Expression of a human cell adhesion molecule, MUC18, in prostate cancer cell lines and tissues

BACKGROUND. Over expression of huMUC18, a cell adhesion molecule in the imm unoglobulin gene superfamily, causes a non-metastatic human melanoma cell l ine to become metastatic in a nude mouse system. To determine if MUC18 expr ession correlates with the malignant progression of prostate cancer, we inv estigated differential expression of human MUC18 (huMUC18) in normal prosta te epithelial cells, prostate cancer cell lines, and prostatic normal and c ancer tissues. METHODS. RT-PCR and Western blot analyses were used to analyze the expressi on of MUC18 mRNA and protein in four human prostate cancer cell lines, cult ured primary normal prostate epithelial cells, normal prostate and malignan t prostate tissues. Immunohistochemistry was used to determine the expressi on of MUC18 antigen in prostatic tissues at different stages of malignancy. RESULTS. Human MUC18 mRNA and protein was expressed in three different pros tate cancer cell lines (TSU-PR1, DU145, and PC-3), but not in one prostate cancer cell line (LNCaP.FGC). HuMUC18 protein was also expressed at high le vels in extracts prepared from tissue sample sections containing high grade prostatic intraepithelial neoplasia (PIN), but weakly expressed in extract s prepared from either cultured primary normal prostatic epithelial cells o r the normal prostate gland. Immunohistochemical analysis showed that huMUC 18 was expressed at higher levels in the epithelial cells of high-grade PIN and prostatic carcinomas and in cells of a lymph node metastasis compared to that in normal or benign hyperplastic epithelium (BPH). CONCLUSIONS. We therefore conclude that MUC18 is expressed at higher levels in premalignant and malignant prostatic epithelium, including metastasis. We suggest that overexpression of MUC18 may be a new marker of human prosta te cancer and also implicates its possible role in development and progress ion of prostate cancer. (C) 2001 Wiley-Liss, Inc.