Immune checkpoint crosstalk: CTLA-4/CD80 engagement as a predictor of anti-PD-1/PD-L1 therapy outcome in NSCLC

Background: CTLA-4/CD80 and PD-1/PD-L1 immune checkpoint pathways play critical roles in regulating T-cell activity within the tumor microenvironment (TME) of non-small cell lung cancer (NSCLC). While immune checkpoint inhibitors (ICIs) targeting PD-1/PD-L1 have improved survival outcomes, response rates vary, and predictive biomarkers' alternative to PD-L1 expression are imperative. Our study aimed to identify PD-1/PD-L1 and CTLA-4/CD80 interaction states as enhanced predictive biomarkers for patient stratification to anti-PD-1/PD-L1 therapies in NSCLC. Methods: platform to quantify CTLA-4/CD80 and PD-1/PD-L1 interaction states in formalin-fixed paraffin-embedded (FFPE) samples from a cohort of 67 NSCLC patients treated with anti-PD-1/PD-L1 therapies. Corroborating prior findings, high PD-1/PD-L1 interaction, measured by FRET efficiency, predicts improved response rates via overall survival (OS) and progression-free survival (PFS). Results: Remarkably, we also identified high CTLA-4/CD80 interaction (FRET efficiency ≥6.41%) as correlating with improved OS and PFS in response to anti-PD-1/PD-L1 therapies. Patients with concurrently high PD-1/PD-L1 and CTLA-4/CD80 interactions exhibited the highest response rates, suggesting synergistic interplay between these checkpoints. In contrast, neither biomarker predicted response to chemotherapy in a separate cohort of 51 lung adenocarcinoma patients, confirming specificity for ICI therapy. Conclusions: as a robust tool for stratifying NSCLC patients for ICI treatment and underscore the clinical relevance of CTLA-4/CD80 interaction as a predictive biomarker, paving the way for personalized immunotherapy strategies.