MEMBRANE SIGNAL TRANSDUCTION IN TUMOR PROMOTION

这些研究的目标是确定所需的生化事件 发生在肿瘤启动子-受体相互作用和激活之间 肿瘤转化的效应因子。候选人第二信使 包括蛋白激酶C(PKC)和蛋白激酶C调节蛋白磷酸化 基因表达的反式激活。推测的C-激酶底物为80 KDA已被发现存在差异的磷酸化 抗促进(P-)、敏感(P+)和肿瘤转化 JB6小鼠表皮细胞，很少或没有磷酸化的80 kDa 转化细胞中可见的磷酸蛋白(Pp80)。西方分析表明 这种p8O在合成水平上被调节，只有很少的或没有p8O 在转化的JB6细胞中可检测到的蛋白质。P8O的cDNA克隆具有 最近通过用p80抗体筛选JB6 P文库而被分离出来。 当用作探针时，该p80cDNA检测到一个2.8kb的RNA，该RNA 在从P-到转换(TX)的过程中逐渐递减 表型。与GenBank相比，该序列显得很新颖。我们 将检验p8O作为肿瘤抑制因子发挥作用的假设。近期 12-0-十四酰-佛波醇-13-乙酸酯(TPA)诱导基因的研究 关注那些受反式作用转录因子AP-1调控的基因 (Jun/Fos Complex)。肿瘤促进剂TPA和表皮生长因子 表皮生长因子(EGF)可诱导P+细胞AP-1调节的基因表达，但不能诱导P-JB6细胞表达AP-1。 这表明AP-1调节的基因表达(1)可能是 肿瘤启动子诱导的转化；以及(2)可能由 在P+细胞中发现激活的前基因，但在P-细胞中未发现。支持这一观点的证据 前基因的作用来自于观察到在转染的P细胞中 激活PRO-1后，细胞同时获得P+表型和AP-1 反式激活反应。差异反式激活的机制 由TPA引起的c-jun的基础和诱导水平似乎不同 MRNA和Jun蛋白。EGF后未发现c-jun差异。 提示TPA和EGF可诱导AP-1依赖 通过不同途径反式激活基因表达。

The goal of these studies is to determine the required biochemical events that occur between tumor promoter-receptor interaction and the activation of effectors of neoplastic transformation. Candidate second messengers include protein phosphorylation by protein kinase C (PKC) and PKC-regulated trans-activation of gene expression. A putative C-kinase substrate of 80 kDa has been found to be differentially phosphorylated in promotion-resistant (P-), -sensitive (P+), and neoplastically transformed JB6 mouse epidermal cells, with little or no phosphorylated 80-kDa phosphoprotein (pp8O) seen in transformed cells. Western analysis indicates that p8O is regulated at the level of synthesis with little or no p8O protein detectable in transformed JB6 cells. A cDNA clone of p8O has recently been isolated by screening a JB6 P- library with p8O antibody. This p8O cDNA, when used as a probe, detects a 2.8-Kb RNA that progressively decreases during the progression from P- to transformed (Tx) phenotype. When compared with GenBank the sequence emerges as novel. We will test the hypothesis that p8O functions as a tumor suppressor. Recent studies on 12-0-tetradecanoyl-phorbol-13-acetate (TPA)-inducible genes have focused on those regulated by the trans-acting transcriptional factor AP-1 (Jun/Fos Complex). The tumor promoters TPA and epidermal growth factor (EGF) induce AP-1-regulated gene expression in P+ but not P- JB6 cells. This indicates that AP-1-regulated gene expression (1) may be required for tumor promoter-induced transformation; and (2) may be controlled by activated pro genes found in P+ but not P- cells. Evidence favoring such a role for pro genes comes from the observation that in P-cells transfected with activated pro 1, the cells acquire both P+ phenotype and AP-1 trans-activation response. The mechanism of differential trans-activation by TPA appears to involve differential basal and induced levels of c-jun mRNA and Jun protein. A c-jun differential was not found after EGF treatment thus suggesting that TPA and EGF induce AP-1-dependent trans-activation of gene expression by different pathways.