Placental leucine aminopeptidase as a potential specific urine biomarker for invasive ovarian cancer

Background: A non-invasive and sensitive biomarker for the detection of ovarian cancer (OvCa) is lacking. We aim to investigate if urinary placental leucine aminopeptidase (P-LAP) can serve as a reliable biomarker for OvCa. Methods: P-LAP activity was measured using a LAP assay kit (Serotech Co., Ltd., Sapporo, Japan) in the urine of 22 patients with benign or borderline malignant ovarian tumors and 18 patients with OvCa. In this assay, L-methionine was added at 20 mM because P-LAP is functional, but other aminopeptidases are inhibited at this dose of L-methionine. Results: The mean urinary P-LAP activity was significantly higher in the OvCa group than in the benign or borderline malignant tumor group. When the cut-off value of P-LAP was determined as 11.00 U/L, its sensitivity and specificity for differentiating invasive cancer were 77.8% and 95.5%, respectively. Conclusion: Although the usefulness of this test should be confirmed in a larger cohort of cases and controls, our study is the first to highlight the importance of urinary P-LAP as a biomarker for OvCa.