CDK6 and plasma cell myeloma: To investigate the effects of CDK6 inhibition and the basis for the synergy with IMiDs in multiple myeloma, we performed quantitative proteomic and phosphoproteomic analyses in MM.1S cells treated with pomalidomide, palbociclib, and CDK6-specific PROTACs alone or in combination (Fig. 6A, Supplementary Data 3).