Metabolic activity was assessed via the XTT assay following 48 h treatment with 1 mM hydroxylamine (HA), 5 mM L-cysteine (LC) or a combination of both. Values are presented as relative to the untreated, normoxic cells within each experimental trial. Error bars represent standard error of the mean (SEM). HK-2 (n = 6), Caki-1 (n = 6), 786-O VHL+ (n = 6), 769-P (n = 5–6), 786-O (n = 5–6). Two-way ANOVA with Dunnett’s multiple comparisons test was used to asses significant differences between groups (normoxic control vs. hypoxia control; †; p < 0.05). Two-way ANOVA with Sidak’s multiple comparisons test was used to assess significant differences between treatments within groups (normoxic control vs. normoxic 1 mM HA; *; p < 0.05).