Objective      To investigate the effects and mechanism of Clostridium butyricum (CB)-induced apoptosis in human colon cancer cell line SW-480.       Methods      SW-480 cells were treated with CB at different concentrations of 1.5×10

3

1.5×10

4

1.5×10

5

1.5×10

6

1.5×10

7

and

1.5×10

8

CFU/mL for different time (24

48

72

or 96 h). Cell viability was tested by CCK-8 assay. Cell morphology was examined by electron microscopy. Annexin V-FITC/PI double-staining was performed to detect cell apoptosis. The activities of Caspase-9 and Caspase-3 were measured by Caspase assay kit. The protein expression of Bcl-2 and Bax was detected by Western blotting.       Results      The inhibitory effect of CB on SW-480 cells showed a significant time-dose fashion. CB with the bacterial concentration of 1.5×10

7

and 1.5×10

8

CFU/mL induced typical apoptotic bodies

increased the activities of caspase-9 and caspase-3

and promoted apoptosis in SW-480 cells (

P

0.01). With the increase of bacterial concentration

the expression of apoptotic protein Bax was enhanced and that of the anti-apoptotic protein Bcl-2 was decreased.       Conclusion      CB effectively induces apoptosis of SW-480 cells

which may involve the expression regulation of apoptosis-related genes Bcl-2

Bax

Caspase-9

and Caspase-3.