in vitro manipulation of genes relevant to oncogenesis

我们已经建立了结肠癌细胞株，其中突变的K-ras基因被正常的K-ras基因，使用同源重组。这些细胞系和亲本细胞系之间的比较分析使得直接评估突变的K-ras基因在肿瘤发生中的作用成为可能。与亲本细胞株相比，缺失突变K-ras基因表达的细胞株在血清刺激下可显著诱导C-fos和C-jun的表达，并抑制血管内皮生长因子（VEGF）的产生。这些结果提示K-ras基因突变可能参与了早期基因表达的抑制和VEGF的产生，我们的研究方法可用于阐明其他癌基因和抑癌基因突变在肿瘤发生中的作用。

We have established the colon cancer cell lines in which the mutated K-ras gene was replaced by the normal K-ras gene, using homologous recombination. The comparative analyzes between these cell lines and the parental cell lines made it feasible to directly assess the role of the mutated K-ras gene in oncogenesis. As compared with the parental cell lines, the cell lines which lack the expression of the mutated K-ras gene showed the remarkable induction of C-fos and C-jun expression by the serum stimulation and the suppression of vascular endothelial growth factor (VEGF) production. These observations indicate that the mutated K-ras gene is involved in the suppression of the immediate early genes expression and the production of VEGF.Our strategy could be applied to clarify the role of the mutation in other oncogenes and tumor suppressor genes in oncogenesis.