miR-34a attenuates glioma cells progression and chemoresistance via targeting PD-L1

TGF-β mRNA levels in circulating extracellular vesicles are associated with response to anti-PD1 treatment in metastatic melanoma

Introduction: Immune checkpoint inhibitors (ICIs) represent the standard therapy for metastatic melanoma. However, a few patients do not respond to ICIs and reliable predictive biomarkers are needed. Methods: This pilot study investigates the association between mRNA levels of programmed cell death-1 (PD-1) ligand 1 (PD-L1), interferon-gamma (IFN-γ), and transforming growth factor-β (TGF-β) in circulating extracellular vesicles (EVs) and survival in 30 patients with metastatic melanoma treated with first line anti-PD-1 antibodies. Blood samples were collected at baseline and RNA extracted from EVs; the RNA levels of PD-L1, IFN-γ, and TGF-β were analysed by digital droplet PCR (ddPCR). A biomarker-radiomic correlation analysis was performed in a subset of patients. Results: Patients with high TGF-β expression (cut-off fractional abundance [FA] >0.19) at baseline had longer median progression-free survival (8.4 vs. 1.8 months; p = 0.006) and overall survival (17.9 vs. 2.63 months; p = 0.0009). Moreover, radiomic analysis demonstrated that patients with high TGF-β expression at baseline had smaller lesions (2.41 ± 3.27 mL vs. 42.79 ± 101.08 mL, p < 0.001) and higher dissimilarity (12.01 ± 28.23 vs. 5.65 ± 8.4; p = 0.018). Discussion: These results provide evidence that high TGF-β expression in EVs is associated with a better response to immunotherapy. Further investigation on a larger patient population is needed to validate the predictive power of this potential biomarker of response to ICIs.

Role of B7 family members in glioma: Promising new targets for tumor immunotherapy

Glioma, is a representative type of intracranial tumor among adults, usually has a weak prognosis and limited treatment options. Traditional therapies, including surgery, chemotherapy, and radiotherapy, have had little impact on patient survival time. Immunotherapies designed to target the programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) signaling pathway have successfully treated various human cancers, informing the development of similar therapies for glioma. However, anti-PD-L1 response rates remain limited in glioma patients. Thus, exploring novel checkpoints targeting additional immunomodulatory pathways for activating durable antitumor immune responses and improving glioma outcomes is needed. Researchers have identified other B7 family checkpoint molecules, including PD-L2, B7-H2, B7-H3, B7-H4, and B7-H6. The current review article evaluates the expression of all 10 reported members of the B7 family in human glioma using The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) data, as well as summarizes studies evaluating the clinical meanings and functions of B7 family molecules in gliomas. B7 family checkpoints may contribute to different immunotherapeutic management options for glioma patients.

Interplay between programmed death-ligand 1 and non-coding RNAs

Programmed death-ligand 1 (PD-L1) is a transmembrane protein with essential roles in the suppression of adaptive immune responses. As an immune checkpoint molecule, PD-L1 can be exploited by cancer cells to evade the anti-tumor attacks initiated by the immune system. Thus, blockade of the PD1/PD-L1 axis can eliminate the suppressive signals and release the antitumor immune responses. Identification of the underlying mechanisms of modulation of the activity of the PD1/PD-L1 axis would facilitate the design of more efficacious therapeutic options and better assignment of patients for each option. Recent studies have confirmed the interactions between miRNAs/lncRNAs/circ-RNAs and the PD1/PD-L1 axis. In the current review, we give a summary of interactions between these transcripts and PD-L1 in the context of cancer. We also overview the consequences of these interactions in the determination of the response of patients to anti-cancer drugs.

MicroRNAs, Key Regulators in Glioma Progression as Potential Therapeutic Targets for Chinese Medicine

Gliomas are tumors of the primary central nervous system associated with poor prognosis and high mortality. The 5-year survival rate of patients with gliomas received surgery combined with chemotherapy or radiotherapy does not exceed 5%. Although temozolomide is commonly used in the treatment of gliomas, the development of resistance limits its use. MicroRNAs are non-coding RNAs involved in numerous processes of glioma cells, such as proliferation, migration and apoptosis. MicroRNAs regulate cell cycle, PI3K/AKT signal pathway, and target apoptosis-related genes (e.g., BCL6), angiogenesis-related genes (e.g., VEGF) and other related genes to suppress gliomas. Evidence illustrates that microRNAs can regulate the sensitivity of gliomas to temozolomide, cisplatin, and carmustine, thereby enhancing the efficacy of these agents. Moreover, traditional Chinese medicine (e.g., tanshinone IIA, xanthohumol, and curcumin) exert antiglioma effects by regulating the expression of microRNAs, and then microRNAs inhibit gliomas through influencing the process of tumors by targeting certain genes. In this paper, the mechanisms through which microRNAs regulate the sensitivity of gliomas to therapeutic drugs are described, and traditional Chinese medicine that can suppress gliomas through microRNAs are discussed. This review aims to provide new insights into the traditional Chinese medicine treatment of gliomas.

Mir-34a: a regulatory hub with versatile functions that controls osteosarcoma networks

Osteosarcoma (OS) is one of the most prevalent and highly aggressive bone malignancies. The treatment strategies of OS is under standard regimens, including surgical resection, chemotherapy, and other adjuvant therapy. However, the 5-year survival rate is still unsatisfactory. Previous studies have demonstrated that the expression of miR-34a decreases in osteosarcoma, which is involved in regulating numerous genes directly or indirectly at the post-transcriptional level and other pathways. Thus, miR-34a plays an important role in mediating OS cell proliferation, differentiation, migration, and apoptosis, and might be a pivotal biomarker for OS with diagnostic and therapeutic potentials. In this review, we aim to summarize the relationship between miR-34a and OS, with an emphasis on the specific mechanisms in OS development referring to miR-34a. Moreover, the potential role of miR-34a as a diagnostic, prognostic, and therapeutic candidate for OS would be presented in detail. However, the molecular mechanisms related to miR-34a and OS remain elusive, and more investigations are needed to reach a comprehensive understanding.

Cationic Nanoparticulate System for Codelivery of MicroRNA-424 and Podophyllotoxin as a Multimodal Anticancer Therapy

Because of the complexity of cancer ecosystems, the efficacy of single-agent chemotherapy is limited. Herein, we report the use of cationic nanoparticles (designated PPCNs) generated from a chemically modified form of the chemotherapeutic agent podophyllotoxin (PPT) to deliver both microRNA-424 (miR-424) and PPT to tumor cells, thus combining chemotherapy and gene therapy. We evaluated the optimal loading ratio of miR-424─which targets programmed cell death ligand 1 (PD-L1) mRNA and reduces PD-L1 production, thus promoting the attack of tumor cells by T cells─for effective delivery of miR-424 and PPCNs into nonsmall-cell lung cancer cells (H460). Because miR-424 can reverse chemotherapy resistance, treatment of the tumor cells with the combination of miR-424 and PPT enhanced their sensitivity to PPT. Because miR-424 and the PPCNs regulated PD-L1 production in different ways, the miR-424@PPCN complexes were significantly more efficacious than either miR-424 or PPCNs alone. We also demonstrated that treatment of tumor-bearing mice with these complexes significantly inhibited tumor growth and extended survival. Moreover, additional in vitro experiments revealed that the complexes could remodel the tumor immune microenvironment, relieve immunosuppression, and achieve immune normalization. This novel system for delivering a combination of PPT and miR-424 shows great potential for the multimodal treatment of lung cancer.

Transcriptional and post-transcriptional regulation of checkpoint genes on the tumour side of the immunological synapse

Cancer is a disease of the genome, therefore, its development has a clear Mendelian component, demonstrated by well-studied genes such as BRCA1 and BRCA2 in breast cancer risk. However, it is known that a single genetic variant is not enough for cancer to develop leading to the theory of multistage carcinogenesis. In many cases, it is a sequence of events, acquired somatic mutations, or simply polygenic components with strong epigenetic effects, such as in the case of brain tumours. The expression of many genes is the product of the complex interplay between several factors, including the organism’s genotype (in most cases Mendelian-inherited), genetic instability, epigenetic factors (non-Mendelian-inherited) as well as the immune response of the host, to name just a few. In recent years the importance of the immune system has been elevated, especially in the light of the immune checkpoint genes discovery and the subsequent development of their inhibitors. As the expression of these genes normally suppresses self-immunoreactivity, their expression by tumour cells prevents the elimination of the tumour by the immune system. These discoveries led to the rapid growth of the field of immuno-oncology that offers new possibilities of long-lasting and effective treatment options. Here we discuss the recent advances in the understanding of the key mechanisms controlling the expression of immune checkpoint genes in tumour cells.

MiR-4763-3p targeting RASD2as a Potential Biomarker and Therapeutic Target for Schizophrenia

Existing diagnostic methods are limited to observing appearance and demeanor, even though genetic factors play important roles in the pathology of schizophrenia. Indeed, no molecular-level test exists to assist diagnosis, which has limited treatment strategies. To address this serious shortcoming, we used a bioinformatics approach to identify 61 genes that are differentially expressed in schizophrenia patients compared with healthy controls. In particular, competing endogenous RNA network revealed the important role of the gene RASD2, which is regulated by miR-4763-3p. Indeed, analysis of blood samples confirmed that RASD2 is downregulated in schizophrenia patients. Moreover, positron emission tomography data collected for 44 human samples identified the prefrontal and temporal lobes as potential key brain regions in schizophrenia patients. Mechanistic studies indicated that miR-4763-3p inhibits RASD2 by base-pairing with the 3’ untranslated region of RASD2 mRNA. Importantly, RASD2 has been shown to interact with β-arrestin2, which contributes to the regulation of the DRD2-dependent CREB response element-binding protein pathway in the dopamine system. Finally, results obtained with a mouse model of schizophrenia revealed that inhibition of miR-4763-3p function alleviated anxiety symptoms and improved memory. The dopamine transporters in the striatal regions were significantly reduced in schizophrenia model mice as compared with wild-type mice, suggesting that inhibition of miR-4763-3p can lessen the symptoms of schizophrenia. Our findings demonstrate that miR-4763-3p may target RASD2 mRNA and thus may serve as a potential biomarker and therapeutic target for schizophrenia, providing a theoretical foundation for further studies of the molecular basis of this disease.

Tumor-derived exosomal PD-L1 in progression of cancer and immunotherapy

Cancer is a gravely important health issue all over the world and has been spreading fast. In recent years immune checkpoint treatment options have been used extensively as a primary line of treatment for different cancer types. PD-1 and its ligand, PD-L1, are members of the immune-checkpoints superfamily. Anti-PD-L1 and anti-PD-1 antibodies have shown efficacy against different cancer types, but fewer than 30% of patients have shown robust therapeutic responses and, therefore, it is hypothesized that exosomal PD-L1 is the mechanism to blame for failure in primary immune checkpoint therapy. The identical membrane topology of exosomal PD-L1 with tumor cell membrane-type provides the possibility to mimic immunosuppressive effects of tumor cell membrane PD-L1. In this review, it is discussed whether exosomal PD-L1 binds to antibodies and hence resistance to immunotherapy will be developed, and targeting exosome biogenesis inhibition can provide a new strategy to overcome tumor resistance to anti-PD-L1 therapy. Diagnostic and prognostic values of exosomal PD-L1 in different cancer types are discussed. Multiple clinical studies conclude that the level of tumor-derived exosomes (TEXs) as a biomarker for diagnosis could distinguish cancer patients from healthy controls. Elevated exosomal PD-L1 levels may be predictive of advanced disease stages, cancer metastasis, lower response to anti-PD-1/PD-L1 therapy, lower overall survival rates, and poor tumor prognosis. These novel findings of TEXs serve as promising therapeutic targets for early diagnosis and prevention of cancer progression.

Differential and Common Signatures of miRNA Expression and Methylation in Childhood Central Nervous System Malignancies: An Experimental and Computational Approach

Epigenetic modifications are considered of utmost significance for tumor ontogenesis and progression. Especially, it has been found that miRNA expression, as well as DNA methylation plays a significant role in central nervous system tumors during childhood. A total of 49 resected brain tumors from children were used for further analysis. DNA methylation was identified with methylation-specific MLPA and, in particular, for the tumor suppressor genes CASP8, RASSF1, MGMT, MSH6, GATA5, ATM1, TP53, and CADM1. miRNAs were identified with microarray screening, as well as selected samples, were tested for their mRNA expression levels. CASP8, RASSF1 were the most frequently methylated genes in all tumor samples. Simultaneous methylation of genes manifested significant results with respect to tumor staging, tumor type, and the differentiation of tumor and control samples. There was no significant dependence observed with the methylation of one gene promoter, rather with the simultaneous presence of all detected methylated genes' promoters. miRNA expression was found to be correlated to gene methylation. Epigenetic regulation appears to be of major importance in tumor progression and pathophysiology, making it an imperative field of study.

GATA1-induced upregulation of LINC01503 promotes carboplatin resistance in ovarian carcinoma by upregulating PD-L1 via sponging miR-766-5p

Background

Ovarian Carcinoma (OCa) is a high-mortality malignancy derived from female reproductive system. Increasing evidence has identified long non-coding RNAs (lncRNAs) as important regulators in OCa chemoresistance. In this study, we intended to explore the role of LINC01503 in OCa resistance to carboplatin (CBP).

Methods

Gene expression was measured by reverse transcription-quantitative PCR (RT-qPCR) in OCa cells. Western blot was adopted to detect protein levels of GATA1, PD-L1, E-cadherin, N-cadherin, Vimentin, Bcl-2, Bax, cleaved caspase-3. To assess the effects of LINC01503 on the resistance of OCa cells to CBP, Cell Counting Kit-8 (CCK-8), colony formation, Transwell, and flow cytometry experiments were performed to evaluate half-maximal inhibitory concentration (IC₅₀), cell viability, migrative and invasive ability, as well as cell apoptosis. Dual-luciferase reporter assay was employed to assess the associations between the genes.

Results

LINC01503 was upregulated in CBP-resistant OCa cells. LINC01503 knockdown reduced CBP resistance in OCa cells. Besides, GATA-binding protein 1 (GATA1) activated LINC01503 transcription in CBP-resistant OCa cells. MiR-766-5p was lowly expressed in CBP-resistant cells and confirmed as a target for LINC01503. In addition, miR-766-5p overexpression increased CBP sensitivity in OCa cells. PD-L1 was verified as the target of miR-766-5p. Besides, LINC01503 upregulated PD-L1 level by regulating miR-766-5p. Furthermore, rescue experiments showed that PD-L1 overexpression abrogated the inhibited impacts of blocking LINC01503 on CBP resistance in OCa cells.

Conclusion

GATA1-induced LINC01503 expedited CBP resistance in OCa cells via the miR-766-5p/PD-L1 axis, providing a new target for improving the efficacy of OCa chemotherapy.

Graphical Abstract

miR-34a inhibits melanoma growth by targeting ZEB1

Melanoma is a highly lethal cutaneous cancer with the tendency for early invasion and metastasis. Integrated miRNA transcriptome sequence analysis of human melanoma tumors and adjacent control tissues identified 17 miRNAs differentially expressed in melanoma tissues: let-7a-5p, let-7b-5p, let-7c, miR-374a-3p, miR-100-5p, miR-7, miR-195, miR-1908, miR-214, miR-221, miR-199a-5p, miR-21, miR-18, miR-34a, miR-199a-3p, miR-92a and miR-106b. Among these, miR-34a was most significantly down-regulated in melanoma tissues, and its expression correlated with TNM melanoma stage. miR-34a overexpression inhibited expression and activity of the transcription factor ZEB1, resulting in decreased proliferation and migration of melanoma cells. Moreover, miR-34a overexpression inhibited ZEB1 expression and melanoma tumor growth in vivo, in a melanoma nude mouse model. Together, these findings demonstrate that miR-34a inhibits melanoma growth by targeting the proto-oncogene ZEB1 and suggest the miR-34a -ZEB1 axis may serve as a novel target for melanoma treatment.

Aspects of the Tumor Microenvironment Involved in Immune Resistance and Drug Resistance

The tumor microenvironment (TME) is a complex and ever-changing "rogue organ" composed of its own blood supply, lymphatic and nervous systems, stroma, immune cells and extracellular matrix (ECM). These complex components, utilizing both benign and malignant cells, nurture the harsh, immunosuppressive and nutrient-deficient environment necessary for tumor cell growth, proliferation and phenotypic flexibility and variation. An important aspect of the TME is cellular crosstalk and cell-to-ECM communication. This interaction induces the release of soluble factors responsible for immune evasion and ECM remodeling, which further contribute to therapy resistance. Other aspects are the presence of exosomes contributed by both malignant and benign cells, circulating deregulated microRNAs and TME-specific metabolic patterns which further potentiate the progression and/or resistance to therapy. In addition to biochemical signaling, specific TME characteristics such as the hypoxic environment, metabolic derangements, and abnormal mechanical forces have been implicated in the development of treatment resistance. In this review, we will provide an overview of tumor microenvironmental composition, structure, and features that influence immune suppression and contribute to treatment resistance.

The comprehensive landscape of miR-34a in cancer research

MicroRNA-34 (miR-34) plays central roles in human diseases, especially cancers. Inactivation of miR-34 is detected in cancer cell lines and tumor tissues versus normal controls, implying its potential tumor-suppressive effect. Clinically, miR-34 has been identified as promising prognostic indicators for various cancers. In fact, members of the miR-34 family, especially miR-34a, have been convincingly proved to affect almost the whole cancer progression process. Here, a total of 512 (miR-34a, 10/21), 85 (miR-34b, 10/16), and 114 (miR-34c, 10/14) putative targets of miR-34a/b/c are predicted by at least ten miRNA databases, respectively. These targets are further analyzed in gene ontology (GO), KEGG pathway, and the Reactome pathway dataset. The results suggest their involvement in the regulation of signal transduction, macromolecule metabolism, and protein modification. Also, the targets are implicated in critical signaling pathways, such as MAPK, Notch, Wnt, PI3K/AKT, p53, and Ras, as well as apoptosis, cell cycle, and EMT-related pathways. Moreover, the upstream regulators of miR-34a, mainly including transcription factors (TFs), lncRNAs, and DNA methylation, will be summarized. Meanwhile, the potential TF upstream of miR-34a/b/c will be predicted by PROMO, JASPAR, Animal TFDB 3.0, and GeneCard databases. Notably, miR-34a is an attractive target for certain cancers. In fact, miR-34a-based systemic delivery combined with chemotherapy or radiotherapy can more effectively control tumor progression. Collectively, this review will provide a panorama for miR-34a in cancer research.

Reprogramming Transcription Factors Oct4 and Sox2 Induce a BRD-Dependent Immunosuppressive Transcriptome in GBM-Propagating Cells

A subset of stem-like cells in glioblastoma (GBM; GSC) underlies tumor propagation, therapeutic resistance, and tumor recurrence. Immune evasion is critical for GSCs to carry out these functions. However, the molecular mechanisms employed by GSCs to escape antitumor immunity remain largely unknown. The reprogramming transcription factors Oct4 and Sox2 function as core multipotency factors and play an essential role in the formation and maintenance of GSCs, but the roles of these transcription factors in GSC immune escape have not been well explored. Here we examine how Oct4/Sox2 coexpression contributes to the immunosuppressive phenotype of GSCs. Combined transcription profiling and functional studies of Oct4/Sox2 coexpressing GSCs and differentiated GBM cells demonstrated that Oct4 and Sox2 cooperatively induce an immunosuppressive transcriptome consisting of multiple immunosuppressive checkpoints (i.e., PD-L1, CD70, A2aR, TDO) and dysregulation of cytokines and chemokines that are associated with an immunosuppressive tumor microenvironment. Mechanistically, induction and function of BRD/H3k27Ac-dependent immunosuppressive genes played a role in the immunosuppressive phenotype of GSCs. Pan-BET bromodomain inhibitors (e.g., JQ1) and shBRD4 constructs significantly inhibited the immunosuppressive transcriptome and immunosuppressive biological responses induced by Oct4/Sox2. Our findings identify targetable mechanisms by which tumor-propagating GSCs contribute to the immunosuppressive microenvironment in GBM. SIGNIFICANCE: This report identifies mechanisms by which the reprogramming transcription factors Oct4 and Sox2 function to drive the immunomodulatory transcriptome of GSCs and contribute to the immunosuppressive microenvironment in GBM.

LncRNA MAFG-AS1 Suppresses the Maturation of miR-34a to Promote Glioblastoma Cell Proliferation

PURPOSE

LncRNA MAFG-AS1 plays critical roles in several types of cancer, while its role in glioblastoma (GBM) is unknown. By analyzing the TCGA dataset, we observed the upregulation of MAFG-AS1 in GBM. This study aimed to investigate the involvement of MAFG-AS1 in GBM cancer.

METHODS

The expression levels of MAFG-AS1, mature miR-34a, and miR-34a precursor in GBM and paired non-tumor tissues of 56 GBM patients were determined by RT-qPCR. Correlations are analyzed using linear regression. Overexpression of MAFG-AS1 was achieved in GBM cells, followed by measurement of the expression levels of mature miR-34a, miR-34a precursor, DICER and Drosha by RT-qPCR. The roles of MAFG-AS1 and miR-34a in regulating GBM cell proliferation were evaluated by CCK-8 assay. Flow cytometry was performed to explore the role of MAFG-AS1 and miR-34a in regulating the apoptosis and cell cycle of GBM cells. Cell scratch experiment was performed to determine the role of MAFG-AS1 and miR-34a in regulating the migration of GBM cells. Subcutaneous tumor animal model was used for in vivo study. The expressions levels of BCL-2 and caspase-3 were detected by Western blot analysis.

RESULTS

MAFG-AS1 was upregulated in GBM, while mature miR-34a was downregulated in GBM. Interestingly, MAFG-AS1 was inversely correlated with mature miR-34a but not miR-34a precursor across GBM tissues. In GBM tissues, the overexpression of MAFG-AS1 did not affect the expression levels of miR-34a precursor but reduced the expression levels of mature miR-34a. MAFG-AS1 promoted the expression of DICER and Drosha in GBM cells. Moreover, the overexpression of MAFG-AS1 promoted the proliferation of GBM cells and reduced the inhibitory effects of miR-34a on cell proliferation but did not affect cell cycle, apoptosis and migration. The overexpression of MAFG-AS1 promoted the progression of GBM in vivo by promoting the proliferation of GBM cells while miR-34a reversed the effect of overexpression of MAFG-AS1.

CONCLUSIONS

MAFG-AS1 may suppress the maturation of miR-34a to promote GBM cell proliferation.

The emerging role of miRNA in the perturbation of tumor immune microenvironment in chemoresistance: Therapeutic implications

Chemoresistance is a major hindrance in cancer chemotherapies, a leading cause of tumor recurrence and cancer-related deaths. Cancer cells develop numerous strategies to elude immune attacks and are regulated by immunological factors. Cancer cells can alter the expression of several immune modulators to upregulate the activities of immune checkpoint pathways. Targeting the immune checkpoint inhibitors is a part of the cancer immunotherapy altered during carcinogenesis. These immune modulators have the capability to reprogram the tumor microenvironment, thereby change the efficacy of chemotherapeutics. In general, the sensitivity of drugs is reduced in the immunosuppressive tumor microenvironment, resulting in chemoresistance and tumor relapse. The regulation of microRNAs (miRNAs) is well established in cancer initiation, progression, and therapy. Intriguingly, miRNA affects cancer immune surveillance and immune response by targeting immune checkpoint inhibitors in the tumor microenvironment. miRNAs alter the gene expression at the post-transcriptional level, which modulates both innate and adaptive immune systems. Alteration of tumor immune microenvironment influences drug sensitivity towards cancer cells. Besides, the expression profile of immune-modulatory miRNAs can be used as a potential biomarker to predict the response and clinical outcomes in cancer immunotherapy and chemotherapy. Recent evidences have revealed that cancer-derived immune-modulatory miRNAs might be promising targets to counteract cancer immune escape, thereby increasing drug efficacy. In this review, we have compiled the role of miRNAs in overcoming the chemoresistance by modulating tumor microenvironment and discussed their preclinical and clinical implications.

Anesthetics may modulate cancer surgical outcome: a possible role of miRNAs regulation

Background

microRNAs (miRNAs) are single-stranded and noncoding RNA molecules that control post-transcriptional gene regulation. miRNAs can be tumor suppressors or oncogenes through various mechanism including cancer cell biology, cell-to-cell communication, and anti-cancer immunity.

Main Body

Anesthetics can affect cell biology through miRNA-mediated regulation of messenger RNA (mRNA). Indeed, sevoflurane was reported to upregulate miR-203 and suppresses breast cancer cell proliferation. Propofol reduces matrix metalloproteinase expression through its impact on miRNAs, leading to anti-cancer microenvironmental changes. Propofol also modifies miRNA expression profile in circulating extracellular vesicles with their subsequent anti-cancer effects via modulating cell-to-cell communication.

Conclusion

Inhalational and intravenous anesthetics can alter cancer cell biology through various cellular signaling pathways induced by miRNAs’ modification. However, this area of research is insufficient and further study is needed to figure out optimal anesthesia regimens for cancer patients.

MicroRNAs in the Tumor Microenvironment

The tumor microenvironment (TME) is decisive for the eradication or survival of any tumor mass. Moreover, it plays a pivotal role for metastasis and for providing the metastatic niche. The TME offers special physiological conditions and is composed of, for example, surrounding blood vessels, the extracellular matrix (ECM), diverse signaling molecules, exosomes and several cell types including, but not being limited to, infiltrated immune cells, cancer-associated endothelial cells (CAEs), and cancer-associated fibroblasts (CAFs). These cells can additionally and significantly contribute to tumor and metastasis progression, especially also by acting via their own deregulated micro (mi) RNA expression or activity. Thus, miRNAs are essential players in the crosstalk between cancer cells and the TME. MiRNAs are small non-coding (nc) RNAs that typically inhibit translation and stability of messenger (m) RNAs, thus being able to regulate several cell functions including proliferation, migration, differentiation, survival, invasion, and several steps of the metastatic cascade. The dynamic interplay between miRNAs in different cell types or organelles such as exosomes, ECM macromolecules, and the TME plays critical roles in many aspects of cancer development. This chapter aims to give an overview on the multiple contributions of miRNAs as players within the TME, to summarize the role of miRNAs in the crosstalk between different cell populations found within the TME, and to illustrate how they act on tumorigenesis and the behavior of cells in the TME context. Lastly, the potential clinical utility of miRNAs for cancer therapy is discussed.

Effect of radiotherapy on T cell and PD-1 / PD-L1 blocking therapy in tumor microenvironment

Cancer is a worldwide problem that threatens human health. Radiotherapy plays an important role in a variety of cancer treatment methods. The administration of radiotherapy can alter the differentiation pathways and functions of T cells, which in turn improves the immune response of T cells. Radiotherapy can also induce up-regulation of PD-L1 expression, which means that it has great potential for enhancing the therapeutic effect of anti-PD-1/PD-L1 inhibitors and reducing the risk of drug resistance toward them. At present, the combination of radiotherapy and anti-PD-1/PD-L1 inhibitors has shown significant therapeutic effects in clinical tumor research. This review focuses on the mechanism of radiotherapy on T cells reported in recent years, as well as related research progress in the application of PD-1/PD-L1 blockers. It will provide a theoretical basis for the rational clinical application of radiotherapy combined with PD-1/PD-L1 inhibitors.

Role of non-coding RNAs in modulating the response of cancer cells to paclitaxel treatment

Paclitaxel is a chemotherapeutic substance that is administered for treatment of an extensive spectrum of human malignancies. In spite of its potent short-term effects against tumor cells, resistance to paclitaxel occurs in a number of patients precluding its long-term application in these patients. Non-coding RNAs have been shown to influence response of cancer cells to this chemotherapeutic agent via different mechanisms. Mechanistically, these transcripts regulate expression of several genes particularly those being involved in the apoptotic processes. Lots of in vivo and in vitro assays have demonstrated the efficacy of oligonucleotide-mediated microRNAs (miRNA)/ long non-coding RNAs (lncRNA) silencing in enhancement of response of cancer cells to paclitaxel. Therefore, targeted therapies against non-coding RNAs have been suggested as applicable modalities for combatting resistance to this agent. In the present review, we provide a summary of studies which assessed the role of miRNAs and lncRNAs in conferring resistance to paclitaxel.

The Extrinsic and Intrinsic Roles of PD-L1 and Its Receptor PD-1: Implications for Immunotherapy Treatment

Programmed death-ligand 1 (PD-L1) is an immune checkpoint inhibitor that binds to its receptor PD-1 expressed by T cells and other immune cells to regulate immune responses; ultimately preventing exacerbated activation and autoimmunity. Many tumors exploit this mechanism by overexpressing PD-L1 which often correlates with poor prognosis. Some tumors have also recently been shown to express PD-1. On tumors, PD-L1 binding to PD-1 on immune cells promotes immune evasion and tumor progression, primarily by inhibition of cytotoxic T lymphocyte effector function. PD-1/PD-L1-targeted therapy has revolutionized the cancer therapy landscape and has become the first-line treatment for some cancers, due to their ability to promote durable anti-tumor immune responses in select patients with advanced cancers. Despite this clinical success, some patients have shown to be unresponsive, hyperprogressive or develop resistance to PD-1/PD-L1-targeted therapy. The exact mechanisms for this are still unclear. This review will discuss the current status of PD-1/PD-L1-targeted therapy, oncogenic expression of PD-L1, the new and emerging tumor-intrinisic roles of PD-L1 and its receptor PD-1 and how they may contribute to tumor progression and immunotherapy responses as shown in different oncology models.

Long Noncoding RNA KCNQ1OT1 Confers Gliomas Resistance to Temozolomide and Enhances Cell Growth by Retrieving PIM1 From miR-761

Many studies have found that the dysregulation of long noncoding RNA (lncRNA) contributed to cancer initiation, progression, and recurrence via multiple signaling pathways. However, the underlying mechanisms of lncRNA in temozolomide (TMZ)-resistant gliomas were not well understood, hindering the improvement of TMZ-based therapies. The present study demonstrated that the lncRNA KCNQ1OT1 increased in TMZ-resistant glioma cells compared to the TMZ-sensitive cells. The introduction of KCNQ1OT1 promoted cell viability, clonogenicity, and rhodamine 123 efflux while hampering TMZ-induced apoptosis. Moreover, KCNQ1OT1 directly sponged miR-761, which decreased in TMZ-resistant sublines. The overexpression of miR-761 attenuated cell viability and clonogenicity, while triggering apoptosis and rhodamine 123 accumulation post-TMZ exposure, leading to a response to TMZ. The interaction between miR-761 and 3'-untranslated region of PIM1 attenuated PIM1-mediated signaling cascades. Furthermore, the knockdown of KCNQ1OT1 augmented the TMZ-induced tumor regression in TMZ-resistant U251 mouse models. Briefly, the present study evaluated that KCNQ1OT1 conferred TMZ resistance by releasing PIM1 expression from miR-761, resulting in the upregulation of PIM-mediated MDR1, c-Myc, and Survivin. The present findings demonstrated that the interplay of KCNQ1OT1: miR-761: PIM1 regulated chemoresistance in gliomas and provided a promising therapeutic target for TMZ-resistant glioma patients.

KCNQ1OT1 contributes to sorafenib resistance and programmed death‑ligand‑1‑mediated immune escape via sponging miR‑506 in hepatocellular carcinoma cells

Drug resistance and immune escape of tumor cells severely compromise the treatment efficiency of hepatocellular carcinoma (HCC). Long non-coding RNA KCNQ1 overlapping transcript 1 (lncRNA KCNQ1OT1) has been shown to be involved in drug resistance in several cancers. The aim of the present study was to investigate the role of KCNQ1OT1 in sorafenib resistance and immune escape of HCC cells. Reverse transcription-quantitative PCR analysis, western blotting and immunohistochemistry were performed to detect the expression of KCNQ1OT1, miR-506 and programmed death-ligand-1 (PD-L1). Cell Counting Kit-8 assay, flow cytometry and Transwell assays were used to evaluate IC₅₀ value, cell apoptosis and metastasis. ELISA was performed to detect the secretion of cytokines. Dual-luciferase reporter assay was conducted to verify the targeting relationships between miR-506 and KCNQ1OT1 or PD-L1. KCNQ1OT1 and PD-L1 were found to be upregulated and miR-506 was downregulated in sorafenib-resistant HCC tissues and cells. Furthermore, KCNQ1OT1 knockdown reduced the IC₅₀ value of sorafenib, suppressed cell metastasis and promoted apoptosis in sorafenib-resistant HCC cells. Moreover, KCNQ1OT1 knockdown changed the tumor microenvironment and T-cell apoptosis in a sorafenib-resistant HCC/T-cell co-culture model. In addition, it was demonstrated that KCNQ1OT1 functioned as a competing endogenous RNA of miR-506 and increased PD-L1 expression in sorafenib-resistant HCC cells. miR-506 inhibition abolished the effects of KCNQ1OT1 knockdown on sorafenib sensitivity, tumor growth, the tumor microenvironment and T-cell apoptosis. In conclusion, KCNQ1OT1 knockdown inhibited sorafenib resistance and PD-L1-mediated immune escape by sponging miR-506 in sorafenib-resistant HCC cells.

Epigenetic Mechanisms of Resistance to Immune Checkpoint Inhibitors

Immune checkpoint inhibitors (ICIs) have demonstrated to be highly efficient in treating solid tumors; however, many patients have limited benefits in terms of response and survival. This rapidly led to the investigation of combination therapies to enhance response rates. Moreover, predictive biomarkers were assessed to better select patients. Although PD-L1 expression remains the only validated marker in clinics, molecular profiling has brought valuable information, showing that the tumor mutation load and microsatellite instability (MSI) status were associated to higher response rates in nearly all cancer types. Moreover, in lung cancer, EGFR and MET mutations, oncogene fusions or STK11 inactivating mutations were associated with low response rates. Cancer progression towards invasive phenotypes that impede immune surveillance relies on complex regulatory networks and cell interactions within the tumor microenvironment. Epigenetic modifications, such as the alteration of histone patterns, chromatin structure, DNA methylation status at specific promoters and changes in microRNA levels, may alter the cell phenotype and reshape the tumor microenvironment, allowing cells to grow and escape from immune surveillance. The objective of this review is to make an update on the identified epigenetic changes that target immune surveillance and, ultimately, ICI responses, such as histone marks, DNA methylation and miR signatures. Translational studies or clinical trials, when available, and potential epigenetic biomarkers will be discussed as perspectives in the context of combination treatment strategies to enhance ICI responses in patients with solid tumors.

Overexpression of LncRNA PSMG3-AS1 Distinguishes Glioblastomas from Sarcoidosis

In clinical practices, glioblastomas (GBM) in some cases can be misdiagnosed as sarcoidosis. This study aimed to develop a biomarker to distinguish GBM from sarcoidosis. In this study, we found that PSMG3-AS1 was upregulated in plasma of GBM patients in comparison with that in sarcoidosis patients and healthy controls. Receiver operating characteristic (ROC) curve analysis showed that upregulation of PSMG3-AS1 effectively separated GBM patients from sarcoidosis patients and healthy controls. In GBM cells, overexpression of PSMG3-AS1 led to downregulated miR-34a and increased methylation of miR-34a gene. In addition, overexpression of PSMG3-AS1 reduced the inhibitory effects of miR-34a on GBM cell proliferation. In conclusion, overexpression of PSMG3-AS1 distinguishes GBM patients from patients with sarcoidosis, and PSMG3-AS1 may promote GBM cell proliferation by downregulating miR-34a through methylation.

Immunomodulatory role for MicroRNAs: Regulation of PD-1/PD-L1 and CTLA-4 immune checkpoints expression

The development and progression of different pathologies including, cancer, are associated with suppressed immune responses. This restrained immune activity could be associated with the activation of different immune checkpoint pathways that mediate immunosuppressive functions. Therapeutic Protocols based on abolishing the activity of immune check points provided a promising potential for treating cancer. Among the distinct known immune checkpoints, PD-1/PD-L1 and CTLA-4, are the most studied and have been the focus for development of different blocking agents. Monoclonal antibodies that can block PD-1, PD-L1 or CTLA4 have been approved for treatment of different cancers. MicroRNAs (miRNAs), short non-coding regulatory RNA molecules, could repress mRNA expression at a post-transcriptional level. Many miRNAs have been reported to modulate the expression of CTLA-4 and PD-1/PD-L1, either directly or indirectly, in multiple pathological cases, mainly cancer. In this review, after a brief introduction about T cell activation and immune checkpoints, the miRNAs regulating the expression of CTLA-4 and PD-1/PD-L1 are discussed with highlights on their role in cancer. Many of these miRNAs could serve as novel treatments in different types of cancer as detailed throughout the review.

Sevoflurane inhibits migration and invasion of glioma cells via regulating miR-34a-5p/MMP-2 axis

Glioma is the most common brain malignancy and surgical resection is the primary option for patient with glioma. Anesthetics could be used to inhibit cancer dissemination and metastasis during surgery. This study aims to assess the function of volatile anesthetic sevoflurane in glioma migration and invasion and explore the potential mechanism. Twenty-five patients with glioma were recruited in this study. LN229 and U251 cells were used in vitro experiments. Cell viability was analyzed by MTT analysis. Cell migration and invasion were examined via transwell analysis. microRNA-34a-5p (miR-34a-5p) and matrix metalloproteinase-2 (MMP-2) levels were measured via quantitative real-time polymerase chain reaction. The relationship of miR-34a-5p and MMP-2 was tested via bioinformatics analysis, luciferase reporter analysis, RNA immunoprecipitation and RNA pull-down. Sevoflurane decreased glioma cell migration and invasion. In glioma cells, sevoflurane up-regulated miR-34a-5p abundance and down-regulated MMP-2 level. Overexpression of miR-34a-5p contributed to sevoflurane-caused suppression of migration and invasion, while its knockdown played an opposite effect. MMP-2 was targeted via miR-34a-5p and MMP-2 silence reversed the influence of miR-34a-5p knockdown under sevoflurane. Sevoflurane exposure represses cell migration and invasion, which might be related to inhibition of MMP-2 by up-regulating miR-34a-5p. This study provides a novel mechanism for understanding the pharmacological effects of sevoflurane on glioma.

MiR-489-3p inhibits cell proliferation, migration, and invasion, and induces apoptosis, by targeting the BDNF-mediated PI3K/AKT pathway in glioblastoma

Among astrocyte tumors, glioblastoma (GBM) is the most malignant glioma, highly aggressive and invasive, with extremely poor prognosis. Previous research has reported that microRNAs (miRNAs) participate in the progression of many cancers. Thus, this study aimed to explore the role and the underlying mechanisms of microRNA (miR)-489-3p in GBM progression. The expression of miR-489-3p and brain-derived neurotrophic factor (BDNF) mRNA was measured by quantitative real-time polymerase chain reaction. Western blot analysis was used to detect BDNF protein and the PI3K/AKT pathway-related protein. Cell proliferation, apoptosis, migration, and invasion were analyzed using CKK-8 assay, flow cytometry, and transwell assay, respectively. The interaction between BDNF and miR-489-3p was explored by luciferase reporter assay and RNA immunoprecipitation (RIP) assay. MiR-489-3p was down-regulated and BDNF was up-regulated in GBM tissues and cells. MiR-489-3p re-expression or BDNF knockdown inhibited GBM cell proliferation, migration, and invasion, and promoted apoptosis. BDNF was a target of miR-489-3p, and BDNF up-regulation reversed the effects of miR-489-3p on GBM cells. The protein levels of p-AKT and p-PI3K were notably reduced in GBM cells by overexpression of miR-489-3p, but were rescued following BDNF up-regulation. Therefore, miR-489-3p inhibited proliferation, migration, and invasion, and induced apoptosis, by targeting the BDNF-mediated PI3K/AKT pathway in GBM, providing new strategies for clinical treatment of GBM.

How microRNAs affect the PD-L1 and its synthetic pathway in cancer

Programmed cell death-ligand 1 (PD-L1) is a glycoprotein that is expressed on the cell surface of both hematopoietic and nonhematopoietic cells. PD-L1 play a role in the immune tolerance and protect self-tissues from immune system attack. Dysfunction of this molecule has been highlighted in the pathogenesis of tumors, autoimmunity, and infectious disorders. MicroRNAs (miRNAs) are endogenous molecules that are classified as small non-coding RNA with approximately 20-22 nucleotides (nt) length. The function of miRNAs is based on complementary interactions with target mRNA via matching completely or incompletely. The result of this function is decay of the target mRNA or preventing mRNA translation. In the past decades, several miRNAs have been discovered which play an important role in the regulation of PD-L1 in various malignancies. In this review, we discuss the effect of miRNAs on PD-L1 expression and consider the effect of miRNAs on the synthetic pathway of PD-L1, especially during cancers.

Current advances in PD-1/PD-L1 axis-related tumour-infiltrating immune cells and therapeutic regimens in glioblastoma

Glioblastoma (GBM) is the most common malignant tumour in the brain, and current treatments are not curative and cannot control recurrence. This limitation indirectly places immunotherapy at the focus of translational GBM research. Many studies on the PD-1/PD-L1 axis in GBM are ongoing, and the immunosuppressive mechanism of PD-1/PD-L1 in GBM is different from that in other solid tumours. This review focuses on the effect of the PD-1/PD-L1 axis on infiltrating immune cells in the suppressive GBM immune microenvironment and summarizes the recent progress in PD-1/PD-L1 axis-related therapies reported in preclinical and clinical GBM studies, providing a reference for the systematic study of PD-1/PD-L1 axis-related anti-GBM immunity.

Ultrasound-Mediated Co-Delivery of miR-34a and sPD-1 Complexed with Microbubbles for Synergistic Cancer Therapy

Background

miR-34a was downregulated and PD-L1 was upregulated in cervical cancer; however, the treatment of cervical cancer lacks precision and targeting. This study explored the ultrasound-mediated co-delivery of miR-34a and sPD-1 complexes with microbubbles for synergistic cancer therapy.

Methods

Cationic lipid microbubbles (CLMBs) were prepared by membrane hydration and mechanical oscillation. U14 subcutaneous xenograft mice were injected with CLMBs-loaded sPD-1 and miR-34a combined with ultrasound targeted destruction, and tumor volume and tumor weight of mice were measured. TUNEL apoptosis test and the mRNA expression of apoptosis-related gene Bcl-2 and Bax were analyzed by qRT-PCR. Antitumor immune-related cytokines IFN-γ were investigated by qRT-PCR, LDH Cytotoxicity Assay Kit were performed to test cytotoxic T lymphocytes (CTL).

Results

CLMBs were successfully prepared and the plasmid bound to its surface. The tumor volume and weight were specifically decreased by ultrasound-mediated co-delivery of miR-34a and sPD-1 complexes with microbubbles, apoptosis was induced and the apoptosis suppressor gene Bcl-2 was downregulated and proapoptotic gene Bax were upregulated. qRT-PCR analysis revealed that antitumor immunity-related IFN-γ was strongly upregulated in mice, which were treated with CLMBs-loaded sPD-1 and miR-34a combined with ultrasound targeted destruction, and the percentage of CTL was increased.

Conclusion

These findings from the study demonstrated that CLMBs could deliver miR-34a and sPD-1, combined with ultrasound targeted destruction, could suppress the tumor tissue growing, induce apoptosis and enhance antitumor immunity in U14 subcutaneous xenograft mice.

The role of cancer-derived microRNAs in cancer immune escape

During malignant transformation, accumulated somatic mutations endow cancer cells with increased invasiveness and immunogenicity. Under selective pressure, these highly immunogenic cancer cells develop multiple strategies to evade immune attack. It has been well established that cancer cells could downregulate the expression of major histocompatibility complex, acquire alterations in interferon pathway, and upregulate the activities of immune checkpoint pathways. Besides, cancer cells secret numerous cytokines, exosomes, and microvesicles to regulate the functions and abundances of components in the tumor microenvironment including immune effector cells and professional antigen presentation cells. As the vital determinant of post-transcriptional regulation, microRNAs (miRNAs) not only participate in cancer initiation and progression but also regulate anti-cancer immune response. For instance, some miRNAs affect cancer immune surveillance and immune escape by interfering the expression of immune attack-associated molecules. A growing body of evidence indicated that cancer-derived immune modulatory miRNAs might be promising targets to counteract cancer immune escape. In this review, we summarized the role of some miRNAs in cancer immune escape and discussed their potential clinical application as treatment targets.

Micro RNA Molecules as Modulators of Treatment Resistance, Immune Checkpoints Controllers and Sensitive Biomarkers in Glioblastoma Multiforme

Based on genome sequencing, it is estimated that over 90% of genes stored in human genetic material are transcribed, but only 3% of them contain the information needed for the production of body proteins. This group also includes micro RNAs representing about 1%–3% of the human genome. Recent studies confirmed the hypothesis that targeting molecules called Immune Checkpoint (IC) open new opportunities to take control over glioblastoma multiforme (GBM). Detection of markers that indicate the presence of the cancer occupies a very important place in modern oncology. This function can be performed by both the cancer cells themselves as well as their components and other substances detected in the patients’ bodies. Efforts have been made for many years to find a suitable marker useful in the diagnosis and monitoring of gliomas, including glioblastoma.

The role of miR-34 in cancer drug resistance

Resistance to conventional chemotherapy remains a major cause of cancer relapse and cancer-related deaths. Therefore, there is an urgent need to overcome resistance barriers. To improve cancer treatment approaches, it is critical to elucidate the basic mechanisms underlying drug resistance. Increasingly, the mechanisms involving micro-RNAs (miRNAs) are studied because miRNAs are also considered practical therapeutic options due to high degrees of specificity, efficacy, and accuracy, as well as their ability to target multiple genes at the same time. Years of research have firmly established miR-34 as a key tumor suppressor miRNA whose target genes are involved in drug resistance mechanisms. Indeed, numerous articles show that low levels of circulating miR-34 or tumor-specific miR-34 expression are associated with poor response to chemotherapy. In addition, elevation of inherently low miR-34 levels in resistant cancer cells effectively restores sensitivity to chemotherapeutic agents. Here, we review this literature, also highlighting some contradictory observations. In addition, we discuss the potential utility of miR-34 expression as a predictive biomarker for chemotherapeutic drug response. Although caution needs to be exercised, miR-34 is emerging as a biomarker that could improve cancer precision medicine.

Functions and clinical significance of circular RNAs in glioma

CircRNAs are a class of single-stranded RNA molecules with a covalently closed loop structure and have been characterized by high stability, abundance, conservation, and display tissue/developmental stage-specific expression, furthermore, based on the abundance in distinct body fluids or exosomes, circRNAs present novel biomarkers and targets for the diagnosis and prognosis of cancers. Recently, the regulatory mechanisms of biogenesis and molecular functions, including miRNAs and RBPs sponge, translation as well as transcriptional and splicing regulation, have been gradually uncovered, although various aspects remained to be elucidated in combination with deep-sequence and bioinformatics. Accumulating studies have indicated that circRNAs are more enriched in neuronal tissues partly due to the abundance of specific genes promoting circularization, suggesting dysregulation of circRNAs is closely related to diseases of the nervous system, including glioma. In this review, we elaborate on the biogenesis, functions, databases as well as novel advances especially involved in the molecular pathways, highlight its great value as diagnostic or therapeutic targets in glioma.

Enhanced histone H3 acetylation of the PD-L1 promoter via the COP1/c-Jun/HDAC3 axis is required for PD-L1 expression in drug-resistant cancer cells

Background

Drug resistance is a major obstacle to treating cancers because it desensitizes cancer cells to chemotherapy. Recently, attention has been focused on changes in the tumor immune landscape after the acquisition of drug resistance. Programmed death-ligand-1 (PD-L1) is an immune suppressor that inhibits T cell-based immunity. Evidence has shown that acquired chemoresistance is associated with increased PD-L1 expression in cancer cells. However, the underlying mechanism is still largely unknown.

Methods

PD-L1 expression in three drug-resistant A549/CDDP, MCF7/ADR and HepG2/ADR cell lines was detected by qRT-PCR, western blotting and flow cytometry, and a T cell proliferation assay was performed to test its functional significance. Then, the potential roles of JNK/c-Jun, histone H3 acetylation, histone deacetylase 3 (HDAC3) and the E3 ligase COP1 in the PD-L1 increase were explored through ChIP assays and gain- and loss-of-function gene studies. Furthermore, murine xenograft tumor models were used to verify the role of JNK/c-Jun and HDAC3 in PD-L1 expression in A549/CDDP cells in vivo. Finally, the correlations of PD-L1, c-Jun and HDAC3 expression in clinical cisplatin-sensitive and cisplatin-resistant non-small cell lung cancer (NSCLC) tissues were analyzed by immunohistochemistry and Pearson’s correlation coefficient.

Results

PD-L1 expression was significantly increased in A549/CDDP, MCF7/ADR and HepG2/ADR cells and was attributed mainly to enhanced JNK/c-Jun signaling activation. Mechanistically, decreased COP1 increased c-Jun accumulation, which subsequently inhibited HDAC3 expression and thereby enhanced histone H3 acetylation of the PD-L1 promoter. Furthermore, PD-L1 expression could be inhibited by JNK/c-Jun inhibition or HDAC3 overexpression in vivo, which could largely reverse inhibited CD3⁺ T cell proliferation in vitro. PD-L1 expression was significantly increased in the cisplatin-resistant clinical NSCLC samples and positively correlated with c-Jun expression but negatively correlated with HDAC3 expression.

Conclusions

Enhanced histone H3 acetylation of the PD-L1 promoter via the COP1/c-Jun/HDAC3 axis was crucial for the PD-L1 increase in drug-resistant cancer cells. Our study reveals a novel regulatory network for the PD-L1 increase in drug-resistant cancer cells and that combined PD-L1-targeting strategies could improve T cell-based immunity in drug-resistant cancers.

The splicing FK506-binding protein-51 isoform plays a role in glioblastoma resistance through programmed cell death ligand-1 expression regulation

Gliomas aberrantly express programmed cell death ligand-1 (PD-L1), which has a pivotal role in immunoevasion. The splicing isoform of FKBP5, termed FKBP51s, is a PD-L1 foldase, assisting the immune checkpoint molecule in maturation and expression on the plasma membrane. The concept that PD-L1 supports tumor-intrinsic properties is increasingly emerging. The aim of the present work was to confirm the pro-tumoral effect of PD-L1 on human glioma cell survival, stemness capacity and resistance, and to address the issue of whether, by targeting its foldase either chemically or by silencing, the aggressive tumor features could be attenuated. PD-L1-depleted glioma cells have a reduced threshold for apoptosis, while PD-L1 forced expression increases resistance. Similar results were obtained with FKBP51s modulation. The ability of PD-L1 to counteract cell death was hampered by FKBP51s silencing. PD-L1 expression was particularly high in glioma cells with a cancer-stem-cell profile. Moreover, PD-L1 sustained the spheroid formation capability of glioma cells. Targeting of FKBP51s by small-interfering RNA (siRNA) or the specific inhibitor SAFit2, reduced the number of formed spheroids, along with PD-L1 expression. Finally, in an orthotopic mouse model of glioblastoma, daily treatment with SAFit2 significantly reduced tumor PD-L1 expression, and tumor growth. In treated mice, caspase-3 activation and reduced vimentin expression were observed in excised tumors. In conclusion, targeting of FKBP51s hampers PD-L1 and its pro-tumoral properties, thereby affecting the self-renewal and growth capacities of glioblastoma cells in vitro and in vivo.

Recent Findings in the Regulation of Programmed Death Ligand 1 Expression

With the recent approvals for the application of monoclonal antibodies that target the well-characterized immune checkpoints, immune therapy shows great potential against both solid and hematologic tumors. The use of these therapeutic monoclonal antibodies elicits inspiring clinical results with durable objective responses and improvements in overall survival. Agents targeting programmed cell death protein 1 (PD-1; also known as PDCD1) and its ligand (PD-L1) achieve a great success in immune checkpoints therapy. However, the majority of patients fail to respond to PD-1/PD-L1 axis inhibitors. Expression of PD-L1 on the membrane of tumor and immune cells has been shown to be associated with enhanced objective response rates to PD-1/PD-L1 inhibition. Thus, an improved understanding of how PD-L1 expression is regulated will enable us to better define its role as a predictive marker. In this review, we summarize recent findings in the regulation of PD-L1 expression.

Diagnostic biomarker and therapeutic target applications of miR-326 in cancers: A systematic review

MicroRNAs (miRNAs) are endogenous mediators of RNA interference and have key roles in the modulation of gene expression under healthy, inflamed, stimulated, carcinogenic, or other cells, and tissues of a pathological state. Many studies have proved the association between miRNAs and cancer. The role of miR-326 as a tumor suppressor miRNA in much human cancer confirmed. We will explain the history and the role of miRNAs changes, especially miR-326 in cancers and other pathological conditions. Attuned with these facts, this review highlights recent preclinical and clinical research performed on miRNAs as novel promising diagnostic biomarkers of patients at early stages, prediction of prognosis, and monitoring of the patients in response to treatment. All related publications retrieved from the PubMed database, with keywords such as epigenetic, miRNA, microRNA, miR-326, cancer, diagnostic biomarker, and therapeutic target similar terms from 1899 to 2018 with limitations in the English language. Recently, researchers have focused on the impacts of miRNAs and their association in inflammatory, autoinflammatory, and cancerous conditions. Recent studies have suggested a major pathogenic role in cancers and autoinflammatory diseases. Investigations have explained the role of miRNAs in cancers, autoimmunity, and autoinflammatory diseases, and so on. The miRNA-326 expression has an important role in cancer conditions and other diseases.

MicroRNA-34a-5p suppresses tumorigenesis and progression of glioma and potentiates Temozolomide-induced cytotoxicity for glioma cells by targeting HMGA2

Glioma is a frequently diagnosed brain tumors and Temozolomide (TMZ) is a common chemotherapeutic drug for glioma. High mobility group AT-hook 2 (HMGA2) was reported to be linked with glioma pathogenesis and Temozolomide (TMZ)-induced cytotoxicity. Our present study aimed to further search for the upstream regulatory microRNAs (miRNAs) of HMGA2 in glioma. RT-qPCR assay was conducted to measure the expression of HMGA2 mRNA and microRNA-34a-5p (miR-34a-5p). HMGA2 protein expression was examined by western blot assay. Cell proliferative ability and cell viability was assessed by CCK-8 assay. Cell migratory and invasive capacities were estimated by Transwell migration and invasion assay. Bioinformatics analysis and luciferase reporter assay was conducted to investigate the potential interaction between miR-34a-5p and HMGA2. Mouse xenograft experiments were performed to further test the roles of TMZ, miR-34a-5p and HMGA2, alone or in combination, in glioma tumorigenesis in vivo. We found HMGA2 expression was notably upregulated in glioma tissues and cells, and associated with glioma grade and poor prognosis. HMGA2 knockdown or miR-34a-5p overexpression inhibited migration, invasion, proliferation and enhanced TMZ-induced cytotoxicity in glioma cells. Moreover, HMGA2 was a target of miR-34a-5p. And, miR-34a-5p expression was remarkably reduced in glioma tissues and cells. MiR-34a-5p exerted its function through targeting HMGA2 in glioma cells. HMGA2 knockdown or miR-34a-5p overexpression inhibited tumor growth and enhanced TMZ-mediated anti-tumor effect in glioma xenograft models. We concluded MiR-34a-5p suppressed tumorigenesis and progression of glioma and potentiated TMZ-induced cytotoxicity for glioma cells by targeting HMGA2, deepening our understanding on molecular basis of HMGA2 in glioma.

MicroRNA-34 family: a potential tumor suppressor and therapeutic candidate in cancer

MicroRNA-34 (miR-34) has been reported to be dysregulated in various human cancers and regarded as a tumor suppressive microRNA because of its synergistic effect with the well-known tumor suppressor p53. Along with the application of MRX34, the first tumor-targeted microRNA drug which based on miR-34a mimics, on phase I clinical trial (NCT01829971), the significance of miR-34 is increasingly recognized. miR-34 plays a crucial role on repressing tumor progression by involving in epithelial-mesenchymal transition (EMT) via EMT- transcription factors, p53 and some important signal pathways. Not only that, numerous preclinical researches revealed the giant potential of miR-34a on cancer therapy through diversiform nano-scaled delivery systems. Here, we provide an overview about the function of miR-34 in various cancers and the mechanism of miR-34 in tumor-associated EMT. Furthermore, its potential role as a microRNA therapeutic candidate is also discussed. Notwithstanding some obstacles existed, the extensive application prospect of miR-34 on oncotherapy cannot be neglected.

The Prognostic and Therapeutic Value of PD-L1 in Glioma

Glioma is the most common type of primary brain tumors. After standard treatment regimen (surgical section, radiotherapy and chemotherapy), the average survival time remains merely around 14 months for glioblastoma (grade IV glioma). Recent immune therapy targeting to the immune inhibitory checkpoint axis, i.e., programmed cell death protein 1 (PD-1) and its ligand PD-L1 (i.e., CD274 or B7-H1), has achieved breakthrough in many cancers but still not in glioma. PD-L1 is considered a major prognostic biomarker for immune therapy in many cancers, with anti-PD-1 or anti-PD-L1 antibodies being used. However, the expression and subcellular distribution of PD-L1 in glioma cells exhibits great variance in different studies, severely impairing PD-L1's value as therapeutic and prognostic biomarker in glioma. The role of PD-L1 in modulating immune therapy is complicated. In addition, endogenous PD-L1 plays tumorigenic roles in glioma development. In this review, we summarize PD-L1 mRNA expression and protein levels detected by using different methods and antibodies in human glioma tissues in all literatures, and we evaluate the prognostic value of PD-L1 in glioma. We also summarize the relationships between PD-L1 and immune cell infiltration in glioma. The mechanisms regulating PD-L1 expression and the oncogenic roles of endogenous PD-L1 are discussed. Further, the therapeutic results of using anti-PD-1/PD-L1 antibodies or PD-L1 knockdown are summarized and evaluated. In summary, current results support that PD-L1 is not only a prognostic biomarker of immune therapy, but also a potential therapeutic target for glioma.

Identification of Grade-associated MicroRNAs in Brainstem Gliomas Based on Microarray Data

Gliomas arising in the brainstem are rare tumours that are difficult to surgically resect, and the microRNAs (miRNAs) and signalling pathways associated with brainstem gliomas (BSGs) are largely unknown. To identify grade-associated miRNAs in BSGs, a microarray analysis of 10 low-grade and 15 high-grade BSGs was performed in this study. Differentially expressed miRNAs (DE-miRNAs) were identified, and the functional DE-miRNAs were selected. The potential target genes and enriched pathways were analysed, and a target gene-associated protein-protein interaction (PPI) network was generated. Grade-associated functional DE-miRNAs were confirmed by real-time quantitative PCR. First, 28 functional DE-miRNAs, including 13 upregulated miRNAs and 15 downregulated miRNAs, were identified. Second, 2546 target genes that were involved in BSG-related pathways, such as signalling pathways regulating the pluripotency of stem cells, the AMPK signalling pathway, the HIF-1 signalling pathway, the PI3K-Akt signalling pathway, the Wnt signalling pathway and the Hippo signalling pathway, were screened. Third, PHLPP2 and VEGFA were identified as hub genes in the PPI network. Last, we found that hsa-miR-34a-5p inhibits BSG cell invasion in vitro. In summary, using integrated bioinformatics analysis, we have identified the potential target genes and pathways of grade-associated functional DE-miRNAs in BSGs, which could improve the accuracy of prognostic evaluation. Furthermore, these hub genes and pathways could be therapeutic targets for the treatment of BSGs.

Potential Epigenetic-Based Therapeutic Targets for Glioma

Glioma is characterized by a high recurrence rate, short survival times, high rates of mortality and treatment difficulties. Surgery, chemotherapy and radiation (RT) are the standard treatments, but outcomes rarely improve even after treatment. With the advancement of molecular pathology, recent studies have found that the development of glioma is closely related to various epigenetic phenomena, including DNA methylation, abnormal microRNA (miRNA), chromatin remodeling and histone modifications. Owing to the reversibility of epigenetic modifications, the proteins and genes that regulate these changes have become new targets in the treatment of glioma. In this review, we present a summary of the potential therapeutic targets of glioma and related effective treating drugs from the four aspects mentioned above. We further illustrate how epigenetic mechanisms dynamically regulate the pathogenesis and discuss the challenges of glioma treatment. Currently, among the epigenetic treatments, DNA methyltransferase (DNMT) inhibitors and histone deacetylase inhibitors (HDACIs) can be used for the treatment of tumors, either individually or in combination. In the treatment of glioma, only HDACIs remain a good option and they provide new directions for the treatment. Due to the complicated pathogenesis of glioma, epigenetic applications to glioma clinical treatment are still limited.

Association Between Genetic Variant in the Promoter of Pri-miR-34b/c and Risk of Glioma

Growing evidence indicates that p53 can regulate the expression of miRNAs, particularly the miR-34 family members, which are described as potential tumor suppressors. Loss of miR-34 suppresses TP53-mediated cell death, whereas over expression of miR-34 induced apoptosis. The study designed to investigate the association between the pir-miR-34b/c rs4938723, TP53 Arg72Pro and the risk of glioma. We genotyped the two polymorphisms in175 glioma patients and 235 healthy controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing assay. Association analysis showed that the CC genotype of the pir-miR-34b/c rs4938723 was associated with a significantly decreased risk of glioma compared to the TT genotype (CC vs. TT: adjusted OR = 0.43;95% CI, 0.21–0.87,P = 0.02). Moreover, a significant association between the patients with glioma and controls was also observed in a recessive model (OR = 0.41; 95% CI, 0.21–0.81, P = 0.007). In contrast, the CC genotype of the TP53 Arg72Pro was associated with a significantly increased risk of glioma compared to the GG genotype (CC vs. GG: adjusted OR = 1.73;95% CI, 1.04–2.89,P = 0.04), and a significant association between the patients with glioma and controls was also observed in a recessive model (OR = 2.00; 95% CI, 1.26–3.18, P = 0.003). These findings suggest that the pri-miR-34b/c rs4938723CC and TP53 Arg72-Pro polymorphisms may be associated with the risk of glioma.

Molecular Determinants of Malignant Brain Cancers: From Intracellular Alterations to Invasion Mediated by Extracellular Vesicles

Malignant glioma cells invade the surrounding brain parenchyma, by migrating along the blood vessels, thus promoting cancer growth. The biological bases of these activities are grounded in profound alterations of the metabolism and the structural organization of the cells, which consequently acquire the ability to modify the surrounding microenvironment, by altering the extracellular matrix and affecting the properties of the other cells present in the brain, such as normal glial-, endothelial- and immune-cells. Most of the effects on the surrounding environment are probably exerted through the release of a variety of extracellular vesicles (EVs), which contain many different classes of molecules, from genetic material to defined species of lipids and enzymes. EV-associated molecules can be either released into the extracellular matrix (ECM) and/or transferred to neighboring cells: as a consequence, both deep modifications of the recipient cell phenotype and digestion of ECM components are obtained, thus causing cancer propagation, as well as a general brain dysfunction. In this review, we first analyze the main intracellular and extracellular transformations required for glioma cell invasion into the brain parenchyma; then we discuss how these events may be attributed, at least in part, to EVs that, like the pawns of a dramatic chess game with cancer, open the way to the tumor cells themselves.