Expression of the SPRRCornification Genes Is Differentially Affected by Carcinogenic Transformation

Abstract

The small proline rich protein ( SPRR) genes constitute a family of conserved genes which are part of the human epidermal differentiation complex (EDC) on chromosome 1q21 and code for precursor proteins of the cornified cell envelope. The expression of these genes is strictly linked to keratinocyte terminal differentiation both in vivoand in vitro.Here we show that cultured cell lines derived from squamous cell carcinoma (SCC) show significantly lower levels of SPRRexpression than normal human keratinocytes. However, the residual SPRRexpression in SCC lines appears to be both gene and cell line specific. Expression of SPRR2appears to correlate well with the residual ability of these cells to differentiate. However, the kinetics of SPRR2expression, following treatment with calcium, an inducer of keratinocyte differentiation, are typical for each cell line and differ substantially from the ones found in normal cells. In most cell lines a rapid transient expression of SPRR2contrasts with a slow induction leading to a high sustained level of expression in normal cells. This pattern of expression is typical for SPRR2and not observed for the other SPRRgenes or involucrin. Our analysis indicates that the expression of various keratinocyte terminal differentiation markers, even when involved in the same biological process (cornification), can be differentially affected by carcinogenic transformation.