Hypsiziprenol A
9 is a polyterpene isolated from the fruiting body of the Japanese edible mushroom Buna-shimeji (
Hypsizigus marmoreus). Although our recent studies revealed that hypsiziprenol A
9 has strong anti-tumor activity against tumor-bearing mice, its mechanism of action remains unclear. To elucidate further its anti-tumor action, we examined in detail hypsiziprenol A
9-induced apoptosis in human cancer cell lines.
We observed that hypsiziprenol A
9 strongly inhibited the growth of human promyelocytic leukemia HL-60 cells and several other cancer cell lines in a dose-dependent manner. Hoechst 33342 staining showed DNA fragmentation and condensation of chromatin in HL-60 cells treated with hypsiziprenol A
9. DNA laddering, a hallmark of apoptosis, was detected using agarose gel electrophoresis. In addition, flow cytometric analysis confirmed that hypsiziprenol A
9 increased sub-G
1/G
0 populations in a time-dependent manner. Hypsiziprenol A
9 also increased activities of caspase-2, -3, -8 and -9 in a dose-dependent manner in the apoptotic HL-60 cell. Furthermore, JC-1 fluorescent staining determined that hypsiziprenol A
9-induced apoptosis was associated with a loss of mitochondrial membrane potential.
These results suggest that hypsiziprenol A
9 inhibits the growth of HL-60 cells by inducing apoptosis that is mediated through mitochondrial membrane potential loss and caspase activation.
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