IFI6 and esophageal squamous cell carcinoma: Consistent with previous study, IFI6 downregulation caused a reduced ER Ca2+ levels, whereas IFI6 overexpression in ESCC cells significantly elevated Ca2+ levels in ER, which was reversed by treatment with compounds able to reduce mitochondrial ATP production (Oligomycin, 1 μM) or its export to the cytosol (Atra, 1 μM) (Fig. 9c, Figure S7A).