GSPT1 partially contributes to cytotoxicity of PROTACs in MHH–CALL-4 cells. (A) Flow cytometry confirmation of sorted cells expressing GFP. (B) Western blot analysis of exogenous expression of FLAG-tagged wild-type GSPT1 and GSPT1-G575N in MHH–CALL-4 cells. (C) Dose-dependent degradation of GSPT1 24 hours after compound (Cmpd) 6 treatment in MHH–CALL-4 cells expressing wild-type GSPT1 or GSPT1-G575N. Cytotoxicity of Cmpd 6 (D), Cmpd 8 (E), and CC-885 (F) in MHH–CALL-4 cells and MHH–CALL-4 cells expressing wild-type GSPT1 or GSPT1-G575N.