Leukaemia cell mobility in childhood acute myeloid leukaemia based on the FAB classification

Leukaemia cell mobility was evaluated by the agarose plate method in 20 children with acute myeloid leukaemia (AML) based on the FAB classification. M1 blasts from 3 patients did not show any migration, probably reflecting their cellular immaturity. Leukaemia cells from 3 of 8 patients with M2 AML showed random migration, but those from the remaining 5 did not have this ability. The results thus demonstrated the heterogeneity of M2 AML in the function as well as the morphology. The M3 leukaemia cells failed to migrate under agarose in 2 patients studied, implying that a certain cytoskeletal defect in the cells. In all of 2 M4, 2 M5A and 3 M5B AML patients, leukaemia cells showed active mobility. The random migration value (mean +/- SD) of M5A and M5B cells was 5.7 +/- 1.7 compared with that of normal monocytes of 4.0 +/- 0.4 (p less than 0.01), indicating the enhanced random migration of leukaemia monocytes. M4 and M5B leukaemia cells had chemotactic responsiveness to zymosan-activated serum comparable to that of normal monocytes, but M5A cells were different from them in lacking apparent chemotactic responsiveness to the factor. Lymphadenopathy and leucocytosis were more prominent in the patients whose leukaemia cells were capable of migration than in those not having such cells. Mobility of leukaemia cells probably reflects their cell lineage, cellular maturity and functional distortion during leukaemic transformation, and appears to be related to clinical features.