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Loss of MSH6 occurred during the progression from an atypical prolactinoma to a pituitary carcinoma, which may have caused resistance to TMZ treatment. This case suggests that preserving MSH6 function is essential for responsiveness to TMZ treatment in MGMT-negative and p53-mutated atypical pituitary adenoma or pituitary carcinoma.

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C o r r e l a t i o n B e t w e e n M I B -1 S t a i n i n g I n d e x a n d t h e I m m u n o r e a c t i v i t y o f p 5 3 P r o t e i n i nR e c u r r e n t a n d N o n -r e c u r r e n t M e n i n g i o m a s Wild type p53 protein has been shown by recent investigations to be involved in the negative regulation of cell proliferation, whereas aberrant p53 protein has lost this negative regulation of cell growth. Wild type pS3 protein, which has a very short half-life, has generally been considered to be undetectable using immunohistochemical methods; however, according to a recent report, wild type p53 protein may accumulate in the nuclei because of a defective ubiquitin pathway. Aberrant pS3 protein has a longer half-life, and thus is visible using immunohistochemical methods. In this study, both the proliferative potential represented by the MIB-1 staining index (SI) and the immunoreactivity of pS3 protein in 51 intracranial meningiomas were studied applying immunohistochemical staining methods to archival paraffin sections.Recurrence of meningiomas is considered to be affected by a variety of clinical, biologic, and histopathologic factors, including the patient's age, sex, tumor location, extent of surgical removal, histopathologic findings, estrogen and progesterone receptors, and receptors for other growth factors. Among these factors, the proliferative potential of meningioma is considered by several investigators to be one of the most important. 1 "" In a previous report, we used an anti-Ki-67 monoclonal antibody, MIB-1, that can detect all proliferative cells in routinely processed paraffin sections, 3,612 and have shown that there is a statistically significant correlation between the MIB-1 staining index (SI) and recurrence of meningi-