Dysregulation of hormones is considered a risk factor for obesity‐mediated breast tumorigenesis; however, obesity is associated with poor outcomes among women diagnosed with triple‐negative breast cancer (TNBC), which is a hormone‐independent breast cancer subtype. Thus, identifying the driving force behind the obesity‐breast cancer relationship is an urgent need. Here it is identified that diet‐induced obesity (DIO) facilitates tumorigenesis of TNBC cells. Mechanistically, DIO induces a metabolic addiction to fatty acid oxidation (FAO), accompanied by coordinated activation of Yes‐associated protein (YAP) signaling. Specifically, YAP governs mitochondrial redox homeostasis via transcriptional regulation of antioxidant‐related enzymes, which renders tumor cells capable of extenuating FAO‐elicited mitochondrial oxidative stress. Moreover, adipocytes‐derived fatty acids are identified to be responsible for enhancing the FAO‐YAP axis and antioxidative capacity, and higher expression of an obesity signature in breast cancer patients is positively correlated with YAP signaling and antioxidant genes. The findings uncover the crucial role of YAP in dictating mitochondrial redox homeostasis for obesity‐mediated metabolic adaptation and breast tumor progression.

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer as it shows a high capacity for metastasis and poor prognoses. Metabolic reprogramming is one of the hallmarks of cancer, and aberrant glycolysis was reported to be upregulated in TNBC. Thus, identifying metabolic biomarkers for diagnoses and investigating cross-talk between glycolysis and invasiveness could potentially enable the development of therapeutics for patients with TNBC. In order to determine novel and reliable metabolic biomarkers for predicting clinical outcomes of TNBC, we analyzed transcriptome levels of glycolysis-related genes in various subtypes of breast cancer from public databases and identified a distinct glycolysis gene signature, which included ENO1, SLC2A6, LDHA, PFKP, PGAM1, and GPI, that was elevated and associated with poorer prognoses of TNBC patients. Notably, we found a transcription factor named Y-box-binding protein 1 (YBX1) to be strongly associated with this glycolysis gene signature, and it was overexpressed in TNBC. A mechanistic study further validated that YBX1 was upregulated in TNBC cell lines, and knockdown of YBX1 suppressed expression of those glycolytic genes. Moreover, YBX1 expression was positively associated with epithelial-to-mesenchymal transition (EMT) genes in breast cancer patients, and suppression of YBX1 downregulated expressions of EMT-related genes and tumor migration and invasion in MDA-MB-231 and BT549 TNBC cells. Our data revealed an YBX1-glycolysis-EMT network as an attractive diagnostic marker and metabolic target in TNBC patients.

Obesity is a well‐known risk factor for breast cancer formation and is associated with elevated mortality and a poor prognosis. An obesity‐mediated inflammatory microenvironment is conducive to the malignant progression of tumors. However, the detailed molecular mechanism is still needed to be clarified. Herein, we identified that breast cancer cells from mice with diet‐induced obesity exhibited increased growth, invasiveness, and stemness capacities. A transcriptome analysis revealed that expressions of interleukin 33 (IL33) signaling pathway‐related genes were elevated in obesity‐associated breast cancer cells. Importantly, IL33 expression was significantly associated with the yes‐associated protein (YAP) signature, and IL33 was transcriptionally regulated by YAP. Suppression of IL33 reduced tumor migration and invasion, while the addition of IL33 activated nuclear factor (NF)‐κB signaling and revived tumor mobility in YAP‐silenced cells. Furthermore, suppression of YAP attenuated IL33 expression which was accompanied by relief of obesity‐mediated immunosuppression. Clinical analyses showed that IL33 expression was markedly associated with macrophage and regulatory T cell infiltration. These findings reveal a crucial role of the YAP/IL33 axis in promoting aggressiveness and immunosuppression of obesity‐associated breast cancer progression.

Obesity is a well-known risk factor for breast cancer formation and is associated with elevated mortality and a poor prognosis. An obesity-mediated inflammatory microenvironment is conducive to the malignant progression of tumors. However, the detailed molecular mechanism is still needed to be clarified. Herein, we identified that breast cancer cells from mice with diet-induced obesity exhibited increased growth, invasiveness, and stemness capacities. A transcriptome analysis revealed that expressions of interleukin 33 (IL33) signaling pathway-related genes were elevated in obesity-associated breast cancer cells. Importantly, IL33 expression was significantly associated with the yes-associated protein (YAP) signature, and IL33 was transcriptionally regulated by YAP. Suppression of IL33 reduced tumor migration and invasion, while the addition of IL33 activated nuclear factor (NF)-κB signaling and revived tumor mobility in YAP-silenced cells. Furthermore, suppression of YAP attenuated IL33 expression which was accompanied by relief of obesity-mediated immunosuppression. Clinical analyses showed that IL33 expression was markedly associated with macrophage and regulatory T cell infiltration. These findings reveal a crucial role of the YAP/IL33 axis in promoting aggressiveness and immunosuppression of obesity-associated breast cancer progression.