The role of JMJD6 in MYC-mediated neuroblastoma

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Project Summary/Abstract Neuroblastoma is a solid tumor that arises from the aberrant growth of neural crest cells of the developing sympathetic nervous system. It is the most common type of cancer in infancy and causes as much as 15% of childhood cancer mortality. Although remarkable improvements in outcome have been achieved for children with low-risk disease, the survival rate of those with high-risk neuroblastoma remains less than 40% despite intensive multimodal therapies. Thus, identifying novel therapeutic targets for neuroblastoma is imperative. MYC oncogenes (C-MYC, MYCN, and MYCL1) are among the most common genetic abnormalities in human cancer, including neuroblastoma, in which MYCN amplification is the most important biological feature. Transgenic mouse and zebrafish models have demonstrated that MYCN drives neuroblastoma. In patients without MYCN amplification, we found that C-MYC was overexpressed, indicating that neuroblastoma is a MYC-driven cancer. However, directly targeting nonhormonal transcription factors such as C-MYC/MYCN is technically challenging. Recent genomic sequencing data have revealed that neuroblastoma has very low frequencies of somatic mutations, suggesting that deregulated epigenetics might be involved in the pathogenesis. Our recent study indicated that MYCN hijacks the histone lysine demethylase KDM4B to facilitate its function. Our subsequent studies showed that the expression of the histone arginine demethylase JMJD6 is correlated with MYCN status and associated with poor outcome, indicating that JMJD6 plays an important role in neuroblastoma. Previous studies by others have shown that JMJD6 physically interacts with BRD4, which regulates C-MYC/MYCN expression. However, whether JMJD6 is important for C-MYC/MYCN expression and/or function is unknown. Here we propose to characterize the function of JMJD6 in MYC-mediated neuroblastoma. We will determine the role of JMJD6 by using in vitro and in vivo models of the disease (Aim 1), thereby validating JMJD6 as a therapeutic target. We will also define JMJD6 functions in neuroblastoma by using RNA-seq, ChIP-seq, and pathway analysis to identify JMJD6 target genes, genomic binding, correlation with its histone substrate modification, and MYC genomic occupancy (Aim 2). The proposed work will explore a new therapeutic target for neuroblastoma and establish the rationale to develop small molecules to pharmaceutically target JMJD6 in cancer treatment. In addition, it will provide new insight about epigenetic modifiers in MYC- mediated pathogenesis. We anticipate that findings from this study will also benefit other types of cancers (e.g., melanoma, lung, and ovarian cancers) that bear JMJD6 amplification. !