The induction of oxidative stress in A-431 cancer cells treated with Y2O3NPs was reflected by the significant concentration-dependent elevations in the level of MDA, a by-product of lipid peroxidation, along with significant decreases in the activities of the antioxidant enzymes CAT and SOD reported after 72 h of A-431 cancer cells exposure to tested concentrations of Y2O3NPs. The gene discussed is SOD1; the disease is cancer.