THE EFFECT OF DIFFERENTIATION ON PHOTOSENSITIZER UPTAKE BY HL-60 CELLS

The capability of human promyelocytic leukemia cells HL60 to be induce d to differentiate to various stages along the monocytic or myelocytic pathway was exploited for investigation of the uptake of selected pho tosensitizers by diverse types of cells of the same origin. The result s showed that there was no substantial difference in photofrin uptake between noninduced HL60 cells, immature monocytes, immature neutrophil s and cells differentiated along the eosinophilic pathway. In contrast , HL60 cells differentiated into macrophages (HL60 Phi) exhibited mark edly increased photofrin uptake, which was further enhanced by their p retreatment with bacterial lipopolysaccharide. Similar results were ob tained with other photosensitizers tested: di-and tetrasulfonated alum inum phthalocyanines (AlPcS(2) and AlPcS(4)), tetrasulfonated zinc pht halocyanine (ZnPcS(4)), tetraphenylporphine tetrasulfonate (TPPS4) and benzoporphyrin derivative monoacid (BPD). Despite marked differences in the state of self-aggregation and other chemical properties of thes e compounds, the degree of their preferential uptake by HL60 Phi cells showed very little variation. In a typical experiment, the uptake of these photosensitizers by HL60 Phi cells was four to five times higher than the uptake by noninduced HL60 cells. In addition to the fluorome tric assay employed in most of the experiments, cellular concentration of AlPcS(4) was determined by measurement of elementary aluminum usin g atomic absorption spectroscopy.