Expression of select BCL2 family proteins in (a) solid and (b) hematological cancer cell lines. c In cells that express high levels of NOXA, this BH3-only protein controls steady-state MCL1 protein levels. NOXA was deleted using CRISPR-Cas9 gene targeting from a selection of cell lines that normally express either low (HELA, KMS-28-BM) or high (HCT116, RS4;11, KMS-12-PE) amounts of NOXA. Blots are representative of at least two independent knockout clones examined for each cell line. d HA-NOXA overexpression promoted MCL1 degradation in cell lines that normally express low amounts of NOXA (e.g., HELA and MCF7), but had minimal impact in those with high NOXA expression (e.g., HCT116 and RS4;11).