c-Met expression in primary tumors and their corresponding distant metastases.

c-Met is a receptor tyrosine kinase that has been implicated in the pathogenesis and growth of a wide variety of human malignancies, including CRC, but its role in metastasis is largely unknown. We compared c-Met expression in primary human colorectal carcinomas and distant metastases from the same patients. Formalin-fixed paraffin-embedded tissue samples from 69 colorectal cancer patients were obtained. The protein expression of c-Met was evaluated immunohistochemically using a commercial antibody. The difference in expression between primary tumors and their corresponding distant metastases was analyzed using the Wilcoxon signed-rank test. c-Met expression was statistically significantly lower in the distant metastases compared to their corresponding primary tumors (p<0.001), whereas no difference was found between lymph node metastases and their corresponding primary tumors (p=0.957). The degree of c-Met expression was not related to clinicopathological characteristics such as tumor grade and Dukes' stage at the time of primary tumor diagnosis, or to the location of the distant metastases. We demonstrated that c-Met expression is often reduced in distant metastases compared to their corresponding primary colorectal tumors. Additional studies of c-Met activation and signal transduction will increase our knowledge about the role of c-Met in colorectal cancer metastasis.