STEAP2 and cancer: As a potentially valuable marker of lung cancer, previous studies have demonstrated that the identification of STEAP1 mRNA in the serum of cancer patients by highly sensitive and specific real-time PCR can distinguish patients with lung cancer from healthy subjects [11], STEAP1 may be a highly specific biomarker in lung cancer [29], for STEAP2, there are few relevant studies in lung cancer, and to date, no studies have evaluated the co-expression of different STEAP proteins.