miR-9 and let-7g enhance the sensitivity to ionizing radiation by suppression of NFκB1

The activation of nuclear factor-kappa B1 (NF kappa B1) in cancer cells may confer resistance to ionizing radiation (IR). To enhance the therapeutic efficiency of IR in lung cancer, we screened for microRNAs (miRNAs) that suppress NF kappa B1 and observed their effects on radiosensitivity in a human lung cancer cell line. From time series data of miRNA expression in gamma-irradiated H1299 human lung cancer cells, we found that the expression of miR-9 was inversely correlated with that of NF kappa B1. Overexpression of miR-9 down-regulated the level of NF kappa B1 in H1299 cells, and the surviving fraction of gamma-irradiated cells was decreased. Interestingly, let-7g also suppressed the expression of NF kappa B1, although there was no canonical target site for let-7g in the NF kappa B1 3' untranslated region. From these results, we conclude that the expression of miR-9 and let-7g could enhance the efficiency of radiotherapy for lung cancer treatment through the inhibition of NF kappa B1