Jolkinolide B, a bioactive diterpene isolated from the roots of Euphorbia fischeriana Steud, is known to induce apoptosis in cancer cells. However, the molecular mecha-nism of its anti-cancer activity have not been fully eluci-dated. In the present study, we found that Jolkinolide B reduced cell viability and induced apoptosis in a dose- and time-dependent manner in human leukemic U937. The induction of apoptosis was also accompanied by the downregulation of PI3K/Akt and the inhibitor of apoptosis protein (IAP) family proteins. Moreover, we observed that Jolkinolide B treatment resulted in activation of caspase-3 and -9, which may partly explain the anti-cancer activity of Jolkinolide B. Taken together, our study for the first time suggest that Jolkinolide B is able to enhance apoptosis of U937 cells, at least in part, through downregulation of PI3K/Akt and IAP family proteins. Moreover, the triggering of caspase-3 and -9 activation mediated apoptotic induction.

Keywords: apoptosis, caspase, Euphorbia fischeriana Steud, Jolkinolide B, U937