Flow Cytometric Assessment of Myeloid Nuclear Differentiation Antigen (MNDA) Expression in Myelodysplastic Syndromes As a Diagnostic Marker,
Authors: Kern Wolfgang , Bellos Frauke , Alpermann Tamara , Haferlach Claudia , Schnittger Susanne , Haferlach Torsten 
Published: October 2019

Abstract
Abstract 3805

Background:
Detection of aberrant antigen expression by multiparameter flow cytometry (MFC) is increasingly used in the diagnostic work-up of myelodysplastic syndromes (MDS). Myeloid nuclear differentiation antigen (MNDA) has been described to be strongly expressed in mature myeloid cells while myeloid progenitor cells show a weak expression only. MNDA has been suggested to be aberrantly expressed in MDS and therefore may improve the diagnostic capabilities of MFC. Aim: To analyze differences in the expression of MNDA between non-MDS cytopenias, MDS, and AML. Patients and methods: Bone marrow samples from a total of 269 patients with cytopenias and suspected MDS were analyzed by cytomorphology and MFC in parallel for diagnostic purposes. MNDA expression was determined by MFC in granulocytes, monocytes, and myeloid progenitor cells using the antibody clone 3C1 (provided by Trillium Diagnostics, Bangor, ME). MNDA expression was compared between patients grouped according to cytomorphology as: no MDS (n=103), MDS (n=85), CMML (n=9), AML (n=19), and possible MDS (n=53, based on cytomorphologic features of dysplasia but not sufficient to diagnose MDS). In addition, MNDA expression was compared between patients with aberrant and normal karyotype (cytogenetics was available in 238/269 patients, an aberrant karyotype was present in 59 patients). Results: A higher percentage of granulocytes (G) and monocytes (M) with weak expression of MNDA (%dimG and %dimM) was consistently found in MDS/AML samples as compared to samples without MDS. In detail, %dimG (mean±SD, 20±20% vs. 8±10%, p<0.001) and %dimM (31±24% vs. 16±11%, p<0.001) were significantly higher in cases with MDS as compared to those without. Furthermore, in patients with MDS, as compared to those without, the mean fluorescence intensity (MFI) of MNDA expression was found to be lower in monocytes (mean MFI, 71±36 vs. 85±27, p=0.004) as well as in myeloid progenitor cells with bright (67±24 vs. 86±66, p=0.007) or dim (2.5±0.9 vs. 2.8±1.2, p=0.037) expression of MNDA. In AML cases, as compared to cases with no MDS, similar figures were observed with higher values for %dimG (27±27% vs. 8±10%, p=0.007) and for %dimM (45±31% vs. 16±11%, p=0.001). In addition, in AML cases MFI of MNDA expression was lower in monocytes (55±39 vs. 85±27, p<0.001). Considering the diagnostically challenging cases with dysplastic features by cytomorphology but not sufficient to diagnose MDS similar although smaller differences were seen as compared to cases with no MDS with higher values for both %dimG (15±22% vs. 8±10%, p=0.026) and %dimM (25±19% vs. 16±11%, p=0.002) as well as a lower MFI of MNDA expression in monocytes (73±26 vs. 85±27, p=0.010). Interestingly, in CMML cases no reduced expression of MNDA could be found in any of the cell lines analyzed which might argue in favour of regarding CMML as myeloproliferative rather than myelodysplastic disease. From the cytogenetic point of view cases with an aberrant karyotype had higher values for both %dimG (22±20% vs. 12±18%, p=0.001) and %dimM (33±24% vs. 23±21%, p=0.004) as compared to those with a normal karyotype. Conclusions: These data suggests that MDS, as compared to non-MDS bone marrow, is associated with a reduced expression of MNDA in different cell lines which in part also applies to AML. Further analyses should define the potential of MNDA assessment to improve the MFC-based approach to diagnose MDS.

Disclosures:
Kern: MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Bellos:MLL Munich Leukemia Laboratory: Employment. Alpermann:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Schnittger:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.