Transcriptional Repression of MMP7 by FXR in Intestinal Epithelial Cells

 描述（由申请人提供）： 结肠癌仍然是退伍军人发病和死亡的主要原因，因为转移性疾病的治疗效果有限。我们的长期目标是通过靶向结肠癌进展背后的关键信号转导分子来开发创新，有效和安全的疗法。法尼醇X受体（FXR），胆汁酸激活转录因子的核受体超家族成员，似乎是这样一个关键分子。FXR是一种肿瘤抑制因子，其在结肠癌中的表达显著降低;在肠肿瘤形成的啮齿动物模型中，FXR缺乏会增加腺瘤的大小和数量。FXR调节细胞增殖、凋亡和Wnt信号传导，但其肿瘤抑制作用的分子机制尚不完全清楚。我们的短期目标是填补这一知识空白。最近，我们进行了开创性的观察，基质金属蛋白酶7（MMP 7）是FXR的靶基因。MMP 7是一种降解细胞外基质的胶原酶，在大多数结肠肿瘤中过表达，并增强细胞增殖、肿瘤侵袭和转移。我们的初步数据表明，FXR是MMP7的转录抑制因子;在正常肠和结肠癌中，FXR水平降低与MMP7表达增加相关。此外，我们发现在人结肠癌细胞中激活FXR会减弱MMP 7的表达，以及异种移植物的生长和侵袭。基于这些新的发现，我们提出了范式转移的中心假设，即FXR激活通过抑制MMP 7基因转录来抑制结肠癌的进展。为了验证这一假设，我们提出了三个具体目标：目标1。检验FXR是MMP 7的直接转录阻遏物的假设，并鉴定MMP 7 FXR反应元件。目标2.测试激活肠道FXR选择性下调MMP 7表达，从而抑制体内肿瘤生长的假设。目标3：检验中和抗MMP 7抗体在体内减弱结肠癌进展的假设。总体影响：我们将揭示FXR作为MMP 7转录抑制因子的新作用，并确定FXR抑制结肠癌细胞增殖和疾病进展的新机制。此外，我们将证明使用fexaramine（一种精氨酸选择性FXR激动剂）进行化疗预防和使用抗MMP 7抗体治疗晚期疾病的临床潜力。

 DESCRIPTION (provided by applicant): Colon cancer remains a leading cause of morbidity and mortality in Veterans because therapy for metastatic disease has limited efficacy. Our long-term goal is to develop innovative, effective, and safe therapies by targeting pivotal signal transduction molecules underlying colon cancer progression. The Farnesoid X Receptor (FXR), a member of the nuclear receptor superfamily of bile acid-activated transcription factors, appears to be such a pivotal molecule. FXR is a tumor suppressor whose expression is strikingly reduced in colon cancer; in rodent models of intestinal neoplasia FXR deficiency increases adenoma size and number. FXR regulates cell proliferation, apoptosis, and Wnt signaling but the molecular mechanisms underlying its tumor-suppressive actions are incompletely understood. Our short-term goal is to fill this gap in knowledge. Recently, we made the seminal observation that matrix metalloproteinase 7 (MMP7) is an FXR target gene. MMP7, a collagenase that degrades extracellular matrix, is over-expressed in most colon tumors and enhances cell proliferation, tumor invasion, and metastasis. Our preliminary data show that FXR is a transcriptional repressor for MMP7; decreased FXR levels correlate with increased MMP7 expression in normal intestine and colon cancer. Also, we found that activating FXR in human colon cancer cells attenuates MMP7 expression, as well as xenograft growth and invasion. Based on these novel findings we propose the paradigm-shifting central hypothesis that FXR activation inhibits colon cancer progression by repressing MMP7 gene transcription. To test this hypothesis we propose three Specific Aims: Aim 1. Test the hypothesis that FXR is a direct transcriptional repressor of MMP7 and identify the MMP7 FXR responsive element. Aim 2. Test the hypothesis that activating intestinal FXR selectively down-regulates MMP7 expression, thereby inhibiting tumor growth in vivo. Aim 3. Test the hypothesis that neutralizing anti-MMP7 antibody attenuates colon cancer progression in vivo. Overall impact: We will reveal a novel role for FXR as a transcriptional repressor of MMP7 and identify a new mechanism whereby FXR suppresses colon cancer cell proliferation and disease progression. Moreover, we will demonstrate the clinical potential of using fexaramine, an intestine-selective FXR agonist, for chemo- prevention and anti-MMP7 antibody for advanced disease.