Sperm-associated antigen 9 (SPAG9) is aberrantly expressed in multiple cancers such as hepatocellular carcinoma, chronic myeloid leukemia, thyroid cancer, bladder cancer, endometrial cancer, gastric cancer, prostate cancer, non-melanoma skin cancer, osteosarcoma, salivary gland tumors and astrocytoma. Here, SPAG9 is linked to prostate cancer.