Biological functions, mechanisms, and clinical significance of circular RNA in pancreatic cancer: a promising rising star

Senescence-related circRNA circHIF-1α is associated with pancreatic cancer progression

Recently, there has been growing interest in the role of circular RNAs (circRNAs) in the progression of human cancers. Cellular senescence, a known anti-tumour mechanism, has been observed in several types of cancer. However, the regulatory interplay of circRNAs with cellular senescence in pancreatic cancer (PC) is still unknown. Therefore, we identified circHIF-1α, hsa_circ_0007976, which was downregulated in senescent cells using circRNA microarray analysis. Meanwhile, significantly upregulated expression of circHIF-1α in pancreatic cancer tissue detected by reverse transcription-polymerase chain reaction (RT-qPCR) and in situ hybridization (ISH). High circHIF-1α expression levels were found to independently predict poor survival outcomes. Subsequent treatments with DOX and H2O2 resulted in significantly lower levels of circHIF-1α. CircHIF-1α knockdown induces cellular senescence and suppresses PC proliferation in vitro experiments. The ability of circHIF-1α knockdown to suppress the progression of PC cells was further confirmed in vivo experiments. Our results showed that circHIF-1α is mainly presented in the nucleus of PC cells, also in the cytoplasm. Mechanistically, circHIF-1α inhibited senescence and accelerated the progression of PC cells through miR-375 sponging, thereby promoting HIF-1α expression levels. Nuclear circHIF-1α interacted with human antigen R protein (HUR) to increase HIF-1α expression. Thus, our results demonstrated that circHIF-1α ameliorates senescence and exacerbates growth in PC cells by increasing HIF-1α through targeting miR-375 and HUR, suggesting that targeting circHIF-1α offers a potential therapeutic candidate for PC.

The emerging role of circular RNAs in cisplatin resistance in ovarian cancer: From molecular mechanism to future potential

Ovarian cancer (OC) is the most common cause of death in female cancers. The prognosis of OC is very poor due to delayed diagnosis and identification of most patients in advanced stages, metastasis, recurrence, and resistance to chemotherapy. As chemotherapy with platinum-based drugs such as cisplatin (DDP) is the main treatment in most OC cases, resistance to DDP is an important obstacle to achieving satisfactory therapeutic efficacy. Consequently, knowing the different molecular mechanisms involved in resistance to DDP is necessary to achieve new therapeutic approaches. According to numerous recent studies, non-coding RNAs (ncRNAs) could regulate proliferation, differentiation, apoptosis, and chemoresistance in many cancers, including OC. Most of these ncRNAs are released by tumor cells into human fluid, allowing them to be used as tools for diagnosis. CircRNAs are ncRNA family members that have a role in the initiation, progression, and chemoresistance regulation of various cancers. In the current study, we investigated the roles of several circRNAs and their signaling pathways on OC progression and also on DDP resistance during chemotherapy.

Hsa_circ_0007590/PTBP1 complex reprograms glucose metabolism by reducing the stability of m6A-modified PTEN mRNA in pancreatic ductal adenocarcinoma

The role of circular RNAs (circRNAs) in glucose metabolism in pancreatic duct adenocarcinoma (PDAC) remains elusive. Through RNA sequencing of cells cultured under conditions of glucose deprivation, we identified hsa_circ_0007590. Sanger sequencing and RNase R and Act D treatments were performed to confirm the circular RNA features of hsa_circ_0007590. RNA in situ hybridization (RNA-ISH) and quantitative reverse transcription PCR (qRT-PCR) were used to estimate hsa_circ_0007590 expression in PDAC clinical specimens and cell lines. hsa_circ_0007590 expression was higher in PDAC patients and closely related to the clinicopathological characteristics of the disease. Cytoplasm‒nuclear fractionation and FISH assays demonstrated that hsa_circ_0007590 was located in the nucleus. Gain-of-function and loss-of-function assays were performed to assess the biological behaviors of PDAC cells. Seahorse XF assays were performed to validate the Warburg effect. hsa_circ_0007590 facilitated the proliferation, migration, and invasion of PDAC cells and promoted the Warburg effect. Mass spectrometry, RNA pulldown, RNA immunoprecipitation (RIP), RNA m6A quantification, m6A dot blot, MeRIP, and Western blotting were conducted to investigate the detailed mechanism through which hsa_circ_0007590 produces these effects. Mechanistically, hsa_circ_0007590 targeted PTBP1 and increased the expression of the m6A reader protein YTHDF2, leading to PTEN mRNA degradation and PI3K/AKT/mTOR pathway activation. Overall, hsa_circ_0007590, which targets PTBP1, reprograms glucose metabolism by attenuating the stability of m6A-modified PTEN mRNA and holds potential promise as a therapeutic target for PDAC.

Biological functions and clinical significance of tRNA-derived small fragment (tsRNA) in tumors: Current state and future perspectives

A new class of noncoding RNAs, tsRNAs are not only abundant in humans but also have high tissue specificity. Recently, an increasing number of studies have explored the correlations between tsRNAs and tumors, showing that tsRNAs can affect biological behaviors of tumor cells, such as proliferation, apoptosis and metastasis, by modulating protein translation, RNA transcription or posttranscriptional regulation. In addition, tsRNAs are widely distributed and stably expressed, which endows them with broad application prospects in diagnosing and predicting the prognosis of tumors, and they are expected to become new biomarkers. However, notably, the current research on tsRNAs still faces problems that need to be solved. In this review, we describe the characteristics of tsRNAs as well as their unique features and functions in tumors. Moreover, we also discuss the potential opportunities and challenges in clinical applications and research of tsRNAs.

A novel method for detection of pancreatic Ductal Adenocarcinoma using explainable machine learning

BACKGROUND AND OBJECTIVE

Pancreatic Ductal Adenocarcinoma (PDAC) is a form of pancreatic cancer that is one of the primary causes of cancer-related deaths globally, with less than 10 % of the five years survival rate. The prognosis of pancreatic cancer has remained poor in the last four decades, mainly due to the lack of early diagnostic mechanisms. This study proposes a novel method for detecting PDAC using explainable and supervised machine learning from Raman spectroscopic signals.

METHODS

An insightful feature set consisting of statistical, peak, and extended empirical mode decomposition features is selected using the support vector machine recursive feature elimination method integrated with a correlation bias reduction. Explicable features successfully identified mutations in Kirsten rat sarcoma viral oncogene homolog (KRAS) and tumor suppressor protein53 (TP53) in the fingerprint region for the first time in the literature. PDAC and normal pancreas are classified using K-nearest neighbor, linear discriminant analysis, and support vector machine classifiers.

RESULTS

This study achieved a classification accuracy of 98.5% using a nonlinear support vector machine. Our proposed method reduced test time by 28.5 % and saved 85.6 % memory utilization, which reduces complexity significantly and is more accurate than the state-of-the-art method. The generalization of the proposed method is assessed by fifteen-fold cross-validation, and its performance is evaluated using accuracy, specificity, sensitivity, and receiver operating characteristic curves.

CONCLUSIONS

In this study, we proposed a method to detect and define the fingerprint region for PDAC using explainable machine learning. This simple, accurate, and efficient method for PDAC detection in mice could be generalized to examine human pancreatic cancer and provide a basis for precise chemotherapy for early cancer treatment.

Prognostic, diagnostic and clinicopathological roles of tsRNAs: a meta-analysis in breast cancer

Breast cancer (BC) is one of the most common malignancies in women and the leading cause of cancer-related death in women. The newly emerged non-coding RNAs tsRNAs (tRNA-derived small RNAs) play an important role in the occurrence and development of BC. The purpose of this study was to comprehensively evaluate the prognostic, diagnostic and clinicopathological roles of tsRNAs in BC. Through literature screening, a total of 13 BC-related tsRNA studies were included in this meta-analysis, all of which passed quality assessment. Prognostic studies showed upregulated tsRNAs to be associated with poor survival outcomes (HR = 1.64, 95%CI 1.51-1.77) and downregulated tsRNAs to be associated with better outcomes (HR = 0.58, 95%CI 0.50-0.68). Results of diagnostic studies showed a combined sensitivity of 72% (95%CI 68-76%) and combined specificity of 64% (95%CI 61-67%); the AUC was 0.72 (95%CI 0.68-0.75) and the DOR 4.62 (95%CI 3.76-5.68). Finally, correlation analysis of clinicopathological features showed that downregulation of tsRNAs correlated significantly with age, TNM stage and lymphatic metastasis. Sensitivity analysis and publication bias showed no significant difference. In conclusion, BC-associated tsRNAs are closely related to the prognosis and clinicopathological features of patients with this disease and can be used to assist in early diagnosis of BC. Therefore, tsRNAs are potential targets for the diagnosis and treatment of BC.

Glycolysis in human cancers: Emphasis circRNA/glycolysis axis and nanoparticles in glycolysis regulation in cancer therapy

The metabolism of cancer has been an interesting hallmark and metabolic reprogramming, especially the change from oxidative phosphorylation in mitochondria to glucose metabolism known as glycolysis occurs in cancer. The molecular profile of glycolysis, related molecular pathways and enzymes involved in this mechanism such as hexokinase have been fully understood. The glycolysis inhibition can significantly decrease tumorigenesis. On the other hand, circRNAs are new emerging non-coding RNA (ncRNA) molecules with potential biological functions and aberrant expression in cancer cells which have received high attention in recent years. CircRNAs have a unique covalently closed loop structure which makes them highly stable and reliable biomarkers in cancer. CircRNAs are regulators of molecular mechanisms including glycolysis. The enzymes involved in the glycolysis mechanism such as hexokinase are regulated by circRNAs to modulate tumor progression. Induction of glycolysis by circRNAs can significantly increase proliferation rate of cancer cells given access to energy and enhance metastasis. CircRNAs regulating glycolysis can influence drug resistance in cancers because of theirimpact on malignancy of tumor cells upon glycolysis induction. TRIM44, CDCA3, SKA2 and ROCK1 are among the downstream targets of circRNAs in regulating glycolysis in cancer. Additionally, microRNAs are key regulators of glycolysis mechanism in cancer cells and can affect related molecular pathways and enzymes. CircRNAs sponge miRNAs to regulate glycolysis as a main upstream mediator. Moreover, nanoparticles have been emerged as new tools in tumorigenesis suppression and in addition to drug and gene delivery, then mediate cancer immunotherapy and can be used for vaccine development. The nanoparticles can delivery circRNAs in cancer therapy and they are promising candidates in regulation of glycolysis, its suppression and inhibition of related pathways such as HIF-1α. The stimuli-responsive nanoparticles and ligand-functionalized ones have been developed for selective targeting of glycolysis and cancer cells, and mediating carcinogenesis inhibition.

The diagnostic and prognostic value of tsRNAs in gastric cancers: a systematic review and meta-analysis

BACKGROUND

Gastric cancer (GC) is one of the most common types of cancer worldwide. Recent studies have shown that tsRNAs play important roles in GC and that changes in the expression levels of tsRNAs can be used for GC diagnosis and treatment response prediction.

RESEARCH DESIGN AND METHODS

Hazard ratios (HRs), odds ratios (ORs) and 95% confidence intervals (CIs) were used to evaluate the correlation between tsRNA expression and prognosis and other clinicopathologic features of GC patients. The sensitivity, specificity, area under the receiver operating characteristic curve (AUC) and diagnostic odds ratio (DOR) were analyzed to evaluate the diagnostic value of tsRNAs.

RESULTS

The results showed that patients with tsRNA upregulation had a poor prognosis (HR = 2.48, 95% CI: 1.85-3.34), while patients with tsRNA downregulation had a favorable prognosis (HR = 0.55, 95% CI: 0.31-0.98). In addition, tsRNA expression was significantly correlated with various clinicopathological features in patients with GC. Finally, in diagnostic studies, GC-related tsRNAs could differentiate healthy controls (AUC = 0.81, DOR = 7.74) from patients with inflammation (AUC = 0.74, DOR = 4.44).

CONCLUSIONS

tsRNAs have potential clinical application in GC diagnosis and prognosis evaluation. It is necessary to further assess and verify the practicability and feasibility of additional specific tsRNAs as GC markers in the future.

Circular RNAs in gynecologic cancers: mechanisms and implications for chemotherapy resistance

Chemotherapy resistance remains a major challenge in the treatment of gynecologic malignancies. Increasing evidence suggests that circular RNAs (circRNAs) play a significant role in conferring chemoresistance in these cancers. In this review, we summarize the current understanding of the mechanisms by which circRNAs regulate chemotherapy sensitivity and resistance in gynecologic malignancies. We also discuss the potential clinical implications of these findings and highlight areas for future research. CircRNAs are a novel class of RNA molecules that are characterized by their unique circular structure, which confers increased stability and resistance to degradation by exonucleases. Recent studies have shown that circRNAs can act as miRNA sponges, sequestering miRNAs and preventing them from binding to their target mRNAs. This can lead to upregulation of genes involved in drug resistance pathways, ultimately resulting in decreased sensitivity to chemotherapy. We discuss several specific examples of circRNAs that have been implicated in chemoresistance in gynecologic cancers, including cervical cancer, ovarian cancer, and endometrial cancer. We also highlight the potential clinical applications of circRNA-based biomarkers for predicting chemotherapy response and guiding treatment decisions. Overall, this review provides a comprehensive overview of the current state of knowledge regarding the role of circRNAs in chemotherapy resistance in gynecologic malignancies. By elucidating the underlying mechanisms by which circRNAs regulate drug sensitivity, this work has important implications for improving patient outcomes and developing more effective therapeutic strategies for these challenging cancers.

Roles of circular RNAs in the pathogenesis and treatment of pancreatic cancer

Circular RNAs are single-stranded RNAs with a covalently closed structure formed by the process of back-splicing. Aberrant expression of circular RNAs contributes to the pathogenesis of a wide range of cancers. Pancreatic cancer is one of the most lethal cancers due to diagnostic difficulties and limited therapeutic options. Circular RNAs are emerging as novel diagnostic biomarkers and therapeutic targets for pancreatic cancer. Moreover, recent advances in the therapeutic application of engineered circular RNAs have provided a promising approach to overcoming pancreatic cancer. This review discusses the roles of circular RNAs in the pathogenesis of pancreatic cancer and in potential treatment applications and their usefulness as diagnostic biomarkers.

Hypoxia-induced exosomal circPDK1 promotes pancreatic cancer glycolysis via c-myc activation by modulating miR-628-3p/BPTF axis and degrading BIN1

Background

circRNA has been established to play a pivotal role in tumorigenesis development in a variety of cancers; nevertheless, the biological functions and molecular mechanisms of hypoxia-induced exosomal circRNAs in pancreatic cancer remain largely unknown.

Methods

Differentially expressed circRNAs in exosomes between hypoxic exosomes and normoxic exosomes in PC cells were verified by RNA sequencing. The expression of circPDK1 in PC tumors and PC patients was evaluated by qRT-PCR and ISH, and the biological functions of circPDK1 in PC were verified through a series of in vitro and in vivo experiments. Using Western blotting, Co-IP, RNA pull-down, ChIP, RIP, dual-luciferase assays, and rescue experiments, the underlying mechanism of circPDK1 was verified.

Results

CircPDK1 was highly abundant in PC tumor tissues and serum exosomes and was associated with poor survival. Exosomal circPDK1 significantly promoted PC cell proliferation, migration, and glycolysis both in vitro and in vivo. Mechanistically, circPDK1 could be activated by HIF1A at the transcriptional level and sponges miR-628-3p to activate the BPTF/c-myc axis. In addition, circPDK1 serves as a scaffold that enhances the interaction between UBE2O and BIN1, inducing the UBE2O-mediated degradation of BIN1.

Conclusions

We found that circPDK1 was activated by HIF1A at the transcriptional level by modulating the miR-628-3p/BPTF axis and degrading BIN1. Exosomal circPDK1 is a promising biomarker for PC diagnosis and prognosis and represents a potential therapeutic target for PC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-022-01348-7.

Role of circular RNAs in disease progression and diagnosis of cancers: An overview of recent advanced insights

Tumor microenvironment (TME) is a crucial regulator of tumor progression and cells in the TME release a number of molecules that are responsible for anaplasticity, invasion, metastasis of tumor, establishing stem cell niches, up-regulation and down-regulation of various pathways in cancer cells, interfering with immune surveillance and immune escape. Moreover, they can serve as diagnostic markers, and determine effective therapies. Among them, CircRNAs have gained special attention due to their involvement in mutated pathways in cancers. By functioning as a molecular sponge for miRNAs, binding with proteins, and directing selective splicing. CircRNAs modify the immunological environment of cancers to promote their growth. Besides of critical role in tumor growth, circRNAs are emerging as potential candidates as biomarkers for diagnosis cancer therapy. Also, circRNAs vaccination even offers a novel approach to tumor immunotherapy. Over the recent years, studies are advocating that circRNAs have tissue specific tumor specific expression patterns, which indicates their potential clinical utility. Especially, circRNAs have emerged as potential predictive and prognostic biomarkers. Although, there has been significant progress in deciphering the role of circRNA in cancers, literature lacks comprehensive overview on this topic. Keeping in view of these significant discoveries, this review systematically discusses circRNA and their role in the tumor in different dimensions.