Abnormal hematopoietic phenotypes in Pim kinase triple knockout mice.
BACKGROUND
Pim (proviral insertion in murine lymphoma) kinases are a small family of constitutively active, highly conservative serine/threonine oncogenic kinases and have 3 members: Pim1, Pim2, and Pim3. Pim kinases are also implicated in the regulation of B- and T- cell responses to cytokines and hematopoietic growth factors. The roles of Pim kinases in the regulation of primitive hematopoietic stem cells (HSCs) are largely unknown.


METHODS
In the current study, Pim1-/-2-/-3-/- triple knockout (TKO) mice were used to determine the role of Pim kinases in hematopoiesis. Peripheral blood hematological parameters were measured in Pim TKO mice and age-matched wild-type (WT) controls. Primary, secondary, and competitive transplantations were performed to assay the long-term repopulating HSCs in Pim TKO mice. In vivo BrdU incorporation assay and ex vivo Ki67 staining and caspase 3 labeling were performed to evaluate the proliferation and apoptosis of HSCs in Pim TKO mice.


RESULTS
Compared to age-matched WT controls, Pim TKO mice had lower peripheral blood platelet count and exhibited erythrocyte hypochromic microcytosis. The bone marrow cells from Pim TKO mice demonstrated decreased hematopoietic progenitor colony-forming ability. Importantly, Pim TKO bone marrow cells had significantly impaired capacity in rescuing lethally irradiated mice and reconstituting hematopoiesis in primary, secondary and competitive transplant models. In vivo BrdU incorporation in long-term HSCs was reduced in Pim TKO mice. Finally, cultured HSCs from Pim TKO mice showed reduced proliferation evaluated by Ki67 staining and higher rate of apoptosis via caspase 3 activation.


CONCLUSIONS
Pim kinases are not only essential in the hematopoietic lineage cell development, but also important in HSC expansion, self-renewal, and long-term repopulation.
Division of Hematology-Oncology, Department of Medicine, Medical University of South Carolina, 86 Jonathan Lucas Street, Hollings Cancer Center Rm# HO307, Charleston, SC 29425, USA.
Ningfei
N
An
Andrew S
AS
Kraft
Yubin
Y
Kang
D000818:Animals; D017209:Apoptosis; D001854:Bone Marrow Cells / Q000473:pathology; D001973:Bromodeoxyuridine; D049109:Cell Proliferation; D016922:Cellular Senescence; D003114:Colony-Forming Units Assay; D005260:Female; D006402:Hematologic Diseases / Q000209:etiology* / Q000401:mortality / Q000473:pathology; D006410:Hematopoiesis; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000473:pathology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D010641:Phenotype; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D051573:Proto-Oncogene Proteins c-pim-1 / Q000502:physiology*; D015996:Survival Rate
C094167:Pim2 protein, mouse; D011518:Proto-Oncogene Proteins; C496636:Pim1 protein, mouse; C488192:Pim3 protein, mouse; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1; D001973:Bromodeoxyuridine