The anticancer effects of hispolon on lung cancer cells.

Hispolon is isolated from Phellinus igniarius and exhibits antitumor activity. Here, we explored the effects of hispolon on the lung cancer A549 and H661 cells. Cells were incubated with various concentrations of hispolon (0, 5, 10, 20, 40, 80 or 160μM) for 12, 24, 48 or 72h. Cell viability was examined by MTT assay. Cell cycle and apoptosis assay were assessed by flow cytometry. Hispolon decreased cell viability in a dose- and time-dependent manner. The cell cycle distribution showed that hispolon enhanced the accumulations of the cells in G0/G1 phase. Mechanically, hispolon decreased the expression of G1-S transition-related proteins: Cyclin D1, cyclin E, CDK2, CDK4 and CDK6, but increased the expression of CDK inhibitor p21(CIP1) and p27(KIP1). Moreover, hispolon induced cell apoptosis through activation of the mitochondrial pathway, evidenced by the loss of mitochondrial membrane potential, the release of cytochrome c into cytosol, and the cleavage of caspase-9, caspase-3 and poly (ADP-ribose) polymerase (PARP) in hispolon-treated cells. Additionally, hispolon enhanced the expression of p53, specific silencing of which almost completely reversed hispolon-mediated antitumor activity. Moreover, hispolon treatment was more effective on H661 cells than on A549 cells in inhibiting cell viability and inducing cell apoptosis. Our results indicate that hispolon inhibits the cell viability, induces G0/G1 cell cycle arrest and apoptosis in lung cancer cells and p53 plays a critical role in hispolon-mediated antitumor activity.