BACKGROUND Galectin‐3 is a carbohydrate‐binding protein whose level of expression has been shown to be correlated with metastatic potential in a number of different tumor types. The purpose of this investigation was to examine 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 demonstrated the presence of galectin‐3. Galectin‐3 was not detected in TSU‐pr1 and LNCaP by Western blot analysis. We furthered our studies by examining a series of human prostate tissue samples for expression of galectin‐3. Overall, approximately 60–70% of the normal tissue examined demonstrated heterogenous expression of galectin‐3. In stage II tumors, however, there was a dramatic 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 tumors also demonstrated a decreased expression of galectin‐3, although this downregulation was not as dramatic, with 35% of PIN samples and 52% of tumor tissue expressing galectin‐3 (P < 0.01). CONCLUSIONS These data demonstrate that galectin‐3 is downregulated in prostate cancer. The altered downregulation pattern of galectin‐3 observed between tumor stages suggests different roles for galectin‐3 in the progression of prostate cancer. Prostate 44:118–123, 2000. © 2000 Wiley‐Liss, Inc.

BACKGROUND.Galectin-3 is a carbohydrate-binding protein whose level of expression has been shown to be correlated with metastatic potential in a number of different tumor types. The purpose of this investigation was to examine 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 demonstrated the presence of galectin-3. Galectin-3 was not detected in TSU-pr1 and LNCaP by Western blot analysis. We furthered our studies by examining a series of human prostate tissue samples for expression of galectin-3. Overall, approximately 60-70% of the normal tissue examined demonstrated heterogenous expression of galectin-3. In stage II tumors, however, there was a dramatic 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 tumors also demonstrated a decreased expression of galectin-3, although this downregulation was not as dramatic, with 35% of PIN samples and 52% of tumor tissue expressing galectin-3 (P < 0.01). CONCLUSIONS. These data demonstrate that galectin-3 is downregulated in prostate cancer. The altered downregulation pattern of galectin-3 observed between tumor stages suggests different roles for galectin-3 in the progression of prostate cancer.

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