To define the role of SCFβ-TrCP1 specifically in multiple myeloma, we generated and characterized murine 5TGM1 multiple myeloma cells stably expressing a dominant negative mutant of the murine homolog of β-TrCP1 (FWD1; F-box/WD40-repeat protein) that lacks the F-box (FWD1ΔF; Figure 1A) [10, 12, 18]. The gene discussed is BTRC; the disease is plasma cell myeloma.