TUNEL assay showing a dose dependent increase in apoptosis in A) human HGF cells or B) human HaCat cells treated with increasing doses of ZA 0.5 μM, 1 μM or 3 μM and compared to control cells (NM) at 24 hours. (Original magnification 200x). C) Annexin V: Assessment of human HGF and HaCat cell apoptosis following 24h treatment with increasing doses of ZA 0.25 μM, 0.5 μM, 1 μM or 3 μM compared to control cells (NM). Results demonstrated dose dependent increase in apoptosis with ZA exposure. D) Annexin V: Assessment of human HGF and HaCat cell apoptosis following 24h treatment with increasing doses of ZA 0.25 μM, 0.5 μM, 1 μM or 3 μM or ZA with siRNA against caspase 3 or 9. Results demonstrate a significant reversal of apoptosis in ZA 1 μM and 3 μM treated cells when treated with either siRNA. Error bars indicate the standard errors of the means. *Statistically significant (p< 0.05) differences compared to NM cells. ** Statistically significant (p< 0.05) differences following siRNA treatment compared to ZA treatment on a dose dependent basis.