Four key proteins, NADH:Ubiquinone oxidoreductase core subunit S1 (NDUFS1), cytochrome b-c1 complex subunit 2 (UQCRC2), SERPINA5 and superoxide dismutase 1 (SOD1), were validated using Western blot in different cancer types, such as testicular cancer, Hodgkin’s disease, leukemia, and lymphoma, in comparison with fertile men (Supplementary Figure S1). Here, SERPINA5 is linked to cancer.