Targeting histone demethylase activity for the treatment of pediatric brainstem glioma

 描述（由申请人提供）：儿童脑干胶质瘤是最具破坏性的儿童癌症之一。由于这些肿瘤发生在脑干，没有手术选择为患者提供缓解，化疗和放射治疗最多提供姑息性缓解。与大多数类型的人类癌症相比， 改善脑干胶质瘤患者的治疗结果。直到最近，脑干胶质瘤治疗缺乏改进，部分原因是用于分析肿瘤分子特征的脑干肿瘤组织采集不频繁：脑干胶质瘤发生的潜在遗传基础在很大程度上仍然未知，直到2012年。幸运的是，两个研究小组通过获得足够数量的脑干肿瘤来进行有意义的突变分析，从而解决了这一信息不足的问题。外显子组测序鉴定了H3F3A基因的复发性突变，导致编码的组蛋白H3.3蛋白中的赖氨酸27被甲硫氨酸（K27 M）取代，在多达60%的这些肿瘤中。迄今为止，这种突变仍然是脑干肿瘤的独特和特异性。K27 M突变导致细胞染色质中组蛋白H3 K27甲基化的显著降低，我们最近表明，抑制组蛋白H3 K27去甲基化酶JMJD3可以恢复脑干神经胶质瘤细胞中的K27甲基化，同时在细胞凋亡和细胞凋亡中显示出有效的抗肿瘤活性。 在脑干胶质瘤的异种移植模型中。这些结果以及其他人发表的结果支持JMJD 3在至少某些类型的癌症中具有促肿瘤活性。然而，脑干肿瘤中的K27甲基化状态很可能受到除了JMJD3之外的活性的影响：有几种酶调节K27甲基化，并且这些活性是否与JMJD3协同作用以促进脑干肿瘤发展，或者相反，对抗肿瘤发展，在很大程度上是未知的。本申请将研究不同的H3 K27甲基转移酶和脱甲基酶活性如何影响脑干肿瘤生长，并确定JMJD3在肿瘤维持中的作用是否依赖于调节K27甲基化的其他蛋白质。此外，该项目还将确定脑干肿瘤如何适应延长的JMJD3抑制，这对于确定用于治疗可能对JMJD3抑制产生耐药性的脑干肿瘤或可能与JMJD3抑制剂联合使用的第二种治疗方法非常重要。最后，该提案将检查当与辐射组合使用时JMJD3抑制的效果，因为受JMJD3抑制影响的细胞特性之一是DNA修复。因此，JMJD3抑制可增强辐射的细胞毒性作用。

 DESCRIPTION (provided by applicant): Pediatric brainstem glioma is among the most devastating childhood cancers. Since these tumors occur in the brainstem, there are no surgical options for providing relief to patients, and chemotherapy as well as radiation therapy provide palliative relief at best. In contrast to most types of human cancer, there has been no significant improvement in treatment outcomes for brainstem glioma patients. Until recently, the lack of improvement for treating brainstem glioma was attributable, in part, to infrequent brainstem tumor tissue acquisition for analyzing tumor molecular characteristics: the underlying genetic basis for brainstem glioma occurrence remained largely unknown, until as recently as 2012. Fortunately, two groups were able to address this information deficiency by acquiring sufficient numbers of brainstem tumors to conduct meaningful mutation analysis. Exome sequencing identified recurrent mutation of the H3F3A gene, resulting in replacement of lysine 27 by methionine (K27M) in the encoded histone H3.3 protein, in as many as 60% of these tumors. To date, this mutation remains unique and specific to brainstem tumors. The K27M mutation causes substantial reduction in histone H3 K27 methylation in cellular chromatin, and we have recently shown that inhibition of the histone H3 K27 demethylase JMJD3 acts to restore K27 methylation in brainstem glioma cells, while demonstrating potent anti-tumor activity, both in cell culture and in xenograft models of brainstem glioma. These results, as well as results published by others, support JMJD3 as having pro-tumorigenic activity in at least some types of cancer. However, it is likely that K27 methylation status in brainstem tumors is influenced by activities i addition to JMJD3: there are several enzymes that regulate K27 methylation, and whether these activities act in concert with JMJD3, to promote brainstem tumor development, or, alternatively, oppose tumor development, is largely unknown. This application will examine how different H3 K27 methyltransferase and demethylase activities influence brainstem tumor growth, and in so doing will determine whether JMJD3's role in tumor maintenance is dependent upon other proteins that regulate K27 methylation. This project will, in addition, determine how brainstem tumors adapt to extended JMJD3 inhibition, which is important for identifying secondary therapeutics to use in treating brainstem tumors that may acquire resistance to JMJD3 inhibition, or that could potentially be used in combination with JMJD3 inhibitors. Finally, this proposal will examine the effects of JMJD3 inhibition when used in combination with radiation, as one of the cellular properties affected by JMJD3 inhibition is DNA repair. JMJD3 inhibition, therefore, may enhance the cytotoxic effects of radiation.