The circRNA circAGFG1 acts as a sponge of miR-195-5p to promote triple-negative breast cancer progression through regulating CCNE1 expression

Upregulated Circular RNA circ-UBE2D2 Predicts Poor Prognosis and Promotes Breast Cancer Progression by Sponging miR-1236 and miR-1287

Emerging evidence suggests that circular RNAs (circRNAs) are linked to the development and progression of human cancers. Nevertheless, their contribution to breast cancer (BC) is still largely unknown. In the current study, we screened and identified a novel circRNA, circ-UBE2D2, which was highly expressed in BC cell lines and tissues and was closely related to aggressive clinical features and dismal prognosis. Small interfering RNA (siRNA)–mediated circ-UBE2D2 silencing notably inhibited the proliferation, migration and invasion of BC cells, whereas circ-UBE2D2 overexpression displayed opposite effects. Mechanistically, circ-UBE2D2 was able to simultaneously function as molecular sponges of miR-1236 and miR-1287 to regulate the expression of their respective target genes. Moreover, circ-UBE2D2–induced tumor-promoting effects could be effectively blocked by miR-1236 or miR-1287 in BC cells. More importantly, therapeutic delivery of cholesterol-conjugated si-circ-UBE2D2 oligonucleotides significantly delayed tumor growth in vivo. Overall, our findings indicate that circ-UBE2D2 plays an essential oncogenic role in BC, and targeting circ-UBE2D2 may be a feasible treatment for BC patients.

Roles of circular RNA in breast cancer: present and future

Breast cancer is one of the most common cancers with the highest morbidity and mortality among women despite the treatment approaches have advanced including surgery, endocrine therapy and targeted therapy. Novel biomarkers are warranted to be discovered for the early detection, treatment and prognosis for breast cancer. CircRNA is a class of covalently closed single-stranded circular RNA molecules without free 5' or 3' end which makes them well expressed and more stable than their linear counterparts. In this review, we mainly discuss the oncogenic or anti-oncogenic roles of circRNAs can be utilized in the treatment and prognosis of breast cancer. A large number of circRNAs have shown great potential to function in carcinogenesis, metastasis or chemoresistance of breast cancer through transcriptional regulation of RNAs including miRNA and mRNA, in addition to their promise as stable biomarkers that can be used for monitoring breast cancer progression. However, the translation phenomenon of circRNAs in breast cancer and the diagnostic value of circRNAs in breast cancer requires further investigation for which the detection of circRNAs in plasma exosomes could be worthy of a try. Above all, engineered exosomes preloaded with engineered anti-oncogenic circRNAs are likely to provide a novel direction in the personal medicine of breast cancer.

MicroRNA-5195-3p enhances the chemosensitivity of triple-negative breast cancer to paclitaxel by downregulating EIF4A2

Background

Chemotherapy based on paclitaxel (PTX) is the standard treatment for a range of cancers, including triple-negative breast cancer (TNBC), but the increasing development of resistance has reduced/has negatively impacted its clinical utility. A previous study demonstrated that miR-5195-3p could suppress lung cancer cell growth. This study was designed to investigate whether miR-5195-3p attenuates chemoresistance to PTX by regulating target genes in TNBC cells.

Methods

The study used both PTX-resistant tumor tissues and PTX-resistant TNBC cell lines. The expression of miR-5195-3p was determined using quantitative real-time PCR. Cell viability, cell cycle distribution and apoptosis were analyzed using CCK-8 and flow cytometry assays. The target genes of miR-5195-3p were predicted with bioinformatics analysis and confirmed using the luciferase reporter assay.

Results

MiR-5195-3p expression was lower in PTX-resistant tumor tissues and PTX-resistant TNBC cell lines. Upregulation of miR-5195-3p enhanced the sensitivity of PTX-resistant TNBC cells to PTX treatment. EIF4A2 was confirmed as a potential target of miR-5195-3p. EIF4A2 knockdown imitated the effects of miR-5195-3p on chemosensitivity, while restoration of EIF4A2 rescued them.

Conclusion

These data demonstrate that miR-5195-3p might be a potential therapeutic target to reverse chemoresistance in TNBC through its targeting of EIF4A2.

CircAGFG1 sponges miR-203 to promote EMT and metastasis of non-small-cell lung cancer by upregulating ZNF281 expression

The circRNA circAGFG1 is reported to be important in triple-negative breast cancer progression. However, the mechanism of circAGFG1 in non-small-cell lung cancer (NSCLC) remains unknown. In this study, expression of circAGFG1 was determined by real-time PCR in 20 pairs of NSCLC tissues and adjacent tissues. Next, functional experiments with circAGFG1 were performed in vitro to evaluate the role of circAGFG1 in tumor metastasis and growth. Meanwhile, a dual luciferase reporter assay, RNA pull-down and RNA immunoprecipitation experiments were used to explore the interaction between circAGFG1 and miR-203. Our results revealed that expression levels of circAGFG1 and miR-203 are upregulated in non-small-cell lung cancer tissues. CircAGFG1 enhances NSCLC cell proliferation, invasion, migration and epithelial-mesenchymal transition in vitro. Mechanistic analyses indicated that circAGFG1 acts as a sponge for miR-203 to repress the effect of miR-203 on its target, ZNF281. In conclusion, our study suggests that circAGFG1 promotes NSCLC growth and metastasis though a circAGFG1/miR-203/ZNF281 axis and may represent a novel therapeutic target.

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.

circLRP6 regulates high glucose-induced proliferation, oxidative stress, ECM accumulation, and inflammation in mesangial cells

Aberrant regulation in mesangial cell proliferation, extracellular matrix (ECM) accumulation, oxidative stress, and inflammation under hyperglycemic condition contributes significantly to the occurrence and development of diabetic nephropathy (DN). However, the mechanisms underlying the hyperglycemia-induced dysregulations have not been clearly elucidated. Here, we reported that high mobility group box 1 (HMGB1) was highly elevated in high glucose (HG)-treated mesangial cells, and induced the phosphorylation, nuclear translocation, and DNA binding activity of NF-κB via toll-like receptor 4 (TLR4). Function assays showed that inhibition of HMGB1 mitigated HG-induced proliferation, oxidative stress, ECM accumulation, and inflammation in mesangial cells via TLR4/NF-κB pathway. Increasing evidence has shown that circRNA, a large class of noncoding RNAs, functions by binding with miRNAs and terminating regulation of their target genes. We further investigated whether HMGB1 is involved in circRNA-miRNA-mRNA regulatory network. First, HMGB1 was identified and confirmed to be the target of miR-205, and miR-205 played a protective role against HG-induced cell injure via targeting HMGB1. Then circLRP6 was found to be upregulated in HG-treated mesangial cells, and regulate HG-induced mesangial cell injure via sponging miR-205. Besides, overexpression of miR-205 or knockdown of circLRP6 inhibited the NF-κB signaling pathway. Collectively, these data suggest that circLRP6 regulates HG-induced proliferation, oxidative stress, ECM accumulation, and inflammation in mesangial cells via sponging miR-205, upregulating HMGB1 and activating TLR4/NF-κB pathway. These findings provide a better understanding for the pathogenesis of DN.

Non-coding RNAs as potential therapeutic targets in breast cancer

Paradigm shifting studies especially involving non-coding RNAs (ncRNAs) during last few decades have significantly changed the scientific perspectives regarding the complexity of cellular signalling pathways. Several studies have shown that the non-coding RNAs, initially ignored as transcriptional noise or products of erroneous transcription; actually regulate plethora of biological phenomena ranging from developmental processes to various diseases including cancer. Current strategies that are employed for the management of various cancers including that of breast fall short when their undesired side effects like Cancer Stem Cells (CSC) enrichment, low recurrence-free survival and development of drug resistance are taken into consideration. This review aims at exploring the potential role of ncRNAs as therapeutics in breast cancer, by providing a comprehensive understanding of their mechanism of action and function and their crucial contribution in regulating various aspects of breast cancer progression such as cell proliferation, angiogenesis, EMT, CSCs, drug resistance and metastasis. In addition, we also provide information about various strategies that can be employed or are under development to explore them as potential moieties that may be used for therapeutic intervention in breast cancer.