Dipeptidyl peptidase IV (DP IV, CD26) is involved in regulation of DNA synthesis in human keratinocytes

Various studies have shown that the membrane ectoenzyme dipeptidyl peptidase IV (DP IV, CD26), expressed on T, NK, and B cells in the human immune system, is involved in the regulation of DNA synthesis and cytokine production. Here, we clearly demonstrate that this enzyme is highly expressed also on human epidermal foreskin and split-skin keratinocytes and that the specific DP IV inhibitors Lys[Z(NO2)]-thiazolidide, Lys[Z(NO2)]-pyrrolidide inhibit the enzymatic activity as well as the DNA synthesis of these cells. These data demonstrate that CD26 plays a role also in regulation of DNA synthesis of epidermal keratinocytes and that the enzymatic activity is required for mediating these effects.