Study On The Application Of SHOX2 And RASSF1A Gene Methylation Detection In Sputum In The Diagnosis Of Lung Cancer

Purpose and Background :Lung cancer has become the most common fatal tumor with the highest mortality.At present,there are a variety of common diagnostic methods for lung cancer,but the invasive and high cost of these tests make the diagnostic role of lung cancer decline.Therefore,it is urgent to explore a non-invasive and sensitive detection method.At present,more and more attention has been paid to epigenetics and the occurrence and development of lung cancer.It has been proved that the methylation of SHOX2 and RASSF1 A genes in serum plays an important role in carcinogenesis.In this study,a more non-invasive and convenient method,sputum sample detection,was used to analyze the methylation of the above two genes in order to explore the clinical significance of gene methylation in the diagnosis of lung cancer.Materials and Methods :The sputum of patients from respiratory department,oncology department and thoracic surgery department of The Second Hospital Of Da Lian Medical University from 2019.09 to 2020.12 were collected.The methylation of SHOX2 and RASSF1 A gene promoter was detected by RT-PCR method.The sensitivity,specificity and accuracy of sputum methylation in the diagnosis of lung cancer were observed.The relationship between clinical data of sputum samples,pathological data of lung cancer and the positive rate of methylation of SHOX2 and RASSF1 A genes was observed.The sensitivity,specificity and diagnostic efficacy of two kinds of gene methylation detection and sputum cytological detection in the diagnosis of lung cancer were compared.Results :1.A total of 309 samples were collected,including 140 cases of primary lung tumors,10 cases of non-primary lung malignant tumors,110 cases of benign pulmonary lesions,49 cases of suspected pulmonary malignant tumor.309 samples were detected by RT-PCR.There were 103 positive and 206 negative cases of RASSF1 A methylation in sputum and 87 cases of positive and 222 negative cases of SHOX2 methylation in sputum.2.The positive rates of SHOX2 and RASSF1 A methylation in sputum in the lung cancer group were 53.6% and 61.4%,while those in the control group were 2.5% and6.7%,respectively.From the above data,the positive rate of gene methylation in the lung cancer group was at least 10 times higher than that in the control group,and there was significant difference between the two groups(P < 0.05).The sensitivity of combined detection of double genes in the diagnosis of lung cancer was 75.7%,which was significantly higher than that of SHOX2 or RASSF1 A gene methylation alone.3.In all types of primary.lung cancer(small cell carcinoma,squamous cell carcinoma,adenocarcinoma and compound cancer),the methylation positive rates of RASSF1 A gene were 84.6%,47.2%,56.7% and 40%,respectively.The methylation rates of SHOX2 gene were 69.2%,66.7%,35% and 60%,respectively.The sensitivity of methylation of the two genes in the diagnosis of small cell lung cancer is higher than that of other types of lung cancer.4.In the primary lung cancer group,the positive rates of SHOX2 gene methylation in peripheral and central lung cancer were 54.2% and 65.2%,respectively.The positive rates of combined detection were 70.8% and 78.3%,respectively.The detection of methylation of the two genes alone or in combination has high sensitivity in the diagnosis of central lung cancer.5.The positive rates of SHOX2 gene methylation in I-IV stage lung cancer were50%,42.3%,61.5% and 51.8%,respectively,while the positive rates of RASSF1 A gene methylation in I-IV stage lung cancer were 66.7%,23.1%,76.9% and 64.3%,respectively.The sensitivity of combined detection of methylation of two genes in the diagnosis of I-IV lung cancer was 66.7%,42.3%,88.5% and 80.4%,respectively.The positive rate of SHOX2 and RASSF1 A genes increased with the increase of clinical TNM stage of lung cancer.6.In the primary lung cancer group,through sputum cytological detection,40 cases of lung cancer were diagnosed(28.6%),32 cases were diagnosed as suspected lung malignant tumor(22.9%),and 68 cases of sputum cytological detection were negative.7.The ROC curves of different diagnostic indexes were drawn and the AUC values were calculated.The AUC values of SHOX2 and RASSF1 A methylation detection alone,combined detection and sputum cytological detection were 0.835,0.865,0.953 and 0.685,respectively.It can be seen that the sensitivity of sputum cytological detection of lung cancer is lower than that of sputum gene methylation detection,and combined gene detection can improve the diagnostic sensitivity of lung cancer.Conclusion :1.Detection of SHOX2 and RASSF1 A gene methylation in sputum samples is an efficient,non-invasive and efficient diagnostic marker.2.In the lung cancer group,the methylation positive rate of SHOX2 or RASSF1 A gene in sputum was significantly higher than that in the control group,the combined detection of the two genes could improve the diagnostic efficiency of lung cancer,especially for small cell lung cancer,and the methylation rate of SHOX2 and RASSF1 A genes was also related to the anatomical location and pathological stage of lung cancer.3.No matter the methylation of SHOX2 or RASSF1 A genes in sputum was detected alone or in combination,the sensitivity of detection was higher than that of sputum cytological detection.