STEAP4 and hepatocellular carcinoma: IF analysis further confirmed the proteomic data, Protein specific IF staining demonstrated that HER2 and STEAP4 expression was upregulated in the HCC-1954 cell line compared to the MDA-MB-231 and the MCF-10A cell lines (Figures 3A, B), whereas CD97 was predominantly present in the MDA-MB-231 cell line (Figure 3D).