Exploring the Interactive Effect of Pectins from Campomanesia xanthocarpa with Galectin-3

Glioblastoma (GBM) is a fast-growing and aggressive primary brain tumor with an average survival time of 12–18 months. GBM growth and invasion rely on multiple and dynamic signaling events in the tumor microenvironment, in which several glycan-binding proteins act as essential mediators. Among them, galectin-3 (Gal-3) plays a key role in cell–cell and cell–extracellular matrix communication. Gal-3 may be inhibited by complex polysaccharides such as pectins, which might reduce GBM aggressiveness and invasiveness. To identify possible interactive mechanisms involving Gal-3, we have selectively modified the structure of pectins extracted fromCampomanesia xanthocarpa Berg to obtain varied GalA:Ara and Gal:Ara ratios along the polysaccharide backbone. The interactive influence of the fully modified structures as well as the individual monosaccharides was monitored by circular dichroism and X-ray diffraction. The impact of all modified pectins on the T98G and U87MG cell viability and Gal-3 expression was also evaluated. Our results suggest that galactose and galacturonic acid may be partly responsible for the protein structural changes. The pectins induced significant cytotoxicity and reduced Gal-3 expression in vitro, suggesting that biomaterials with a similar Gal:Ara ratio may be employed as adjuvants in GBM therapy.