GNAL-driven calcium signaling reshapes the spatiotemporal immune landscape in ER+ breast cancer: causal insights and prognostic implications

Background: Endocrine-resistant estrogen receptor-positive (ER+) breast cancer often presents with an immune-cold phenotype, yet the upstream regulators driving immune evasion remain unclear. GNAL, a G-protein subunit involved in calcium signaling, has emerged as a potential player in modulating the tumor immune microenvironment, but its role in ER+ breast cancer has not been systematically investigated. This study aims to systematically investigate GNAL’s biological functions, molecular mechanisms, and prognostic relevance in endocrine-resistant ER+ breast cancer, as well as its role in regulating the tumor immune microenvironment. Methods: To elucidate the regulatory role of GNAL, we integrated summary-based Mendelian randomization (SMR), single-cell RNA sequencing, and spatial transcriptomics. Causal inference, cell-type mapping, and intercellular communication networks were analyzed, and a multi-omics prognostic model was constructed and validated across The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) cohorts. Results: SMR analysis identified GNAL as a causal gene for ER+ breast cancer, with loss of expression was associated with increased recurrence risk. GNAL was specifically enriched in stromal stem-like subpopulations and decreased along with the stem cell differentiation trajectory. Spatial analyses revealed that GNAL+ stem-like cells recruited B cells via the MIF-CD74 signaling axis and established long-range communication with endothelial cells. A four-gene risk model (CD24, KDM3B, CEBPD, KRT14) predicted poor prognosis and was independent of Tumor (T), Node (N), and Metastasis (M) staging. High-risk tumors exhibited a 42% reduction in CD8+ T cell infiltration. Molecular docking identified stable hydrogen-bond interactions between GNAL and CEBPD. Conclusions: GNAL regulates the spatiotemporal immune remodeling of ER+ breast cancer via calcium signaling and stem-like cell differentiation. The multi-omics risk model offers clinical prognostic value and highlights GNAL as a potential target for precision immunotherapy.