Gene expression changes between lenalidomide (LEN)-sensitive and LEN-resistant human multiple myeloma (MM) cell lines

To investigate the relationship between the LEN resistance and gene expression profile, we generated LEN-resistant (LEN-R) cell clones using U266 and NCU-MM1 cell lines by chronically exposing low dose of LEN (0.1 to 10 μM). The parental and LEN-R MM cells were incubated with either DMSO or LEN (10 μM) for 24 h. MM cells were maintained in RPMI 1640 supplemented with 10% FBS at 37 ℃ in 5% CO2 humidified atmosphere.