Comparative analysis of differential expression of sialic acids and adhesion molecules on mononuclear cells of bone marrow and peripheral blood in childhood acute lymphoblastic leukaemia at diagnosis and clinical remission.

Childhood acute lymphoblastic leukaemia (ALL) is characterized by the neoplasm of immature haematopoietic precursor cells (HPCs). We report significant differences between the expression of sialoglycoproteins and adhesion molecules on mononuclear cells (MNCs) of bone marrow (BM) and peripheral blood (PB) from individual children at diagnosis of the disease. Lymphoblasts in PB predominantly expressed 9-O-acetylated sialoglycoproteins (Neu5,9Ac2-GPs), sialic acid, alpha2-3 linked sialic acid, L- and P-selectins and vascular cell adhesion molecule -1 (VCAM-1) on their surface compared to BM, as determined with selective lectins and monoclonal antibodies (mAbs) by flow cytometric analysis. CD34+CD38+ cells present either in diagnostic PB or BM always showed enhanced expression of both alpha2-3 and alpha2-6 linked sialic acids, Neu5,9Ac2-GPs, L- and P-selectins and VCAM-1, compared to CD34+CD38- population, as confirmed by higher mean fluorescence intensity (MFI). Expression of ICAM-1 was reverse. However, MFI of Neu5,9Ac2-GPs was always higher both in CD34+CD38+ and CD34+CD38- population in PB compared to BM. Diverse trend of these cell surface macromolecules was observed during clinical remission. This is the first comparative study between PB and BM, where significant differential distribution of sialylated macromolecules and adhesion molecules was observed. Hence, supervising these cell surface macromolecules at various stages of treatment might help in minimal residual disease detection, identifying mobilization factor(s) and in isolation of normal HPCs for autologous BM transplantation.