Basic and Translational studies of Ras-mutant colorectal cancer

描述（由申请人提供）：每年有超过140，000名美国人被诊断患有结直肠癌（CRC），近52，000人死于CRC。降低CRC相关死亡的频率无疑需要针对癌症中发生的特定突变量身定制个体治疗。K-Ras和N-Ras癌蛋白的激活突变在CRC中很常见，并且与对常规和靶向治疗的反应特别差有关。我们的首要目标是了解突变Ras蛋白的致癌特性的机制，以开发有针对性的治疗策略。我们项目的前半部分将研究Ras的活化形式如何与炎症相互作用，以影响CRC的发生和进展。慢性炎症是CRC的主要风险因素，并且我们最近已经表明突变型Ras可以通过NF κ B途径影响信号传导（Lau等人，PLoS one 7：e41343，2012），NF κ B途径是主要的炎症信号传导途径。在本实验中，我们将研究突变Ras是否改变CRC对IAP信号传导抑制剂的反应，IAP信号传导抑制剂增强促炎细胞因子TNF-α诱导的细胞死亡。我们项目的后半部分涉及我们最近发现的一种新的Ras -赖氨酸乙酰化的翻译后调节机制。我们已经证明乙酰化Ras对GEF诱导的核苷酸交换具有抗性，因此使核苷酸结合平衡向GDP结合的非活性状态移动（Yang等人，Proc. Natl Acad. Sci. USA 109：10843-10848，2012）。基于这一发现，我们现已鉴定SIRT 2和HDAC 6为调节Ras乙酰化状态的酶（Yang等人，Mol. Cancer Res. In press）。在目标2中，我们将在生物化学水平上剖析Ras蛋白和SIRT 2/HDAC 6之间的相互作用，并确定这些脱乙酰酶的缺失如何影响Ras突变形式的致癌特性。我们预计，这种双管齐下的方法来了解Ras生物学将导致建立一个新的治疗模式K-Ras突变CRC。

DESCRIPTION (provided by applicant): More than 140,000 Americans are diagnosed with colorectal cancer (CRC) each year and almost 52,000 individuals die from it. Decreasing the frequency of CRC-related death will undoubtedly require tailoring an individual's treatment to the specific mutations that have occurred in their cancer. Activating mutations in the K-Ras and N-Ras oncoproteins are common in CRC and are associated with particularly poor response to both conventional and targeted therapies. Our overarching goal is to understand the mechanisms underlying the oncogenic properties of mutant Ras proteins in order to develop targeted therapeutic strategies. The first half of our project will examine how activated forms of Ras interact with inflammation to affect the onset and progression of CRC. Chronic inflammation is a major risk factor for CRC and we have recently shown that mutant Ras can influence signaling through the NFkB pathway (Lau et al. PLoS one 7: e41343, 2012), a major inflammatory signaling pathway. In this experimental context, we will study whether mutant Ras alters the response of CRCs to inhibitors of IAP signaling, which enhance cell death induced by the pro-inflammatory cytokine TNF-a. The second half of our project relates to our recent discovery of a novel post- translational regulatory mechanism for Ras - lysine acetylation. We have demonstrated that acetylated Ras is resistant to GEF-induced nucleotide exchange, therefore shifting the nucleotide binding equilibrium toward the GDP-bound, inactive state (Yang et al. Proc. Natl Acad. Sci. USA 109: 10843-10848, 2012). Building upon this discovery, we have now identified SIRT2 and HDAC6 as the enzymes that regulate the acetylation state of Ras (Yang et al. Mol. Cancer Res. In press). In Aim 2, we will dissect the interaction between Ras proteins and SIRT2/HDAC6 at the biochemical level and we will determine how loss of these deacetylases affects oncogenic properties of mutant forms of Ras. We anticipate that this two-pronged approach to understanding Ras biology will lead to the establishment of a new therapeutic paradigm for K-Ras-mutant CRC.