Bond Jane, Jones Christopher, Haughton Michele, DeMicco Catherine, Kipling David, Wynford-Thomas David
Department of Pathology, University of Wales College of Medicine, Cardiff CF14 4XN, UK.
Exp Cell Res. 2004 Jan 1;292(1):151-6. doi: 10.1016/j.yexcr.2003.09.021.
The selective pressure for disruption of the cyclin-dependent kinase inhibitor p16(INK4a) in human cancer has been postulated to reflect its role in mediating growth arrest, both in response to telomere erosion (replicative senescence) and to oncogene-induced and other "stress" signals. Given the known species-specific differences in regulation of senescence, we have tested this hypothesis in human, as opposed to rodent, cells by designing a small interfering RNA (siRNA) to knock down p16(INK4a) expression. Transfection of this siRNA into late-passage normal human diploid fibroblasts allowed at least temporary escape from entry into replicative senescence. Furthermore, in our in vitro model of early-stage, RAS-induced thyroid tumorigenesis, sequential transfections with this siRNA allowed outgrowth of small clusters of proliferating epithelial cells, consistent with escape from the spontaneous "senescence", which normally curtails their proliferative response to mutant RAS. These data provide the first direct evidence that p16(INK4a) is necessary for the initiation of both telomere-dependent and telomere-independent senescence in human cells.
细胞周期蛋白依赖性激酶抑制剂p16(INK4a)在人类癌症中被破坏的选择压力，被认为反映了其在介导生长停滞中的作用，这一作用既响应端粒侵蚀（复制性衰老），也响应癌基因诱导的和其他“应激”信号。鉴于已知衰老调控存在物种特异性差异，我们通过设计一种小干扰RNA（siRNA）来敲低p16(INK4a)的表达，在人类而非啮齿动物细胞中对这一假设进行了测试。将这种siRNA转染到传代后期的正常人二倍体成纤维细胞中，可使其至少暂时逃避进入复制性衰老。此外，在我们早期的、RAS诱导的甲状腺肿瘤发生的体外模型中，用这种siRNA进行连续转染可使小簇增殖上皮细胞生长，这与逃避通常会限制其对突变RAS增殖反应的自发“衰老”一致。这些数据提供了首个直接证据，表明p16(INK4a)对于人类细胞中端粒依赖性和端粒非依赖性衰老的启动都是必需的。
