KLK3 and cancer: The majority of such biomarker tests, including the PCA3 test (PCA3 and KLK3), MiPS (serum PSA plus urine TMPRSS2:ERG and PCA3) and ExosomeDX Prostate Intelliscore (ERG, PCA3, SPDEF), rely on detecting transcripts from a very small number of genes which may not be expressed in every cancer [9,10,11].