Gymnosis is the process of the delivery of antisense oligodeoxynucleotides to cells, in the
absence of any carriers or conjugation, that produces sequence-specific gene silencing. While gymnosis was originally demonstrated using locked nucleic acid (LNA) gapmers, 2′-deoxy-2′fluoroarabino nucleic acid (2′F-ANA) phosphorothioate gapmer oligonucleotides (oligos) when targeted to the Bcl-2 and androgen receptor (AR) mRNAs in multiple cell lines in tissue culture, are approximately as effective at silencing of Bcl-2 expression as the iso-sequential LNA congeners. In LNCaP prostate cancer cells, gymnotic silencing of the AR by a 2′F-ANA phosphorothioate gapmer oligo led to downstream silencing of cellular prostate-specific antigen (PSA) expression even in the presence of the androgenic steroid R1881 (metribolone), which stabilizes cytoplasmic levels of the AR. Furthermore, gymnotic silencing occurs in the absence of serum, and silencing by both LNA and 2′F-ANA oligos is augmented in serum-free (SF) media in some cell lines when they are treated with oleic acid and a variety of ω-6 polyunsaturated fatty acids (ω-6 PUFAs), but not by an aliphatic (palmitic) fatty acid. These results significantly expand our understanding of and ability to successfully manipulate the cellular delivery of single-stranded oligos in vitro.
2′F-ANA; endocytosis; gymnosis; LNA; oleic acid; phosphorothioate oligonucleotides; polyunsaturated fatty acids
Systemic iron homeostasis is mainly controlled by the liver through synthesis of the peptide hormone hepcidin (encoded by Hamp), the key regulator of duodenal iron absorption and macrophage iron release. Here we show that the liver-specific microRNA miR-122 is important for regulating Hamp mRNA expression and tissue iron levels. Efficient and specific depletion of miR-122 by injection of a locked-nucleic-acid–modified (LNA-modified) anti-miR into WT mice caused systemic iron deficiency, characterized by reduced plasma and liver iron levels, mildly impaired hematopoiesis, and increased extramedullary erythropoiesis in the spleen. Moreover, miR-122 inhibition increased the amount of mRNA transcribed by genes that control systemic iron levels, such as hemochromatosis (Hfe), hemojuvelin (Hjv), bone morphogenetic protein receptor type 1A (Bmpr1a), and Hamp. Importantly, miR-122 directly targeted the 3′ untranslated region of 2 mRNAs that encode activators of hepcidin expression, Hfe and Hjv. These data help to explain the increased Hamp mRNA levels and subsequent iron deficiency in mice with reduced miR-122 levels and establish a direct mechanistic link between miR-122 and the regulation of systemic iron metabolism.
Background & Aim
The miR-221/222 cluster is upregulated in malignant plasma cells from multiple myeloma (MM) patients harboring the t(4;14) translocation. We previously reported that silencing of miR-221/222 by an antisense oligonucleotide induces anti-MM activity and upregulates canonical miR-221/222 targets. The in vivo anti-tumor activity occurred when miR-221/222 inhibitors were delivered directly into MM xenografts. The aim of the present study was to evaluate the anti-MM activity of a novel phosphorothioate modified backbone 13-mer locked nucleic acid (LNA)-Inhibitor-miR-221 (LNA-i-miR-221) specifically designed for systemic delivery.
In vitro anti-MM activity of LNA-i-miR-221 was evaluated by cell proliferation and BrdU uptake assays. In vivo studies were performed with non-obese diabetic/severe combined immunodeficient (NOD.SCID) mice bearing t(4;14) MM xenografts, which were intraperitoneally or intravenously treated with naked LNA-i-miR-221. RNA extracts from retrieved tumors were analyzed for miR-221 levels and modulation of canonical targets expression. H&E staining and immunohistochemistry were performed on retrieved tumors and mouse vital organs.
In vitro, LNA-i-miR-221 exerted strong antagonistic activity against miR-221 and induced upregulation of the endogenous target p27Kip1. It had a marked anti-proliferative effect on t(4;14)-translocated MM cells but not on MM cells not carrying the translocation and not overexpressing miR-221. In vivo, systemic treatment with LNA-i-miR-221 triggered significant anti-tumor activity against t(4;14) MM xenografts; it also induced miR-221 downregulation, upregulated p27Kip1 and reduced Ki-67. No behavioral changes or organ-related toxicity were observed in mice as a consequence of treatments.
LNA-i-miR-221 is a highly stable, effective agent against t(4;14) MM cells, and is suitable for systemic use. These data provide the rationale for the clinical development of LNA-i-miR-221 for the treatment of MM.
MicroRNA-122 (miR-122) is an abundant liver-specific miRNA, implicated in fatty acid and cholesterol metabolism as well as hepatitis C viral replication. Here, we report that a systemically administered 16-nt, unconjugated LNA (locked nucleic acid)-antimiR oligonucleotide complementary to the 5′ end of miR-122 leads to specific, dose-dependent silencing of miR-122 and shows no hepatotoxicity in mice. Antagonism of miR-122 is due to formation of stable heteroduplexes between the LNA-antimiR and miR-122 as detected by northern analysis. Fluorescence in situ hybridization demonstrated uptake of the LNA-antimiR in mouse liver cells, which was accompanied by markedly reduced hybridization signals for mature miR-122 in treated mice. Functional antagonism of miR-122 was inferred from a low cholesterol phenotype and de-repression within 24 h of 199 liver mRNAs showing significant enrichment for miR-122 seed matches in their 3′ UTRs. Expression profiling extended to 3 weeks after the last LNA-antimiR dose revealed that most of the changes in liver gene expression were normalized to saline control levels coinciding with normalized miR-122 and plasma cholesterol levels. Combined, these data suggest that miRNA antagonists comprised of LNA are valuable tools for identifying miRNA targets in vivo and for studying the biological role of miRNAs and miRNA-associated gene-regulatory networks in a physiological context.
MicroRNAs (miRNAs) play an important role in diverse physiological processes and are potential therapeutic agents. Synthetic oligonucleotides (ONs) of different chemistries have proven successful for blocking miRNA expression. However, their specificity and efficiency have not been fully evaluated. Here, we show that peptide nucleic acids (PNAs) efficiently block a key inducible miRNA expressed in the haematopoietic system, miR-155, in cultured B cells as well as in mice. Remarkably, miR-155 inhibition by PNA in primary B cells was achieved in the absence of any transfection agent. In mice, the high efficiency of the treatment was demonstrated by a strong overlap in global gene expression between B cells isolated from anti-miR-155 PNA-treated and miR-155-deficient mice. Interestingly, PNA also induced additional changes in gene expression. Our analysis provides a useful platform to aid the design of efficient and specific anti-miRNA ONs for in vivo use.
Anti-miRs are oligonucleotide inhibitors complementary to miRNAs that have been used extensively as tools to gain understanding of specific miRNA functions and as potential therapeutics. We showed previously that peptide nucleic acid (PNA) anti-miRs containing a few attached Lys residues were potent miRNA inhibitors. Using miR-122 as an example, we report here the PNA sequence and attached amino acid requirements for efficient miRNA targeting and show that anti-miR activity is enhanced substantially by the presence of a terminal-free thiol group, such as a Cys residue, primarily due to better cellular uptake. We show that anti-miR activity of a Cys-containing PNA is achieved by cell uptake through both clathrin-dependent and independent routes. With the aid of two PNA analogues having intrinsic fluorescence, thiazole orange (TO)-PNA and [bis-o-(aminoethoxy)phenyl]pyrrolocytosine (BoPhpC)-PNA, we explored the subcellular localization of PNA anti-miRs and our data suggest that anti-miR targeting of miR-122 may take place in or associated with endosomal compartments. Our findings are valuable for further design of PNAs and other oligonucleotides as potent anti-miR agents.
The liver-expressed microRNA-122 (miR-122) is essential for hepatitis C virus (HCV) RNA accumulation in cultured liver cells, but its potential as a target for antiviral intervention has not been assessed. Here, we show that treatment of chronically infected chimpanzees with a locked nucleic acid (LNA)-modified oligonucleotide (SPC3649) complementary to miR-122 leads to long-lasting suppression of HCV viremia with no evidence for viral resistance or side effects in the treated animals. Furthermore, transcriptome and histological analyses of liver biopsies demonstrated derepression of target mRNAs with miR-122 seed sites, down-regulation of interferon-regulated genes (IRGs) and improvement of HCV-induced liver pathology. The prolonged virological response to SPC3649 treatment without HCV rebound holds promise of a new antiviral therapy with a high barrier to resistance.
For the past 15–20 years, the intracellular delivery and silencing activity of oligodeoxynucleotides have been essentially completely dependent on the use of a delivery technology (e.g. lipofection). We have developed a method (called ‘gymnosis’) that does not require the use of any transfection reagent or any additives to serum whatsoever, but rather takes advantage of the normal growth properties of cells in tissue culture in order to promote productive oligonucleotide uptake. This robust method permits the sequence-specific silencing of multiple targets in a large number of cell types in tissue culture, both at the protein and mRNA level, at concentrations in the low micromolar range. Optimum results were obtained with locked nucleic acid (LNA) phosphorothioate gap-mers. By appropriate manipulation of oligonucleotide dosing, this silencing can be continuously maintained with little or no toxicity for >240 days. High levels of oligonucleotide in the cell nucleus are not a requirement for gene silencing, contrary to long accepted dogma. In addition, gymnotic delivery can efficiently deliver oligonucleotides to suspension cells that are known to be very difficult to transfect. Finally, the pattern of gene silencing of in vitro gymnotically delivered oligonucleotides correlates particularly well with in vivo silencing. The establishment of this link is of particular significance to those in the academic research and drug discovery and development communities.
MicroRNAs (miRNAs) are short noncoding RNAs, which bind to messenger RNAs and regulate protein expression. The biosynthesis of miRNAs includes two precursors, a primary miRNA transcript (pri-miRNA) and a shorter pre-miRNA, both of which carry a common stem-loop bearing the mature miRNA. MiR-122 is a liver-specific miRNA with an important role in the life cycle of hepatitis C virus (HCV). It is the target of miravirsen (SPC3649), an antimiR drug candidate currently in clinical testing for treatment of HCV infections. Miravirsen is composed of locked nucleic acid (LNAs) ribonucleotides interspaced throughout a DNA phosphorothioate sequence complementary to mature miR-122. The LNA modifications endow the drug with high affinity for its target and provide resistance to nuclease degradation. While miravirsen is thought to work mainly by hybridizing to mature miR-122 and blocking its interaction with HCV RNA, its target sequence is also present in pri- and pre-miR-122. Using new in vitro and cellular assays specifically developed to discover ligands that suppress biogenesis of miR-122, we show that miravirsen binds to the stem-loop structure of pri- and pre-miR-122 with nanomolar affinity, and inhibits both Dicer- and Drosha-mediated processing of miR-122 precursors. This inhibition may contribute to the pharmacological activity of the drug in man.
Hepatitis C virus (HCV) is the major etiological agent of non-A, non-B hepatitis. Current therapies are not effective in all patients and can result in the generation of resistant mutants, leading to a need for new therapeutic options. HCV has an RNA genome that contains a well-defined and highly conserved secondary structure within the 5′-untranslated region. This structure is known as the internal ribosomal entry site (IRES) and is necessary for translation and viral replication. Here, we test the hypothesis that antisense peptide nucleic acid (PNA) and locked nucleic acid (LNA) oligomers can bind key IRES sequences and block translation. We used lipid-mediated transfections to introduce PNAs and LNAs into cells. Our data suggest that PNAs and LNAs can invade critical sequences within the HCV IRES and inhibit translation. Seventeen base PNA or LNA oligomers targeting different regions of the HCV IRES demonstrated a sequence-specific dose–response inhibition of translation with EC50 values of 50–150 nM. Inhibition was also achieved by PNAs ranging in length from 15 to 21 bases. IRES-directed inhibition of gene expression widens the range of mechanisms for antisense inhibition by PNAs and LNAs and may provide further therapeutic lead compounds for the treatment of HCV.
MicroRNAs (miRNAs) are small endogenous non-coding RNAs that regulate post-transcriptional gene expression and are important in many biological processes. Disease-associated miRNAs have been shown to become potential targets for therapeutic intervention. Functions of miRNAs can be inhibited by using antisense oligonucleotides, called anti-miRs, complimentary to the miRNA sequences. Here, we show that systemic delivery of a chemically stabilized anti-miR-122 complexed with interfering nanoparticles (iNOPs) effectively silences the liver-expressed miR-122 in mice. Intravenous administration of 2 mg kg−1 chemically modified anti-miR-122 complexed with iNOP-7 resulted in 83.2 ± 3.2% specific silencing of miR-122, which was accompanied by regulating gene expression in liver and lowering of plasma cholesterol. The specific silencing of miR-122 was long lasting and did not induce an immune response. Our results demonstrate that iNOPs can successfully deliver anti-miR to specifically target and silence miRNA in clinically acceptable and therapeutically affordable doses.
Objective: MicroRNAs (miRNAs) are endogenous non-coding RNAs, 19-25 nucleotides in length involved in post-transcriptional regulation of gene expression in a considerable majority of mRNAs. In many tumors, up- or down-regulation of different miRNAs has been reported. In acute myeloid leukemia up-regulation of miR-92a has been reported in humans in vitro studies. In this study it is mainly aimed to assess the effect of inhibition of miR-92a in viability of acute promyelocytic leukemia (APL).
Materials and Methods: We performed inhibition of miR-92a in an acute promyelocytic leukemia (APL) cell line (HL-60) using locked nucleic acid (LNA) antagomir. At different time points after LNA-anti-miR92a transfection, miR-92a quantitation and cell viability were assessed by qRT-real-time-polymerase chain reaction (PCR) and MTT assays. The data was processed using the ANOVA test.
Results: Down-regulation of miR-92a in APL cell line (HL-60) by LNA antagomir extensively decreased cell viability in APL. Cell viability gradually decreased over time as the viability of LNA-anti-miR transfected cells was less than 50% of untreated cells at 72 h post-transfection. The difference of cell viability between LNA-anti-miR and control groups was statistically significant (p<0.024).
Conclusion: Based on our findings, it is concluded that inhibition of miR-92a may represent a potential novel therapeutic approach for treatment of APL.
Conflict of interest:None declared.
microRNA; miR-92a; Acute promyelocytic leukemia; Locked Nucleic Acid
Development of artificial nucleic acids for therapeutic applications warrants that the oligomers be endowed with high specificity, enzymatic stability and with no/reduced off-target effects. The balance between strength of the duplex with target RNA and enzyme stability is therefore the key factor for the designed modification. The chiral serinol derivative combines the attributes of amino- and methoxy- substitution when at 2′- position and at 3′- and 5′- ends, effectively balancing the duplex stability and resistance to hydrolytic enzymes. The biological effect seen is the remarkable improvement in splice correction by the steric blocking antisense oligonucleotide with just 4 modified units, i.e ~20% substitution with R-aminomethoxypropyloxy (R-AMP)-thymidine within the 2′-OMe 18mer sequence.
splice correction; steric-blocking; antisense; oligonucleotides
Proper coordination of cholesterol biosynthesis and trafficking is essential to human health. The sterol regulatory element binding proteins (SREBPs) are key transcription regulators of genes involved in cholesterol biosynthesis/uptake. We show here that microRNAs (miR-33a/b) embedded within introns of the SREBP genes target the ATP-binding cassette transporter A1 (ABCA1), an important regulator of high-density lipoprotein (HDL) synthesis and reverse cholesterol transport, for post-transcriptional repression. Antisense inhibition of miR-33 in cell lines causes upregulation of ABCA1 expression and increased cholesterol efflux, and injection of mice on a western-type diet with locked nucleic acid (LNA)-antisense oligonucleotides results in elevated plasma HDL. Collectively, our findings indicate that miR-33 acts in concert with the SREBP host genes to control cholesterol homeostasis, and suggest that miR-33 may represent a therapeutic target for ameliorating cardiometabolic diseases.
Antisense inhibition of oncogenic or other disease-related miRNAs and miRNA families in vivo may provide novel therapeutic strategies. However, this approach relies on the development of potent miRNA inhibitors and their efficient delivery into cells. Here, we introduce short seed-directed LNA oligonucleotides (12- or 14-mer antiseeds) with a phosphodiester backbone (PO) for efficient miRNA inhibition. We have analyzed such LNA (PO) antiseeds using a let-7a-controlled luciferase reporter assay and identified them as active miRNA inhibitors in vitro. Moreover, LNA (PO) 14-mer antiseeds against ongogenic miR-17–5p and miR-20a derepress endogenous p21 expression more persistently than corresponding miRNA hairpin inhibitors, which are often used to inhibit miRNA function. Further analysis of the antiseed-mediated derepression of p21 in luciferase reporter constructs - containing the 3′-UTR of p21 and harboring two binding sites for miRNAs of the miR-106b family - provided evidence that the LNA antiseeds inhibit miRNA families while hairpin inhibitors act in a miRNA-specific manner. The derepression caused by LNA antiseeds is specific, as demonstrated via seed mutagenesis of the miR-106b target sites. Importantly, we show functional delivery of LNA (PO) 14-mer antiseeds into cells upon complexation with polyethylenimine (PEI F25-LMW), which leads to the formation of polymeric nanoparticles. In contrast, attempts to deliver a functional seed-directed tiny LNA 8-mer with a phosphorothioate backbone (PS) by formulation with PEI F25-LMW remained unsuccessful. In conclusion, LNA (PO) 14-mer antiseeds are attractive miRNA inhibitors, and their PEI-based delivery may represent a promising new strategy for therapeutic applications.
miRNA; miR-17-92; let-7a; antimiR; antiseed; LNA; PEI; p21; cancer
miR-122, an abundant liver-specific microRNA (miRNA), regulates cholesterol metabolism and promotes hepatitis C virus (HCV) replication. Reduced miR-122 expression in hepatocellular carcinoma (HCC) correlates with metastasis and poor prognosis. Nevertheless, the consequences of sustained loss of function of miR-122 in vivo have not been determined. Here, we demonstrate that deletion of mouse Mir122 resulted in hepatosteatosis, hepatitis, and the development of tumors resembling HCC. These pathologic manifestations were associated with hyperactivity of oncogenic pathways and hepatic infiltration of inflammatory cells that produce pro-tumorigenic cytokines, including IL-6 and TNF. Moreover, delivery of miR-122 to a MYC-driven mouse model of HCC strongly inhibited tumorigenesis, further supporting the tumor suppressor activity of this miRNA. These findings reveal critical functions for miR-122 in the maintenance of liver homeostasis and have important therapeutic implications, including the potential utility of miR-122 delivery for selected patients with HCC and the need for careful monitoring of patients receiving miR-122 inhibition therapy for HCV.
MicroRNAs (miRNAs) play important roles in many developmental processes, including cell differentiation and apoptosis. Transition of proliferative ovarian granulosa cells to terminally differentiated luteal cells in response to the ovulatory surge of luteinizing hormone (LH) involves rapid and pronounced changes in cellular morphology and function. MicroRNA 21 (miR-21, official symbol Mir21) is one of three highly LH-induced miRNAs in murine granulosa cells, and here we examine the function and temporal expression of Mir21 within granulosa cells as they transition to luteal cells. Granulosa cells were transfected with blocking (2′-O-methyl) and locked nucleic acid (LNA-21) oligonucleotides, and mature Mir21 expression decreased to one ninth and one twenty-seventh of its basal expression, respectively. LNA-21 depletion of Mir21 activity in cultured granulosa cells induced apoptosis. In vivo, follicular granulosa cells exhibit a decrease in cleaved caspase 3, a hallmark of apoptosis, 6 h after the LH/human chorionic gonadotropin surge, coincident with the highest expression of mature Mir21. To examine whether Mir21 is involved in regulation of apoptosis in vivo, mice were treated with a phospho thioate-modified LNA-21 oligonucleotide, and granulosa cell apoptosis was examined. Apoptosis increased in LNA-21-treated ovaries, and ovulation rate decreased in LNA-21-treated ovaries, compared with their contralateral controls. We have examined a number of Mir21 apoptotic target transcripts identified in other systems; currently, none of these appear to play a role in the induction of ovarian granulosa cell apoptosis. This study is the first to implicate the antiapoptotic Mir21 (an oncogenic miRNA) as playing a clear physiologic role in normal tissue function.
In vivo and in vitro loss of microRNA 21, an LH-induced microRNA, results in mouse granulosa cell apoptosis.
apoptosis,; granulosa cells,; luteinizing hormone,; microRNA,; ovary
Vectors based on adeno-associated virus (AAV) are effective in gene delivery in vivo. Tissue-specific gene expression is often needed to minimize ectopic expression in unintended cells and undesirable consequences. Here we investigated if incorporation of target sequences of tissue-specific microRNA (miRNA) into AAV vectors could inhibit ectopic expression in tissues such as the liver and hematopoietic cells. First we inserted liver-specific miR-122 target sequences (miR-122T) into the 3′ untranslated region (UTR) of a number of AAV vectors. After intravenous delivery in mice, we found that 5 copies of the 20mer miR-122T reduced liver expression of luciferase by 50-fold and β-galactosidase (LacZ) by 70-fold. Five copies of miR-122T also reduced mRNA levels of a secretable protein (myostatin propeptide) from the AAV vector plasmid by 23–fold in the liver. However, gene expression in other tissues including the heart was not inhibited. Similarly, we inserted 4 copies of miR-142-3pT or miR-142-5pT, both hematopoietic lineage-specific, into the 3′ UTR of the AAV-luciferase vector. We wished to see if they could prolong transgene expression by inhibiting expression in antigen-presenting cells. However, in vivo luciferase gene expression in major tissues declined with time regardless of the miR-142 target sequences used. Quantitative analysis of the vector DNA in various tissues revealed that the decline of transgene expression in vivo was mainly due to promoter shut-off other than loss of AAV-transduced cells by immune destruction. Moreover, transgene expression was not detected in circulating mononuclear cells after delivering AAV9 vector with or without miR142T. These results demonstrate that live-specific miR-122 target sequence in AAV vectors was highly efficient in reducing liver expression, whereas hematopoietic miR-142 target sequences were ineffective in preventing decline of AAV vector gene expression in non-hematopoietic tissues resulted from promoter shut-off.
Myocardial infarction (MI) is a leading cause of death worldwide. Because endogenous cardiac repair mechanisms are not sufficient for meaningful tissue regeneration, MI results in loss of cardiac tissue and detrimental remodeling events. MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression in a sequence dependent manner. Our previous data indicate that miRNAs are dysregulated in response to ischemic injury of the heart and actively contribute to cardiac remodeling after MI.
This study was designed to determine whether miRNAs are dysregulated on ischemic damage in porcine cardiac tissues and whether locked nucleic acid (LNA)-modified anti-miR chemistries can target cardiac expressed miRNAs to therapeutically inhibit miR-15 on ischemic injury.
Methods and Results
Our data indicate that the miR-15 family, which includes 6 closely related miRNAs, is regulated in the infarcted region of the heart in response to ischemia-reperfusion injury in mice and pigs. LNA-modified chemistries can effectively silence miR-15 family members in vitro and render cardiomyocytes resistant to hypoxia-induced cardiomyocyte cell death. Correspondingly, systemic delivery of miR-15 anti-miRs dose-dependently represses miR-15 in cardiac tissue of both mice and pigs, whereas therapeutic targeting of miR-15 in mice reduces infarct size and cardiac remodeling and enhances cardiac function in response to MI.
Oligonucleotide-based therapies using LNA-modified chemistries for modulating cardiac miRNAs in the setting of heart disease are efficacious and validate miR-15 as a potential therapeutic target for the manipulation of cardiac remodeling and function in the setting of ischemic injury.
microRNA; ischemia reperfusion; miR-15 family; anti-miR therapy
Locked nucleic acids (LNAs) and double-stranded small interfering RNAs (siRNAs) are rather new promising antisense molecules for cell culture and in vivo applications. Here, we compare LNA–DNA–LNA gapmer oligonucleotides and siRNAs with a phosphorothioate and a chimeric 2′-O-methyl RNA–DNA gapmer with respect to their capacities to knock down the expression of the vanilloid receptor subtype 1 (VR1). LNA–DNA–LNA gapmers with four or five LNAs on either side and a central stretch of 10 or 8 DNA monomers in the center were found to be active gapmers that inhibit gene expression. A comparative co-transfection study showed that siRNA is the most potent inhibitor of VR1–green fluorescent protein (GFP) expression. A specific inhibition was observed with an estimated IC50 of 0.06 nM. An LNA gapmer was found to be the most efficient single-stranded antisense oligonucleotide, with an IC50 of 0.4 nM being 175-fold lower than that of commonly used phosphorothioates (IC50 ∼70 nM). In contrast, the efficiency of a 2′-O-methyl-modified oligonucleotide (IC50 ∼220 nM) was 3-fold lower compared with the phosphorothioate. The high potency of siRNAs and chimeric LNA–DNA oligonucleotides make them valuable candidates for cell culture and in vivo applications targeting the VR1 mRNA.
Use of antisense oligonucleotides is a versatile strategy for achieving control of gene expression. Unfortunately, the interpretation of antisense-induced phenotypes is sometimes difficult, and chemical modifications that improve the potency and specificity of antisense action would be useful. The introduction of locked nucleic acid (LNA) bases into oligonucleotides confers exceptional improvement in binding affinity, up to 10°C per substitution, making LNAs an exciting option for the optimization of antisense efficacy. Here we examine the rules governing antisense gene inhibition within cells by oligonucleotides that contain LNA bases. LNA- containing oligomers were transfected into cells using cationic lipid and accumulated in the nucleus. We tested antisense gene inhibition by LNAs and LNA–DNA chimeras complementary to the 5′-untranslated region, the region surrounding the start codon and the coding region of mRNA, and identified effective antisense agents targeted to each of these locations. Our data suggest that LNA bases can be used to develop antisense oligonucleotides and that their use is a versatile approach for efficiently inhibiting gene expression inside cells.
The loss of microRNA-122 (miR-122) expression correlates to many characteristic properties of hepatocellular carcinoma (HCC) cells, including clonogenic survival, anchorage-independent growth, migration, invasion, epithelial-mesenchymal transition, and tumorigenesis. However, all of these findings do not sufficiently explain the oncogenic potential of miR-122. In the current study, we used two-dimensional differential in-gel electrophoresis to measure changes in the expression of thousands of proteins in response to the inhibition of miR-122 in human hepatoma cells. Several proteins that were upregulated on miR-122 inhibition were involved in the unfolded protein response (UPR) pathway. The overexpression of miR-122 resulted in the repression of UPR pathway activation. Therefore, miR-122 may act as an inhibitor of the chaperone gene expression and negatively regulate the UPR pathway in HCC. We further showed that the miR-122 inhibitor enhanced the stability of the 26S proteasome non-ATPase regulatory subunit 10 (PSMD10) through the up-regulation of its target gene cyclin-dependent kinase 4 (CDK4). This process may activate the UPR pathway to prevent chemotherapy-mediated tumor cell apoptosis. The current study suggests that miR-122 negatively regulates the UPR through the CDK4-PSMD10 pathway. The down-regulation of miR-122 activated the CDK4-PSMD10-UPR pathway to decrease tumor cell anticancer drug-mediated apoptosis. We identified a new HCC therapeutic target and proclaimed the potential risk of the therapeutic use of miR-122 silencing.
MicroRNAs (miRNAs) have been implicated in the orchestration of diverse cellular processes including differentiation, proliferation, and apoptosis and are believed to play pivotal roles as oncogenes and tumor suppressors. miR-122, a liver specific miRNA, is significantly down-regulated in most hepatocellular carcinomas (HCCs) but its role in tumorigenesis remains poorly understood. Here we identify AKT3 as a novel and direct target of miR-122. Restoration of miR-122 expression in HCC cell lines decreases AKT3 levels, inhibits cell migration and proliferation, and induces apoptosis. These anti-tumor phenotypes can be rescued by reconstitution of AKT3 expression indicating the essential role of AKT3 in miR-122 mediated HCC transformation. In vivo, restoration of miR-122 completely inhibited xenograft growth of HCC tumor in mice. Our data strongly suggest that miR-122 is a tumor suppressor that targets AKT3 to regulate tumorigenesis in HCCs and a potential therapeutic candidate for liver cancer.
MicroRNAs inhibit mRNA translation or promote mRNA degradation by binding complementary sequences in 3′ untranslated regions of target mRNAs. MicroRNA-21 (miR-21) is upregulated in response to cardiac stress, and its inhibition by a cholesterol-modified antagomir has been reported to prevent cardiac hypertrophy and fibrosis in rodents in response to pressure overload. In contrast, we have shown here that miR-21–null mice are normal and, in response to a variety of cardiac stresses, display cardiac hypertrophy, fibrosis, upregulation of stress-responsive cardiac genes, and loss of cardiac contractility comparable to wild-type littermates. Similarly, inhibition of miR-21 through intravenous delivery of a locked nucleic acid–modified (LNA-modified) antimiR oligonucleotide also failed to block the remodeling response of the heart to stress. We therefore conclude that miR-21 is not essential for pathological cardiac remodeling.
In the search of facile and efficient methods for cellular delivery of peptide nucleic acids (PNA), we have synthesized PNAs conjugated to oligophosphonates via phosphonate glutamine and bis-phosphonate lysine amino acid derivatives thereby introducing up to twelve phosphonate moieties into a PNA oligomer. This modification of the PNA does not interfere with the nucleic acid target binding affinity based on thermal stability of the PNA/RNA duplexes. When delivered to cultured HeLa pLuc705 cells by Lipofectamine, the PNAs showed dose-dependent nuclear antisense activity in the nanomolar range as inferred from induced luciferase activity as a consequence of pre-mRNA splicing correction by the antisense-PNA. Antisense activity depended on the number of phosphonate moieties and the most potent hexa-bis-phosphonate-PNA showed at least 20-fold higher activity than that of an optimized PNA/DNA hetero-duplex. These results indicate that conjugation of phosphonate moieties to the PNA can dramatically improve cellular delivery mediated by cationic lipids without affecting on the binding affinity and sequence discrimination ability, exhibiting EC50 values down to one nanomolar. Thus the intracellular efficacy of PNA oligomers rival that of siRNA and the results therefore emphasize that provided sufficient in vivo bioavailability of PNA can be achieved these molecules may be developed into potent gene therapeutic drugs.