Level of oxidative stress and Klotho promoter methylation in the plasma of patients with non-small cell lung cancer

Abstract:

Objective：To investigate the level of oxidative stress and Klotho promoter methylation in the plasma of patients with non-small cell lung cancer（NSCLC） and their clinical significance. Methods：Plasma samples were collected from 66 patients，who were diagnosed with NSCLC in Sichuan Provincial People’s Hospital（as observation group），and 50 healthy people（as control group）. Assay kits were used to determine the levels of superoxide dismutase（SOD），malondialdehyde（MDA），and catalase（CAT） in plasma. The mRNA and protein expression of Klotho in plasma was measured/determined by qPCR and Western blot，respectively. Pearson correlation analysis was performed for the correlation between Klotho expression level and oxidative stress. Klotho methylation level was determined by methylation-specific PCR（MS-PCR）. The methylation rate of CpG islands was determined by pyrosequencing. Results：Compared with the control group，the observation group had significantly reduced levels of SOD[（79.86±18.24） mU/L vs. （94.56±16.40） mU/L，t=4.487，P=0.000] and CAT[（18.50±4.62） U/mg vs. （25.26±3.54） U/mg，t=8.605，P=0.000]，but there was no significant difference in MDA level between the observation group and the control group[（2.87±2.26） pg/mL vs. （2.52±1.06） pg/mL，t= 1.675，P=0.097]. The mRNA and protein expression levels of Klotho in plasma were significantly lower in the obser－vation group than in the control group（mRNA：0.66±0.16 vs. 1.04±0.10，t=14.93，P=0.000；protein：0.70±0.20 vs. 1.04±0.10，t=10.92，P= 0.000）. There was a positive correlation between the protein expression of Klotho and the levels of SOD（r=0.768，P=0.000） and CAT（r=0.708，P=0.000）. Meanwhile，the observation group had an increased methylation level of CpG islands in the Klotho promoter. Conclusion：Klotho methylation may be a clinical marker of oxidative stress in the plasma of patients with NSCLC.