CDC 25 is a dual phosphatase responsible for dephosphorylation and, thus, activation of CDC 2 kinase in G(2). Abnormal activation of cyclin B-associated CDC 2 kinase has been in;plicated in apoptosis induced by cancer chemotherapeutic agents such as paclitaxel (Taxol) and etoposide (VP-16), In this study, we found that the CDC 2 kinase could be transiently activated when nasopharyngeal carcinoma NPC-TW01 cells were treated for 3 h with a new anticancer agent, GL331, GL331 treatment also induced a concomitant increase in CDC 25A phosphatase activity and a reduced level of Tyr-15-phosphorylated CDC 2 in NPC-TW01 cells, Furthermore, subsequent apoptotic DNA fragmentation induced by GL331 could be interrupted by treatment of the cells with the cyclin B1-specific antisense oligonucleotides, suggesting that abnormal activation of cyclin B1-associated CDC 2 kinase and CDC 25A phosphatase was involved in GL331-induced apoptosis, Raf-1 has been shown to associate with CDC 25A and, thus, to stimulate its phosphatase activity, Our results revealed that GL331 could facilitate the association of CDC 25A with Raf-1, resulting in the cascade of CD0C 25A phosphatase activation and CDC 2 kinase activation, as well as related signaling pathways, and ultimately causing apoptosis in cancer cells.
