Expression of collagen genes (e.g., COL1A1 and COL1A2) is induced in tumor stromal cells such as cancer-associated fibroblasts (CAFs) and in tumor cells by transforming growth factor beta 1 (TGFβ1)-mediated phosphorylated SMAD3 (pSMAD3) signaling. This evidence concerns the gene TGFB1 and cancer.