p53N236S获得耐药表型的分子机制研究

p53 is an important tumor suppress gene, mutant p53 not only lost tumor suppressive functions, some of the mutant p53 also gain some functions, including gain-of-resistant, that promote tumorigensis. In previous study, we found the p53S (p53N236S, p53N239S in human) mutation lost wild type p53 function, what's more, p53S cross-talked with H-RasV12 to facilitated the cell growth and tumorigenesis. The p53S context cells (p53s/s+Ras and p53s/s cell lines) are more resistant to doxorubicin treatment; furthermore, the expression of Ras in cells has been shown to increase the drug resistance. These data suggested that p53S might gain of resistant function through transcriptionally regulate downstream genes that related to drug resistance. And there might be a potential mechanism that p53S cooperate with Ras to aggravate the drug resistance. Therefore, in this project, we will analyze the downstream genes of p53S by ChIP-on-Chip and try to explain the gain-of-resistance mechanism of p53S and moreover the mechanism that p53S cooperate with Ras to aggravate the drug resistance. This study might contribute to the clinical treatment strategy in targeting p53 mutant.

p53是一个非常重要的抑癌基因，其突变不仅会导致其癌症抑制功能的丧失，某些突变的p53还会获得促进肿瘤形成的功能，例如获得性耐药等。在前期研究中我们发现p53N236S（简写为p53S）不但丧失了野生型p53的功能，还能与H-RasV12协同促进细胞增殖和肿瘤形成。与野生型细胞相比，p53S背景的细胞株对阿霉素有较强耐受性，且Ras的表达进一步加强了细胞对药物的耐受性。这提示p53S可能通过转录调控某些与耐药相关的下游基因获得耐药功能，并且可能存在p53S与Ras协同进一步增强细胞药物耐受性的潜在机制。因此，本项目通过ChIP-on-Chip及转录组分析，从研究p53S调控的下游基因入手，以期阐明p53S突变获得性耐药的分子机理，进一步探索p53S与Ras协同促进药物耐受性的潜在相互作用机制，从而摸索临床上用于以p53S为药物靶点的用药策略。

作为最重要的抑癌基因之一，p53突变不仅会导致其癌症抑制功能的丧失，某些突变的p53还会获得促进肿瘤形成的功能，例如获得性耐药等。在本项目中我们发现p53S（p53N236S，人类中为p53N239S）细胞对抗肿瘤药物阿霉素（Dox）处理耐受，而该表型并不主要依赖于通过survivin，aparf 1等对凋亡通路的调控。而通过对p53S调控的DNA损伤修复通路的研究发现，p53S能够通过增强细胞的同源重组，增强细胞对Dox造成的DNA双链断裂的修复，赋予细胞耐药潜能。此外，Ras可以通过激活p-p38，p-ERK这两条MAPK途径协同进一步促进p53S/S细胞的耐药表型。进一步研究发现，用拓扑异构酶抑制剂类药物依托泊苷（Etoposide）以及喜树碱（Camptothecin）处理后，p53S/S细胞均表现出了明显的耐药现象，而用DNA加合物药物，如：顺铂，卡莫司汀（Carmustine）处理后p53S/S细胞表现出了略微高于野生型细胞凋亡的现象。本项目的研究初步阐明p53S获得性耐药的分子机制及与Ras协同促进耐药的分子机制，初步建立针对p53S肿瘤细胞的用药策略。为临床上用于以p53S和Ras为药物靶点的用药策略提供理论参考。