ROLE OF EDR3 IN NORMAL DEVELOPMENT AND TUMORIGENESIS

EDR3 在正常发育和肿瘤发生中的作用

• 批准号: 6806554
• 负责人: MARC F HANSEN
• 金额: $ 34.94万
• 依托单位: UNIVERSITY OF CONNECTICUT SCH OF MED/DNT
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-29 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6806554
• 关键词: 3T3 cells; carcinogenesis; cell differentiation; cell growth regulation; clinical research; flow cytometry; gel mobility shift assay; gene deletion mutation; human genetic material tag; human tissue; immunofluorescence technique; immunoprecipitation; mass spectrometry; mesenchyme; neoplasm /cancer genetics; northern blottings; osteoblasts; osteosarcoma; polymerase chain reaction; southern blotting; stem cells; tumor suppressor genes; western blottings

DESCRIPTION (provided by applicant): We identified Early Developmental Regulator 3 (EDR3), as a candidate tumor suppressor gene in a screen of a region of human chromosome 3q26 previously shown to undergo LoH in osteosarcoma. We found intragenic deletions in the EDR3 gene consistent with a tumor suppressor etiology in osteosarcoma primary tumors and tumor cell lines. Examination of the expression pattern of EDR3 revealed that both mRNA and protein showed a near ubiquitous pattern of expression in adult and embryonic tissues. EDR3 is a homolog of the Drosophila Polyhomeotic gene and a member of the Polycomb Group (PcG) family of proteins. The PcG family of proteins acts as long-term repressors by contributing to the formation and stable transmission of heterochromatin. By co-immunoprecipitation, we found that the EDR3 protein was bound to E2F6, Bmi1, YY1 and M33 but not pRB1 or CtBP. This suggested that EDR3 was part of a previously described human Polycomb repressive complex (hPRC-H), which contains E2F6 and is active in G0. Consistent with this observation, we found that as cells entered G0, EDR3 localization in the nucleus changed from a diffuse to a highly punctuate pattern. This shift coincided with the ability of the EDR3-containing complex to bind to YY1 and E2F DNA-binding sites and to the c-myc promoter. When we tested co-localization of EDR3 with E2F6 and Bmi1, we found that the shift to a punctuate pattern of localization as the cells entered G0, was shared by EDR3 and E2F6 but not Bmi1. We found that EDR3 was affected in >70% of osteosarcoma tumors. Examination of other tumors showed that EDR3 protein was absent in other tumors suggesting that this could be a checkpoint, which is commonly lost in tumorigenesis. Consistent with this model, we found that EDR3 could act as a growth suppressor when overexpressed in normal cells, or when inducibly expressed in tumor cells. Our hypothesis is that the EDR3 protein acts as part of a repressor complex to regulate long-term maintenance of G0 in developing osteoblasts and mesenchymal stem cells. A corollary hypothesis is that loss of EDR3 function in osteoblast progenitor cells could lead to a loss of the ability to maintain G0 and thus favor tumorigenesis. To test our hypotheses, we propose the following specific aims: 1) To examine the role of EDR3 in osteosarcoma tumorigenesis and osteoblastic differentiation; 2) To characterize the components of the PcG complex containing EDR3 and E2F6; and 3) To identify the targets of EDR3 regulation.

描述（由申请人提供）：我们确定了早期发育调节剂3（EDR3），是候选肿瘤抑制基因，在先前显示在骨肉瘤中经历LOH的人类染色体3q26区域的筛选中。我们在EDR3基因中发现了与骨肉瘤原发性肿瘤和肿瘤细胞系中肿瘤抑制病学一致的基因内缺失。对EDR3的表达模式的检查表明，mRNA和蛋白质在成年和胚胎组织中均显示出近乎无处不在的表达模式。 EDR3是果蝇多瘤基因的同源物，也是Polycomb组（PCG）蛋白质家族的成员。 PCG蛋白质家族通过促进异染色质的形成和稳定传播来充当长期阻遏物。通过共免疫沉淀，我们发现EDR3蛋白与E2F6，BMI1，YY1和M33结合，而不是PRB1或CTBP。这表明EDR3是先前描述的人Polycomb抑制复合物（HPRC-H）的一部分，该复合物（HPRC-H）包含E2F6，并且在G0中活跃。与该观察结果一致，我们发现，随着细胞进入G0，EDR3在细胞核中的定位从弥漫性变为高度点状的模式。这种转移与含EDR3的复合物与YY1和E2F DNA结合位点以及C-MYC启动子结合的能力一致。当我们测试EDR3与E2F6和BMI1的共定位时，我们发现，随着输入G0的细胞，转向标点的定位模式，EDR3和E2F6共享，而不是BMI1。我们发现EDR3在> 70％的骨肉瘤肿瘤中受到影响。对其他肿瘤的检查表明，其他肿瘤中没有EDR3蛋白，这表明这可能是一个检查点，通常在肿瘤发生中丢失。与该模型一致，我们发现在正常细胞中过表达或在肿瘤细胞中诱导表达时，EDR3可以作为生长抑制剂。我们的假设是，EDR3蛋白充当阻遏物复合物的一部分，以调节开发成骨细胞和间质干细胞中G0的长期维持。推论假设是成骨细胞祖细胞中EDR3功能的丧失可能导致维持G0的能力丧失，从而有利于肿瘤发生。为了检验我们的假设，我们提出了以下特定目的：1）检查EDR3在骨肉瘤肿瘤发生和成骨细胞分化中的作用； 2）表征包含EDR3和E2F6的PCG复合物的组件； 3）确定EDR3调节的目标。