Human kallikrein 8 (hK8; neuropsin) is a serine protease and new member of the hK family. The aim of this study was to examine if hK8 may serve as a novel cancer biomarker. An hk8-ELISA, developed in-house, was used to study the distribution of hK8 in various biological fluids and tissue extracts from healthy individuals and ovarian cancer patients of different stages of the disease (International Federation of Obstetrics and Gynecology II-IV). For ovarian cancer patients, very high levels in ascites fluid were observed (<or=1000 microg/liter; n = 85 samples). Elevated serum levels were seen in 24 of 40 (62%) of ovarian cancer patients. Higher ascites fluid hK8 concentration was associated with better ovarian cancer progression-free survival (P = 0.02). In both serum and ascites fluid, there is a significant correlation between hK8 and CA125 concentration (r = 0.51 and 0.58, respectively). The serum concentration of hK8 was an indicator of progression on regression on longitudinal monitoring of an ovarian cancer patient. These data suggest that hK8 protein is detectable in ovarian cancer tissue extracts, serum, and ascites fluid, indicating that it may serve as a new ovarian cancer marker.
