The Differentiation of Pancreatic Tumor-Initiating Cells by Vitronectin Can Be Blocked by Cilengitide

Abstract

Pancreatic cancer is a leading cancer type and its molecular pathology is poorly understood. The only potentially curative therapeutic option available is complete surgical resection; however, this is inadequate as most of the patients are diagnosed at an advanced or metastatic stage. Tumor-initiating cells (TICs) constitute a subpopulation of cells within a solid tumor that sustain tumor growth, metastasis, and chemo/radioresistance. Within pancreatic cancer, TICs have been identified based on the expression of specific cell surface markers. We use a sphere formation assay to enrich putative TICs and use human serum as a driver of differentiation. We demonstrate by using specific blocking reagents that we can inhibit the differentiation process and maintain TIC-associated markers and genes. We can induce differentiation of pancreatospheres with the addition of human serum, and we identified vitronectin as an inducer of differentiation. We inhibit differentiation by human serum using an arginine-glycine-aspartate-specific peptide, which is Cilengitide; hence, demonstrating this differentiation is mediated via specific integrin receptors. Overall, our studies further the definition of pancreatic TICs and provide further insight into both the maintenance and differentiation of this lethal population.