THE VASCULAR CELL-ADHESION MOLECULE (VCAM-1) IS EXPRESSED ON A SUBSETOF LYMPHOID AND MYELOID LEUKEMIAS

The expression of the Vascular cell adhesion molecule (VCAM-1), recent ly identified as cytokine-inducible ligand of the beta 1-integrin VLA- 4, was investigated on normal and malignant haemopoietic precursors as well as on haemopoietic cell lines. VCAM-1 was demonstrated on >20% b lasts in 4/22 acute myeloid leukaemia (AML) and 6/10 acute lymphoblast ic leukaemia (ALL) specimens but was absent from CD34(+) normal bone m arrow precursor cells. Interestingly the VCAM-1(+) AMLs classified as M1 and M5 simultaneously expressed N-CAM (CD56), a member of the immun oglobulin family. In ALL, VCAM-1 expression was restricted to Calla(+) CD19(+) precursors of the c-ALL subtype. VCAM-1 was also found on som e cell lines, mainly of the B-lymphocytic type. Furthermore, in 13/20 chronic lymphocytic leukaemia (CLL) samples >20% of the CD19(+) B-lymp hocytic precursors carried VCAM-1, which seemed to correlate with more advanced disease. Therefore VCAM-1 expression appeared to characteriz e leukaemic cells of the B-cell lineage as well as a CD56(+) subset of AML. Since its expression was clinically correlated with dermal infil trates of leukaemic cells in AML and with advanced Rai stages in CLL, VCAM-1 may play a role in enhanced adhesion of the malignant cells to tissues and/or to each other.