A Molecular Tool Set for Measurement of Lung Cancer-Associated Protein Biomarker CIZ1B-FibA in Human Plasma

BACKGROUND: CIZ1B is an alternatively spliced protein fragment of the Cyclin-dependent kinase interacting protein 1 (CIP1)-interacting zinc finger protein (CIZ1) complexed with fibrinogen alpha chain (FibA), forming a single parameter protein analyte (CIZ1B-FibA). The CIZ1B blood biomarker has potential to indicate the presence of early-stage lung cancer and could alter clinical practice. METHODS: We report configuration and calibration of a sandwich ELISA for measurement of CIZ1B-FibA that uses a new and highly specific CIZ1B exon junction-selective monoclonal antibody to capture the analyte, and an anti-fibrinogen antibody to detect it, in microliter quantities of plasma from lung cancer patients. RESULTS: The format is tested across 3 independent sample sets encompassing cancer and control samples, yielding Receiver Operating Characteristic area under curve (ROC AUC) values of 0.82 for Set 1 (n = 48), 0.81 for Set 2 (n = 38), and 0.86 for Set 3 (n = 57), indicating discrimination for individuals with lung cancer including those with stage I or II disease (Set 3). However, comparison of the control plasma samples in each set, which were sourced in 3 countries with site-specific plasma isolation processes, revealed baseline differences indicating a note of caution regarding sensitivity to pre-analytic variables. Application of set-specific thresholds, determined by the maximum Youden Index, returned negative predictive values (NPV) of 95%, 77%, and 97% for Sets 1, 2 and 3, respectively. CONCLUSION: We describe an affordable and scalable blood test which can measure CIZ1B-FibA and now requires further validation of analytical parameters and investigation of potential biological variables.