Cheng C, Tennenbaum T, Dempsey P J, Coffey R J, Yuspa S H, Dlugosz A A
Laboratory of Cellular Carcinogenesis and Tumor Promotion, National Cancer Institute, Bethesda, Maryland 20892.
Cell Growth Differ. 1993 Apr;4(4):317-27.
Cytokeratins 8 and 18 (Endo A and B) are among the earliest expressed embryonic genes and the major components of the cytoskeleton in simple epithelia of the adult. Recent data indicate that these cytokeratins are aberrantly expressed in several epithelial tumor types and that expression in cultured mouse keratinocytes is linked to activation of the rasHa oncogene. Furthermore, up-regulation of K8/K18 in keratinocytes is associated with reciprocal suppression of K1. We now show that the aberrant expression of K8 and K18 and suppression of K1 in cultured keratinocytes transduced with the v-rasHa gene are mediated by a factor secreted into the culture medium. Furthermore, transforming growth factor alpha (TGF-alpha) and epidermal growth factor elicit an identical pattern of K8/K18 expression and K1 suppression in normal keratinocytes. The factor in medium from v-rasHa keratinocytes is TGF-alpha, as a specific blocking antibody for rat and mouse TGF-alpha prevents the expression of K8 and restores expression of K1. The tyrosine kinase inhibitor genistein also prevents K8 induction in v-rasHa keratinocytes and in normal keratinocytes treated with TGF-alpha- or v-rasHa-conditioned medium. However, simply stimulating proliferation of keratinocytes by cholera toxin does not result in expression of K8 or suppression of K1. Finally, tumor grafts from neoplastic epidermal cells overexpressing TGF-alpha via retroviral transduction of human TGF-alpha complementary DNA in vitro show coordinate expression of K8 and human TGF-alpha. These studies indicate that K8 expression in keratinocytes, and derivative neoplastic cells, in vivo and in vitro is regulated by epidermal growth factor receptor ligands. Since the expression of cytokines and K8/K18 in early embryogenesis is often coincident, cytokines may be the physiological mediators of K8/K18 expression in embryonic cells.
细胞角蛋白8和18（内源性A和B）是最早表达的胚胎基因之一，也是成体简单上皮细胞中细胞骨架的主要成分。最近的数据表明，这些细胞角蛋白在几种上皮肿瘤类型中异常表达，并且在培养的小鼠角质形成细胞中的表达与rasHa癌基因的激活有关。此外，角质形成细胞中K8/K18的上调与K1的相互抑制有关。我们现在表明，用v-rasHa基因转导的培养角质形成细胞中K8和K18的异常表达以及K1的抑制是由分泌到培养基中的一种因子介导的。此外，转化生长因子α（TGF-α）和表皮生长因子在正常角质形成细胞中引发相同模式的K8/K18表达和K1抑制。来自v-rasHa角质形成细胞的培养基中的因子是TGF-α，因为针对大鼠和小鼠TGF-α的特异性阻断抗体可阻止K8的表达并恢复K1的表达。酪氨酸激酶抑制剂染料木黄酮也可阻止v-rasHa角质形成细胞以及用TGF-α或v-rasHa条件培养基处理的正常角质形成细胞中K8的诱导。然而，简单地用霍乱毒素刺激角质形成细胞增殖并不会导致K8的表达或K1的抑制。最后，通过体外逆转录病毒转导人TGF-α互补DNA使肿瘤表皮细胞过表达TGF-α的肿瘤移植物显示K8和人TGF-α的协同表达。这些研究表明，角质形成细胞以及体内和体外的衍生肿瘤细胞中K8的表达受表皮生长因子受体配体调节。由于细胞因子和K8/K18在早期胚胎发生中的表达通常是一致的，细胞因子可能是胚胎细胞中K8/K18表达的生理介质。
