Circular RNA ciRS-7 triggers the migration and invasion of esophageal squamous cell carcinoma via miR-7/KLF4 and NF-κB signals

Circular RNA CDR1-AS contributes to pemetrexed and cisplatin chemoresistance through EGFR/PI3K signaling pathway in lung adenocarcinoma

Recent studies found circRNAs were involved in tumorigenesis and became new tumor biomarkers and therapeutic targets in lung adenocarcinoma (LUAD), which played a critical role in various biological processes and had been implicated in resistance to chemotherapeutic drugs. However, the role of CDR1-AS in chemoresistance of LUAD to pemetrexed (PTX) and cisplatin (CDDP) is poorly understood. Here, we found that CDR1-AS was up-regulated in LUAD tissues and cell lines, its high-expression was relevant to smoking history, T stage and neoadjuvant chemotherapy (PTX and CDDP) of LUAD patients. CDR1-AS was an independent prognostic biomarker for LUAD patients. CDR1-AS was highly expressed in PTX and CDDP resistant LUAD tissues and cell line (A549/CR). Silence of CDR1-AS re-sensitized A549/CR cells to PTX and CDDP. CDR1-AS was closely related with EGFR/PI3K signaling pathway in A549/CR cells. The activating of EGFR/PI3K pathway mostly restored the effecting of CDR1-AS silence on PTX and CDDP sensitivity in A549/CR cells, CDR1-AS contributed to PTX and CDDP chemoresistance through EGFR/PI3K signaling pathway in LUAD. In conclusion, the CDR1-AS is high-expressed in LUAD and is an independent prognostic biomarker for LUAD patients. The high-expression of CDR1-AS is related with the PTX and CDDP insensitivity of LUAD patients, CDR1-AS promotes PTX and CDDP chemoresistance through EGFR/PI3K signaling pathway in LUAD.

Diagnostic Accuracy of circRNAs in Esophageal Cancer: A Meta-Analysis

Purpose

Early detection of esophageal cancer is beneficial to the survival and prognosis of patients. Circular RNAs (circRNAs) have been shown to be a potential biomarker for cancer, which can be used for the diagnosis of esophageal cancer. However, the roles of circRNAs in the diagnosis of esophageal cancer has been controversial. The present study, therefore, is aimed at determining the diagnostic accuracy of circRNAs in esophageal cancer.

Methods

Relevant researches were searched from PubMed, Embase, Cochrane Library, OVID, and ISI Web of Science online databases up to March 11, 2019. The estimation of diagnostic indicators, threshold effect, and publication bias were measured by a bivariate binomial mixed model, the Spearman correlation, and Deeks' funnel plot asymmetry test, respectively.

Results

Five studies from 4 articles were included in this meta-analysis. The pooled sensitivity, specificity, overall positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and area under the receiver operating characteristics curve (AUC) were 0.79 (95% CI: 0.69-0.87), 0.85 (95% CI: 0.68-0.94), 5.27 (95% CI: 2.46-11.32), 0.24 (95% CI: 0.16-0.36), 21.66 (95% CI: 9.33-50.30), and 0.88 (95% CI: 0.84-0.90), respectively. The Spearman correlation coefficient was 0.60 (P = 0.285). The P value of Deeks' funnel plot was 0.81.

Conclusion

The above-mentioned results suggested that circRNAs possess a relatively higher diagnostic performance in distinguishing esophageal cancer patients from healthy individuals. Therefore, they may serve as potential clinical biomarkers for esophageal cancer diagnosis.

Emerging roles of circular RNAs in colorectal cancer

Circular RNAs (circRNAs) are a newly discovered class of endogenous non-coding RNAs. Owing to the development of high-throughput sequencing, researchers have identified thousands of circRNAs. Emerging evidence suggests that circRNAs are involved in various tumor cell processes, including proliferation, apoptosis, invasion and migration. Because of their high stability and abundance, tissue-specific expression, and easy detection, circRNAs are considered ideal biomarkers for cancer diagnosis and prognosis. An increasing number of studies have recently demonstrated that circRNAs are closely associated with colorectal cancer (CRC). CRC is the third most common cancer and the second leading cause of cancer-related death globally. Thus, understanding the molecular mechanisms involved in the development and progression of CRC is vital. In this review, we summarize the current literature regarding human circRNAs related to CRC and present an overview of the potential clinical implications of circRNAs with respect to CRC.

Circular RNA CDR1as acts as a sponge of miR-135b-5p to suppress ovarian cancer progression

Background and objectives: Ovarian cancer is the most fatal primary malignancy among gynecological cancers. Circular RNAs (circRNAs) play an important role in the development of various cancers, but the functions of circRNAs in ovarian cancer development have not been studied. We aim to explore the function and mechanism of CDR1as in the progression of ovarian cancer and to provide a new target for the diagnosis and treatment of ovarian cancer.

Methods: Ovarian cancer cell proliferation was assessed according to proliferating cell nuclear antigen (PCNA) and Ki67 protein expression levels and MTT and CCK8 assays. The migration ability of cells was detected by scratch-wound assays, and the invasion ability of the cells was determined by Transwell^® assays. qRT-PCR and Western blotting were used to verify miRNA and protein expression.

Results: CDR1as expression in ovarian tissues was significantly lower in ovarian cancer patients than in patients without ovarian cancer. CDR1as overexpression inhibited the proliferation, invasion and migration of ovarian cancer cells. Silencing CDR1as increased the expression of miR-135b-5p and decreased the expression of hypoxia-inducible factor 1-alpha inhibitor (HIF1AN), thus increasing the proliferation capacity of ovarian cancer cells.

Conclusions: CDR1as, acting as a sponge of miR-135b-5p, promotes the expression of HIF1AN and therefore plays a role in tumor inhibition.

Current Status of Functional Studies on Circular RNAs in Bladder Cancer and their Potential Role as Diagnostic and Prognostic Biomarkers: A Review

Worldwide, bladder cancer represents the ninth most common malignancy and is the 13^th cause of cancer-associated death. Although surgery combined with chemotherapy and radiotherapy has improved patient outcomes, the prognosis remains poor for most patients with muscle-invasive bladder cancer. The exact mechanisms and critical regulators of bladder cancer remain unknown. Circular RNAs (circRNAs) are a distinct type of endogenous non-coding RNA. Recent studies have shown that circRNAs participate in many processes, including proliferation, invasion, migration, and apoptosis in multiple types of malignancy, including bladder cancer. Some circRNAs are dysregulated in bladder cancer and play essential roles in cancer progression. Importantly, some circRNAs may serve as diagnostic and prognostic biomarkers for bladder cancer. This review aims to summarize the findings from recent studies that have focused on the roles of human circRNAs in bladder cancer and discusses the clinical roles for circRNAs, including their potential roles as diagnostic or prognostic biomarkers.

Circular RNAs as potential biomarkers and therapeutics for cardiovascular disease

Circular RNAs (circRNAs) are genetic regulators that were earlier considered as "junk". In contrast to linear RNAs, they have covalently linked ends with no polyadenylated tails. CircRNAs can act as RNA-binding proteins, sequestering agents, transcriptional regulators, as well as microRNA sponges. In addition, it is reported that some selected circRNAs are transformed into functional proteins. These RNA molecules always circularize through covalent bonds, and their presence has been demonstrated across species. They are usually abundant and stable as well as evolutionarily conserved in tissues (liver, lung, stomach), saliva, exosomes, and blood. Therefore, they have been proposed as the "next big thing" in molecular biomarkers for several diseases, particularly in cancer. Recently, circRNAs have been investigated in cardiovascular diseases (CVD) and reported to play important roles in heart failure, coronary artery disease, and myocardial infarction. Here, we review the recent literature and discuss the impact and the diagnostic and prognostic values of circRNAs in CVD.

Aging, Melatonin, and the Pro- and Anti-Inflammatory Networks

Aging and various age-related diseases are associated with reductions in melatonin secretion, proinflammatory changes in the immune system, a deteriorating circadian system, and reductions in sirtuin-1 (SIRT1) activity. In non-tumor cells, several effects of melatonin are abolished by inhibiting SIRT1, indicating mediation by SIRT1. Melatonin is, in addition to its circadian and antioxidant roles, an immune stimulatory agent. However, it can act as either a pro- or anti-inflammatory regulator in a context-dependent way. Melatonin can stimulate the release of proinflammatory cytokines and other mediators, but also, under different conditions, it can suppress inflammation-promoting processes such as NO release, activation of cyclooxygenase-2, inflammasome NLRP3, gasdermin D, toll-like receptor-4 and mTOR signaling, and cytokine release by SASP (senescence-associated secretory phenotype), and amyloid-β toxicity. It also activates processes in an anti-inflammatory network, in which SIRT1 activation, upregulation of Nrf2 and downregulation of NF-κB, and release of the anti-inflammatory cytokines IL-4 and IL-10 are involved. A perhaps crucial action may be the promotion of macrophage or microglia polarization in favor of the anti-inflammatory phenotype M2. In addition, many factors of the pro- and anti-inflammatory networks are subject to regulation by microRNAs that either target mRNAs of the respective factors or upregulate them by targeting mRNAs of their inhibitor proteins.