Fibrosis of normal tissues often accompanies radiation treatment of cancer. Activation of the transforming growth factor-β (TGF-β) signaling pathway is thought to play a major role in radiation-induced fibrosis and has prompted the development and assessment of low molecular weight inhibitors of the pathway. Previous studies with halofuginone have shown it to inhibit TGF-β signaling in vitro and protect mice from radiation-induced leg contraction (a model for soft tissue fibrosis). The current study confirms these findings for HaCaT cells stimulated with exogenous TGF-β treatment. Reducing the halifuginone treatment from 7 days/week (used previously) to 5 days/week post-radiation exposure provided significant protection against radiation-induced leg contraction in mice 3 and 4 months post-radiation treatment. Halofuginone treatment was shown to attenuate TGF-β signaling molecules taken from irradiated skin including TGF-βRII, pSmad3, Smad7, and TSP1. The latter, TSP1, a co-activator of TGF-β may serve as a suitable biomarker for monitoring the efficacy of halofuginone should it be evaluated in a clinical setting for protection against radiation-induced fibrosis.

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