Value Of FHIT, MGMT And RASSF1A Genes Promoter Hypermethylation In The Diagnosis Of Lung Cancer

BackgroudAt present, the incidence and mortality of lung cancer are in the first place of theworld, which is the main cause of death in many coutry. Diagnosing lung cancerdefinitely by means of iconography, bronchoscope, lung puncture is commonly usedin clinical. But75%of lung cancer is diagnosed as to be advanced or metastatic. Inwestern countries, five years survival rate of lung cancer is less than15%.Futhermore, the five years survival rate of lung cancer is less than9%in thedeveloping countries. As we all know, the development of iconography, bronchoscope,lung puncture is increasingly mature and advanced, but the morality rate of lungcancer has not been much reduced and improved. Therefore, not only should we try tofing the sensitive and specific method to diagnose early-stage pulmonary carcinoma,but also actively explore the early warning sign of pulmonary carcinoma. In recentyears, screening and mining biomarkers of lung cancer has become a hot researchdirection. Epigenetics is defined that gene function is reversible and heritable withoutaltering tne gene sequence. DNA methylation is not only apparent and main form ofepigenetics， but also is common and early event. Thus, DNA methylation is used asa new marker for the early diagnosis of lung cancer. Along with the increased level ofmethylation of CpG island in the promoter region of suppressor gene, it can inducethe tumor by means of thanscriptional inactivation of the suppressor gene. Lungcancer, gastric cancer, breast cancer, colon cancer, liver cancer, malignant tumor ofprostate cancer is associated with promoter methylation in CpG sites. Themethylation of FHIT, MGMT and RASSF1A gene promoter has become the mainmechanism of lung cancer. Accordingly, the Detecting the methylation levels of FHIT, MGMT and RASSF1A gene promoters may become a new method in early diagnosisand screening of lung cancer.ObjectiveTo investigate if the development of lung cancer is related to the methylationlevel of cancer suppressor genes like fragile histidine triad (FHIT), O6-Methylguanine-DNA methyltransferase (MGMT), Ras association domain family1A(RASSF1A) genes in periphera blood.Materials and methods:1. The collection of materials:137patients suffer from primay lung cancer werecollected from the First Affiliated Hospital of Zhengzhou University and the chesthospital during Octorber2012to march2013. All patients have been comfirmed aslung cancer by cytology and pathology without operation and chemotherapy.138patients with lung benign disease and141normal controls were also collected fromthe First Affiliated Hospital of Zhengzhou University and the Henan Provincial ChestHospital at the same time.2. Testing genes methylation level: to test gene promoters methylation level ofFHIT, MGMT and RASSF1A in peripheral blood, we use Real-time quantitativemethylation specific PCR.3. Using SPSS12.0to analyse the data. The continuous variables which do notmeet the normal distribution are frequently describled by the median (M) and fourspacing (P25, P75). Qualitative data is analysed by χ2test. For the skeweddistribution of quantitative data, Mann-Whitney U test is adopted at the comparisonbetween the two independent samples, and then anlysing the comparision amongthree independent samples by Krskal Wallis test. Multiple-factor non-conditionallogistic regression analysis is used to analyse the relationship between risk factors,such as age, gender, smoking and methylation level of the referred gene promotersand lung cancer. Evaluating the diagnostic value of methylation level among FHIT,MGMT and RASSF1A genes for lung cancer by receiver operating characteristics(ROC) curve,=0.05for the standard test (bilateral). Results1. The levels of FHIT, MGMT, RASSF1A gene methylation in lung cancer arehigher than normal contol group and pulmonary benign group, there were statisticalsignificances among all the differences (P=0.000, P=0.000， P=0.001)；Mann-Whitney U test and Krskal Wallis test are used to analyse the associationbetween age, gender, smoking, histological types, lymph node metastasis, clinicalstages and FHIT, MGMT, RASSF1A gene promoter methylation levels, thedifferences were not significant (P>0.05).2. With the increasing of FHIT, MGMT and RASSF1A gene methylation level,the risk of lung cancer increased (P<0.05). High age and smoking can increase therisk of lung cancer (P<0.05).3. Measuring the methylation levels of all three genes jointly was more valuablethan single detection for the lung cancer. The value of FHIT, MGMT and RASSF1Adetection in diagnosis for lung cancer is AUC=0.776, AUC=0.781, AUC=0.729.Measuring the methylation levels of all three genes jointly was more valuable thansingle detection for the stage I+II lung cancer. The value of FHIT, MGMT andRASSF1A detection in diagnosis for the stage I+II lung cancer is AUC=0.797,AUC=0.783, AUC=0.725.Conclusion1. The methylation of FHIT, MGMT and RASSF1A gene promoter in peripheralblood is related to lung cancer. Among patients of different age, gender and smokinghistory, the methylation levels of FHIT, RASSF1A and FHIT have no difference.Different histological types, lymph node metastasis and clinical stages also have nocorrelationship with methylation level of FHIT, RASSF1A and FHIT.2. With the development of FHIT, MGMT and RASSF1A gene promotermethylation level increases, the risk of lung cancer increased.3. The combined detection of FHIT, MGMT and RASSF1A gene promotermethylation levels is more valuable for the diagnosis of lung cancer. The detection ofFHIT, MGMT and RASSF1A gene promoter methylation is helpful to the lung cancerby Real-time methylation specific PCR.