Human kallikrein 10 ELISA development and validation in breast cancer sera

Background: Human kallikrein 10 (hK10) is a putative secreted serine protease belonging to the same gene family as prostate specific antigen (hK3; PSA). There is significant interest in measuring hK10 which may act as a tumor suppressor in some cancers. We have developed an ELISA for hK10 and determined its analytical and clinical performance in normal and breast cancer sera. Methods: The assay used a previously described pair of monoclonal anti-hK10 antibodies and recombinant hK10 protein. Serum hK10 was detected quantitatively in a 2-step sandwich ELISA with colorimetric detection. The assay was analytically validated and used to determine serum levels of hK10 in a set of breast cancer, benign breast disease and normal samples. Results: The assay covered a linear range of 0.2 to 15 ng/mL and had a detection limit of 0.08 ng/mL. The within-run and between-run imprecision was < 9%. The average spike and dilution linearity recoveries were 96 and 103% respectively. Mean hK10 concentration in normal female sera was 0.79 ± 0.26 ng/mL. Concentrations were not age related and were not significantly different from benign fibrocystic disease or breast cancer. However, in a subset of breast cancer patients with both early and late stage disease, serum hK10 levels were elevated, at > 1.55 ng/mL, above all normal female and benign disease samples. Conclusions: We report in detail the analytical performance of a colorimetric hK10 ELISA validated in human serum and report for the first time the hK10 serum concentration in benign and breast cancer samples.