Oncogenic B-Raf(V600E) induces spindle abnormalities, supernumerary centrosomes, and aneuploidy in human melanocytic cells.
Activating B-Raf mutations arise in 60% to 70% of human melanomas and are thought to play a vital role in tumorigenesis, although how this occurs remains poorly understood. Wild-type B-Raf is critical for normal mitosis of human somatic cells, suggesting that mutational activation of B-Raf might compromise mitosis. We examined this hypothesis by introducing oncogenic mutant B-Raf(V600E) into established human melanoma cells, assessing the effects on mitosis and their possible relationship to extracellular signal-regulated kinase (ERK) pathway activation. Exogenous expression of this activated B-Raf mutant led to a high incidence of aberrant spindles and supernumerary centrosomes. These mitotic abnormalities were suppressed by expression of a B-Raf(V600E) mutant-specific shRNA or by the addition of the mitogen-activated protein/ERK kinase-specific inhibitor U0126. Mitotic abnormalities generated by B-Raf(V600E) also caused missegregation of chromosomes leading to aneuploidy. Because activating B-Raf mutations are detected frequently in benign nevi, we extended our studies to primary human melanocytes. Remarkably, short-term expression of B-Raf(V600E) was sufficient to induce aneuploidy in human melanocytes or in immortalized human mammary epithelial cells. Collectively, our studies identify a novel role for the B-Raf oncogene in driving aneuploidy in melanocytic cells. We propose that disruption of mitotic controls by oncogenic B-Raf has important implications for understanding melanoma tumor development.
Cui
Yongping
Y
Department of Molecular Oncology and Analytic Microscopy Core Facility, H. Lee Moffitt Cancer Center and Research Institute and Cancer Biology Graduate Program, University of South Florida, Tampa, Florida 33612, USA.
Borysova
Meghan K
MK
Johnson
Joseph O
JO
Guadagno
Thomas M
TM
D000782:Aneuploidy; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D018385:Centrosome / Q000473:pathology*; D002869:Chromosome Aberrations; D020090:Chromosome Segregation; D004847:Epithelial Cells / Q000473:pathology; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000473:pathology; D008544:Melanocytes / Q000473:pathology / Q000502:physiology*; D008545:Melanoma / Q000235:genetics* / Q000473:pathology; D008938:Mitosis / Q000235:genetics; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D008941:Spindle Apparatus / Q000235:genetics / Q000473:pathology*; D019098:Telomerase / Q000494:pharmacology
C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; C509186:TERT protein, human; D019098:Telomerase