The activation of ferroptosis is a new effective way to treat drug-resistant solid tumors. Ferroptosis is an iron-mediated form of cell death caused by the accumulation of lipid peroxides. The intracellular imbalance between oxidant and antioxidant due to the abnormal expression of multiple redox active enzymes will promote the produce of reactive oxygen species (ROS). So far, a few pathways and regulators have been discovered to regulate ferroptosis. In particular, the cystine/glutamate antiporter (System Xc −), glutathione peroxidase 4 (GPX4) and glutathione (GSH) (System Xc −/GSH/GPX4 axis) plays a key role in preventing lipid peroxidation-mediated ferroptosis, because of which could be inhibited by blocking System Xc −/GSH/GPX4 axis. This review aims to present the current understanding of the mechanism of ferroptosis based on the System Xc −/GSH/GPX4 axis in the treatment of drug-resistant solid tumors.

System Xc −/GSH/GPX4 axis: An important antioxidant system for the ferroptosis in drug-resistant solid tumor therapy

SIRT6 silencing overcomes resistance to sorafenib by promoting ferroptosis in gastric cancer

Background: Circular RNAs (circRNA) play an essential role in the tumorigenesis of non-small cell lung cancer (NSCLC). CircDTL is a novel identified circRNA with little information regarding its biological role. However, the role of circDTL in NSCLC has not been investigated yet.

Method: In this study, the levels of circDTL in tissues and cells were measured by RT-PCR. Cell viability was measured by the CCK-8 assay. Cell migration and invasion were evaluated using the wound healing assay and transwell assay, respectively. Cell death was measured by the cell death ELISA kit. The levels of Fe2+, ROS, MDA and GSH were measured using the commercial kits. The interactions between miR-1287-5p and circDTL/3′UTR GPX4 were verified by dual-luciferase activity assay. The effects of circDTL on tumor growth were evaluated in vivo.

Results: CircDTL was found to be upregulated and acted as an oncogene in NSCLC cells. Knockdown of circDTL promoted both apoptosis and ferroptosis of NSCLC cells. It was identified that circDTL exerts its oncogenic effects via the circDTL/miR-1287-5p/GPX4 axis and GPX4 inhibits both ferroptosis and apoptosis. Finally, this study showed that silencing of circDTL promoted the sensitivity of NSCLC cells to chemotherapeutic agents and inhibited the growth of tumors in vivo.

Conclusion: CircDTL acts as an oncogene and exerts its effects via the miR-1287-5p/GPX4 axis in NSCLC, providing a potential therapeutic target for NSCLC cancer therapy.

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CircDTL Functions as an Oncogene and Regulates Both Apoptosis and Ferroptosis in Non-small Cell Lung Cancer Cells.

Ferroptosis is a type of cell death that depends on iron and reactive oxygen species (ROS). The accumulation of iron and lipid peroxidation primarily initiates oxidative membrane damage during ferroptosis. The core molecular mechanism of ferroptosis includes the regulation of oxidation and the balance between damage and antioxidant defense. Tumor cells usually contain a large amount of H2O2, and ferrous/iron ions will react with excessive H2O2 in cells to produce hydroxyl radicals and induce ferroptosis in tumor cells. Here, we reviewed the latest studies on the regulation of ferroptosis in tumor cells and introduced the tumor-related signaling pathways of ferroptosis. We paid particular attention to the role of noncoding RNA, nanomaterials, the role of drugs, and targeted treatment using ferroptosis drugs for mediating the ferroptosis process in tumor cells. Finally, we discussed the currently unresolved problems and future research directions for ferroptosis in tumor cells and the prospects of this emerging field. Therefore, we have attempted to provide a reference for further understanding of the pathogenesis of ferroptosis and proposed new targets for cancer treatment. 

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Regulatory pathways and drugs associated with ferroptosis in tumors

Lung cancer is one of the most common cancers in the world. Although medical treatment has made impressive progress in recent years, it is still one of the leading causes of cancer-related deaths in men and women. Ferroptosis is a type of non-apoptotic cell death modality, usually characterized by iron-dependent lipid peroxidation, rather than caspase-induced protein cleavage. Excessive or lack of ferroptosis is associated with a variety of diseases, including cancer and ischaemia-reperfusion injury. Recent preclinical evidence suggests that targeting ferroptotic pathway is a potential strategy for the treatment of lung cancer. In this review, we summarize the core mechanism and regulatory network of ferroptosis in lung cancer cells, and highlight ferroptosis induction-related tumor therapies. The reviewed information may provide new insights for targeted lung cancer therapy.

The role of ferroptosis in lung cancer.

Inhibition of GPX4 or mTOR overcomes resistance to Lapatinib via promoting ferroptosis in NSCLC cells.

Background This study aimed to evaluate the properties and functions of polysaccharide-based porous microsphere (PPM) for drug delivery, as well as its inhibitory effect on malignant tumors. Materials and Methods PPM was prepared using the inverse emulsion polymerization method. FT-IR measurements were conducted to measure the wavenumber of PPM. Particle size distribution was tested with a particle analyzer, and surface morphologies of PPM were observed using a scanning electron microscope (SEM). Dialysis method, Cell Counting Kit-8 (CCK-8), and cell apoptosis analysis were adopted to evaluate the drug release, cytotoxicity and biocompatibility of mitomycin-C (MMC), respectively. Finally, an in vivo study was performed in C57BL/6 mice to confirm the function of MMC-loaded PPM on tumor growth. Results FT-IR spectra proved the successful preparation of MMC-loaded PPM. PPM had an average size of 25.90 ± 0.34 μm and then increased to 30.10 ± 0.20 μm after drug loading. Under SEM, the surface morphology was lotus seedpod surface-like, with macropits on the surface and micropores in macropits. Compared with the free MMC group, MMC-loaded PPM exhibited a delayed drug release rate in a pH-dependent manner and higher cell viability. Flow cytometry results showed that the cell apoptosis in the PPM/MMC group was lower than that in the free MMC group. In vivo experiment revealed the inhibitory efficacy of MMC-loaded PPM on malignant tumors. Conclusion In summary, MMC-loaded PPM exhibited favorable surface morphology, sustained drug release ability, nontoxicity and excellent biocompatibility, suggesting that PPM might be a potential drug carrier for tumor treatment.

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Jiangwei Ni

Papers

Inhibition of GPX4 or mTOR overcomes resistance to Lapatinib via promoting ferroptosis in NSCLC cells.

Polysaccharide-Based Lotus Seedpod Surface-Like Porous Microsphere as an Efficient Drug Carrier for Cancer Treatment.