Halofuginone enhances the radiation sensitivity of human tumor cell lines

Transforming growth factor beta (TGF-beta) is implicated in radiation-induced fibrosis of normal tissues in patients receiving radiotherapy. Inhibiting the TGF-beta signaling pathway by various means has been shown to reduce radiation-induced fibrosis in pre-clinical studies. The present study evaluated the effects of interfering with the TGF-beta signaling pathway on the radiosensitivity of selected human tumor cell lines using the plant-derived alkaloid, halofuginone. Halofuginone treatment inhibited cell growth, halted cell cycle progression, decreased radiation-induced DNA damage repair, and decreased TGF-beta receptor II protein levels, leading to increased cellular radiosensitization. These data further support the goal of manipulating the TGF-beta pathway to achieve a positive increase in the therapeutic gain in clinical radiotherapy.