Thep53tumor suppressor gene is frequently mutated in glioblastomas. Mutations within thep53gene often result in aberrant expression of the p53 protein leading to protein accumulation within the nucleus of the cells which can be detected by immunochemistry. Many studies have correlated alterations of p53 protein expression withp53gene mutations. Positive staining of tumor cells for p53 protein has been widely assumed, perhaps incorrectly, to signify the presence ofp53gene mutations. This study compared the immunostaining patterns for p53 protein in 37 glioblastomas with the molecular genetic data obtained by the single strand conformation polymorphism assay.p53gene mutations were detected in 46 (17 of 37) of glioblastomas, while 65 (24 of 37) of glioblastomas were positive for protein accumulation by immunohistochemistry. Although 30 of 37 glioblastomas analyzed showed concordance for p53 protein expression andp53gene mutations, a subset of seven glioblastomas showed discordant accumulation of the p53 protein in the absence of any detectablep53gene mutations. The mdm‐2 gene was assessed in 17 glioblastomas for gene rearrangements or amplification, but none were found. This result suggests that a mechanism other thanp53gene mutation can result in altered p53 protein expressio
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