PiRNA-Hsap_1847317 may serve as a novel biomarker of PD-1 inhibitor resistance in patients with advanced non-small cell lung cancer

BACKGROUND: Acquired resistance to programmed cell death protein 1 (PD-1) inhibitors presents a major clinical challenge in the treatment of non-small cell lung cancer (NSCLC). This study aims to elucidate the epigenetic mechanisms underlying PD-1 inhibitor resistance, with a specific focus on the expression profiles of PIWI-interacting RNAs (piRNAs) and their associated signaling networks. METHODS: High-throughput RNA sequencing was performed on matched pre- and post-resistance plasma samples from three NSCLC patients to identify differentially expressed piRNAs. The top five candidate piRNAs were selected for subsequent verification. Plasma piRNA levels and comprehensive clinical data from an independent cohort of 50 NSCLC patients (evaluated at both pre- and post-resistance stages) were analyzed. Downstream target genes of the candidate piRNAs were predicted using TargetScan and miRanda algorithms, followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses. Target gene expression was experimentally validated via quantitative real-time PCR (qRT-PCR). Spearman's rank correlation was utilized to assess the relationship between piRNA expression and systemic inflammatory indices. Diagnostic performance was evaluated using receiver operating characteristic (ROC) curves. RESULTS: Five candidate piRNAs (Hsap_2765751, Hsap_249, Hsap_1847317, Hsap_681799, and Hsap_857420) exhibited significant differential expression. Notably, Hsap_1847317 was robustly upregulated following the development of resistance (P < 0.001). Bioinformatic and experimental analyses implicated Hsap_1847317 is implicated in the Wnt signaling pathway, while qRT-PCR demonstrated significantly higher AXIN2 mRNA expression after resistance (P < 0.001). these associative data do not establish direct regulation. Furthermore, the systemic neutrophil-to-lymphocyte ratio (NLR) significantly increased during the resistance phase (P < 0.001) and exhibited a positive correlation with Hsap_1847317 expression (r = 0.395, P = 0.005). ROC curve analysis demonstrated excellent predictive efficacy, yielding an area under the curve (AUC) of 0.944 for Hsap_1847317 and 0.720 for NLR in this cohort. CONCLUSION: Our findings indicate that plasma Hsap_1847317 and NLR are candidate non-invasive biomarkers for monitoring acquired resistance to PD-1 inhibitors in NSCLC. This study association between Hsap_1847317, Wnt-related enrichment, and AXIN2 mRNA provides a hypothesis for further mechanistic testing rather than evidence of a causal Hsap_1847317/Wnt/AXIN2 axis.