Overexpression Of Let-7 Research Articles

YTHDC1-mediated microRNA maturation is essential for hematopoietic stem cells maintenance

YTHDC1, a reader of N6-methyladenosine (m6A) modifications on RNA, is posited to exert significant influence over RNA metabolism. Despite its recognized importance, the precise function and underlying mechanisms of YTHDC1 in the preservation of normal hematopoietic stem cell (HSCs) homeostasis remain elusive. Here, we investigated the role of YTHDC1 in normal hematopoiesis and HSCs maintenance in vivo. Utilizing conditional Ythdc1 knockout mice and Ythdc1/Mettl3 double knockout mice, we demonstrated that YTHDC1 is required for HSCs maintenance and self-renewal by regulating microRNA maturation. YTHDC1 deficiency resulted in HSCs apoptosis. Furthermore, we uncovered that YTHDC1 interacts with HP1BP3, a nuclear RNA binding protein involved in microRNA maturation. Deletion of YTHDC1 brought about significant alterations in microRNA levels. However, over-expression of mir-125b, mir-99b, and let-7e partially rescued the functional defect of YTHDC1-null HSCs. Taken together, these findings indicated that the nuclear protein YTHDC1-HP1BP3-microRNA maturation axis is essential for the long-term maintenance of HSCs.

Let-7 reduces the proliferation and migration of oral cancer cells via PI3K/AKT signaling pathway.

The involvement of let-7 in the occurrence and progression of various cancers has been well-documented. However, the precise molecular mechanisms underlying its impact on oral cancer development remain unclear. In this study, we aimed to elucidate the role of let-7 in oral cancer progression and investigate its underlying molecular mechanisms. The expression of let-7 and high mobility group A2 (HMGA2) mRNA was assessed using the quantitative reverse transcription polymerase chain reaction. Western blot analysis was employed to detect the expression of key proteins in the PI3K/AKT signaling pathway as well as HMGA2 protein levels. The targeting relationship between let-7 and HMGA2 was predicted through bioinformatics methods and confirmed via luciferase reporter gene assay. The effects of let-7 and HMGA2 on the functionality of oral cancer cells were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation assay, Transwell assay, wound healing assay, and Annexin V/PI apoptosis assay. Additionally, the impact of let-7 on the growth of oral cancer cells in vivo was investigated by inducing subcutaneous tumor formation in nude mice. Let-7 effectively suppresses the proliferation, migration, and invasion of oral cancer cells by inhibiting the activation of the PI3K/AKT signaling pathway. HMGA2, a downstream target gene of let-7, exhibits high expression in oral cancer. However, overexpression of HMGA2 diminishes the inhibitory effects induced by let-7 overexpression on the proliferation, migration, and invasion of oral cancer cells. The occurrence and progression of oral cancer cells are inhibited by Let-7 through the downregulation of HMGA2, potentially mediated by the inhibition of PI3K/AKT signaling pathway activation.

Let-7 suppresses liver fibrosis by inhibiting hepatocyte apoptosis and TGF-β production

ObjectiveFAS-mediated apoptosis of hepatocytes and aberrant TGF-β signaling are major drivers of liver fibrosis. Decreased miRNA let-7 expression in the livers of patients and animals with fibrosis suggests a mechanistic link of let-7 to hepatic fibrogenesis. MethodsUsing transient transfection we tested the effects of let-7 overexpression and TET3 siRNA knockdown on FAS and TGF-β1 expression and FAS-mediated apoptosis in human and mouse primary hepatocytes. We assessed the therapeutic activity of let-7 miRNA delivered via adeno-associated viral vectors in mouse models of carbon tetrachloride (CCl4)-induced and bile duct ligation (BDL)-induced liver fibrosis. ResultsLet-7 decreased TGF-β1 production from hepatocytes through a negative feedback loop involving TET3. On the other hand, let-7 post-transcriptionally inhibits FAS expression, thereby suppressing hepatocyte apoptosis. Hepatic-specific delivery of let-7 miRNA mitigated liver fibrosis in both CCl4 and BDL mouse models. ConclusionsLet-7 is a crucial node in the signaling networks that govern liver fibrosis progression. Let-7 and/or its derivatives may be used as therapeutic agents for liver fibrosis.

Hypothalamic α7 nicotinic acetylcholine receptor (α7nAChR) is downregulated by TNFα-induced Let-7 overexpression driven by fatty acids.

The α7nAChR is crucial to the anti-inflammatory reflex, and to the expression of neuropeptides that control food intake, but its expression can be decreased by environmental factors. We aimed to investigate whether microRNA modulation could be an underlying mechanism in the α7nAchR downregulation in mouse hypothalamus following a short-term exposure to an obesogenic diet. Bioinformatic analysis revealed Let-7 microRNAs as candidates to regulate Chrna7, which was confirmed by the luciferase assay. Mice exposed to an obesogenic diet for 3 days had increased Let-7a and decreased α7nAChR levels, accompanied by hypothalamic fatty acids and TNFα content. Hypothalamic neuronal cells exposed to fatty acids presented higher Let-7a and TNFα levels and lower Chrna7 expression, but when the cells were pre-treated with TLR4 inhibitor, Let-7a, TNFα, and Chrna7 were rescued to normal levels. Thus, the fatty acids overload trigger TNFα-induced Let-7 overexpression in hypothalamic neuronal cells, which negatively regulates α7nAChR, an event that can be related to hyperphagia and obesity predisposition in mice.

The involvement of let-7 in hCG-induced progesterone synthesis via regulating p27Kip1 and p21Cip1 expression

Progesterone is essential in females to maintain a regular menstrual cycle and pregnancy. The luteinizing hormone (LH) surge induces the luteinization of granulosa cells and thecal cells to form the corpus luteum, which is responsible for progesterone synthesis. However, the specific mechanism of how hCG, the analog of LH, regulates progesterone synthesis has yet to be fully discovered. In this study, we found that progesterone level was increased in adult wild-type pregnant mice 2 and 7 days post-coitum, along with a decrease in let-7 expression compared with the estrus stage. Besides, the let-7 expression was negatively correlated with progesterone level in post-delivery day 23 wild-type female mice after being injected with PMSG and hCG. Then, using let-7 transgenic mice and a human granulosa cell line, we found that overexpression of let-7 antagonized progesterone level via targeting p27Kip1 and p21Cip1 and steroidogenic acute regulatory protein (StAR) expression, which is a rate-limiting enzyme in progesterone synthesis. Furthermore, hCG suppressed let-7 expression by stimulating the MAPK pathway. This study elucidated the role of microRNA let-7 in regulating hCG-induced progesterone production and provided new insights into its role in clinical application.

MicroRNA Let-7 Plays an Important Role in the Immunopathology of COVID-19: A Systematic Review

COVID-19 has presented itself as a challenging task to medical teams and researchers throughout the world, since the outbreak of SARS-CoV-2 started in the Chinese city of Wuhan. To this day, there are still new variants emerging, and the knowledge about the mechanisms used by the virus to infect cells and perpetuate itself are still not well understood. The scientific community is still trying to catch up with the velocity of new variants and, consequently, the new physiological pathways that appear along with it. It is known that the new coronavirus plays a role in changing many molecular pathways to take control of the infected cells. Many of these pathways are related to control genomic expression of certain genes by epigenetic ways, allowing the virus to modulate immune responses and cytokines production. The let-7 family of microRNAs, for instance, are known to promote increased viral fusion in the target cell through a mechanism involving the transmembrane serine protease 2 (TMPRSS2). It was also demonstrated they are able to increase the inflammatory activity through the NF-κB/IL-6/let-7/LIN-28 axis. In addition, let-7 overexpression led to a reduction in inflammatory cytokines and chemokines expression (IL-6, IL-8 and TNF-α). Interestingly, the cytokines modulated by the let-7 family are related to COVID-19-induced cytokine storm observed in patients undergoing clinical phase three. Thus, let-7 can be considered a novel and attractive biomarker for therapeutic purpose. Based on that, the present study aims to critically analyze the immunopathological mechanisms of the microRNA let-7 in the infection caused by SARS-CoV-2.

Role of let-7 family in the invasion and metastasis of osteosarcoma.

Role of let-7 family in the invasion and metastasis of osteosarcoma.

MicroRNA let-7 Suppresses Influenza A Virus Infection by Targeting RPS16 and Enhancing Type I Interferon Response.

Given the frequent emergence of drug-resistant influenza virus strains and new highly pathogenic influenza virus strains, there is an urgent need to identify new antiviral drugs and targets. We found that influenza A virus (IAV) infection caused a significant decrease of microRNA let-7 expression in host cells; that overexpression of let-7 increased interferon expression and effectively inhibit IAV infection; and that let-7 targets the 3’-untranslated region (UTR) of the ribosomal protein 16 (RPS16) gene, decreasing its expression. Knocking down the expression of RPS16 increased the expression of type I interferon and inhibited viral replication. The present study uncovered the regulatory effect of let-7b and let-7f on influenza A infection, which is a potential biomarker of IAV infection. In addition, let-7 may be a promising therapeutic agent against influenza A.

MEDB-63. Deciphering the role of LIN28B in Group 3 medulloblastoma

BACKGROUND: Children with Group 3 medulloblastoma (MB) have a very poor long-term outcome and many do not survive beyond 5 years. Several drivers for Group 3 MB have been identified but none have resulted in targeted therapy to date. LIN28B is a stem cell factor that is upregulated in Group 3 medulloblastoma and is associated with worse survival. Here we investigate the role of the LIN28B pathway in Group 3 MB development. Pharmacologic inhibition of the LIN28B pathway is feasible and may provide a unique opportunity to target this tumor. METHODS: Using LIN28B knockdown and overexpression in G3 MB cells we test LIN28B’s effect on proliferation, self-renewal and metastasis. Similarly, we used shRNAs targeting PBK and demonstrate a similar effect on G3 MB growth. We also investigate the role of let-7 as a target of LIN28B by introducing let-7 mimetics and overexpression vectors into MB cells. Finally, we use a LIN28 inhibitor 1632 and a PBK inhibitor HITOPK032 to treat G3 MB cell lines and then assess their impact on proliferation and apoptosis. RESULTS: We find that down-regulation of LIN28B or PBK using shRNA results in significant reduction in cell proliferation. In contrast overexpression of LIN28B increases Group 3 cell proliferation and tumor sphere formation. LIN28B knockdown also significantly (p< 0.01) increases survival in mice with orthotopic Group 3 tumors. The LIN28 inhibitor 1632 also leads to significant reduction in G3 MB growth through decreased cell cycle entry and increased apoptosis. In addition, HITOPK032 also demonstrates significant reduction in Group 3 MB cell proliferation at low (nanomolar to low micromolar) concentration. CONCLUSIONS: Our study establishes a critical role for the LIN28B-let-7-PBK pathway in Group3 MB and provides encouraging preliminary preclinical results for drugs that target this pathway.

MicroRNA let-7 is required for hormonal regulation of metamorphosis in the silkworm, Bombyx mori

The heterochronic microRNA let-7, which was first identified in Caenorhabditis elegans, controls the timing of developmental programs, and let-7 triggers the onset of the juvenile-adult transition in bilaterians. The expression of let-7 is strongly induced during the last larval stage of C. elegans and is highly expressed in the late last instar larvae/nymphs of the fly Drosophila melanogaster and the cockroach Blattella germanica. In the silkworm Bombyx mori, the expression of let-7 remarkably increases in the corpus cardiacum-corpus allatum complex (CC-CA) at the beginning of the last larval instar and is maintained at high levels during this instar. To determine the biological function of let-7 in B. mori, we generated a let-7 knockout line and a transgenic UAS-let-7 line. The let-7 knockout larvae were developmentally arrested in the prepupal stage and became pupal-adult intermediates after apolysis. When let-7 was ubiquitously overexpressed under the transcriptional control of an Actin3-GAL4 driver, developmental timing and growth of larvae were severely impaired in the penultimate (L4) instar, and these larvae underwent precocious metamorphosis from L4. Furthermore, our results showed that reception and signaling of ecdysteroids and juvenile hormones (JHs) normally occurred in the absence of let-7, whereas the biosynthesis of ecdysone and JHs were affected by disruption and overexpression of let-7. Together, the present study demonstrates that let-7 is required for the coordination of the biosynthesis of ecdysone and JH to ensure the developmental transition during the metamorphosis of B. mori.

Novel lncRNA lncRNA001074 participates in the low salinity-induced response in the sea cucumber Apostichopus japonicus by targeting the let-7/NKAα axis.

Salinity fluctuations have severe impacts on sea cucumbers and therefore important consequences in sea cucumber farming. The responses of sea cucumbers to salinity changes are reflected in the expression profiles of multiple genes and non-coding RNAs (ncRNAs). The microRNA (let-7) which is a developmental regulator, the ion transporter gene sodium potassium ATPase gene (NKAα), and the long ncRNA lncRNA001074 were previously shown to be involved in responses to salinity changes in various marine species. To better understand the relationship between ncRNAs and target genes, the let-7/NKAα/lncRNA001074 predicted interaction was investigated in this study using luciferase reporter assays and gene knockdowns in the sea cucumber Apostichopus japonicus. The results showed that NKAα was the target gene of let-7 and NKAα expression levels were inversely correlated with let-7 expression based on the luciferase reporter assays and western blots. The let-7 abundance was negatively regulated by lncRNA001074 and NKAα both in vitro and in vivo. Knockdown of lncRNA001074 led to let-7 overexpression. These results demonstrated that lncRNA001074 binds to the 3'-UTR binding site of let-7 in a regulatory manner. Furthermore, the expression profiles of let-7, NKAα, and lncRNA001074 were analyzed in sea cucumbers after the knockdown of each of these genes. The results found that lncRNA001074 competitively bound let-7 to suppress NKAα expression under low salinity conditions. The downregulation of let-7, in conjunction with the upregulation of lncRNA001074 and NKAα, may be essential for the response to low salinity change in sea cucumbers. Therefore, the dynamic balance of the lncRNA001074, NKAα, and let-7 network might be a potential response mechanism to salinity change in sea cucumbers.

The steroid-induced microRNA let-7 regulates developmental growth by targeting cdc7 in the Drosophila fat body.

In insects, 20-hydroxyecdysone (20E) limits systemic growth by triggering developmental transitions. Previous studies have shown that 20E-induced let-7 exhibits crosstalk with the cell cycle. Here, we examined the underlying molecular mechanisms and physiological functions of 20E-induced let-7 in the fat body, an organ for energy storage and nutrient mobilization which plays a critical role in the larval growth. First, the overexpression of let-7 decreased the body size and led to the reduction of both nucleolus and cell sizes in the larval fat body. In contrast, the overexpression of let-7-Sponge increased the nucleolus and cell sizes. Moreover, we found that cdc7, encoding a conserved protein kinase that controls the endocycle, is a target of let-7. Notably, the mutation of cdc7 in the fat body resulted in growth defects. Overall, our findings revealed a novel role of let-7 in the control of endoreduplication-related growth during larval-prepupal transition in Drosophila.

Let-7 microRNA is a critical regulator in controlling the growth and function of silk gland in the silkworm

ABSTRACTThe silk gland is characterized by high protein synthesis. However, the molecular mechanisms controlling silk gland growth and silk protein synthesis remain undetermined. Here we demonstrated that CRISPR/Cas9-based knockdown of let-7 or the whole cluster promoted endoreduplication and enlargement of the silk gland, accompanied by changing silk yield, whereas transgenic overexpression of let-7 led to atrophy and degeneration of the silk gland. Mechanistically, let-7 controls cell growth in the silk gland through coordinating nutrient metabolism processes and energy signalling pathways. Transgenic overexpression of pyruvate carboxylase, a novel target of let-7, resulted in enlargement of the silk glands, which is consistent with the abnormal phenotype of the let-7 knockdown. Overall, our data reveal a previously unknown miRNA-mediated regulation of silk gland growth and physiology and shed light on involvement of let-7 as a critical stabilizer and booster in carbohydrate metabolism, which may have important implications for understanding of the molecular mechanism and physiological function of specialized organs in other species.

LIN28B Impairs the Transition of hESC-Derived β Cells from the Juvenile to Adult State.

SummaryDifferentiation of human embryonic stem cells into pancreatic β cells holds great promise for the treatment of diabetes. Recent advances have led to the production of glucose-responsive insulin-secreting cells in vitro, but resulting cells remain less mature than their adult primary β cell counterparts. The barrier(s) to in vitro β cell maturation are unclear. Here, we evaluated a potential role for microRNAs. MicroRNA profiling showed high expression of let-7 family microRNAs in vivo, but not in in vitro differentiated β cells. Reduced levels of let-7 in vitro were associated with increased levels of the RNA binding protein LIN28B, a negative regulator of let-7 biogenesis. Ablation of LIN28B during human embryonic stem cell (hESC) differentiation toward β cells led to a more mature glucose-stimulated insulin secretion profile and the suppression of juvenile-specific genes. However, let-7 overexpression had little effect. These results uncover LIN28B as a modulator of β cell maturation in vitro.

Abstract TMIM-065: MICRO-RNA LET-7 REGULATION AND FUNCTION IN OVARIAN CANCER AND EARLY EMBRYONIC DEVELOPMENT

Abstract INTRODUCTION: Epithelial ovarian cancer (EOC) is the fifth deadliest malignancy in women in the United States, with a high death-to-incidence ratio and five-year survival of 30%. Aggressiveness and recurrence of EOC has been attributed to cancer stem cells (CSC) within tumors, which contribute to chemoresistance and relapse. Deregulation of miRNAs has been linked to cancer initiation, progression, and the stem cell state. We focus on let-7 miRNA, which is repressed in many cancers and is associated with decreased survival. Let-7 is essential for cell differentiation, and its repression is required for reprogramming. Decreased let-7 level in cancer is associated with stemness. OBJECTIVE: Purpose for our research is to understand let-7 expression and function in EOC cell-lines and patients-derived samples in order to understand mechanisms of its abnormal regulation and develop novel treatments. MATERIALS AND METHODS: Patient-derived samples are used along with EOC cell-lines. Over-expression of Let-7 is achieved by mimic transfection and confirmed via RT-qPCR. Level of miRNA and pluripotency markers mRNA is detected via RT-qPCR, and protein expression confirmed by Western blot. Functional assays to analyze cancer phenotype include wound healing, invasion and spheroid formation assays. Embryoid body (EB) formation is used to mimic murine early embryonic development and guided toward primitive streak via cytokines. Let-7 expression is analyzed via RT-qPCR. RESULTS: We demonstrate that patient-derived EOC samples have decreased Let-7 levels and increased expression of pluripotency markers, therefore, we hypothesize that up-regulation of let-7 in EOC will decrease aggressiveness and increase chemosensitivity. We have demonstrated that up-regulation of let-7 via mimic transfection reduced cancer stem cell properties demonstrated by reduction of pluripotency markers and spheroid formation. Let-7 also decreased in vitro migration and invasion. Our data show that let-7 suppresses stem cell-like phenotype of EOC, indicating that it may be a treatment option in conjunction with conventional chemotherapies. In order to understand deregulation of let-7 in cancer, understanding its normal regulation and function during development is essential. By using mESCs we demonstrate that let-7 is dynamically expressed, contradicting conventional belief that let-7 levels slowly increase upon differentiation. Previously published data demonstrating that Hmga2, a let-7 target, peaks and is required upon exit from pluripotency supports our results. CONCLUSION: In conclusion, let-7 is repressed in EOC, and its over-expression demonstrates tumor suppressive functions via decreasing stemness, migration, invasion, and spheroid formation. During development let-7 is dynamically expressed, demonstrating complex regulation. Citation Format: Evgeny A Chirshev, Anthony Nguyen, Hojo Nozomi, Hill Alyse, Juli Unternaehrer. MICRO-RNA LET-7 REGULATION AND FUNCTION IN OVARIAN CANCER AND EARLY EMBRYONIC DEVELOPMENT [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr TMIM-065.

MicroRNA let-7-TGFBR3 signalling regulates cardiomyocyte apoptosis after infarction

BackgroundMyocardial infarction (MI) is a life-threatening disease, often leading to heart failure. Defining therapeutic targets at an early time point is important to prevent heart failure. MethodsMicroRNA screening was performed at early time points after MI using paired samples isolated from the infarcted and remote myocardium of pigs. We also examined the microRNA expression in plasma of MI patients and pigs. For mechanistic studies, AAV9-mediated microRNA knockdown and overexpression were administrated in mice undergoing MI. FindingsMicroRNAs let-7a and let-7f were significantly downregulated in the infarct area within 24 h post-MI in pigs. We also observed a reduction of let-7a and let-7f in plasma of MI patients and pigs. Inhibition of let-7 exacerbated cardiomyocyte apoptosis, induced a cardiac hypertrophic phenotype, and resulted in worsened left ventricular ejection fraction. In contrast, ectopic let-7 overexpression significantly reduced those phenotypes and improved heart function. We then identified TGFBR3 as a target of let-7, and found that induction of Tgfbr3 in cardiomyocytes caused apoptosis, likely through p38 MAPK activation. Finally, we showed that the plasma TGFBR3 level was elevated after MI in plasma of MI patients and pigs. InterpretationTogether, we conclude that the let-7-Tgfbr3-p38 MAPK signalling plays an important role in cardiomyocyte apoptosis after MI. Furthermore, microRNA let-7 and Tgfbr3 may serve as therapeutic targets and biomarkers for myocardial damage. FundMinistry of Science and Technology, National Health Research Institutes, Academia Sinica Program for Translational Innovation of Biopharmaceutical Development-Technology Supporting Platform Axis, Thematic Research Program and the Summit Research Program, Taiwan.

Abstract 3668: A LIN28B-PBK Axis promotes neuroblastoma dissemination and aggression

Abstract LIN28B is an RNA binding protein that plays key roles in normal development and, when deregulated, oncogenesis; mechanistically, it blocks the processing of the let-7 family of tumor suppressors and binds mRNAs directly. We previously demonstrated that LIN28B induces neuroblastoma proliferation, in part by regulating the expression of RAN GTPase and Aurora kinase A (AURKA). However, given the widespread metastases seen within neuroblastoma, we speculated that LIN28B might also influence neuroblastoma dissemination. We used gain and loss of function approaches to genetically manipulate transcripts of interest in neuroblastoma cells and measured effects on self-renewal, invasion, and downstream signaling. To examine the impact of LIN28B on dissemination, we generated GFP-luciferase expressing neuroblastoma cell line models in which LIN28B levels were manipulated, injected these lines into the tail veins of NSG mice, and tracked dissemination using an IVIS Spectrum system. Results show that depletion of LIN28B significantly delayed the onset of tumor metastasis, reduced tumor burden, and extended mouse survival (104 days versus 50 days, p&amp;lt;0.0001) compared to control cells. While LIN28B did not impact anoikis resistance, it did increase both tumorsphere number and size, linking self-renewal to metastatic dissemination. Additionally, LIN28B promoted cellular invasion. These effects were largely opposed by let-7. We next sought to understand how LIN28B promotes aggression and metastasis, specifically focusing on novel networks that are currently therapeutically targetable. Given our discovery of AURKA as a novel LIN28B target, we speculated that LIN28B might promote the expression of additional oncogenic kinases, perhaps revealing novel therapeutic possibilities to target the LIN28B network. We evaluated the TARGET dataset of neuroblastoma tumors and, focusing on the top 10 kinases most significantly and positively correlated with high LIN28B expression, nominated PBK for further study (4/10 of top correlated kinases). PBK (PDZ-binding kinase) is a Ser/Thr protein kinase expressed in normal embryonic tissues and various tumor types that plays a role in both mitosis and metastasis. Depletion of PBK mimicked the effects of LIN28B depletion, with respect to self-renewal and invasion. Depletion of LIN28B and overexpression of let-7 both reduced PBK protein expression, suggesting that PBK is a direct or indirect let-7 target. Taken together, our findings suggest that LIN28B/let-7 shapes neuroblastoma aggression, in part through influencing PBK, a kinase not previously implicated in the pathogenesis of neuroblastoma or other aggressive pediatric solid tumors. Current studies are further dissecting the functional and molecular relationships among LIN28B, let-7, and PBK in neuroblastoma. Citation Format: Dongdong Chen, Julie Cox, Jayabhargav Annam, Melanie Weingart, Grace Essien, Komal Rathi, Priya Khurana, Selma M. Cuya, Robert W. Schnepp. A LIN28B-PBK Axis promotes neuroblastoma dissemination and aggression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3668.

Stem cell-like characteristics of patient-derived high-grade serous ovarian cancer xenografts are reversed by miRNA let-7 overexpression

Objective: Aggressiveness and recurrence of epithelial ovarian cancer has been attributed to cancer stem cells (CSC) within tumors. Deregulation of miRNAs has been linked to cancer progression and the stem cell state. Current experiments focused on the tumor suppressor miRNA let-7, which in many cancers is associated with decreased survival. We aimed to understand the role of let-7 in the stem cell-like properties (stemness) of ovarian cancer cells derived from patients.

Let-7 inhibits the migration and invasion of extravillous trophoblast cell via targeting MDM4

AimsExtravillous trophoblast (EVT) cells migration and invasion are important causes to preeclampsia (PE). Studies have shown that let-7 was involved in inhibiting proliferation and invasion of several cancer cells, however, its effect on EVT cells migration and invasion has hardly been reported. This study aimed to explore the relation between let-7 and EVT cell migration and invasion. MethodsMicroRNA (miRNA) and genes expression levels were measured by reverse transcription polymerase chain reaction (RT-PCR) and Western blot (WB). Cell proliferation, migration and invasion were detected by cell counting kit-8 (CCK-8) assay, wound-healing assay and transwell assay. The binding site between let-7 and murine double minute 4 (MDM4) was identified using TargetScan. The targeting relation between let-7 and MDM4 was verified using dual luciferase reporter assay. ResultsThe results revealed that in placental tissues of PE patients, let-7, matrix metalloproteinase-2 (MMP-2) and MMP-9 were lowly expressed and tissue inhibitors of metalloproteinase-1 (TIMP-1) and TIMP-2 were highly expressed. Let-7 silencing promoted the proliferation, migration, invasion of HTR8/SVneo cells and the expression levels of MMP-2 and MMP-9, however, it inhibited TIMP-1 and TIMP-2 expression levels, while overexpression of let-7 produced the opposite results. Furthermore, MDM4 is a target gene of let-7. Rescue experiments suggested that MDM4 siRNA partially reversed the effects of let-7 silencing on cells. ConclusionsLet-7 silencing promoted proliferation, migration and invasion in EVT cells through the up-regulation of MDM4. Our study provided new insights into the molecular mechanism of PE.

LncRNA H19/miR-let-7 axis participates in the regulation of ox-LDL-induced endothelial cell injury via targeting periostin

Oxidized-low density lipoprotein (ox-LDL)-induced endothelial cell dysfunction is a crucial event in the pathogenesis of atherosclerosis (AS). Long noncoding RNAs (lncRNAs) have been shown to play important roles in this process. The purpose of this study was to investigate the biological effects of lncRNA H19 on the ox-LDL-induced endothelial cell injury and to explore the underlying molecular mechanisms. In the present study, the expression of H19 in the serum of patients with AS and in the ox-LDL-treated human umbilical vein endothelial cells (HUVECs) was significantly up-regulated. H19 knockdown by transfection with H19 siRNAs in ox-LDL-treated HUVECs remarkably promoted cell viability, suppressed the secretion of interleukin (IL)-1β, IL-6, and tumour necrosis factor (TNF)-α, decreased the expression of vascular cell adhesion molecule 1 (VCAM1), intercellular adhesion molecule 1 (ICAM1) and E-selectin, reduced levels of reactive oxygen species (ROS) and malondialdehyde (MDA), increased superoxide dismutase (SOD) levels, and reduced cell apoptosis. Moreover, H19 knockdown significantly down-regulated the ox-LDL-induced expression of periostin, but did not affect the expression of let-7a, which directly targets the 3′-UTR of periostin mRNA. In addition, periostin overexpression partly reversed the biological effects of H19 knockdown in ox-LDL-treated HUVECs, which were almost recapitulated by let-7 overexpression. In conclusion, these data suggest that H19 knockdown suppressed ox-LDL-induced inflammation, apoptosis and oxidative stress in HUVECs, which may be related to the down-regulation of periostin by interfering with let-7 bioavailability.