We previously reported the expression of hepatocyte growth factor (HGF), a ligand for c-MET, at the level of mRNA and protein in human prostate tissues. The present study was carried out to evaluate the relationship between c-MET expression and cancer cell proliferation or effect of cancer therapy. The expression both in mRNA and protein levels of c-MET proto-oncogene was determined semi-quantitatively by reverse transcription-competitive polymerase chain reaction (RT-competitive PCR) and Western blot analysis for prostate tissues from 32 Japanese male subjects. In addition, tissue localization of c-MET translation product was examined by immunohistochemistry for corresponding specimens. Although there was significantly higher c-MET protein expression in malignant (prostate cancer treated with/without neoadjuvant endocrine therapy) than in non-malignant prostate tissues (normal prostate and benign prostate hyperplasia; BPH), unexpectedly, c-MET mRNA showed high expression in the non-malignant group. Thus, there was no parallelism between mRNA and protein expressions of c-MET. Endocrine therapy did not alter c-MET mRNA and protein expressions in human prostate cancer. Immunohistochemical localization and expression of c-MET protein was found to be intense in cancer cells and weak in epithelia of normal and hyperplastic prostates. Unconcerted expression of mRNA and protein of c-MET, the reason of which is uninterpretable, is supposed to be one of characteristics of human prostate cancer.

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