Increased Circulating Levels of Galectin Proteins in Patients with Breast, Colon, and Lung Cancer

SIMPLE SUMMARY: Galectins are a family of lectins that function to recognize carbohydrate groups, such as those on glycosylated proteins. Throughout tumor development, changes in the glycosylation patterns of surface proteins occur, often varying as the disease progresses. We show increased circulating levels of certain galectins in a biorepository of samples from patients with breast, colon, and lung cancer. Patterns of overexpression in cancer relative to healthy controls were observed, with galectins-1 and -3 increased in breast, colon, and lung cancer, while the level of galectin-7 was increased in breast and squamous cell lung cancer, and the level of galectin-9 was increased in colon and lung cancer. No noticeable trends in galectin levels were observed between cancer stages. These data suggest that dysregulation of galectins occurs early in oncogenesis. We also identified histologic subsets in lung cancer for which further investigation of galectins may yield useful diagnostic biomarkers. ABSTRACT: Galectins are proteins with high-affinity β-galactoside-binding sites that function in a variety of signaling pathways through interactions with glycoproteins. The known contributions of galectins-1, -3, -7, -8, and -9 to angiogenesis, metastasis, cell division, and evasion of immune destruction led us to investigate the circulating levels of these galectins in cancer patients. This study compares galectin concentrations by enzyme-linked immunosorbent assay (ELISA) from each stage of breast, lung, and colon cancer. Galectins-1 and -7, which share a prototype structure, were found to have statistically significant increases in breast and lung cancer. Of the tandem-repeat galectins, galectin-8 showed no statistically significant change in these cancer types, but galectin-9 was increased in colon and lung cancer. Galectin-3 is the only chimera-type galectin and was increased in all stages of breast, colon, and lung cancer. In conclusion, there were significant differences in the galectin levels in patients with these cancers compared with healthy controls, and galectin levels did not significantly change from stage to stage. These findings suggest that further research on the roles of galectins early in disease pathogenesis may lead to novel indications for galectin inhibitors.