Circular RNA circRHOT1 contributes to pathogenesis of non-small cell lung cancer by epigenetically enhancing C-MYC expression through recruiting KAT5

Circular RNA in cancer

Over the past decade, circular RNA (circRNA) research has evolved into a bona fide research field shedding light on the functional consequence of this unique family of RNA molecules in cancer. Although the method of formation and the abundance of circRNAs can differ from their cognate linear mRNA, the spectrum of interacting partners and their resultant cellular functions in oncogenesis are analogous. However, with 10 times more diversity in circRNA variants compared with linear RNA variants, combined with their hyperstability in the cell, circRNAs are equipped to influence every stage of oncogenesis. This is an opportune time to address the breadth of circRNA in cancer focused on their spatiotemporal expression, mutations in biogenesis factors and contemporary functions through each stage of cancer. In this Review, we highlight examples of functional circRNAs in specific cancers, which satisfy critical criteria, including their physical co-association with the target and circRNA abundance at stoichiometrically valid quantities. These considerations are essential to develop strategies for the therapeutic exploitation of circRNAs as biomarkers and targeted anticancer agents.

Emerging roles for Mitochondrial Rho GTPases in tumor biology

Mitochondrial Rho GTPases (MIRO1 and MIRO2) are primarily studied for their role as resident mitochondrial anchor proteins that facilitate mitochondria trafficking in neurons. However, it is now appreciated that these proteins have critical roles in cancer. In this review, we focus on examining the role of MIROs in cancer, including expression changes in tumors and the molecular mechanisms by which MIROs impact tumor cell growth, invasion, and metastasis. Additionally, we give an overview of how MIRO's functions in normal cells within the tumor microenvironment can support or inhibit tumor growth and metastasis. Although this is still an emerging field, the current consensus is that the MIROs primarily promote tumor progression of disparate tumor types. As mitochondrial proteins are now being targeted in the clinic, we discuss their potential as novel proteins to target in cancer.

Circ_0007432 promotes non-small cell lung cancer progression and macrophage M2 polarization through SRSF1/KLF12 axis

Circular RNAs (circRNAs) plays critical roles in non-small cell lung cancer (NSCLC) development. Herein, we illustrated the effects of circ_0007432 on malignant features of NSCLC. We found that circ_0007432 played a promoting role in NSCLC progression, lying in accelerating cell viability, migration and invasion of NSCLC cells, promoting M2 macrophage polarization, suppressing cell apoptosis of NSCLC cells, and enhancing tumor growth in vivo. Mechanistically, the interactions among circ_0007432, SRSF1, KLF12, and IL-8 were validated by RNA-binding protein immunoprecipitation (RIP), electrophoretic mobility shift assay (EMSA), RNA pull-down, dual luciferase reporter assay and chromatin immunoprecipitation (ChIP) assays. Circ_0007432 upregulated KLF12 by recruiting SRSF1. KLF12 facilitated IL-8 expression and release by binding to IL-8 promoter. Furthermore, the role of circ_0007432/SRSF1/KLF12/IL-8 axis in malignant phenotypes of tumor cells or macrophage polarization was investigated using rescue experiments. In conclusion, circ_0007432 bound with SRSF1 to stabilize KLF12 and then promote IL-8 release, thus promoting malignant behaviors of NSCLC cells and M2 macrophage polarization.

CircRHOT1 restricts gastric cancer cell ferroptosis by epigenetically regulating GPX4

Background

Gastric cancer (GC) is a malignant form of cancer that severely threatens human health. Despite developments on treatment, the prognosis of patients with advanced GC remains poor. Hence, the identification of detailed molecular mechanisms and potential therapeutic targets is of great importance for GC study. In recent years, circular RNAs have been widely reported to be important regulators in cancer initiation and progression. This study sought to evaluate the function of circRHOT1 in GC development.

Methods

Clinical specimens were collected from patients with GC to detect the level of circRHOT1. The expression of circRHOT1 in several GC cell lines was detected by quantitative real-time polymerase chain reaction. Cell Counting Kit 8 (CCK-8), colony formation, and xenograft tumor growth experiments were performed to check cell proliferation. Cell ferroptosis was determined by the levels of intracellular iron, Fe2+ (Divalent iron ion), lipid reactive oxygen species, malondialdehyde, and glutathione. The protein levels of SLC7A11 and glutathione peroxidase-4 (GPX4) were detected by western blot assays. The epigenetic regulation of the GPX4 gene was analyzed by chromatin immunoprecipitation assays.

Results

CircRHOT1 was more highly expressed in the GC tumors than the adjacent non-tumor tissues. The knockdown of circRHOT1 significantly suppressed cell growth (P<0.05) and stimulated the ferroptosis of the GC cells (P<0.05). CircRHOT1 recruited KAT5 (Acetyltransferase Tip60) to promote the acetylation of lysine 27 on histone H3 protein subunit (H3k27Ac) of the GPX4 gene and stimulated gene transcription. The overexpression of KAT5 and GPX4 notably reversed the anti-proliferation effect of circRHOT1 depletion (P<0.05).

Conclusions

CircRHOT1 promoted GC progression and suppressed ferroptosis by recruiting KAT5 to initiate GPX4 transcription. Our findings showed that cirRHOT1 is a promising target for GC treatment.

Circular RNAs in ferroptosis: regulation mechanism and potential clinical application in disease

Ferroptosis, an iron-dependent non-apoptotic form of cell death, is reportedly involved in the pathogenesis of various diseases, particularly tumors, organ injury, and degenerative pathologies. Several signaling molecules and pathways have been found to be involved in the regulation of ferroptosis, including polyunsaturated fatty acid peroxidation, glutathione/glutathione peroxidase 4, the cysteine/glutamate antiporter system Xc-, ferroptosis suppressor protein 1/ubiquinone, and iron metabolism. An increasing amount of evidence suggests that circular RNAs (circRNAs), which have a stable circular structure, play important regulatory roles in the ferroptosis pathways that contribute to disease progression. Hence, ferroptosis-inhibiting and ferroptosis-stimulating circRNAs have potential as novel diagnostic markers or therapeutic targets for cancers, infarctions, organ injuries, and diabetes complications linked to ferroptosis. In this review, we summarize the roles that circRNAs play in the molecular mechanisms and regulatory networks of ferroptosis and their potential clinical applications in ferroptosis-related diseases. This review furthers our understanding of the roles of ferroptosis-related circRNAs and provides new perspectives on ferroptosis regulation and new directions for the diagnosis, treatment, and prognosis of ferroptosis-related diseases.

Knockdown of KAT5/KIF11 induces autophagy and promotes apoptosis in anaplastic thyroid cancer cells

K (lysine) acetyltransferase (KAT) 5, which is a member of the KAT family of enzymes, has been found to act as a regulatory factor in various types of cancer. However, the role of KAT5 in anaplastic thyroid carcinoma (ATC) and its underlying mechanism is still elusive. The expression levels of KAT5 and kinesin family member 11 (KIF11) in ATC cells were assessed utilizing reverse transcription-quantitative PCR and western blot analyses. The cell proliferative ability was assessed via Cell Counting Kit-8 assay and using 5-ethynyl-2'-deoxyuridine staining. Flow cytometry and western blot analyses were applied for the assessment of cell apoptosis. Cell autophagy was investigated by employing western blot analysis and immunofluorescence staining. In addition, the enrichment of histone H3 lysine 27 acetylation (H3K27ac) and RNA polymerase II (RNA pol II) was analyzed by chromatin immunoprecipitation assay. It was shown that KAT5 expression was markedly increased in ATC cells. KAT5 depletion suppressed the cell proliferative capability but promoted the induction of apoptosis and autophagy. In addition, the autophagy inhibitor 3-methyladenine reversed the effects of KAT5 deficiency on the proliferative and apoptotic activities of 8505C cells. With regard to the mechanism, it was found that KAT5 inhibited the expression of KIF11 by repressing the enrichment of H3K27ac and RNA pol II. Upregulation of KIF11 expression reversed the effects of KAT5 silencing on the proliferative activity, apoptosis and autophagy of 8505C cells. In conclusion, the results indicated that KAT5 induced autophagy and promoted apoptosis of ATC cells by targeting KIF11, which may provide a promising target for the treatment of ATC.

Circular RNAs in chemotherapy resistance of lung cancer and their potential therapeutic application

Lung cancer is one of the high malignancy-related incidence and mortality worldwide, accounting for about 13% of total cancer diagnoses. Currently, the use of anti-cancer agents is still the main therapeutic method for lung cancer. However, cancer cells will gradually show resistance to these drugs with the progress of treatment. And the molecular mechanisms underlying chemotherapy agents resistance remain unclear. circRNAs are newly identified noncoding RNAs molecules with covalently closed circular structures. Previous studies have shown that circRNAs are associated with tumorigenesis and progression of various cancers, including lung cancer. Recently, growing reports have suggested that circRNAs could contribute to drug resistance of lung cancer cell through different mechanisms. Therefore, in this review, we summarized the functions and underlying mechanisms of circRNAs in regulating chemoresistance of lung cancer and discussed their potential applications for diagnosis, prognosis, and treatment of lung cancer.

Circular RNAs: Emerging regulators of glucose metabolism in cancer

Aberrant glucose metabolism is one of the most striking characteristics of metabolic reprogramming in cancer. Thus, clarifying the regulatory mechanism of glucose metabolism is crucial to understanding tumor progression and developing novel therapeutic strategies for cancer patients. Recent developments in circular RNAs have explained the regulatory mechanism of glucose metabolism from a new dimension. In this review, we briefly summarize the recent advances in circRNA research on cancer glucose metabolism and emphasize the different regulatory mechanisms, including acting as miRNA sponges, interacting with proteins and being translated into proteins. Additionally, we discuss the future research directions of circular RNAs in the field of glucose metabolism.

Long Noncoding RNAs and Circular RNAs Regulate AKT and Its Effectors to Control Cell Functions of Cancer Cells

AKT serine-threonine kinase (AKT) and its effectors are essential for maintaining cell proliferation, apoptosis, autophagy, endoplasmic reticulum (ER) stress, mitochondrial morphogenesis (fission/fusion), ferroptosis, necroptosis, DNA damage response (damage and repair), senescence, and migration of cancer cells. Several lncRNAs and circRNAs also regulate the expression of these functions by numerous pathways. However, the impact on cell functions by lncRNAs and circRNAs regulating AKT and its effectors is poorly understood. This review provides comprehensive information about the relationship of lncRNAs and circRNAs with AKT on the cell functions of cancer cells. the roles of several lncRNAs and circRNAs acting on AKT effectors, such as FOXO, mTORC1/2, S6K1/2, 4EBP1, SREBP, and HIF are explored. To further validate the relationship between AKT, AKT effectors, lncRNAs, and circRNAs, more predicted AKT- and AKT effector-targeting lncRNAs and circRNAs were retrieved from the LncTarD and circBase databases. Consistently, using an in-depth literature survey, these AKT- and AKT effector-targeting database lncRNAs and circRNAs were related to cell functions. Therefore, some lncRNAs and circRNAs can regulate several cell functions through modulating AKT and AKT effectors. This review provides insights into a comprehensive network of AKT and AKT effectors connecting to lncRNAs and circRNAs in the regulation of cancer cell functions.

Non-coding RNAs in ferroptotic cancer cell death pathway: meet the new masters

Despite the recent advances in cancer therapy, cancer chemoresistance looms large along with radioresistance, a major challenge in dire need of thorough and minute investigation. Not long ago, cancer cells were reported to have proven refractory to the ferroptotic cell death, a newly discovered form of regulated cell death (RCD), conspicuous enough to draw attention from scholars in terms of targeting ferroptosis as a prospective therapeutic strategy. However, our knowledge concerning the underlying molecular mechanisms through which cancer cells gain immunity against ferroptosis is still in its infancy. Of late, the implication of non-coding RNAs (ncRNAs), including circular RNAs (circRNAs), microRNAs (miRNAs), and long non-coding RNAs (lncRNAs) in ferroptosis has been disclosed. Nevertheless, precisely explaining the molecular mechanisms behind the contribution of ncRNAs to cancer radio/chemotherapy resistance remains a challenge, requiring further clarification. In this review, we have presented the latest available information on the ways and means of regulating ferroptosis by ncRNAs. Moreover, we have provided important insights about targeting ncRNAs implicated in ferroptosis with the hope of opening up new horizons for overcoming cancer treatment modalities. Though a long path awaits until we make this ambitious dream come true, recent progress in gene therapy, including gene-editing technology will aid us to be optimistic that ncRNAs-based ferroptosis targeting would soon be on stream as a novel therapeutic strategy for treating cancer.

Vacuolar protein sorting-associated protein 72 homolog (VPS72) binding to lysine acetyltransferase 5 (KAT5) promotes the proliferation, invasion and migration of hepatocellular carcinoma through regulating phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway

Hepatocellular carcinoma, a fatal malignancy that occurs in the liver, poses a major public health challenge. This paper attempted to clarify the role and mechanism of vacuolar protein sorting-associated protein 72 homolog (VPS72) in the progression of hepatocellular carcinoma. Firstly, VPS72 expression in hepatocellular carcinoma tissues and the prognostic correlation were analyzed by GEPIA2 database. Western blotting and RT-qPCR assays were used to evaluate VPS72 expression in several hepatocellular carcinoma cell lines. Then, cell proliferation was assessed by cell counting kit-8 and colony formation in HuH-7 cells with VPS72 silencing. Measurement of cell invasion and migration by transwell and wound healing assays. Next, the relationship between VPS72 and lysine acetyltransferase 5 (KAT5) was predicted by bioGRID, STRING and GEIPA2 databases, which was confirmed by Co-immunoprecipitation assay. Subsequently, KAT5 was overexpressed to explore whether VPS72 could regulate the progression of hepatocellular carcinoma by binding to KAT5. And the expression of proteins related to PI3K/AKT signaling was tested with western blotting. Results indicated that VPS72 was highly expressed in hepatocellular carcinoma tissues and cell lines and was associated with poor prognosis. VPS72 knockdown inhibited the proliferation, invasion and migration of HuH-7 cells. In addition, VPS72 could bind to KAT5. KAT5 overexpression reversed the suppressive impacts of VPS72 knockdown on the proliferation, invasion and migration in HuH-7 cells. Besides, VPS72 silencing downregulated p-PI3K and p-AKT expression, which was restored by KAT5 overexpression. Collectively, VPS72 binding to KAT5 promotes the progression of hepatocellular carcinoma through the regulation of PI3K/AKT signaling pathway.

Local anesthetic levobupivacaine inhibits stemness of osteosarcoma cells by epigenetically repressing MAFB though reducing KAT5 expression

Osteosarcoma is the most prevalent bone cancer and accounts for over half of sarcomas. In this study, we identified that the treatment of levobupivacaine suppressed proliferation of osteosarcoma cells in vitro. The tumor xenograft analysis showed that levobupivacaine significantly repressed the osteosarcoma cell growth in the nude mice. The treatment of levobupivacaine improved the apoptosis rate and attenuated invasion and migration abilities of osteosarcoma cells. The sphere formation capabilities of osteosarcoma cells were repressed by levobupivacaine. The protein levels of Sox-2, Oct3/4, and Nanog were inhibited by the treatment of levobupivacaine in osteosarcoma cells. Regarding mechanism, we identified that levobupivacaine inhibited MAFB and KAT5 expression in osteosarcoma cells. We observed that lysine acetyltransferase 5 could enriched in the promoter region of MAF BZIP transcription factor B, while levobupivacaine treatment could repressed the enrichment. The suppression of KAT5 by siRNA repressed the enrichment of histone H3 acetylation at lysine 27 and RNA polymerase II on promoter of MAFB. The expression of MAFB was decreased by KAT5 knockdown in osteosarcoma cells. The expression of MAFB was repressed by levobupivacaine, while the overexpression of KAT5 could reverse the repression of MAFB. KAT5 contributes to the cell proliferation and stemness of osteosarcoma cells. The overexpression of KAT5 or MAFB could reverse levobupivacaine-attenuated cell proliferation and stemness of osteosarcoma cells. Therefore, we concluded that local anesthetic levobupivacaine inhibited stemness of osteosarcoma cells by epigenetically repressing MAFB though reducing KAT5 expression. Levobupivacaine may act as a potential therapeutic candidate for osteosarcoma by targeting cancer stem cells.

Circular RNA RHOT1 Regulates miR-142-5p/CCND1 to Participate in Chondrocyte Autophagy and Proliferation in Osteoarthritis

Background

Osteoarthritis (OA) serves as one of the most prevalent types of joint disorders and is a leading cause of symptoms of stiffness, swelling, and arthralgia. Circular RNAs (circRNAs) have been reported to participate in various cellular processes by competing with microRNAs. Meanwhile, cyclinD1 (CCND1) is a key cell cycle regulatory protein and plays a crucial role in OA progression. Nevertheless, the function of circRHOT1 in the modulation of OA progression is still obscure. Here, we explored the effect of circRHOT1 on autophagy and extracellular matrix (ECM) in OA.

Methods

The expression of circRHOT1 and autophagy markers was detected in OA samples. The effect of circRHOT1 on OA was analyzed in the OA rat model. The function of circRHOT1 in the regulation of OA was assessed by CCK-8, colony formation, flow cytometry analysis, quantitative real-time PCR, Western blot analysis, and luciferase reporter gene assay in chondrocytes.

Results

We observed that autophagy markers, including LC3 and beclin1, were repressed in clinical OA samples. The expression of circRHOT1 and CCND1 was induced but the miR-142-5p expression was reduced in clinical OA samples. The miR-142-5p expression was negatively correlated with circRHOT1 and CCND1, and the circRHOT1 expression was positively associated with CCND1 in clinical OA samples. Meanwhile, the apoptosis was induced in OA rats but the depletion of circRHOT1 could block the phenotype in the rats. The articular cartilage degeneration was promoted in OA rats, while the knockdown of circRHOT1 repressed the degeneration. The serum levels of CTX-II and COMP were increased in OA rats, and the silencing of circRHOT1 downregulated levels of these proteins. In addition, the expression of collagen II and aggrecan was promoted by the depletion of circRHOT1 in the OA rats. Significantly, the expression of LC3 and beclin1 was suppressed in OA rats, in which the knockdown of circRHOT1 could reverse the effect. Moreover, the depletion of circRHOT1 repressed the cell viability and proliferation but induced apoptosis of chondrocytes. The expression levels of LC3, beclin1, collagen II, and aggrecan were induced by circRHOT1 knockdown. Mechanically, circRHOT1 was able to enhance the CCND1 expression by sponging miR-142-5p in chondrocytes. The overexpression of CCND1 or the inhibition of miR-142-5p reversed circRHOT1 depletion-mediated chondrocyte phenotypes.

Conclusions

Circular RNA RHOT1 enhances the CCND1 expression by sponging miR-142-5p to inhibit chondrocyte autophagy and promote chondrocyte proliferation in osteoarthritis. Our findings provided a promising therapeutic target for OA.

Circular RNA Foxo3 Relieves Myocardial Ischemia/Reperfusion Injury by Suppressing Autophagy via Inhibiting HMGB1 by Repressing KAT7 in Myocardial Infarction

Introduction

Myocardial infarction is coronary artery-related heart disease, and the leading cause of mortality globally. Circular RNAs (circRNAs) are a new type of regulatory RNAs and participate in multiple pathological cardiac progression.

Methods

However, the function of circFoxo3 in MI-induced myocardial injury remains obscure.

Results

Significantly, we identified that circFoxo3 was downregulated in the MI rat model and the overexpression of circFoxo3 ameliorated MI-induced cardiac dysfunction and attenuated MI-induced autophagy in rat model. Meanwhile, the overexpression of circFoxo3 repressed oxygen–glucose deprivation (OGD)-induced autophagy, apoptosis, inflammation, and injury of cardiomyocyte in vitro. Mechanically, we identified that the expression of KAT7 was reduced by circFoxo3 overexpression in cardiomyocytes. Meanwhile, the expression of HMGB1 was repressed by the depletion of KAT7 in cardiomyocytes. The enrichment of histone H3 lysine 14 acetylation (H3K14ac) and RNA polymerase II (RNA pol II) on HMGB1 promoter was inhibited by the knockdown of KAT7. Moreover, the overexpression of circFoxo3 suppressed HMGB1 expression and KAT7 overexpression rescued the expression of HMGB1 in cardiomyocytes. The enrichment of KAT7, H3K14ac, and RNA poly II on HMGB1 promoter was decreased by circFoxo3 overexpression, while the overexpression of KAT7 could reverse the effect. The overexpression of KAT7 or HMGB1 could reverse circFoxo3-attenuated cardiomyocyte injury and autophagy in vitro. Thus, we conclude that circular RNA circFoxo3 relieved myocardial ischemia/reperfusion injury by suppressing autophagy via inhibiting HMGB1 by repressing KAT7 in MI.

Discussion

Our finding provides new insight into the mechanism by which circFoxo3 regulates MI-related cardiac dysfunction by targeting KAT7/HMGB1 axis.