Meso-Tetra (p-Sulfophenyl) Porphine as a Potential Tumor-Localizing Agent

Abstract

The selective localization of well-defined chemical materials in malignant tumors has been a long-range objective of many lines of research. Since the observation in 1924 that porphyrins caused red fluorescence in tumors but not in other tissues of experimental animals, much research on porphyrins as tumor-localizing agents has appeared. (For a recent review see Tsutsui et al. (11)). A significant advance in this area was the introduction of the synthetic porphyrin, tetraphenylporphine sulfonate (TPPS), by Winkelman. Using this compound in rats bearing the Walker 256 carcinoma, Winkelman was able to demonstrate that TPPS concentrated exclusively in tumors relative to other tissues and organs (12). This study has remained one of the few quantitative examinations of porphyrin localization in tumors and has established TPPS as a potential candidate for a useful drug. Unfortunately, although the phenomenon of porphyrin localization in tumors has been observed for over half a century, little is known about it on a cellular basis, and it has not been examined quantitatively on a sufficient number of tumor systems to adequately assess its potential. Accordingly, we have studied the interactions of highly purified TPPS₄ (completely tetra sulfonated; Winkelmanfs TPPS was a mixture of mono, di, tri, and tetra sulfonated material), both in vivo and in vitro, with normal and tumor tissues