N6-isopentenyladenosine inhibits cell proliferation and induces apoptosis in a human colon cancer cell line DLD1

N6-isopentenyladenosine (i6A) is a modified nucleoside with a pentaatomic isopentenyl derived from mevalonate that induces inhibition of tumor cell proliferation and apoptosis in several tumor cell lines. In this study, we reported that N6-isopentenyladenosine inhibited the proliferation and promotes apoptosis in DLD1 human colon cancer cells. It suppressed the proliferation of cells through inhibition of DNA synthesis, causing a cell cycle arrest that correlated with a decrease in the levels of cyclin E, cyclin A and cyclin D1 and with a concomitant increase in the levels of cyclin-dependent kinase inhibitor p21waf and p27kip1. Moreover, it induced apoptosis through an increase in the number of annexin V-positive cells, a downregulation of antiapoptotic products and caspase-3 activation. The apoptotic effects of N6-isopentenyladenosine were accompanied by sustained phosphorylation and activation of c-jun N-terminal kinase (JNK) that induced phosphorylation of c-jun. Overall, our data show that JNK, could play an important role in i6A-mediated apoptosis in DLD1 human colon cancer cells © 2008 Wiley-Liss, Inc.