VLA molecule expression may be involved in the release of acute myeloid leukaemic cells from the bone marrow

Acute myeloid leukaemia (AML) cells have a variable capacity to egress from bone marrow into peripheral blood. This may be due to a variable lack of adhesion molecules on leukaemic cells. The expression of VLA1, 3, 4, 5, 6, beta 1-chain, LFA1, beta 2-chain, ICAM1 and NCAM appeared to be higher in bone marrow as compared to peripheral blood leukaemic cells, although this only reached significance for beta 1-chain (p less than 0.01). The number of cases with more than 20% positive cells in bone marrow leukaemic cells was lower in immature FAB-subtypes (M1, M5a) as opposed to more mature subtypes (M2, M3, M4, M5b) for the adhesion molecules tested. This reached significance for VLA5 (p less than 0.05) and beta 1-chain (p less than 0.007), while there was trend for VLA4. It is discussed that VLA4 and 5 may play a role in the release of leukaemic cells from the bone marrow.