Vitamin D3 and Intestinal Tumorigenesis

描述（由申请人提供）： 维生素D3摄入量和血清水平是确定人类结肠癌风险的关键决定因素，维生素D3已被证明可抑制AOM诱导的异常隐窝病灶和ApcMin小鼠肿瘤的发展。大多数机制研究集中在培养的结肠上皮细胞系上，记录了对增殖和/或凋亡的显著影响，以及与这些细胞反应相关的途径。然而，我们最近发现，在体外，维生素D3破坏，在维生素D受体依赖性的方式，巨噬细胞刺激结肠肿瘤细胞生长的能力，并已解剖了一个特定的机制和级联信号事件破坏维生素D3在巨噬细胞通过它们的信号上皮细胞。我们将使用一种新的VDRflox/flox小鼠，其中我们将通过分别引入cfms-cre或villin-cre转基因来靶向灭活巨噬细胞/单核细胞或上皮细胞的维生素D受体。通过将这些构建体引入Apc 1638 N/+小鼠，我们将确定不同细胞区室对维生素D3对肠道稳态和预防肿瘤前变化和肿瘤发展的影响的贡献，并将确定维生素D3在这些小鼠中对我们发现的途径之间的特定串扰的影响。维生素D3在体内靶向巨噬细胞以及上皮细胞，并中止它们发出的刺激肿瘤上皮细胞生长的信号的建立，将建立一个关于维生素D3如何化学预防结肠癌的新范例。 公共卫生相关性： 人体中维生素D3水平低与结肠癌（和其他）癌症的风险较高有关，并且已证明维生素D3的升高对人类肠道肿瘤的发展以及该疾病的大鼠和小鼠模型具有化学保护作用。大多数关于维生素D如何影响肿瘤发展的研究都集中在它如何影响肿瘤上皮细胞的生长，即入侵和转移的实际恶性细胞。然而，肿瘤是由许多不同的细胞类型组成的，我们最近发现肿瘤中的其他细胞（巨噬细胞/单核细胞）可以向上皮细胞发送特定信号，使其更快地生长，并且已经解剖了哪些分子参与了巨噬细胞和上皮细胞的“串扰”。引人注目的是，维生素D3可以抑制巨噬细胞产生和发送这些信号的能力，从而表明巨噬细胞可能是维生素D3如何抑制癌症发展和进展的关键目标。我们有一种新的小鼠，它们经过基因操作，只有上皮细胞或巨噬细胞/单核细胞才能对维生素D3产生反应。我们将使用这些来证明巨噬细胞也是维生素D3抑制肠道肿瘤的关键靶点，并且还将确定这些动物中的分子靶点是否与我们在巨噬细胞和上皮细胞作为纯化细胞共同培养时发现的分子靶点相同。

DESCRIPTION (provided by applicant): Vitamin D3 intake and serum levels are key determinants in establishing risk for human colon cancer, and vitamin D3 has been shown to inhibit the development of AOM induced aberrant crypt foci, and tumors in ApcMin mice. Most studies of mechanism have focused on colon epithelial cell lines in culture, documenting significant effects on proliferation and/or apoptosis, and pathways associated with these cellular responses. However, we recently discovered that in vitro, vitamin D3 disrupts, in a vitamin D receptor-dependent manner, the ability of macrophages to stimulate colon tumor cell growth, and have dissected a specific mechanism and cascade of signaling events disrupted by vitamin D3 in the macrophages by which they signal to the epithelial cells. We will use a novel VDRflox/flox mouse, in which we will target inactivation of the vitamin D receptor to macrophages/monocytic or epithelial cells by introduction of a cfms-cre or villin-cre transgene, respectively. By introducing these constructs into the Apc1638N/+ mouse, we will determine the contribution of the different cell compartments to the effects of vitamin D3 on intestinal homeostasis and prevention of preneoplastic changes and tumor development, and will determine the effects of vitamin D3 in these mice on the specific cross-talk between pathways we have discovered. Establishment that vitamin D3 targets macrophages, as well as epithelial cells, in vivo, and aborts the signals they send to stimulate tumor epithelial cell growth, will establish a new paradigm regarding how vitamin D3 is chemopreventive for colon cancer. PUBLIC HEALTH RELEVANCE: Low levels of vitamin D3 in humans are linked to higher risk for colon (and other) cancers, and elevating vitamin D3 has been shown to be chemoprotective for intestinal tumor development in humans, and in rat and mouse models of the disease. Most studies of how vitamin D influences tumor development have focused on how it affects the growth of epithelial cells of the tumor, the actual malignant cell that invades and metastasizes. However, tumors are made up of many different cell types, and we have recently discovered that other cells in the tumor (macrophages/monocytic cells) can send specific signals to the epithelial cells to cause them to grow more rapidly, and have dissected just which molecules are involved both in the macrophages and the epithelial cells in the "cross-talk". Strikingly, vitamin D3 can inhibit the ability of the macrophages to make and send these signals, thus indicating that macrophages may be a key target in how vitamin D3 inhibits the development and progression of cancer. We have novel mice which have been genetically manipulated so that only the epithelial cells or the macrophages/monocytic cells can respond to vitamin D3. We will use these to prove that macrophages are also key targets in vitamin D3 inhibition of intestinal tumors, and will also determine whether the molecular targets in these animals are the same as those we have discovered when macrophages and epithelial cells are co-cultured together as purified cells.