MAPK in p53 induced growth arrest/senescence

p53功能丧失是人类恶性肿瘤中最常见的遗传变化。有证据表明p53失活可能参与细胞的永生。p53阴性膀胱肿瘤细胞诱导p53表达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失活来促进肿瘤的进化。我们已经证明，在某些细胞环境下，这种终端分化程序可以同步诱导p53过表达。我们进一步确定了一种新的p53信号反应，涉及持续的MAPK激活，并产生了初步证据，表明这种反应有助于生长停滞表型。这一建议是专门针对阐明MAPK激活在p53诱导的生长停滞/衰老中的作用，负责的机制和涉及的效应途径。在Aim 1中，我们计划在不同细胞类型中将MAPK激活与p53诱导的生长停滞联系起来，利用tet可调节表达来研究活化的MAPK对肿瘤细胞永久生长停滞的贡献，并从遗传学上解剖MAPK在DNA损伤剂应答中的作用。在Aim 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aims 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功能，并建立涉及wt p53或活化的MEK转基因的动物模型。这些研究将使研究这些基因诱导的体外生长停滞/衰老反应的体内相关性成为可能。该项目的长期目标是了解MAPK激活如何促进p53诱导的永久性生长停滞/衰老，作为开发新的治疗方法的一种手段，通过靶向肿瘤细胞中的这一终端分化程序。

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.