Early detection of pancreatic ductal adenocarcinoma by measuring the abnormal urinary fragmentation ratios of kininogen

Abstract

Abstract Background Intact kininogen (KNG), the precursor of kinin that originates from the liver, is fragmented by proteases. A recent research showed an increase in the serum levels of KNG fragments in cancer patients (pts), which were possibly produced by proteases in the tumor microenvironment. We hypothesized that urinary excretion of KNG fragments would also be elevated in pancreatic ductal adenocarcinoma (PDAC) pts. This study was conducted to investigate the diagnostic usefulness of urinary KNG fragment measurement by the multiple-reaction-monitoring technique (MRM). Methods Treatment-naive PDAC pts and healthy participants for whom pooled frozen urine specimens were available were enrolled in this study. Urine samples from resectable PDAC pts were collected prior to the surgery. The urinary proteins were digested with trypsin, and the resultant peptides were measured by MRM analysis; the degree of protein fragmentation was estimated by the ratio of the amount of a protein fragment to that of a constant region of the original protein. Fragments for which the fragmentation ratios were higher in resectable PDAC pts than in the healthy participants were defined as having abnormal protein fragments. The diagnostic capability of each abnormal protein fragment and CA19-9 for discriminating resectable PDAC pts from healthy participants was evaluated by receiver operating characteristic (ROC) curve analysis. Results A total of 19 pts with resectable PDAC (median age 73 years, male 74%) and 30 healthy participants (median age 34 years, male 40%) were analyzed. The fragmentation ratios for three fragments were found to be higher in the resectable PDAC pts than in the healthy participants, and these fragments were determined as abnormal protein fragments. The areas under the ROC curves were 0.73, 0.78 and 0.82, respectively (CA19-9: 0.82). Conclusion Measurement of the urinary fragmentation ratios of KNG enabled discrimination between resectable PDAC pts and healthy volunteers.