The c-met protein, known as the hepatocyte growth factor (HGF) receptor, is a transmembrane 190 kDa heterodimer having tyrosine kinase activity, and it is encoded by the c-met oncogene, The HGF/c-met signaling pathway has been shown to demonstrate various cellular responses including mitogenic, proliferative, morphogenic and angiogenic activities. Although HGF and c-met are known to be expressed in a variety of organs and they play important roles in signal transduction, studies on its expression and its correlation to the clinicopathological parameters of breast cancer are very rare.

In this study, we examined the c-met mRNA and the comet protein expression by utilizing RT-PCR and immunohistochemical methods for 50 cases of invasive ductal carcinomas (lDCs) and 20 cases of normal breast tissues.

The c-met mRNA amplification was detected in 35 cases of IDCs (70%), but not in the normal tissues. The c-met protein overexpression was detected in 27 cases of IDes (54%) and 2 cases of normal breast tissue (10%). Both the m RNA amplification and protein overexpression rates were significantly higher in tumor than in the normal breast tissue. The c-met mRNA amplification showed a tendency to increase in an invasive cancer and nodal metastasis. The comet protein overexpression was significantly correlated with the well differentiated grade of tumor and it showed a tendency to decrease in the metastatic tumors. The concordance between both the mRNA amplification and protein expressions were not observed.

These results suggest that the HGF/c-met signal pathway may be associated with the development of breast cancer. c-met mRNA amplification may play important roles both in tumor progression and metastasis. c-met protein overexpres-sion may contribute to the morphogenesis of well-differentiated tumor.