Abstract PO3-25-12: Tigecycline-Induced Metabolic Reprogramming and Cytokine Modulation Suppress the Characteristics of Breast Cancer Cells
Authors: Yu Haochen , Tang Lingfeng , Liu Shengchun 
Published: May 2024

Abstract
Objective: Patients with advanced breast cancer are prone to recurrence and metastasis. Hence, there is still a need to find new potential drugs or adjuvants to improve prognosis.
The Warburg effect, which is highly dependent on glycolysis, has been found to be present in the energy metabolism of tumors, including breast cancer. The effect also promotes the production of cytokines, to adapt the inflammatory microenvironment of tumor. However, drugs targeting Warburg effect and inflammatory environment are rarely reported in the treatment of breast cancer.
Tigecycline (Tige) is a commonly used glycylcycline antibiotic. Previous research has indicated it impede mitochondrial oxidative phosphorylation (OXPHOS) in various solid tumors. Based on the team's previous research, our study aimed to investigate whether Tige could inhibit breast cancer development by interfering with the Warburg effect and the inflammatory environment.
Methods: MB231, MB468 and MCF7, T47D, which represent triple-negative and estrogen receptor positive breast cancers, were treated with Tige at different concentrations for different periods of time. CCK8, colony formation and sphere formation assays were used to evaluate the effects on proliferation and tumor stemness in vitro, respectively. The effects on migration and invasion were evaluated by wound healing assay and Transwell. RNA sequencing was used to explore the genes altered and analyze the pathways involved. After labeling with probes, the changes of reactive oxygen species (ROS) were detected by fluorescence microscope, microplate reader, and flow cytometry. Cell cycle and apoptosis were detected by flow cytometry. Liquid cytokine chip was used to analyze the secretion of cytokines. Electron microscopy was performed to observe the changes in mitochondrial morphology. RT-PCR was used to detect the expression of rate-limiting enzymes in glycolysis pathway. Glucose consumption, lactate and pyruvate production were measured using glucose, lactate and pyruvate detection kits, respectively. Western blot was used to detect the changes of respiratory chain protein complex and other related pathway proteins in OXPHOS.
Results: Four breast cancer cells showed a significant decrease in cell proliferation, invasion and migratory ability after Tige treatment. Sphere-forming assays also showed that Tige had an effect on the stemness of breast cancer. RNA-sequencing showed that glycolysis, cell cycle, and immune-related pathways were inhibited after Tige treatment, and ROS production analysis revealed a decrease in ROS production. Flow cytometry also revealed that the cell cycle was arrested in S phase without significant apoptosis. Cytokine liquid chip analysis showed that the secretion of many cytokines, mainly interleukin (such as IL-1B), was inhibited after Tige intervention. RT-PCR results showed that the expression of several rate-limiting enzymes of the glycolytic pathway decreased. Glucose, lactate and pyruvate assay results showed that Tige reduced glucose uptake and lactate, pyruvate production. Electron microscopy results revealed that mitochondria in Tige treated cells showed significant contractures. WB results also showed a decrease in the expression of OXPHOS-related proteins. However, due to the heterogeneity of the four breast cancer cells, the degree of change in these capacities was not entirely consistent.
Conclusions: Tige not only inhibits mitochondrial OXPHOS, but also inhibits the glycolysis pathway, which results in the inhibition of glucose uptake and the production of pyruvate and lactate. The secretion of early pro-inflammatory cytokines also affected. Therefore, this study suggests that Tige may change the glucose metabolism and energy metabolism, and also change the inflammatory environment of breast tumors, which provides new evidence for the anti-tumor effect of Tige in breast cancer.
Citation Format: Haochen Yu, Lingfeng Tang, Shengchun Liu. Tigecycline-Induced Metabolic Reprogramming and Cytokine Modulation Suppress the Characteristics of Breast Cancer Cells [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-25-12.