RARRES2 regulates lipid metabolic reprogramming to mediate the development of brain metastasis in triple negative breast cancer

Background Triple negative breast cancer(TNBC),the most aggressive subtype of breast cancer,is characterized by a high incidence of brain metastasis(BrM)and a poor prognosis.As the most lethal form of breast cancer,BrM remains a major clinical challenge due to its rising incidence and lack of effective treatment strategies.Recent evidence suggested a potential role of lipid metabolic reprogramming in breast cancer brain metastasis(BCBrM),but the underlying mechanisms are far from being fully elucidated.Methods Through analysis of BCBrM transcriptome data from mice and patients,and immunohistochemical validation on patient tissues,we identified and verified the specific down-regulation of retinoic acid receptor responder 2(RARRES2),a multifunctional adipokine and chemokine,in BrM of TNBC.We investigated the effect of aberrant RARRES2 expression of BrM in both in vitro and in vivo studies.Key signaling pathway components were evaluated using multi-omics approaches.Lipidomics were performed to elucidate the regulation of lipid metabolic reprogramming of RARRES2.Results We found that downregulation of RARRES2 is specifically associated with BCBrM,and that RARRES2 deficiency promoted BCBrM through lipid metabolic reprogramming.Mechanistically,reduced expression of RARRES2 in brain metastatic potential TNBC cells resulted in increased levels of glycerophospholipid and decreased levels of triacylglycerols by regulating phosphatase and tensin homologue(PTEN)-mammalian target of rapamycin(mTOR)-sterol regulatory element-binding protein 1(SREBP1)signaling pathway to facilitate the survival of breast cancer cells in the unique brain microenvironment.Conclusions Our work uncovers an essential role of RARRES2 in linking lipid metabolic reprogramming and the development of BrM.RARRES2-dependent metabolic functions may serve as potential biomarkers or therapeutic targets for BCBrM.

The roles and mechanisms of SREBP1 in cancer development and drug response

Cancer occurrence and development are closely related to increased lipid produc-tion and glucose consumption.Lipids are the basic component of the cell membrane and play a significant role in cancer cell processes such as cell-to-cell recognition,signal transduction,and energy supply,which are vital for cancer cell rapid proliferation,invasion,and metastasis.Sterol regulatory element-binding transcription factor 1(SREBP1)is a key transcription factor regulating the expression of genes related to cholesterol biosynthesis,lipid homeostasis,and fatty acid synthesis.In addition,SREBP1 and its upstream or downstream target genes are implicated in various metabolic diseases,particularly cancer.However,no review of sREBP1 in cancer biology has yet been published.Herein,we summarized the roles and mechanisms of SREBP1 biological processes in cancer cells,including SREBP1 modification,lipid metabolism and reprogramming,glucose and mitochondrial metabolism,immunity,and tumor microenvi-ronment,epithelial-mesenchymal transition,cell cycle,apoptosis,and ferroptosis.Addition-ally,we discussed the potential role of SREBP1 in cancer prognosis,drug response such as drug sensitivity to chemotherapy and radiotherapy,and the potential drugs targeting SREBP1 and its corresponding pathway,elucidating the potential clinical application based on SREBP1 and its corresponding signal pathway.