[Synergistic effect of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and doxorubicin on human colon cancer SW480 cells].

BACKGROUND & OBJECTIVE: Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) could selectively kill tumor cells. This effect could be improved using some therapeutic agents. The aim of this study was to determine the sensitivity of SW480 cells to TRAIL, the interaction of TRAIL and doxorubicin against colon cancer cells and its possible mechanism.

METHODS

SW480 cells were cultured with RPMI1640 medium in regular condition. Cytotoxicity was examined by MTT assay. Cell apoptosis was detected by flow cytometry. The subcellular morphology was observed by electron microscopy. The changes of p53 and Bcl-2 in protein level were quantified by Western blot analysis.

RESULTS

(1)SW480 cells were not sensitive to TRAIL,and the IC(50) was more than 1,000 ng/ml. 100 ng/ml of TRAIL could only kill 7.8% of the cells. (2)Concentration-dependent cytotoxicity of doxorubicin was exhibited in SW480 cells, with IC(50) of 65 micromol/L. 0.86 micromol/L of doxorubicin did not affect cell growth. (3)The combination of TRAIL and doxorubicin exhibited synergistic effect on SW480 cells. Subtoxic TRAIL(100 ng/ml)and subtoxic doxorubicin(0.86 micromol/L) killed 80% of the cells. The synergistic cytotoxicity was large partly attributed to cell apoptosis, which was proved by simultaneous flow cytometry assay and electron microscopy. However, TRAIL and doxorubicin did not affect p53 and Bcl-2 protein expression.

CONCLUSION

TRAIL in combination with subtoxic doxorubicin could effectively kill SW480 cells, which did not respond to TRAIL alone. Apoptosis was the main manner of this killing effect, and the apoptotic pathway induced by TRAIL and doxorubicin did not involved in the change of p53 and Bcl-2 protein expression.