Abstract: Objective To detect the expression of leucine-rich repeats and immunoglobulin like domain protein 1 (Lrig1) in human colon cancer tissues and cell lines,normal colon tissue,and colonic epithelium and to compare the expressions in cancer and normal tissures.Methods We collected 70 colon adenocarcinoma tissue samples and 36 normal colon tissues adjacent to the tumors from 70 inpatients with surgery but without radiotherapy or chemotherapy before the operation.We used immunohistochemical method to detect Lrig1 expression in colon cancer tissues and adjacent normal tissues;we also used reverse transcriptase-PCR (RT-PCR) and Western blot to detect Lrig1 mRNA and protein in colonic epithelial cells;then the differences in the expressions in different tissues were analyzed.Results The expression of Lrig1 in colon cancer tissues (31.43%,22/70) was obviously lower than that (86.11%,31/36) in normal tissues adjacent to the tumor.The expression of Lrig1 in colon cancer tissues was correlated with the differentiation and staging of tumors and the status of lymph node metastasis (P<0.05 for all) but not related to tumor size,gender and age of the patients (P>0.05 for all).The results of RT-PCR illustrated that the relative expression of Lrig1 mRNA in colon cancer cells (SW480 and HCT116) was significantly lower than in normal colon epithelial cells (NCM460) (0.65±0.09 and 0.47±0.6 vs.0.95±0.12) (both P<0.05);the relative expressions of Lrig1 protein in the SW480 and HCT116 cells (0.71±0.06 and 0.54±0.05) were also significantly lower than that in the NCM460 cells (both P<0.05) based on the results of Western blot test.Conclusion Lrig1 may play the role of a cancer suppressor gene in the occurrence and development of colon cancer.