Abstract
The molecular changes induced by alemtuzumab following binding of CD52 on B tumor cells were investigated. Alemtuzumab alone had no detectable impact on cell signaling but cross-linking of alemtuzumab on the surface of B tumor lines with anti-human Fc antibodies induced a transient Ca(2+) flux followed by phosphorylation of several kinases involved in stress and survival pathways, and expression of associated proteins including TNF-α. Cross-linking of alemtuzumab also induced capping and caspase-dependent apoptosis of the tumor lines. When using primary cells from B-CLL patients, alemtuzumab alone was capable of inducing protein phosphorylation and apoptosis through the cross-linking of alemtuzumab by FcγRIIb receptors on B-CLL cells. Apoptosis was prevented by blocking of FcγRIIb receptors with anti-CD32 antibody. Overall, our results indicate that cross-linking of alemtuzumab on B tumor cells can occur naturally through Fc receptor interaction and leads to the activation of specific cellular pathways and induction of apoptosis.
MeSH terms
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Alemtuzumab
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Antibodies / immunology
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Antibodies / pharmacology
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Antibodies, Monoclonal, Humanized / pharmacology*
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Antineoplastic Agents / pharmacology
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Apoptosis / drug effects*
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B-Lymphocytes / drug effects*
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B-Lymphocytes / metabolism
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B-Lymphocytes / pathology
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Calcium / metabolism
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Cell Line, Tumor
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Gene Expression Profiling
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Gene Expression Regulation, Leukemic / drug effects
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Humans
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Immunoblotting
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Intracellular Space / drug effects
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Intracellular Space / metabolism
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Leukemia, Lymphocytic, Chronic, B-Cell / genetics
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Leukemia, Lymphocytic, Chronic, B-Cell / metabolism
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Leukemia, Lymphocytic, Chronic, B-Cell / pathology
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Phosphorylation / drug effects
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Proto-Oncogene Proteins c-akt / genetics
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Proto-Oncogene Proteins c-akt / metabolism
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Receptors, IgG / immunology
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction / drug effects*
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Tumor Cells, Cultured
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Tumor Necrosis Factor-alpha / genetics
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Tumor Necrosis Factor-alpha / metabolism
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p38 Mitogen-Activated Protein Kinases / genetics
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p38 Mitogen-Activated Protein Kinases / metabolism
Substances
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Antibodies
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Antibodies, Monoclonal, Humanized
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Antineoplastic Agents
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Receptors, IgG
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Tumor Necrosis Factor-alpha
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Alemtuzumab
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Proto-Oncogene Proteins c-akt
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p38 Mitogen-Activated Protein Kinases
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Calcium