Cancer processes probed by multivalency: investigations with galectin-3 and lactose functionalized dendrimers

Abstract

Cancer has become a prevalent disease that is the second leading cause of death in the United States. Various cancers have been identified as either over or under expressing a sugar binding protein: galectin-3. The target of this research is to investigate cancerous events that are impacted by galectin-3 and mediate these events through the use of a multivalent binding partner to galectin-3. This binding partner is lactose functionalized PAMAM dendrimers. Apoptosis has been reported as another phenomenon that galectin-3 impacts. By using a reporter assay, viability, cytotoxicity and apoptosis were observed for cancer cell line A549 in the presence of exogenously added galectin-3 and/or lactose functionalized dendrimers. It was found that exogenous galectin-3 and glycodendrimers did not have any significant impact on these cell viability tests. Therefore, glycodendrimers can be used to probe multivalent effects without threat of toxicity. Metastasis was investigated through a modified in vitro scratch assay. By monitoring the migration of cancer cells, it was found that exogenously added galectin-3 retarded cell migration. When glycodendrimers were included, migration was partially restored. This revealed the implications of exogenous galectin-3 regarding the metastatic potential of carcinomas. When the implications of the domains of galectin-3 were investigated, it was found that the truncated galectin-3 containing only the carbohydrate recognition domain (CRD) was unable to replicate the same effects observed in full length galectin-3. Immunofluorescence microscopy was used to locate the multivalent binding partner and galectin-3 in the assay. While endocytosis of galectin-3 was observed, no colocalization with the multivalent binding partner was observed intracellularly, supporting the hypothesis of an extracellular interaction mediating the results. Multivalent interactions between glycodendrimers and galectin-3 impacted cellular migration. Angiogenesis revealed that exogenous galectin-3 induced neovascularization. Glycodendrimers impacted galectin-3 mediated angiogenesis. Glycodendrimers alone could elicit effects either enhancing or negating angiogenesis depending on the dendrimer generation. Fluorescent tags revealed glycodendrimer accumulation on or inside the cells and galectin-3 on the surface of cell groups. Overall, these studies show that glycodendrimers can interact multivalently and affect cellular processes.