Association of MDM2 with cell-cycle regulatory proteins in p53-positive and p53-negative MM-derived cell lines and PCL patient cells. Total cell lysates of MM cell lines (ARH-77, RPMI 8226, and OCI-My5) and PCL patient cells (PCL1 and PCL2) were immunoprecipitated with H-22 anti-CDK4 pAb, C-20 anti–E2F-1 MoAb, C-19 anti-p21 pAb, or SMP14 anti-MDM2 MoAb, followed by immunoblotting with SMP14 anti-MDM2 MoAb. These cell lysates were immunoprecipitated and immunoblotted using the same Abs as positive controls.