The degradation of MAF protein was abrogated by inhibition of GSK3β activity. HMCL cells harboring t(14;16) (A) or t(4;14) (B) were treated with 5 μg/mL CHX for indicated time points. MM144 (C), 8226 (D), or other HMCLs (E) were treated with or without SB216763 in the presence of CHX for indicated times. M144 cells (F) were cultured in serum-free medium for 16 hours and treated with or without 100 ng/mL IGF-1 for indicated times in the presence of 5 μg/mL CHX. A panel of MM cell lines (G) cultured in serum-free medium for 16 hours was treated with or without 100 ng/mL IGF-1 for 6 hours in the presence of CHX. Cell lysates were isolated and MAF protein levels determined. The anti-MAF antibody recognizes 2 bands, of which the upper band represents the phosphorylated form. An anti-β-actin was used to indicate protein loading for each cell line.