ACTA1 and neoplasm: Additionally, in mouse lungs with SCC micrometastasis from implanted flank SCCs, activated αSMA+ fibroblasts were coincidental with strong TGFβ1 and p-SMAD3, which were not evident in lungs without micrometastasis in tumor-bearing mice (Figures 8A,B), further suggesting the critical role of TGFβ1 in activating fibroblasts to prepare the metastatic niche.