STEAP1 and prostate adenocarcinoma: Interestingly, canonical prostate adenocarcinoma cell-surface targets KLK2 and STEAP1 had significantly lower expression in the LumB versus LumA samples (Fig. 6B and C; Supplementary Fig. S16A and S16B), and STEAP2 (Fig. 6D; Supplementary Fig. S16C) also had a trend toward lower expression in LumB, in contrast to FOLH1, which was highly expressed in both luminal CTC phenotypes (Fig. 2E; Supplementary Fig. S6D).