BCR-ABL and constitutively active erythropoietin receptor (cEpoR) activate distinct mechanisms for growth factor-independence and inhibition of apoptosis in Ba/F3 cell line.
The interleukin-3 dependent murine Ba/F3 cell line has been widely used as an experimental model of cell transformation by BCR-ABL oncogenes as assessed by induction of growth-factor-independence and inhibition of apoptosis in vitro. The signaling pathways used by BCR-ABL oncogenes to exert these effects are unknown. To gain insights into this phenomenon, we have introduced the p190- and p210-encoding BCR-ABL oncogenes as well as the constitutively activated oncogenic murine erythropoietin receptor (cEpoR) into Ba/F3 and compared the behavior of individual clones in response to apoptotic stimuli. Both p210 and p190 BCR-ABL vectors induced IL-3-independent growth and the same result was obtained with the cEpo-R vector. Individual clones of Ba/F3 cells expressing BCR-ABL exhibited significant resistance to apoptosis induced by either etoposide, serum deprivation or growth-factor withdrawal. In contrast, Ba/F3 cells expressing the constitutively active cEpoR behaved like parental Ba/F3 cells undergoing apoptosis when similarly treated with etoposide or upon serum deprivation. Bc12 and Bax levels were similar in all BCR-ABL and cEpoR-transfected clones. However, in band-shift assays, nuclear extracts from growth-factor-independent Ba/F3 clones expressing cEpoR had no detectable STAT activity as opposed to the constitutive STAT activation detected in all Ba/F3 clones expressing p210 or p190 BCR-ABL. Our results indicate that although both constitutively activated cEpoR and BCR-ABL oncogenes induce growth-factor independence in Ba/F3 cells, only BCR-ABL is able to protect cells from etoposide and serum-deprivation-induced apoptosis and induce a strong constitutive activation of STAT factors, suggesting a role for these molecules in the anti-apoptotic activity of BCR-ABL.
Ahmed
M
M
CNRS-URA 1461, Paris, France.
Dusanter-Fourt
I
I
Bernard
M
M
Mayeux
P
P
Hawley
R G
RG
Bennardo
T
T
Novault
S
S
Bonnet
M L
ML
Gisselbrecht
S
S
Varet
B
B
Turhan
A G
AG
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002460:Cell Line / Q000166:cytology / Q000187:drug effects; D004921:Erythropoietin / Q000378:metabolism; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D005822:Genetic Vectors; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D009857:Oncogenes / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000502:physiology*; D015398:Signal Transduction; D014162:Transfection; D051028:bcl-2-Associated X Protein
C494827:Bax protein, mouse; D007377:Interleukin-3; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017467:Receptors, Erythropoietin; D051028:bcl-2-Associated X Protein; D004921:Erythropoietin; D016044:Fusion Proteins, bcr-abl