metallothionein and Ependymoma

Children with ependymoma may experience a relapse in up to 50% of cases depending on the extent of resection. Key biological events associated with recurrence are unknown.. To discover the biology behind the recurrence of ependymomas, we performed CGHarray and a dual-color gene expression microarray analysis of 17 tumors at diagnosis co-hybridized with the corresponding 27 first or subsequent relapses from the same patient. As treatment and location had only limited influence on specific gene expression changes at relapse, we established a common signature for relapse. Eighty-seven genes showed an absolute fold change ≥2 in at least 50% of relapses and were defined as the gene expression signature of ependymoma recurrence. The most frequently upregulated genes are involved in the kinetochore (ASPM, KIF11) or in neural development (CD133, Wnt and Notch pathways). Metallothionein (MT) genes were downregulated in up to 80% of the recurrences. Quantitative PCR for ASPM, KIF11 and MT3 plus immunohistochemistry for ASPM and MT3 confirmed the microarray results. Immunohistochemistry on an independent series of 24 tumor pairs at diagnosis and at relapse confirmed the decrease of MT3 expression at recurrence in 17/24 tumor pairs (p = 0.002). Conversely, ASPM expression was more frequently positive at relapse (87.5% vs 37.5%, p = 0.03). Loss or deletion of the MT genes cluster was never observed at relapse. Promoter sequencing after bisulfite treatment of DNA from primary tumors and recurrences as well as treatment of short-term ependymoma cells cultures with a demethylating agent showed that methylation was not involved in MT3 downregulation. However, in vitro treatment with a histone deacetylase inhibitor or zinc restored MT3 expression.. The most frequent molecular events associated with ependymoma recurrence were over-expression of kinetochore proteins and down-regulation of metallothioneins. Metallothionein-3 expression is epigenetically controlled and can be restored in vitro by histone deacetylase inhibitors.

Topics: Biomarkers, Tumor; Child; Child, Preschool; Disease Progression; Ependymoma; Female; Follow-Up Studies; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Humans; Infant; Male; Metallothionein; Oligonucleotide Array Sequence Analysis; Recurrence

Intracranial ependymomas are the third most common primary brain tumor in children. A variety of chemotherapy protocols have been introduced for the treatment of ependymoma although overall these have not contributed to patients outcome. To our knowledge, data on the prognostic value of immunoexpression of the chemoresistance-related proteins (ChRPs) in ependymomas are absent. Seventy-six patients with intracranial ependymomas who received combined treatment were studied retrospectively. Tumor specimens were immunohistochemically examined with antibodies to metallothioneins (MT), glutathione S-transferase pi (GST pi) and P-glycoprotein (P-GP). The results demonstrated significant preponderance of expression of all the above-mentioned ChRPs for the low-grade tumors. The progression-free survival time was found to be significantly shorter for immunonegative tumors in both tumor grades. Multivariate analysis using a Cox hazard model revealed that recurrence-free survival time is significantly associated with tumor grade, and MT and P-GP expression. Risk of recurrence increased for the high-grade ependymomas (hazard ratio 2.85; P = 0.004), and decreased for the MT-positive tumors (hazard ratio -2.72; P = 0.005) and for the P-GP-positive tumors (hazard ratio -2.02; P = 0.02). The obtained results allow one to conclude that ChRPs expression is closely associated with low-grade ependymomas and immunohistochemical findings may be estimated as a predictor for local tumor progression.

Topics: Adolescent; Adult; ATP Binding Cassette Transporter, Subfamily B, Member 1; Brain Neoplasms; Child; Drug Resistance, Neoplasm; Ependyma; Ependymoma; Female; Follow-Up Studies; Glutathione Transferase; Humans; Male; Metallothionein; Neoplasm Recurrence, Local; Predictive Value of Tests; Prognosis; Proportional Hazards Models; Survival Analysis; Treatment Outcome