Wu X, Rubin M, Fan Z, DeBlasio T, Soos T, Koff A, Mendelsohn J
Laboratory of Receptor Biology, Memorial Sloan-Kettering Cancer Center, NY, NY 10021, USA.
Oncogene. 1996 Apr 4;12(7):1397-403.
Activation of the cyclin dependent kinases (CDK4/CDK6 and CDK2) is required for G1 phase progression and entry into S-phase. The activation of these kinases is regulated by checkpoints that monitor environmental and intracellular conditions. Progression into S-phase is controlled, in part, by the availability of growth factors, and we have investigated the relationship between growth factor availability and the activation of the CDK kinases. Blocking activation of epidermal growth factor (EGF) receptor tyrosine kinase with anti-EGF receptor monoclonal antibody (mAb) 225 induces G1 phase cell cycle arrest in DiFi human colon adenocarcinoma cells. When DiFi cells are treated with mAb 225 for 24 h, we observe marked decreases in the activities of CDK2 kinase and cyclin E-associated CDK kinase which are not accompanied by reduced levels of cyclin E and CDK2 proteins. However, the amount of cyclin/CDK kinase inhibitor p27KIP1 increases in the mAb-treated cells and p27KIP1 is bound to CDK2 in increasing amounts. Immunodepletion of p27KIP1 removes an inhibitory activity from lysates of mAb-treated cells: the immunodepleted and heated lysates lose the capacity to inhibit cyclin E/CDK2 activity in an in vitro assay. The results suggest that G1 arrest in the cell cycle induced by EGF receptor blockade involves p27KIP1.
细胞周期蛋白依赖性激酶（CDK4/CDK6和CDK2）的激活是G1期进展和进入S期所必需的。这些激酶的激活受监测环境和细胞内状况的检查点调控。进入S期部分受生长因子可用性的控制，我们已经研究了生长因子可用性与CDK激酶激活之间的关系。用抗表皮生长因子（EGF）受体单克隆抗体（mAb）225阻断EGF受体酪氨酸激酶的激活可诱导DiFi人结肠腺癌细胞发生G1期细胞周期停滞。当用mAb 225处理DiFi细胞24小时时，我们观察到CDK2激酶和细胞周期蛋白E相关CDK激酶的活性显著降低，而细胞周期蛋白E和CDK2蛋白水平并未降低。然而，细胞周期蛋白/CDK激酶抑制剂p27KIP1在mAb处理的细胞中含量增加，并且p27KIP1与CDK2的结合量也在增加。p27KIP1的免疫去除消除了mAb处理细胞裂解物中的抑制活性：在体外试验中，免疫去除并加热的裂解物失去了抑制细胞周期蛋白E/CDK2活性的能力。结果表明，EGF受体阻断诱导的细胞周期G1期停滞涉及p27KIP1。
