G6PD and cancer: However, data from the Human Protein Atlas database (HPA; https://www.proteinatlas.org/; accessed on 19 August 2024) provide comparative antibody staining information across various cancer tissues [56], generally supporting our findings in PCa cell lines: GSTP1 staining is almost always negative in prostate cancer samples; CAT and MARC2 show moderate staining in 10 to 40% of samples; and GSR, G6PD, and IDH1 exhibit moderate to strong positivity in most of the samples tested.