Simple epithelial nature of some simian virus-40-transformed human epidermal keratinocytes

Previous studies have indicated that some Simian-virus-40-transformed human epidermal keratinocytes (SV40-HE) undergo significant changes in their growth and differentiated properties. To better understand the significance of these changes, we have characterized the keratins of SV40-HE cells by one- and two-dimensional immunoblot analysis using the subfamily-specific AE1 and AE3 monoclonal antikeratin antibodies. The results indicate that our SV40-HE cells have lost the Mr 58,000 (No. 5), Mr 56,000 (No. 6), Mr 50,000 (No. 14/15), Mr 48,000 (No. 16), and Mr 46,000 (No. 17) keratins that are expressed by cultured normal human keratinocytes. Instead, these cells express mainly Mr 52,000 (No. 8), Mr 45,000 (No. 18), and Mr 40,000 (No. 19) keratins, a set highly characteristic of simple epithelial cells. Furthermore, our SV40-HE cells have ceased to express involucrin, another marker for keratinocytes, and have a greatly diminished ability to undergo in vitro stratification. These results suggest that epidermal cells can sometimes lose their keratinocyte features as a consequence of viral transformation. This finding may have important implications regarding the mechanisms of epithelial differentiation and tumorigenesis and in the use of keratinocyte markers for tumor diagnosis.