INTRACELLULAR MECHANISMS OF TUMOR PROMOTION

肿瘤促进的细胞内机制

• 批准号: 6341878
• 负责人: BRUCE E. MAGUN
• 金额: $ 31.13万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1984
• 资助国家: 美国
• 起止时间: 1984-07-01 至 2001-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6341878
• 关键词: DNA binding protein; DNA footprinting; calcium; cellular oncology; cycloheximide; endothelin; enzyme activity; gel mobility shift assay; gene expression; gene induction /repression; genetic enhancer element; intermolecular interaction; intracellular; messenger RNA; mitogen activated protein kinase; phosphorylation; protein biosynthesis; protein kinase; regulatory gene; thapsigargin; tissue /cell culture; transcription factor; tumor promoters

The ability of tumor promoters to stimulate clonal selection and outgrowth of initiated cell populations is generally attributed to their ability to induce a coordinated change in the expression of various immediate early genes associated with cell proliferation. We have shown that both the phorbol ester tumor promoter 12-0-tetradecanoyl-phorbol acetate and the sesquiterpene tumor promoter thapsigargin can effect the coordinate regulation of immediate early genes including c-fos and the endogenous murine retrovirus VL30. Although proximal targets have been identified for several major classes of tumor promoters, the precise pathways by which disparate tumor promoters act to inhibit the Ca2 plus -ATPase of the endoplasmic reticulum. However, it is not known how this aberration of calcium homoestasis is transduced into induction of c-fos and VL30. In our progress report, we present data indicating that thapsigargin treatment results in an inhibition of protein synthesis, which is associated with decreased MAP kinase phosphatase (MKP-1) activity and increased activation of the stress-activated protein kinases SAPK/JNK and p38/HOG1. Based on these observations, we hypothesize that treatment with thapsigargin results in the activation of protein kinase R (PKR), which phosphorylates eIF2 alpha. Phosphorylation of elF2 alpha results in a block to translation initiation, and decreased synthesis of MKP-1. Loss of MKP-1 results in increased activation of MAP kinases, and this leads to increased phosphorylation of the transcription factor Elk-1 and induction of c-fos mRNA. We propose to test the applicability of this model to calcium-dependent induction of VL30 and c-fos. We plan to identify the transcription factors responsible for induction of VL30. We will also characterize the role of CBF/A, a putative negative regulator of VL30 expression which acts via the VL30 CArG element. Since the c-fos promoter bears significant sequence similarity to the VL30 enhancer, including the presence of a CArG motif, we will determine whether CBF/A and other modulators of VL30 enhancer, including the presence of a CArG motif, we will determine whether CBF/A and other modulators of VL30 expression can also modulate c-fos expression. The role of a PKR-dependent pathway in mediating the response to thapsigargin will be determined for both VL30 and c-fos. These experiments will include determination of possible PKR-dependent changes in the phosphorylation and activation of the transcription factor(s) operating on the promoters for these two genes. The research described in this proposal will provide new insight into the molecular mechanisms by which tumor promoters cause coordinated changes in the expression of proliferation-associated genes.

肿瘤启动子刺激克隆选择和产物的能力 通常的细胞群体通常归因于它们的能力 引起各种立即表达的协调变化 与细胞增殖相关的基因。 我们已经证明了这两个 Phorbol酯肿瘤启动子12-0-四烷酰基 - 乙酸酯和 倍苯二酚肿瘤启动子Thapsigargin可以影响坐标 调节包括C-FOS和内源性在内的直接早期基因 鼠逆转录病毒VL30。 尽管已经确定了近端目标 几个主要类别的肿瘤启动子，这是确切的途径 不同的肿瘤启动子起作 内质网。 但是，尚不知道这种畸变是如何 钙均转化为C-FOS和VL30的诱导。 在我们的进度报告中，我们提供了指示Thapsigargin的数据 治疗导致抑制蛋白质合成，即 与MAP激酶磷酸酶（MKP-1）活性降低相关，并且 增加应力激活蛋白激酶SAPK/JNK的激活增加 p38/hog1。 基于这些观察，我们假设 Thapsigargin导致蛋白激酶R（PKR）的激活，这 磷酸化EIF2α。 ELF2α的磷酸化导致A 块到翻译起始，并减少MKP-1的合成。 损失 MKP-1的of导致MAP激酶的激活增加，这导致 转录因子ELK-1和诱导的磷酸化增加 c-fos mRNA。 我们建议测试该模型对 VL30和C-FOS的钙依赖性诱导。 我们计划确定 负责诱导VL30的转录因子。 我们也会 表征CBF/A的作用，VL30的假定负调节器 通过VL30 CARG元件起作用的表达。 由于C-Fos启动子 具有与VL30增强器的显着序列相似性，包括 存在carg图案，我们将确定CBF/A和其他 VL30增强器的调节剂，包括Carg主题的存在，我们 将确定CBF/A和VL30表达式的其他调节器是否可以 还调节C-FOS表达。 PKR依赖性途径在 介导对Thapsigargin的反应将确定VL30和 c-fos。 这些实验将包括确定可能的 PKR依赖性变化的磷酸化和激活的变化 这两个基因在启动子上运行的转录因子。 本提案中描述的研究将为您提供新的见解 肿瘤启动子引起协调变化的分子机制 增殖相关基因的表达。