The Interplay of the LncRNA AFAP1-AS1 and the Soluble Immune Checkpoint Proteins sPD-1/sPD-L1 in Breast Cancer: Tumor-Immune Crosstalk.

Breast cancer (BC) remains a major health issue worldwide. Immuno-oncology has recently garnered much attention with unprecedented bench-to-bedside revolutions in cancer diagnosis and treatment. The PD-1/PD-L1 pathway is an adaptive mechanism in cancer immune escape that can be regulated epigenetically via long non-coding RNAs (lncRNAs). In this study, we sought to investigate the potential clinical utility of the circulating lncRNA AFAP1-AS1 and soluble immune checkpoint proteins sPD-1 and sPD-L1 as liquid biopsy biomarkers in BC patients. Serum expression levels of AFAP1-AS1 was quantified via qRT‒PCR in a cohort comprising 90 BC patients (45 metastatic and 45 nonmetastatic) and 20 healthy controls, while serum sPD-1 and sPD-L1 levels were determined by ELISA. Computational bioinformatics approaches were employed to investigate molecular interactions among AFAP1-AS1, PD-1, and PD-L1, and to assess their functional roles in oncogenesis. Serum AFAP1-AS1, sPD-1 and sPD-L1 levels exhibited significant elevation in BC patients compared to controls, with further increases observed in metastatic versus non-metastatic cases. These biomarkers demonstrated significant association with positive lymph node involvement (p<0.05). AFAP1-AS1 showed significant correlations with sPD-1 and sPD-L1, and their molecular interactions were demonstrated through in silico predictive analyses. ROC analysis revealed robust diagnostic and prognostic discriminatory potential. In conclusion, this study underscores the clinical potential of the circulating lncRNA AFAP1-AS1, sPD-1 and sPD-L1 as promising non-invasive biomarkers in BC and may collectively reflect a coordinated immune evasion axis. The interplay between epigenetic modifications and immune checkpoint pathways represents a novel therapeutic target for enhancing antitumor immunity and halting metastasis.