Arsenic Primes Human Bone Marrow CD34+ Cells for Erythroid Differentiation

Arsenic trioxide exhibits therapeutic effects on certain blood malignancies, at least partly by modulating cell differentiation. Previousin vitrostudies in human hematopoietic progenitor cells have suggested that arsenic may inhibit erythroid differentiation. However, these effects were all observed in the presence of arsenic compounds, while the concomitant cytostatic and cytotoxic actions of arsenic might mask a prodifferentiating activity. To eliminate the potential impacts of the cytostatic and cytotoxic actions of arsenic, we adopted a novel protocol by pretreating human bone marrow CD34+ cells with a low, noncytotoxic concentration of arsenic trioxide, followed by assaying the colony forming activities in the absence of the arsenic compound. Bone marrow specimens were obtained from chronic myeloid leukemia patients who achieved complete cytogenetic remission. CD34+ cells were isolated by magnetic-activated cell sorting. We discovered that arsenic trioxide enhanced the erythroid colony forming activity, which was accompanied by a decrease in the granulomonocytic differentiation function. Moreover, in erythroleukemic K562 cells, we showed that arsenic trioxide inhibited erythrocyte maturation, suggesting that arsenic might have biphasic effects on erythropoiesis. In conclusion, our data provided the first evidence showing that arsenic trioxide could prime human hematopoietic progenitor cells for enhanced erythroid differentiation.

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Use of Merocyanine 540 for the Isolation of Quiescent, Primitive Human Bone Marrow Hematopoietic Progenitor Cells

Journal of Hematotherapy ◽

10.1089/106161299320460 ◽

1999 ◽

Vol 8 (2) ◽

pp. 189-198 ◽

Cited By ~ 3

Author(s):

Robert E. Pyatt ◽

Laura L. Jenski ◽

Ruth Allen ◽

Ken Cornetta ◽

Rafat Abonour ◽

...

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Human Bone ◽

Human Bone Marrow ◽

Hematopoietic Progenitor Cells ◽

Hematopoietic Progenitor ◽

Merocyanine 540

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Protein kinase C-α isoform is involved in erythropoietin-induced erythroid differentiation of CD34+ progenitor cells from human bone marrow

Blood ◽

10.1182/blood.v95.2.510 ◽

2000 ◽

Vol 95 (2) ◽

pp. 510-518 ◽

Cited By ~ 50

Author(s):

June Helen Myklebust ◽

Erlend B. Smeland ◽

Dag Josefsen ◽

Mouldy Sioud

Keyword(s):

Bone Marrow ◽

Protein Kinase C ◽

Protein Kinase ◽

Progenitor Cells ◽

Erythroid Differentiation ◽

Human Bone ◽

Human Bone Marrow ◽

Kinase C ◽

Pkc Isoforms ◽

Cd34 Cells

Protein kinase C (PKC) is a family of serine/threonine protein kinases involved in many cellular responses. Although the analysis of PKC activity in many systems has provided crucial insights to its biologic function, the precise role of different isoforms on the differentiation of normal hematopoietic progenitor cells into the various lineages remains to be investigated. The authors have assessed the state of activation and protein expression of PKC isoforms after cytokine stimulation of CD34+ progenitor cells from human bone marrow. Freshly isolated CD34+ cells were found to express PKC-, PKC-β2, and PKC-ɛ, whereas PKC-δ, PKC-γ, and PKC-ζ were not detected. Treatment with erythropoietin (EPO) or with EPO and stem cell factor (SCF) induced a predominantly erythroid differentiation of CD34+ cells that was accompanied by the up-regulation of PKC- and PKC-β2 protein levels (11.8- and 2.5-fold, respectively) compared with cells cultured in medium. Stimulation with EPO also resulted in the nuclear translocation of PKC- and PKC-β2 isoforms. Notably, none of the PKC isoforms tested were detectable in CD34+ cells induced to myeloid differentiation by G-CSF and SCF stimulation. The PKC inhibitors staurosporine and calphostin C prevented EPO-induced erythroid differentiation. Down-regulation of the PKC-, PKC-β2, and PKC-ɛ expression by TPA pretreatment, or the down-regulation of PKC- with a specific ribozyme, also inhibited the EPO-induced erythroid differentiation of CD34+ cells. No effect was seen with PKC-β2–specific ribozymes. Taken together, these findings point to a novel role for the PKC- isoform in mediating EPO-induced erythroid differentiation of the CD34+ progenitor cells from human bone marrow.

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