Severaldrug-resistantvariantshavebeendevelopedbygrowingtheparentalMELcellsinpresenceofcolchicine,adriamycinandvincristinerespectivelywithstepwiseincreasingconcentration.Boththecolchicine-resistantSc9(ColO)andvincristine-resis-tantSc9(VCR5)cellsdisplayedanacceleratedHMBA-inducedcommitmenttoterminalcelldifferentiation,whereastheadriamycin-resistantSC9(A120)showednoaccelerationbutratherasubstantialdelayinHMBA-induceddifferentiation.ThestudiesprovidemorecluesaswellasexperimentalmodelsforfurtherstudyonthemechanismofinduceddifferentiationofMELcells.