ACTA1 and breast cancer: In addition, a previous study reported that there were 2 distinct myofibroblastic (α-SMA+) CAF subtypes in breast cancer: (a) FAP–α-SMA+ myofibroblasts, which mainly contribute to the regulation of the cytoskeleton, and (b) FAP+α-SMA+ myofibroblasts, which possess the ability to attract and retain Tregs (18).