Biologic significance of pharmacological inhibition of TP53RK by IMiDs in MM cells. (A) MM.1S cells were cultured with Len (2.5 μM) or Pom (2.5 μM) in the presence (40 nM) or absence of Dox for 48 hours. (B, C) MM.1S and H929 cells were treated with Len (1.3 μM) or Pom (3 μM) for 48 hours. Nuclear proteins were subjected to (B) western blot or (C) p53 DNA binding activity assay. Nucleolin served as a loading control. P.C., plasma cell. (D) MM.1S cells were treated with Len (2.5 μM) or Pom (2.5 μM) in the presence or absence of Dox (40 nM) for 48 hours. (E) MM.1S cells were treated with Thal or Pom for 48 hours. In each case, western blot was carried out using cell lysates and the indicated Abs. (F, G) H929 cells were transfected with Sc or TP53RK siRNA. Extracted mRNA was subjected to qPCR (F) and western blot (G) for RRM1 and p18. (H) H929 cells were treated with Pom for 48 hours and subjected to GSEA for proteasome pathway. Extracted RNA/mRNA and cell lysates were subjected to GSEA (I), western blot (J), or telomerase activity assay (K). All western blots were carried out using whole cell lysates and the indicated Abs.