Myeloid Nuclear Differentiation Antigen (MNDA) Protein Expression in Myelodysplastic Syndrome (MDS) Is Reduced in Maturing Myeloid Cells.

Abstract

Expression of the human MNDA protein is restricted to hematopoietic cells, and occurs at uniformly high level only in the normal granulocyte/monocyte lineage. Myeloblasts and all later stages of the lineage express MNDA, while stem cells do not (Hum Pathol 1999; 30:1040). Gene expression analyses of MDS cases have shown that MNDA mRNA is significantly down regulated in familial MDS and in high-risk sporadic MDS cases (Blood 2000; 100:3553 and Leukemia 2004; 18:449). We evaluated MNDA protein expression in patients with MDS.Methods: We directly conjugated Alexa 488 (Molecular Probes) to a rat monoclonal antibody specific for MNDA for use in multiparameter cytometric analysis with CD45/CD34 and DRAQ5 (DNA content). Patients' (n=17) clinical histories, laboratory data, cytogenetics, and morphology were reviewed for confirmation of diagnoses and blinded to study results. Patients lacking primary marrow disease (n=9) were used as controls. Analysis was performed using Winlist 5.0 software (Verity Software) with DDE links to ModFitLT 3.0 using modifications of published methods along with Esoterix Center for Innovation generated algorithms. Analyses were blinded to clinical results.Results: The normal dataset revealed MNDA expression in expected cell populations, with only a small subset of CD34+ cells exhibiting MNDA (7.5% on average). Expression of MNDA protein in maturing myeloid forms in normals was consistently greater than in MDS samples (MFI=802 vs. 569 in MDS; MFI=mean fluorescence intensity defined by the linear mean of each population). Six of 17 MDS cases displayed greater than 10% maturing myeloid forms lacking MNDA protein expression (never observed in normals). The % MNDA+/CD34+ cells was identical in the two datasets (7.5% in normal vs. 7.6% in MDS).Discussion: Our results suggest that MNDA protein expression in MDS patients follows a pattern similar to that in gene expression analyses. We additionally demonstrate that MNDA protein expression at the cellular level is variable in MDS, versus uniform expression in normals; parallel data for MNDA message expression at the cellular level is not available. The finding of MNDA-negative myeloid forms in MDS may have diagnostic utility, and may provide insight into both impaired myeloid differentiation in MDS and the biologic role of MNDA.