ACTA1 and cancer: However, changes in fibroblast populations and extracellular matrix structure associated with the tumor process (Mayorca-Guiliani et al, 2017; Affo et al, 2021) may influence cancer immunity by following organ-specific rules, as suggested by the immune suppressive effect of genetic deletion of type I collagen in α-Sma + myofibroblasts described by Chen and colleagues in mouse models of pancreatic cancer (Chen et al, 2021).