Wnt signaling in obesity-associated colorectal cancer

项目摘要 肥胖影响着42%的美国人口，是患结直肠癌的主要风险因素。 肥胖的结直肠癌患者的死亡风险是正常体重的五倍。 对口单位。然而，肥胖增加结直肠癌进展和 对肿瘤转移知之甚少，这限制了有效预防和治疗的发展。 肥胖者结直肠癌的治疗策略。绝大多数的结直肠癌是由丢失引起的。 肿瘤抑制基因APC在结肠干细胞中的表达，以及随后Wnt信号的激活 路径。WNT信号也是维持晚期结直肠癌和转移所必需的。 我们小组的研究表明，饮食诱导的肥胖显著上调Wnt信号。 通过促进PPAR-d促进肠道和结肠干细胞 转录程序，这反过来又增加了癌症的发展。这些发现表明，抑制 WNT信号是治疗肥胖相关结直肠癌的一种极具吸引力的治疗策略。我们和其他人 已经证明，结肠癌是由Lgr5+癌症干细胞和单细胞RNA维持的 我们实验室的测序数据显示，这些细胞是WNT活性的，而非癌症干细胞是WNT低活性的。 然而，用于治疗APC缺陷癌症或靶向癌症干细胞的Wnt抑制剂的开发已经 事实证明，这是难以捉摸的。Rac1-GTP是Rho家族GTP酶中的一员，是一种细胞内转导因子， 通过调节β-连环蛋白的核转位促进Wnt信号转导。Prex1是特定于RAC的RHO GTP酶鸟嘌呤核苷酸交换因子，通过促进GTP到GTP的交换来激活rac1。 我们发现Prex1和活性的rac1-GTP在接受治疗的小鼠的肠道和结肠癌中高度丰富 高脂饮食或PPAR-d激动剂。Rac1信号的丢失显著降低肠道肿瘤的发生 通过抑制Wnt的激活。我们的长期目标是了解Wnt在结直肠中的激活机制 癌症，并开发这种疾病的新治疗策略。在这里，我们假设依赖于Prex1 Rac1-GTP活性通过诱导Lgr5+肿瘤干细胞中的Wnt信号介导肥胖诱导的肿瘤发生 细胞。在目标1中，我们将确定Prex1信号在高脂饮食和PPAR-d介导的肠道中的作用 干细胞再生和肿瘤启动。在目标2中，我们将确定Prex1/rac1-GTP的功能 高脂饮食中的信号轴与PPAR-d依赖的结直肠癌干细胞功能。在《目标3》中，我们将 确定PPAR-d转录靶点在结直肠癌干细胞功能中的作用 诱导性肥胖。这项提议的目标是确定肥胖诱导Wnt信号传递的机制 促进结直肠癌的进展。我们的研究将为临床试验提供临床前测试的理论基础。 Rac1-GTP抑制剂通过抑制Wnt治疗结直肠癌，特别是肥胖者 发信号。

Project Summary Obesity affects 42% of the U.S. population and is a major risk factor for the development of colorectal cancer. Obese colorectal cancer patients have a five-fold increased risk of death compared to normal weight counterparts. However, the mechanisms by which obesity increases colorectal cancer progression and metastasis are poorly understood, which limits the development of effective prevention and treatment strategies for colorectal cancer in obese individuals. The vast majority of colorectal cancers are initiated by loss of the tumor suppressor gene Apc in colonic stem cells, and subsequent activation of the Wnt signaling pathway. Wnt signaling is also required for maintenance of advanced colorectal cancers and metastases. Research from our group demonstrates that diet-induced obesity markedly upregulates Wnt signaling in intestinal and colonic stem cells by promoting a peroxisome proliferator-activated receptor delta (PPAR-d) transcriptional program, which in turn increases cancer development. These findings suggest that inhibition of Wnt signaling is a highly attractive therapeutic strategy for obesity-associated colorectal cancer. We and others have demonstrated that colon tumors are maintained by Lgr5+ cancer stem cells, and single cell RNA sequencing data from our lab shows that these cells are Wnt-active, while non-cancer stem cells are Wnt-low. However, development of Wnt inhibitors to treat Apc-deficient cancers or to target cancer stem cells has proven elusive. Rac1-GTP, a member of the Rho family of GTPases, is an intracellular transducer that promotes Wnt signaling by mediating nuclear translocation of beta-catenin. Prex1 is a Rac-specific Rho GTPase guanine nucleotide exchange factor that activates Rac1 by facilitating the exchange of GTP to GTP. We found that Prex1 and active Rac1-GTP are highly enriched in intestines and colon cancers of mice treated with high fat diet or an agonist of PPAR-d. Loss of Rac1 signaling markedly reduces intestinal tumor initiation by inhibiting Wnt activation. Our long-term goal is to understand mechanisms of Wnt activation in colorectal cancer and to develop new treatment strategies for this disease. Here, we hypothesize that Prex1-dependent Rac1-GTP activity mediates obesity-induced tumorigenesis by inducing Wnt signaling in Lgr5+ cancer stem cells. In Aim 1, we will determine the role of Prex1 signaling in high fat diet and PPAR-d-mediated intestinal stem cell regeneration and tumor initiation. In Aim 2, we will determine the function of the Prex1 / Rac1-GTP signaling axis in high fat diet and PPAR-d-dependent colorectal cancer stem cell function. In Aim 3, we will identify the role of PPAR-d transcriptional targets in colorectal cancer stem cell function in the setting of diet- induced obesity. The goal of this proposal is to identify mechanisms by which obesity-induced Wnt signaling promotes colorectal cancer progression. Our studies will provide preclinical rationale for clinical trials to test Rac1-GTP inhibitors for the treatment of colorectal cancer, particularly in obese individuals, by inhibiting Wnt signaling.