Intermediate cells in normal and malignant prostate epithelium express c‐MET: Implications for prostate cancer invasion

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Abstract
BACKGROUND Analysis of keratin (K) expression discriminates luminal (K18) and intermediate (K5/18) cells in prostate carcinoma, while basal (K5/14) cells are absent. Intermediate cells have been proposed as targets of malignant transformation in prostate cancer and precursors of androgen-independent tumor progression. We demonstrate localization of hepatocyte growth factor (HGF) receptor c-MET in intermediate cells in both normal and malignant prostate epithelium. METHODS Receptor localization was analyzed using triple staining for c-MET, K5, K14, and K18. The percentage of strongly c-MET positive cells was determined in 15 prostate cancer patients undergoing androgen-deprivation and 14 patients without neo-adjuvant treatment. Effects of HGF were investigated on prostate cancer cell line DU145. RESULTS c-MET expression in non-malignant epithelium was strong in intermediate cells absent in differentiated cells, and heterogeneous in basal cells. In prostate cancer, intermediate cells displayed high c-MET levels coupled with mild expression in differentiated cells. During androgen-deprivation, 7.6% of tumor cells revealed high c-MET expression compared to 1.7% without treatment (P = 0.02). Matrigel penetration of DU145 was 8.2 ± 1.7 mm2 after HGF stimulation compared to 3.6 ± 2.4 mm2 in controls (P < 0.02). CONCLUSIONS Intermediate cells in normal and malignant prostate epithelium express high c-MET levels, indicating that they are prone to stromal invasion in prostate carcinoma. Prostate 51: 98–107, 2002.