Purpose: to evaluate the biological and clinical significance of circulating CD34(+) cells in patients with myelodysplastic syndromes (MDS).
Methods: the relative count of CD34(+) cells in peripheral blood was evaluated by flow cytometry and the results were recorded on the total number of mononuclear cells (MNCs). CD34(+) status was correlated with the percentage of circulating and bone marrow blasts, cytogenetic studies, CFU-GM colony growth, overall survival and transformation to acute myeloid leukemia (AML).
Results: the number of MNC positive for anti-CD34 monoclonal antibody in the healthy control group ranged from 0.00% to 0.73%. Therefore, the cutoff value for overexpression of CD34 antigen on peripheral blood MNC of MDS patients was ≥ 1% (CD34(+) cases). The mean number of circulating CD34(+) MNCs in 30 MDS patients was significantly higher than in the control group (p=0.009). The proportion of circulating CD34(+) MNCs did not correlate with the blast count in the peripheral blood (r=0.282, p=0.131), neither with the blast count in the bone marrow. In contrast, the proportion of circulating CD34(+) cells in MDS patients was significantly correlated with the proportion of bone marrow CD34(+) cells (r=0.461, p=0.035). The proportion of circulating CD34(+) cells did not correspond to the percentage of blast count in the bone marrow, neither with the presence of cytogenetic abnormalities or abnormal growth of GM-progenitors. The median actuarial survival of 19 patients with elevated proportion of circulating CD34(+) cells was 16 months, as compared to >57 months in 11 patients with CD34(+) cells within normal range (p=0.16). Five patients with elevated proportion of circulating CD34(+) cells progressed to AML, as compared to only one of CD34(-)negative (CD34(-)) cases.
Conclusion: the presence of circulating CD34(+) cells is a common finding in MDS, but no significant correlations with clinical and/or biological features of the disease have been found.