Long Noncoding RNA CUDR Regulates HULC and β-Catenin to Govern Human Liver Stem Cell Malignant Differentiation

Uncovering the roles of long non-coding RNAs in cancer stem cells

Cancer has been a major public health problem that has threatened human life worldwide throughout history. The main causes that contribute to the poor prognosis of cancer are metastasis and recurrence. Cancer stem cells are a group of tumor cells that possess self-renewal and differentiation ability, which is a vital cause of cancer metastasis and recurrence. Long non-coding RNAs refer to a class of RNAs that are longer than 200 nt and have no potential to code proteins, some of which can be specifically expressed in different tissues and different tumors. Long non-coding RNAs have great biological significance in the occurrence and progression of cancers. However, how long non-coding RNAs interact with cancer stem cells and then affect cancer metastasis and recurrence is not yet clear. Therefore, this review aims to summarize recent studies that focus on how long non-coding RNAs impact tumor occurrence and progression by affecting cancer stem cell self-renewal and differentiation in liver cancer, prostate cancer, breast cancer, and glioma.

Inflammatory cytokine IL6 cooperates with CUDR to aggravate hepatocyte-like stem cells malignant transformation through NF-κB signaling

Inflammatory cytokines and lncRNAs are closely associated with tumorigenesis. Herein, we reveal inflammatory cytokines IL6 cooperates with long noncoding RNA CUDR to trigger the malignant transformation of human embryonic stem cells-derived hepatocyte-like stem cells. Mechanistically, IL6 cooperates with CUDR to cause MELLT3 to interact with SUV39h1 mRNA3′UTR and promote SUV39h1 expression. Moreover, the excessive SUV39h1 also increases tri-methylation of histone H3 on nineth lysine (H3K9me3). Intriguingly, under inflammatory conditions, H3K9me3 promotes the excessive expression and phosphorylation of NF-κB, and in turn, phorsphorylated NF-κB promotes the expression and phosphorylation of Stat3. Furthermore, that the phosphorylated Stat3 loads onto the promoter region of miRs and lncRNAs. Ultimately, the abnormal expression of miRs and lncRNAs increased telomerase activity, telomere length and microsatellite instability (MSI), leading to malignant transformation of hepatocyte-like stem cells.

HULC cooperates with MALAT1 to aggravate liver cancer stem cells growth through telomere repeat-binding factor 2

The dysregulation of lncRNAs has increasingly been linked to many human diseases, especially in cancers. Our results demonstrate HULC, MALAT1 and TRF2 are highly expressed in human hepatocellular carcinoma tissues, and HULC plus MALAT1 overexpression drastically promotes the growth of liver cancer stem cells. Mechanistically, both HULC and MALAT1 overexpression enhanced RNA polII, P300, CREPT to load on the promoter region of telomere repeat-binding factor 2(TRF2), triggering the overexpression, phosphorylation and SUMOylation of TRF2. Strikingly, the excessive TRF2 interacts with HULC or MALAT1 to form the complex that loads on the telomeric region, replacing the CST/AAF and recruiting POT1, pPOT1, ExoI, SNM1B, HP1 α. Accordingly, the telomere is greatly protected and enlonged. Furthermore, the excessive HULC plus MALAT1 reduced the methylation of the TERC promoter dependent on TRF2, increasing the TERC expression that causes the increase of interplay between TRET and TERC. Ultimately, the interaction between RFC and PCNA or between CDK2 and CyclinE, the telomerase activity and the microsatellite instability (MSI) are significantly increased in the liver cancer stem cells. Our demonstrations suggest that haploinsufficiency of HULC/MALAT1 plays an important role in malignant growth of liver cancer stem cell.

HULC: an oncogenic long non-coding RNA in human cancer

Highly up‐regulated in liver cancer (HULC) was originally identified as the most overexpressed long non‐coding RNA in hepatocellular carcinoma. Since its discovery, the aberrant up‐regulation of HULC has been demonstrated in other cancer types, including gastric cancer, pancreatic cancer, osteosarcoma and hepatic metastasis of colorectal cancer. Recent discoveries have also shed new light on the upstream molecular mechanisms underlying HULC deregulation. As an oncogene, HULC promotes tumorigenesis by regulating multiple pathways, such as down‐regulation of EEF1E1, promotion of abnormal lipid metabolism, and up‐regulation of sphingosine kinase 1. Pertinent to clinical practice, a genetic variant in the HULC gene has been found to alter the risk for hepatocellular carcinoma and oesophageal cancer, whereas cancer patients with high or low expression of HULC exhibit different clinical outcome. These findings highlighted the pathogenic role and clinical utility of HULC in human cancers. Further efforts are warranted to promote the development of HULC‐directed therapeutics.

Double mutant P53 (N340Q/L344R) promotes hepatocarcinogenesis through upregulation of Pim1 mediated by PKM2 and LncRNA CUDR

P53 is frequently mutated in human tumors as a novel gain-of-function to promote tumor development. Although dimeric (M340Q/L344R) influences on tetramerisation on site-specific post-translational modifications of p53, it is not clear how dimeric (M340Q/L344R) plays a role during hepatocarcinogenesis. Herein, we reveal that P53 (N340Q/L344R) promotes hepatocarcinogenesis through upregulation of PKM2. Mechanistically, P53 (N340Q/L344R) forms complex with CUDR and the complex binds to the promoter regions of PKM2 which enhances the expression, phosphorylation of PKM2 and its polymer formation. Thereby, the polymer PKM2 (tetramer) binds to the eleventh threonine on histone H3 that increases the phosphorylation of the eleventh threonine on histone H3 (pH3T11). Furthermore, pH3T11 blocks HDAC3 binding to H3K9Ac that prevents H3K9Ac from deacetylation and stabilizes the H3K9Ac modification. On the other hand, it also decreased tri-methylation of histone H3 on the ninth lysine (H3K9me3) and increases one methylation of histone H3 on the ninth lysine (H3K9me1). Moreover, the combination of H3K9me1 and HP1 α forms more H3K9me3-HP1α complex which binds to the promoter region of Pim1, enhancing the expression of Pim1 that enhances the expression of TERT, oncogenic lncRNA HOTAIR and reduces the TERRA expression. Ultimately, P53 (N340Q/L344R) accerlerates the growth of liver cancer cells Hep3B by activating telomerase and prolonging telomere through the cascade of P53 (N340Q/L344R)-CUDR-PKM2-pH3T11- (H3K9me1-HP1α)-Pim1- (TERT-HOTAIR-TERRA). Understanding the novel functions of P53 (N340Q/L344R) will help in the development of new liver cancer therapeutic approaches that may be useful in a broad range of cancer types.

Identification of long noncoding RNA expression profile in oxaliplatin-resistant hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most prevalent and malignant type of liver cancer. Besides the high incidence, the resistance to chemotherapy is a major problem that leads to the high mortality of HCC. Recently, aberrant expression of long noncoding RNAs (lncRNAs) has been considered as a primary feature of many types of cancer. However, the genome-wide expression pattern and associated functional implications of lncRNAs in chemo-resistant HCC cells remain unknown. In this study, we identified 120 differentially expressed lncRNAs with 61 up-regulated and 59 down-regulated (fold change>2, p<0.05) along with 421 differentially expressed mRNAs with 228 up-regulated and 193 down-regulated (fold change>2, p<0.05) in oxaliplatin-resistant (MHCC97H-OXA) HCC cells, compared to parental oxaliplatin-sensitive (MHCC97H) by microarray. The underlying pathways were related to cell death, proliferation, cellular response to stimulus, including p53 pathway, ErbB pathway and MAPK pathway. Further, 16 lncRNAs were selected for validation of microarray results with quantitative PCR, and a strong correlation was identified between the qPCR results and microarray data. We demonstrated for the first time that ENST00000438347, NR_073453 and ENST00000502804 were up-regulated in MHCC97H-OXA cells as well as chemo-resistant HCC cancerous tissues. Moreover, the expression of ENST00000518376 was significantly associated with the tumor size and differentiation. Overall survival analysis showed that high expression of ENST00000438347 and ENST00000518376 was associated with poor prognosis in HCC patients. Taken together, our results reveal that the expression profile in oxaliplatin-resistant HCC is significantly altered including lncRNAs. And a series of de novo lncRNAs play important functions in HCC oxaliplatin resistance and HCC progression.

Long Noncoding RNA ROR Regulates Proliferation, Invasion, and Stemness of Gastric Cancer Stem Cell

Gastric cancer remains an incurable malignance and the second leading cause of cancer death globally. Recent progress in gastric cancer research has demonstrated the crucial roles of cancer stem cells (CSCs) in the development, metastasis, and drug resistance of this disease. Various studies have highlighted the role of long noncoding RNAs (lncRNAs) in the pathogenesis of gastric cancer. In this study, through fluorescence-activated cell sorting, we isolated gastric CSCs (GCSCs) from MKN-45 cells and demonstrated for the first time that lncRNA ROR was highly expressed in CD133⁺ GCSCs. Overexpression of lncRNA ROR significantly increased, but knockdown of lncRNA ROR inhibited the proliferation and invasion of GCSCs. Most importantly, lncRNA ROR led to upregulation of several key stemness transcriptional factors, such as OCT4, SOX2, and NANOG, as well as CD133 GCSC. Our data demonstrated that lncRNA ROR was associated with core stemness transcriptional factors and the pluripotent state of GCSCs. These results further improved our understanding of the functional cross talking network during development of GCSCs and may provide novel target for the diagnostics and therapeutics of gastric cancer.

Long Noncoding RNA GCASPC, a Target of miR-17-3p, Negatively Regulates Pyruvate Carboxylase-Dependent Cell Proliferation in Gallbladder Cancer

Long noncoding RNAs (lncRNA) are being implicated in the development of many cancers. Here, we report the discovery of a critical role for the lncRNA GCASPC in determining the progression of gallbladder cancer. Differentially expressed lncRNAs and mRNAs between gallbladder cancer specimens and paired adjacent nontumor tissues from five patients were identified and validated by an expression microarray analysis. Quantitative real-time PCR was used to measure GCASPC levels in tissues from 42 gallbladder cancer patients, and levels of GCASPC were confirmed further in a separate cohort of 89 gallbladder cancer patients. GCASPC was overexpressed or silenced in several gallbladder cancer cell lines where molecular and biological analyses were performed. GCASPC levels were significantly lower in gallbladder cancer than adjacent nontumor tissues and were associated with tumor size, American Joint Committee on Cancer tumor stage, and patient outcomes. GCASPC overexpression suppressed cell proliferation in vitro and in vivo, whereas GCASPC silencing had opposite effects. By RNA pull-down and mass spectrometry, we identified pyruvate carboxylase as an RNA-binding protein that associated with GCASPC. Because GCASPC is a target of miR-17-3p, we confirmed that both miR-17-3p and GCASPC downregulated pyruvate carboxylase level and activity by limiting protein stability. Taken together, our results defined a novel mechanism of lncRNA-regulated cell proliferation in gallbladder cancer, illuminating a new basis for understanding its pathogenicity. Cancer Res; 76(18); 5361-71. ©2016 AACR.

Long noncoding RNAs in normal and pathological pluripotency

The striking similarities between pluripotent and cancer cells, such as immortality and increased stress resistance, have long been acknowledged. Numerous studies searched for and successfully identified common molecular players and pathways, thus providing an entirely new challenge and potential therapeutic angle by targeting cancer cells or a specific stem population of the tumor via pluripotency associated processes. However, these strategies have until now mainly been restricted to proteins. Nonetheless, it has become clear over the past decade that the overwhelming majority of the genome produces noncoding transcripts, many of which have proven both functional and crucial for key cellular processes, including stemness maintenance. Moreover, numerous long noncoding RNAs are deregulated in cancer, but little is known concerning their functions and molecular mechanisms. Consequently, it seems essential to integrate the noncoding transcripts into the picture of the stemness-cancer connection. Whereas a number of studies have addressed the expression of lncRNAs in cancer stem cells, no systematic approach has yet been undertaken to identify lncRNAs implicated in the maintenance of the embryonic stemness state that is hijacked by cancer cells. The aim of this review is to highlight long noncoding RNAs with shared functions in stemness and cancer and to outline the current state of a field in its infancy, the search for long noncoding transcripts in cancer stem cells.

Long noncoding RNAs in digestive system cancers: Functional roles, molecular mechanisms, and clinical implications (Review)

Long noncoding RNAs (lncRNAs) are emerging as new players in various diseases including cancer. LncRNAs have been shown to play multifaceted roles in the development, progression, and metastasis of cancer. In this review, we highlight the lncRNAs that are critically involved in the pathogenesis of digestive system cancers (DSCs). We summarize the roles of the lncRNAs in DSCs and the underlying mechanisms responsible for their functions. The DSC-associated lncRNAs interact with a wide spectrum of molecules to regulate gene expression at transcriptional, post-transcriptional, and translational levels. We also provide new insights into the clinical significance of these lncRNAs, which are found to be closely associated with the aggressiveness of DSCs and could predict the prognosis of DSC patients. Moreover, lncRNAs have been suggested as promising therapeutic targets in DSCs. Therefore, better understanding of the functional roles of lncRNAs will provide new biomarkers for DSC diagnosis, prognosis, and therapy.

Insight Into the Role of Long Noncoding RNA in Cancer Development and Progression

Long noncoding RNA (LncRNA) is a large class of RNA molecules with size larger than 200 nucleotides. They exhibit cellular functions although having no protein-coding capability. Accumulating evidence suggests that long noncoding RNA play crucial roles in cancer biology. Studies showed that deregulation of lncRNA was frequently observed in various types of cancers which contributed heavily to malignant phenotypical changes. Aberration of lncRNA can be induced by a number of factors such as dysregulated signaling pathway, response to catastrophic effect, viral infection, and contact with carcinogens. Meanwhile, alterations of lncRNA expression or function drive subsequent malignant development such as cell transformation or acquisition of stemness characteristics. Here, we give perspectives on recent findings on the involvement of lncRNAs in carcinogenesis and response to adverse tumor environment. Then, we discuss the role of lncRNAs in cancer stem cell which is an important model of cancer emergence. Last, we provide insight on the potential of lncRNAs in modulating environment favorable of cancer development and progression, and evaluate the diagnostic and prognostic value of lncRNAs in cancer management.

Long Noncoding RNA Highly Upregulated in Liver Cancer Regulates the Tumor Necrosis Factor-α-Induced Apoptosis in Human Vascular Endothelial Cells

Atherosclerosis is the major cause of myocardial infarction and stroke, which is a leading cause of morbidity and mortality in developed countries. During the pathological process of atherosclerosis, inflammation participates in all stages of atherosclerosis. Tumor necrosis factor-α (TNF-α), one of the most important inflammatory factor, induces apoptosis of endothelial cells, which play a central role in endothelial dysfunction. However, the underlying mechanism involved in long noncoding RNA (lncRNA) remains unclear. In the present study, we demonstrated the role of lncRNA highly upregulated in liver cancer (HULC) in TNF-α-induced apoptosis. HULC expression was decreased with TNF-α treatment. Restoring HULC expression rescued the apoptosis induced by TNF-α. HULC regulated TNF-α-induced apoptosis through regulation of miR-9 expression. Furthermore, RNA immunoprecipitation and RNA pull-down assays showed that HULC modulated miR-9 expression through association with DNA methyltransferases and suppression of miR-9 expression. HULC-miR-9 pathway may be a potential target for treating atherosclerosis.

Non-coding RNAs Functioning in Colorectal Cancer Stem Cells

In recent years, the hypothesis of the presence of tumor-initiating cancer stem cells (CSCs) has received a considerable support. This model suggested the existence of CSCs which, thanks to their self-renewal properties, are able to drive the expansion and the maintenance of malignant cell populations with invasive and metastatic potential in cancer. Increasing evidence showed the ability of such cells to acquire self-renewal, multipotency, angiogenic potential, immune evasion, symmetrical and asymmetrical divisions which, along with the presence of several DNA repair mechanisms, further enhance their oncogenic potential making them highly resistant to common anticancer treatments. The main signaling pathways involved in the homeostasis of colorectal (CRC) stem cells are the Wnt, Notch, Sonic Hedgehog, and Bone Morfogenic Protein (BMP) pathways, which are mostly responsible for all the features that have been widely referred to stem cells. The same pathways have been identified in colorectal cancer stem cells (CRCSCs), conferring a more aggressive phenotype compared to non-stem CRC cells. Recently, several evidences suggested that non-coding RNAs (ncRNAs) may play a crucial role in the regulation of different biological mechanisms in CRC, by modulating the expression of critical stem cell transcription factors that have been found active in CSCs. In this chapter, we will discuss the involvement of ncRNAs, especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in stemness acquisition and maintenance by CRCSCs, through the regulation of pathways modulating the CSC phenotype and growth, carcinogenesis, differentiation, and epithelial to mesenchymal transition (EMT).