zinostatin and Cell-Transformation--Viral

The subcellular site of action of a proteinaceous antitumor antibiotic neocarzinostatin (NCS) was studied using normal human lymphocytes, Epstein-Barr virus transformed lymphoblastoid cells, osmotically burst lymphoblastoid cells, and colicin E1 plasmid DNA. The rate of DNA strand break in these different types of DNA was found to be in the following order: Colicin DNA > burst cell DNA > lymphoblastoid cell DNA > normal lymphocyte DNA. Furthermore, fluorescence microscopy revealed that lymphoblastoid cells incorporated more fluorescein isothiocyanate labeled NCS than normal cells. High uptake of NCS in lymphoblastoid cells coincided with a high killing rate; low uptake of NCS in lymphocytes resulted in very little cell killing. Uptake velocity using fluorescein diacetate (FDA) also showed that the lymphoblastoid cells exhibited a higher uptake of FDA coinciding with a higher killing rate. The cell killing activity of NCS appears to be closely associated with the rate of intracellular uptake of NCS and subsequent direct degradation of DNA by the drug. This notion is reinforced by the reported finding that the dose required for DNA strand scission is only about 1/100 of that for the inhibition of cap formation. Thus DNA strand scission, rather than the cell membrane, appears to be the primary target of NCS. Enhanced incorporation of many substances is commonly observed upon transformation of cells by viruses, and our present results may provide an important clue toward the explanation of the selective toxicity toward tumor cells of NCS.

Topics: Antibiotics, Antineoplastic; Cell Line; Cell Survival; Cell Transformation, Viral; DNA; Herpesvirus 4, Human; Humans; Kinetics; Lymphocytes; Plasmids; Zinostatin

Topics: Animals; Antibiotics, Antineoplastic; Antigen-Antibody Complex; Avidin; Biotin; Cell Line; Cell Survival; Cell Transformation, Viral; Dactinomycin; G(M1) Ganglioside; Immunodiffusion; Kirsten murine sarcoma virus; Leukemia L5178; Leukemia, Experimental; Liposomes; Mice; Phosphatidylethanolamines; Zinostatin

Effect of a protein antitumor antibiotic, neocarzinostatin (NCS) was examined on Epstein-Barr virus (EBV)-carrying human lymphoid cell lines and normal human lymphocytes. A marked cytotoxic effect of NCS on umbilical cord lymphocytes freshly transformed by EBV was observed, whereas the cells before transformation were affected only very little by NCS. Majority of long-term cultured cell lines were affected only slightly, while shorter-term cultured lines were more susceptible to the effect of NCS. An uptake of FITC-labeled NCS into cells was examined by fluorescence microscopy. The incorporation by the freshly transformed cells was higher than that by the longer-term cultured cell lines. Normal lymphyocytes or heat-killed cells, however, incorporated FITC-NCS very little. On the basis of the known mode of action of NCS on DNA and the present observation, the cytotoxicity of NCS appeared to be exerted within the cells.

Topics: Antibiotics, Antineoplastic; Cell Division; Cell Line; Cell Membrane Permeability; Cell Transformation, Viral; Cells, Cultured; Herpesvirus 4, Human; Humans; Lymphocytes; Zinostatin