Bile acids and synthetic bile acid derivatives induce apop-tosis in various kinds of cancer cells and thus have anti-cancer properties. Recently, it has been suggested that autop-hagy may play an important role in cancer therapy. How-ever, few data are available regarding the role of autophagy in oral cancers and there have been no reports of autophagic cell death in OSCCs (oral squamous cell carcinoma cells) in-duced by HS-1200, a synthetic bile acid derivative. We thus examine whether HS-1200 modulates autophagy in OSCCs. Our findings indicate that HS-1200 has anticancer effects in OSCCs, and we observed in these cells that autophagic vacuoles were visible by monodansylcadaverine (MDC)and acridine orange staining. When we analyzed HS-1200-treated OSCC cells for the presence of biochemical markers, we observed that this treatment directly affects the conversion of LC-3II, degradation of p62/SQSTM1 and full-length beclin-1, clea-vage of ATG5-12 and the activation of caspase. An autop-hagy inhibitor suppressed HS-1200-induced cell death in OSCCs, confirming that autophagy acts as a pro-death signal in these cells. Furthermore, HS-1200 shows anticancer acti-vity against OSCCs via both autophagy and apoptosis. Our current findings suggest that HS-1200 may potentially cont-ribute to oral cancer treatment and thus provide useful infor-mation for the future development of a new therapeutic agent.

Bcl-2 protects tumor cells from the apoptotic effects of various anti-neoplastic agents. Increased expression of Bcl-2 has been associated with a poor response to chemotherapy in various malignancies, including leukemia. Hence, bypassing the resistance conferred by anti-apoptotic factors such as Bcl-2 represents an attractive therapeutic strategy against cancer cells, including leukemic cells. This study was undertaken to examine whether the anticancer drug, cisplatin and the synthetic chenodeoxycholic acid (CDCA) derivative, HS-1200 show anti-tumor activity in U937 and U937/Bcl-2 cells. Viability assays revealed that HS-1200 overcomes the resistance conferred by Bcl-2 in human leukemic U937 cells. Various apoptosis assessment assays further demonstrated that HS-1200 overcomes the resistance conferred by Bcl-2 in human leukemic U937 cells by inducing apoptosis. In addition HS-1200, but not cisplatin, overcomes the anti-apoptotic effects of Bcl-2 in Bcl-2 over-expressing human leukemic cells (U937/Bcl-2 cells). Notably, we observed that the HS-1200-induced formation of mature promyelocytic leukemia (PML) nuclear bodies (NBs) correlates with a suppression of the anti-apoptotic effects of Bcl-2 in human leukemic cells over-expressing this protein (U937/Bcl-2 cells). Furthermore, HS-1200 was found to induce the association between PML and SUMO-1, Daxx, Sp100, p53 or CBP in the aggregated PML-NBs of U937/Bcl-2 cells. Thus, PML protein and the formation of mature PML-NBs could be considered as therapeutic targets that may help to bypass the resistance to apoptosis conferred by Bcl-2. Elucidating the exact mechanism by which PML regulates Bcl-2 will require further work.