Hypoxia-induced LncRNA PCGEM1 promotes invasion and metastasis of gastric cancer through regulating SNAI1. Clin Transl Oncol. 2019;21:1142-1151. [PMID: 30690667 DOI: 10.1007/s12094-019-02035-9]

The strict regulation of HIF-1α by non-coding RNAs: new insight towards proliferation, metastasis, and therapeutic resistance strategies

The hypoxic environment is prominently witnessed in most solid tumors and is associated with the promotion of cell proliferation, epithelial-mesenchymal transition (EMT), angiogenesis, metabolic reprogramming, therapeutic resistance, and metastasis of tumor cells. All the effects are mediated by the expression of a transcription factor hypoxia-inducible factor-1α (HIF-1α). HIF-1α transcriptionally modulates the expression of genes responsible for all the aforementioned functions. The stability of HIF-1α is regulated by many proteins and non-coding RNAs (ncRNAs). In this article, we have critically discussed the crucial role of ncRNAs [such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), Piwi-interacting RNAs (piRNAs), and transfer RNA (tRNA)-derived small RNAs (tsRNAs)] in the regulation of stability and expression of HIF-1α. We have comprehensively discussed the molecular mechanisms and relationship of HIF-1α with each type of ncRNA in either promotion or repression of human cancers and therapeutic resistance. We have also elaborated on ncRNAs that are in clinical examination for the treatment of cancers. Overall, the majority of aspects concerning the relationship between HIF-1α and ncRNAs have been discussed in this article.

Construction of a hypoxia-immune-related prognostic panel based on integrated single-cell and bulk RNA sequencing analyses in gastric cancer

Introduction

Gastric cancer (GC) is the fifth most common tumor, contributing to the third-highest number of cancer-related deaths. Hypoxia is a major feature of the tumor microenvironment. This study aimed to explore the influence of hypoxia in GC and establish a hypoxia-related prognostic panel.

Methods

The GC scRNA-seq data and bulk RNA-seq data were downloaded from the GEO and TCGA databases, respectively. AddModuleScore() and AUCell() were used to calculate module scores and fractions of enrichment for hypoxia-related gene expression in single cells. Least absolute shrinkage and selection operator cox (LASSO-COX) regression analysis was utilized to build a prognostic panel, and hub RNAs were validated by qPCR. The CIBERSORT algorithm was adopted to evaluate immune infiltration. The finding of immune infiltration was validated by a dual immunohistochemistry staining. The TIDE score, TIS score and ESTIMATE were used to evaluate the immunotherapy predictive efficacy.

Results

Hypoxia-related scores were the highest in fibroblasts, and 166 differentially expressed genes were identified. Five hypoxia-related genes were incorporated into the hypoxia-related prognostic panel. 4 hypoxia-related genes (including POSTN, BMP4, MXRA5 and LBH) were significantly upregulated in clinical GC samples compared with the normal group, while APOD expression decreased in GC samples. Similar results were found between cancer-associated fibroblasts (CAFs) and normal fibroblasts (NFs). A high hypoxia score was associated with advanced grade, TNM stage, N stage, and poorer prognosis. Decreased antitumor immune cells and increased cancer-promoting immune cells were found in patients with high hypoxia scores. Dual immunohistochemistry staining showed high expression of CD8 and ACTA2 in gastric cancer tissue. In addition, the high hypoxia score group possessed higher TIDE scores, indicating poor immunotherapy benefit. A high hypoxia score was also firmly related to sensitivity to chemotherapeutic drugs.

Discussion

This hypoxia-related prognostic panel may be effective in predicting the clinical prognosis, immune infiltrations, immunotherapy, and chemotherapy in GC.

Molecular regulation of hypoxia through the lenses of noncoding RNAs and epitranscriptome

Cells maintain homeostasis in response to environmental stress through specific cell stress responses. Hypoxic stress, well known to be associated with diverse solid tumors, is one of the main reasons for cancer-related mortality. Although cells can balance themselves well during hypoxic stress, the underlying molecular mechanisms are not well understood. The enhanced appreciation of diverse roles played by noncoding transcriptome and epigenome in recent years has brought to light the involvement of noncoding RNAs and epigenetic modifiers in hypoxic regulation. The emergence of techniques like deep sequencing has facilitated the identification of large numbers of long noncoding RNAs (lncRNAs) that are differentially regulated in various cancers. Similarly, proteomic studies have identified diverse epigenetic modifiers such as HATs, HDACs, DNMTs, polycomb groups of proteins, and their possible roles in the regulation of hypoxia. The crosstalk between lncRNAs and epigenetic modifiers play a pivotal role in hypoxia-induced cancer initiation and progression. Besides the lncRNAs, several other noncoding RNAs like circular RNAs, miRNAs, and so forth are also expressed during hypoxic conditions. Hypoxia has a profound effect on the expression of noncoding RNAs and epigenetic modifiers. Conversely, noncoding RNAs/epigenetic modifies can regulate the hypoxia signaling axis by modulating the stability of the hypoxia-inducible factors (HIFs). The focus of this review is to illustrate the molecular orchestration underlying hypoxia biology, especially in cancers, which can help in identifying promising therapeutic targets in hypoxia-induced cancers. This article is categorized under: RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease RNA Structure and Dynamics > RNA Structure, Dynamics and Chemistry.

Interaction Among Noncoding RNAs, DNA Damage Reactions, and Genomic Instability in the Hypoxic Tumor: Is it Therapeutically Exploitable Practice?

Hypoxia is a classical function of the tumor's microenvironment with a substantial effect on the development and therapeutic response of cancer. When put in hypoxic environments, cells undergo several biological reactions, including activation of signaling pathways that control proliferation, angiogenesis, and death. These pathways have been adapted by cancer cells to allow tumors to survive and even develop in hypoxic conditions, and poor prognosis is associated with tumor hypoxia. The most relevant transcriptional regulator in response to hypoxia, Hypoxia-inducible factor-1 alpha (HIF-1α), has been shown to modulate hypoxic gene expression and signaling transduction networks significantly. The significance of non-coding RNAs in hypoxic tumor regions has been revealed in an increasing number of studies over the past few decades. In regulating hypoxic gene expression, these hypoxia-responsive ncRNAs play pivotal roles. Hypoxia, a general characteristic of the tumor's microenvironment, significantly affects the expression of genes and is closely associated with the development of cancer. Indeed, the number of known hypoxia-associated lncRNAs has increased dramatically, demonstrating the growing role of lncRNAs in cascades and responses to hypoxia signaling. Decades of research have helped us create an image of the shift in hypoxic cancer cells' DNA repair capabilities. Emerging evidence suggests that hypoxia can trigger genetic instability in cancer cells because of microenvironmental tumor stress. Researchers have found that critical genes' expression is coordinately repressed by hypoxia within the DNA damage and repair pathways. In this study, we include an update of current knowledge on the presentation, participation, and potential clinical effect of ncRNAs in tumor hypoxia, DNA damage reactions, and genomic instability, with a specific emphasis on their unusual cascade of molecular regulation and malignant progression induced by hypoxia.

Epithelial-mesenchymal transition-related long noncoding RNAs in gastric carcinoma

As an evolutionarily phenotypic conversion program, the epithelial-mesenchymal transition (EMT) has been implicated in tumour deterioration and has facilitated the metastatic ability of cancer cells via enhancing migration and invasion. Gastric cancer (GC) remains a frequently diagnosed non-skin malignancy globally. Most GC-associated mortality can be attributed to metastasis. Recent studies have shown that EMT-related long non-coding RNAs (lncRNAs) play a critical role in GC progression and GC cell motility. In addition, lncRNAs are associated with EMT-related transcription factors and signalling pathways. In the present review, we comprehensively described the EMT-inducing lncRNA molecular mechanisms and functional perspectives of EMT-inducing lncRNAs in GC progression. Taken together, the statements of this review provided a clinical implementation in identifying lncRNAs as potential therapeutic targets for advanced GC.

Interactome battling of lncRNA CCDC144NL-AS1: Its role in the emergence and ferocity of cancer and beyond

Long non-coding RNAs (lncRNAs) were, once, viewed as "noise" for transcription. Recently, many lncRNAs are functionally linked to several human disorders, including cancer. Coiled-Coil Domain Containing 144 N-Terminal-Like antisense1 (CCDC144NL-AS1) is a newly discovered cytosolic lncRNA. Aberrant CCDC144NL-AS1 expression was discovered in hepatocellular carcinoma (HCC), ovarian cancer (OC), gastric cancer (GC), non-small cell lung cancer (NSCLC), and osteosarcoma. CCDC144NL-AS1 could be a promising prognostic biological marker and therapeutic target for cancer. In this review, we will collect and highlight the available information about CCDC144NL-AS1 role in various cancers. Moreover, we will discuss the diagnostic and prognostic utility of CCDC144NL-AS1 as a new molecular biomarker for several human malignancies, besides its potential therapeutic importance.

Effects of Ion-Transporting Proteins on the Digestive System Under Hypoxia

Hypoxia refers to a state of oxygen limitation, which mainly mediates pathological processes in the human body and participates in the regulation of normal physiological processes. In the hypoxic environment, the main regulator of human body homeostasis is the hypoxia-inducible factor family (HIF). HIF can regulate the expression of many hypoxia-induced genes and then participate in various physiological and pathological processes of the human body. Ion-transporting proteins are extremely important types of proteins. Ion-transporting proteins are distributed on cell membranes or organelles and strictly control the inflow or outflow of ions in cells or organelles. Changes in ions in cells are often closely related to extensive physiological and pathological processes in the human body. Numerous studies have confirmed that hypoxia and its regulatory factors can regulate the transcription and expression of ion-transporting protein-related genes. Under hypoxic stress, the regulation and interaction of ion-transporting proteins by hypoxia often leads to diseases of various human systems and even tumors. Using ion-transporting proteins and hypoxia as targets to explore the mechanism of digestive system diseases and targeted therapy is expected to become a new breakthrough point.

HIF in Gastric Cancer: Regulation and Therapeutic Target

HIF means hypoxia-inducible factor gene family, and it could regulate various biological processes, including tumor development. In 2021, the FDA approved the new drug Welireg for targeting HIF-2a, and it is mainly used to treat von Hippel-Lindau syndrome, which demonstrated its good prospects in tumor therapy. As the fourth deadliest cancer worldwide, gastric cancer endangers the health of people all across the world. Currently, there are various treatment methods for patients with gastric cancer, but the five-year survival rate of patients with advanced gastric cancer is still not high. Therefore, here we reviewed the regulatory role and target role of HIF in gastric cancer, and provided some references for the treatment of gastric cancer.

DARS-AS1 recruits METTL3/METTL14 to bind and enhance DARS mRNA m6A modification and translation for cytoprotective autophagy in cervical cancer

Cervical cancer (CC) is one of the most prevalent malignancies among females. Cytoprotective autophagy could confer cancer cell tolerance to hypoxic stress, promoting cell survival and adaptation. Aspartyl-tRNA synthetase 1 antisense 1 (DARS-AS1) is an oncogenic long non-coding RNA (lncRNA) in various cancers, but how DARS-AS1 regulates cytoprotective autophagy in hypoxic environment in CC remains unclear. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays were conducted to explore the interaction between hypoxia-inducible factor 1 subunit alpha (HIF1α) and DARS-AS1 promoter. Methylated RNA immunoprecipitation (MeRIP) followed by quantitative real-time polymerase-chain reaction (RT-qPCR) detected methylated RNA level. The process of autophagic maturation was monitored by immunofluorescence staining. Higher DARS-AS1 expression was found in CC tissues and cytoprotective. We also uncovered that hypoxic exposure induced cytoprotective autophagy via HIF1α/DARS-AS1/DARS axis. Moreover, DARS-AS1 was validated to facilitate DARS translation via recruiting N6-adenosine-methyltransferase methyltransferase like 3 (METTL3) and methyltransferase like 14 (METTL14), which bound with DARS mRNA DARS mRNA 5’ untranslated region (5ʹUTR) and promoting its translation. The present study demonstrated that the ‘HIF1α/DARS-AS1/DARS/ATG5/ATG3’ pathway regulated the hypoxia-induced cytoprotective autophagy of CC and might be a promising target of therapeutic strategies for patients afflicted with CC.

Stressing the Regulatory Role of Long Non-Coding RNA in the Cellular Stress Response during Cancer Progression and Therapy

Cellular stress response is an important adaptive mechanism for regulating cell fate decision when cells confront with stress. During tumorigenesis, tumor progression and the course of treatment, cellular stress signaling can activate subsequent response to deal with stress. Therefore, cellular stress response has impacts on the fate of tumor cells and tumor responsiveness relative to therapeutic agents. In recent years, attention has been drawn to long non-coding RNAs (lncRNAs), a novel class of RNA molecules with more than 200 nucleotides in length, which has little protein-coding potential and possesses various functions in multiple biological processes. Accumulating evidence has shown that lncRNAs are also engaged in the regulation of cellular stress response, particularly in cancers. Here, we summarize lncRNAs that have been reported in the adaptive response to major types of cellular stress including genotoxic, hypoxic, oxidative, metabolic and endoplasmic reticulum stress, all of which are often encountered by cancer cells. Specifically, the molecular mechanisms of how lncRNAs regulate cellular stress response during tumor progression or the development of therapy resistance are emphasized. The potential clinical applications of stress-responsive lncRNAs as biomarkers will also be discussed.

Construction of a Prognostic Model for Hypoxia-Related LncRNAs and Prediction of the Immune Landscape in the Digestive System Pan-Cancer

Digestive system pan-cancer is a general term for digestive system tumors including colorectal carcinoma (CRC), esophageal carcinoma (ESCA), stomach adenocarcinoma (STAD), and liver hepatocellular carcinoma (LIHC). Since the anatomical location, function and metabolism are closely related, there may be similarities in development and progression of these tumors. Hypoxia is the consequence of an imbalance between oxygen demand and supply, and intracellular hypoxia is associated with malignant progression, treatment resistance, and poor prognosis in tumors. Therefore, an urgent and challenging task is to investigate the molecular mechanisms associated with hypoxia in digestive system pan-cancer for the prognosis and treatment of digestive tract tumors. In this study, we identified 18 hypoxia-related lncRNAs (HRlncRNAs) by co-expression analysis between hypoxia genes and lncRNAs from digestive system pan-cancer. Six HRlncRNAs were then obtained using lasso regression and multivariate cox analysis to construct a prognostic model. Next, the Akaike information criterion (AIC) values for 3-year receiver operating curve (ROC) were counted to determine the cut-off point and establish an optimal model to distinguish between high- or low-risk groups among patients with digestive system pan-cancer. To evaluate the stability of the prognosis model, we validated it in terms of survival outcomes, clinicopathological stage, tumor-infiltrating immune cells, immune checkpoint inhibitors (ICIs) and anticancer drugs sensitivity. The results suggested that high- risk group had a worse prognosis and a more positive association with tumor-infiltrating immune cells such as B cells, cancer-associated fibroblasts, endothelial cells, monocytes, macrophages and bone marrow dendritic cells in digestive system pan-cancer. Immune checkpoint inhibitors (ICIs) related biomarkers discovered that high-risk group was positively correlated with high expression of HAVCR2 in digestive system pan-cancer. The anticancer drugs sensitivity analysis showed that the high-risk group was associated with the lower half-inhibitory centration (IC50) of Imatinib in digestive system pan-cancer. In conclusion, the prognostic model of HRlncRNAs showed a promising clinical prediction value and may provide a useful reference for the diagnosis and treatment of the digestive system tumors.

A positive feedback loop between gastric cancer cells and tumor-associated macrophage induces malignancy progression

BACKGROUND

Hypoxia and inflammation tumor microenvironment (TME) play a crucial role in tumor development and progression. Although increased understanding of TME contributed to gastric cancer (GC) progression and prognosis, the direct interaction between macrophage and GC cells was not fully understood.

METHODS

Hypoxia and normoxia macrophage microarrays of GEO database was analyzed. The peripheral blood mononuclear cell acquired from the healthy volunteers. The expression of C-X-C Motif Chemokine Ligand 8 (CXCL8) in GC tissues and cell lines was detected by quantitative reverse transcription PCR (qRT-PCR), western-blot, Elisa and immunofluorescence. Cell proliferation, migration, and invasion were evaluated by cell counting kit 8 (CCK8), colony formation, real-time imaging of cell migration and transwell. Flow Cytometers was applied to identify the source of cytokines. Luciferase reporter assays and chromatin immunoprecipitation were used to identify the interaction between transcription factor and target gene. Especially, a series of truncated and mutation reporter genes were applied to identify precise binding sites. The corresponding functions were verified in the complementation test and in vivo animal experiment.

RESULTS

Our results revealed that hypoxia triggered macrophage secreted CXCL8, which induced GC invasion and proliferation. This macrophage-induced GC progression was CXCL8 activated C-X-C Motif Chemokine Receptor 1/2 (CXCR1/2) on the GC cell membrane subsequently hyperactivated Janus kinase 1/ Signal transducer and activator of transcription 1 (JAK/STAT1) signaling pathway. Then, the transcription factor STAT1 directly led to the overexpression and secretion of Interleukin 10 (IL-10). Correspondingly, IL-10 induced the M2-type polarization of macrophages and continued to increase the expression and secretion of CXCL8. It suggested a positive feedback loop between macrophage and GC. In clinical GC samples, increased CXCL8 predicted a patient's pessimistic outcome.

CONCLUSION

Our work identified a positive feedback loop governing cancer cells and macrophage in GC that contributed to tumor progression and patient outcome.

LncRNA PCGEM1 in Human Cancers: Functions, Mechanisms and Promising Clinical Utility

As novel members of the noncoding RNA family, long noncoding RNAs (lncRNAs) have been widely reported to function as powerful regulators in gene expression processes, including chromosome remodeling, transcription interference and posttranscriptional modification. With the rapid development of metagenomic sequencing, numerous studies have indicated that the dysregulation of lncRNAs is closely associated with diverse human diseases, especially cancers. Prostate Gene Expression Marker 1 (PCGEM1), a recently identified lncRNA, has been reported to play a crucial role in the initiation and progression of multiple tumors by interacting with pivotal regulators of tumor-related signaling pathways. In this review, we will retrospectively review the recent studies of the expression of lncRNA PCGEM1 in human cancers and comprehensively describe the underlying regulatory mechanism by which PCGEM1 functions in tumors. More importantly, based on the relationship between PCGEM1 and cancers, the potential application of PCGEM1 in clinical diagnosis, prognosis and therapeutic treatment will also be highlighted.

PCGEM1 promotes proliferation, migration and invasion in prostate cancer by sponging miR-506 to upregulate TRIAP1

BACKGROUND

The important role of long noncoding RNAs (lncRNAs) in cancer has been demonstrated in many studies. Prostate cancer gene expression marker 1 (PCGEM1) is a lncRNA specifically expressed within the prostate and overexpressed in many cancer cells. Numerous studies have shown that PCGEM1 promotes cell proliferation, invasion and migration. However, the specific mechanism of PCGEM1 within prostate cancer (PCa) has not been elucidated. MicroRNA-506-3p (miR-506-3p) is a noncoding RNA, and studies have indicated that miR-506-3p is downregulated in prostate cancer cell lines and functions as a tumor suppressor.

METHODS

The TCGA (GEPIA) database ( http://gepia.cancer-pku.cn/ ) was employed to measure PCGEM1 levels in PCa. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to determine the PCGEM1 gene level. CCK-8 (Cell Counting Kit-8) and colony formation assays were used to detect cell proliferation, and Transwell assays were applied to assess cell invasion and migration. The interacting ability of miR-506-3p with PCGEM1 or TRIAP1 was validated through a dual-luciferase reporter assay. TRIAP1 protein expression was detected by Western blotting.

RESULTS

PCGEM1 expression was increased in PCa tissues and cells. In PCa tissues, High PCGEM1 expression was associated with high Gleason score, distant metastasis and extracapsular extension. In addition, PCGEM1 knockdown inhibited PCa cell (C4-2B and PC-3) proliferation, invasion and migration. miR-506-3p may interact with PCGEM1 or TRIAP1, and the suppressive effect of PCGEM1 knockdown was reversed when TRIAP1 or a miR-506-3p inhibitor was cotransfected.

CONCLUSION

PCGEM1 expression increased in PCa cells and tissues, enhancing PCa cell proliferation, migration and invasion by sponging miR-506 to upregulate TRIAP1.

Hypoxia associated lncRNA HYPAL promotes proliferation of gastric cancer as ceRNA by sponging miR-431-5p to upregulate CDK14

Gastric cancer (GC) is a common malignant solid tumor that is characterized by high hypoxia. The transcription of genes associated with hypoxia affects tumor occurrence and development. Long non-coding RNAs (lncRNAs) have been reported to play important roles in cancer development. In this study, we screened for differentially expressed ncRNAs (non-coding RNA) and mRNAs between hypoxia-inducible factor-1 (HIF-1α) knockdown GC cells and scrambled GC cells. Microarray data revealed that HIF-1α regulated the expression of LINC01355 (Hypoxia Yield Proliferation Associated LncRNA, HYPAL). HYPAL was found to be significantly upregulated in GC cells and tissues and was correlated with poor GC prognosis. Chromatin immunoprecipitation (ChIP) and luciferase reporter assays revealed that HIF-1α promoted HYPAL expression by binding the promoter region. A regulatory network for the competing endogenous RNA (ceRNA) was constructed using bioinformatics tools. Mechanistic studies revealed that HYPAL acted as a ceRNA of miR-431-5p to regulate CDK14 expression. Carcinogenic effects of HYPAL were evaluated in vitro and in vivo. The HIF-1α/HYPAL/miR-431-5p/CDK14 (Cyclin-dependent kinase 14) axis activated the Wnt/β-catenin signaling pathway and induced GC cell proliferation while inhibiting apoptosis. In conclusion, HYPAL is a potential molecular target for GC therapy.

Hypoxic Breast Cancer Cell-Derived Exosomal SNHG1 Promotes Breast Cancer Growth and Angiogenesis via Regulating miR-216b-5p/JAK2 Axis

Background

Hypoxia is an important process that involved in the tumor microenvironment. In addition, hypoxic tumor cell-derived exosomes could promote tumor growth and angiogenesis. Thus, we aimed to investigate whether exosomes could regulate tumor development and progression under hypoxia in breast cancer.

Methods

The level of SNHG1 in hypoxic breast cancer cells and exosomes derived from hypoxic breast cancer cells was determined by real-time qPCR assay. Bioinformatics prediction and dual-luciferase reporter assays were used to determine the interaction between SNHG1, miR-216b-5p and JAK2.

Results

We found that comparing with exosomes derived from normoxia breast cancer cells, exosomes derived from hypoxic breast cancer cells could promote the proliferation, migration and angiogenesis of human umbilical vein endothelial cells (HUVECs). In addition, SNHG1 level was significantly upregulated in exosomes derived from hypoxic breast cancer cells. Moreover, exosome-mediated delivery of SNHG1 siRNA3 markedly reversed the effects of exosome-mediated delivery of SNHG1 on HUVECs. Mechanically, SNHG1 could increase the level of JAK2 by competitively binding to miR-216b-5p. Additionally, exosome-mediated delivery of SNHG1 was found to promote breast cancer growth in vivo.

Conclusion

Collectively, our study revealed that exosomal SNHG1 from hypoxic breast cancer cells could promote tumor angiogenesis and growth via regulating miR-216b-5p/JAK2 axis, suggesting that SNHG1 may serve as a potential therapeutic target for breast cancer.

Long non-coding RNAs: Biogenesis, functions, and clinical significance in gastric cancer

Gastric cancer (GC) is one of the most prevalent malignant tumor types and the third leading cause of cancer-related death worldwide. Its morbidity and mortality are very high due to a lack of understanding about its pathogenesis and the slow development of novel therapeutic strategies. Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs with a length of more than 200 nt. They play crucial roles in a wide spectrum of physiological and pathological processes by regulating the expression of genes involved in proliferation, differentiation, apoptosis, cell cycle, invasion, metastasis, DNA damage, and carcinogenesis. The aberrant expression of lncRNAs has been found in various cancer types. A growing amount of evidence demonstrates that lncRNAs are involved in many aspects of GC pathogenesis, including its occurrence, metastasis, and recurrence, indicating their potential role as novel biomarkers in the diagnosis, prognosis, and therapeutic targets of GC. This review systematically summarizes the biogenesis, biological properties, and functions of lncRNAs and highlights their critical role and clinical significance in GC. This information may contribute to the development of better diagnostics and treatments for GC.

Tumor immune microenvironment lncRNAs

Long non-coding ribonucleic acids (RNAs) (lncRNAs) are key players in tumorigenesis and immune responses. The nature of their cell type-specific gene expression and other functional evidence support the idea that lncRNAs have distinct cellular functions in the tumor immune microenvironment (TIME). To date, the majority of lncRNA studies have heavily relied on bulk RNA-sequencing data in which various cell types contribute to an averaged signal, limiting the discovery of cell type-specific lncRNA functions. Single-cell RNA-sequencing (scRNA-seq) is a potential solution for tackling this limitation despite the lack of annotations for low abundance yet cell type-specific lncRNAs. Hence, updated annotations and further understanding of the cellular expression of lncRNAs will be necessary for characterizing cell type-specific functions of lncRNA genes in the TIME. In this review, we discuss lncRNAs that are specifically expressed in tumor and immune cells, summarize the regulatory functions of the lncRNAs at the cell type level and highlight how a scRNA-seq approach can help to study the cell type-specific functions of TIME lncRNAs.

The role of hypoxia-induced long noncoding RNAs (lncRNAs) in tumorigenesis and metastasis

Long noncoding RNAs (lncRNAs) are noncoding RNAs with length greater than 200 nt. The biological roles and mechanisms mediated by lncRNAs have been extensively investigated. Hypoxia is a proven microenvironmental factor that promotes solid tumor metastasis. Epithelial-mesenchymal transition (EMT) is one of the major mechanisms induced by hypoxia to contribute to metastasis. Many lncRNAs have been shown to be induced by hypoxia and their roles have been delineated. In this review, we focus on the hypoxia-inducible lncRNAs that interact with protein/protein complex and chromatin/epigenetic factors, and the mechanisms that contribute to metastasis. The role of a recently discovered lncRNA RP11-390F4.3 in hypoxia-induced EMT is discussed. Whole genome approaches to delineating the association between lncRNAs and histone modifications are discussed. Other topics related to hypoxia-induced tumor progression but require further investigation are also mentioned. The clinical significance and treatment strategy targeted against lncRNAs are discussed. The review aims to identify suitable lncRNA targets that may provide feasible therapeutic venues for hypoxia-involved cancers.

A hypoxia related long non-coding RNA signature could accurately predict survival outcomes in patients with bladder cancer

Hypoxia plays a significant role in tumor progression. This study aimed to develop a hypoxia-related long noncoding RNA (lncRNA) signature for predicting survival outcomes of patients with bladder cancer (BC). The transcriptome and clinicopathologic data were downloaded from The Cancer Genome Atlas (TCGA) database. Univariate Cox regression analysis and Lasso regression analysis were used to screened lncRNAs. Ten lncRNAs were screened out and included into the hypoxia lncRNA signature. The risk score based on hypoxia lncRNA signature could accurately predict the survival outcomes of BC patients. Immune infiltration analysis showed that six types of immune cells had significant different infiltration. Tumor mutation burden (TMB) analysis showed that the risk scores between the wild types and the mutation types of TP53, FGFR3, and RB1 were significantly different. Gene Set Enrichment Analysis (GSEA) showed that cancer-associated pathways belonged to the high risk groups and immune-related signal pathways were enriched into the low risk group. Then, we constructed a predictive model with the risk score, age, and clinical stage, which showed a robust prognostic performance. An lncRNA-mRNA coexpression network was constructed, which contained 62 lncRNA-mRNA links among 10 lncRNAs and 40 related mRNAs. In summary, the hypoxia lncRNA signature could accurately predict prognosis, chemotherapy and immunotherapy response in patients with BC and was relevant to clinicopathologic parameters and immune cell infiltration.

LncRNA PCGEM1 induces proliferation and migration in non-small cell lung cancer cells through modulating the miR-590-3p/SOX11 axis

Background

Non-small cell lung cancer (NSCLC) is one of the most prevalent cancers. As reported, long non-coding RNAs (lncRNAs) induce various biological behaviors in cancers. LncRNA PCGEM1 prostate-specific transcript (PCGEM1) is reported to exert carcinogenic effect on certain cancers. Our research aimed to explore the role of PCGEM1 in NSCLC.

Methods

We enrolled forty NSCLC patients to explore PCGEM1 expression in clinical NSCLC tissues. Colony formation assay, CCK-8, Transwell assay were conducted to reveal cell proliferation, viability, migration and invasion. Luciferase reporter assay, RNA pull down, and RIP assay were performed to investigate the downstream axis of PCGEM1.

Results

PCGEM1 was significantly upregulated in NSCLC cells and tissues. Subsequently, in vitro loss-of-function experiments illustrated the carcinogenic role of PCGEM1 in NSCLC through promoting viability, proliferation, migration, and invasion. MiR-590-3p was confirmed to be a downstream gene of PCGEM1. Furthermore, SRY-box transcription factor 11 (SOX11) was verified to be a target of miR-590-3p. Additionally, rescue experiments indicated that miR-590-3p inhibitor or pcDNA3.1/SOX11 rescued the impacts of downregulated PCGEM1 on NSCLC cell proliferation, viability, migration and invasion.

Conclusions

LncRNA PCGEM1 aggravated proliferative and migrative abilities in NSCLC via the miR-590-3p/SOX11 axis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01600-9.

Role of ZEB family members in proliferation, metastasis and chemoresistance of prostate cancer cells: Revealing signaling networks

Prostate cancer (PCa) is one of the leading causes of death worldwide. A variety of strategies including surgery, chemotherapy, radiotherapy and immunotherapy are applied for PCa treatment. PCa cells are responsive towards therapy at early stages, but they can obtain resistance in the advanced stage. Furthermore, their migratory ability is high in advanced stages. It seems that genetic and epigenetic factors play an important in this case. Zinc finger E-box-binding homeobox (ZEB) is a family of transcription with two key members including ZEB1 and ZEB2. ZEB family members are known due to their involvement in promoting cancer metastasis via EMT induction. Recent studies have shown their role in cancer proliferation and inducing therapy resistance. In the current review, we focus on revealing role of ZEB1 and ZEB2 in PCa. ZEB family members that are able to significantly promote proliferation and viability of cancer cells. ZEB1 and ZEB2 enhance migration and invasion of PCa cells via EMT induction. Overexpression of ZEB1 and ZEB2 is associated with poor prognosis of PCa. ZEB1 and ZEB2 upregulation occurs during PCa progression and can provide therapy resistance to cancer cells. PRMT1, Smad2, and non-coding RNAs can function as upstream mediators of the ZEB family. Besides, Bax, Bcl-2, MRP1, N-cadherin and E-cadherin can be considered as downstream targets of ZEB family in PCa.

Epithelial-to-Mesenchymal Transition in the Light of Plasticity and Hybrid E/M States

Epithelial-to-mesenchymal transition (EMT) is a cellular program which leads to cells losing epithelial features, including cell polarity, cell-cell adhesion and attachment to the basement membrane, while gaining mesenchymal characteristics, such as invasive properties and stemness. This program is involved in embryogenesis, wound healing and cancer progression. Over the years, the role of EMT in cancer progression has been heavily debated, and the requirement of this process in metastasis even has been disputed. In this review, we discuss previous discrepancies in the light of recent findings on EMT, plasticity and hybrid E/M states. Moreover, we highlight various tumor microenvironmental cues and cell intrinsic signaling pathways that induce and sustain EMT programs, plasticity and hybrid E/M states. Lastly, we discuss how recent findings on plasticity, especially on those that enable cells to switch between hybrid E/M states, have changed our understanding on the role of EMT in cancer metastasis, stemness and therapy resistance.

Hypoxia-Induced MALAT1 Promotes the Proliferation and Migration of Breast Cancer Cells by Sponging MiR-3064-5p

Hypoxia, a common process during tumor growth, can lead to tumor aggressiveness and is tightly associated with poor prognosis. Long noncoding RNAs (lncRNAs) are long ribonucleotides (>200 bases) with limited ability to translate proteins, and are known to affect many aspects of cellular function. One of their regulatory mechanisms is to function as a sponge for microRNA (miRNA) to modulate its biological functions. Previously, MALAT1 was identified as a hypoxia-induced lncRNA. However, the regulatory mechanism and functions of MALAT1 in breast cancer are still unclear. Therefore, we explored whether MALAT1 can regulate the functions of breast cancer cells through miRNAs. Our results showed the expression levels of MALAT1 were significantly up-regulated under hypoxia and regulated by HIF-1α and HIF-2α. Next, in contrast to previous reports, nuclear and cytoplasmic fractionation assays and fluorescence in situ hybridization indicated that MALAT1 was mainly located in the cytoplasm. Therefore, the labeling of MALAT1 as a nuclear marker should be done with the caveat. Furthermore, expression levels of miRNAs and RNA immunoprecipitation using antibody against AGO2 showed that MALAT1 functioned as a sponge of miRNA miR-3064-5p. Lastly, functional assays revealed that MALAT1 could promote cellular migration and proliferation of breast cancer cells. Our findings provide evidence that hypoxia-responsive long non-coding MALAT1 could be transcriptionally activated by HIF-1α and HIF-2α, act as a miRNA sponge of miR-3064-5p, and promote tumor growth and migration in breast cancer cells. These data suggest that MALAT1 may be a candidate for therapeutic targeting of breast cancer progression.

Visfatin facilitates gastric cancer malignancy by targeting snai1 via the NF-κB signaling

BACKGROUND

Visfatin acts as an oncogenic factor in numerous tumors through a variety of cellular processes. Visfatin has been revealed to promote cell migration and invasion in gastric cancer (GC). Snai1 is a well-known regulator of EMT process in cancers. However, the relationship between visfatin and snai1 in GC remains unclear. The current study aimed to explore the role of visfatin in GC.

METHODS

The RT-qPCR and western blot analysis were used to measure RNA and protein levels, respectively. The cell migration and invasion were tested by Trans-well assays and western blot analysis.

RESULTS

Visfatin showed upregulation in GC cells. Additionally, Visfatin with increasing concentration facilitated epithelial-mesenchymal transition (EMT) process by increasing E-cadherin and reducing N-cadherin and Vimentin protein levels in GC cells. Moreover, endogenous overexpression and knockdown of visfatin promoted and inhibited migratory and invasive abilities of GC cells, respectively. Then, we found that snai1 protein level was positively regulated by visfatin in GC cells. In addition, visfatin activated the NF-κB signaling to modulate snai1 protein expression. Furthermore, the silencing of snai1 counteracted the promotive impact of visfatin on cell migration, invasion and EMT process in GC.

CONCLUSION

Visfatin facilitates cell migration, invasion and EMT process by targeting snai1 via the NF-κB signaling, which provides a potential insight for the treatment of GC.

Exosome-mediated communication between tumor cells and tumor-associated macrophages: implications for tumor microenvironment

Exosomes are extracellular vesicles released from numerous types of cells that are involved in multiple tumors development. Exosomes contribute to the modulation of tumor microenvironment (TME) through intercellular communication. As essential immune stromal cells in the TME, tumor-associated macrophages (TAMs) participate in tumor development by mediating angiogenesis, metastasis, chemoresistance, and immune escape. Due to communication with multiple cells in the TME, they exhibit plasticity and heterogeneity during the progress of polarization from monocytes to macrophages. Previous studies suggest that targeting TAMs is a promising therapeutic strategy; however, the detailed mechanism by which TAMs regulate tumor development still remains unclear. In this review, we provide an overview of the roles of exosomes as messengers in the communication between tumor cells and polarization of TAMs; we also describe the effects of their interaction on tumor development. Finally, we comprehensively discussed the potential application of exosomes as the promising tumor immunotherapy strategy.

Xanthohumol: A Metabolite with Promising Anti-Neoplastic Potential

The overwhelming globalburden of cancer has posed numerous challenges and opportunities for developing anti-cancer therapies. Phytochemicalshave emerged as promising synergistic compounds with potential anti-cancer effects to supplement chemo- and immune-therapeutic regimens. Anti cancer synergistic effects have been investigated in the interaction between phytocompounds derived from flavonoids such as quercetin, apigenin, kaempferol, hesperidin, emodin etc., and conventional drugs. Xanthohumol is one of the prenylatedphytoflavonoid that has demonstrated key anti-cancer activities in in vitro (anti proliferation of cancer cell lines) and in vivo(animal models of xenograft tumours)studies, and has been explored from different dimensions for targeting cancer subtypes. In the last decade, xanthohumol has been investigated how it induces the anti-cancer effects at cellular and molecular level.The different signalling cascades and targets of xanthohumolare summarized in thisreview.Overall, this reviewsummarizes the current advances made in the field of natural compounds with special reference to xanthohumol and its promising anti-cancer effectsto inhibit tumour progression.The present review hasalso touched upon the potential of xanthohumol transitioning into a lead candidate from nano-therapy viewpoint along with the challenges which need to be addressed for extensive pre-clinical and clinical anti-cancer studies.

LncRNA PCGEM1 contributes to malignant behaviors of glioma by regulating miR-539-5p/CDK6 axis

Background: Glioma, one of the most prevalent and aggressive cancers, is regulated by long noncoding RNAs (lncRNAs). This study aims to research the functional mechanism of lncRNA PCGEM1 involved in glioma progression.

Methods: Expression levels of PCGEM1, miR-539-5p and CDK6 were analyzed by qRT-PCR in NHA, U251, U87, and LN229 cells or glioma tissues. shRNAs were used to knock down PCGEM1 in U251 and LN229 cells. Kaplan-Meier curve and log rank test were utilized to examine survival rate. CCK8 (Cell Counting Kit-8) assay, colony formation assay and EdU staining were conducted to detect cell proliferation. Transwell assay was performed to evaluate cell migration and invasion. Luciferase reporter assay was conducted to assess RNA interaction between PCGEM1 and miR-539-5p. Nude mice were used for tumor xenograft assay.

Results: LncRNA PCGEM1 was upregulated in glioma tissues and tumor cell lines. PCGEM1 upregulation predicted unsatisfactory prognosis. PCGEM1 knockdown inhibited proliferation, colony formation, migration and invasion. PCGEM1 knockdown delayed tumor growth in vivo. PCGEM1 played as a competing endogenous RNA (ceRNA) for miR-539-5p to promote CDK6 expression. MiR-539-5p mimics repressed glioma progression while CDK6 overexpression reversed the roles of PCGEM1 knockdown.

Conclusion: PCGEM1 knockdown suppressed glioma progression through sponging miR-539-5p and regulating CDK6 expression, implying PCGEM1 as a potential therapeutic target.

LncRNA PCGEM1 promotes renal carcinoma progression by targeting miR-433-3p to regulate FGF2 expression

Long non-coding RNAs (lncRNAs) are implicated in the development of carcinomas, containing renal carcinoma. The competing endogenous RNA (ceRNA) network is well-known in modulating the pathological and physiological processes of tumors. Still and all, the function role of oncogenic lncRNA PCGEM1 prostate-specific transcript (PCGEM1) in renal carcinoma was undefined till now. This paper aimed to figure out the role and mechanism of PCGEM1 in renal carcinoma. In this study, PCGEM1 was observed to be lifted in renal carcinoma cells. Loss-of-function experiments displayed that silencing of PCGEM1 repressed cell proliferation and migration, and activated apoptosis in renal carcinoma. FISH assay and subcellular fractionation assay indicated that PCGEM1 was largely located in the cytoplasm. As demonstrated, PCGEM1 interacted with microRNA433-3p (miR-433-3p). Subsequently, luciferase reporter and RIP experiments together with qRT-PCR certified that PCGEM1 and fibroblast growth factor 2 (FGF2) functioned as ceRNA for miR-433-3p, leading to the upregulation of FGF2 expression. Finally, rescue assays exhibited that FGF2 overexpression rescued the inhibited cell progression caused by PCGEM1 downregulation. MiR-433-3p inhibitor could reverse the cell growth and migration caused by PCGEM1 downregulation. The present research investigated the molecular mechanism underlying PCGEM1 in renal carcinoma, exposing a PCGEM1-mediated therapy for the treatment of patients with renal carcinoma.

Development and validation of a three-long noncoding RNA signature for predicting prognosis of patients with gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most frequently diagnosed gastrointestinal cancers throughout the world. Novel prognostic biomarkers are required to predict the prognosis of GC.

AIM

To identify a multi-long noncoding RNA (lncRNA) prognostic model for GC.

METHODS

Transcriptome data and clinical data were downloaded from The Cancer Genome Atlas. COX and least absolute shrinkage and selection operator regression analyses were performed to screen for prognosis associated lncRNAs. Receiver operating characteristic curve and Kaplan-Meier survival analyses were applied to evaluate the effectiveness of the model.

RESULTS

The prediction model was established based on the expression of AC007991.4, AC079385.3, and AL109615.2 Based on the model, GC patients were divided into “high risk” and “low risk” groups to compare the differences in survival. The model was re-evaluated with the clinical data of our center.

CONCLUSION

The 3-lncRNA combination model is an independent prognostic factor for GC.

Interplay of long non-coding RNAs and HIF-1α: A new dimension to understanding hypoxia-regulated tumor growth and metastasis

Hypoxia is a feature of the solid tumor microenvironment that is associated with poor clinical outcomes in multiple tumor types. Hypoxia-induced factor-1 alpha (HIF-1α) is a master regulator of hypoxic adaption, has been demonstrated to modulate hypoxic gene expression profiling and signaling transduction networks, and is thus a potential therapeutic target. Despite hypoxic response signaling having being extensively studied, the involvement of long non-coding RNAs (lncRNAs) in the hypoxic response has become a new focus of attention. Emerging evidence has documented complex interactions between HIF-1α and lncRNAs, which contribute to the acquisition of multiple hallmarks of cancer. In this review, we focus on recent advances in the study of hypoxia and HIF-1α-regulated lncRNAs, and summarize the molecular mechanisms and functional outcomes of the interplay between lncRNAs and HIF-1α, which may provide important insights into cancer diagnosis and prognosis, enabling better control of cancer.

Role of hypoxia inducible factor-1 in cancer stem cells (Review)

Cancer stem cells (CSCs) have been found to play a decisive role in cancer recurrence, metastasis, and chemo‑, radio‑ and immuno‑resistance. Understanding the mechanism of CSC self‑renewal and proliferation may help overcome the limitations of clinical treatment. The microenvironment of tumor growth consists of a lack of oxygen, and hypoxia has been confirmed to induce cancer cell invasion, metastasis and epithelial‑mesenchymal transition, and is usually associated with poor prognosis and low survival rates. Hypoxia inducible factor‑1 (HIF‑1) can be stably expressed under hypoxia and act as an important molecule to regulate the development of CSCs, but the specific mechanism remains unclear. The present review attempted to explain the role of HIF‑1 in the generation and maintenance of CSCs from the perspective of epigenetics, metabolic reprogramming, tumor immunity, CSC markers, non‑coding RNA and signaling pathways associated with HIF‑1, in order to provide novel targets with HIF‑1 as the core for clinical treatment, and extend the life of patients.

Down-regulation of lncRNA PCGEM1 inhibits cervical carcinoma by modulating the miR-642a-5p/LGMN axis

LncRNA PCGEM1 (PCGEM1) has been reported to exert essential effects on the development and progress of various tumors, while the detailed effects and possible mechanisms of PCGEM1 in cervical carcinoma remain unknown. In the present study, PCGEM1 was over-expressed in cervical carcinoma cells as evidenced by real-time quantitative polymerase chain reaction (RT-qPCR) assay. Knockdown of PCGEM1 significantly repressed proliferation, migration, and invasion, while induced G1 arrest in cervical carcinoma cells. In addition, PCGEM1 was predicted to target miR-642a-5p by bioinformatics software, which was further confirmed by luciferase reporter assay. Besides, RT-qPCR assay indicated that miR-642a-5p expression was decreased in cervical carcinoma cells and knockdown of PCGEM1 could accelerate miR-642a-5p expression. Moreover, inhibition of miR-642a-5p partly abolished the functions of PCGEM1 knockdown on proliferation, cell cycle, migration and invasion of cervical carcinoma cells. Furthermore, miR-642a-5p could bind to the 3'-UTR of LGMN, which was over-expressed in the cervical carcinoma cells. Suppression of LGMN partly restored the functions of miR-642a-5p inhibitor on proliferation, cell cycle distribution, migration and invasion in the cervical carcinoma cells treated with the PCGEM1 shRNA. Taken together, our data indicated that knockdown of PCGEM1 inhibited proliferation, migration and invasion in cervical carcinoma by modulating the miR-642a-5p/ LGMN axis.

Long noncoding RNA CA3-AS1 suppresses gastric cancer migration and invasion by sponging miR-93-5p and targeting BTG3

The long noncoding RNAs (lncRNAs) are a class of noncoding RNAs that are broadly expressed in various biological cells and function in regulating gene expression. However, the function of lncRNAs and the role of lncRNAs in gastric cancer remain to be determined. Herein, the function of lncRNA CA3-AS1 was investigated in gastric cancer. Firstly, we found that the expression level of CA3-AS1 was decreased in gastric cancer cell lines and tissues. Then, CA3-AS1 overexpression inhibited the gastric cancer cells migration and invasion and knockdown of CA3-AS1 enhanced the gastric cancer cells migration and invasion. Moreover, FISH assays and qPCR results revealed that CA3-AS1 was mainly expressed in the cytoplasm of gastric cancer cells. Then, the relationship between CA3-AS1 and miR-93-5p was explored. Luciferase reporter assays results showed that miR-93-5p was a direct target of CA3-AS1 in SGC-7901 and BCG-823. Furthermore, BTG3 was identified as a direct target gene of miR-93-5p. Restore experiments showed that CA3-AS1 upregulated the expression level of BTG3 and inhibited the gastric cancer cells invasion by sponging miR-93-5p. Finally, we found that CA3-AS1 inhibited the metastasis ability of gastric cancer cells in vivo. Above results suggested that CA3-AS1 acted as anti-oncogene in gastric cancer and might become a vital target for clinical treatment.

[Mechanism of long-chain noncoding RNA PCGEM1 in the regulation of the invasion and metastasis of oral squamous carcinoma cells via transforming growth factor β2/Smad2 signaling pathway]

OBJECTIVE

To investigate the mechanism underlying the regulation of the invasion and metastasis of oral squamous cell carcinoma (OSCC) by long-chain noncoding RNA (lncRNA) PCGEM1 through the transforming growth factor (TGF) β2/Smad2 signaling pathways.

METHODS

A total of 60 OSCC cases were collected. Cancer tissues and normal tissues more than 2 cm away from cancer tissues were also collected. Real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect the expression of miR-148a and lncRNA PCGEM1 in OSCC, adjacent normal tissues, oral mucosa epithelial cells, KB, BcaCD885, SCC-4, CAL27, and SCC-15. The relationship between the expression of lncRNA PCGEM1 and miR-148a and the clinicopathological information of patients was analyzed. The lncRNA PCGEM1-silenced cell line KB-siPCGEM1 and negative control (KB-NC) group were constructed, and KB was used as the blank control group. The effects of lncRNA PCGEM1 on the proliferation, invasion, and migration of KB cells were determined via MTT, Transwell, and scratch assays. The bioinformatics website starBase was used to predict the complementary binding microRNA (miRNA) of lncRNA PCGEM1. Furthermore, the genes that the miRNA could target and bind were predicted in accordance with the website www.microRNA.org. Western blotting analysis was used to detect the expression of TGF β2/Smad2 signaling pathway proteins.

RESULTS

qRT-PCR results showed that the expression level of lncRNA PCGEM1 and miR-148a in OSCC tissues was higher than that in normal tissues (P<0.05). The expression of lncRNA PCGEM1 and miR-148a in the cancer tissues of patients with different TNM grades, lymph node metastasis, and tissue differentiation was statistically significant (P<0.05). Compared with those in the blank control group and the KB-NC group, OD492 nm value was significantly decreased and cell mobility was significantly reduced in the KB-siPCGEM1 group (P<0.05). Bioinformatics predictions showed that lncRNA PCGEM1 could bind to miR-148a in a complementary manner and that miR-148a had a targeted binding site with TGF β2. qRT-PCR and Western blotting analysis results showed that the expression levels of miR-148a, TGF β2, and p-Smad2 in the KB-siPCGEM1 group were significantly lower than those in the blank control and KB-NC groups (P<0.05), and no statistically significant difference between the blank control group and the KB-NC group was observed (P>0.05).

CONCLUSIONS

LncRNA PCGEM1 is highly expressed in OSCC. The high expression of lncRNA PCGEM1 may enhance the TGF β2/Smad2 signaling pathway by upregulating miR-148a, thus promoting the development of OSCC.

RUNX1 regulates TGF-β induced migration and EMT in colorectal cancer

Colorectal cancer (CRC) was one of the most malignant tumors worldwide due to its metastasis. Epithelial-to-mesenchymal transition (EMT) plays an important role in CRC migration, and transforming growth factor-β (TGF-β) works as a dominating cytokine in CRC EMT process. Here, we originally identified RUNX1 as an important factor among TGF-β induced EMT in CRC. We found that RUNX1 was overexpressed with the treatment of TGF-β, accompanied with enhanced cancer cell migration and EMT which was characterized by up-graded N-Cadherin levels. Vice versa, knockdown of RUNX1 attenuated the migration ability of TGF-β induced CRC cells. In addition, decreased expression of N-Cadherin suggested that EMT was also attenuated after knocking down RUNX1. Similar decrease was observed in EMT regulator snail family transcriptional repressor 1 (SNAI1). And the knockdown effect of RUNX1 cannot be reversed by the addition of TGF-β. Moreover, we observed that RUNX1 expression was higher in CRC tumor tissues than in normal epithelial tissues. The enhanced expression was detected in cancer cell nucleus. These results revealed RUNX1 could regulate colorectal cancer migration via TGF-β signaling pathway, and RUNX1 might serve as a potential target for preventing CRC metastasis.

PTEN, a Barrier for Proliferation and Metastasis of Gastric Cancer Cells: From Molecular Pathways to Targeting and Regulation

Cancer is one of the life-threatening disorders that, in spite of excellent advances in medicine and technology, there is no effective cure for. Surgery, chemotherapy, and radiotherapy are extensively applied in cancer therapy, but their efficacy in eradication of cancer cells, suppressing metastasis, and improving overall survival of patients is low. This is due to uncontrolled proliferation of cancer cells and their high migratory ability. Finding molecular pathways involved in malignant behavior of cancer cells can pave the road to effective cancer therapy. In the present review, we focus on phosphatase and tensin homolog (PTEN) signaling as a tumor-suppressor molecular pathway in gastric cancer (GC). PTEN inhibits the PI3K/Akt pathway from interfering with the migration and growth of GC cells. Its activation leads to better survival of patients with GC. Different upstream mediators of PTEN in GC have been identified that can regulate PTEN in suppressing growth and invasion of GC cells, such as microRNAs, long non-coding RNAs, and circular RNAs. It seems that antitumor agents enhance the expression of PTEN in overcoming GC. This review focuses on aforementioned topics to provide a new insight into involvement of PTEN and its downstream and upstream mediators in GC. This will direct further studies for evaluation of novel signaling networks and their targeting for suppressing GC progression.

Long-Noncoding RNA (lncRNA) in the Regulation of Hypoxia-Inducible Factor (HIF) in Cancer

Hypoxia is dangerous for oxygen-dependent cells, therefore, physiological adaption to cellular hypoxic conditions is essential. The transcription factor hypoxia-inducible factor (HIF) is the main regulator of hypoxic metabolic adaption reducing oxygen consumption and is regulated by gradual von Hippel-Lindau (VHL)-dependent proteasomal degradation. Beyond physiology, hypoxia is frequently encountered within solid tumors and first drugs are in clinical trials to tackle this pathway in cancer. Besides hypoxia, cancer cells may promote HIF expression under normoxic conditions by altering various upstream regulators, cumulating in HIF upregulation and enhanced glycolysis and angiogenesis, altogether promoting tumor proliferation and progression. Therefore, understanding the underlying molecular mechanisms is crucial to discover potential future therapeutic targets to evolve cancer therapy. Long non-coding RNAs (lncRNA) are a class of non-protein coding RNA molecules with a length of over 200 nucleotides. They participate in cancer development and progression and might act as either oncogenic or tumor suppressive factors. Additionally, a growing body of evidence supports the role of lncRNAs in the hypoxic and normoxic regulation of HIF and its subunits HIF-1α and HIF-2α in cancer. This review provides a comprehensive update and overview of lncRNAs as regulators of HIFs expression and activation and discusses and highlights potential involved pathways.

LncRNA PCGEM1 enhances metastasis and gastric cancer invasion through targeting of miR-129-5p to regulate P4HA2 expression

AIM

Aberrantly expressed long non-coding RNAs (lncRNAs) are critical instigators of gastric cancer (GC) progression and metastasis. The ceRNA (competing endogenous RNAs) network is well-known in modulating tumor pathological and physiological processes. This research aims to determine the more effective molecular mechanisms of lncRNA PCGEM1 (prostate cancer gene expression marker 1).

METHODS

Bioinformatics database and Ago2-RIP were performed to predict and verify the potential targets of lncRNA PCGEM1. Both gain- and loss-of-function experiments were carried out to dissect the biological functions of RNAs. Fluorescence in situ hybridization, dual-luciferase reporter assays, western blot, and real-time PCR (RT-PCR) experiments were utilized to determine the pathophysiological pathways of competitive endogenous RNAs (ceRNAs).

RESULTS

GC cells expressed high levels of cytoplasmic PCGEM1. Loss-of-function experiments displayed that the silencing of PCGEM1 suppressed metastatic and invasive cell qualities. PCGEM1 was also found to have associations with miR-129-5p. Subsequently, luciferase reporter and RIP experiments, together with RT-PCR, verified that PCGEM1 functioned as a ceRNA of P4HA2 (Prolyl 4-Hydroxylase Subunit Alpha 2) via sponging miR-129-5p to up-regulate P4HA2 expression. Finally, the rescue assays determined that P4HA2 overexpression rescued the inhibited cell invasion and metastasis caused by PCGEM1 down-regulation.

CONCLUSION

These findings found that an over-expression of PCGEM1 in GC acts as a miR-129-5p sponge, leading to higher levels of P4HA2. The PCGEM1/miR-129-5p/P4HA2 axis was confirmed to possess a crucial role in GC metastasis and invasion, suggesting its utility as a potential diagnostic and therapeutic biomarker.

Hypoxia-Induced lncRNA-NEAT1 Sustains the Growth of Hepatocellular Carcinoma via Regulation of miR-199a-3p/UCK2

Objective: The long noncoding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) has emerged as a novel player in hepatocellular carcinoma (HCC). Hypoxia is a common characteristic of the microenvironment of HCC. This study aimed to investigate whether lncRNA-NEAT1 is induced by hypoxia in HCC, and the mechanism that underlies LncRNA-NEAT1 function.

Methods: The expression changes of lncRNA-NEAT1 in HCC cell lines under hypoxic conditions were examined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The regulatory effect of HIF-1α on lncRNA-NEAT1 was confirmed with chromatin immunoprecipitation (ChIP) and luciferase reporter assays. The function of lncRNA-NEAT1 on HCC cell growth under hypoxic conditions was determined by CCK-8 assay and flow cytometry. lncRNA -NEAT1 was predicted to serve as a competing endogenous RNA (ceRNA) within microRNA (miRNA)/mRNA axes based on microarray data, public HCC-related datasets and integrative bioinformatics analysis, and the miR-199a-3p/UCK2 axis was selected and validated by qRT-PCR, western blotting, RNA immunoprecipitation, and luciferase reporter analyses. The role of miR-199a-3p/UCK2 in HCC and its functional association with lncRNA-NEAT1 were assessed both in vitro and in vivo.

Results: LncRNA-NEAT1 expression was significantly induced by hypoxia in SNU-182 and HUH7 cells. HIF-1α was shown to regulate lncRNA-NEAT1 transcription. Under hypoxic conditions, lncRNA-NEAT1 maintained the growth of HCC cells and inhibited apoptosis and cell cycle arrest. LncRNA-NEAT1 was predicted to regulate a panel of HCC-associated miRNA-mRNA pairs consisting of 8 miRNAs and 13 mRNAs. LncRNA-NEAT1 was shown to function as a ceRNA of miR-199a-3p/UCK2 both in HCC cells under hypoxic conditions and in an animal model.

Conclusion: LncRNA-NEAT1 is a hypoxia-responsive lncRNA in HCC cell lines Insilico evidence suggested that LncRNA-NEAT1 may sustainthe growth of HCC cells by regulating HCC-associated mRNAs that interact with tumor-suppressive miRNAs. The lncRNA-NEAT1/miR-199a-3p/UCK2 pathway may contribute to the progression of HCC cell lines in a hypoxic microenvironment and therefore may represent a novel therapeutic target for HCC.

Exosome-transmitted lncRNA PCGEM1 promotes invasive and metastasis in gastric cancer by maintaining the stability of SNAI1

PURPOSE

Clinically, hypoxia is associated with increased distant metastasis and poor survival in gastric cancer (GC). In this study, we set out from the cellular interaction to further explain the molecular mechanism of invasion in GC cells under hypoxic conditions.

METHODS

Gastric cancer cells were cultured under 1% O₂ (hypoxia-cultured gastric cancer cells, HGC) and 20% O₂ condition (normoxic-cultured gastric cancer cells, NGC). NGC was co-cultured with HGC-medium. Scrape and Transwell were used to evaluate invasion and migration. Exosomes from GC were extracted by ultracentrifugation. Electron microscopy images, western-blot used to analyze the size distributions and the number of exosomes.

RESULTS

HGC-medium induced NGC dissociated. Long non-coding RNA (lncRNA) prostate cancer gene expression marker 1 (PCGEM1) was specifically expressed in HGC exosomes. HGC-derived PCGEM1-riched exosomes could promote the invasion and migration of NGC. On the mechanism, PCGEM1 maintained stability and reduced the degradation of SNAI1, which could induce the epithelial-mesenchymal transition of GC.

CONCLUSION

LncRNA PCGEM1 was overexpressed in GC cells. And part of the PCGEM1 can be encapsulated into exosomes. These exosomes promoted invasion and migration of other GC cells. We considered PCGEM1 might act as a "scaffold" combined with SNAI1 and prompt the invasion and migration of GC.

Signaling in and out: long-noncoding RNAs in tumor hypoxia

Over the past few years, long non-coding RNAs (lncRNAs) are recognized as key regulators of gene expression at chromatin, transcriptional and posttranscriptional level with pivotal roles in various biological and pathological processes, including cancer. Hypoxia, a common feature of the tumor microenvironment, profoundly affects gene expression and is tightly associated with cancer progression. Upon tumor hypoxia, the central regulator HIF (hypoxia-inducible factor) is upregulated and orchestrates transcription reprogramming, contributing to aggressive phenotypes in numerous cancers. Not surprisingly, lncRNAs are also transcriptional targets of HIF and serve as effectors of hypoxia response. Indeed, the number of hypoxia-associated lncRNAs (HALs) identified has risen sharply, illustrating the expanding roles of lncRNAs in hypoxia signaling cascade and responses. Moreover, through extra-cellular vesicles, lncRNAs could transmit hypoxia responses between cancer cells and the associated microenvironment. Notably, the aberrantly expressed cellular or exosomal HALs can serve as potential prognostic markers and therapeutic targets. In this review, we provide an update of the current knowledge about the expression, involvement and potential clinical impact of lncRNAs in tumor hypoxia, with special focus on their unique molecular regulation of HIF cascade and hypoxia-induced malignant progression.

Hypoxia-induced lncRNA RP11-390F4.3 promotes epithelial-mesenchymal transition (EMT) and metastasis through upregulating EMT regulators

Hypoxia-induced long noncoding RNAs (lncRNAs) have been shown to induce tumor metastasis. However, lncRNAs that are regulated by hypoxia/HIF-1α and subsequently control the expression of multiple epithelial-mesenchymal transition (EMT) regulators have not been identified. To identify such lncRNAs, analysis of RNA-sequencing datasets was performed. The lncRNA RP11-390F4.3 was shown to be induced by hypoxia and directly activated by HIF-1α. Overexpression of lncRNA RP11-390F4.3 induced EMT and metastasis. LncRNA RP11-390F4.3 was essential for hypoxia-induced EMT and metastasis. LncRNA RP11-390F4.3 overexpression induced the expression of multiple EMT regulators. This report demonstrates that LncRNA RP11-390F4.3 is induced by hypoxia/HIF-1α and is essential for hypoxia-induced EMT and metastasis via the activation of multiple EMT regulators.

Overexpression of long non-coding RNA RP11-363E7.4 inhibits proliferation and invasion in gastric cancer

LncRNA RP11‐363E7.4 has been shown to be downregulated in gastric cancer (GC), while the effect of lncRNA RP11‐363E7.4 on GC and its potential molecular mechanisms is unclear. The purpose of this study was to explore the functional role and underlying molecular mechanisms of lncRNA RP11‐363E7.4 involved in GC progress.To address the question, quantitative real‐time PCR assay was performed to confirm lncRNA RP11‐363E7.4 expression levels in GC tissues and cell lines. Cell proliferation, apoptosis, migration and invasion were estimated using Cell Counting Kit‐8, colony formation, scratch wound healing and Transwell assays. Potential molecular mechanisms were evaluated using western blot assay. The results showed that lncRNA RP11‐363E7.4 was significantly downregulated in GC cell lines and 82 paired tissues. The correlation between expression and clinicopathological features indicated that low expression of lncRNA RP11‐363E7.4 was associated with T stage (P = .010). Functional experiments showed that overexpression of lncRNA RP11‐363E7.4 prevented proliferation, migration, and invasion and induced apoptosis of GC cells. Western blot assay revealed that lncRNA RP11‐363E7.4 functioned via the p53, Bax/Bcl‐2, β‐catenin pathway. In summary, this study revealed that lncRNA RP11‐363E7.4 functioned as a tumour suppressor by inhibiting proliferation, migration, and invasion and inducing apoptosis of GC cells. Significance of the study:LncRNA RP11‐363E7.4 has been shown to be downregulated in GC, while the effect of lncRNA RP11‐363E7.4 on GC and its potential molecular mechanism is unclear. We revealed that lncRNA RP11‐363E7.4 functioned as a tumour suppressor by inhibiting proliferation, migration, and invasion and inducing apoptosis of GC cells. LncRNA RP11‐363E7.4 might become an attractive diagnostic and prognostic biomarker of GC and a promising target for GC treatment.

The Roles of Hypoxia-Inducible Factors and Non-Coding RNAs in Gastrointestinal Cancer

Hypoxia-inducible factors (HIFs) are transcription factors that play central roles in cellular responses against hypoxia. In most cancers, HIFs are closely associated with tumorigenesis by regulating cell survival, angiogenesis, metastasis, and adaptation to the hypoxic tumor microenvironment. Recently, non-coding RNAs (ncRNAs) have been reported to play critical roles in the hypoxic response in various cancers. Here, we review the roles of hypoxia-response ncRNAs in gastrointestinal cancer, with a particular focus on microRNAs and long ncRNAs, and discuss the functional relationships and regulatory mechanisms between HIFs and ncRNAs.

Controversies around epithelial-mesenchymal plasticity in cancer metastasis

Experimental evidence accumulated over decades has implicated epithelial-mesenchymal plasticity (EMP), which collectively encompasses epithelial-mesenchymal transition and the reverse process of mesenchymal-epithelial transition, in tumour metastasis, cancer stem cell generation and maintenance, and therapeutic resistance. However, the dynamic nature of EMP processes, the apparent need to reverse mesenchymal changes for the development of macrometastases and the likelihood that only minor cancer cell subpopulations exhibit EMP at any one time have made such evidence difficult to accrue in the clinical setting. In this Perspectives article, we outline the existing preclinical and clinical evidence for EMP and reflect on recent controversies, including the failure of initial lineage-tracing experiments to confirm a major role for EMP in dissemination, and discuss accumulating data suggesting that epithelial features and/or a hybrid epithelial-mesenchymal phenotype are important in metastasis. We also highlight strategies to address the complexities of therapeutically targeting the EMP process that give consideration to its spatially and temporally divergent roles in metastasis, with the view that this will yield a potent and broad class of therapeutic agents.