Most studies have shown that there are association between the development and malignancy of brain tumors and tumor suppressor genes and oncogenes. the aim of this project is to investigate the p53 gene mutations in exon 8 and c-myc oncogene expression in patients with astrocytoma type’s brain tumor.
Methods
In this present survey, the dna isolation from 30 samples of brain tissue was done by phenol-chloroform protocols. after pcr amplification for p53 at exon 8, screening by sscp (single -strand conformation polymorphism) was performed to determine the mobility shifts. samples that have shift were sequenced. then the cells were extracted from fresh-frozen human brain tissue for analysis of c-myc oncogene expression by flow cytometric assay.
Results
As a result, two malignant mis-sense nucleotide changes (g.13851a>g and g.13864c>g) was found at exon 8 in a sample with grade 4 of astrocytoma; sequence changes at protein level of this mutations is k291e and p295r respectively. also one mis-sense nucleotide changes (g.13783a>t) was detected at exon 8 in a sample with grade 3 of astrocytoma. moreover it was observed that c-myc expression in meningioma was significantly less than astrocytoma samples (p<0.05).
Conclusion
Based on this finding, it may be responsible to conclude that, the above nucleotide change which found within the protein's dna binding domain could be pathogenic mutation. this mutation can result in prevent tumor suppressing function of p53 and possibly causes cancer. in this project mutations was observed in mostly malignant astrocytoma brain tumor type. also, since the c-myc gene expression in astrocytoma brain tumors was higher than meningioma type of brain tumors. these factors may be important in early diagnosis and gene therapy of malignant brain tumors.
