title: Expression of endogenous oncogenic V600EB-raf induces proliferation and developmental defects in mice and transformation of primary fibroblasts.
abstract: Mutations of the human B-RAF gene are detected in approximately 8% of cancer samples, primarily in cutaneous melanomas (70%). The most common mutation (90%) is a valine-to-glutamic acid mutation at residue 600 (V600E; formerly V599E according to previous nomenclature). Using a Cre/Lox approach, we have generated a conditional knock-in allele of (V600E)B-raf in mice. We show that widespread expression of (V600E)B-Raf cannot be tolerated in embryonic development, with embryos dying approximately 7.5 dpc. Directed expression of mutant (V600E)B-Raf to somatic tissues using the IFN-inducible Mx1-Cre mouse strain induces a proliferative disorder and bone marrow failure with evidence of nonlymphoid neoplasia of the histiocytic type leading to death within 4 weeks of age. However, expression of mutant B-Raf does not alter the proliferation profile of all somatic tissues. In primary mouse embryonic fibroblasts, expression of endogenous (V600E)B-Raf induces morphologic transformation, increased cell proliferation, and loss of contact inhibition. Thus, (V600E)B-Raf is able to induce several hallmarks of transformation in some primary mouse cells without evidence for the involvement of a cooperating oncogene or tumor suppressor gene.
authors.affiliation: Department of Biochemistry, University of Leicester, UK.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Mercer
authors.forename: Susan
authors.initials: S
authors.lastname: Giblett
authors.forename: Stuart
authors.initials: S
authors.lastname: Green
authors.forename: David
authors.initials: D
authors.lastname: Lloyd
authors.forename: Silvy
authors.initials: S
authors.lastname: DaRocha Dias
authors.forename: Mark
authors.initials: M
authors.lastname: Plumb
authors.forename: Richard
authors.initials: R
authors.lastname: Marais
authors.forename: Catrin
authors.initials: C
authors.lastname: Pritchard
mesh_terms: D000818:Animals; D017209:Apoptosis; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology; D002448:Cell Adhesion; D049109:Cell Proliferation; D000013:Congenital Abnormalities / Q000235:genetics*; D004622:Embryo, Mammalian / Q000002:abnormalities*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology*; D019426:Integrases; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020929:Mitogen-Activated Protein Kinase Kinases; D009154:Mutation / Q000235:genetics*; D011247:Pregnancy; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D048493:Proto-Oncogene Proteins B-raf; D020929:Mitogen-Activated Protein Kinase Kinases; C045073:Cre recombinase; D019426:Integrases