EIF2AK4 and acute myeloid leukemia: To determine if Rylaze-induced serine upregulation is mediated by the AAR pathway, we treated AML cell lines with Rylaze alone (0.1 μg/mL) or in combination with a small molecule inhibitor for GCN2 (GCN2-IN-1) and examined the effect on AAR pathway proteins and PHGDH expression, the enzyme that catalyzes the first step in the serine biosynthesis pathway.