COMPARISON OF SENSITIVITY TOWARDS PHOTODYNAMIC THERAPY OF CUTANEOUS RESIDENT AND INFILTRATING CELL-TYPES IN-VITRO

Background and Objective: Photodynamic therapy (PDT) combines photosen sitizers absorbing light in the visible spectral region and irradiatio n with light of corresponding wavelengths. We analysed the sensitivity of cell lines established from resident cutaneous cells and from tran sformed lymphocytes towards PDT.Study Design/Materials and Methods: PD T was performed employing either 630 or 662 nm light or polychromatic red light (600-700 nm) and photosensitizers Photosan-3, delta-aminolev ulinic acid, or methylene blue. Proliferation measured by H-3-TdR upta ke was determined in human immortalized keratinocytes (HaCaT) and mous e fibroblasts (NIH/3T3) in comparison to human transformed T-(HuT78) a nd B-lymphocytes (RA1). Additionally, uptake of the photosensitizers w as estimated employing video-intensified fluorescence-microscopy (VIFM ). Results: Depending on the photosensitizer tested HaCaT and NIH/3T3 exhibited an ED(50) up to 10-fold as high as the lymphocytic lines. Po lychromatic red light was at least as effective at inducing photodynam ic reactions as 630 or 662 nm light. VIFM revealed a positive correlat ion between sensitivity of a given cell type towards PDT and uptake of the photosensitizers. The differential uptake observed in vitro was c onfirmed in vivo: A photosensitizer applied topically on a lesion of a patient with mycosis fungoides was found to accumulate preferentially in the lymphocytic infiltrate. Conclusion: Selective topical polychro matic PDT seems to be a feasible goal for the treatment of cutaneous l ymphomas. (C) 1996 Wiley-Liss, Inc.