OBJECTIVETo investigate the expression of cathepsin B (CatB) in colorectal cancer tissues and serum levels of CatB in patients with colorectal carcinoma and to study the association of CatB expression with lymph node and li ver metastasis.

METHODSImmunohistochemistry was used to detect CatB expression in tissues, and enzyme linked immunosorbent assay was applied to test CatB levels in peripheral vein blood in 83 patients with colorectal cancer.

RESULTSThe expression rates of CatB in primary lesions, normal colon mucosa, lymph node metastases and hepatic metastases were 56.6%, 31.3%, 88.4%, 85.0% respectively. The positive rates of CatB in primary lesions, hepatic and lymph node metastases were higher than that in normal mucosa (chi (2)=45.6124, P< 0.01). The CatB expression rates in lymph node and hepatic metastases were higher than that in primary lesions chi (2)=11.5982, 4.3747, P< 0.05). The positive rate of CatB was higher in Dukes C and D tumors than that in Dukes A and B tumors (chi (2)=18.8871, 25.1650, P< 0.01), higher in poorly differentiated and mucous adenocarcinomas than that in well-moderately differentiated adenocarcinomas chi (2)=14.2338, P< 0.05). The mean serum level of CatB in 83 patients with colorectal cancer was (5.9+/- 2.9) ng/ml, higher than (2.3+/- 1.1) ng/ml in the controls of 30 healthy volunteers (t=6.6975, P< 0.01). The serum level of CatB in the patients with Dukes C, D stages were higher than that with Dukes A, B stages.

CONCLUSIONSEnhanced expression of CatB in colorectal cancer tissues is associated with tumor infiltration and metastasis. Monitoring serum CatB level in patients with colorectal cancer is important in the prediction and diagnosis of lymph node and hepatic metastasis,and valuable for evaluation of the therapeutic effect.