively target cancer cells, we found that 6-[(1-naphthylmethyl) sulfanyl]-9H-purine (NMMP), a derivative of 6-mercaptopurine (6-MP), could reduce the viability of five human cancer cell lines. Further study suggested that NMMP inhibition of the proliferation of hepatocellular carcinoma (HepG2) cells was associated with G2/M phase cell cycle arrest, and reduced cyclin-dependent kinase (CDK) 4 and cyclin B1/D1 levels. In addition, NMMP induced cell apoptosis, as determined by TUNEL assay. Immunoblot analysis revealed that the expression of cleaved caspase-9 and caspase-3 as well as the ratio of Bax/Bcl-2 protein increased significantly. Overall, our results suggest that NMMP exerts anti-tumor activities through induction of G2/M phase arrest and mitochondria-dependent cell apoptosis, implicating its potential therapeutic value for the treatment of cancer.