TGFB1 and cancer: CAFs directly increase the local concentration of TGF-β by expressing it [48], and indirectly by promoting the release of matrix-associated TGF-β through enhanced contractility (see section “CAFs stiffen the matrix, triggering pro-cancer mechanical and biochemical modifications to the tumor microenvironment” and Figure 1), which increases the actual local concentration of TGF-β available.