title: KRAS(G12V) enhances proliferation and initiates myelomonocytic differentiation in human stem/progenitor cells via intrinsic and extrinsic pathways.
abstract: In human hematopoietic malignancies, RAS mutations are frequently observed. Yet, little is known about signal transduction pathways that mediate KRAS-induced phenotypes in human CD34(+) stem/progenitor cells. When cultured on bone marrow stroma, we observed that KRAS(G12V)-transduced cord blood (CB) CD34(+) cells displayed a strong proliferative advantage over control cells, which coincided with increased early cobblestone (CAFC) formation and induction of myelomonocytic differentiation. However, the KRAS(G12V)-induced proliferative advantage was transient. By week three no progenitors remained in KRAS(G12V)-transduced cultures and cells were all terminally differentiated into monocytes/macrophages. In line with these results, LTC-IC frequencies were strongly reduced. Both the ERK and p38 MAPK pathways, but not JNK, were activated by KRAS(G12V) and we observed that proliferation and CAFC formation were mediated via ERK, while differentiation was predominantly mediated via p38. Interestingly, we observed that KRAS(G12V)-induced proliferation and CAFC formation, but not differentiation, were largely mediated via secreted factors, since these phenotypes could be recapitulated by treating non-transduced cells with conditioned medium harvested from KRAS(G12V)-transduced cultures. Multiplex cytokine arrays and genome-wide gene expression profiling were performed to gain further insight into the mechanisms by which oncogenic KRAS(G12V) can contribute to the process of leukemic transformation. Thus, angiopoietin-like 6 (ANGPTL6) was identified as an important factor in the KRAS(G12V) secretome that enhanced proliferation of human CB CD34(+) cells.
authors.affiliation: Department of Hematology, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands.
authors.forename: Szabolcs
authors.initials: S
authors.lastname: Fatrai
authors.forename: Djoke
authors.initials: D
authors.lastname: van Gosliga
authors.forename: Lina
authors.initials: L
authors.lastname: Han
authors.forename: Simon M G J
authors.initials: SM
authors.lastname: Daenen
authors.forename: Edo
authors.initials: E
authors.lastname: Vellenga
authors.forename: Jan Jacob
authors.initials: JJ
authors.lastname: Schuringa
mesh_terms: D019943:Amino Acid Substitution; D000091308:Angiopoietin-Like Protein 6; D000075802:Angiopoietin-like Proteins; D042682:Angiopoietins / Q000235:genetics / Q000378:metabolism; D018952:Antigens, CD34; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D016207:Cytokines / Q000096:biosynthesis / Q000235:genetics; D055106:Genome-Wide Association Study; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D007938:Leukemia / Q000235:genetics / Q000378:metabolism; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D020125:Mutation, Missense; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D014161:Transduction, Genetic; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C477601:ANGPTL6 protein, human; D000091308:Angiopoietin-Like Protein 6; D000075802:Angiopoietin-like Proteins; D042682:Angiopoietins; D018952:Antigens, CD34; D016207:Cytokines; C117307:KRAS protein, human; D011518:Proto-Oncogene Proteins; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins