Olah E, Kote Z, Natsumeda Y, Yamaji Y, Jarai G, Lapis E, Financsek I, Weber G
Department of Molecular Biology, National Institute of Oncology, Budapest, Hungary.
Cancer Biochem Biophys. 1990 Apr;11(2):107-17.
There was an overexpression of the c-myc gene (11-fold) and of the c-Ha-ras gene (2-fold) in rat hepatoma 3924A cells compared to normal rat liver as measured by dot-blot analysis of total cytoplasmic RNA. The overexpression of c-myc was attributed to a 10- to 14-fold amplification and rearrangement of the c-myc sequences as determined by Southern blot analysis. The expression of the c-myc also was dependent upon the proliferative state of the hepatoma cells. Tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide; NSC 286193), an inhibitor of the activity of IMP dehydrogenase (EC 1.1.1.205), the rate-limiting enzyme of GTP biosynthesis, resulted in a rapid drop (less than 1 h) to 50% of control in the target enzyme activity in the hepatoma cells and in a subsequent marked decrease to 55% in GTP concentration. These events were followed at 12 h of tiazofurin treatment by a 3-fold reduction in the expression of the c-myc gene and a 9-fold decline in that of the c-Ha-ras gene. These results in the hepatoma cells provide evidence in support of the earlier demonstrated correlation in K562 cells between GTP concentration and expression of c-myc and c-ras genes (Olah et al., 1989). These genes might depend on GTP for their expression in hepatoma cells and they might cooperate in a signal pathway that controls cell proliferation.
通过对总细胞质RNA进行斑点印迹分析，与正常大鼠肝脏相比，大鼠肝癌3924A细胞中的c-myc基因（11倍）和c-Ha-ras基因（2倍）存在过表达。通过Southern印迹分析确定，c-myc的过表达归因于c-myc序列10至14倍的扩增和重排。c-myc的表达也取决于肝癌细胞的增殖状态。替唑呋林（2-β-D-呋喃核糖基噻唑-4-甲酰胺；NSC 286193）是一种肌苷酸脱氢酶（EC 1.1.1.205）活性的抑制剂，肌苷酸脱氢酶是GTP生物合成的限速酶，它导致肝癌细胞中靶酶活性迅速下降（不到1小时）至对照的50%，随后GTP浓度显著下降至55%。在替唑呋林处理12小时后，这些事件伴随着c-myc基因表达下降3倍，c-Ha-ras基因表达下降9倍。肝癌细胞中的这些结果为早期在K562细胞中证明的GTP浓度与c-myc和c-ras基因表达之间的相关性提供了证据（奥拉赫等人，1989年）。这些基因在肝癌细胞中的表达可能依赖于GTP，并且它们可能在控制细胞增殖的信号通路中协同作用。
