[Expression and prognosis effect of methylation-regulated SLIT3 and SPARCL1 genes in smoking-related lung adenocarcinoma].

Objective: To investigate the expression and prognosis effect of methylation-regulated SLIT3 and SPRCL1 genes in smoking-related lung adenocarcinoma. Methods: The expression levels of SLIT3 and in cigarette smoke-induced malignant transformed cell (S30) and lung adenocarcinoma (LUAD) cell lines were measured by real-time fluorescence quantitative PCR (qPCR). Datasets of mRNA expression, DNA methylation and patient information data were obtained from The Cancer Genome Altas (TCGA) database. The mRNA expression levels of SLIT3 and duanyu1842RCL1 were validated in LUAD tissues. The 10-year survival curve of LUAD patients with different smoking history was plotted, and the correlation between mRNA expression level and DNA methylation level of LUAD patients was further analyzed. S30 cells were treated with 5-azacytidine (5-aza), an inhibitor of DNA methyltransferase, to analyze the methylation regulatory mechanism of SLIT3 and SPRCL1. Results: The qPCR results showed the significant down-regulation of SLIT3 and duanyu1842RCL1 in S30 cell and four LUAD cell lines (SLIT3: 0.493±0.134 and 0.041±0.014, 0.161±0.023, 0.277±0.055, 0.035±0.005; 0.507±0.131 and 0.453±0.045, 0.420±0.040, 0.153±0.035, 0.430±0.050; all P<0.01). Bioinformatics analysis showed that SLIT3 and duanyu1842RCL1 were low expressed in LUAD tissue (8.12±1.58 vs 10.84±0.69 and 11.46±1.06 vs 13.57±0.67; both P<0.001) compared with adjacent peritumoral tissues, and expression levels of SLIT3 and duanyu1842RCL1 were significantly correlated with smoking history (both P<0.001). Non-smoker with high expression of SLIT3 and duanyu1842RCL1 was associated with better prognosis among LUAD patients. There was a significant negative correlation between promoter methylation and mRNA expression level of the two genes (r=-0.208, -0.574; both P<0.001). 5-aza treatment significantly up-regulated the expression levels of SLIT3 and duanyu1842RCL1 genes in S30 cells (2.137±0.281, 3.657±0.882; both P<0.01). Conclusion: SLIT3 and duanyu1842RCL1 can be regulated by DNA methylation and down-regulated in LUAD tissue, which has important prognostic significance on the smoking-induced LUAD patients.

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