IDENTIFICATION OF TARGET GENES FOR ETS-1 GENE PRODUCT

在静息T细胞中，ETS 1基因以高水平表达， 活化T细胞，ETS 1基因产物降低到低水平， 这表明ETS 1可能在分化中起主导作用， 停止细胞生长。 为了确定ETS 1基因产物是否具有任何 肿瘤抑制活性，人ETS 1表达载体是 转染到人结肠癌细胞系DLD-1中，其显示没有 ETS 1的可检测表达。 我们获得了五个独立的细胞系， 在不同水平表达ETS 1。 这些转染子显示出减少的 软琼脂和裸鼠集落形成试验中的致瘤性 测定。 致瘤性的抑制程度取决于 1级。 由于ETS 1在NIH/3 T3细胞中的过表达， 显示出增加致瘤性，似乎致癌和抗- 由ETS 1显示的致癌活性依赖于细胞类型。 使用二维凝胶的Western印迹分析，我们已经鉴定了 在一个转染细胞系中角蛋白8（K8）蛋白减少 表达丰富的ETS 1。 K8 mRNA的水平没有改变之间的 转染子和对照细胞系。 实验正在进行中， 描述K8水平降低的机制， 鉴定结肠癌细胞中ETS 1的推定靶基因。

In resting T-cells, the ETS1 gene is expressed at high levels and, upon activation of T-cells, ETS1 gene products are decreased to low levels, suggesting that ETS1 may play a dominant role in differentiation and cessation of cell growth. To identify if ETS1 gene products have any tumor-suppressive activity, the human ETS1 expression vector was transfected into the human colon cancer cell line, DLD-1, which shows no detectable expression of ETS1. We obtained five independent cell lines expressing ETS1 at different levels. These transfectants showed reduced tumorigenicity in colony formation assays in soft agar and in nude mice assays. The degree of suppression of tumorigenicity was dependent on the levels of ETS1. Since overexpression of ETS1 in NIH/3T3 cells has been shown to increase tumorigenicity, it appears that the oncogenic and anti- oncogenic activities displayed by ETS1 are dependent on the cell types. Using Western blot analysis of a two-dimensional gel, we have identified a decrease of keratin 8 (K8) protein in one transfectant cell line expressing abundant ETS1. Levels of K8 mRNA did not change between the transfectant and control cell lines. Experiments are in progress to characterize the mechanisms involved in a decrease of K8 levels and to identify putative target genes for ETS1 in colon cancer cells.