Sensitization of B-cell chronic lymphocytic leukemia cells to recombinant immunotoxin by immunostimulatory phosphorothioate oligodeoxynucleotides.
A recombinant anti-CD25 immunotoxin, LMB-2, has shown clinical efficacy in hairy cell leukemia and T-cell neoplasms. Its activity in B-cell chronic lymphocytic leukemia (B-CLL) is inferior but might be improved if B-CLL cells expressed higher numbers of CD25 binding sites. It was recently reported that DSP30, a phosphorothioate CpG-oligodeoxynucleotide (CpG-ODN) induces immunogenicity of B-CLL cells by up-regulation of CD25 and other antigens. The present study investigated the antitumor activity of LMB-2 in the presence of DSP30. To this end, B-CLL cells from peripheral blood of patients were isolated immunomagnetically to more than 98% purity. Incubation with DSP30 for 48 hours augmented CD25 expression in 14 of 15 B-CLL samples, as assessed by flow cytometry. DSP30 increased LMB-2 cytotoxicity dose dependently whereas a control ODN with no CpG motif did not. LMB-2 displayed no antitumor cell activity in the absence of CpG-ODN as determined colorimetrically with an (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay. In contrast, B-CLL growth was inhibited in 12 of 13 samples with 50% inhibition concentrations (IC(50)) in the range of LMB-2 plasma levels achieved in clinical studies. Two samples were not evaluable because of spontaneous B-CLL cell death in the presence of DSP30. Control experiments with an immunotoxin that does not recognize hematopoietic cells, and an anti-CD22 immunotoxin, confirmed that sensitization to LMB-2 was specifically due to up-regulation of CD25. LMB-2 was much less toxic to normal B and T lymphocytes compared with B-CLL cells. In summary, immunostimulatory CpG-ODNs efficiently sensitize B-CLL cells to a recombinant immunotoxin by modulation of its target. This new treatment strategy deserves further attention.
Decker
Thomas
T
3rd Department of Medicine, Technical University of Munich, Munich, Germany. t.decker@lrz.tum.de
Hipp
Susanne
S
Kreitman
Robert J
RJ
Pastan
Ira
I
Peschel
Christian
C
Licht
Thomas
T
D000276:Adjuvants, Immunologic / Q000494:pharmacology* / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents / Q000494:pharmacology / Q000627:therapeutic use; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D005098:Exotoxins; D005260:Female; D006801:Humans; D000922:Immunotoxins / Q000494:pharmacology* / Q000627:therapeutic use; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000188:drug therapy* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology* / Q000627:therapeutic use; D015375:Receptors, Interleukin-2 / Q000096:biosynthesis / Q000187:drug effects / Q000276:immunology; D011994:Recombinant Proteins / Q000494:pharmacology / Q000627:therapeutic use; D013873:Thionucleotides / Q000494:pharmacology / Q000627:therapeutic use; D014407:Tumor Cells, Cultured / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
D000276:Adjuvants, Immunologic; D000911:Antibodies, Monoclonal; D000970:Antineoplastic Agents; C077707:B3(Fv)-PE38KDEL recombinant immunotoxin; C408982:CPG-oligonucleotide; D005098:Exotoxins; D000922:Immunotoxins; D009838:Oligodeoxyribonucleotides; D015375:Receptors, Interleukin-2; D011994:Recombinant Proteins; D013873:Thionucleotides