Abstract
Medulloblastoma (MB) is the most common type of childhood brain cancer worldwide. Although current treatment with surgery and extensive chemoradiation has led to increased survival rates, many MB patients still die from the disease. Moreover, surviving patients suffer severe long-term side effects as a consequence of treatment. It is therefore crucial to develop more effective and less toxic therapies. The most aggressive subtype of MB tumors often exhibits amplification or overexpression of the MYC oncogene. Patients with MYC-amplified MB exhibit a high frequency of cerebrospinal tumor dissemination, often experience treatment resistance and have extremely poor prognoses. While the MYC oncogene is established as the oncogenic driver in Group 3 MB, it has remained undruggable. Thus, targeting regulatory components of MYC and the signaling pathways regulated by it is of great potential therapeutic value. Studies have revealed that MB has very few germline mutations in cancer predisposition genes, suggesting that dysregulated epigenetic pathways might be critical in MB pathogenesis. Particularly, dysregulation of epigenetic modifiers, including histone methyltransferases and histone demethylases, is very common in Group 3 MB, compared to other MB subgroups. Therefore, it is important to identify such epigenetic modifiers that may have controls on MYC and its tumorigenic activities and explore these as the epigenetic drug-candidate targets in Group 3 (MYC-driven) MB. In this regard, we found that protein arginine demethylase Jumonji C domain-containing protein 6 (JMJD6), an emerging key epigenetic enzyme in cancers, is a novel regulator of MYC expression in MYC-driven MB. We observed high levels of JMJD6 that not only mirror MYC expression in the most aggressive MB but also correlate with poor outcomes in these patients. Knockdown of JMJD6 decreased MYC expression, cellular proliferation/survival and stemness in MYC-amplified MB cells. Mechanistically, our results revealed that JMJD6 forms complexes with proteins involved in maintaining and regulating the promoter-pause at super-enhancers, suggesting that JMJD6 can regulate MYC at the transcription level. Moreover, our in vivo analyses of JMJD6 inhibition, either with inducible gene knockdown or a pharmacologic small molecule inhibitor, demonstrated anti-MB potential with suppressed MYC expression. Based on this background and preliminary observations, we hypothesize that JMJD6 plays crucial roles in the most aggressive MB by regulating MYC expression and hence MYC-driven tumorigenesis. Accordingly, we hypothesize that targeting the JMJD6-MYC axis by JMJD6 inhibition can serve as a powerful therapeutic strategy for MYC-driven MB. Citation Format: Matthew Kling, Devendra Kumar, Sutapa Ray, Shantaram Joshi, Don Coulter, Nagendra K. Chaturvedi. JMJD6 as a novel tumorigenic factor and therapeutic target in group 3 (MYC-driven) medulloblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3346.