Decreased galectin-3 expression in prostate cancer

BACKGROUND. Galectin-3 is a carbohydrate-binding protein whose level of exp ression has been shown to be correlated with metastatic potential in a numb er of different tumor types. The purpose of this investigation was to exami ne galectin-3 expression in several tumorigenic and nontumorigenic prostate cell lines and prostate tissue samples. METHODS. The expression of galectin-3 in cell lines and tissue samples was evaluated by tissue immunohistochemistry and Western blot analysis. RESULTS. Human cell lines PC-3M, PC-3, DU-145, PrEC-1, and MCF10A demonstra ted the presence of galectin-3. Galectin-3 was not detected in TSU-prl and LNCaP by Western blot analysis. We furthered our studies by examining a ser ies of human prostate tissue samples for expression of galectin-3. Overall, approximately 60-70% of the normal tissue examined demonstrated heterogeno us expression of galectin-3. In stage II tumors, however, there was a drama tic decrease in galectin-3 expression in both PIN and tumor sections, with only 10.5% (2/19) of these samples expressing this protein. Stage III tumor s also demonstrated a decreased expression of galectin-3, although this dow nregulation was not as dramatic, with 35% of PIN samples and 52% of tumor t issue expressing galectin-3 (P < 0.01). CONCLUSIONS. These data demonstrate that galectin-3 is downregulated in pro state cancer. The altered downregulation pattern of galectin-3 observed bet ween tumor stages suggests different roles for galectin-3 in the progressio n of prostate cancer. Prostate 44:118-123, 2000. (C) 2000 Wiley-Liss, Inc.