Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017636 (glioblastoma)
 18,345 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this review is to provide an up-to-date summary of the current knowledge and understanding of the molecular alterations and pathways relevant to the clinical outcome of glioblastoma patients and their potential use in designing personalized treatment for these patients. This article also discusses the potential of molecular profiling as a diagnostic modality, possible therapeutic implications of MGMT promoter methylation, the targeted inhibition of angiogenesis, and assessment of the tumor's molecular background with respect to PI3K/AKT pathway activation and associated molecules (EGFR, EGFRvIII, PTEN).
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PMID:Molecular profiling in glioblastoma: prelude to personalized treatment. 1908 Jul 42

Gliomas account for more than 70% of all brain tumors, and of these, glioblastoma is the most frequent and malignant histologic type (World Health Organization [WHO] grade IV). There is a tendency toward a higher incidence of gliomas in highly developed, industrialized countries. Some reports indicate that Caucasians have a higher incidence than African or Asian populations. With the exception of pilocytic astrocytomas (WHO grade I), the prognosis of glioma patients is still poor. Fewer than 3% of glioblastoma patients are still alive at 5 years after diagnosis, older age being the most significant and consistent prognostic factor of poorer outcome. Gliomas are components of several inherited tumor syndromes, but the prevalence of these syndromes is very low. Many environmental and lifestyle factors including several occupations, environmental carcinogens, and diet have been reported to be associated with an elevated glioma risk, but the only factor unequivocally associated with an increased risk is therapeutic X-irradiation. In particular, children treated with X-irradiation for acute lymphoblastic leukemia show a significantly elevated risk of developing gliomas and primitive neuroectodermal tumors, often within 10 years after therapy. Significant correlation between G:C --> A:T transitions in the TP53 gene and promoter methylation of the O6 -methylguanine-DNA methyltransferase (MGMT) gene in glio-mas have been reported in several studies, suggesting the possible involvement of O6-methylguanine DNA adducts, which may be produced by exogenous or endogenous alkylating agents in the development of gliomas.
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PMID:Epidemiology of brain tumors. 1910 40

We analyzed the methylation status of the O6-methylguanine-DNA methyltransferase (MGMT) promoter using a methylation-specific polymerase chain reaction (MSP) in glioblastoma patients treated with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU) plus cisplatin followed by radiation therapy. Forty-eight patients with interpretable MSP results were included in this study. The MGMT promoter was methylated in 26 patients (54.2%, methylated group) and unmethylated in 22 patients (45.8%, unmethylated group). Comparison of clinical outcomes between the two groups revealed that the methylation status of the MGMT gene promoter was not a prognostic factor for overall survival (P = 0.516) or a predictive factor for radiological response to ACNU plus cisplatin treatment (P = 0.529). The most noteworthy explanation for the result is that the synergistic antitumor effects of ACNU and cisplatin resulting from inactivation of MGMT by cisplatin in MGMT active tumors offset the drug resistance.
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PMID:Methylation status of the MGMT gene promoter fails to predict the clinical outcome of glioblastoma patients treated with ACNU plus cisplatin. 1917 Aug 94

Phosphorylation of histone H2AX is a sensitive marker of DNA damage, particularly of DNA double strand breaks. Using multiparameter cytometry we explored effects of etoposide and temozolomide (TMZ) on three glioblastoma cell lines with different p53 status (A172, T98G, YKG-1) and on normal human astrocytes (NHA) correlating the drug-induced phosphorylated H2AX (gammaH2AX) with cell cycle phase and induction of apoptosis. Etoposide induced gammaH2AX in all phases of the cell cycle in all three glioblastoma lines and led to an arrest of T98G and YKG-1 cells in S and G(2)/M. NHA cells were arrested in G(1) with no evidence of gammaH2AX induction. A172 responded by rise in gammaH2AX throughout all phases of the cycle, arrest at the late S- to G(2)/M-phase, and appearance of senescence features: induction of p53, p21(WAF1/CIP1), p16(INK4A) and beta-galactosidase, accompanied by morphological changes typical of senescence. T98G cells showed the presence of gammaH2AX in S phase with no evidence of cell cycle arrest. A modest degree of arrest in G(1) was seen in YKG-1 cells with no rise in gammaH2AX. While frequency of apoptotic cells in all four TMZ-treated cell cultures was relatively low it is conceivable that the cells with extensive DNA damage were reproductively dead. The data show that neither the status of p53 (wild-type vs. mutated, or inhibited by pifithrin-alpha) nor the expression of O(6)-methylguanine-DNA methyltransferase significantly affected the cell response to TMZ. Because of diversity in response to TMZ between individual glioblastoma lines our data suggest that with better understanding of the mechanisms, the treatment may have to be customized to individual patients.
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PMID:Diversity of DNA damage response of astrocytes and glioblastoma cell lines with various p53 status to treatment with etoposide and temozolomide. 1930 57

Despite recent and significant progress, the prognosis of glioblastoma remains extremely poor. Concomitant chemoradiotherapy with temozolomide is now the standard of care for newly diagnosed glioblastoma. This treatment is well-tolerated and results in improvement of overall survival and dramatic increase of long term survivor rate, especially in good performance status patients. Besides, this benefit is particularly marked in patients with MGMT (methylguanine methyltransferase) methylated tumor, suggesting a growing place of molecular markers in pattern of care of such patients. At recurrence, the combination of bevacizumab (anti-VEGF) with irinotecan has shown surprising high response rates in a phase II trial for recurrent malignant gliomas. Many other targeted therapies are currently under investigation, alone or in association, at recurrence or up-front and during radiotherapy. For this reason, in the future a more precise understanding of gliomagenesis is needed for a better molecular stratification of patients.
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PMID:[Association of radiotherapy and chemotherapy-targeted therapies in glioblastomas]. 1931 7

Epigenetic gene regulation of specific genes strongly affects clinical outcome of malignant glioma. MGMT is the best studied gene for the connection of promoter methylation and clinical course in glioblastoma. While MGMT promoter methylation analysis currently does not alter treatment of glioblastoma patients, mainly because of a lack of convincing therapy to radiotherapy and concomitant administration of alkylating drugs, there is increasing interest on the part of patients and physicians in having this molecular parameter assessed. This chapter gives a short overview of the physiological characteristics of the epigenome in normal cells and tissues and the changes in epigenetic gene regulation following malignant transformation. It discusses the technical aspects, advantages, and shortcomings of currently used approaches for single-gene and genome-wide methylation analyses. Finally, an outlook is given on potential therapeutic avenues and targets to overcome tumor-suppressor gene silencing by aberrant promoter methylation in gliomas.
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PMID:Gene regulation by methylation. 1932 47

Malignant gliomas are the most prevalent type of primary brain tumor in adults. They are classified into astrocytomes, oligodendrogliomes and oligo-astrocytomes on the presumed cell of origin. They are then classified according to their degree of malignancy into low-grade gliomas (I and II) and high-grade gliomas (III an IV) according to WHO classification. Conventional therapy includes surgery, radiotherapy and chemotherapy and is mostly palliative. Because patients with a same histologic diagnosis have variable outcomes, there is a need to develop better prognostic markers to predict tumor behaviour and response to therapy. For patients with low-grade gliomas, several clinical parameters affect prognosis and therapeutic options: histological type, tumor measurements, young age, performance status. Prognostic scores have been established based on a combination of these different clinical factors. For high-grade tumors, prognostic and predictive molecular markers have been identified. The combined loss of 1p and 19q is strongly correlated with the oligodendroglial phenotype and is associated with both chemotherapeutic response and prolonged overall survival in anaplastic (grade III) oligodendrogliomas treated with PCV chemotherapy and probably with temozolomide. Many glioblastomas have dysregulated epidermal growth factor receptor and among them, the co-expression of the mutant receptor subtype EGFRvIII. The clinical significance of these EGFR alterations is still debated. Nevertheless, co-expression of EGFRvIII and PTEN seem to be predictive factor of response to EGFR inhibitors currently tested in glioblastomas. In addition, the MGMT-methylation status is an independent predictor for glioblastoma patients treated with an alkylating agent: the epigenetic inactivation of the DNA repair gene MGMT is associated with a better response to chemotherapy and a better outcome. This status may have important implications for the design of future trials.
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PMID:[Prognostic and predictive factors for gliomas in adults]. 1935 11

Glioblastomas are the most frequent and malignant brain tumors in adults. Surgical cure is virtually impossible and despite radiation and chemotherapy the clinical course is very poor. Epigenetic silencing of MGMT has been associated with a better response to temozolomide-chemotherapy. We previously showed that temozolomide increases the median survival time of patients with tumors harbouring deletions on 9p within the region for p15(INK4b), p16(INK4a), and 10q (MGMT). The aim of this study was to investigate the methylation status of p15, p16, p14ARF and MGMT in glioblastomas (n=27) and to correlate the results with the clinical data. Only patients with KPS >70, radical tumor resection, radiation and temozolomide-chemotherapy after recurrence were included. We observed promoter methylation of MGMT in 56% and of p15 in 37% of the tumors, whereas methylation of p16 and p14ARF were rare. Interestingly, methylation of p15 emerged as a significant predictor of shorter overall survival (16.9 vs. 23.8 months, p=0.025), whereas MGMT promoter methylation had no significant effect on median overall survival under this treatment regimen (22.5 vs. 22.1 months, p=0.49). In the presence of other clinically relevant factors, p15 methylation remains the only significant predictor (p=0.021). Although these results need to be confirmed in larger series as well as under different treatment conditions, our retrospective study shows clear evidence that p15 methylation is an important prognostic factor for survival and underlines that this tumor suppressor, involved in cell cycle control, is an attractive candidate for therapeutic approaches in glioblastomas.
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PMID:p15 promoter methylation - a novel prognostic marker in glioblastoma patients. 1942 93

O(6)-methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that removes alkyl groups from the O(6) position of guanine. MGMT is transcriptionally silenced by promoter hypermethylation in several human neoplasia. We used methylation-specific PCR (MSP) to analyze the MGMT promoter methylation status of 50 glioblastoma tumors. Hypermethylation was detected in 24 of 50 (48%) samples. We also analyzed mutant p53 expression by immunohistochemical analysis of glioblastoma tissue samples. A significant association was found between MGMT methylation and p53 mutation status (p< .05). These results suggested that epigenetic inactivation of MGMT plays an important role in the survival of glioblastoma patients and this inactivated gene involved in p53 mutation.
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PMID:Association between MGMT promoter hypermethylation and p53 mutation in glioblastoma. 1954 11

Pseudoprogression (PsPD) is a pathological feature recently reported by some authors in malignant glioma patients treated with radiotherapy in combination with temozolomide. In radiological imaging, it is shown as an increase in the size of the tumor lesion and contrast enhancement occurring within a few months from the completion of radio-chemotherapy without worsening of the neurological signs and symptoms. In 21%-50% of the patients, the same lesion disappears a few months after its appearance. In 12 glioblastoma patients treated with radio-chemotherapy, 4 cases of early radiological progression without discontinuation of temozolomide treatment are reported. At the sunsequent tumor assessment, 2 cases (13%) were revealed to be PsPD. The two patients who experienced PsPD had the longest progression and survival times of all patients. In both patients with PsPD, the O(6)-methylguanine-DNA methyltransferase (MGMT) promoter was found to be methylated. The PsPD phenomenon opens the prospect of a new era for the management of glioblastoma patients undergoing radio-chemotherapy.
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PMID:Pseudoprogression and MGMT status in glioblastoma patients: implications in clinical practice. 1959 35


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