EIF2AK4 and pancreatic neoplasm: To examine if ISR is an active signaling pathway in human pancreatic cancer cells, we treated pancreatic cancer line, Pa03C with two well-characterized ISR activators, Halofuginone (HF) and Thapsigargin (Thap), which are specific activators of GCN2 and PERK, respectively (Figure 1A; 28–30).