During the development of oral cancer (OC), cancer-associated fibroblasts (CAFs) create a supporting niche by maintaining a bidirectional crosstalk with cancer cells, mediated by classically secreted factors and nanometer-sized vesicles, called exosomes. Little is known about the molecular alterations in CAFs that determine their unique functional properties and how exosomes contribution to OC progression. To investigate stromal heterogeneity in OCs we isolated and characterized human fibroblasts from resected tumors (CAFs) and adjacent tissue (AFs). We employed shotgun proteomics to identify CAF-associated proteins in total lysate, conditioned media and exosomes. Our comprehensive dataset of 4247 proteins represents a detailed signature of a pro-tumorigenic stroma. Gene ontology enrichment analysis has shown that proteins involved in regulation of cancer cell migration are enriched in the exosomal fraction. To validate our findings we have shown a significant effect of CAF-derived exosomes on OC cells motility, proliferation and the activation of the MAPK pathway. Quantitative proteomics was then applied to highlight differentially expressed proteins in exosomes from CAFs and AFs and generate a short list of proteins specific to the CAF-like state. Significant differences were observed in proteins involved in metabolism, suggesting that metabolic synergy between CAFs and cancer cells could involve exosomal cargo. In summary, integrative proteomics identified a signature of CAF-enriched exosomal proteins involved in pathways mediating tumor-stromal crosstalk. Here, we show that fibroblast-secreted exosomes affect OC cells growth, motility and glucose metabolism. Our data provide a foundation to investigate how the tumor microenvironment affects OC progression.

Learning Objectives:

• Learn how quantitative proteomics is applied to highlight differentially expressed proteins in exosomes from cancer-associated fibroblasts (CAFs) and adjacent tissue (AFs)
• Learn how fibroblast-secreted exosomes affect OC cells growth, motility and glucose metabolism