Epitope mapping of human prostate specific antigen and glandular kallikrein expressed in insect cells

Two human prostate gland proteases were expressed in insect cells using recombinant baculovirus expression system. Prostate specific antigen (PSA) is an established serum marker of prostate cancer whereas the clinical utility of its close homologue, human glandular kallikrein (hK2) is presently unknown. The production levels using Trichoplusia ni cells were roughly 300 &mgr;g/l and 6 mg/l for hK2 and PSA, respectively. On western-blot we estimated the size for both proteins to be approximately 33 kDa which was consistent with PSA purified from seminal plasma. Nine anti-PSA monoclonal antibodies (Mabs) out of 26 tested, representing five independent epitopes, also reacted with hK2. The results obtained in this study may help in designing more accurate diagnostic assays for detection and monitoring of prostate cancer.