Role of IPMK in generation of small intestinal carcinoid

5-羟色胺分泌性小肠神经内分泌肿瘤（SI-NET）是原发于小肠的恶性肿瘤， 小肠当临床确认时，受折磨的患者通常表现为晚期疾病， 5年预后差（~36%）。手术是SI-NET最常见的治疗方法。的遗传基础 家族性SI-NET与散发性SI-NET不同。唯一报道的与家族性SI-NET相关的突变是 IPMK（肌醇多磷酸多激酶）基因中的四个碱基对缺失突变。IPMK蛋白是 416个氨基酸长，突变将其截短为333，消除了C末端ATP结合位点 和部分核定位信号。IPMK杂合突变显示其激酶减少 活性和核定位。IPMK是肌醇高级合成的限速酶 途径并产生肌醇五磷酸。在哺乳动物细胞中，IPMK也充当PI 3激酶。 IPMK主要富集在细胞核中，并且IPMK的功能丧失损害p53介导的细胞凋亡。 转录。由于p53功能的丧失与几种肠癌高度相关，我们希望研究 IPMK突变体（在SI-NET患者中发现）在p53介导凋亡或细胞周期停滞中的重要性 恶性肿瘤的起源和肿瘤的形成。如何，纯合子IPMK功能丧失和 IPMK杂合突变体形式损害p53介导的凋亡和细胞周期停滞， 未知的，值得研究，以了解SI-NET起源的分子机制。使用 Cre-Lox技术，我们开发了一种肠上皮细胞特异性IPMK条件homo， 杂合子KO小鼠的研究，以了解IPMK介导的SI-NET发育的机制。我们 提出三个具体目标--目标1。确定IPMK基因剂量如何影响SI-NET的程度， 小鼠将进行组织病理学、免疫组织化学和生化分析， 了解IPMK的杂合和纯合丢失如何影响肠道内稳态以及 SI-NET以年龄依赖的方式生成。目标2.确定IPMK是否必要和充分 以增强细胞增殖和细胞周期调节。将进行细胞生物学和流式细胞术分析。 为了了解IPMK在调节细胞增殖和凋亡中的关键功能，进行了以下研究：目标3. 确定p53是否是IPMK信号诱导的细胞凋亡和细胞周期停滞所必需的。

Serotonin secreting small intestinal neuroendocrine tumors (SI-NET) are primary malignancies of the small bowel. When clinically recognized, afflicted patients often present with advanced disease and a poor 5-year prognosis (~36%). Surgery is the most common treatment of SI-NET. The genetic basis of Familial SI-NET is distinct from sporadic SI-NET. The only reported mutation linked to familial SI-NET is four base pair deletion mutations in the IPMK (Inositol polyphosphate multikinase) gene. IPMK protein is 416 amino acids in length,and the mutation truncates it to 333, eliminating the C-terminal ATP binding site and partial nuclear localization signal. IPMK heterozygous mutation exhibits a reduction of its kinase activity and nuclear localization. IPMK is the rate-limiting enzyme in the higher-order inositol synthesis pathway and generates inositol penta-phosphate. In mammalian cells, IPMK also acts as a PI3kinase. IPMK is primarily enriched in the nucleus, and loss of function of IPMK impairs p53 mediated transcription. As loss of p53 function is highly linked to several intestinal cancers, we like to investigate the importance of IPMK mutant (found in SI-NET patients) in p53 mediated apoptosis or cell cycle arrest in the origination of malignancies and tumor formation. How, homozygous loss of function of IPMK and a heterozygous mutant form of IPMK impair p53 mediated apoptosis and cell cycle arrest is entirely unknown and worth investigating to understand the molecular mechanism of SI-NET origination. Using Cre-Lox technology, we developed an intestinal epithelial cell-specific IPMK conditional homo and heterozygous KO mouse to understand the mechanism of IPMK mediated SI-NET development. We propose three specific aims—Aim 1. Determine how IPMK gene dosage affects the extent of SI-NET in mice. The histo-pathological, immuno-histochemical, and biochemical analysis will be performed to understand how hetero and homozygous loss of IPMK affects intestinal homeostasis and the extent of SI-NET generation in an age dependent manner. Aim 2. To determine if IPMK is necessary and sufficient to enhance cell proliferation and cell cycle regulation. Cell biological and flow-cytometric analysis will be performed to understand the critical function of IPMK in regulating cell proliferation and apoptosis. Aim 3. Determine if p53 is necessary for IPMK signaling-induced apoptosis and cell cycle arrest.