Low grade gliomas in children and adults can be molecularly graded

Ph.D.Gliomas are the most common primary brain tumors in adults and children. Gliomas are subdivided in the 2016 WHO classification of tumors of the Central Nervous System (CNS) by histological grade and molecular features, particularly IDH. In this study, I focused on low-grade gliomas in adults and children. According to the 2016 WHO classification, Isocitrate dehydrogenase (IDH) gene is a crucial requisite for the classification of lower-grade astrocytomas in adults. Adult astrocytomas are classified as IDH-mutant or IDH-wildtype based on IDH status and the lack of 1p/19q codeletion. Adult IDH-mutant lower-grade astrocytomas (IDH-mutant LGGs) comprise diffuse astrocytoma, Grade II and anaplastic astrocytoma, Grade III. Pediatric low-grade gliomas (PLGGs) are a heterogeneous group, however, and the 2016 WHO classification did not specify a classification for PLGGs.IDH mutation is now regarded as a good prognostic marker in adult lower-grade astrocytomas. Yet, the molecular and clinical heterogeneities of IDH-mutant lower-grade astrocytomas have not been extensively investigated. Pediatric low-grade gliomas (PLGGs) consist of a number of entities with overlapping histological features. PLGGs have much better prognosis than the adult counterparts, but a significant proportion of PLGGs suffer from tumor progression and recurrence. I hypothesize the adult IDH-mutant LGGs can be further stratification for risk. The same applies to pediatric low-grade gliomas.To identify the distinct molecular features of adult IDH-mutant lower-grade astrocytomas and pediatric low-grade gliomas and, we evaluated in two large cohorts of 160 IDH-mutant LGGs and 289 PLGGs a list of biomarkers and examined their clinical relevance. TERT promoter (TERTp), H3F3A and BRAF V600E mutations were detected by direct sequencing. ATRX nuclear loss and p53 expression were examined by immunohistochemistry. CDKN2A deletion, CDK4 amplification, PDGFRA amplification, KIAA1549-BRAF fusion, and MYB amplification were determined by fluorescence in situ hybridization (FISH).In 160 adult IDH-mutant LGGs, we found PDGFRA amplification, CDKN2A deletion, and CDK4 amplification in 18.8%, 15.0 %, and 18.1% of our cohort respectively, and these alterations occurred in mutually exclusive fashion. PDGFRA amplification was associated with shorter PFS (p = 0.0003) and OS (p < 0.0001). In a subset of tumors without PDGFRA amplification, CDKN2A deletion was associated with a shorter PFS (p = 0.038). Tumors were divided into three risk groups based on the presence of molecular alterations: high-risk (PDGFRA amplification), intermediate-risk (CDKN2A deletion or CDK4 amplification) and low-risk (neither CDKN2A deletion, CDK4 amplification nor PDGFRA amplification). These three risk groups were significantly different in overall survival with mean survival of 40.5, 62.9, and 71.5 months. The high-risk group also demonstrated a shorter PFS compared to intermediate- (p = 0.036) and low-risk (p < 0.0001) groups. Our data illustrate that IDH-mutant lower-grade astrocytomas is not homogeneous entity and should be molecularly stratified for risk.In 289 PLGGs, TERTp, H3F3A, and BRAF V600E mutations were identified in 2.5, 6.4, and 7.4% of PLGGs, respectively. ATRX loss was found in 4.9% of PLGGs. CDKN2A deletion, KIAA1549-BRAF fusion and MYB amplification were detected in 8.8, 32.0 and 10.6% of PLGGs, respectively. Survival analysis revealed that TERTp mutation, H3F3A mutation, and ATRX loss were significantly associated with poorer PFS (p < 0.0001, p < 0.0001, and p = 0.0002) and OS (p < 0.0001, p < 0.0001, and p < 0.0001). BRAF V600E was associated with shorter PFS (p = 0.011) and OS (p = 0.032) in a subset of PLGGs. KIAA1549-BRAF fusion was a good prognostic marker for longer PFS (p = 0.0017) and OS (p = 0.0029). MYB amplification was also a favorable marker for a longer PFS (p = 0.040). Importantly, we showed that these molecular biomarkers can be used to stratify PLGGs into low- (KIAA1549-BRAF fusion or MYB amplification), intermediate-I (BRAF V600E and/or CDKN2A deletion), intermediate-II (no biomarker), and high-risk (TERTp or H3F3A mutation or ATRX loss) groups with distinct PFS (p < 0.0001) and OS (p < 0.0001). This scheme should aid in clinical decision-making.In summary, my study identified clinically relevant molecular biomarkers in IDH-mutant LGGs and PLGGs. The study also illustrated IDH-mutant LGGs and PLGGs can be further stratified for risk. My study enhanced understanding on genetic and biological heterogeneity of PLGGs and IDH-mutant LGGs.膠質瘤是成人和兒童中最常見的原發性腦腫瘤。膠質瘤通過組織學分級和分子特徵，特別是IDH，細分為2016年WHO中樞神經系統（CNS）腫瘤分類。在這項研究中，我專注於成人和兒童的低級別膠質瘤。 根據2016年WHO分類，異檸檬酸脫氫酶（IDH）基因是成人低級別星形細胞瘤分類的關鍵要素。 根據IDH狀態和缺乏1p / 19q編碼，成人星形細胞瘤被分類為IDH-突變體或IDH-野生型。成人IDH-突變體低級別星形細胞瘤（IDH-突變體LGGs）包括瀰漫性星形細胞瘤，II級和間變性星形細胞瘤，III級。 兒科低級別膠質瘤（PLGGs）是一個異質性組，但2016年WHO分類未指定PLGG特異性分類。IDH突變現在被認為是成人低級別星形細胞瘤的良好預後標誌物。然而，IDH突變體低級別星形細胞瘤的分子和臨床異質性尚未得到廣泛研究。小兒低級別膠質瘤（PLGG）由許多具有重疊組織學特徵的實體組成。 PLGG預後比成人預後好得多，但很大比例的PLGG患有腫瘤進展和復發。 我假設成人IDH突變LGG可以進一步分層風險。這同樣適用於兒科低級別膠質瘤。為了確定兒童低級別膠質瘤和IDH-突變型低級別星形細胞瘤的獨特分子特徵，我們在160個IDH-突變型低級別星形細胞瘤和289個兒童低級別膠質瘤的大量隊列中評估了生物標記物列表並檢查了它們的臨床關聯。通過直接測序檢測TERT啟動子（TERTp），H3F3A和BRAF V600E突變。 通過免疫組織化學檢查ATRX核丟失和p53表達。 通過熒光原位雜交（FISH）測定CDKN2A缺失，CDK4擴增，PDGFRA擴增，KIAA1549-BRAF融合和MYB擴增。在160個成人IDH-突變型低級別星形細胞瘤中，我們發現PDGFRA擴增，CDKN2A缺失和CDK4擴增分別占我們隊列的18.8％，15.0％和18.1％，並且這些改變以相互排斥的方式發生。 PDGFRA擴增與較短的PFS（p =0.0003）和OS（p <0.0001）相關。 在沒有PDGFRA擴增的腫瘤子集中，CDKN2A缺失與較短的PFS相關（p = 0.038）。 基於分子改變的存在將腫瘤分成三個風險組：高風險（PDGFRA擴增），中等風險（CDKN2A缺失或CDK4擴增）和低風險（CDKN2A缺失，CDK4擴增和PDGFRA擴增）。 這三個風險組的總生存率存在顯著差異，平均存活率分別為40.5，62.9和71.5個月。 與中度（p = 0.036）和低風險（p <0.0001）組相比，高風險組也表現出更短的PFS。 我們的數據表明，IDH突變體低級別星形細胞瘤不是同質實體，應根據風險進行分子分層。在289個兒童低級別膠質瘤中，分別在2.5％，6.4％和7.4％的PLGG中鑑定出TERTp，H3F3A和BRAF V600E突變。 在4.9％的PLGG中發現ATRX損失。分別在8.8, 32.0和10.6％的PLGG中檢測到CDKN2A缺失，KIAA1549-BRAF融合和MYB擴增。 生存分析顯示TERTp突變，H3F3A突變和ATRX缺失與差的PFS顯著相關（p <0.0001，p <0.0001和p = 0.0002）和OS（p <0.0001，p <0.0001，和p <0.0001）。 BRAF V600E在PLGG子集中與較短的PFS（p = 0.011）和OS（p = 0.032）相關。 由於較長的PFS（p = 0.0017）和OS（p = 0.0029），KIAA1549-BRAF融合是良好的預後標誌物。 MYB擴增也是較長PFS的有利標誌物（p = 0.040）。 重要的是，我們發現這些分子生物標誌物可用於將PLGG分層為低-風險（KIAA1549-BRAF融合或MYB擴增），中等-I-風險（BRAF V600E和/或CDKN2A缺失），中等-II-風險（無生物標誌物）和高-風險（TERTp或H3F3A突變或ATRX缺失）組，其具有不同的PFS（p <0.0001）和OS（p