Genetically encoded fluorescent probes to assist in the diagnosis of small cell lung cancer.

Small cell lung cancer (SCLC) is one of the most aggressive malignancies, with early detection being crucial for improving patient outcomes. Serum biomarkers, neuron-specific enolase (NSE), and pro-gastrin releasing peptide (ProGRP), play significant roles in the early screening and pathological classification of SCLC. In the study, the affinity peptides of NSE and ProGRP were screened by phage display technology, which were then assessed for binding affinity using enzyme-linked immunosorbent assay (ELISA) and biolayer interferometry (BLI). Circularly permuted fluorescent protein (cpFP) probes were constructed by genetically encoding the selected peptides as binding domains. The E1 probe for NSE and the P10 probe for ProGRP demonstrated high sensitivity and specificity in detecting their respective targets. The E1 probe with a concentration of 4 μg/mL reacted well with NSE (1-16,000 ng/mL), and the reaction exhibited a good linear relationship when the NSE concentration was between 1 and 100 ng/mL. The 4 μg/mL P10 probe reacted well with ProGRP (0.01-2000 ng/mL) and showed good linear relationship between 0.01 and 50 ng/mL. Clinical validation revealed that adjusting the upper limit of normal concentrations significantly improved the probes' diagnostic sensitivity and specificity for SCLC. These probes offer a high-sensitivity, specific, rapid, and cost-effective approach to SCLC detection, holding promise for early diagnosis and improved patient management . KEY POINTS: In this study, peptides targeting NSE and ProGRP were selected by phage display technology, and the peptides obtained have good affinity with the corresponding proteins. Based on R-GECO1, cpFP probes were constructed using peptides as binding domains, and E1 probe for NSE and P10 probe for ProGRP were obtained. E1 probe and P10 probe have good sensitivity and specificity for the diagnosis of SCLC.