Single-cell and spatial transcriptomics map lung-adaptive metastasis programs through Exoc4, Cd36-vasculogenic...

Triple-negative breast cancer (TNBC) is an aggressive subtype associated with high metastatic potential and poor outcomes, with lung metastasis representing one of the most frequent and life-threatening events. However, the mechanism how cellular plasticity and reprogramming that enable TNBC cells to colonize in the lung remain incompletely understood. Here, we integrated single-cell RNA sequencing and spatial transcriptomics on paired MMTV-PyMT primary mammary tumors and lung metastatic tumors, complemented by functional assays in 4T1 mouse models, to delineate the cellular heterogeneity and molecular mechanisms driving TNBC lung metastasis. We identified three metastasis-associated subtypes-C12-Cd, Cdh5-like, and Wfdc12-each enriched in metastatic lesions and exhibiting distinct biological programs. The C12-Cd subcluster was characterized by the upregulation of Exoc4, a vesicle-trafficking regulator associated with a poor prognosis in patients with TNBC. The Cdh5-like cluster displayed a hypoxia-driven vascular phenotype, in which Hif-2α-mediated Cd36 expression promoted vasculogenic mimicry and metastatic colonization. The Wfdc12 cluster secreted Cxcr2 ligands (Cxcl1/2) and Cxcr2 blockade significantly reduced lung metastasis in vivo, underscoring therapeutic potential. Notably, cross-subtypes of lung metastatic TNBC analysis revealed Sftpc upregulation, reflecting organ-adaptive transcriptional reprogramming that may facilitate tumor cell survival in the pulmonary niche. Collectively, our findings provide a comprehensive cellular and molecular atlas of TNBC lung metastasis. We establish Exoc4, the Hif-2α-Cd36 vasculogenic mimicry axis, Cxcrl1/2-Cxcr2 signaling, and Sftpc as critical mediators of metastatic adaptation. These results not only bridge key knowledge gaps in metastatic heterogeneity and organ-specific adaptation but also highlight novel prognostic markers and therapeutic vulnerabilities with translational potential for treating TNBC lung metastasis.