Gonadotropin beta-subunit nicking enzyme (GBNE), a potential marker of early malignancies

GBNE is an arginine-specific metalloprotease that cleaves human chorionic gonadotropin free beta-subunit in pregnancy serum. We tested GBNE activity in 539 serum samples, from individuals that were healthy, with benign diseases, or with a broad mixture of cancers. The mean GBNE activity in 130 samples from healthy individuals, 151 from those with benign disease, and 258 from cancer patients was 5.4 +/- 0.32, 5.8 +/- 0.20 and 16 +/- 1.2 units, respectively. ROC analysis indicated 86% discrimination between control samples and cancer. A cut-off of 12 units was selected. This was equaled or exceeded by 3.1% of samples from healthy individuals, 3.9% from those with benign disease, and 57% from those with cancer. There was no significant difference in detection of the different cancer primaries, breast (sensitivity 56%), gastrointestinal (53%), genitourinary (62%), gynecological (58%) and lung (55%) cancers. Sensitivity was highest for early stage, and lowest for advanced malignancies, for all cancer primaries. Taken together, sensitivity was 70, 44, 43 and 24%, for stages I, II, III and IV, respectively. GBNE is suggested to be a nonorgan site-restricted tumor marker with high sensitivity for early stage cancers.