Effect of L‐NAC on IR‐induced cell adhesion of MDA‐MB‐231 cells onto fibronectin and surface expression of activated b1 integrin

Abstract

Adhesion of tumor cells onto the extracellular matrix plays an important role in cancer metastasis. Previous studies have shown that ionizing radiation (IR) can induce the cell adhesion mediated by integrins, and reactive oxygen species (ROS) generated by IR can perturb the metastasis ability of tumor cells. Therefore, the purpose of this study is to evaluate the effect of ROS scavenger N‐acetyl‐L‐cysteine (L‐NAC) on the modulation of cell adhesion to fibronectin in irradiated MDA‐MB‐231 breast cancer cells and H1299 lung cancer cells, and the surface expression of integrins. Static cell adhesion assay was used and flow cytometry was used to determine the expression of activated β1 integrins on cell surface. The intracellular ROS was determined by the fluorescence dye carboxy‐ 2,7‐dichlorodihydrofluorescin diacetate. Our data showed that IR (20 Gy) significantly induced the breast cancer and lung cancer cell adhesion onto fibronectin at 24 hr post‐irradiation. And this induction of cell adhesion was markedly reduced by L‐NAC (10 mM) treatment for 24 hr post‐IR in MDA‐MB‐231 cells, but not in H1299 cells. This reduction was correlated with a down‐regulation of IR‐induced surface expression of activated integrin β1, ROS elevation and vimentin expression, an epithelial–mesenchymal transition marker (EMT). Interestingly, adding a one‐hour pre‐treatment of L‐NAC alleviated or diminished the effect of the post‐IR treatment of L‐NAC on cell adhesion or surface expression of activated integrin β1 respectively. Furthermore, the one‐hour pre‐treatment followed by a two‐hour post‐IR treatment has no effect on IR‐induced cell adhesion, but caused a significant elevation of ROS and cell surface expression of activated integrin β1 compared to IR treatment alone. Our results suggest that long‐term post‐IR treatment of L‐NAC might potentailly reduce radiation‐induced breast cancer cell adhesion, and thus metastatic potential. This work was supported by NIH RO1CA086928 (to S. Wu)