SLC25A13 and lung adenocarcinoma: Glioblastoma, glioblastoma multiforme, lung adenocarcinoma, and stomach adenocarcinoma samples were ranked according to expression level of NAGS, CPS1, or citrin mRNA and divided into quartiles based on the expression levels of the three genes, followed by comparison of survival times of patients with the highest and the lowest expression of the three genes (Figure 2).