IN VIVO FLUORESCENCE OF TUMORS AFTER TREATMENT WITH DERIVATIVES OF HEMATOPORPHYRIN

Abstract— Administration of a mixture of porphyrins termed HPD (hematoporphyrin derivative) to mice bearing the Lewis lung tumor leads to preferential accumulation of fluorescence at tumor loci in vivo after 48 h. HPLC analysis shows that the fluorescent species consist of hematoporphyrin and its dehydration products. But injection of these porphyrins does not lead to fluorescence localization. The intracellular fluorescence which is observed apparently arises from intracellular degradation of the tumor-localizing component of HPD. These fluorescent species represent only a small fraction of the total accumulated porphyrin pool; a larger weakly-fluorescent porphyrin pool is also present, and may be the major factor in tumor photosensitization.