Thomas Kislinger
University of Toronto, Toronto, Canada

Solid tumours are complex tissues composed of different cell types and non-cellular components such as extracellular matrix, soluble factors, pH, oxygen tension and interstitial pressure. While decades of research have identified key oncogenic signalling pathways and more recently through next-gen sequencing (epi)genetic alterations, current therapeutic strategies are still inefficient in curing most cancers. It has become evident that the highly complex crosstalk within the tumour microenvironment actively modulates tumour growth, metastasis and response to therapy. This intracellular crosstalk is mediated by cell-surface receptors, soluble ligands and extracellular vesicles. In-depth studies of membrane proteins have proven to be difficult because of their low abundance and hydrophobicity. However, recent advances in proteomic technologies make it possible to investigate membrane proteins to an impressive depth. Here, I will present our recent work using in-depth proteomics to obtain novel insights into head and neck cancer. Cell-surface labeling strategies, such as silica-bead coating, have enabled us to interrogate the head and neck cancer surfaceome to an unprecedented depth. Integration of these results with publicly available genomics data enabled us to discover novel, previously unstudied surface markers that could serve as novel drugable targets. Functional data on some surface markers will be presented. Cancer-associated fibroblasts (CAFs) represent the most abundant cell type of the stroma and are key components involved in regulating carcinogenesis. Recently, CAF-secreted exosomes were shown to be important mediators of paracrine signals that promote motility and metastasis in breast cancer. To investigate stromal heterogeneity in OSCCs we isolated matched pairs of human primary fibroblasts from resected tumours (CAFs) and adjacent tissue (AFs) and characterized them according to established CAF markers. Comprehensive proteomics identified a signature of CAF-enriched exosomal proteins potentially involved in pathways mediating tumor-stromal crosstalk. Functional experiments in the context of migration, metabolic coupling and radiation response are in progress.