Epilepsy-associated Brain Tumors:A Clinical,Radiological And Pathological Study

Epilepsy is a chronic disease characterized by abnormal neuron discharges caused by recurrent,episodic and transient central nervous system dysfunction.Brain tumors are one of the most important causes of epilepsy.Epilepsy-associated brain tumors,with unique manifestations and biological habits,grow slowly and relatively insidiously.Epilepsy is always the main and even the only symptom.Most patients respond poorly to anti-epileptic drugs,but can be efficiently treated by complete resection of the lesion.Glioneuronal tumors(GNTs),including gangliogliomas(GGs)and dysembryoplastic neuroepithelial tumors(DNTs),are the most common histological type of epilepsy-associated brain tumors.The serine threonine kinase v-RAF murine sarcoma viral oncogene homologue B1(BRAF)gene is a member of the RAF family of serine/threonine protein kinases involved in the RAS/RAF/MEK/ERK kinase signaling pathway.Missense mutations at amino acid position 600 account for the vast majority of BRAF mutations,resulting in an exchange of valine by glutamate in the activating segment of the kinase domain of BRAF,which is referred to as BRAF V600E.Recently,BRAF V600E mutations were detected in up to 50%GGs and in a few DNTs.However,the data of BRAF V600E mutations in Chinese population is lacking,and its correlation with clinicopathological features in epileptic patients has been rarely explored before.Autophagy,a process in which cytoplasmic components such as organelles and proteins are delivered to the lysosomal compartment for degradation,plays an essential role in the maintenance of cellular homeostasis.Several proteins are involved in the autophagy process;of these proteins,microtubule-associated protein light chain 3(LC3)and Beclin-1 are the most widely monitored proteins while assessing the autophagy activity.Focal cortical dysplasia and tuberous sclerosis complex were characterized by severe intractable seizures,which may have similar developmental pathogenesis with GNTs as some studies suggested.Previous studies have indicated the autophagy abnormalities in focal cortical dysplasia and tuberculosis sclerosis.However,the evaluation of autophagy-related protein expression in GNTs is still lacking.Therefore,in the first part of my doctoral thesis,we retrospectively analyzed brain tumor patients treated surgically at the epilepsy center of the Second Affiliated Hospital of Zhejiang University School of Medicine.Histopathology results were evaluated and reviewed.In order to gain a deep insight of the disease,clinical,radiological and pathological features of epilepsy-associated brain tumors were further investigated.In the second part,we examined the BRAF V600E mutation rate of epilepsy-associated glial neurons in Chinese population and explored the association between the mutation and clinical features.In the third part,we reviewed the expression of autophagy-related proteins in epilepsy-associated glial neuronal tumors and analyzed the association between them and the BRAF V600E mutation as well as clinical-pathological features.Part1 Clinicalpathological features of epilepsy-associated brain tumorsPurposeTo investigate the clinicopathological features of epilepsy-associated brain tumors.MethodsWe collected clinical,radiologic,electroencephalogram and follow-up results of 60 patients who underwent surgical resection of the epileptic onset zone from July 2012 to June 2016 at the Second Affiliated Hospital of Zhejiang University School of Medicine.With hematoxylin-eosin and immunohistochemical staining,clinicopathologic features were reviewed retrospectively..ResultsAmong the 60 cases,the male to female proportion is 1.7 to 1,of which 49 cases were diagnosed as refractory epilepsy.The average age of epilepsy was 22.2 years,and 80 percent were 35 years old and younger.The average duration of epilepsy was 4.7 years,and more than half of them had a duration of more than 2 years.The majority of tumors are located in the temporal lobe,followed by the frontal lobe.Histopathological subtypes include 24 cases of ganglioglioma,11 cases of dysembryoplastic neuroepithelial tumor,11 cases of diffuse astrocytoma,7 cases of oligodendroglioma,4 cases of oligoastrocytoma,1 case of pilomyxoid astrocytoma,pleomorphic xanthoastrocytoma and angiocentric glioma respectively.9 patients were also diagnosed with focal cortical dysplasia coexisting with brain tumors.47 patients achieved seizure free after surgery.ConclusionEpilepsy-associated brain tumors are prevalent in children and adolescents,and are often located in the temporal lobe.Clinicopathologically,they are slow-growing glial tumors or low-grade gliomas.Drug-resistance epilepsy is the prominent clinical symptom.Surgery is the first choice of therapy,always with a good prognosis after complete resection of the lesion.Part 2 BRAF V600E mutation in epilepsy-associated glioneuronal tumors:Prevalence and correlation with clinical featuresPurposeGlioneuronal tumors(GNTs)are the most common histological type of brain tumors in patients who received epilepsy surgery,and part of them presented with BRAF V600E mutation.We aimed to verify the presence of the BRAF V600E mutation in epilepsy-associated GNTs from Chinese population and evaluate the association with clinical features.MethodsData from 35 patients diagnosed with GNTs,including 24 gangliogliomas(GGs)and 11 dysembryoplastic neuroepithelial tumors(DNTs),were retrospectively collected.DNA was extracted from GNTs tissues and BRAF V600E mutation was examined by DNA sequencing.The correlations between BRAF V600E mutation and clinical features were analyzed.ResultsTotally,BRAF V600E mutations were detected in 11 patients with GNTs,the rate of mutation were 33.3%and 27.3%in GGs(8/24)and DNTs(3/11),respectively.The probability of BRAF V600E mutation in females(7/12,58.3%)was significantly higher than that in males(4/23,17.4%)(P = 0.022).Moreover,patients with BRAF-mutated GNTs had a significantly wider variety of seizure types compared to GNTs with BRAF wild-type status(P = 0.027).However,no significant correlation between the BRAF status and certain clinical features,such as age of seizure onset,duration of epilepsy,age at surgery,location of the tumor and postoperative seizure free,were observed.ConclusionWe demonstrated the presence of BRAF V600E mutation in Chinese epileptic patients with GNTs,which was significantly correlated with gender and multiple seizure types.Large sample studies and long-term follow-up are required for further confirmation.Part 3 Expression of autophagy-related proteins in epilepsy-associated glioneuronal tumors and BRAF V600E mutation as well as clinical features:a correlation analysisPurposeThe aim of this study was to explore the expression level of autophagy-related proteins in epileptic patients with glioneuronal tumors(GNTs)and evaluate the association with clinicopathological features.MethodsWe obtained the brain specimens from 33 patients with GNTs,including 22 gangliogliomas(GGs)and 11 dysembryoplastic neuroepithelial tumors(DNTs).The expression of two autophagy-related proteins(LC3 and Beclin-1)was evaluated by immunohistochemistry,and BRAF V600E mutation was examined by DNA sequencing.The correlations between autophagy-related protein expression and clinicopathological features were analyzed.Results Among 33 epileptic patients with GNTs,the frequency of high expression of LC3was 36.4%(12/33),and that of Beclin-1 was 39.4%(13/33).High expression of LC3 and Beclin-1 proteins was significantly associated with BRAF V600E mutation in GNTs(P = 0.008;P = 0.018),and LC3 overexpression was also correlated with temporal location of GNTs(P = 0.002).In GGs alone,high expression of LC3 revealed significant correlation with BRAF V600E mutation and temporal location(P = 0.020;P＝0.015),while Beclin-1 showed no correlation with them(P>0.05).Furthermore,autophagy-related proteins did not show any association with other studied clinicopathological features,such as gender,age at seizure onset,epilepsy duration and postoperative seizure outcome.ConclusionOur observations demonstrated that impaired autophagy may be associated with BRAF V600E mutation.However,large sample studies with long-term follow-up were required.