title: BRAF(V600E) efficient transformation and induction of microsatellite instability versus KRAS(G12V) induction of senescence markers in human colon cancer cells.
abstract: In colorectal cancer, BRAF and KRAS oncogenes are mutated in about 15% and 35% respectively at approximately the same stage of the adenoma-carcinoma sequence. Since these two mutations rarely coexist, further analysis to dissect their function of transformation in colon cancer is required. Caco-2 human colon adenocarcinoma cells were stably transfected with BRAF(V600E) (Caco-BR cells) or KRAS(G12V) (Caco-K cells) oncogenes. BRAF(V600E) is more efficient in transforming Caco-2 cells and altering their morphology. The dominant nature of BRAF(V600E) is evident by its ability to render Caco-2 cells tumorigenic in vivo all be it through selective extracellular signal-related kinase (ERK) 2 phosphorylation and high levels of cyclin D1. As a consequence, the cell cycle distribution of parental cells is altered and microsatellite instability is introduced. Attenuated ERK activation observed correlated with KSR downregulation by BRAF(V600E) without further implications to signaling. Highly activated ERK in case of KRAS(G12V) (Caco-K cells) leads to mild transformation causing Caco-K cells to express premature senescence-related markers and acquire growth factor-dependent viability. Interestingly, BRAF(WT)gets equally activated by upstream KRAS mutations present in colon adenocarcinoma cells such as DLD-1 and SW620. Taken together, these results suggest that the two oncogenes have different transforming capability in colon cancer, although they both use the mitogen-activated protein (MAP) kinase pathway to carry out their effect. In general, BRAF(V600E) presents greater potential in mediating tumorigenic effect as compared to KRAS(G12V) both in vivo and in vitro. These findings may have implications in personalised diagnosis and targeted therapeutics.
authors.affiliation: Laboratory of Signal Mediated Gene Expression, Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, 11635 Athens, Greece.
authors.forename: Eftychia
authors.initials: E
authors.lastname: Oikonomou
authors.forename: Eleni
authors.initials: E
authors.lastname: Makrodouli
authors.forename: Maria
authors.initials: M
authors.lastname: Evagelidou
authors.forename: Tobias
authors.initials: T
authors.lastname: Joyce
authors.forename: Lesley
authors.initials: L
authors.lastname: Probert
authors.forename: Alexander
authors.initials: A
authors.lastname: Pintzas
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D015153:Blotting, Western; D018938:Caco-2 Cells; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D016922:Cellular Senescence / Q000235:genetics*; D003110:Colonic Neoplasms / Q000235:genetics*; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D020935:MAP Kinase Signaling System / Q000502:physiology; D053842:Microsatellite Instability; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D018631:ras Proteins / Q000235:genetics*
chemical_list: D014408:Biomarkers, Tumor; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins