P53 and Thymidine Dimer Induction in Daily Low Emission Broad Band UV Treatment

Abstract

Background/purpose: Phototherapy is widely used as treatment modality for psoriasis. Recently we reported that daily low-dose phototherapy can be effective as treatment for psoriasis patients. To study the carcinogenic effects in patients receiving this treatment, nineteen patients underwent skin biopsies. Methods: P53 and thymidine dimers were assessed in skin biopsies of psoriasis patients (8 controls, 7 patients with daily low emission broad band UV- treatment, 4 conventional NB-UVB-treatment). Results: Staining for the presence of p53 in epidermal cells was unremarkable and not significantly different between daily low-dose UV treatment (1/7=14.3% p53 positive) and treatment without phototherapy (2/8=25.0% p53 positive) (p=1.0). Thymidine dimers were investigated by FACS analysis. No difference was found in the amount of fluorescence of the cells between daily low-dose UV-treatment and no phototherapy groups (p=0.189) or in the percentage of dimers found (p=0.463). A significant (p = 0.006) difference in amount of thymidine dimers was found in patients undergoing conventional TL01 phototherapy compared to the daily low-emission UV-treated group as well as compared to patients not undergoing phototherapy. Conclusion: These results suggest that treatment of psoriasis patients with daily low-dose UV result in a low carcinogenic risk. Further studies however are needed to confirm these results.