Effect of retinoic acid on apoptosis and DNA repair in human keratinocytes after UVB irradiation

BACKGROUND: Skin cancer is extremely common. Epidemiological studies indicated that ultraviolet radiation (UV) is the primary cause for skin cancers, and that retinoic acid (RA) is able to inhibit this UV-induced skin carcinogenesis; however, the molecular mechanism of the anti-UV action of RA is unclear. OBJECTIVE: The purpose of this study is to investigate if RA enhances the removal of UV-induced DNA damage. METHODS: The effect of RA on UV-induced apoptosis and DNA repair was investigated by ELISA apoptosis assay and CAT assay. RESULTS: Both all-trans-RA and 9-cis-RA did not promote UV-induced apoptosis nor the repair of UV-damaged DNA in human keratinocytes. Furthermore, RA did not induce the expression of p53. CONCLUSION: The inhibition of RA on skin carcinogenesis is not due to enhanced removal of UV-damaged DNA. Therefore, RA does not inhibit skin cancer development at the initiation stage, but possibly at the promotion and progression stages.