TRIB3 Promotes Triple-Negative Breast Cancer Metastasis by Restricting Lipophagy Through the PI3K/AKT/mTOR Signaling Pathway

BACKGROUND:Lipophagy-driven metabolic reprogramming is increasingly recognized as a determinant of tumor progression. TRIB3, a key regulator of lipid metabolism, has been implicated in cancer aggressiveness, with elevated expression linked to poor outcomes in triple-negative breast cancer. Here, we investigated whether TRIB3 promotes TNBC metastasis through regulation of lipophagy and lipid metabolism. METHODS:Public datasets (Oncomine, GEPIA, Kaplan-Meier Plotter) were analyzed to assess TRIB3 expression and its prognostic relevance in breast cancer. Immunohistochemistry and Western blotting validated TRIB3 expression in TNBC tissues and adjacent normal samples. Functional assays, including wound healing, Transwell migration, and EMT marker detection, were used to determine the effects of TRIB3 on cell migration and invasion. Subcutaneous xenograft and lung metastasis models were established in nude mice to evaluate its role in vivo. Potential upstream regulators were identified by dual-luciferase reporter assays, while downstream pathways were investigated using RNA sequencing, pathway enrichment, and functional annotation. The impact of TRIB3 on lipophagy was examined by transmission electron microscopy, immunofluorescence, and Western blotting, and further validated using autophagy inhibitors. RESULTS:TRIB3 was significantly overexpressed in TNBC and correlated with unfavourable prognosis. Functional assays demonstrated that TRIB3 enhanced TNBC cell invasion and metastasis both in vitro and in vivo. Mechanistically, TRIB3 negatively regulated MSI2 protein expression and activated the PI3K/AKT/mTOR pathway, thereby disrupting lipid droplet redistribution and inhibiting lipophagy, which facilitated tumor migration and metastasis. CONCLUSIONS:Our findings uncover a previously unrecognized mechanism by which TRIB3 regulates lipophagy to drive TNBC metastasis. We delineate the critical role of the TRIB3-MSI2 regulatory axis and its association with the PI3K/AKT/mTOR pathway, as well as the potential upstream involvement of FOXA1, in orchestrating this process. These results highlight TRIB3 as a central mediator of TNBC progression and suggest novel therapeutic strategies targeting lipophagy for this aggressive breast cancer subtype.