Mechanisms of RASSF1A tumor suppressor gene inactivation by de novo methylation of the promoter CpG island during carcinogenesis

表观遗传沉默导致的肿瘤抑制基因失活很可能是体细胞中癌症形成的主要原因。然而，责任机制仍然没有解决。我们希望阐明肿瘤病变中表观遗传沉默的分子机制。在我们以前的研究中，我们已经鉴定并克隆了一个新的肿瘤抑制基因RASSF1A（Ras ASociation domain Family 1A），它与哺乳动物的Ras效应子具有同源性。RASSF1A在很大比例的人类癌症中表观遗传学失活。RASSF1A表达缺失是肺癌和其他实体瘤发病机制中最常见和最早的事件之一。我们希望揭示肿瘤发生过程中RASSF1A表观遗传失活的机制。因此，我们将建立一个细胞培养模型来研究从头甲基化的机制。人乳腺上皮细胞将在引起基因组变化的条件下生长。我们将研究RASSF1基因的染色质结构、DNA复制、RNA表达和甲基化模式的变化。将用致癌物处理细胞，并测试对RASSF1A表达的表观遗传沉默效应。了解癌症中表观遗传失活的分子机制可能会导致治疗癌症和其他由基因失调引起的疾病的新药物和方法。

Inactivation of tumor suppressor genes by epigenetic silencing is most likely the main cause of cancer formation in somatic cells. Still the responsible mechanisms remain unsolved. We want to elucidate the molecular mechanisms of epigenetic silencing in neoplastic lesions. In our previous studies, we have identified and cloned a new tumor suppressor gene named RASSF1A (Ras ASSociation domain Family 1A), which has homology to a mammalian Ras effector. RASSF1A is epigenetically inactivated in a large percentage of human carcinomas. Loss of RASSF1A expression is one of the most common and earliest events in the pathogenesis of lung cancer and other solid tumors. We want to reveal the mechanisms of epigenetic inactivation of RASSF1A during tumorigenesis. Therefore we will create a cell culture model to examine the mechanism of de novo methylation. Human mammary epithelial cells will be grown under conditions, which cause genomic changes. We will examine changes in chromatin structure, DNA replication, RNA expression and methylation pattern of the RASSF1 gene. Cells will be treated with carcinogens and the epigenetic silencing effect on RASSF1A expression will be tested. Understanding the molecular mechanisms of epigenetic inactivation in cancer may lead to novel drugs and methods for the cure of cancer and other diseases brought on by gene misregulation.