Role of galectin-1 in urinary bladder urothelial carcinoma cell invasion through the JNK pathway

Human galectin-1 is a member of the galectin family, proteins with conserved carbohydrate-recognition domains that bind galactoside. Galectin-1 is highly expressed in various tumors and participates in various oncogenic processes. However, detailed descriptions of the function of galectin-1 in urinary bladder urothelial carcinoma have not been reported. Our previous cohort investigation showed that galectin-1 is associated with tumor invasiveness and is a possible independent prognostic marker of urinary bladder urothelial carcinoma. The present study aimed to clarify the relevance of galectin-1 expression level to tumor progression and invasion. In order to decipher a mechanism for the contribution of galectin-1 to the malignant behavior of urinary bladder urothelial carcinoma, two bladder cancer cell lines (T24 and J82) were established with knockdown of galectin-1 expression by shRNA. Bladder cancer cells with LGALS1 gene silencing showed reduced cell proliferation, lower invasive capability, and lower clonogenicity. Extensive signaling pathway studies indicated that galectin-1 participated in bladder cancer cell invasion by mediating the activity of MMP9 through the Ras-Rac1-MEKK4-JNK-AP1 signaling pathway. Our functional analyses of galectin-1 in urinary bladder urothelial carcinoma provided novel insights into the critical role of galectin-1 in tumor progression and invasion. These results revealed that silencing the galectin-1-mediated MAPK signaling pathway presented a novel strategy for bladder cancer therapy.