Despite the high frequency of prostate cancer, therapeutic options for advanced disease are limited to chemotherapy, radiation or hormonal therapy and eventually fail in all patients. Therefore, alternative approaches need to be developed. We previously reported that FTY720, a metabolite from Isaria sinclarii, is a unique antitumor agent for an androgen‐independent prostate cancer cell line and requires caspase‐3 activation in apoptosis. In our study, we have evaluated the effect of FTY720 on a family of mitogen‐activated protein kinases (MAPKs), focal adhesion kinase (FAK), mitochondrial transmembrane potential, caspase‐9 and caspase‐8 and analyzed the expression of some cell‐cycle regulator proteins in DU145 cells in order to understand the various antitumor effects of FTY720. Apoptosis was quantified by phosphatidylserine exposure. Activation of MAPKs, cleavage of caspase‐9 and caspase‐8, status of cyclin‐dependent kinases (CDKs) and Cip1/p21, a cyclin‐dependent kinase inhibitor, were evaluated by Western blot analysis, in addition to FAK and phospho‐FAK immunoprecipitation and cell‐cycle analysis by FACScan. We found that in DU145 cells, 40 μM FTY720 caused activation of p38 MAPK and the upstream kinase MKK3/MKK6 but not SAPK/JNK. Mitochondrial transmembrane potential, FAK and ERK1/2 were reduced while caspase‐9 and caspase‐8 were cleaved. The p38‐specific inhibitor had no effect on apoptosis induced by FTY720, whereas z‐VAD.FMK, a broad‐spectrum caspase inhibitor, did not inhibit the p38 MAPK activation. An amount of 20 μM FTY720 resulted in G₁ arrest and a decrease of CDK2 as well as CDK4, whereas it induced Cip1/p21. FTY720 may exert anticarcinogenic effects against prostate cancer cells possibly involving modulation of mitogenic signaling, cell‐cycle regulators, induction of G₁ arrest and apoptotic death in DU145 cells. © 2001 Wiley‐Liss, Inc.