Fig. 7

A proposed model to illustrate the reciprocal positive feedback loop between GrB and TGF-β1 in CRC cells. Cancer cells express and secrete both TGF-β1 and GrB. Extracellular GrB induces the release of active TGF-β1 by ECM (Ref. 56), leading to increase TGF-β1 levels in the tumor microenvironment. High TGF-β1 levels upmodulate tumor production of GrB (Refs. 52, 55), which further increases the extracellular level of TGF-β1