The Role of a Novel Vitamin E Metabolite in Colon Cancer Prevention and Therapy

描述（由申请方提供）：环氧合酶（COX：考克斯-1/-2）和5-脂氧合酶（5-LOX）催化的反应在结肠癌进展中发挥重要作用。包括布洛芬在内的考克斯抑制剂（称为非甾体抗炎药（NSAID））已被证明是对抗结肠癌的有效抗癌剂。然而，使用这些酶的特异性抑制剂的关键障碍是相关的不良反应，包括胃毒性和考克斯抑制剂的心血管疾病风险增加。因此，我们需要寻找新的预防和治疗策略，这些策略具有强大的抗癌作用，同时可能降低毒性。我们最近已经证明，维生素E形式，包括3-生育酚（3 T），4-生育酚（4 T）和3-生育三烯酚（3 TE）代谢为长链羧基色原烷醇和它们的硫酸化对应物在人类细胞和大鼠。重要的是，13 '-羧基苯并二氢吡喃醇（13'-COOH），含有13-碳长羧基化侧链的E代谢物，是考克斯-1/-2的有效竞争性抑制剂，其效力与布洛芬相似，而3 T、4 T和3 TE或更短侧链的羧基苯并二氢吡喃醇是弱得多的考克斯抑制剂。我们的初步数据表明，13 '-COOH也抑制5-LOX催化的白三烯B4（LTB 4）。COX和5-LOX的双重抑制不仅可以产生更有效的抗炎和抗癌作用（通过抑制多种促炎途径），而且还可以减少由花生四烯酸代谢中的分流到任一途径引起的潜在不良作用。因此，我们推测13 '-COOH可能是优异的抗癌剂。该假设将通过在细胞培养和动物研究中追求以下特定目的来测试：1）研究4- 13 '-COOH（衍生自4-生育酚的13'-COOH）在结肠上皮细胞中的抗炎和抗癌活性，并阐明通过酶动力学抑制5-LOX的潜在机制，和2）研究4- 13 '-COOH在小鼠模型中的体内抗癌活性，其中结肠癌发生由氧化偶氮甲烷（AOM）诱导，并由葡聚糖硫酸钠（DSS）引起的结肠炎症加速。将4- 13 '-COOH的功效与其未代谢的前体4 T和常用的NSAID布洛芬进行比较。还将研究长期补充期间4- 13 '-COOH的生物利用度和潜在不良反应。拟议的研究可能会发现一类新的有效抗癌剂，即，长链羧基苯并二氢吡喃醇，其可能比NSAID和维生素E形式更有效，并且由于其独特的性质而表现出很少的副作用。这些研究将把基于机制的发现扩展和转化为临床相关的癌症模型，并为人类临床研究获得重要的临床前数据。 公共卫生相关性：环氧化酶和5-脂氧合酶催化的反应对结肠癌的发展有重要作用。我们最近已经证明，长链羧基苯并二氢吡喃醇，这是新的维生素E代谢物，有效地抑制环氧合酶和5-脂氧合酶介导的反应。本申请研究长链羧基色原烷醇在结肠癌细胞和小鼠结肠癌模型中的抗癌活性。这些研究可能发现一类新的具有潜在低毒性的有效抗癌剂，将基于机制的发现扩展并转化为临床相关的动物模型，并将收集对人类临床研究重要的必要临床前数据。

DESCRIPTION (provided by applicant): Cyclooxygenases (COXs: COX-1/-2) and 5-lipoxygenase (5-LOX) catalyzed reactions play significant roles in colon cancer progression. COX inhibitors including ibuprofen, known as non-steroid anti- inflammatory drugs (NSAIDs), have been shown to be effective anticancer agents against colon cancer. However, a critical barrier to utilize the specific inhibitors of these enzymes is associated adverse effects including gastrotoxicity and increased risk of cardiovascular diseases for COX inhibitors. Therefore, we need to search for new prevention and therapeutic strategies that have strong anti-cancer effects with potentially reduced toxicity. We have recently demonstrated that vitamin E forms including 3-tocopherol (3T), 4-tocopherol (4T) and 3-tocotrienol (3TE) are metabolized to long-chain carboxychromanols and their sulfated counterparts in human cells and in rats. Importantly, 13'-carboxychromanol (13'-COOH), the E metabolite containing 13-carbon-length carboxylated side chain, is a potent competitive inhibitor of COX-1/-2 with the potency similar to ibuprofen, while 3T, 4T and 3TE or shorter-side chain carboxychromanols are much weaker COX inhibitors. Our preliminary data indicate that 13'-COOH also inhibited 5-LOX catalyzed leukotriene B4 (LTB4). The dual inhibition of COXs and 5-LOX may not only result in more potent anti-inflammatory and anti-cancer effect (by inhibiting multiple proinflammatory pathways), but may also reduce potential adverse effect caused by a shunt in arachidonate metabolism to either pathway. Therefore, we hypothesize that 13'-COOHs may be excellent anticancer agents. This hypothesis will be tested by pursuit of the following Specific Aims in cell culture and animal studies:1) investigate anti-inflammatory and anticancer activity of 4-13'-COOH (a 13'-COOH derived from 4-tocopherol) in colon epithelial cells and elucidate the mechanism underlying the inhibition of 5-LOX by enzyme kinetics, and 2) investigate in vivo anti-cancer activity of 4-13'-COOH in a mouse model, in which colon carcinogenesis is induced by azoxymethane (AOM) and is accelerated by dextran sulfate sodium (DSS)-caused colon inflammation. The efficacy of 4-13'-COOH will be compared with its unmetabolized precursor 4T and a commonly used NSAID, ibuprofen. The bioavailability and potential adverse effects of 4-13'-COOH during long-term supplementation will also be investigated. The proposed studies may discover a new class of effective anticancer agents, i.e., long-chain carboxychromanols, which may be more effective than NSAIDs and vitamin E forms, and exhibit few adverse effects due to their unique properties. These studies will extend and translate mechanism- based findings to a clinically relevant cancer model and obtain important preclinical data for human clinical studies. PUBLIC HEALTH RELEVANCE: Cyclooxygenases and 5-lipoxygenase catalyzed reactions contribute significantly to the development of colon cancer. We have recently demonstrated that long-chain carboxychromanols, which are novel vitamin E metabolites, potently inhibit cyclooxygenases- and 5-lipoxygenase-mediated reactions. This application is to investigate the anticancer activities of a long-chain carboxychromanol in colon cancer cells and in a colon cancer model in mice. These studies may discover a new class of effective anticancer agents with potentially low toxicity, will extend and translate mechanism-based findings to a clinically relevant animal model, and will gather necessary preclinical data important to human clinical studies.