| Background and objective:Lung cancer is the most common malignant tumor in the world today,which causes serious damage to human life.The survival rate of lung cancer is associated with clinical stage,while many patients were in the middle or late stage when they have been diagnosed with lung cancer.To improve the survival rate of patients with lung cancer,we need to look for less trauma and effective exam for early detection of lung cancer.Abnormal DNA methylation of tumor suppressor genes in the promoter region is one of the important mechanisms of gene inactivation,and closely related to the occurrence and development of tumor.The abnormal methylation of gene promoter can be detected in a variety of malignant tumors,and it is expected to become an early diagnosis of lung cancer.By detecting SHOX2 and RASSF1A gene promoter methylation in the bronchoalveolar lavage fluid in our reseach,we analyze their status in lung cancer and benign disease group,and then assess the value of SHOX2 and RASSF1A methylation detection in the diagnosis of lung cancer.Methods:Bronchoalveolar lavage fluid of Run Run Shaw Hospital affiliated to Zhejiang University were collected during July 2014 to October 2015.SHOX2 and RASSF1A gene promoter methylation were detected by real-time PCR(RT-PCR)and sequencing ·methods,meanwhile histological and liquid based cytology results were collected.Thesensitivity and specificity of SHOX2 and RASSF1A methylation for the detection of lung cancer were calculated,and then we compared the methylation and liquid based cytology results for lung cancer diagnosis efficiency.Results:1.The bronchoalveolar lavage fluid of 305 patients were collected,including 178 cases(58.4%)of men and 127 cases(41.6%)of women,ranging from 23 to 85 years old,mainly concentrated in the 50-69 years old.There were 123 cases of primary lung cancer,18 cases of malignant tumors of other parts,112 cases of lung benign lesions and 52 cases of pulmonary shadows or nodules(indefinite diagnosis).2.We detected SHOX2 methylation of bronchoalveolar lavage positive for 97 cases and negative for 208 cases by RT-PCR.Meanwhile we detected RASSF1A methylation positive for 72 cases and negative for 233 cases.In the lung cancer group,the positive rate of SHOX2 and RASSF1A methylation were 64.2%and 50.4%.In control group,the positive rate of were 7.7%and 3.8%respectively.There was asignificant difference of SHOX2 and RASSF1A methylation between lung cancer and control groups(P<0.01).Combining SHOX2 and RASSF1A gene methylation analysisincreased the sensitivity up to 71.5%,which can improve the diagnostic sensitivity of lung cancer.3.There were 94 cases positive and 211 cases negative for SHOX2 methylation detected by sequencing.Meanwhile,there were 72 cases positive and 233 cases negative for RASSF1A methylation.4.The coincidence rates of the SHOX2 and RASSF1A methylation detected by RT-PCR and sequencing were 99%and 100%respectively.5.In 123 cases of primary lung cancer,seven cases were diagnosed with cancer by liquid based cytology,diagnosis of carcinoma of doubt or abnormal cells in 16 cases.The sensitivity of SHOX2 and RASSF1A gene methylation to detect primary lung cancer is significantly higher than the sensitivity of liquid based cytology.Conclusion:1.By RT-PCR method,the positive rate of SHOX2 and RASSF1A methylation in the lung cancer group and the control group with a statistically significant difference.2.The positive rates of SHOX2 and RASSF1A methylation in lung squamous carcinoma and small cell carcinoma are higher than in lung adenocarcinoma.3.The RT-PCR method to detect SHOX2 and RASSF1A gene methylation has high consistency with sequencing method.4.SHOX2 and RASSF1A methylation detection has higher sensitivity than cytologic examination.5.Joint detection of SHOX2 and RASSF1A methylation could increase the sensitivity indiagnosis of lung cancer,and the joint detection of the two indexes is expected to become the early diagnosis biomarkers of lung cancer. |
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