MiR-21 controls in situ expansion of CCR6⁺ regulatory T cells through PTEN/AKT pathway in breast cancer

Association of microRNA-21 expression with breast cancer subtypes and its potential as an early biomarker

Breast cancer has become the most diagnosed cancer worldwide in 2020 with high morbidity and mortality rates. The alarming increase in breast cancer incidence has sprung many researchers to focus on developing novel screening tests to identify early breast cancer which will allow clinicians to provide timely and effective treatments. With much evidence supporting the notion that the deregulation of miRNAs (a class of non-coding RNA) greatly contributes to cancer initiation and progression, the promising role of miRNAs as cancer biomarkers is gaining traction in the research world. Among the upregulated miRNAs identified in breast carcinogenesis, miR-21 was shown to be significantly expressed in breast cancer tissues and bodily fluids of breast cancer patients. Therein, this review paper aims to provide an overview of breast cancer, the role and significance of miR-21 in breast cancer pathogenesis, and its potential as a breast cancer biomarker. The paper also discusses the current types of tumor biomarkers and their limitations, the presence of miR-21 in extracellular vesicles and plasma, screening methods available for miRNA detection along with some challenges faced in developing diagnostic miR-21 testing for breast cancer to provide readers with a comprehensive outlook based on using miR-21 in clinical settings.

MicroRNAs mediated interaction of tumor microenvironment cells with breast cancer cells during bone metastasis

Breast cancer (BC) bone metastasis is primarily osteolytic and has limited therapeutic options. Metastasized BC cells prime the secondary environment in bone by forming a tumor niche, which favors their homing and colonization. The tumor microenvironment (TME) is primarily generated by the cancer cells. Bone TME is an intricate network of multiple cells, including altered bone, tumor, stromal, and immune cells. Recent findings highlight the significance of small non-coding microRNAs (miRNAs) in influencing TME during tumor metastasis. MiRNAs from TME-resident cells facilitate the interaction between the tumor and its microenvironment, thereby regulating the biological processes of tumors. These miRNAs can serve as oncogenes or tumor suppressors. Hence, both miRNA inhibitors and mimics are extensively utilized in pre-clinical trials for modulating the phenotypes of tumor cells and associated stromal cells. This review briefly summarizes the recent developments on the functional role of miRNAs secreted directly or indirectly from the TME-resident cells in facilitating tumor growth, progression, and metastasis. This information would be beneficial in developing novel targeted therapies for BC.

Acute myeloid leukemia-derived exosomes deliver miR-24-3p to hinder the T-cell immune response through DENN/MADD targeting in the NF-κB signaling pathways

BACKGROUND

microRNAs (miRNAs) are known as potent gene expression regulators, and several studies have revealed the prognostic value of miRNAs in acute myeloid leukemia (AML) patient survival. Recently, strong evidence has indicated that miRNAs can be transported by exosomes (EXOs) from cancer cells to recipient immune microenvironment (IME) cells.

RESULTS

We found that AML blast-released EXOs enhance CD3 T-cell apoptosis in both CD4 and CD8 T cells. We hypothesized that miRNAs present in EXOs are key players in mediating the changes observed in AML T-cell survival. We found that miR-24-3p, a commonly overexpressed miRNA in AML, was present in released EXOs, suggesting that EXO-miR-24-3p was linked to the increased miR-24-3p levels detected in isolated AML T cells. These results were corroborated by ex vivo-generated miR-24-3p-enriched EXOs, which showed that miR-24-3p-EXOs increased apoptosis and miR-24-3p levels in T cells. We also demonstrated that overexpression of miR-24-3p increased T-cell apoptosis and affected T-cell proliferation by directly targeting DENN/MADD expression and indirectly altering the NF-κB, p-JAK/STAT, and p-ERK signaling pathways but promoting regulatory T-cell (Treg) development.

CONCLUSIONS

These results highlight a mechanism through which AML blasts indirectly impede T-cell function via transferred exosomal miR-24-3p. In conclusion, by characterizing the signaling network regulated by individual miRNAs in the leukemic IME, we aimed to discover new nonleukemic immune targets to rescue the potent antitumor function of T cells against AML blasts. Video Abstract.

OncomiRs as noncoding RNAs having functions in cancer: Their role in immune suppression and clinical implications

Currently, microRNAs have been established as central players in tumorigenesis, but above all, they have opened an important door for our understanding of immune and tumor cell communication. This dialog is largely due to onco-miR transfer from tumor cells to cells of the tumor microenvironment by exosome. This review outlines recent advances regarding the role of oncomiRs in enhancing cancer and how they modulate the cancer-related immune response in the tumor immune microenvironment.

MicroRNAs (miRNAs) are a type of noncoding RNA that are important posttranscriptional regulators of messenger RNA (mRNA) translation into proteins. By regulating gene expression, miRNAs enhance or inhibit cancer development and participate in several cancer biological processes, including proliferation, invasion metastasis, angiogenesis, chemoresistance and immune escape. Consistent with their widespread effects, miRNAs have been categorized as oncogenes (oncomiRs) or tumor suppressor (TS) miRNAs. MiRNAs that promote tumor growth, called oncomiRs, inhibit messenger RNAs of TS genes and are therefore overexpressed in cancer. In contrast, TS miRNAs inhibit oncogene messenger RNAs and are therefore underexpressed in cancer. Endogenous miRNAs regulate different cellular pathways in all cell types. Therefore, they are not only key modulators in cancer cells but also in the cells constituting their microenvironments. Recently, it was shown that miRNAs are also involved in intercellular communication. Indeed, miRNAs can be transferred from one cell type to another where they regulate targeted gene expression. The primary carriers for the transfer of miRNAs from one cell to another are exosomes. Exosomes are currently considered the primary carriers for communication between the tumor and its surrounding stromal cells to support cancer progression and drive immune suppression. Exosome and miRNAs are seen by many as a hope for developing a new class of targeted therapy. This review outlines recent advances in understanding the role of oncomiRs in enhancing cancer and how they promote its aggressive characteristics and deeply discusses the role of oncomiRs in suppressing the anticancer immune response in its microenvironment. Additionally, further understanding the mechanism of oncomiR-related immune suppression will facilitate the use of miRNAs as biomarkers for impaired antitumor immune function, making them ideal immunotherapy targets.

The modulatory role of dendritic cell-T cell cross-talk in breast cancer: Challenges and prospects

Antigen recognition and presentation are highlighted as the first steps in developing specialized antigen responses. Dendritic cells (DCs) are outstanding professional antigen-presenting cells (APCs) responsible for priming cellular immunity in pathological states, including cancer. However, the diminished or repressed function of DCs is thought to be a substantial mechanism through which tumors escape from the immune system. In this regard, DCs obtained from breast cancer (BC) patients represent a notably weakened potency to encourage specific T-cell responses. Additionally, impaired DC-T-cell cross-talk in BC facilitates the immune evade of cancer cells and is connected with tumor advancement, immune tolerance, and adverse prognosis for patients. In this review we aim to highlight the available knowledge on DC-T-cell interactions in BC aggressiveness and show its therapeutic potential in BC treatment.

Impact of non-coding RNAs on cancer directed immune therapies: Now then and forever

Accumulating evidence demonstrates that the host genome's epigenetic modifications are essential for living organisms to adapt to extreme conditions. DNA methylation, covalent modifications of histone, and inter-association of non-coding RNAs facilitate the cellular manifestation of epigenetic changes in the genome. Out of various factors involved in the epigenetic programming of the host, non-coding RNAs (ncRNAs) such as microRNA (miRNA), long non-coding RNA (lncRNA), circular RNA, snoRNA and piRNA are new generation non-coding molecules that influence a variety of cellular processes like immunity, cellular differentiation, and tumor development. During tumor development, temporal changes in miRNA/LncRNA rheostat influence sterile inflammatory responses accompanied by the changes in the carcinogenic signaling in the host. At the cellular level, this is manifested by the up-regulation of Inflammasome and inflammatory pathways, which promotes cancer-related inflammation. Given this, we discuss the potential of lncRNAs, miRNAs, circular RNA, snoRNA and piRNA in regulating inflammation and tumor development in the host. This article is protected by copyright. All rights reserved.

Breast Cancer Drug Resistance: Overcoming the Challenge by Capitalizing on MicroRNA and Tumor Microenvironment Interplay

The clinical management of breast cancer reaches new frontiers every day. However, the number of drug resistant cases is still high, and, currently, this constitutes one of the major challenges that cancer research has to face. For instance, 50% of women affected with HER2 positive breast cancer presents or acquires resistance to trastuzumab. Moreover, for patients affected with triple negative breast cancer, standard chemotherapy is still the fist-line therapy, and often patients become resistant to treatments. Tumor microenvironment plays a crucial role in this context. Indeed, cancer-associated stromal cells deliver oncogenic cues to the tumor and vice versa to escape exogenous insults. It is well known that microRNAs are among the molecules exploited in this aberrant crosstalk. Indeed, microRNAs play a crucial function both in the induction of pro-tumoral traits in stromal cells and in the stroma-mediated fueling of tumor aggressiveness. Here, we summarize the most recent literature regarding the involvement of miRNAs in the crosstalk between tumor and stromal cells and their capability to modulate tumor microenvironment characteristics. All up-to-date findings suggest that microRNAs in the TME could serve both to reverse malignant phenotype of stromal cells, modulating response to therapy, and as predictive/prognostic biomarkers.

The regulatory role of pivotal microRNAs in the AKT signaling pathway in breast cancer

Breast cancer is the most prevalent type of cancer among women, and it remains the main challenge despite improved treatments. MicroRNAs (miRNAs) are a small non-coding family of RNAs that play an indispensable role in regulating major physiological processes, including differentiation, proliferation, invasion, migration, cell cycle regulation, stem cell maintenance, apoptosis, and organ development. The dysregulation of these tiny molecules is associated with various human malignancies. More than 50% of these non-coding RNA sequences estimated have been placed on genomic regions or fragile sites linked to cancer. Following the discovery of the first signatures of specific miRNA in breast cancer, numerous researches focused on involving these tiny RNAs in breast cancer physiopathology as a new therapeutic approach or as reliable prognostic biomarkers. In the current review, we focus on recent findings related to the involvement of miRNAs in breast cancer via the AKT signaling pathway and the related clinical implications.

Tumor Immune Microenvironment and Its Related miRNAs in Tumor Progression

MiRNA is a type of small non-coding RNA, by regulating downstream gene expression that affects the progression of multiple diseases, especially cancer. MiRNA can participate in the biological processes of tumor, including proliferation, invasion and escape, and exhibit tumor enhancement or inhibition. The tumor immune microenvironment contains numerous immune cells. These cells include lymphocytes with tumor suppressor effects such as CD8+ T cells and natural killer cells, as well as some tumor-promoting cells with immunosuppressive functions, such as regulatory T cells and myeloid-derived suppressor cells. MiRNA can affect the tumor immune microenvironment by regulating the function of immune cells, which in turn modulates the progression of tumor cells. Investigating the role of miRNA in regulating the tumor immune microenvironment will help elucidate the specific mechanisms of interaction between immune cells and tumor cells, and may facilitate the use of miRNA as a predictor of immune disorders in tumor progression. This review summarizes the multifarious roles of miRNA in tumor progression through regulation of the tumor immune microenvironment, and provides guidance for the development of miRNA drugs to treat tumors and for the use of miRNA as an auxiliary means in tumor immunotherapy.

RNA Flow Cytometry for the Study of T Cell Metabolism

T cells undergo activation and differentiation programs along a continuum of states that can be tracked through flow cytometry using a combination of surface and intracellular markers. Such dynamic behavior is the result of transcriptional and post-transcriptional events, initiated and sustained by the activation of specific transcription factors and by epigenetic remodeling. These signaling pathways are tightly integrated with metabolic routes in a bidirectional manner: on the one hand, T cell receptors and costimulatory molecules activate metabolic reprogramming; on the other hand, metabolites modify T cell transcriptional programs and functions. Flow cytometry represents an invaluable tool to analyze the integration of phenotypical, functional, metabolic and transcriptional features, at the single cell level in heterogeneous T cell populations, and from complex microenvironments, with potential clinical application in monitoring the efficacy of cancer immunotherapy. Here, we review the most recent advances in flow cytometry-based analysis of gene expression, in combination with indicators of mitochondrial activity, with the aim of revealing and characterizing major metabolic pathways in T cells.

Tiny miRNAs Play a Big Role in the Treatment of Breast Cancer Metastasis

Simple Summary

MicroRNAs (miRNAs) have emerged as important regulators of tumour progression and metastasis in breast cancer. Through a review of multiple studies, this paper has identified the key regulatory roles of oncogenic miRNAs in breast cancer metastasis including the potentiation of angiogenesis, epithelial-mesenchymal transition, the Warburg effect, and the tumour microenvironment. Several approaches have been studied for selective targeting of breast tumours by miRNAs, ranging from delivery systems such as extracellular vesicles and liposomes to the use of prodrugs and functionally modified vehicle-free miRNAs. While promising, these miRNA-based therapies face challenges including toxicity and immunogenicity, and greater research on their safety profiles must be performed before progressing to clinical trials.

Abstract

Distant organ metastases accounts for the majority of breast cancer deaths. Given the prevalence of breast cancer in women, it is imperative to understand the underlying mechanisms of its metastatic progression and identify potential targets for therapy. Since their discovery in 1993, microRNAs (miRNAs) have emerged as important regulators of tumour progression and metastasis in various cancers, playing either oncogenic or tumour suppressor roles. In the following review, we discuss the roles of miRNAs that potentiate four key areas of breast cancer metastasis—angiogenesis, epithelial-mesenchymal transition, the Warburg effect and the tumour microenvironment. We then evaluate the recent developments in miRNA-based therapies in breast cancer, which have shown substantial promise in controlling tumour progression and metastasis. Yet, certain challenges must be overcome before these strategies can be implemented in clinical trials.

Impact of Bone Marrow miR-21 Expression on Acute Myeloid Leukemia T Lymphocyte Fragility and Dysfunction

BACKGROUND

Acute myeloid leukemia (AML) is a hematopoietic malignancy in which antitumor immunity is impaired. The therapeutic management of AML requires understanding the mechanisms involved in the fragility and immune dysfunction of AML T lymphocytes.

METHODS

In this study, T lymphocytes from healthy donors (HD) and AML patients were used. Extracellular vesicles (EVs) from leukemic cells were screened for their microRNA content and impact on T lymphocytes. Flow cytometry, transcriptomic as well as lentiviral transduction techniques were used to carry out the research.

RESULTS

We observed increased cell death of T lymphocytes from AML patients. EVs from leukemia myeloid cell lines harbored several miRNAs, including miR-21, and were able to induce T lymphocyte death. Compared to that in HD, miR-21 was overexpressed in both the bone marrow fluid and infiltrating T lymphocytes of AML patients. MiR-21 induces T lymphocyte cell death by upregulating proapoptotic gene expression. It also increases the immunosuppressive profile of T lymphocytes by upregulating the IL13, IL4, IL10, and FoxP3 genes.

CONCLUSIONS

Our results demonstrate that miR-21 plays a significant role in AML T lymphocyte dysfunction and apoptosis. Targeting miR-21 may be a novel approach to restore the efficacy of the immune response against AML.

Epidermal growth factor stimulates exosomal microRNA-21 derived from mesenchymal stem cells to ameliorate aGVHD by modulating regulatory T cells

Regulatory T cells (Tregs), a subset of CD4⁺ T cells, may exert inhibitory effects on alloimmune responses including acute graft-versus-host disease (aGVHD), and several microRNAs are implicated in the pathophysiological process of GVHD. Therefore, we aimed in the present study to characterize the functional relevance of epidermal growth factor (EGF)-stimulated microRNA-21 (miR-21) in regulating bone marrow-derived mesenchymal stem cells (BMSCs) in a mouse model of aGVHD. We first isolated and cultured BMSCs and Tregs. Then, we examined effects of miR-21 knockdown or overexpression and EGF on cell activities of BMSCs and the expression of PTEN, Foxp3, AKT phosphorylation, and extent of c-jun phosphorylation by gain- and loss-of-function approaches. The results showed that miR-21 promoted the proliferation, invasion, and migration of BMSCs. Furthermore, miR-21 in BMSCs-derived exosomes inhibited PTEN, but enhanced AKT phosphorylation and Foxp3 expression in Tregs. In addition, EGF enhanced c-jun phosphorylation to elevate the miR-21 expression. Furthermore, EGF significantly increased the efficacy of BMSCs in a mouse model of aGVHD, manifesting in reduced IFN-γ expression and lesser organ damage. Moreover, EGF treatment promoted the Foxp3 expression of Tregs in BMSCs-treated aGVHD mice. Taken together, EGF induced the BMSCs-derived exosomal miR-21 expression, which enhanced Foxp3 expression in Tregs, thereby improving the therapeutic effect of BMSCs on aGVHD.

Noncoding RNAs in cancer immunity: functions, regulatory mechanisms, and clinical application

It is well acknowledged that immune system is deeply involved in cancer initiation and progression, and can exert both pro-tumorigenic and anti-tumorigenic effects, depending on specific microenvironment. With the better understanding of cancer-associated immune cells, especially T cells, immunotherapy was developed and applied in multiple cancers and exhibits remarkable efficacy. However, currently only a subset of patients have responses to immunotherapy, suggesting that a boarder view of cancer immunity is required. Non-coding RNAs (ncRNAs), mainly including microRNAs (miRNAs) and long noncoding RNAs (lncRNAs), are identified as critical regulators in both cancer cells and immune cells, thus show great potential to serve as new therapeutic targets to improve the response of immunotherapy. In this review, we summarize the functions and regulatory mechanisms of ncRNAs in cancer immunity, and highlight the potential of ncRNAs as novel targets for immunotherapy.

Role of microRNAs in remodeling the tumor microenvironment (Review)

MicroRNAs (miRNAs) are short non-coding RNAs that are known to regulate gene expression at the post-transcriptional level. miRNA expression is often deregulated in several human cancers, affecting the communication between tumor stroma and tumor cells, among other functions. Understanding the role of miRNAs in the tumor microenvironment is crucial for fully elucidating the molecular mechanisms underlying tumor progression and exploring novel diagnostic biomarkers and therapeutic targets. The present review focused on the role of miRNAs in remodeling the tumor microenvironment, with an emphasis on their impact on tumor growth, metastasis and resistance to treatment, as well as their potential clinical applications.

Cancer Immunotherapies Targeting Tumor-Associated Regulatory T Cells

Tumor-associated regulatory T cells (Tregs) are important effectors in the tumor microenvironment (TME), acting as accomplices in the promotion of tumor progression. Currently, the importance of removing the immunosuppressive activity in the TME has received its due attention, and Tregs have been focused on. The cytokine-receptor axes are among the essential signaling pathways in immunocytes, and tumor-associated Tregs are no exception. Therefore, manipulating cytokine-receptor pathways may be a promising effective strategy for treating various malignancies. Here, we summarize the classification, immunosuppressive mechanisms, existing immunotherapies, and potential biomarkers related to tumor-infiltrating Tregs to guide the development of effective cancer immunotherapies.

MicroRNA‑30a controls the instability of inducible CD4+ Tregs through SOCS1

Inducible regulatory T cells (iTregs) are an important subset of Tregs and play a role in the maintenance of peripheral tolerance, and the occurrence of a number of diseases, including tumors and autoimmune diseases. However, the instability of iTregs is a major obstacle for their potential application in clinical trials. The underlying mechanism of iTreg instability remains largely unknown. In the present study, the expression level of microRNA (miRNA/miR)‑30a in murine iTregs was evaluated using reverse transcription‑quantitative PCR. miR‑30a mimics and a miR‑negative control (NC) were transiently transfected into iTregs using Nucleofector technology. The effects of miR‑30a on the suppressive function of murine iTregs in vitro and in vivo were investigated using MTT, adoptive cell transfer (ACT) and flow cytometry assays, as well as a murine model of lung cancer. In the present study, it was identified that the expression level of miR‑30a was lower in murine iTregs in vitro compared with natural (n)Tregs. Furthermore, compared with miR‑NC, miR‑30a mimics impaired the suppressive function of murine iTregs on murine CD4+ T cell proliferation in vitro, which was accompanied by the altered expression of cytotoxic T lymphocyte‑associated antigen 4 and glucocorticoid induced tumor necrosis factor receptor, as well as transforming growth factor‑β and interleukin‑10. It was also observed that, compared with miR‑NC, miR‑30a mimics abrogated the suppressive effects of murine iTregs on murine CD8+ T cell function in vivo, producing an effective antitumor effect in mice bearing 3LL lung cancer cells in the ACT assay. From a mechanistic point, the expression level of suppressor of cytokine signaling 1, a putative target of miR‑30a, was elevated, altering the activation of the Akt and STAT1 pathway in the miR‑30a mimic transfected group compared with the miR‑NC group, reducing the suppressive function of murine iTregs. The present study identified a role for miR‑30a in the instability of iTregs and provided a novel insight into the development of therapeutic strategies for promoting T‑cell immunity via the regulation of iTreg instability by targeting specific miRNAs.

Antisense Oligonucleotides against miR-21 Inhibit the Growth and Metastasis of Colorectal Carcinoma via the DUSP8 Pathway

Accumulating research has documented that microRNA-21 (miR-21) plays an important role in the development of human colorectal carcinoma (CRC). Our recent work also showed that antisense oligonucleotides (ASOs) against miR-21 can impair the growth of CRC cells in vitro. However, the potential role of miR-21 in gene therapy against CRC remains to be fully elucidated. Here, we further observed the effect of ASOs against miR-21 on the growth and metastasis of CRC in vivo using a xenograft model of human CRC. We found that ASOs could effectively inhibit the growth and metastasis of CRC in vivo, accompanied by downregulated expression of miR-21 and reduced transduction of the AKT and ERK pathway. Mechanically, global gene expression analysis showed that the expression of DUSP8, a novel target of miR-21, was upregulated in tumor mass. Furthermore, overexpression of DUSP8 could remarkably suppress the proliferation and migration of CRC cells in vitro. Finally, downregulation of DUSP8 could abrogate the effects of ASOs against miR-21 on the proliferation and migration of CRC cells, as well as altered transduction of the AKT and ERK signaling pathway. Together, these data suggest that ASOs against miRNAs are an attractive and potential therapeutic for the treatment of human CRC and warrant further development.

MicroRNAs: Pleiotropic Regulators in the Tumor Microenvironment

MicroRNAs (miRNAs) are small non-coding RNAs that typically inhibit the translation and stability of messenger RNAs (mRNAs). They are ~22 nucleotides long and control both physiological and pathological processes. Altered expression of miRNAs is often associated with human diseases. Thus, miRNAs have become important therapeutic targets, and some clinical trials investigating the effect of miRNA-based therapeutics in different types of diseases have already been conducted. The tumor microenvironment (TME) comprises cells such as infiltrated immune cells, cancer-associated endothelial cells (CAEs) and cancer-associated fibroblasts (CAFs), and all the components participate in the complicated crosstalk with tumor cells to affect tumor progression. Altered miRNAs expression in both these stromal and tumor cells could drive tumorigenesis. Thus, in this review, we discuss how aberrantly expressed miRNAs influence tumor progression; summarize the crosstalk between infiltrated immune cells, CAEs, CAFs, and tumor cells through miRNAs, and clarify the important roles of miRNAs in the tumor microenvironment, which may facilitate the clinical application of miRNA-based therapies.

Overview upon miR-21 in lung cancer: focus on NSCLC

Considering the high mortality rate encountered in lung cancer, there is a strong need to explore new biomarkers for early diagnosis and also improved therapeutic targets to overcome this issue. The implementation of microRNAs as important regulators in cancer and other pathologies expanded the possibilities of lung cancer management and not only. MiR-21 represents an intensively studied microRNA in many types of cancer, including non-small cell lung cancer (NSCLC). Its role as an oncogene is underlined in multiple studies reporting the upregulated expression of this sequence in patients diagnosed with this malignancy; moreover, several studies associated this increased expression of miR-21 with a worse outcome within NSCLC patients. The same pattern is supported by the data existent in the Cancer Genome Atlas (TCGA). The carcinogenic advantage generated by miR-21 in NSCLC resides in the target genes involved in multiple pathways such as cell growth and proliferation, angiogenesis, invasion and metastasis, but also chemo- and radioresistance. Therapeutic modulation of miR-21 by use of antisense sequences entrapped in different delivery systems has shown promising results in impairment of NSCLC. Hereby, we review the mechanisms of action of miR-21 in cancer and the associated changes upon tumor cells together a focused perspective on NSCLC signaling, prognosis and therapy.

miR-466a Targeting of TGF-β2 Contributes to FoxP3+ Regulatory T Cell Differentiation in a Murine Model of Allogeneic Transplantation

The promise of inducing immunological tolerance through regulatory T cell (Treg) control of effector T cell function is crucial for developing future therapeutic strategies to treat allograft rejection as well as inflammatory autoimmune diseases. In the current study, we used murine allograft rejection as a model to identify microRNA (miRNA) regulation of Treg differentiation from naïve CD4 cells. We performed miRNA expression array in CD4+ T cells in the draining lymph node (dLN) of mice which received syngeneic or allogeneic grafts to determine the molecular mechanisms that hinder the expansion of Tregs. We identified an increase in miRNA cluster 297-669 (C2MC) after allogeneic transplantation, in CD4+ T cells, such that 10 of the 27 upregulated miRNAs were all from this cluster, with one of its members, mmu-miR-466a-3p (miR-466a-3p), targeting transforming growth factor beta 2 (TGF-β2), as identified through reporter luciferase assay. Transfection of miR-466a-3p in CD4+ T cells led to a decreased inducible FoxP3+ Treg generation while inhibiting miR-466a-3p expression through locked nucleic acid resulting in increased Tregs and a reduction in effector T cells. Furthermore, in vivo inhibition of miR-466a-3p in an allogeneic skin-graft model attenuated T cell response against the graft through an increase in TGF-β2. TGF-β2 was as effective as TGF-β1 at both inducing Tregs and through adoptive transfer, mitigating host effector T cell response against the allograft. Together, the current study demonstrates for the first time a new role for miRNA-466a-3p and TGF-β2 in the regulation of Treg differentiation and thus offers novel avenues to control inflammatory disorders.

MicroRNA-126 deficiency enhanced the activation and function of CD4+ T cells by elevating IRS-1 pathway

Recent evidence has shown that microRNA-126 (miR-126) has been involved in the development and function of immune cells, which contributed to the pathogenesis of related clinical diseases. However, the potential role of miR-126 in the development and function of CD4+ T cells remains largely unknown. Here we first found that the activation and proliferation, as well as the expression of interferon (IFN)-γ, of CD4+ T cells from miR-126 knock-down (KD) mice using the miRNA-sponge technique were enhanced significantly in vitro, compared with those in CD4+ T cells from wild-type (WT) mice. To monitor further the possible effect of miR-126 deficiency on the function of CD4+ T cells in vivo, we used dextran sulphate sodium (DSS)-induced murine model of acute autoimmune colitis and found that miR-126 deficiency could elevate the pathology of colitis. Importantly, the proportion of CD4+ T cells in splenocytes increased significantly in miR-126KD mice. Moreover, the expression levels of CD69 and CD44 on CD4+ T cells increased significantly and the expression level of CD62L decreased significantly. Of note, adoptive cell transfer assay showed that the pathology of colitis was more serious in carboxyfluorescein succinimidyl ester (CFSE)-labelled miR-126KD CD4+ T cell-transferred group, compared with that in the CFSE-labelled WT CD4+ T cells transferred group. Consistently, the expression levels of CD69 and CD44 on CFSE+ cells increased significantly. Furthermore, both the proliferation and IFN-γ secretion of CFSE+ cells also increased significantly in the CFSE-labelled miR-126KD CD4+ T cell-transferred group. Mechanistic evidence showed that the expression of insulin receptor substrate 1 (IRS-1), as a functional target of miR-126, was elevated in CD4+ T cells from miR-126KD mice, accompanied by altered transduction of the extracellular regulated kinase, protein B (AKT) and nuclear factor kappa B (NF-κB) pathway. Our data revealed a novel role in which miR-126 was an intrinsic regulator in the function of CD4+ T cells, which provided preliminary basis for exploring further the role of miR-126 in the development, function of CD4+ T cells and related clinical diseases.

Micro-RNA 10a Is Increased in Feline T Regulatory Cells and Increases Foxp3 Protein Expression Following In Vitro Transfection

CD4⁺CD25⁺Foxp3⁺ T regulatory (Treg) cells are activated during the course of lentiviral infection and exhibit heightened suppressor function when compared to Treg cells from uninfected controls. Foxp3 is essential to Treg cell function and multiple studies have documented that lentivirus-activated Treg cells exhibit heightened Foxp3 expression when compared to Treg cells from uninfected controls. Our hypothesis was that lentivirus-induced micro-RNAs (miRNAs) contribute to heightened Treg cell suppressor function by stabilizing Foxp3 expression. We demonstrated that CD4⁺CD25⁺ T cells from both feline immunodeficiency virus infected (FIV⁺) cats and uninfected control cats exhibit increased miRNA 10a and 21 levels compared to autologous CD4⁺CD25- T cells but there was no difference in the levels of these miRNAs when Treg cells from FIV⁺ cats were compared to Treg cells from uninfected controls. Further, there was no increase in Foxp3 mRNA following transfection of miRNA 10a or 21 into a feline cell line. However, transfection with miRNA 10a resulted in increased Foxp3 protein expression.

New Insights into Regulatory T Cells: Exosome- and Non-Coding RNA-Mediated Regulation of Homeostasis and Resident Treg Cells

Regulatory T (Treg) cells are a group of cells that are heterogeneous in origin and in functional activity. Treg cells comprise a necessary balance to adaptive immune responses. As key regulators of self-tolerance, Treg cells have been involved in a series of pathologic processes and considered as therapeutic targets. Here, we summarize recent research regarding Treg cell origins and their functional classification, highlight the role of exosomes and non-coding RNA in modulating Treg cell homeostasis, and discuss the current understanding of resident Treg cells.

Triptolide reduces proliferation and enhances apoptosis of human non-small cell lung cancer cells through PTEN by targeting miR-21

Triptolide is used in traditional Chinese medicine. It has the advantages of a unique mechanism of action, a wide antitumor spectrum, multiple targets, multi-channel effects and low toxicity. The current study was conducted to evaluate whether the potential anticancer effects of triptolide reduces proliferation and enhances apoptosis of human non‑small cell lung cancer (NSCLC) cells, and to assess the underlying anticancer mechanisms. In PC‑9 cells, treatment with triptolide reduced cell proliferation and increased cell apoptosis and caspase‑3 and 9 activity. Triptolide treatment reduced miR‑21 expression and enhanced phosphatase and tensin homolog (PTEN) protein expression levels in the PC‑9 cells. Furthermore, the upregulation of miR‑21 expression levels suppressed the effect of triptolide on cell viability and PTEN protein expression levels in PC‑9 cells. To the best of our knowledge, the present study is the first to demonstrate that triptolide reduced the proliferation and enhanced the apoptosis of human NSCLC cells through PTEN by targeting miR-21.

Noncoding RNAs and pancreatic cancer

Noncoding RNAs (ncRNAs) represent a class of RNA molecules that typically do not code for proteins. Emerging data suggest that ncRNAs play an important role in several physiological and pathological conditions such as cancer. The best-characterized ncRNAs are the microRNAs (miRNAs), which are short, approximately 22-nucleotide sequences of RNA of approximately 22-nucleotide in length that regulate gene expression at the posttranscriptional level, through transcript degradation or translational repression. MiRNAs can function as master gene regulators, impacting a variety of cellular pathways important to normal cellular functions as well as cancer development and progression. In addition to miRNAs, long ncRNAs, which are transcripts longer than 200 nucleotides, have recently emerged as novel drivers of tumorigenesis. However, the molecular mechanisms of their regulation and function, and the significance of other ncRNAs such as piwi-interacting RNAs in pancreas carcinogenesis are largely unknown. This review summarizes the growing body of evidence supporting the vital roles of ncRNAs in pancreatic cancer, focusing on their dysregulation through both genetic and epigenetic mechanisms, and highlighting the promise of ncRNAs in diagnostic and therapeutic applications of pancreatic cancer.