CD44 in canine leukemia: Analysis of mRNA and proteinexpression in peripheral blood

Hyaluronan receptor CD44 mediates interaction between cells and extracellular matrix.The expression of standard form and its variants is dysregulated in human leukemias andis associated with metastasis and prognosis. The aim of this work is the evaluation of CD44mRNA and protein expression in canine leukemia. Peripheral blood from 20 acute leukemias(AL) (10 acute lymphoblastic, 6 acute myeloid and 4 acute undifferentiated leukemias),21 chronic lymphocytic leukemias (CLL) and thirteen healthy dogs were collected. ThemRNA expression of all CD44 variants presenting exons 1–5 and/or 16–20 (CD44 ex1–5and CD44 ex16–20) and CD44 protein were determined by real-time RT-PCR and flowcytometry, using the mean fluorescent index (MFI), respectively. CD44 MFI was signifi-cantly higher in leukemic samples compared to controls and a higher expression was foundin AL in respect with CLL. No significant differences were found when considering differentphenotypic subtypes of AL and CLL. CD44 ex1–5 mRNA expression was significantly higherin AL compared to controls, whereas there was no difference in CLL compared to controlsand AL. CD44 es16–20 showed the same trend, but without differences among groups. Thehigh CD44 expression found in canine leukemias could be considered a step toward thedefinition of their molecular features.