Proteomic Assessment of the Murine Mammary Gland Extracellular Matrix

The extracellular matrix (ECM) is a molecular scaffold mainly comprising fibrous proteins, glycoproteins, proteoglycans, and polysaccharides. Aside from acting as a structural support, the ECM's composition dictates cell-matrix interactions at the biochemical and biophysical level. In the context of cancer, the ECM is a critical component of the tumor microenvironment (TME) and dysregulation of its deposition and remodelling has been shown to promote tumor onset, progression, and metastasis. Here, we describe a robust protocol for the isolation and subsequent proteomic analysis of the ECM of murine mammary glands, for downstream assays studying the role of the ECM in breast cancer. The protocol yields sufficient protein amounts to enable not only the global quantitation of protein expression but furthermore the enrichment and quantitative analysis of post-translationally modified peptides to study aberrant signalling.