StarD13 3'-untranslated region functions as a ceRNA for TP53INP1 in prohibiting migration and invasion of breast cancer cells by regulating miR-125b activity

Coding, or non-coding, that is the question

The advent of high-throughput sequencing uncovered that our genome is pervasively transcribed into RNAs that are seemingly not translated into proteins. It was also found that non-coding RNA transcripts outnumber canonical protein-coding genes. This mindboggling discovery prompted a surge in non-coding RNA research that started unraveling the functional relevance of these new genetic units, shaking the classic definition of "gene". While the non-coding RNA revolution was still taking place, polysome/ribosome profiling and mass spectrometry analyses revealed that peptides can be translated from non-canonical open reading frames. Therefore, it is becoming evident that the coding vs non-coding dichotomy is way blurrier than anticipated. In this review, we focus on several examples in which the binary classification of coding vs non-coding genes is outdated, since the same bifunctional gene expresses both coding and non-coding products. We discuss the implications of this intricate usage of transcripts in terms of molecular mechanisms of gene expression and biological outputs, which are often concordant, but can also surprisingly be discordant. Finally, we discuss the methodological caveats that are associated with the study of bifunctional genes, and we highlight the opportunities and challenges of therapeutic exploitation of this intricacy towards the development of anticancer therapies.

Advanced Insights into Competitive Endogenous RNAs (ceRNAs) Regulated Pathogenic Mechanisms in Metastatic Triple-Negative Breast Cancer (mTNBC)

Triple-negative breast cancer is aggressive and challenging to treat because of a lack of targets and heterogeneity among tumors. A paramount factor in the mortality from breast cancer is metastasis, which is driven by genetic and phenotypic alterations that drive epithelial-mesenchymal transition, stemness, survival, migration and invasion. Many genetic and epigenetic mechanisms have been identified in triple-negative breast cancer that drive these metastatic phenotypes; however, this knowledge has not yet led to the development of effective drugs for metastatic triple-negative breast cancer (mTNBC). One that may not have received enough attention in the literature is post-translational regulation of broad sets of cancer-related genes through inhibitory microRNAs and the complex competitive endogenous RNA (ceRNA) regulatory networks they are influenced by. This field of study and the resulting knowledge regarding alterations in these networks is coming of age, enabling translation into clinical benefit for patients. Herein, we review metastatic triple-negative breast cancer (mTNBC), the role of ceRNA network regulation in metastasis (and therefore clinical outcomes), potential approaches for therapeutic exploitation of these alterations, knowledge gaps and future directions in the field.

miR-125 in Breast Cancer Etiopathogenesis: An Emerging Role as a Biomarker in Differential Diagnosis, Regenerative Medicine, and the Challenges of Personalized Medicine

Breast Cancer (BC) is one of the most common cancer types worldwide, and it is characterized by a complex etiopathogenesis, resulting in an equally complex classification of subtypes. MicroRNA (miRNA or miR) are small non-coding RNA molecules that have an essential role in gene expression and are significantly linked to tumor development and angiogenesis in different types of cancer. Recently, complex interactions among coding and non-coding RNA have been elucidated, further shedding light on the complexity of the roles these molecules fulfill in cancer formation. In this context, knowledge about the role of miR in BC has significantly improved, highlighting the deregulation of these molecules as additional factors influencing BC occurrence, development and classification. A considerable number of papers has been published over the past few years regarding the role of miR-125 in human pathology in general and in several types of cancer formation in particular. Interestingly, miR-125 family members have been recently linked to BC formation as well, and complex interactions (competing endogenous RNA networks, or ceRNET) between this molecule and target mRNA have been described. In this review, we summarize the state-of-the-art about research on this topic.

Obesity as a Risk Factor for Breast Cancer-The Role of miRNA

Breast cancer (BC) is the most common cancer diagnosed among women in the world, with an ever-increasing incidence rate. Due to the dynamic increase in the occurrence of risk factors, including obesity and related metabolic disorders, the search for new regulatory mechanisms is necessary. This will help a complete understanding of the pathogenesis of breast cancer. The review presents the mechanisms of obesity as a factor that increases the risk of developing breast cancer and that even initiates the cancer process in the female population. The mechanisms presented in the paper relate to the inflammatory process resulting from current or progressive obesity leading to cell metabolism disorders and disturbed hormonal metabolism. All these processes are widely regulated by the action of microRNAs (miRNAs), which may constitute potential biomarkers influencing the pathogenesis of breast cancer and may be a promising target of anti-cancer therapies.

Tanshinone IIA attenuates the stemness of breast cancer cells via targeting the miR-125b/STARD13 axis

BACKGROUND

Tanshinone II A is an effective component extracted from Salvia miltiorrhiza and the roles of Tanshinone IIA in regulating the stemness of tumor cells remain unclear. This work aims to explore the roles and underlying mechanisms of Tanshinone IIA in breast cancer stemness.

METHODS

In vitro mammary spheroid formation, flow cytometry assay on CD24^-/CD44⁺ sub-population, ALDH activity detection, cell viability assay and western blot analysis, and in vivo tumor-initiating analysis were performed to examine the effects of Tanshinone IIA on the stemness of breast cancer cells. MiRNAs-based transcriptome sequencing and data analysis, online dataset analysis, luciferase reporter assay combined with rescuing experiments were constructed to explore the underlying mechanisms.

RESULTS

Tanshinone IIA attenuated the stemness of breast cancer cells, evident by downregulating the expression of stemness markers, hindering the capacity of spheroid formation, decreasing the CD24^-/CD44⁺ sub-population in a concentration-dependent manner and reducing the tumor-initiating ability of breast cancer cells. Additionally, Tanshinone IIA enhanced adriamycin sensitivity and attenuated adriamycin resistance of breast cancer cells. Combined with miRNAs-based transcriptome sequencing assay, it was found that Tanshinone IIA downregulated miR-125b level and upregulated its target gene STARD13 (StAR-related lipid transfer protein 13) level, thus inactivating the miR-125b/STARD13 axis, which had been previously confirmed to promote breast cancer progression. Notably, miR-125b overexpression enhanced the stemness of breast cancer cells, and miR-125b overexpression or STARD13 knockdown impaired the inhibitory effects of Tanshinone IIA on the stemness of breast cancer cells.

CONCLUSIONS

Tanshinone IIA could attenuate the stemness of breast cancer cells via targeting the miR-125b/STARD13 axis.

A comprehensive map of alternative polyadenylation in African American and European American lung cancer patients

Deciphering the post-transcriptional mechanisms (PTM) regulating gene expression is critical to understand the dynamics underlying transcriptomic regulation in cancer. Alternative polyadenylation (APA)-regulation of mRNA 3'UTR length by alternating poly(A) site usage-is a key PTM mechanism whose comprehensive analysis in cancer remains an important open challenge. Here we use a method and analysis pipeline that sequences 3'end-enriched RNA directly to overcome the saturation limitation of traditional 5'-3' based sequencing. We comprehensively map the APA landscape in lung cancer in a cohort of 98 tumor/non-involved tissues derived from European American and African American patients. We identify a global shortening of 3'UTR transcripts in lung cancer, with notable functional implications on the expression of both coding and noncoding genes. We find that APA of non-coding RNA transcripts (long non-coding RNAs and microRNAs) is a recurrent event in lung cancer and discover that the selection of alternative polyA sites is a form of non-coding RNA expression control. Our results indicate that mRNA transcripts from EAs are two times more likely than AAs to undergo APA in lung cancer. Taken together, our findings comprehensively map and identify the important functional role of alternative polyadenylation in determining transcriptomic heterogeneity in lung cancer.

Long non-coding RNA DUXAP9 promotes hepatocellular carcinoma cell stemness via directly interacting with sox9

Long non-coding RNA (LncRNA) DUXAP9 expression was recently found to be higher in hepatocellular carcinoma (HCC) tissues and cells, and correlated with a shorter overall survival of HCC patients. However, its roles in HCC progression have never been revealed. Here, the roles of DUXAP9 in HCC cell stemness are explored as cancer stem cells (CSCs) contribute to one of the root of cancer progression. We found that DUXAP9 positively regulated HCC cell stemness, as characterized by the change of sphere-formation ability, ALDH activity and stemness marker expression. Further luciferase reporter, mRNA stability and RNA-RNA in vitro interaction assays indicated that DUXAP9 directly bound to the 3' untranslated region (UTR) of sox9, enhanced the mRNA stability of sox9 and thus increased sox9 expression. Notably, the effects induced by DUXAP9 on HCC cell stemness depended on sox9 expression. Therefore, this work identifies a novel DUXAP9/sox9 axis essential for HCC cell stemness.

Transmembrane protein TMEM119 facilitates the stemness of breast cancer cells by activating Wnt/β-catenin pathway

The effects of transmembrane protein 119 (TMEM119) on breast cancer progression have not been elucidated. This study aims to investigate the roles of TMEM119 in breast cancer progression. Clinical samples and online datasets were used to determine TMEM119 expression and its correlation between patients’ survival. Wound healing, transwell invasion, mammary spheroid formation, and ALDH activity were performed to detect the effects of TMEM119. RNA-sequencing, Luciferase report analysis, Co-IP, and ChIP analysis were constructed to reveal the underlying mechanisms. We found that TMEM119 was highly expressed in breast cancer tissues and cells compared to that in normal tissues and cells. Additionally, TMEM119 expression was negatively correlated with the survival of breast cancer patients. TMEM119 knockdown reduced the expression of stemness markers, mammary spheroid-formation ability and ALDH activity. RNA-sequencing analysis indicated that Wnt/β-catenin signaling was enriched in cells with TMEM119 overexpression. Further co-IP experiments indicated that TMEM119 interacted with β-catenin and maintained its protein stability. Conversely, β-catenin directly bound to TMEM119 gene promoter and thus increased TMEM119 transcriptional activity and its expression. Finally, we demonstrated that TMEM119-mediated effects depended on Wnt/β-catenin signaling. Thus, this work reveals a novel TMEM119-β-catenin positive feedback loop essential for breast cancer cell stemness.

StarD13 differentially regulates migration and invasion in prostate cancer cells

Prostate cancer is the second most commonly diagnosed cancer in men and one of the main leading causes of cancer deaths among men worldwide. Rapid uncontrolled growth and the ability to metastasize to other sites are key hallmarks in cancer development and progression. The Rho family of GTPases and its activators the GTPase-activating proteins (GAPs) are required for regulating cancer cell proliferation and migration. StarD13 is a GAP for Rho GTPases, specifically for RhoA and Cdc42. We have previously shown that StarD13 acts as a tumor suppressor in astrocytoma as well as breast and colorectal cancer. In this study, we performed a functional comparative analysis of StarD13 targets/and or interacting molecules to understand the general role that StarD13 plays in cancers. Our data highlight the importance of StarD13 in modulating several hallmarks of cancer. Findings from database mining and immunohistochemistry revealed that StarD13 is underexpressed in prostate cancers, in addition knocking down Stard13 increased cancer cell proliferation, consistent with its role as a tumor suppressor. Stard13 depletion, however, led to an increase in cell adhesion, which inhibited 2D cell migration. Most interestingly, StarD13 depletion increases invasion and matrix degradation, at least in part, through its regulation of Cdc42. Altogether, the data presented suggest that StarD13 acts as a tumor suppressor inhibiting prostate cancer cell invasion.

Essential functions of miR-125b in cancer

MicroRNAs (miRNAs) are small and highly conserved non-coding RNAs that silence target mRNAs, and compelling evidence suggests that they play an essential role in the pathogenesis of human diseases, especially cancer. miR-125b, which is the mammalian orthologue of the first discovered miRNA lin-4 in Caenorhabditis elegans, is one of the most important miRNAs that regulate various physiological and pathological processes. The role of miR-125b in many types of cancer has been well established, and so here we review the current knowledge of how miR-125b is deregulated in different types of cancer; its oncogenic and/or tumour-suppressive roles in tumourigenesis and cancer progression; and its regulation with regard to treatment response, all of which are underlined in multiple studies. The emerging information that elucidates the essential functions of miR-125b might help support its potentiality as a diagnostic and prognostic biomarker as well as an effective therapeutic tool against cancer.

MMP1 3'UTR facilitates the proliferation and migration of human oral squamous cell carcinoma by sponging miR-188-5p to up-regulate SOX4 and CDK4

Growing evidence indicates that the non-coding 3'-untranslated region (3'UTR) of genes acts as competing endogenous RNAs (ceRNAs) to exert their roles in a number of diseases, including cancer. In the present study, MMP1 messenger RNA was identified to be significantly up-regulated in oral squamous cell carcinoma (OSCC) tissues, and both MMP1 and its 3'UTR promoted tumor growth and cell motility. Further mechanism investigations indicated that MMP1 3'UTR was able to antagonize miR-188-5p; in addition, overexpression of MMP1 3'UTR up-regulated the expression level of SOX4 and CDK4, target genes of miR-188-5p, which have also been identified as oncogenic driver genes in OSCC. Therefore, a ceRNA regulatory network among MMP1, SOX4, and CDK4 mediated via competing for binding to miR-188-5p was proved. Taken together, the present study demonstrates for the first time that MMP1 mRNA participates in the development of OSCC via ceRNA regulatory mechanism and genes involved in the ceRNA network may provide a novel avenue for target therapy.

CFIm25-regulated lncRNA acv3UTR promotes gastric tumorigenesis via miR-590-5p/YAP1 axis

Accumulating evidences indicate that 3ʹUTR of the coding gene can act as crucial regulators in gastric cancer (GC). However, the detailed mechanisms and responsive targets are not well established. Here, we found that acvr1b gene 3ʹUTR (acv3UTR) was elevated in GC tissue, the expression of which was significantly correlated with advanced pTNM-stage and poor outcome in clinical patients. Forced expression of acv3UTR promoted GC cells growth in vitro and in vivo. Mechanistically, our results suggested that acv3UTR functioned as an oncogenic competing endogenous RNA via sponging miR-590-5p and enhancing YAP1 level. Tumor suppressor miR-590-5p was a molecular module in acv3UTR regulatory axis, the forced expression of which led to impairing of oncogenic potential of acv3UTR. The positive correlation of acv3UTR and YAP1 expression, and the negative correlation of acv3UTR and miR-590-5p expression, were verified in GC patients. Moreover, CFIm25 was identified as a key regulator contributing to acv3UTR aberrant expression in GC binding to UGUA-264 motif. Overall, our finding defines a mechanism for understanding the potential role of acv3UTR transcription in GC tumorigenesis, and indicates a correlation between 3ʹUTR trans-regulatory effect and GC development.

The Emerging Roles of miR-125b in Cancers

MicroRNAs (miRNAs) are endogenous, noncoding, single-stranded RNA molecules of 22 nucleotides in length. MiRNAs have both tumor-suppressive properties and oncogenic properties that can control critical processes in tumors. Mature miR-125b originates from miR-125b-1 and miR-125b-2 and leads to the degradation of target mRNAs or the inhibition of translation through binding to the 3′ untranslated regions (3′-UTR) of target mRNAs. Importantly, miR-125b is involved in regulating NF-κB, p53, PI3K/Akt/mTOR, ErbB2, Wnt, and another signaling pathways, thereby controlling cell proliferation, differentiation, metabolism, apoptosis, drug resistance and tumor immunity. This review aims to summarize the recent literature on the role of miR-125b in the regulation of tumorigenesis and to explore its potential clinical application in the diagnosis, prognosis and clinical treatment of tumors.

WITHDRAWN: Tanshinone IIA-mediated inhibition on miR-125b/STARD13 axis attenuates the stemness and enhances adriamycin sensitivity of breast cancer cells

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Steroid hormone calcitriol and its analog tacalcitol inhibit miR-125b expression in a human breast cancer MCF-7 cell line

MiR-125b belongs to the class of microRNAs, which are short endogenous non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. Recently, it was reported that miR-125b was found to promote migration and invasion of MCF-7 cells and was involved in chemotherapeutic resistance. Decreasing miR-125b expression would have potential therapeutic significance in preventing dissemination of breast cancer cells. The objective of this study was to evaluate miR-125b expression levels in MCF-7 cells following treatment with 1,25-dihydroxyvitamin D₃ (calcitriol) and 1,24-dihydroxyvitamin D₃ (tacalcitol), active metabolite and synthetic analog of vitamin D₃, respectively. We found that treatment with both calcitriol and tacalcitol caused a decrease in miR-125b expression. In addition, treatment with calcitriol and tacalcitol resulted in an increase in the level of pro-apoptotic BAK1 protein encoded by the target gene of miR-125b. We are discussing the putative mechanism of inhibition of the miR-125b expression by vitamin D receptor (VDR) agonists and we suggest that calcitriol and tacalcitol may be used as a miR-125b inhibitor in breast cancer cells expressing VDR.

DLC2 operates as a tumor suppressor gene in breast cancer via the RhoGTPase pathway

Deleted in liver cancer 2 (DLC2) is a tumor suppressor, associated with various types of cancer. The aim of the present study was to analyze the expression of DLC2 in breast cancer, its clinical significance and its effect on breast cancer cell behavior. The expression of DLC2 was evaluated by immunohistochemistry in 131 cases of breast cancer. Associations among DLC2 expression and clinicopathological features were analyzed, and its effects on proliferation, motility, migration and invasion in DLC2-knockdown breast cancer cell lines were observed. The results indicated that DLC2 was expressed in 42.75% of breast cancer cases (56/131) and in 79.39% of adjacent normal tissues (104/131). Lower expression of DLC2 in breast cancer was associated with tumor differentiation (P<0.001), lymph node metastasis (P<0.001) and poor prognosis (P<0.001). The silencing of the DLC2 gene in human breast cancer cell indicated an increased number of cells entering S phase, and increased abilities of clone formation, cell migration and invasion. Downregulated expression of DLC2 was associated with activated Ras homolog family member A and decreased Rac family small GTPase 1, cell division cycle 42 and Rho-associated protein kinase-2 expression levels, indicating that DLC2 may serve a regulatory function in breast cancer cell proliferation and invasion via the RhoGTPase pathway. The results of the present study suggested that DLC2 serves as a suppressor gene in the development of breast cancer and may be a prognostic marker for patients with breast cancer.

Robust analysis of novel mRNA-lncRNA cross talk based on ceRNA hypothesis uncovers carcinogenic mechanism and promotes diagnostic accuracy in esophageal cancer

Background

ceRNAs have emerged as pivotal players in the regulation of gene expression and play a crucial role in the physiology and development of various cancers. Nevertheless, the function and underlying mechanisms of ceRNAs in esophageal cancer (EC) are still largely unknown.

Methods

In this study, profiles of DEmRNAs, DElncRNAs, and DEmiRNAs between normal and EC tumor tissue samples were obtained from the Cancer Genome Atlas database using the DESeq package in R by setting the adjusted P<0.05 and |log₂(fold change)|>2 as the cutoff. The ceRNA network (ceRNet) was initially constructed to reveal the interaction of these ceRNAs during carcinogenesis based on the bioinformatics of miRcode, miRDB, miRTarBase, and TargetScan. Then, independent microarray data of GSE6188, GSE89102, and GSE92396 and correlation analysis were used to validate molecular biomarkers in the initial ceRNet. Finally, a least absolute shrinkage and selection operator logistic regression model was built using an oncogenic ceRNet to diagnose EC more accurately.

Results

We successfully constructed an oncogenic ceRNet of EC, crosstalk of hsa-miR372-centered CADM2-ADAMTS9-AS2 and hsa-miR145-centered SERPINE1-PVT1. In addition, the risk-score model -0.0053*log₂(CADM2)+0.0168*log₂(SERPINE1)-0.0073*log₂(ADAMTS9-AS2)+0.0905*log₂(PVT1)+0.0047*log₂(hsa-miR372)-0.0193*log₂(hsa-miR145), (log₂[gene count]) could improve diagnosis of EC with an AUC of 0.988.

Conclusion

We identified two novel pairs of ceRNAs in EC and its role of diagnosis. The pairs of hsa-miR372-centered CADM2-ADAMTS9-AS2 and hsa-miR145-centered SERPINE1-PVT1 were likely potential carcinogenic mechanisms of EC, and their joint detection could improve diagnostic accuracy.

Competing endogenous RNA (ceRNA) cross talk and language in ceRNA regulatory networks: A new look at hallmarks of breast cancer

Breast cancer (BC) is the most frequently occurring malignancy in women worldwide. Despite the substantial advancement in understanding the molecular mechanisms and management of BC, it remains the leading cause of cancer death in women. One of the main reasons for this obstacle is that we have not been able to find the Achilles heel for the BC as a highly heterogeneous disease. Accumulating evidence has revealed that noncoding RNAs (ncRNAs), play key roles in the development of BC; however, the involving of complex regulatory interactions between the different varieties of ncRNAs in the development of this cancer has been poorly understood. In the recent years, the newly discovered mechanism in the RNA world is "competing endogenous RNA (ceRNA)" which proposes regulatory dialogues between different RNAs, including long ncRNAs (lncRNAs), microRNAs (miRNAs), transcribed pseudogenes, and circular RNAs (circRNAs). In the latest BC research, various studies have revealed that dysregulation of several ceRNA networks (ceRNETs) between these ncRNAs has fundamental roles in establishing the hallmarks of BC development. And it is thought that such a discovery could open a new window for a better understanding of the hidden aspects of breast tumors. Besides, it probably can provide new biomarkers and potential efficient therapeutic targets for BC. This review will discuss the existing body of knowledge regarding the key functions of ceRNETs and then highlights the emerging roles of some recently discovered ceRNETs in several hallmarks of BC. Moreover, we propose for the first time the "ceRnome" as a new term in the present article for RNA research.

MicroRNA-125b mimic inhibits ischemia reperfusion-induced neuroinflammation and aberrant p53 apoptotic signalling activation through targeting TP53INP1

BACKGROUND

Ischemia reperfusion (IR) injury affects neuronal function through multiple pathogeneses that induce neuroinflammation and cellular apoptosis. The important roles of microRNAs (miRs) in the regulation of spinal cord IR have been recently reported. Among these roles, we investigated whether miR-125b and its downstream targets regulated the p53 signalling network and participated in both inflammation and apoptosis.

METHODS

An IR model was established via 12-min occlusion of the aortic arch. The direct interaction between miR-125b and TP53INP1 was demonstrated by Western blotting and luciferase assays. The cellular distributions of TP53INP1 were visualised by double immunofluorescence labelling. The effects of miR-125b on the expression of TP53INP1, p53 and release of proinflammatory cytokines were evaluated by synthetic miRs. Additionally, the detection of hind-limb motor function in vivo and motor neuronal apoptosis in vitro were evaluated to explore the potential mechanisms.

RESULTS

IR-induced alterations in hind-limb motor function were closely related to the temporal changes in miR-125b and TP53INP1 expression. The miR-125b/TP53INP1 gene pair was confirmed by luciferase assay. Compared with Sham controls, IR treatment resulted in increased TP53INP1 immunoreactivity that was primarily distributed in neurons. Treatment with miR-125b mimic markedly decreased the protein levels of TP53INP1, p53 and cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α, whereas miR-125b control or inhibitor did not have the above-mentioned effects. Moreover, miR-125b mimic improved motor function in vivo and attenuated neuronal apoptosis in vitro, as demonstrated by the increased average Tarlov scores in lower limbs and lower percentages of neurons in the A4 and A2 quadrants of flow cytometry. Fluorescent staining and quantification further indicated that miR-125b mimic decreased the immunoreactivities of p53 and cleaved caspase 3 in neurons and simultaneously reduced the number of double-labelled cells with TP53INP1.

CONCLUSIONS

miR-125b mimic partially protected neurons against neuroinflammation and aberrant p53 network activation-induced apoptosis during IR injury through downregulation of TP53INP1.

LncRNA THOR increases the stemness of gastric cancer cells via enhancing SOX9 mRNA stability

This work aims to explore the roles and mechanisms of long non coding RNA (lncRNA) THOR in regulating the stemness of gastric cancer cells. RNA-sequencing combined with quantitative real-time PCR (qRT-PCR) indicated that lncRNA THOR level was significantly upregulated in gastric cancer tissues compared with that in normal adjacent tissues. Knockdown of THOR attenuated the stemnness of gastric cancer cells, evident by the decrease of stemness markers expression and capacity of cells spheroid formation. Further RNA-sequencing combined with qRT-PCR and western blot analysis demonstrated that expression of transcriptional factor SOX9 was remarkably decreased in gastric cancer cells with THOR stable knockdown. Additionally, RNA immunoprecipitation (RIP) combined with luciferase reporter assay revealed that THOR directly bound to SOX9 3' untranslated region (3'UTR), but not its 5'UTR or coding area. Notably, overexpression of SOX9 rescued THOR knockdown-mediated inhibition on the stemness of gastric cancer cells. Thus, our results suggest that THOR could potentiate the stemness of gastric cancer cells via directly binding to SOX9 3'UTR.

NT21MP negatively regulates paclitaxel-resistant cells by targeting miR‑155‑3p and miR‑155-5p via the CXCR4 pathway in breast cancer

Evidence has shown that microRNAs (miRNAs) are vital in cell growth, migration, and invasion by inhibiting their target genes. A previous study demonstrated that miRNA (miR)-155-3p and miR-155-5p exerted opposite effects on cell proliferation, apoptosis, migration and invasion in breast cancer cell lines. An miRNA microarray was used to show that miR-155-3p was downregulated whereas miR-155-5p was upregulated in paclitaxel-resistant (PR) cells compared with parental breast cancer cells. However, the role of miR-155 in breast cancer cell invasion and metastasis remains to be elucidated. A 21-residue peptide derived from the viral macrophage inflammatory protein II (NT21MP), competes with the ligand of CXC chemokine receptor 4 (CXCR4) and its ligand stromal cell-derived factor-1α, inducing cell apoptosis in breast cancer. The present study aimed to identify the underlying mechanism of action of miR-155-3p/5p and NT21MP in PR breast cancer cells. Quantitative polymerase chain reaction, western blotting, wound-healing, cell cycle and apoptosis assays, and Cell Counting kit-8 assay were used to achieve this goal. The combined overexpression of miR-155-3p with NT21MP decreased the migration and invasion ability and increased the number of apoptotic and arrested cells in the G0/G1 phase transition in vitro. The knockdown of miR-155-5p combined with NT21MP had a similar effect on PR breast cancer cells. Furthermore, the ectopic expression of their target gene myeloid differentiation primary response gene 88 (MYD88) or tumor protein 53-induced nuclear protein 1 (TP53INP1) combined with NT21MP enhanced the sensitivity of the breast cancer cells to paclitaxel. Taken together, these findings suggested that miR-155-3p/5p and their target genes MYD88 and TP53INP1 may serve as novel biomarkers for NT21MP therapy through the CXCR4 pathway for improving sensitivity to paclitaxel in breast cancer.