A transcript map of the chromosome 19q-arm glioma tumor suppressor region

Saliva: diagnostics and therapeutic perspectives

For the past two decades, salivary diagnostic approaches have been developed to monitor oral diseases such as periodontal diseases and to assess caries risk. Recently, the combination of emerging biotechnologies and salivary diagnostics has extended the range of saliva-based diagnostics from the oral cavity to the whole physiologic system as most compounds found in blood are also present in saliva. Accordingly, saliva can reflect the physiologic state of the body, including emotional, endocrinal, nutritional and metabolic variations and acts as a source for the monitoring of oral and also systemic health. This review presents an update on the status of saliva diagnostics and delves into their applications to the discovery of biomarkers for cancer detection and therapeutic applications. Translating scientific findings of nucleic acids, proteins and metabolites in body fluids to clinical applications is a cumbersome and challenging journey. Our research group is pursuing the biology of salivary analytes and the development of technologies for detection of distinct biomarkers with high sensitivity and specificity. The avenue of saliva diagnostics incorporating transcriptomic, proteomic and metabolomic findings will enable us to connect salivary molecular analytes to monitor therapies, therapeutic outcomes, and finally disease progression in cancer.

Oligodendroglial tumors: diagnostic and molecular pathology

Oligodendroglial tumors, which encompass pure oligodendroglioma and mixed oligoastrocytoma, represent the second most common glioma in adults after glioblastoma. They remain controversial neoplasms in the realm of surgical neuropathology. The early recognition of their more favorable prognosis and responsiveness to treatment when compared with diffusely infiltrating astrocytomas has influenced the pathologic diagnostic interpretation, and resulted in a pervasive interobserver variability. The more recent finding of an increased frequency of 1p/19q deletion in these tumors by cytogenetic analysis, and the association of this molecular abnormality with a better prognosis has greatly impacted the field of neuro-oncology. In this review, we focus on important histopathologic aspects in the evaluation of oligodendroglial tumors, key differential diagnoses, and highlight particular clinical and molecular characteristics, as well as current diagnostic and conceptual controversies.

hHSS1: a novel secreted factor and suppressor of glioma growth located at chromosome 19q13.33

The completion of the Human Genome Project resulted in discovery of many unknown novel genes. This feat paved the way for the future development of novel therapeutics for the treatment of human disease based on novel biological functions and pathways. Towards this aim, we undertook a bioinformatics analysis of in-house microarray data derived from purified hematopoietic stem cell populations. This effort led to the discovery of HSS1 (Hematopoietic Signal peptide-containing Secreted 1) and its splice variant HSM1 (Hematopoietic Signal peptide-containing Membrane domain-containing 1). HSS1 gene is evolutionarily conserved across species, phyla and even kingdoms, including mammals, invertebrates and plants. Structural analysis showed no homology between HSS1 and known proteins or known protein domains, indicating that it was a truly novel protein. Interestingly, the human HSS1 (hHSS1) gene is located at chromosome 19q13.33, a genomic region implicated in various cancers, including malignant glioma. Stable expression of hHSS1 in glioma-derived A172 and U87 cell lines greatly reduced their proliferation rates compared to mock-transfected cells. hHSS1 expression significantly affected the malignant phenotype of U87 cells both in vitro and in vivo. Further, preliminary immunohistochemical analysis revealed an increase in hHSS1/HSM1 immunoreactivity in two out of four high-grade astrocytomas (glioblastoma multiforme, WHO IV) as compared to low expression in all four low-grade diffuse astrocytomas (WHO grade II). High-expression of hHSS1 in high-grade gliomas was further supported by microarray data, which indicated that mesenchymal subclass gliomas exclusively up-regulated hHSS1. Our data reveal that HSS1 is a truly novel protein defining a new class of secreted factors, and that it may have an important role in cancer, particularly glioma.

Abdominal undifferentiated small round cell tumor with unique translocation (X;19)(q13;q13.3)

We describe a male with a large abdominal mass, most likely originating from the liver, with capsule rupture and tumor dissemination into the abdominal cavity. Adherence of the tumor to the diaphragm and lower right colon also were noted. A comprehensive evaluation of the mass revealed no tumor-defining histopathologic, immunocytochemical, ultrastructural, cytogenetic, or translocation features. The malignant tumor was found to have a novel translocation (X;19)(q13;13.3), which has not been reported in small round cell tumors of childhood or adults. The final diagnosis rendered was an undifferentiated small round cell tumor of uncertain cell of origin.

Salivary transcriptomic biomarkers for detection of resectable pancreatic cancer

BACKGROUND & AIMS

Lack of detection technology for early pancreatic cancer invariably leads to a typical clinical presentation of incurable disease at initial diagnosis. New strategies and biomarkers for early detection are sorely needed. In this study, we have conducted a prospective sample collection and retrospective blinded validation to evaluate the performance and translational utilities of salivary transcriptomic biomarkers for the noninvasive detection of resectable pancreatic cancer.

METHODS

The Affymetrix HG U133 Plus 2.0 Array (Affymetrix, Santa Clara, CA) was used to profile transcriptomes and discover altered gene expression in saliva supernatant. Biomarkers discovered from the microarray study were subjected to clinical validation using an independent sample set of 30 pancreatic cancer patients, 30 chronic pancreatitis patients, and 30 healthy controls.

RESULTS

Twelve messenger RNA biomarkers were discovered and validated. The logistic regression model with the combination of 4 messenger RNA biomarkers (KRAS, MBD3L2, ACRV1, and DPM1) could differentiate pancreatic cancer patients from noncancer subjects (chronic pancreatitis and healthy control), yielding a receiver operating characteristic plot, area under the curve value of 0.971 with 90.0% sensitivity and 95.0% specificity.

CONCLUSIONS

The salivary biomarkers possess discriminatory power for the detection of resectable pancreatic cancer, with high specificity and sensitivity. This report provides the proof of concept of salivary biomarkers for the noninvasive detection of a systemic cancer and paves the way for prediction model validation study followed by pivotal clinical validation.

GLTSCR2/PICT-1, a putative tumor suppressor gene product, induces the nucleolar targeting of the Kaposi's sarcoma-associated herpesvirus KS-Bcl-2 protein

KS-Bcl-2, encoded by Kaposi's sarcoma-associated herpesvirus (KSHV), is a structural and functional homologue of the Bcl-2 family of apoptosis regulators. Like several other Bcl-2 family members, KS-Bcl-2 protects cells from apoptosis and autophagy. Using a yeast two-hybrid screen and coimmunoprecipitation assays, we identified a novel KS-Bcl-2-interacting protein, referred to as protein interacting with carboxyl terminus 1 (PICT-1), encoded by a candidate tumor suppressor gene, GLTSCR2. Confocal laser scanning microscopy revealed nucleolar localization of PICT-1, whereas KS-Bcl-2 was located mostly at the mitochondrial membranes with a small fraction in the nucleoli. Ectopic expression of PICT-1 resulted in a large increase in the nucleolar fraction of KS-Bcl-2, and only a minor fraction remained in the cytoplasm. Furthermore, knockdown of endogenous PICT-1 abolished the nucleolar localization of KS-Bcl-2. However, ectopically expressed PICT-1 did not alter the cellular distribution of human Bcl-2. Subsequent analysis mapped the crucial amino acid sequences of both KS-Bcl-2 and PICT-1 required for their interaction and for KS-Bcl-2 targeting to the nucleolus. Functional studies suggest a correlation between nucleolar targeting of KS-Bcl-2 by PICT-1 and reduction of the antiapoptotic activity of KS-Bcl-2. Thus, these studies demonstrate a cellular mechanism to sequester KS-Bcl-2 from the mitochondria and to downregulate its virally encoded antiapoptotic activity. Additional characterization of the interaction of KS-Bcl-2 and PICT-1 is likely to shed light on the functions of both proteins.

DNA repair gene polymorphisms and risk of adult meningioma, glioma, and acoustic neuroma

Although the etiology of primary brain tumors is largely unknown, prior studies suggest that DNA repair polymorphisms may influence risk of glioma. Altered DNA repair is also likely to affect the risk of meningioma and acoustic neuroma, but these tumors have not been well studied. We estimated the risk of glioma (n = 362), meningioma (n = 134), and acoustic neuroma (n = 69) in non-Hispanic whites with respect to 36 single nucleotide polymorphisms from 26 genes involved in DNA repair in a hospital-based, case-control study conducted by the National Cancer Institute. We observed significantly increased risk of meningioma with the T variant of GLTSCR1 rs1035938 (OR(CT/TT) = 3.5; 95% confidence interval: 1.8-6.9; P(trend) .0006), which persisted after controlling for multiple comparisons (P = .019). Significantly increased meningioma risk was also observed for the minor allele variants of ERCC4 rs1800067 (P(trend) .01); MUTYH rs3219466 (P(trend) .02), and PCNA rs25406 (P(trend) .03). The NBN rs1805794 minor allele variant was associated with decreased meningioma risk (P(trend) .006). Risk of acoustic neuroma was increased for the ERCC2 rs1799793 (P(trend) .03) and ERCC5 rs17655 (P(trend) .05) variants and decreased for the PARP1 rs1136410 (P(trend) .03). Decreased glioma risk was observed with the XRCC1 rs1799782 variant (P(trend) .04). Our results suggest that common DNA repair variants may affect the risk of adult brain tumors, especially meningioma.

Polysomy for chromosomes 1 and 19 predicts earlier recurrence in anaplastic oligodendrogliomas with concurrent 1p/19q loss

PURPOSE

Loss of chromosome arms 1p and 19q is a molecular feature of oligodendroglial tumors characterized by responsiveness to chemotherapy and a favorable prognosis. The purpose of this study was to evaluate the prognostic significance of polysomy of chromosomes 1 and 19 in the setting of 1p/19q codeletion.

EXPERIMENTAL DESIGN

We analyzed 64 anaplastic oligodendrogliomas with 1p/19q loss or maintenance diagnosed at Massachusetts General Hospital and Brigham and Women's Hospital from 1996 to 2005; fluorescence in situ hybridization for 1p/19q and Ki-67 immunohistochemistry was done. Polysomy was defined as more than two 1q and 19p signals in >30% of the cells with concurrent 1p/19q deletion. Tumors were divided into groups based on their 1p/19q status and compared for progression-free survival, overall survival, and 5-year survival probabilities.

RESULTS

Forty-six tumors (72%) in our cohort had 1p/19q loss and 18 (28%) had 1p/19q maintenance. Of those with loss, 19 (41%) had concurrent polysomy and 27 (59%) lacked polysomy. In agreement with previous studies, the group of anaplastic oligodendrogliomas with 1p/19q loss had significantly better progression-free survival and overall survival than anaplastic oligodendrogliomas with 1p/19q maintenance (P = 0.0009 and P < 0.0003, respectively). Among anaplastic oligodendrogliomas with 1p/19q loss, those with polysomy showed shorter progression-free survival than those with 1p/19q loss without polysomy (P = 0.0048). Overall survival was similar in tumors with and without polysomy. The Ki-67 labeling index was not associated with polysomy and did not have prognostic significance.

CONCLUSION

The presence of polysomy in anaplastic oligodendrogliomas with deletion of 1p/19q is a marker of earlier recurrence.

Beyond grade: molecular pathology of malignant gliomas

High-grade gliomas (HGGs) represent a heterogenous group of tumors and account for most primary brain tumors. Despite aggressive therapies, they are invariably associated with poor patient outcome. These tumors include the anaplastic (World Health Organization [WHO] grade III) histologies of astrocytomas, oligodendrogliomas, and ependymomas and the WHO grade IV glioblastoma multiforme (GBM). The recent elucidation of the fundamental molecular alterations associated with these tumors has begun to unravel the critical events in their tumorigenesis but for the most part has done little to alter patient survival. Prognostication for patients with these tumors has relied principally on tumor grade and clinical factors (age, performance status, and so on) and has been inexact at best in identifying those with long-term survival potential. An even greater challenge has been to identify predictive biomarkers of therapy in the hope of tailoring a patient's therapy based on their tumor's molecular characteristics. This review discusses the molecular pathology of high-grade gliomas, with particular emphasis on anaplastic astrocytomas and GBMs because these represent the most common forms of malignant gliomas. It also focuses on the molecular signatures defined by large-scale gene expression profiling experiments because these studies are at the forefront in developing new biomarkers and identifying new therapeutic targets.

Reprogramming of the transcriptome in a novel chromosome 3 transfer tumor suppressor ovarian cancer cell line model affected molecular networks that are characteristic of ovarian cancer

Tumor suppression as a consequence of the transfer of chromosome 3p fragments was previously observed in a novel epithelial ovarian cancer (EOC) OV-90 cell line model harboring loss of 3p. Microarray analysis revealed that tumor suppression was associated with a modified transcriptome. To investigate the relevance of the altered transcriptome, the differentially expressed genes identified by Affymetrix analysis in the 3p transfer studies, were integrated with a comparative microarray analysis of normal ovarian surface epithelial (NOSE) cells and malignant ovarian (TOV) cancers. Data from 219 significantly differentially expressed genes exhibited patterns in the direction predicted by the analysis of 3p transfer study. The 30 genes with the highest statistically significant differences (P < 1 x 10(-8)) in expression were found consistently differentially expressed between NOSE and TOV samples. The investigation of these genes in benign serous ovarian tumors and EOC cell lines also exhibited predictable expression patterns. Within the group of differentially expressed genes were SPARC, DAB2, CP, EVI1, ELF3, and EHD2, known to play a role in ovarian cancer, genes implicated in other cancers, such as GREM1 and GLIPR1, as well as genes not previously reported in a cancer context such as AKAP2 and ATAD4. A number of the differentially expressed genes are implicated in the TGF-beta signaling pathway. These findings suggest that the reprogramming of the transcriptome that occurred as a consequence of the chromosome 3 transfer and tumor suppression affected molecular networks that are characteristic of ovarian carcinogenesis thus validating our novel ovarian cancer cell line model.

PTEN and the PI3-kinase pathway in cancer

PI3-kinase and PTEN are major positive and negative regulators, respectively, of the PI3-kinase pathway, which regulates growth, survival, and proliferation. These key signaling components are two of the most frequently mutated proteins in human cancers, resulting in unregulated activation of PI3K signaling and providing irrefutable genetic evidence of the central role of this pathway in tumorigenesis. PTEN regulates PI3K signaling by dephosphorylating the lipid signaling intermediate PIP(3), but PTEN may have additional phosphatase-independent activities, as well as other functions in the nucleus. In this review, we highlight current work showing cancer-relevant complexities in the regulation of PTEN and PI3K activity, potential novel functions for PTEN, and feedback regulation within the pathway. The significance and complexity of PI3K signaling make it an important but challenging therapeutic target for cancer.

Cancer-related transcriptional targets of the circadian gene NPAS2 identified by genome-wide ChIP-on-chip analysis

The transcription factor NPAS2 is one of nine human core circadian genes that influence a variety of biological processes by regulating the 24-h circadian rhythm. Recently, it has been shown that NPAS2 is a risk biomarker in human cancers and plays a role in tumorigenesis by affecting cancer-related gene expression, and relevant biological pathways. However, it is difficult to study the biological involvement of NPAS2 in cancer development, as little is known about its direct transcriptional targets. The aim of the current study is to create a transcriptional profile of genes regulated by NPAS2, using a human binding ChIP-on-chip analysis of NPAS2 in MCF-7 cells. This genome-wide mapping approach identified 26 genes that contain potential NPAS2 binding regions. Subsequent real-time PCR assays confirmed 16 of these targets, and 9 of these genes (ARHGAP29, CDC25A, CDKN2AIP, CX3CL1, ELF4, GNAL, KDELR1, POU4F2, and THRA) have a known role in tumorigenesis. In addition, a networking analysis of these validated NPAS2 targets revealed that all nine genes, together with REN, are involved in a "Cancer, Cell cycle, Neurological Disease" network. These results report the first list of direct transcriptional targets of NPAS2 and will shed light on the role of circadian genes in tumorigenesis.

Suppression of putative tumour suppressor gene GLTSCR2 expression in human glioblastomas

Glioma tumour-suppressor candidate region gene 2 (GLTSCR2/PICT-1) is localized within the well-known 1.4 Mb tumour-suppressive region of chromosome 19q, which is frequently altered in various human tumours, including diffuse gliomas. Aside from its chromosomal localization, several lines of evidence, including PTEN-phosphorylating and cell-killing activities, suggests that GLTSCR2 participates in the suppression of tumour growth and development. However, little is known about the biological functions and molecular mechanisms of GLTSCR2 as a tumour suppressor gene. We investigated the pathological significance of GLTSCR2 expression in association with the development and progression of glioblastomas, the most common malignant brain tumour. We used real-time PCR and western blot analysis to examine the expression levels of GLTSCR2 mRNA and protein in glioblastomas, normal brain tissue and in non-glial tumour tissue of different origin, and found that GLTSCR2 expression is down-regulated in glioblastomas. In addition, direct sequencing analysis and fluorescence in situ hybridization clearly demonstrates the presence of genetic alterations, such as a nonsense mutation and deletion, in the GLTSCR2 gene in glioblastomas. Finally, our immunohistochemical study demonstrates that GLTSCR2 is sequentially down-regulated according to the histological malignant progression of the astrocytic glial tumour. Taken together, our results suggest that GLTSCR2 is involved in astrocytic glioma progression.

Molecular pathology of malignant gliomas

Malignant gliomas, the most common type of primary brain tumor, are a spectrum of tumors of varying differentiation and malignancy grades. These tumors may arise from neural stem cells and appear to contain tumor stem cells. Early genetic events differ between astrocytic and oligodendroglial tumors, but all tumors have an initially invasive phenotype, which complicates therapy. Progression-associated genetic alterations are common to different tumor types, targeting growth-promoting and cell cycle control pathways and resulting in focal hypoxia, necrosis, and angiogenesis. Knowledge of malignant glioma genetics has already impacted clinical management of these tumors, and researchers hope that further knowledge of the molecular pathology of malignant gliomas will result in novel therapies.

PTEN: its deregulation and tumorigenesis

The tumor suppressor phosphatase and tensin homolog (PTEN) functions as a phosphoinositide 3-phosphatase, that antagonizes phosphatidylinositol 3-kinase action, and negatively regulates cell proliferation and survival signals. Inactivation of PTEN by loss-of-function mutations gives rise to deregulated hyperproliferation of cells, leading to oncogenic transformation. Recent studies have identified a number of upstream regulatory factors for PTEN and unveiled that the impairment in the PTEN regulatory system potentially becomes a causal factor for oncogenic transformation of cells. This article will review the PTEN inactivation mechanism which is linked to human tumorigenesis, particularly focusing on recent research progress in PTEN regulators.

GLTSCR2 Sensitizes Cells to Hypoxic Injury without Involvement of Mitochondrial Apoptotic Cascades

OBJECTIVE

We attempted to identify novel genes that induce hypoxic cell death to better understand the molecular mechanisms underlying hypoxia-induced cell death. Through this process the GLTSCR2 gene was found. The purpose of this work was to investigate the role of GLTSCR2 in hypoxic cell death pathways.

METHODS

This work focuses on an investigation of roles and mechanisms of GLTSCR2 in hypoxic cell death by means of subtractive hybridization, RT-PCR, Western blot, immunocytochemistry, cell death assay, transient gene overexpression, and determination of mitochondrial membrane potential.

RESULTS

We found that GLTSCR2 was transcriptionally suppressed by hypoxia, and ectopic expression of GLTSCR2 sensitized cells to hypoxic injury. Interestingly, while the majority of hypoxia-inducible pro-death proteins signal through mitochondrion-dependent pathways, GLTSCR2-overexpressed cells underwent apoptosis in a mitochondrion- and caspase-independent manner.

CONCLUSION

Our data categorizes GLTSCR2 as a proapoptotic protein sensitizing cells to hypoxic injury when overexpressed.

Mutations in SIRT2 deacetylase which regulate enzymatic activity but not its interaction with HDAC6 and tubulin

Human SIRT2 is a cytoplasmic NAD-dependent deacetylase implicated in the mitotic regulation of microtubule dynamics by its association with the class II histone deacetylase 6 (HDAC6). We have previously reported that SIRT2 is multiply phosphorylated in a cell cycle dependent pattern. Here, we demonstrate that HDAC6 binds to both phosphorylated and unphosphorylated forms of SIRT2 and that tubulin binds only to the SIRT2-HDAC6 complex. Tubulin does not bind to either HDAC6 or SIRT2 individually. In addition, we show that replacement of specific serines with alanines in either isoform of SIRT2 regulates its enzymatic activity. We also found that overexpression of isoform2 was deleterious to cell survival. SIRT2 was found to be phosphorylated at serines 368 and 372, outside the conserved core domain of the Sir2 protein family. Double replacement of S368A and S372A reduced SIRT2 deacetylase activity by 44% compared to wildtype activity. Replacements of other serine, threonine, and tyrosine residues, which did not alter the phosphorylation pattern, had varying effects on SIRT2 deacetylase activity but no effect on tubulin/HDAC6 binding.

The putative tumor suppressor gene GLTSCR2 induces PTEN-modulated cell death

Glioma tumor suppressor candidate region gene 2 (GLTSCR2/PICT-1) is localized within the well-known 1.4-Mb tumor suppressive region of chromosome 19q, which is frequently altered in various human tumors, including diffuse gliomas. Aside from its localization on the chromosome, several lines of evidence, such as PTEN phosphorylation, support that GLTSCR2 partakes in the suppression of tumor growth and development. However, much remains unknown about the molecular mechanisms of the tumor suppressive activity of GLTSCR2. The purpose of this study was to investigate the molecular mechanisms of GLTSCR2 in cell death pathways in association with its binding partner PTEN. In this work, we show that GLTSCR2 is a nucleus-localized protein with a discrete globular expression pattern. In addition to phosphorylating PTEN, GLTSCR2 induces caspase-independent PTEN-modulated apoptotic cell death when overexpressed. However, the cytotoxic activity of GLTSCR2 is independent of its ability to phosphorylate PTEN, suggesting that the GLTSCR2-induced cell death pathway is divergent from PTEN-induced death pathways. Our results suggest that the induction of PTEN-modulated apoptosis is one of the putative mechanisms of tumor suppressive activity by GLTSCR2.

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.

Loss of heterozygosity at 15q21.3 correlates with occurrence of metastases in head and neck cancer

Deletions on the long arm of chromosome 15 suggesting the presence of potential tumor suppressor genes have been found in several tumors including carcinomas of the colorectum, urinary bladder, breast, lung, and head and neck. Here, we analyzed allelic imbalance on chromosome 15q in head and neck carcinomas and corresponding lymph node metastases to define common regions of aberrations with potential involvement in development and progression of these tumors. We studied a panel of 40 polymorphic microsatellite markers, spanning 15q13-15q26, in 63 head and neck carcinomas and 38 lymph node metastases. Loss of heterozygosity (LOH) could be demonstrated in 34 primary tumors (54%) and 35 metastases (92%). Aberration mapping defined three minimum regions of aberrations: a region between the markers D15S106 and D15S1029 in 15q21.3 (estimated as 3.9 Mb; region 1) was affected in the majority of tumors, whereas two other regions between D15S144 and D15S1040 in 15q13.3-14 (estimated as 2.4 Mb; region 2) and between D15S130 and D15S985 in 15q26.2-26.3 (estimated as 4.7 Mb; region 3) were less often involved. Allelic loss in region 1 correlated with T stages (P=0.0029) and metastatic potential (P=0.0018). LOH in regions 2 and 3 occurred predominantly in metastases (P=0.0129 and P=0.0013, respectively). No correlation with grading, localization, or clinical outcome could be established for any of the affected regions. Our data hint at aberrations in 15q21.3 as a possible important characteristic for head and neck squamous cell carcinomas with risk of progression.

Critical role of PICT-1, a tumor suppressor candidate, in phosphatidylinositol 3,4,5-trisphosphate signals and tumorigenic transformation

The tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN) regulates diverse cellular functions by dephosphorylating the lipid second messenger, phosphatidylinositol 3,4,5-trisphosphate (PIP(3)). Recent study revealed that PICT-1/GLTSCR2 bound to and stabilized PTEN protein in cells, implicating its roles in PTEN-governed PIP(3) signals. In this study, we demonstrate that RNA interference-mediated knockdown of PICT-1 in HeLa cells down-regulated endogenous PTEN and resulted in the activation of PIP(3) downstream effectors, such as protein kinase B/Akt. Furthermore, the PICT-1 knockdown promoted HeLa cell proliferation; however the proliferation of PTEN-null cells was not altered by the PICT-1 knockdown, suggesting its dependency on PTEN status. In addition, apoptosis of HeLa cells induced by staurosporine or serum-depletion was alleviated by the PICT-1 knockdown in the similar PTEN-dependent manner. Most strikingly, the PICT-1 knockdown in HeLa and NIH3T3 cells promoted anchorage-independent growth, a hallmark of tumorigenic transformation. Furthermore, PICT-1 was aberrantly expressed in 18 (41%) of 44 human neuroblastoma specimens, and the PICT-1 loss was associated with reduced PTEN protein expression in spite of the existence of PTEN mRNA. Collectively, these results suggest that PICT-1 plays a role in PIP(3) signals through controlling PTEN protein stability and the impairment in the PICT-1-PTEN regulatory unit may become a causative factor in human tumor(s).

Genetically distinct and clinically relevant subtypes of glioblastoma defined by array-based comparative genomic hybridization (array-CGH)

To optimize treatment strategies for patients with glioblastoma, a more precise understanding of the molecular basis of this disease clearly is necessary. Therefore, numerous studies have focused on the molecular biology of glioblastoma and its linkage to clinical behavior. Here we investigated 70 glioblastomas using the array-based comparative genomic hybridization (array-CGH) with GenoSensor Array 300 to identify recurrent DNA copy number imbalances associated with patient outcomes. Univariate log-rank analysis of array-CGH data revealed 46 copy number aberrations (CNAs) associated with outcome. Among them, 26 CNAs were associated with shortened survival whereas the remaining 20 CNAs correlated with good prognosis. A hierarchical cluster analysis disclosed two genetically distinct groups of glioblastomas (1 and 2; 56 and 14 tumors, respectively). Univariate log-rank test discerned significant difference in survival between both genetic subsets while the 5-year survival rate consisted of 0 for group 1 and 63% for group 2. Multivariate analysis revealed that unfavorable genetic signature is an independent prognostic factor increasing a risk of patient death (hazard ratio, 4.38; P=0.00001). In conclusion, our current study suggests that glioblastomas can be subdivided into clinically relevant genetic subsets. Therefore, array-CGH screening of glioblastomas could provide clinically useful information and, perhaps, potentially improve the quality of treatment.

Novel PLA2G4C polymorphism as a molecular diagnostic assay for 19q loss in human gliomas

PLA2G4C, encoding cytosolic phospholipase A2-gamma (cPLA2-gamma), is a 17-exon gene located on chromosome 19q13.3 within the putative glioma tumor suppressor gene region. Given the clinical importance of assessing 1p and 19q loss in human gliomas, the development of convenient and practical assays for detecting allelic loss is of considerable priority in neuro-oncology. We report a minisatellite polymorphism in the untranslated region of exon 1, with allelic variants that have one, two or three 27-bp repeats. The polymorphism is informative in 55.7% of a reference population, and accurately detects allelic loss of 19q in human gliomas. This novel marker offers distinct advantages for assessing 19q status in malignant gliomas. The relatively large size of the repeats allows detection of allelic variants with standard ethidium bromide-stained agarose gels and the PLA2G4C marker is the closest polymorphism to the smallest common deletion area in the putative glioma tumor suppressor gene region. These characteristics suggest that the PLA2G4C polymorphism will be a convenient and practical assay for clinical and research evaluation of 19q status in human gliomas.

A new method for gene discovery in large-scale microarray data

Microarrays are an effective tool for monitoring genome-wide gene expression levels. In current microarray analyses, the majority of genes on arrays are frequently eliminated for further analysis because the changes in their expression levels (ratios) are considered to be not significant. This strategy risks failure to discover whole sets of genes related to a quantitative trait of interest, which is generally controlled by several loci that make various contributions. Here, we describe a high-throughput gene discovery method based on correspondence analysis with a new index for expression ratios [arctan (1/ratio)] and three artificial marker genes. This method allows us to quickly analyze the whole microarray dataset and discover up-/down-regulated genes related to a trait of interest. We employed an example dataset to show the theoretical advantage of this method. We then used the method to identify 88 cancer-related genes from a published microarray data from patients with breast cancer. This method also allows us to predict the phenotype of a given sample from the gene expression profile. This method can be easily performed and the result is also visible in 3D viewing software that we have developed.

Current Strategies in Treatment of Oligodendroglioma: Evolution of Molecular Signatures of Response

Oligodendroglioma frequently (≥ 70%) responds to radiation and chemotherapy, and is the first CNS neoplasm in which a genetic signature (1p and 19q deletion) has been associated with outcome within the context of large clinical trials. Current translational investigations focus on deletions or mutations of potential tumor suppressor genes, epigenetic alterations, amplification or mutation of growth factor and regulatory genes, and characterization of signaling events and regulatory protein expression. The most compelling data has involved 1p and 19q loss, which is observed in over 50% of anaplastic oligodendrogliomas. In two randomized phase III trials (Radiation Therapy Oncology Group 9402 and European Organisation for Research and Treatment of Cancer 26951), the addition of neoadjuvant or adjuvant procarbazine, lomustine, and vincristine (PCV; respectively) to radiotherapy did not produce superior survival as compared with radiotherapy alone. A modest increase in progression-free survival was observed with the addition of PCV, but at the cost of increased toxicity. Combined 1p and 19q loss identified a favorable prognostic group in both studies, which appeared to be independent of treatment arms. However, it is unclear whether these deletions represent surrogate markers of a favorable biologic tumor behavior, or are predictive of outcome after specific treatment. Currently, there is insufficient data to allow therapeutic decisions to be made solely on the basis of 1p and 19q gene deletion status. Future phase III trials are evaluating other chemotherapeutic and targeted agents, including temozolomide, and include correlative investigations of aberrant molecular events in these neoplasms, which may lead to future therapeutic strategies that are based on specific molecular signatures.

The molecular epidemiology of gliomas in adults

In this paper the authors highlight recent findings from molecular epidemiology studies of glioma origin and prognosis and suggest promising paths for future research. The reasons for variation in glioma incidence according to time period of diagnosis, sex, age, ancestry and ethnicity, and geography are poorly understood, as are factors that affect prognosis. High-dose therapeutic ionizing irradiation and rare mutations in highly penetrant genes associated with certain rare syndromes—the only two established causes of glioma—can be called upon to explain few cases. Both familial aggregation of gliomas and the inverse association of allergies and immune-related conditions with gliomas have been shown consistently, but the explanations for these associations are inadequately developed or unknown. Several bio-markers do predict prognosis, but only evaluation of loss of 1p and 19q in oligodendroglial tumors are incorporated in clinical practice. Ongoing research focuses on classifying homogeneous groups of tumors on the basis of molecular markers and identifying inherited polymorphisms that may influence survival or risk. Because most cases of glioma have yet to furnish either an environmental or a genetic explanation, the greatest potential for discovery may lie in genomic studies in conjunction with continued evaluation of environmental and developmental factors. Large sample sizes and multidisciplinary teams with expertise in neuropathology, genetics, epidemiology, functional genomics, bioinformatics, biostatistics, immunology, and neurooncology are required for these studies to permit exploration of potentially relevant pathways and modifying effects of other genes or exposures, and to avoid false-positive findings. Improving survival rates for patients harboring astrocytic tumors will probably require many randomized clinical trials of novel treatment strategies.

Molecular genetics of oligodendrogliomas: a model for improved clinical management in the field of neurooncology

Over the last several years, oligodendroglial tumors have become a model for the positive role of molecular genetics in improved treatment of patients with brain tumors. Oligodendrogliomas, in contrast to astrocytic gliomas, frequently respond to chemotherapy and have a better overall prognosis. Combined loss of chromosomes 1p and 19q has proven to be a powerful predictor of chemotherapeutic response and survival in oligodendrogliomas. In contrast, other genetic alterations, such as TP53 and PTEN mutations, EGFR amplification, and homozygous deletion of CDKN2A have been correlated with worse outcome in these tumors. Furthermore, 1p/19q loss has been shown to correlate with unequivocal oligodendroglial tumor histology, location and growth pattern of tumors within the brain, and magnetic resonance imaging characteristics. Although much is also known about the molecular pathological characteristics of astrocytic gliomas, the significance of this information to clinical management in patients with these tumors has not been as striking as has been the case for oligodendrogliomas; possible reasons for this are discussed. In this paper the author will summarize these advances, thus attempting to highlight the molecular genetic study of oligodendrogliomas as a model for improved clinical management in the field of neurooncology.

ERCC1 and ERCC2 polymorphisms and adult glioma

ERCC2 and ERCC1 are important in DNA nucleotide excision repair and lie on chromosome 19q13.3 near a putative glioma suppressor region. We genotyped constitutive variants ERCC1 C8092A and ERCC2 K751Q and R156R in approximately 450 adults with glioma and 500 controls from two independent population-based series, uniformly reviewed patients' tumors to determine histopathologic category, and determined a variety of tumor markers among astrocytic tumors. Odds ratios (ORs) for glioblastoma for those carrying two ERCC1 A alleles versus none or one were 1.67 in series 1 and 1.64 in series 2, which yielded a combined OR of 1.67 (95% CI, 0.93-3.02; P = 0.09), adjusted for age, gender, ethnicity, and series. Odds ratios for the ERCC2 variants were not consistently elevated or reduced for the two series in all cases versus controls. However, among whites, for those with ERCC2 K751Q genotype QQ versus QK/KK, the OR for nonglioblastoma histologies versus controls was 1.82 (95% CI, 0.97-3.44; P = 0.06). Also, among whites, glioma patients were significantly more likely than controls to be homozygous for variants in both ERCC1 C8092A and ERCC2 K751Q (OR, 3.2; 95% CI, 1.1-9.3). Given the numbers of comparisons made, these findings could be due to chance. However, the results might warrant clarification in additional series in conjunction with the nearby putative glioma suppressor genes (GLTSCR1 and GLTSCR2).

Biologie moléculaire des tumeurs oligodendrogliales

Oligodendrogliomas have been the focus of considerable interest over the last decade, ever since they were recognized as chemosensitive tumors. However, the histological diagnosis remains highly controversial and unsatisfactory. Meanwhile, our understanding of glioma oncogenesis improved greatly. Gliomas are the consequence of specific genetic or epigenetic alterations - activations of oncogenes and inactivation of tumor suppressor genes - resulting in the disruption of critical cellular pathways and leading to phenotypic changes. Such genetic information complements the existing WHO morphological classification and, more importantly, provides additional prognostic markers. Indeed, 1p/19q deletion has been correlated with chemosensitivity in oligodendrogliomas, and is becoming more and more widely used in clinical practice. There is little doubt that emerging techniques, such as CGH-array and gene profiling will be very helpful in clinical practice for refining both classification and therapeutic indications of oligodendroglial tumors.

Polymorphisms in GLTSCR1 and ERCC2 are associated with the development of oligodendrogliomas

BACKGROUND

Deletions of 19q have been associated with gliomas, especially oligodendrogliomas. In addition, cases with oligodendrogliomas with the 19q deletion have been observed to have a better survival compared with cases without the 19q deletion. The authors have previously described a 150-kilobase minimal deletion region in gliomas that maps to 19q13.33 and contains 3 novel candidate genes (GLTSCR1, EHD2, and GLTSCR2).

METHODS

The authors performed an association study using 141 cases with gliomas (61 cases with astrocytomas, 40 cases with oligodendrogliomas, 40 cases with mixed oligoastrocytomas) and 108 general controls. They evaluated 7 single nucleotide polymorphisms (SNPs) in 6 genes within and nearby the minimal 19q deletion region (ERCC2, RAI, ASE-1, ERCC1, GLTSCR1, and LIG1).

RESULTS

The prevalence of a germline GLTSCR1-exon-1 T allele (SNP rs1035938) was 40% in cases with oligodendrogliomas compared with 27% in controls (P = 0.029), and the prevalence of an ERCC2-exon-22 T allele (SNP rs1052555) was 35% in cases with oligodendrogliomas compared with 18% in controls (P = 0.043). One high-risk and 1 low-risk haplotype were associated with oligodendroglioma development (P = 0.003 and 0.026, respectively). Cases with oligodendrogliomas with the 19q deletion had a significantly higher frequency of the GLTSCR1-exon-1 T allele compared with cases without the 19q deletion (P = 0.01). It was noteworthy that cases with gliomas who were homozygous for the GLTSCR1-exon-1 T allele had a significantly better survival: 77% and 68% survival at 2 and 5 years compared with 56% and 34% for other genotypes (P = 0.02, log-rank test). Multivariable analysis identified grade, age, and the GLTSCR1-exon-1 and ERCC2-exon-22 genotypes as independent predictors for survival.

CONCLUSIONS

These results suggested that alterations in GLTSCR1 (or a closely linked gene) were associated with the development and progression of oligodendroglioma.

Molecular pathogenesis of oligodendroglial tumors

Based on their histopathological appearances, most diffusely infiltrative gliomas can be classified either as astrocytic tumors (As), pure oligodendroglial tumors (Os) or mixed oligoastrocytic tumors (OAs). The latter two may be grouped together as oligodendroglial tumors (OTs). The distinction between As and OTs is important because of the more favorable clinical behavior of OTs. Unfortunately, the histopathological delineation of OAs, Os and As can be difficult because of vague and subjective histopathological criteria. Over the last decade, the knowledge on the molecular genetic background of OTs has drastically increased. This review provides an overview of molecular genetic aberrations in OTs and discusses the pathobiological and clinical significance of these aberrations. In contrast to As, OTs frequently show frequent loss of heterozygosity on chromosome arms 1p and 19q. Since these aberrations are significantly correlated with clinically relevant parameters, such as prognosis and chemosensitivity, and given the difficulties in histopathological typing and grading of glial tumors, genetic testing should be included in routine glioma diagnostics. It is to be expected that the identification of the relevant tumor suppressor genes located on 1p and 19q will lead to more refined genetic tests for OTs. Furthermore, as microarray technology is rapidly increasing, it is likely that clinically relevant markers for OTs will be identified on other chromosomes and need to be included into routine glioma diagnostics as well.

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.

Regulation of PTEN phosphorylation and stability by a tumor suppressor candidate protein

The tumor suppressor PTEN plays an essential role in regulating signaling pathways involved in cell growth and apoptosis and is inactivated in a wide variety of tumors. In this study, we have identified a protein, referred to as PICT-1 (protein interacting with carboxyl terminus 1), that binds to the C terminus of PTEN and regulates its phosphorylation and turnover. Down-regulation of PICT-1 in MCF7 cells by RNA interference enhances the degradation of PTEN with a concomitant decrease in its phosphorylation. PTEN C-terminal tumor-associated mutants, which are highly susceptible to protein degradation, have lost the ability to bind to PICT-1 along with their reduced phosphorylation, suggesting that their rapid turnover results from impaired binding to PICT-1. Our results identify PICT-1 as a PTEN-interacting protein that promotes the phosphorylation and stability of PTEN. These findings suggest a novel molecular mechanism underlying the turnover of PTEN, which also provides an explanation for the loss of PTEN function due to C-terminal mutations.

Pathology and molecular genetics of oligodendroglial tumors

Oligodendroglial gliomas are second only to astrocytic gliomas in frequency. The lack of stringent diagnostic criteria cause high interobserver variation in regard to classification and grading of these tumors. Previous studies have described oligodendrogliomas with features that overlap with those of neurocytic tumors, thus further complicating diagnostic decisions. The increasing need for standardized diagnostic criteria in this subset of gliomas is emphasized by the benefit of adjuvant therapies in patients with anaplastic oligodendrogliomas. Characteristic chromosomal aberrations have been successfully determined for oligodendroglial tumors in recent years. In contrast to astrocytomas, however, no genes in the affected regions have been clearly linked to their pathogenesis. However, the molecular findings promise to be helpful for diagnostic and therapeutic decisions. This review compiles clinical, pathological, and molecular genetic findings on WHO grades II and III oligodendrogliomas and oligoastrocytomas.

Identification and analysis of rat homologous gene to human HBV pre-S1 protein-binding protein

AIM: To identify and analyze rat homologous gene to human hepatitis B virus (HBV) pre-S1-binding protein (PS1BP) coding gene.

METHODS: The human PS1BP was screened and identified from a hepatocyte expressive cDNA library by phage display technique with purified recombinant pre-S1 protein of HBV as the solidified matrix. The nucleotide sequence database GenBank, established by National Center for Biotechnology Information (NCBI), National Library of Medicine (NLM), National Institute of Health (NIH), was searched for rat cDNA sequence homologous to human PS1BP cDNA by BLASTn tools online. A homologous cDNA sequence was identified as the rat PS1BP cDNA. The similarity and identity of rat PS1BP cDNA and amino acid (aa) sequences to human and mouse PS1BP genes were compared. The potential functional domains were predicted by online analysis tools.

RESULTS: The human PS1BP cDNA was identified by phage display technique. The rat PS1BP cDNA was identified by bioinformatics methods. The rat PS1BP cDNA consisted of 1 455 nt, and encoded a protein of 484 aa. The identity of rat PS1BP protein to human and mouse PS1BP proteins was 80.79% (391/484) and 92.98% (450/484), respectively. In the rat PS1BP protein sequence, several potential modification domains were identified.

CONCLUSION: Rat PS1BP cDNA and protein primary sequences are identified and analyzed.

The gene for soluble N-ethylmaleimide sensitive factor attachment protein alpha is mutated in hydrocephaly with hop gait (hyh) mice

The spontaneous autosomal recessive mouse mutant for hydrocephaly with hop gait (hyh) exhibits dramatic cystic dilation of the ventricles at birth and invariably develops hopping gait. We show that the gene for soluble N-ethylmaleimide sensitive factor attachment protein alpha, also known as alpha-SNAP, is mutated in hyh mice. alpha-SNAP plays a key role in a wide variety of membrane fusion events in eukaryotic cells, including the regulated exocytosis of neurotransmitters. Homozygous mutant mice harbor a missense mutation M105I in a conserved residue in one of the alpha-helical domains. We demonstrate that the hyh mutant is not a null allele and is expressed; however, the mutant protein is 40% less abundant in hyh mice. The hyh mutant provides a valuable in vivo model to study vesicle/membrane trafficking and provides insight into the potential roles of alpha-SNAP in embryogenesis and brain development.

Influence of Oxygen on the Radiosensitivity of Human Glioma Cell Lines

We have investigated the influence of hypoxia on the radiosensitivity of 4 early-passage tumor cell lines that were established from malignant glioma patients at our Institute. These cell lines were M006, M059J (a highly radiosensitive line), M059K (a radioresistant line derived from the same biopsy as M059J), and M010b. The GM637 human fibroblast cell line was used as a normal control. The oxygen enhancement ratios (OERs) for these cell lines, determined using a clonogenic survival assay, were approximately 3.6 (GM637), approximately 3.7 (M006), approximately 2.5 (M010b), approximately 2.1 (M059K), and approximately 3.5 (M059J). The broad range of OERs for these glioma lines was not related to cellular glutathione levels or to differences in intrinsic cellular radiosensitivity. Because studies with rodent cell lines indicate that defects in certain DNA repair genes, including ERCC1, can greatly influence cellular OERs, and because several such repair genes, including ERCC1, localize to a region of chromosome 19q that is close to a common deletion in human glioma, we reasoned that such deletions might contribute to the diverse OERs of these tumor cell lines. However, measurements of ERCC1 protein levels using immunofluorescence staining or Western blotting, of ERCC1 mRNA levels using Northern blotting, and of functional nucleotide excision repair capability using the UV/adenovirus reactivation assay, failed to indicate any deficit in these activities. Thus, although the effect of hypoxia on the radiosensitivity of different human glioma cell lines can vary widely, the mechanism of this effect remains unknown. The potential implications of this finding for radiation therapy, and especially for hypoxia imaging-guided intensity-modulated radiation therapy (IMRT) treatment planning, are discussed.

Gene structure and tissue expression of human selenoprotein W, SEPW1, and identification of a retroprocessed pseudogene, SEPW1P

We have determined that the human SEPW1 (selenoprotein W) gene maps to chromosome 19q13.3, spans approximately 6.3 kb and comprises six exons, in contrast to the previously published five exons. The gene lacks canonical TATA and CAAT boxes, but has numerous Sp1 consensus binding sites upstream of multiple transcription start sites. SEPW1 is expressed in all of the 22 tissues assayed, and shows highest expression in skeletal muscle and heart. Additionally, we have also identified a retroprocessed SEPW1 pseudogene, SEPW1P, which maps to chromosome 1p34-35.

The human DDX and DHX gene families of putative RNA helicases

Nucleic acid helicases are characterized by the presence of the helicase domain containing eight motifs. The sequence of the helicase domain is used to classify helicases into families. To identify members of the DEAD and DEAH families of human RNA helicases, we used the helicase domain sequences to search the nonredundant peptide sequence database. We report the identification of 36 and 14 members of the DEAD and DEAH families of putative RNA helicases, including several novel genes. The gene symbol DDX had been used previously for both DEAD- and DEAH-box families. We have now adopted DDX and DHX symbols to denote DEAD- and DEAH-box families, respectively. Members of human DDX and DHX families of putative RNA helicases play roles in differentiation and carcinogenesis.

Recent advances in the molecular genetics of primary gliomas

Primary brain tumors, particularly glioblastomas, remain a challenge for oncology. Uncontrolled cellular proliferation, lack of apoptosis, invasion, and angiogenesis are among the biologic processes that render these tumors both aggressive and difficult to treat. An understanding of the genetics and molecular events regulating these aggressive tumors is beginning to emerge, partly because of recent knowledge in genomics, gene expression analysis, and mouse tumor models. As a result, it is now generally accepted that brain tumors, particularly those arising from cells of glial lineage, result from stepwise accumulation of deleterious genetic alterations. Several genetic abnormalities have been described, and current research is aimed at elucidating their causal association with brain tumor formation and progression. The purpose of this review is to summarize some of the most important recently published findings on the molecular genetics of primary gliomas.

Pediatric oligodendrogliomas: a study of molecular alterations on 1p and 19q using fluorescence in situ hybridization

Oligodendrogliomas (OGs) are rare in children and have not been well characterized from a molecular viewpoint. In adults, losses on chromosomes 1p and/or 19q are common in "oligodendroglial" neoplasms and are highly associated with chemosensitivity and greater length of survival, especially in the anaplastic category. We have analyzed the 1p/19q status of pediatric OGs and compared it with similar alterations in adult OGs. Paraffin sections from 26 pediatric OGs (21 WHO Grade II OGs: 2 anaplastic oligodendrogliomas [AOGs]: and 3 mixed oligo-astrocytomas [MOA]) were retrieved. Fluorescence in situ hybridization (FISH) was performed using probes spanning the 1p32 and 19q13 regions. In tumors from children 0 to 9 years of age (n = 15), none had any deletions on 1p or 19q, but 2 had polysomies for 1p and/or 19q. All are alive and 4 have had recurrences. In tumors from children > 9 years, losses were identified on chromosomes 1p (5/11; 45%) and/or 19q (3/11; 27%), but to a much lesser extent than that observed in adult OGs. Tumors from 6 older patients also had polysomies for 1p and/or 19q. Although the majority of the older children are alive, 4 had recurrences. Curiously, 2 of the older children with AOGs had combined losses and polysomies on 1p and 19q, but responded poorly to treatment and died within a year. We conclude that alterations on 1p or 19q are infrequent in pediatric compared to adult OGs and are virtually absent in OGs presenting in the first decade of life. Compared to adults therefore, different genetic pathways are likely involved in the pathogenesis of most pediatric OGs. Genomic screening on a larger series is clearly indicated to delineate the unique molecular characteristics of these rare pediatric tumors.

Oligodendroglioma: toward molecular definitions in diagnostic neuro-oncology

Oligodendroglial tumors have attracted great interest in both basic and clinical neuro-oncology over the past decade. This interest is mainly due to the clinical observation that anaplastic oligodendrogliomas and anaplastic oligoastrocytomas, in contrast to the vast majority of anaplastic astrocytomas and glioblastomas, frequently respond favorably to chemotherapy. In addition, oligodendroglial tumors are associated with longer survival times than the diffuse astrocytic gliomas. These differences in response to therapy and in prognosis have been associated with distinct genetic aberrations, in particular the frequent loss of alleles on chromosome arms 1p and 19q in oligodendroglial tumors. In addition, other genetic changes have been reported as indicators of poor response to therapy and short survival, including homozygous deletion of the CDKN2A gene at 9p21, mutation of the PTEN gene at 10q23, and amplification of the EGFR gene at 7p12. In this review we summarize the current state of the art concerning the molecular genetics of oligodendroglial tumors. A particular focus is placed on the role of molecular genetic findings in the diagnostic and prognostic assessment of these neoplasms. As a result of the recent advances in the field, we propose that clinical decisions in the management of patients with oligodendroglial tumors should be based on the combined assessment of clinical and neuroimaging features, histological classification and grading, as well as molecular genetic characteristics.

Population-based genetic alterations in Ewing's tumors from Japanese and European Caucasian patients

BACKGROUND

The incidence of Ewing's tumors (ETs) is lower in Asians or African-Americans than in Caucasians.

PATIENTS AND METHODS

Japanese ETs were available for analysis of chromosomal aberrations by comparative genomic hybridization (n = 16) and for expression of chimeric EWS transcripts by reverse-transcriptase polymerase chain reaction (n = 11). These results in Japanese patients were compared with those of 62 ETs in European Caucasian patients registered in the European Intergroup Cooperative Ewing's Sarcoma Study.

RESULTS

Japanese patients with ET had lower overall survival (P = 0.0446) and relapse-free survival (P = 0.0371) compared with European Caucasian patients. Ten of 11 Japanese ETs and 31 of 62 European Caucasian ETs had type I (EWS exon 7 to FLI1 exon 6) fusion transcripts. In Japanese ETs, the median numbers of chromosomal aberrations were 2.0 and 6.0 in 11 primary tumors and five relapsed tumors, respectively. In European Caucasian ETs, the median number of changes were 2.5 and 5.0 in 52 primary and 10 relapsed tumors, respectively. Frequent gains were 8q (38%), 8p (31%) and 12q (25%) in Japanese ETs and 8q (52%), 8p (48%) and 12q (19%) in European Caucasian ETs. Frequent losses were 19q (44%), 19p (38%) and 17p (25%) in Japanese ETs and 16q (21%), 19q (18%) and 17p (15%) in European Caucasian ETs. The incidence of losses of 19p (P = 0.0215) and 19q (P = 0.0277) were significantly higher in Japanese ETs than in European Caucasian ETs. An amplification (1p33-p34) was observed in only one Japanese ET.

CONCLUSIONS

Japanese patients with ET in this study had a worse prognosis than European Caucasian patients. In molecular genetic analyses, Japanese ETs had a higher frequency of loss of chromosome 19 than European Caucasian ETs. Different genetic aberrations may explain the different incidences and prognoses of ET between Caucasian and Japanese patients.

High-resolution genome-wide allelotype analysis identifies loss of chromosome 14q as a recurrent genetic alteration in astrocytic tumours

Diffusely infiltrative astrocytic tumours are the most common neoplasms in the human brain. To localise putative tumour suppressor loci that are involved in low-grade astrocytomas, we performed high-resolution genome-wide allelotype analysis on 17 fibrillary astrocytomas. Non-random allelic losses were identified on chromosomal arms 10p (29%), 10q (29%), 14q (35%), 17p (53%), and 19q (29%), with their respective common regions of deletions delineated at 10p14-15.1, 10q25.1-qter, 14q212.2-qer, 17p11.2-pter and 19q12-13.4. These results suggest that alterations of these chromosomal regions play important roles in the development of astrocytoma. We also allelotyped 21 de novo glioblastoma multiforme with an aim to unveil genetic changes that are common to both types of astrocytic tumours. Non-random allelic losses were identified on 9p (67%), 10p (62%), 10q (76%), 13q (60%), 14q (50%), and 17p (65%). Allelic losses of 10p, 10q, 14q and 17p were common genetic alterations detectable in both fibrillary astrocytomas and glioblastoma multiforme. In addition, two common regions of deletions on chromosome 14 were mapped to 14q22.3-32.1 and 14q32.1-qter, suggesting the presence of two putative tumour suppressor genes. In conclusion, our comprehensive allelotype analysis has unveiled several critical tumour suppressor loci that are involved in the development of fibrillary astrocytomas and glioblastoma multiforme. Although these two types of brain tumours are believed to evolve from different genetic pathways, they do share some common genetic changes. Our results indicate that deletions of chromosome 14q is a recurrent genetic event in the development of astrocytoma and highlight the subchromosomal regions on this chromosome that are likely to contain putative tumour suppressor genes involved in the oncogenesis of astrocytic tumours.

Glioblastomas with an oligodendroglial component: a pathological and molecular study

Glioblastoma (GBM) is considered by the WHO classification to represent the most malignant grade of the astrocytic tumors. However, a subset of GBM includes recognizable areas with oligodendroglial features, suggesting that some GBM may also have an oligodendroglial origin. The aim of this study was to analyze the molecular profile of GBM associated with an oligodendroglial component (GBMO). We analyzed a series of 25 GBMO. Loss of heterozygosity (LOH) on 1p and 19q, known as common markers of oligodendroglial tumors, were observed in 40% and 60% of cases, respectively; 72% of the tumors displayed one or both of these markers. All but 4 tumors (84%) showed alterations known to be preferentially involved in the progression of astrocytic tumors to GBM, such as EGFR amplification (44%), P16 deletion (48%), LOH on 10q (64%), PTEN (20%), and TP53 (24%) mutations. Therefore, GBMO displayed all the genetic aberrations found in "standard" GBM with a comparable incidence, but differed from GBM by having a higher rate of LOH on 1p and 19q. These results suggest that GBMO might represent a subgroup of tumors of oligodendroglial origin that is distinct from the "standard" GBM in terms of tumorigenesis pathway.

Oligodendroglial neoplasms: current concepts, misconceptions, and folklore

Given current prognostic and therapeutic implications, the accurate classification and grading of oligodendroglial neoplasms has become critical. However, the prevalence of morphologically ambiguous gliomas, subjective histologic criteria, personal biases, oligodendroglioma mimics, and the lack of specific oligodendroglioma markers has led to high interobserver variability and created a contentious problem encountered daily in active surgical neuropathology practices. Since histologic assessment is still a powerful prognosticator, it appropriately remains the diagnostic gold standard. However, recent efforts have focused on identifying the most reproducible and clinically relevant criteria, standardizing classification and grading schemes, and searching for useful ancillary biologic and genetic markers capable of further stratifying an otherwise heterogeneous patient population. This paper reviews the morphologic and genetic spectrum of oligodendroglial neoplasms, recent diagnostic and prognostic developments, and potential future directions.