ATF4 and neoplasm: Furthermore, the combination drug decreased the mRNA expression levels of downstream c-Myc targets, including CDK4, PABPC1, ATF4, BCL2L12, and HMGA 31, in MDA-MB-231 (Fig. 6K) and BT-549 (Fig. S5B) cells, which are important effectors of c-Myc inhibition-induced tumor suppression.