In vitro expansion of erythroid progenitors from polycythemia vera patients leads to decrease in JAK2V617F allele

Gaikwad, Amos; Nussenzveig, Roberto; Liu, Enli; Gottshalk, Stephen; Chang, KoTung; Prchal, Josef T.

doi:10.1016/j.exphem.2006.12.007

« Previous Next »Experimental Hematology
Volume 35, Issue 4 , Pages 587-595, April 2007

In vitro expansion of erythroid progenitors from polycythemia vera patients leads to decrease in JAK2^V617F allele

Amos Gaikwad
- Department of Pediatric-Hematology Oncology, Baylor College of Medicine, Houston, Tex., USA
- Texas Children's Cancer Center, Baylor College of Medicine, Houston, Tex., USA
Roberto Nussenzveig
- Department of Leukemia, MD Anderson Cancer Center, Houston, Tex., USA
Enli Liu
- Texas Children's Cancer Center, Baylor College of Medicine, Houston, Tex., USA
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Tex., USA
Stephen Gottshalk
- Department of Pediatric-Hematology Oncology, Baylor College of Medicine, Houston, Tex., USA
- Department of Immunology, Baylor College of Medicine, Houston, Tex., USA
- Texas Children's Cancer Center, Baylor College of Medicine, Houston, Tex., USA
- Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Tex., USA
KoTung Chang
- Division of Hematology, University of Utah, Salt Lake City, Utah, USA
Josef T. Prchal
- Institute of Pathological Physiology, Charles University School of Medicine, Prague, Czech Republic
- Division of Hematology, University of Utah, Salt Lake City, Utah, USA
- Offprint requests to: Josef T. Prchal, M.D., School of Medicine, Hematology, University of Utah, Salt Lake City, UT 84124

Received 24 August 2006; received in revised form 20 December 2006; accepted 20 December 2006.

Objectives

A G>T transversion in a tyrosine kinase JAK2 (V617F) was reported in over 80% of patients with polycythemia vera (PV). Current evidence suggests that JAK2^V617F somatic mutation is involved in the pathogenesis of PV, as it confers erythropoietin-independent proliferation to erythroid progenitor cells. However, several unanswered questions regarding the essential role of JAK2^V617F arose as 1) it is not a dominant mutation, 2) it is not PV-specific as it is found in several myeloproliferative disorders, and 3) some (∼20%) PV patients lack the JAK2^V617F mutation. We investigated the relative frequency of JAK2^V617F in in vitro–expanded PV progenitors.

Methods

In vitro expansion of erythroid progenitors from mononuclear cells was optimized. Frequency of JAK2^V617F allele was measured by using allele-specific real-time polymerase chain reaction. Clonality was performed using established procedure.

Results

In vitro expansion of PV erythroid progenitors and differentiated dendritic cells resulted in a decrease of the frequency of JAK2^V617F allele compared with granulocytes or CD235⁺ erythroid progenitors. Clonality analysis demonstrated that although granulocytes of these PV patients were clonal, expanded erythroid cells were polyclonal. However, in vitro–expanded PV erythroid progenitors still had approximately a twofold increased proliferative capacity in comparison with erythroid progenitors from healthy individuals. Erythropoietin favors the cells without JAK2^V617F allele. Dendritic cells in one out of three patients remained clonal.

Conclusion

JAK2^V617F mutation does not provide a proliferative/survival advantage to the PV clone during in vitro expansion. These data suggest that the JAK2^V617F mutation plays an important role in the biology of PV, yet it may not be the PV-initiating event.