By examining the time points of ROS and ERS production in AML 12 cells through corresponding probes and observing that 4-PBA (an ERS inhibitor) could inhibit abnormally elevated ROS levels and that BHA (an antioxygen) failed to relieve ATF4-positive cells at 3 h, we proposed that the occurrence of ERS might be anterior to ROS production. Here, ATF4 is linked to acute myeloid leukemia.