Non-coding RNAs, metabolic stress and adaptive mechanisms in cancer

Epigenetics in T-cell driven inflammation and cancer

For decades, scientists have been investigating how processes such as gene expression, stem cell plasticity, and cell differentiation can be modulated. The discovery of epigenetics helped unravel these processes and enabled the identification of major underlying mechanisms that, for example, are central for T cell maturation. T cells go through various stages in their development evolving from progenitor cells into double positive CD4/CD8 T cells that finally leave the thymus as naïve T cells. One major mechanism driving T cell maturation is the modulation of gene activity by temporally sequenced transcription of spatially exposed gene loci. DNA methylation, demethylation, and acetylation are key processes that enable a sequenced gene expression required for T cell differentiation. In vivo, differentiated T cells are subjected to enormous pressures originating from the microenvironment. Signals from this environment, particularly from an inflammatory or a tumor microenvironment, can push T cells to differentiate into specific effector and memory T cells, and even prompt T cells to adopt a state of dysfunctional exhaustion, en route of an epigenetically controlled mechanism. Fundamentals of these processes will be discussed in this review highlighting potential therapeutic interventions, in particular those beneficial to revive exhausted T cells.

Long noncoding RNA MyD88 functions as a promising diagnostic biomarker in hepatocellular carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most frequent malignancies. Alpha-fetoprotein (AFP) has some limitations in diagnosing early HCC. Recently, long noncoding RNAs (lncRNAs) showed great potential as tumor diagnostic biomarkers, and lnc-MyD88 was previously identified as a carcinogen in HCC. Here, we explored its diagnostic value as a plasma biomarker.

MATERIALS AND METHODS

Quantitative real-time PCR was adopted to detect lnc-MyD88 expression in plasma samples of 98 HCC patients, 52 liver cirrhosis (LC) patients, and 105 healthy people. The correlation between lnc-MyD88 and clinicopathological factors was analyzed through chi-square test. The receiver operating characteristic (ROC) curve was used to analyze the sensitivity, specificity, Youden index, and area under the curve (AUC) of lnc-MyD88 and AFP alone and in combination for the diagnosis of HCC. The relationship between MyD88 and immune infiltration was analyzed by single sample gene set enrichment analysis (ssGSEA) algorithm.

RESULTS

Lnc-MyD88 was highly expressed in plasma samples of HCC and hepatitis B virus (HBV)-associated HCC patients. Lnc-MyD88 had better diagnostic value than AFP in HCC patients using healthy people or LC patients as control (healthy people, AUC: 0.776 vs. 0.725; LC patients, AUC: 0.753 vs. 0.727). The multivariate analysis showed that lnc-MyD88 had great diagnostic value for distinguishing HCC from LC and healthy people. Lnc-MyD88 had no correlation with AFP. Lnc-MyD88 and AFP were independent diagnostic factors for HBV-associated HCC. The AUC, sensitivity, and Youden index of the combined diagnosis of lnc-MyD88 and AFP combined were higher than those of lnc-MyD88 and AFP alone. The ROC curve of lnc-MyD88 for the diagnosis of AFP-negative HCC was plotted with a sensitivity of 80.95%, a specificity of 79.59%, and an AUC value of 0.812 using healthy people as control. The ROC curve also presented its great diagnostic value using LC patients as control (sensitivity: 76.19%, specificity: 69.05%, AUC value: 0.769). Lnc-MyD88 expression was correlated with microvascular invasion in HBV-associated HCC patients. MyD88 was positively correlated with infiltrating immune cells and immune-related genes.

CONCLUSION

The high expression of plasma lnc-MyD88 in HCC is distinct and could be utilized as a promising diagnostic biomarker. Lnc-MyD88 had great diagnostic value for HBV-associated HCC and AFP-negative HCC, and it had higher efficacy in combination with AFP.

Decreased EMILIN2 correlates to metabolism phenotype and poor prognosis of ovarian cancer

This study aimed to explore the function and related mechanisms of elastin microfibril interfacer 2 (EMILIN2) in ovarian cancer. First, the expression level of EMILIN2 was detected in patient tissues and its correlation with overall survival rate was analyzed. Then, EMILIN2 was overexpressed in ovarian cancer cell lines to observe its function and effect on Warburg effect. By detecting its promoter region methylation, the epigenetic regulatory role was explored. Finally, through the luciferase reporter assay and siRNA tools, the regulatory mechanism of p53 on EMILIN2 was investigated. It was detected in clinical samples that down-regulated EMILIN2 was associated with poor prognosis of ovarian cancer. It was further found that EMILIN2 regulated the metabolic phenotype of ovarian cancer cells. The expression of EMILIN2 was epigenetically regulated by its promoter methylation. Also, it was found that p53 regulated the expression of EMILIN2, and the p53/EMILIN2 axis regulated the Warburg effect in ovarian cancer cells. EMILIN2 was inhibited by methylation in ovarian cancer. In summary, p53 can promote and regulate its transcription by binding to the promoter region of EMILIN2, thereby affecting the Warburg effect and inhibiting tumors. Therefore, EMILIN2 might be a potential target for clinical diagnosis and treatment of ovarian cancer.

The long noncoding RNA glycoLINC assembles a lower glycolytic metabolon to promote glycolysis

Non-covalent complexes of glycolytic enzymes, called metabolons, were postulated in the 1970s, but the concept has been controversial. Here we show that a c-Myc-responsive long noncoding RNA (lncRNA) that we call glycoLINC (gLINC) acts as a backbone for metabolon formation between all four glycolytic payoff phase enzymes (PGK1, PGAM1, ENO1, and PKM2) along with lactate dehydrogenase A (LDHA). The gLINC metabolon enhances glycolytic flux, increases ATP production, and enables cell survival under serine deprivation. Furthermore, gLINC overexpression in cancer cells promotes xenograft growth in mice fed a diet deprived of serine, suggesting that cancer cells employ gLINC during metabolic reprogramming. We propose that gLINC makes a functional contribution to cancer cell adaptation and provide the first example of a lncRNA-facilitated metabolon.

Tumor-Derived Exosomal Non-Coding RNAs: The Emerging Mechanisms and Potential Clinical Applications in Breast Cancer

Breast cancer (BC) is the most frequent malignancy and is ranking the leading cause of cancer-related death among women worldwide. At present, BC is still an intricate challenge confronted with high invasion, metastasis, drug resistance, and recurrence rate. Exosomes are membrane-enclosed extracellular vesicles with the lipid bilayer and recently have been confirmed as significant mediators of tumor cells to communicate with surrounding cells in the tumor microenvironment. As very important orchestrators, non-coding RNAs (ncRNAs) are aberrantly expressed and participate in regulating gene expression in multiple human cancers, while the most reported ncRNAs within exosomes in BC are microRNAs (miRNAs), long-noncoding RNAs (lncRNAs), and circular RNAs (circRNAs). Notably, ncRNAs containing exosomes are novel frontiers to shape malignant behaviors in recipient BC cells such as angiogenesis, immunoregulation, proliferation, and migration. It means that tumor-derived ncRNAs-containing exosomes are pluripotent carriers with intriguing and elaborate roles in BC progression via complex mechanisms. The ncRNAs in exosomes are usually excavated based on specific de-regulated expression verified by RNA sequencing, bioinformatic analyses, and PCR experiments. Here, this article will elucidate the recent existing research on the functions and mechanisms of tumor-derived exosomal miRNA, lncRNA, circRNA in BC, especially in BC cell proliferation, metastasis, immunoregulation, and drug resistance. Moreover, these tumor-derived exosomal ncRNAs that existed in blood samples are proved to be excellent diagnostic biomarkers for improving diagnosis and prognosis. The in-depth understanding of tumor-derived exosomal ncRNAs in BC will provide further insights for elucidating the BC oncogenesis and progress and exploring novel therapeutic strategies for combating BC.

SUMOylation of IGF2BP2 promotes vasculogenic mimicry of glioma via regulating OIP5-AS1/miR-495-3p axis

Rationale: Glioma is the most common primary malignant tumor of human central nervous system, and its rich vascular characteristics make anti-angiogenic therapy become a therapeutic hotspot. However, the existence of glioma VM makes the anti-angiogenic therapy ineffective. SUMOylation is a post-translational modification that affects cell tumorigenicity by regulating the expression and activity of substrate proteins.

Methods: The binding and modification of IGF2BP2 and SUMO1 were identified using Ni²⁺-NTA agarose bead pull-down assays, CO-IP and western blot; and in vitro SUMOylation assays combined with immunoprecipitation and immunofluorescence staining were performed to explore the detail affects and regulations of the SUMOylation on IGF2BP2. RT-PCR and western blot were used to detect the expression levels of IGF2BP2, OIP5-AS1, and miR-495-3p in glioma tissues and cell lines. CCK-8 assays, cell transwell assays, and three-dimensional cell culture methods were used for evaluating the function of IGF2BP2, OIP5-AS1, miR-495-3p, HIF1A and MMP14 in biological behaviors of glioma cells. Meantime, RIP and luciferase reporter assays were used for inquiring into the interactions among IGF2BP2, OIP5-AS1, miR-495-3p, HIF1A and MMP14. Eventually, the tumor xenografts in nude mice further as certained the effects of IGF2BP2 SUMOylation on glioma cells.

Results: This study proved that IGF2BP2 mainly binds to SUMO1 and was SUMOylated at the lysine residues K497, K505 and K509 sites, which can be reduced by SENP1. SUMOylation increased IGF2BP2 protein expression and blocked its degradation through ubiquitin-proteasome pathway, thereby increasing its stability. The expressions of IGF2BP2 and OIP5-AS1 were up-regulated and the expression of miR-495-3p was down-regulated in both glioma tissues and cells. IGF2BP2 enhances the stability of OIP5-AS1, thereby increasing the binding of OIP5-AS1 to miR-495-3p, weakening the binding of miR-495-3p to the 3'UTR of HIF1A and MMP14 mRNA, and ultimately promoting the formation of VM in glioma.

Conclusions: This study first revealed that SUMOylation of IGF2BP2 regulated OIP5-AS1/miR-495-3p axis to promote VM formation in glioma cells and xenografts growth in nude mice, providing a new idea for molecular targeted therapy of glioma.

The pan-cancer lncRNA PLANE regulates an alternative splicing program to promote cancer pathogenesis

Genomic amplification of the distal portion of chromosome 3q, which encodes a number of oncogenic proteins, is one of the most frequent chromosomal abnormalities in malignancy. Here we functionally characterise a non-protein product of the 3q region, the long noncoding RNA (lncRNA) PLANE, which is upregulated in diverse cancer types through copy number gain as well as E2F1-mediated transcriptional activation. PLANE forms an RNA-RNA duplex with the nuclear receptor co-repressor 2 (NCOR2) pre-mRNA at intron 45, binds to heterogeneous ribonucleoprotein M (hnRNPM) and facilitates the association of hnRNPM with the intron, thus leading to repression of the alternative splicing (AS) event generating NCOR2-202, a major protein-coding NCOR2 AS variant. This is, at least in part, responsible for PLANE-mediated promotion of cancer cell proliferation and tumorigenicity. These results uncover the function and regulation of PLANE and suggest that PLANE may constitute a therapeutic target in the pan-cancer context.

lncRNA TRMP-S directs dual mechanisms to regulate p27-mediated cellular senescence

Long noncoding RNAs (lncRNAs) undergo extensive alternative splicing, but little is known about isoform functions. A prior investigation of lncRNA RP11-369C8.1 reported that its splice variant TRMP suppressed p27 translation through PTBP1. Here we characterize a second major splice variant, TRMP-S (short variant), whose enforced loss promotes cancer cell-cycle arrest and p27-dependent entry into cellular senescence. Remarkably, despite sharing a single common exon with TRMP, TRMP-S restrains p27 expression through distinct mechanisms. First, TRMP-S stabilizes UHRF1 protein levels, an epigenetic inhibitor of p27, by promoting interactions between UHRF1 and its deubiquitinating enzyme USP7. Alternatively, binding interactions between TRMP-S and FUBP3 prevent p53 mRNA interactions with RPL26 ribosomal protein, the latter essential for promoting p53 translation with ensuing suppression of p53 translation limiting p27 expression. Significantly, as TRMP-S is itself transactivated by p53, this identifies negative feedback regulation between p53 and TRMP-S. Different splicing variants of the RP11-369C8.1 gene thereby exert distinct roles that converge on the homeostatic control of p27 expression, providing an important precedent for understanding the actions of alternatively spliced lncRNAs.