Targeting ROS by a p53-activating agent for selective killing of cancer cells

描述(申请人提供)：摘要DNA损伤通过化疗药物诱导细胞死亡是癌症治疗中最广泛使用的策略。然而，选择性仍然是癌症化疗中一个非常令人担忧的问题，因为破坏DNA的药物既能杀死癌细胞，又能杀死周围的正常细胞，这是癌症化疗副作用的一个重要原因，并严重限制了目前的治疗方案。功能性P53缺乏症在人类肿瘤中很常见，并导致对化疗或放疗具有侵袭性的耐药表型，因此为癌症治疗提供了一个潜在的靶点。近年来恢复wt-P53活性的几次尝试已经导致了许多P53调节剂的鉴定。然而，在wt-p53或p53缺陷的肿瘤中，模仿p53激活转录反应的策略仍有待探索。我们进行了一项基于细胞的高通量筛选，以寻找在癌细胞中触发p53靶标转录的小分子。在几种提高P53蛋白含量的候选药物中，一种自然产生的新型P53调节剂，PPLGM(PPLGM)对这一应用最感兴趣，因为它以P53依赖和P53非依赖的方式选择性地杀死癌细胞，而正常细胞不受影响。该化合物有效地增加了P53蛋白及其促凋亡靶点的基础水平。此外，体内实验表明，该化合物在低浓度下具有很强的抗肿瘤活性，对正常器官和组织功能没有明显的不良影响。我们还发现，活性氧簇(ROS)的显著升高是该化合物潜在的癌细胞特异性作用机制。因此，靶向ROS可能是一种选择性杀伤癌细胞的策略，但不能通过额外的ROS产生来杀死未转化或正常细胞，因为癌细胞拥有比正常细胞高得多的ROS基础水平。这一应用的主要目的是了解PPLGM在体外和体内癌细胞中不寻常的选择性作用的潜在机制。对这种化合物在癌细胞和正常细胞中的作用机制的详细了解将为基于靶点的抗癌选择性治疗策略提供新的见解，也可能需要在临床前和临床环境中进行进一步的测试。 公共卫生相关性：在癌症化疗中，选择性仍然是一个非常令人担忧的问题，因为破坏DNA的药物既会杀死癌细胞，也会杀死周围的正常细胞，这是癌症化疗期间产生副作用的一个重要原因。这项应用的目标是了解一种新发现的P53激活剂不寻常的癌症特异性选择性作用的潜在机制。

DESCRIPTION (provided by applicant): Abstract DNA damage-induced cell death through chemo-drugs is the most widely used strategy in cancer therapy. However, selectivity remains a great concern in cancer chemotherapy because DNA damaging drugs kill both cancer cells and the surrounding normal cells, which is an important cause of side effects during cancer chemotherapy, and severely limits current treatment regimes. Functional p53 deficiency is common in human tumors and contributes to an aggressive chemo- or radiotherapy-resistant phenotype, therefore providing a potential target for cancer therapy. Several attempts in recent years to restore wt- p53 activity have led to the identification of numerous p53 modulators. However, strategies mimicking p53 activated transcriptional responses in wt-p53 or p53-deficient tumors have yet to be explored. We carried out a high-throughput cell-based screen for small molecules that trigger a p53 target transcription in cancer cells. Among several candidates that elevate the amounts of p53 proteins, a naturally occurring novel p53 modulator, piperlongumine (PPLGM) is of most interest for this application because it selectively kills cancer cells in both p53-dependent and p53-independent ways, while leaving normal cells unaffected. This compound effectively increases basal levels of p53 protein and its proapoptotic targets. Furthermore, in vivo experiments demonstrate potent anti-tumor activities of this compound at low concentrations, which have no apparent adverse effects on normal organ and tissue function. We also identified significant elevation of reactive oxygen species (ROS) as a potential cancer cell specific mechanism of action for this compound. Therefore, targeting ROS could be a strategy to be developed to selectively kill cancer cells but not untransformed or normal cells by additional ROS production, because cancer cells possess a much higher basal level of ROS in comparison to normal cells. The main goal of this application is to understand the underlying mechanisms for the unusual selective effect of PPLGM in cancer cells in vitro and in vivo. A detailed understanding of the mechanism of action of this compound in both cancer cells and normal cells should provide novel insights into the target based selective therapeutic strategies against cancer, and may also warrant further testing in preclinical and clinical settings. PUBLIC HEALTH RELEVANCE: In cancer chemotherapy, selectivity remains a great concern because DNA damaging drugs kill both cancer cells and the surrounding normal cells, which is an important cause of side effects during cancer chemotherapy. The goal of this application is to understand the underlying mechanisms for the unusual cancer specific selective effect of a newly identified p53 activator.