Significance of CD34(-) and CD34(+) cell apoptosis and proliferation in bone marrow of patients with MDS and their impact on survival.

Alteration in the balance between cell apoptosis and proliferation is one of the pathophysiological mechanisms of the myelodysplastic syndromes (MDS). The question of whether the excessive apoptosis and/or proliferation predominantly involve the subset of progenitor cells (CD34(+) cells) or mature cells (CD34(-) cells) remains a controversial issue. This study was purpose to analyze the apoptosis and proliferation status of CD34(+) and CD34(-) cells in bone marrow (BM) of patients with MDS, to investigate the pathogenesis of MDS and to determine the relation of apoptosis and proliferation status of CD34(+) and CD34(-) cells with prognosis of MDS. The proportion of CD34(+) cells, the apoptosis and proliferation ratio (A/P) of CD34(+) and CD34(-) cells in BM of 40 patients with MDS, including 20 cases of high-risk MDS and 20 cases of low-risk MDS, and 10 normal persons as control were detected by flow cytometry; the influence of CD34(+) and CD34(-) cell apoptosis and proliferation levels on prognosis of MDS was evaluated by univariate and multivariate analysis of survival. The results showed that the proportion of CD34(+) cells in BM of high-risk MDS patients was significantly higher than that in BM of low-risk MDS patients and in normal BM [(1.92 ± 0.10)%, (1.09 ± 0.04)%, (1.03 ± 0.05)% respectively]. The apoptotic rates (AR) of both CD34(+) and CD34(-) cells were significantly higher in low-risk MDS [(54.75 ± 2.18)%, (80.36 ± 1.68)%] than in high-risk MDS [(24.87 ± 2.69)%, (23.12 ± 1.23)%] and in normal BM [(18.51 ± 2.74)%, (20.98 ± 2.21)%]. When compared between CD34(+) cells and CD34(-) cells in low-risk MDS, a greater AR of CD34(-) cells was found. However, the higher proliferative rate of CD34(+) cells was observed in high-risk MDS. In low-risk MDS, a higher A/P ratio was found in CD34(-) cells than in CD34(+) cells; whereas this ratio was equalized or inverted in high-risk MDS. In addition, the survival and prognosis correlated significantly with AR of CD34(+) cells. It is concluded that the early MDS is predominantly associated with excessive apoptosis of the mature CD34(-) cells. The proliferation rate of cells increases with the disease progression in MDS subsets, especially, in the subset of CD34(+) cells. Surprisingly, the apoptosis of CD34(+) cells may be a useful prognostic factor, and the inhibition of apoptotic mechanisms may induce the transformation of MDS to leukemia.