Proteomic atlas of peritoneal tissue: sampling the “soil” for the metastatic seed in carcinomatosis

Peritoneal carcinomatosis (PC) occurs when the parietal and visceral peritoneum are involved with multifocal metastatic tumors, most commonly arising from abdominopelvic organ sites. The peritoneal cavity and its lining of mesothelial tissue serves as the ‘soil’ onto which metastatic cancer cells attach and grow during PC. In this study, we explored the use of liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based proteomic assays on fresh frozen and formalin-fixed/paraffin-embedded (FFPE) peritoneal tissue samples, analyzed using an ultra-high resolution timsTOF mass spectrometer. The yield of unique proteins in peritoneal lining tissue was lower than that observed from similar studies of visceral organ tissue. Extracellular matrix proteins were present in high abundance, and may be contributory to cancer cell attachment and invasion in PC. We further quantified key signal transduction and metabolic proteins known to contribute to cancer progression, along with defined tumor suppressor and oncoproteins. Our findings represent a baseline catalog of the proteomic composition of the peritoneal lining, as a comparison dataset for future studies focused on alterations in pathologic states such as PC.