Tumor-Intrinsic PD-1 Regulatory Network Drives Lapatinib Resistance in HER2⁺ Breast Cancer: An Integrative Bioinformatics Analysis

Background: Lapatinib resistance evolution in HER2+ breast cancer is still a crucial therapeutic hurdle, with immune microenvironmental reprogramming playing a minimally explored role. Beyond its canonical expression on T cells, programmed cell death protein 1 (PD-1/PDCD1) is intrinsically induced in resistant breast tumors. Through the binding of tumor-intrinsic PD-1 to PD-L1 on adjacent tumor or stromal cells, inhibitory signals are generated, establishing an immunosuppressive microenvironment. Methods: This exploratory study investigated the tumor-intrinsic (PD-1)-lapatinib resistance (PLR) regulatory network driving lapatinib resistance in HER2⁺/ER–/PR– breast cancer using an integrative bioinformatics analysis. The GSE38376 dataset and PDCD1 co-expressed genes were utilized to construct the protein-protein interaction (PPI) of the PLR regulatory network. Gene expression patters were visualized using a complex heatmap. Gene ontology, KEGG functional enrichment, gene-metabolite interaction network, immune cell infiltration, comparative gene expression profiling, correlation analysis of PDCD1-hub genes, survival analysis, and genetic alterations analysis were performed on the PLR regulatory network to elucidate the mechanisms of lapatinib resistance. Results: Pathways and gene-metabolite analyses showed that the PLR regulatory network genes were enriched in immune regulation pathways and lipid metabolic reprogramming. The top 10 PLR-hub genes were identified. Expression profiling in lapatinib-resistant cells revealed the upregulation of PDCD1, B2M, and ITGB2, while other genes, particularly those involved in interferon response and antigen presentation, were downregulated. Immune infiltration analysis indicated exhausted T cells and an immunosuppressive microenvironment. Comparative gene expression and survival analyses of PLR-hub genes implicated the PLR regulatory network in lapatinib resistance. Genetic alterations were infrequent, suggesting that regulation may occur epigenetically or transcriptionally. Conclusion: The findings revealed that the PLR regulatory network is associated with HER2⁺/ER–/PR– lapatinib resistance through multiple mechanisms, including interferon signaling silencing, T cell exhaustion, and the fostering of an immunosuppressive niche. These insights pave the way for interventions aimed at overcoming lapatinib resistance in HER2⁺ breast cancer.