GREM1 and cancer: Some of the proteins identified using this strategy include SLIT2, FGF2, PRRX1, which have been mentioned in the context of fibroblast biology37,38, LOXL4, with a role in collagen crosslinking39, and GREM1, COL11A1, LRRC15, all differentially associated with cancer-associated fibroblasts but not quiescent skin fibroblasts40,41 (Fig. 4c, d).