Protein kinase C mediates mutant N-Ras-induced developmental abnormalities in normal human erythroid cells.
RAS mutations are one of the most frequent molecular abnormalities associated with myeloid leukemia and preleukemia, yet there is a poor understanding of how they contribute to the pathogenesis of these conditions. Here, we describe the consequences of ectopic mutant N-Ras (N-Ras*) expression on normal human erythropoiesis. We show that during early (erythropoietin [EPO]-independent) erythropoiesis, N-Ras* promoted the amplification of a phenotypically primitive but functionally defective subpopulation of CD34(+) erythroblasts. N-Ras* also up-regulated the expression of megakaryocyte antigens on human erythroblasts. Although early erythroblasts expressing N-Ras* were able to respond to erythropoietin and generate mature progeny, this occurred with greatly reduced efficiency, probably explaining the poor colony growth characteristics of these cells. We further report that this oncogene promoted the expression and activation of protein kinase C (PKC) and that the effects of N-Ras* on erythropoiesis could be abrogated or attenuated by inhibition of PKC. Similarly, the effects of this oncogene could be partially mimicked by treatment with PKC agonist. Together, these data suggest that expression of N-Ras* is able to subvert the normal developmental cues that regulate erythropoiesis by activating PKC. This gives rise to phenotypic and functional abnormalities commonly observed in preleukemia, suggesting a direct link between RAS mutations and the pathogenesis of preleukemia.
Darley
Richard L
RL
Leukaemia Research Fund Differentiation Group, Department of Haematology, University of Wales College of Medicine, Cardiff, United Kingdom. darley@cf.ac.uk
Pearn
Lorna
L
Omidvar
Nader
N
Sweeney
Marion
M
Fisher
Janet
J
Phillips
Sarah
S
Hoy
Terry
T
Burnett
Alan K
AK
D015703:Antigens, CD / Q000187:drug effects / Q000378:metabolism; D018952:Antigens, CD34 / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D004920:Erythropoiesis / Q000187:drug effects*; D005312:Fetal Blood; D006801:Humans; D016130:Immunophenotyping; D009154:Mutation; D040201:Platelet Membrane Glycoprotein IIb / Q000187:drug effects; D011289:Preleukemia / Q000209:etiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D014161:Transduction, Genetic; D018631:ras Proteins / Q000235:genetics / Q000494:pharmacology*
D015703:Antigens, CD; D018952:Antigens, CD34; D040201:Platelet Membrane Glycoprotein IIb; D011493:Protein Kinase C; D018631:ras Proteins