S100A7 and psoriasis: Methods: rtPCR and northern blotting of RIS-1/psoriasin and the retinoid-metabolizing genes CYP26AI and CRABP-II were performed in cells cultures (keratinocytes, sebocytes, fibroblasts, endothelial cells, melanocytes, lymphocytes and prostate cells; native and treated with retinoids) and in situ hybridization in normal and inflamed skin (acne, psoriasis).