CD44 and acute lymphoblastic leukemia: To address HA-mediated biological effects on MLL+ALL cells, we next examined thymidine uptake after 4-day culture with or without various concentrations of ULMW-HA or HMW-HA, and found that thymidine uptake in CD44-high cell lines was markedly suppressed after culture with 2.5 mg/ml of ULMW-HA (% inhibition; 78.6±9.6%, mean±S.E).