DEREGULATION OF ONCOGENE EXPRESSION IN HUMAN TUMORS

该提案的长期目标是阐明 两类放松管制机制的重要性 人类肿瘤中的癌基因；也就是说，原型中的突变 癌基因本身（顺式作用）和反式作用的突变 监管机构。 研究重点是 c-myc，因为该基因 在许多不同类型的人类肿瘤中表达。 什么是 c-myc 表达在这些肿瘤中的重要性？ 表达式为 推测是由于影响 myc 调节的突变所致 电路。 有哪些不同类型的突变具有这种特征 效果？ 该提案的目的包括分析顺式 来自人类的两个不同 myc 位点克隆的作用改变 肿瘤。 在一种情况下，一个 LINE-1 序列（一系列序列之一） 重复转座因子存在于数千个拷贝中 人类基因组）已被插入到 myc 的内含子 2 中。 的 插入是肿瘤特异性的。 插入将被克隆并 对增强子元件的存在进行测序和分析 编码参与该过程的蛋白质的能力 换位。 研究中的第二个基因座产生 myc 信息 其水平比正常白细胞高 50 倍。 该位点包含多个删除、插入、重复， 和点突变。 这些像差的确切作用 放松管制将由 e 决定。 这样做的第二个目标 提案是分析导致的交易改变 三分之二的人类腺癌中 c-myc 的失调 冒号。 使用细胞间体细胞杂交的实验 表达受调节的 c-myc 和表达的结肠癌细胞 myc 失调导致 myc 受到调节的杂交细胞 通常。 基于此结果的工作假设 实验发现，结肠癌细胞的基因缺陷 亲本已使反式作用基因座的两个等位基因失活 调节 myc（例如阻遏蛋白）并且缺陷是 由亲本表达调节的完整基因座补充 myc。 这些实验将被用来确定有多少这样的 可能存在反式作用基因座，它们映射的人类染色体是什么 这些病变的分子机制是什么 位点导致 c-myc 失调。 这项工作最终可能会 具有临床意义，因为这些的正常等位基因 基因可以通过克隆并提供给肿瘤细胞 使用合适的载体，例如逆转录病毒。 通过使用 这种“基因移植疗法”改变了表型 肿瘤细胞可能会被逆转。

The long range objective of this proposal is to elucidate the importance of two classes of mechanisms of deregulation of proto- oncogenes in human tumors; that is, mutations in the proto- oncogenes itself (cis-acting) and mutations in trans-acting regulators. The studies focus on c-myc because this gene is expressed in many different types of human tumors. What is the importance of c-myc expression in these tumors? The expression is presumed to be due to mutation that affect the myc regulatory circuit. What are the different types of mutations that have this effect? The aims of this proposal include an analysis of cis- acting alterations in two different myc loci clones from human tumors. In one case, a LINE-1 sequence (one of a family of repetitive transposable elements present in thousands of copies in the human genome) has become inserted into intron 2 of myc. The insertion is tumor specific. The insertion will be cloned and sequenced and analyzed for the presence of enhancer elements and for the capacity to code for proteins involved in the process of transposition. The second locus under study produces myc message levels 50 times greater than those found in normal leukocytes. The locus contains multiple deletions, insertions, duplications, and point mutations. The exact role of each of these aberrations in the deregulation will e determine. A second aim of this proposal is to analyze trans-acting alterations that result in deregulation of c-myc in two thirds of human adenocarcinomas of the colon. Experiments employing somatic cell hybrids between cells expressing regulated c-myc and colon carcinoma cells expressing deregulated myc result in hybrid cells in which myc is regulated normally. A working hypothesis, based on the results of this experiments, is that genetic defects in the colon carcimona cell parent have inactivated both alleles of a trans-acting locus that regulates myc (such as a repressor) and that the defects are complemented by an intact locus in the parent expressing regulated myc. These experiments will be pursued to determine how many such trans-acting loci there might be, what human chromosomes they map to, an what the molecular mechanism is by which lesions in these loci result in deregulation of c-myc. This work might ultimately have clinical significance in that the normal alleles of these genes could be cloned and supplied to the tumor cells through the use of suitable vectors such aS retroviruses. Through the use of such "gene transplant therapy" the transformed phenotype of the tumor cells might be reversed.