Abstract: Objective To investigate the effect of phorbol-12-myristate-13-acetate （PMA） on cyclooxygenase-2 （COX-2） mRNA and protein expression in cultured human HaCaT keratinocytes, and the mechanism for cytotoxity of PMA against keratinocytes. Methods RT-PCR and Western blot were utilized to detect the expression of COX-2 mRNA and protein in cultured HaCaT cells at 24 hours after the treatment with various concentrations of PMA （0.1, 1.0, 10 mg/L）. Results Without any treatment, there was no or a weak expression of COX-2 mRNA and protein in HaCaT cells; incubation with PMA resulted in the induction of the expression of COX-2 in HaCaT cells. The expression levels of COX-2 mRNA and protein in 10 mg/L PMA-pretreated HaCaT cells were significantly higher than those in 1.0 mg/L PMA-pretreated HaCaT cells, which was in turn higher than that in 0.1 mg/L PMA-pretreated cells and untreated cells; the difference was statistically significant （all P < 0.01）. Conclusion These results suggest that PMA may be involved in keratinocyte tumorigenesis by upregulating the expression of COX-2 as well as synthesis and release of prostaglandin in keratinocytes.

Key words: Phorbol-12-Myristate-13-Acetate (PMA), HaCat cells, cyclooxygenase (COX-2)