Paraffin section p53 protein immunohistochemistry in neuroectodermal tumors

Genomic and Molecular Characterization of Brain Tumors in Asian and Non-Asian Patients of Los Angeles: A Single Institution Analysis

Background

Worldwide, approximately 2% of new cancers are of the brain. Five-year survival rates among brain cancer patients have been reported as a little over a third. Differences in clinical outcomes between brain tumor patients of different races remain poorly understood.

Methods

A retrospective chart review was performed on brain tumor resection patients≥18 years old. Demographics, treatment variables, and survival outcomes were collected. Primary outcomes were length of stay, recurrence rate, progression-free survival (PFS), and overall survival (OS).

Results

A total of 452 patients were included in analysis. Females and males had nearly a 1:1 ratio (n=242 and n=220, respectively). Mean age was 54.8 years (SD: 14.5 range: 18–90). Females composed 69% (n=48) of Asian patients; males constituted 31% (n=22). Mean age of the Asian patients was 55.9 years (SD: 14.6 range: 26–89). Asian-only cohort tumor pathologies included glioblastoma (GBM) (n=14), high-grade glioma (n=7), low-grade glioma (n=4), meningioma (n=38), and metastases (n=7). Of the 185 meningioma patients, non-Asian patients comprised 79% of the group (n=146). Of the 65 GBM patients in total, non-Asian patients made up 89% of the GBM cohort (n=58). There were no statistically significant differences between these groups of both cohorts in recurrence (p=0.1580 and p=0.6294, respectively), PFS (p=0.9662 and p=0.4048, respectively), or OS (p=0.3711 and p=0.8183, respectively).

Conclusion

Studies evaluating the survival between patients of different racial backgrounds against several tumor varieties are rare. Patients of certain racial backgrounds may need additional consideration when being attended to despite the same mutational composition as their counterparts. Repeated studies using national databases may yield more conclusive results.

Prognostic value of Mdm2, p53 and p16 in patients with astrocytomas

Surgical cure of gliomas infiltrating into the brain is practically impossible and their clinical course is primarily determined by the biological behavior of the tumor cell. The purpose of this study was to analyze retrospectively prognostic input of p53, Mouse double minute-2 (Mdm2) and p16 in 103 uniformly treated patients with astrocytic tumors. The expression of these molecules was measured by immunohistochemical procedure. Prognostic evaluation was performed with the multivariate proportional hazards model. The follow-up period lasted 19 (5-122) months for the survivors. We observed that 66% of gliomas showed mutated p53, while only 17% overexpressed Mdm2, the p53-regulatory molecule. Besides, almost 50% of gliomas lost p16 immunopositivity. Only p53 labeling showed a positive correlation with the grade of malignancy, according with the WHO classification. The association between mutated p53 and histological grade remained when prognostic variables were considered in a multivariate analysis. No association between p53 status and overall survival was found. On the other hand, Mdm2 overexpression and, unexpectedly, p16 immunopositivity were associated with a shorter survival in an univariate analysis. However, Cox-regression analysis showed that only Mdm2 in female patients was an independent prognostic factor, associated with shorter survival. In conclusion, our results suggest that Mdm2 could be a relevant marker in determining the evolution of glioma patients and could provide a more objective way to classify astrocytomas.

Glioblastoma multiforme in an Asian population: evidence for a distinct genetic pathway

In Singapore astrocytic tumours occur in only 25% of patients with primary brain tumours compared to 40-60% in other series. Glioblastoma multiforme arises either de novo as a primary glioblastomas associated with epidermal growth factor receptor (EGFR) and mdm2 over-expression or as a secondary glioblastomas, through malignant progression from low-grade astrocytomas, associated with p53 mutations and PDGFR-alpha over-expression. Using immunohistochemical methods and DNA sequencing, we studied our population of glioblastomas for overexpression of EGFR, mdm2, p53, and PDGFR-alpha as well directly for mutations of the p53 gene. While levels of over-expression of EGFR and mdm2 were consistent with levels expected for primary glioblastomas, levels of p53 and PDGFR-alpha were consistent with levels documented for secondary glioblastomas. Notably 96% of the samples over-expressed p53 as detected with monoclonal antibody pAb 240. Of the 39 samples available for DNA sequencing 18% (7/39) had p53 mutations, including three mutations previously undocumented in glioblastomas. These results provide strong evidence that glioblastomas in Asian patients do not conform to currently accepted models of glioblastoma development, and that clinically defined glioblastomas in these patients show genetic changes consistent with both 'primary' and 'secondary' glioblastomas.

Analysis of 2 antiapoptotic factors in gliomas: bcl-2 overexpression and p53 mutations

BACKGROUND

p53 mutations and immunoreactivity have been described in human gliomas. During the past few years, some authors have found bcl-2 overexpression in astrocytomas, although their correlation with histological grade is a matter of disagreement. A relation between bcl-2 overexpression and p53 immunoreactivity has also been suggested.

OBJECTIVES

To analyze the frequency of presentation of bcl-2 and p53, their clinicopathologic implications, and their possible coexpression.

METHODS

We studied p53 and bcl-2 with immunohistochemical and molecular methods in 61 gliomas (including 21 astrocytomas, 9 anaplastic astrocytomas, 29 glioblastomas, 1 oligodendroglioma, and 1 mixed glioma).

RESULTS

We discovered a high level of bcl-2 overexpression (57%). Overexpression of bcl-2 can be an early event in gliomas tumorigenesis, although no correlation was found with any of the clinicopathologic parameters studied. p53 mutations were present in a small proportion of gliomas (17%). p53 immunoreactivity was present in 34 cases (57%), and it was related to histological grade and a supratentorial location. A high percentage of tumors (26 cases, 42%) presented p53 immunoreactivity without p53 mutations.

CONCLUSIONS

Since there was no relation between bcl-2 overexpression and p53 mutations or p53 immunoreactivity, both factors may not act together in the genesis and evolution of gliomas.

p53 protein expression in grade II astrocytomas: immunohistochemical study of 100 cases with long-term follow-up

p53 protein expression was evaluated by immunohistochemistry in a homogeneous series of 100 supratentorial grade II astrocytomas with long-term follow-up. The staining was positive in 72 cases. The proportion of p53 positive tumors was slightly higher in younger patients. The tumor regrowths which derived from p53 positive tumors were themselves p53 positive, and this p53 immunopositivity was often stronger than in the initial tumors. All of the 10 gemistocytic astrocytomas included in our series were p53 positive, and age more than histological type appeared decisive in prognosis. p53 protein expression did not quite reach statistical significance as an independent predictive variable in multivariate analysis, whereas survival was related with age, mass effect, surgery and tumor location. Only a tendency to a longer survival was observed on the curves in younger patients with mildly positive tumors.

Apoptosis is associated with atypical or malignant change in meningiomas. An in situ labelling and immunohistochemical study

AIMS

Although necrosis is an important phenomenon with implications for grading and prognostication in meningiomas, the alternate form of cell death, apoptosis, has not been extensively studied. In this series, we aimed to determine whether apoptosis in meningiomas correlated with histological types and grading. We also looked for a relationship between expression of apoptosis-related genes bcl-2, p53, c-myc and apoptosis meningiomas.

METHODS AND RESULTS

Fifty-one meningiomas of diverse histological subtypes and grades were investigated with in situ end-labelling of DNA fragments as well as immunohistochemical analysis of three apoptosis-related genes: p53, bcl-2 and c-myc. Our results showed that the apoptosis index was significantly higher in high-grade meningiomas (0.12%, n = 12) in than the benign meningiomas (0.023%, n = 39) P = 0.001) but there was no difference among the different histological subtypes of the benign meningiomas (P = 0.125). There is no obvious relationship between p53, bcl-2 and c-myc staining and apoptosis index in this group of meningiomas.

CONCLUSION

We conclude that apoptosis is an important phenomenon in meningiomas and that it is associated with atypical or malignant changes in meningiomas. Apoptosis in meningiomas has no clearcut relationship with expression of p53, bcl-2 and c-myc.

The molecular genetics of central nervous system tumors

Over the past few years, although much has been learned about the molecular genetics of central nervous system (CNS) tumors, researchers and pathologists are only beginning to understand the scientific basis of the development of these tumors. Data accumulated so far support the division of glioblastoma into two clinical and molecular subsets. Primary or de novo glioblastomas occur in older patients, are clinically aggressive and exhibit epidermal growth factor receptor amplification or overexpression. Secondary glioblastomas develop from pre-existing low-grade astrocytomas, have a more protracted clinical course, and frequently contain p53 mutations. Both types of tumors show deletions of chromosome 10 and possibly mutations of the PTEN/MMAC1 gene as an endstage event. Oligodendrogliomas have been shown to have genetic abnormalities distinct from those of the astrocytic tumors, commonly involving chromosomes 1p and 19q. As regards meningiomas, loss of chromosome 22q and mutations of the neurofibromatosis type 2 gene are frequent events and loss of chromosome 14q and 10q may be seen in atypical or malignant transformation. Such genetic findings, apart from providing a better understanding of neoplastic transformation in brain tumors, are beginning to form the basis of a new approach to neuro-oncology.

Analysis of proliferation markers and p53 expression in gliomas of astrocytic origin: relationships and prognostic value

Consecutive paraffin sections of 105 astrocytomas and 15 oligoastrocytomas were examined for expression of p53, MIB-1 (Ki-67), and proliferating cell nuclear antigen (PCNA). The tumors had been examined previously for genetic abnormalities and by flow cytometry. Regardless of the tumor's stage and grade and the patient's age and gender, p53 expression was found in 40% of tumors. Although p53 expression was associated with a loss on chromosome 17p and was more frequent in aneuploid tumors, it had no association with survival time. The MIB-1 and PCNA labeling indices increased with increasing tumor grade but showed no association with other clinicopathological parameters. In individual tumors, there was poor concordance between any of the variables (MIB-1, PCNA, and p53). Results for p53 and MIB-1 were similar for both astrocytomas and oligoastrocytomas. The MIB-1 and PCNA values appeared to have prognostic utility in univariate analysis but not after adjusting for patient age and tumor grade. The poor concordance between MIB-1 and PCNA in individual tumors indicates that any one means of assessing proliferative potential in gliomas may not be reliable.

p53 in cutaneous melanoma: immunoreactivity and correlation with prognosis

p53 protein immunoreactivity was investigated in cutaneous Spitz naevi (n = 7), superficial spreading (n = 21) and nodular (n = 6) melanomas using the monoclonal antibody DO-7. Nuclear immunostaining for p53 protein was observed in 41% of all the melanomas but not in any of the Spitz naevi studied. This difference in p53 immunoreactivity appeared statistically significant (P = 0.0001; chi 2 test). There were also differences in p53 immunoreactivity between superficial spreading and nodular melanomas (P = 0.001, chi 2 test), where up to 38% of superficial spreading melanomas and 50% of nodular melanomas had demonstrated p53 nuclear immunostaining. An apparently significant correlation was observed between melanomas with poor prognostic histological indices and p53 immunoreactivity (P = 0.0016; chi 2 test). In conclusion, increased p53 protein immunoreactivity is found in melanomas and is associated with poorer prognosis. The differences in p53 immunohistological expression between cutaneous melanomas and Spitz naevi suggest that alterations of the protein may be important in the pathogenesis of the tumour.