〔Abstract〕 Objective To study the expression of dihydrolipoamide-S-succinyltransferase (DLST) in human epidermal growth factor receptor 2(HER2)-positive breast cancer patients and its impact on survival prognosis, as well as to clarify its possible involvement in the occurrence and development of HER2-positive breast cancer. Methods (1) Firstly, the CancerSEA database was used to screen for abnormal expression of DLST in various types of cancer, and then the Kaplan-Meier Plotter database was used to analyze the impact of DLST on the prognosis of various types breast cancer patients. (2) The CancerSEA database was used to explore and verify DLST-related signaling pathways. The interaction between DLST and proteins in breast cancer was studied through immunoprecipitation and GST-pull-down experiments. (3) The association between DLST and immune cell infiltration was analyzed using the TIMER 2.0 database. Results DLST was expressed at higher levels in HER2-positive subtype breast cancer patients, and the higher the expression level, the poorer the prognosis and the shorter the survival period of HER2-positive breast cancer patients. In invasive breast cancer, DLST was significantly negatively correlated with the apoptosis pathway. DLST was elevated in M2 macrophages in HER2-positive breast cancer. Neddylation-modified PTEN protein interacted with DLST. Conclusion DLST is highly expressed in breast cancer patient samples, and is positively correlated with the malignant progression of HER2- positive breast cancer, and is not conducive to the overall survival of HER2-positive breast cancer patients. Preliminary mechanism research suggests that DLST interacts with neddylation-modified PTEN protein, and inhibits tumor cell apoptosis and promotes M2 macrophage infiltration. Therefore, this study believes that DLST can be a potential therapeutic target and prognostic marker for clinical HER2-positive breast cancer patients.