Halofuginone mediated protection against radiation-induced leg contracture.

Fibrosis of normal tissues often accompanies radiation treatment of cancer. Activation of the transforming growth factor-beta (TGF-beta) 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-beta 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-beta 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-beta signaling molecules taken from irradiated skin including TGF-betaRII, pSmad3, Smad7, and TSP1. The latter, TSP1, a co-activator of TGF-beta 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.