Publication Date:
2014-12-06
Description:
Aberrant thrombopoietin (TPO)/MPL signaling has been hypothesized to contribute to the pathogenesis of myelofibrosis (MF) (Kaushansky K. J Clin Invest. 2005; 115: 3339; Moliterno AR, et al. N Engl J Med.1998; 338:572). Agents that would be capable of inhibiting this signaling pathway are possible novel therapeutic agents that might be effective for MF treatment. A peptide antagonist of TPO, LCP4, has been created which is highly antagonistic to CB CD34+ cell proliferation and differentiation induced by TPO. In this report we examined the effect of LCP4 on the proliferation of MF CD34+ cells and their differentiation to megakaryocytes (Mk). Elevated levels of TPO (345±114ng/ml, n=13) were detected in MF plasmas as compared to that detected in normal plasma (10±4ng/ml, n=6, P=0.049), indicating the possibility that TPO affects MF hematopoietic stem cells (HSC) and progenitor cells (HPC). MF splenic CD34+ cells (2.5×104/mL) were incubated in serum free expansion media (SFEM) alone, with 50 ng/ml SCF+ varying doses of TPO (0, 10, 30,100 ng/mL) or 50 ng/ml SCF +varying doses of TPO+ varying concentrations of LCP4 (0, 10, 50, 100, 500, 1000nM) for 1 or 2 wks. Cells were then enumerated and stained with CD34, lineage cocktail, CD15 and CD41a mAbs. When splenic MF CD34+ cells were cultured in the presence of SCF and varying concentrations of TPO, 100ng/ml TPO resulted in the generation of the greatest numbers of CD34+Lin-, CD41a+CD34-CD15- and CD15+CD34-CD41a- cells, suggesting that TPO promotes the proliferation of MF HSCs/HPCs and the production of MF MKs and myeloid cells. By contrast, after 1 wk of treatment of MF CD34+ cells (n=8; 5 MF spleens and 3 MF PB) with 100nM and 500nM LCP4, the numbers of MF total cells, CD34+Lin- (MF HSCs/HPCs), CD34+CD41a+ (immature Mks), CD41a+CD34-CD15- (mature Mks), CD15+CD34-CD41a- cells (myeloid cells) as well as hematopoietic colonies (HC), including CFU-Mk, CFU-GM, BFU-E/CFU-E, CFU-GEMM, were all significantly reduced (P all
Print ISSN:
0006-4971
Electronic ISSN:
1528-0020
Topics:
Biology
,
Medicine
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