SELECTIVE KILLING OF TUMOR-CELLS IN-VITRO BY IMMUNOTOXIN COMPOSES OF ANTITUMOR ANTIBIOTIC STREPTONIGRIN AND POLYCLONAL SPECIFIC ANTIBODIES

Streptonigrin N-hydroxysuccinimide ester (STN-COONSu) was obtained by carbodiimide synthesis. Poly-L-lysine (PLL) was loaded with STN-COONSu and conjugated to polyclonal rabbit immunoglobulin G (IgG) activated with sodium periodate. Non-specific IgG and IgG against Ehrlich carcin oma cells were used to construct non-specific and specific immunotoxin s. Immunotoxins contained 100 molecules of streptonigrin per 1 molecul e of IgG. The streptonigrin concentration that caused 50% of inhibitio n of [H-3]thymidine incorporation in Ehrlich carcinoma cells (IC50) wa s 0.8 mu g/ml for specific immunotoxin, 16 mu g/ml for non-specific im munotoxin, and 20 mu g/ml for the poly-L-lysine-streptonigrin conjugat e (PLL-STN) used as the initial water-soluble form of antibiotic. Our results demonstrate that the toxicity for target cells of streptonigri n conjugated to specific IgG was 25 times higher than that of the init ial water soluble form of antibiotic. This specific immumotoxin was no n-toxic for non-target cells.