ACTA1 and neoplasm: In parallel, SCS of tumor stroma revealed at least three functionally unique populations of CAFs acting within the TME as shown in breast or pancreatic cancers (Kieffer et al. 2020; Elyada et al. 2019): (a) ECM-producing high-α-SMA/low-cytokine (TGF-β-responsive) myofibroblastic CAFs (myCAFs), (b) pro-inflammatory low-α-SMA/high-cytokine (interleukin (IL)-6/IL-11) CAFs (iCAFs), and (c) antigen-presenting CAFs (apCAFs).