Abstract: BACKGROUND AND AIM: To study the expression differences of O6-methulguanine-DNA methyltransferase (MGMT) and mutant P53 protein between primary and secondary glioblastomas(GBM) and the biological implications. MATERIALS AND METHODS: Immunohistochemistry(IHC) methods was used to measure the expressions of MGMT and mutant P53 protein in 39 cases of GBM(13 primary and 26 secondary),and the correlation with prognosis. The relationship between these gene expressions in primary and secondary GBM were analyzed. RESULTS: The differences of positive rate and expression intensity of mutant P53 protein expression were statistically signifiant between primary and secondary GBM (P<0.01；P<0.01 ,respectively). Moreover, there was an inverse correlation between MGMT and mutant P53 protein expression intensity in secondary GBM(r=-0.602, P<0.01).but in primary GBM, there is no correlation between MGMT and mutant P53 protein expression(P>0.05).Kaplan-Meier analysis revealed that primary GBM and high expression of MGMT were significantly related to short survival(Log-rank test，P<0.05,P<0.01, respectively).Cox multivariate analysis revealed that subtype of GBM and MGMT expression were prognosticators for GBM(P<0.05, P<0.01, respectively). The survival period of GBM patients was not associated with age,gender,tumour size or mutant P53 protein expression. CONCLUSION: P53 gene mutations was frequent in tumorigenesis of secondary GBM,and the strong mutant P53 protein expression might be related to the weak MGMT expression. But in primary GBM, there is no correlation between MGMT and mutant P53 protein expression.It implicates different genetic pathways of developing in primary and secondary GBM. The subtype of GBM and MGMT expression were prognosticators for GBM.

Key words: Glioblastoma, p53 gene, MGMT