COL1A1 and cancer: Given a recent report that fibroblast-derived ColI (containing Col1a1/Col1a2 heterotrimers) is distinct from PDAC cancer cell–derived ColI (containing Col1a1 homotrimers that possess oncogenic properties) (60), we then asked whether the differential immunomodulatory capacity of CAF-derived versus UPS cell–derived ECM resulted from the production of heterotrimeric versus homotrimeric ColI, respectively.