In Vitro Photodynamic Treatment of Normal and Human Papilloma Virus-Transfected Keratinocytes With Photofrin II and Red Light

• Photodynamic therapy involves the use of light of appropriate wavelength to excite a photosensitizer to result in tissue destruction. The photosensitizer dihematoporphyrin ether and red light were used to treat normal and human papilloma virus type 18—transfected keratinocytes in vitro. Although both cell lines were sensitive to treatment, normal keratinocytes retained more dihematoporphyrin ether and were more sensitive to photodynamic therapy than were transfected cells. In vitro data fail to show the selective retention of dihematoporphyrin ether reported elsewhere in the literature in papillomas and tumors. We did not find selective uptake or retention of dihematoporphyrin ether by human papilloma virus-transfected cells, despite previously published in vivo data to the contrary. Dihematoporphyrin ether retention and thus selective photosensitivity of papillomas in vivo is not caused by individual cellular differences in the processing of dihematoporphyrin ether. In addition, because in vitro results may not parallel in vivo results, both in vivo and in vitro models must be investigated in the study of phototherapeutic agents. ( Arch Dermatol. 1991;127:683-687)