SFRP4 and prostate cancer: One such test is the Oncotype DX GPS assay, which detects the expression of 12 genes (BGN, COL1A1, SFRP4, AZGP1, KLK2, SRD5A2, FAM13C, FLNC, GSN, GSTM2, and TPM2, TPX2) associated with prostate cancer aggressiveness, along with 5 housekeeping genes (RF1, ATP5E, CLTC, GPS1, and PGK1) [25].