Inhibition of hsa_circ_0003489 shifts balance from autophagy to apoptosis and sensitizes multiple myeloma cells to bortezomib via miR-874-3p/HDAC1 axis

The diagnostic and therapeutic potential of multiple myeloma-associated circular RNAs

Circular RNA (circRNA) was first discovered in viruses in 1974; they are primarily formed through back splicing, where a downstream splice donor is joined to an upstream splice acceptor, resulting in a closed circRNA transcript. Under normal conditions, most circRNAs are stably expressed; however, in pathological conditions, circRNAs can play critical roles in the disease process of multiple myeloma (MM) through mechanisms such as competing endogenous RNAs (ceRNAs), regulation of transcription and splicing, affecting protein expression and localization, and even direct encoding of peptides. In recent years, there has been increasing interest in the role of circRNAs in MM and their regulatory functions during the disease process. Numerous studies have revealed that circRNAs are involved in the pathogenesis and prognosis of MM, aiding in the identification of reliable prognostic markers and potential therapeutic targets. Therefore, this review summarizes the structural characteristics of circRNAs, and their regulatory roles in MM, and introduces the latest advancements in understanding the novel functions of circRNAs in MM.

Role of circular RNAs in cancer therapy resistance

Over the past decade, circular RNAs (circRNAs) have gained recognition as a novel class of genetic molecules, many of which are implicated in cancer pathogenesis via different mechanisms, including drug resistance, immune escape, and radio-resistance. ExosomalcircRNAs, in particular, facilitatecommunication between tumour cells and micro-environmental cells, including immune cells, fibroblasts, and other components. Notably, micro-environmental cells can reportedly influence tumour progression and treatment resistance by releasing exosomalcircRNAs. circRNAs often exhibit tissue- and cancer-specific expression patterns, and growing evidence highlights their potential clinical relevance and utility. These molecules show strong promise as potential biomarkers and therapeutic targets for cancer diagnosis and treatment. Therefore, this review aimed to briefly discuss the latest findings on the roles and resistance mechanisms of key circRNAs in the treatment of various malignancies, including lung, breast, liver, colorectal, and gastric cancers, as well as haematological malignancies and neuroblastoma.This review will contribute to the identification of new circRNA biomarkers for the early diagnosis as well as therapeutic targets for the treatment of cancer.

Novel insights into the circ_0003489/let-7b-5p/GLUT1 axis and its possible role in multiple myeloma

BACKGROUND

Circular RNAs (circRNAs) act as vital players in multiple myeloma (MM). Herein, we focused on the function of hsa_circ_0003489 (circ_0003489) in MM development and bortezomib (BTZ) resistance.

METHODS

Relative RNA levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Relative protein levels were evaluated by Western blotting or immunohistochemistry (IHC). The 5'-ethynyl-2'-deoxyuridine (EdU) and cell colony formation (CF) assays were conducted for cell proliferation. Cell counting kit-8 assay was used to evaluate the BTZ resistance. Flow cytometry analysis was performed for cell apoptosis analysis. Glycolysis was determined by detecting the levels of ECAR, glucose consumption, and lactate production. Dual-luciferase reporter and RNA pull-down assays were carried out to analyze the relationships of circ_0003489 with let-7b-5p microRNA and glucose transporter 1 (GLUT1) glucose transporter protein. Xenograft models were conducted to assess the function of circ_0003489 in vivo.

RESULTS

Indeed, as shown by qRT-PCR, bone marrow samples of MM patients showed an upregulation of circ_0003489 RNA in comparison to normal controls (P < 0.0001). In in vitro experiments in MM cells, silencing of circ_0003489 repressed cell proliferation, BTZ resistance, and glycolysis. Furthermore, blocking circ_0003489 facilitated in vitro the apoptosis of MM cells. In vivo experiments showed that silencing circ_0003489 decreased tumor formation. Signaling experiments demonstrated that circ_0003489 sponged let-7b-5p microRNA and negatively regulated let-7b-5p microRNA expression. Loss of let-7b-5p microRNA ameliorated circ_0003489 silencing-mediated effects on MM cell malignant behaviors and BTZ resistance. Moreover, we showed that GLUT1 glucose transporter was targeted by let-7b-5p mircoRNA. GLUT1 enhancement reversed the repressive impacts of let-7b-5p upregulation on MM cell malignant behaviors and BTZ resistance.

CONCLUSION

We suggest that circ_0003489 RNA knockdown inhibited MM progression and reversed BTZ-induced resistance of MM growth by let-7b-5p microRNA regulated function of GLUT1 glucose transporter.

Circular RNA_0003489 reflects unfavorable treatment response and shortened survival in newly diagnosed multiple myeloma patients who receive bortezomib-based induction therapy

OBJECTIVES

Circular RNA_0003489 (Circ_0003489) promotes multiple myeloma (MM) progression and bortezomib resistance in MM cells, while its potential as a biomarker in newly diagnosed MM (NDMM) patients is unclear. Thus, this study aimed to investigate the association of circ_0003489 expression with treatment response and survival in NDMM patients who received bortezomib-based induction therapy.

METHODS

Bone marrow (BM) specimens from 85 NDMM patients at diagnosis or before treatment and from 15 donor controls during BM examination were retrieved in this retrospective study. Circ_0003489 derived from BM plasma cells was detected by reverse transcription-quantitative polymerase chain reaction and cut by quartile and median for further analysis.

RESULTS

Circ_0003489 expression was increased in NDMM patients versus donor controls (P < 0.001). Circ_0003489 quartile was positively correlated with BM plasma cells (P = 0.040), international staging system (ISS) stage (P = 0.007), the revision of ISS stage (P = 0.003), beta-2-microglobulin (P = 0.011), and lactate dehydrogenase (P = 0.042) in NDMM patients. Increased circ_0003489 quartile was linked with a lower possibility of achieving complete response (P = 0.020) and partial response or better (P = 0.041) in NDMM patients. Elevated circ_0003489 expression cut by quartile (P = 0.020) and cut by median (P = 0.006) were linked with decreased progression-free survival (PFS) in NDMM patients. Increased circ_0003489 expression cut by median was associated with shortened overall survival (OS) in NDMM patients (P = 0.038). Meanwhile, higher circ_0003489 quartile independently forecasted poorer PFS (hazard ratio = 1.342, P = 0.045), but not OS in NDMM patients.

CONCLUSION

Circ_0003489 expression is increased and reflects unfavorable treatment response and survival in NDMM patients who receive bortezomib-based induction therapy.

Non-coding RNAs are involved in tumor cell death and affect tumorigenesis, progression, and treatment: a systematic review

Cell death is ubiquitous during development and throughout life and is a genetically determined active and ordered process that plays a crucial role in regulating homeostasis. Cell death includes regulated cell death and non-programmed cell death, and the common types of regulatory cell death are necrosis, apoptosis, necroptosis, autophagy, ferroptosis, and pyroptosis. Apoptosis, Necrosis and necroptosis are more common than autophagy, ferroptosis and pyroptosis among cell death. Non-coding RNAs are regulatory RNA molecules that do not encode proteins and include mainly microRNAs, long non-coding RNAs, and circular RNAs. Non-coding RNAs can act as oncogenes and tumor suppressor genes, with significant effects on tumor occurrence and development, and they can also regulate tumor cell autophagy, ferroptosis, and pyroptosis at the transcriptional or post-transcriptional level. This paper reviews the recent research progress on the effects of the non-coding RNAs involved in autophagy, ferroptosis, and pyroptosis on tumorigenesis, tumor development, and treatment, and looks forward to the future direction of this field, which will help to elucidate the molecular mechanisms of tumorigenesis and tumor development, as well as provide a new vision for the treatment of tumors.

Hsa_circ_0003489 Drives PTX Resistance of Human NSCLC Cells Through Modulating miR-98-5p/IGF2

Background

Circular RNAs (circRNAs) demonstrated critical roles within developing tumors and treatment resistance in an increasing body of research. The aim was to look into the functions and processes of hsa_circ_0003489 in the non-small cell lung cancer (NSCLC) paclitaxel (PTX) resistance.

Methods

NSCLC cell-based cultures including A549 and H460 were employed for such an investigation. hsa_circ_0003489, miR-98-5p, and insulin-like growth factor 2 (IGF2) expression-profiles were evaluated with a quantitative real-time polymerase chain reaction (RT-qPCR). The PTX resistance was determined using MTT assay, and the ELISA test measured IGF2 expression. Facilitating corroboration for miR-98-5p relation and hsa_circ_0003489 or IGF2, a dual-luciferase reporter method was applied.

Results

The hsa_circ_0003489 level was raised in cells and tissues from PTX-resistant (PR) NSCLC. In PR NSCLC cells, hsa_circ_0003489 knockdown reduced PTX resistance. For the purpose of the mechanism study, hsa_circ_0003489 knockdown substantially reduced IGF2 expression via miR-98-5p sponging, improving PTX sensitivity in PR NSCLC.

Conclusion

Through miR-98-5p/IGF2 axis control, hsa_circ_0003489 knockdown helped NSCLC overcome PTX resistance, suggesting a potential circRNA-targeted therapy for the disease.

Regulatory miRNAs in cancer cell recovery from therapy exposure and its implications as a novel therapeutic strategy for preventing disease recurrence

The desired outcome of cancer therapies is the eradication of disease. This can be achieved when therapy exposure leads to therapy-induced cancer cell death as the dominant outcome. Theoretically, a permanent therapy-induced growth arrest could also contribute to a complete response, which has the potential to lead to remission. However, preclinical models have shown that therapy-induced growth arrest is not always durable, as recovering cancer cell populations can contribute to the recurrence of cancer. Significant research efforts have been expended to develop strategies focusing on the prevention of recurrence. Recovery of cells from therapy exposure can occur as a result of several cell stress adaptations. These include cytoprotective autophagy, cellular quiescence, a reversable form of senescence, and the suppression of apoptosis and necroptosis. It is well documented that microRNAs regulate the response of cancer cells to anti-cancer therapies, making targeting microRNAs therapeutically a viable strategy to sensitization and the prevention of recovery. We propose that the use of microRNA-targeting therapies in prolonged sequence, that is, a significant period after initial therapy exposure, could reduce toxicity from the standard combination strategy, and could exploit new epigenetic states essential for cancer cells to recover from therapy exposure. In a step toward supporting this strategy, we survey the available scientific literature to identify microRNAs which could be targeted in sequence to eliminate residual cancer cell populations that were arrested as a result of therapy exposure. It is our hope that by successfully identifying microRNAs which could be targeted in sequence we can prevent disease recurrence.

Autophagy as a self-digestion signal in human cancers: Regulation by microRNAs in affecting carcinogenesis and therapy response

Autophagy is defined as a "self-digestion" signal, and it is a cell death mechanism its primary function is degrading toxic agents and aged organelles to ensure homeostasis in cells. The basic leve ls of autophagy are found in cells, and when its levels exceed to standard threshold, cell death induction is observed. Autophagy dysregulation in cancer has been well-documented, and regulation of this pathway by epigenetic factors, especially microRNAs (miRNAs), is interesting and noteworthy. miRNAs are considered short endogenous RNAs that do not encode functional proteins, and they are essential regulators of cell death pathways such as apoptosis, necroptosis, and autophagy. Accumulating data has revealed miRNA dysregulation (upregulation or downregulation) during tumor progression, and their therapeutic manipulation provides new insight into cancer therapy. miRNA/autophagy axis in human cancers has been investigated an exciting point is the dual function of both autophagy and miRNAs as oncogenic and onco-suppressor factors. The stimulation of pro-survival autophagy by miRNAs can increase the survival rate of tumor cells and mediates cancer metastasis via EMT inductionFurthermore, pro-death autophagy induction by miRNAs has a negative impact on the viability of tumor cells and decreases their survival rate. The miRNA/autophagy axis functions beyond regulating the growth and invasion of tumor cells, and they can also affect drug resistance and radio-resistance. These subjects are covered in the current review regarding the new updates provided by recent experiments.

Non-coding RNAs and exosomal ncRNAs in multiple myeloma: An emphasis on molecular pathways

One of the most common hematological malignancies is multiple myeloma (MM) that its mortality and morbidity have increased. The incidence rate of MM is suggested to be higher in Europe and various kinds of therapeutic strategies including stem cell transplantation. However, MM treatment is still challenging and gene therapy has been shown to be promising. The non-coding RNAs (ncRNAs) including miRNAs, lncRNAs and circRNAs are considered as key players in initiation, development and progression of MM. In the present review, the role of ncRNAs in MM progression and drug resistance is highlighted to provide new insights for future experiments for their targeting and treatment of MM. The miRNAs affect proliferation and invasion of MM cells, and targeting tumor-promoting miRNAs can induce apoptosis and cell cycle arrest, and reduces proliferation of MM cells. Furthermore, miRNA regulation is of importance for modulating metastasis and chemotherapy response of tumor cells. The lncRNAs exert the same function and determine proliferation, migration and therapy response of MM cells. Notably, lncRNAs mainly target miRNAs in regulating MM progression. The circRNAs also target different molecular pathways in regulating MM malignancy that miRNAs are the most well-known ones. Furthermore, clinical application of ncRNAs in MM is discussed.

circEXOC5 promotes acute lung injury through the PTBP1/Skp2/Runx2 axis to activate autophagy

To understand the pathogenesis of acute lung injury (ALI), we focused on circEXOC5, a significantly up-regulated circular RNA in ALI. Using the in vivo cecal ligation and puncture (CLP)-induced ALI mouse model and in vitro LPS-challenged mouse pulmonary microvascular endothelial cell (MPVEC) model, we examined the impacts of knockdown circEXOC5 on lung injury, inflammation, and autophagy. The regulation between circEXOC5, polypyrimidine tract-binding protein 1 (PTBP1), S-phase kinase-associated protein 2 (Skp2), and Runt-related transcription factor 2 (Runx2) was investigated by combining RNA immunoprecipitation, qRT-PCR, mRNA stability, and ubiquitination assays. The significance of PTBP1 in circEXOC5-induced ALI phenotypes was examined both in vitro and in vivo. circEXOC5 was up-regulated and associated with increased inflammation and activated autophagy in cecal ligation and puncture-induced ALI lung tissues and LPS-challenged MPVECs. Through the interaction with PTBP1, circEXOC5 accelerated Skp2 mRNA decay, an E3 ubiquitin ligase for Runx2, and therefore increased Runx2 expression. Functionally, overexpressing PTBP1 reversed shcircEXOC5-inhibited ALI, inflammation, or autophagy. The signaling cascade circEXOC5/PTBP1/Skp2/Runx2, by essentially regulating inflammation and autophagy in MPVECs, aggravates sepsis-induced ALI.

Circular RNA in multiple myeloma: A new target for therapeutic intervention

Circular RNAs (circRNAs) are RNA molecules with a stable closed-loop structure that are found in a variety of organisms. CircRNAs are highly stable and conserved, and they play important roles in transcriptional regulation and splicing. Multiple Myeloma (MM) is a malignant proliferative disease for which there are currently no effective and comprehensive treatments. Numerous circRNAs may contribute to the development and progression of MM by acting as oncogenes or regulators. Due to the unique function of circRNAs, they have a high potential for regulating the biological functions (including proliferation and apoptosis) of MM cells, and their expression levels and molecular mechanism are closely related to their diagnostic value, therapeutic sensitivity, and clinical prognosis of MM patients. In this review, we aim to provide a detailed overview of the structure and function of circRNAs and demonstrate the potential therapeutic value and potential mechanism of circRNAs in MM via experiments and clinical trials.

Circular RNA-regulated autophagy is involved in cancer progression

Circular RNAs (circRNAs) are a sort of long, non-coding RNA molecules with a covalently closed continuous ring structure without 5'-3' polarity and poly-A tail. The modulative role of circRNAs in malignant diseases has been elucidated by many studies in recent years via bioinformatics and high-throughput sequencing technologies. Generally, circRNA affects the proliferative, invasive, and migrative capacity of malignant cells via various mechanisms, exhibiting great potential as novel biomarkers in the diagnoses or treatments of malignancies. Meanwhile, autophagy preserves cellular homeostasis, serving as a vital molecular process in tumor progression. Mounting studies have demonstrated that autophagy can not only contribute to cancer cell survival but can also induce autophagic cell death in specific conditions. A growing number of research studies have indicated that there existed abundant associations between circRNAs and autophagy. Herein, we systemically reviewed and discussed recent studies on this topic in different malignancies and concluded that the circRNA–autophagy axis played crucial roles in the proliferation, metastasis, invasion, and drug or radiation resistance of different tumor cells.

Comprehensive elaboration of circular RNA in multiple myeloma

Circular RNAs (circRNAs), a novel category of endogenous non-coding RNAs, are usually well conserved across different species with a covalent closed-loop structure. Existing and emerging evidence confirms that circRNAs can function as regulators of alternative splicing, microRNA and RNA-binding protein sponges and translation, as well as gene transcription. In consideration of their multi-faceted functions, circRNAs are critically involved in hematological malignancies including multiple myeloma (MM). In particular, circRNAs have been found to play vital roles in tumor microenvironment and drug resistance, which may grant them potential roles as biomarkers for MM diagnosis and targeted therapy. In this review, we comprehensively elaborate the current state-of-the-art knowledge of circRNAs in MM, and then focus on their potential as biomarkers in diagnosis and therapy of MM.

CircRNAs: novel therapeutic targets in multiple myeloma

BACKGROUND

Circular RNA (circRNA) is a type of non-coding RNA that has recently attracted the attention of researchers. Multiple myeloma (MM) is a hematological malignancy with a dismal prognosis that indicates a pressing need for better treatment alternatives, particularly in terms of biological indicators. According to recent research findings, the presence of circRNA is also closely related to the incidence and progression of malignant hemopathy. There have been, however, only a few investigations of circRNA in MM.

MATERIAL AND METHODS

This review will be on the biological properties and functions of circRNA in MM and a discussion of the clinical utility of circRNA in the diagnosis, prognosis, and treatment of MM.

CONCLUSIONS

CircRNA is involved in gene transcription, translation, and epigenetic modification as well as the regulation of cancer cell proliferation, invasion, and metastasis, and hence, promotes or inhibits the occurrence and progression of MM. Therefore, circRNA holds promise as a potential future MM biomarker.

The Multiple Myeloma Landscape: Epigenetics and Non-Coding RNAs

Simple Summary

Recent findings in multiple myeloma have led to therapies which have improved patient life quality and expectancy. However, frequent relapse and drug resistance emphasize the need for more efficient therapeutic approaches. The discovery of non-coding RNAs as key actors in multiple myeloma has broadened the molecular landscape of this disease, together with classical epigenetic factors such as methylation and acetylation. microRNAs and long non-coding RNAs comprise the majority of the described non-coding RNAs dysregulated in multiple myeloma, while circular RNAs are recently emerging as promising molecular targets. This review provides a comprehensive overview of the most recent knowledge on this topic and suggests new therapeutic strategies.

Abstract

Despite advances in available treatments, multiple myeloma (MM) remains an incurable disease and represents a challenge in oncohematology. New insights into epigenetic factors contributing to MM development and progression have improved the knowledge surrounding its molecular basis. Beyond classical epigenetic factors, including methylation and acetylation, recent genome analyses have unveiled the importance of non-coding RNAs in MM pathogenesis. Non-coding RNAs have become of interest, as their dysregulation opens the door to new therapeutic approaches. The discovery, in the past years, of molecular techniques, such as CRISPR-Cas, has led to innovative therapies with potential benefits to achieve a better outcome for MM patients. This review summarizes the current knowledge on epigenetics and non-coding RNAs in MM pathogenesis.

miR-874: An Important Regulator in Human Diseases

miR-874 is located at 5q31.2, which is frequently deleted in cancer. miR-874 is downregulated in 22 types of cancers and aberrantly expressed in 18 types of non-cancer diseases. The dysfunction of miR-874 is not only closely related to the diagnosis and prognosis of tumor patients but also plays an important role in the efficacy of tumor chemotherapy drugs. miR-874 participates in the ceRNA network of long non-coding RNAs or circular RNAs, which is closely related to the occurrence and development of cancer and other non-cancer diseases. In addition, miR-874 is also involved in the regulation of multiple signaling pathways, including the Wnt/β-catenin signaling pathway, Hippo signaling pathway, PI3K/AKT signaling pathway, JAK/STAT signaling pathway, and Hedgehog signaling pathway. This review summarizes the molecular functions of miR-874 in the biological processes of tumor cell survival, apoptosis, differentiation, and tumorigenesis, and reveal the value of miR-874 as a cancer biomarker in tumor diagnosis and prognosis. Future work is necessary to explore the potential clinical application of miR-874 in chemotherapy resistance.