DISTRIBUTION OF DISULFONATED AND TETRASULFONATED ALUMINUM PHTHALOCYANINE BETWEEN MALIGNANT AND HOST-CELL POPULATIONS OF A MURINE FIBROSARCOMA

Levels of disulfonated and tetrasulfonated aluminum phthalocyanines (AlPcS2,4) were measured in cells derived from FsaR tumors (murine fibrosarcoma) using a fluorescence-activated cell sorter (FACS). The tumors were excised from animals injected with the sensitizer 24 h earlier and enzymatically dissociated. Before flow cytometry, the cells were stained with fluorescein isothiocyanate-conjugated anti-mouse monoclonal antibodies to specific immune cell membrane markers (Mac1, Fc receptor (FcR) or CD45). Staining to FcR and CD45 was combined with a DNA stain Hoechst 33342. This enabled concomitant discrimination to be made by the FACS between different populations of tumor-infiltrating host cells and malignant cells. The results showed on average 1.49 times higher AlPcS2 levels and 1.16 times higher AlPcS4 levels in Mac1-positive (Mac1+) compared with Mac1-negative (Mac1-) tumor cell populations. The same type of experiments performed with SCCVII tumor (squamous cell carcinoma) gave average Mac1+/Mac1- ratios of 1.75 and 1.45 for AlPcS2 and AlPcS4 respectively. The data using other antibodies and DNA staining are consistent with the conclusion that, based on average per cell content, elevated levels of AlPcS2, and to a lesser extent AlPcS4, are retained in tumor-associated macrophages (TAM). The levels of these photosensitizers in other leukocytes and in non-immune host cells were not substantially different from those in malignant tumor cells. It is also shown that elevated levels of AlPcS2 and AlPcS4 are not localized in all TAM, but rather in a fraction of this cell population characterized by extremely high photosensitizer content.