Circ0060467 sponges miR-6805 to promote hepatocellular carcinoma progression through regulating AIFM2 and GPX4 expression

BACKGROUND

Circular RNAs (circRNAs) represent a subset of non-coding RNAs implicated in the regulation of diverse biological processes, including tumorigenesis. However, the expression and functional implications of circ0060467 in hepatocellular carcinoma (HCC) remain elusive. In this study, we aimed to elucidate the role of circ0060467 in modulating the progression of HCC.

METHODS

Differentially expressed circRNAs in HCC tissues were identified through circRNA microarray assays. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays revealed the upregulation of circ0060467 in both HCC cell lines and tissues. Various assays were conducted to investigate the roles of circ0060467 in HCC progression. Additionally, RNA immunoprecipitation (RIP) assays and luciferase assays were carried out to assess the interactions between circ0060467, microRNA-6085 (miR-6085), apoptosis-inducing factor mitochondria-associated 2 (AIFM2), and glutathione peroxidase 4 (GPX4) in HCC.

RESULTS

Microarray and qRT-PCR analyses demonstrated a marked elevation of circ0060467 in HCC tissues and cell lines. Knockdown of circ0060467 suppressed HCC cell proliferation. Luciferase reporter and RIP assays confirmed the binding of circ0060467, AIFM2, and GPX4 to miR-6805. Subsequent experiments revealed that circ0060467 competes with AIFM2 and GPX4, thereby inhibiting cancer cell ferroptosis by binding to miR-6085 and promoting hepatocellular carcinoma progression.

CONCLUSIONS

Collectively, circ0060467 modulates the levels of AIFM2 and GPX4, crucial regulators of tumor cell ferroptosis, by acting as a sponge for miR-6085 in HCC. Thus, circ0060467 may represent a novel diagnostic marker and therapeutic target for HCC.

Prognostic and Immunological Role of Key Genes of Ferroptosis in Pan-Cancer

Solute carrier family 7 member 11 (SLC7A11), glutathione peroxidase 4 (GPX4), and apoptosis inducing factor mitochondria associated 2 (AIFM2) are the key regulators in ferroptosis. However, the expression patterns and prognostic roles of these genes in pan-cancer are still largely unclear. The expression patterns and prognostic roles of SLC7A11, GPX4, and AIFM2 and the relationships between the expression levels of these genes and immune infiltration levels in pan-cancer were analyzed by using TIMER, gene expression profiling interactive analysis (GEPIA), Oncomine, and Kaplan–Meier databases. Our results showed that both SLC7A11 and GPX4 were overexpressed in colorectal cancer, and SLC7A11 was overexpressed in lung cancer. High levels of SLC7A11 and AIFM2 were significantly linked with the shortened disease-free survival and overall survival (OS) in adrenocortical carcinoma (ACC), respectively. And high expression of SLC7A11, GPX4, and AIFM2 were significantly correlated with the shortened OS of acute myeloid leukemia patients. In esophageal carcinoma (ESCA), GPX4 expression was significantly associated with the infiltration of macrophage and myeloid dendritic cell, and AIFM2 expression was significantly associated with the infiltration of CD4⁺ T cell. Importantly, GPX4 expression was positively correlated with the expression levels of monocyte markers (CD14 and CD115) and M2 macrophage markers (VSIG4 and MS4A4A) both in ESCA and in head and neck squamous cell carcinoma (HNSC). In summary, SLC7A11, GPX4, and AIFM2 are dysregulated in many types of cancers, and are candidate prognostic biomarkers for many types of cancers, and can be used to evaluate the infiltration of immune cells in tumor tissues.

CircGFRA1 facilitates the malignant progression of HER-2-positive breast cancer via acting as a sponge of miR-1228 and enhancing AIFM2 expression

CircRNAs (circular RNA) are reported to regulate onset and progress multiple cancers. Nonetheless, the function along with the underlying mechanisms of circRNAs in HER-2-positive breast cancer (BC) remains unclear. CircRNA microarrays were performed to elucidate expression profiles of HER-2-positive BC cells. circRNA levels were quantified using qRT-PCR assay. Various in vitro along with in vivo assays were employed to further explore the effects of circGFRA1 in the progress of HER-2-positive BC and interactions of circGFRA1, miR-1228 and AIFM2 in Her-2-positive BC. CircGFRA1 was remarkably upregulated in HER-2-positive BC. Knockdown of circGFRA1 could attenuate HER-2-positive BC progression by inhibiting the proliferation, infiltration and migratory ability of HER-2-positive BC cells. Through ceRNA mechanism, circGFRA1 could bind to miR-1228 and alleviate inhibitory activity of miR-1228 on targeted gene AIFM2. In summary, circGFRA1-miR-1228-AIFM2 axis regulates HER-2-positive BC. CircGFRA1 is a novel promising treatment option for HER-2-positive BC.

ATF6 aggravates acinar cell apoptosis and injury by regulating p53/AIFM2 transcription in Severe Acute Pancreatitis

Background: There is no curative therapy for severe acute pancreatitis (SAP) due to poor understanding of its molecular mechanisms. Endoplasmic reticulum (ER) stress is involved in SAP and increased expression of ATF6 has been detected in SAP patients. Here, we aimed to investigate the role of ATF6 in a preclinical SAP mouse model and characterize its regulatory mechanism. Methods: Pancreatic tissues of healthy and SAP patients were collected during surgery. Humanized PRSS1 transgenic mice were treated with caerulein to mimic the SAP development, which was crossed to an ATF6 knockout mouse line, and pancreatic tissues from the resulting pups were screened by proteomics. Adenovirus-mediated delivery to the pancreas of SAP mice was used for shRNA-based knockdown or overexpression. The potential functions and mechanisms of ATF6 were clarified by immunofluorescence, immunoelectron microscopy, Western blotting, qRT-PCR, ChIP-qPCR and luciferase reporter assay. Results: Increased expression of ATF6 was associated with elevated apoptosis, ER and mitochondrial disorder in pancreatic tissues from SAP patients and PRSS1 mice. Knockout of ATF6 in SAP mice attenuated acinar injury, apoptosis and ER disorder. AIFM2, known as a p53 target gene, was identified as a downstream regulatory partner of ATF6, whose expression was increased in SAP. Functionally, AIFM2 could reestablish the pathological disorder in SAP tissues in the absence of ATF6. p53 expression was also increased in SAP mice, which was downregulated by ATF6 knockout. p53 knockout significantly suppressed acinar apoptosis and injury in SAP model. Mechanistically, ATF6 promoted AIFM2 transcription by binding to p53 and AIFM2 promoters. Conclusion: These results reveal that ATF6/p53/AIFM2 pathway plays a critical role in acinar apoptosis during SAP progression, highlighting novel therapeutic target molecules for SAP.

AIFM2 blocks ferroptosis independent of ubiquinol metabolism

Ferroptosis is a multi-step regulated cell death that is characterized by excessive iron accumulation and lipid peroxidation. Cancer cells can acquire resistance to ferroptosis by the upregulation of anti-ferroptotic proteins or by the downregulation of pro-ferroptotic proteins. Apoptosis-inducing factor mitochondria-associated 2 (AIFM2, also known as FSP1 or PRG3) has been recently demonstrated as an endogenous ferroptosis suppressor, but its mechanism remains obscure. Here, we show that AIFM2 blocks erastin-, sorafenib-, and RSL3-induced ferroptotic cancer cell death through a mechanism independent of ubiquinol, the reduced and active antioxidant form of coenzyme Q10. In contrast, AIFM2-dependent endosomal sorting complexes required for transport (ESCRT)-III recruitment in the plasma membrane is responsible for ferroptosis resistance through the activation of a membrane repair mechanism that regulates membrane budding and fission. Importantly, the genetic inhibition of the AIFM2-dependent ESCRT-III pathway increases the anticancer activity of sorafenib in a xenograft tumor mouse model. These findings shed new light on the mechanism involved in ferroptosis resistance during tumor therapy.

Activation of AIFM2 enhances apoptosis of human lung cancer cells undergoing toxicological stress

Application of cisplatin (DDP) for treating lung cancer is restricted due to its toxicity and lung cancer's drug resistance. In this study, we examined the effect of Jinfukang (JFK), an effective herbal medicine against lung cancer, on DDP-induced cytotoxicity in lung cancer cells. Morphologically, we observed that JFK increases DDP-induced pro-apoptosis in A549 cells in a synergistic manner. Transcriptome profiling analysis indicated that the combination of JFK and DDP regulates genes involved in apoptosis-related signaling pathways. Moreover, we found that the combination of JFK and DDP produces synergistic pro-apoptosis effect in other lung cancer cell lines, such as NCI-H1975, NCI-H1650, and NCI-H2228. Particularly, we demonstrated that AIFM2 is activated by the combined treatment of JFK and DDP and partially mediates the synergistic pro-apoptosis effect. Collectively, this study not only offered the first evidence that JFK promotes DDP-induced cytotoxicity, and activation of AIFM2 enhances apoptosis of human lung cancer cells undergoing toxicological stress, but also provided a novel insight for improving cytotoxicity by combining JFK with DDP to treat lung cancer cells.