Oncogenic and Non-Malignant Pancreatic Exosome Cargo Reveal Distinct Expression of Oncogenic and Prognostic Factors Involved in Tumor Invasion and Metastasis

Abstract

Exosomes are small extracellular membrane vesicles important in intercellular communication, with their oncogenic cargo attributed to tumor progression and pre-metastatic niche formation. To gain an insight into key differences in oncogenic composition of exosomes, human non-malignant epithelial and pancreatic cancer cell models and purified and characterized resultant exosome populations are utilized. Proteomic analysis reveals the selective enrichment of known exosome markers and signaling proteins in comparison to parental cells. Importantly, valuable insights into oncogenic exosomes (362 unique proteins in comparison to non-malignant exosomes) of key metastatic regulatory factors and signaling molecules fundamental to pancreatic cancer progression (KRAS, CD44, EGFR) are provided. It is reported that oncogenic exosomes contain factors known to regulate the pre-metastatic niche (S100A4, F3, ITGβ5, ANXA1), clinically-relevant proteins which correlate with poor prognosis (CLDN1, MUC1) as well as protein networks involved in various cancer hallmarks including proliferation (CLU, CAV1), invasion (PODXL, ITGA3), metastasis (LAMP1, ST14) and immune surveillance escape (B2M). The presence of these factors in oncogenic exosomes offers an understanding of select differences in exosome composition during tumorigenesis, potential components as prognostic and diagnostic biomarkers in pancreatic cancer, and highlights the role of exosomes in mediating crosstalk between tumor and stromal cells.

Keywords: exosomes; metastasis; pancreatic cancer; pre-metastatic niche; proteomics.