Regulation of Lipid Droplets and FOXO3 in Intestinal Epithelial Cell Proliferatio

描述（由申请人提供）：肥胖和超重，在过去二十年中在发达国家已经是巨大的流行病，与广泛的疾病有关，包括不同器官如结肠的癌症。迄今为止，这些关联的基本机制尚未完全了解。其中一种可能性是，肥胖个体组织中积累的过量脂质直接刺激结肠肿瘤的进展。细胞内脂质储存在脂滴（LD）中，脂滴是脂肪组织以及许多人类肿瘤中发现的动态细胞器。据信LD是驱动增殖的能量来源，增殖是肿瘤进展的标志;然而，它们的调节和功能还没有很好地理解。我们的初步数据表明，LD积累增加，在结肠肥胖小鼠以及在发炎和肿瘤性结肠组织。此外，LDs受肿瘤抑制因子FOXO 3负调控，而刺激LDs积累导致FOXO 3活性丧失。因此，我们提出存在LD-FOXO 3网络，该网络还包括PI 3 K和SIRT 6（甘油三酯（TG）的负调节因子）。此外，初步数据表明，LD-FOXO 3网络在结肠癌细胞的增殖中至关重要，并且还在肥胖影响结肠上皮中起作用。 支持LD-FOXO 3网络由EGFR和/或PGE 2上游控制，而下游修饰细胞周期调节剂和甘油三酯合成。该提议的中心假设是，由LD-FOXO 3网络控制的结肠细胞中的增殖导致协调的LD积累和依赖于FOXO 3损失的细胞周期进展是负责肥胖相关结肠肿瘤进展的一种机制。提出了以下具体目标：目标1。评估LD诱导的结肠癌细胞增殖反应是否依赖于FOXO 3活性，通过（a）EGFR活化以及这是否依赖于PGE 2，（B）PI 3 K依赖性FOXO 3细胞周期停滞丧失，和（c）SIRT 6依赖性，一种结肠癌细胞中TG的负调节因子。目标2.为了确定TNF诱导的增殖和随后的LD积累是否是由于EGFR、PGE 2的活化和FOXO 3细胞周期停滞和SIRT 6（体外）的丧失，以及（B）为了发现在TNF处理的FOXO 3中LD的选择性阻断是否 或EGFR缺陷型小鼠通过促进Foxo 3依赖性SIRT 6和细胞周期停滞和TG抑制结肠上皮细胞增殖。目标3.评估肥胖和Foxo 3缺乏是否（a）在DSS/AOM模型中加剧腺瘤进展，导致G 0-G1检查点和TG调节物的改变，（B）是否通过选择性阻断LD、PGE 2或TNF抑制腺瘤进展，以及（c）鉴定调节脂质代谢的Foxo 3依赖性基因。 这项研究的结果将通过将LD-FOXO 3网络作为一种新的治疗靶点对人类健康产生显著的积极影响。虽然结肠癌进展的机制是复杂的，但在肥胖促进结肠肿瘤进展的患者中，LD的抑制可提供对肿瘤进展的有效阻断。

DESCRIPTION (provided by applicant): Obesity and overweight, which have been immense epidemics in developed countries for the last two decades, are associated with a wide array of diseases including cancer of different organs such as the colon. To date, the underlying mechanisms for these associations are not completely understood. One of emerging possibilities is that excess lipids accumulated in the tissue of obese individuals directly stimulates progression of colonic tumors. Intracellular lipids are stored in lipid droplets (LDs), dynamic organelles found in adipose tissue, as well as in many human tumors. It is believed that LDs are the source of energy that drives proliferation, a hallmark of tumor progression; however, their regulation and function are not well understood. Our preliminary data reveals that LD accumulation is increased in the colon of obese mice as well as in inflamed and neoplastic colonic tissue. Moreover, LDs are negatively regulated by tumor suppressor FOXO3, while stimulating LDs accumulation leads to a loss of FOXO3 activity. Thus we propose the existence of an LD-FOXO3 network that also includes PI3K and SIRT6 (a negative regulator of triglycerides (TGs). Moreover, preliminary data suggested that the LD-FOXO3 network is critical in proliferation of colonic cancer cells and also operates in obesity influence colonic epithelium. There is support that the LD-FOXO3 network is upstream control by EGFR and/or PGE2, while downstream modifies cell cycle regulators and triglyceride synthesis. The central hypothesis of this proposal is that proliferation in colonic cells controlled by LD-FOXO3 network leads to coordinate LD accumulation and cell cycle progression dependent on loss of FOXO3 is one mechanism responsible for obesity related colon tumor progression. The following Specific Aims are proposed: Aim 1. To assess if the LD induced proliferative response in colonic cancer cells depends on FOXO3 activity via (a) activation of EGFR and whether this is dependent on PGE2, (b) PI3K dependent loss of FOXO3 cell cycle arrest, and (c) SIRT6 dependent, a negative regulator of TGs in colon cancer cells. Aim 2. To determine if TNF-induced proliferation and consequent LD accumulation are due to activation of EGFR, PGE2 and a loss of FOXO3 cell cycle arrest and SIRT6 (in vitro), and (b) to find if selective blockade of LD in TNF treated Foxo3 or EGFR deficient mice suppresses proliferation of colonic epithelia by promoting Foxo3 dependent SIRT6 and cell cycle arrest and TGs. Aim 3. To assess if obesity and a deficiency in Foxo3 (a) exacerbated adenoma progression in DSS/AOM model leading to alterations in regulators of G0-G1 checkpoint and TGs, (b) if adenoma progression is suppressed by selective blockade of LD, PGE2, or TNF, and (c) to identify the Foxo3 dependent genes regulating lipid metabolism. Findings from the proposed study would have significant positive effects on human health by presenting the LD-FOXO3 network as a novel therapeutic target. Although mechanisms of colon cancer progression are complex, the inhibition of LDs may provide an effective blockade to tumor progression in patients with obesity promoted colonic tumor progression.