Long noncoding RNA CCAT1 acts as an oncogene and promotes chemoresistance in docetaxel-resistant lung adenocarcinoma cells

CCAT1 lncRNA is chromatin-retained and post-transcriptionally spliced

Super-enhancers are unique gene expression regulators widely involved in cancer development. Spread over large DNA segments, they tend to be found next to oncogenes. The super-enhancer c-MYC locus forms long-range chromatin looping with nearby genes, which brings the enhancer and the genes into proximity, to promote gene activation. The colon cancer-associated transcript 1 (CCAT1) gene, which is part of the MYC locus, transcribes a lncRNA that is overexpressed in colon cancer cells through activation by MYC. Comparing different types of cancer cell lines using RNA fluorescence in situ hybridization (RNA FISH), we detected very prominent CCAT1 expression in HeLa cells, observed as several large CCAT1 nuclear foci. We found that dozens of CCAT1 transcripts accumulate on the gene locus, in addition to active transcription occurring from the gene. The accumulating transcripts are released from the chromatin during cell division. Examination of CCAT1 lncRNA expression patterns on the single-RNA level showed that unspliced CCAT1 transcripts are released from the gene into the nucleoplasm. Most of these unspliced transcripts were observed in proximity to the active gene but were not associated with nuclear speckles in which unspliced RNAs usually accumulate. At larger distances from the gene, the CCAT1 transcripts appeared spliced, implying that most CCAT1 transcripts undergo post-transcriptional splicing in the zone of the active gene. Finally, we show that unspliced CCAT1 transcripts can be detected in the cytoplasm during splicing inhibition, which suggests that there are several CCAT1 variants, spliced and unspliced, that the cell can recognize as suitable for export.

Role of long non-coding RNAs in cholangiocarcinoma: A systematic review and meta-analysis

BACKGROUND

Cholangiocarcinoma (CCA), as a rare malignancy of the biliary tree, has a poor prognosis most of the time. CCA is highly epigenetically regulated and several long non-coding RNAs (lncRNA) have been investigated to have a diagnostic and prognostic role in CCA. The current study aimed to assess the studies finding relevant lncRNAs in CCA systematically.

METHODS

International databases, including PubMed, Cochrane Library, and Embase, were comprehensively searched in order to identify studies investigating any lncRNA in CCA. After screening by title/abstract and full-text, necessary data were extracted. Random-effect meta-analysis was performed for pooling the areas under the curve (AUCs), specificity, and sensitivity of lncRNAs for the diagnosis of CCA.

RESULTS

A total of 33 studies were chosen to be included in the final analysis, comprised of 2677 patients. Meta-analysis of AUCs for evaluation of CCA resulted in pooled AUC of 0.79 (95% CI: 0.75-0.82; I2 = 69.11, p < .01). Additionally, overall sensitivity of 0.80 (95% CI 0.75-0.84) and specificity of 0.77 (95% CI: 0.68-0.84) were observed. Measurement of lncRANs in the assessment of CCA also improved overall survival significantly (effect size 1.61, 95% CI: 1.39-1.82). A similar result was found for progression-free survival (effect size 1.57, 95% CI: 1.20-1.93).

CONCLUSION

Based on our findings, lncRNAs showed promising results as biomarkers in the diagnosis of CCA since they had acceptable sensitivity and specificity, in addition to the fact that improved survival in this poor prognosis cancer. Further studies might be needed to address this issue and find the best clinically useful lncRNA.

Long non-coding RNAs in non-small cell lung cancer: implications for preventing therapeutic resistance

Lung cancer has the highest mortality and morbidity rates among all cancers worldwide. Despite many complex treatment options, including radiotherapy, chemotherapy, targeted drugs, immunotherapy, and combinations of these treatments, efficacy is low in cases of resistance to therapy, metastasis, and advanced disease, contributing to low overall survival. There is a pressing need for the discovery of novel biomarkers and therapeutic targets for the early diagnosis of lung cancer and to determine the efficacy and outcomes of drug treatments. There is now substantial evidence for the diagnostic and prognostic value of long noncoding RNAs (lncRNAs). This review briefly discusses recent findings on the roles and mechanisms of action of lncRNAs in the responses to therapy in non-small cell lung cancer.

Long non-coding RNAs in lung cancer: Unraveling the molecular modulators of MAPK signaling

Lung cancer (LC) continues to pose a significant global medical burden, necessitating a comprehensive understanding of its molecular foundations to establish effective treatment strategies. The mitogen-activated protein kinase (MAPK) signaling system has been scientifically associated with LC growth; however, the intricate regulatory mechanisms governing this system remain unknown. Long non-coding RNAs (lncRNAs) are emerging as crucial regulators of diverse cellular activities, including cancer growth. LncRNAs have been implicated in LC, which can function as oncogenes or tumor suppressors, and their dysregulation has been linked to cancer cell death, metastasis, spread, and proliferation. Due to their involvement in critical pathophysiological processes, lncRNAs are gaining attention as potential candidates for anti-cancer treatments. This article aims to elucidate the regulatory role of lncRNAs in MAPK signaling in LC. We provide a comprehensive review of the key components of the MAPK pathway and their relevance in LC, focusing on aberrant signaling processes associated with disease progression. By examining recent research and experimental findings, this article examines the molecular mechanisms through which lncRNAs influence MAPK signaling in lung cancer, ultimately contributing to tumor development.

Long Noncoding RNAs in Taxane Resistance of Breast Cancer

Breast cancer is a common cancer in women and a leading cause of mortality. With the early diagnosis and development of therapeutic drugs, the prognosis of breast cancer has markedly improved. Chemotherapy is one of the predominant strategies for the treatment of breast cancer. Taxanes, including paclitaxel and docetaxel, are widely used in the treatment of breast cancer and remarkably decrease the risk of death and recurrence. However, taxane resistance caused by multiple factors significantly impacts the effect of the drug and leads to poor prognosis. Long noncoding RNAs (lncRNAs) have been shown to play a significant role in critical cellular processes, and a number of studies have illustrated that lncRNAs play vital roles in taxane resistance. In this review, we systematically summarize the mechanisms of taxane resistance in breast cancer and the functions of lncRNAs in taxane resistance in breast cancer. The findings provide insight into the role of lncRNAs in taxane resistance and suggest that lncRNAs may be used to develop therapeutic targets to prevent or reverse taxane resistance in patients with breast cancer.

LncFALEC recruits ART5/PARP1 and promotes castration-resistant prostate cancer through enhancing PARP1-meditated self PARylation

Accumulating evidence indicates that long noncoding RNAs (lncRNAs) are abnormal expression in various malignant tumors. Our previous research demonstrated that focally amplified long non-coding RNA (lncRNA) on chromosome 1 (FALEC) is an oncogenic lncRNA in prostate cancer (PCa). However, the role of FALEC in castration-resistant prostate cancer (CRPC) is poorly understood. In this study, we showed FALEC was upregulated in post-castration tissues and CRPC cells, and increased FALEC expression was associated with poor survival in post-castration PCa patients. RNA FISH demonstrated FALEC was translocated into nucleus in CRPC cells. RNA pulldown and followed Mass Spectrometry (MS) assay demonstrated FALEC directly interacted with PARP1 and loss of function assay showed FALEC depletion sensitized CRPC cells to castration treatment and restored NAD⁺. Specific PARP1 inhibitor AG14361 and NAD⁺ endogenous competitor NADP⁺ sensitized FALEC-deleted CRPC cells to castration treatment. FALEC increasing PARP1 meditated self PARylation through recruiting ART5 and down regulation of ART5 decreased CRPC cell viability and restored NAD⁺ through inhibiting PARP1meditated self PARylation in vitro. Furthermore, ART5 was indispensable for FALEC directly interaction and regulation of PARP1, loss of ART5 impaired FALEC and PARP1 associated self PARylation. In vivo, FALEC depleted combined with PARP1 inhibitor decreased CRPC cell derived tumor growth and metastasis in a model of castration treatment NOD/SCID mice. Together, these results established that FALEC may be a novel diagnostic marker for PCa progression and provides a potential new therapeutic strategy to target the FALEC/ART5/PARP1 complex in CRPC patients.

MARCKSL1-2 reverses docetaxel-resistance of lung adenocarcinoma cells by recruiting SUZ12 to suppress HDAC1 and elevate miR-200b

Background

Long non-coding RNAs (lncRNAs) are implicated in the development of multiple cancers. In our previous study, we demonstrated that HDAC1/4-mediated silencing of microRNA-200b (miR-200b) enhances docetaxel (DTX)-resistance of human lung adenocarcinoma (LAD) cells.

Methods and results

Herein, we probed the function of LncRNA MARCKSL1–2 (MARCKSL1-transcript variant 2, NR_052852.1) in DTX resistance of LAD cells. It was found that MARCKSL1–2 expression was markedly reduced in DTX-resistant LAD cells. Through gain- or loss- of function assays, colony formation assay, EdU assay, TUNEL assay, and flow cytometry analysis, we found that MARCKSL1–2 suppressed the growth and DTX resistance of both parental and DTX-resistant LAD cells. Moreover, we found that MARCKSL1–2 functioned in LAD through increasing miR-200b expression and repressing HDAC1. Mechanistically, MARCKSL1–2 recruited the suppressor of zeste 12 (SUZ12) to the promoter of histone deacetylase 1 (HDAC1) to strengthen histone H3 lysine 27 trimethylation (H3K27me3) of HDAC1 promoter, thereby reducing HDAC1 expression. MARCKSL1–2 up-regulated miR-200b by blocking the suppressive effect of HDAC1 on the histone acetylation modification at miR-200b promoter. Furthermore, in vivo analysis using mouse xenograft tumor model supported that overexpression of MARCKSL1–2 attenuated the DTX resistance in LAD tumors.

Conclusions

We confirmed that MARCKSL1–2 alleviated DTX resistance in LAD cells by abolishing the inhibitory effect of HDAC1 on miR-200b via the recruitment of SUZ12. MARCKSL1–2 could be a promising target to improve the chemotherapy of LAD.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12943-022-01605-w.

Exosome-mediated transfer of SNHG7 enhances docetaxel resistance in lung adenocarcinoma

Long noncoding RNA (lncRNA) small nucleolar RNA host gene 7 (SNHG7) has been widely reported in various cancers, including lung adenocarcinoma (LUAD). However, it is largely unknown whether SNHG7 is involved in docetaxel resistance of LUAD. In the current study, we identified the high expression of SNHG7 in docetaxel-resistant cells. Through functional assays, we determined that silencing of SNHG7 decreased IC₅₀ value of LUAD cells to docetaxel and suppressed proliferation and autophagy in LUAD cells, and reversed M2 polarization in macrophages. Mechanistically, we uncovered that SNHG7 promoted autophagy via recruiting human antigen R (HuR) to stabilize autophagy-related genes autophagy related 5 (ATG5) and autophagy related 12 (ATG12). Moreover, exosomal SNHG7 was transmitted from docetaxel-resistant LUAD cells to parental LUAD cells and thus facilitated docetaxel resistance. Additionally, exosomal SNHG7 activated the phosphatidylinositol 3-kinase (PI3K)/AKT pathway to promote M2 polarization in macrophages via recruiting cullin 4A (CUL4A) to induce ubiquitination and degradation of phosphatase and tensin homolog (PTEN). Taken together, we concluded that exosomal SNHG7 enhances docetaxel resistance of LUAD cells through inducing autophagy and macrophage M2 polarization. All findings in the study suggested that SNHG7 may be a promising target for relieving docetaxel resistance in LUAD.

CCAT1/FABP5 promotes tumour progression through mediating fatty acid metabolism and stabilizing PI3K/AKT/mTOR signalling in lung adenocarcinoma

Long non‐coding RNA (lncRNA) colon cancer associated transcript 1 (CCAT1) has been identified as an oncogene in many cancers, but its role in lung adenocarcinoma (LUAD) remains to be further investigated. We identified the upregulation of CCAT1 in LUAD tissues and LUAD cells. Through RNA pull‐down and mass spectrometry analysis, we obtained the interacting proteins with CCAT1 and discovered their functional relation with ‘signal transduction’, ‘energy pathways’ and ‘metabolism’ and revealed the potential of CCAT1 on fatty acid (FA) metabolism. For mechanism exploration, we uncovered the mediation of CCAT1 on the translocation of fatty acid binding protein 5 (FABP5) into nucleus by confirming their interaction and localization. Also, CCAT1 was discovered to promote the formation of the transcription complex by RXR and PPARγ so as to activate the transcription of CD36, PDK1 and VEGFA. Moreover, we found that CCAT1 regulated the activity of AKT by promoting the ubiquitination of FKBP51 through binding with USP49. Subsequently, cell function assays revealed the enhancement of CCAT1 on LUAD cell proliferation and angiogenesis in vitro and in vivo. Collectively, CCAT1 regulated cell proliferation and angiogenesis through regulating FA metabolism in LUAD, providing a novel target for LUAD treatment.

Role of mammalian long non-coding RNAs in normal and neuro oncological disorders

Long non-coding RNAs (lncRNAs) are expressed at lower levels than protein-coding genes but have a crucial role in gene regulation. LncRNA is distinct, they are being transcribed using RNA polymerase II, and their functionality depends on subcellular localization. Depending on their niche, they specifically interact with DNA, RNA, and proteins and modify chromatin function, regulate transcription at various stages, forms nuclear condensation bodies and nucleolar organization. lncRNAs may also change the stability and translation of cytoplasmic mRNAs and hamper signaling pathways. Thus, lncRNAs affect the physio-pathological states and lead to the development of various disorders, immune responses, and cancer. To date, ~40% of lncRNAs have been reported in the nervous system (NS) and are involved in the early development/differentiation of the NS to synaptogenesis. LncRNA expression patterns in the most common adult and pediatric tumor suggest them as potential biomarkers and provide a rationale for targeting them pharmaceutically. Here, we discuss the mechanisms of lncRNA synthesis, localization, and functions in transcriptional, post-transcriptional, and other forms of gene regulation, methods of lncRNA identification, and their potential therapeutic applications in neuro oncological disorders as explained by molecular mechanisms in other malignant disorders.

Long noncoding RNA SNHG20 regulates cell migration, invasion, and proliferation via the microRNA-19b-3p/RAB14 axis in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most common digestive tumors, which has high mortality rate. Long non-coding RNAs (lncRNA) and MicroRNAs (miRNAs) are associated with the cell cycle and differentiation during the occurrence and development of malignant tumors. This research aimed to investigate the effects of lncRNA SNHG20 on the progress of oral squamous cell carcinoma (OSCC) cells. Ninety pairs of tumor tissues and paracancerous tissues were collected from patients with OSCC and the CAL27 and SCC25 OSCC cells were selected for the following experiments. RT-qPCR was used for detecting the expression of SNHG20, miR-19b-3p, and RAB14. Western blotting was used to detect the protein levels of RAB14. MTT assay was employed to assess cell proliferation. Transwell assay was used to determine the cell migration and invasion abilities. Furthermore, luciferase reporter and RNA pull-down assays were used to verify the binding of SNHG20/RAB14 to miR-19b-3p. Then, the function of the SNHG20/miR-19b-3p/RAB14 axis in OSCC was explored. The results indicated that lncRNA SNHG20 was upregulated in the tissues. Furthermore, bioinformatic analysis showed that both SNHG20 and RAB14 could bind to miR-19b-3p. RAB14 was upregulated, and miR-19b-3p was downregulated in the tissues. The knockdown of SNHG20 inhibited cell proliferation, migration, and invasion. Contrarily, the knockdown of miR-19b-3p reversed the effects of si-SNHG20 on cell proliferation, migration, and invasion, and the overexpression of RAB14 reversed the effects of miR-19b-3p mimic on the cell biological functions. LncRNA SNHG20 affects cell proliferation, migration, and invasion via the miR-19b-3p/RAB14 axis in OSCC.

Targeting Epigenetics in Lung Cancer

The epigenetic landscape, which in part includes DNA methylation, chromatin organization, histone modifications, and noncoding RNA regulation, greatly contributes to the heterogeneity that makes developing effective therapies for lung cancer challenging. This review will provide an overview of the epigenetic alterations that have been implicated in all aspects of cancer pathogenesis and progression as well as summarize clinical applications for targeting epigenetics in the treatment of lung cancer.

The Role of LncRNAs in Translation

Long non-coding RNAs (lncRNAs), a group of non-protein coding RNAs with lengths of more than 200 nucleotides, exert their effects by binding to DNA, mRNA, microRNA, and proteins and regulate gene expression at the transcriptional, post-transcriptional, translational, and post-translational levels. Depending on cellular location, lncRNAs are involved in a wide range of cellular functions, including chromatin modification, transcriptional activation, transcriptional interference, scaffolding and regulation of translational machinery. This review highlights recent studies on lncRNAs in the regulation of protein translation by modulating the translational factors (i.e, eIF4E, eIF4G, eIF4A, 4E-BP1, eEF5A) and signaling pathways involved in this process as wells as their potential roles as tumor suppressors or tumor promoters.

Role of LINC00152 in non-small cell lung cancer

Non-small cell lung cancer (NSCLC) accounts for about 85% of all lung cancer cases. The pathogenesis of NSCLC involves complex gene networks that include different types of non-coding RNAs, such as long non-coding RNAs (lncRNAs). The role of lncRNAs in NSCLC is gaining an increasing interest as their function is being explored in various human cancers. Recently, a new oncogenic lncRNA, LINC00152 (cytoskeleton regulator RNA (CYTOR)), has been identified in different tumor types. In NSCLC, the high expression of LINC00152 in tumor tissue and peripheral blood samples has been shown to be associated with worse prognoses of NSCLC patients. Overexpression of LINC00152 has been confirmed to promote the proliferation, invasion, and migration of NSCLC cells in vitro, as well as increase tumor growth in vivo. This review discusses the role of LINC00152 in NSCLC.

Long non-coding RNA CCAT1 promotes non-small cell lung cancer progression by regulating the miR-216a-5p/RAP2B axis

The long non-coding RNA colon cancer-associated transcript 1 (CCAT1) has been investigated to involve in the progression of non-small cell lung cancer (NSCLC). Thus, this study aims to explore the detailed molecular mechanisms of CCAT1 in NSCLC. The expression of CCAT1, miR-216a-5p, RAP2B, Bax, Bcl-2, and cleaved caspase 3 was detected by qRT-PCR or Western blot. Cell proliferation, apoptosis, migration, and invasion were analyzed using cell counting kit-8, flow cytometry or Transwell assays, respectively. The interaction between miR-216a-5p and CCAT1 or RAP2B was analyzed by luciferase reporter, RNA immunoprecipitation, and pull-down assays. The expression of CCAT1 was elevated in NSCLC, and CCAT1 deletion could inhibit NSCLC cell proliferation, migration, and invasion but induce apoptosis in vitro as well as imped tumor growth in vivo. MiR-216a-5p was confirmed to be a target of CCAT1, and silencing miR-216a-5p could reverse CCAT1 depletion-mediated inhibitory effects on cell tumorigenesis in NSCLC. Besides that, miR-216a-5p was decreased in NSCLC, and miR-216a-5p restoration inhibited cell tumorigenesis by regulating RAP2B, which was verified to be a target of miR-216a-5p. Additionally, co-expression analysis suggested that CCAT1 indirectly regulated RAP2B level by targeting miR-216a-5p in NSCLC cells. Taken together, CCAT1 deletion could inhibit cell progression in NSCLC through miR-216a-5p/RAP2B axis, indicating a novel pathway underlying NSCLC cell progression and providing new potential targets for NSCLC treatment.

Long non-coding RNAs as potential biomarkers in the prognosis and diagnosis of lung cancer: A review and target analysis

Long non-coding RNAs (lncRNA) have been emerged as a novel class of molecular regulators in cancer. They are dysregulated in many types of cancer; however, there is not enough knowledge available on their expression and functional profiles. Lung cancer is the leading cause of the cancer deaths worldwide. Generally, lncRNAs may be associated with lung tumor pathogenesis and they may act as biomarkers for the cancer prognosis and diagnosis. Compared to other invasive prognostic and diagnostic methods, detection of lncRNAs might be a user-friendly and noninvasive method. In this review article, we selected 27 tumor-associated lncRNAs by literature reviewing to further discussing in detail for using as diagnostic and prognostic biomarkers in lung cancer. Also, in an in silico target analysis, the "Experimentally supported functional regulation" approach of the LncTarD web tool was used to identifying the target genes and regulatory mechanisms of the selected lncRNAs. The reports on diagnostic and prognostic potential of all selected lncRNAs were discussed. However, the target genes and regulatory mechanisms of the 22 lncRNAs were identified by in silico analysis and we found the pathways that are controlled by each target group of lncRNAs. They use epigenetic mechanisms, ceRNA mechanisms, protein interaction and sponge mechanism. Also, 10, 23, 5, and 28 target genes for each of these mechanisms were identified, respectively. Finally, each group of target genes controls 50, 12, 7, and 2 molecular pathways, respectively. In conclusion, LncRNAs could be used as biomarkers in lung cancer due to their roles in control of several signaling pathways related to lung tumors. Also, it seems that lncRNAs, which use epigenetic mechanisms for modulating a large number of pathways, could be considered as important subjects for lung cancer-related diagnostic and prognostic biomarkers.

Long noncoding RNAs in cancer immunity: a new avenue in drug discovery

The central role of the nonprotein-coding portion of the genome, such as long noncoding (lnc)RNAs is emerging as a hidden player manipulating the immune system in cancer. lncRNAs, in association with their interacting partners, regulate the expression of various immune system genes, which are perturbed during cancer. The tissue-specific expression of lncRNAs and their importance in cellular proliferation, the tumor microenvironment (TME), epithelial-mesenchymal transition (EMT), and modulation of the cells of the innate and adaptive immune system have novel therapeutic implications in establishing lncRNAs as biomarkers and targets to overcome cancer-associated immunosuppression. In this review, we establish and strengthen the link between lncRNAs and cancer immunity.

The role of long non-coding RNAs in drug resistance of cancer

Long non-coding RNAs (lncRNAs), a class of long RNAs, are longer than 200 nucleotides in length but lack protein-coding capacity. LncRNAs, as critical genomic regulators, are involved in genomic imprinting regulation, histone modification and gene expression regulation as well as tumor initiation and progression. However, it is also found that lncRNAs are associated with drug resistance in several types of cancer. Drug resistance is an important reason for clinical chemotherapy failure, and the molecular mechanism of tumor resistance is complex, which is a process of multi-cause, multi-gene and multi-signal transduction pathway interaction. Then comprehending the mechanisms of chemoresistance will help find ways to control the tumor progression effectively. Therefore, in this review, we will construct lncRNAs /drug resistance interaction network and shed light on the role of lncRNAs in drug resistance.

The Non-coding Side of Medulloblastoma

Medulloblastoma (MB) is the most common pediatric brain tumor and a primary cause of cancer-related death in children. Until a few years ago, only clinical and histological features were exploited for MB pathological classification and outcome prognosis. In the past decade, the advancement of high-throughput molecular analyses that integrate genetic, epigenetic, and expression data, together with the availability of increasing wealth of patient samples, revealed the existence of four molecularly distinct MB subgroups. Their further classification into 12 subtypes not only reduced the well-characterized intertumoral heterogeneity, but also provided new opportunities for the design of targets for precision oncology. Moreover, the identification of tumorigenic and self-renewing subpopulations of cancer stem cells in MB has increased our knowledge of its biology. Despite these advancements, the origin of MB is still debated, and its molecular bases are poorly characterized. A major goal in the field is to identify the key genes that drive tumor growth and the mechanisms through which they are able to promote tumorigenesis. So far, only protein-coding genes acting as oncogenic drivers have been characterized in each MB subgroup. The contribution of the non-coding side of the genome, which produces a plethora of transcripts that control fundamental biological processes, as the cell choice between proliferation and differentiation, is still unappreciated. This review wants to fill this major gap by summarizing the recent findings on the impact of non-coding RNAs in MB initiation and progression. Furthermore, their potential role as specific MB biomarkers and novel therapeutic targets is also highlighted.

Role of long non-coding RNAs and MYC interaction in cancer metastasis: A possible target for therapeutic intervention

The c-MYC is one of the most commonly discussed oncogenes in almost all cancers. c-MYC, as a proto-oncogene in normal cells, has found to be tightly controlled and regulated, both genetically and epigenetically. Evasion of the controlled checkpoint mechanisms during cancer causes a deregulated expression of c-MYC. Overexpression of c-MYC causes the onset of many hallmarks of cancer. Despite c-MYC being centrally located in several cancers, it is not feasible to target c-MYC in therapeutic resistant cancers. Similarly, long non-coding RNAs (lncRNAs) are deregulated during the genesis and progression of different cancers. LncRNAs contribute to almost 27% human genome and recent findings by tumor genome sequencing revealed many of the lncRNAs loci that are modified, deleted, amplified, and mutated during the different stages of cancer development. Recent studies also reported that multiple lncRNAs regulate c-MYC by different mechanisms and vice versa. Thus, oncogenic lncRNAs and c-MYC interaction are positioned to provide an interesting choice for therapeutic interventions in cancers. In this mini-review, we summarize the recent discoveries and explain how the interaction between oncogenic lncRNAs and c-MYC could be used as a possible target for therapeutic intervention in cancers, especially the therapeutic resistant metastatic cancers.

Non-coding RNAs in drug resistance of head and neck cancers: A review

Head and neck cancer (HNC), which includes epithelial malignancies of the upper aerodigestive tract (oral cavity, oropharynx, pharynx, hypopharynx, larynx, and thyroid), are slowly but consistently increasing, while the overall survival rate remains unsatisfactory. Because of the multifunctional anatomical intricacies of the head and neck, disease progression and therapy-related side effects often severely affect the patient's appearance and self-image, as well as their ability to breathe, speak, and swallow. Patients with HNC require a multidisciplinary approach involving surgery, radiation therapy, and chemotherapeutics. Chemotherapy is an important part of the comprehensive treatment of tumors, especially advanced HNC, but drug resistance is the main cause of poor clinical efficacy. The most important determinant of this phenomenon is still largely unknown. Recent studies have shown that non-coding RNAs have a crucial role in HNC drug resistance. In addition, they can serve as biomarkers in the diagnosis, treatment, and prognosis of HNCs. In this review, we summarize the relationship between non-coding RNAs and drug resistance of HNC, and discuss their potential clinical application in overcoming HNC chemoresistance.

Long non-coding RNA CCAT1 promotes colorectal cancer progression by regulating miR-181a-5p expression

The vital roles of long noncoding RNAs (lncRNAs) have been implicated in growing number of studies in tumor development. LncRNA CCAT1 has been recognized as associated with tumor development, yet its relation with colorectal cancer (CRC) remains elusive. Our study aimed at elucidating the function and mechanisms of long non-coding RNA CCAT1 in CRC. From a lncRNA profile dataset of 38 pairs of matched tumor-control colon tissues from colorectal patients housed in The Cancer Genome Atlas (TCGA), we detected 10 upregulated and 10 down-regulated lncRNAs in CRC. Fifty cases of CRC patients were enrolled to analyze the correlation between the expression of CCAT1 and clinical pathology. The inverse correlation of expression and target relationship between CCAT1 and miR-181a-5p were verified using qRT-PCR and dual-luciferase reporter gene assay. Cell viability, colony formation ability, aggression and apoptosis were determined by MTT assay, colony formation assay, Transwell and wound healing assays and flow cytometry analysis. Furthermore, Xenograft model was used to show that knockdown of CCAT1 inhibits tumor growth in vivo. The expression of lncRNA CCAT1 was significantly upregulated in CRC tissues. The CCAT1 expression was positively associated with cancer stage (American Joint Committee on Cancer stage, P<0.05). CCAT1 promoted cell proliferation, growth and mobility by targeting miR-181a-5p and the silence of CCAT1 increased the cell apoptosis. Same effect was observed in an in vivo xenograft model, which the tumor size and pro-tumor proteins were significantly diminished by knocking down of CCAT1.

Identification and validation of potential key long noncoding RNAs in sorafenib-resistant hepatocellular carcinoma cells

As the first-line treatment, sorafenib has been used for advanced hepatocellular carcinoma (HCC), but the chemoresistance commonly restricts to the clinical efficiency. In this study, we intend to investigate the genome-wide expression pattern of long noncoding RNAs (lncRNAs) in sorafenib-resistant HCC. Herein, we identified thousands of differentially expressed lncRNAs in sorafenib-resistant HCC cells by high-throughput sequencing compared to the parental. Besides, based on GO (Gene Ontology) term enrichment analysis, these differentially expressed lncRNAs are mainly related to binding and catalytic activity and biological regulation of metabolic processes in both the sorafenib-resistant Huh7 cells (Huh7-S) and sorafenib-resistant HepG2 cells (HepG2-S) compared to the parental cells. Moreover, when analyzed by KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway, the differentially expressed genes were significantly related to the tight junction. Among them, the expression of TCONS_00284048 and TCONS_00006019 was consistently up-regulated in sorafenib-resistant HCC cell lines, whereas when either was knocked down, the sensitivity of Huh7-S and HepG2-S cells to sorafenib was increased. Taken together, our data demonstrate that the lncRNA expression profile is significantly altered in sorafenib-resistant HCC cells as well as differentially expressed lncRNAs may play crucial functions on HCC sorafenib resistance and HCC progression.

Long Non-coding RNA CCAT1 Sponges miR-454 to Promote Chemoresistance of Ovarian Cancer Cells to Cisplatin by Regulation of Surviving

Purpose

Colon cancer-associated transcript 1 (CCAT1) was identified as an oncogenic long non-coding RNA (lncRNA) in a variety of cancers. However, there was a lack of understanding of the mechanism by which CCAT1 conferred cisplatin (also known as DDP) resistance in ovarian cancer cells.

Materials and Methods

Cell viability of A2780, SKOV3, A2780/DDP, and SKOV3/DDP cells upon cisplatin treatment was monitored by MTT assay. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) detected the expression levels of CCAT1 and miR-454. The effect of sh-CCAT1 on cisplatin response was investigated in xenografts study. Bioinformatic analysis, luciferase reporter assay and qRT-PCR were conducted to validate the direct interaction among CCAT1, miR-454, and survivin. Apoptosis was determined by flow cytometry after dual staining of Annexin-V-FITC/propidium iodide, and the expression of apoptosis-related proteins Bcl-2, Bax and survivin were detected by qRT-PCR and Western blotting. Xenograft study was conducted to monitor in vivo tumor formation.

Results

CCAT1 was highly expressed in cisplatin-resistant ovarian cancer cell line A2780/DDP and SKOV3/DDP. Knockdown of CCAT1 restored sensitivity to cisplatin in vitro and in vivo. Our data revealed that silencing of CCAT1 promoted cisplatin-induced apoptosis via modulating the expression of pro- or anti-apoptotic proteins Bax, Bcl-2, and survivin. CCAT1 directly interacted with miR-454, and miR-454 overexpression potentiated cisplatin-induced apoptosis. Survivin was identified as a functional target of miR-454, restoration of survivin attenuated the effect of miR-454 on cisplatin response. In addition, miR-454 inhibitor or overexpression of survivin was found to abolish sh-CCAT1–induced apoptosis upon cisplatin treatment.

Conclusion

CCAT1/miR-454/survivin axis conferred cisplatin resistance in ovarian cancer cells.

Knockdown of lncRNA CCAT1 enhances sensitivity of paclitaxel in prostate cancer via regulating miR-24-3p and FSCN1

Drug resistance limits the efficacy of chemotherapy in human cancers. Previous studies reported that long noncoding RNA colon cancer-associated transcript 1 (CCAT1) regulated progression of prostate cancer (PCa). However, the potential role of CCAT1 in the sensitivity of paclitaxel (PTX) in PCa and its mechanism remain largely unknown. The PTX-resistant PCa cells were established in PC3 and DU145 cells by increasing concentrations of PTX. The expressions of CCAT1, microRNA-24-3p (miR-24-3p) and fascin1 (FSCN1) were measured by quantitative real-time polymerase chain reaction. The viability and apoptosis were detected by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, flow cytometry and western blot, respectively. The interaction among CCAT1, miR-24-3p and FSCN1 was explored by luciferase activity, RNA immunoprecipitation, RNA pull-down and western blot, respectively. Results showed that the expressions of CCAT1 were up-regulated and miR-24-3p was down-regulated in PCa and PTX-resistant PCa cells (PC3-TXR and DU145-TXR). Knockdown of CCAT1 or overexpression of miR-24-3p inhibited survival rate, half maximal inhibitory concentration (IC50) of PTX but increased apoptosis in PC3-TXR and DU145-TXR cells after treatment of PTX. miR-24-3p was bound to CCAT1 and its abrogation reversed knockdown of CCAT1-mediated increase of PTX sensitivity in PC3-TXR and DU145-TXR cells. Moreover, FSCN1 restoration attenuated miR-24-3p-mediated inhibition of PTX resistance. Besides, FSCN1 level was enhanced in PCa and PTX-resistant PCa cells and regulated by CCAT1 and miR-24-3p. Our data suggested interference of CCAT1 contributed to PTX sensitivity in PCa by regulating miR-24-3p and FSCN1, indicating a novel avenue for treatment of PCa through regulating chemoresistance.

Non-coding RNAs in Lung Cancer Chemoresistance

Background:

Lung cancer is the leading cause of cancer-associated death worldwide with limited treatment options. The major available treatment options are surgery, radiotherapy, chemotherapy and combinations of these treatments. In chemotherapy, tyrosine kinase inhibitors and taxol are the first lines of chemotherapeutics used for the treatment of lung cancer. Often drug resistance in the clinical settings hinders the efficiency of the treatment and intrigues the tumor relapse. Drug-resistance is triggered either by intrinsic factors or due to the prolonged cycles of chemotherapy as an acquired-resistance. There is an emerging role of non-coding RNAs (ncRNAs), including notorious microRNAs (miRNAs), proposed to be actively involved in the regulations of various tumor-suppressor genes and oncogenes.

Result:

The altered gene expression by miRNA is largely mediated either by the degradation or by interfering with the translation of targeted mRNA. Unlike miRNA, other type of ncRNAs, such as long non-coding RNAs (lncRNAs), can target the transcriptional activator or the repressor, RNA polymerase, and even DNA-duplex to regulate the gene expressions. Many studies have confirmed the crucial role of ncRNAs in lung adenocarcinoma progression and importantly, in the acquisition of chemoresistance. Recently, ncRNAs have become early biomarkers and therapeutic targets for lung cancer.

Conclusion:

Targeting ncRNAs could be an effective approach for the development of novel therapeutics against lung cancer and to overcome the chemoresistance.

Silencing of LINC00461 enhances radiosensitivity of lung adenocarcinoma cells by down-regulating HOXA10 via microRNA-195

Lung adenocarcinoma is recognized as one of the most recurrent tumours in adults. Long non‐coding RNAs (lncRNAs) are non–protein‐coding transcripts and have been demonstrated to regulate biological functions during tumorigenesis. Our study aims to investigate the underlying molecular mechanisms of LINC00461/microRNA‐195 (miR‐195)/HOXA10 responsible for its involvement in lung adenocarcinoma. We firstly selected differentially expressed lncRNAs and genes by the Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO). The functional role of LINC00461 in lung adenocarcinoma was then determined using ectopic expression, knockdown and reporter assay experiments. Besides, we detected the expression profiles of LINC00461, miR‐195, HOXA10 and apoptosis‐ and invasion‐related genes. Cell proliferation, migration and invasion were evaluated. In vivo tumour formation ability was analysed. Overexpressed LINC00461 and HOXA10 but down‐regulated miR‐195 were observed in primary and metastatic lung adenocarcinoma. LINC00461 negatively regulated miR‐195, while miR‐195 negatively regulated HOXA10. Forced LINC00461 expression decreased expression of miR‐195 and Bax, increased expression of HOXA10, MMP‐2, MMP‐9 and Bcl‐2, promoted cell proliferation, migration and invasion as well as tumour formation, and enhanced radiosensitivity of lung adenocarcinoma cells. However, these effects were reversed by lentivirus‐mediated miR‐195–forced expression, thereby suggesting that miR‐195 could antagonize the harmful effect of LINC00461 on lung adenocarcinoma cells. Collectively, the present study provides evidence supporting the inhibitory effect of LINC00461 silencing on lung adenocarcinoma, which suppresses lung adenocarcinoma cell migration, invasion and radiosensitivity via HOXA10 by binding to miR‐195, which provides a promising basis for the targeted intervention treatment for human lung adenocarcinoma.

Long Non-Coding RNA in Drug Resistance of Non-Small Cell Lung Cancer: A Mini Review

Lung cancer is one of main causes of cancer mortality and 83% of lung cancer cases are classified as non-small cell lung cancer (NSCLC). Patients with NSCLC usually have a poor prognosis and one of the leading causes is drug resistance. With the progress of drug therapy, the emergence and development of drug resistance affected the prognosis of patients severely. Accumulating evidence reveals that long non-coding RNAs (lncRNAs), as “dark matters” of the human genome, is of great significance to drug resistance in NSCLC. Herein, we review the role of lncRNAs in drug resistance in NSCLC.

Long non-coding RNA in lung cancer

Lung cancer is the leading cause of cancer-related death worldwide. Owing to the difficulty in early diagnosis and the lack of effective treatment strategies, the 5-year survival rates for lung cancer remain very low. With the development of whole genome and transcriptome sequencing technology, long non-coding RNA (lncRNA) has attracted increasing attention. LncRNAs regulate gene expression at the epigenetic, transcriptional and post-transcriptional levels and are widely involved in a variety of diseases, including tumorigenesis. In lung cancer studies, multiple differentially expressed lncRNAs have been identified; several lncRNAs were identified as oncogenic lncRNAs with tumor-driving effects, while other lncRNAs play a role in tumor inhibition and are called tumor-suppressive lncRNAs. These tumor-suppressive lncRNAs are involved in multiple physiological processes such as cell proliferation, apoptosis, and metastasis and thus participate in tumor progression. In this review, we discussed the oncogenic and tumor-suppressive lncRNAs in lung cancer, as well as their biological functions and regulatory mechanisms. Furthermore, we found the potential significance of lncRNAs in clinical diagnosis and treatment.

Long non-coding RNAs in non-small cell lung cancer: functions and distinctions from other malignancies

Lung cancer leads to the most cancer-related death in the world. It was shown from the increasing evidences that long non-coding RNAs (lncRNAs) are emerging as molecules for diagnosis, prognosis and even therapy of lung cancer and other malignancies. The biological functions or involved signaling pathways of lncRNAs are always found to be inconsistent among different types of malignancies. However, no available literature has systemically summarized differences in the functions and underlying molecular mechanisms of lncRNAs between lung cancer and other cancers. In this review, the biological functions and molecular mechanisms of lncRNAs in lung cancer were introduced. Furthermore, their functional differences between lung cancer and other malignancies were discussed. Finally, their potential clinical applications in future lung cancer therapy were focused on.

Colon Cancer-Associated Transcripts 1 and 2: Roles and functions in human cancers

The long noncoding RNAs (lncRNAs) Colon Cancer-Associated Transcripts 1 and 2 (CCAT1 and CCAT2) are located in a recurrently amplified region in cancers. Their proximity with the Myc oncogene and their interactions with its promoter provided further evidence for their contribution in the tumorigenesis processes. Several cell line and clinical studies have shown upregulation of these lncRNAs in diverse malignancies. Moreover, some single nucleotide variants within these genes have been associated with cancer risk or therapeutic response in different populations. Besides, these two lncRNAs act as sponges for some tumor suppressor microRNAs (miRNAs), thus promoting cancer evolution. In the current study, we review recent literature about their expression level, interaction with cancer-related pathways, their role in determination of cell fate and their contribution in malignant phenotype characteristics. Taken together, the current literature shows that these lncRNAs are putative targets for design of novel treatment strategies. Moreover, their expression levels in biopsied samples, exosomes, and sera of patients might be applied as diagnostic biomarkers or markers for patient follow-up.

The functions and oncogenic roles of CCAT1 in human cancer

In various human cancers, long non-coding RNAs (lncRNAs), a novel class of RNAs longer than 200 nucleotides without protein-coding potential, are implicated in a variety of biological processes, such as cell proliferation, invasion, metastasis, and apoptosis through regulation of gene expression at various levels including chromatin, splicing, transcriptional and post-transcriptional levels. However, the mechanisms underlying these are still elusive. Colon cancer-associated transcript 1(CCAT1) has received increased attention among those lncRNAs. Studies have shown high expression pattern and oncogenic role of CCAT1 in different types of cancer, and aberrant expression of CCAT1 has been involved in tumor-genesis, progression, metastasis, and patient survival via regulating different target genes and signaling pathways. In this review, we first introduce the concept, identification, and biological function of CCAT1; we then describe the mechanisms by which CCAT1 regulate the cancer proliferation and progression. In the last, we discuss emerging insights into the role of CCAT1 as potential biomarker and therapeutic target for novel treatment paradigms in cancer.

The effects of cigarette smoking extracts on cell cycle and tumor spread: novel evidence

Cigarette smoking is a major preventable risk factor for lung cancer, contributing to lung cancer progression and metastasis. Moreover, cigarette smoking correlates with increased metastasis frequency of pancreatic, breast and bladder cancer. The aim of this review was to examine the role of cigarette smoke extract in cell cycle and cancer progression. Clinical impact and the effects of cigarette smoke extract on carcinogenesis are discussed. 98 of the over 5000 chemicals in tobacco smoke are known carcinogens that can act on cancer genes such as K-RAS and p53. Through various mechanisms these compounds can activate molecules involved in the cell cycle, such as cyclins, and molecules involved in apoptosis and autophagy, such as Beclin-1 or LC3B. A search of the literature, including in vitro and in vivo studies, was carried out and the results summarized.

There is evidence of cancerogenic effects of cigarette smoke compounds. Cigarette smoke extract is a tobacco condensate obtained by filtration processes. Studies have shown that it can modify the cell cycle, inducing uncontrolled cell proliferation. This effect occurs through activation of genetic and epigenetic pathways and increasing the expression of proteins involved in inflammation. The pathways activated by cigarette smoke extract open up opportunities for researchers to develop new targeted therapies toward the specific molecules involved. Furthermore, the effects exerted by cigarette smoke extract on normal epithelial cells hold potential for use in the development of prevention medicine and early cancer diagnosis.

Downregulation of lncRNA CCAT1 enhances 5-fluorouracil sensitivity in human colon cancer cells

BACKGROUND

The purpose of this study was to determine the aberrant expression of the long noncoding RNA (lncRNA) colon cancer-associated transcript 1 (CCAT1) in 5-fluorouracil-resistant colonic neoplasm cells and to elucidate its effects on the 5-fluorouracil sensitivity of human colonic neoplasm cells. The aberrant expression of lncRNAs in normal tissues and colonic neoplasm tissues was detected by microarray assay. qRT-PCR analysis was performed to assess CCAT1 expression levels in colonic neoplasm cell lines and corresponding normal tissues. After constructing the 5-FU-resistant cell lines and validating the resistance by measuring the IC₅₀ value, the CCAT1 expression levels in parental and artificially resistant cell lines were determined by qRT-PCR. Transfection was used to modulate the expression of CCAT1. Cell proliferation and apoptosis were then detected by CCK-8 and flow cytometry, respectively.

RESULTS

CCAT1 in colon cancer tissues was higher than that in noncancer tissues, and the levels of CCAT1 in HCT 116, SW1417, HT-29, and KM12 cell lines were higher than those in the human normal colon epithelial NCM460 cell line. Moreover, the expression levels of CCAT1 were high in HCT 116/5-FU and HT-29/5-FU cell lines, whose apoptosis rates induced by 5-FU were lower than those in corresponding parental cells. The results of qRT-PCR and CCK-8 assay showed that enhancement of lncRNA CCAT1 expression levels in HCT 116 and HT-29 cell lines increased their IC₅₀ of 5-FU and decreased their apoptosis rates. Meanwhile, siRNA-CCAT1 effectively inhibited the expression of CCAT1 and enhanced the 5-FU-sensitivity of HCT 116/5-FU and HT-29/5-FU, in which apoptosis rates were increased at the same time.

CONCLUSIONS

Downregulation of CCAT1 effectively reversed the resistance of HCT 116/5-FU and HT-29/5-FU cells to 5-FU chemotherapeutic, opening a new avenue in colon cancer therapy.

CCAT1 lncRNA Promotes Inflammatory Bowel Disease Malignancy by Destroying Intestinal Barrier via Downregulating miR-185-3p

BACKGROUND

The long noncoding RNA (lncRNA) colon cancer-associated transcript-1 (CCAT1) has been reported to play a vital role in the development of cancer. Although the link between inflammation and cancer initiation is well established, whether CCAT1 is involved in inflammation and promotes inflammatory bowel disease (IBD) malignancy remains undetermined. We aimed to investigate the expression of CCAT1 in IBD and the effect of CCAT1 overexpression on intestinal epithelial barrier function.

METHODS

The relationship between CCAT1 and the inflammation-related pathway was analyzed in both colorectal cancer (CRC) and IBD patients. Gene expression was detected by real-time polymerase chain reaction and Western blot. Transepithelial electrical resistance (TEER) and FD-4 flux measurement were used to test the effect of CCAT1 and miR-185-3p on intestinal epithelial barrier function. Luciferase assay was performed to validate the target site of miR-185-3p on 3'-UTR of MLCK mRNA.

RESULTS

Gene set enrichment analysis revealed that several inflammation-related genes were enriched in the CCAT1 high-expressed group of CRC patients. The relationship between CCAT1 and inflammation activation in IBD patients was further confirmed. CCAT1 expression positively correlated with MLCK, which acts as a protein kinase to phosphorylate myosin light chain and induces tight junction protein distribution, whereas it was negatively correlated with miR-185-3p in IBD tissues. We also determined that CCAT1 overexpression increased Caco-2 monolayer permeability and upregulated MLCK. Furthermore, CCAT1-induced MLCK overexpression and IBD disease progression were significantly attenuated by miR-185-3p.

CONCLUSIONS

The CCAT1/miR-185-3p/MLCK signaling pathway is strongly activated to destroy barrier function and promotes the pathogenesis of IBD.

Downregulation of long noncoding RNA PVT1 attenuates paclitaxel resistance in glioma cells

BACKGROUND

Drug resistance in clinical cancer treatment has become an issue.

OBJECTIVE

We focus on abnormally expressed lncRNAs in glioma and investigating the function of PVT1.

METHODS

The paclitaxel-resistant glioma cells SHG-44 RE was obtained through screening the SHG 44 cells that were cultured in medium containing a certain concentration of paclitaxel. Cell survival of SHG 44 RE and SHG 44 cells under the treatment of paclitaxel was detected by MTT assay. The aberrant expressed lncRNAs were screened out with microarray analysis. Further qRT-PCR was utilized to validate the expression of lncRNA PVT1 in the two cells. After manipulating the expression of PVT1, cell viability and apoptosis were measured by MTT and flow cytometry respectively.

RESULTS

LncRNA PVT1 was overexpressed in glioma cells SHG-44 RE compared with parent SHG-44 cells. Down-regulation of lncRNA PVT1 inhibited the SHG-44 RE cell viability and increased glioma SHG-44 RE cells apoptosis after paclitaxel treatment, suggesting that inhibition of lncRNA PVT1 improved paclitaxel sensibility in human glioma cells.

CONCLUSION

Down-regulation of PVT1 could enhance chemosensitivity of paclitaxel, induce apoptosis of glioma cells and noteworthy inhibit glioma cells proliferation. Our findings of PVT1 could contribute to attenuate paclitaxel resistance in clinical medicine.

Long Noncoding RNAs: Emerging Players in Medulloblastoma

Central Nervous System tumors are the leading cause of cancer-related death in children, and medulloblastoma has the highest incidence rate. The current therapies achieve a 5-year survival rate of 50-80%, but often inflict severe secondary effects demanding the urgent development of novel, effective, and less toxic therapeutic strategies. Historically identified on a histopathological basis, medulloblastoma was later classified into four major subgroups-namely WNT, SHH, Group 3, and Group 4-each characterized by distinct transcriptional profiles, copy-number aberrations, somatic mutations, and clinical outcomes. Additional complexity was recently provided by integrating gene- and non-gene-based data, which indicates that each subclass can be further subdivided into specific subtypes. These deeper classifications, while getting over the typical tumor heterogeneity, indicate that different forms of medulloblastoma hold different molecular drivers that can be successfully exploited for a greater diagnostic accuracy and for the development of novel, targeted treatments. Long noncoding RNAs are transcripts that lack coding potential and play relevant roles as regulators of gene expression in mammalian differentiation and developmental processes. Their cell type- and tissue-specificity, higher than mRNAs, make them more informative about cell- type identity than protein-coding genes. Remarkably, about 40% of long noncoding RNAs are expressed in the brain and their aberrant expression has been linked to neuro-oncological disorders. However, while their involvement in gliomas and neuroblastomas has been extensively studied, their role in medulloblastoma is still poorly explored. Here, we present an overview of current knowledge regarding the function played by long noncoding RNAs in medulloblastoma biology.

lncRNA profile study reveals the mRNAs and lncRNAs associated with docetaxel resistance in breast cancer cells

Resistance to adjuvant systemic treatment, including taxanes (docetaxel and paclitaxel) is a major clinical problem for breast cancer patients. lncRNAs (long non-coding RNAs) are non-coding transcripts, which have recently emerged as important players in a variety of biological processes, including cancer development and chemotherapy resistance. However, the contribution of lncRNAs to docetaxel resistance in breast cancer and the relationship between lncRNAs and taxane-resistance genes are still unclear. Here, we performed comprehensive RNA sequencing and analyses on two docetaxel-resistant breast cancer cell lines (MCF7-RES and MDA-RES) and their docetaxel-sensitive parental cell lines. We identified protein coding genes and pathways that may contribute to docetaxel resistance. More importantly, we identified lncRNAs that were consistently up-regulated or down-regulated in both the MCF7-RES and MDA-RES cells. The co-expression network and location analyses pinpointed four overexpressed lncRNAs located within or near the ABCB1 (ATP-binding cassette subfamily B member 1) locus, which might up-regulate the expression of ABCB1. We also identified the lncRNA EPB41L4A-AS2 (EPB41L4A Antisense RNA 2) as a potential biomarker for docetaxel sensitivity. These findings have improved our understanding of the mechanisms underlying docetaxel resistance in breast cancer and have provided potential biomarkers to predict the response to docetaxel in breast cancer patients.

Pivotal prognostic and diagnostic role of the long non‑coding RNA colon cancer‑associated transcript 1 expression in human cancer (Review)

Long non‑coding RNAs (lncRNAs) have been classically defined as regulatory RNA members >200 nucleotides in length, without detectable open‑reading frames to encode proteins. Previous studies have demonstrated that lncRNAs serve critical roles in multiple cancer types. Colon cancer‑associated transcript 1 (CCAT1), a novel cancer‑associated lncRNA, is significantly overexpressed in a number of malignancies. Functionally, as an oncogenic lncRNA, CCAT1 is involved in proliferation, migration, cell cycle progression, apoptosis, chemoresistance and other biological processes of cancer cells through complex regulation mechanisms in the cytoplasm or nucleus. In clinical applications, CCAT1 is additionally positively associated with histological differentiation, tumour node metastasis stage, vascular invasion, overall survival and recurrence‑free survival, which demonstrates its important role as a diagnostic and prognostic marker in cancer. The present review summarises the current research progress of the oncogenic potential and clinical uses of CCAT1 in various human cancer types.

An expression signature model to predict lung adenocarcinoma-specific survival

Background

The current TNM staging system plays a central role in lung adenocarcinoma (LUAD) prognosis. However, it may not adequately stratify the risk of tumor recurrence. With the aid of gene expression profiling, we identified 31 lncRNAs whose expressions in tumor tissues could be used as a risk indicator for the guidance of lung cancer therapy. This exploratory analysis may shed new light on identification of potential prognostic factors.

Materials and methods

A survival prediction scoring model was developed from the data that are publicly available in The Cancer Genome Atlas (TCGA) LUAD RNA Sequencing dataset. Multivariate Cox regression analysis and Kaplan–Meier analysis were performed on a cohort of 254 stage I lung carcinoma patients with survival records.

Results

Our model indicates that the panels comprising 31 lncRNAs are highly associated with overall survival (OS): 18.9% (95% CI: 10.4%–34.5%) and 89.5% (95% CI: 80.7%–99.2%) for the high- and low-risk group, respectively. The specificity and sensitivity of the model are verified, which show that the area under receiver operating characteristic curve yields 0.881, meaning our model has good accuracy and it is feasible for further applications.

Conclusion

The 31-lncRNA model might be able to predict OS in patients with LUAD with high accuracy. Its further applications in biomolecular experiments using clinical samples with independent cohorts of patients are needed to verify the results.

Identification of abnormally expressed lncRNAs induced by PM2.5 in human bronchial epithelial cells

To investigate the effect of stimulation of human bronchial epithelial cells (HBECs) by arterial traffic ambient PM2.5 (TAPM2.5) and wood smoke PM2.5 (WSPM2.5) on the expression of long non-coding RNAs (lncRNAs) in order to find new therapeutic targets for treatment of chronic obstructive pulmonary disease (COPD). HBECs were exposed to TAPM2.5 and WSPM2.5 at a series of concentrations. The microarray analysis was used to detect the lncRNA and mRNA expression profiles. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis and gene ontology (GO) enrichment were conducted to analyze the differentially expressed lncRNAs and mRNAs. Quantitative real-time PCR (qRT-PCR) was performed to confirm the differential expression of lncRNAs. Western blot was performed to study the expression of autophagy and apoptosis-associated proteins. Flow cytometry was used to detect the apoptotic cells. The results indicated that fine particulate matter (PM2.5)-induced cell damage of HBECs occurred in a dose-dependent manner. The microarray analysis indicated that treatment with TAPM2.5 and WSPM2.5 led to the alteration of lncRNA and mRNA expression profiles. LncRNA maternally expressed gene 3 (MEG3) was significantly up-regulated in HBECs after PM2.5 treatment. The results of Western blot showed that PM2.5 induced cell apoptosis and autophagy by up-regulating apoptosis-associated gene, caspase-3, and down-regulating autophagy-associated markers, Bcl-2 and LC3 expression. In addition, we demonstrated that TAPM2.5 and WSPM2.5 accelerated apoptosis of human bronchial (HBE) cells, silencing of MEG3 suppressed apoptosis and autophagy of HBE cells. These findings suggested that the lncRNA MEG3 mediates PM2.5-induced cell apoptosis and autophagy, and probably through regulating the expression of p53.

The Network of Non-coding RNAs in Cancer Drug Resistance

Non-coding RNAs (ncRNAs) have been implicated in most cellular functions. The disruption of their function through somatic mutations, genomic imprinting, transcriptional and post-transcriptional regulation, plays an ever-increasing role in cancer development. ncRNAs, including notorious microRNAs, have been thus proposed to function as tumor suppressors or oncogenes, often in a context-dependent fashion. In parallel, ncRNAs with altered expression in cancer have been reported to exert a key role in determining drug sensitivity or restoring drug responsiveness in resistant cells. Acquisition of resistance to anti-cancer drugs is a major hindrance to effective chemotherapy and is one of the most important causes of relapse and mortality in cancer patients. For these reasons, non-coding RNAs have become recent focuses as prognostic agents and modifiers of chemo-sensitivity. This review starts with a brief outline of the role of most studied non-coding RNAs in cancer and then highlights the modulation of cancer drug resistance via known ncRNAs based mechanisms. We identified from literature 388 ncRNA-drugs interactions and analyzed them using an unsupervised approach. Essentially, we performed a network analysis of the non-coding RNAs with direct relations with cancer drugs. Within such a machine-learning framework we detected the most representative ncRNAs-drug associations and groups. We finally discussed the higher integration of the drug-ncRNA clusters with the goal of disentangling effectors from downstream effects and further clarify the involvement of ncRNAs in the cellular mechanisms underlying resistance to cancer treatments.

Hypoxia and Noncoding RNAs in Taxane Resistance

Taxanes are chemotherapeutic drugs employed in the clinic to treat a variety of malignancies. Despite their overall efficacy, cancer cells often display resistance to taxanes. Therefore, new strategies to increase the effectiveness of taxane-based chemotherapeutics are urgently needed. Multiple molecular players are linked to taxane resistance; these include efflux pumps, DNA repair mechanisms, and hypoxia-related pathways. In addition, emerging evidence indicates that both non-coding RNAs and epigenetic effectors might also be implicated in taxane resistance. Here we focus on the causes of taxane resistance, with the aim to envisage an integrated model of the 'taxane resistance phenome'. This model could help the development of novel therapeutic strategies to treat taxane-resistant neoplasms.

Overexpression of the long noncoding RNA CCAT1 promotes metastasis via epithelial-to-mesenchymal transition in lung adenocarcinoma

The long noncoding RNA (lncRNA) colon cancer-associated transcript 1 (CCAT1) has been identified as an oncogene in multiple types of human malignancy, and the aberrant expression of CCAT1 has been associated with the tumorigenesis and progression of cancer. However, the underlying mechanism of how CCAT1 affects malignant behaviors in lung adenocarcinoma cells remains unknown. In the current study, the expression of CCAT1 was identified to be increased in lung adenocarcinoma tissues (n=96) by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and its expression level was associated with epidermal growth factor receptor (EGFR) expression (P=0.011), lymphatic metastasis (P=0.003) and tumor node metastasis (TNM) stage (P=0.003). In vitro, by using Transwell assays, the overexpression of CCAT1 was demonstrated to promote the migration and invasion of H358 lung adenocarcinoma cells; while downregulation of CCAT1 expression inhibited H1650 cell migration and invasion. Furthermore, western blot analysis indicated that aberrant CCAT1 expression may induce epithelial-to-mesenchymal transition (EMT) by regulating the expression levels of EMT markers (E-cadherin, N-cadherin and vimentin). In conclusion, these results indicate that CCAT1 is able to promote the metastasis of lung adenocarcinoma cells by inducing EMT.

Long noncoding RNA CCAT1 promotes cell proliferation and metastasis in human medulloblastoma via MAPK pathway

BACKGROUND

Medulloblastoma is the most common posterior fossa tumor in children and one that easily metastasizes. The mechanisms of how the medulloblastoma develops and progresses remain to be elucidated. The present study aimed to assess the role of long noncoding colon cancer-associated transcript-1 (lncRNA CCAT1) in cell proliferation and metastasis in human medulloblastoma.

METHODS

Levels of CCAT1 were measured in samples and cell lines of medulloblastoma. Cell cycle progression, cell viability assay, colony formation assay, wound-healing and Transwell assays Corning, Cambridge, MA, USA were used to investigate the viability and motility of cells. Western blot assay was used to investigate the levels of CCAT1 and other proteins.

RESULTS

The initial findings indicated that CCAT1 was significantly up-regulated in clinical cancerous tissues and expressed differently in a series of medulloblastoma cell lines. CCAT1 knockdown significantly slowed cell proliferation rates and inhibited cell clonogenic potential in Daoy cells and D283 cells. Cell cycle progression was disrupted with cell proportions in the G0/G1 phase decreased and the proportion in the S phase and G2/M phases increased, in Daoy cells and D283 cells. Concordantly, medulloblastoma tumor cell growth rates were found to be impaired in xenotransplanted mice. After CCAT1 knockdown, cell wound recovery ability was significantly inhibited. Furthermore, the phosphorylated levels of MAPK, ERK and MEK, but not their total levels decreased after the down-regulation of CCAT1 in Daoy and D283 cells.

CONCLUSIONS

Our results suggested that the lncRNA CCAT1 promotes cell proliferation and metastasis in human medulloblastoma by possibly regulating the MAPK pathway.

Long non-coding RNA CCAT1 as a diagnostic and prognostic molecular marker in various cancers: a meta-analysis

PURPOSE

Long non-coding RNA colon cancer-associated transcript-1 (CCAT1) is newly found to be related with diagnoses and prognosis of cancer. This meta-analysis was performed to investigate the relationship between CCAT1 expression and clinical parameters, including survival condition, lymph node metastasis and tumor node metastasis grade.

MATERIALS AND METHODS

The primary literatures were collected through initial search criteria from electronic databases, including PubMed, OVID Evidence-based medicine Reviews and others (up to May 12, 2017). Eligible studies were identified and selected by the inclusion and exclusion criteria. Data was extracted and computed into Hazard ratio (HR) for the assessment of overall survival, subgroup analyses were prespecified based on the digestive tract cancer or others. Analysis of different CCAT1 expression related with lymph node metastasis or tumor node metastasis grade was conducted. Risk of bias was assessed by the Newcastle-Ottawa Scale.

RESULTS

9 studies were included. This meta-analysis showed that high CCAT1 expression level was related to poor overall survival, the pooled HR was 2.42 (95% confidence interval, CI: 1.86-3.16; P < 0.001; fix- effects model), similarly in the cancer type subgroups: digestive tract cancer (HR, 2.42; 95% CI, 1.79-3.29; P < 0.001; fix- effects model) and others (HR, 2.42; 95% CI, 1.42-4.13; P = 0.001; fix- effects model). The analysis showed that high CCAT1 was strongly related to positive lymph node metastasis (Odds ratio, OR: 3.24; 95% CI, 2.04-5.16; P < 0.001; fix- effects model), high tumor node metastasis stage (OR, 3.87; 95% CI, 2.53-5.92; P < 0.001; fix- effects model).

CONCLUSIONS

In conclusion, this meta-analysis revealed that CCAT1 had potential as a diagnostic and prognostic biomarker in various cancers.