Detection of a novel point mutation in the p53 gene in grade II astrocytomas by PCR-SSCP analysis with additional
B Chawengchao1, S Petmitr, M Ponglikitmongkol
1Neuro-Behavioural Biology Center, Institute of Science and Technology for Research and Development, Mahidol University, Salaya, Nakomfathom, Thailand.
Abstract:
Using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) with additional Klenow treatment and direct sequencing mutations in the p53 tumor suppressor gene were analyzed from 21 cases of human astrocytomas. Three cases had p53 gene mutations: two of them were glioblastomas showing a point mutation, one in exon 5 and the other in 6. The last one was a gemistocytic astrocytoma showing a point mutation in exon 5. The frequency of p53 gene mutations in the astrocytomas examined was 14.3% (3 out of 21). No SSCP alterations were observed in any of the p53 fragments amplified from WHO grade I pilocytic astrocytomas and WHO grade III anaplastic astrocytomas. Further examination by direct sequencing showed that two mutations of glioblastomas had single-base substitutions resulting in silent and missense mutations, whereas one of the gemistocytic astrocytomas had a double-base substitution resulting in a missense mutation. The present studies revealed that all mutations were located outside the hot spots and, interestingly, one of them disclosed a missense mutation in exon 5 at codon 166, which was first detected in a grade II astrocytoma (gemistocytic type). It is possible that the missense mutation at this codon may be associated with special risk factors for the development of astrocytic tumors in Thai patients.
Insights
p53 gene mutations were found in 14.3% of human astrocytomas, with specific mutations identified in glioblastomas and gemistocytic astrocytomas. These findings may indicate unique risk factors for astrocytic tumors in Thai patients.
Area of Science:
- Neuro-oncology
- Molecular Genetics
- Cancer Research
Background:
- The p53 tumor suppressor gene plays a critical role in preventing tumor formation.
- Mutations in the p53 gene are frequently observed in various human cancers, including brain tumors.
- Astrocytomas represent a significant group of primary brain tumors with diverse molecular characteristics.
Purpose of the Study:
- To investigate the presence and types of mutations in the p53 gene in human astrocytomas.
- To determine the frequency of p53 gene mutations across different grades of astrocytomas.
- To explore potential associations between p53 mutations and specific astrocytoma subtypes or patient populations.
Main Methods:
- Polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) was employed to screen for mutations.
- Klenow treatment and direct sequencing were utilized for precise mutation identification.
- Analysis was performed on 21 cases of human astrocytomas, including various WHO grades.
Main Results:
- p53 gene mutations were detected in 3 out of 21 (14.3%) astrocytoma cases.
- Two glioblastomas exhibited point mutations in exons 5 and 6, with single-base substitutions leading to silent and missense mutations.
- One gemistocytic astrocytoma (WHO grade II) showed a double-base substitution in exon 5, resulting in a missense mutation at codon 166, located outside known hot spots.
Conclusions:
- p53 gene mutations occur in a subset of human astrocytomas, with varying frequencies depending on tumor grade.
- The identified mutations, particularly the novel missense mutation in a gemistocytic astrocytoma, may hold significance for understanding astrocytoma development.
- The specific missense mutation at codon 166 could be associated with particular risk factors for astrocytic tumors in the Thai population.
