DEREGULATION OF ONCOGENE EXPRESSION IN HUMAN TUMORS

本建议的长远目标是阐明 两类机制的重要性解除管制的原， 人类肿瘤中的癌基因;也就是说，原癌基因中的突变， 癌基因本身（顺式作用）和反式作用突变 监管部门 这些研究集中在c-myc上，因为这个基因是 在许多不同类型的人类肿瘤中表达。 是什么 c-myc表达在这些肿瘤中的重要性？ 表情 推测是由于突变影响myc调节 电路. 有哪些不同类型的突变 效果？ 本建议的目的包括分析顺- 人两个不同myc基因座克隆的作用改变 肿瘤的 在一种情况下，LINE-1序列（LINE-1家族中的一个）可以被插入。 重复的转座因子存在于数千个拷贝中， 人类基因组）已经插入到myc的内含子2中。 的 插入是肿瘤特异性的。 插入将被克隆， 测序并分析增强子元件的存在， 编码蛋白质的能力 换位 研究中的第二个位点产生myc信息 比正常白细胞高50倍。 该基因座包含多个缺失，插入，重复， 和点突变 这些畸变的确切作用 放松管制的程度将由我们决定。 第二个目的是 建议是分析导致 在三分之二的人乳腺癌中c-myc的失调 结肠 使用细胞间体细胞杂交的实验 表达调控的c-myc和表达调控的c-myc的结肠癌细胞 myc的失调导致了myc受到调节的杂交细胞 正常情况下 一个工作假设，基于这个结果， 实验表明，结肠癌细胞中的遗传缺陷 亲本已经失活了反式作用基因座的两个等位基因， 调节myc（如阻遏物），缺陷是 由亲本中表达受调节的 Myc。 这些实验将继续进行，以确定有多少这样的 可能存在的反式作用基因座，它们绘制的人类染色体 这些病变的分子机制是什么 基因座导致c-myc的失调。 这项工作最终可能 具有临床意义，因为这些正常等位基因 基因可以被克隆，并通过 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”是指通过基因移植治疗， 肿瘤细胞可以逆转。

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.