Galectin‐4 functions as a tumor suppressor of human colorectal cancer

Abstract

Development of colorectal cancer (CRC) involves a series of genetic alterations with altered expression of proteins and cell signaling pathways. Here, we identified that galectin‐4 (gal‐4), a marker of differentiation, was down‐regulated in CRC. The goal of this work was to determine the function of gal‐4 in CRC. Toward this goal, the human colon biopsies and tissue microarrays containing a gradient of pathology were analyzed for gal‐4 expression by immunohistochemistry. Cell proliferation, migration, motility, forced expression, knockdown, cell cycle and apoptosis assays were used to characterize gal‐4 function. Immunohistochemistry identified that gal‐4 expression was significantly down‐regulated in adenomas and was essentially absent in invasive carcinomas. Forced expression of gal‐4 in gal‐4 −ve cells induced cell cycle arrest and retarded cell migration and motility. Further, gal‐4 sensitized the cells to camptothecin‐induced apoptosis. Gal‐4 knockdown resulted in increased cell proliferation, migration and motility. Gal‐4 was found to be associated with Wnt signaling proteins. Finally, gal‐4 expression led to down‐regulation of Wnt signaling target genes. This study demonstrates that loss of gal‐4 is a common and specific event in CRC. This study also shows that gal‐4 exhibits tumor suppressive effects in CRC cells in vitro . Through its ability to interact with and down‐regulate the functions of Wnt signaling pathway, gal‐4 reveals a new dimension in the control of the Wnt signaling pathway. Thus, gal‐4 may prove to be an important molecule in understanding the biology of CRC.