The effect of cyclosporin A on epidermal cells. II. Cyclosporin A inhibits proliferation of normal and transformed keratinocytes.

Cyclosporin A (CSA) is a potent immunosuppressive drug that inhibits the proliferation of activated T cells by blocking the production of interleukin 2. Recent studies have demonstrated that CSA also inhibits the proliferation of neoplastic cells of hematopoietic and nonhematopoietic origin. CSA has also been reported to be effective in the treatment of psoriasis, which is characterized by epidermal hyperproliferation. As so many of the therapeutically effective agents in psoriasis are antiproliferative, we sought to determine whether CSA affects the proliferation of keratinocytes. We studied the effect of CSA on the proliferation of normal and transformed keratinocytes and demonstrated that CSA inhibits DNA synthesis and proliferation of keratinocytes. CSA also inhibits DNA synthesis of other neoplastic cells of hematopoietic and nonhematopoietic origin. These findings indicate the CSA inhibits the proliferation of various cell types.