Shi Y, Zou M, Farid N R, al-Sedairy S T
Department of Biological and Medical Research, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
Br J Cancer. 1996 Nov;74(9):1336-41. doi: 10.1038/bjc.1996.546.
Eukaryotic cell cycle progression is controlled by a host of cyclin/cyclin-dependent kinases (Cdks), that are themselves regulated by multiple factors, including a group of small cyclin-Cdk inhibitor proteins (p15, p16, p21 and p27). The involvement of Cdk inhibitors in carcinogenesis has been demonstrated by the studies of p16. p53 is frequently mutated in thyroid carcinomas and p21/Waf1 is a downstream effector of p53. It is conceivable that genetic defects of genes downstream in the p53 pathway could also be oncogenic. We, therefore, examined a series of 57 thyroid tumour specimens (eight follicular adenomas and 49 carcinomas) for deletion and point mutation of the p21/Waf1 gene. Three different kinds of deletions ranging from 349 to 450 bp were detected in five papillary carcinoma specimens by reverse transcription-polymerase chain reaction (RT-PCR). All the deletions were involved in the second exon of the p21/Waf1 gene. RT-PCR single strand conformational polymorphism (SSCP) analysis of remaining samples failed to reveal any point mutations in the coding region of the gene, except for a polymorphism at codon 31 (Ser to Arg). Genomic Southern blot analysis did not demonstrate any gene deletion or rearrangement in these samples, indicating abnormal RNA splicing may be involved. Analysis of intron-exon boundary and the coding region of the second exon did not reveal any mutation except for a point mutation (C to G) located 16 bp downstream from the splice donor site of the second intron in three out of five samples with p21/Waf1 deletions. Whether the mutation plays any role in aberrant RNA splicing remains to be determined. Among the five samples with p21/Waf1 gene deletions, none of them simultaneously carried a p53 or retinoblastoma (Rb) gene mutation. No p21/Waf1 abnormality was found in the benign adenomas. Thus, 12.5% (5/40) of thyroid papillary carcinoma specimens harboured p21/Waf1 gene deletions. Our data suggest that p21/Waf1 gene deletion is involved in thyroid carcinogenesis and may play an important role in thyroid cell transformation.
真核细胞周期进程受众多细胞周期蛋白/细胞周期蛋白依赖性激酶（Cdks）控制，而这些激酶本身又受多种因素调节，包括一组小的细胞周期蛋白-Cdk抑制蛋白（p15、p16、p21和p27）。对p16的研究已证实Cdk抑制因子与肿瘤发生有关。p53在甲状腺癌中常发生突变，p21/Waf1是p53的下游效应分子。可以想象，p53途径下游基因的遗传缺陷也可能具有致癌性。因此，我们检测了57例甲状腺肿瘤标本（8例滤泡性腺瘤和49例癌）中p21/Waf1基因的缺失和点突变情况。通过逆转录-聚合酶链反应（RT-PCR）在5例乳头状癌标本中检测到3种不同类型的缺失，缺失长度在349至450 bp之间。所有缺失均累及p21/Waf1基因的第二外显子。对其余样本进行RT-PCR单链构象多态性（SSCP）分析，除第31密码子（丝氨酸突变为精氨酸）存在多态性外，未在该基因编码区发现任何点突变。基因组Southern印迹分析未显示这些样本中有任何基因缺失或重排，提示可能涉及异常RNA剪接。对内含子-外显子边界和第二外显子编码区的分析未发现任何突变，除了在5例p21/Waf1基因缺失样本中的3例中，在第二内含子剪接供体位点下游16 bp处有一个点突变（C突变为G）。该突变是否在异常RNA剪接中起作用尚待确定。在5例p21/Waf1基因缺失的样本中，均未同时携带p53或视网膜母细胞瘤（Rb）基因突变。在良性腺瘤中未发现p21/Waf1异常。因此，12.5%（5/40）的甲状腺乳头状癌标本存在p21/Waf1基因缺失。我们的数据表明，p21/Waf1基因缺失与甲状腺癌发生有关，可能在甲状腺细胞转化中起重要作用。
