Long non-coding RNA RP11-284P20.2 promotes cell proliferation and invasion in hepatocellular carcinoma by recruiting EIF3b to induce c-met protein synthesis

Role of lncRNAs in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is among the deadliest cancer in human malignancies. It is the most common and severe type of primary liver cancer. However, the molecular mechanisms underlying HCC pathogenesis remain poorly understood. Long non-coding RNAs (lncRNAs), a new kind of RNA and epigenetic factors, play a crucial role in tumorigenesis and the progression of HCC. LncRNAs are capable of promoting the autophagy, proliferation, and migration of tumor cells by targeting and modulating the expression of downstream genes in signaling pathways related to cancer; these transcripts modify the activity and expression of various tumor suppressors and oncogenes. LncRNAs could act as biomarkers for treatment approaches such as immunotherapy, chemotherapy, and surgery to effectively treat HCC patients. Improved knowledge regarding the aetiology of HCC may result from an advanced understanding of lncRNAs. Enhanced oxidative stress in the mitochondrial and Endoplasmic reticulum leads to the activation of unfolded protein response pathway that plays a crucial role in the pathophysiology of hepatocellular carcinoma. The mutual regulation between LncRNAs and Endoplasmic reticulum (ER) stress in cancer and simultaneous activation of the unfolded protein response (UPR) pathway determines the fate of tumor cells in HCC. Mitochondria-associated lncRNAs work as essential components of several gene regulatory networks; abnormal regulation of mitochondria-associated lncRNAs may lead to oncogenesis, which provides further insight into the understanding of tumorigenesis and therapeutic strategies.

mRNAsi-related genes can effectively distinguish hepatocellular carcinoma into new molecular subtypes

Background

Recent studies have shown that the mRNA expression-based stemness index (mRNAsi) can accurately quantify the similarity of cancer cells to stem cells, and mRNAsi-related genes are used as biomarkers for cancer. However, mRNAsi-driven tumor heterogeneity is rarely investigated, especially whether mRNAsi can distinguish hepatocellular carcinoma (HCC) into different molecular subtypes is still largely unknown.

Methods

Using OCLR machine learning algorithm, weighted gene co-expression network analysis, consistent unsupervised clustering, survival analysis and multivariate cox regression etc. to identify biomarkers and molecular subtypes related to tumor stemness in HCC.

Results

We firstly demonstrate that the high mRNAsi is significantly associated with the poor survival and high disease grades in HCC. Secondly, we identify 212 mRNAsi-related genes that can divide HCC into three molecular subtypes: low cancer stemness cell phenotype (CSCP-L), moderate cancer stemness cell phenotype (CSCP-M) and high cancer stemness cell phenotype (CSCP-H), especially over-activated ribosomes, spliceosomes and nucleotide metabolism lead to the worst prognosis for the CSCP-H subtype patients, while activated amino acids, fatty acids and complement systems result in the best prognosis for the CSCP-L subtype. Thirdly, we find that three CSCP subtypes have different mutation characteristics, immune microenvironment and immune checkpoint expression, which may cause the differential prognosis for three subtypes. Finally, we identify 10 robust mRNAsi-related biomarkers that can effectively predict the survival of HCC patients.

Conclusions

These novel cancer stemness-related CSCP subtypes and biomarkers in this study will be of great clinical significance for the diagnosis, prognosis and targeted therapy of HCC patients.

Keep your eyes peeled for long noncoding RNAs: Explaining their boundless role in cancer metastasis, drug resistance, and clinical application

Cancer metastasis and drug resistance are two major obstacles in the treatment of cancer and therefore, the leading cause of cancer-associated mortalities worldwide. Hence, an in-depth understanding of these processes and identification of the underlying key players could help design a better therapeutic regimen to treat cancer. Earlier thought to be merely transcriptional junk and having passive or secondary function, recent advances in the genomic research have unravelled that long noncoding RNAs (lncRNAs) play pivotal roles in diverse physiological as well as pathological processes including cancer metastasis and drug resistance. LncRNAs can regulate various steps of the complex metastatic cascade such as epithelial-mesenchymal transition (EMT), invasion, migration and metastatic colonization, and also affect the sensitivity of cancer cells to various chemotherapeutic drugs. A substantial body of literature for more than a decade of research evince that lncRNAs can regulate gene expression at different levels such as epigenetic, transcriptional, posttranscriptional, translational and posttranslational levels, depending on their subcellular localization and through their ability to interact with DNA, RNA and proteins. In this review, we mainly focus on how lncRNAs affect cancer metastasis by modulating expression of key metastasis-associated genes at various levels of gene regulation. We also discuss how lncRNAs confer cancer cells either sensitivity or resistance to various chemo-therapeutic drugs via different mechanisms. Finally, we highlight the immense potential of lncRNAs as prognostic and diagnostic biomarkers as well as therapeutic targets in cancer.

LncRNA AIRN influences the proliferation and apoptosis of hepatocellular carcinoma cells by regulating STAT1 ubiquitination

Long non-coding RNAs (LncRNAs) have been implicated in the pathogenesis of various human diseases. In this study, we probed into the role and potential mechanisms of the antisense of IGF2R non-protein coding RNA (LncRNA AIRN) in the progression of hepatocellular carcinoma (HCC). Using a quantitative real-time polymerase chain reaction, we corroborated that LncRNA AIRN expression was raised in the HCC tissues and cells. The bioinformatic analysis revealed that a potential interaction between LncRNA AIRN and STAT1, which was verified by the RNA pull-down and RNA immunoprecipitation. In the cycloheximide-chase assay, the knockdown of LncRNA AIRN enhanced the stability of STAT1 protein. In the immunoprecipitation assay, the knockdown of LncRNA AIRN restrained the cullin 4A (CUL4A)-mediated ubiquitination of STAT1 protein. The cell transfection, MTT and flow cytometry assays expounded that the LncRNA AIRN/STAT1 axis was bound up with the regulation of the proliferation and apoptosis of HCC cells. The in vivo experiments corroborated that the knockdown of LncRNA AIRN restrained the tumor growth of HCC. Our data expounded that the knockdown of LncRNA AIRN restrained HCC cell proliferation and boosted cell apoptosis by restraining the CUL4A-mediated ubiquitination of STAT1 protein.

The Role of LncRNAs in Translation

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

RNA-Binding Proteins as Important Regulators of Long Non-Coding RNAs in Cancer

The majority of the genome is transcribed into pieces of non-(protein) coding RNA, among which long non-coding RNAs (lncRNAs) constitute a large group of particularly versatile molecules that govern basic cellular processes including transcription, splicing, RNA stability, and translation. The frequent deregulation of numerous lncRNAs in cancer is known to contribute to virtually all hallmarks of cancer. An important regulatory mechanism of lncRNAs is the post-transcriptional regulation mediated by RNA-binding proteins (RBPs). So far, however, only a small number of known cancer-associated lncRNAs have been found to be regulated by the interaction with RBPs like human antigen R (HuR), ARE/poly(U)-binding/degradation factor 1 (AUF1), insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), and tristetraprolin (TTP). These RBPs regulate, by various means, two aspects in particular, namely the stability and the localization of lncRNAs. Importantly, these RBPs themselves are commonly deregulated in cancer and might thus play a major role in the deregulation of cancer-related lncRNAs. There are, however, still many open questions, for example regarding the context specificity of these regulatory mechanisms that, in part, is based on the synergistic or competitive interaction between different RBPs. There is also a lack of knowledge on how RBPs facilitate the transport of lncRNAs between different cellular compartments.