Tanaka, R.; Umaru, B.; Sobo, M.; Senthil Kumar, S.; Dorris, K.; Hovestadt, V.; Ramaswamy, V.; Remke, M.; Margol, A.; Stevenson, C. B. B.; Asgharzadeh, S.; Goldman, S.; Miles, L.; Huang, J.; vonHoff, K.; Rutkowski, S.; Onar-Thomas, A.; Tabori, U.; Taylor, M.; Pfister, S. M.; Salloum, R.; Fouladi, M.; Drissi, R.

Background: Telomerase reactivation, a hallmark of many cancers, is associated with expression of its catalytic subunit, hTERT. However, the prognostic significance of telomere maintenance mechanisms in pediatric medulloblastoma remains poorly defined. Methods: In this multi-institutional retrospective study of telomerase expression and hTERT regulation in newly diagnosed children with medulloblastoma, hTERT and MYC expression were assessed by qRT-PCR, normalized to non-neoplastic brain control samples. hTERT promoter methylation was analyzed using quantitative pyrosequencing and Illumina 450k methylation array. Cox proportional-hazard regression analyses evaluated the association of hTERT expression with progression-free survival (PFS) or overall survival (OS). Spearman correlation and Kruskal-Wallis tests correlated hTERT promoter methylation and expression and assessed variations among medulloblastoma subgroups, respectively. Results: Among 74 patients with available hTERT expression and outcome data, higher expression was associated with worse OS (HR=1.22, 95% CI: 1.01-1.47, p=0.036) and PFS (HR=1.17, 95% CI: 1.00-1.37, p=0.051) after adjusting for subgroup. Similar results were obtained when adjusting for metastatic status. Group 3 patients had the highest hTERT expression (p=0.001). Pyrosequencing data were available for 61 patients and 450k methylation array data for 292 patients. hTERT promoter was differentially methylated across subgroups with WNT followed by group 3 demonstrating the highest methylation on 450k (p<0.0001), findings that were confirmed by pyrosequencing. hTERT promoter methylation positively correlated with hTERT expression (Spearman correlation=0.42, p=0.02 by 450k and 0.34, p=0.007 by pyrosequencing). No significant correlation was observed between hTERT and MYC expression. Conclusion: Elevated hTERT expression is associated with worse PFS and OS in medulloblastoma across subgroups, supporting telomerase inhibition as a potential therapeutic strategy.