RESUMO
BACKGROUND: O6-methylguanine DNA-methyl transferase (MGMT) promoter methylation status is predictive for alkylating chemotherapy, but there are non-benefiting subgroups. METHODS: This is the long-term update of NOA-08 (NCT01502241), which compared efficacy and safety of radiotherapy (RT, n = 176) and temozolomide (TMZ, n = 193) at 7/14 days in patients >65 years old with anaplastic astrocytoma or glioblastoma. DNA methylation patterns and copy number variations were assessed in the biomarker cohort of 104 patients and in an independent cohort of 188 patients treated with RT+TMZ-containing regimens in Heidelberg. RESULTS: In the full NOA-08 cohort, median overall survival (OS) was 8.2 [7.0-10.0] months for TMZ treatment versus 9.4 [8.1-10.4] months for RT; hazard ratio (HR) = 0.93 (95% CI: 0.76-1.15) of TMZ versus RT. Median event-free survival (EFS) [3.4 (3.2-4.1) months vs 4.6 (4.2-5.0) months] did not differ, with HR = 1.02 (0.83-1.25). Patients with MGMT methylated tumors had markedly longer OS and EFS when treated with TMZ (18.4 [13.9-24.4] mo and 8.5 [6.9-13.3] mo) versus RT (9.6 [6.4-13.7] mo and 4.8 [4.3-6.2] mo, HR 0.44 [0.27-0.70], P < 0.001 for OS and 0.46 [0.29-0.73], P = 0.001 for EFS). Patients with glioblastomas of the methylation classes receptor tyrosine kinase I (RTK I) and mesenchymal subgroups lacked a prognostic impact of MGMT in both cohorts. CONCLUSION: MGMT promoter methylation is a strong predictive biomarker for the choice between RT and TMZ. It indicates favorable long-term outcome with initial TMZ monotherapy in patients with MGMT promoter-methylated tumors primarily in the RTK II subgroup.
Assuntos
Astrocitoma , Neoplasias Encefálicas , Metilação de DNA , Metilases de Modificação do DNA , Enzimas Reparadoras do DNA , Temozolomida , Proteínas Supressoras de Tumor , Idoso , Antineoplásicos Alquilantes/uso terapêutico , Astrocitoma/tratamento farmacológico , Astrocitoma/enzimologia , Astrocitoma/genética , Neoplasias Encefálicas/tratamento farmacológico , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/radioterapia , Variações do Número de Cópias de DNA , Metilases de Modificação do DNA/genética , Metilases de Modificação do DNA/metabolismo , Enzimas Reparadoras do DNA/genética , Enzimas Reparadoras do DNA/metabolismo , Glioblastoma/tratamento farmacológico , Glioblastoma/genética , Humanos , Regiões Promotoras Genéticas , Proteínas Proto-Oncogênicas c-ret/genética , Proteínas Proto-Oncogênicas c-ret/metabolismo , Temozolomida/uso terapêutico , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/metabolismo , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismoRESUMO
Measuring concentrations of the differentiation-promoting hormone retinoic acid (RA) in glioblastoma tissues would help to understand the reason why RA treatment has been inefficient in clinical trials involving brain tumor patients. Here, we apply a recently established extraction and measurement protocol to screen glioblastoma tissues for the levels of the RA precursor retinol and biologically active RA. Combining this approach with mRNA analyses of 26 tumors and 8 normal brains, we identify a multifaceted disturbance of RA synthesis in glioblastoma, involving multiple aldehyde dehydrogenase 1 family and retinol dehydrogenase enzymes. Through database studies and methylation analyses, we narrow down chromosomal deletions and aberrant promoter hypermethylation as potential mechanisms accounting for these alterations. Employing chromatin immunoprecipitation analyses and cell-culture studies, we further show that chromatin at RA target genes is poised to RA substitution, but most glioblastoma cell cultures are completely resistant to RA treatment. This paradoxical RA response is unrelated to alternative RA signaling through the fatty acid-binding protein 5/peroxisome proliferator-activated receptor delta axis. Our data suggest a multifaceted disturbance of RA synthesis in glioblastoma and contribute to reconsider current RA treatment strategies.
