12-O-tetradecanoylphorbol-13-acetate and the induction of prostaglandin E2 generation by human keratinocytes: a re-evaluation.

12-O-Tetradecanoylphorbol-13-acetate (TPA) induces prostaglandin E2 (PGE2) synthesis in mouse keratinocytes and is associated with the induction of keratinocyte proliferation as well as accelerated differentiation. In human keratinocytes, TPA has been reported not to induce the release of either 3H-labeled arachidonic acid or 3H-labeled prostaglandins, even though cell differentiation is stimulated. Because PGE2 has been associated with the modulation of cell differentiation and because of technical problems inherent in evaluating arachidonic acid metabolism using only radiolabeled substrates, we evaluated the ability of TPA to induce endogenous PGE2 generation by cultured human keratinocytes using a specific and sensitive enzyme immunoassay. With this technique, TPA was found to induce a dose-dependent (1.6 x 10(-12)-1.6 x 10(-8) M) increase in PGE2 generation. These results are consistent with observations made not only in mouse keratinocytes but in other mammalian and human cell types. Documenting the ability of TPA to stimulate PGE2 production in human keratinocytes is very relevant to current theories regarding the role of PGE2 in keratinocyte differentiation as well as to establishing parallels between the murine and human skin models.