CD47 expression in canine leukemias: an explorative flow cytometric study

Introduction Canine leukemias are heterogeneous neoplasms, with dramatically different prognosis. CD47 is involved in the process of immune tolerance, and has prognostic and therapeutic role in human leukemias. The aim of this study is to assess CD47 expression in different subtypes of canine leukemias by flow cytometry (FC). Material and methods Peripheral blood samples obtained for diagnostic purposes from dogs with leukemias were included and classified by FC and morphological assessment. CD47 (antibody clone: BRIC126) expression was quantified as the Median Fluorescence Intensity (MFI) Ratio between stained and unstained cells, gating only on neoplastic cells. Samples were considered positive if MFI was >1. Statistical differences in CD47 expression among leukemia subtypes were assessed. Results Forty-one samples were examined, including 18 (43.9%) from acute (AL), and 23 (56.1%) from chronic leukemias (CL). All samples expressed CD47 (median MFI ratio 3.99; range, 1.45-13.80). Median MFI ratio did not differ between AL (3.65; range, 1.69-13.8) and CL (4.48; range, 1.45-9.79) (p=0.655). Myeloid AL tended to have higher median MFI (6.98; range, 5.61-8.35) than other AL (3.44; range, 1.69-13.81) (p=0.118), whereas the only myeloid CL of the study had lower MFI (1.45) than lymphoid CL (median MFI, 4.54; range, 2.11-9.79) (p=0.087). Conclusions Canine leukemias consistently express CD47. Similar MFI ratios are found in AL and CL, whereas myeloid subtypes show differences compared to lymphoid leukemias. Further studies are needed to assess the prognostic role of CD47 expression. The ubiquitous expression of this molecule may open new therapeutic perspectives for the acute leukemias in dogs.