Breaking the mucin barrier: a new affinity chromatography-mass spectrometry approach to unveil potential cell markers and pathways altered in Pseudomyxoma peritonei

Pseudomyxoma peritonei (PMP) is a rare, malignant tumour with unknown underlying molecular mechanisms characterised by a progressive accumulation of mucin and secreting tumour cells within the abdomen and pelvis. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is the only therapeutic option currently available for its treatment and recurrence with a fatal outcome is common despite its use. The lack of information available about the molecular mechanisms underlying this condition is mainly due to the physicochemical characteristics of mucin, whose main purpose is to protect epithelial cells, which makes it inaccessible to a proteomic analysis. In this paper we describe the first protocol available to break this barrier and offer a chance to isolate proteins from soft and hard mucinous tumour tissues. This approach is based on the depletion of glycoproteins, immunoglobins, and albumins by affinity liquid chromatography, which makes the mucin available for label free quantification by mass spectrometry. As in the case of non mucinous tissues, our protocol yields a mix of total proteins and has allowed us to establish the first protein profile in mucinous tumours. In addition, our protein-protein interaction networks and pathway enrichment analyses revealed MUC13 and TFF1 as potential therapeutic targets in this disease.