Novel circulating microRNA signature for early detection and prognostication of checkpoint inhibitor-related pneumonitis

Background Checkpoint inhibitor-related pneumonitis (CIP) represents a highly lethal immune-related adverse event. Early diagnosis of CIP is crucial for timely intervention and improved prognosis; however, the absence of precise and effective diagnostic techniques often leads to underdiagnosis and misdiagnosis. This study aims to identify microRNA (miRNA) features from serum and extracellular vesicles (EVs) for the early CIP detection and prognosis. Methods Small RNA sequencing identified candidate miRNAs in 27 serum-derived EV samples from persons with lung cancer and CIP (CIP group) and those without, including immunotherapy-treated persons with lung cancer without CIP (immune checkpoint inhibitor, ICI group) and patients with infectious pneumonia (PNE group). These miRNAs were validated in EV samples in a discovery cohort (n=48) using a quantitative reverse transcription-PCR (qRT-PCR). Diagnostic models for the biomarkers were developed using a training cohort (ICI:47, PNE:28, CIP:31) and validated in a separate validation cohort (ICI:32, PNE:19, CIP:21) using qRT-PCR in both EV and serum samples, and logistic regression. Using a Cox regression model, we built a prognostic risk stratification for patients with CIP based on three miRNAs. Results Sequencing analysis initially screened and identified 13 overexpressed miRNAs in patients with CIP. Subsequently, qRT-PCR demonstrated that three miRNAs (EVs miR-193a-5p, serum miR-193a-5p, and serum miR-378a-3p) effectively distinguished CIP from non-CIP individuals (training cohort: area under the curve (AUC)=0.870; validation cohort: AUC=0.837). Notably, this miRNA signature was equally robust in differentiating CIP from ICI (training cohort: AUC=0.823; validation cohort: AUC=0.845) and PNE groups (training cohort: AUC=0.892; validation cohort: AUC=0.907). Furthermore, when combined with lymphocyte levels, the miRNA signature significantly enhanced the overall diagnostic accuracy in distinguishing CIP from the non-CIP group (training cohort: AUC=0.900; validation cohort: AUC=0.932), and maintained its robustness in distinguishing CIP from the ICI group (training cohort: AUC=0.898; validation cohort: AUC=0.946) and the PNE group (training cohort: AUC=0.938; validation cohort: AUC=0.959). Additionally, the three-miRNA panel was independently and significantly associated with overall survival in patients with CIP (HR: 2.827; p=0.040). Conclusions Our circulating miRNA-based signature represents a non-invasive and robust diagnostic tool for patients with CIP and could accurately predict their prognosis. This signature may facilitate early detection and personalized management of these patients.