8-hydroxyguanine and Central-Nervous-System-Neoplasms

The major mechanism of resistance to alkylnitrosourea therapy involves the DNA repair protein O(6)-alkylguanine-DNA alkyltransferase (AGT), which removes chloroethylation or methylation damage from the O(6) position of guanine. O(6)-benzylguanine (O(6)-BG) is an AGT substrate that inhibits AGT by suicide inactivation. We conducted a phase I trial of carmustine (BCNU) plus O(6)-BG to define the toxicity and maximum-tolerated dose (MTD) of BCNU in conjunction with the preadministration of O(6)-BG with recurrent or progressive malignant glioma.. Patients were treated with O(6)-BG at a dose of 100 mg/m(2) followed 1 hour later by BCNU. Cohorts of three to six patients were treated with escalating doses of BCNU, and patients were observed for at least 6 weeks before being considered assessable for toxicity. Plasma samples were collected and analyzed for O(6)-BG, 8-oxo-O(6)-BG, and 8-oxoguanine concentration.. Twenty-three patients were treated (22 with glioblastoma multiforme and one with anaplastic astrocytoma). Four dose levels of BCNU (13.5, 27, 40, and 55 mg/m(2)) were evaluated, with the highest dose level being complicated by grade 3 or 4 thrombocytopenia and neutropenia. O(6)-BG rapidly disappeared from plasma (elimination half-life = 0. 54 +/- 0.14 hours) and was converted to a longer-lived metabolite, 8-oxo-O(6)-BG (elimination half-life = 5.6 +/- 2.7 hours) and further to 8-oxoguanine. There was no detectable O(6)-BG 5 hours after the start of the O(6)-BG infusion; however, 8-oxo-O(6)-BG and 8-oxoguanine concentrations were detected 25 hours after O(6)-BG infusion. The mean area under the concentration-time curve (AUC) of 8-oxo-O(6)-BG was 17.5 times greater than the mean AUC for O(6)-BG.. These results indicate that the MTD of BCNU when given in combination with O(6)-BG at a dose of 100 mg/m(2) is 40 mg/m(2) administered at 6-week intervals. This study provides the foundation for a phase II trial of O(6)-BG plus BCNU in nitrosourea-resistant malignant glioma.

Topics: Adult; Antineoplastic Combined Chemotherapy Protocols; Astrocytoma; Carmustine; Central Nervous System Neoplasms; Drug Administration Schedule; Glioblastoma; Guanine; Humans; Middle Aged; Neoplasm Recurrence, Local

Primary central nervous system lymphoma (PCNSL) in immunocompetent patients is highly malignant and has a poor prognosis. The PCNSL molecular features are reminiscent to some degree of diffuse large B-cell lymphoma (DLBCL), yet PCNSL shows unique molecular profiles and a distinct clinical behavior. This article characterizes the histopathology and expression profiles of metallothionein-I + II (MT-I + II) and their receptor megalin along with proliferation, oxidative stress, and apoptosis in PCNSL and in central nervous system (CNS) lymphomas due to relapse from DLBCL (collectively referred to as CNS lymphoma). We show for the first time that MT-I + II and megalin are significantly altered in CNS lymphoma relative to controls (reactive lymph nodes and non-lymphoma brain tissue with neuropathology). MT-I + II are secreted in the CNS and are found mainly in the lymphomatous cells, while their receptor megalin is increased in cerebral cells. This morphology likely reflects the CNS lymphoma microenvironment and molecular interactions between lymphomatous and neuronal cells.

Topics: Aged; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Brain; Cell Cycle Proteins; Cell Proliferation; Central Nervous System Neoplasms; DNA-Binding Proteins; Guanine; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Low Density Lipoprotein Receptor-Related Protein-2; Lymph Nodes; Lymphoma, Large B-Cell, Diffuse; Malondialdehyde; Metallothionein; Middle Aged; Minichromosome Maintenance Complex Component 7; Nuclear Proteins; Oxidative Stress; Tyrosine