CRISPR/Cas9 system is extensively used for different kinds of cancer biomarkers including virus nucleic acids, ctDNAs (i.e., EGFR mutation), miRNAs (i.e., miR-17, miR-31), proteins (i.e., TGF-β1, CEA, PSA, AFP), and extracellular vesicles.90 CRISPR/Cas9 can combine with other assays for tumor biomarker identification, such as qPCR, FISH, and nanotechnology, providing an efficient way for tumor biomarker discovery. Here, KLK3 is linked to cancer.