Mechanisms of p53 Engagement and Action at the Benign-to-Malignant Transition in Sporadic Tumorigenesis

项目总结 转录因子P53是肿瘤发生最关键的障碍之一。超过一半的人P53基因发生突变 所有人类肿瘤和p53突变肿瘤的预后通常都较差。作为一种肿瘤抑制因子，p53 似乎在良性疾病向恶性疾病的转变过程中起作用，防止具有 已经获得了一些促肿瘤的特征，例如癌基因激活或DNA损伤。几十年的研究 我试图找出是什么使p53成为一种有效的肿瘤抑制因子，因为这种知识可以告诉我们有效的 癌症预防和治疗的策略。这项研究表明，P53可以被多种因素激活 进而激活的P53可以调节多种细胞过程，包括细胞存活， 衰老、基因组稳定性和可塑性。然而，P53的诱导物和作用因环境而异，并且 在早期肿瘤形成过程中，是什么信号作用于P53，以及哪些生物学程序尚未达成共识 对于它的肿瘤抑制功能是最重要的。此外，我们仍然不知道关键事件 在P53基因丢失后，使其能够转变为恶性肿瘤。获取这种知识的尝试受到了阻碍。 由于缺乏工具来直接研究内源性转化的特定细胞中的p53 上下文。为了解决这些知识上的差距，我们将研究围绕p53激活和丢失的事件 在胰腺导管癌(PDAC)的初始阶段，P53缺失的侵袭性癌 发生在70%的PDAC中--使良性前驱病变进展为全面的癌症。我们 最近开发的新的PDAC小鼠模型，使我们能够在细胞通过 从良性到恶性的转变。在癌前胰腺细胞中，我们发现了一个亚群 它与已建立的肿瘤细胞有许多共同的转录特征，因此这些细胞似乎是 从癌前病变过渡到恶性病变。这些过渡细胞也是P53最强的细胞 因此，它们为研究P53的参与和肿瘤抑制功能提供了独特的机会 从良性到恶性的转变。使用单细胞转录和空间分析，新的计算 推断细胞状态转变的方法，以及我们建立的快速遗传扰动平台 在体内，我们将定义导致这种P53活性转换细胞状态的细胞内在和细胞外在事件。 此外，我们还将研究激活的p53抑制肿瘤转化的机制。 在过渡细胞中，以及在p53丢失后立即影响癌症启动的事件。 该项目将为推动PDAC启动的机制提供新的见解，并提供直接和 P53在内源性环境中作用的详细特征。鉴于TP53的高流行率 对于人类癌症中的突变，我们预计对肿瘤发生的洞察将适用于许多癌症类型。

PROJECT SUMMARY The transcription factor p53 is one of the most critical barriers to tumorigenesis. p53 is mutated in over half of all human tumors, and p53-mutant tumors typically carry a worse prognosis. As a tumor suppressor, p53 appears to act at the transition from benign to malignant disease, preventing transformation of cells that have already acquired some pro-tumor features, such as oncogene activation or DNA damage. Decades of research have sought to identify what makes p53 a potent tumor suppressor, as such knowledge could inform effective strategies for cancer prevention and treatment. This research has shown that p53 can be activated by a variety of signals, and in turn activated p53 can regulate a wide variety of cellular processes, including cell survival, senescence, genomic stability, and plasticity. However, the inducers and actions of p53 vary with context, and there is still no consensus on what signals engage p53 during early neoplasia and what biological programs are most important for its tumor-suppressive functions. Furthermore, we still do not know the key events following p53 loss that enable transition to malignancy. Attempts to gain this knowledge have been hampered by a lack of tools to directly study p53 in the specific cells undergoing transformation within endogenous contexts. To address these gaps in knowledge, we will study the events surrounding p53 activation and loss during the initiation of pancreatic ductal carcinoma (PDAC), an aggressive cancer in which p53 loss—which occurs in 70% of PDACs—enables progression from benign precursor lesions to full-blown cancer. We recently developed new mouse models of PDAC that allow us to “see” p53 in action as cells progress through the benign-to-malignant transition. Among the premalignant pancreas cells, we discovered a subpopulation that shares many transcriptional features with established tumor cells, and thus these cells appear to be transitioning from premalignant to malignant. These transitioning cells are also the cells with the strongest p53 activation, and so they provide a unique opportunity to study p53 engagement and tumor-suppressive function at the benign-to-malignant transition. Using single-cell transcriptional and spatial analyses, new computational approaches to infer cell state transitions, and our well-established platform for rapid genetic perturbations in vivo, we will define the cell-intrinsic and cell-extrinsic events that lead to this p53-active transitioning cell state. Furthermore, we will investigate the mechanisms by which activated p53 suppresses neoplastic transformation in the transitioning cells, as well as the events that influence cancer initiation immediately following p53 loss. This project will provide novel insight into the mechanisms that drive PDAC initiation and provide a direct and detailed characterization of p53 in action in endogenous contexts. Given the high prevalence of TP53 mutations in human cancers, we expect the insights into tumorigenesis to be applicable to many cancer types.