TGFB2-AS1 inhibits triple-negative breast cancer progression via interaction with SMARCA4 and regulating its targets TGFB2 and SOX2.

Triple-negative breast cancer (TNBC) is the most challenging breast cancer subtype for its high rates of relapse, great metastatic potential, and short overall survival. How cancer cells acquire metastatic potency through the conversion of noncancer stem-like cells into cancer cells with stem-cell properties is poorly understood. Here, we identified the long noncoding RNA (lncRNA) TGFB2-AS1 as an important regulator of the reversibility and plasticity of noncancer stem cell populations in TNBC. We revealed that TGFB2-AS1 impairs the breast cancer stem-like cell (BCSC) traits of TNBC cells in vitro and dramatically decreases tumorigenic frequency and lung metastasis in vivo. Mechanistically, TGFB2-AS1 interacts with SMARCA4, a core subunit of the SWI/SNF chromatin remodeling complex, and results in transcriptional repression of its target genes including TGFB2 and SOX2 in an in cis or in trans way, leading to inhibition of transforming growth factor ß (TGFß) signaling and BCSC characteristics. In line with this, TGFB2-AS1 overexpression in an orthotopic TNBC mouse model remarkably abrogates the enhancement of tumor growth and lung metastasis endowed by TGFß2. Furthermore, combined prognosis analysis of TGFB2-AS1 and TGFß2 in TNBC patients shows that high TGFB2-AS1 and low TGFß2 levels are correlated with better outcome. These findings demonstrate a key role of TGFB2-AS1 in inhibiting disease progression of TNBC based on switching the cancer cell fate of TNBC and also shed light on the treatment of TNBC patients.

Long non-coding RNA ARHGAP5-AS1 inhibits migration of breast cancer cell via stabilizing SMAD7 protein.

PURPOSE: Tumor metastasis is the main cause of death from breast cancer patients and cell migration plays a critical role in cancer metastasis. Recent studies have shown long non-coding RNAs (lncRNAs) play an essential role in the initiation and progression of cancer. In the present study, the role of an LncRNA, Rho GTPase Activating Protein 5- Antisense 1 (ARHGAP5-AS1) in breast cancer was investigated. METHODS: RNA sequencing was performed to find out dysregulated LncRNAs in MDA-MB-231-LM2 cells. Transwell migration assays and F-actin staining were utilized to estimate cell migration ability. RNA pulldown assays and RNA immunoprecipitation were used to prove the interaction between ARHGAP5-AS1 and SMAD7. Western blot and immunofluorescence imaging were used to examine the protein levels. Dual luciferase reporter assays were performed to evaluate the activation of TGF-ß signaling. RESULTS: We analyzed the RNA-seq data of MDA-MB-231 and its highly metastatic derivative MDA-MB-231-LM2 cell lines (referred to as LM2) and identified a novel lncRNA (NR_027263) named as ARHGAP5-AS1, which expression was significantly downregulated in LM2 cells. Further functional investigation showed ARHGAP5-AS1 could inhibit cell migration via suppression of stress fibers in breast cancer cell lines. Afterwards, SMAD7 was further identified to interact with ARHGAP5-AS1 by its PY motif and thus its ubiquitination and degradation was blocked due to reduced interaction with E3 ligase SMURF1 and SMURF2. Moreover, ARHGAP5-AS1 could inhibit TGF-ß signaling pathway due to its inhibitory role on SMAD7. CONCLUSION: ARHGAP5-AS1 inhibits breast cancer cell migration via stabilization of SMAD7 protein and could serve as a novel biomarker and a potential target for breast cancer in the future.

Hypoxia activated long non-coding RNA HABON regulates the growth and proliferation of hepatocarcinoma cells by binding to and antagonizing HIF-1 alpha.

The adaptation of tumour cells to hypoxic microenvironment is one of the most significant characteristics of many malignant tumour diseases including hepatocarcinoma. Recently, long non-coding RNAs (lncRNAs) have been reported to play important roles in the various levels of gene regulation thus functioning in growth and survival of tumour cells. Here, new hypoxia-related lncRNAs in hepatocarcinoma cells were screened and validated by lncRNA chip-array as well as real-time RT-PCR. Among them, a hypoxia-activated lncRNA that we identified and termed Hypoxia-Activated BNIP3 Overlapping Non-coding RNA (HABON), was not only regulated by hypoxic-induced factor-1α (HIF-1α) but its expression increased significantly under hypoxia in tumour cells. We deciphered the biological characteristics of HABON including its cell localization, genomic location, as well as its full-length sequence, and proved HABON could promote growth, proliferation and clone-formation of hepatocarcinoma cells under hypoxia. Then, we revealed that HABON was transcriptionally activated by HIF-1α in hypoxic cells, furthermore, it could interact with HIF-1α and promote its protein degradation, thus affecting transcription of HIF-1α's target genes to exert its effects on cells. Besides, the elevated expression of HABON under hypoxia could promote the transcriptional activation of BNIP3 through HIF-1α, and increasing the expression level of BNIP3. This research provides a novel clue for the adaptive survival and growth mechanism of tumour under hypoxia, and gives a way to reveal the nature of tumour cells' resistance characteristics to harsh microenvironment.

Long non-coding RNA DNM3OS promotes tumor progression and EMT in gastric cancer by associating with Snail.

Long non-coding RNAs (lncRNAs) act as tumor suppressors or oncogenes in tumor development and progression. In the present study, we explored the expression and biological role of the lncRNA DNM3OS in gastric cancer (GC). We observed that DNM3OS was upregulated in GC tissues and cell lines, and high DNM3OS expression was correlated with malignant features and served as an indicator of a poor prognosis for GC patients. DNM3OS knockdown inhibited the proliferation of GC cells, and reduced DNM3OS suppressed tumor growth in vivo. Moreover, DNM3OS depletion inhibited the migration and invasion of GC cells through the suppression of the Snail-mediated epithelial-mesenchymal transition (EMT). In conclusion, we demonstrated that DNM3OS serves as an oncogenic lncRNA in GC, and we implicated DNM3OS as a promising prognostic factor and a potential therapeutic target for GC patients.

miR-128 and its target genes in tumorigenesis and metastasis.

MicroRNAs (miRNAs) are a class of endogenous, non-coding, 18-24 nucleotide length single-strand RNAs that could modulate gene expression at post-transcriptional level. Previous studies have shown that miR-128 enriched in the brain plays an important role in the development of nervous system and the maintenance of normal physical functions. Aberrant expression of miR-128 has been detected in many types of human tumors and its validated target genes are involved in cancer-related biological processes such as cell proliferation, differentiation and apoptosis. In this review, we will summarize the roles of miR-128 and its target genes in tumorigenesis and metastasis.

SIRT2 regulates extracellular vesicle-mediated liver-bone communication.

The interplay between liver and bone metabolism remains largely uncharacterized. Here, we uncover a mechanism of liver-bone crosstalk regulated by hepatocyte SIRT2. We demonstrate that hepatocyte SIRT2 expression is increased in aged mice and elderly humans. Liver-specific SIRT2 deficiency inhibits osteoclastogenesis and alleviates bone loss in mouse models of osteoporosis. We identify leucine-rich α-2-glycoprotein 1 (LRG1) as a functional cargo in hepatocyte-derived small extracellular vesicles (sEVs). In SIRT2-deficient hepatocytes, LRG1 levels in sEVs are upregulated, leading to increased transfer of LRG1 to bone-marrow-derived monocytes (BMDMs), and in turn, to inhibition of osteoclast differentiation via reduced nuclear translocation of NF-κB p65. Treatment with sEVs carrying high levels of LRG1 inhibits osteoclast differentiation in human BMDMs and in mice with osteoporosis, resulting in attenuated bone loss in mice. Furthermore, the plasma level of sEVs carrying LRG1 is positively correlated with bone mineral density in humans. Thus, drugs targeting hepatocyte-osteoclast communication may constitute a promising therapeutic strategy for primary osteoporosis.

LncRNA HABON promoted liver cancer cells survival under hypoxia by inhibiting mPTP opening.

Hypoxia is an important feature of the tumor microenvironment (TME). While targeting hypoxic TME is emerging as a potential strategy for treating solid tumors including liver cancer. Recent studies have shown that hypoxia can regulate tumor adaptation to hypoxic TME through long non-coding RNA (lncRNA). In the previous study, we identify a novel hypoxia-activated lncRNA and termed it as HABON. Here, we demonstrated that knockdown of HABON caused necroptosis of tumor tissue and inhibited the subcutaneous tumor growth of SMMC-7721 cells in nude mice. Moreover, knockdown of HABON increased RIPK1 and MLKL expression as well as their phosphorylation level in SMMC-7721 and Huh7 liver cancer cells. Meanwhile, Necrostatin-1 and GSK872 could restore cell death of liver cancer cells caused by knockdown of HABON under hypoxia. The above results suggested that HABON could inhibit hypoxia-induced necroptosis of liver cancer cells. Mechanically, knockdown of HABON in liver cancer cells aggravated mitochondrial dysfunction caused by hypoxia. Furthermore, the RNA pull-down combined with mass spectrometry analysis identified HABON can interact with mitochondria-related protein VDAC1 and the RNA immunoprecipitation (RIP) analysis proved the interaction. In addition, we proved that VDAC1 mediated the mitochondrial permeability transition pore (mPTP) opening, mitochondrial dysfunction, as well as necroptosis caused by knockdown of HABON. Overall, our work demonstrates HABON can reduce hypoxia-induced necroptosis of liver cancer cells and suggests that inhibition of HABON in the hypoxic TME is a potential therapeutic strategy for treating liver cancer.

Delivery of LINC00589 via mesoporous silica nanoparticles inhibits peritoneal metastasis in gastric cancer.

Peritoneal metastasis is one of the common forms of metastasis in gastric cancer (GC). In this study, we identified the expression pattern of LINC00589 in GC patients and investigate the biological function in GC cells. RNA-pulldown assay was performed to explore the underlying molecular mechanism. Further, we utilize polyethyleneimine-modified mesoporous silica nanoparticles (PMSNs) as the nanocarriers for delivery of LINC00589 encoding plasmid and tested its therapeutic potential for GC with peritoneal dissemination. We revealed that LINC00589 was downregulated in GC tissues and suppressed the metastatic ability of GC cells. Mechanistically, LINC00589 exerted tumor suppressive function by promoting hnRNPA1 protein ubiquitination and proteasomal degradation, thus blocking alternative splicing of PKM to PKM2. Furthermore, LINC00589 delivered by PMSNs could suppress the peritoneal metastasis of GC in vivo and in vitro. This work may provide a new treatment option in GC peritoneal metastasis.

SIRT2-mediated deacetylation and deubiquitination of C/EBPß prevents ethanol-induced liver injury.

Protein acetylation has emerged to play pivotal roles in alcoholic liver disease (ALD). Sirutin 2 (SIRT2) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase involved in the regulation of aging, metabolism, and stress. However, the role of SIRT2 in ALD remains unclear. Here, we report that the SIRT2-mediated deacetylation-deubiquitination switch of CCAAT/enhancer-binding protein beta (C/EBPß) prevents ALD. Our results showed that hepatic SIRT2 protein expression was negatively correlated with the severity of alcoholic liver injury in ALD patients. Liver-specific SIRT2 deficiency sensitized mice to ALD, whereas transgenic SIRT2 overexpression in hepatocytes significantly prevented ethanol-induced liver injury via normalization of hepatic steatosis, lipid peroxidation, and hepatocyte apoptosis. Mechanistically, we identified C/EBPß as a critical substrate of SIRT2 implicated in ALD. SIRT2-mediated deacetylation at lysines 102 and 211 decreased C/EBPß ubiquitination, resulting in enhanced protein stability and subsequently increased transcription of C/EBPß-target gene LCN2. Importantly, hepatic deacetylated C/EBPß and LCN2 compensation reversed SIRT2 deletion-induced ALD aggravation in mice. Furthermore, C/EBPß protein expression was positively correlated with SIRT2 and LCN2 expression in the livers of ALD patients and was inversely correlated with ALD development. Therefore, activating SIRT2-C/EBPß-LCN2 signaling pathway is a potential therapy for ALD.

Sirtuins in mitochondrial stress: Indispensable helpers behind the scenes.

Mitochondria play an essential part in guaranteeing normal cellular physiological functions through providing ATP and participating in diverse processes and signaling pathways. Recently, more and more studies have revealed the vital roles of mitochondria in coping with stressors in the aging process, metabolic disturbances and neurological disorders. Mitochondrial stress responses, including the mitochondrial unfolded protein response (UPRmt), antioxidant defense, mitochondrial fission, mitochondrial fusion and mitophagy, are induced to maintain cellular integrity in response to stress. The sirtuin family, a group of NAD+-dependent deacetylases, has been the focus of much attention in recent years for their multiple regulatory functions, especially in aging and metabolism. Recent reports validated the significant link between mitochondrial stress responses and the sirtuin family, which may help to elucidate the pathogenesis and therapies for diseases such as Alzheimer's disease or Parkinson's disease. This review will summarize recent related studies and illuminate the interplay between sirtuins and mitochondrial stress.