Transcription Factor Activating Enhancer-Binding Protein 4/Acidic Nuclear Phosphoprotein 32 Family Member E Axis Increases Lactate Production to Promote Triple-Negative Breast Cancer Stemness

Abstract

Tumor growth, metastasis, and therapy are significantly affected by cancer stem cells. Dysregulation of acidic nuclear phosphoprotein 32 family member E (ANP32E) expression is associated with the progression of various human malignancies. Furthermore, ANP32E promotes tumor stemness. Uncertainty persists regarding the role of ANP32E in triple-negative breast cancer (TNBC) as well as the molecular processes controlling cancer stemness. The expression of ANP32E in triple-negative breast cancer was detected by bioinformatics analyses and molecular experiments. The correlation analysis of ANP32E and glycolysis pathway marker genes (pyruvate dehydrogenase kinase 1 (PDK1), MYC, and hexokinase 2 (HK2)) and stemness index was conducted to identify the potential transcription factor upstream of ANP32E and binding sites. The dual luciferase assay and chromatin immunoprecipitation (ChIP) confirmed their binding relationship. Stemness was evaluated by assessing cell cloning ability, cell sphere formation ability, and expression of stem cell markers CD133, Nanog, and CD44. Cell glycolysis ability was analyzed by measuring extracellular acidification rate (ECRA), glucose consumption, lactate production, adenosine triphosphate (ATP) level, and LDHA expression. TNBC had an upregulated level of ANP32E, and ANP32E knockdown reduced TNBC cell stemness. ANP32E was positively correlated with the marker genes of glycolysis (PDK1, MYC, and HK2). Overexpression of ANP32E stimulated the glycolysis of tumor cells and raised lactate production. Furthermore, the transcription factor activating enhancer-binding protein 4 (TFAP4) was an upstream regulatory factor of ANP32E. By binding to ANP32E and activating its transcription, TFAP4 increased lactate production through the glycolysis pathway, which in turn promoted the stemness of TNBC. This study revealed a novel mechanism by which the TFAP4/ANP32E axis promotes tumor cell stemness in TNBC through the elevation of lactate production, indicating that the TFAP4/ANP32E axis may serve as a potential target for the TNBC treatment.