The effect of ultra violet B (TL-01) phototherapy on epidermal expression of p53 protein in psoriatic plaques

Background: Psoriasis is a genetically determined inflammatory skin disease. It is now recognized that narrow band TL-01 phototherapy is an effective treatment for psoriasis. However, ultraviolet (UV) exposure induces p53 mutations in keratinocytes and repeated exposure of skin to UV radiation results in clonal expansion of these initiated p53-mutant cells within the epidermis. Aim: The present study aims to examine epidermal p53 expression in the skin of psoriatic patients at different time points following TL-01 phototherapy. Methods: Skin samples from patients suffering from plaque-type psoriasis, collected before, during and at the final stages of TL-01 phototherapy were examined for p53 expression by immunohistochemistry. Results/Conclusion: Our results showed an increase in p53 expressing keratinocytes following TL-01 phototherapy. Some of these cells were arranged spatially, as conical clones arising from putative stem cell compartments, suggesting that the chronic TL-01 treatment might have triggered cell growth and clonal expansion, an important step in initiating skin carcinogenesis.