Flow Cytometric Characterization of Peripheral Blood CD34+ Cells in Patients with Primary Myelofibrosis
AM Agarwal, SN Preobrazhensky, S Samuelson, SL Perkins, ME Salama, JT Prchal, DW Bahler. University of Utah, Salt Lake City, UT; ARUP Laboratories, Salt Lake City, UT
Background: Primary myelofibrosis (PMF) is a chronic myeloproliferative neoplasm characterized by the accumulation of abnormal megakaryocytes in the bone marrow (BM), variable degrees of BM fibrosis, tear-drop erythrocytes, circulating nucleated red blood cells with increased CD34+ blasts, and extramedullary hematopoiesis. The antigenic characteristics of circulating CD34 + cells in PMF may yield clues to disease pathogenesis and/or diagnosis, but have not been extensively studied.
Design: Peripheral blood CD34+ cells from 15 well characterized PMF patients and 10 healthy controls were examined by 5-color flow cytometry using a large panel of antibodies. Bone marrow biopsies, molecular and cytogenetic studies, and clinical parameters were also reviewed and correlated with the flow cytometry findings.
Results: As expected, the percentages of peripheral-blood CD34 cells were significantly higher in the PMF patients (mean 1.38%, range, range 0.065-7.15) compared to the controls (mean 0.05%, range 0.01- 0.57). All but one PMF case showed phenotypic abnormalities on the CD34+ cells with 5/15 cases having 2 abnormalities, and 2/15 having ≥3 . Abnormalities included increased mean fluorescence intensity (MFI) values of HLA-DR (more than 3 fold) in 10/15(66%) cases, and increased levels of CD13 in 4/15 (26%) of patients. Aberrant expression of lymphoid antigens was also observed with 4/15(26%) cases expressing CD7, 2/15(13%) showing CD4, and 4/15 (26%) expressing CD56. The majority of CD34+ cells phenotypically resembled megakaryocyte-erythroid precursors (CD45RA-, CD123-) in 2 cases, granulocyte-macrophage progenitors (CD45RA+, CD123+) in 6 cases, and common myeloid progenitors (CD45RA-, CD123+) in 7 cases.
Conclusions: Phenotypically abnormal circulating CD34+ cells are seen in the majority (93%) of the patients with PMF. Patterns of aberrant antigen expression on CD34 positive cells in PMF appear to differ from those described in other non-CML myeloproliferative neoplasms which may help in diagnosis and/or monitoring treatment responses. Most of the circulating CD34+ blasts in PMF represent early hematopoietic progenitor cells, with only two cases phenotypically resembling megakaryocytic precursors.
Tuesday, March 23, 2010 1:00 PM
Poster Session IV # 181, Tuesday Afternoon