LncRNA LOC730101 promotes osteosarcoma cell survival under energy stress

Transcriptional stress induces the overexpression of novel lncRNAs that regulate the BRCA1 locus

Long non-coding RNAs (lncRNAs) have been shown to play a role during transcriptional regulation in response to stress. However, their function under stress caused by transcriptional inhibition has not yet been addressed. Using genome-wide assays to elucidate the transcriptional response in human cells caused by RNA polymerase II transcription inhibition, we found three novel regulatory lncRNAs, TILR-1 , TILR-2 , and LINC00910 , that are upregulated as a response to this transcriptional stress. Knockdown experiments showed that the expression of these RNAs is interdependent, and together, they regulate transcription of the nearby BRCA1 locus. The lack of these novel regulatory transcripts also resulted in an increase in cellular proliferation and survival. Public transcriptomic data from different cell lines treated with a variety of transcriptional inhibitors or with heat shock and arsenic stress showed that TILR-1 , TILR-2 , and LINC00910 are commonly upregulated in a broad array of stress conditions. Evolutionary analysis showed that TILR-1 , TILR-2 , and LINC00910 are highly conserved among primates, and their emergence correlates with the duplication of the bidirectional promoter of BRCA1 and NBR1 . We conclude that that coordinate transcription of TILR-1 , TILR-2 , and LINC00910 is stimulated generally by stress and the resulting lncRNAs are novel, functionally-conserved regulators of the BRCA1 locus.

LncRNA LOC730101 Promotes Darolutamide Resistance in Prostate Cancer by Suppressing miR-1-3p

Antiandrogen is part of the standard-of-care treatment option for metastatic prostate cancer. However, prostate cancers frequently relapse, and the underlying resistance mechanism remains incompletely understood. This study seeks to investigate whether long non-coding RNAs (lncRNAs) contribute to the resistance against the latest antiandrogen drug, darolutamide. Our RNA sequencing analysis revealed significant overexpression of LOC730101 in darolutamide-resistant cancer cells compared to the parental cells. Elevated LOC730101 levels were also observed in clinical samples of metastatic castration-resistant prostate cancer (CRPC) compared to primary prostate cancer samples. Silencing LOC730101 with siRNA significantly impaired the growth of darolutamide-resistant cells. Additional RNA sequencing analysis identified a set of genes regulated by LOC730101, including key players in the cell cycle regulatory pathway. We further demonstrated that LOC730101 promotes darolutamide resistance by competitively inhibiting microRNA miR-1-3p. Moreover, by Hi-C sequencing, we found that LOC730101 is located in a topologically associating domain (TAD) that undergoes specific gene induction in darolutamide-resistant cells. Collectively, our study demonstrates the crucial role of the lncRNA LOC730101 in darolutamide resistance and its potential as a target for overcoming antiandrogen resistance in CRPC.

Non-coding RNAs in metabolic reprogramming of bone and soft tissue sarcoma: Fundamental mechanism and clinical implication

Sarcomas, comprising approximately 1% of human malignancies, show a poor response to treatment and easy recurrence. Metabolic reprogramming play an important role in tumor development in sarcomas. Accumulating evidence shows that non-coding RNAs (ncRNAs) participate in regulating the cellular metabolism of sarcomas, which improves the understanding of the development of therapy-resistant tumors. This review addresses the regulatory roles of metabolism-related ncRNAs and their implications for sarcoma initiation and progression. Dysregulation of metabolism-related ncRNAs is common in sarcomas and is associated with poor survival. Emerging studies show that abnormal expression of metabolism-related ncRNAs affects cellular metabolism, including glucose, lipid, and mitochondrial metabolism, and leads to the development of aggressive sarcomas. This review summarizes recent advances in the roles of dysregulated metabolism-related ncRNAs in sarcoma development and stemness and describes their potential to serve as biological biomarkers for disease diagnosis and prognosis prediction, as well as therapeutic targets for treating refractory sarcomas.

AMPK: An odyssey of a metabolic regulator, a tumor suppressor, and now a contextual oncogene

Metabolic reprogramming is a unique but complex biochemical adaptation that allows solid tumors to tolerate various stresses that challenge cancer cells for survival. Under conditions of metabolic stress, mammalian cells employ adenosine monophosphate (AMP)-activated protein kinase (AMPK) to regulate energy homeostasis by controlling cellular metabolism. AMPK has been described as a cellular energy sensor that communicates with various metabolic pathways and networks to maintain energy balance. Earlier studies characterized AMPK as a tumor suppressor in the context of cancer. Later, a paradigm shift occurred in support of the oncogenic nature of AMPK, considering it a contextual oncogene. In support of this, various cellular and mouse models of tumorigenesis and clinicopathological studies demonstrated increased AMPK activity in various cancers. This review will describe AMPK's pro-tumorigenic activity in various malignancies and explain the rationale and context for using AMPK inhibitors in combination with anti-metabolite drugs to treat AMPK-driven cancers.

Noncoding RNAs as sensors of tumor microenvironmental stress

The tumor microenvironment (TME) has been demonstrated to modulate the biological behavior of tumors intensively. Multiple stress conditions are widely observed in the TME of many cancer types, such as hypoxia, inflammation, and nutrient deprivation. Recently, accumulating evidence demonstrates that the expression levels of noncoding RNAs (ncRNAs) are dramatically altered by TME stress, and the dysregulated ncRNAs can in turn regulate tumor cell proliferation, metastasis, and drug resistance. In this review, we elaborate on the signal transduction pathways or epigenetic pathways by which hypoxia-inducible factors (HIFs), inflammatory factors, and nutrient deprivation in TME regulate ncRNAs, and highlight the pivotal roles of TME stress-related ncRNAs in tumors. This helps to clarify the molecular regulatory networks between TME and ncRNAs, which may provide potential targets for cancer therapy.

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.

Metabolism-induced tumor activator 1 (MITA1), an Energy Stress-Inducible Long Noncoding RNA, Promotes Hepatocellular Carcinoma Metastasis

Metastasis is the main cause of cancer-related death, yet the underlying mechanisms are still poorly understood. Long noncoding RNAs (lncRNAs) are emerging as crucial regulators of malignancies; however, their functions in tumor metastasis remain largely unexplored. In this study, we identify a lncRNA, termed metabolism-induced tumor activator 1 (MITA1), which is up-regulated in hepatocellular carcinoma (HCC) and contributes to metastasis. MITA1, a chromatin-enriched lncRNA discovered by our nuclear RNA sequencing, is significantly induced by energy stress. This induction of MITA1 is governed by the liver kinase B1-adenosine monophosphate-activated protein kinase (LKB1-AMPK) pathway and DNA methylation. Knockdown of MITA1 dramatically inhibits the migration and invasion of liver cancer cells in vitro and HCC metastasis in vivo. Mechanistically, MITA1 promotes the epithelial-mesenchymal transition, an early and central step of metastasis, which may partly attribute to an increase in Slug (snail family zinc finger 2) transcription. MITA1 deficiency reduces the expression of the mesenchymal cell markers, especially Slug, whereas Slug overexpression greatly impairs the effects of MITA1 deficiency on HCC migration and invasion. Correspondingly, there is a positive correlation between the levels of MITA1 and Slug precursors in HCC tissues. Conclusion: Our data reveal MITA1 as a crucial driver of HCC metastasis, and highlight the identified AMPK-MITA1-Slug axis as a potential therapeutic strategy for HCC.

Nobiletin induces growth inhibition and apoptosis in human nasopharyngeal carcinoma C666-1 cells through regulating PARP-2/SIRT1/AMPK signaling pathway

BACKGROUND/AIM

Nobiletin, a major polymethoxyflavones (PMFs) from citri reticulatae pericarpium (CRP), can inhibit several forms of cancer proliferation. However, the effects of nobiletin on nasopharyngeal carcinoma (NPC) C666-1 cells remain largely unknown.

MATERIALS AND METHODS

Cell counting kit 8 (CCK8) assay was used to measure cell vitality. Flow cytometry was performed to measure the apoptosis rate. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot analysis were applied to determine the expression of mRNA and protein, respectively.

RESULTS

We showed that the proliferation rate of C666-1 cells was inhibited and the apoptosis rate was raised after treating with nobiletin. Moreover, nobiletin inhibited the expression of poly(ADP-ribose)polymerase-2 (PARP-2), and the tumor suppression effect of nobiletin on C666-1 is associated with PARP-2-dependent pathway.

CONCLUSION

We demonstrated for the first time that nobiletin inhibited the growth of C666-1 cells, which may be relative to its regulation on PARP-2/SIRT1/AMPK signaling pathway. Our result implied that nobiletin may serve as a strategy to treat nasopharyngeal carcinoma.

Transcriptional Profiling of Hypoxia-Regulated Non-coding RNAs in Human Primary Endothelial Cells

Hypoxia occurs in human atherosclerotic lesions and has multiple adverse effects on endothelial cell metabolism. Recently, key roles of long non-coding RNAs (lncRNAs) in the development of atherosclerosis have begun to emerge. In this study, we investigate the lncRNA profiles of human umbilical vein endothelial cells subjected to hypoxia using global run-on sequencing (GRO-Seq). We demonstrate that hypoxia regulates the nascent transcription of ~1800 lncRNAs. Interestingly, we uncover evidence that promoter-associated lncRNAs are more likely to be induced by hypoxia compared to enhancer-associated lncRNAs, which exhibit an equal distribution of up- and downregulated transcripts. We also demonstrate that hypoxia leads to a significant induction in the activity of super-enhancers next to transcription factors and other genes implicated in angiogenesis, cell survival and adhesion, whereas super-enhancers near several negative regulators of angiogenesis were repressed. Despite the majority of lncRNAs exhibiting low detection in RNA-Seq, a subset of lncRNAs were expressed at comparable levels to mRNAs. Among these, MALAT1, HYMAI, LOC730101, KIAA1656, and LOC339803 were found differentially expressed in human atherosclerotic lesions, compared to normal vascular tissue, and may thus serve as potential biomarkers for lesion hypoxia.