Understanding the role of autophagy-regulated cell death in the escape from replicative crisis

摘要 肿瘤细胞在逃离限制人类细胞增殖的两个截然不同的关键障碍时产生， 复制性衰老和危机。处于复制衰老状态的细胞永久停止，同时继续 新陈代谢，由短端粒触发。然而，通过损害主细胞来避免衰老进入 P53和Rb肿瘤抑制通路控制的周期检查点。在衰老旁路和 继续增殖，细胞经历危机，这是一个突出的阶段，大量端粒失去保护 以及广泛的细胞死亡。危机是一种严格的肿瘤抑制屏障，因为它移除了绝大多数细胞 可以避免衰老。然而，很少有细胞克服这一障碍并成为肿瘤细胞。分子 危机和自发逃避危机中细胞死亡的机制和途径尚不清楚。 在这里，有人建议研究逃脱危机和绕过危机的分子机制， 期望由此产生的发现将对我们对早期 癌症发展的几个步骤。这里提供的初步数据为复制危机提出了一个新的概念 这意味着自噬是细胞死亡的主要调节因素。自噬抑制允许细胞绕过 危机并继续扩散，同时积累了多种基因组异常。这一发现具有深远的意义 对于理解基因组不稳定性如何在癌症发展的早期阶段演变具有重要意义。 此外，这一发现表明，自噬抑制剂可能会产生反作用，并促进 建立肿瘤细胞，而不是消灭它们。在三个具体目标中，建议破译 从功能失调的端粒到自噬控制的激活的确切信号通路 细胞死亡(目标1)，以确定端粒驱动的自噬和自噬抑制的后果 在危机期间(目标2)，并了解在危机中自噬驱动的细胞死亡在肿瘤发展中的作用 体内实验(目标3)。总而言之，这项拨款提案集中在细胞死亡的潜在机制上 复制危机，自噬如何被激活和调节以应对复制危机的机制， 以及在危机期间抑制自噬如何使基因组不稳定的细胞逃脱这最后的障碍 抗肿瘤细胞的建立和驱使恶性肿瘤。因此，我们将探索我们的新假设，其中 对自噬细胞死亡的暂时或永久抵抗是出现 危机后细胞和基因组的不稳定性骤然上升，导致了肿瘤细胞的建立。

Abstract Tumor cells arise upon escape from two distinct and critical barriers that limit proliferation of human cells, replicative senescence and crisis. Cells in replicative senescence arrest permanently while continuing to metabolize, triggered by short telomeres. Senescence entry however, is avoided by impairment of the main cell cycle checkpoints controlled by the p53 and Rb tumor suppressive pathways. Following senescence bypass and continued proliferation, cells undergo crisis, which is a phase highlighted by substantial telomere deprotection and widespread cell death. Crisis is a stringent tumor-suppressive barrier, as it removes the vast majority of cells that avoid senescence. However, rarely cells overcome this barrier and become neoplastic. The molecular mechanisms and pathways underlying cell death in crisis and spontaneous crisis evasion are not understood. Here, it is proposed to investigate the molecular mechanisms underlying the escape from crisis and crisis bypass, with the expectation that the resulting discoveries will have a strong impact on our understanding of the early steps in cancer development. The preliminary data presented here suggest a novel concept for replicative crisis that implicates autophagy as a major regulator of cell death. Autophagy suppression allowed cells to bypass crisis and continue to proliferate, while accumulating multiple genomic aberrations. This discovery is of profound significance for understanding how genome instability evolves during the early steps of cancer development. Furthermore, the finding suggests that autophagy inhibitors might have counterproductive effects and promote the establishment of neoplastic cells instead of eliminating them. In three specific aims it is proposed to decipher the exact signaling pathways that lead from dysfunctional telomeres to the activation of autophagy-controlled cell death (Aim 1), to determine the consequences of telomere-driven autophagy and of autophagy inhibition during crisis (Aim 2), and to understand the role of autophagy-driven cell death in crisis on tumor development in vivo (Aim 3). In summary, this grant proposal focuses on the mechanisms underlying cell death during replicative crisis, the mechanism of how autophagy is activated and regulated in response to replicative crisis, and how inhibition of autophagy during crisis enables cells with an unstable genome to escape this final barrier against tumor cell establishment and drive malignancy. We will thereby explore our novel hypothesis, in which temporary or permanent resistance to autophagic cell death is the initial event required for the emergence of post-crisis cells and an abrupt rise in genome instability, leading to the establishment of neoplastic cells.