CRBN mutations identified in our cohort confer lenalidomide resistance in OCI-MY5 cells. OCI-MY5 cells are resistant to IMiD treatment because of low CRBN expression levels. IMiD sensitivity can be restored by CRBN wt overexpression. (A) All 3 CRBN mutants failed to resensitize the cell line; thus, the mutations conferred IMiD resistance. (B) Protein expression by western blot.