Expression And Significance Of MGMT And K-ras In The Glioma

Objective: The brain glioma is the most common primary malignant tumor in the human central nervous system,the annual incidence of glioma is about five in a hundred thousand.Our country is an area of high incidence of glioma disease,the number of new onset and the death toll from glioma rise year by year,and the glioma have treasures,such as invasive growth,easy to relapse,and unable to cure etc,which has become a global expert headaches.The occurrence and development of glioma is a process with multiple genes involved in and multiple stages of development,the occurrence and development of glioma contains the joint factors of environment and genetic,on the one hand,the body is derived from the environment risk factors cause DNA damage to proto-oncogene activation and/or tumor suppressor gene inactivation.On the other hand because of the existence of genetic individual differences,individuals with susceptible genotype can get disease with a small amount of stimulation from a small amount of dangerous factors.The environmental harmful factors can damage to human body cell DNA,and lead it to mutation,however our body has a corresponding self-protection mechanism.O6 methylguanine � DNA methyltransferase(MGMT)is the DNA repair enzyme in human body cells,it can repair the DNA damage on guanine O(6)loci,which caused by alkylating agent and other harmful factors,thus DNA returns to its original structure and function.k-ras belongs to a member of the ras gene family,which is proto-oncogenes in the cell,k-ras protein plays an important role in the growth signal transmission,which is the key factor of cell proliferation regulation.When mutations are happened in k-ras gene or its control area,the body cells' proliferation has changed.k-ras gene mutation is one of the key elements of the "start" canceration.Through the research on the expression of MGMT and k-ras in the glioma,their relationship with the level of glioma,which may find a new approach for the early prevention,timely diagnosis and proper treatment,prolong patient survival of glioma.Through the research of MGMT and k-ras,in normal brain tissue and the low level,the high grade glioma.We can study their role in the occurrence and development of glioma.Methods: Since December 2014 to June 2015,we collected glioma specimens of neurosurgery in the operating room,the 2nd Hospital of Hebei Medical University.When the glioma tissue is cutted out,we choose the appropriate tissue to save.Tissues prepared for IHC is fixed by 10% formalin in the room temperature,and tissues prepared for PCR is saved in the liquid nitrogen container.We have collected 50 specimens in total from the surgery of glioma patients.After verification,these glioma patients who have been collected specimens have not received any chemoradiotherapy and other anti-tumor treatment before the surgery.According to the WHO 2007 version of the classification of the central nervous system tumors,we classify 50 specimens into two group,26 cases of ?~? level belong to low grade gliomas,24 cases of ? ~? level belong to high grade glioma,all the 50 cases of specimens have pathological report issued by the Department of Pathology.Moreover we collect 12 cases of normal brain tissue specimens as control group from the cerebral hemorrhage or cerebral trauma surgery,the collection method is the same as collecting glioma tissues.In the normal brain tissue and glioma tissues,the expression of MGMT and k-ras is detected by the IHC method and RT-PCR respectively.The data of the experiment is analyzed by the nonparametric test methods in SPSS19.0 statistics software.Results:1 The result of IHC shows:In the three of normal brain tissue low grade and high grade glioma groups,the positive expression rate of MGMT is 92%,81%,71% respectively;the positive expression rate of k-ras is 33%,81%,96% separately.The experimental data of MGMT and k-ras has been statistically analyzed.The result shows: the comparison in the three groups shows statistically significant difference(P = 0.000),and the contrast between pairwise groups show significant statistical difference(P < 0.05).So we can see from the above results,with the increasing level of glioma,the expression of MGMT gradually reduce,and the expression of k-ras gradually increase.MGMT and k-ras expressed in the whole of three groups are significantly negative correlation(r =-0.399,P = 0.001),at the same time,the expression of low level glioma and normal brain tissue show negative correlation(r =-0.384,P = 0.017),the expression of the high grade glioma and normal brain tissue also show negative correlation(r =-0.454,P = 0.005).But there is no correlation in the high-level and low-level glioma group,which may be associated with less samples.2 The result of RT-PCR shows:according to the calculation of expression data from MGMT and k-ras PCR,with the increasing of glioma grade,the median of MGMT gradually reduce,and the median of k-ras gradually rise.In addition,after statistical analysis,the comparison between three groups showes significant statistical difference(P = 0.000),and the contrast between pairwise groups show significant statistical difference(P < 0.05).This can be proved that,with the increasing level of tumor,the expression of MGMT gradually reduced,and the expression of k-ras increased,the conclusion is identical with IHC results.By the calculation of correlation analysis,MGMT and k-ras expressed in three groups show a negative correlation(r =-0.539,P = 0.000).At the same time,the expression of low level glioma and normal brain tissue show negative correlation(r =-0.375,P = 0.020),the expression of the high grade glioma and normal brain tissue also show negative correlation(r =-0.531,P = 0.001).But there is no correlation in the high-level and low-level glioma group,which may be associated with less samples.Conclusions:1 The comparison of MGMT between three groups and pairwise groups,the expression shows significant statistical difference.This demonstrates that the decrease of MGMT expression is related with the occurrence and development of glioma,which is associated with MGMT protecting glial cells DNA from damage,thus preventing gene mutation.MGMT can prevent glial cell from degeneration.2 The contrasts of k-ras expression in the three groups and the pairwise groups have significant statistical difference.This demonstrates that the k-ras expression increase is related with the occurrence and development of glioma.This stuation is associated with that k-ras protein transmits cell division signals.With the degree of k-ras gene mutation rise,the malignant degree of gliomas increase.3 The expression of MGMT and k-ras in gliomas exist interconnectedness.With the expression of MGMT reduced,the expression of k-ras increased.As the repair gene,MGMT gene can repair the damage in k-ras,thus preventing glial cell from mutation.4 Through the research on MGMT and k-ras in this experiment,it can provide one direction for the diagnosis and targeted therapy of glioma.