15-LOX-1 effects on colitis and colon cancer

描述（由申请人提供）：本研究的长期目标是基于结直肠肿瘤发生中关键事件的分子靶向，帮助开发改善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（PGE 2）是花生四烯酸的促炎产物，可激活过氧化物酶体增殖物激活受体-δ（PPAR-d）并促进结肠肿瘤发生。花生四烯酸通常由亚油酸形成，特别是在癌细胞中。15-脂氧合酶-1（15-LOX-1）直接代谢亚油酸生成13-羟基十八碳二烯酸（13-S-HODE）具有抗肿瘤和抗肿瘤作用。15-LOX-1和13-S-HODE在人结肠肿瘤发生过程中下调。15-LOX-1在结肠癌细胞中的再表达通过13-S-HODE下调PPAR-d并在体外和体内抑制结肠癌细胞生长。待检验的假设是，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结肠肿瘤发生的促进作用，降低亚油酸转化为花生四烯酸和PGE 2的可用性，从而抑制PPAR-d。目标1：确定15-LOX-1对慢性结肠炎发展过程中结肠上皮细胞中膳食亚油酸转化为13-S-HODE vs. PGE 2的影响。LC/MS/MS将用于检查小鼠结肠上皮粘膜中靶向转基因15-LOX-1表达对经葡聚糖硫酸钠（DSS）处理以诱导结肠炎的小鼠中氘代亚油酸（补充至结肠隐窝细胞）转化为13-S-HODE和PGE 2的影响。目的2：确定15-LOX-1是否抑制慢性结肠炎。将在患有由DSS或IL-10敲除诱导的结肠炎的小鼠中检查15-LOX-1表达对临床和组织学结肠炎评分的影响。目的3：确定15-LOX-1是否阻止结肠炎诱导的结肠肿瘤发生。将在用AOM-DSS和IL-10敲除小鼠处理的小鼠中检查转基因15-LOX-1表达对结肠肿瘤发病率和多样性的影响。在有和没有膳食PGE 2补充的小鼠中，15-LOX-1表达对13- S-HODE和PGE 2水平的影响将阐明减少的PGE 2相对于增加的13-S-HODE对目的2和3中15-LOX-1的抗肿瘤和抗肿瘤作用的贡献。目标4：确定PPAR-d过表达是否有助于结肠炎诱导的结肠肿瘤发生的促进以及15-LOX-1是否通过PPAR-d下调抑制肿瘤发生。将在用AOM-DSS处理的小鼠中研究靶向绒毛蛋白-PPAR-d过表达对结肠炎诱导的结肠肿瘤发生的促进的作用。双基因PPAR-d和15-LOX-1转基因小鼠将用于研究PPAR-d下调对15-LOX-1对结肠炎诱导的结肠肿瘤发生的促进作用的贡献。该项目产生的信息将为结肠肿瘤发生的分子机制提供重要见解，从而有助于开发结肠癌化学预防的新干预措施。公共卫生相关性：15-脂氧合酶-1（15-LOX-1）的产生减少与结肠癌的发展有关;然而，所涉及的分子机制需要澄清。该项目旨在提高对15-LOX-1缺失导致结肠炎和结肠癌的分子机制的理解。这种改进的理解有望促进结肠癌预防新策略的分子靶点的鉴定。

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.