We observed GPX4 accumulation in tumor cells that also accumulated GSH; notably, the level of GPX4 appeared to be affected by that of NCF-1, as indicated by a comparison between cells transfected with the control and NCF-1 siRNAs (Fig. 3D, upper panel, GSH and GPX4; lower panel, NCF-1 and GPX4). Here, NCF1 is linked to neoplasm.