Demonstration of p53 protein and TP53 gene mutations in oligodendrogliomas

TP53 Mutation Is a Prognostic Factor in Lower Grade Glioma and May Influence Chemotherapy Efficacy

BACKGROUND

Identification of prognostic biomarkers in cancers is a crucial step to improve overall survival (OS). Although mutations in tumour protein 53 (TP53) is prevalent in astrocytoma, the prognostic effects of TP53 mutation are unclear.

METHODS

In this retrospective study, we sequenced TP53 exons 1 to 10 in a cohort of 102 lower-grade glioma (LGG) subtypes and determined the prognostic effects of TP53 mutation in astrocytoma and oligodendroglioma. Publicly available datasets were analysed to confirm the findings.

RESULTS

In astrocytoma, mutations in TP53 codon 273 were associated with a significantly increased OS compared to the TP53 wild-type (HR (95% CI): 0.169 (0.036-0.766), p = 0.021). Public datasets confirmed these findings. TP53 codon 273 mutant astrocytomas were significantly more chemosensitive than TP53 wild-type astrocytomas (HR (95% CI): 0.344 (0.13-0.88), p = 0.0148). Post-chemotherapy, a significant correlation between TP53 and YAP1 mRNA was found (p = 0.01). In O (6)-methylguanine methyltransferase (MGMT) unmethylated chemotherapy-treated astrocytoma, both TP53 codon 273 and YAP1 mRNA were significant prognostic markers. In oligodendroglioma, TP53 mutations were associated with significantly decreased OS.

CONCLUSIONS

Based on these findings, we propose that certain TP53 mutant astrocytomas are chemosensitive through the involvement of YAP1, and we outline a potential mechanism. Thus, TP53 mutations may be key drivers of astrocytoma therapeutic efficacy and influence survival outcomes.

The predictive capability of immunohistochemistry and DNA sequencing for determining TP53 functional mutation status: a comparative study of 41 glioblastoma patients

Tumor protein 53 (p53) regulates fundamental pathways of cellular growth and differentiation. Aberrant p53 expression in glioblastoma multiforme, a terminal brain cancer, has been associated with worse patient outcomes and decreased chemosensitivity. Therefore, correctly identifying p53 status in glioblastoma is of great clinical significance. p53 immunohistochemistry is used to detect pathological presence of the TP53 gene product. Here, we examined the relationship between p53 immunoreactivity and TP53 mutation status by DNA Sanger sequencing in adult glioblastoma. Of 41 histologically confirmed samples, 27 (66%) were immunopositive for a p53 mutation via immunohistochemistry. Utilizing gene sequencing, we identified only eight samples (20%) with TP53 functional mutations and one sample with a silent mutation. Therefore, a ≥10% p53 immunohistochemistry threshold for predicting TP53 functional mutation status in glioma is insufficient. Implementing this ≥10% threshold, we demonstrated a remarkably low positive-predictive value (30%). Furthermore, the sensitivity and specificity with ≥10% p53 immunohistochemistry to predict TP53 functional mutation status were 100% and 42%, respectively. Our data suggests that unless reliable sequencing methodology is available for confirming TP53 status, raising the immunoreactivity threshold would increase positive and negative predictive values as well as the specificity without changing the sensitivity of the immunohistochemistry assay.

Chromosomal Aberrations in Canine Gliomas Define Candidate Genes and Common Pathways in Dogs and Humans

Spontaneous gliomas in dogs occur at a frequency similar to that in humans and may provide a translational model for therapeutic development and comparative biological investigations. Copy number alterations in 38 canine gliomas, including diffuse astrocytomas, glioblastomas, oligodendrogliomas, and mixed oligoastrocytomas, were defined using an Illumina 170K single nucleotide polymorphism array. Highly recurrent alterations were seen in up to 85% of some tumor types, most notably involving chromosomes 13, 22, and 38, and gliomas clustered into 2 major groups consisting of high-grade IV astrocytomas, or oligodendrogliomas and other tumors. Tumor types were characterized by specific broad and focal chromosomal events including focal loss of the INK4A/B locus in glioblastoma and loss of the RB1 gene and amplification of the PDGFRA gene in oligodendrogliomas. Genes associated with the 3 critical pathways in human high-grade gliomas (TP53, RB1, and RTK/RAS/PI3K) were frequently associated with canine aberrations. Analysis of oligodendrogliomas revealed regions of chromosomal losses syntenic to human 1p involving tumor suppressor genes, such as CDKN2C, as well as genes associated with apoptosis, autophagy, and response to chemotherapy and radiation. Analysis of high frequency chromosomal aberrations with respect to human orthologues may provide insight into both novel and common pathways in gliomagenesis and response to therapy.

Revisiting TP53 Mutations and Immunohistochemistry--A Comparative Study in 157 Diffuse Gliomas

The association between p53 immunohistochemistry and TP53 mutation status has been controversial. The present study aims to re-evaluate the efficacy of p53 immunohistochemistry to predict the mutational status of TP53. A total of 157 diffuse gliomas (World Health Organization grades II-IV) were assessed by exon-by-exon DNA sequencing from exon 4 through 10 of TP53 using frozen tissue samples. Immunohistochemistry with a p53 antibody (DO-7) on paired formalin-fixed paraffin-embedded materials was assessed for the extent and intensity of reactivity in all cases. A total of 72 mutations were detected in 66 samples. They included 60 missense mutations, five nonsense mutations, four deletions and three alterations in the splicing sites. A receiver operating characteristic curve analysis revealed that strong p53 immunoreactivity in more than 10% of cells provided the most accurate prediction of mutation. Using this cutoff value, 52 of 55 immunopositive cases harbored a mutation, whereas only 14 of 102 immunonegative cases showed mutations, sensitivity and specificity being 78.8% and 96.7%. Tumors with frameshift mutations frequently showed negative immunostaining. Staining interpretation by an independent observer yielded comparable accuracy. We thus propose p53 immunohistochemistry as a moderately sensitive and highly specific marker to predict TP53 mutation.

TP53 and p53 statuses and their clinical impact in diffuse low grade gliomas

TP53 is a pivotal gene frequently mutated in diffuse gliomas and particularly in astrocytic tumors. The majority of studies dedicated to TP53 in gliomas were focused on mutational hotspots located in exons 5-8. Recent studies have suggested that TP53 is also mutated outside the classic mutational hotspots reported in gliomas. Therefore, we have sequenced all TP53 coding exons in a retrospective series of 61 low grade gliomas (LGG) using high throughput sequencing technology. In addition, TP53 mutational status was correlated with: (i) p53 expression, (ii) tumor type, (iii) chromosome arms 1p/19q status and (iv) clinical features of patients. The cohort included 32 oligodendrogliomas (O), 21 oligoastrocytomas (M) and 8 astrocytomas (A). TP53 mutation was detected in 52.4% (32/61) of tumors (34% of O, 71.4% of M and 75% of A). All mutations (38 mutations in 32 samples) were detected in exons 4, 5, 6, 7, 8 and 10. Missense and non-missense mutations, including seven novel mutations, were detected in 42.6 and 9.8% of tumors respectively. TP53 mutations were almost mutually exclusive with 1p/19q co-deletion and were associated with: (i) astrocytic phenotype, (ii) younger age, (iii) p53 expression. Using a threshold of 10% p53-positive tumor cells, p53 expression is an interesting surrogate marker for missense TP53 mutations (Se = 92%; Sp = 79.4%) but not for non-missense mutation (18.4% of mutations). TP53 and p53 statuses were not prognostic in LGG. In conclusion, we have identified novel TP53 mutations in LGG. TP53 mutations outside exons 4-8 are rare. Although it remains imperfect, p53 expression with a threshold of 10% is a good surrogate marker for missense TP53 mutations and appears helpful in the setting of LGG phenotype diagnosis.

p53 in neurodegenerative diseases and brain cancers

More than thirty years elapsed since a protein, not yet called p53 at the time, was detected to bind SV40 during viral infection. Thousands of papers later, p53 evolved as the main tumor suppressor involved in growth arrest and apoptosis. A lot has been done but the protein has not yet revealed all its secrets. Particularly important is the observation that in totally distinct pathologies where apoptosis is either exacerbated or impaired, p53 appears to play a central role. This is exemplified for Alzheimer's and Parkinson's diseases that represent the two main causes of age-related neurodegenerative affections, where cell death enhancement appears as one of the main etiological paradigms. Conversely, in cancers, about half of the cases are linked to mutations in p53 leading to the impairment of p53-dependent apoptosis. The involvement of p53 in these pathologies has driven a huge amount of studies aimed at designing chemical tools or biological approaches to rescue p53 defects or over-activity. Here, we describe the data linking p53 to neurodegenerative diseases and brain cancers, and we document the various strategies to interfere with p53 dysfunctions in these disorders.

IDH/MGMT-driven molecular classification of low-grade glioma is a strong predictor for long-term survival

BACKGROUND

Low-grade gliomas (LGGs) are rare brain neoplasms, with survival spanning up to a few decades. Thus, accurate evaluations on how biomarkers impact survival among patients with LGG require long-term studies on samples prospectively collected over a long period.

METHODS

The 210 adult LGGs collected in our databank were screened for IDH1 and IDH2 mutations (IDHmut), MGMT gene promoter methylation (MGMTmet), 1p/19q loss of heterozygosity (1p19qloh), and nuclear TP53 immunopositivity (TP53pos). Multivariate survival analyses with multiple imputation of missing data were performed using either histopathology or molecular markers. Both models were compared using Akaike's information criterion (AIC). The molecular model was reduced by stepwise model selection to filter out the most critical predictors. A third model was generated to assess for various marker combinations.

RESULTS

Molecular parameters were better survival predictors than histology (ΔAIC = 12.5, P< .001). Forty-five percent of studied patients died. MGMTmet was positively associated with IDHmut (P< .001). In the molecular model with marker combinations, IDHmut/MGMTmet combined status had a favorable impact on overall survival, compared with IDHwt (hazard ratio [HR] = 0.33, P< .01), and even more so the triple combination, IDHmut/MGMTmet/1p19qloh (HR = 0.18, P< .001). Furthermore, IDHmut/MGMTmet/TP53pos triple combination was a significant risk factor for malignant transformation (HR = 2.75, P< .05).

CONCLUSION

By integrating networks of activated molecular glioma pathways, the model based on genotype better predicts prognosis than histology and, therefore, provides a more reliable tool for standardizing future treatment strategies.

Molecular profile of oligodendrogliomas in young patients

Several studies on molecular profiling of oligodendrogliomas (OGs) in adults have shown a distinctive genetic pattern characterized by combined deletions of chromosome arms 1p and 19q, O6-methylguanine-methyltransferase (MGMT) methylation, and isocitrate dehydrogenase 1 (IDH1) mutation, which have potential diagnostic, prognostic, and even therapeutic relevance. OGs in pediatric and young adult patients are rare and have been poorly characterized on a molecular and biological basis, and it remains uncertain whether markers with prognostic significance in adults also have predictive value in these patients. Fourteen cases of OGs in young patients (age, ≤ 25 years) who received a diagnosis over 7 years were selected (7 pediatric patients age ≤ 18 years and 7 young adults aged 19-25 years). The cases were evaluated for 1p/19q status, MGMT promoter methylation, p53 mutation, and IDH1 mutation. None of the pediatric cases showed 1p/19q deletion. In young adults, combined 1p/19q loss was observed in 57% and isolated 1p loss in 14% of cases. The majority of cases in both subgroups (71% in each) harbored MGMT gene promoter methylation. TP53 and IDH1 mutations were not seen in any of the cases in both the groups. To our knowledge, this is the first study to show that molecular profile of OGs in pediatric and young adult patients is distinct. Further large-scale studies are required to identify additional clinically relevant genetic alterations in this group of patients.

Expression of hypoxia inducible factor-1alpha in tumors of patients with glioblastoma multiforme and transitional meningioma

Hypoxia-inducible factor-1 alpha (HIF-1alpha) is the major transcriptional factor involved in the adaptive response to hypoxia. The aim of this study was to assess HIF-1alpha in 22 patients with transitional meningioma (TM) and 26 patients with glioblastoma multiforme (GBM). HIF-1alpha was assessed using a commercially available enzyme-linked immunosorbent assay-based HIF-1 transcription factor assay. Levels of HIF-1alpha in TM and GBM were measured using optical density at 450nm, and median values were found to be 0.35 for TM and 0.37 OD for GBM, respectively. There was no statistically significant difference between the two types of tumor (p=0.264). These findings indicate that HIF-1alpha is elevated in both TM and GBM, suggesting that although hypoxia is one of the most important and powerful stimuli for HIF-1alpha elevation and consequently angiogenesis, other mechanisms may play roles in HIF-1alpha stimulation in benign brain tumors such as TM.

Molecular pathogenesis of adult brain tumors and the role of stem cells

Primary brain tumors consist of neoplasms with varied molecular defects, morphologic phenotypes, and clinical outcomes. The genetic and signaling abnormalities involved in tumor initiation and progression of the most prevalent adult primary brain tumors, including gliomas, meningiomas, and medulloblastomas, are described in this article. The current understanding of the cell-of-origin of these neoplasms is reviewed, which suggests that the malignant phenotype is propelled by cells with stem-like qualities. A comprehensive understanding of the molecular basis of transformation and the cell-of-origin of these neoplasms will enable the formulation of more targeted treatment alternatives that could improve survival and quality of life.

P53 expression in squamous cell carcinomas of the supraglottic larynx and its lymph node metastases: new results for an old question

BACKGROUND

Although p53 overexpression is frequent in head and neck squamous cell carcinomas (HNSCCs), controversy remains regarding the prognostic significance of that overexpression. The objective of this study was to investigate the expression pattern and prognostic significance of p53 expression in HNSCC of the same location, treated in the same way, and with long-term follow-up.

METHODS

P53 expression was determined by immunohistochemistry in paraffin-embedded tissue specimens from 107 consecutive patients (107 primary squamous cell carcinomas of the supraglottic larynx and 46 matched lymph node metastases). All patients underwent surgical resection and bilateral neck dissection.

RESULTS

A strong correlation was observed between p53 expression in the primary tumor and in the matched lymph node metastases (P=.0001). P53 overexpression in the lymph nodes was an independent predictor of regional recurrence (P=.027). Likewise, expression of p53 in the lymph nodes correlated significantly with disease-specific survival (P=.018). Five years after treatment, 70% of patients with p53-negative, metastatic lymph nodes remained alive, whereas only 30% of patients with p53-positive lymph nodes remained alive. In multivariate analysis, lymph node status and p53 expression in the lymph nodes remained associated with survival.

CONCLUSIONS

The current data suggested that, although p53 overexpression is common in supraglottic carcinomas, its expression in the primary tumor is of limited clinical significance. However, the results supported the role of p53 in the lymph node metastases as an independent predictor of regional failure and a poor prognosis in patients with HNSCC. A prospective trial is indicated to validate these findings.

Cytochrome P450 1B1 Expression in Glial Cell Tumors: An Immunotherapeutic Target

PURPOSE

Among central nervous system malignancies, cytochrome P450 1B1 (CYP1B1) expression has only been characterized in medulloblastoma. An immunotherapeutic agent targeting this antigen was shown to safely stimulate a good immune response. To evaluate the viability of further research efforts targeting this antigen, we examined the expression of CYP1B1 in glial cell malignancies.

EXPERIMENTAL DESIGN

We studied the frequency and extent of CYP1B1 expression by immunohistochemical analysis in 269 glial tumors (including all major pathologic types) on a tissue microarray. Results were categorized by percentage of cells stained and intensity of cytoplasmic staining within cells. Correlation of CYP1B1 expression with patient prognosis was evaluated by univariate and multivariate analyses.

RESULTS

Overall, increased CYP1B1 expression in glial tumors was associated with decreased patient survival time (P < 0.0014 for both percentage and intensity of staining). A significant difference existed in percentage and intensity of staining between astrocytic and oligodendroglial tumors (P = 0.0002 and 0.0003, respectively), between grades of tumors (P < 0.0001 and 0.0079), and between pathologic types of tumors (P < 0.0001 and 0.0339). Positive CYP1B1 staining was seen in 81% of glioblastomas, 84% of anaplastic astrocytomas, 61% of oligodendrogliomas, and 67% of anaplastic oligodendrogliomas. Paradoxically, within specific tumor pathologies, there was a trend toward increased survival as CYP1B1 expression increased. However, in the multivariate analysis, this trend disappeared, and CYP1B1 expression seemed prognostically neutral.

CONCLUSION

CYP1B1 is frequently expressed in a variety of gliomas and could be used as a target for immunotherapy.

Chromosome 1p and 19q status and p53 and p16 expression patterns as prognostic indicators of oligodendroglial tumors: A clinicopathological study using fluorescence in situ hybridization

To verify the prognostic implications of the statuses of chromosome 1p and 19q and the expressions of p53, p16 and GFAP in oligodendrogliomas, we investigated these parameters and correlated the results with patient outcome. Twenty-seven cases of low-grade oligodendroglioma (LO) and 29 cases of anaplastic oligodendroglioma (AO) were analyzed by FISH for 1p and 19q status and by immunohistochemistry for p53, p16, and GFAP expression using a tissue microarray. Direct sequencing of the p53 gene was also performed. 1p deletion was observed in 39 of 56 patients (69.9%), and 19q deletion in 41 of 56 (73.2%). Combined loss of 1p and 19q was found in 38 of 56 (67.9%) and exhibited distinct concomitant deletion (P = 0.000). p53 overexpression was observed in 17 cases (30.3%), GFAP expression in 18 cases (32.1%), and p16 loss in 40 cases (74%) of oligodendrogliomas. The expressions of p53 and GFAP were more frequent in AO than in LO (P= 0.015 and 0.001). In contrast, p53 expression was more common in oligodendrogliomas with an intact 19q (P= 0.029), or an intact 1p (P= 0.071). Only five of 14 patients with p53 expression showed TP53 mutation, which was inversely correlated with 1p deletion (P= 0.036). Patients with combined loss of 1p and 19q exhibited better overall survival (P = 0.045). Patients with p53 expression without combined 1p and 19q loss showed poor overall survival (P < 0.000). However, TP53 mutation along with 1p and 19q status could not predict patient outcome. Patients with p16 loss without combined 1p and 9q loss showed poor overall survival (P = 0.011). Therefore, in oligodendrogliomas, the absence of the combined deletion of 1p and 19q and the aberrant expression of p53 or loss of p16 could be used as poor prognostic markers.

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.

Altered molecular pathways in gliomas: An overview of clinically relevant issues

Primary central nervous system (CNS) tumors constitute a small fraction of the overall incidence of human cancer, but they represent a major source of cancer-related morbidity and mortality. The most common CNS tumor subtype in adults, high-grade astrocytoma, confers a dismal prognosis with a median survival of only 1 to 2 years. Other common adult CNS tumors, ie, low-grade astrocytomas and oligodendrogliomas, carry a less ominous, yet still poor prognosis. Unfortunately, there has been little progress in extending the survival or quality of life for glioma patients, despite nearly four decades of extensive research. This research has, however, greatly increased our understanding of the underlying molecular biology of these tumors, examples of which include the determination of elevated epidermal growth factor receptor (EGFR) as well as platelet-derived growth factor receptor (PDGF) signaling, and the inactivation of p53 , p16 , and PTEN tumor-suppressor genes (TSGs) that negatively regulate specific enzymatic activities in normal glial cells. Such observations have greatly improved our understanding of the pathogenesis of these tumors and have potential diagnostic as well as therapeutic relevance. With respect to the latter of these two issues, the identification of aberrant enzymatic activities in gliomas has promoted the development of novel therapeutic agents that target specific signaling effectors, and whose inhibition should, in theory, prove to be cytostatic, if not cytotoxic, to tumor cells. Several clinical trials are currently underway for testing these therapeutic agents in patients with primary brain tumors, and it is hoped that the targeting of pro-tumorigenic enzymatic activities will lead to better patient outcomes. In this review, we will describe the most pertinent genetic and signaling pathway alterations that are clinically relevant to the management of glial tumors.

The impact of p53 tumor suppressor gene on glioma biology

The tumor suppressor gene, p53, is important in glioma biology. The authors of this paper review its role in cell physiology, epidemiology, glioma progression, prognosis, and therapeutic advances.

The diversity of p53 mutations among human brain tumors and their functional consequences

The p53 tumor suppressor is implicated in cell cycle control, DNA repair, replicative senescence and programmed cell death. Inactivation of the p53 contributes to the wide range of human tumors, including glial neoplasms. In this review, we describe the regulation and biochemical properties of p53 protein that may explain its ability to activate various genetic programs underlying cellular responses to stress conditions. The overall spectrum of p53 mutations is rather shared between tumor types indicating that these mutations are not tumor type-specific. However, there is one example of germ-line mutation of p53 gene (the deletion of the codon 236) that is associated with a familiar brain tumor syndrome. We compare the frequency and type of most common mutations among various brain tumours (focusing on glioblastomas) and their consequences on protein functions. Furthermore, we discuss the most promising approaches of potential brain tumor therapy, including an adenovirus-mediated p53 gene transfer. Human glioblastomas are highly sensitive to the effects of p53 activity when the wild-type p53 is introduced ectopically. It suggests that the genetic or pharmacological modulation of the p53 pathway is potentially important strategy in the treatment of human cancers.

Proliferation and apoptosis in long-term surviving low grade gliomas in relation to radiotherapy

Identification of patients with a low grade glioma with a long-term recurrence-free survival is of clinical value as radiotherapy can be postponed until recurrence. The recurring glioma may increase in malignancy compared to the original tumor, which is possibly related to radiotherapy. We studied proliferation by counting mitotic figures and by MIB-1 labeling, apoptosis by TUNEL and expression of proteins related to cell cycle regulation by immunohistochemical analysis of p53, p21, bcl-2 and bax expression in 48 low grade gliomas. Astrocytomas (A, n = 14) and oligodendrogliomas (O, n = 4) with a recurrence-free survival of more than 9 years after surgery had a signficantly lower p53 index compared to A (n = 18) and O (n = 12) with a histopathologically documented recurrence. Additionally, the recurrence-free A had a higher p21 index. No significant differences were observed in MIB-LI, TUNEL-LI, bcl-2 and bax expression. Initially low grade gliomas and their corresponding recurrences were compared (n = 30). In the gliomas without radiotherapy (n = 15), no differences in mitotic rate, TUNEL-LI, p53, p21, bcl-2 and bax expression were found between primary tumors and their recurrences. Only MIB-LI was higher in the recurrent tumors. In the gliomas with radiotherapy (n = 15) no differences were detected in these parameters between the original tumor and the recurrent tumor except for a higher number of mitoses in the recurrent tumors. We conclude that low grade gliomas with a long-term recurrence-free survival were characterized by a low p53 protein expression and, in the case of A, a higher p21 index. We found no evidence that radiotherapy is involved in changes of proliferation, apoptosis or expression of proteins related to cell cycle regulation in recurring gliomas.

Low incidence of SV40-like sequences in ependymal tumours

Between 1955 and 1963, millions of children and adults were exposed to SV40-contaminated poliovirus vaccines. The oncogenic potential of this polyomavirus was revealed when intracerebral inoculation of SV40 into newborn hamsters resulted in the development of ependymomas and choroid plexus papillomas. Subsequently, SV40-like sequences were repeatedly detected in human ependymomas with broadly ranging incidence rates of 7-90%. Most epidemiological studies, however, have not described an increased occurrence of ependymomas. To gain more data on this controversial issue, this study examined 62 archived ependymal tumours from 31 children and 31 adults who underwent surgery between 1990 and 1999. Only three (5%) of the tumours--including 24 classical, 20 anaplastic, and 12 myxopapillary ependymomas; one subependymoma; and five ependymoblastomas--revealed subgenomic SV40 sequences. None of the ependymomas in patients born between 1920 and 1960 demonstrated SV40-like sequences. The positive tumours represent 7% of grade II and III ependymomas (two paediatric and one adult tumour). DNA sequencing of the PCR product revealed identical sequences of SV40 in the positive ependymal tumours. Compared with the results from other countries, this incidence rate is relatively low. Therefore, it seems likely that significant differences between individual countries exist regarding the prevalence of SV40-positive ependymomas. These differences may reflect different degrees of exposure to SV40-contaminated polio vaccine.

Expression of hypoxia-inducible factor-1 alpha in oligodendrogliomas: its impact on prognosis and on neoangiogenesis

BACKGROUND

Hypoxia-inducible factor (HIF)1 alpha is considered to play a key role in the adaptation of cells to hypoxia by stimulating angiogenesis via regulation of vascular endothelial growth factor and by metabolic adaptation to O(2) deprivation.

METHODS

Expression of HIF-1 alpha protein and p53 was investigated by immunohistochemistry in 51 specimens of supratentorial pure oligodendrogliomas. Microvessels density (MVD) was determined by anti-CD34 immunostaining. The influence of HIF-1 alpha expression on survival was investigated using univariate and multivariate analysis.

RESULTS

Strong expression of HIF-1 alpha was observed in 12 (23.5%) specimens, moderate in 21 (41.2%) specimens, and weak in 8 (15.7%) cases, and no expression was found in 10 samples (19.6%). There was no correlation of HIF-1 alpha expression with histologic grading (P = 0.428, Mann-Whitney test). Hypoxia-inducible factor-1 alpha expression and MVD showed a strong correlation (P < 0.001, r = 0.735, Spearman coefficient of correlation). Overexpression of p53 was observed in only two cases. Patients with strong or moderate expression of HIF-1 alpha had a significantly shorter overall survival rate compared with those with low or no expression in univariate (P = 0.0434; log-rank test) and multivariate analysis (P = 0.0187).

CONCLUSIONS

Overexpression of HIF-1 alpha indicates a diminished prognosis in oligodendrogliomas, independent of p53 status. This finding may be explained by the strong vascularization of these tumors that prevents hypoxia and allows O(2) diffusion and henceforth tumor progression.

Antiapoptotic Bcl-2 family protein expression increases with progression of oligodendroglioma

BACKGROUND

Altered expression of Bcl-2 family proteins has been associated with tumorigenesis and tumor progression as well as resistance to radiotherapy and chemotherapy. In the current study, Bcl-2 family protein expression was examined in oligodendrogliomas and anaplastic oligodendrogliomas, and an attempt was made to determine whether these proteins accumulate during disease progression and to search for protein expression patterns predictive of time to progression and overall survival.

METHODS

A total of 42 oligodendroglioma tissue samples, 26 de novo World Health Organization (WHO) Grade 2 oligodendrogliomas, and 16 de novo WHO Grade 3 anaplastic oligodendrogliomas were studied. Nineteen Grade 2 tumors progressed: 10 again were Grade 2 oligodendrogliomas and 8 had progressed to higher grade lesions. Eight anaplastic oligodendrogliomas progressed: five again were WHO Grade 3 tumors and three were glioblastoma multiforme. Expression of Bcl-2, Bax, Bcl-X, and Mcl-1 proteins and of the proliferation marker Ki-67 was evaluated by immunohistochemistry. Apoptotic cells were quantified by in situ nick translation (ISNT).

RESULTS

De novo WHO Grade 2 oligodendrogliomas had higher Bcl-2 scores (P = 0.037), lower MIB-1 scores (P = 0.0012), and lower ISNT scores (P = 0.049) compared with de novo WHO Grade 3 anaplastic oligodendrogliomas. In de novo oligodendrogliomas, low numbers of Bax positive cells were associated with a short time to disease progression (P = 0.043). In de novo anaplastic oligodendrogliomas, low numbers of Bcl-2 positive cells correlated with short survival (P = 0.029). In tumors that had progressed from WHO Grade 3 anaplastic oligodendrogliomas, the authors found significantly more Bcl-X positive (P = 0.005), Mcl-1 positive (P = 0.002), and Bax positive (P = 0.03) cells.

CONCLUSIONS

The results of the current study show that progression of oligodendrogliomas and anaplastic oligodendrogliomas is associated with an enhanced expression of antiapoptotic Bcl-2 family proteins.

Molecular genetic analysis of non-astrocytic gliomas

AIMS

Oligodendroglial tumours follow genetic pathways different from but overlapping with those of astrocytic tumours. The aim of this study was to examine whether major genetic events such as loss of chromosome 10 and p53 mutation found in astrocytic gliomas are also involved in the development and anaplastic transformation of non-astrocytic gliomas and to correlate the findings with histopathological subtypes of these tumours.

METHODS AND RESULTS

Sixty-one formalin-fixed, paraffin-embedded oligodendroglial and ependymal tumours (16 oligodendrogliomas, 12 anaplastic oligodendrogliomas, seven oligoastrocytomas, 24 ependymomas and two anaplastic ependymomas) were examined for allelic deletions on chromosome 10q23 and 10q25-26 regions, mutations of PTEN/MMAC1 and p53, MDM2 gene amplification and apoptosis. The frequencies of allelic deletions at marker D10S2491 (which mapped within PTEN/MMAC1) and between markers D10S209 and D10S587 (where DMBT1 was located) were found to be < 30% in both types of non-astrocytic gliomas. High frequency of allelic deletions was detected at marker D10S215 (80%) at the proximal 10q23 region in both oligodendroglial and ependymal tumours and between markers D10S216 (42%) and D10S169 (67%) at distal 10q25-26 region in oligodendroglial tumours. No mutations of PTEN/MMAC1 were found. p53 mutations were detected in three oligoastrocytomas and one ependymoma; three out of five mutations were found in exon 4. MDM2 gene amplification was found in one ependymoma harbouring wild-type p53. The apoptotic index was lower in p53-mutated tumours than in tumours with wild-type p53.

CONCLUSION

The telomeric end of chromosome 10q could be involved in the development and anaplastic transformation of oligodendroglial tumours. Mutations of PTEN/MMAC1 and p53, amplification of the MDM2 gene and allelic loss on chromosome 10q do not play a major part in the pathogenesis or anaplastic transformation of oligodendrogliomas and ependymal tumours.

Is p53 an independent prognostic factor in patients with laryngeal carcinoma?

BACKGROUND

Carcinoma of the true vocal cord represents the earliest clinically recognizable invasive malignancy in the head and neck region and provides a unique model for studying possible prognostic genetic markers. The aim of this study was to determine whether p53 overexpression correlated with tumor recurrence in a homogenous population of patients with early stage glottic carcinoma treated with radiotherapy alone.

METHODS

One hundred and fourteen patients with T1N0M0 squamous cell carcinoma of the glottis were treated with curative radiotherapy between 1976 and 1990. With a median follow-up of 6 years, actuarial local control was 80% with 23 local recurrences. Laryngeal biopsy specimens obtained prior to radiation therapy were analyzed retrospectively in 22 patients. Forty-five patients with local control were used as a control group. p53 overexpression indicating a mutated p53 gene was analyzed by immunohistochemistry using the mouse monoclonal antibody D0-7.

RESULTS

Approximately 82% of carcinomas that recurred locally expressed p53 compared with only 29% of those with local control (P < 0.001). No significant relation was noted between p53 expression and histologic grade. Intensity of staining did not predict tumor recurrence.

CONCLUSIONS

The authors believe that this case-controlled study demonstrated the role of p53 as an independent prognostic factor in patients with early stage glottic carcinoma.