EFFECT OF PHOTODYNAMIC PRETREATMENT ON THE SUSCEPTIBILITY OF MURINE TUMOR-CELLS TO MACROPHAGE ANTITUMOR MECHANISMS

In vitro photodynamic treatment of YAC-1 murine T-lymphoma cells with the hematoporphyrin derivative Photosan 3 and red light resulted in do se-dependent phototoxicity. Photodynamic pretreatment, however, did no t render these cells more susceptible to macrophage-mediated tumor cyt otoxicity or Phe cytotoxic effects of macrophage-derived antitumor med iators like tumor necrosis factor alpha (TNF-alpha) or interferon beta (IFN-beta). Independent of the degree of photosensitization used, the cytotoxicity values obtained with macrophages or the different mediat ors were shifted by the respective values for phototoxicity, suggestin g these effects to be additive ansi thus not interdependent. These dat a show that while higher overall tumor cytotoxicity care be achieved b y a combination of photodynamic treatment and macrophage-mediated. tum or destruction, this apparently is not a result of enhanced sensitivit y of photodynamically treated tumor sells to macrophage antitumor mech anisms in general.