ACTA1 and neoplasm: Most mesenchymal cells are tumor-associated fibroblasts (CAFs) expressing α-smooth muscle actin (α-SMA), which can be derived from fibroblasts, smooth muscle cells, endothelial cells, epithelial cells, bone-marrow-derived cells (e.g., mesenchymal stem cells (MSCs)) [133,134], and tumor-associated fibroblasts, and can promote organ fibrosis, tumor cell growth, infiltration, and migration [135].