Inhibition of γ-glutamylcysteine synthetase boosts the cytotoxic effects of xCT inhibition. (A) Heat maps showing the relative cell counts at day 3 of a panel of AML cell lines grown in a concentration range of the xCT inhibitor SSZ in combination with a concentration range of the inhibitor of γ-glutamylcysteine synthetase, BSO. (B) Experiment as in panel A, but effects on viability are shown. (C) Heat maps showing the relative cell counts at day 3 of 5 primary AML samples grown in a range of concentrations of the xCT inhibitor SSZ in combination with a range of concentrations of the inhibitor of γ-glutamylcysteine synthetase, BSO. (D) Experiment as in panel C, but effects on viability are shown. (E) Heat maps showing the relative cell counts and relative viability at day 3 of CB-derived CD34⁺ cells grown in a range of concentrations of the xCT inhibitor SSZ in combination with a range of concentrations of the inhibitor of γ-glutamylcysteine synthetase, BSO. (F) Correlation curve between RNA sequencing data from AMLs in panels C and D and SSZ/BSO sensitivity. GPX4 and MGST1 expression correlated with insensitivity to SSZ/BSO. (G) Gene set enrichment analysis (GSEA) using the Pearson correlations depicted in panel E. Statistical analysis by ordinary 1-way ANOVA; ∗P < .05, ∗∗P < .01, ∗∗∗P < .001, ∗∗∗∗P <.0001. FDR, false discovery rate; NES, normalized enrichment score; Rel., relative.