Constitutive activation of extracellular signal-regulated kinase predisposes diffuse large B-cell lymphoma cell lines to CD40-mediated cell death.
CD40 promotes survival, proliferation, and differentiation of normal B cells but can cause activation-induced cell death in malignant B lymphocytes. CD40 ligand and anti-CD40 antibodies have been used successfully to induce apoptosis in lymphoma lines both in vitro and in xenograft tumor models. Although this makes CD40 an attractive target for antitumor therapies, the response of malignant B cells to CD40 signaling is variable, and CD40 stimulation can enhance proliferation and can increase chemoresistance in some cell lines. It would therefore be useful to identify markers that predict whether a specific cell line or tumor will undergo apoptosis when stimulated with CD40 and to identify targets downstream of CD40 that affect only the apoptotic arm of CD40 signaling. We have analyzed gene expression patterns in CD40-sensitive and CD40-resistant diffuse large B-cell lymphoma (DLBCL) cell lines to identify signaling pathways that are involved in CD40-mediated apoptosis. CD40-resistant lines expressed pre-B-cell markers, including RAG and VPREB, whereas CD40-sensitive cells resembled mature B cells and expressed higher levels of transcripts encoding several members of the CD40 signaling pathway, including LCK and VAV. In addition, CD40-sensitive DLBCL cell lines also displayed constitutive activation of extracellular signal-regulated kinase (ERK) and failed to undergo apoptosis when ERK phosphorylation was inhibited. In contrast, CD40-resistant lines showed no constitutive activation of ERK and no increase in ERK activity in response to CD40 stimulation. Our results suggest that constitutive activation of ERK may be required for death signaling by CD40.
Neuroimmunology Unit, Montreal Neurological Institute, Departments of Medicine and Human Genetics, McGill University, Duff Medical Bldg. Room 717, 3775 University Street, Montreal, Quebec, Canada H3A 2B4. sharkies10k@hotmail.com
C Annette
CA
Hollmann
Trevor
T
Owens
Josephine
J
Nalbantoglu
Thomas J
TJ
Hudson
Robert
R
Sladek
D017209:Apoptosis / Q000502:physiology*; D019013:CD40 Antigens / Q000502:physiology*; D045744:Cell Line, Tumor; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D016393:Lymphoma, B-Cell / Q000201:enzymology* / Q000276:immunology / Q000473:pathology*; D008228:Lymphoma, Non-Hodgkin / Q000201:enzymology / Q000276:immunology / Q000473:pathology*; D020935:MAP Kinase Signaling System; D010766:Phosphorylation; D051567:Proto-Oncogene Proteins c-vav / Q000378:metabolism
D019013:CD40 Antigens; D051567:Proto-Oncogene Proteins c-vav; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D048049:Extracellular Signal-Regulated MAP Kinases