Comparison of Fluorescence and Photodynamic Activities of Whole Hematoporphyrin Derivative and Its Enriched Active Components&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;

J M Nelson ,William W Wright ,Michael W Berns

doi:10.1093/jnci/75.6.1135

Abstract

The in vivo biologic activities of the hematoporphyrin derivative (Photofrin) and the enriched, so-called "active fraction" (Photofrin II) were determined by measuring the necrosis produced in implanted tumors in DBA/2Ha mice exposed to various total doses of light (20-100 J/cm2) after ip administration of 10 mg/kg standard doses of either Photofrin or Photofrin II. Total relative percentage increase in fluorescence in tumor tissue, as compared to fluorescence in control tissue, also was measured for both Photofrin and Photofrin II. In response to total light doses (630 nm) of 40-100 J/cm2, mice that received Photofrin had comparable amounts of tumor necrosis to those mice that received Photofrin II. At doses of 40-60 J/cm2, 80% tumor destruction resulted, and at 80-100 J/cm2, tumor destruction was 100%. However, at a total light dose of 20 J/cm2, the tumors that received Photofrin II exhibited 60-80% tumor necrosis, whereas those animals that received Photofrin had only small areas of patchy necrosis associated with signs of vascular thrombosis and hemorrhage into the surrounding perivascular stroma. A 25.2% total increase in maximal tissue fluorescence over that in controls was observed for animals that received Photofrin II, as compared to 13.9% for those animals that received Photofrin. It is concluded that the greater demonstrable efficacy of treatment with Photofrin II, as compared to treatment with Photofrin, is due to enrichment of those nonpolar hydrophobic components of the hematoporphyrin derivative mixture that are thought to be primarily responsible for the in vivo biologic activities.

Highlights

Added to the armamentarium of the oncologist has been the development of photodynamic therapy (PDT) after sensitization with the porphyrin derivatives [1,2]
Hematoporphyrin derivative used for clinical studies proves to be a complex mixture of 4 major porphyrins that are somewhat variable in composition
Several porphyrins in hematoporphyrin derivative (HpD) previously were separated by high-pressure liquid chromatography (HPLC) and gel filtration methods and have been identified as hematoporphyrin, hydroxyethylvinyldeuteroporphyrin, and protoporphyrin [12,13,14,15]

Summary

Introduction

Added to the armamentarium of the oncologist has been the development of PDT after sensitization with the porphyrin derivatives [1,2]. The basic concept for the use of PDT for malignant tumors is that certain molecules can function as photosensitizers. The presence of these photosensitizers in certain cells makes these cells vulnerable to light at the appropriate wavelength and intensity. In 1981, Dougherty et al [8] described a gel filtration procedure designed to isolate the unknown structure thought to be the material primarily responsible for the photosensitizing activity of the HpD mixture, both in vitro and in vivo. In vitro and in vivo studies led Dougherty et al to conclude that the active ingredient had twice the cytotoxic activity of that of the native HpD. In our study we used a well-defined murine tumor system, in a standard series of histopathologic and fluorescence microscopy experiments, to compare the activity of Photofrin and the concentrated, presumably active fraction of HpD (Photofrin II)

Methods

Results

Conclusion