Molecular events contributing to cell death in malignant human hematopoietic cells elicited by an IgG3-avidin fusion protein targeting the transferrin receptor.
We have previously reported that an anti-human transferrin receptor IgG3-avidin fusion protein (anti-hTfR IgG3-Av) inhibits the proliferation of an erythroleukemia-cell line. We have now found that anti-hTfR IgG3-Av also inhibits the proliferation of additional human malignant B and plasma cells. Anti-hTfR IgG3-Av induces internalization and rapid degradation of the TfR. These events can be reproduced in cells treated with anti-hTfR IgG3 cross-linked with a secondary Ab, suggesting that they result from increased TfR cross-linking. Confocal microscopy of cells treated with anti-hTfR IgG3-Av shows that the TfR is directed to an intracellular compartment expressing the lysosomal marker LAMP-1. The degradation of TfR is partially blocked by cysteine protease inhibitors. Furthermore, cells treated with anti-hTfR IgG3-Av exhibit mitochondrial depolarization and activation of caspases 9, 8, and 3. The mitochondrial damage and cell death can be prevented by iron supplementation, but cannot be fully blocked by a pan-caspase inhibitor. These results suggest that anti-hTfR IgG3-Av induces lethal iron deprivation, but the resulting cell death does not solely depend on caspase activation. This report provides insights into the mechanism of cell death induced by anti-TfR Abs such as anti-hTfR IgG3-Av, a molecule that may be useful in the treatment of B-cell malignancies such as multiple myeloma.
Ng
Patrick P
PP
Division of Surgical Oncology, Department of Surgery, University of California-Los Angeles, 10833 Le Conte Avenue, Los Angeles, CA 90095-1782, USA. penichet@microbio.ucla.edu
Helguera
Gustavo
G
Daniels
Tracy R
TR
Lomas
Simon Z
SZ
Rodriguez
Jose A
JA
Schiller
Gary
G
Bonavida
Benjamin
B
Morrison
Sherie L
SL
Penichet
Manuel L
ML
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001360:Avidin / Q000494:pharmacology*; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003432:Cross-Linking Reagents; D003676:Deferoxamine / Q000494:pharmacology; D019337:Hematologic Neoplasms / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000628:therapy*; D006801:Humans; D007074:Immunoglobulin G / Q000494:pharmacology*; D007501:Iron / Q000494:pharmacology; D007952:Leukemia, Plasma Cell / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D009101:Multiple Myeloma / Q000378:metabolism / Q000473:pathology / Q000628:therapy; D011990:Receptors, Transferrin / Q000037:antagonists & inhibitors* / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D017262:Siderophores / Q000494:pharmacology
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D003432:Cross-Linking Reagents; D007074:Immunoglobulin G; D011990:Receptors, Transferrin; D011993:Recombinant Fusion Proteins; D017262:Siderophores; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D001360:Avidin; D007501:Iron; D003676:Deferoxamine