Doki Y, Imoto M, Han E K, Sgambato A, Weinstein I B
Herbert Irving Comprehensive Cancer Center, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA.
Carcinogenesis. 1997 Jun;18(6):1139-48. doi: 10.1093/carcin/18.6.1139.
In the present study we have characterized eight human esophageal squamous carcinoma cell lines for levels of expression of cyclins D1, E, A and B1; CDKs 1, 2 and 4; the CDK inhibitors p16INK4, p21WAF1 and p27KIP1; the retinoblastoma (Rb) protein; and in vitro CDK2- and CDK4-associated kinase activity; and also compared the growth properties of these cell lines. The level of the cyclin D1 protein varied by over 30-fold amongst the eight cell lines. The high level in two cell lines was associated with amplification of this gene, but in three cell lines it was due to post-transcriptional events. Amongst the eight cell lines there was a significant correlation between the levels of cyclin D1, Rb and p27KIP1 proteins, and CDK4-associated kinase activity. Furthermore, when an exogenous cyclin D1 cDNA was over-expressed in the EC109 cell line by transfection, this led to increased expression of both Rb and p27KIP1. There was, however, no correlation between the level of cyclin D1 expression and the cell doubling times, duration of the G1 phase, or colony-forming efficiency in agar. Two of the cell lines displayed a high level of the cyclin E protein, low levels of cyclin D1, lacked expression of the Rb protein and expressed high levels of the p16INK4 protein. One of these cell lines displayed amplification of the latter gene. There was no correlation between the levels of cyclins E or A and in vitro CDK2 kinase activity, but CDK2 kinase activity was inversely correlated with the duration of the G1 phase of the cell cycle. Taken together, these studies indicate marked heterogeneity in the expression of cell cycle-related proteins amongst a series of esophageal carcinoma cell lines. The correlation between the levels of the cyclin D1, Rb and p27Kip1 proteins suggest the existence of a homeostatic feedback loop between positive and negative acting components of the cell cycle machinery.
在本研究中，我们对8种人食管鳞状癌细胞系进行了特征分析，检测了细胞周期蛋白D1、E、A和B1；细胞周期蛋白依赖性激酶（CDK）1、2和4；CDK抑制剂p16INK4、p21WAF1和p27KIP1；视网膜母细胞瘤（Rb）蛋白的表达水平；以及体外CDK2和CDK4相关激酶活性；并比较了这些细胞系的生长特性。在这8种细胞系中，细胞周期蛋白D1蛋白水平的差异超过30倍。两种细胞系中的高水平与该基因的扩增有关，但在三种细胞系中，这是由于转录后事件所致。在这8种细胞系中，细胞周期蛋白D1、Rb和p27KIP1蛋白水平与CDK4相关激酶活性之间存在显著相关性。此外，当通过转染在EC109细胞系中过表达外源性细胞周期蛋白D1 cDNA时，这导致Rb和p27KIP1的表达均增加。然而，细胞周期蛋白D1表达水平与细胞倍增时间、G1期持续时间或琼脂中的集落形成效率之间没有相关性。其中两种细胞系显示细胞周期蛋白E蛋白水平高、细胞周期蛋白D1水平低、缺乏Rb蛋白表达且p16INK4蛋白表达水平高。其中一种细胞系显示后一个基因发生扩增。细胞周期蛋白E或A的水平与体外CDK2激酶活性之间没有相关性，但CDK2激酶活性与细胞周期G1期的持续时间呈负相关。综上所述，这些研究表明在一系列食管癌细胞系中，细胞周期相关蛋白的表达存在明显的异质性。细胞周期蛋白D1、Rb和p27Kip1蛋白水平之间的相关性表明，细胞周期机制的正负作用成分之间存在稳态反馈环。
