Objective To investigate the expression and distribution of tight junction proteins in colorectal carcinoma.Methods Real time reverse transcription PCR, Western blot and immunohistochemistry were used to check the expression of claudins(CL-1 to-4),occludin(OC),zona occludens proteins(ZO-1 and ZO-2)in 35 colorectal carcinomas and matched adjacent normal tissues.Results The expression of claudin-1 and claudin-2 in cancer tissues was 0.97 and 0.34 respectively.Either of them was higher than that in normal tissues.Compared with adjacent normal tissues,it increased by 26.3-and 30.4-fold respectively at the mRNA level.Immunohistochemistry analysis showed different distribution patterns for occludin,ZO2,claudin 1,claudin 2 and claudin 4 between the cancer and normal tissues.Normal colonic epithelium exhibited n cytoplasmic staining for claudin-1,whereas the strong plasma membrane staining was presented in carcinoma cells. The claudin-2 proteins were detected mainly under the epithehal cells and presented spot granular staining in normal epithelium,whereas much more spot granular staining existed in the whole epithelial cells of carcinomas.Conclusions There was close association between abnormal expression and distilbution of tight junction proteins and colorectal cancer.And these proteins may be good candidates for the diagnoses and therapy for colorectal cancer.