MGMT Promoter Methylation in Glioblastoma Stem Cells: Stability During Differentiation and Comparison With Surgically-resected Tumors.

OBJECTIVE: This study was undertaken primarily to investigate the epigenetic and prognostic role of H3K4 methyltransferase (MLL4) and H3K27 demethylase (UTX) in PFS and OS of glioblastoma patients who were treated with radiotherapy and/or chemotherapy after surgical resection. METHODS: The medical records of 76 patients with glioblastoma newly diagnosed and histologically proven from January 2002 to December 2013 at our hospital were reviewed retrospectively. Immunohistochemical staining was performed on archived paraffin-embedded tissues obtained by surgical resection for MLL4 and UTX. The methylation status of MGMT promoter was determined retrospectively by MS-PCR analysis. RESULTS: During follow-up period (mean duration of 27.5 months, ranged from 4.1 to 43.5 months), 68 patients (89.5%) died. MGMT promoter was methylated in 49 patients (64.5%) and unmethylated in 27 (35.5%). In terms of immunoreactivity of UTX-MLL4 complex, overexpression was found in 42 samples (55.3%) and underexpression in 34 samples (44.7%). Median PFS was 9.2 months (95% confidence interval [CI] of 6.8-11.6 months). Extent of surgery and methylation status of MGMT promoter was associated with PFS in multivariate analysis of factors predicting PFS. Median OS was 18.6 months (95% CI of 16.3-20.9 months). Age of patients (p = 0.004), performance status (p < 0.05), extent of surgery (p < 0.05), RPA class (p < 0.05), methylation status of MGMT promoter (p = 0.010), and immunoreactivity of UTX-MLL4 complex (p = 0.001) were associated with OS in multivariate analysis of factors predicting OS. Interestingly, in the patients with unmethylated MGMT promoter, immunoreactivity of UTX-MLL4 complex was not associated with OS (p = 0.350). However, in the patients with methylated MGMT promoter, immunoreactivity was strongly associated with OS (p < 0.001). Even patients with underexpression of UTX-MLL4 complex did not have statistical difference in OS between methylated MGMT promoter (p = 0.589) and unmethylated MGMT promoter (p = 0.838). CONCLUSION: This study suggests that overexpression of UTX-MLL4 complex should influence on the better outcome of glioblastoma patients with methylated MGMT promoter.

Inter- and intratumoral heterogeneity is a hallmark of glioblastoma (GBM) that facilitates recurrence, treatment resistance, and worse prognosis. O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation is a significant prognostic marker for Temozolomide (TMZ) resistance in GBM patients. YKL-40 is a molecular marker for the mesenchymal subtype of GBMs and is responsible for TMZ resistance. However, underlying mechanisms by which MGMT epigenetics impacts patient outcomes and the function of YKL-40 are not fully determined. Herein, we performed in vitro and in vivo experiments, six human IDH1/2 wild-type glioblastoma stem-like cells (GSCs) were established and studied to further determine a potential interaction of YKL-40 and MGMT promoter methylation. We demonstrated that YKL-40 functioned differently in human IDH1/2 wild-type GSCs. In MGMT promoter-methylated (MGMT-m) GSCs, it acted as a tumor suppressor gene. On the other hand, in MGMT promoter-unmethylated (MGMT-um) GSCs, it promoted tumorigenesis. Notably, the reason that YKL-40 played different roles in GSCs could not be interpreted by the molecular classification of each GSCs, but is a function of MGMT promoter methylation status and involves the RAS–MEK–ERK pathway. YKL-40 mediated TMZ sensitivity by activating DNA damage responses (DDRs) in MGMT-m GSCs, and it mediated resistance to TMZ by inhibiting DDRs in MGMT-um GSCs. Our report demonstrated that MGMT promoter methylation status might influence a gene’s function in human cancer. Moreover, our data also highlight the point that gene function should be investigated not only according to the molecular tumor classification, but also the epigenetic signature.

Glioblastoma multiforme (GBM) is the most common type of primary malignant brain cancer and has a very poor prognosis. A subpopulation of cells known as GBM stem-like cells (GBM-SC) have the capacity to initiate and sustain tumor growth and possess molecular characteristics similar to the parental tumor. GBM-SCs are known to be enriched in hypoxic niches and may contribute to therapeutic resistance. Therefore, to identify genetic determinants important for the proliferation and survival of GBM stem cells, an unbiased pooled shRNA screen of 10,000 genes was conducted under normoxic as well as hypoxic conditions. A number of essential genes were identified that are required for GBM-SC growth, under either or both oxygen conditions, in two different GBM-SC lines. Interestingly, only about a third of the essential genes were common to both cell lines. The oxygen environment significantly impacts the cellular genetic dependencies as 30% of the genes required under hypoxia were not required under normoxic conditions. In addition to identifying essential genes already implicated in GBM such as CDK4, KIF11, and RAN, the screen also identified new genes that have not been previously implicated in GBM stem cell biology. The importance of the serum and glucocorticoid-regulated kinase 1 (SGK1) for cellular survival was validated in multiple patient-derived GBM stem cell lines using shRNA, CRISPR, and pharmacologic inhibitors. However, SGK1 depletion and inhibition has little effect on traditional serum grown glioma lines and on differentiated GBM-SCs indicating its specific importance in GBM stem cell survival.Implications: This study identifies genes required for the growth and survival of GBM stem cells under both normoxic and hypoxic conditions and finds SGK1 as a novel potential drug target for GBM. Mol Cancer Res; 16(1); 103-14. ©2017 AACR.

Objective To study the correlations between O (6) -methylguanine-DNA-methyltransferase (MGMT) gene promoter methylation status in malignant glioma tissues and both MGMT protein expression and survival prognosis in these patients, and evaluate the significance of MGMT gene methylation status analyzing with methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) method in chemotherapy of brain glioma.Methods Thirty-nine patients with gliomas confirmed by pathology (WHO grade Ⅲ and grade Ⅳ)were collected in our study; the patient's overall survival (OS) after chemotherapy was tracked.MGMT protein expression of glioma tissues was detected by immunohistochemical staining,and MGMT promoter methylation status was detected by MS-MLPA method. Results Statistical difference of OS time was noted between patients with MGMT-negative and patients with MGMT-positive/-weak-positive (P=0.003).The prognosis in patients with positive MGMT protein expression was obviously poorer than that in patients with negative expression. In the groups of MGMT promoter un-methylation, mild hypermethylation, moderate hypermethylation and extensive hypermethylation, significant statistical difference of OS time was noted between each 2 groups (P＜0.05); the higher degree of methylation,the better prognosis. Statistical correlation was noted between MGMT protein expression and promoter methylation status (r=0.697,P=0.000); the higher degree ofmethylation,the lower protein exression of MGMT. Conclusion Both MGMT protein expression and promoter methylation status can be regarded as prognostic indicator of OS in patients with malignant glioma accepted alkylating agent chemotherapy; MS-MLPA is a reliable method to detect MGMT gene promoter methylation status. Key words: Glioma; O(6)-methylguanine-DNA-methyltransferase; Promoter methylation; Methylation-specific multiplex ligation-dependent probe amplification

Glioblastoma multiforme (GBM) is the most frequent tumor in the adult brain and remains a highly lethal diseases. Recent studies have suggested that lack of targeted therapies for brain tumor stem cells (BTSC) is one of the reasons for the limited efficacy of the current therapies. Identification of the molecular target in BTSC is crucial to the development of GBM therapy. Maternal embryonic leucine zipper kinase (MELK) is a member of Snf1/AMP serine/threonine kinase family and abundantly expressed in multiple cancers, including GBM. Previously, we demonstrated that the RNA expression of MELK is elevated in patient-derived tumor stem-like cells in GBM. Knockdown of MELK of tumor stem-like cells by siRNA resulted in apoptosis in vitro. In contrast, knockdown of MELK did not induce significant apoptosis in normal neural progenitors derived from mouse brains, raising a possibility that MELK is likely required for survival of tumor stem cells but not the normal counterpart. However, the difference in the mechanism of MELK action between tumor and normal stem cells is unknown. Here we investigated to discriminate the signaling pathways that regulate survival and proliferation of BTSC and normal neural stem cells. Immunohistochemistry showed that MELK is abundantly expressed in surgical specimens of GBM and is mainly localized in the nuclei. Immunocytochemistry with patient-derived GBM spheres demonstrated that MELK is preferentially expressed by GBM stem-like cells but not in the differentiated tumor cells. We also found that MELK is phosphorylated at serine and threonine residues in GBM stem-like cells. To determine the signaling pathways that regulate MELK phophorylation in GBM stem cells, we treated GBM stem-like cells with a variety of the kinase inhibitors. Interestingly, a mitogen-activated protein (MAP) kinase inhibitor reduced the MELK protein expression in GBM stem-like cells but not in the normal counterpart. The MAP kinase pathway was up-regulated in GBM stem-like cells in comparison to the normal progenitors derived from human fetal brains, further supporting the significance of this pathway in GBM stem cells. Collectively, our data indicate that MAP kinase may regulate MELK phosphorylation and activation specifically in GBM stem cells but not in the normal neural stem cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4236.

ABSTRACTBACKGROUND: Treatment of glioblastoma (GB), the most common malignant primary brain tumor in adults, can include alkylating chemo-therapeutic agents. Two molecular biomarkers of treatment response are MGMT (O6-methylguanine-DNA methyltransferase) promoter methylation and IDH (isocitrate dehydrogenase) mutations, which prevent repair of tumor cell DNA damage caused by alkylating chemotherapy. The status of MGMT promoter methylation and IDH mutation are associated with longer survival and a better response to chemotherapy.OBJECTIVE: Assess the prognostic value of MGMT methylation status and IDH mutation in adult Saudi glioblastoma patients.DESIGN: Retrospective, comparative survival analysis.SETTING: Tertiary care center.PATIENTS AND METHODS: The status of the MGMT promoter methylation and IDH mutation was assessed in adult patients diagnosed with GB between 2006 and 2019. A PCR-based assay was used to analyze for methylation of the MGMT promoter. A qualitative assay combining PCR clamping and amplification refractory mutation system technology was used to search for any of the 12 most common mutations in IDH1 and IDH2. Differences in survival were compared between those with and without MGMT promoter methylation and IDH mutation and between other subgroups.MAIN OUTCOME MEASURES: Survival of GB patients relative to MGMT promoter methylation and IDH mutation status.SAMPLE SIZE: 146 patients (80 males and 66 females).RESULTS: Of 43 (29.5%) cases tested for MGMT promoter methylation, 14 (32.5%) were positive. Of 65 (44.5%) cases screened for IDH mutation, 6 cases (9.2%) tested positive. The 36-month survival rate was 47% for the MGMT methylated cohort compared to 27% for their unmethylated counterparts. The 18-month survival rate for the IDH-mutant was 75% compared to 48% for their IDH-wildtype counterparts.CONCLUSION: The findings confirm the positive impact of both MGMT promoter methylation and IDH mutation on the overall survival of Saudi GB patients.LIMITATIONS: Single institute study with relatively few tested cases.CONFLICT OF INTEREST: None.

Simple SummaryA common issue in glioblastoma stem cells (GSCs) studies is the need to efficiently and precisely target GSCs using reliable biomedical markers. Using single-cell RNA sequencing datasets, we quantitatively evaluated an extensive number of GSCs markers with multiple parameters that dictate the feasibility of various laboratory and therapeutic applications. We present promising marker candidates with their scores on the corresponding parameters and apply sequential selection based on these parameters. Both previously approved and novel markers are proposed according to the evaluation. We demonstrate the possibility of choosing a biomedical marker in a nonarbitrary way and provide quantitative references for potential GSCs markers.Targeting glioblastoma (GBM) stem-like cells (GSCs) is a common interest in both the laboratory investigation and clinical treatment of GBM. Most of the currently applied GBM stem-like markers lack validation and comparison with common standards regarding their efficiency and feasibility in various targeting methods. Using single-cell RNA sequencing datasets from 37 GBM patients, we obtained a large pool of 2173 GBM stem-like marker candidates. To evaluate and select these candidates quantitatively, we characterized the efficiency of the candidate markers in targeting the GBM stem-like cells by their frequencies and significance of being the stem-like cluster markers. This was followed by further selection based on either their differential expression in GBM stem-like cells compared with normal brain cells or their relative expression level compared with other expressed genes. The cellular location of the translated protein was also considered. Different combinations of selection criteria highlight different markers for different application scenarios. By comparing the commonly used GSCs marker CD133 (PROM1) with markers selected by our method regarding their universality, significance, and abundance, we revealed the limitations of CD133 as a GBM stem-like marker. Overall, we propose BCAN, PTPRZ1, SOX4, etc. for laboratory-based assays with samples free of normal cells. For in vivo targeting applications that require high efficiency in targeting the stem-like subtype, the ability to distinguish GSCs from normal brain cells, and a high expression level, we recommend the intracellular marker TUBB3 and the surface markers PTPRS and GPR56.

The study investigated the pattern of MGMT promoter methylation and the expression of MGMT, P53, EGFR, MDM2 and PTEN proteins in glioblastomas multiforme (GBM) and evaluated their prognostic significance. We carried out a retrospective study of 80 GBM. Expression of MGMT as well as of P53, EGFR, MDM2 and PTEN was investigated by immunohistochemistry. MGMT promoter methylation was investigated by methylation specific-PCR of bisulfite-treated DNA. Twenty-five GBM exhibited MGMT expression. Methylation of MGMT promoter was detected in 35.1% of cases. No significant concordance was reported between MGMT promoter methylation and protein expression (κ=-0.047, p=0.11). MGMT promoter methylation was significantly associated only with PTEN expression (p=0.001): no other significant association was identified with clinical parameters as well as with expression of P53, EGFR and MDM2 (p >0.05). Tumor recurrence was significantly associated with unmethylated MGMT promoter (p=0.01) but not with MGMT expression (p=0.51). Recurrence-free survival (RFS) was significantly better among patients with methylated MGMT promoter (log rank, p <0.0001) and PTEN expression (log rank, p=0.025) but not with MGMT expression (log rank, p=0.308). As well, using univariate analysis, MGMT promoter methylation (p=0.001) and PTEN expression (p=0.044) were significantly associated with RFS. In multivariate analysis, only MGMT promoter methylation was significantly associated with RFS (p=0.003). Together, our findings support that MGMT protein expression doesn't reflect the MGMT promoter methylation status. Furthermore, MGMT promoter methylation remains a useful prognostic marker in Tunisian patients with GBM. PTEN expression could be a potential prognostic marker of this tumor.

Heterogeneous glioblastoma multiforme (GBM) was categorized based on transcriptional signatures into four subtypes (proneural (PN), neural, classical, and mesenchymal (MES)). In order to develop effective targeted therapeutic strategies, understanding the heterogeneous gene expression and molecular features of these subtypes is crucial. De-regulation of microRNA expression and activity has been shown to play an important role in tumor initiation and progression, including gliomagenesis. We have previously reported that expression of microRNA-128 (miR-128) is significantly down regulated in GBM and it diminishes self-renewal of GBM stem-like cells (GSCs) and sensitizes them to irradiation. Proneural-to-mesenchymal transition (PMT) manifested by concomitant up regulation of MES markers and down regulation of PN markers, is associated with increased malignancy, therapy-resistance and worse prognosis, but the underlying causes of PMT have not been convincingly characterized yet. In this study, we have demonstrated that miR-128 can regulate the PMT in GSC subsets. We showed that the expression of miR-128 in PN GSCs was significantly higher compared to MES subtype. As a tumor suppressive microRNA, miR-128 inhibited the MES GSC-specific high expression of Bmi1 and Suz12, two components of Polycomb Repressor Complexes (PRC) 1 and 2, respectively. In both GSC subtypes, miR-128 driven targeting of PRCs suppressed their epigenetic activity measured by ubiquitination of H2AK119 and tri-methylation of H3K27. Stable down regulation of miR-128 in PN GSCs significantly increased the expression of MES-specific gene signature (BCL2A1, CD44, WT-1, LYN, and MET) while its stable up regulation in MES GSCs resulted in the restoration of PN specific gene signature (CD133, SOX2, NES, OLIG2, and NOTCH1). We also showed that stable expression of miR-128 in GSCs could regulate the process of irradiation-induced PMT. Our in vivo studies showed the anti-tumorigenic role of miR-128 in both PN and MES GSC-derived intracranial tumor models. Taken together, we demonstrated that altering levels of miR-128 was sufficient to cause or reverse PMT, most likely by targeting the level/functions of PRCs and their target genes in GBM. Citation Format: Arun K. Rooj, Marco Mineo, Franz Ricklefs, Agnieszka Bronisz, Ennio Chiocca, Jakub Godlewski. The novel role of microRNA-128 in proneural to mesenchymal subtype transition in glioblastoma stem cells by targeting components of pro-oncogenic Polycomb Repressor Complex. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1929.

Temozolomide In Acute Myeloid Leukemia: A MGMT Promoter Methylation Status–Based Treatment Stratification

Understanding the molecular landscape of glioblastoma (GBM) is increasingly important in the age of targeted therapy. O-6-Methylguanine-DNA methyltransferase (MGMT) promoter methylation and EGFR amplification are markers that may play a role in prognostication, treatment, and/or clinical trial eligibility. Quantification of MGMT and EGFR protein expression may offer an alternative strategy towards understanding GBM. Here, we quantify baseline expression of MGMT and EGFR protein in newly diagnosed GBM samples using mass spectrometry. We correlate findings with MGMT methylation and EGFR amplification statuses and survival. We retrospectively identified adult patients with newly diagnosed resected GBM. MGMT and EGFR protein expression were quantified using a selected reaction monitoring mass spectrometry assay. Protein levels were correlated with MGMT methylation and EGFR amplification and survival data. We found a statistically significant association between MGMT protein expression and promoter methylation status (p = 0.02) as well as between EGFR protein expression and EGFR amplification (p < 0.0001). EGFR protein expression and amplification were more tightly associated than MGMT protein expression and methylation. Only MGMT promoter methylation was statistically significantly associated with progression-free and overall survival. Unlike EGFR protein expression and EGFR amplification which are strongly associated, only a weak association was seen between MGMT protein expression and promoter methylation. Quantification of MGMT protein expression was inferior to MGMT methylation for prognostication in GBM. Discordance was observed between EGFR amplification and EGFR protein expression; additional study is warranted to determine whether EGFR protein expression is a better biomarker than EGFR amplification for clinical decisions and trial enrollment.

The protein MGMT (O6-methylguanine-DNA-methyltransferase) is responsible for the DNA repair from damage in O6 position of guanine induced by alkylating agent such as temozolomide, which represent the conventional treatment of gliomas. Silencing of the MGMT gene by epigenetic methylation of its promoter may disable this repair mechanism, thus increasing the cytotoxicity of chemotherapy. Previous studies showed that glioblastama patients, with a methylated MGMT gene promoter in tumour tissue, are more sensitive to the action of alkylating agents and experience higher survival. The aim of the study was to verify the feasibility and the utility of monitoring the state of methylation of MGMT in circulating DNA as a predictive marker of prognosis and response to treatment. Fiftyeight patients with glioma (12 with low and 46 with high grade) who underwent surgical resection and who were eligible for therapy with temozolomide, were enrolled in the study. Blood samples for the analysis of MGMT methylation status were collected before any treatment (T0) and during the treatment at the time of each magnetic resonance imaging (about every 3 months). The methylation status of the MGMT gene promoter in circulating DNA was investigated using PCR with a specific probe for the methylated sequence. The MGMT promoter methylation status in tumour tissue and in plasma was highly concordant: in the 79% of the patients the MGMT promoter was methylated both in tumour tissue and plasma, while in the 21% of patients MGMT promoter was methylated in tissue but not in plasma (Cohen's kappa coefficient = 0.75, p &amp;lt;0.001). The overall survivals (OS) was higher in methylated versus unmethylated MGMT promoter patients both in tumour tissue and plasma, even if with a borderline statistically significance (p = 0.06 by the log-rank test for plasma). The risk of death increased in patients with unmethylated MGMT promoter both in tumour tissue (Adjusted HR=2.23; 95%CI 0.99-5.04) and in plasma (Adjusted HR1.73; 95%CI 0.92-3.22) Finally, in all patients after one year from diagnosis we noticed a decrease of the state of methylation of MGMT promoter in plasma. At the end of follow up in the 98% of patients who presented the methylation of the MGMT promoter at T0, a complete unmethylation was observed. In conclusion the results of this study confirm the feasibility of monitoring the state of methylation of MGMT in circulating DNA in glioma patients. MGMT promoter methylation status may be a prognostic marker of clinical interest in tissue and in plasma. Furthermore the complete unmethylation of MGMT promoter in the 98% of the glioma patients after one year from diagnosis, is a potentially important finding for future researches on biological history and treatment of gliomas. Citation Format: Valentina Fiano, Morena Trevisan, Carlotta Sacerdote, Anna Castiglione, Elisa Trevisan, Rebecca Senetta, Anna Gillio Tos, Laura De Marco, Paola Cassoni, Riccardo Soffietti, Franco Merletti. Gliomas: methylation status of MGMT gene monitoring in plasma DNA of patients receiving chemotherapy with alkylating agents. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 653. doi:10.1158/1538-7445.AM2013-653

Background/Aims: O⁶-methylguanine-methyltransferase (MGMT) is an important enzyme of DNA repair. MGMT promoter methylation is detectable in a subset of pancreatic neuroendocrine neoplasms (pNEN). A subset of pNEN responds to the alkylating agent temozolomide (TMZ). We wanted to correlate MGMT promoter methylation with MGMT protein loss in pNEN, correlate the findings with clinico-pathological data and determine the role of MGMT to predict response to TMZ chemotherapy. Methods: We analysed a well-characterized collective of 141 resected pNEN with median follow-up of 83 months for MGMT protein expression and promoter methylation using methylation-specific PCR (MSP). A second collective of 10 metastasized, pretreated and progressive patients receiving TMZ was used to examine the predictive role of MGMT by determining protein expression and promoter methylation using primer extension-based quantitative PCR. Results: In both collectives there was no correlation between MGMT protein expression and promoter methylation. Loss of MGMT protein was associated with an adverse outcome, this prognostic value, however, was not independent from grade and stage in multivariate analysis. Promoter hypermethylation was significantly associated with response to TMZ. Conclusion: Loss of MGMT protein expression is associated with adverse outcome in a surgical series of pNET. MGMT promoter methylation could be a predictive marker for TMZ chemotherapy in pNEN, but further, favourably prospective studies will be needed to confirm this result and before this observation can influence clinical routine.

BackgroundGlioblastoma multiforme (GBM) is an incurable tumor, with a median survival rate of only 14–15 months. Along with heterogeneity and unregulated growth, a central matter in dealing with GBMs is cell invasiveness. Thus, improving prognosis requires finding new agents to inhibit key multiple pathways, even simultaneously. A subset of GBM stem-like cells (GSCs) may account for tumorigenicity, representing, through their pathways, the proper cellular target in the therapeutics of glioblastomas. GSCs cells are routinely enriched and expanded due to continuous exposure to specific growth factors, which might alter some of their intrinsic characteristic and hide therapeutically relevant traits.MethodsBy removing exogenous growth factors stimulation, here we isolated and characterized a subset of GSCs with a “mitogen-independent” phenotype (I-GSCs) from patient’s tumor specimens. Differential side-by-side comparative functional and molecular analyses were performed either in vitro or in vivo on these cells versus their classical growth factor (GF)-dependent counterpart (D-GSCs) as well as their tissue of origin. This was performed to pinpoint the inherent GSCs’ critical regulators, with particular emphasis on those involved in spreading and tumorigenic potential. Transcriptomic fingerprints were pointed out by ANOVA with Benjamini-Hochberg False Discovery Rate (FDR) and association of copy number alterations or somatic mutations was determined by comparing each subgroup with a two-tailed Fisher’s exact test. The combined effects of interacting in vitro and in vivo with two emerging GSCs’ key regulators, such as Wnt5a and EphA2, were then predicted under in vivo experimental settings that are conducive to clinical applications. In vivo comparisons were carried out in mouse-human xenografts GBM model by a hierarchical linear model for repeated measurements and Dunnett’s multiple comparison test with the distribution of survival compared by Kaplan–Meier method.ResultsHere, we assessed that a subset of GSCs from high-grade gliomas is self-sufficient in the activation of regulatory growth signaling. Furthermore, while constitutively present within the same GBM tissue, these GF-independent GSCs cells were endowed with a distinctive functional and molecular repertoire, defined by highly aggressive Wnt5aHigh/EphA2Low profile, as opposed to Wnt5aLow/EphA2High expression in sibling D-GSCs. Regardless of their GBM subtype of origin, I-GSCs, are endowed with a raised in vivo tumorigenic potential than matched D-GSCs, which were fast-growing ex-vivo but less lethal and invasive in vivo. Also, the malignant I-GSCs’ transcriptomic fingerprint faithfully mirrored the original tumor, bringing into evidence key regulators of invasiveness, angiogenesis and immuno-modulators, which became candidates for glioma diagnostic/prognostic markers and therapeutic targets. Particularly, simultaneously counteracting the activity of the tissue invasive mediator Wnt5a and EphA2 tyrosine kinase receptor addictively hindered GSCs’ tumorigenic and invasive ability, thus increasing survival.ConclusionWe show how the preservation of a mitogen-independent phenotype in GSCs plays a central role in determining the exacerbated tumorigenic and high mobility features distinctive of GBM. The exploitation of the I-GSCs' peculiar features shown here offers new ways to identify novel, GSCs-specific effectors, whose modulation can be used in order to identify novel, potential molecular therapeutic targets. Furthermore, we show how the combined use of PepA, the anti-Wnt5a drug, and of ephrinA1-Fc to can hinder GSCs’ lethality in a clinically relevant xenogeneic in vivo model thus being conducive to perspective, novel combinatorial clinical application.

BACKGROUND Glioblastoma patients showing hypermethylation of the promoter of the O6-methylguanine-methyltransferase (MGMT) gene have significantly improved survival when treated with temozolomide compared to patients with hypomethylated MGMT promoters. However, the prognostic and predictive significance of partial MGMT promoter methylation is unclear. METHODS The National Cancer Database was queried for patients newly diagnosed in 2018 with histopathologically-confirmed IDH-wildtype glioblastoma. MGMT promoter methylation status was correlated with overall survival (OS) using multivariable Cox regression with Bonferroni correction for multiple testing (p&amp;lt; 0.008 was significant). RESULTS 3,663 patients were identified with newly diagnosed, histopathologically-confirmed IDH-wildtype glioblastoma and known MGMT promoter methylation. Of the 2,807 patients who received single agent chemotherapy (i.e. likely temozolomide), the MGMT promoter was unmethylated, partially methylated, hypermethylated, and methylated not otherwise specified (NOS) in 57.9%, 5.0%, 3.1%, and 34.0% of cases, respectively, with the later group likely consisting predominantly of hypermethylated cases. Multivariable analysis demonstrated that among patients receiving temozolomide, those with unmethylated MGMT promoters had significantly worse OS than patients with partially methylated MGMT promoters (hazard ratio (HR) 1.94; 95% confidence interval (CI), 1.54-2.44; p&amp;lt; 0.001). However, the OS of hypermethylated patients (HR 1.02; 95% CI, 0.72-1.46; p=0.9) and methylated NOS patients (HR 0.99; 95% CI, 0.78-1.26; p=0.928) were not statistically different from the OS of partially methylated patients. CONCLUSIONS IDH-wildtype glioblastoma patients with partial methylation of the MGMT promoter treated with temozolomide have improved OS compared to their unmethylated counterparts, supporting the use of temozolomide therapy in these patients.