Expression and Diagnostic Utility of CD200 in Hematologic Malignancies.
Jean Coviello-Malle, Daisy Alapat, Bart Barlogie, John D Shaughnessy, Robert B Lorsbach. University of Arkansas for Medical Sciences, Little Rock
Background: CD200 is normally expressed by several hematopoietic cell types. Although the expression of CD200 in chronic lymphocytic leukemia (CLL) has been reported, its expression in several other hematolymphoid malignancies has not been well characterized. Further, the diagnostic utility, if any, of CD200 expression in these malignancies is largely unknown.
Design: To assess CD200 expression, 4- or 6-color flow cytometry was performed on an array of hematolymphoid malignancies, using a FACSCanto II flow cytometer and FACSDiva software for data analysis. Cell populations were evaluated semi-quantitatively for CD200 expression. In PCMs where gene expression profiling (GEP) was performed, RNA was extracted from CD138 purified PCs and analyzed using an Affymetrix-based platform with hybridization to U133 gene chip microarrays.
Results: 11/13 B-ALLs, 0/4 T-ALLs and 2/21 AMLs/MDSs were CD200+. CD200 was also highly expressed in BM CD34+/CD19+ B-cell progenitors (BPs). Compared to normal BPs, CD200 was aberrantly over/under-expressed in 7/12 B-ALLs. 16/16 CLLs and 0/3 mantle cell lymphomas (MCLs) were CD200+. The expression of CD200 in three immunophenotypically atypical cases of CLL (FMC-7+, surface light chainbright) and MCL (CD5-; partial CD23+) was also evaluated and was positive and negative, respectively, similar to what was observed for CLL and MCL with a typical immunophenotype. CD200 was expressed by 37/52 plasma cell myelomas (PCMs). The relative level of CD200 transcript expression observed by GEP correlated with the flow cytometry findings. Interestingly, CD200- PCMs included a significantly higher percentage of proliferation type disease and was associated with a significantly higher GEP risk score than CD200bright PCMs.
Conclusions: A high percentage of B-ALLs are CD200+, with aberrant over/under-expression in many cases, a finding which may aid in distinction between normal BPs and leukemic B-lymphoblasts. CLL and MCL are uniformly positive and negative for CD200 expression, confirming previously published findings. Importantly, CD200 expression appears to reliably distinguish between CLL and MCL even in those cases in which there are significant variations from the typical lymphoma immunophenotype. Finally, the majority of PCMs are CD200+; negativity for CD200 is associated with the proliferation subtype of PCM and a significantly higher disease risk score as determined by GEP. Therefore, assessment of CD200 expression may have prognostic importance in PCM.
Tuesday, March 1, 2011 9:30 AM
Poster Session III # 238, Tuesday Morning