Objective     To observe the effects of oxaliplatin on proliferation in human colon carcinoma cell lines HT29 in vitro and investigate the mechanism.      Methods     The inhibition of proliferation in HT29 cell was estimated by MTT test. Morphologic changes were observed under electron microscope. Distribution of cell cycle and apoptosis was analyzed by using flow cytometry. The expression of cell cycle protein and apoptosis-associated gene protein was detected with immunohistochemical technique.      Results     Oxaliplatin could inhibit the proliferation of HT29 cells and the inhibition depended on the exposure dose and time. When treated with ox

aliplatin for 72 h

apoptotic cells and apoptotic body could be found under the transmission electronic microscope. The analysis of cell cycle indicated that oxaliplatin blocked cells at G

2

/M phases and cells of G

0

/G

1

and S phase reduced. The expression of Fas and Bax was up-regulated; Bcl-2

CyclinB

1

  and PCNA down-regulated.      Conclusion      Oxaliplatin could inhibit proliferation of the colon carcinoma cell lines HT29. The mechanism of inhibited proliferation is related to the induced apoptosis and the blocked cells.