S1P Lyase in colon cancer

描述（由申请人提供）： 膳食鞘脂如神经酰胺和鞘氨醇促进细胞凋亡和防止肠道肿瘤发生。然而，这些鞘脂可以在肠细胞内转化为鞘氨醇-1-磷酸（S1 P），一种有效的促有丝分裂剂和血管生成因子。因此，这些鞘脂代谢产物之间存在微妙的平衡，在肠道上皮细胞，改变可能会影响肠道肿瘤的发生。S1 P被酶S1 P裂解酶（SPL）不可逆地降解，所述酶促进细胞凋亡并且是最大细胞凋亡反应所需的。SPL在肠道上皮中高度表达，在那里它维持低S1 P水平并促进正常细胞更新。然而，我们发现SPL在早期Min小鼠息肉和人类结肠癌中下调。我们假设SPL下调是肠道肿瘤发生的早期事件，代表了一种关键的遗传变化，导致有利于S1 P在肠粘膜中积累的生化开关，从而激活促有丝分裂和血管生成信号，促进肿瘤进展。为了检验这种可能性，我们提出了四个相互关联的具体目标：1。描述伴随肠道肿瘤发生的S1 P代谢变化。我们推测，遗传和/或表观遗传变化导致S1 P积累是常见的，在肠道肿瘤发生的早期事件。比较人肠息肉、结直肠癌、不同分期的Min小鼠息肉和相应的未受累组织中鞘脂水平和S1 P代谢相关酶的活性、表达和定位; 2.探讨SPL表达对永生化和恶性结肠上皮细胞体外生长特性的影响。SPL表达将使用siRNA、腺病毒和稳定表达系统在恶性和非恶性结肠上皮细胞系中调节。将确定SPL对增殖、凋亡、迁移和致瘤性的影响以及作用机制。3.确定SPL下调是否会增加肠道致瘤性并改变对饮食鞘脂的反应。将可用的SPL敲除小鼠模型与Min小鼠背景杂交，以探索以下假设：小鼠肠组织中SPL表达减少和S1 P水平增加将增强肠息肉病的速率、发病率、生长、血管分布和侵袭性特征，并限制或逆转膳食鞘脂的化学预防作用; 4.确定SPL下调是否在肠肿瘤发生的早期是可逆的。我们将研究SPL下调是SPL基因组位点DNA甲基化的表观遗传变化的结果这一假设。拟议的研究计划应确定SPL下调是否是一个早期和可逆的事件，有助于肠道肿瘤的发生。在完成这些研究的过程中，我们将更接近我们的长期目标，即采用化学预防措施，在肿瘤发生的早期恢复微妙的鞘脂代谢平衡。项目叙述结肠癌是男性和女性第二大常见癌症，也是癌症死亡的第三大原因。据估计，在美国，每年花费84亿美元用于照顾患有这种疾病的患者。确定疾病发生和进展的分子和环境决定因素是一个关键目标，可能有助于揭示新的生物标志物，用于早期检测和治疗干预，以帮助50%或更多的晚期或难治性疾病患者。如果我们的中心假设是正确的，S1 P代谢基因的状态可能成为预测结果和对治疗和饮食方案的反应的信息生物标志物。我们的研究计划应该建立这一假设的有效性，并提供必要的信息，以实现我们的最终目标，这是确定和验证新的治疗方法，绕过或逆转鞘脂代谢开关，并恢复正常的S1 P代谢癌前和/或恶性细胞。

DESCRIPTION (provided by applicant): Dietary sphingolipids such as ceramide and sphingosine promote apoptosis and protect against intestinal tumorigenesis. However, these sphingolipids can be converted within intestinal cells to sphingosine-1- phosphate (S1P), a potent mitogen and angiogenic factor. Thus, a delicate balance exists between these sphingolipid metabolites in gut epithelial cells, alterations of which may influence intestinal tumorigenesis. S1P is irreversibly degraded by the enzyme S1P lyase (SPL), which promotes apoptosis and is required for maximal apoptotic responses. SPL is highly expressed in gut epithelium, where it maintains low S1P levels and promotes normal cell turnover. However, we have found that SPL is downregulated in early Min mouse polyps and in human colon cancer. We hypothesize that SPL downregulation is an early event in intestinal tumorigenesis, representing a critical genetic change that leads to a biochemical switch favoring S1P accumulation in the intestinal mucosa, thereby activating mitogenic and angiogenic signals that contribute to tumor progression. To test this possibility, we have proposed four interrelated specific aims: 1. To characterize the changes in S1P metabolism that accompany intestinal tumorigenesis. We hypothesize that genetic and/or epigenetic changes leading to S1P accumulation are common and early events in intestinal tumorigenesis. Sphingolipid levels and the activity, expression and localization of enzymes involved in S1P metabolism will be compared in human intestinal polyps, CRC, Min mouse polyps of different stages and corresponding uninvolved tissues; 2. To establish whether SPL expression affects the growth characteristics of immortalized and malignant colonic epithelial cells in vitro. SPL expression will be modulated in malignant and nonmalignant colon epithelial cell lines using siRNA, adenoviral and stable expression systems. Effects on proliferation, apoptosis, migration and tumorigenicity and mechanism of SPL action will be determined. 3. To establish whether SPL downregulation increases intestinal tumorigenicity and alters the response to dietary sphingolipids. Available SPL knockout mouse models crossed into the Min mouse background will be used to explore the hypothesis that reduced SPL expression and increased S1P levels in mouse intestinal tissues will enhance the rate, incidence, growth, vascularity and invasive characteristics of intestinal polyposis and limit or reverse the chemopreventive effect of dietary sphingolipids; 4. To determine whether SPL downregulation is reversible early in intestinal tumorigenesis. We will investigate the hypothesis that SPL downregulation is the result of epigenetic changes involving DNA methylation at the SPL genomic locus. The proposed research plan should establish whether SPL downregulation is an early and reversible event that contributes to intestinal tumorigenesis. In accomplishing the proposed studies, we will move closer to our long term goal of employing chemopreventive measures to restore the delicate sphingolipid metabolic balance early in the process of tumorigenesis.Project Narrative Colon cancer is the second most common cancer of men and women and the third leading cause of cancer mortality. It is estimated that $8.4 billion per year is spent caring for patients with this disease in the US. Identifying the molecular and environmental determinants of disease incidence and progression is a critical goal that may help to reveal novel biomarkers for earlier detection and therapeutic intervention to help the 50% or more of patients suffering from advanced or refractory disease. If our central hypothesis is correct, the status of S1P metabolic genes may become informative biomarkers in predicting outcome and the response to therapeutic and dietary regimens. Our Research Plan should establish the validity of this hypothesis and provide information necessary for achieving our ultimate goal, which is to identify and validate novel therapeutic approaches that bypass or reverse the sphingolipid metabolic switch and restore normal S1P metabolism in premalignant and/or malignant cells.