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）是花生四烯酸的促炎产物，可激活过氧化物酶体增殖激活受体- δ (PPAR-d)，促进结肠肿瘤的发生。花生四烯酸通常由亚油酸形成，尤其是在癌细胞中。15-脂氧合酶-1 （15- lox -1）将亚油酸直接代谢为13-羟基十八烯二烯酸（13-S-HODE），具有抗肿瘤和抗炎作用。15-LOX-1和13-S-HODE在人类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，抑制结肠癌细胞的体外和体内生长。待验证的假设是，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发生，减少亚油酸转化为花生四烯酸和PGE2的可用性，从而抑制PPAR-d。目的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和PGE2的影响。采用LC/MS/MS检测小鼠结肠上皮黏膜中转基因15-LOX-1靶向表达对经葡聚糖硫酸钠（DSS）诱导结肠炎小鼠中补充于结肠隐窝细胞的重亚油酸转化为13-S-HODE和PGE2的影响。目的2：确定15-LOX-1是否抑制慢性结肠炎。15-LOX-1表达对DSS或IL-10敲除诱导结肠炎小鼠临床和组织学结肠炎评分的影响将被检测。目的3：确定15-LOX-1是否能阻止结肠炎诱导的结肠肿瘤发生。我们将在AOM-DSS和IL-10敲除小鼠中检测transgenic15-LOX-1表达对结肠肿瘤发病率和多样性的影响。在目的2和目的3中，研究15-LOX-1表达对添加和不添加PGE2的小鼠中13-S-HODE和PGE2水平的影响，将阐明PGE2减少与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过表达是否有助于结肠炎诱导的结肠肿瘤发生，以及15-LOX-1是否通过PPAR-d下调抑制肿瘤发生。在AOM-DSS处理的小鼠中，我们将研究靶向绒毛蛋白- ppar -d过表达对结肠炎诱导的结肠肿瘤发生的影响。利用双基因PPAR-d和15-LOX-1转基因小鼠，研究PPAR-d下调对15-LOX-1在结肠炎诱导下促进结肠肿瘤发生的作用的贡献。该项目产生的信息将为结肠癌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。这一改进的认识有望促进结肠癌预防新策略的分子靶点的确定。

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.