Weinberg W C, Azzoli C G, Kadiwar N, Yuspa S H
Laboratory of Cellular Carcinogenesis, National Cancer Institute, Bethesda, Maryland 20892.
Cancer Res. 1994 Nov 1;54(21):5584-92.
Epidermal keratinocyte cultures were established from newborn mice expressing a null mutation in the p53 gene to explore the contribution of p53 to epidermal growth regulation and neoplasia. Keratinocytes were initiated by transduction with a replication-defective retrovirus encoding the v-rasHa oncogene and grafted onto nude mouse hosts. Tumors arising from keratinocytes heterozygous or null for functional p53 in the presence of v-rasHa have growth rates approximately 5-fold higher than those derived from p53(+/+) controls and rapidly form carcinomas, in contrast to the benign phenotype observed in p53(+/+)/v-rasHa grafts. In vitro, p53-deficient keratinocytes with and without v-rasHa expression display decreased responsiveness to the negative growth regulators transforming growth factors beta 1 and beta 2. In combination with v-rasHa, p53-deficient keratinocytes also exhibit decreased responsiveness to elevated Ca2+. These differences between genotypes cannot be attributed to changes in transforming growth factor beta receptor types present or altered levels of epidermal growth factor receptor and are independent of c-myc transcript levels. mRNA expression for the p-53 inducible protein WAF1 correlates with p53 gene dosage, but low levels are still detectable in p53(-/-) keratinocytes. The altered responsiveness of p53 deficient keratinocytes to negative growth regulators may provide a growth advantage to such cells in vivo and render them more susceptible to genetic alterations and malignant conversion.
从p53基因发生无效突变的新生小鼠建立表皮角质形成细胞培养物，以探究p53对表皮生长调节和肿瘤形成的作用。用编码v-rasHa癌基因的复制缺陷型逆转录病毒转导启动角质形成细胞，并移植到裸鼠宿主上。在v-rasHa存在的情况下，来自功能性p53杂合或缺失的角质形成细胞产生的肿瘤生长速率比来自p53(+/+)对照的肿瘤高约5倍，并迅速形成癌，这与在p53(+/+)/v-rasHa移植中观察到的良性表型形成对比。在体外，有或无v-rasHa表达的p53缺陷型角质形成细胞对负性生长调节因子转化生长因子β1和β2的反应性降低。与v-rasHa联合时，p53缺陷型角质形成细胞对升高的Ca2+的反应性也降低。这些基因型之间的差异不能归因于存在的转化生长因子β受体类型的变化或表皮生长因子受体水平的改变，并且与c-myc转录水平无关。p-53诱导蛋白WAF1的mRNA表达与p53基因剂量相关，但在p53(-/-)角质形成细胞中仍可检测到低水平。p53缺陷型角质形成细胞对负性生长调节因子反应性的改变可能在体内为这类细胞提供生长优势，并使它们更容易发生基因改变和恶性转化。
