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

描述（由申请人提供）：环氧合酶（cox: COX-1/-2）和5-脂氧合酶（5-LOX）催化的反应在结肠癌的进展中起重要作用。COX抑制剂包括布洛芬，被称为非甾体抗炎药（NSAIDs），已被证明是结肠癌的有效抗癌药物。然而，利用这些酶的特异性抑制剂的一个关键障碍是与COX抑制剂相关的副作用，包括胃毒性和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，具有强大的抗癌作用，并可能降低毒性。我们最近证明，维生素E形式包括3-生育酚（3T）， 4-生育酚（4T）和3-生育三烯醇（3TE）在人体细胞和大鼠体内代谢为长链羧基铬醇及其硫酸化对应物。重要的是，13′-羧基蒽醌醇（13′-COOH）是含有13碳长度羧化侧链的E代谢物，是COX-1/ 2的有效竞争性抑制剂，其效价与布洛芬相似，而3T、4T和3TE或更短侧链的羧基蒽醌醇是弱得多的COX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 （LTB4）。COXs和5-LOX的双重抑制不仅可能导致更有效的抗炎和抗癌作用（通过抑制多种促炎途径），而且还可能减少花生四烯酸酯代谢向任何一种途径转移所引起的潜在不良影响。因此，我们推测13'- cooh可能是很好的抗癌物质。这一假设将通过以下特定目标在细胞培养和动物研究中得到验证：1)研究4-13'-COOH（来自4-生育酚的13'-COOH）在结肠上皮细胞中的抗炎和抗癌活性，并通过酶动力学阐明抑制5-LOX的机制；2)研究4-13'-COOH在小鼠模型中的体内抗癌活性。其中，偶氮氧甲烷（AOM）诱导结肠癌发生，并被葡聚糖硫酸钠（DSS）引起的结肠炎症加速。4-13'-COOH的疗效将与其未代谢的前体4T和常用的非甾体抗炎药布洛芬进行比较。长期补充4-13'-COOH的生物利用度和潜在的不良影响也将进行研究。这些研究可能会发现一类新的有效的抗癌药物，即长链羧酸铬醇，它可能比非甾体抗炎药和维生素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并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。

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.