α-Lipoic acid prevents the ionizing radiation-induced epithelial-mesenchymal transition and enhances the radiosensitivity in breast cancer cells

Radiotherapy is routinely used in the treatment of breast cancer. However, its efficiency is often limited by the development of radioresistance and metastasis. The cancer cells surviving irradiation show epithelial-mesenchymal transition (EMT) along with increased migration, invasion and metastasis. In this study, we have evaluated the role of α-lipoic acid in preventing the radiation-induced EMT and in sensitizing the breast cancer cells to radiation. The breast cancer cell lines, MCF-7 and MDA-MB-231 were pretreated with lipoic acid, irradiated and the changes associated with cell growth, clonogenicity, migration, matrix metalloproteinases (MMPs), EMT and TGFβ signaling were measured. Our data showed that lipoic acid pretreatment sensitized the breast cancer cells to the ionizing radiation and inhibited the radiation-induced migration and the release of MMP2 and MMP9. Lipoic acid also prevented the TGFβ1 release and inhibited the radiation-induced EMT in breast cancer cells. The inhibition of TGFβ signaling by lipoic acid is associated with the inhibition of radiation-induced activation and translocation of NF-κB. These results suggest that α-lipoic acid inhibits the radiation-induced TGFβ signaling and nuclear translocation of NF-κB, thereby inhibiting the radiation-induced EMT and sensitizing the breast cancer cells to ionizing radiation.