Objective    To investigate the effect of poly (ADP-ribose)polymerase (PARP) expression inhibited by 5-AIQ on the liver metastasis in colorectal carcinoma CT26 cell lines.     Methods    Liver metastasis model of colorectal carcinoma was established by intrasplenic inoculation of colorectal carcinoma CT26 cell in BALB/c mice. Treated by 5-AIQ (100 or 500 μmol/L)

  CT26 cells were inoculated to the spleen of the mice

or the rats were first inoculated of CT26 cells

then treated by  5-AIQ (3 or 10 mg/kg) ip.  The changes spleen primary carcinoma and liver metastasis carcinoma were observed.  The PARP expression in spleen primary carcinoma was detected by Western blotting.     Results    Significant difference was found in the splenic carcinoma size

the number of liver metastatic nodules

the grading of liver metastatic nodules in the 5-AIQ treated group and control group（P0.05）

but no statistical significance was observed in the mice treated with different drug dosages （P0.05）.  The PARP expression of spleen primary carcinoma in 5-AIQ treated groups was lower significantly than that in control group （P0.05）.      Conclusion    5-AIQ can inhibit PARP expression in the CT26 cell lines and the growth of  primary splenic carcinoma and liver metastasis after CT26 cell inoculation in vivo.