Miyaji K, Tani E, Shindo H, Nakano A, Tokunaga T
Department of Neurosurgery, Hyogo College of Medicine, Japan.
J Neurosurg. 1994 Sep;81(3):411-9. doi: 10.3171/jns.1994.81.3.0411.
The effects of tyrphostin, a selective protein tyrosine kinase inhibitor, on epidermal growth factor (EGF)-stimulated cell growth and EGF-receptor tyrosine kinase activity were studied in four human glioma cell lines. Stimulation by EGF induced variable enhancements of cell growth as well as tyrosine phosphorylation of EGF receptor and intracellular target proteins in all glioma cell lines. The level of immunoreactive EGF receptor detected with antibodies against extra- and intracellular domains was moderate in all four glioma cell lines, but markedly decreased with the latter antibody in two glioma cell lines. This variation was associated with considerable reduction of the EGF-stimulated tyrosine autophosphorylation level. Tyrphostin inhibited dose-dependently the EGF-stimulated cell growth and tyrosine autophosphorylation in all glioma cell lines, and the optimum time for the maximum inhibitory effect on tyrosine autophosphorylation was 12 to 18 hours after treatment with tyrphostin. The antiproliferative activity of tyrphostin nearly correlated quantitatively with its potency as an inhibitor of the EGF-stimulated EGF receptor tyrosine kinase activity. Tyrphostin had no significant effect on the immunoreactive EGF receptor levels, on the affinity constants and numbers of EGF receptor, or on the down-regulation and specific internalization of EGF receptor in any glioma cell line, suggesting that the effects of tyrphostin are not likely to be the results of reduction in EGF receptor and EGF binding capacity. In addition, the serum-stimulated cell growth was also inhibited dose-dependently by higher concentrations of tyrphostin in all glioma cell lines. It might be suggested, therefore, that tyrphostin inhibits EGF-stimulated cell growth by a specific suppression of EGF receptor tyrosine kinase activity, and at higher concentrations there appears to be some degree of either nonspecific inhibition or inhibition of serum-stimulated protein tyrosine kinase activity to induce the cell growth inhibition of gliomas.
在四种人胶质瘤细胞系中研究了选择性蛋白酪氨酸激酶抑制剂 tyrphostin 对表皮生长因子（EGF）刺激的细胞生长及 EGF 受体酪氨酸激酶活性的影响。EGF 刺激在所有胶质瘤细胞系中均诱导了细胞生长的不同程度增强以及 EGF 受体和细胞内靶蛋白的酪氨酸磷酸化。用针对胞外和胞内结构域的抗体检测到的免疫反应性 EGF 受体水平在所有四种胶质瘤细胞系中均为中等，但在两种胶质瘤细胞系中用后一种抗体检测时显著降低。这种变化与 EGF 刺激的酪氨酸自身磷酸化水平的显著降低相关。Tyrphostin 在所有胶质瘤细胞系中均剂量依赖性地抑制 EGF 刺激的细胞生长和酪氨酸自身磷酸化，对酪氨酸自身磷酸化产生最大抑制作用的最佳时间是在用 tyrphostin 处理后 12 至 18 小时。Tyrphostin 的抗增殖活性在数量上几乎与其作为 EGF 刺激的 EGF 受体酪氨酸激酶活性抑制剂的效力相关。Tyrphostin 对任何胶质瘤细胞系中的免疫反应性 EGF 受体水平、EGF 受体的亲和常数和数量，或 EGF 受体的下调和特异性内化均无显著影响，这表明 tyrphostin 的作用不太可能是 EGF 受体和 EGF 结合能力降低的结果。此外，在所有胶质瘤细胞系中，较高浓度的 tyrphostin 也剂量依赖性地抑制血清刺激的细胞生长。因此，可能提示 tyrphostin 通过特异性抑制 EGF 受体酪氨酸激酶活性来抑制 EGF 刺激的细胞生长，并且在较高浓度下似乎存在某种程度的非特异性抑制或对血清刺激的蛋白酪氨酸激酶活性的抑制，从而诱导胶质瘤细胞生长的抑制。
