Characterization of Intra‐tumoral Porphyrin Following Injection of Hematoporphyrin Derivative or Its Purified Component*

Photodynamic therapy (PDT) utilizes either hematoporphyrin derivative (Hpd) or a purified form of Hpd termed DHE, as photosensitizers for treatment of a variety of solid tumors in man. The reasons for long retention of these porphyrins in a wide range of histologically diverse tumors remain obscure. We have found that the RIF fibrosarcoma and SMT-F mammary carcinoma in mice, a intrapancreatic tumor in the hamster and a tumor removed from a patient with a myxoid sarcoma, make take up Hpd or DHE by endocytosis. On the other hand the RIF tumor cells in vitro show a tendency for selective uptake and retention of the more hydrophobic components of the mixture.