The extracellular matrix (ECM) is a complex meshwork of cross-linked proteins 
providing both biophysical and biochemical cues that are important regulators of 
cell proliferation, survival, differentiation, and migration. We present here a 
proteomic strategy developed to characterize the in vivo ECM composition of 
normal tissues and tumors using enrichment of protein extracts for ECM 
components and subsequent analysis by mass spectrometry. In parallel, we have 
developed a bioinformatic approach to predict the in silico "matrisome" defined 
as the ensemble of ECM proteins and associated factors. We report the 
characterization of the extracellular matrices of murine lung and colon, each 
comprising more than 100 ECM proteins and each presenting a characteristic 
signature. Moreover, using human tumor xenografts in mice, we show that both 
tumor cells and stromal cells contribute to the production of the tumor matrix 
and that tumors of differing metastatic potential differ in both the tumor- and 
the stroma-derived ECM components. The strategy we describe and illustrate here 
can be broadly applied and, to facilitate application of these methods by 
others, we provide resources including laboratory protocols, inventories of ECM 
domains and proteins, and instructions for bioinformatically deriving the human 
and mouse matrisome.