Hypoxia contributes to galectin-3 expression in renal carcinoma cells

Galectin-3 is supposed as a prognostic factor and therapeutic target for many cancers. In a previous study, we have reported that galectin-3 was related to the development of renal cell cancer and served a therapeutic target for renal cell carcinoma (RCC). However, the mechanisms underlying the regulation of galectin-3 in RCC are still not known. In this study, we detected the expression of galectin-3 and hypoxia-inducible factor 1 (HIF-1) alpha in RCC using immunohistochemistry, and then conducted in vitro experiments to verify the regulation of galectin-3 by hypoxia in RCC. Our results showed that the expression of galectin-3 and HIF-1 alpha were remarkably high in RCC tissues compared with those in the paracancerous tissues. Interestingly, hypoxia significantly promoted cytoplasmic and nuclear HIF-1 alpha and galectin-3 expression in renal carcinoma cell lines, but not in renal tubular epithelial cell (HK-2). Renal carcinoma cell line (Caki-1), but not HK-2 showed significant increase of luciferase reporter activity of galectin-3 encoding the fragment from the site of -845 to +50 upon hypoxic insult. Moreover, HIF-1 alpha overexpression vector promoted, while HIF-1 alpha silencing vector reduced luciferase reporter activity of galectin-3 in Caki-1 and HK-2 cells in both normal and hypoxia conditions. A direct interaction of HIF-1 alpha with Gal-3 promoter was also verified by electrophoretic mobility shift assay and chromatin immunoprecipitation. Together, our data indicated that hypoxia was critical for galectin-3 expression in RCC in a HIF-1 alpha-dependent manner.

Automated summary

In renal cell carcinoma, the expression of galectin-3 and HIF-1α is significantly elevated, and hypoxia can further promote their expression. HIF-1α plays a critical role in the regulation of galectin-3 in RCC.