TGFB1 and neoplasm: TGFβ1 is a well‐known inducer of collagen deposition and promoter of stromal cell differentiation.13 It also regulates the activities of matrix metalloproteinases and is thus critical for ECM remodeling in tumors.14 Treating GL261 tumors with an anti‐TGFβ antibody significant reduced the density and the overall collagen content within the tumor matrix (Figure3a).