Abstract
Chronic lymphocytic leukaemia cells survive and proliferate in patients but rapidly die in culture. The microenvironment that sustains leukaemic cells in vivo contains both stromal cell elements and T cells. We defined changes in Bcl-2 family protein expression on culture with CD40 ligand (CD154) expressed on mouse fibroblast L cells, and interleukin-4 (IL-4; CD154/IL-4 system): conditions that support survival and proliferation. Unexpectedly, Bcl-2 protein expression decreased whilst pro-survival Bcl-x(L) (as well as A1 and Mcl-1) increased. However, the CD154-L cell/IL-4 system also increased the pro-apoptotic proteins, Bid and Noxa, suggesting that an increased pool of pro-survival factors and not the effects of a single protein mediate survival. Most pro-apoptotic proteins were not induced in drug or spontaneous apoptosis, but expression of Bcl-x(S), a pro-apoptotic BCL2L1 isoform, was associated with cell death. This was post-transcriptionally controlled, and, therefore, alternative splicing at the Bcl-x locus appears to have a role in the regulation of chronic lymphocytic leukaemia (CLL) cell survival. This study demonstrated a switch in pro-survival proteins associated with the transition from quiescence to CD154-driven proliferation. CLL therapies targeting Bcl-2 may need to be modified to antagonize proliferation centre-specific pro-survival proteins.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antineoplastic Agents / pharmacology
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Antineoplastic Agents / therapeutic use
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Apoptosis Regulatory Proteins / analysis
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Apoptosis Regulatory Proteins / metabolism
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BH3 Interacting Domain Death Agonist Protein / metabolism
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Blotting, Western
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CD40 Ligand / pharmacology*
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Cell Proliferation
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Cell Survival
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Gene Expression
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Gene Expression Regulation, Neoplastic*
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Humans
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Immunohistochemistry
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Interleukin-4 / pharmacology
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Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy
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Leukemia, Lymphocytic, Chronic, B-Cell / metabolism*
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Lymph Nodes / chemistry
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Mice
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Minor Histocompatibility Antigens
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Myeloid Cell Leukemia Sequence 1 Protein
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Neoplasm Proteins / analysis
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Neoplasm Proteins / metabolism
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Protein Kinase C / antagonists & inhibitors
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Proto-Oncogene Proteins / analysis
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Proto-Oncogene Proteins / metabolism
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Proto-Oncogene Proteins c-bcl-2 / analysis
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Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors
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Proto-Oncogene Proteins c-bcl-2 / genetics*
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Staurosporine / pharmacology
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Tumor Cells, Cultured
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Vidarabine / analogs & derivatives
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Vidarabine / pharmacology
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bcl-X Protein / analysis
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bcl-X Protein / metabolism
Substances
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Antineoplastic Agents
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Apoptosis Regulatory Proteins
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BBC3 protein, human
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BCL2-related protein A1
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BCL2L1 protein, human
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BH3 Interacting Domain Death Agonist Protein
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Mcl1 protein, mouse
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Minor Histocompatibility Antigens
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Myeloid Cell Leukemia Sequence 1 Protein
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Neoplasm Proteins
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PMAIP1 protein, human
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Proto-Oncogene Proteins
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Proto-Oncogene Proteins c-bcl-2
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bcl-X Protein
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CD40 Ligand
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Interleukin-4
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Protein Kinase C
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Vidarabine
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Staurosporine
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fludarabine