Histone Methyltransferases as a Target for Lung Cancer Prevention

描述（由申请人提供）：肺癌新靶向和化疗的进展，虽然实现了晚期肺癌中位生存期的适度改善，但没有提供明确的药物途径，使其成为目前转移性乳腺癌所见的慢性疾病。虽然戒烟可以降低死亡率，但50%的肺癌病例是在前吸烟者中诊断出来的，因此需要有效的预防药物。开发肺癌预防药物也具有挑战性，因为这种疾病在遗传和表观遗传改变方面具有异质性，并且缺乏替代组织来非侵入性地询问治疗功效的中间生物标志物。二十多年来，我们的团队一直专注于了解肺癌病因，开发和验证早期检测的生物标志物，并评估动物模型中治疗和预防干预措施的有效性。令人兴奋的认识是，损伤的领域从肺延伸到鼻上皮的基因表达变化提供了新的机会，评估新的一级预防策略的有效性，通过评估生物标志物预测的反应在鼻上皮。我们的烟草致癌物诱导的人支气管上皮细胞（HBEC）转化的体外模型为促进癌前病变的最早步骤和靶点提供了关键的新见解。它们包括最显著的调节上皮向间充质转化的microRNA的转录抑制和首先由EZH 2和/或G9 a催化的染色质重塑介导的肿瘤抑制基因的沉默，随后在恶性进展期间密集的从头DNA甲基化。由染色质重塑和胞嘧啶甲基化介导的表观遗传沉默影响数百个基因，这些基因可能驱动癌前上皮细胞的启动和克隆生长，导致恶性肿瘤。这些发现和染色质重塑可以用非基因毒性剂逆转的事实（不像胞嘧啶-DNA甲基化，其需要用基因毒性胞苷类似物治疗以实现稳健的去甲基化）提供了令人兴奋的新机会来测试预防性干预，所述预防性干预集中于诱导这些表观遗传学调节的基因的再表达，所述表观遗传学调节的基因反过来应该阻止或逆转癌前病变。本申请中的三个综合具体目标将通过首先使用HBEC模型来定义调节这些癌症相关组蛋白甲基转移酶的表达对其基因靶点和转化过程的影响来推进这些发现。其次，我们将评估饮食、药理学和/或EZH 2和G9 a的特异性小分子抑制剂是否可以减轻这些基因靶点的转录抑制和体外转化，并预防体内肿瘤发展。最后，这项工作将通过一项预防研究进行转化，该研究的重点是评估前吸烟者补充omega脂肪酸是否可以调节鼻上皮中EZH 2调节基因的表达谱，这些基因在HBEC转化过程中发生改变。

DESCRIPTION (provided by applicant): The evolution of new targeted and chemotherapies for lung cancer, while achieving modest improvement in median survival for advanced lung cancer, offer no clear path to drugs that could make this a chronic disease as seen today for metastatic breast cancer. While smoking cessation reduces mortality, 50% of lung cancer cases are diagnosed in former smokers, necessitating the need for effective preventive agents. Developing lung cancer preventive drugs has also been challenging because of the heterogeneity of this disease with respect to genetic and epigenetic alterations and the lack of a surrogate tissue to noninvasively interrogate intermediate biomarkers of response for therapeutic efficacy. Our group has focused for more than two decades on understanding lung cancer etiology, developing and validating biomarkers for early detection, and assessing efficacy of interventions for therapy and prevention in animal models. The exciting realization that the field of injury extends from the lungs to the nasal epithelium for gene expression changes provides new opportunities to evaluate the effectiveness of novel primary prevention strategies by assessing biomarkers predictive of response in the nasal epithelium. Our tobacco carcinogen-induced in vitro model for transformation of human bronchial epithelial cells (HBECs) has provided key new insights into the earliest steps and targets contributing to pre-malignancy. They include most notably transcriptional repression of microRNAs regulating epithelial to mesenchymal transition and silencing of tumor suppressor genes mediated first by chromatin remodeling catalyzed by either EZH2 and/or G9a, with subsequent dense de novo DNA methylation during progression to malignancy. Epigenetic silencing mediated by chromatin remodeling and cytosine methylation affects hundreds of genes that likely drive initiation and clonal outgrowth of premalignant epithelial cells leading to malignancy. These discoveries and fact that chromatin remodeling can be reversed with non-genotoxic agents (unlike cytosine-DNA methylation which requires treatment with genotoxic cytidine analogs for robust demethylation) offer exciting new opportunities to test preventive interventions focused on inducing the re-expression of these epigenetically regulated genes that in turn, should impede or reverse pre- malignancy. The three integrated specific aims in this application will advance these discoveries by first using the HBEC model to define the effect of modulating the expression of these cancer-associated histone methyltransferases on their gene targets and the transformation process. Second, we will assess whether diet, pharmacologic, and/or specific small molecule inhibitors to EZH2 and G9a can mitigate the transcriptional repression at these gene targets and transformation in vitro and prevent tumor development in vivo. Finally, this work will be translated through a prevention study focused on evaluating whether omega fatty acid supplementation in former smokers can modulate the expression profile in nasal epithelium of EZH2 regulated genes that are altered during transformation of HBECs.