FOXO1 knockdown results in increased keratinocyte apoptosis. NHEK cells were transfected with control or FOXO1 siRNAs for 48 h. (A) Apoptotic keratinocytes were measured by TUNEL staining. Quantitative analysis of TUNEL-positive NHEK cells. The percentage of TUNEL-positive nuclei is reported as mean ± SD. (B) Apoptotic keratinocytes were confirmed by cell death detection ELISA. Real-time PCR analysis of Bim (C), FAS ligand (D), and caspase-6 (E) mRNA levels in FOXO1 knockdown keratinocytes. Data show mean ± SEM of at least three independent measurements. Asterisks indicate significant increase compared with cells transfected with siRNA control (P < 0.05).