The Mechanism and Therapeutic Potential of Targeting the Ninjurin Pathway for Tumors Carrying Wild-Type p53

项目摘要/摘要 抑癌基因P53常被称为“基因组的守护者”。P53基因的突变 基因存在于约50%的人类癌症中，而P53功能的丧失被认为在肿瘤中起着核心作用 进展和转移。在暴露于应激信号时，如DNA损伤，P53转录 因子被激活，然后诱导一系列有利于生存和有利于死亡的基因。由于它的强大作用 在肿瘤抑制方面，P53是抗肿瘤新药开发的一个有吸引力的靶点。神经 损伤诱导蛋白1和NINJ2共同构成细胞黏附的Ninsurin家族 分子，参与免疫反应等多种病理过程。 然而，NINJ1和NINJ2在肿瘤发生中的作用尚不清楚。我们之前已经证明了NINJ1 是P53的靶标，进而抑制P53的mRNA翻译。因此，NINJ1和P53形成阴性 反馈环路。值得注意的是，我们的初步研究表明，NINJ1和NINJ2通过 它们的N端胞外域。我们还发现，和NINJ1一样，NINJ2也形成否定 与P53的调控环。为了确定NINJ1-NINJ2-P53环的生物学意义，我们 研究表明：(1)NINJ1或NINJ2的缺失抑制了细胞的迁移和肿瘤球体的形成， 乳腺癌细胞中的克隆并促进小鼠胚胎成纤维细胞中的细胞衰老 (2)缺乏忍者1或忍者2的小鼠容易发生慢性炎症，这是 可能是由于野生型P53依赖的NLRP3激活增强了下睑下垂 炎症体；(3)N-末端α螺旋衍生的两个小肽，称为Pep-1A和Pep-2A NINJ1和NINJ2蛋白的结构域能够破坏NINJ1-NINJ2复合体的形成，并 导致经济增长受到抑制。这些观察结果促使我们假设NINJ1和NINJ2 通过P53途径在肿瘤发生中起关键作用。为了测试这一点，我们将确定：(1) NINJ1和NINJ2之间以及P53和忍者蛋白家族之间的反馈调控环；(2) NINJ1-NINJ2-P53环在肿瘤抑制中的生物学意义； 忍者2-P53环可以靶向杀伤携带野生型P53的肿瘤细胞。

Project Summary/Abstract The tumor suppressor p53 is often referred to as the “guardian of the genome”. Mutations of the p53 gene occur in ~50% of human cancer and loss of p53 function is known to play a central role in tumor progression and metastasis. Upon exposure to a stress signal, such as DNA damage, p53 transcription factor is activated and then induces an array of pro-survival and pro-death genes. Due to its potent role in tumor suppression, p53 is an attractive target for the development of new anticancer drugs. Nerve injury-induced protein 1 (Ninjurin1, NINJ1) and NINJ2 constitute the Ninjurin family of cell adhesion molecules and have been implicated in various pathological processes such as immune response. However, the role of NINJ1 and NINJ2 in tumorigenesis is unclear. We showed previously that NINJ1 is a target of p53 and in turn represses p53 mRNA translation. Thus, NINJ1 and p53 forms a negative feedback loop. Notably, our pilot study showed that NINJ1 and NINJ2 interact with each other through their N-terminal extracellular domains. We also found that like NINJ1, NINJ2 forms a negative regulatory loop with p53. To determine the biological significance of the NINJ1-NINJ2-p53 loop, we showed that: (1) loss of NINJ1 or NINJ2 inhibits cell migration and formation of tumor spheres and colonies in breast cancer cells and promote cellular senescence in mouse embryonic fibroblasts in a p53- dependent manner; (2) mice deficient in Ninj1 or Ninj2 are prone to chronic inflammation, which is likely due to enhanced pyroptosis through wild-type p53-dependent activation of NLRP3 inflammasome; (3) two small peptides, called Pep-1A and Pep-2A derived from N-terminal alpha helix domain of NINJ1 and NINJ2 protein were able to disrupt the formation of NINJ1-NINJ2 complex and elicit growth suppression. These observations prompt us to hypothesize that both NINJ1 and NINJ2 play a critical role in tumorigenesis through the p53 pathway. To test this, we will determine: (1) the feedback regulatory loops between NINJ1 and NINJ2 and between p53 and the Ninjurin family; (2) the biological significance of the NINJ1-NINJ2-p53 loop in tumor suppression; (3) whether the Ninj1- Ninj2-p53 loop can be targeted to kill tumor cells carrying wild-type p53.