A Novel Approach For Monitoring Tgf-Beta Signaling In Vivo In Colon Cancer

The TGF-beta receptor kinase inhibitors (TRKI) have been reported to inhibit tumorigenicity in colon cancer. However, there is no direct evidence showing that these inhibitors function through inhibiting the TGF-beta- mediated tumor-promoting effects in vivo. We established a TGF-beta inducible reporter system by inserting a luciferase reporter gene to the vector downstream of TGF-beta-inducible promoter elements, and transfected it into colon cancer cell lines. TRKIs SB431542 and LY2109761 were used to treat TGF-beta inducible cells in vitro and in vivo. The luciferase activity was induced 5.24-fold by TGF-beta in CT26 inducible cells, while it was marginally changed in MC38 inducible cells lacking Smad4 expression. Temporary treatment of mice with SB431542 inhibited the TGF-beta pathway and TGF-beta induced bioluminescence activity in vivo. Long-term treatment with LY2109761 inhibited tumorigenicity and liver metastasis in vivo in concomitant with reduced luciferase activity in the tumor. In this study, we established a model to monitor the TGF-beta pathway in vivo and to compare the antitumor effects of TRKIs. Based on this novel experimental tool, we provided direct evidences that LY2109761 inhibits tumorigenicity and liver metastasis by blocking the pro- oncogenic functions of TGF-beta in vivo.