The role of long non-coding RNAs in drug resistance of cancer.

Long non-coding RNAs (lncRNAs), a class of long RNAs, are longer than 200 nucleotides in length but lack protein-coding capacity. LncRNAs, as critical genomic regulators, are involved in genomic imprinting regulation, histone modification and gene expression regulation as well as tumor initiation and progression. However, it is also found that lncRNAs are associated with drug resistance in several types of cancer. Drug resistance is an important reason for clinical chemotherapy failure, and the molecular mechanism of tumor resistance is complex, which is a process of multi-cause, multi-gene and multi-signal transduction pathway interaction. Then comprehending the mechanisms of chemoresistance will help find ways to control the tumor progression effectively. Therefore, in this review, we will construct lncRNAs /drug resistance interaction network and shed light on the role of lncRNAs in drug resistance.

Identification of circRNA-miRNA networks for exploring an underlying prognosis strategy for breast cancer.

Aim: Circular RNAs (circRNAs) still have many potential functions in the process of tumor development that are not completely understood. The study aims to explore novel circRNAs and their mechanisms of action in breast cancer (BCa). Materials & methods: A combination strategy of RNA-sequencing (RNA-seq) technique, quantitative real-time PCR and bioinformatic analysis was employed to identify the potential mechanisms involving differentially expressed circRNAs in the serum exosomes and tissues of BCa patients. Results: The expression levels of hsa-circRNA-0005795 and hsa-circRNA-0088088 were significantly different both in serum exosomes and tissues and might function as competing endogenous RNAs and play vital roles in BCa development. Conclusion: We constructed two circRNA-miRNA networks and provided new insight into the prognosis and therapy of BCa using circRNAs from serum exosomes.

Circular RNA circVAPA regulates breast cancer cell migration and invasion via sponging miR-130a-5p.

Aim: We aimed to explore the roles of circular RNA, circVAPA in regulating cell migration and invasion of breast cancer. Materials & methods: CircVAPA expression was detected in breast cancer tissues and cells. The role of circVAPA was evaluated by MTT assay, wound-healing and transwell assay. The relationship between circVAPA and miR-130a-5p and the location of circVAPA were explored. Results: We discovered that circVAPA was dysregulated in breast cancer tissues and cells. Ectopic circVAPA regulated breast cancer migration, invasion and proliferation. CircVAPA was mainly expressed in the cytoplasm and could act as a miRNA sponge for miR-130a-5p, but did not regulate its parental gene. Conclusion: CircVAPA may promote migration and invasion capacity of breast cancer via harboring miR-130a-5p.

Circular RNA expression in pancreatic ductal adenocarcinoma.

The regulatory roles of circular RNAs (circRNAs) in cancer are attracting increasing attention. The aim of the present study was to explore the roles of circRNAs in pancreatic ductal adenocarcinoma (PDAC) using microarray data. The circRNA and microRNA (miRNA) microarray data were downloaded from Gene Expression Omnibus. A total of 256 differentially expressed circRNAs were obtained by analyzing the circRNA microarray data from 26 pairs of PDAC and adjacent normal tissues. Differentially expressed miRNAs were analyzed using a dataset of 6 PDAC tissues and 5 non-neoplastic pancreas samples (GSE43796); 20 differentially expressed miRNAs were detected. circRNA/miRNA interactions were predicted between differentially expressed circRNAs and miRNAs using miRanda and RNAhybrid algorithms and 51 circRNA/miRNA interactions were obtained. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis using gene symbols of differentially expressed circRNAs demonstrated that 41 circRNAs were enriched in 17 pathways. Subnetworks that were associated with apoptosis or proliferation were extracted from the 17 pathways and a new network was constructed using Cytoscape software, which identified that mitogen-activated protein kinase, PI3K/AKT and WNT/ß-catenin signaling pathways may be associated with PDAC development. In conclusion, 256 differentially expressed circRNAs and 20 differentially expressed miRNAs were identified in PDAC tissues compared with normal tissues; the circRNA/miRNA interactions and the networks of KEGG pathways provided a global view of the function of these differentially expressed circRNAs and miRNAs.

The emerging role of circular RNAs in breast cancer.

Breast cancer (BCa) is one of the most frequently diagnosed cancers and leading cause of cancer deaths among females worldwide. Circular RNAs (circRNAs) are a new class of endogenous regulatory RNAs characterized by circular shape resulting from covalently closed continuous loops that are capable of regulating gene expression at transcription or post-transcription levels. With the unique structures, circRNAs are resistant to exonuclease RNase R and maintain stability more easily than linear RNAs. Recently, an increasing number of circRNAs are discovered and reported to show different expression in BCa and these dysregulated circRNAs were correlated with patients' clinical characteristics and grade in the progression of BCa. CircRNAs participate in the bioprocesses of carcinogenesis of BCa, including cell proliferation, apoptosis, cell cycle, tumorigenesis, vascularization, cell invasion, migration as well as metastasis. Here we concentrated on biogenesis and function of circRNAs, summarized their implications in BCa and discussed their potential as diagnostic and therapeutic targets for BCa.

Clinical and pathological significance of Homo sapiens ceramide synthase 2 (CerS-2) in diverse human cancers.

Homo sapiens ceramide synthase 2 (CerS-2) plays an important role in inhibiting invasion and metastasis of tumor cells and has been reported as a tumor metastasis suppressor gene in diverse cancers. Thus, low level of CerS-2 protein might suggest a bad prognosis and up-regulation of CerS-2 protein might act as a promising therapeutic strategy for malignant tumors. In this review, we discussed the expression, as well as the clinical and pathological significance of CerS-2 in diverse human cancers. The pathological processes and molecular pathways regulated by CerS-2 were also summarized.

Circular RNA circASS1 is downregulated in breast cancer cells MDA-MB-231 and suppressed invasion and migration.

AIM: The study aimed to investigate the role of circular RNA circASS1 in breast cancer cells. MATERIALS & METHODS: Circular RNAs microarray expression profile were analyzed in MCF-7, MDA-MB-231, and qRT-PCR and western blotting were used to quantify expression of circASS1 and its parental gene ASS1. Wound healing, migration and invasion assay were performed. Luciferase assay system was used to detect harbored miRNA. RESULTS: CircASS1 in MDA-MB-231 is downregulated comparing to MCF-7, and overexpression of circASS1 could suppress invasion and migration. While silence, it could promote invasion and migration. MiR-4443 functioning as a tumor promoter gene could be captured by circASS1. ASS1 is upregulated in loss-of-function experiments, while downregulated in gain-of-function experiments. CONCLUSION: CircASS1 suppresses invasion and migration capacity of breast cancer cells and harbored miR-4443.

Exosome: a novel mediator in drug resistance of cancer cells.

Exosomes are small membrane vesicles with a diameter of 40-100 nm, which are released into the intracellular environment. Exosomes could influence the genetic and epigenetic changes of receptor cells by promoting the horizontal transfer of various proteins or RNAs, especially miRNAs. Moreover, exosomes also play an important role in tumor microenvironment. Exosomes could promote the short- and long-distance exchanges of genetic information by acting as mediators of cell-to-cell communication. In addition, exosomes participate in drug resistance of tumor cells by genetic exchange between cells. It is reported that exosomes could be absorbed by recipient cells and transmit chemoresistance from drug-resistant tumor cells to sensitive ones. Then understanding the mechanisms of chemotherapy failure and controlling tumor progression effectively will be a major challenge for us. Therefore, in this review, we will briefly reveal the role of exosomes in drug resistance.

Circular RNA hsa_circ_0052112 promotes cell migration and invasion by acting as sponge for miR-125a-5p in breast cancer.

OBJECTIVES: Accumulating evidence has been reported that circular RNAs (circRNAs) are a class of relatively stable, non-coding RNAs, which are involved in the progression of many types of diseases. However, the mechanism of hsa_circ_0052112 in breast cancer cells is not entirely clear. Hsa_circ_0052112, generated from the ZNF83 gene, is selected by analyzing circRNA expression profiles of breast cancer cell by using microarray assay. In this study, we will show the role of hsa_circ_0052112 in regulating cell invasion and migration in breast cancer. METHODS: The expression level of hsa_circ_0052112 in MCF-7 and MDA-MB-231 cells was detected by RT-qPCR; we performed transwell assay to evaluate breast cancer cells' migration and invasion; predicated circRNA/miRNAs interaction using the miRanda and RNAhybrid software; identified the relationship between hsa_circ_0052112 and miR-125a-5p by luciferase activity assay and show the localization of hsa_circ_0052112 by FISH assay and show the significance of ZNF83 in clinical prognosis by Kaplan-Meier survival analysis. RESULTS: Hsa_circ_0052112 expression was significantly higher in MDA-MB-231 cells than that in MCF-7 cells. Overexpression of hsa_circ_0052112 promoted cell migration and invasion in breast cancer. Inversely, down-regulation of hsa_circ_0052112 suppressed breast cancer cells migration and invasion. Hsa_circ_0052112 was mostly located in cytoplasm. Hsa_circ_0052112 could directly sponge to miR-125a-5p; overexpression of miR-125a-5p significantly inhibited breast cancer cells migration and invasion. However, high or low expression of miR-125a-5p was not correlated with relapse free survival (RFS) by TCGA database validation, but high expression of ZNF83 was closely correlated with poor RFS by Kaplan-Meier plotter. CONCLUSIONS: These data suggest that hsa_circ_0052112 may be a potent biomarker for breast cancer, and may provide a new perspective on treatment of breast cancer.

Circular RNA hsa_circ_0072995 promotes breast cancer cell migration and invasion through sponge for miR-30c-2-3p.

AIM: To study the role of hsa_circ_0072995 in regulating the invasion and migration of breast cancer cells. MATERIALS & METHODS: Hsa_circ_0072995 expression was confirmed by quantitative real-time PCR; evaluating the migration and invasion of breast cancer cells through transwell assay; predicating circRNA/microRNAs interaction using the miRanda and RNAhybrid software; identifying the relationship between hsa_circ_0072995 and miR-30c-2-3p by luciferase activity assay; detecting the location of hsa_circ_0072995 by Fluorescence in situ hybridization assay. RESULTS: Hsa_circ_0072995 was significantly upregulated in MDA-MB-231 cells compared with MCF-7 cells. Hsa_circ_0072995 regulated the invasion and migration of breast cancer cells. Hsa_circ_0072995 existed in the nucleus and cytoplasm, and the proportion of the two was roughly equal. Hsa_circ_0072995 bound to miR-30c-2-3p. Overexpression of miR-30c-2-3p inhibited breast cancer cells migration and invasion. Low expression of miR-30c-2-3p was correlated with poor overall survival by The Cancer Genome Atlas database. CONCLUSION: Hsa_circ_0072995 may be a novel biomarker for breast cancer, and may function in metastasis of breast cancer.

The role of circRNAs in cancers.

Circular RNAs (circRNAs) are recently regarded as a naturally forming family of widespread and diverse endogenous noncoding RNAs (ncRNAs) that may regulate gene expression in mammals. At present, above 30000 circRNAs have already been found, with their unique structures to maintain stability more easily than linear RNAs. Several previous literatures stressed on the important role of circRNAs, whose expression was relatively correlated with patients' clinical characteristics and grade, in the carcinogenesis of cancer. CircRNAs are involved in many regulatory bioprocesses of malignance, including cell cycle, tumorigenesis, invasion, metastasis, apoptosis, vascularization, through adsorbing RNA as a sponge, binding to RNA-binding protein (RBP), modulating transcription, or influencing translation. Therefore, it is inevitable to further study the interactions between circRNAs and tumors and to develop novel circRNAs as molecular markers or potential targets, which will provide promising applications in early diagnosis, therapeutic evaluation, prognosis prediction of tumors and even gene therapy for tumors.

Predictive role of GSTP1-containing exosomes in chemotherapy-resistant breast cancer.

Anthracycline/taxane-based chemotherapy regimens are usually used as neoadjuvant chemotherapies to decrease tumour size and prevent metastasis of advanced breast cancer. However, patients have a high risk of developing chemo-resistance during treatment through still unknown mechanisms. Glutathione S-transferase P1 (GSTP1), which belongs to the family of phase II metabolic enzymes, has been reported to function in detoxifying several anti-cancer drugs by conjugating them with glutathione. Previous studies have identified GSTP1 as a predictor of prognosis and chemo-resistance in breast cancer patients, but the mechanisms governing GSTP1-dependent drug resistance are still unclear. We have found that GSTP1 expression is much higher in adriamycin-resistant cells and their corresponding exosomes. The role of GSTP1-containing exosomes in conferring drug resistance was analysed through cell apoptosis and immunofluorescence staining assays. Furthermore, we analysed 42 cases of paired breast cancer tissues collected before and after anthracycline/taxane-based neoadjuvant chemotherapy by immunohistochemistry. Higher GSTP1 expression was shown in the progressive disease (PD)/stable disease (SD) group than in the partial response (PR)/complete response (CR) group both in the samples collected before and after the chemotherapy treatment. Interestingly, GSTP1 partly re-localized from the cell nucleus to the cytoplasm upon treatment, and similar results were obtained for the exosomal marker Tumour susceptibility gene 101 protein (TSG101), which also increased in the cytoplasm after chemotherapy. After analysing the serum exosomes of 30 patients treated with anthracycline/taxane-based neoadjuvant chemotherapy, we discovered that the levels of GSTP1 in exosomes from patients in the PD/SD group were significantly higher than those in the PR/CR group. Here, for the first time, we investigated a novel role for GSTP1-containing exosomes and their capability to transfer drug resistance and evaluated their clinical use in predicting chemo-resistance.

miR-4443 Participates in the Malignancy of Breast Cancer.

PURPOSE: Chemo-resistance is the leading cause of failure in cancer therapy, however, much remains to be understood about the intrinsic mechanisms. In the present study, we discovered the novel miR-4443 that regulated malignancy of breast cancer both in vitro and in vivo. METHODS: We examined the expression of miR-4443 in MDA-MB-231/S and MDA-MB-231 Epirubicin-resistant cell lines with 76 breast cancer formalin-fixed paraffin-embedded tissues by real-time PCR. Also, we investigated the loss- and gain-functions of miR-4443 by MTT assay and flow cytometry. Furthermore, we detected miR-4443 mediated tissue inhibitor of metalloproteinase 2 expression in cells by TargetScan, RT-qPCR and western blot. RESULTS: We identified the up-regulated expression of miR-4443 in Epi-resistant cell lines versus MDA-MB-231/S cell(Epi versus S) and in post-chemotherapy FFPE tissues, along with statistically differential expressions in PR(partial response) versus SD(stable disease)/PD(progressive disease) patients. Overexpression of miR-4443 increased the IC50 value of Epi for the target cells transfected, while inhibition of miR-4443 could restored sensitivity of the target cells to Epi. Besides, down-regulation of endogenous miR-4443 by miRNA-inhibitors significantly enhanced Epi-induced apoptosis while up-regulation of miR-4443 by miRNA-mimics lead to less Epi-induced apoptotic cells. Consequently, changes in TIMP2 mRNA and protein expression revealed that miR-4443 mimics suppressed expression of TIMP2 and induced migration in breast cancer cells. Furthermore, TIMP2 expression associated with better prognosis(HR = 0.721, 95%CI: 0.529-0.983). CONCLUSIONS: We revealed that miR-4443 induced malignancy of breast cancer mainly in chemo-resistance aspect for the very first time, providing a novel biomarker in breast cancer diagnosis and therapy.