DNA Methylation of miR-7 is a Mechanism Involved in Platinum Response through MAFG Overexpression in Cancer Cells

Current data and future perspectives on DNA methylation in ovarian cancer (Review)

Ovarian cancer (OC) represents the most prevalent malignancy of the female reproductive system. Its distinguishing features include a high aggressiveness, substantial morbidity and mortality, and a lack of apparent symptoms, which collectively pose significant challenges for early detection. Given that aberrant DNA methylation events leading to altered gene expression are characteristic of numerous tumor types, there has been extensive research into epigenetic mechanisms, particularly DNA methylation, in human cancers. In the context of OC, DNA methylation is often associated with the regulation of critical genes, such as BRCA1/2 and Ras‑association domain family 1A. Methylation modifications within the promoter regions of these genes not only contribute to the pathogenesis of OC, but also induce medication resistance and influence the prognosis of patients with OC. As such, a more in‑depth understanding of DNA methylation underpinning carcinogenesis could potentially facilitate the development of more effective therapeutic approaches for this intricate disease. The present review focuses on classical tumor suppressor genes, oncogenes, signaling pathways and associated microRNAs in an aim to elucidate the influence of DNA methylation on the development and progression of OC. The advantages and limitations of employing DNA methylation in the diagnosis, treatment and prevention of OC are also discussed. On the whole, the present literature review indicates that the DNA methylation of specific genes could potentially serve as a prognostic biomarker for OC and a therapeutic target for personalized treatment strategies. Further investigations in this field may yield more efficacious diagnostic and therapeutic alternatives for patients with OC.

A review on regulation of DNA methylation during post-myocardial infarction

Myocardial infarction (MI) imposes a huge medical and economic burden on society, and cardiac repair after MI involves a complex series of processes. Understanding the key mechanisms (such as apoptosis, autophagy, inflammation, and fibrosis) will facilitate further drug development and patient treatment. Presently, a substantial body of evidence suggests that the regulation of epigenetic processes contributes to cardiac repair following MI, with DNA methylation being among the notable epigenetic factors involved. This article will review the research on the mechanism of DNA methylation regulation after MI to provide some insights for future research and development of related drugs.

Prediction of Chemoresistance-How Preclinical Data Could Help to Modify Therapeutic Strategy in High-Grade Serous Ovarian Cancer

High-grade serous ovarian cancer (HGSOC) is one of the most lethal tumors generally and the most fatal cancer of the female genital tract. The approved standard therapy consists of surgical cytoreduction and platinum/taxane-based chemotherapy, and of targeted therapy in selected patients. The main therapeutic problem is chemoresistance of recurrent and metastatic HGSOC tumors which results in low survival in the group of FIGO III/IV. Therefore, the prediction and monitoring of chemoresistance seems to be of utmost importance for the improvement of HGSOC management. This type of cancer has genetic heterogeneity with several subtypes being characterized by diverse gene signatures and disturbed peculiar epigenetic regulation. HGSOC develops and metastasizes preferentially in the specific intraperitoneal environment composed mainly of fibroblasts, adipocytes, and immune cells. Different HGSOC subtypes could be sensitive to distinct sets of drugs. Moreover, primary, metastatic, and recurrent tumors are characterized by an individual biology, and thus diverse drug responsibility. Without a precise identification of the tumor and its microenvironment, effective treatment seems to be elusive. This paper reviews tumor-derived genomic, mutational, cellular, and epigenetic biomarkers of HGSOC drug resistance, as well as tumor microenvironment-derived biomarkers of chemoresistance, and discusses their possible use in the novel complex approach to ovarian cancer therapy and monitoring.

miR-124 as a Liquid Biopsy Prognostic Biomarker in Small Extracellular Vesicles from NSCLC Patients

Despite advances in non-small cell lung cancer (NSCLC) research, this is still the most common cancer type that has been diagnosed up to date. microRNAs have emerged as useful clinical biomarkers in both tissue and liquid biopsy. However, there are no reliable predictive biomarkers for clinical use. We evaluated the preclinical use of seven candidate miRNAs previously identified by our group. We collected a total of 120 prospective samples from 88 NSCLC patients. miRNA levels were analyzed via qRT-PCR from tissue and blood samples. miR-124 gene target prediction was performed using RNA sequencing data from our group and interrogating data from 2952 NSCLC patients from two public databases. We found higher levels of all seven miRNAs in tissue compared to plasma samples, except for miR-124. Our findings indicate that levels of miR-124, both free-circulating and within exosomes, are increased throughout the progression of the disease, suggesting its potential as a marker of disease progression in both advanced and early stages. Our bioinformatics approach identified KPNA4 and SPOCK1 as potential miR-124 targets in NSCLC. miR-124 levels can be used to identify early-stage NSCLC patients at higher risk of relapse.

microRNA-660 Enhances Cisplatin Sensitivity via Decreasing SATB2 Expression in Lung Adenocarcinoma

Increasing evidence suggests that microRNAs' (miRNAs) abnormal expression is one of the main factors of chemotherapy resistance in various cancers. However, the role of miRNAs in lung adenocarcinoma (LUAD) resistance to cisplatin is still unclear. In this study, we analyzed a microarray dataset to investigate miRNAs related to cisplatin resistance in LUAD. The expression of miRNAs in LUAD tissues and cell lines was detected using real-time quantitative polymerase chain reaction (RT-qPCR). Special AT-Rich Sequence-Binding Protein 2 (SATB2) in LUAD cell lines was detected using RT-qPCR and Western blot. Cell proliferation was measured by CCK8 and colony formation assays, while cell cycle and apoptosis were measured by flow cytometry. A dual-luciferase reporter assay was performed to confirm that SATB2 is a target gene of microRNA-660 (miR-660). We showed that the expression of miR-660 was not only decreased in LUAD cells and tissues but also further decreased in the cisplatin-resistant A549 cell line. The overexpression of miR-660 increased cisplatin sensitivity in LUAD cells. In addition, we identified SATB2 as a direct target gene of miR-660. We also revealed that miR-660 increased cisplatin sensitivity in LUAD cells via targeting SATB2. In conclusion, miR-660/SATB2 axis is a key regulator of cisplatin resistance in LUAD.

NRF2 signaling pathway: A comprehensive prognostic and gene expression profile analysis in breast cancer

Breast cancer is the most frequently diagnosed malignant tumor in women and a major public health concern. NRF2 axis is a cellular protector signaling pathway protecting both normal and cancer cells from oxidative damage. NRF2 is a transcription factor that binds to the gene promoters containing antioxidant response element-like sequences. In this report, differential expression of NRF2 signaling pathway elements, as well as the correlation of NRF2 pathway mRNAs with various clinicopathologic characteristics, including molecular subtypes, tumor grade, tumor stage, and methylation status, has been investigated in breast cancer using METABRIC and TCGA datasets. In the current report, our findings revealed the deregulation of several NRF2 signaling elements in breast cancer patients. Moreover, there were negative correlations between the methylation of NRF2 genes and mRNA expression. The expression of NRF2 genes significantly varied between different breast cancer subtypes. In conclusion, substantial deregulation of NRF2 signaling components suggests an important role of these genes in breast cancer. Because of the clear associations between mRNA expression and methylation status, DNA methylation could be one of the mechanisms that regulate the NRF2 pathway in breast cancer. Differential expression of Hippo genes among various breast cancer molecular subtypes suggests that NRF2 signaling may function differently in different subtypes of breast cancer. Our data also highlights an interesting link between NRF2 components' transcription and tumor grade/stage in breast cancer.

Cisplatin Resistance: Genetic and Epigenetic Factors Involved

Cisplatin (CDDP) is the drug of choice against different types of cancer. However, tumor cells can acquire resistance to the damage caused by cisplatin, generating genetic and epigenetic changes that lead to the generation of resistance and the activation of intrinsic resistance mechanisms in cancer cells. Among them, we can find mutations, alternative splicing, epigenetic-driven expression changes, and even post-translational modifications of proteins. However, the molecular mechanisms by which CDDP resistance develops are not clear but are believed to be multi-factorial. This article highlights a description of cisplatin, which includes action mechanism, resistance, and epigenetic factors involved in cisplatin resistance.

The role of non-coding RNAs in chemotherapy for gastrointestinal cancers

Gastrointestinal (GI) cancers, including colorectal, gastric, hepatic, esophageal, and pancreatic tumors, are responsible for large numbers of deaths around the world. Chemotherapy is the most common approach used to treat advanced GI cancer. However, chemoresistance has emerged as a critical challenge that prevents successful tumor elimination, leading to metastasis and recurrence. Chemoresistance mechanisms are complex, and many factors and pathways are involved. Among these factors, non-coding RNAs (ncRNAs) are critical regulators of GI tumor development and subsequently can induce resistance to chemotherapy. This occurs because ncRNAs can target multiple signaling pathways, affect downstream genes, and modulate proliferation, apoptosis, tumor cell migration, and autophagy. ncRNAs can also induce cancer stem cell features and affect the epithelial-mesenchymal transition. Thus, ncRNAs could possibly act as new targets in chemotherapy combinations to treat GI cancer and to predict treatment response.

Transcriptional epigenetic regulation of Fkbp1/Pax9 genes is associated with impaired sensitivity to platinum treatment in ovarian cancer

Background

In an effort to contribute to overcoming the platinum resistance exhibited by most solid tumors, we performed an array of epigenetic approaches, integrating next-generation methodologies and public clinical data to identify new potential epi-biomarkers in ovarian cancer, which is considered the most devastating of gynecological malignancies.

Methods

We cross-analyzed data from methylome assessments and restoration of gene expression through microarray expression in a panel of four paired cisplatin-sensitive/cisplatin-resistant ovarian cancer cell lines, along with publicly available clinical data from selected individuals representing the state of chemoresistance. We validated the methylation state and expression levels of candidate genes in each cellular phenotype through Sanger sequencing and reverse transcription polymerase chain reaction, respectively. We tested the biological role of selected targets using an ectopic expression plasmid assay in the sensitive/resistant tumor cell lines, assessing the cell viability in the transfected groups. Epigenetic features were also assessed in 189 primary samples obtained from ovarian tumors and controls.

Results

We identified PAX9 and FKBP1B as potential candidate genes, which exhibited epigenetic patterns of expression regulation in the experimental approach. Re-establishment of FKBP1B expression in the resistant OVCAR3 phenotype in which this gene is hypermethylated and inhibited allowed it to achieve a degree of platinum sensitivity similar to the sensitive phenotype. The evaluation of these genes at a translational level revealed that PAX9 hypermethylation leads to a poorer prognosis in terms of overall survival. We also set a precedent for establishing a common epigenetic signature in which the validation of a single candidate, MEST, proved the accuracy of our computational pipelines.

Conclusions

Epigenetic regulation of PAX9 and FKBP1B genes shows that methylation in non-promoter areas has the potential to control gene expression and thus biological consequences, such as the loss of platinum sensitivity. At the translational level, PAX9 behaves as a predictor of chemotherapy response to platinum in patients with ovarian cancer. This study revealed the importance of the transcript-specific study of each gene under potential epigenetic regulation, which would favor the identification of new markers capable of predicting each patient’s progression and therapeutic response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01149-8.

LINC01436 Inhibited miR-585-3p Expression and Upregulated MAPK1 Expression to Promote Gastric Cancer Progression

BACKGROUND

Gastric cancer (GC) is a prevalent type of digestion system malignancies. Dysregulation of long non-coding RNAs (lncRNAs) has been proven to be prognostic factors and biological regulators in human cancers.

AIMS

The current study aimed to explore the role of long intergenic non-protein coding RNA 1436 (LINC01436) and its underlying mechanism in the progression of GC.

METHODS

RT-qPCR was conducted to measure RNA expression. Western blot was used for exploration of protein level. CCK-8, caspase-3 activity, and transwell assays were applied to evaluate the proliferative, apoptotic, and migratory abilities of GC cells, respectively. Mechanical experiments were used to probe the molecular interplay between genes.

RESULTS

High LINC01436 level suggested low overall survival in GC patients, and LINC01436 was highly expressed in GC tissues and cells. Besides, LINC01436 knockdown hampered cell proliferation and migration, while facilitated cell apoptosis. Mechanistically, LINC01436 upregulated mitogen-activated protein kinase 1 (MAPK1) expression by competitively binding with miR-585-3p and inhibiting miR-585-3p expression. Furthermore, LINC01436 negatively regulated miR-585-3p expression by enhancing the zeste 2 polycomb repressive complex 2 subunit (EZH2)-induced trimethylation of histone H3 at lysine 27 (H3K27me3) on miR-585-3p promoter. Final rescue assays revealed that overexpression of MAPK1 could rescue the suppressive influence of LINC01436 depletion on GC progression.

CONCLUSIONS

LINC01436 epigenetically silences miR-585-3p and acts as miR-585-3p to upregulate MAPK1 expression and promote GC progression.

Systematic Investigation of DNA Methylation Associated With Platinum Chemotherapy Resistance Across 13 Cancer Types

Background: Platinum resistance poses a significant problem for oncology clinicians. As a result, the role of epigenetics and DNA methylation in platinum-based chemoresistance has gained increasing attention from researchers in recent years. A systematic investigation of aberrant methylation patterns related to platinum resistance across various cancer types is urgently needed.

Methods: We analyzed the platinum chemotherapy response-related methylation patterns from different perspectives of 618 patients across 13 cancer types and integrated transcriptional and clinical data. Spearman’s test was used to evaluate the correlation between methylation and gene expression. Cox analysis, the Kaplan-Meier method, and log-rank tests were performed to identify potential risk biomarkers based on differentially methylated positions (DMPs) and compare survival based on DMP values. Support vector machines and receiver operating characteristic curves were used to identify the platinum-response predictive DMPs.

Results: A total of 3,703 DMPs (p value < 0.001 and absolute delta beta >0.10) were identified, and the DMP numbers of each cancer type varied. A total of 39.83% of DMPs were hypermethylated and 60.17% were hypomethylated in platinum-resistant patients. Among them, 405 DMPs (Benjamini and Hochberg adjusted p value < 0.05) were found to be associated with prognosis in tumor patients treated with platinum-based regimens, and 664 DMPs displayed the potential to predict platinum chemotherapy response. In addition, we defined six DNA DMPs consisting of four gene members (mesothelin, protein kinase cAMP-dependent type II regulatory subunit beta, msh homeobox 1, and par-6 family cell polarity regulator alpha) that may have favorable prognostic and predictive values for platinum chemotherapy.

Conclusion: The methylation-transcription axis exists and participates in the complex biological mechanism of platinum resistance in various cancers. Six DMPs and four associated genes may have the potential to serve as promising epigenetic biomarkers for platinum-based chemotherapy and guide clinical selection of optimal treatment.

Double Insurance for OC: miRNA-Mediated Platinum Resistance and Immune Escape

Ovarian cancer (OC) is still the leading cause of death among all gynecological malignancies, despite the recent progress in cancer therapy. Immune escape and drug resistance, especially platinum-based chemotherapy, are significant factors causing disease progression, recurrence and poor prognosis in OC patients. MicroRNAs(miRNAs) are small noncoding RNAs, regulating gene expression at the transcriptional level. Accumulating evidence have indicated their crucial roles in platinum resistance. Importantly, they also act as mediators of tumor immune escape/evasion. In this review, we summarize the recent study of miRNAs involved in platinum resistance of OC and systematically analyses miRNAs involved in the regulation of OC immune escape. Further understanding of miRNAs roles and their possible mechanisms in platinum resistance and tumor escape may open new avenues for improving OC therapy.

A MAPK/miR-29 Axis Suppresses Melanoma by Targeting MAFG and MYBL2

The miR-29 family of microRNAs is encoded by two clusters, miR-29b1~a and miR-29b2~c, and is regulated by several oncogenic and tumor suppressive stimuli. While in vitro evidence suggests a tumor suppressor role for miR-29 in melanoma, the mechanisms underlying its deregulation and contribution to melanomagenesis have remained elusive. Using various in vitro systems, we show that oncogenic MAPK signaling paradoxically stimulates transcription of pri-miR-29b1~a and pri-miR-29b2~c, the latter in a p53-dependent manner. Expression analyses in melanocytes, melanoma cells, nevi, and primary melanoma revealed that pri-miR-29b2~c levels decrease during melanoma progression. Inactivation of miR-29 in vivo with a miRNA sponge in a rapid melanoma mouse model resulted in accelerated tumor development and decreased overall survival, verifying tumor suppressive potential of miR-29 in melanoma. Through integrated RNA sequencing, target prediction, and functional assays, we identified the transcription factors MAFG and MYBL2 as bona fide miR-29 targets in melanoma. Our findings suggest that attenuation of miR-29b2~c expression promotes melanoma development, at least in part, by derepressing MAFG and MYBL2.

The Role of miRNA-7 in the Biology of Cancer and Modulation of Drug Resistance

MicroRNAs (miRNAs, miRs) are small non-coding RNA (ncRNA) molecules capable of regulating post-transcriptional gene expression. Imbalances in the miRNA network have been associated with the development of many pathological conditions and diseases, including cancer. Recently, miRNAs have also been linked to the phenomenon of multidrug resistance (MDR). MiR-7 is one of the extensively studied miRNAs and its role in cancer progression and MDR modulation has been highlighted. MiR-7 is engaged in multiple cellular pathways and acts as a tumor suppressor in the majority of human neoplasia. Its depletion limits the effectiveness of anti-cancer therapies, while its restoration sensitizes cells to the administered drugs. Therefore, miR-7 might be considered as a potential adjuvant agent, which can increase the efficiency of standard chemotherapeutics.

Revisiting chemoresistance in ovarian cancer: Mechanism, biomarkers, and precision medicine

Among the gynecological cancers, ovarian cancer is the most lethal. Its therapeutic options include a combination of chemotherapy with platinum-based compounds and cytoreductive surgery. Most ovarian cancer patients exhibit an initial response to platinum-based therapy, however, platinum resistance has led to up to 80% of this responsive cohort becoming refractory. Ovarian cancer recurrence and drug resistance to current chemotherapeutic options is a global challenge. Chemo-resistance is a complex phenomenon that involves multiple genes and signal transduction pathways. Therefore, it is important to elucidate on the underlying molecular mechanisms involved in chemo-resistance. This inform decisions regarding therapeutic management and help in the identification of novel and effective drug targets. Studies have documented the individual biomarkers of platinum-resistance in ovarian cancer that are potential therapeutic targets. This review summarizes the molecular mechanisms of platinum resistance in ovarian cancer, novel drug targets, and clinical outcomes.

Nanoparticle delivery systems to combat drug resistance in ovarian cancer

Due to the lack of early symptoms and difficulty of accurate diagnosis, ovarian cancer is the most lethal gynecological cancer faced by women. First-line therapy includes a combination of tumor resection surgery and chemotherapy regimen. However, treatment becomes more complex upon recurrence due to development of drug resistance. Drug resistance has been linked to many mechanisms, including efflux transporters, apoptosis dysregulation, autophagy, cancer stem cells, epigenetics, and the epithelial-mesenchymal transition. Thus, developing and choosing effective therapies is exceptionally complex. There is a need for increased specificity and efficacy in therapies for drug-resistant ovarian cancer, and research in targeted nanoparticle delivery systems aims to fulfill this challenge. Although recent research has focused on targeted nanoparticle-based therapies, few of these therapies have been clinically translated. In this review, non-viral nanoparticle delivery systems developed to overcome drug-resistance in ovarian cancer were analyzed, including their structural components, surface modifications, and drug-resistance targeted mechanisms.

Ursolic acid protects against cisplatin‑induced ototoxicity by inhibiting oxidative stress and TRPV1‑mediated Ca2+‑signaling

Cisplatin (CDDP) is widely used in clinical settings for the treatment of various cancers. However, ototoxicity is a major side effect of CDDP, and there is an associated risk of irreversible hearing loss. We previously demonstrated that CDDP could induce ototoxicity via activation of the transient receptor potential vanilloid receptor 1 (TRPV1) pathway and subsequent induction of oxidative stress. The present study investigated whether ursolic acid (UA) treatment could protect against CDDP‑induced ototoxicity. UA is a triterpenoid with strong antioxidant activity widely used in China for the treatment of liver diseases. This traditional Chinese medicine is mainly isolated from bearberry, a Chinese herb. The present results showed that CDDP increased auditory brainstem response threshold shifts in frequencies associated with observed damage to the outer hair cells. Moreover, CDDP increased the expression of TRPV1, calpain 2 and caspase‑3 in the cochlea, and the levels of Ca2+ and 4‑hydroxynonenal. UA co‑treatment significantly attenuated CDDP‑induced hearing loss and inhibited TRPV1 pathway activation. In addition, UA enhanced CDDP‑induced growth inhibition in the human ovarian cancer cell line SKOV3, suggesting that UA synergizes with CDDP in vitro. Collectively, the present data suggested that UA could effectively attenuate CDDP‑induced hearing loss by inhibiting the TRPV1/Ca²+/calpain‑oxidative stress pathway without impairing the antitumor effects of CDDP.

Roles of microRNAs in Ovarian Cancer Tumorigenesis: Two Decades Later, What Have We Learned?

Ovarian cancer is one of the top gynecological malignancies that cause deaths among females in the United States. At the molecular level, significant progress has been made in our understanding of ovarian cancer development and progression. MicroRNAs (miRNAs) are short, single-stranded, highly conserved non-coding RNA molecules (19–25 nucleotides) that negatively regulate target genes post-transcriptionally. Over the last two decades, mounting evidence has demonstrated the aberrant expression of miRNAs in different human malignancies, including ovarian carcinomas. Deregulated miRNAs can have profound impacts on various cancer hallmarks by repressing tumor suppressor genes. This review will discuss up-to-date knowledge of how the aberrant expression of miRNAs and their targeted genes drives ovarian cancer initiation, proliferation, survival, and resistance to chemotherapies. Understanding the mechanisms by which these miRNAs affect these hallmarks should allow the development of novel therapeutic strategies to treat these lethal malignancies.

MiR-7 Functions as a Tumor Suppressor by Targeting the Oncogenes TAL1 in T-Cell Acute Lymphoblastic Leukemia

BACKGROUND

T-cell acute lymphoblastic leukemia is a hematologic malignancy characterized by T-cell proliferation, and in many cases, the ectopic expression of the oncogenic transcription factor T-cell acute lymphocytic leukemia protein 1 (TAL1). MicroRNA-7 has been shown to play a critical role in proliferation, migration, and treatment sensitivity in a diverse array of cancers. In this study, we sought to establish a novel link between microRNA-7 and T-cell acute lymphoblastic leukemia oncogenesis.

MATERIAL AND METHOD

To do so, we characterized gene expression of microRNA-7 as well as TAL1 in both T-cell acute lymphoblastic leukemia patient-derived tissue and cell lines, as well as performing functional luciferase assays to assess microRNA-7 binding to the TAL1 3'-untranslated region. We also performed growth, apoptosis, and migration experiments using 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide, Annexin V, and transwell assays in the context of microRNA-7 overexpression.

RESULTS

We found that microRNA-7 expression is attenuated and inversely correlated with TAL1 expression in TAL1 + T-cell acute lymphoblastic leukemia cells. Additionally, microRNA-7 directly targets and suppresses TAL1 levels. Finally, microRNA-7 overexpression reduces growth, motility, and migration while inducing apoptosis in T-cell acute lymphoblastic leukemia cells, phenotypes that can be rescued by concomitant overexpression of TAL1.

CONCLUSIONS

These results indicate that microRNA-7 functions as a potent tumor suppressor by inhibiting the oncogene TAL1 and suggest microRNA-7 could function as a prognostic biomarker and possible therapeutic in the clinical management of T-cell acute lymphoblastic leukemia.

MicroRNA-654-3p enhances cisplatin sensitivity by targeting QPRT and inhibiting the PI3K/AKT signaling pathway in ovarian cancer cells

Dysregulation of microRNAs serves a crucial role in the chemosensitivity to cisplatin (DDP) in ovarian cancer (OVC). The abnormal expression of microRNA (miR)-654-3p has been reported in several types of human cancer. However, the association between miR-654-3p and cisplatin resistance in human OVC remains unclear. The present study aimed to investigate the role and mechanism of miR-654-3p in DDP resistance in OVC. The results demonstrated that miR-654-3p was significantly downregulated in ovarian cancer tissues and cells, as well as DDP-resistant IGROV-1/DDP cells, compared with adjacent non-tumoral tissue and IOSE386 cells. Overexpression of miR-654-3p significantly suppressed the proliferation and migration of ovarian cancer cells and increased the sensitivity of IGROV-1/DDP cells to DDP. Luciferase reporter assay demonstrated that quinolinate phosphoribosyl transferase (QPRT) was a target of miR-654-3p; overexpression of miR-654-3p inhibited QPRT expression by binding to the 3'-untranslated region of QPRT. In addition, inhibition of miR-654-3p reversed the suppressive effects of QPRT-targeting short interfering RNA on the proliferation and chemoresistance of ovarian cancer cells. Therefore, the results of the present study revealed a previously unrecognized regulatory mechanism that miR-654-3p enhances DDP sensitivity of OVC cells by downregulating QPRT expression; in addition, the present study highlighted the therapeutic implications of miR-654-3p upregulation in OVC.

When Oxidative Stress Meets Epigenetics: Implications in Cancer Development

Cancer is one of the leading causes of death worldwide and it can affect any part of the organism. It arises as a consequence of the genetic and epigenetic changes that lead to the uncontrolled growth of the cells. The epigenetic machinery can regulate gene expression without altering the DNA sequence, and it comprises methylation of the DNA, histones modifications, and non-coding RNAs. Alterations of these gene-expression regulatory elements can be produced by an imbalance of the intracellular environment, such as the one derived by oxidative stress, to promote cancer development, progression, and resistance to chemotherapeutic treatments. Here we review the current literature on the effect of oxidative stress in the epigenetic machinery, especially over the largely unknown ncRNAs and its consequences toward cancer development and progression.

microRNAs as biomarkers of ovarian cancer

Introduction: Ovarian carcinoma (OC) is the leading cause of death in women with gynecologic cancers. Most patients are diagnosed at an advanced stage with a low five-year survival rate of 20-30%. Discovering novel biomarkers for early detection and outcome prediction of OC is an urgent medical need. miRNAs, a group of small non-coding RNAs, play critical roles in multiple biologic processes and cancer pathogenesis.Areas covered: We provide an in-depth look at the functions of miRNAs in OC, particularly focusing on their roles in chemoresistance and metastasis in OC. We also discuss the biological and clinical significance of miRNAs in exosomes and expand on long non-coding RNA which acts as ceRNA of miRNAs.Expert opinion: miRNAs participate in many biological processes including proliferation, apoptosis, chemoresistance, metastasis, epithelial-mesenchymal transition, and cancer stem cell. They will substantially contribute to our understanding of OC pathogenesis. Given their resistance to the degradation of ribonucleases and availability in plasma exosomes, miRNAs may serve as emerging biomarkers for cancer detection, therapeutic assessment, and prognostic prediction. Being a messenger, exosomal miRNAs are crucial for the crosstalk between cancer cells and stromal cells in tumor microenvironment.

A Novel Role for the Tumor Suppressor Gene ITF2 in Tumorigenesis and Chemotherapy Response

Despite often leading to platinum resistance, platinum-based chemotherapy continues to be the standard treatment for many epithelial tumors. In this study we analyzed and validated the cytogenetic alterations that arise after treatment in four lung and ovarian paired cisplatin-sensitive/resistant cell lines by 1-million microarray-based comparative genomic hybridization (array-CGH) and qRT-PCR methodologies. RNA-sequencing, functional transfection assays, and gene-pathway activity analysis were used to identify genes with a potential role in the development of this malignancy. The results were further explored in 55 lung and ovarian primary tumors and control samples, and in two extensive in silico databases. Long-term cell exposure to platinum induces the frequent deletion of ITF2 gene. Its expression re-sensitized tumor cells to platinum and recovered the levels of Wnt/β-catenin transcriptional activity. ITF2 expression was also frequently downregulated in epithelial tumors, predicting a worse overall survival. We also identified an inverse correlation between ITF2 and HOXD9 expression, revealing that Non-small cell lung cancer (NSCLC) patients with lower expression of HOXD9 had a better overall survival rate. We defined the implication of ITF2 as a molecular mechanism behind the development of cisplatin resistance probably through the activation of the Wnt-signaling pathway. This data highlights the possible role of ITF2 and HOXD9 as novel therapeutic targets for platinum resistant tumors.

DNA Hypomethylation of miR-30a Mediated the Protection of Hypoxia Postconditioning Against Aged Cardiomyocytes Hypoxia/Reoxygenation Injury Through Inhibiting Autophagy

BACKGROUND

Ischemic postconditioning (IPostC) is an endogenous protective mechanism to reduce ischemia-reperfusion (I/R) injury. However, whether IPostC protects aged cardiomyocytes against I/R injury is not fully understood. Considering the protective function of microRNA 30a (miR-30a) against ischemia-induced injury in H9C2 cells, its role in the protective effects of IPostC on I/R injury of aged cardiomyocytes was investigated further.Methods and Results:To mimic I/R and IPostC in vitro, the aged cardiomyocyte model for hypoxia postconditioning (HPostC) treatment was established by 9 days of incubation with 8 mg/mL D-galactose and then followed by exposure to hypoxic environment. HPostC significantly alleviated hypoxia/reoxygenation (H/R) injury and reduced autophagy of aged cardiomyocytes, as evidenced by decreased LC3B-II expression and increased p62 by Western blot. Quantified by quantitative real-time polymerase chain reaction (qRT-PCR), miR-30a was increased in aged cardiomyocytes treated with HPostC compared with I/R injury group. Overexpression of miR-30a by LV3-rno-miR-30a mimic promoted cardioprotective effect of HPostC in aged cardiomyocytes by suppressing BECN1-mediated autophagy, all of which was abrogated by knockdown of miR-30a expression. Epigenetic analyses demonstrated that HPostC reduced DNA methyltransferase 3b-mediated DNA hypomethylation levels at miR-30a promoter, leading to upregulation of miR-30a.

CONCLUSIONS

HPostC protected aged cardiomyocytes survival against H/R injury via DNMT3b-dependent activation of miR-30a. miR-30a could be a potential therapeutic target for ischemic myocardial infarction.

Investigation of the Genome-Wide Genetic and Epigenetic Networks for Drug Discovery Based on Systems Biology Approaches in Colorectal Cancer

Colorectal cancer (CRC) is the third most commonly diagnosed type of cancer worldwide. The mechanisms leading to the progression of CRC are involved in both genetic and epigenetic regulations. In this study, we applied systems biology methods to identify potential biomarkers and conduct drug discovery in a computational approach. Using big database mining, we constructed a candidate protein-protein interaction network and a candidate gene regulatory network, combining them into a genome-wide genetic and epigenetic network (GWGEN). With the assistance of system identification and model selection approaches, we obtain real GWGENs for early-stage, mid-stage, and late-stage CRC. Subsequently, we extracted core GWGENs for each stage of CRC from their real GWGENs through a principal network projection method, and projected them to the Kyoto Encyclopedia of Genes and Genomes pathways for further analysis. Finally, we compared these core pathways resulting in different molecular mechanisms in each stage of CRC and identified carcinogenic biomarkers for the design of multiple-molecule drugs to prevent the progression of CRC. Based on the identified gene expression signatures, we suggested potential compounds combined with known CRC drugs to prevent the progression of CRC with querying Connectivity Map (CMap).

Hypermethylation of Anti-oncogenic MicroRNA 7 is Increased in Emphysema Patients

INTRODUCTION

MicroRNA-7 (miR-7) has a suppressive role in lung cancer and alterations in its DNA methylation may contribute to tumorigenesis. As COPD patients with emphysema have a higher risk of lung cancer than other COPD phenotypes, we compared the miR-7 methylation status among smoker subjects and patients with various COPD phenotypes to identify its main determinants.

METHODS

30 smoker subjects without airflow limitation and 136 COPD patients without evidence of cancer were recruited in a prospective study. Clinical and functional characteristics were assessed and patients were classified into: frequent exacerbator, emphysema, chronic bronchitis and asthma COPD overlap (ACO). DNA collected from buccal epithelial samples was isolated and bisulfite modified. miR-7 methylation status was evaluated by quantitative methylation-specific polymerase chain reaction (qMSP).

RESULTS

miR-7 Methylated levels were higher in COPD patients than in smokers without airflow limitation (23.7±12.4 vs. 18.5±8.8%, p=0.018). Among COPD patients, those with emphysema had higher values of methylated miR-7 (27.1±10.2%) than those with exacerbator (19.4±9.9%, p=0.004), chronic bronchitis (17.3±9.0%, p=0.002) or ACO phenotypes (16.0±7.2%, p=0.010). After adjusting for clinical parameters, differences between emphysematous patients and those with other phenotypes were retained. In COPD patients, advanced age, mild-moderate airflow limitation, reduced diffusing capacity and increased functional residual capacity were identified as independent predictors of methylated miR-7 levels.

CONCLUSION

The increase of miR-7 methylation levels experienced by COPD patients occurs mainly at the expense of the emphysema phenotype, which might contribute to explain the higher incidence of lung cancer in these patients.

Methylation-mediated silencing of miR-133a-3p promotes breast cancer cell migration and stemness via miR-133a-3p/MAML1/DNMT3A positive feedback loop

Background

miR-133a-3p has been recently discovered to be down-regulated in various human malignancies, including breast cancer, and reduced miR-133a-3p levels have been significantly associated with breast cancer cell growth and invasion. However, the regulatory mechanisms leading to abnormal expression of miR-133a-3p in breast cancer remain obscure.

Methods

qRT-PCR was applied to detect the expression of miR-133a-3p in breast cancer tissues and cell lines. Bisulfite sequencing was used to detect the degree of methylation of the miR-133a-3p promoter. The effects of miR-133a-3p on breast cancer in vitro were examined by cell proliferation assay, transwell assay, flow cytometry, and western blotting. Bioinformatic analysis, dual-luciferase assay and RIP assay were employed to identify the interaction between miR-133a-3p and MAML1. A xenograft model was used to show the metastasis of breast cancer cells.

Results

We confirmed that miR-133a-3p was silenced by DNA hypermethylation in breast cancer cell lines and tissues, which predicted poor prognosis in breast cancer patients, and reducing miR-133a-3p expression led to a significant increase in the migration, invasion, proliferation, and stemness of breast cancer cells in vitro. Mastermind-like transcriptional coactivator 1 (MAML1) was confirmed to be a target of miR-133a-3p involved in regulating breast cancer metastasis both in vitro and in vivo. Moreover, a series of investigations indicated that MAML1 initiated a positive feedback loop, which could up-regulate DNA methyltransferase 3A (DNMT3A) to promote hypermethylation of the miR-133a-3p promoter.

Conclusion

Taken together, our findings revealed a novel miR-133a-3p/MAML1/DNMT3A positive feedback loop in breast cancer cells, which may become a potential therapeutic target for breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1400-z) contains supplementary material, which is available to authorized users.

Effects of AntagomiRs on Different Lung Diseases in Human, Cellular, and Animal Models

INTRODUCTION

MiRNAs have been shown to play a crucial role among lung cancer, pulmonary fibrosis, tuberculosis (TBC) infection, and bronchial hypersensitivity, thus including chronic obstructive pulmonary disease (COPD) and asthma. The oncogenic effect of several miRNAs has been recently ruled out. In order to act on miRNAs turnover, antagomiRs have been developed.

MATERIALS AND METHODS

The systematic review was conducted under the PRISMA guidelines (registration number is: CRD42019134173). The PubMed database was searched between 1 January 2000 and 30 April 2019 under the following search strategy: (((antagomiR) OR (mirna antagonists) OR (mirna antagonist)) AND ((lung[MeSH Terms]) OR ("lung diseases"[MeSH Terms]))). We included original articles, published in English, whereas exclusion criteria included reviews, meta-analyses, single case reports, and studies published in a language other than English.

RESULTS AND CONCLUSIONS

A total of 68 articles matching the inclusion criteria were retrieved. Overall, the use of antagomiR was seen to be efficient in downregulating the specific miRNA they are conceived for. The usefulness of antagomiRs was demonstrated in humans, animal models, and cell lines. To our best knowledge, this is the first article to encompass evidence regarding miRNAs and their respective antagomiRs in the lung, in order to provide readers a comprehensive review upon major lung disorders.

miR-7 methylation as a biomarker to predict poor survival in early-stage non-small cell lung cancer patients

Non-small-cell lung cancer (NSCLC) is the most common malignancy worldwide. Platinum-based chemotherapy is the standard of care for these patients. Recent research showed that miR-7 methylation status is a biomarker of cisplatin resistance in lung and ovarian cancer cells, which is one of the major limitations associated with their clinical management. The aim of the present study is to provide clinical insights associated with this novel potential biomarker in NSCLC patients by comparing the miR-7 methylation status with the cisplatin treatment response. Our results analyzed in 81 samples show that miR-7 methylation is a common event in tumor tissue and it is more frequent as the stage of the disease advances, remaining in 75% of metastatic patients. Tumor miR-7 unmethylation trend to a better PFS in early stages, and when our data was validated in an extended "in silico" cohort of 969 patients we obtained a significant increment in PFS and OS in those patients harboring miR-7 unmethylated (p = 0.010 and p = 0.007 respectively). When we select those early-stages patients harbouring miR-7 methylation, we observed that adenocarcinoma patients present a dramatic decrease in PFS compared with squamous cell carcinoma patients (median 18.9 versus 59.7 months, p = 0.002). In conclusion, our results show that presence of miR-7 methylation in early-stage NSCLC is suggestive of aggressive behavior, especially for adenocarcinoma patients. One major challenge in early diagnosis in NSCLC is identify the subgroup of patients that could benefit for adjuvant therapy, our data establish the basis for epigenetic classification on early-stage NSCLC that could influence treatment decisions in the future.

LncRNA MAFG-AS1 boosts the proliferation of lung adenocarcinoma cells via regulating miR-744-5p/MAFG axis

Lung adenocarcinoma (LUAD) is typically featured by a low 5-year survival rate, hence there is a necessary to investigate new biomarkers in LUAD progression. Competing endogenous RNA (ceRNA) network has been widely reported in the regulation of tumor processes, which is also the main direction of this paper. Based on the data of GEPIA database, lncRNA MAFG-AS1 was upregulated in LUAD tissues, which was associated with poor prognosis of patients. Proliferation or apoptosis of LUAD cells were measured by CCK-8, EdU and caspase-3 activity assays followed by Western blot. The results indicated that silencing of MAFG-AS1 suppressed cell proliferation but induced cell apoptosis. RNA FISH staining showing the cytoplasmic localization of MAFG-AS1 in LUAD cells. Mechanism detection revealed that MAFG-AS1 served as a molecular sponge of miR-744-5p to upregulate its nearby gene MAF bZIP transcription factor G (MAFG) in LUAD cells. Functionally, MAFG overexpression attenuated the cellular processes mediated by MAFG-AS1 knockdown. In summary, this study unveiled the MAFG-AS1/miR-744-5p/MAFG axis in LUAD, providing a potent and promising therapeutic target for LUAD patients.

MicroRNA‑214 suppresses the viability, migration and invasion of human colorectal carcinoma cells via targeting transglutaminase 2

Colorectal carcinoma (CRC) is a common malignancy of the digestive tract. MicroRNA (miR)-214 is considered a key hub that controls tumor networks; therefore, the effects of miR-214 on CRC were examined and its target gene was investigated in this study. The expression levels of transglutaminase 2 (TGM2) and miR-214 were detected in CRC and adjacent normal tissues by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting, and luciferase activity was analyzed by dual luciferase reporter analysis. In addition, cell viability, invasion and migration were measured by Cell Counting kit-8 and Transwell assays, respectively. The expression levels of epithelial-mesenchymal transition-related proteins, and phosphoinositide-3 kinase (PI3K)/protein kinase B (Akt) signaling-associated factors were detected using RT-qPCR and western blotting. The results demonstrated that miR-214 expression was downregulated in CRC tissue, whereas TGM2 expression was upregulated. According to TargetScan prediction, miR-214 possesses a binding site to TGM2. In addition, transfection with miR-214 mimics markedly suppressed the viability of LoVo cells. miR-214 overexpression also inhibited cell invasion and migration by increasing E-cadherin and tissue inhibitor of metalloproteinases-2 expression, and decreasing matrix metalloproteinase (MMP)-2 and MMP-9 expression. Furthermore, miR-214 downregulated phosphorylation of PI3K and Akt; however, the expression levels of total PI3K and Akt were not affected by miR-214. In conclusion, this study indicated that TGM2 was a target gene of miR-214, and a negative correlation between miR-214 and TGM2 expression was determined in CRC. Notably, miR-214 markedly suppressed the viability, invasion and migration of CRC cells, which may be associated with a downregulation in PI3K/Akt signaling. These findings suggested that miR-214 may be considered a novel target for the treatment of CRC.

Long non-coding RNA TPTEP1 inhibits hepatocellular carcinoma progression by suppressing STAT3 phosphorylation

BACKGROUND

Hepatocellular carcinoma (HCC) is still the most common cause of tumor-related death worldwide and accumulating studies report that long non-coding RNAs (LncRNAs) are closely related with HCC development, metastasis and prognosis. Cisplatinum, a well-known chemotherapeutic drug, has been widely used for treatment of numerous human cancers including HCC. This study aimed to investigate the differential expressions of LncRNAs in HCC cells treated with cisplatinum and its underlying mechanism.

METHODS

The differential expressions of LncRNAs in HCC cells treated with cisplatinum were determined by RNA-seq. The roles of TPTEP1 in HCC development by applying gene function gain and loss analysis in MHCC97H and QYG-7703 cell lines were detected by quantitative real-time polymerase chain reaction (qRT-PCR), cell proliferation, colony formation, cell invasion and flow cytometry assays. The underlying mechanism of TPTEP1 sensitizing hepatocellular carcinoma cells to cisplatinum was examined by RNA-pull down, western blotting, subcellular fractionation, RNA immunoprecipitation and dual luciferase reporter assays. The effect of TPTEP1 on tumorigenesis in vivo was performed with a subcutaneous xenograft mouse model of HCC. In addition, TPTEP1 expression was detected in clinical tumor tissue samples by qRT-PCR.

RESULTS

LncRNA TPTEP1 was highly expressed in cisplatinum-treated HCC cells, which sensitizes hepatocellular carcinoma cell to cisplatinum-induced apoptosis. TPTEP1 overexpression inhibited, while TPTEP1 knockdown promoted HCC cell proliferation, tumorigenicity and invasion. Furthermore, TPTEP1 exerted its tumor suppressing activities by interacting with signal transducer and activator of transcription 3 (STAT3) to inhibit its phosphorylation, homodimerization, nuclear translocation and down-stream genes transcription. Moreover, TPTEP1 overexpression obviously inhibits tumor masses in vivo in a subcutaneous xenograft mouse model of HCC and TPTEP1 is frequently downregulated in HCC tissues, compared to its corresponding pre-tumor tissues.

CONCLUSION

LncRNA TPTEP1 inhibits hepatocellular carcinoma cells progression by affecting IL-6/STAT3 signaling. Taken together, our findings suggest a tumor suppressing role of TPTEP1 in HCC progression and provide a novel understanding of TPTEP1 during the chemotherapy for HCC.

miR‑210‑3p regulates cell growth and affects cisplatin sensitivity in human ovarian cancer cells via targeting E2F3

The potential role of microRNA (miR)‑210‑3p in carcinogenesis and the cisplatin sensitivity of ovarian cancer were evaluated in the present study. The relative expression levels of miR‑210‑3p in cisplatin‑sensitive SKOV‑3 cells and cisplatin‑resistant SKOV‑3/DDP cells were determined using reverse transcription‑quantitative polymerase chain reaction analysis. miR‑210‑3p mimics and inhibitors were transfected into SKOV‑3/DDP cells. Cell Counting Kit‑8, scratch and Transwell invasion assays and flow cytometry were conducted to evaluate the role of miR‑210‑3p in ovarian cancer cells. A luciferase reporter assay was used to verify the association between miR‑210‑3p and E2F transcription factor 3 (E2F3). Drug sensitivity was evaluated by treating the cells with cisplatin. The expression level of miR‑210‑3p was lower in SKOV‑3/DDP cells than in SKOV‑3 cells. Compared with the untransfected control, SKOV‑3 cells transfected with miR‑210‑3p exhibited a significantly higher survival rate. The overexpression of miR‑210‑3p inhibited SKOV‑3/DDP cell proliferation, migration and invasion, and promoted cell apoptosis. By contrast, the inhibition of miR‑210‑3p promoted cell migration and invasion. The luciferase reporter assay confirmed that E2F3 was a direct target gene of miR‑210‑3p. Cisplatin treatment resulted in a sharp decrease in the survival rate of SKOV‑3/DDP cells transfected with the miR‑210‑3p mimics. The decrease in cell survival rate caused by the overexpression of miR‑210‑3p was rescued by the overexpression of E2F3 in SKOV‑3/DDP cells. Taken together, these results suggest that miR‑210‑3p may act as a tumor suppressor in ovarian cancer cells and affect the sensitivity of cells to cisplatin by directly targeting E2F3. This indicates its potential use as a therapeutic target for improving drug resistance in ovarian cancer.

MiR-26b regulates 5-FU-resistance in human colorectal cancer via down-regulation of Pgp

Chemotherapy resistance frequently drives tumor progression. However, the underlying molecular mechanisms remain unclear. In this study, we found that the expression level of miR-26b was down-regulated in the human colorectal cancer tissues and the resistant cells strains: HT-29/5-FU and LOVO/5-FU cells. Meanwhile, we showed that miR-26b improved sensibility of colorectal cancer cells to 5-FU in vitro and enhanced the potency of 5-FU in the inhibition of tumor growth in vivo. We further demonstrated that the tumor suppressive role of miR-26b was mediated by negatively regulating P-glycoprotein (Pgp) protein expression. Furthermore, studies of colorectal cancer specimens indicated that the expression of miR-26b and Pgp had inverse correlation. Importantly, we found that CpG islands in the miR-26b promoter region were hypermethylated in 5-FU resistant cells. Our study is the first to identify the tumor suppressive role of over-expressed miR-26b in chemo-sensitivity. Identification of a novel miRNA-mediated pathway that regulates chemo-sensitivity in colorectal cancer will facilitate the development of novel therapeutic strategies in the future.

MAFG is a potential therapeutic target to restore chemosensitivity in cisplatin-resistant cancer cells by increasing reactive oxygen species

Adjuvant chemotherapy for solid tumors based on platinum-derived compounds such as cisplatin is the treatment of choice in most cases. Cisplatin triggers signaling pathways that lead to cell death, but it also induces changes in tumor cells that modify the therapeutic response, thereby leading to cisplatin resistance. We have recently reported that microRNA-7 is silenced by DNA methylation and is involved in the resistance to platinum in cancer cells through the action of the musculoaponeurotic fibrosarcoma oncogene family, protein G (MAFG). In the present study, we first confirm the miR-7 epigenetic regulation of MAFG in 44 normal- and/or tumor-paired samples in non-small-cell lung cancer (NSCLC). We also provide translational evidence of the role of MAFG and the clinical outcome in NSCLC by the interrogation of two extensive in silico databases of 2019 patients. Moreover, we propose that MAFG-mediated resistance could be conferred due to lower reactive oxygen species production after cisplatin exposure. We developed specifically selected aptamers against MAFG, with high sensitivity to detect the protein at a nuclear level probed by aptacytochemistry and histochemistry analyses. The inhibition of MAFG activity through the action of the specific aptamer apMAFG6F increased the levels of reactive oxygen species production and the sensitivity to cisplatin. We report first the specific nuclear identification of MAFG as a novel detection method for diagnosis in NSCLC, and then we report that MAFG modulates the redox response and confers cell protection against free radicals generated after platinum administration, thus also being a promising therapeutic target.

miR-7 Suppresses Tumor Progression by Directly Targeting MAP3K9 in Pancreatic Cancer

Extensive research has suggested that miR-7 plays a critical role in cancer progression. However, the biological function of miR-7 in pancreatic cancer (PC) progression is poorly understood. Therefore, in the present study, we investigated the function of miR-7 and its molecular mechanism in PC progression. We used multiple methods, such as MTT, FACS, Transwell assay, RT-PCR, western blotting, and transfection to investigate the role of miR-7 in PC cells. We found that miR-7 suppressed cell growth, migration, and invasion but induced apoptosis in PC cells. Moreover, overexpression of miR-7 repressed tumor growth in mice, suggesting that miR-7 could exert its tumor-suppressive function in PC. Mechanistically, we validated that MAP3K9 is a direct target of miR-7, which significantly enhanced PC cell proliferation and inhibited cell apoptosis partly through activation of the MEK/ERK pathway and NF-κB pathway. Moreover, rescue experiments also showed that miR-7 suppressed PC cell proliferation and induced PC cell apoptosis by directly targeting MAP3K9, leading to inhibition of the MEK/ERK and NF-κB pathways. Taken together, these results suggest that miR-7/MAP3K9 is critically involved in PC progression and that miR-7 may be a potential target for PC treatment.

MiR-1294 confers cisplatin resistance in ovarian Cancer cells by targeting IGF1R

BACKGROUND

Dysregulation of miRNAs is critical for chemosensitivity to platinum-based agents in ovarian cancer (OC) which is the most aggressive gynecological cancer. However, the underlying mechanisms of miRNA-regulated platinum resistance in ovarian cancer remain unclear. In this study, we intended to investigate the effect of miR-1294 on platinum-resistant OC.

METHODS

The expression of miR-1294 in OC tissues (n = 30) and cell lines was measured by qRT-PCR. Cell transfection was carried out to establish miR-1294 overexpression or knockdown. MTT and clone formation assays were performed to examine proliferation in OC cells. Additionally, wound healing and tumor invasion assays were used to investigate cell migration and invasion, respectively. Finally, the expression of epithelial-to-mesenchymal transition (EMT)-associated proteins was measured in OC cells by western blot.

RESULTS

Our results showed that miR-1294 dysregulation manipulated OC cisplatin resistance through regulating IGF1R. Knockdown of IGF1R decreased SKOVP/DDP cell proliferation, migration, invasion and EMT. Moreover, overexpression of miR-1294 prevented OC cisplatin resistance.

CONCLUSION

Our results indicated that epigenetic regulation of IGF1R via miR-1294 was essential for cisplatin resistance in OC and provide a new avenue for OC treatment.

An epigenomic approach to identifying differential overlapping and cis-acting lncRNAs in cisplatin-resistant cancer cells

Long noncoding RNAs (lncRNAs) are critical regulators of cell biology whose alteration can lead to the development of diseases such as cancer. The potential role of lncRNAs and their epigenetic regulation in response to platinum treatment are largely unknown. We analyzed four paired cisplatin-sensitive/resistant non-small cell lung cancer and ovarian cancer cell lines. The epigenetic landscape of overlapping and cis-acting lncRNAs was determined by combining human microarray data on 30,586 lncRNAs and 20,109 protein coding mRNAs with whole-genome bisulfite sequencing. Selected candidate lncRNAs were further characterized by PCR, gene-ontology analysis, and targeted bisulfite sequencing. Differential expression in response to therapy was observed more frequently in cis-acting than in overlapping lncRNAs (78% vs. 22%, fold change ≥1.5), while significantly altered methylation profiles were more commonly associated with overlapping lncRNAs (29% vs. 8%; P value <0.001). Moreover, overlapping lncRNAs contain more CpG islands (CGIs) (25% vs. 17%) and the majority of CGI-containing overlapping lncRNAs share these CGIs with their associated coding genes (84%). The differences in expression between sensitive and resistant cell lines were replicated in 87% of the selected candidates (P<0.05), while our bioinformatics approach identifying differential methylation was confirmed in all of the selected lncRNAs (100%). Five lncRNAs under epigenetic regulation appear to be involved in cisplatin resistance (AC091814.2, AC141928.1, RP11-65J3.1-002, BX641110, and AF198444). These novel findings provide new insights into epigenetic mechanisms and acquired resistance to cisplatin that highlight specific lncRNAs, some with unknown function, that may signal strategies in epigenetic therapies.