Loss of heterozygosity on chromosome 10 is more extensive in primary (de novo) than in secondary glioblastomas

Homozygous 10q23/PTEN deletion and its impact on outcome in glioblastoma: a prospective translational study on a uniformly treated cohort of adult patients

Tumors from a prospective cohort of adult patients with newly diagnosed glioblastoma (n=73), treated uniformly with radiochemotherapy, were examined for 10q23/PTEN deletion by fluorescence in situ hybridization (FISH). Statistical methods were employed to evaluate the degree of association between 10q23/PTEN deletion status and patient age. Survival analysis was performed using Kaplan-Meier log-rank test and multivariable Cox models to assess the prognostic value of 10q23/PTEN deletion. Interestingly, 10q23/PTEN homozygous deletion was frequent in patients >45 years of age (P=0.034) and the median age of patients harboring PTEN homozygous deletions was significantly higher than those with the retained status (P=0.019). 10q23/PTEN homozygous deletion was associated with shorter survival in the entire cohort as well in patients >45 years (P<0.05), indicating that loss of 10q23/PTEN showed clinical importance in elderly patients. Our study highlights the independent prognostic/predictive value of 10q23/PTEN deletion status as identified by FISH, particularly in glioblastoma patients aged >45 years.

Distinct molecular signatures in pediatric infratentorial glioblastomas defined by aCGH

Glioblastomas (GBM) are rare in children, but reportedly have more varied outcome which suggests differences in tumor etiology compared to typical GBM of adults. To investigate this we performed high resolution array comparative genomic hybridization (aCGH) analysis on three pediatric infratentorial GBM, ages 3.5, 7 and 14 years. Two of these tumors occurred in the brainstem and one in the spinal cord. While histologically typical, one brainstem tumor showed mainly pleomorphic astrocytic cells, whereas the other brainstem and spinal tumors showed a GFAP positive small cell component. Whole chromosomal gains (#1 and #2) and loss (#20) were seen only in the pleomorphic brainstem GBM, which also showed a high level of segmental genomic copy number changes. Segmental loss involving chromosome 8 was seen in all three tumors (Chr8;133039446-136869494, Chr8;pter-3581577, and Chr8;pter-30480019 respectively), whereas loss involving chromosome 16 was seen in only 2 cases with small cell components (Chr16;31827239-qter and Chr16;pter-29754532). Segmental gain of chromosome 7 was shared only between the 2 brainstem cases (Chr7;17187166-qter and Chr7;69824947-qter). Chromosome 17 showed segmental gain of 17q in the backdrop of loss of 17p only in case 1. Segmental gain of chromosome 1q was seen only in case 2. The spinal GBM showed a relatively stable karyotype with a unique loss of Chr19;32848902-qter. None of the frequent losses, gains and amplifications known to occur in adult GBM were identified, suggesting that pediatric infratentorial glioblastomas show a molecular karyotype that was more characteristic of pediatric embryonal tumors than adult GBM.

The pathobiology of glioma tumors

The ongoing characterization of the genetic and epigenetic alterations in the gliomas has already improved the classification of these heterogeneous tumors and enabled the development of rodent models for analysis of the molecular pathways underlying their proliferative and invasive behavior. Effective application of the targeted therapies that are now in development will depend on pathologists' ability to provide accurate information regarding the genetic alterations and the expression of key receptors and ligands in the tumors. Here we review the mechanisms that have been implicated in the pathogenesis of the gliomas and provide examples of the cooperative nature of the pathways involved, which may influence the initial therapeutic response and the potential for development of resistance.

Faithfull modeling of PTEN loss driven diseases in the mouse

A decade of work has indisputably defined PTEN as a pivotal player in human health and disease. Above all, PTEN has been identified as one of the most commonly lost or mutated tumor suppressor genes in human cancers. For this reason, the generation of a multitude of mouse models has been an invaluable strategy to dissect the function and consequences-of-loss of this essential, evolutionary conserved lipid phosphatase in tumor initiation and progression.In this chapter, we will summarize the mouse models that have allowed us to faithfully recapitulate features of human cancers and to highlight the network of connections between the PTEN signaling cascade and other oncogenic or tumor suppressive pathways.Notably, PTEN represents one of the most extensively modeled genes involved in human cancer and exemplifies the strength of genetic mouse modeling as an approach to gain information aimed to improve our understanding of and ability to alleviate human disease.

Genetic alterations and signaling pathways in the evolution of gliomas

Gliomas are the most common primary brain tumors. They account for more than 70% of all neoplasms of the central nervous system and vary considerably in morphology, location, genetic alterations, and response to therapy. Most frequent and malignant are glioblastomas. The vast majority (>90%) develops rapidly after a short clinical history and without evidence of a less malignant precursor lesion (primary or de novo glioblastoma). Secondary glioblastomas develop more slowly through progression from low-grade or anaplastic astrocytoma. These glioblastoma subtypes constitute distinct disease entities that affect patients of different age, develop through distinct genetic pathways, show different RNA and protein expression profiles, and may differ in their response to radio- and chemotherapy. Recently, isocitrate dehydrogenase 1 (IDH1) mutations have been identified as a very early and frequent genetic alteration in the pathway to secondary glioblastomas as well as that in oligodendroglial tumors, providing the first evidence that low-grade astrocytomas and oligodendrogliomas may share common cells of origin. In contrast, primary glioblastomas very rarely contain IDH1 mutations, suggesting that primary and secondary glioblastomas may originate from different progenitor cells, despite the fact that they are histologically largely indistinguishable. In this review, we summarize the current status of genetic alterations and signaling pathways operative in the evolution of astrocytic and oligodendroglial tumors.

Glioblastoma multiforme: a review of therapeutic targets

Glioblastoma is the commonest primary brain tumor, as well as the deadliest. Malignant gliomas such as glioblastoma multiforme (GBM) present some of the greatest challenges in the management of cancer patients worldwide, despite notable recent achievements in oncology. Even with aggressive surgical resections using state-of-the-art preoperative and intraoperative neuroimaging, along with recent advances in radiotherapy and chemotherapy, the prognosis for GBM patients remains dismal: survival after diagnosis is about 1 year. Established prognostic factors are limited, but include age, Karnofsky performance status, mini-mental status examination score, O6-methylguanine methyltransferase promoter methylation and extent of surgery. Standard treatment includes resection of > 95% of the tumor, followed by concurrent chemotherapy and radiotherapy. Nevertheless, GBM research is being conducted worldwide at a remarkable pace, in the laboratory and at the bedside, with some of the more recent promising studies focused on identification of aberrant genetic events and signaling pathways to develop molecular-based targeted therapies, tumor stem cell identification and characterization, modulation of tumor immunological responses and understanding of the rare long-term survivors. With this universally fatal disease, any small breakthrough will have a significant impact on survival and provide hope to the thousands of patients who receive this diagnosis annually. This review describes the epidemiology, clinical presentation, pathology and tumor immunology, with a focus on understanding the molecular biology that underlies the current targeted therapeutics being tested.

Alterations of BCCIP, a BRCA2 interacting protein, in astrocytomas

Background

Loss of heterozygosity of chromosome 10q26 has been shown to be associated with the aggressiveness of astrocytic tumors (or astrocytomas), but the responsible gene(s) residing in this region has not been fully identified. The BCCIP gene is located at chromosome 10q26. It encodes a BRCA2 and CDKN1A (p21) interacting protein. Previous studies have shown that down-regulation of BCCIP impairs recombinational DNA repair, G1/S cell cycle checkpoint, p53 trans-activation activity, cytokinesis, and chromosome stability, suggesting a potential role of BCCIP in cancer etiology. In this study, we investigated whether BCCIP is altered in astrocytomas.

Methods

Genomic DNA from 45 cases of grade IV astrocytic tumor (glioblastoma) tissues and 12 cases of normal tissues were analyzed by quantitative PCR. The BCCIP protein expression in 96 cases of grade II–IV astrocytic tumors was detected by immunohistochemistry (IHC). IHC staining of glial fibrillary acid protein (GFAP), a marker for astrocytic cells, was used to identify cells of the astrocytic lineage.

Results

We found that BCCIP protein is expressed in normal cells with positive staining of GFAP. However, BCCIP protein expression was not detectable in ~45% of all astrocytic tumors, and in > 60% in the grade IV glioblastoma. About 45% glioblastoma have significant (p < 0.01) reduction of BCCIP gene copy number when compared to normal DNA. Furthermore, the frequency of lacking BCCIP expression is associated with the aggressiveness of astrocytic tumors.

Conclusion

Our data implicate a role of BCCIP in astrocytic tumorigenesis, and lack of BCCIP may be used as a marker for astrocytomas.

Advances in the genetics of glioblastoma: are we reaching critical mass?

Glioblastoma is the most common and highest-grade brain tumor, causing over 10,000 deaths each year in the US alone. Given the resistance of this tumor to standard surgery, radiation and chemotherapy, an understanding of the underlying genetic lesions is vital. Recent efforts to comprehensively profile glioblastomas using the latest technologies, both by The Cancer Genome Atlas (TCGA) project and by other groups, are addressing this need. Some genetic aberrations in glioblastoma have been known for decades, but early output from the new profiling initiatives has further illuminated the relevant genetics in this disease. Some genetic lesions, such as TP53 mutation, NF1 deletion or mutation, and ERBB2 amplification, have been found to be more common than was previously reported. New and unexpected discoveries have also been made, such as frequent mutations of the IDH1 and IDH2 genes in secondary glioblastoma. We might be tempted to speculate that we are approaching a comprehensive knowledge of the genetic lesions involved in glioblastoma, although other major discoveries doubtless remain to be made. In addition, the complex task of incorporating our updated knowledge into new--and possibly personalized--therapies for patients with glioblastoma still lies ahead.

Interferon-beta, MCNU, and conventional radiotherapy for pediatric patients with brainstem glioma

BACKGROUND

Most children with brainstem glioma die within 2 years of diagnosis, and the median survival time for patients with this condition is less than 1 year. The role of chemotherapy in the treatment of children with brainstem glioma is not well defined. The primary aim of this study is to evaluate the effects of treatment with interferon-beta (IFN-beta), ranimustine (MCNU), and radiotherapy (IMR therapy) administered to brainstem glioma patients treated at our institution. We also determined patient response to IMR therapy by evaluating O(6)-methylguanine-DNA methyltransferase (MGMT) promoter methylation in serum DNA.

PROCEDURES

We retrospectively reviewed 15 patients who were newly diagnosed to have brainstem tumors and were administered IFN-beta (1-2 MIU/day, days 1-7; 0.5-1 MIU/day, days 8-14) and MCNU (80 mg/m(2) on day 2) concurrently with conventional radiotherapy. Responses were assessed by MRI scan, and data on clinical course and toxicity were obtained from the medical records. The MGMT promoter methylation in serum DNA of five patients was assayed by methylation-specific PCR.

RESULTS

Of the 15 patients, partial response, stable disease, and progressive disease were noted in 5 patients each. The median overall survival time and the median progression-free survival time were 14.7 and 4.6 months, respectively. The protocol was not terminated in any of the patients because of hematological toxicity, nephrotoxicity, or neurotoxicity. The MGMT promoter methylation status in the serum appeared to correlate with a positive response to IMR therapy.

CONCLUSIONS

The IMR combination therapy is well tolerated and may be a promising treatment for brainstem glioma.

Glioblastoma with adipocyte-like tumor cell differentiation--histological and molecular features of a rare differentiation pattern

We report on three adult patients with primary glioblastomas showing prominent adipocytic (lipomatous) differentiation, hence referred to as "glioblastomas with adipocyte-like tumor cell differentiation." Histologically, the tumors demonstrated typical features of glioblastoma but additionally contained areas consisting of glial fibrillary acidic protein (GFAP)-positive astrocytic tumor cells resembling adipocytes, that is, containing large intracellular lipid vacuoles. Comparative genomic hybridization (CGH) and focused molecular genetic analyses demonstrated gains of chromosomes 7, losses of chromosomes 9 and 10, as well as homozygous deletion of p14(ARF) in one of the tumors. The second tumor showed gains of chromosomes 3, 4, 8q and 12 as well as losses of chromosomes 10, 13, 15q, 19 and 22. In addition, this tumor carried homozygous deletions of CDKN2A and p14(ARF) as well as point mutations in the TP53 and PTEN genes. The third tumor also had a mutation in the PTEN gene. None of the tumors demonstrated EGFR, CDK4 or MDM2 amplification. Taken together, our results define a rare glioblastoma differentiation pattern and indicate that glioblastomas with adipocyte-like tumor cell differentiation share common molecular genetic features with other primary glioblastomas.

p16 promoter methylation in the serum as a basis for the molecular diagnosis of gliomas

OBJECTIVE

Deoxyribonucleic acid (DNA) methylation of tumor origin can be detected in the serum/plasma of cancer patients. The aim of this study was to detect aberrant p16 promoter methylation as a potential diagnostic marker in the serum of patients with diffuse glioma to differentiate between gliomas and, particularly, to differentiate those in the brainstem from others; this was done by using the modified methylation-specific polymerase chain reaction technique.

METHODS

The methylation-specific polymerase chain reaction was used to detect p16 methylation in the DNA extracted from 20 astrocytic tumors and 20 oligodendroglial tumors and the corresponding serum samples. Serum samples from 10 healthy individuals were used as controls. The association of p16 hypermethylation in the serum DNA of glioma patients with clinicopathological characteristics was analyzed. In addition, the serum DNA in 7 patients with a brainstem tumor (4 gliomas, 1 schwannoma, 1 cavernous angioma, and 1 ependymoma) was analyzed.

RESULTS

We found p16 methylation in 12 (60%) of the 20 tissues with astrocytoma, but in only 1 of the tissues with oligodendroglioma. Similar methylations were detected in the serum of 9 (75%) of the 12 patients with aberrant methylation in the tumor tissues. No methylated p16 sequences were detected in the peripheral serum of the patients having tumors without these methylation changes or in the 10 healthy controls. Additionally, p16 promoter methylation in the serum was observed in all brainstem astrocytoma cases, but not in other cases.

CONCLUSION

This assay has potential for use as a serum-based molecular diagnosis technique for diffuse glioma.

Glioblastoma Multiforme Oncogenomics and Signaling Pathways

In the adult population, glioblastoma multiforme is one of the most common primary brain tumors encountered. Unfortunately, this highly malignant tumor represents over 50% of all types of primary central nervous system gliomas. The vast majority of GBMs develops quite rapidly without clinical, radiological, or morphologic evidence of a less malignant precursor lesion (primary or de novo GBMs), as compared to secondary GBMs that develop slowly by progression from diffuse low-grade astrocytomas. These GBM subtypes must be kept in mind because they may constitute distinct disease entities. Even though they look histologically quite similar, they likely involve different genetic alterations and signaling pathways. Decades of surgical therapy, radiotherapy, and chemotherapy have failed to drastically change survival. Clearly, we do not fully understand this tumor; however, the exciting genetic revolution in glioma research over the past decade is providing a promising outlook for exploring this tumor at the genetic level. Science has begun to elucidate the numerous genetic alterations and critical signaling pathways, and it has opened new exciting areas of research such as glioma stem cell biology and neoangiogenesis. This work has already begun to improve our understanding of GBM cell proliferation, migration, and invasion. Indeed, exciting novel targeted therapies are making their way to clinical trials based on this increased knowledge. This review provides the current understanding of GBM oncogenomics, signaling pathways, and glioma stem cell biology and discusses the potential new therapeutic targets on the horizon.

IDH1 mutations are early events in the development of astrocytomas and oligodendrogliomas

IDH1 encodes isocitrate dehydrogenase 1, which participates in the citric acid cycle and was recently reported to be mutated in 12% of glioblastomas. We assessed IDH1 mutations in 321 gliomas of various histological types and biological behaviors. A total of 130 IDH1 mutations was detected, and all were located at amino acid residue 132. Of these, 91% were G-->A mutations (Arg-->His). IDH1 mutations were frequent in low-grade diffuse astrocytomas (88%) and in secondary glioblastomas that developed through progression from low-grade diffuse or anaplastic astrocytoma (82%). Similarly, high frequencies of IDH1 mutations were found in oligodendrogliomas (79%) and oligoastrocytomas (94%). Analyses of multiple biopsies from the same patient (51 cases) showed that there were no cases in which an IDH1 mutation occurred after the acquisition of either a TP53 mutation or loss of 1p/19q, suggesting that IDH1 mutations are very early events in gliomagenesis and may affect a common glial precursor cell population. 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. The frequent presence of IDH1 mutations in secondary glioblastomas and their near-complete absence in primary glioblastomas reinforce the concept that despite their histological similarities, these subtypes are genetically and clinically distinct entities.

PTEN: a new guardian of the genome

The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) tumor suppressor is a phosphatase that antagonizes the phosphoinositol-3-kinase/AKT signaling pathway and suppresses cell survival as well as cell proliferation. PTEN is the second most frequently mutated gene in human cancer after p53. Germline mutations of PTEN have been found in cancer susceptibility syndromes, such as Cowden syndrome, in which over 80% of patients have mutations of PTEN. Homozygous deletion of Pten causes embryonic lethality, suggesting that PTEN is essential for embryonic development. Mice heterozygous for Pten develop spontaneous tumors in a variety of organs comparable with the spectrum of its mutations in human cancer. The mechanisms of PTEN functions in tumor suppression are currently under intense investigation. Recent studies demonstrate that PTEN plays an essential role in the maintenance of chromosomal stability and that loss of PTEN leads to massive alterations of chromosomes. The tumor suppressor p53 is known as a guardian of the genome that mediates the cellular response to environmental stress, leading to cell cycle arrest or cell death. Through completely different mechanisms, PTEN also protects the genome from instability. Thus, we propose that PTEN is a new guardian of the genome. In this review, we will discuss new discoveries on the role of PTEN in tumor suppression and explore mechanisms by which PTEN maintains genomic stability.

Assessing the cytoskeletal system and its elements in C6 glioma cells and astrocytes by atomic force microscopy

OBJECT

To investigate how the characteristic structure of the cytoskeleton in glioma cells is associated with invasiveness.

METHODS

The whole cytoskeletal system was characterized by atomic force microscopy (AFM), while single cytoskeletal elements were exhibited by AFM and using cytoskeletal protein inhibitors to inhibit microfilaments or/and microtubules and displayed by immunofluorescence microscopy. The fluorescence intensity of F-actin was measured by flow cytometry and the structural difference between C6 glioma cells and astrocytes was studied.

RESULTS

Cytoskeletons in both cells presented network structures, however, the C6 glioma cells showed an irregular edge root and their microfilaments were creber and dense. Intermediate filaments were extensive network structure with non-polarized multipoint connections. The microtubules were relatively big and long and formed tight bundles with close connections between bundles. Astrocytes had a regular and smooth edge, with sparse microfilaments, while the intermediate filaments were dense and interwoven and the microtubules were dense bundled, but only loosely connected each other. Besides, the fluorescence intensity of F-actin was significantly higher in C6 glioma cells (202.54 +/- 11.06) than in the astrocytes (62.64 +/- 10.23), P < 0.01.

CONCLUSION

Whole cytoskeleton and its elements of C6 cells were disclosed of characteristic structures associated with invasiveness. Meanwhile, the content of F-actin could be used as a parameter for measuring cell invasiveness.

GPR26: a marker for primary glioblastoma?

Glioblastomas are highly malignant brain tumours; they have been described as one of the most deadly human cancers. Two conceptual classifications of the condition exist: primary (de novo), which does not exhibit prior disease and secondary glioblastoma, which develops from a pre-existing glioma. This study investigates whether GPR26 is differentially transcribed in glioblastoma tissue from patients of different ages, in order to define a candidate genetic marker. The transcriptional profile of GPR26 was compared in nine samples: seven glioblastoma tissues and two normal brain tissues using PCR. Despite GPR26 being present in the glioblastoma tissues, it was not transcribed in any of the four cell lines tested. GPR26 transcription ratios were compared between normal and cancerous samples, also age categories <50 and >60 years were compared. Results suggested differential transcription of GPR26, which is significantly less transcribed in tissues from older patients, implied by a p-value of 0.03. This study has identified GPR26 to be a genetic indicator of primary glioblastoma, suggesting that it could be a suppressor of primary glioblastoma development.

6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3) is up-regulated in high-grade astrocytomas

The bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2) controls the glycolytic flux via the allosteric activator fructose 2,6-bisphosphate. Because of its proto-oncogenic character, the PFK-2/FBPase-2 of the PFKFB3 gene is assumed to play a critical role in tumorigenesis. We investigated the PFKFB3 expression in 40 human astrocytic gliomas and 20 non-neoplastic brain tissue specimens. The PFKFB3 protein levels were markedly elevated in high-grade astrocytomas relative to low-grade astrocytomas and corresponding non-neoplastic brain tissue, whereas no significant increase of PFKFB3 mRNA was observed in high-grade astrocytomas when compared with control tissue. In the group of glioblastomas the PFKFB3 protein inversely correlates with EGFR expression. The findings demonstrate that PFKFB3 up-regulation is a hallmark of high-grade astrocytomas offering an explanation for high glycolytic flux and lactate production in these tumors.

Genetic pathways to primary and secondary glioblastoma

Glioblastoma is the most frequent and most malignant human brain tumor. The prognosis remains very poor, with most patients dying within 1 year after diagnosis. Primary and secondary glioblastoma constitute distinct disease subtypes, affecting patients of different age and developing through different genetic pathways. The majority of cases (>90%) are primary glioblastomas that develop rapidly de novo, without clinical or histological evidence of a less malignant precursor lesion. They affect mainly the elderly and are genetically characterized by loss of heterozygosity 10q (70% of cases), EGFR amplification (36%), p16(INK4a) deletion (31%), and PTEN mutations (25%). Secondary glioblastomas develop through progression from low-grade diffuse astrocytoma or anaplastic astrocytoma and manifest in younger patients. In the pathway to secondary glioblastoma, TP53 mutations are the most frequent and earliest detectable genetic alteration, already present in 60% of precursor low-grade astrocytomas. The mutation pattern is characterized by frequent G:C-->A:T mutations at CpG sites. During progression to glioblastoma, additional mutations accumulate, including loss of heterozygosity 10q25-qter ( approximately 70%), which is the most frequent genetic alteration in both primary and secondary glioblastomas. Primary and secondary glioblastomas also differ significantly in their pattern of promoter methylation and in expression profiles at RNA and protein levels. This has significant implications, particularly for the development of novel, targeted therapies, as discussed in this review.

Cell cycle-related kinase: a novel candidate oncogene in human glioblastoma

BACKGROUND

Median survival for patients with glioblastoma multiforme, the most aggressive glioma, is only 12-15 months, despite multimodal treatment that includes surgery, chemotherapy, and radiotherapy. Thus, identification of genes that control the progression of glioblastoma multiforme is crucial for devising new therapies. We investigated the involvement of cell cycle-related kinase (CCRK), a novel protein kinase that is homologous to cyclin-dependent kinase 7, in glioblastoma multiforme carcinogenesis.

METHODS

We analyzed the expression levels of CCRK in 26 glioma patient samples (19 high-grade and seven low-grade) and normal brain by semiquantitative reverse transcription-polymerase chain reaction assays. CCRK expression was knocked down in human glioma U-373 MG and U-87 MG cells with small-interfering RNAs and short hairpin RNAs (siCCRK and shCCRK, respectively), and cell proliferation, cell cycle distribution, and cyclin-dependent kinase 2 (CDK2) phosphorylation were examined. A subcutaneous nude mouse xenograft model (n = 4 mice per group) was used to study the effect of CCRK knockdown and overexpression on tumorigenicity and growth of glioblastoma multiforme cells in vivo. All statistical tests were two-sided.

RESULTS

CCRK mRNA was elevated at least 1.5-fold and as much as 3.7-fold in 14 (74%) of 19 high-grade glioblastoma multiforme patient samples and in four (80%) of five glioma cell lines examined compared with normal brain tissue. Suppression of CCRK by siCCRK inhibited the proliferation of U-373 MG and U-87 MG glioblastoma cells in a time- and dose-dependent manner. The growth-inhibiting effect of siCCRK was mediated via G1- to S-phase cell cycle arrest and reduced CDK2 phosphorylation. CCRK knockdown statistically significantly suppressed glioma cell growth in vivo as indicated by the mean tumor volumes at week 6 after tumor cell injection (U-373-control = 1352 mm3, U-373-shCCRK = 294 mm3, difference = 1058 mm3, 95% confidence interval [CI] = 677 to 1439 mm3, P<.001; U-87-control = 1910 mm3, U-87-shCCRK = 552 mm3, difference = 1358 mm3, 95% CI = 977 to 1739 mm3, P<.001).

CONCLUSIONS

CCRK is a candidate oncogene in glioblastoma multiforme tumorigenesis.

Low HER2-expressing glioblastomas are more often secondary to anaplastic transformation of low-grade glioma

BACKGROUND

Anti-Human Epithelial Receptor Type 2 (HER2) antibodies have the ability to induce in vitro apoptosis of glioblastoma (GBM) cells. This study was designed to evaluate the variability of HER2 expression in GBM and its role as a possible prognosis factor.

METHODS

Data of 57 patients with GBM and 16 patients with grade III gliomas were retrospectively analyzed. The expression of HER2 was determined by immunohistochemistry and intensity was noted from 0+ to 3+. We compared the HER2 expression in de novo GBM and in GBM resulting from anaplastic transformation of low-grade glioma ("secondary GBM"). Statistical analysis was performed using univariate analysis and the Kaplan-Meier method.

FINDINGS

All GBM expressing highly HER2 (2+ and 3+) were de novo GBM. All secondary GBM expressed HER2 with low intensity (0+ and 1+). Survival time was significantly longer when HER2 expression was low (Log Rank test P = 0.04). The patterns of HER2 expression were similar between grade III gliomas and secondary GBM.

CONCLUSIONS

To our best knowledge, our study showed for the first time a significant association between HER2 expression and the type of GBM, with subsequent influence on survival rate. GBM with low-HER2 expression are more likely to be secondary GBM, carrying a better prognosis than de novo GBM.

Cytogenetic analyses in 81 patients with brain gliomas: correlation with clinical outcome and morphological data

Specific gene mutations, loss of heterozygosity, deletions and/or amplifications of entire chromosomal regions and gene silencing have been described in gliomas. 82 samples from 81 patients were investigated to detect the deletion of TP53, RB1, CDKN2A genes, deletion of 1p36 and 19q13.3 region, amplification of EGFR gene, trisomy of chromosome 7 and monosomy of chromosome 10 in glial cells. Dual-colour interphase fluorescence in situ hybridization (I-FISH) with locus-specific and/or chromosome enumeration DNA probes were used for cytogenetic analyses. In the study, molecular cytogenetic analyses were successfully performed in 74 patients (91.3%) and were uninformative in 7 only (8.7%). The cytogenetic analyses were correlated with morphological data and clinical outcome. I-FISH was the essential part of diagnostics. In comparison with the clinical data, the patients' age seems to be a factor more important for the overall survival, rather than cytogenetic findings in glial tumours. The combined deletion of 1p36 and 19q13.3 chromosomal regions predicts longer overall survival for patients with oligodendroglial tumours.

Methylation of the PTEN promoter defines low-grade gliomas and secondary glioblastoma

Glioblastoma multiforme (GBM) can present as either de novo or secondary tumors arising from previously diagnosed low-grade gliomas. Although these tumor types are phenotypically indistinguishable, de novo and secondary GBMs are associated with distinct genetic characteristics. PTEN mutations, which result in activation of the phosphoinositide 3-kinase (PI3K) signal transduction pathway, are frequent in de novo but not in secondary GBMs or their antecedent low-grade tumors. Results we present here show that grade II astrocytomas, oligodendrogliomas, and oligoastrocytomas commonly display methylation of the PTEN promoter, a finding that is absent in nontumor brain specimens and rare in de novo GBMs. Methylation of the PTEN promoter correlates with protein kinase B (PKB/Akt) phosphorylation, reflecting functional activation of the PI3K pathway. Our results also demonstrate frequent methylation of the PTEN promoter in grade III astrocytomas and secondary GBMs, consistent with the hypothesis that these tumors arise from lower grade precursors. PTEN methylation is rare in de novo GBMs and is mutually exclusive with PTEN mutations. We conclude that methylation of the PTEN promoter may represent an alternate mechanism by which PI3K signaling is increased in grade II and III gliomas as well as secondary GBMs, a finding that offers new therapeutic approaches in these patients.

Prognosis factors of survival time in patients with glioblastoma multiforme: a multivariate analysis of 340 patients

BACKGROUND

The prognosis of glioblastoma multiforme remains poor despite recent therapeutic advances. Several clinical and therapeutic factors as well as tumour characteristics have been reported as significant to survival. A more efficient determination of the prognostic factors is required to optimize individual therapeutic management. The aim of our study was to evaluate by univariate then multivariate analysis the factors that influence prognosis and particularly survival.

METHODS

Data of 340 patients with newly-diagnosed GBM were retrospectively analyzed. Univariate analysis of prognosis factors of survival time was performed. Factors that seemed determinant were evaluated by Kaplan-Meier survival curves. Finally, the significant factors found in univariate analysis were tested in multivariate analysis using the COX regression method.

FINDINGS

Using multivariate analysis, the following factors were found to influence survival: radiotherapy was the predominant factor followed by radical surgery, tumour location, age and chemotherapy. Patients treated with temozolomide had a markedly better survival rate than patients treated with other chemotherapies (Log-rank test P < 0.005). The values of GBM type (de novo or secondary), as well as repeated surgery and partial surgery (vs. simple biopsy) were suggested by univariate analysis but not confirmed by the COX regression method. After radical surgery, progression-free survival was correlated to overall survival (r = 0.87, P < 10e-5). CONCLUSIONS; The influence of radiotherapy on survival was greater than the influence of age, an argument supporting the proposition of radiotherapy for patients until at least age 70. In the case of recurrence, the correlation between overall survival and progression-free survival is an important factor when considering the therapeutic options. Initial radical surgery and repeated procedures dramatically influence survival. The benefit of partial surgery remains difficult to evaluate. Partial surgery could be used to decrease intracranial pressure and to minimize residual tumours in order to enable treatment by chemotherapy and radiotherapy. The value of temozolomide treatment was confirmed.

Molecular pathogenesis of pediatric astrocytic tumors

Astrocytomas are the most common pediatric brain tumors, accounting for 7%-8% of all childhood cancers. Relatively few studies have been performed on their molecular properties; therefore, classification of pediatric astrocytic tumors into genetic subtypes similar to that of adult tumors remains to be defined. Here, we report an extensive characterization of 44 pediatric astrocytomas--16 diffuse astrocytomas (WHO grade II), 10 anaplastic astrocytomas (WHO grade III), and 18 glioblastomas (WHO grade IV)--in terms of genetic alterations frequently observed in adult astrocytomas. Some form of p53 mutation was found in three diffuse astrocytomas, in three anaplastic astrocytomas, and in six glioblastomas examined; PTEN mutations were detected only in two glioblastomas. EGFR amplification was detected in only one anaplastic astrocytoma and two glioblastomas, but no amplification was observed for the PDGFR-alpha gene. Loss of heterozygosity (LOH) on 1p/19q and 10p/10q was less common in pediatric astrocytic tumors than in those seen in adults, but the frequency of LOH on 22q was comparable, occurring in 44% of diffuse astrocytomas, 40% of anaplastic astrocytomas, and 61% of glioblastomas. Interestingly, a higher frequency of p53 mutations and LOH on 19q and 22q in tumors from children six or more years of age at diagnosis was found, compared with those from younger children. Our results suggest some differences in children compared to adults in the genetic pathways leading to the formation of de novo astrocytic tumors. In addition, this study suggests potentially distinct developmental pathways in younger versus older children.

Association of loss of heterozygosity and PTEN gene abnormalities with paraclinical, clinical modalities and survival time of glioma patients in Malaysia

BACKGROUND

The pattern of allelic loss of heterozygosity (LOH) and PTEN mutations appear to be associated with the progression of gliomas leading to a decrement in the survival rate of patients. This present study was carried out to determine the LOH and PTEN mutational status in glioma patients and its association with patients' survival.

METHODS

Thirty-seven Malaysian glioma patients of the Malay race were subject to PTEN mutational analysis and the presence of LOH using the cold single-strand conformation polymorphism method, and their clinical and paraclinical response were correlated.

RESULTS

Among analysed glioma patients, seven (21.6%) cases with PTEN mutations were detected and 12 (32.4%) of 37 patients showed presence of LOH. Univariate analysis showed that tumour grade, vascularization, PTEN mutation, LOH and combination of both PTEN mutation and LOH were significantly associated with glioma patients' survival. Multivariate analysis revealed that no factors contributed to survival time.

CONCLUSION

The results show that PTEN mutation and LOH are quite frequent in Malaysian glioma patients. However, they have no impact on the survival outcome of patients.

Malignant glioma progression and nitric oxide

Glioblastoma multiforme, the most common of the malignant gliomas, carries a dismal prognosis in spite of the most aggressive therapy and recent advances in molecular pathways of glioma progression. Although it has received relatively little attention in the setting of malignant gliomas, nitric oxide metabolism may be intimately associated with the disease process. Interestingly, nitric oxide has both physiological roles (e.g., neurotransmitter-like activity, stimulation of cyclic GMP), and pathophysiological roles (e.g., neoplastic transformation, tumor neovascularization, induction of apoptosis, free radical damage). Moreover, whether nitric oxide is neuroprotective or neurotoxic in a given disease state, or whether it enhances or diminishes chemotherapeutic efficacy in malignant neoplasia, is unresolved. This review discusses the multifaceted activity of nitric oxide with particular reference to malignant gliomas.

TGF-beta1, TNF-alpha and cytochrome c in human astrocytic tumors: a short-term follow up and correlation with survival

OBJECTIVES

To evaluate the association of signals of apoptosis namely, TGF-beta1, TNF-alpha and cytochrome c release in cytoplasm with survival rate to determine the potential use of such parameters as predictive markers for patients with astrocytomas.

DESIGN AND METHODS

We measured TGF-beta1, TNF-alpha and cytoplasmic cytochrome c in 30 astrocytic tumors Grade II, III and IV.

RESULTS

We found that TNF-alpha and cytochrome c release in Grade IV tends to be significantly lower than those in Grade II, whereas TGF-beta1 did not significantly change in the different grades. Patients with astrocytic tumors having elevated cytochrome c showed a better survival rate compared to those with less release. There is neither a correlation shown between TNF-alpha and cytochrome c release nor between TNF-alpha and patient survival. TGF-beta1 was positively correlated with cytochrome c release. Patients showing such correlation had increased survival rate over 18 months follow up period.

CONCLUSION

These data suggest that TGF-beta1 and cytochrome c may be useful prognostic markers that help patients' stratification and in adjusting the disciplines of therapy.

PTEN modulates hepatitis B virus-X protein induced survival signaling in Chang liver cells

PTEN gene, a novel tumor suppressor is frequently mutated or deleted in several malignancies including human hepatocellular carcinoma (HCC). We report previously that human hepatitis B virus-X (HBx) protein achieves protection from apoptotic cell death through-PI3K-Akt-Bad signaling that is p53-independent in liver cells (JBC; 276, 16969 (2000)). In this report, we demonstrated the PTEN effect on HBx induced anti-apoptotic signaling in Chang liver cells (CHL). Expression of PTEN in CHL cells downregulate HBx induced PI3K, Akt activities, Akt, Bad phosphorylations, decreased caspase 3 activity and protection from DNA fragmentations. PTEN suppression of CHL cell growth at G1 phase (JBC;278,4057(2003)) in cell cycle analysis, which is overcome by HBx activated Akt/PKB further confirmed that same PI3K/Akt pathway is involved in cell survival and apoptosis by HBx and PTEN. PTEN suppression of HBx-mediated cell survival through PI3K pathway is specific, since PTEN does not suppress the effect of HBx on the protection from Fas-mediated apoptosis. Taken together, these findings demonstrate that PTEN potently modulate HBx-mediated signaling and is a viable target in therapeutic approaches to inhibit the formation of HCC caused by HBV infections.

p14ARF deletion and methylation in genetic pathways to glioblastomas

The CDKN2A locus on chromosome 9p21 contains the p14ARF and p16INK4a genes, and is frequently deleted in human neoplasms, including brain tumors. In this study, we screened 34 primary (de novo) glioblastomas and 16 secondary glioblastomas that had progressed from low-grade diffuse astrocytomas for alterations of the p14ARF and p16INK4a genes, including homozygous deletion by differential PCR, promoter hypermethylation by methylation-specific PCR, and protein expression by immunohistochemistry. A total of 29 glioblastomas (58%) had a p14ARF homozygous deletion or methylation, and 17 (34%) showed p16INK4a homozygous deletion or methylation. Thirteen glioblastomas showed both p14ARF and p16INK4a homozygous deletion, while nine showed only a p14ARF deletion. Immunohistochemistry revealed loss of p14ARF expression in the majority of glioblastomas (38/50, 76%), and this correlated with the gene status, i.e. homozygous deletion or promoter hypermethylation. There was no significant difference in the overall frequency of p14ARF and p16INK4a alterations between primary and secondary glioblastomas. The analysis of multiple biopsies from the same patients revealed hypermethylation of p14ARF (5/15 cases) and p16INK4a (1/15 cases) already at the stage of low-grade diffuse astrocytoma but consistent absence of homozygous deletions. These results suggest that aberrant p14ARF expression due to homozygous deletion or promoter hypermethylation is associated with the evolution of both primary and secondary glioblastomas, and that p14ARF promoter methylation is an early event in subset of astrocytomas that undergo malignant progression to secondary glioblastoma.

Granular cell astrocytomas show a high frequency of allelic loss but are not a genetically defined subset

Granular cell astrocytomas (GCA) are an uncommon morphologic variant of infiltrative glioma that contains a prominent population of atypical granular cells. As a rule, they are biologically aggressive compared to similar tumors without granular features. We sought to determine whether GCAs possess distinct genotypic alterations that might reflect their unique morphology or clinical behavior. Eleven GCAs occurring in 7 men and 4 women ranging in age from 46 to 75 years were investigated for genetic alterations of known significance in glial tumorigenesis, including LOH at 1p, 9p, 10q, 17p, and 19q, point mutations of TP53, deletions of p16(CDKN2A) and p14ARF, as well as EGFR amplifications. Tumors included had an infiltrative growth pattern and consisted of large, round cells packed with eosinophilic, PAS-positive granules that varied in quantity, ranging from 30 to 100% of tumor cells. Three tumors were of WHO grade II, one was grade III, and 7 were grade IV lesions. Overall, the tumors showed higher frequencies of LOH at 1p, 9p, 10q, 17p, and 19q than typical infiltrating astrocytomas of similar grades. Losses on 9p and 10q occurred in nearly all cases, including low grade lesions. TP53 mutations were identified in 2 grade IV GCAs, while combined p14ARF and p16(CDKN2A) homozygous deletions were noted in only one grade IV lesion. None showed EGFR amplification. We found no genetic alterations specific for GCA. Instead, it appears that granular cell change occurs across genetic subsets. The high frequency of allelic loss, especially on 9p and 10q, may confer aggressive growth potential and be related to their rapid clinical progression.

Allelic Losses of Chromosome 10 in Glioma Tissues Detected by Quantitative Single-Strand Conformation Polymorphism Analysis

Background: Detection of loss of heterozygosity (LOH) in clinical tissue samples is frequently difficult because samples are usually contaminated with noncancerous cells or because tumor cells in single tissues have genetic heterogeneity, and the precision of available techniques is insufficient for reliable analysis in such materials. We hypothesized that single-strand conformation polymorphism (SSCP) analysis can precisely quantify the gene dosage in mixed samples and is suitable for detection of LOH in clinical tissue samples.

Methods: We assessed the accuracy of a fluorescent SSCP method for the quantification of single-nucleotide polymorphism (SNP) alleles, using DNAs that were composed of cancerous DNA mixed with noncancerous DNA at various ratios. We applied this method to precisely characterize LOH in glioma tissue samples, using 96 SNPs that were evenly distributed throughout chromosome 10.

Results: LOH could be detected even in the cancerous DNA heavily contaminated (up to 80%) with noncancerous DNA. Using this method, we obtained LOH profiles of 56 gliomas with resolution at the SNP level (i.e., 1.5-Mbp interval). Anaplastic astrocytomas exhibited both 10p and 10q LOH, whereas diffuse astrocytomas frequently (63% of the cases) exhibited loss of 10p alone. We also found a possible new LOH region (around 10p13) in gliomas.

Conclusions: The present method is effective for precise mapping of LOH region in surgically obtained tumor tissues and could be applicable to the genetic diagnosis of cancers other than gliomas.

Frequent HRK inactivation associated with low apoptotic index in secondary glioblastomas

To detect and identify the genetic alterations and methylation status of the HRK gene in human glioblastomas, we analyzed a cohort of astrocytic tumors for hypermethylation, loss of heterozygosity on 12q13.1, and gene expression. Our study examined a series of 36 diffuse low-grade astrocytomas, 32 anaplastic astrocytomas, 64 primary glioblastomas, and 28 secondary glioblastomas that had evolved from either 24 low-grade diffuse astrocytomas or 4 anaplastic astrocytomas. The region around the HRK transcription start site was methylated in 19% of diffuse astrocytomas, in 22% of anaplastic astrocytomas, in 27% of primary glioblastomas, and in 43% of secondary glioblastomas. HRK expression was significantly reduced in 61% of secondary glioblastomas as compared to other types of tumors, and aberrant methylation was closely associated with loss of expression. Reverse transcription-PCR analysis also demonstrated a clear agreement between reduced HRK protein levels and low or absent HRK transcripts. Lack of HRK immunoreactivity was significantly correlated with a low apoptotic index, whereas a strong association between methylation status and apoptosis was found only in secondary glioblastomas. Abnormal methylation of HRK was detected in astrocytic tumors concurrent with methylation of multiple genes, including p16(INK4a) and p14(ARF). Interestingly, these epigenetic changes in secondary glioblastoma were further associated with wild-type p53. Our findings suggest that HRK is inactivated mainly by aberrant DNA methylation in astrocytic tumors and that reduced HRK expression contributes to the loss of apoptotic control in high-grade tumors. Reduced expression of HRK may serve as one important molecular mechanism in progression to secondary glioblastoma.

Loss of Heterozygosity on Chromosome 10p14–p15 in Colorectal Carcinoma

High frequencies of loss of heterozygosity (LOH) on chromosome 10p14-p15 have been reported in various tumors, including gliomas, pulmonary carcinoid tumors and cervical, hepatic, prostatic and esophageal carcinomas. However, LOH on chromosome 10p14-p15 in colorectal tumors has not been reported. Therefore, we examined LOH on chromosome 10p14-p15 in 60 colorectal carcinomas (21 superficial and 39 advanced types) by microsatellite assay. Three microsatellite loci, D10S191 (10p14), D10S558 and D10S249 (10p15) were examined by polymerase chain reaction [early colorectal carcinomas, LOH of markers D10S191 (36%), D10S558 (7%) and D10S249 (11%), and in advanced colorectal carcinomas, LOH of markers D10S191 (20%), D10S558 (13%) and D10S249 (33%)]. There were no significant associations between LOH on chromosome 10p14-p15 and clinicopathologic features, including patient age, sex, tumor location, depth of invasion, histologic type, lymph node metastasis and prognosis. These data suggest that a putative tumor suppressor gene associated with colorectal carcinogenesis may be located on chromosome 10p14-p15 and that alteration of this gene may be involved in the development but not progression of colorectal tumors.

Does vasculogenic mimicry exist in astrocytoma?

Vasculogenic mimicry (VM) has been observed in melanoma and in some nonmelanoma tumor types. It is unknown whether a similar VM phenomenon exists in astrocytoma. The present study was to examine 45 astrocytomas (including World Health Organization grade II 15 cases, grade III 15 cases, and grade IV 15 cases) by CD34 endothelial marker periodic acid-Schiff (PAS) dual staining to see if VM existing in these tumors. The results demonstrated that endothelium-lined vessels dominated the tumor microvasculature and stained positively for PAS, laminin, and endothelial marker. PAS-positive pattern of VM was found in two grade IV astrocytomas. Channels stained positively for PAS, laminin, and negatively for CD34 of the VM entrapped in the tumor tissue. Erythrocytes could be observed in some of these channels. In these networks of PAS-positive pattern, spots of weak reaction for CD34 were observed, suggesting the incorporation of VM channel and normal vessel. Furthermore, in astrocytoma, especially glioblastoma, focus of anaplastic tumor cells appeared with CD34 expression, whereas some tumor cells lost glial fibrillary acid protein expression. It is assumed that genetically deregulated tumor cells in astrocytoma could lose the astrocyte-specific protein and express inappropriate markers not expected in cells of astrocyte lineage. The present results suggest that VM phenomenon exists in some malignant astrocytoma.

Pathology and molecular genetics of astrocytic gliomas

Astrocytic gliomas are the most common primary brain tumours. Here we summarize the characteristic neuropathological features of the different types of astrocytic neoplasms according to the World Health Organization classification of tumours of the nervous system. In addition, we report on the present state of the art concerning the molecular genetics of these tumours. Over the past 20 years a number of recurrent chromosomal,genetic and epigenetic alterations have been found to be associated with the different histological types and malignancy grades of astrocytic tumours. However, we are still far from understanding the complex mechanisms that underly tumour initiation and progression in the individual case. Furthermore, the clinical significance of molecular parameters for the diagnostic and prognostic assessment of astrocytic gliomas is still limited. Therefore further investigation of the molecular mechanisms underlying oncogenesis and progression of these most common brain tumours is necessary to improve their diagnostic assessment and to devise novel, individually tailored treatment strategies.

Array Comparative Genomic Hybridization Identifies Genetic Subgroups in Grade 4 Human Astrocytoma

Alterations of DNA copy number are believed to be important indicators of tumor progression in human astrocytoma. We used an array of bacterial artificial chromosomes to map relative DNA copy number in 50 primary glioblastoma multiforme tumors at approximately 1.4-Mb resolution. We identified 33 candidate sites for amplification and homozygous deletion in these tumors. We identified three major genetic subgroups within these glioblastoma multiforme tumors: tumors with chromosome 7 gain and chromosome 10 loss, tumors with only chromosome 10 loss in the absence of chromosome 7 gain, and tumors without copy number change in chromosomes 7 or 10. The significance of these genetic groups to therapeutics needs further study.

Alterations of cell cycle regulators in gliomatosis cerebri

Gliomatosis cerebri (GC) is regarded as a rare glial neoplasm of unknown origin, and a detailed analysis of molecular alterations underlying this disease has started only recently. However, because GC characteristically affects large parts of the brain and spinal cord, the distribution of genetic alterations may be highly variable between different tumor areas. Additionally, tumor areas with varying degrees of differentiation may be present, raising the possibility to model the genetic events associated with astrocytoma progression. Here we analyzed various tumor regions with features of low-grade and high-grade astrocytomas from 9 autopsy-proven GC cases for the immunoexpression of the cell cycle-controlling proteins mdm2, p21, p27/kip1, p16, and Rb. The samples were also screened for EGFR expression, and for amplification of the EGFR and MDM2 genes. Furthermore, allelic losses of the CDKN2A gene and of a PTEN flanking region of chromosome 10 were determined. We detected tumor regions with immunoexpression of p21 only rarely in our series, without association to the tumor grade. No MDM2 gene amplification was detected. In contrast, three cases demonstrated maintained Rb expression. The expression of p27(kip1) showed a clear reduction with increasing astrocytoma malignancy in 7 cases. Allelic loss of the CDKN2A gene occurred in 5 patients but was not related to the tumor grading, nor to the intensity of p16 immunoexpression. No homozygous CDKN2Adeletions were detected. EGFR amplification was also absent in our series, but one case demonstrated EGFR expression only in the high-grade tumor area. Allelic losses on chromosome 10 were found in one out of six informative cases. However, marked differences in the immunoexpression, as well as in the distribution of genetic aberrations were seen between different tumor samples within a given case. The distribution of the alterations suggests that these molecular genetic changes represent secondary events, which may develop within tumor clones derived from a common founder tumor clone characterized by extraordinary spreading through the brain. Moreover, the detected aberrations in gliomatosis cerebri can reflect the tumor progression associated with secondary malignant astrocytoma formation even within a single case.

Genetic pathways to glioblastomas

Glioblastomas, the most frequent and malignant human brain tumors, may develop de novo (primary glioblastoma) or by progression from low-grade or anaplastic astrocytoma (secondary glioblastoma). These glioblastoma subtypes constitute distinct disease entities that affect patients of different ages and develop through different genetic pathways. Our recent population-based study in the Canton of Zürich, Switzerland, shows that primary glioblastomas develop in older patients (mean age, 62 years) and typically show LOH on chromosome 10q (69%) and other genetic alterations (EGFR amplification, TP53 mutations, p16INK4a deletion, and PTEN mutations) at frequencies of 24-34%. Secondary glioblastomas develop in younger patients (mean, 45 years) and frequently show TP53 mutations (65%) and LOH 10q (63%). Common to both primary and secondary glioblastoma is LOH on 10q, distal to the PTEN locus; a putative suppressor gene at 10q25-qter may be responsible for the glioblastoma phenotype. Of the TP53 point mutations in secondary glioblastomas, 57% were located in hotspot codons 248 and 273, while in primary glioblastomas, mutations were more widely distributed. Furthermore, G:C-->A:T mutations at CpG sites were more frequent in secondary than in primary glioblastomas (56% vs 30%). These data suggest that the TP53 mutations in these glioblastoma subtypes arise through different mechanisms. There is evidence that G:C-->A:T transition mutations at CpG sites in the TP53 gene are significantly more frequent in low-grade astrocytomas with promoter methylation of the O6-methylguanine-DNA methyltransferase (MGMT) gene than in those without methylation. This suggests that, in addition to deamination of 5-methylcytosine (the best known mechanism of formation of G:C-->A:T transitions at CpG sites), involvement of alkylating agents that produce O6-methylguanine or related adducts recognized by MGMT cannot be excluded in the pathway leading to secondary glioblastomas.

Frequent LOH on 22q12.3 and TIMP-3 inactivation occur in the progression to secondary glioblastomas

Frequent allelic losses on the long arm of chromosome 22 (22q) in gliomas indicate the presence of tumor suppressor gene (TSG) at this location. However, the target gene(s) residing in this chromosome are still unknown and their putative roles in the development of astrocytic tumors, especially in secondary glioblastoma, have not yet been defined. To compile a precise physical map for the region of common deletions in astrocytic tumors, we performed a high-density loss of heterozygosity (LOH) analysis using 31 polymorphic microsatellite markers spanning 22q in a series of grade II diffuse astrocytomas, anaplastic astrocytomas, primary glioblastomas, and secondary glioblastomas that had evolved from lower grade astrocytomas. LOH was found at one or more loci in 33% (12/36) of grade II diffuse astrocytomas, in 40% (4/10) of anaplastic astrocytomas, in 41% (26/64) of primary glioblastomas, and in 82% (23/28) of secondary glioblastomas. Characterization of the 22q deletions in primary glioblastomas identified two sites of minimally deleted regions at 22q12.3-13.2 and 22q13.31. Interestingly, 22 of 23 secondary glioblastomas affected shared a deletion in the same small (957 kb) region of 22q12.3, a region in which the human tissue inhibitor of metalloproteinases-3 (TIMP-3) is located. Investigation of the promoter methylation and expression of this gene indicated that frequent hypermethylation correlated with loss of TIMP-3 expression in secondary glioblastoma. This epigenetic change was significantly correlated to poor survival in eight patients with grade II diffuse astrocytoma. Our results suggest that a 957 kb locus, located at 22q12.3, may contain the putative TSG, TIMP-3, that appears to be relevant to progression to secondary glioblastoma and subsequently to the prognosis of grade II diffuse astrocytoma. In addition, the possibility of other putative TSGs on 22q12.3-13.2 and 22q13.31 that may also be involved in the development of primary glioblastomas cannot be ruled out.

Comparative genomic hybridization analysis of astrocytomas: prognostic and diagnostic implications

Astrocytoma is comprised of a group of common intracranial neoplasms that are classified into four grades based on the World Health Organization histological criteria and patient survival. To date, histological grade, patient age, and clinical performance, as reflected in the Karnofsky score, are the most reliable prognostic predictors. Recently, there has been a significant effort to identify additional prognostic markers using objective molecular genetic techniques. We believe that the identification of such markers will characterize new chromosomal loci important in astrocytoma progression and aid clinical diagnosis and prognosis. To this end, our laboratory used comparative genomic hybridization to identify DNA sequence copy number changes in 102 astrocytomas. Novel losses of 19p loci were detected in low-grade pilocytic astrocytomas and losses of loci on 9p, 10, and 22 along with gains on 7, 19, and 20 were detected in a significant proportion of high-grade astrocytomas. The Cox proportional hazards statistical modeling showed that the presence of +7q and -10q comparative genomic hybridization alterations significantly increased a patient's risk of dying, independent of histological grade. This investigation demonstrates the efficacy of comparative genomic hybridization for identifying tumor suppressor and oncogene loci in different astrocytic grades. The cumulative effect of these loci is an important consideration in their diagnostic and prognostic implications.

Molecular pathogenesis of astrocytic tumours

Our current knowledge of the molecular pathogenesis of the diffuse adult astrocytic tumours is vast if compared to 20 years ago, yet we are far from understanding the details of this process at the molecular level and using such an understanding to logically and specifically treat patients' tumours. In other astrocytic tumours we have little or no knowledge of the molecular processes. This article will attempt to summarise the histological classification criteria and genetic data for all the astrocytic tumours. The current World Health Organisation classification lists six entities, some with subgroups. Common problems associated with the diagnosis of these tumours are outlined. While the molecular findings are not as yet used clinically, we are approaching a time when the histological investigation will have to be supplemented with molecular data to ensure the best choice of treatment for the patient and as an accurate indicator of prognosis.

Cyclin-dependent kinase inhibition by the KLF6 tumor suppressor protein through interaction with cyclin D1

Kruppel-like factor 6 (KLF6) is a tumor suppressor gene inactivated in prostate and colon cancers, as well as in astrocytic gliomas. Here, we establish that KLF6 mediates growth inhibition through an interaction with cyclin D1, leading to reduced phosphorylation of the retinoblastoma protein (Rb) at Ser(795). Furthermore, introduction of KLF6 disrupts cyclin D1-cyclin-dependent kinase (cdk) 4 complexes and forces the redistribution of p21(Cip/Kip) onto cdk2, which promotes G(1) cell cycle arrest. Our data suggest that KLF6 converges with the Rb pathway to inhibit cyclin D1/cdk4 activity, resulting in growth suppression.

Frequent LOH at chromosome 12q22-23 and Apaf-1 inactivation in glioblastoma

Glioblastoma (GB) often has loss of heterozygosity on the chromosomes, 1p, 10p, 10q, 11p, 17p, 19q, 22q, and several others. In the case of chromosome 12q, however, it remains to be seen whether LOH occurs. Apaf-1, the apoptotic protease activating factor-1, located at chromosome 12q22-23, is a major effecter of the p53 mediated apoptosis pathway, and Apaf-1 inactivation due to chromosome 12q22-23 LOH and hypermethylation may be involved in some of the neoplasms in malignancy. However, little is known about the frequency of the 12q22-23 LOH or the state of Apaf-1 in GB. To elucidate their involvement in GB, we analyzed a series of 33 GBs for chromosome 12q22-23 LOH, Apaf-1 mRNA expression, and Apaf-1 protein expression, using microsatellite analysis, reverse transcription (RT)-PCR analysis, and immunohistochemical (IHC) analysis, respectively. We also evaluated if and how the 12q22-23 LOH correlated with the p53 gene mutation and EGFR gene amplification. Chromosome 12q22-23 LOH was detected in 14 (42%) of 33 cases. Among the examined cases with LOH at 12q22-23, a low expression of Apaf-1 mRNA was detected in 9 (69%) of 13 cases, and a low expression of Apaf-1 protein was detected in 12 (86%) of 14 cases. The 12q22-23 LOH was significantly correlated with low expression of mRNA and protein (p<0.05, p<0.001 respectively). The p53 gene mutation and EGFR gene amplification were found in 13 cases (39%) and 8 cases (24%), respectively, and these gene alterations were inversely correlated. However, 12q22-23 LOH had no correlations with the p53 gene mutation or EGFR gene amplification. Six of 9 GBs (67%) with neither p53 gene mutation nor EGFR gene amplification tested positive for 12q22-23 LOH. These GBs are likely to belong to another subset independent from the 2 common genetic subsets in GB (one with p53 gene mutation and without EGFR gene amplification, and the other with EGFR gene amplification and without p53 gene mutation). Twenty-three (70%) out of the 33 GBs with the 12q22-23 LOH also tested positive for Apaf-1 inactivation or p53 gene mutation. This high frequency of alterations in the apoptosis-associated factors prompts a speculation that abrogation of the Apaf-1 and p53 mediated apoptosis pathway may play an important role in the tumorigenesis of GB.

Methyl-[11C]- l-methionine uptake as measured by positron emission tomography correlates to microvessel density in patients with glioma

Positron emission tomography (PET) using methyl-[(11)C]- l-methionine ([(11)C]MET) is a useful tool in the diagnosis of brain tumours. The main mechanism of [(11)C]MET uptake is probably increased transport via the L-transporter system located in the endothelial cell membrane. We used [(11)C]MET-PET and microvessel count in glioma specimens to investigate whether the increased amino acid uptake is related to angiogenesis. Twenty-one patients with newly diagnosed and histologically confirmed glioma were investigated with [(11)C]MET-PET before open surgery. [(11)C]MET uptake was determined within an 8-mm region of interest in the area of the tumour showing the highest uptake, and the ratio to uptake in the corresponding contralateral region was calculated. To measure angiogenesis, immunostaining with factor VIII antibody was applied to sections from tumour tissue, and highlighted microvessels were counted in the area of highest vascularisation. In the entire patient group, a positive correlation was found between microvessel count and [(11)C]MET uptake (Spearman: r=0.89, P<0.001). This correlation was also significant in subgroups of patients [patients with grade II and III astrocytomas (Spearman: r=0.77, P<0.01) and patients with glioblastoma (Spearman: r=0.64, P<0.05)]. Angiogenesis, as assessed by microvessel count, and increased amino acid uptake, as assessed by [(11)C]MET-PET, are closely related events in gliomas. [(11)C]MET-PET offers a direct measure of amino acid transport and an indirect measure of microvessel density. [(11)C]MET-PET might be a useful tool to select potential responders to anti-angiogenic therapy and to monitor patients during such therapy.

PTEN tumor suppressor regulates p53 protein levels and activity through phosphatase-dependent and -independent mechanisms

We show in this study that PTEN regulates p53 protein levels and transcriptional activity through both phosphatase-dependent and -independent mechanisms. The onset of tumor development in p53(+/-);Pten(+/-) mice is similar to p53(-/-) animals, and p53 protein levels are dramatically reduced in Pten(-/-) cells and tissues. Reintroducing wild-type or phosphatase-dead PTEN mutants leads to a significant increase in p53 stability. PTEN also physically associates with endogenous p53. Finally, PTEN regulates the transcriptional activity of p53 by modulating its DNA binding activity. This study provides a novel mechanism by which the loss of PTEN can functionally control "two" hits in the course of tumor development by concurrently modulating p53 activity.

Genomic structure of the human BCCIP gene and its expression in cancer

Human BCCIPalpha (Tok-1alpha) is a BRCA2 and CDKN1A (Cip1, p21) interacting protein. Our previous studies have showed that overexpression of BCCIPalpha inhibits the growth of certain tumor cells [Oncogene 20 (2001) 336]. In this study, we report the genomic structure of the human BCCIP gene, which contains nine exons. Alternative splicing of the 3'-terminal exons produces two isoforms of BCCIP transcripts, BCCIPalpha and BCCIPbeta. The BCCIP gene is flanked by two genes that are transcribed in the opposite orientation of the BCCIP gene. It lies head-to-head and shares a bi-directional promoter with the uroporphyrinogen III synthase (UROS) gene. The last three exons of BCCIP gene overlap the 3'-terminal seven exons of a DEAD/H helicase-like gene (DDX32). Using a matched normal/tumor cDNA array, we identified a reduced expression of BCCIP in kidney tumor, suggesting a role of BCCIP in cancer etiology.

Influence of p53 mutations on prognosis of patients with glioblastoma

BACKGROUND

The influence of p53 mutations on the biology of astrocytic tumors is controversial. p53 is thought to be inactivated in the early stage of gliomagenesis; however, what role its inactivation plays in the malignancy of gliomas remains unknown. To understand the significance of p53 inactivation, the authors identified the locus of p53 gene mutation in glioma samples at different stages of progression and studied the correlation between the mutation and clinical behavior.

METHODS

Samples from newly diagnosed gliomas, including pure and mixed astrocytomas, were analyzed for p53 mutations using a yeast functional assay. To determine the locus of the gene mutations, DNA sequencing was performed.

RESULTS

The incidence of p53 mutations was higher in anaplastic astrocytomas (AA, 48%) than glioblastomas (GBM, 31%). There was no significant difference in the average ages of GBM patients with and without p53 mutations (54.9 years +/- 2.3 and 53.2 years +/- 4.6, respectively). In GBM patients, the mutation did not affect progression free survival or overall survival. Astrocytomas and GBM differed in the distribution of p53 mutation loci.

CONCLUSIONS

The p53 gene mutation does not markedly affect the survival of GBM patients. The difference in the location of p53 mutations between AA and GBM suggests that in gliomas, the p53 mutation may contribute not only to tumorigenesis (as an early event) but also to progression to malignancy (as a late event).