Clinic Pathological Application Of IDH1 Mutation, Chromosome 1p/19q Co-deletion And ATRX Expression Loss In Lower Grade Gliomas

Background Glioma is one of the most common brain tumors. According to World Health Organization Classification of tumor, Pathology and Genetics tumors of the Nervous system, gliomas are divided into 4 levels: pilocytic astrocytoma belongs to WHO Ⅰ and WHO Ⅳ is of glioblastoma. There are plenty of subtype in WHOⅡ and Ⅲ. Nowadays, Glioma epigenetic research found that although the two levels were diverse in histological morphology, the biological creature and genetic alteration remained variable and similar and there were overlaps existing. So some institutes nominated the two levels with “lower grade glioma” to facility relative researches. IDH1, 1p/19 q and ATRX are vital molecular markers in gliomas and have important significant in clinical diagnosis, therapy and prognosis. Isocitrate Dehydrogenase(IDH) mutation mainly occurs in gradeⅡ&Ⅲ gliomas and secondary glioblastoma, the frequency reaches to 70%-80%, while it rarely happens in primary glioblastomas(less than 5%). IDH mutation is associated with a better prognosis in gliomas. Researches show that 1p/19 q codeletions are common in oligodendrogliomas and oligoastrocytomas, whose frequency is up to 70% to 90%. ATRX gene is alpha thalassemia/mental retardationsyndrome X-linked causative gene. In the following articles, ATRX mutation was reported in astrocytoma while it seldom mutated in oligodendroglioma. And ATRX mutation reminded a well prognosis. Nowadays, WHO grade Ⅱ and grade Ⅲ gliomas are nominated as lower-grade glioma(Ler GG). It is difficult to direct clinical therapy and prognosis evaluation. Hence, diagnosis made by both morphological features and genetic molecular alteration is in heat debates. Genetics alteration detection of gliomas is still under initial stage in domestic development, the coincidence between article reports and domestic situation is still in veil, and the application of gliomas diagnosis and clinical evaluation is unclear. This article will analyze domestic glioma-associated genetics alteration to assess the application in clinical pathology.Objective 1. To identify the alteration of IDH1 mutation, 1p/19 q loss and ATRX expression loss in lower grade gliomas. Search the relationship between molecular alterations and tumor’s clinical pathological features. 2. Analyze clinical and histological features and its relationship with IDH1 mutation, 1p/19 q co-deletion and ATRX expression loss comprehensively to evaluate its function in lower grade glioma’s diagnosis and prognosis assessment.Methods 1. Collect 179 specimens of gradeⅡ and grade Ⅲ glioma in pathology department, Xi Jing hospital, the first hospital attached to fourth military medical university from January 2008 to April 2014. Follow-up messages were attained by telephone calls or letters. 2. IDH1 mutation was tested by En Vison immunohistochemistry staining and gene sequencing; chromosome 1p/19 q deletion was examined by FISH and ATRX was by En Vison staining. Identify the alterations in lower grade glioma and analyze histological features and IDH1 mutations, 1p/19 q deletion and ATRX expression loss. 3. Chi-square test was used to examine the relationship between genetic alterations and clinical pathological features.4. Kaplan-Meier analysis and Cox regression analysis was used to evaluate the prognosis affected by the molecular alterations and design the survival curve of lower grade glioma. 5. Meta analysis was used to evaluate the prognostic value of IDH1 mutation, 1p/19 q deletion and ATRX low expression in lower grade glioma.Result 1. IDH1 mutation is related to age of lower-grade glioma and patients less than 40-years-old are easier to gain the mutation(57.00% vs. 36.71%). Female acquires more alterations than male but there is no statistical significance(54.76% vs. 42.11%). IDH1 mutation is more common in grade Ⅱ glioma than grade Ⅲ glioma(52.76% vs. 36.54%) and is more popular oligdendroglima than in astrocytoma(56.98% vs. 39.78%), which is significant different. IDH1 mutation is associated with glioma’s prognosis(log-rank : χ2=22.908, p < 0.005) and the median overall survival is extended(74.039±3.296(positive)) vs. 45.675±3.384(negative)). 2. The coincidence rate between immunohistochemistry staining and gene sequencing is 94.41% and Mc Nemar test shows that P<0.005, which means there is no statistical significance between the examine results of two methods. Kappa=0.754 suggests the coincidence is strong and has statistical significance. 3. 1p/19 q deletion has no relationship with patients’ age and gender(P=0.957(age) and P=2.301(gender) respectively).The alteration is common in grade Ⅲ glioma and oligodendroglioma. Meanwhile, it is the independent factor of glioma’s prognosis evaluation( log-rank:χ2=8.119,P=0.004) and patients with alterations has a better outcome and an extended survival(median overall survival:69.850±4.439(positive) vs. 52.013±3.237(negative)). 4. ATRX expression loss is no association with age, gender and tumor grade. It is common in astrocytoma and astrocytic components of oligoastrocytoma. There is no connection between ATRX expression loss and lower grade glioma’s prognosis. 5. Comprehensive analysis shows that IDH1 mutation, combined with 1p/19 q deletion is unable to predict a better outcome further; IDH1 mutation or ATRX expression lossalone suggest a relative better prognosis than the tumor with both or neither alterations. ATRX cannot predict prognosis in 1p/19 q deletion glioma while remind a worse outcome in 1p/19q-intact patients, with no statistical differences. 6. Meta analysis shows that IDH1 mutation and 1p/19 q deletion are independent prognostic factors in lower grade glioma that predict a better outcome(IDH1: HR=0.33; 95%CI: 0.25-0.40; P=0.213; 1p/19q: HR=0.36; 95%CI: 0.30-0.43;P=0.269). ATRX plays no role in the prognosis of lower grade glioma.Conclusion In the specimens, IDH1 mutation, 1p/19 q deletion and ATRX expression-loss are vital epigenetic alterations. IDH1 mutation plays an important role in pathological diagnosis and prognosis of Ler GG, meanwhile, the two examine methods, immonohistochemistry and gene sequencing, have a obvious coincidence, so pathologists could monitor this mutation by immunohistochemistry for intial diagnosis and some specimen with few tumor cells(such as tumor’s margin) could be more precisely detected by immunohistochemistry. 1p/19 q deletion are as important as IDH1 mutation in Ler GG. 1p/19 q deletion is considered as oligodendrogliomas’ feature and suggests a better outcome. ATRX expression-loss tend to occur in astrocytic tumors. Meta analysis shows that IDH1 mutation and 1p/19 q deletion are relative to Ler GG and prompt a better outcome, which is consistent to our result, however, our relevance ratio is not as high as the average lever of articles. It hints that there may be ethnic difference existing, and we will conduct some molecular experiment to analyze the possible reason for further research.