To determine whether ER stress contributes to ASS1 synthesis in HCC microenvironments, we analyzed the effects of thapsigargin (TG) and tunicamycin (TM), which induce ER stress and the unfolded protein response (UPR), on regulation of ASS1 expression in Huh7 and SNU475 cells. The gene discussed is ASS1; the disease is hepatocellular carcinoma.