Impact of the glutathione synthesis pathway on sulfasalazine-treated endometrial cancer

Identification of predictive biomarkers for endometrial cancer diagnosis and treatment response monitoring using plasma metabolome profiling

BACKGROUND

Endometrial cancer (EMC) is the most common female genital tract malignancy with an increasing prevalence in many countries including Japan, a fact that renders early detection and treatment necessary to protect health and fertility. Although early detection and treatment are necessary to further improve the prognosis of women with endometrial cancer, biomarkers that accurately reflect the pathophysiology of EMC patients are still unclear. Therefore, it is clinically critical to identify biomarkers to assess diagnosis and treatment efficacy to facilitate appropriate treatment and development of new therapies for EMC.

METHODS

In this study, wide-targeted plasma metabolome analysis was performed to identify biomarkers for EMC diagnosis and the prediction of treatment responses. The absolute quantification of 628 metabolites in plasma samples from 142 patients with EMC was performed using ultra-high-performance liquid chromatography with tandem mass spectrometry.

RESULTS

The concentrations of 111 metabolites increased significantly, while the concentrations of 148 metabolites decreased significantly in patients with EMC compared to healthy controls. Specifically, LysoPC and TGs, including unsaturated fatty acids, were reduced in patients with stage IA EMC compared to healthy controls, indicating that these metabolic profiles could be used as early diagnostic markers of EMC. In contrast, blood levels of amino acids such as histidine and tryptophan decreased as the risk of recurrence increased and the stages of EMC advanced. Furthermore, a marked increase in total TG and a decrease in specific TGs and free fatty acids including polyunsaturated fatty acids levels were observed in patients with EMC. These results suggest that the polyunsaturated fatty acids in patients with EMC are crucial for disease progression.

CONCLUSIONS

Our data identified specific metabolite profiles that reflect the pathogenesis of EMC and showed that these metabolites correlate with the risk of recurrence and disease stage. Analysis of changes in plasma metabolite profiles could be applied for the early diagnosis and monitoring of the course of treatment of EMC patients.

Sulfasalazine inhibits esophageal cancer cell proliferation by mediating ferroptosis

This study aimed to explore the potential mechanism by which sulfasalazine (SAS) inhibits esophageal cancer cell proliferation. A cell counting kit-8 (CCK-8) assay was used to detect the effect of SAS (0, 1, 2, and 4 mM) on the proliferation of TE-1 cells. Subsequently, TE-1 cells were divided into control group, SAS group, SAS + ferrostatin-1 (ferroptosis inhibitor) group, and SAS + Z-VAD (OH)-FMK (apoptosis inhibitor) group, and cell proliferation was measured using a CCK-8 assay. Real-time quantitative polymerase chain reaction and western blotting were used to determine the expression of solute carrier family member 7 11 (SLC7A11, also called xCT), glutathione peroxidase 4 (GPX4), and acyl-CoA synthase long-chain family member 4 (ACSL4) in TE-1 cells. Measurement of ferroptosis in TE-1 cells was achieved by flow cytometry. Compared with the control group (0 mM SAS), the proliferation of TE-1 cells was significantly inhibited by different concentrations of SAS for different time lengths, and 4 mM SAS treatment for 48 h could obtain the maximum inhibition rate (53.9%). In addition, SAS treatment caused a significant decrease in the mRNA and protein expression of xCT and GPX4, and a significant increase in ACSL4 expression in TE-1 cells treated with SAS. Flow cytometry results showed that the ferroptosis level was significantly increased after SAS treatment. However, the activation of ferroptosis by SAS was partially eliminated by treatment with ferrostatin-1 or Z-VAD (OH)-FMK. In conclusion, SAS inhibits the proliferation of esophageal carcinoma cells by activating the ferroptosis pathway.

Mechanism of Cell Death by Combined Treatment with an xCT Inhibitor and Paclitaxel: An Alternative Therapeutic Strategy for Patients with Ovarian Clear Cell Carcinoma

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian carcinoma that responds poorly to chemotherapy. Glutathione (GSH) is a primary antioxidant, which protects cells against reactive oxygen species (ROS). High levels of GSH are related to chemotherapeutic resistance. The glutamine/cystine transporter xCT is essential for intracellular GSH synthesis. However, whether xCT inhibition can overcome the resistance to chemotherapeutic agents in OCCC remains unclear. This study demonstrated that combined treatment with paclitaxel (PTX) and the xCT inhibitor sulfasalazine (SAS) significantly enhanced cytotoxicity more than the individual drugs did in OCCC cells. Treatment with PTX and SAS induced apoptosis more effectively than did individual drug treatments in the cells with significant generation of ROS. Moreover, combined treatment with PTX and SAS induced ferroptosis in the cells with low expression of glutathione peroxidase (GPx4), high levels of intracellular iron and significant lipid ROS accumulation. Therefore, our findings provide valuable information that the xCT inhibitor might be a promising therapeutic target for drug-resistant OCCC. The strategy of combined administration of PTX and SAS can potentially be used to treat OCCC and help to develop novel therapeutic methods.

Mitochondrial Regulation of Ferroptosis in Cancer Therapy

Ferroptosis, characterized by glutamate overload, glutathione depletion, and cysteine/cystine deprivation during iron- and oxidative-damage-dependent cell death, is a particular mode of regulated cell death. It is expected to effectively treat cancer through its tumor-suppressor function, as mitochondria are the intracellular energy factory and a binding site of reactive oxygen species production, closely related to ferroptosis. This review summarizes relevant research on the mechanisms of ferroptosis, highlights mitochondria's role in it, and collects and classifies the inducers of ferroptosis. A deeper understanding of the relationship between ferroptosis and mitochondrial function may provide new strategies for tumor treatment and drug development based on ferroptosis.

The amino acid transporter SLC7A11-mediated crosstalk implicated in cancer therapy and the tumor microenvironment

The solute carrier family 7 member 11 (SLC7A11), an amino acid transporter protein is frequently overexpressed in human malignancies. The expression and activity of SLC7A11 is finely regulated by oncogenes and tumor suppressors in tumor cells through various mechanisms and is highly specific for cystine and glutamate. Cystine is mainly transported intracellularly by SLC7A11 in the tumor microenvironment (TME) and is involved in GSH synthesis, which leads to ferroptosis resistance in tumor cells and promotes tumorigenesis and progression. The downregulation of SLC7A11 presents a unique drug discovery opportunity for ferroptosis-related diseases. Experimental work has shown that the combination of targeting SLC7A11 and tumor immunotherapy triggers ferroptosis more potently. Moreover, immunotargeting of SLC7A11 increases the chemosensitivity of cancer stem cells to doxorubicin, suggesting that it may act as an adjuvant to chemotherapy. Thus, SLC7A11 could be a promising target to overcome resistance mechanisms in conventional cancer treatments. This review provides an overview of the regulatory network of SLC7A11 in the TME and progress in the development of SLC7A11 inhibitors. In addition, we summarize the cytotoxic effects of blocking SLC7A11 in cancer cells, cancer stem cells and immune cells.

Ferroptosis: Opportunities and Challenges in Treating Endometrial Cancer

Ferroptosis, a new way of cell death, is involved in many cancers. A growing number of studies have focused on the unique role of ferroptosis on endometrial cancer. In this study, we made a comprehensive review of the relevant articles published to get deep insights in the association of ferroptosis with endometrial cancer and to present a summary of the roles of different ferroptosis-associated genes. Accordingly, we made an evaluation of the relationships between the ferroptosis-associated genes and TNM stage, tumor grade, histological type, primary therapy outcome, invasion and recurrence of tumor, and accessing the different prognosis molecular typing based on ferroptosis-associated genes. In addition, we presented an introduction of the common drugs, which targeted ferroptosis in endometrial cancer. In so doing, we clarified the opportunities and challenges of ferroptosis activator application in treating endometrial cancer, with a view to provide a novel approach to the disease.