KLK3 and prostate carcinoma: The major form which is bound to ACT is known as complexed PSA (cPSA) and the smaller unbound portion as free PSA (fPSA) cPSA and fPSA represent the main fraction of total PSA (tPSA) (2) cPSA is the dominant form in prostate cancer, whereas fPSA represents a bigger fraction in patients with benign prostatic hyperplasia.