MAPK in p53 induced growth arrest/senescence

P53功能缺失是人类恶性肿瘤中最常见的基因改变。有证据表明，P53失活可能与细胞永生化有关。在P53阴性的EJ膀胱肿瘤细胞中诱导P53表达可导致永久性生长停滞/衰老。因此，衰老似乎代表了一个重要的细胞程序，可能需要P53失活才能使肿瘤进化。我们已经证明，这种末端分化程序可以在某些细胞环境中响应P53的过度表达而被同步诱导。我们进一步确定了一个新的涉及MAPK持续激活的P53信号反应，并产生了初步证据表明，这种反应有助于生长停滞表型。本研究旨在阐明MAPK激活在P53诱导的生长停滞/衰老中的作用、相关机制和涉及的效应通路。在目标1中，我们计划在不同类型的细胞中将MAPK激活与P53诱导的生长停滞相关联，利用TET可调节的表达来研究MAPK激活在肿瘤细胞永久性生长停滞中的作用，并从基因上剖析MAPK在DNA损伤剂反应中的作用。在目标2中，我们将研究P53激活MAPK级联的生化途径，包括可能的自分泌生长因子的研究。在目标3中，我们将利用遗传学方法研究MAPK效应通路及其在生长停滞中的作用，并建立涉及wt p53或激活的MEK转基因的动物模型。这些研究应该可以在体内研究这些基因诱导的体外生长停滞/衰老反应的相关性。这个项目的长期目标是了解MAPK激活如何在P53诱导的永久性生长停滞/衰老中起作用，作为一种通过靶向肿瘤细胞中的这种末端分化程序来开发新的治疗方法的手段。

Loss of p53 function is the most common genetic change in human malignancy. There is evidence that p53 inactivation may be involved in cell immortalization. Induced p53 expression in p53 negative EJ bladder tumor cell causes permanent growth arrest/senescence. Thus, senescence appears to represent an important cell program that may require p53 inactivation for tumor evolution. We have shown that this terminal differentiation program can be synchronously induced in response to p53 over-expression in some cell contexts. We have further identified a novel p53 signaling response involving sustained MAPK activation, and generated preliminary evidence that this response contributes to the growth arrest phenotype. This proposal is specifically directed at elucidating the role of MAPK activation in p53 induced growth arrest/senescence, the mechanisms responsible and the effector pathways involved. In Aim 1, we plan to correlate MAPK activation with p53 induced growth arrest in different cell types, investigate the contribution of activated MAPK to permanent growth arrest of tumor cells using tet regulatable expression, and genetically dissect the role of MAPK in response to DNA damaging agents. In Aim 2, we will investigate the biochemical pathways by which p53 activates the MAPK cascade including investigations of possible autocrine growth factors. In Aim 3, we will investigate MAPK effector pathways and their functions in growth arrest utilizing genetic approaches as well as establish animal models involving wt p53 or activated MEK transgenes. These studies should make it possible to investigate in vivo correlates of the in vitro growth arrest/senescence response induced by these genes. The long term goals of this project are to understand how MAPK activation contributes to p53 induced permanent growth arrest/senescence as a means of developing novel approaches to therapy by targeting this terminal differentiation program in tumor cells.