Abstract:
Objective To investigate the expression of DNA methyltransferase 3b (DNMT3b) and SPG20 methylation in lung adenocarcinoma tissue, and to analyze their correlation and clinical significance in the pathogenesis of lung adenocarcinoma.
Methods Seventy cases of lung adenocarcinoma and paracancerous tissue were collected in The Affiliated Hospital of Chengde Medical College from April 2020 to April 2021. The methylation level of SPG20 was detected by pyrophosphate sequencing; the expressions of SPG20 and DNMT3b mRNA were detected by a real-time fluorescence quantitative polymerase chain reaction, and the expressions of the SPG20 and the DNMT3b proteins were detected by immunohistochemical tests and Western blot. The correlation of the SPG20 methylation level and the DNMT3b, and the clinical case characteristics were statistically analyzed. The Si-RNA of downregulated DNMT3b was constructed and then transfected with A549 cells, using liposome-mediated methods in DNMT3b si-RNA negative control si-RNA, and blank controls. RT-qPCR and Western blot were used to detect DNMT3b mRNA and protein expression levels. SPG20 gene methylation was detected by pyrophosphate sequencing.
Results In the cancerous and paracancerous tissue, the methylation rates of the SPG20 were 76.25%±5.74% and 13.45%±2.41%. The relative expression of the SPG20 mRNA was 0.18±0.03 and 1.21±0.17, and the differences were statistically significant (P<0.05). The relative expression of DNMT3b mRNA was 1.62±0.27, higher than in the paracancerous tissue 0.32±0.05. Immunohistochemical results showed that the positive expression rate of the protein was 27.14% and 72.86% in the cancerous and paracancerous tissue respectively. This difference was statistically significant (P<0.05). Western blot results showed that the expression of DNMT3b was 68.57%±3.18% in cancerous tissue and 25.29%±1.35% in paracancerous tissue. The expression of SPG20 was 16.87%±1.56% in cancerous tissue and 58.75%±2.68% in paracancerous tissue. The differences were statistically significant (P<0.05). Hence, SPG20 methylation and DNMT3b were associated in lung adenocarcinoma tissue (r=0.437, P<0.05). SPG20 methylation and DNMT3b were closely related to tumor TNM staging, tissue differentiation, and lymph node metastasis (P<0.05). The results of in vitro experiments had further revealed that both the DNMT3b mRNA expression in the DNMT3b si-RNA group after RNA interference, and the SPG20 methylation rate, decreased significantly.
Conclusions DNMT3b is significantly related to SPG20 gene methylation during lung adenocarcinoma lesions. A higher DNMT3b expression may be an important molecular event before the methylation of the SPG20 gene and has important potential value in the diagnosis and treatment of early lesions of lung adenocarcinoma.