TGFB1 and cancer: However, although multiple mechanisms exist by which TGFβ1 modulates the tumour microenvironment to promote cancer (Fig. 2; Pickup et al. 2013), we still have a relative paucity of empirical in vivo data firmly establishing those TGFβ1-driven stromal responses that are the direct result of the αv integrin activation of TGFβ.