Okami K, Reed A L, Cairns P, Koch W M, Westra W H, Wehage S, Jen J, Sidransky D
Department of Otolaryngology-Head & Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2196, USA.
Oncogene. 1999 Jun 10;18(23):3541-5. doi: 10.1038/sj.onc.1202837.
Progression through the G1 phase of the cell cycle is mediated by phosphorylation of the retinoblastoma protein (pRb) resulting in the release of essential transcription factors such as E2F-1. The phosphorylation of pRb is regulated positively by cyclin D1/CDK4 and negatively by CDK inhibitors, such as p16 (CDKN2/MTS-1/INK4A). The p16/cyclin D1/Rb pathway plays a critical role in tumorigenesis and many tumor types display a high frequency of inactivation of at least one component of this pathway. In order to determine the overall contribution of these three components to progression of head and neck squamous cell carcinoma (HNSCC), we examined p16 inactivation, cyclin D1 amplification, and pRb expression in 23 primary HNSCC tumors and five cell lines. p16 inactivation was detected in 19/23 (83%) primary tumors by detailed genetic analysis and was confirmed by immunohistochemistry (IHC). Absence of Rb protein expression indicative of pRb inactivation was identified in 2/23 (9%) tumors. In this set of tumors, there was a perfect inverse correlation between p16 and pRb inactivation. Using fluorescence in situ hybridization (FISH) cyclin D1 amplification was identified in 4/5 (80%) cell lines and 4/11 (36%) primary tumors. However, 2/4 cell lines and all four primary tumors with cyclin D1 amplification contained a concomitant alteration of p16. Therefore 21/ 23 (91%) of primary HNSCC contained at least one alteration in the p16/cyclin D1/Rb pathway. Although p16 and Rb alteration are apparently exclusive, cyclin D1 amplification occurs concomitantly with the loss of p16 suggesting an additional role for this amplification in HNSCC.
细胞周期G1期的进展是由视网膜母细胞瘤蛋白（pRb）的磷酸化介导的，这导致了诸如E2F-1等重要转录因子的释放。pRb的磷酸化由细胞周期蛋白D1/细胞周期蛋白依赖性激酶4（CDK4）正向调节，并由CDK抑制剂如p16（细胞周期蛋白依赖性激酶抑制剂2/多肿瘤抑制因子1/细胞周期蛋白依赖性激酶4抑制剂A）负向调节。p16/细胞周期蛋白D1/Rb通路在肿瘤发生中起关键作用，许多肿瘤类型中该通路至少一个组分的失活频率较高。为了确定这三个组分对头颈鳞状细胞癌（HNSCC）进展的总体贡献，我们检测了23例原发性HNSCC肿瘤和5种细胞系中的p16失活、细胞周期蛋白D1扩增及pRb表达。通过详细的基因分析在19/23（83%）的原发性肿瘤中检测到p16失活，并经免疫组织化学（IHC）证实。在2/23（9%）的肿瘤中鉴定出缺乏Rb蛋白表达，提示pRb失活。在这组肿瘤中，p16和pRb失活之间存在完全负相关。使用荧光原位杂交（FISH）在4/5（80%）的细胞系和4/11（36%）的原发性肿瘤中鉴定出细胞周期蛋白D1扩增。然而，4个细胞系中的2个以及所有4例细胞周期蛋白D1扩增的原发性肿瘤均伴有p16的改变。因此，21/23（91%）的原发性HNSCC在p16/细胞周期蛋白D1/Rb通路中至少有一处改变。虽然p16和Rb改变明显相互排斥，但细胞周期蛋白D1扩增与p16缺失同时发生，提示该扩增在HNSCC中具有额外作用。
