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There are significant differences in the expression patterns of the tumour suppressor gene p53, the cellular oncogene mdm2, epidermal growth factor receptor (EGFR) and the msh2 protein (part of the DNA mismatch repair system) in initial, as opposed to recurrent, glioblastoma multiforme. In particular, msh2 expressions may be affected by chemotherapy.
Twenty six adult patients were followed up whose tumour had been totally resected, 7 of whom were operated on for recurrence. Twenty three died at a mean of 532 days from diagnosis, while the mean progression free interval survival time was 204 days.
Recurrent lesions were characterised by reduced expression of p53 and msh2 while the numbers of mdm2, EGFR and msh2 positive specimens were reduced. The investigators suggest three possible reasons for reduced immunostaining: the antibody used in the study might not detect differentially expressed proteins; the expression level might actually decrease; or recurrent glioblastoma multiforme might represent a tumour stage of generally reduced protein expression caused by further dedifferrentiation.
Immunohistochemical findings showed no association with survival. However, chemotherapy (mainly cisplatin/tamoxifen) was associated with reduced msh2 expression.