Changes in microRNA (miRNA) expression in response to photon irradiation have been analyzed in a variety of cell lines including cells derived from breast, lung, prostate, and oral cancers. Several different miRNAs were responsive to the irradiation. Interestingly, individual miRNA species showing a response in specific cell types were not identified in other cells. These previous studies therefore suggested that selected miRNAs are regulated in a cell- or tumor-specific manner.C-ions with high energy transfer (LET) have a major big advantage over X-rays in treating tumors, and comprehensive gene expression analyses have identified C-ion- or X-ray-specific gene expression profiles. However, no detailed miRNA expression analysis after C-ion irradiation has been reported. We recently demonstrated X-ray irradiation-induced expression of selected miRNAs in the A549 cell line, which is derived from human non-small cell lung cancer (NSCLC). One of these miRNAs, miR-574-3p, has been implicated in suppressing the enhancer of rudimentary homolog (ERH) gene, which has a role in cell cycle control. This study examined C-ion induced expression of miRNAs in the A549 cell line. We found that four miRNA molecules were induced by 1 Gy of C-ion irradiation, compared to 2 Gy of X-ray irradiation needed for the same result. These data suggested that these four miRNA genes use common transcriptional machinery in responding to both X-ray and C-ion irradiation.BMB201
