Urine-based
biomarkers are a rational and promising approach for the detection of
bladder cancer due to the proximity of urine to the location of the
tumor site and the non-invasive nature of its sampling. A well-known and highly investigated
biomarker for
bladder cancer is
survivin. For detection of very small amounts of urinary
survivin protein a highly sensitive assay was developed. The assay is based on the immuno-PCR technology, more precisely a solid-phase proximity
ligation assay (spPLA). The limit of detection for the
survivin spPLA was 1.45 pg/mL, resulting in an improvement of the limit of detection by
a factor of approximately 23 compared to the previously in-house developed
survivin ELISA. A key step in development was the initial isolation of
survivin by a molecular fishing rod based on magnetic beads. Interfering matrix compounds pose a special challenge for further analytical application, but can be overcome by this isolation step. The assay is designed to work with only 500 μL of voided urine. The
survivin spPLA showed a sensitivity of 30% and specificity of 89% for
bladder cancer detection in this study of 110
bladder cancer cases and 133 clinical controls. Moreover, the results demonstrated again that
survivin is a useful complementary marker in combination with UBC® Rapid by increasing the overall sensitivity to 70% with a specificity of 86%. Although the performance for detection of
bladder cancer was rather low, the herein developed assay might serve as a new tool for
survivin biomarker research in diverse human fluids, even if the
biological matrix is complex or
survivin is only present in small amounts.