Akira Nakagawara

Enhancer of Zeste Homolog 2 (EZH2) is highly expressed in various cancers and is thought to contribute to cancer malignancy through the methylation of lysine 27 on histone H3 (H3K27). Therefore, EZH2 is an H3K27 methylase and a target of cancer epigenetic treatments. Here, we investigated the effects and functions of a small-molecule EZH2 inhibitor (EZH2i) in aggressive neuroblastoma (NB). To identify genes associated with the sensitivity to EZH2i, we classified NB cell lines into sensitive and resistant groups. EZH2i suppressed proliferation and induced cell cycle arrest in EZH2-sensitive NB cells. Transcriptome analysis revealed the de-repression of gene sets related to differentiation and cell cycle arrest. To investigate whether the gene repression in resistant cells is mediated by mechanisms other than H3K27 methylation, methylome analysis was conducted to evaluate the significance of DNA methylation. The effect of combined treatment with an EZH2 inhibitor and a DNA methylation inhibitor (DNMTi) on the growth of resistant NB cells was subsequently assessed both in vitro and in vivo, even in cells resistant to EZH2 inhibition. Genes such as TRIM63, VSTM2L, GPNMB, and TIMP3, which are de-repressed by EZH2is in sensitive cells. Furthermore, the promoters of some of these genes are hypermethylated in EZH2i-resistant cells and NB tissues. Additionally, the combined treatment with EZH2i and 5-aza-dC significantly inhibited cell proliferation with MYCN destabilization at protein level, c-MYC suppression at RNA and protein level and induced a robust differentiation phenotype. Our study identified gene expression profiles that can distinguish the responsiveness to EZH2i in neuroblastoma, and demonstrated that DNMTi not only de-repression in gene expression but also suppress neuroblastoma growth through inhibition of MYC. These results confirm the importance of epigenetic regulation in NB biology and provide information for developing epigenetic therapies for patients with advanced NB.

It is critical to share knowledge and harmonize approaches to optimize progress in rare cancers. The International Neuroblastoma Risk Group (INRG) Task Force was formed by the 4 major neuroblastoma cooperative groups in 2004 to achieve this goal. Strategies developed for neuroblastoma are an exemplar for other rare malignancies. Data from an initial cohort of 8800 patients were transferred to the INRG Data Commons, and a data-sharing model was developed. Currently, information on more than 25 000 patients is available to the research community. The INRG staging and risk classification systems have led to harmonized approaches for therapeutic groupings. INRG consensus manuscripts have led to uniform criteria for classifying biological data, evaluating the extent of disease, and defining treatment response. More than 40 INRG research studies have been performed by investigators from around the world, including analyses of rare patients, which would not otherwise be possible. The success of this approach for neuroblastoma has been leveraged to create the Pediatric Cancer Data Commons and the Data for the Common Good. Efforts to enrich the INRG Commons with additional genomic and biomarker data, extracted electronic health records, and digital medical images are ongoing. The international networking model developed by the INRG Task Force has led to new research discoveries and progress in neuroblastoma. The approach has now been applied to 16 other cancers and conditions, including rhabdomyosarcoma, germ cell tumor, Lynch syndrome, and cancer predisposition. This framework of international collaboration and data sharing serves as a model for advancing rare adult malignancies.

In Asia, a few countries have a long and established history of collaborative clinical trials successfully formed national children's cancer study groups, but many still do not have such groups. The process of forming national children's cancer groups is fraught with many hurdles, which varies among the countries. One of the basic requirements for running clinical trials is an affordable health care system in which most of the children with cancer can receive the proposed treatment. The health insurance coverage for children with cancer varies from <20% to as high as 100% among Asian countries, and the operation of clinical trials must also be adjusted accordingly. Shortage of research personnel is common, including medical, nursing, research coordinators, and data managers. The establishment of the Asian Pediatric Hematology and Oncology Group aims to provide a good platform for promotion of international clinical trials in the Asian countries.