TFF1-mediated suppression of the TCA cycle promotes bone metastasis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive subtype of breast cancer characterized by limited treatment options and poor prognosis. While TNBC exhibits a lower incidence of bone metastasis compared to luminal subtypes, its occurrence is associated with substantial morbidity and mortality. The metabolic mechanisms enabling TNBC cells to colonize bone remain largely undefined. In this study, a bone-tropic TNBC subline (MDA-MB-231/BM) was developed through iterative intracardiac inoculation in mice, followed by transcriptomic profiling to identify genes with altered expression. A CRISPR/Cas9 knockout library screen in MDA-MB-231 cells further revealed critical regulators of bone metastasis. Notably, dual-omics analysis demonstrated a consistent downregulation of key enzymes in the tricarboxylic acid (TCA) cycle within bone-metastatic TNBC cells. Functional experiments showed that PDHA1 knockout impaired cell migration, invasion, and mitochondrial respiration, underscoring the TCA cycle's essential role in metastasis. Among the identified regulators, TFF1 emerged as a potent suppressor of TCA cycle gene expression. Deletion of TFF1 enhanced mitochondrial function, reduced metastatic burden in vivo, and extended survival in mouse models. Supporting clinical relevance, TCGA data showed significantly higher TFF1 expression in luminal breast cancer compared to TNBC, aligning with the greater propensity for bone metastasis in luminal subtypes. These findings reveal that TFF1-mediated suppression of the TCA cycle contributes to the metabolic adaptation of TNBC cells for bone colonization, offering a potential therapeutic vulnerability and advocating for subtype-specific metabolic interventions.