Due to their fundamental role in cellular physiology and disease pathology, the sensitive and specific detection of proteins—particularly disease biomarkers, such as carcinoembryonic antigen (CEA), prostate-specific antigen (PSA), and HER2—is essential for early diagnosis, prognosis, and monitoring of therapeutic efficacy in conditions like cancer, cardiovascular diseases, and neurodegeneration [164,165,166,167,168]. The gene discussed is KLK3; the disease is cancer.