CD34 and myelodysplastic syndrome: One study showed that CXCR4 protein expression on the CD34(+) cell surface is lower in the low-grade myelodysplastic syndrome than in high-grade myelodysplastic syndrome; CD34(+) cell apoptosis is significantly higher in low-grade myelodysplastic syndrome, and apoptosis is negatively correlated with CXCR4 expression (42).