Emerging role of long non-coding RNAs in cisplatin resistance

Evaluation of Long Non-coding RNA (LncRNA) in the Pathogenesis of Chemotherapy Resistance in Cervical Cancer: Diagnostic and Prognostic Approach

Cervical cancer (CC), caused by human papillomavirus (HPV), is a leading cause of female malignancies worldwide. Therefore, understanding the underlying mechanisms of CC development and identifying novel therapeutic targets are significantly important. Cisplatin resistance is a significant challenge in the management of CC. Recent studies highlighted the critical role of long non-coding RNAs (lncRNAs) in modulation of cisplatin resistance. This comprehensive review aims to collect the current understanding roles of lncRNAs and their involvement in cisplatin resistance in CC by highlighting key processes of cancer progression, including apoptosis, proliferation, angiogenesis and epithelial-to-mesenchymal transition (EMT). We discussed the role of lncRNA in CC resistance to cisplatin through molecular pathways and examined gene expression changes. We also discussed treatment strategies and factors that reduce CC resistance to cisplatin by targeting them.

Long noncoding RNAs and their possible roles in tumorigenesis and drug resistance in cancer chemotherapy

Cancer is still one of the most important diseases that have a high mortality rate around the world. The management of cancer involves many procedures, which include surgery, radiotherapy, and chemotherapy. Drug resistance in cancer chemotherapy is considered one of the most important problems in clinical oncology. A good understanding of the tumorigenesis process and the mechanisms of developing chemotherapy resistance in cancer cells will help achieve significant advances in cancer treatment protocols. In recent years, there has been an increasing interest in long noncoding RNAs (lncRNAs). LncRNAs are no longer just a transcriptional noise, and many investigations proved their possible roles in regulating mandatory cellular functions. A lot of newly published studies confirmed the implication of lncRNAs in the tumor formation process and the multiple drug resistance in cancer chemotherapy. The main aim of this review is to focus on the lncRNAs' functions in the cell, their possible roles in the tumor formation process, and their roles in the development of chemotherapy resistance in different cancer cells.

Moving beyond cisplatin resistance: mechanisms, challenges, and prospects for overcoming recurrence in clinical cancer therapy

Cisplatin, a classical platinum-based chemotherapy agent, has been a frontline treatment for various cancers for decades. However, its effectiveness has been hindered by the development of resistance, leading to cancer relapse. Addressing this challenge is crucial for both clinical practice and research. Hence, the imperative to unravel the intricate mechanisms underpinning cisplatin resistance and to uncover novel strategies to overcome this barrier holds immense significance. Within this review, we summarized the classification of platinum agents, highlighting their roles in therapeutic landscapes. We discussed the diverse mechanisms behind cisplatin resistance, including diminished intracellular cisplatin accumulation, intracellular detoxification, DNA repair, autophagy responses, heat shock proteins, tumor microenvironment, cancer stem cells, epigenetic regulation, ferroptosis resistance, and metabolic reprogramming. Drawing from this comprehensive understanding, we offered a series of prospective solutions to surmount cisplatin resistance and consequently mitigate the specter of disease recurrence within the realm of clinical cancer therapy.

Targeting MAGI2-AS3-modulated Akt-dependent ATP-binding cassette transporters as a possible strategy to reverse temozolomide resistance in temozolomide-resistant glioblastoma cells

Drug resistance is a major impediment to the successful treatment of glioma. This study aimed to elucidate the effects and mechanisms of the long noncoding RNA membrane-associated guanylate kinase inverted-2 antisense RNA 3 (MAGI2-AS3) on temozolomide (TMZ) resistance in glioma cells. MAGI2-AS3 expression in TMZ-resistant glioblastoma (GBM) cells was analyzed using the Gene Expression Omnibus data set GSE113510 and quantitative real-time PCR (qRT-PCR). Cell viability and TMZ half-maximal inhibitory concentration values were determined using the MTT assay. Apoptosis and cell cycle distribution were evaluated using flow cytometry. The expression of multidrug resistance 1 (MDR1), ATP-binding cassette superfamily G member 2 (ABCG2), protein kinase B (Akt), and phosphorylated Akt was detected using qRT-PCR and/or western blot analysis. MAGI2-AS3 was expressed at low levels in TMZ-resistant GBM cells relative to that in their parental cells. MAGI2-AS3 re-expression alleviated TMZ resistance in TMZ-resistant GBM cells. MAGI2-AS3 overexpression also accelerated TMZ-induced apoptosis and G2/M phase arrest. Mechanistically, MAGI2-AS3 overexpression reduced MDR1 and ABCG2 expression and inhibited the Akt pathway, whereas Akt overexpression abrogated the reduction in MDR1 and ABCG2 expression induced by MAGI2-AS3. Moreover, activation of the Akt pathway inhibited the effects of MAGI2-AS3 on TMZ resistance. MAGI2-AS3 inhibited tumor growth and enhanced the suppressive effect of TMZ on glioma tumorigenesis in vivo. In conclusion, MAGI2-AS3 reverses TMZ resistance in glioma cells by inactivating the Akt pathway.

A state-of-art of underlying molecular mechanisms and pharmacological interventions/nanotherapeutics for cisplatin resistance in gastric cancer

The fourth common reason of death among patients is gastric cancer (GC) and it is a dominant tumor type in Ease Asia. One of the problems in GC therapy is chemoresistance. Cisplatin (CP) is a platinum compound that causes DNA damage in reducing tumor progression and viability of cancer cells. However, due to hyperactivation of drug efflux pumps, dysregulation of genes and interactions in tumor microenvironment, tumor cells can develop resistance to CP chemotherapy. The current review focuses on the CP resistance emergence in GC cells with emphasizing on molecular pathways, pharmacological compounds for reversing chemoresistance and the role of nanostructures. Changes in cell death mechanisms such as upregulation of pro-survival autophagy can prevent CP-mediated apoptosis that results in drug resistance. Moreover, increase in metastasis via EMT induction induces CP resistance. Dysregulation of molecular pathways such as PTEN, PI3K/Akt, Nrf2 and others result in changes in CP response of GC cells. Non-coding RNAs determine CP response of GC cells and application of pharmacological compounds with activity distinct of CP can result in sensitivity in tumor cells. Due to efficacy of exosomes in transferring bioactive molecules such as RNA and DNA molecules among GC cells, exosomes can also result in CP resistance. One of the newest progresses in overcoming CP resistance in GC is application of nanoplatforms for delivery of CP in GC therapy that they can increase accumulation of CP at tumor site and by suppressing carcinogenic factors and overcoming biological barriers, they increase CP toxicity on cancer cells.

Breaking the Mold: Epigenetics and Genomics Approaches Addressing Novel Treatments and Chemoresponse in TGCT Patients

Testicular germ-cell tumors (TGCT) have been widely recognized for their outstanding survival rates, commonly attributed to their high sensitivity to cisplatin-based therapies. Despite this, a subset of patients develops cisplatin resistance, for whom additional therapeutic options are unsuccessful, and ~20% of them will die from disease progression at an early age. Several efforts have been made trying to find the molecular bases of cisplatin resistance. However, this phenomenon is still not fully understood, which has limited the development of efficient biomarkers and precision medicine approaches as an alternative that could improve the clinical outcomes of these patients. With the aim of providing an integrative landscape, we review the most recent genomic and epigenomic features attributed to chemoresponse in TGCT patients, highlighting how we can seek to combat cisplatin resistance through the same mechanisms by which TGCTs are particularly hypersensitive to therapy. In this regard, we explore ongoing treatment directions for resistant TGCT and novel targets to guide future clinical trials. Through our exploration of recent findings, we conclude that epidrugs are promising treatments that could help to restore cisplatin sensitivity in resistant tumors, shedding light on potential avenues for better prognosis for the benefit of the patients.

MicroRNAs as the critical regulators of autophagy-mediated cisplatin response in tumor cells

Chemotherapy is one of the most common therapeutic methods in advanced and metastatic tumors. Cisplatin (CDDP) is considered as one of the main first-line chemotherapy drugs in solid tumors. However, there is a high rate of CDDP resistance in cancer patients. Multi-drug resistance (MDR) as one of the main therapeutic challenges in cancer patients is associated with various cellular processes such as drug efflux, DNA repair, and autophagy. Autophagy is a cellular mechanism that protects the tumor cells toward the chemotherapeutic drugs. Therefore, autophagy regulatory factors can increase or decrease the chemotherapy response in tumor cells. MicroRNAs (miRNAs) have a pivotal role in regulation of autophagy in normal and tumor cells. Therefore, in the present review, we discussed the role of miRNAs in CDDP response through the regulation of autophagy. It has been reported that miRNAs mainly increased the CDDP sensitivity in tumor cells by inhibition of autophagy. PI3K/AKT signaling pathway and autophagy-related genes (ATGs) were the main targets of miRNAs in the regulation of autophagy-mediated CDDP response in tumor cells. This review can be an effective step to introduce the miRNAs as efficient therapeutic options to increase autophagy-mediated CDDP sensitivity in tumor cells.

Regulation of cisplatin resistance in bladder cancer by epigenetic mechanisms

Bladder cancer is one of the most common malignancies in the world. Cisplatin is one of the most potent and widely used anticancer drugs and has been employed in several malignancies. Cisplatin-based combination chemotherapies have become important adjuvant therapies for bladder cancer patients. Cisplatin-based treatment often results in the development of chemoresistance, leading to therapeutic failure and limiting its application and effectiveness in bladder cancer. To develop improved and more effective cancer therapy, research has been conducted to elucidate the underlying mechanism of cisplatin resistance. Epigenetic modifications have been demonstrated involved in drug resistance to chemotherapy, and epigenetic biomarkers, such as urine tumor DNA methylation assay, have been applied in patients screening or monitoring. Here, we provide a systematic description of epigenetic mechanisms, including DNA methylation, noncoding RNA regulation, m6A modification and posttranslational modifications, related to cisplatin resistance in bladder cancer.

Identification of platinum resistance-related gene signature for prognosis and immune analysis in bladder cancer

Purpose: Currently, there is limited knowledge about platinum resistance-related long non-coding RNAs (lncRNAs) in bladder cancer. We aim to identify platinum resistance-related lncRNAs and construct a risk model for accurate prognostic prediction of bladder cancer. Methods: Transcriptomic and clinical data were extracted from The Cancer Genome Atlas (TCGA) database, and platinum resistance-related genes were obtained from HGSOC-Platinum. The platinum resistance-related lncRNAs were obtained by the Spearman correlation analysis. Then, we constructed a risk score model through Cox regression analysis and the LASSO algorithm. The model was verified by analyzing the median risk score, Kaplan-Meier curve, receiver operating characteristic (ROC) curve, and heatmap. We also developed a nomogram and examined the relationship between the risk score model, immune landscape, and drug sensitivity. Lastly, we assessed the differential expression of PRR-lncRNAs in the cisplatin-resistant bladder cancer cell line and the normal bladder cancer cell line using qRT-PCR. Results: We developed and validated an eight-platinum resistance-related lncRNA risk model for bladder cancer. The risk model showed independent prognostic significance in univariate and multivariate Cox analyses. Based on multivariate analysis, we developed a nomogram. The modified model is both good predictive and clinically relevant after evaluation. Furthermore, immune-related and drug-sensitivity analyses also showed significant differential expression between high and low-risk groups. The qRT-PCR demonstrated that most of the lncRNAs were upregulated in cisplatin-resistance cancerous tissues than in control tissues. Conclusion: We have developed a predictive model based on eight platinum resistance-related lncRNAs, which could add meaningful information to clinical decision-making.

Emerging roles of non-coding RNAs in colorectal cancer oxaliplatin resistance and liquid biopsy potential

Colorectal cancer (CRC) is one of the most common malignancies of the digestive tract, with the annual incidence and mortality increasing consistently. Oxaliplatin-based chemotherapy is a preferred therapeutic regimen for patients with advanced CRC. However, most patients will inevitably develop resistance to oxaliplatin. Many studies have reported that non-coding RNAs (ncRNAs), such as microRNAs, long non-coding RNAs, and circular RNAs, are extensively involved in cancer progression. Moreover, emerging evidence has revealed that ncRNAs mediate chemoresistance to oxaliplatin by transcriptional and post-transcriptional regulation, and by epigenetic modification. In this review, we summarize the mechanisms by which ncRNAs regulate the initiation and development of CRC chemoresistance to oxaliplatin. Furthermore, we investigate the clinical application of ncRNAs as promising biomarkers for liquid CRC biopsy. This review provides new insights into overcoming oxaliplatin resistance in CRC by targeting ncRNAs.

Silencing the expression of lncRNA SNHG15 may be a novel therapeutic approach in human breast cancer through regulating miR-345-5p

BACKGROUND

Long noncoding RNA (lncRNA) short nucleolar RNA host gene 15 (SNHG15) has been found to have an oncogenic function in numerous malignancies. Nevertheless, the biological function and regulatory mechanisms of SNHG15 in breast cancer have not been fully elucidated.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of SNHG15 and in MDA-MB-231 breast cancer cells. The expression of SNHG15 was silenced using small interfering RNA (siRNA) technology. The proliferation and migration of the cells were examined by colony formation assays, cell counting kit 8 (CCK-8) assays, and transwell assays. For the zebrafish xenograft injection experiments, cultured cells labelled with the fluorescent dye CM-DiI were injected into the perivitelline space of the larvae.

RESULTS

This present study revealed that the expression of lncRNA SNHG15 (lnc-SNHG15) was significantly upregulated in breast cancer cells, and its overexpression was associated with the tumor. The relative expression of lnc-SNHG15 could be downregulated using siRNAs, and silencing lnc-SNHG15 inhibited the proliferation and the migration of MDA-MB-231 cells. In vivo experiments using the zebrafish xenograft model showed similar results. Mechanistically, the knockdown effect of lnc-SNHG15 could be restored by inhibiting the expression of the miR-345-5p, confirming the negative regulation between lnc-SNHG15 and miR-345-5p. Interestingly, cisplatin treatment combined with SNHG15 knockdown effectively inhibited MDA-MB-231 cell proliferation and migration in the zebrafish xenograft compared to negative controls.

CONCLUSIONS

In conclusion, lnc-SNHG15 knockdown increased miR-345-5p expression and negated cisplatin resistance in breast cancer cells, and thus, lnc-SNHG15 may be a potential novel target for breast cancer therapy.

Integrated Molecular Analysis Reveals 2 Distinct Subtypes of Pure Seminoma of the Testis

Objective

Testicular germ cell tumors (TGCT) are the most common solid malignancy in adolescent and young men, with a rising incidence over the past 20 years. Overall, TGCTs are second in terms of the average life years lost per person dying of cancer, and clinical therapeutics without adverse long-term side effects are lacking. Platinum-based regimens for TGCTs have heterogeneous outcomes even within the same histotype that frequently leads to under- and over-treatment. Understanding of molecular differences that lead to diverse outcomes of TGCT patients may improve current treatment approaches. Seminoma is the most common subtype of TGCTs, which can either be pure or present in combination with other histotypes.

Methods

Here we conducted a computational study of 64 pure seminoma samples from The Cancer Genome Atlas, applied consensus clustering approach to their transcriptomic data and revealed 2 clinically relevant seminoma subtypes: seminoma subtype 1 and 2.

Results

Our analysis identified significant differences in pluripotency stage, activity of double stranded DNA breaks repair mechanisms, rates of loss of heterozygosity, and expression of lncRNA responsible for cisplatin resistance between the subtypes. Seminoma subtype 1 is characterized by higher pluripotency state, while subtype 2 showed attributes of reprograming into non-seminomatous TGCT. The seminoma subtypes we identified may provide a molecular underpinning for variable responses to chemotherapy and radiation.

Conclusion

Translating our findings into clinical care may help improve risk stratification of seminoma, decrease overtreatment rates, and increase long-term quality of life for TGCT survivors.

Targeting CLK4 inhibits the metastasis and progression of breast cancer by inactivating TGF-β pathway

Triple-negative breast cancer (TNBC) represents the most aggressive subtype of breast cancer that is highly resistant to current therapeutic options. According to the public databases Oncomine and KM plotter, the CLK4 expression is correlated with poor patient survival in TNBC, especially in mesenchymal-like TNBC (MES-TNBC) that has strong metastatic potential. Therefore, we investigated the potential involvement of CLK4 in the metastasis and progression of MES-TNBC. In the MES-TNBC cell lines, the CLK4 expression was elevated. Notably, the RNAi-mediated silencing of CLK4 reduced the expression of multiple epithelial-mesenchymal transition (EMT) genes that mediate metastasis. Furthermore, CLK4 silencing reduced both the invasive behaviors of the cultured cells and tumor metastasis in the mouse xenograft model. It is also noteworthy that CLK4 silencing repressed the invasive and cancer stem cell (CSC) properties that are induced by the TGF-β signaling. Importantly, the pharmacological inhibition of CLK4 potently repressed the invasion and proliferation of MES-TNBC cell lines and patient-derived cells, which demonstrates its clinical applicability. Collectively, our results suggest that CLK4 plays a crucial role in invasion and proliferation of MES-TNBC, especially in the processes that are induced by TGF-β. Also, this study characterizes CLK4 as a novel therapeutic target in breast cancer.

Human Satellite III long non-coding RNA imparts survival benefits to cancer cells

Long non-coding RNAs (lncRNAs) are heterogeneous group of transcripts that lack coding potential and have essential roles in gene regulations. Recent days have seen an increasing association of non-coding RNAs with human diseases, especially cancers. One interesting group of non-coding RNAs strongly linked to cancers are heterochromatic repetitive Satellite RNAs. Satellite RNAs are transcribed from pericentromeric heterochromatic region of the human chromosomes. Satellite II RNA, most extensively studied, is upregulated in wide variety of epithelial cancer. Similarly, alpha satellite is over expressed in BRCA1- deficient tumors. Though much is known about alpha satellites and SatII repeats, little is known about Satellite III (SatIII) lncRNAs in human cancers. SatIII repeats, though transcriptionally silent in normal conditions is actively transcribed under condition of stress, mainly heat shock. In the present study, we show that colon and breast cancer cells aberrantly transcribes SatIII, in a Heat shock factor I (HSF1)-independent manner. Our study also reveals that, overexpression of SatIII RNA favours cancer cell survival by overriding chemo drug-induced cell death. Interestingly, knockdown of SatIII sensitizes cells towards chemotherapeutic drugs. This sensitization is possibly mediated by restoration of p53 protein expression that facilitates cell death. Heat shock however helps SatIII to continue with its pro-cell survival function. Our results, therefore suggest SatIII to be an important regulator of human cancers. Induction of SatIII is not only a response to the oncogenic stress but also facilitates cancer progression by a distinct pathway that is different from heat stress pathway. This article is protected by copyright. All rights reserved.

lncRNA lnc-POP1-1 upregulated by VN1R5 promotes cisplatin resistance in head and neck squamous cell carcinoma through interaction with MCM5

Cisplatin resistance is a major therapeutic challenge in advanced head and neck squamous cell carcinoma (HNSCC). Here, we aimed to investigate the key signaling pathway for cisplatin resistance in HNSCC cells. Vomeronasal type-1 receptor 5 (VN1R5) was identified as a cisplatin resistance-related protein and was highly expressed in cisplatin-resistant HNSCC cells and tissues. The long noncoding RNA (lncRNA) lnc-POP1-1 was confirmed to be a downstream target induced by VN1R5. VN1R5 transcriptionally regulated lnc-POP1-1 expression by activating the specificity protein 1 (Sp1) transcription factor via the cyclic AMP (cAMP)/protein kinase A (PKA) pathway. VN1R5 promoted cisplatin resistance in HNSCC cells in a lnc-POP1-1-dependent manner. Mechanistically, lnc-POP1-1 bound to the minichromosome maintenance deficient 5 (MCM5) protein directly and decelerated MCM5 degradation by inhibiting ubiquitination of the MCM5 protein, which facilitated the repair of DNA damage caused by cisplatin. In summary, we identified the cisplatin resistance-related protein VN1R5 and its downstream target lnc-POP1-1. Upon upregulation by VN1R5, lnc-POP1-1 promotes DNA repair in HNSCC cells through interaction with MCM5 and deceleration of its degradation.

LncRNA OTUD6B-AS1 Induces Cisplatin Resistance in Cervical Cancer Cells Through Up-Regulating Cyclin D2 via miR-206

Cervical cancer is one of the most common gynecological cancers. Cisplatin resistance remains a major hurdle in the successful treatment of cervical cancer. Aberrant expression of long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are implicated in cisplatin resistance. However, the regulatory functions of lncRNAs and miRNAs in cervical cancer cisplatin resistance and the underlying mechanisms are still elusive. Our qRT-PCR assays verified that miR-206 levels were down-regulated in cisplatin-resistant cervical cancer cells. The introduction of miR-206 sensitized cisplatin-resistant cervical cancer cells to cisplatin. Our qRT-PCR and luciferase reporter assays showed that Cyclin D2 (CCND2) was the direct target for miR-206 in cervical cancer cells. The cisplatin-resistant cervical cancer cells expressed higher CCND2 expression than the parental cells, whereas inhibition of CCND2 could sensitize the resistant cells to cisplatin treatment. Furthermore, we demonstrated that lncRNA OTUD6B-AS1 was up-regulated in cisplatin-resistant cervical cancer cells, and knocking down OTUD6B-AS1 expression induced re-acquirement of chemosensitivity to cisplatin in cervical cancer cells. We also showed that OTUD6B-AS1 up-regulated the expression of CCND2 by sponging miR-206. Low miR-206 and high OTUD6B-AS1 expression were associated with significantly poorer overall survival. Taken together, these results suggest that OTUD6B-AS1-mediated down-regulation of miR-206 increases CCND2 expression, leading to cisplatin resistance. Modulation of these molecules may be a therapeutic approach for cisplatin-resistant cervical cancer.

Transcriptomics Profiling Identifies Cisplatin-Inducible Death Receptor 5 Antisense Long Non-coding RNA as a Modulator of Proliferation and Metastasis in HeLa Cells

Cisplatin is a well-known cancer chemotherapeutic agent but how extensively long non-coding RNA (lncRNA) expression is modulated by cisplatin is unknown. It is imperative to employ a comprehensive approach to obtain a better account of cisplatin-mediated changes in the expression of lncRNAs. In this study, we used a transcriptomics approach to profile lncRNAs in cisplatin-treated HeLa cells, which resulted in identification of 10,214 differentially expressed lncRNAs, of which 2,500 were antisense lncRNAs. For functional analyses, we knocked down one of the cisplatin inducible lncRNAs, death receptor 5 antisense (DR5-AS) lncRNA, which resulted in a morphological change in HeLa cell shape without inducing any cell death. A second round of transcriptomics-based profiling revealed differential expression of genes associated with immune system, motility and cell cycle in DR5-AS knockdown HeLa cells. Cellular analyses showed that DR5-AS reduced cell proliferation and caused a cell cycle arrest at S and G2/M phases. Moreover, DR5-AS knockdown reduced the invasive capacity of HeLa cells in zebrafish xenograft model. These results suggest that cisplatin-mediated pleiotropic effects, such as reduction in cell proliferation, metastasis and cell cycle arrest, may be mediated by lncRNAs.

Curcumin-cisplatin chemotherapy: A novel strategy in promoting chemotherapy efficacy and reducing side effects

The efficacy of chemotherapy in cancer therapy is limited due to resistance, treatment selectivity, and severe adverse effects. Immunotherapy, chemotherapy, targeted therapy, radiation, and surgery are the most common therapeutic strategies for treatment, with chemotherapy being the most successful. Nonetheless, these treatments exhibit poor effectiveness due to toxicity and resistance. Therefore, combination therapies of natural products may be used as an effective and novel strategy to overcome such barriers. Cisplatin is a platinum-based chemotherapy agent, and when administered alone, it can lead to severe adverse effects and resistance mechanism resulting in therapeutic failure. Curcumin is a polyphenolic compound extracted from turmeric (Curcuma longa) exhibiting anticancer potential with minimal adverse effects. The combination therapy of curcumin and cisplatin is a novel strategy to mitigate/attenuate cisplatin-related adverse effects and improve the barrier of resistance reducing unwanted effects. However, there are uncertainties on the efficacy of curcumin, and more in depth and high-quality studies are needed. This review aims to explain the adverse effects related to individual cisplatin delivery, the positive outcome of individual curcumin delivery, and the combination therapy of curcumin and cisplatin from nano platform as a novel strategy for cancer therapy.

Exosomal noncoding RNAs: key players in glioblastoma drug resistance

Glioma, as one of the most severe human malignancies, is defined as the Central Nervous System's (CNS) tumors. Glioblastoma (GBM) in this regard, is the most malignant type of gliomas. There are multiple therapeutic strategies to cure GBM, for which chemotherapy is often the first-line treatment. Still, various cellular processes, such as uncontrolled proliferation, invasion and metastasis, may disturb the treatment efficacy. Drug resistance is another process in this way, which can also cause undesirable effects. Thereupon, identifying the mechanisms, involved in developing drug resistance and the relevant mechanisms can be very helpful in GBM management. The discovery of exosomal non-coding RNAs (ncRNAs), RNA molecules that can be transferred between the cells and different tissues using the exosomes, was a milestone in this regard. It has been revealed that the key exosomal ncRNAs, including circular RNAs, microRNAs, and long ncRNAs, are able to modulate GBM drug resistance through different signaling pathways or by affecting regulatory proteins and their corresponding genes. Nowadays, researchers are trying to overcome the limitations of chemotherapy by targeting these RNA molecules. Accordingly, this review aims to clarify the substantial roles of exosomal ncRNAs in GBM drug resistance and involved mechanisms.

CircHIPK2 Contributes to DDP Resistance and Malignant Behaviors of DDP-Resistant Ovarian Cancer Cells Both in vitro and in vivo Through circHIPK2/miR-338-3p/CHTOP ceRNA Pathway

Background

Cisplatin (DDP) is standard-of-care and first-line management for ovarian cancer (OvCa). Circular RNA HIPK2 (circHIPK2) is abnormally upregulated in serum of OvCa patients. However, its role in DDP resistance remains unclear.

Methods

Expression of cirHIPK2, microRNA (miR)-338-3p and chromatin target of protein arginine methyltransferase (CHTOP) was detected by quantitative reverse transcription PCR and Western blotting. Functional experiments were performed using cell counting kit-8 assay, flow cytometry, transwell assays, Western blotting, and xenograft experiment. The interaction among cirHIPK2, miR-338-3p and CHTOP was confirmed by dual-luciferase reporter assay and RNA pull-down assay.

Results

Expression of circHIPK2 and CHTOP was upregulated, and miR-338-3p was downregulated in human DDP-resistant OvCa tumors and cells. Blocking circHIPK2 could promote apoptosis and suppress the 50% inhibitory concentration (IC50) of DDP, cell proliferation, cell cycle entrance, migration and invasion in SKOV3/DDP and A2780/DDP cells. Allied with that was decreased B cell lymphoma (Bcl)-2, matrix metalloproteinase 2 (MMP2) and MMP9 levels, and increased Bcl-2-associated X protein (Bax) level. Similarly, overexpression of miR-338-3p functioned suppressive role in SKOV3/DDP and A2780/DDP cells. MiR-338-3p was a target for circHIPK2, and CHTOP was targeted by miR-338-3p, whereas silencing miR-338-3p counteracted the role of circHIPK2 knockdown, and restoring CHTOP either cancelled miR-338-3p role. The growth of A2780/DDP cells in nude mice was restrained by silencing circHIPK2 under DDP treatment or not.

Conclusion

CircHIPK2 might be a tumor promoter in OvCa and was associated with DDP resistance. Silencing circHIPK2 might suppress DDP-resistant OvCa through regulating miR-338-3p/CHTOP axis.

MCM3AP-AS1 promotes cisplatin resistance in gastric cancer cells via the miR-138/FOXC1 axis

The dysregulation of long non-coding RNAs (lncRNAs) serves a pivotal role in the pathogenesis and development of multiple types of human cancer, including gastric cancer (GC). MCM3AP-antisense 1 (MCM3AP-AS1) has been reported to function as a tumor promoter in various types of cancer. However, the biological function of MCM3AP-AS1 in the resistance of GC cells to cisplatin (CDDP) remains to be elucidated. The present study aimed to elucidate the mechanisms of MCM3AP-AS1 in the resistance of GC cells to CDDP. The expression levels of MCM3AP-AS1, miR-138 and FOXC1 were measured via reverse transcription-quantitative PCR. In addition, cell viability, migration and invasion were assessed via the Cell Counting Kit-8, wound healing and transwell assays, respectively. The interaction between genes was confirmed via the dual-luciferase reporter and pull-down assays. Western blot analysis was performed to detect FOXC1 protein expression. In the present study, it was demonstrated that MCM3AP-AS1 expression was upregulated in CDDP-resistant GC cells and that MCM3AP-AS1-knockdown suppressed CDDP resistance in GC cells. Moreover, the examination of the molecular mechanism indicated that MCM3AP-AS1 upregulated FOXC1 expression by sponging microRNA (miR)-138. Additionally, it was identified that the overexpression of FOXC1 abolished MCM3AP-AS1-knockdown- or miR-138 mimic-mediated inhibitory effects on CDDP resistance in GC cells. In conclusion, the present findings suggested that MCM3AP-AS1 enhanced CDDP resistance by sponging miR-138 to upregulate FOXC1 expression, indicating that MCM3AP-AS1 may be a novel promising biomarker for the diagnosis and treatment of patients with GC.

Competing endogenous RNAs in lung cancer

Competing endogenous RNAs (ceRNAs) containing microRNA response elements can competitively interact with microRNA via miRNA response elements, which can combine non-coding RNAs with protein-coding RNAs through complex ceRNA networks. CeRNAs include non-coding RNAs (long non-coding RNAs, circular RNAs, and transcribed pseudogenes) and protein-coding RNAs (mRNAs). Molecular interactions in ceRNA networks can coordinate many biological processes; however, they may also lead to ceRNA network imbalance and thus contribute to cancer occurrence when disturbed. Recent studies indicate that many dysregulated RNAs derived from lung cancer may function as ceRNAs to regulate multitudinous biological functions for lung cancer, including tumor cell proliferation, apoptosis, growth, invasion, migration, and metastasis. This study therefore reviewed the research progress in the field of non-coding and protein-coding RNAs as ceRNAs in lung cancer, and highlighted validated ceRNAs involved in biological lung cancer functions. Furthermore, the roles of ceRNAs as novel prognostic and diagnostic biomarkers were also discussed. Interpreting the involvement of ceRNAs networks in lung cancer will provide new insight into cancer pathogenesis and treatment strategies.

LncRNA MIR4435-2HG mediates cisplatin resistance in HCT116 cells by regulating Nrf2 and HO-1

PURPOSE

Cisplatin resistance is still a serious problem in the clinic. However, the underlying mechanism remains unknown. In our study, we investigated cisplatin resistance by using the cisplatin-resistant cell line HCT116R.

METHODS

The HCT116 cell line, a colon cancer cell line, was purchased. Cell viability was determined using CCK-8 Assay Kit. The gene expression levels of MIR4435-2HG, Nrf2, and HO-1, and caspase activity were determined using qRT-PCR and Caspase 3 Assay Kit, respectively.

RESULTS

In this study, we found that the levels of the lncRNA MIR4435-2HG were dramatically increased in the cisplatin-resistant cell line HCT116R. Knockdown of MIR4435-2HG in HCT116R cells significantly restored the sensitivity to cisplatin, inhibited cell proliferation and promoted cell apoptosis. Furthermore, Nrf2 and HO-1 mRNA levels, as critical molecules in the oxidative stress pathway, were inhibited by siRNAs targeting MIR4435-2HG, suggesting that MIR4435-2HG-mediated cisplatin resistance occurs through the Nrf2/HO-1 pathway.

CONCLUSION

Our findings demonstrate that the lncRNA MIR4435-2HG is a main factor driving the cisplatin resistance of HCT116 cells.

LncRNAs in Ovarian Cancer Progression, Metastasis, and Main Pathways: ceRNA and Alternative Mechanisms

Ovarian cancer (OvCa) develops asymptomatically until it reaches the advanced stages with metastasis, chemoresistance, and poor prognosis. Our review focuses on the analysis of regulatory long non-coding RNAs (lncRNAs) competing with protein-coding mRNAs for binding to miRNAs according to the model of competitive endogenous RNA (ceRNA) in OvCa. Analysis of publications showed that most lncRNAs acting as ceRNAs participate in OvCa progression: migration, invasion, epithelial-mesenchymal transition (EMT), and metastasis. More than 30 lncRNAs turned out to be predictors of survival and/or response to therapy in patients with OvCa. For a number of oncogenic (CCAT1, HOTAIR, NEAT1, and TUG1 among others) and some suppressive lncRNAs, several lncRNA/miRNA/mRNA axes were identified, which revealed various functions for each of them. Our review also considers examples of alternative mechanisms of actions for lncRNAs besides being ceRNAs, including binding directly to mRNA or protein, and some of them (DANCR, GAS5, MALAT1, and UCA1 among others) act by both mechanisms depending on the target protein. A systematic analysis based on the data from literature and Panther or KEGG (Kyoto Encyclopedia of Genes and Genomes) databases showed that a significant part of lncRNAs affects the key pathways involved in OvCa metastasis, EMT, and chemoresistance.

LINC00973 Induces Proliferation Arrest of Drug-Treated Cancer Cells by Preventing p21 Degradation

Overcoming drug resistance of cancer cells is the major challenge in molecular oncology. Here, we demonstrate that long non-coding RNA LINC00973 is up-regulated in normal and cancer cells of different origins upon treatment with different chemotherapeutics. Bioinformatics analysis shows that this is a consequence of DNA damage response pathway activation or mitotic arrest. Knockdown of LINC0973 decreases p21 levels, activates cellular proliferation of cancer cells, and suppresses apoptosis of drug-treated cells. We have found that LINC00973 strongly increases p21 protein content, possibly by blocking its degradation. Besides, we have found that ectopic over-expression of LINC00973 inhibits formation of the pro-survival p53-Ser15-P isoform, which preserves chromosome integrity. These results might open a new approach to the development of more efficient anti-cancer drugs.

Novel role of lncRNA CHRF in cisplatin resistance of ovarian cancer is mediated by miR-10b induced EMT and STAT3 signaling

Ovarian Cancer (OC) is a highly lethal gynecological cancer which often progresses through acquired resistance against the administered therapy. Cisplatin is a common therapeutic for the treatment of OC patients and therefore it is critical to understand the mechanisms of resistance against this drug. We studied a paired cell line consisting of parental and cisplatin resistant (CR) derivative ES2 OC cells, and found a number of dysregulated lncRNAs, with CHRF being the most significantly upregulated lncRNA in CR ES2 cells. The findings corroborated in human patient samples and CHRF was significantly elevated in OC patients with resistant disease. CHRF was also found to be elevated in patients with liver metastasis. miR-10b was found to be mechanistically involved in CHRF mediated cisplatin resistance. It induced resistance in not only ES2 but also OVCAR and SKOV3 OC cells. Induction of epithelial-to-mesenchymal-transition (EMT) and activation of STAT3 signaling were determined to be the mechanisms underlying the CHRF-miR-10b axis-mediated cisplatin resistance. Down-regulation of CHRF reversed EMT, STAT3 activation and the resulting cisplatin resistance, which could be attenuated by miR-10b. The results were also validated in an in vivo cisplatin resistance model wherein CR cells were associated with increased tumor burden, CHRF downregulation associated with decreased tumor burden and miR-10b again attenuated the CHRF downregulation effects. Our results support a novel role of lncRNA CHRF in cisplatin resistance of OC and establish CHRF-miR-10b signaling as a putative therapeutic target for sensitizing resistant OC cells.

Pharmacogenomics to Predict Tumor Therapy Response: A Focus on ATP-Binding Cassette Transporters and Cytochromes P450

Pharmacogenomics is an evolving tool of precision medicine. Recently, due to the introduction of next-generation sequencing and projects generating "Big Data", a plethora of new genetic variants in pharmacogenes have been discovered. Cancer resistance is a major complication often preventing successful anticancer treatments. Pharmacogenomics of both somatic mutations in tumor cells and germline variants may help optimize targeted treatments and improve the response to conventional oncological therapy. In addition, integrative approaches combining copy number variations and long noncoding RNA profiling with germline and somatic variations seem to be a promising approach as well. In pharmacology, expression and enzyme activity are traditionally the more studied aspects of ATP-binding cassette transporters and cytochromes P450. In this review, we briefly introduce the field of pharmacogenomics and the advancements driven by next-generation sequencing and outline the possible roles of genetic variation in the two large pharmacogene superfamilies. Although the evidence needs further substantiation, somatic and copy number variants as well as rare variants and common polymorphisms in these genes could all affect response to cancer therapy. Regulation by long noncoding RNAs has also been shown to play a role. However, in all these areas, more comprehensive studies on larger sets of patients are needed.

Back to the Future: Rethinking the Great Potential of lncRNAS for Optimizing Chemotherapeutic Response in Ovarian Cancer

Ovarian cancer (OC) is one of the most fatal cancers in women worldwide. Currently, platinum- and taxane-based chemotherapy is the mainstay for the treatment of OC. Yet, the emergence of chemoresistance results in therapeutic failure and significant relapse despite a consistent rate of primary response. Emerging evidence substantiates the potential role of lncRNAs in determining the response to standard chemotherapy in OC. The objective of this narrative review is to provide an integrated, synthesized overview of the current state of knowledge regarding the role of lncRNAs in the emergence of resistance to platinum- and taxane-based chemotherapy in OC. In addition, we sought to develop conceptual frameworks for harnessing the therapeutic potential of lncRNAs in strategies aimed at enhancing the chemotherapy response of OC. Furthermore, we offered significant new perspectives and insights on the interplay between lncRNAs and the molecular circuitries implicated in chemoresistance to determine their impacts on therapeutic response. Although this review summarizes robust data concerning the involvement of lncRNAs in the emergence of acquired resistance to platinum- and taxane-based chemotherapy in OC, effective approaches for translating these lncRNAs into clinical practice warrant further investigation.

Knockdown of Long Non-Coding RNA HOTAIR Suppresses Cisplatin Resistance, Cell Proliferation, Migration and Invasion of DDP-Resistant NSCLC Cells by Targeting miR-149-5p/Doublecortin-Like Kinase 1 Axis

Background

Long non-coding RNA (lncRNA) HOTAIR has been reported to be associated with cisplatin (DDP) resistance in different human cancers including non-small cell lung cancer (NSCLC). However, the mechanism of HOTAIR in cisplatin resistance of NSCLC remains largely undefined.

Materials and Methods

Expression of HOTAIR, miR-149-5p and doublecortin-like kinase 1 (DCLK1) was detected using real-time quantitative PCR (RT-qPCR) and Western blotting. Cisplatin resistance was determined with cell counting kit (CCK)-8 assay and transwell assays in vitro, and xenograft tumor models in vivo. The target binding between miR-149-5p and either HOTAIR or DCLK1 was predicted on Diana Tools website, and confirmed by dual-luciferase reporter assay and RNA immunoprecipitation.

Results

Expression of HOTAIR was upregulated in DDP-resistant NSCLC tumor tissues and cell lines (A549/DDP and H1299/DDP). Knockdown of HOTAIR decreased the acquired cisplatin resistance of A549/DDP and H1299/DDP cells, as evidenced by attenuated 50% inhibitory concentration (IC50) of DDP, cell proliferation, migration and invasion in vitro, as well as tumor growth inhibition in vivo. Mechanically, HOTAIR negatively regulated miR-149-5p expression via targeting, and DCLK1 was a downstream target for miR-149-5p. DCLK1 was indirectly regulated by HOTAIR in DDP-resistant NSCLC cells as well. Functionally, miR-149-5p deletion could counteract the inhibitory effect of HOTAIR knockdown on cisplatin resistance; contrarily, restoring miR-149-5p exhibited the similar inhibition on cisplatin resistance in DDP-resistant cells in vitro, which was then abated by DCLK1 upregulation.

Conclusion

Knockdown of HOTAIR enhances DDP-resistant NSCLC cells to overcome cisplatin resistance partially via regulating miR-149-5p/DCLK1 axis.

NEAT1 Knockdown Suppresses the Cisplatin Resistance in Ovarian Cancer by Regulating miR-770-5p/PARP1 Axis

Background

Long noncoding RNAs play essential roles in regulating drug resistance in cancers. However, how and whether lncRNA nuclear paraspeckle assembly transcript 1 (NEAT1) could mediate cisplatin resistance in ovarian cancer remain poorly understood.

Patients and Methods

Eighteen cisplatin-sensitive and 19 cisplatin-resistant patients with ovarian cancer were recruited. Cisplatin-resistant ovarian cancer cells were used for this study. The expression levels of NEAT1, microRNA (miR)-770-5p and poly adenosine diphosphate-ribose polymerase 1 (PARP1) were detected by quantitative real-time polymerase chain reaction or Western blot. Cisplatin resistance was assessed by the half-maximal inhibitory concentration (IC50) of cisplatin, cell viability and apoptosis using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide, flow cytometry and Western blot, respectively. The target association between miR-770-5p and NEAT1 or PARP1 was investigated by dual-luciferase reporter assay. The xenograft model was used to investigate cisplatin resistance in vivo.

Results

NEAT1 expression is elevated in cisplatin-resistant ovarian cancer tissues and cells. Knockdown of NEAT1 repressed cisplatin resistance by decreasing the IC50 of cisplatin, cell viability and increasing apoptosis. MiR-770-5p was bound to NEAT1 and PARP1 was confirmed as a target of miR-770-5p. MiR-770-5p inhibition or PARP1 restoration could abate the effect of NEAT1 silencing on cisplatin resistance in cisplatin-resistant ovarian cancer cells. Moreover, NEAT1 knockdown reduced PARP1 expression by increasing miR-770-5p. Interference of NEAT1 decreased xenograft tumor growth by regulating miR-770-5p and PARP1.

Conclusion

Knockdown of NEAT1 inhibited cisplatin resistance in ovarian cancer cells by up-regulating miR-770-5p and down-regulating PARP1, providing a new target for improving the efficacy of cisplatin-based therapy in ovarian cancer.

Predictive and prognostic value of EPIC1 in patients with breast cancer receiving neoadjuvant chemotherapy

Background:

EPIC1 is an oncogenic long non-coding ribonucleic acid (RNA) that promotes cell growth and cell-cycle progression and inhibits apoptosis in several cancer cell lines. However, clinical studies on EPIC1 in breast cancer, specifically in the neoadjuvant setting, are relatively few.

Methods:

Patients treated with weekly paclitaxel–cisplatin-based neoadjuvant chemotherapy after core-needle biopsy were included in the study. Real-time quantitative polymerase chain reaction assays were performed to detect EPIC1 expression.

Results:

Among all patients included in this study (n = 111), higher EPIC1 expression was associated with estrogen receptor negativity, human epidermal growth factor receptor 2 positivity, higher Ki67 index, and higher histologic grade. Multivariate analysis suggested that EPIC1 expression was an independent predictive factor for pathological complete response, with a significant interaction between EPIC1 expression and age. The Kaplan–Meier Plotter dataset suggested that the EPIC1 high-expression group showed a worse 10-year distant metastasis-free survival and post-progression survival when compared with the EPIC1 low-expression group. The Cancer Genome Atlas dataset suggested that the overall survival in the EPIC1 high-expression group was inferior to that in the EPIC1 low-expression group, specifically in hormone receptor (HorR)-positive patients and patients aged <50 years. Pathway analysis revealed the top pathways that indicated the potential mechanisms of EPIC1 in chemoresistance, including the daunorubicin and doxorubicin metabolic processes.

Conclusions:

Our study suggests that EPIC1 may be a promising biomarker for both neoadjuvant chemosensitivity and long-term clinical outcomes in breast cancer, specifically in the HorR-positive premenopausal subgroup. It may also help identify candidate responders and determine treatment strategies.

The functional role of long noncoding RNA in resistance to anticancer treatment

Chemotherapy is one of the fundamental methods of cancer treatment. However, drug resistance remains the main cause of clinical treatment failure. We comprehensively review the newly identified roles of long noncoding RNAs (lncRNAs) in oncobiology that are associated with drug resistance. The expression of lncRNAs is tissue-specific and often dysregulated in human cancers. Accumulating evidence suggests that lncRNAs are involved in chemoresistance of cancer cells. The main lncRNA-driven mechanisms of chemoresistance include regulation of drug efflux, DNA damage repair, cell cycle, apoptosis, epithelial-mesenchymal transition (EMT), induction of signaling pathways, and angiogenesis. LncRNA-driven mechanisms of resistance to various antineoplastic agents have been studied extensively. There are unique mechanisms of resistance against different types of drugs, and each mechanism may have more than one contributing factor. We summarize the emerging strategies that can be used to overcome the technical challenges in studying and addressing lncRNA-mediated drug resistance.

HOTTIP Predicts Poor Survival in Gastric Cancer Patients and Contributes to Cisplatin Resistance by Sponging miR-216a-5p

Gastric cancer (GC) is a significant public health burden worldwide, and cisplatin resistance is the leading cause for the failure of chemotherapy in this disease. Previous studies have revealed that HOXA transcript at the distal tip (HOTTIP) is involved in the pathology of GC and is associated with poor overall survival. However, the functional role of HOTTIP in GC chemoresistance remains unclear. In this study, quantitative real-time PCR was used to analyze HOTTIP expression in GC cell lines and in tissues of GC patients who received cisplatin-based chemotherapy. The mechanism of HOTTIP-mediated chemoresistance was assessed using cell viability, apoptosis, and autophagy assays. The relationships among HOTTIP, miR-216a-5p, and Bcl-2 were determined using luciferase reporter and western blot assays. HOTTIP was markedly upregulated in the tissues of GC patients who were treated with gastrectomy and cisplatin chemotherapy, especially in those with recurrent tumors. Further, HOTTIP was increased in the cisplatin-resistant cell line, SGC7901/DDP, compared to the parental cells, SGC7901. Functional assays demonstrated that HOTTIP expression promoted cisplatin resistance and inhibited apoptosis and autophagy in GC cells. Mechanistic investigations revealed that HOTTIP may regulate the functions of GC cells by sponging miR-216a-5p. MiR-216a-5p overexpression decreased Bcl-2 expression, enhanced Beclin1 expression, and active autophagy. Taken together, our study demonstrated that HOTTIP is closely associated with recurrence in GC patients. HOTTIP expression confers cisplatin resistance by regulating the miR-216a-5p/BCL-2/Beclin1/autophagy pathway, which provides a novel strategy to overcome resistance to chemotherapy in GC.

TUG1/miR-133b/CXCR4 axis regulates cisplatin resistance in human tongue squamous cell carcinoma

Background

Long noncoding RNA taurine upregulated 1 (TUG1) has been reported to play an important role in human cancers. However, little is known about the role of TUG1 in drug resistance and its mechanism in tongue squamous cell carcinoma (TSCC).

Methods

Twenty-one cisplatin-sensitive or resistant TSCC patients were enrolled in this study. Cisplatin-resistant cells (SCC25/CDDP and CAL27/CDDP) were used for experiments in vitro. Transfection was performed using Lipofectamine 2000 transfection reagent. The levels of TUG1, microRNA-133b (miR-133b) and cysteine-X-cysteine chemokine receptor 4 (CXCR4) were measured by quantitative real-time polymerase chain reaction or western blot. The cisplatin resistance was investigated by cell viability, transwell invasion and apoptosis assays. The interactions among TUG1, miR-133b and CXCR4 were evaluated by luciferase reporter assay and RNA immunoprecipitation. Murine xenograft model was established using the stably transfected CAL27/CDDP cells.

Results

TUG1 expression was elevated in cisplatin-resistant TSCC tissues and cells compared with that in sensitive group and its knockdown inhibited cisplatin resistance to SCC25/CDDP and CAL27/CDDP cells. miR-133b was targeted via TUG1 and its overexpression suppressed cisplatin resistance. Moreover, CXCR4 was a target of miR-133b. CXCR4 silence repressed cisplatin resistance, which was reversed by miR-133b knockdown. The level of CXCR4 protein was decreased by inhibition of TUG1 and recuperated by miR-133b knockdown. Besides, interference of TUG1 attenuated tumor growth by regulating miR-133b and CXCR4 in vivo.

Conclusion

Downregulation of TUG1 impeded cisplatin resistance in TSCC-resistant cells by mediating miR-133b and CXCR4, indicating TUG1 as a promising target for TSCC chemotherapy.

Cisplatin resistance-associated circRNA_101237 serves as a prognostic biomarker in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a leading cause of cancer-associated mortality worldwide. Despite clinical advances, the survival rate of patients with HCC remains low, as most patients are diagnosed with HCC when they are already at the advanced stage. Certain circular RNAs (circRNAs) are closely associated with the development of liver cancer. In the present study, a circRNA array was performed to screen differentially expressed circRNAs in HCC tissues. The further analysis focused on the newly identified circRNA_101237, the host gene of which, cyclin-dependent kinase 8, is located at chr13:26974589-26975761. CircRNA_101237 was determined to be upregulated in tumor tissue and serum of patients with HCC as compared with that in paracancerous tissues and the serum of healthy controls, respectively. In addition, the expression of circRNA_101237 was associated with tumor size, lymph node metastasis, distant metastasis and TNM stage. Univariate and multivariate analysis indicated that serum circRNA_101237 levels were an independent predictor of survival prognosis in patients with HCC. The overall survival of patients with high expression of circRNA_101237 was reduced compared with that of patients with low expression of circRNA_101237. Of note, cisplatin induced the expression of circRNA_101237 in HCC cells in a dose- and time-dependent manner in vitro, and the levels of circRNA_101237 in the serum of patients with cisplatin-resistant HCC and in cisplatin-resistant Huh7 cells were increased. The present study provided novel insight into the use of circRNA_101237 as a diagnostic biomarker for HCC and a potential therapeutic target.

Long Non-coding RNAs Involved in Resistance to Chemotherapy in Ovarian Cancer

Ovarian cancer (OC) accounts for more than 150,000 deaths worldwide every year. Patients are often diagnosed at an advanced stage with metastatic dissemination. Although platinum- and taxane-based chemotherapies are effective treatment options, they are rarely curative and eventually, the disease will progress due to acquired resistance. Emerging evidence suggests a crucial role of long non-coding RNAs (lncRNAs) in the response to therapy in OC. Transcriptome profiling studies using high throughput approaches have identified differential expression patterns of lncRNAs associated with disease recurrence. Furthermore, several aberrantly expressed lncRNAs in resistant OC cells have been related to increased cell division, improved DNA repair, up-regulation of drug transporters or reduced susceptibility to apoptotic stimuli, supporting their involvement in acquired resistance. In this review, we will discuss the key aspects of lncRNAs associated with the development of resistance to platinum- and taxane-based chemotherapy in OC. The molecular landscape of OC will be introduced, to provide a background for understanding the role of lncRNAs in the acquisition of malignant properties. We will focus on the interplay between lncRNAs and molecular pathways affecting drug response to evaluate their impact on treatment resistance. Additionally, we will discuss the prospects of using lncRNAs as biomarkers or targets for precision medicine in OC. Although there is still plenty to learn about lncRNAs and technical challenges to be solved, the evidence of their involvement in OC and the development of acquired resistance are compelling and warrant further investigation for clinical applications.

The influence of long non-coding RNAs on the response to chemotherapy in ovarian cancer

With 240,000 new cases and 152,000 deaths per year, ovarian cancer is the leading cause of death from gynecologic malignancies. Late diagnosis because of asymptomatic development in early stages and resistance to existing treatments are the major causes of therapeutic failure in ovarian cancer. The recent discovery of tens of thousands of long non-coding RNAs and their action as oncogenes or tumor suppressors in pathways matching all the hallmarks of cancer in most - if not all - malignancies have attracted attention of the scientific community. A growing number of studies have implicated lncRNAs in diverse aspects of ovarian carcinoma biology. We present lncRNAs which have been involved in response to the different drugs currently used for the treatment of ovarian cancers, from first-line platinum salts and taxanes to the newly available PARP inhibitors. The data already available supports the potential use of several lncRNAs, alone or in combination with other molecules, as potential biomarkers for the prediction of response to treatment. Understanding the determinants of their action might reveal new potential therapeutic targets.

lncRNA CCAT1 is a biomarker for the proliferation and drug resistance of esophageal cancer via the miR-143/PLK1/BUBR1 axis

Recent evidence indicates that long noncoding RNA colon cancer-associated transcript-1 (lncRNA CCAT1) is abundantly expressed in esophageal cancer and is closely related to the occurrence, development, invasion, metastasis, and drug resistance of this disease. However, the role and molecular mechanisms of CCAT1 in the cell proliferation and chemoresistance of esophageal cancer are largely unknown. The correlation between CCAT1 expression and drug resistance to cisplatin (CDDP) in esophageal squamous cell carcinoma (ESCC) cells was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and quantitative real-time polymerase chain reaction (qRT-PCR) assays. CCAT1 knockdown and miR-143 overexpression or inhibition were used to verify the effects on proliferation and drug resistance via MTT, western blotting, flow cytometry, and immunofluorescence assays. qRT-PCR and western blotting were applied to detect the potential regulatory relationship among CCAT1, miR-143, PLK1, and BUBR1. A xenograft tumor assay was performed to validate the role of CCAT1 in vivo. The expression of CCAT1 was positively correlated with drug resistance in several ESCC cell lines. CCAT1 knockdown and miR-143 overexpression inhibited cell proliferation and CDDP drug resistance. Moreover, the downstream target of CCAT1 was found to be miR-143, which can regulate the expression of PLK1 and BUBR1. In vivo assays showed that CCAT1 knockdown suppressed tumor growth and enhanced the sensitivity of tumors to CDDP in nude mice. Taken together, we discovered a novel mechanism by which CCAT1 promotes cell proliferation and enhances drug resistance by regulating the miR-143/PLK1/BUBR1 signaling axis both in vitro and in vivo. Our findings further suggest that lncRNA CCAT1 may be a potential therapeutic target for overcoming chemoresistance in esophageal cancer.

LncRNA-MALAT1 mediates cisplatin resistance via miR-101-3p/VEGF-C pathway in bladder cancer

Cisplatin (CDDP)-based chemotherapy is a standard strategy for the clinical treatment of patients with bladder cancer (BC). However, the anti-tumor efficacy of cisplatin is affected by multiple chemoresistance with complex molecular mechanisms. Recent evidence highlights the crucial regulatory roles of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in the progression of cancers and development of drug resistance. However, the roles and underlying molecular mechanisms of MALAT1 in cisplatin resistance of the BC cells remain largely unclear. In this study, we firstly demonstrated that MALAT1 expression was up-regulated in the BC tissues compared to the normal adjacent tissues and elevated in the cancer cells compared to the epithelial immortalized cells. Secondly, we found that suppression of MALAT1 enhanced the chemotherapeutic drug sensitivity and inhibited the cisplatin resistance of the BC cells. Thirdly, we showed that MALAT1 affected the cisplatin resistance of the BC cells via regulating the miR-101-3p/VEGF-C pathway. In summary, this study demonstrates that MALAT1, miR-101-3p and VEGF-C form a regulatory axis to affect the chemo-resistance of BC cells to CDDP, and provides novel potential targets for treatment of BC.

miR-152-3p Sensitizes Glioblastoma Cells Towards Cisplatin Via Regulation Of SOS1

Background

Accumulating evidences suggest that microRNAs (miRNAs) play key roles in mediating glioblastoma progression. Decreased expression of miR-152-3p was reported in several cancer types including glioblastoma.

Methods

The sensitivity of glioblastoma cells to cisplatin was assessed by the cell counting kit-8 assay and flow cytometry analysis. The expression of miR-152-3p was determined by RT-qPCR method. Bioinformatic analysis, dual luciferase reporter assay and Western blot were used to explore the target gene of miR-152-3p. The association between miR-152-3p and SOS1 was confirmed in glioblastoma tissues by Pearson correlation analysis.

Results

In the current study, we discovered that overexpression of miR-152-3p increased cisplatin sensitivity while inhibition of miR-152-3p decreased cisplatin sensitivity in glioblastoma cells (T98G and U87). In addition, miR-152-3p augmented cell apoptosis induced by cisplatin treatment. It was further predicted and validated that SOS1, a protein involved in regulating chemotherapy sensitivity, was a direct target gene of miR-152-3p. SOS1 was proven to suppress the cytotoxic effect of cisplatin in glioblastoma. Transfection of recombinant SOS1 could effectively reverse the increased cisplatin sensitivity induced by miR-152-3p overexpression in T98G. Furthermore, overexpression of SOS1 reduced the percentage of apoptotic cells increased by miR-152-3p mimic in the presence of cisplatin in T98G. More importantly, a significant negative correlation between miR-152-3p levels and SOS1 levels was observed in glioblastoma tissues collected from 40 patients.

Conclusion

Our study identified miR-152-3p as a chemotherapy sensitizer in glioblastoma.

Recent Progress in Characterizing Long Noncoding RNAs in Cancer Drug Resistance

Drug resistance is an important cause of failure in cancer chemotherapies. A large number of long noncoding RNAs (lncRNAs) have been found to be related to drug resistance in cancers. Therefore, lncRNAs provide potential targets for cancer therapies. The lncRNAs involved in cancer drug resistance are attracting interest from an increasing number of researchers. This review summarizes the latest research on the mechanisms and functions of lncRNAs in cancer drug resistance and envisages their future developments and therapeutic applications. This research suggests that lncRNAs regulate drug resistance through multiple mechanisms. LncRNAs do not affect drug resistance directly; usually, they do so by regulating the expression of some intermediate regulatory factors. In addition, lncRNAs exhibit a diversity of functions in cancer drug resistance. The overexpression of most lncRNAs promotes drug resistance, while a few lncRNAs have inhibitory effects.

Silencing long intergenic non-coding RNA 00707 enhances cisplatin sensitivity in cisplatin-resistant non-small-cell lung cancer cells by sponging miR-145

The aberrant expression of long non-coding RNAs is closely associated with drug resistance in multiple types of cancer. Long intergenic non-coding RNA 00707 (LINC00707) has previously been reported to be an oncogene able to promote lung adenocarcinoma cell proliferation and metastasis. However, its role in the progression of cisplatin (DDP) resistance in non-small-cell lung cancer (NSCLC) requires further elucidation. In the present study, LINC00707 and microRNA (miR)-145 expression levels were measured using reverse transcription-quantitative PCR (RT-qPCR). MTT and flow cytometric assays were performed to evaluate the IC₅₀ value of DDP and cell apoptosis, respectively. Bcl-2, Bax, multidrug resistance protein 1 (MRP1) and P-glycoprotein (P-gp) mRNA and protein expression were detected using RT-qPCR and western blotting, respectively. The interaction between LINC00707 and miR-145 was explored using a luciferase reporter assay. LINC00707 expression was found to be significantly upregulated in DDP-resistant A549 cells (A549/DDP) cells when compared with that in parental A549 cells. LINC00707 knockdown reduced the IC₅₀ value of DDP, enhanced apoptosis and inhibited Bcl-2, MRP1 and P-gp expression, while promoting Bax expression in A549/DDP cells. miR-145 expression was found to be significantly decreased in A549/DDP cells when compared with in A549 cells. LINC00707 directly interacted with miR-145 and negatively regulated its expression. Furthermore, miR-145 downregulation weakened the effect of LINC00707 knockdown in A549/DDP cells. Therefore, silencing of LINC00707 enhanced DDP sensitivity in A549/DDP cells by sponging miR-145, thereby shedding light on LINC00707 and its corresponding molecular mechanisms involved in the progression of DDP resistance in NSCLC cells.

Characterization of ceRNA network to reveal potential prognostic biomarkers in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a particular subtype of breast malignant tumor with poorer prognosis than other molecular subtypes. Previous studies have demonstrated that some abnormal expression of non-coding RNAs including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) were closely related to tumor cell proliferation, apoptosis, invasion, migration and drug sensitivity. However, the role of non-coding RNAs in the pathogenesis of TNBC is still unclear. In order to characterize the molecular mechanism of non-coding RNAs in TNBC, we downloaded RNA data and miRNA data from the cancer genome atlas database. We successfully identified 686 message RNAs (mRNAs), 26 miRNAs and 50 lncRNAs as key molecules for high risk of TNBC. Then, we hypothesized that the lncRNA–miRNA–mRNA regulatory axis positively correlates with TNBC and constructed a competitive endogenous RNA (ceRNA) network of TNBC. Our series of analyses has shown that five molecules (TERT, TRIML2, PHBP4, mir-1-3p, mir-133a-3p) were significantly associated with the prognosis of TNBC, and there is a prognostic ceRNA sub-network between those molecules. We mapped the Kaplan–Meier curve of RNA on the sub-network and also suggested that the expression level of the selected RNA is related to the survival rate of breast cancer. Reverse transcription-quantitative polymerase chain reaction showed that the expression level of TRIML2 in TNBC cells was higher than normal. In general, our findings have implications for predicting metastasis, predicting prognosis and discovering new therapeutic targets for TNBC.

The nuclear hypoxia-regulated NLUCAT1 long non-coding RNA contributes to an aggressive phenotype in lung adenocarcinoma through regulation of oxidative stress

Lung cancer is the leading cause of cancer death worldwide, with poor prognosis and a high rate of recurrence despite early surgical removal. Hypoxic regions within tumors represent sources of aggressiveness and resistance to therapy. Although long non-coding RNAs (lncRNAs) are increasingly recognized as major gene expression regulators, their regulation and function following hypoxic stress are still largely unexplored. Combining profiling studies on early-stage lung adenocarcinoma (LUAD) biopsies and on A549 LUAD cell lines cultured in normoxic or hypoxic conditions, we identified a subset of lncRNAs that are both correlated with the hypoxic status of tumors and regulated by hypoxia in vitro. We focused on a new transcript, NLUCAT1, which is strongly upregulated by hypoxia in vitro and correlated with hypoxic markers and poor prognosis in LUADs. Full molecular characterization showed that NLUCAT1 is a large nuclear transcript composed of six exons and mainly regulated by NF-κB and NRF2 transcription factors. CRISPR-Cas9-mediated invalidation of NLUCAT1 revealed a decrease in proliferative and invasive properties, an increase in oxidative stress and a higher sensitivity to cisplatin-induced apoptosis. Transcriptome analysis of NLUCAT1-deficient cells showed repressed genes within the antioxidant and/or cisplatin-response networks. We demonstrated that the concomitant knockdown of four of these genes products, GPX2, GLRX, ALDH3A1, and PDK4, significantly increased ROS-dependent caspase activation, thus partially mimicking the consequences of NLUCAT1 inactivation in LUAD cells. Overall, we demonstrate that NLUCAT1 contributes to an aggressive phenotype in early-stage hypoxic tumors, suggesting it may represent a new potential therapeutic target in LUADs.

Systematic identification of dysregulated lncRNAs associated with platinum-based chemotherapy response across 11 cancer types

Aberrant expression of long non-coding RNAs (lncRNAs) leads to the development of chemoresistance by regulating a series of biological processes, which is one of the major obstacles in the cancer treatment. This study aimed to identify some key lncRNAs that are associated with platinum-based chemoresistance in multiple cancers. Regulating the expression levels of these lncRNAs can enhance the sensitivity of patients to chemotherapy drugs and improve the therapeutic effect of cancer. By systematically analyzing 648 samples regarding platinum drug response from the Cancer Genome Atlas (TCGA), we have identified 32 dysregulated lncRNAs across 11 cancer types that could affect platinum-based chemotherapy response, of which 78.125% (25/32) were significantly down-regulated in drug-resistant samples. Drug response prediction model that had been constructed based on the expression pattern of these dysregulated lncRNAs could accurately predict the chemotherapy response of tumor patients, and the area under the curve (AUC) was between 0.8034 and 0.9984. In particular, all of these dysregulated lncRNAs that we identified were cancer-specific. They were significantly associated with the survival of tumor patients and could serve as cancer-specific biomarkers for prognosis. In conclusion, this study will contribute to improving the drug resistance of tumor patients during chemotherapy, and it is of real significance for selecting effective chemotherapy drugs and achieving precision medicine.

Multiple Roles of Exosomal Long Noncoding RNAs in Cancers

Long noncoding RNAs (lncRNAs) are not transcriptional noise, as previously understood, but are currently considered to be multifunctional. Exosomes are derived from the internal multivesicular compartment and are extracellular vesicles (EVs) with diameters of 30–100 nm. Exosomes play significant roles in the intercellular exchange of information and material. Exosomal lncRNAs may be promising biomarkers for cancer diagnosis and potential targets for cancer therapies, since they are increasingly understood to be involved in tumorigenesis, tumor angiogenesis, and chemoresistance. This review mainly focuses on the roles of emerging exosomal lncRNAs in cancer. In addition, the biogenesis of exosomes, the functions of lncRNAs, and the mechanisms of lncRNAs in exosome-mediated cell-cell communication are also summarized.