Terry L A, Boyd J, Alcorta D, Lyon T, Solomon G, Hannon G, Berchuck A, Beach D, Barrett J C
Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA.
Mol Carcinog. 1996 Aug;16(4):221-8. doi: 10.1002/(SICI)1098-2744(199608)16:4<221::AID-MC6>3.0.CO;2-I.
p21/WAF1/CIP1/SDI1 is an important cell-cycle mediator with tumor suppressor gene capabilities, and its inactivation could potentially lead to tumor progression. Because tumor suppressor genes are commonly inactivated by somatic and germline mutations, we analyzed a variety of human tumor cell lines for p21 mutations. We used single-strand conformational analysis and direct sequencing to identify possible mutations in the p21 coding region. Two base-alterations were observed in 41 immortalized human tumor cell lines. A previously reported polymorphism that results in a serine-to-arginine amino-acid substitution at codon 31 was found in 24% (10 of 41) of the tumor cell lines but was also found in 10% (six of 62) of normal parental DNAs tested and 7% (three of 43) of normal DNAs from patients with primary endometrial tumors. Another nucleotide substitution found at codon 80 resulted in the replacement of threonine with methionine. Codon 80 changes were found in 7% (three of 41) of the tumor cell lines (all endometrial) and in 2% (one of 62) of the normal parental DNAs. This change was not found in any of the primary endometrial tumors examined. The biological activity of these base changes was analyzed by using in vitro cyclin-dependent kinase 2-cyclin A kinase assays and calcium phosphate transfections. We observed that wild-type p21 and the p21 variants had similar growth-inhibitory abilities. Thus, our results suggest that mutation of the p21 gene is not prevalent in human tumor cell lines and is not a probable mechanism of inactivation of this gene.
p21/WAF1/CIP1/SDI1是一种具有肿瘤抑制基因功能的重要细胞周期调节因子，其失活可能导致肿瘤进展。由于肿瘤抑制基因通常通过体细胞和种系突变而失活，我们分析了多种人类肿瘤细胞系中的p21突变情况。我们使用单链构象分析和直接测序来鉴定p21编码区的可能突变。在41种永生化人类肿瘤细胞系中观察到两个碱基改变。在24%（41个中的10个）的肿瘤细胞系中发现了一种先前报道的多态性，该多态性导致密码子31处丝氨酸到精氨酸的氨基酸替换，但在10%（62个中的6个）测试的正常亲本DNA以及7%（43个中的3个）原发性子宫内膜肿瘤患者的正常DNA中也发现了该多态性。在密码子80处发现的另一个核苷酸替换导致苏氨酸被甲硫氨酸取代。在7%（41个中的3个）的肿瘤细胞系（均为子宫内膜细胞系）和2%（62个中的1个）的正常亲本DNA中发现了密码子80的改变。在所检查的任何原发性子宫内膜肿瘤中均未发现这种改变。通过使用体外细胞周期蛋白依赖性激酶2 - 细胞周期蛋白A激酶测定和磷酸钙转染来分析这些碱基改变的生物学活性。我们观察到野生型p21和p21变体具有相似的生长抑制能力。因此，我们的结果表明，p21基因的突变在人类肿瘤细胞系中并不普遍，也不是该基因失活的可能机制。
