Sangfelt O, Erickson S, Einhorn S, Grandér D
Department of Oncology/Pathology, Radiumhemmet, Karolinska Hospital and Institute, Stockholm, Sweden.
Oncogene. 1997 Jan 30;14(4):415-23. doi: 10.1038/sj.onc.1200832.
One prominent effect of IFNs is their cell growth inhibitory activity. The exact molecular mechanism behind this inhibition of proliferation remains to be elucidated. Possible effectors for IFN-induced growth inhibition are the recently discovered cyclin-dependent kinase inhibitors. The effect of IFN-alpha treatment on the members of the Ink4 and Cip/Kip families of Cdk inhibitors was investigated in three hematopoietic cell lines Daudi, U-266 and H9. Two of these cell lines, Daudi and U-266, respond to IFN-alpha by G1 arrest, whereas the H9 cell line is not growth arrested by IFN-alpha. We show that a p53-independent upregulation of p21 mRNA occurs following IFN-alpha treatment in all three cell lines. In Daudi and U-266 cells, the mRNA induction is accompanied by an increase in p21 protein, followed by an increased binding of p21 to Cdk2 and a subsequent decrease in Cdk2 activity, temporally coinciding with G1 arrest. In both these cell lines, there was also an increased binding of p21 to Cdk4. In contrast, p21 protein was not expressed in H9 cells, despite high levels of p21 mRNA following IFN-alpha treatment. In U-266 cells, IFN-alpha increased not only p21 but also p15 mRNA and protein levels, followed by an increased association of p15 with Cdk4. Furthermore, IFN-alpha treatment caused a four- to sixfold induction of the p16 E1beta transcript in U-266 cells. Expression levels of the other Ink4 and Cip/Kip Cdk inhibitors were not induced by IFN treatment in any of the cell lines. We conclude that IFN-alpha can act as a potent regulator of Cdk-inhibitor expression, correlating with decreased Cdk activity and cell growth inhibition. One mechanism for resistance to IFN may be loss of the ability of cells to upregulate these proteins.
干扰素（IFN）的一个显著作用是其细胞生长抑制活性。这种增殖抑制背后的确切分子机制仍有待阐明。干扰素诱导生长抑制的可能效应分子是最近发现的细胞周期蛋白依赖性激酶抑制剂。在三种造血细胞系Daudi、U - 266和H9中研究了α干扰素治疗对Cdk抑制剂Ink4和Cip/Kip家族成员的影响。其中两种细胞系Daudi和U - 266，对α干扰素的反应是G1期停滞，而H9细胞系不受α干扰素的生长停滞影响。我们发现，在所有三种细胞系中，α干扰素治疗后都会出现不依赖p53的p21 mRNA上调。在Daudi和U - 266细胞中，mRNA诱导伴随着p21蛋白增加，随后p21与Cdk2的结合增加，Cdk2活性随之降低，在时间上与G1期停滞一致。在这两种细胞系中，p21与Cdk4的结合也增加。相比之下，尽管α干扰素治疗后H9细胞中p21 mRNA水平很高，但p21蛋白并未表达。在U - 266细胞中，α干扰素不仅增加了p21，还增加了p15 mRNA和蛋白水平，随后p15与Cdk4的结合增加。此外，α干扰素治疗使U - 266细胞中p16 E1β转录本诱导增加了4至6倍。在任何细胞系中，其他Ink4和Cip/Kip Cdk抑制剂的表达水平均未被干扰素治疗诱导。我们得出结论，α干扰素可作为Cdk抑制剂表达的有效调节因子，与Cdk活性降低和细胞生长抑制相关。对干扰素产生抗性的一种机制可能是细胞上调这些蛋白的能力丧失。
