-transfected Tumorigenic Clones of the Human HaCaT Cell Line ras Epidermal Morphogenesis and Keratin Expression in c-Ha-

Several tumorigenic (benign and malignant) clones have been raised from the human epidermal cell line HaCaT after transfection with the cllu-ruv oncogene (val 12) (P. Boukamp et a/.. Cancer Res., 50: 28402847, 1990). In culture, these HaCaT-nu clones expressed epidermal differentiation markers, such as keratins Kl and 10, at high density or upon depletion of retinoic acid. Accordingly, as HaCaT cells, the clones formed well-differentiated stratified epithelia synthesizing Kl and 10 in surface transplants, while simple and internal epithelial keratins seen in culture were suppressed (as upon retinoic acid depletion in vitro). In transplants of HaCaT cells, in contrast to those of normal keratinocytes, Kl appeared prematurely already in basal cells, while K10 localized rather normally in the suprabasal position. Keratins 1 and 10 were also synthesized in transplants of IIa( ;il-rav clones (again Kl preceding K10), but both generally shifted toward upper layers. This was particu larly evident in thicker transplants of malignant clones. Staining for both keratins persisted "suprabasally" in invasive tissue masses, and this corresponded to their marked expression in solid carcinomas (after s.c. injection), seen by immunofluorescence and two-dimensional gel electrophoresis. Thus, notwithstanding some variations, differentiation potential was not significantly reduced in these clones disregarding levels of ras oncogene expression and malignant properties.