The role of TGFBI (βig-H3) in gastrointestinal tract tumorigenesis.

BACKGROUND: TGFβ-induced (TGFBI/βig-H3) is a protein inducible by TGFβ1 and secreted by many types of cells. It binds to collagen, forms part of the extracellular matrix (ECM), and interacts with integrins on cell surfaces. In this study, we investigated the role of TGFBI in tumorigenesis and the underlying mechanisms.

METHODS: Patient serum TGFBI levels were determined by ELISA. TGFBI transgenic and gene knockout mice and TGFBI-overexpressing liver cells were used for mechanistic studies.

RESULTS: We demonstrated that patients with cholangiocarcinomas, hepatic carcinomas or gastric carcinomas presented significantly elevated serum TGFBI levels, and the excess TGFBI was derived from the tumor masses. TGFBI overexpression in mice resulted in increased incidence of spontaneous tumors and N,N-diethylnitrosamine (DEN)-induced liver tumor nodules, compared to that in wild type (WT) mice, while TGFBI knockout mice were comparable to WT controls in these 2 aspects. TGFBI promoted the survival of Aml-12 liver cells with DNA damage after irradiation, and augmented their post-irradiation proliferation. It activated the FAK/AKT/AKT1S1/PRS6/EIF4EBP pathway, which is known to modulate cell survival and proliferation.

CONCLUSIONS: Our data suggest that TGFBI functions as a promoter of certain gastrointestinal tract cancers. It provides a survival advantage to cells with DNA damage. Over a long time span, this advantage could translate into increased tumor risks.