For example, several protein biomarkers can be selected for measurement in a cancer type-specific manner (e.g. prostate-specific antigen (PSA) for prostate cancer, Her2, progesterone receptor, and estrogen receptor α (ERα) for breast cancer, etc.), and then the degree of upregulation/downregulation would be measured for each selected protein 35. Here, KLK3 is linked to prostate cancer.