Reexpression of fetal characters in simian virus 40-transformed human keratinocytes.

Normal human keratinocytes are able to stratify, form cornified squames, and terminally differentiate in tissue culture. These properties are frequently impaired by malignant transformation. In the present paper, we show that, in addition, transformation by SV40 results in the coordinate reexpression of a whole set of fetal characters. Moreover, a comparison of two SV40-transformed human keratinocyte cell lines, one still showing a certain degree of stratification and terminal differentiation (HE-SV) and the other almost completely unable to differentiate (SVK14), suggests that the impairment of differentiation and the intensity of reexpression of fetal markers are correlated. Particularly, a set of three keratin polypeptides, absent in adult stratified epithelia but normally found in the nonstratified fetal epidermis, is present in much larger amounts in SVK14 cells than in HE-SV cells. On the other hand, the inability of SVK14 cells, in contrast to HE-SV cells, to form cornified envelopes seems to be due to the inability of those cells to accumulate involucrin.