Interestingly, MEFs express lower Got1 but higher Csad protein compared to A549 cells (Figure 5—figure supplement 2A), and NSCLC cell lines were uniformly low for CSAD and high for GOT1 (Figure 5—figure supplement 3A) suggesting that expression of CSA metabolic enzymes may be a key determining factor in the generation of HTAU vs. SO32-. Here, CSAD is linked to non-small cell lung carcinoma.