In addition, using a similar principle, the FRET system combined with ratiometric fluorescence detection or time-resolved Förster resonance energy transfer (TR-LRET) can be used to detect prostate-specific antigen PAS [145], miRNA-21 [146], glutathione GSH [147], etc. These research advances can promote rapid and non-invasive screening of tumors in the context of rising cancer incidence, achieve labeling and tracing of cancer cells, and provide valuable insights for future clinical treatment. The gene discussed is KLK3; the disease is cancer.