Abstract:
Objective To study the adaptive response of the X-ray radiation to apoptosis of non-small cell lung cancer (NSCLC) A549 cell, and to screen microRNAs (miRNAs) related to the adaptive effect of radiation.
Methods NSCLC A549 cells were irradiated in 6 groups, namely, the50 mGy+20 Gy, 200 mGy+20 Gy, 20 Gy, 50 mGy, and 200 mGy irradiation groups and the 0 Gy as control group. The cells in the first two groups were irradiated with initial doses of 50 mGy and 200 mGy respectively, and were then irradiated with an effective dose of 20 Gy after culturs for 6 hours. The 20 Gy, 50 mGy, and 200 mGy groups were irradiated at the same time. The apoptosis of A549 cellswas detected by flow cytometry after 24 hours of culturing. Small RNA sequencing was performing to detect the expression of miRNAs in different irradiation groups, and quantitative real-time PCR (qRT-PCR) was used to verify some differentially expressed miRNAs. The target genes of differentially expressed miRNAs were predicted and then analyzed via gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) analyses. The data between two groups were compared by performing Welch's t-test.
Results The cell apoptosis rates of A549 cells in the 50 mGy+20 Gy and 200 mGy+20 Gy groups were (1.81±0.11)% and (2.17±0.19)% respectively, which were significantly lower than (4.54±0.23)% in the 20 Gy group (t=10.680, 8.006; all P<0.01). Meanwhile, the small RNA sequencing results show that compared with the 20 Gy irradiation group, 1 miRNA (miR-3662) was up-regulated and 15 miRNAs (miR-185-3p, miR-1908-5p, miR-1307-5p, miR-182-3p, miR-92a-3p, miR-582-5p, miR-501-3p, miR-138-5P, miR-1260b, miR-484, miR-378d, miR-193b-3P, miR-127-3p, miR-1303 and miR-654-5p) were down-regulated in the 50 mGy+20 Gy and 200 mGy+20 Gy irradiation groups. GO enrichment analysis reveal that the functions of target genes were significantly enriched in cell communication regulation, positive regulation of the metabolic process, regulation of the metabolic signal, enzyme binding and catalytic activity, whereas the KEGG analysis showed that the target genes related signal pathways were significantly enriched in lysosome, mitogen-activated protein kinase, Ras, endocytosis and other signal pathways. qRT-PCR was used to validate the expression of miRNAs, and the expression levels of 10 miRNAs were consistent with the sequencing results.
Conclusions The X-ray of 50 mGy and 200 mGy radiation dose can induce an adaptive response in the cell apoptosis of A549 cells. A group of differently expressed miRNAs detected in 50 mGy+20 Gy and 200 mGy+20 Gy groups may play important roles in the adaptive response of low dose radiation and may become potential targets to regulate have effects of radiation.