Clonal analysis of the response of human promyelocytic leukemia (HL-60) cells to photosensitization induced by a pyrene-containing fatty acid.
Incubation of cells with 12-(1-pyrene) dodecanoic acid (P12), a fatty acid to which a pyrene nucleus has been covalently linked, followed by irradiation with long-wave ultra-violet light (LUV) at 366 nm, resulted in cytotoxicity. Syntheses of macromolecules was significantly decreased after 30 min, while an accumulation of trypan-blue positive, non-viable cells was observed several hours following irradiation. Cloning of the irradiated cells in semi-solid medium showed an exponential dose-response survival curve. Above a threshold dose colony number decreased, although the rate of clonal development and the final size were not affected. The sensitivity of detecting rare surviving cells could be increased by incubating the irradiated cells for several hours in liquid culture followed by concentrating intact cells by gradient sedimentation. Using this procedure, one surviving clonogenic cell could be detected in 10(7) irradiated cells/dish. More than 10 min of irradiation at 773 microV/cm was required to photosensitize the population below detection by this method. The possibility was considered that colonies derived from cells surviving sub-maximal LUV doses represent clones that are resistant to photosensitization, a phenomenon attributed to either inability to take up or metabolize P12, or resistance to the radiation-induced toxicity. Analysis of P12 uptake in the surviving clonal populations showed no significant difference as compared to the parental population. The results suggest that surviving cells reflect a phenotypic heterogeneity caused by variation in the physiological state such as the respective position in the cell cycle and are not genetically resistant mutants.
D002462:Cell Membrane / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells / Q000187:drug effects / Q000528:radiation effects; D004247:DNA / Q000096:biosynthesis; D006801:Humans; D007700:Kinetics; D007850:Lauric Acids / Q000494:pharmacology*; D007951:Leukemia, Myeloid / Q000378:metabolism / Q000473:pathology*; D008855:Microscopy, Electron, Scanning; D008856:Microscopy, Fluorescence; D014176:Protein Biosynthesis; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
D007850:Lauric Acids; C040596:12-(1-pyrene)dodecanoic acid; D004247:DNA