Inhibition of TGF-β signaling with halofuginone can enhance the antitumor effect of irradiation in Lewis lung cancer

Abstract

Purpose: It was reported that halofuginone has inhibitory effects on transforming growth factor-beta (TGF-β) signaling pathway. The study was aimed to: 1) evaluate the antitumor effects of halofuginone in combination with radiation therapy; and 2) preliminarily explore the possible mechanisms associated with these effects. Materials and methods: Lewis lung cancer (LLC) cell lines and xenograft model mice randomly received ionizing radiation, halofuginone, or combination treatment. The changes associated with antitumor effect of halofuginone, including hepatic and pulmonary metastases and survival, were observed. The migratory and invasive capabilities of LLC cells were investigated by using scratch assay and transwell chamber assay. The expression level of TGF-β and its activation were assessed with enzyme-linked immunosorbent assay, immunohistochemistry, and Western blotting. Chi-square test and survival analysis were performed for statistical analysis. P<0.05 was regarded as statistically significant. Unless otherwise specified, data were expressed as mean ± standard deviation (x̅ ± s). Results: After irradiation, the migratory and invasive capabilities of LLC cells were strengthened, and the TGF-β pathway was activated. The addition of halofuginone can significantly inhibit the migratory and invasive trend induced by irradiation, and the TGF-β pathway was also inhibited. In animal xenograft model, the addition of halofuginone to irradiation inhibited the growth of subcutaneously implanted xenografts, reduced hepatic and pulmonary metastases, and improved survival of the mice. The effect was accompanied by a decrease in TGF-β levels. In addition, halofuginone inhibited type I collagen expression and angiopoiesis. Conclusion: Halofuginone treatment not only produces significant radiation-sensitizing effects but also inhibits hepatic and pulmonary metastases. The underlying mechanisms of these phenomena warrant additional studies.