TP53 deleted cells in de novo glioblastomas using fluorescence in situ hybridization

Frequency and clinical significance of chromosome 7 and 10 aneuploidies, amplification of the EGFR gene, deletion of PTEN and TP53 genes, and 1p/19q deficiency in a sample of adult patients diagnosed with glioblastoma from Southern Brazil

Glioblastoma stands out as the most frequent central nervous system neoplasia, presenting a poor prognosis. The aim of this study was to verify the frequency and clinical significance of the aneuploidy of chromosomes 7 and 10, EGFR amplification, PTEN and TP53 deletions and 1p/19q deficiency in adult patients diagnosed with glioblastoma. The sample consisted of 40 patients treated from November 2011 to March 2015 at two major neurosurgery services from Southern Brazil. Molecular cytogenetic analyses of the tumor were performed through fluorescent in situ hybridization (FISH). The clinical features evaluated consisted of age, sex, tumor location, clinical symptoms, family history of cancer, type of resection and survival. The mean age of the patients was 59.3 years (ranged from 41 to 83). Most of them were males (70%). The median survival was 145 days. Chromosome 10 monosomy was detected in 52.5% of the patients, chromosome 7 polysomy in 50%, EGFR amplification in 42.5%, PTEN deletion in 35%, TP53 deletion in 22.5%, 1p deletion in 5% and 19q deletion in 7.5%. Age was shown to be a prognostic factor, and patients with lower age presented higher survival (p = 0.042). TP53 and PTEN deletions had a negative impact on survival (p = 0.011 and p = 0.037, respectively). Our data suggest that TP53 and PTEN deletions may be associated with a poorer prognosis. These findings may have importance over prognosis determination and choice of the therapy to be administered.

Engineering of clinical glioma treatment: prediction of pro-invasive molecular events in treated gliomas

The diffusely infiltrative nature of malignant gliomas is the main obstacle to successful treatment approaches. Advanced simulation models of the in vivo response to therapy conditions are expected to improve malignant glioma treatment substantially. In parallel experiments, human malignant glioma cells underwent either radiation or chemotherapy treatment (chemotreatment) with temozolomide alone, or combined chemoradiation. Cells were treated according to diverse, clinically relevant, therapeutic algorithms. Quantitative 'real-time' polymerase chain reaction (PCR) measurements were performed for target genes, namely vascular endothelial growth factor, p53, and cyclooxygenase-2, which allow a comparative evaluation of pro-invasive molecular events in treated gliomas. The proof-of-principle study simulated variable intratumoural regional conditions. Pro-invasive molecular patterns were strongly dependent on the treatment algorithm, cellular density, and drug delivery. The highest pro-invasive potential was demonstrated for simulated peripheral regions under continued chemoradiation. This result strongly supports the clinical observations of increased aggressiveness and relatively poor response to second-line therapies in post-operatively chemoradiation-treated malignant gliomas at the time of relapse. Individualized and potentially the most effective treatment algorithms can be designed using established gene expression patterns applied on primary cell cultures obtained from individual patients. Individual drug toxicity and response to anti-cancer therapy can be predicted.

Up-regulation of vimentin expression in low-density malignant glioma cells as immediate and late effects under irradiation and temozolomide treatment

Nervous system tumors are one of the leading causes of cancer related death. Specific mechanisms facilitating the invasive behavior of gliomas remain obscure. Advanced simulation models of the in vivo response to therapy conditions should potentially improve malignant glioma treatment. Expressional profiling of vimentin--one of reliable pro-invasive tumor makers--in those simulation models was the goal of this study, in order to estimate a pro-invasive response of surviving malignant glioma cells under clinically relevant therapeutic conditions. Human U87-MG malignant glioma cells were used. These cells are characterized by the wild p53-phenotype, which is relevant for the majority of primary malignant glioblastomas. Experimental design foresaw the cells to undergo either irradiation or chemo-treatment with temozolomide alone, or combined treatment. Expression profiling of vimentin was performed by quantitative "Real-Time"-PCR under all treatment conditions simulating diverse tumor regions. Here we demonstrated that vimentin expression patterns in human malignant glioma cells strongly depend on cellular density, algorithms of drug delivery and chemo/radio treatment. Substantial differences were recognized between immediate and late therapy effects. Significant increase in vimentin expression levels was detected particularly in low-density cell cultures under durable treatment with constant concentration levels of temezolomide. Simulation of variable intratumoral regional conditions (central intratumoral regions vs. disseminated malignant cells in peripheral regions) demonstrated differential response of vimentin expression in malignant glioma cell cultures treated under clinically relevant conditions. Slight ebbing of expression levels as late effects of the treatment in confluent cultures may correspond to necrotic processes clinically observed in central intratumoral regions. Contrary, in disseminated malignant cells of peripheral regions therapy resulted in vimentin-inducing effects. This is in agreement with the clinical observations of an increased aggressiveness and malignancy grade of post-operatively chemo/radio-treated malignant gliomas.

Non-sufficient cell cycle control as possible clue for the resistance of human malignant glioma cells to clinically relevant treatment conditions

OBJECTIVES

Human gliomas have a catastrophic prognosis with a median survival in the range of one year even after therapeutic treatment. Relatively high resistance towards apoptotic stimuli is the characteristic feature of malignant gliomas. Since cell cycle control has been shown to be the key mechanism controlling both apoptosis and proliferation, this study focuses on DNA damage analysis and protein expression patterns of essential cell cycle regulators P53 and P21waf1/cip1 in glioma under clinically relevant therapeutic conditions.

MATERIAL AND METHODS

U87MG cell line, characterised by wild p53-phenotype relevant for the majority of primary malignant glioblastomas, was used. Glioma cells underwent either irradiation or temozolomide treatment alone, or combined radio/chemo treatment. DNA damage was analysed by the "Comet Assay". Expression rates of target proteins were analysed using "Western-Blot" technique.

RESULTS AND CONCLUSIONS

"Comet Assay" demonstrated extensive DNA damage caused by temozolomide treatment alone and in combination with irradiation, correlating well with the low survival rate observed under these treatment conditions. In contrast, irradiation alone resulted in a relatively low DNA damage, correlating well with a high survival rate and indicating a poor therapeutic efficiency of irradiation alone. Unusually low up-regulation of P53 and P21waf1/cip1 expression patterns was produced by the hereby tested stressful conditions. A deficit in cell cycle control might be the clue to the high resistance of malignant glioma cells to established therapeutic approaches.

Pro-invasive gene regulating effect of irradiation and combined temozolomide-radiation treatment on surviving human malignant glioma cells

The current chemotherapeutic treatment of glioblastoma patients has minor success. Little is known about the molecular and cellular mechanisms of the resistance of gliomas towards current therapies. This study investigated both suppressive cellular effects and regulation of extracellular matrix remodeling proteins with pro-invasive activity in surviving human glioblastoma cells under clinically relevant treatments. All cellular and molecular biological investigations were performed on the genetically well-defined and clinically relevant p53-wild type U87Mg glioma cells. Malignant glioma cells underwent either radiation or temozolomide treatments alone, or combined chemo/radio treatment. Protein expression patterns were investigated by two-dimensional polyacrylamide gel electrophoresis followed by protein spot identification using tandem mass spectrometry analysis. Specific expression levels were quantified by Western-blotting. Extracellular gelatinase activities for both metalloproteinases MMP-2 and MMP-9 were determined by zymogramms. Survival curves indicated no effective suppression of glioma cells under all treatment conditions tested. Morphological changes demonstrated sub-lethal effect of both temozolomide and combined treatment. Expression of MMP-2, MMP-9, and membrane type 1 matrix metalloproteinases (MT1-MMP) was differentially up-regulated by increasing cellular density and treatment conditions. A significantly enhanced extracellular degrading activity under all treatment conditions tested was demonstrated for MMP-2 only. Being a marker for brain tumour progression and angiogenesis, lysozyme c was highly up-regulated under the combined chemo/radio treatment. The activation of proteins with pro-invasive activity indicates an increasing malignancy grade of surviving glioma cells under treatment conditions tested correlating well with more aggressive tumour phenotypes observed clinically in recurrences of treated glioblastomas.

Classification of glioblastoma multiforme in adults by molecular genetics

Recent advances in cytogenetic and molecular methodologies have elucidated certain principal characteristics of oncogenesis in glioblastoma multiforme. The earliest clues implicate gene sequence alterations, such as gene amplification and numerical gain or loss of function in specific chromosomes. Genetic classification and expression patterns have thus been constructed, conferring the likelihood of two types of glioblastoma, primary (de novo) as opposed to secondary (evolving from a pre-existing low-grade glioma). The former group of tumors exhibits more frequent occurrences of EGFR gene amplification, whereas the latter group relies strongly on TP53 gene inactivation. Many other tumor suppressor genes and oncogenes have been discovered. Most gene alterations induce cell cycle dysfunction on a complex molecular level. Further insight into tumor genesis by means of genomic assays may aid in predicting the clinical behavior of glioblastoma and in providing individualized potential targets for therapeutic agents.