siRNA-induced immunostimulation through TLR7 promotes antitumoral activity against HPV-driven tumors in vivo

Development and Perspectives: Multifunctional Nucleic Acid Nanomedicines for Treatment of Gynecological Cancers

Gynecological malignancies are a significant cause of morbidity and mortality across the globe. Due to delayed presentation, gynecological cancer patients are often referred late in the disease's course, resulting in poor outcomes. A considerable number of patients ultimately succumb to chemotherapy-resistant disease, which reoccurs at advanced stages despite treatment interventions. Although efforts have been devoted to developing therapies that demonstrate reduced resistance to chemotherapy and enhanced toxicity profiles, current clinical outcomes remain unsatisfactory due to treatment resistance and unfavorable off-target effects. Consequently, innovative biological and nanotherapeutic approaches are imperative to strengthen and optimize the therapeutic arsenal for gynecological cancers. Advancements in nanotechnology-based therapies for gynecological malignancies offer significant advantages, including reduced toxicity, expanded drug circulation, and optimized therapeutic dosing, ultimately leading to enhanced treatment effectiveness. Recent advances in nucleic acid therapeutics using microRNA, small interfering RNA, and messenger RNA provide novel approaches for cancer therapeutics. Effective single-agent and combinatorial nucleic acid therapeutics for gynecological malignancies have the potential to transform cancer treatment by giving safer, more tailored approaches than conventional therapies. This review highlights current preclinical studies that effectively exploit these approaches for the treatment of gynecological malignant tumors and malignant ascites.

Antisense Oligonucleotides and Small Interfering RNA for the Treatment of Dyslipidemias

The burden of atherosclerotic disease worldwide necessitates implementing the treatment of its risk factors. Among them, hypercholesterolemia has a central role. In addition to conventional small organic compounds and the recently introduced monoclonal antibodies, new technologies are arising such as the antisense oligonucleotides and small interfering RNAs (siRNAs) that operate upstream, blocking the mRNA translation of the proteins specifically involved in lipid metabolism. In this review, we briefly explain the mechanisms of action of these molecules and discuss the difficulties related to their in vivo use as therapeutical agents. We go over the oligonucleotides tested in clinical trials that could potentially revolutionize the care of patients by acting on proteins involved in the lipoprotein metabolism and regulation, namely: angiopoietin-like protein 3 (ANGPTL3); lipoprotein a (Lp(a)); apolipoprotein B (Apo B); apolipoprotein C III (Apo C-III); and proprotein convertase subtilisin–kexin type 9 (PCSK9). Finally, the differences between ASOs and siRNAs, their future possible clinical applications, and the role of Inclisiran, a siRNA direct against PCSK9 to reduce LDL-C, were reviewed in detail.

Activation of Innate Immunity by Therapeutic Nucleic Acids

Nucleic acid-based therapeutics have gained increased attention during recent decades because of their wide range of application prospects. Immunostimulatory nucleic acids represent a promising class of potential drugs for the treatment of tumoral and viral diseases due to their low toxicity and stimulation of the body’s own innate immunity by acting on the natural mechanisms of its activation. The repertoire of nucleic acids that directly interact with the components of the immune system is expanding with the improvement of both analytical methods and methods for the synthesis of nucleic acids and their derivatives. Despite the obvious progress in this area, the problem of delivering therapeutic acids to target cells as well as the unresolved issue of achieving a specific therapeutic effect based on activating the mechanism of interferon and anti-inflammatory cytokine synthesis. Minimizing the undesirable effects of excessive secretion of inflammatory cytokines remains an unsolved task. This review examines recent data on the types of immunostimulatory nucleic acids, the receptors interacting with them, and the mechanisms of immunity activation under the action of these molecules. Finally, data on immunostimulatory nucleic acids in ongoing and completed clinical trials will be summarized.

CRISPR/Cas9-loaded stealth liposomes effectively cleared established HPV16-driven tumours in syngeneic mice

Gene-editing has raised the possibility of being able to treat or cure cancers, but key challenges remain, including efficient delivery, in vivo efficacy, and its safety profile. Ideal targets for cancer therapy are oncogenes, that when edited, cause cell death. Here, we show, using the human papillomavirus (HPV) type 16 cancer cell line TC1, that CRISPR/Cas9 targeting the E7 oncogene and packaged in PEGylated liposomes cleared established tumours in immunocompetent mice. Treatment caused no significant toxicity in the spleen or liver. An ideal therapeutic outcome would be the induction of an immunogenic cell death (ICD), such that recurrent tumours would be eliminated by the host immune system. We show here for the first time that CRISPR/Cas9-mediated cell death via targeting E7 did not result in ICD. Overall, our data show that in vivo CRISPR/Cas targeting of oncogenes is an effective treatment approach for cancer.

Molecular Mechanism of the Antiproliferative Activity of Short Immunostimulating dsRNA

Small double-stranded RNAs with certain sequence motifs are able to interact with pattern-recognition receptors and activate the innate immune system. Recently, we identified a set of short double-stranded 19-bp RNA molecules with 3-nucleotide 3′-overhangs that exhibited pronounced antiproliferative activity against cancer cells in vitro, and antitumor and antimetastatic activities in mouse models in vivo. The main objectives of this study were to identify the pattern recognition receptors that mediate the antiproliferative action of immunostimulating RNA (isRNA). Two cell lines, epidermoid carcinoma KB-3-1 cells and lung cancer A549 cells, were used in the study. These lines respond to the action of isRNA by a decrease in the growth rate, and in the case of A549 cells, also by a secretion of IL-6. Two sets of cell lines with selectively silenced genes encoding potential sensors and signal transducers of isRNA action were obtained on the basis of KB-3-1 and A549 cells. It was found that the selective silencing of PKR and RIG-I genes blocked the antiproliferative effect of isRNA, both in KB-3-1 and A549 cells, whereas the expression of MDA5 and IRF3 was not required for the antiproliferative action of isRNA. It was shown that, along with PKR and RIG-I genes, the expression of IRF3 also plays a role in isRNA mediated IL-6 synthesis in A549 cells. Thus, PKR and RIG-I sensors play a major role in the anti-proliferative signaling triggered by isRNA.

Liposomal Delivery of miR-34b-5p Induced Cancer Cell Death in Thyroid Carcinoma

This study aims to determine the functional roles of microRNA-34b-5p (miR-34b) in the suppression of anaplastic thyroid carcinoma. We used hydration-of-freeze-dried-matrix (HFDM) formulated liposomes (liposome-loaded miR-34b) for effective delivery of miR-34b to anaplastic thyroid carcinoma in vitro and in vivo. Real time polymerase chain was used to determine the level of miR-34b. Immunocytochemistry, Western blot and ELISA were carried out to determine the effect of this manipulation on VEGF-A expression. In addition, an in vivo xenotransplantation mouse model was used to investigate the functional roles of overexpression of miR-34b in the carcinoma. In anaplastic thyroid carcinoma cells, miR-34b expression was low and significant overexpression (p < 0.05) was noted following transfection with liposome-loaded miR-34b. The miR-34b overexpressed thyroid carcinoma cell lines showed reduction in VEGF-A protein expression, decreased cell proliferation, decreased wound healing, reduced cell cycle progression and increased apoptosis (p < 0.05). In in vivo experiments, when compared to control groups, smaller tumours formed upon intravenous administration of liposome-loaded miR-34b. To conclude, the current study confirmed the tumour suppressor properties of miR-34b via VEGF-A regulation in anaplastic thyroid carcinoma. In addition, delivery of miR-34b using cationic liposome could be a useful therapeutic strategy for targeting therapy in the carcinoma.

Advances in Designing and Developing Vaccines, Drugs and Therapeutic Approaches to Counter Human Papilloma Virus

Human papillomavirus (HPV) is a viral infection with skin-to-skin based transmission mode. HPV annually caused over 500,000 cancer cases including cervical, anogenital and oropharyngeal cancer among others. HPV vaccination has become a public-health concern, worldwide, to prevent the cases of HPV infections including precancerous lesions, cervical cancers, and genital warts especially in adolescent female and male population by launching national programs with international alliances. Currently, available prophylactic and therapeutic vaccines are expensive to be used in developing countries for vaccination programs. The recent progress in immunotherapy, biotechnology, recombinant DNA technology and molecular biology along with alternative and complementary medicinal systems have paved novel ways and valuable opportunities to design and develop effective prophylactic and therapeutic vaccines, drugs and treatment approach to counter HPV effectively. Exploration and more researches on such advances could result in the gradual reduction in the incidences of HPV cases across the world. The present review presents a current global scenario and futuristic prospects of the advanced prophylactic and therapeutic approaches against HPV along with recent patents coverage of the progress and advances in drugs, vaccines and therapeutic regimens to effectively combat HPV infections and its cancerous conditions.

Synthetic siRNA targeting human papillomavirus 16 E6: a perspective on in vitro nanotherapeutic approaches

High-risk human papillomaviruses infect skin and mucosa, causing approximately 5% of cancers worldwide. In the search for targeted nanotherapeutic approaches, siRNAs against the viral E6 transcript have been molecules of interest but have not yet seen successful translation into the clinic. By reviewing the past approximately 15 years of in vitro literature, we identify the need for siRNA validation protocols which concurrently evaluate ranges of key treatment parameters as well as characterize downstream process restoration in a methodical, quantitative manner and demonstrate their implementation using our own data. We also reflect on the future need for more appropriate cell culture models to represent patient lesions as well as the application of personalized approaches to identify optimal treatment strategies.

A Simple and Cost-Effective Approach for In Vitro Production of Sliced siRNAs as Potent Triggers for RNAi

We have studied the molecular properties of in-vitro-transcribed sliced small interfering RNAs (tsli-siRNAs) as an alternative RNAi agent for chemically synthesized siRNA. We describe here a simple and cost-effective procedure for high-purity production of tsli-siRNA using bacteriophage T7 RNA polymerases. tsli-siRNAs exhibit potent gene knockdown effects, with efficacy comparable with that of chemically synthesized sli-siRNAs and classical siRNAs. Furthermore, we found that it is very easy to prepare potent tsli-siRNAs with modified bases, such as 2′-fluorine- or biotin-16-modified tsli-siRNAs. tsli-siRNAs can cause a mild innate immune response, which can be easily eliminated by alkaline phosphatase treatment. On the other hand, this feature, which can be useful as a trigger of the innate immune response, can be enhanced by polynucleotide kinase treatment. Because of the simplicity of preparation and purification, the procedure presented here could be useful for the production of RNAi or immunostimulatory reagents.

Immunotherapy of Dual-Function Vector with Both Immunostimulatory and B-Cell Lymphoma 2 (Bcl-2)-Silencing Effects on Gastric Carcinoma

BACKGROUND Tumorigenesis is a kind of pathology marked by infinite proliferation and restrained apoptosis compared with normal cells. The abnormal expression of some proto-oncogenes and apoptosis inhibition are essential for tumor growth, which has been confirmed by molecular biologic and immunologic studies. The hypofunction of the host immune system also drives the development and metastasis of malignant tumors. Bcl-2, which has a critical role in regulating apoptosis, is overexpressed in several cancers. MATERIAL AND METHODS In this study, we constructed a dual-function small hairpin RNA (shRNA) vector containing an Bcl-2-silencing shRNA and a TLR7-stimulating ssRNA and examined it effect on tumor cell growth and proliferation. RESULTS Stimulation with this bi-functional vector in vitro promoted significant apoptosis of MFC cells by regulating the expression of apoptosis-related proteins and induced secretion of type I IFNs. Most importantly, this bi-functional vector more effectively inhibited subcutaneous MFC cell growth than did single shRNA and ssRNA treatment in vivo. Natural killer (NK) and CD4+ T cells were required for effective tumor suppression, and TLR7 was shown to play a helper role in the activation of NK cells and CD4+ T cells, possibly by regulating the expression of receptors or secretion of cytokines. CONCLUSIONS This bi-functional vector that contained ssRNA and shRNA may represent a promising approach for tumor therapy.

Rabies virus lipopeptide conjugated to a TLR7 agonist improves the magnitude and quality of the Th1-biased humoral immune response in mice

In this study, we conjugated the rabies-derived lipopeptide CE536 to a TLR7 agonist, imiquimod, and evaluated its adjuvanticity. The synthetic construct (Lipo-I) targeted to TLR7, induced dendritic cell phenotypic maturation and production of both type I interferon and pro-inflammatory cytokines more efficiently than unconjugated TLR7 ligands or lipopeptide alone. The immunostimulatory effects of the conjugate were apparently the result of IκBα degradation and sustained p38 and JNK phosphorylation. The analysis of IgG isotypes and T cell differentiation showed that IgG2a dominant Th1-biased humoral and CD8(+) IFN-γ T cell responses were induced by Lipo-I. Lipo-I could facilitate the rabies vaccine to induce the production of an earlier and more vigorous rabies virus neutralizing antibody. In the post-exposure test, the Lipo-I adjuvanted vaccine provided a 73.3% survival rate, while the traditional vaccine bestowed only a 26.7% survival. Therefore, Lipo-I is a promising adjuvant for the development of more effective rabies vaccines.

Antitumor and Antimetastatic Effect of Small Immunostimulatory RNA against B16 Melanoma in Mice

Small interfering RNAs, depending on their structure, delivery system and sequence, can stimulate innate and adaptive immunity. The aim of this study was to investigate the antitumor and antimetastatic effects of immunostimulatory 19-bp dsRNA with 3'- trinucleotide overhangs (isRNA) on melanoma B16 in C57Bl/6 mice. Recently developed novel cationic liposomes 2X3-DOPE were used for the in vivo delivery of isRNA. Administration of isRNA/2X3-DOPE complexes significantly inhibits melanoma tumor growth and metastasis. Histopathological analysis of spleen cross sections showed hyperplasia of the lymphoid white pulp and formation of large germinal centers after isRNA/2X3-DOPE administration, indicating activation of the immune system. The treatment of melanoma-bearing mice with isRNA/2X3-DOPE decreases the destructive changes in the liver parenchyma. Thus, the developed isRNA displays pronounced immunostimulatory, antitumor and antimetastatic properties against melanoma B16 and may be considered a potential agent in the immunotherapy of melanoma.

siRNA and RNAi optimization

The discovery and examination of the posttranscriptional gene regulatory mechanism known as RNA interference (RNAi) contributed to the identification of small interfering RNA (siRNA) and the comprehension of its enormous potential for clinical purposes. Theoretically, the ability of specific target gene downregulation makes the RNAi pathway an appealing solution for several diseases. Despite numerous hurdles resulting from the inherent properties of siRNA molecule and proper delivery to the target tissue, more than 50 RNA-based drugs are currently under clinical testing. In this work, we analyze the recent literature in the optimization of siRNA molecules. In detail, we focused on describing the most recent advances of siRNA field aimed at optimize siRNA pharmacokinetic properties. Special attention has been given in describing the impact of RNA modifications in the potential off-target effects (OTEs) such as saturation of the RNAi machinery, passenger strand-mediated silencing, immunostimulation, and miRNA-like OTEs as well as to recent developments on the delivery issue. The novel delivery systems and modified siRNA provide significant steps toward the development of reliable siRNA molecules for therapeutic use. WIREs RNA 2016, 7:316-329. doi: 10.1002/wrna.1337 For further resources related to this article, please visit the WIREs website.

2'Fluoro Modification Differentially Modulates the Ability of RNAs to Activate Pattern Recognition Receptors

Although the use of RNAs has enormous therapeutic potential, these RNA-based therapies can trigger unwanted inflammatory responses by the activation of pattern recognition receptors (PRRs) and cause harmful side effects. In contrast, the immune activation by therapeutic RNAs can be advantageous for treating cancers. Thus, the immunogenicity of therapeutic RNAs should be deliberately controlled depending on the therapeutic applications of RNAs. In this study, we demonstrated that RNAs containing 2'fluoro (2'F) pyrimidines differentially controlled the activation of PRRs. The activity of RNAs that stimulate toll-like receptors 3 and 7 was abrogated by the incorporation of 2'F pyrimidine. By contrast, incorporation of 2'F pyrimidines enhanced the activity of retinoic acid-inducible gene 1-stimulating RNAs. Furthermore, we found that transfection with RNAs containing 2'F pyrimidine and 5' triphosphate (5'ppp) increased cell death and interferon-β expression in human cancer cells compared with transfection with 2'hydroxyl 5'ppp RNAs, whereas RNAs containing 2'O-methyl pyrimidine and 5'ppp completely abolished the induction of cell death and cytokine expression in the cells. Our findings suggest that incorporation of 2'F and 2'O-methyl nucleosides is a facile approach to differentially control the ability of therapeutic RNAs to activate or limit immune and inflammatory responses depending on therapeutic applications.

Immunotherapy of hepatocellular carcinoma with small double-stranded RNA

Background

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide with limited therapeutic options. Since HCC has been shown to be immunogenic, immunotherapy is considered a promising therapeutic approach. Small interfering RNAs (siRNAs), depending on their structure and sequence, can trigger the innate immune system, which can potentially enhance the adaptive anticancer immune response in the tumor-bearing subjects. Immunostimulatory properties of nucleic acids can be applied to develop adjuvants for HCC treatment.

Methods

The transplantable HCC G-29 tumor in male CBA/LacSto (CBA) mice was used to study the effects of immunostimulatory RNA on tumor growth. Tumor size, metastases area in different organs of mice and mouse survival rate were analyzed. Furthermore the mouse serum IFN-α levels were measured using ELISA.

Results

In the present study, we found that a 19-bp RNA duplex (ImmunoStimulattory RNA or isRNA) with 3-nt overhangs at the 3′-ends of specific sequence displays immunostimulatory, antitumor, and antimetastatic activities in mice bearing HCC G-29. Our results demonstrate that isRNA strongly increases the level of interferon-α (IFN-α) by up to 25-fold relative to the level in mice injected with Lipofectamine alone (Mock), and to a lesser extent increases the level of proinflammatory cytokine interleukin-6 (IL-6) (by up to 5.5-fold relative to the Mock level), in mice blood serum. We showed that isRNA reliably (P < 0.05) inhibits primary tumor growth in mice compared to the mock group. Furthermore, injections of isRNA significantly enhanced necrotic processes in the center of the primary tumor, and decreased by twofold the width of the undifferentiated peripheral zone and the number of mitotic cells in this zone. The results showed that isRNA efficiently reduces the area of metastases in the liver, kidneys, and heart of CBA/LacSto mice with HCC.

Conclusions

The obtained results clearly demonstrate immunostimulatory and antimetastatic properties of the isRNAs in mice with HCC. Consequently, this short double-stranded RNA can be considered as a potential adjuvant for the therapy of HCC.

Immunotherapy for hepatoma using a dual-function vector with both immunostimulatory and pim-3-silencing effects

Tumorigenesis is an immortalization process in which the growth of normal cells is uncontrolled and programmed cell death is suppressed. Molecular biologic and immunologic studies have revealed that the aberrant expression of some proto-oncogenes boosts proliferation and inhibits apoptosis, which is vital for tumor development. The hypofunction of the host immune system also drives the development and metastasis of malignant tumors. Pim-3, a member of the Pim family, is aberrantly expressed in several cancers. Data suggest that Pim-3 inhibits apoptosis by phosphorylating the proapoptotic BH3-only protein Bad. Here, we constructed a dual-function small hairpin RNA (shRNA) vector containing an shRNA targeting Pim-3 and a TLR7-stimulating ssRNA. Stimulation with this bi-functional vector in vitro promoted significant apoptosis of Hepa1-6 cells by regulating the expression of apoptosis-related proteins and induced secretion of type I IFNs. Most importantly, this bi-functional vector more effectively inhibited subcutaneous Hepa1-6 cell growth than did single shRNA and ssRNA treatment in vivo. Natural killer (NK), CD4(+) T, and CD8(+) T cells and macrophages were required for effective tumor suppression, and CD4(+) T cells were shown to play a helper role in the activation of NK cells, possibly by regulating the secretion of Th1 or Th2 cytokines. This ssRNA-shRNA bi-functional vector may represent a promising approach for tumor therapy.

Restoration of MAGI-1 expression in human papillomavirus-positive tumor cells induces cell growth arrest and apoptosis

The cancer-causing high-risk human papillomavirus (HPV) E6 oncoproteins target a number of cellular proteins that contain PDZ domains. However, the role of many of these interactions in either the HPV life cycle or in HPV-induced malignancy remains to be defined. Previous studies had shown that MAGI-1 was one of the most strongly bound PDZ domain-containing substrates of E6, and one consequence of this interaction appeared to facilitate the perturbation of tight junctions (TJs) by E6. In this study, we describe the generation of a mutation, K499E, within the MAGI-1 PDZ1 domain, which is resistant to E6 targeting. This mutant allows restoration of MAGI-1 expression in HPV-positive cells and defines additional activities of MAGI-1 that are overcome as a consequence of the association with E6. The reexpression of MAGI-1 in HPV-positive cells results in an increased recruitment of ZO-1 and PAR3 to sites of cell-cell contact, repression of cell proliferation, and induction of apoptosis. While the K499E mutation does not significantly affect these intrinsic activities of MAGI-1 in HPV-negative cells, its resistance to E6 targeting in an HPV-positive setting results in more cells expressing the mutant MAGI-1 than the wild-type MAGI-1, with a corresponding increase in TJ assembly, induction of apoptosis, and reduction in cell proliferation. These studies provide compelling evidence of a direct role for the perturbation of MAGI-1 function by E6 in the HPV life cycle and in HPV-induced malignancy.

IMPORTANCE

It is clear that the targeting of PDZ-containing substrates by E6 is important for the normal viral life cycle and for the progression to malignancy. Nevertheless, which of these PDZ domain-containing proteins is relevant for HPV pathology is still elusive. In a previous study, we provided evidence that MAGI-1 is a sensitive proteolytic substrate for both the HPV-16 and HPV-18 E6 oncoproteins; however, the biological consequences associated with loss of MAGI-1 expression in HPV-positive cervical cancer cells are still poorly understood. Using a mutant MAGI-1, resistant to E6-mediated degradation, we show that its expression in cervical cancer cells promotes membrane recruitment of the tight junction-associated proteins ZO-1 and PAR3, represses cell proliferation, and promotes apoptosis. These findings suggest that E6-mediated inhibition of MAGI-1 function contributes to HPV pathology by perturbing tight junction assembly with concomitant stimulation of proliferation and inhibition of apoptosis.

Challenging the future of siRNA therapeutics against cancer: the crucial role of nanotechnology

The identification of numerous deregulated signaling pathways on cancer cells and supportive stromal cells has revealed several molecular targets whose downregulation can elicit significant benefits for cancer treatment. In this respect, gene downregulation can be efficiently achieved by exploiting the RNA interference mechanism, particularly by the delivery of chemical synthesized small-interfering RNAs (siRNAs), which have the ability to mediate, in a specific manner, the degradation of any mRNA with complementary nucleotide sequence. However, several concerns regarding off-target effects and immune stimulation have been raised. Depending on their sequence, siRNAs can trigger an innate immune response, which might mediate undesirable side effects that ultimately compromise their clinical utility. This is a very relevant effect that will be discussed in the present manuscript. Moreover, the major drawback in the translation of siRNAs into the clinical practice is undoubtedly their inability to accumulate in tumor sites, particularly in organs other than the liver. In fact, upon systemic administration, owing to siRNAs physico-chemical features, they are rapidly cleared from the blood stream. Therefore, the development of a proper drug delivery system is of utmost importance. In this review, some of the latest advances on different nanotechnological platforms for siRNA delivery under clinical evaluation will be discussed. Along with this, targeting approaches towards cancer and/or endothelial cells will also be addressed, as these are some of the most promising strategies to enhance specific tumor accumulation while avoiding healthy tissues. Finally, clinical information on ongoing studies in patients with advanced solid tumors will be also provided.

2'-OMe-phosphorodithioate-modified siRNAs show increased loading into the RISC complex and enhanced anti-tumour activity

Improving small interfering RNA (siRNA) efficacy in target cell populations remains a challenge to its clinical implementation. Here, we report a chemical modification, consisting of phosphorodithioate (PS2) and 2'-O-Methyl (2'-OMe) MePS2 on one nucleotide that significantly enhances potency and resistance to degradation for various siRNAs. We find enhanced potency stems from an unforeseen increase in siRNA loading to the RNA-induced silencing complex, likely due to the unique interaction mediated by 2'-OMe and PS2. We demonstrate the therapeutic utility of MePS2 siRNAs in chemoresistant ovarian cancer mouse models via targeting GRAM domain containing 1B (GRAMD1B), a protein involved in chemoresistance. GRAMD1B silencing is achieved in tumours following MePS2-modified siRNA treatment, leading to a synergistic anti-tumour effect in combination with paclitaxel. Given the previously limited success in enhancing siRNA potency with chemically modified siRNAs, our findings represent an important advance in siRNA design with the potential for application in numerous cancer types.

In vivo comparison of local versus systemic delivery of immunostimulating siRNA in HPV-driven tumours

Small interfering RNAs (siRNAs) to inhibit oncogene expression and also to activate innate immune responses via Toll-like receptor (TLR) recognition have been shown to be beneficial as anti-cancer therapy in certain cancer models. In this study, we investigated the effects of local versus systemic delivery of such immune-stimulating Dicer-substrate siRNAs (IS-DsiRNAs) on a human papillomavirus (HPV)-driven tumour model. Localized siRNA delivery using intratumour injection of siRNA was able to increase siRNA delivery to the tumour compared with intravenous (IV) delivery and potently activated innate immune responses. However, IV injection remained the more effective delivery route for reducing tumour growth. Although IS-DsiRNAs activated innate immune cells and required interferon-α (IFNα) for full effect on tumour growth, we found that potent silencing siRNA acting independently of IFNα were overall more effective at inhibiting TC-1 tumour growth. Other published work utilising IS-siRNAs have been carried out on tumour models with low levels of major histocompatibility complex (MHC)-class 1, a target of natural killer cells that are potently activated by IS-siRNA. As TC-1 cells used in our study express high levels of MHC-class I, the addition of the immunostimulatory motifs may not be as beneficial in this particular tumour model. Our data suggest that selection of siRNA profile and delivery method based on tumour environment is crucial to developing siRNA-based therapies.

Nanomedicine therapeutic approaches to overcome cancer drug resistance

Nanomedicine is an emerging form of therapy that focuses on alternative drug delivery and improvement of the treatment efficacy while reducing detrimental side effects to normal tissues. Cancer drug resistance is a complicated process that involves multiple mechanisms. Here we discuss the major forms of drug resistance and the new possibilities that nanomedicines offer to overcome these treatment obstacles. Novel nanomedicines that have a high ability for flexible, fast drug design and production based on tumor genetic profiles can be created making drug selection for personal patient treatment much more intensive and effective. This review aims to demonstrate the advantage of the young medical science field, nanomedicine, for overcoming cancer drug resistance. With the advanced design and alternative mechanisms of drug delivery known for different nanodrugs including liposomes, polymer conjugates, micelles, dendrimers, carbon-based, and metallic nanoparticles, overcoming various forms of multi-drug resistance looks promising and opens new horizons for cancer treatment.

Therapeutic recovery of hepatitis B virus (HBV)-induced hepatocyte-intrinsic immune defect reverses systemic adaptive immune tolerance

Hepatitis B virus (HBV) persistence aggravates hepatic immunotolerance, leading to the failure of cell-intrinsic type I interferon and antiviral response, but whether and how HBV-induced hepatocyte-intrinsic tolerance influences systemic adaptive immunity has never been reported, which is becoming the major obstacle for chronic HBV therapy. In this study, an HBV-persistent mouse, established by hydrodynamic injection of an HBV-genome-containing plasmid, exhibited not only hepatocyte-intrinsic but also systemic immunotolerance to HBV rechallenge. HBV-specific CD8(+) T-cell and anti-HBs antibody generation were systemically impaired by HBV persistence in hepatocytes. Interestingly, HBV-induced hepatocyte-intrinsic immune tolerance was reversed when a dually functional vector containing both an immunostimulating single-stranded RNA (ssRNA) and an HBx-silencing short hairpin RNA (shRNA) was administered, and the systemic anti-HBV adaptive immune responses, including CD8(+) T-cell and anti-HBs antibody responses, were efficiently recovered. During this process, CD8(+) T cells and interferon-gamma (IFN-γ) secreted play a critical role in clearance of HBV. However, when IFN-α/β receptor was blocked or the Toll-like receptor (TLR)7 signaling pathway was inhibited, the activation of CD8(+) T cells and clearance of HBV was significantly impaired.

CONCLUSION

These results suggest that recovery of HBV-impaired hepatocyte-intrinsic innate immunity by the dually functional vector might overcome systemic adaptive immunotolerance in an IFN-α- and TLR7-dependent manner. The strategy holds promise for therapeutic intervention of chronic persistent virus infection and associated cancers.

Efficient Biodistribution and Gene Silencing in the Lung epithelium via Intravenous Liposomal Delivery of siRNA

RNA interference (RNAi) may provide a therapeutic solution to many pulmonary epithelium diseases. However, the main barrier to the clinical use of RNAi remains the lack of efficient delivery vectors. Research has mainly concentrated on the intranasal route of delivery of short interfering RNA (siRNA) effector molecules for the treatment of respiratory diseases. However, this may be complicated in a diseased state due to the increased fluid production and tissue remodeling. Therefore, we investigated our hydration of a freeze-dried matrix (HFDM) formulated liposomes for systemic delivery to the lung epithelium. Here, we show that 45 ± 2% of epithelial murine lung cells receive siRNA delivery upon intravenous (IV) liposomal administration. Furthermore, we demonstrate that liposomal siRNA delivery resulted in targeted gene and protein knockdown throughout the lung, including lung epithelium. Taken together, this is the first description of lung epithelial delivery via cationic liposomes, and provides a proof of concept for the use of IV liposomal RNAi delivery to specifically knockdown targeted genes in the respiratory system. This approach may provide an attractive alternate therapeutic delivery strategy for the treatment of lung epithelium diseases.

Potent inhibition of Hendra virus infection via RNA interference and poly I:C immune activation

Hendra virus (HeV) is a highly pathogenic zoonotic paramyxovirus that causes fatal disease in a wide range of species, including humans. HeV was first described in Australia in 1994, and has continued to re-emerge with increasing frequency. HeV is of significant concern to human health due to its high mortality rate, increasing emergence, absence of vaccines and limited post exposure therapies. Here we investigate the use of RNA interference (RNAi) based therapeutics targeting HeV in conjunction with the TLR3 agonist Poly I:C and show that they are potent inhibitors of HeV infection in vitro. We found that short interfering RNAs (siRNAs) targeting the abundantly expressed N, P and M genes of HeV caused over 95% reduction of HeV virus titre, protein and mRNA. Furthermore, we found that the combination of HeV targeting siRNA and Poly I:C had an additive effect in suppressing HeV infection. Our results demonstrate for the first time that RNAi and type I interferon stimulation are effective inhibitors of HeV replication in vitro and may provide an effective therapy for this highly lethal, zoonotic pathogen.

siRNA and cancer immunotherapy

Immunotherapeutic approaches have been gaining attention in the field of cancer treatment because of their possible ability to eradicate cancer cells as well as metastases by recruiting the host immune system. On the other hand, RNA-based therapeutics with the ability to silence expression of specific targets are currently under clinical investigation for various disorders including cancer. As the mechanisms of tumor evasion from the host immune system are versatile, different molecules have the capacity to be targeted by RNAi technology in order to enhance the immune response against tumors. This technology has been used to silence specific targets in tumor cells, as well as immune cells in cancer cell lines, animal models and clinical trials. siRNAs can also stimulate innate immune responses through activation of Toll-like receptors. Although currently clinical trials of the application of siRNA in cancer immunotherapy are few, it is predicted that in future this technology will be used broadly in cancer treatment.

Toll-like receptors in human papillomavirus infection

Infection with human papillomaviruses (HPVs) often causes cutaneous benign lesions, cervical cancer, and a number of other tumors. The mechanisms of host immune system to prevent and control HPV infection still remain poorly understood. Toll-like receptors (TLRs) are specific pattern recognition molecules that bind to microbial components to trigger innate immunity and direct adaptive immunity in the face of immunological danger. TLRs have been established to play an essential role in sensing and initiating antiviral immune responses. Recent accumulating evidence demonstrated that HPVs modulate TLR expression and interfere with TLR signaling pathways, leading to persistent viral infection and carcinogenesis. This review summarizes current knowledge on the roles of TLR during HPV infection, focusing on TLR recognition, modulation of TLR expression and signaling, regulatory receptors involved in TLR signaling, and cross-talk of TLRs with antimicrobial peptides. Immunotherapeutic strategies based on TLR agonists have emerged to be one of the novel promising avenues in treatment of HPV-associated diseases in the future.

Learning from the messengers: innate sensing of viruses and cytokine regulation of immunity - clues for treatments and vaccines

Virus infections are a major global public health concern, and only via substantial knowledge of virus pathogenesis and antiviral immune responses can we develop and improve medical treatments, and preventive and therapeutic vaccines. Innate immunity and the shaping of efficient early immune responses are essential for control of viral infections. In order to trigger an efficient antiviral defense, the host senses the invading microbe via pattern recognition receptors (PRRs), recognizing distinct conserved pathogen-associated molecular patterns (PAMPs). The innate sensing of the invading virus results in intracellular signal transduction and subsequent production of interferons (IFNs) and proinflammatory cytokines. Cytokines, including IFNs and chemokines, are vital molecules of antiviral defense regulating cell activation, differentiation of cells, and, not least, exerting direct antiviral effects. Cytokines shape and modulate the immune response and IFNs are principle antiviral mediators initiating antiviral response through induction of antiviral proteins. In the present review, I describe and discuss the current knowledge on early virus–host interactions, focusing on early recognition of virus infection and the resulting expression of type I and type III IFNs, proinflammatory cytokines, and intracellular antiviral mediators. In addition, the review elucidates how targeted stimulation of innate sensors, such as toll-like receptors (TLRs) and intracellular RNA and DNA sensors, may be used therapeutically. Moreover, I present and discuss data showing how current antimicrobial therapies, including antibiotics and antiviral medication, may interfere with, or improve, immune response.

RNA interference for the treatment of papillomavirus disease

Human Papillomavirus (HPV)-induced diseases are a significant burden on our healthcare system and current therapies are not curative. Vaccination provides significant prophylactic protection but effective therapeutic treatments will still be required. RNA interference (RNAi) has great promise in providing highly specific therapies for all HPV diseases yet this promise has not been realised. Here we review the research into RNAi therapy for HPV in vitro and in vivo and examine the various targets and outcomes. We discuss the idea of using RNAi with current treatments and address delivery of RNAi, the major issue holding back clinical adoption. Finally, we present our view of a potential path to the clinic.

Human Toll-like receptor 8 can be cool too: implications for foreign RNA sensing

Recent advances in our understanding of foreign nucleic acid sensing indicate an important role for the human Toll-like receptor (TLR) 8 in the initiation of immune responses to certain pathogens. However, TLR8, far too often grouped together with TLR7 for its common ability to detect RNA, has a function on its own in the initiation of specific proinflammatory responses to viruses and bacteria. Here, we present an overview of what is currently known of human TLR8 biology, from genetic regulation to its function in innate immunity, and discuss how TLR8 could present novel therapeutic opportunities in viral and cancer diseases.

RNA mediated Toll-like receptor stimulation in health and disease

Besides their well known functions in storage and translation of information nucleic acids have emerged as a target of pattern recognition receptors that drive activation of innate immunity. Due to the paucity of building block monomers used in nucleic acids, discrimination of host and microbial nucleic acids as a means of self/foreign discrimination is a complicated task. Pattern recognition receptors rely on discrimination by sequence, structural features and spatial compartmentalization to differentiate microbial derived nucleic acids from host ones. Microbial nucleic acid detection is important for the sensing of infectious danger and initiating an immune response to microbial attack. Failures in the underlying recognitions systems can have severe consequences: thus, inefficient recognition of microbial nucleic acids may increase susceptibility to infectious diseases. On the other hand, excessive immune responses as a result of failed self/foreign discrimination are associated with autoimmune diseases. This review gives a general overview over the underlying concepts of nucleic acid sensing by Toll-like receptors. Within this general framework, we focus on bacterial RNA and synthetic RNA oligomers.

Involvement of activation of PKR in HBx-siRNA-mediated innate immune effects on HBV inhibition

RNA interference (RNAi) of virus-specific genes offers the possibility of developing a new anti-hepatitis B virus (anti-HBV) therapy. Recent studies have revealed that siRNAs can induce an innate immune response in vitro and in vivo. Here, HBVx (HBx) mRNA expression and HBV replication were significantly inhibited, followed by the enhancement of expression of type I interferons (IFNs), IFN-stimulated genes (ISG15 and ISG56) and proinflammatory cytokines after HepG2.2.15 cells were transfected with chemically synthesized HBx-siRNAs. Transfection with HBx-siRNAs also significantly increased expression of dsRNA-dependent protein kinase R (PKR) in HepG2.2.15 cells, followed by activation of downstream signaling events such as eukaryotic initiation factor 2α (eIF2-α). In PKR-over-expressing HepG2.2.15 cells, HBx-siRNAs exerted more potent inhibitory effects on HBV replication and greater production of type I IFNs. By contrast, the inhibitory effect of HBx-siRNAs on HBV replication was attenuated when PKR was inhibited or silenced, demonstrating that HBx-siRNAs greatly promoted PKR activation, leading to the higher production of type I IFN. Therefore, we concluded that PKR is involved in the innate immune effects mediated by HBx-siRNAs and further contributes to HBV inhibition. The bifunctional siRNAs with both gene silencing and innate immune activation properties may represent a new potential strategy for treatment of HBV.

Silencing disease genes in the laboratory and the clinic

Synthetic nucleic acids are commonly used laboratory tools for modulating gene expression and have the potential to be widely used in the clinic. Progress towards nucleic acid drugs, however, has been slow and many challenges remain to be overcome before their full impact on patient care can be understood. Antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs) are the two most widely used strategies for silencing gene expression. We first describe these two approaches and contrast their relative strengths and weaknesses for laboratory applications. We then review the choices faced during development of clinical candidates and the current state of clinical trials. Attitudes towards clinical development of nucleic acid silencing strategies have repeatedly swung from optimism to depression during the past 20 years. Our goal is to provide the information needed to design robust studies with oligonucleotides, making use of the strengths of each oligonucleotide technology.