Importantly, IDH and TERTp co-occurred in 75% of 1p/19q intact, TP53 wild-type oligodendrogliomas, highlighting the potential of the co-mutations in assisting diagnosis of oligodendrogliomas in tumors with clear cell morphology and non-codeleted 1p/19q status.
Considering the p53 labeling index and the apoptosis index together, this congenital oligodendroglioma may be regarded as potentially malignant despite the benign morphological features.
IDH1 mutations were co-present with TP53 mutations in 63% of low-grade diffuse astrocytomas and with loss of heterozygosity 1p/19q in 64% of oligodendrogliomas; they were rare in pilocytic astrocytomas (10%) and primary glioblastomas (5%) and absent in ependymomas.
Thus, we analyzed the expression of p-CREB in a series of astrocytomas and oligodendrogliomas of different histologic grades by immunohistochemistry and Western blot analysis. p53 overexpression and the Ki-67 labeling index were also assessed in all the tumors. p-CREB immunohistochemical expression was present in 100% of the astrocytic tumors, but in only 46% of oligodendrogliomas (P = .0033 for grade II; P = .0041 for grade III tumors).
In conclusion, evaluation of p53 protein accumulation reflected the clinical course of oligodendrogliomas better than the mere presence of TP53 gene mutations.
We analyzed markers, including IDH mutation(IDHmut), 1p19q codeletion(1p19qcodel), ATRX expression loss(ATRX loss) and p53 overexpression, and outcomes in 159 patients with WHO grade II oligodendroglioma, oligoastrocytoma, and astrocytoma (2003-2012).
Since accumulation of wild-type and mutant p53 are both associated with a poor prognosis, it is suggested to include immunohistochemical evaluation of p53 protein in routine diagnostics of oligodendrogliomas.
The results of the p53 studies are consistent with findings of previous investigations that such mutations are less common in oligodendrogliomas than they are in astrocytomas.
Our previous and present data show alterations of at least one of TP53 promoter methylation, p14ARF promoter methylation, and TP53 mutations in 43/49 (88%) of low-grade astrocytomas, 15/18 (83%) of oligoastrocytomas, and 35/42 (83%) oligodendrogliomas, suggesting that disruption of the TP53/p14ARF pathway is frequent in all histological types of low-grade glioma.
Combined loss of 1p and 19q was found in 38 of 56 (67.9%) and exhibited distinct concomitant deletion (P = 0.000). p53 overexpression was observed in 17 cases (30.3%), GFAP expression in 18 cases (32.1%), and p16 loss in 40 cases (74%) of oligodendrogliomas.
LGGs are further divided into isocitrate dehydrogenase (IDH) wild type or mutant, which is further classified into either oligodendroglioma that harbors 1p/19q codeletion or diffuse astrocytoma that has an intact 1p/19q loci but enriched for ATRX loss and TP53 mutation.
Recently, mutations in IDH1 and IDH2 have been reported as an early and common genetic alteration in diffuse gliomas, being possibly followed by 1p/19q loss in oligodendrogliomas and TP53 mutations in astrocytomas.
Moreover two additional genetic alterations are recorded in grade II and III gliomas: TP53 mutations that characterize astrocytomas and 1p19q codeletion (as the result of t(1;19)(q10;p10) translocation) recorded in oligodendrogliomas.
We carried out gene expression profiling on 17 oligodendrogliomas (93% with LOH 1p and/or 19q) and 15 low-grade astrocytomas (71% with a TP53 mutation), using a cDNA array containing 1176 cancer-related genes.
In this study, we screened 28 oligodendrogliomas (WHO grade II) and 20 anaplastic oligodendrogliomas (WHO grade III) for alterations in the RB1/CDK4/p16INK4a/p15INK4b and TP53/p14ARF/MDM2 pathways.
The p73 gene encodes a protein structurally and functionally homologous to TP53, and maps to chromosomal band 1p36.33, where loss of heterozygosity has been observed in up to 90% of oligodendrogliomas and in 10-25% of diffuse astrocytomas.
The effect of allergy on survival was significant (p = 0.025, HR 0.525, 95% CI 0.299-0.924), independent of the effect of chromosome 1p (p < 0.001, HR 93.4, 95% CI 16-546) and 19q (p = 0.801, HR 1.2, 95% CI 0.23-6.9) codeletion or TP53 mutation (p = 0.015, HR 2.7, 95% CI 1.2-5.9), unrelated to TERT expression (p = 0.365, HR 1.1, 95% CI 0.89-1.4) or ATRX mutation (p = 0.904, HR 1.04, 95% CI 0.51-2.14), independent of tumor grade (grade 2 versus grade 3, p = 0.004, HR 2.2, 95% CI 1.3-3.8), not independent of histology (oligodendroglioma and oligoastrocytoma, NOS versus astrocytoma, p = 0.08, HR 0.62, 95% CI 0.36-1.1).
LOH 1p/19q typically occurred in tumors without TP53 mutations and were most frequent in oligodendrogliomas (69%), followed by oligoastrocytomas (45%), but were rare in fibrillary astrocytomas (7%) and absent in gemistocytic astrocytomas.
All xenograft-producing gliomas harbored "lineage-defining" mutations in CIC (oligodendroglioma) or TP53 (astrocytoma), and 6 of 8 additionally had activating mutations in PIK3CA or amplification of PDGFRA, MET, or N-MYC.
Detection of chromosome 1p/19q status combined with p53 protein immunohistochemistry might be beneficial to improve the pathological diagnosis and to determine the prognosis of patients with oligodendrogliomas.
Histologically, those oligoastrocytomas with TP53 mutations were more often astrocytoma-predominant, while those with chromosome 19q loss were more often oligodendroglioma-predominant.