OBJECTIVE: To investigate whether TRAIL can synergize with adriamycin (ADM) to kill osteosarcoma cells (U2OS) in vitro, and its possible molecular mechanism. METHODS: MTT was used to evaluate the cytotoxic effect of TRAIL and ADM either used alone or in combination at 24 hours after treatment to U20S cells. Cell apoptosis and its proportion were detected by flow cytometry assay. Acridine orange fluorescence microscopy and transmission electron microscopy were used to examine cellular and ultrastructural changes of apoptosis. The changes of cFLIP in mRNA and protein level were semi-quantified by RT-PCR and Western blot analysis. RESULTS: (1) U2OS cells were not sensitive to TRAIL (IC(50) > 1 mg/L); the cells were relatively more responsive to ADM in an apparent dose-effect fashion. (2) The combination of TRAIL and ADM presented a synergistic effect on U2OS cells. Subtoxic concentration of TRAIL (0.1 mg/L) combined with subtoxic concentration of ADM (1.0 micromol/l) killed (49.54 +/- 2.79)% of U2OS cells. (3) The cytotoxicity was mainly attributed to cell apoptosis as demonstrated by flow cytometry assay, fluorescence microscopy and electron microscopy. CONCLUSION: Subtoxic dose of TRAIL can effectively kill osteosarcoma cells (U2OS) in combination with subtoxic dose of ADM, but not effective when used alone. Apoptosis is the main mechanism of this killing effect induced by combination of TRAIL and ADM. Down regulation of cFLIP at mRNA and protein level is involved in this apoptosis pathway.
OBJECTIVE: To investigate whether TRAIL can synergize with adriamycin (ADM) to kill osteosarcoma cells (U2OS) in vitro, and its possible molecular mechanism. METHODS:MTT was used to evaluate the cytotoxic effect of TRAIL and ADM either used alone or in combination at 24 hours after treatment to U20S cells. Cell apoptosis and its proportion were detected by flow cytometry assay. Acridine orange fluorescence microscopy and transmission electron microscopy were used to examine cellular and ultrastructural changes of apoptosis. The changes of cFLIP in mRNA and protein level were semi-quantified by RT-PCR and Western blot analysis. RESULTS: (1) U2OS cells were not sensitive to TRAIL (IC(50) > 1 mg/L); the cells were relatively more responsive to ADM in an apparent dose-effect fashion. (2) The combination of TRAIL and ADM presented a synergistic effect on U2OS cells. Subtoxic concentration of TRAIL (0.1 mg/L) combined with subtoxic concentration of ADM (1.0 micromol/l) killed (49.54 +/- 2.79)% of U2OS cells. (3) The cytotoxicity was mainly attributed to cell apoptosis as demonstrated by flow cytometry assay, fluorescence microscopy and electron microscopy. CONCLUSION: Subtoxic dose of TRAIL can effectively kill osteosarcoma cells (U2OS) in combination with subtoxic dose of ADM, but not effective when used alone. Apoptosis is the main mechanism of this killing effect induced by combination of TRAIL and ADM. Down regulation of cFLIP at mRNA and protein level is involved in this apoptosis pathway.