Expression of CD304 (Neuropilin-1) in Acute Leukemia and Hematopoietic Cells
LC Ho, HJ Meyerson. University Hospitals Case Medical Center, Cleveland, OH
Background: CD304 (neuropilin-1 or BDCA-4) is a transmembrane C-type lectin that plays an important role in angiogenesis and neuronal guidance. CD304 and another C-type lectin, CD303 (BDCA-2), are useful in the immunophenotypic identification of plasmacytoid dendritic cells (PDCs); however, the expression of CD304 on normal hematopoietic cells and acute leukemia has not been well-established.
Design: We evaluated the expression of CD304 on blasts in 89 patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL), as well as the distribution of expression of CD304 in 36 blood and bone marrow specimens by flow cytometry.
Results: CD304 was expressed in 32% of acute leukemias and was expressed significantly more frequently in precursor B-cell ALL (14/22, 64%, median level of expression 70%) than in acute myeloid leukemia (11/56, 20%), p<0.0001. CD304 expression demonstrated no subtype specificity in AML. CD304 was detected in 1 of 5 precursor T-cell ALL but was not detected on blasts in the few myelodysplasia samples (0/4) or the single juvenile myelomonocytic leukemia specimen examined. All cases (3/3) of PDC leukemia evaluated at our institution were positive. CD303 was not detected in any acute leukemia analyzed (0/50) with the exception of the 3 cases of PDC leukemia. On normal hematopoietic elements, there was weak to moderate expression of CD304 on erythroid progenitors (CD71bright, CD45-), weak expression on B-cell progenitors (both early precursor-B cells, CD34+CD20-CD10+CD19+, and late precursor-B cells, CD34-CD20+CD10+CD19+, with median expression level of 17% and 27%, respectively), moderate expression on plasma cells (CD38brightCD45dim), and moderate expression on PDCs (CD303+CD45+). A small subpopulation of lymphocytes, likely regulatory T lymphocytes, also expressed CD304.
Conclusions: Our findings indicate that CD304 is expressed on a wide variety of hematopoietic cells and its expression is not restricted to PDCs. Its expression on a variety of leukemias limits its specificity in identifying PDC neoplasms. Finally, expression of CD304 on precursor-B cell ALL was generally stronger than that observed on normal precursor-B cells, suggesting that it may have utility in the detection of minimal residual disease in ALL.
Wednesday, March 11, 2009 1:00 PM
Poster Session VI # 175, Wednesday Afternoon