MCF7 LTED Y537S CDK4 6i R and MCF7 LTED D538G CDK4 6i R cell lines were developed by exposing MCF7 LTED Y537S and MCF LTED D538G cells, respectively, to increasing concentrations of the respective CDK4 6i to a final concentration of 500 nM for palbociclib, 1 ОјM for ribociclib, and 250 nM for abemaciclib better business bureau online pharmacy priligy