The c-Met protein, known as the hepatocyte growth factor (HGF) receptor, is a transmembrane 190 kDa heterodimer with tyrosine kinase activity, encoded by the c-met oncogene. The HGF/c-Met signalling 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 play important roles in signal transduction, studies of its expression correlated with clinico-pathological parameters in breast cancer are rare.

In this study we examined c-met mRNA and c-Met protein expression by means of RT-PCR and immunohistochemical methods in 50 cases of invasive ductal carcinomas and 20 normal breast tissue samples.

c-met mRNA amplification was detected in 35 cases (70%), but not in normal tissues. c-Met protein overexpression was detected in 27 cases (54%) and two cases (10%), respectively. Both mRNA amplification and protein overexpression rates were significantly higher in tumor than in normal tissue. The c-met mRNA amplification exhibited an increased tendency according to tumor invasiveness and nodal metastasis. The c-Met protein overexpression was significantly correlated with well differentiated grade and showed decreased tendency in metastatic tumor. The concordance between both mRNA amplification and protein expressions were not recognized.

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