Lymphoma cells protected from apoptosis by dysregulated bcl-2 continue to bind annexin V in response to B-cell receptor engagement: a cautionary tale.
Translocation of phosphatidylserine (PS) from the inner to outer leaflet of the surface membrane lipid bilayer, a characteristic early event of cells entering the apoptotic program, is routinely assessed by the Ca(2+)-dependent binding of Annexin V (AV). Here, we show that lymphoma cells protected from apoptosis by expression of a bcl-2 transgene or by virtue of the t(14;18)(q32;q21) translocation continue to register enhanced AV binding in response to BCR crosslinking. Induced AV binding appeared BCR-selective in that it did not proceed in Bcl-2(high) cells in response to calcium ionophore or the antidepressant fluoxetine, each of which activate the full apoptotic program in Bcl-2(low) equivalents. AV-positive cells did increase on crosslinking the BCR co-receptor CD19, despite it being a completely non-apoptotic signal. These findings advise caution when interpreting studies where Annexin V binding is used as a sole, or major, indicator of apoptotic death among lymphoma B cells.
Holder
Michelle J
MJ
MRC Centre for Immune Regulation, The Medical School, University of Birmingham, Vincent Drive B15 2TT, UK.
Barnes
Nicholas M
NM
Gregory
Christopher D
CD
Gordon
John
J
D017304:Annexin A5 / Q000378:metabolism*; D018687:Antidepressive Agents, Second-Generation / Q000494:pharmacology; D018941:Antigens, CD19 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D001402:B-Lymphocytes / Q000378:metabolism* / Q000473:pathology; D001693:Biological Transport, Active / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002883:Chromosomes, Human, Pair 14 / Q000235:genetics / Q000378:metabolism; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics / Q000378:metabolism; D005473:Fluoxetine / Q000494:pharmacology; D006801:Humans; D007476:Ionophores / Q000494:pharmacology; D008051:Lipid Bilayers / Q000378:metabolism; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010718:Phosphatidylserines / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D051562:Proto-Oncogene Proteins c-bcr / Q000378:metabolism; D014162:Transfection; D019076:Transgenes / Q000235:genetics; D014178:Translocation, Genetic / Q000235:genetics
D017304:Annexin A5; D018687:Antidepressive Agents, Second-Generation; D018941:Antigens, CD19; D007476:Ionophores; D008051:Lipid Bilayers; D010718:Phosphatidylserines; D019253:Proto-Oncogene Proteins c-bcl-2; D005473:Fluoxetine; C496613:BCR protein, human; D051562:Proto-Oncogene Proteins c-bcr