Inactivation of erythrocytic, lymphocytic and myelocytic leukemic cells by photoexcitation of endogenous porphyrins

The photodynamic sensitization of leukemic cells (erythrocytic, myelocytic and lymphocytic) via light activation of endogenous porphyrins is described. Human myelocytic-erythrocytic K562 cells and murine Friend erythroleukemia (FELC) and T-cell lymphoma Eb-Esb cells were stimulated to synthesize and accumulate porphyrins. K562 cells accumulated high amounts of protoporphyrin by stimulation with 5-aminolevulinic acid (ALA) plus sodium butyrate or hemin. For Friend and Eb-Ebs cells ALA was an adequate stimulator. The high-metastatic Esb lymphoma cells accumulated comparatively more porphyrin than the low-metastatic Eb cell line. Maximal porphyrin accumulation produced mortality rates of more than 99% after 10 min of photoactivation of the three leukemic lines. Thymidine incorporation was inhibited by the photodynamic effect depending on porphyrin concentration. These results confirm the photodynamic ability of endogenous porphyrins to inactivate cancer cells of different origins.