Targeting NgR1/NogoA Signalling Enhances Natural Killer Cell Cytotoxicity and Alters Immune and Oncogenic Pathways in TNBC Cells

Triple-negative breast cancer (TNBC) is an aggressive subtype with limited therapeutic options, and impairment of natural killer (NK) cell cytotoxicity within the tumour microenvironment remains a major challenge. The present study investigated the role of the NogoA/Nogo receptor 1 (NgR1) axis in modulating NK cell-mediated cytotoxicity against TNBC cells. NK-92 and MDA-MB-231 cells were co-cultured at optimised effector-to-target ratios, followed by treatment with the NgR1 antagonist NEP1-40. Cell viability was assessed by WST-1 assay, apoptosis was evaluated using AO/DAPI staining, gene expression was analysed by RT-PCR, and downstream pathways together with immune infiltration were examined in silico. Blockade of NogoA/NgR1 signalling increased NK-92-mediated cytotoxicity (p < 0.0001). NEP1-40 reduced tumour cell viability from approximately 81% to 50% and significantly increased apoptotic cell death (p < 0.0001). Expression analysis revealed repression of oncogenic and migration-associated genes, including CDK4, MYC, NF-κB1, VEGFA, FGF1, N-cadherin and CD155, consistent with enhanced NK cell-mediated cytotoxicity and reduced tumour immune evasion. Functional annotation identified the PI3K/AKT pathway alongside cell cycle-related processes as candidate downstream mechanisms, while correlation analysis showed that most NogoA-regulated genes were significantly negatively associated with NK cell infiltration (p < 0.05), highlighting their role in immune escape. These findings suggest that NogoA regulates both tumour behaviour and immune remodelling in TNBC by enhancing NK cell-mediated cytotoxicity, promoting apoptosis and suppressing immune evasion pathways. Targeting the NgR1/NogoA axis may therefore represent a promising approach to strengthen NK cell-based immunotherapy, offering a novel therapeutic avenue in TNBC.