C-RAF-1 serine/threonine kinase is required in BCR/ABL-dependent and normal hematopoiesis.
BCR/ABL oncogenic tyrosine kinase is responsible for initiating and maintaining the leukeic phenotype of Philadelphia chromosome-positive cells. c-RAF-1 serine/threonine kinase is known to be activated by receptor and nonreceptor tyrosine kinases. To determine whether c-RAF-1 plays a role in the growth of BCR/ABL-dependent cells, we examined whether c-RAF-1 associates with and/or is regulated by BCR/ABL and, if so, whether this interaction is functionally significant for BCR/ABL-dependent growth of chronic myelogenous leukemia cells and for growth factor-dependent proliferation of normal bone marrow cells. We show that c-RAF-1 enzymatic activity is regulated by BCR/ABL, although the protein does not associate with BCR/ABL. Downregulation of c-RAF-1 expression with antisense oligodeoxynucleotides or cDNA constructs, and inhibition of c-RAF-1 activity by its dominant negative mutants, inhibited both BCR/ABL-dependent growth of chronic myelogenous leukemia cells and growth factor-dependent proliferation of normal hematopoietic progenitors and the MO7 cell line without affecting the BCR/ABL-and growth factor-independent proliferation of HL-60 cells. These results indicate that c-RAF-1 plays an important role in Philadelphia chromosome-positive and normal hematopoiesis.
Skorski
T
T
Department of Microbiology and Immunology, Jefferson Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Nieborowska-Skorska
M
M
Szczylik
C
C
Kanakaraj
P
P
Perrotti
D
D
Zon
G
G
Gewirtz
A
A
Perussia
B
B
Calabretta
B
B
D001483:Base Sequence; D002455:Cell Division / Q000502:physiology; D004789:Enzyme Activation; D016044:Fusion Proteins, bcr-abl / Q000502:physiology*; D006410:Hematopoiesis / Q000502:physiology*; D006413:Hematopoietic System / Q000166:cytology* / Q000201:enzymology* / Q000502:physiology; D006801:Humans; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology*; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism / Q000502:physiology
D011518:Proto-Oncogene Proteins; D016044:Fusion Proteins, bcr-abl; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)