Correction: Cysteine dioxygenase 1 is a metabolic liability for non-small cell lung cancer

To investigate the NRF2-dependent regulation of CDO1 protein in NSCLC, we generated a doxycycline-inducible lentiviral expression system to reintroduce GFP, CDO1^WT or a catalytically inactive CDO1 mutant (Y157F, Ye et al., 2007) at single copy into the panel of NRF2^LOW and NRF2^HIGH NSCLC cell lines (Figure 3D, figure 3—figure supplement 2). The level of CDO1 protein expression in these cells was similar with the physiological Cdo1 levels in mouse lung and liver (Figure 3—figure supplement 2B), with liver being one of the highest CDO1-expressing tissues that is responsible for supplying TAU to the body (Stipanuk et al., 2015). We find that CDO1 accumulated to higher levels in NRF2^HIGH cells than NRF2^LOW, although accumulation was observed in many NRF2^LOW cell lines as well (Figure 3D).

To investigate the NRF2-dependent regulation of CDO1 protein in NSCLC, we generated a doxycycline-inducible lentiviral expression system to reintroduce GFP, CDO1^WT or a catalytically inactive CDO1 mutant (Y157F, Ye et al., 2007) at single copy into the panel of KEAP1^WT and KEAP1^MUT NSCLC cell lines (Figure 3D, figure 3—figure supplement 2). The level of CDO1 protein expression in these cells was similar with the physiological Cdo1 levels in mouse lung and liver (Figure 3—figure supplement 2B), with liver being one of the highest CDO1-expressing tissues that is responsible for supplying TAU to the body (Stipanuk et al., 2015). We find that CDO1 accumulated to higher levels in KEAP1^MUT cells than KEAP1^WT, although accumulation was observed in many KEAP1^WT cell lines as well (Figure 3D).

Next, we examined the toxicity of CDO1 products to NSCLC cell lines. Treatment of cells with CSA and Na₂SO₃, but not HTAU, led to cytotoxicity (Figure 5—figure supplement 4A). We found that (CYS)₂ starvation and Na₂SO₃ treatment were universally toxic to NSCLC cell lines, which did not depend on NRF2 activity (Figure 5—figure supplement 4B,C). In addition, CDO1, CSA and Na₂SO₃ sensitized A549 cells to oxidative stress (Figure 5—figure supplement 4D,E), consistent with their ability to deplete (CYS)₂. Collectively, these results demonstrate that CSA and SO₃^2- are toxic to NSCLC cells regardless of NRF2 activity, suggesting that resistance to (CYS)₂ starvation is not an inherent phenotype of NRF2^HIGH cells. Rather, they are sensitive to CDO1 expression due to high intracellular CYS and CDO1 stabilization.

Next, we examined the toxicity of CDO1 products to NSCLC cell lines. Treatment of cells with CSA and Na₂SO₃, but not HTAU, led to cytotoxicity (Figure 5—figure supplement 4A). We found that (CYS)₂ starvation and Na₂SO₃ treatment were universally toxic to NSCLC cell lines, which did not depend on KEAP1 mutation status (Figure 5—figure supplement 4B,C). In addition, CDO1, CSA and Na₂SO₃ sensitized A549 cells to oxidative stress (Figure 5—figure supplement 4D,E), consistent with their ability to deplete (CYS)₂. Collectively, these results demonstrate that CSA and SO₃^2- are toxic to NSCLC cells regardless of KEAP1 mutation status, suggesting that resistance to (CYS)₂ starvation is not an inherent phenotype of KEAP1 mutant cells. Rather, they are sensitive to CDO1 expression due to high intracellular CYS and CDO1 stabilization.

The article has been corrected accordingly.