Recombinant single-chain immunotoxins against T and B cell leukemias.
Interleukin 2 (IL2) receptors (IL2R's) are found on malignant cells in many human leukemias and lymphomas and are expressed by activated T cells in many autoimmune disorders. Anti-Tac(Fv), a single-chain protein composed of the variable heavy and light domains of the anti-IL2R monoclonal antibody anti-Tac, can be genetically fused to derivatives of Pseudomonas exotoxin (PE) or diphtheria toxin (DT) to form potent immunotoxins. We have shown that anti-Tac(Fv) binds to low affinity IL2R's on fresh chronic lymphocytic leukemia (CLL) and adult T-cell leukemia (ATL) cells and can target either toxin to kill those cells. Anti-Tac(Fv)-PE40, containing the truncated form of PE without its binding domain, was cytotoxic to malignant cells from 8 of 8 ATL patients tested, with IC50's ranging from 0.11 to 5.5 ng/ml. Anti-Tac(Fv)-PE40KDEL, a derivative of anti-Tac(Fv)-PE40 which contains the KDEL carboxyl terminus, was more cytotoxic toward cells from all ATL patients and also killed CLL cells from 8 of 16 patients. DT388-anti-Tac(Fv), containing amino acids 1-388 of DT fused to the amino terminus of anti-Tac(Fv), was less cytotoxic than anti-Tac(Fv)-PE40 on ATL cells from 4 of 5 patients, but was cytotoxic toward CLL cells from 12 of 16 patients. DT388-IL2, where IL2 is substituted for anti-Tac(Fv), is similar to DAB389IL2, an IL2-toxin currently in clinical trials. DT388-IL2 and DAB389IL2 differ by only a few amino acids and have equal cytotoxic activity. DT388-IL2 was cytotoxic toward ATL cells from all patients tested, but usually required much higher concentrations than anti-Tac(Fv)-PE40 and was poorly active against CLL cells. Thus, recombinant toxins containing anti-Tac(Fv) are cytotoxic toward freshly isolated CLL and ATL cells and will be studied further as potential therapy for IL2R-related disorders.
Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
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Kreitman
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Pastan
D036002:ADP Ribose Transferases; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins / Q000627:therapeutic use / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D004167:Diphtheria Toxin / Q000627:therapeutic use / Q000633:toxicity; D005098:Exotoxins / Q000627:therapeutic use / Q000633:toxicity; D006801:Humans; D007143:Immunoglobulin Heavy Chains; D007148:Immunoglobulin mu-Chains; D000922:Immunotoxins / Q000096:biosynthesis / Q000627:therapeutic use* / Q000633:toxicity*; D015448:Leukemia, B-Cell / Q000628:therapy*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell; D015458:Leukemia, T-Cell / Q000628:therapy*; D015459:Leukemia-Lymphoma, Adult T-Cell; D008969:Molecular Sequence Data; D015375:Receptors, Interleukin-2 / Q000276:immunology*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000627:therapeutic use / Q000633:toxicity; D014407:Tumor Cells, Cultured; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D000911:Antibodies, Monoclonal; D001427:Bacterial Toxins; D004167:Diphtheria Toxin; D005098:Exotoxins; D007143:Immunoglobulin Heavy Chains; D007148:Immunoglobulin mu-Chains; D000922:Immunotoxins; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A