MCL1 and plasma cell myeloma: ATF4 has also been demonstrated to facilitate anti-neoplastic agent bortezomib‐induced upregulation of anti‐apoptotic myeloid cell leukemia-1 (Mcl-1) protein, which is an anti-apoptotic Bcl-2 family protein that plays essential roles in multiple myeloma survival and drug resistance in many tumor types (Figure 2) (Hu et al., 2012).