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

项目总结/摘要 抑癌基因p53通常被称为“基因组的守护者”。p53突变 p53基因存在于约50%的人类癌症中，并且已知p53功能的丧失在肿瘤中起中心作用 进展和转移。当暴露于应激信号，如DNA损伤，p53转录 因子被激活，然后诱导一系列促生存和促死亡基因。由于其强大的作用 在肿瘤抑制中，p53是开发新抗癌药物的有吸引力的靶点。神经 损伤诱导蛋白1（Ninjurin 1，NINJ 1）和NINJ 2构成细胞粘附的Ninjurin家族 分子，并已涉及各种病理过程，如免疫反应。 然而，NINJ 1和NINJ 2在肿瘤发生中的作用尚不清楚。我们之前已经证明了NINJ 1 是p53的靶点，并反过来抑制p53 mRNA的翻译。因此，NINJ 1和p53形成负性的 反馈回路值得注意的是，我们的初步研究表明，NINJ 1和NINJ 2通过以下方式相互作用： 它们的N-末端胞外结构域。我们还发现，与NINJ 1一样，NINJ 2也会形成一个负性的 p53调控环。为了确定NINJ 1-NINJ 2-p53环的生物学意义，我们 显示：（1）NINJ 1或NINJ 2的缺失抑制细胞迁移和肿瘤球的形成， 在乳腺癌细胞中的集落，并促进小鼠胚胎成纤维细胞的细胞衰老，在p53- （2）Ninj 1或Ninj 2缺陷的小鼠容易发生慢性炎症， 可能是由于通过野生型p53依赖性NLRP 3激活而增强的焦亡 （3）两个小肽，称为Pep-1A和Pep-2A，它们来源于N-末端α螺旋 NINJ 1和NINJ 2蛋白的结构域能够破坏NINJ 1-NINJ 2复合物的形成， 引发生长抑制。这些观察结果促使我们假设NINJ 1和NINJ 2都 通过p53途径在肿瘤发生中起关键作用。为了验证这一点，我们将确定：（1） NINJ 1和NINJ 2之间以及p53和Ninjurin家族之间的反馈调节环;（2）NINJ 1和NINJ 2之间的反馈调节环; NINJ 1-NINJ 2-p53环在肿瘤抑制中的生物学意义;（3）NINJ 1-p53环是否在肿瘤抑制中起作用。 Ninj 2-p53环可以靶向杀死携带野生型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.