ATF4 and neoplasm: Both low and high proliferative luminal tumours showed weak positive correlation between GLS2 protein and ALDH18A1 (p < 0.001), ALDH4A1 (p < 0.01), ATF4 (p = 0.001), PRODH (p < 0.001), SLC38A2 (p ≤ 0.001) and SLC7A11 (Table 4, p < 0.001).