Metallothionein isoform 3 expression in the human prostate and cancer-derived cell lines

BACKGROUND Expression of metallothionein isoform 3 (MT‐3) was initially reported to be confined to neural tissues. However, it was recently demonstrated that MT‐3 is expressed in epithelial cells of the human kidney. This motivated the current examination of the expression of MT‐3 in the human prostate. METHODS Immunohistochemistry (IHC) was used to localize the expression of MT‐3, RT‐PCR to determine the expression of MT‐3 mRNA, and Western blot analysis to determine the level of MT‐3 protein. RESULTS Selected epithelial and stromal cells of the normal human prostate were shown to have low levels of MT‐3 expression. MT‐3 was increased in prostatic intraepithelial neoplasia (PIN) lesions and further increased in a highly variable fashion in prostatic adenocarcinoma. In some adenocarcinomas, MT‐3 expression exceeded that of nerve. Three cell culture models of prostate cancer were also shown to variably express MT‐3. Restriction enzyme analysis confirmed the expression of MT‐3 in the cells and tissues. CONCLUSIONS MT‐3 is expressed in the normal human prostate, and expression is enhanced and highly variable in PIN lesions and primary prostate cancer cells. The variable nature of MT‐3 expression was also noted in commonly utilized prostate cancer cell lines. Prostate 41:196–202, 1999. © 1999 Wiley‐Liss, Inc.