Expression of markers of differentiation in a transformed human keratinocyte line induced by coculture with a fibroblast line.

SVK14, an SV40-transformed human keratinocyte line, has previously been reported to be almost completely unable to differentiate, and indeed, to express a set of keratins characteristic of simple epithelia rather than the stratifying epithelium from which they were derived. We have recently shown that IGF I stimulation of SVK14 results in expression of keratin 14, a marker of stratifying epithelia, as well as expression of markers which are characteristic of differentiation in normal human keratinocytes such as involucrin and keratin 10. To study further the capacity of SVK14 to differentiate, we have cocultured SVK14 with a variety of fibroblastic cell lines with a view to examining whether the cocultured partner can promote or interfere with their differentiation. We have observed that SVK14, when cocultured with Swiss 3T3, form organized structures through specific cell-cell interactions in which SVK14 express keratins 14 and 5 and involucrin, while maintaining T-antigen expression. These results are interesting since they show coculturing of a transformed human keratinocyte cell line and a particular fibroblast line can result in induction of characteristics of stratifying epithelia in a cell line with characteristics of simple epithelia. This may be analogous to the epithelial-mesenchymal interactions seen during epithelial development in the very early embryo.