Six-transmembrane epithelial antigen of the prostate 1 (STEAP1), a member of the STEAP family, is a general tumor antigen. However, no information has been available to date regarding the function of STEAP1 in the progression of endometrial carcinoma. In this study, we used in vitro and in vivo strategies to prove that STEAP1 plays an important role in the progression of endometrial carcinoma. Immunohistochemistry, immunocytochemistry, quantitative reverse transcription polymerase chain reaction (RT-qPCR), and Western blot analysis were used to detect the expression of STEAP1 in normal endometrial cells and endometrial cancer cell lines. The progression of the cell cycle, plate clone formation assay, and transwell migration and invasion assays were performed to examine the effects of STEAP1 on cell proliferation, clonogenicity, migration, and their invasive capacity. In addition, we confirmed that STEAP1 was tightly correlated with the development of tumor in vivo. The relationship between epithelial to mesenchymal transition (EMT) and STEAP1 expression was evaluated by RT-qPCR and Western blot analysis. Matrix metalloproteinase (MMP) zymography assay was used to detect the activities of MMP2 and MMP9. STEAP1 was restrictively expressed in endometrial carcinoma and downregulation of the STEAP1 gene increased proliferation and clonogenicity, as well as promoted cell migration, invasion, and the progress of EMT. STEAP1 is downregulated in endometrial carcinoma and can restrict migration and invasion of endometrial carcinoma cells. Overall, STEAP1 may be an ideal target for tumor therapy and diagnosis in the future. K E Y W O R D S endometrial carcinoma, epithelial to mesenchymal transition, invasion, migration, six-transmembrane epithelial antigen of the prostate 1A standard streptavidin-biotin-peroxidase staining procedure was used, wherein formalin-fixed, paraffin-embedded endometrial tissues were cut into 5-μm slices. After a series of processing steps, such as dewaxing in xylene, rehydration, and antigen retrieval, sections were incubated with the mouse anti-human STEAP1 monoclonal antibody (ab117454; Abcam) at a dilution of 1﹕200 . Six-transmembrane epithelial antigen of the prostate 1 is associated with tumor invasion and migration in endometrial carcinomas.
