SPAG9 promotes prostate cancer proliferation and metastasis via MAPK signaling pathway

Prostate cancer (PCa) is a worldwide malignant tumor which seriously threats the reproductive health of middle-aged and senior male. Sperm-associated antigen 9 (SPAG9), which belongs to the cancer testis (CT) antigen, overexpressed in multiple human malignant tumors and promoted tumor proliferation, invasion and metastasis. However, little attention has been focused on the relationship between SPAG9 and PCa. SPAG9 protein level was measured by immunohistochemical staining in the PCa tissues. SPAG9 mRNA and protein expression were investigated in various PCa cells by qRT-PCR and Western blot. Depletion and overexpression of SPAG9 were proceeded in PCa cells to evaluate their effects by various malignant approaches in vitro and in vivo. SPAG9 was significantly upregulated in the PCa tissues, mainly expressed in the cytoplasm and occasionally in the nucleus of some cells, while SPAG9 was not detected in normal prostate tissue. SPAG9 protein was detected in three PCa cells. Furthermore, these results revealed that upregulation of SPAG9 could promote cell proliferation, migration, motility and cycle of PC-3 cell line, vice versa, downregulation of SPAG9 resulted in the opposite effect. In vivo, knockout of SPAG9 expression induced suppression of tumor growth in athymic nude mice. In summary, the present study indicated that SPAG9 was closely related to the Gleason scores of PCa. SPAG9 could promote cell proliferation, migration, motility and cell cycle via MAPK signaling pathway, suggesting that SPAG9 may be a potential therapeutic target for PCa.