TGF-/βSmads Signaling Affects Radiation Response and Prolongs Survival by Regulating DNA Repair Genes in Malignant Glioma

To understand the molecular mechanism underlying the causal relationship between aberrant upregulation of transforming growth factor beta (TGF-) and radio-resistance in glioma. The mouse glioma cell GL261 was irradiated, and relative expression of TGF-/Smad signaling genes was determined by real-time PCR and western blotting. The DNA repair response on exogenous TGF- or LY2109761 was evaluated by quantification of diverse genes by real-time PCR and western blotting. Xenograft mice were employed for in vivo investigation to assess the response to irradiation and LY2109761 either alone or in combination. The expression of DNA repair genes was further determined in the xenograft tumor. The TGF-/Smad signaling pathway was activated by radiation in the GL261 cell line. The exogenous complement of TGF- significantly stimulated DNA repair response. Administration of LY2109761 suppressed DNA repair genes. Simultaneous treatment with LY2109761 abrogated the upregulation of DNA repair genes in GL261. In the xenograft tumor model, LY2109761 synergistically improved the therapeutic effect of radiation via improvement of sensitivity. Our data suggested that LY2109761 treatment re-sensitized glioma to radiation via antagonizing TGF-/Smad-induced DNA repair.