Abstract: AIM: To study the molecular mechanism of the cell proliferation inhibition and apoptosis induction effects of 5-Fluorouracil (5-Fu) on human colorectal carcinoma cell line Lovo in vitro. METHODS: By means of MTT reduction assay, the effect of 5-Fu on the proliferation of Lovo cells was measured.Morphological changes were observed under the electron and opitical microscopy. Apoptotic cell cycle arrest was detected by Flow Cytometry.The expressions of PCNA, P53 and Bax were determined by immunohistochemical S-P method. RESULTS: 5-Fu could significantly inhibit the proliferation and aggressivity of Lovo cells and the inhibitory effects were dose-and-time-dependent.The action was mainly attribute to cell apoptosis as proved by flow cytometry assay and electron microscopy.The PCNA expressions of cells of experimental groups were lower than those of control group.The expression of apoptosis related gene bax of the experimental groups was significantly enhanced (P<0.01).The expression of P53 was not found in both experimental and control groups. CONCLUSION: 5-fu could significantly inhibit the proliferation and aggressivity of Lovo cells.Activation of apoptosis related gene bax and G₂/M phase arrest were important mechanisms of 5-fu-induced apoptosis.

Key words: 5-Fluorouracil, apoptosis, colorectal colorectal, P53, Bax