Deregulation of CTCF in Epigenetic Gene Silencing in Human Cancers

CTCF 在人类癌症表观遗传基因沉默中的失调

• 批准号: 8107910
• 负责人: Beverly Marie Emerson
• 金额: $ 39.53万
• 依托单位: SALK INSTITUTE FOR BIOLOGICAL STUDIES
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8107910
• 关键词: Binding; Biochemical; Biological Models; Boundary Elements; Breast; Breast Cancer Cell; CCCTC-binding factor; CDH1 gene; CDKN2A gene; Cancer cell line; Cancerous; Cell Line; Cells; Chromatin; Chromosome Territory; Chromosome abnormality; Co-Immunoprecipitations; Complex; DNA; Defect; Disease; Dissociation; Epigenetic Process; Epithelial Cells; Event; Exhibits; Gene Expression; Gene Expression Regulation; Gene Silencing; Genes; Genetic; Genetic Transcription; Genomics; Growth; Heterochromatin; Human; Hypermethylation; Immunoblotting; Lead; Malignant Neoplasms; Mammary gland; Mass Spectrum Analysis; Mediating; Modeling; Modification; Molecular; Molecular Chaperones; Multiple Myeloma; Pattern; Post-Translational Protein Processing; Proteins; Regulation; Role; Staging; Structure; System; T47D; Telomere Shortening; Tumor Suppressor Genes; Variant; age related; base; breast tumorigenesis; cancer cell; carcinogenesis; gene function; insight; malignant breast neoplasm; nucleolin; programs; protein complex; public health relevance; research study; restoration; small hairpin RNA; uncontrolled cell growth

DESCRIPTION (provided by applicant): Project Summary. Silencing of tumor suppressor genes by epigenetic deregulation is a common occurrence in human malignancies. We find that loss of CTCF-dependent chromatin boundaries, which protects genes from adjacent heterochromatin domains, results in transcriptional inactivation of the p16INK4a tumor suppressor gene, which is a frequent target of epigenetic silencing in many types of human cancers and considered to be an early event in breast carcinogenesis. Loss of CTCF binding also correlates with hypermethylation and silencing of two other tumor suppressor genes, RASSF1A and CDH1, in breast cancer cell lines. CTCF dissociation from the boundary elements of these tumor suppressor genes results from defective poly(ADP-ribosyl)ation of CTCF, which abrogates its proper function. In this proposal, we plan to use primary human mammary epithelial cells (HMECs) to analyze the role of CTCF in molecular aberrations that initiate breast tumorigenesis. In this system, distinct subpopulations of cells emerge from normal HMECs that have overcome barriers to indefinite growth. The first barrier exhibited by "variant" HMECs coincides with p16 gene silencing followed by increasing epigenetic plasticity and chromosomal aberrations similar to those observed in early human breast cancers. Our specific aims are to: characterize native CTCF protein complexes from HMECs and p16-silenced vHMECs using biochemical approaches (Aim 1); examine the basis of defective CTCF PARlation in vHMECs using cell- based (Aim 2) [and biochemical studies (Aim 3)]; and [analyze the role of CTCF protein complexes in p16 gene regulation (Aim 4).] We postulate that destabilization of specific chromosomal boundaries by dysfunctional CTCF complexes may be an initiating event in the genesis of human breast cancers by early inactivation of critical tumor suppressor genes and loss of normal genomic patterns of epigenetic regulation. PUBLIC HEALTH RELEVANCE: Public Health Relevance. The genetic information in all human cells is highly organized into distinct territories by chromosomal "boundaries" that when breached, can lead to loss of gene function and potentially uncontrolled cell growth as observed in cancer and many age-related diseases. In this proposal, we will investigate the underlying cause of chromosomal disorganization and ways to therapeutically reverse this defect to restore normal gene regulation in human cancer cells.

描述（由申请人提供）： 项目摘要。通过表观遗传失调而沉默肿瘤抑制基因在人类恶性肿瘤中很常见。我们发现，CTCF 依赖性染色质边界的丢失（保护基因免受相邻异染色质域的影响）会导致 p16INK4a 肿瘤抑制基因的转录失活，该基因是许多类型人类癌症中表观遗传沉默的常见目标，并被认为是乳腺癌发生的早期事件。 CTCF 结合的丧失还与乳腺癌细胞系中另外两个肿瘤抑制基因 RASSF1A 和 CDH1 的高甲基化和沉默相关。 CTCF 与这些抑癌基因边界元件的解离是由于 CTCF 的聚（ADP-核糖基）化缺陷造成的，从而消除了其正常功能。在本提案中，我们计划使用原代人乳腺上皮细胞（HMEC）来分析 CTCF 在引发乳腺肿瘤发生的分子畸变中的作用。在这个系统中，正常的 HMEC 中出现了不同的细胞亚群，这些细胞已经克服了无限生长的障碍。 “变体”HMEC 表现出的第一个障碍与 p16 基因沉默同时发生，随后表观遗传可塑性和染色体畸变增加，类似于在早期人类乳腺癌中观察到的情况。我们的具体目标是： 使用生化方法表征来自 HMEC 和 p16 沉默的 vHMEC 的天然 CTCF 蛋白复合物（目标 1）；使用基于细胞的（目标 2）[和生化研究（目标 3）] 检查 vHMEC 中 CTCF PARlation 缺陷的基础；并[分析 CTCF 蛋白复合物在 p16 基因调控中的作用（目标 4）。]我们假设功能失调的 CTCF 复合物导致的特定染色体边界的不稳定可能是人类乳腺癌发生的起始事件，其原因是关键肿瘤抑制基因的早期失活和表观遗传调控的正常基因组模式的丧失。 公共卫生相关性： 公共卫生相关性。所有人类细胞中的遗传信息都通过染色体“边界”高度组织成不同的区域，一旦突破，就会导致基因功能丧失，并可能导致细胞生长失控，正如在癌症和许多与年龄相关的疾病中所观察到的那样。在这项提案中，我们将研究染色体紊乱的根本原因以及治疗性逆转这种缺陷以恢复人类癌细胞中正常基因调控的方法。