Direct antiproliferative effect of cyclosporin A on cultured keratinocytes and fibroblasts.

SIR, We were interested to read the recently published report' demonstrating a direct antiproliferative effect of cyclosporin A on cultured keratinocytes and fibroblasts. These authors observed a reversible, dose-dependent inhibitory effect and that the presence of serum attenuated this response. These findings were of interest to us because we previously observed the same phenomena and reported them in several earlier publications,^'' We cannot understand these citation omissions of our in vitro findings because they were properly cited by investigators confirming an in vivo direct antiproliferative effect on keratinocytes* and this reference was included in the bibliography of their paper. The authors raised the question of the possible molecular mechanism by which cyclosporin A inhibits keratinocyte growth, and we suggest that it may exert its antiproliferative effect by decreasing the number of high affinity epidermal growth factor receptors,'