Adipocyte-rich microenvironment promotes TNBC progression through SIRT6-associated ACSL5 dysregulation and lipid...

Triple-negative breast cancer (TNBC) is highly aggressive and has strong metastatic potential, and effective targeted therapies remain limited. There is growing evidence that the adipocyte microenvironment plays an important role in tumor progression, but its specific mechanism remains to be studied. As a key enzyme for the activation of long-chain fatty acids, the role and regulatory mechanism of ACSL5 in TNBC have not been clarified.

ACSL5 expression and clinical relevance were assessed using public datasets, clinical specimens, and TNBC cell models. The effect of ACSL5 knockdown and overexpression on the malignant phenotype of TNBC cells were evaluated. An adipocyte-TNBC co-culture system, PA/OA treatment, SIRT6 manipulation, co-immunoprecipitation, pan-acetylation assays, and ACSL5 K212/213 mutant analysis were used to investigate the SIRT6-ACSL5 regulatory mechanism. Lipid-associated phenotypes were examined by Oil Red O staining, TG measurement, FASN/CPT1A detection, and Seahorse analysis. In vivo validation was performed using an orthotopic mammary fat pad model in female NOD/SCID mice.

ACSL5 expression was reduced in TNBC tissues and cell lines, and lower ACSL5 expression was associated with aggressive disease features. Functionally, ACSL5 knockdown promoted TNBC cell viability, colony formation, migration, invasion, and EMT-associated changes, whereas ACSL5 overexpression exerted opposite effects. Adipocyte co-culture and PA exposure induced SIRT6 upregulation and ACSL5 downregulation, while SIRT6 knockdown partially restored ACSL5 expression. Mechanistically, SIRT6 interacted with ACSL5 and regulated ACSL5 pan-acetylation. Mutagenesis of a candidate K212/213-containing lysine motif suggested that this region may contribute to ACSL5 acetylation-associated functional regulation. Adipocyte co-culture and SIRT6 overexpression increased lipid droplet accumulation, intracellular TG storage, FASN expression, and EMT-associated changes, while reducing CPT1A expression. ACSL5 restoration partially reversed these lipid storage-associated malignant phenotypes. In an orthotopic mammary fat pad model using female NOD/SCID mice, ACSL5 overexpression suppressed tumor growth, lung metastatic involvement, Ki67 expression, tumor TG accumulation, and lipid metabolism-related marker changes, whereas ACSL5 knockdown produced the opposite effects.

These findings suggest that adipocyte-derived fatty-acid cues may promote TNBC progression partly through SIRT6-associated ACSL5 dysregulation and lipid storage-associated phenotypic changes, highlighting ACSL5 as a potential lipid-related regulatory node in adipocyte-driven TNBC progression.