15-LOX-1 effects on colitis and colon cancer

描述(由申请人提供)：这项研究的长期目标是基于对结直肠癌发生中的关键事件的分子靶向，帮助开发改进的结直肠癌化学预防干预措施。炎症有助于结肠癌的发生。前列腺素E2(PGE2)是花生四烯酸的前炎性产物，可激活PPAR-d，促进结肠肿瘤的发生。花生四烯酸通常是由亚油酸形成的，尤其是在癌细胞中。15-脂氧合酶-1(15-LOX-1)直接代谢亚油酸为13-羟基十八碳二烯酸(13-S-HODE)具有抗肿瘤和抗炎作用。15-LOX-1和13-S-HODE在人结肠肿瘤发生过程中表达下调。15-LOX-1在结肠癌细胞中的重新表达通过13-S-HODE下调PPAR-d，并在体内外抑制结肠癌细胞生长。需要检验的假设是，恢复15-LOX-1的表达，从而恢复13-S-HODE的产生，将阻止结肠炎诱导的促进结肠肿瘤的发生，减少亚油酸转化为花生四烯酸和前列腺素E_2的可获得性，从而抑制PPAR-d。目的：探讨15-LOX-1在慢性结肠炎发病过程中对结肠上皮细胞亚油酸转化为13-S-HODE和前列腺素E_2的影响。采用LC/MS/MS方法研究小鼠结肠上皮细胞靶向表达15-LOX-1基因对葡聚糖硫酸钠诱导小鼠结肠炎模型中重氢亚油酸转化为13-S-HODE和前列腺素E_2的影响。目的2：确定15-LOX-1是否抑制慢性结肠炎。15-LOX-1的表达对临床和组织学结肠炎评分的影响将在DSS或IL-10基因敲除诱导的结肠炎小鼠中进行检测。目的3：确定15-LOX-1是否能阻止结肠炎诱导的促进结肠肿瘤发生。转基因15-LOX-1表达对结肠癌发病率和多样性的影响将在AOM-DSS和IL-10基因敲除小鼠治疗的小鼠中检验。15-LOX-1的表达对补充和不补充PGE_2的小鼠13-S-HODE和PGE_2水平的影响，将阐明在AIMS 2和AIMS 3中，PGE_2减少和13-S-HODE增加对15-LOX-1抗炎和抗肿瘤作用的贡献。目的4：确定PPAR-d过表达是否促进结肠炎诱导的结肠肿瘤发生，以及15-LOX-1是否通过PPAR-d下调抑制肿瘤的发生。在使用AOM-DSS治疗的小鼠中，将研究靶向Villin-PPAR-d过表达在结肠炎诱导的促进结肠肿瘤形成中的作用。将利用双基因PPAR-d和15-LOX-1转基因小鼠来研究PPAR-d下调在15-LOX-1促进结肠炎诱导的结肠肿瘤发生中的作用。该项目产生的信息将为结肠癌发生的分子机制提供重要的见解，从而有助于开发新的结肠癌化学预防干预措施。公共卫生相关性：酶15-脂氧合酶-1(15-LOX-1)的产生减少与结肠癌的发生有关；然而，涉及的分子机制需要澄清。这项拟议的项目旨在提高对15-LOX-1缺失导致结肠炎和结肠癌的分子机制的理解。这一更好的理解有望促进为结肠癌预防的新策略识别分子靶点。

DESCRIPTION (provided by applicant): The long-term goal of this research is to help develop improved chemopreventive interventions for colorectal cancer based on molecular targeting of crucial events in colorectal tumorigenesis. Inflammation contributes to colon carcinogenesis. Prostaglandin E2 (PGE2), a proinflammatory product of arachidonic acid, activates peroxisome proliferator-activated receptor-delta (PPAR-d) and promotes colonic tumorigenesis. Arachidonic acid is frequently formed from linoleic acid especially in cancer cells. Direct metabolism of linoleic acid by 15- lipoxygenase-1 (15-LOX-1) to 13-hydroxyoctadecadienoic acid (13-S-HODE) has antitumorigenic and antiinflammatory effects. 15-LOX-1 and 13-S-HODE are downregulated during human colonic tumorigenesis. 15-LOX-1 re-expression in colon cancer cells downregulates PPAR-d via 13-S-HODE and inhibits colon cancer cell growth in vitro and in vivo. The hypothesis to be tested is that restoring 15-LOX-1 expression, and thus 13- S-HODE production, will prevent colitis-induced promotion of colonic tumorigenesis, reduce the availability of linoleic acid for conversion to arachidonic acid and PGE2, and thus suppress PPAR-d. Aim 1: To determine the effects of 15-LOX-1 on the conversion of dietary linoleic acid in colonic epithelial cells into 13-S-HODE vs. PGE2 during the development of chronic colitis. LC/MS/MS will be used to examine the effects of targeted transgenic 15-LOX-1 expression in mouse colonic epithelial mucosa on the conversion of deuterated linoleic acid (supplemented to colonic crypt cells) into 13-S-HODE and PGE2 in mice treated with dextran sodium sulfate (DSS) to induce colitis. Aim 2: To determine whether 15-LOX-1 suppresses chronic colitis. The effects of 15-LOX-1 expression on clinical and histologic colitis scores will be examined in mice with colitis induced by DSS or IL-10 knockout. Aim 3: To determine whether 15-LOX-1 prevents colitis-induced promotion of colonic tumorigenesis. The effects of transgenic15-LOX-1 expression on colon tumor incidence and multiplicity will be examined in mice treated with AOM-DSS and IL-10 knockout mice. The effects of 15-LOX-1 expression on 13- S-HODE and PGE2 levels in mice with and without dietary PGE2 supplementation, will clarify the contribution of reduced PGE2 vs. increased 13-S-HODE to the 15-LOX-1 antiinflammatory and antitumorigenic effects of 15-LOX-1 in Aims 2 and 3. Aim 4: To determine whether PPAR-d overexpression contributes to colitis-induced promotion of colonic tumorigenesis and whether 15-LOX-1 inhibits tumorigenesis via PPAR-d downregulation. The effects of targeted villin-PPAR-d overexpression on colitis-induced promotion of colonic tumorigenesis will be studied in mice treated with AOM-DSS. Bigenic PPAR-d and 15-LOX-1 transgenic mice will be used to study the contribution of PPAR-d downregulation to the effects of 15-LOX-1 on colitis-induced promotion of colonic tumorigenesis. The project-generated information will provide important insights into the molecular mechanisms involved in colonic tumorigenesis and thus help develop new interventions for the chemoprevention of colon cancer. PUBLIC HEALTH RELEVANCE: Decreased production of the enzyme 15-lipoxygenase-1 (15-LOX-1) is associated with colon cancer development; however, the molecular mechanisms involved need to be clarified. The proposed project aims to improve understanding of the molecular mechanisms by which loss of 15-LOX-1 contributes to both colitis and colon cancer. This improved understanding is expected to facilitate the identification of molecular targets for new strategies for colon cancer prevention.