Discovering Nrf2 inhibitors to enhance cancer chemotherapy and radiotherapy

描述（由申请方提供）：核因子红细胞-2相关因子2（Nrf 2）是一种氧化还原敏感性转录因子，可调节亲电体和异源生物质解毒酶和外排蛋白的表达，从而在正常细胞中提供抗氧化应激和细胞凋亡的细胞保护。我们和其他人已经报道了Nrf 2抑制剂，Kelch样ECH相关蛋白（Keap 1）的功能突变缺失导致非小细胞肺癌，乳腺癌，胆囊癌和最近的前列腺癌中Nrf 2功能的组成性激活。我们最近发现，肺癌和前列腺癌细胞中Nrf 2的组成性激活促进致瘤性，并通过上调谷胱甘肽、硫氧还蛋白以及参与亲电体和广谱药物解毒的药物外排途径而导致化疗耐药性。RNAi介导的Nrf 2表达减少抑制肺癌和前列腺癌细胞的生长，并导致体外和体内对化疗药物诱导的细胞死亡的敏感性增加。使用裸siRNA双链体与卡铂组合抑制Nrf 2表达显著抑制肺癌皮下模型中的肿瘤生长。因此，我们推测，Nrf 2-Keap 1通路的失调是一种新的决定因素的化学抗性/放射抗性和抑制Nrf 2信号将提高化疗和放疗的疗效。然而，siRNA的有效递送和持续作用仍然是限制其用于治疗实体瘤的主要挑战，Nrf 2的小分子抑制剂将克服这一障碍并证明在这种情况下非常有益。具体目标：开发Nrf 2的小分子抑制剂，以避免治疗耐药性并提高化疗和放疗的疗效。Sigma LOPAC文库的初步筛选用我们优化的基于细胞的筛选测定鉴定了几种推定的Nrf 2抑制剂，但它们在抑制Nrf 2依赖性信号传导方面不是非常有效。我们建议筛选MLSMR储存库的小分子，其中包含超过300，000合成和天然化合物。筛选和鉴定有效的Nrf 2小分子抑制剂将为调节肿瘤患者的Nrf 2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型药物的潜力，这些药物可用作辅助药物，以提高化疗和放疗的疗效。该项目的成功完成将为癌症治疗开发新的治疗策略。

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.