Discovering Nrf2 inhibitors to enhance cancer chemotherapy and radiotherapy

描述(申请人提供)：核因子红系相关因子2(NRF2)是一种氧化还原敏感的转录因子，调节电泳性和外源解毒酶以及外排蛋白的表达，从而在正常细胞中提供细胞保护，防止氧化应激和细胞凋亡。我们和其他人已经报道了Nrf2抑制因子Kelch样ECH相关蛋白(Keap1)功能突变的丧失，导致非小细胞肺癌、乳腺癌、胆囊癌以及最近的前列腺癌中Nrf2功能的结构性激活。我们最近发现，肺癌和前列腺癌细胞中Nrf2的结构性激活促进了肿瘤的发生，并通过上调谷胱甘肽、硫氧还蛋白以及参与亲电体解毒和广谱药物的药物外排途径，促进了化疗耐药性的产生。RNAi介导的Nrf2表达下调抑制了肺癌和前列腺癌细胞的生长，并在体内外增加了对化疗药物诱导的细胞死亡的敏感性。在肺癌皮下模型中，使用裸露的siRNA双链结合卡铂抑制Nrf2的表达可显著抑制肿瘤生长。因此，我们假设Nrf2-Keap1通路的失调是化疗耐药/放射耐药的新的决定因素，抑制Nrf2信号将增强化疗和放射治疗的疗效。然而，siRNA的有效传递和持续作用仍然是限制其在实体瘤治疗中使用的主要挑战，Nrf2的小分子抑制剂将克服这一障碍，并被证明在这种情况下非常有益。目的：开发小分子Nrf2抑制剂，以克服化疗耐药，提高化疗和放疗的疗效。通过对Sigma Lopac文库的初步筛选，我们基于优化筛选细胞的方法确定了几个可能的Nrf2抑制剂，但它们在抑制Nrf2依赖的信号转导方面并不是非常有效。我们建议筛选MLSMR小分子信息库，其中包含30多万种合成和天然化合物。筛选和鉴定有效的Nrf2小分子抑制剂将为调节肿瘤患者的Nrf2活性和提高癌症治疗的疗效提供新的机会。 公共卫生相关性：本项目中提出的研究具有开发新药的潜力，这些新药可以用作辅助来提高化疗和放射治疗的疗效。该项目的成功完成将为癌症治疗开发一种新的治疗策略。

DESCRIPTION (provided by applicant): Nuclear factor erythroid-2-related factor 2 (Nrf2) is a redox-sensitive transcription factor that regulates the expression of electrophile and xenobiotic detoxification enzymes and efflux proteins, which confer cytoprotection against oxidative stress and apoptosis in normal cells. We and others have reported that loss of function mutations in the Nrf2 inhibitor, Kelch-like ECH-associated protein (Keap1), results in constitutive activation of Nrf2 function in non-small cell lung cancer, breast cancer, gall bladder cancer and more recently in prostate cancer. We recently showed that constitutive activation of Nrf2 in lung cancer and prostate cancer cells promotes tumorigenicity and contributes to chemoresistance by up-regulation of glutathione, thioredoxin, and the drug efflux pathways involved in detoxification of electrophiles and broad spectrum of drugs. RNAi-mediated reduction of Nrf2 expression suppressed growth of lung cancer and prostate cancer cells, and resulted in increased sensitivity to chemotherapeutic drug-induced cell death in vitro and in vivo. Inhibiting Nrf2 expression using naked siRNA duplexes in combination with carboplatin significantly inhibits tumor growth in a subcutaneous model of lung cancer. Thus we hypothesize that dysregulated Nrf2-Keap1 pathway is a novel determinant of chemoresistance/radioresistance and inhibition of Nrf2 signaling will enhance the efficacy of chemotherapeutic and radiotherapy. However, efficient delivery and sustained action of siRNA still remains a major challenge limiting its use in treatment of solid tumors and small molecule inhibitors of Nrf2 will overcome this hurdle and prove very beneficial in this scenario. Specific Aim: To develop small molecule inhibitors of Nrf2 for circumventing therapeutic resistance and enhancing the efficacy of chemotherapy and radiotherapy. A pilot screening of Sigma LOPAC library identified few putative inhibitors of Nrf2 with our optimized screening cell based assay but they were not very effective in inhibiting Nrf2 dependent signaling. We propose to screen MLSMR repository of small molecules, which contains more than 300,000 synthetic and natural compounds. Screening and identification of potent small molecule inhibitors of Nrf2 will provide novel opportunities to modulate Nrf2 activity in patients with tumors and increase the efficacy of cancer therapy. PUBLIC HEALTH RELEVANCE: The studies proposed in this project have potential for developing novel drugs which can be used as adjuvant to enhance the efficacy of chemotherapy and radiotherapy. Successful completion of this project will develop a new therapeutic strategy for cancer treatment.