RNAi-based Therapy Research Articles

Preclinical and Clinical Development of Noncoding RNA Therapeutics for Cardiovascular Disease.

RNA modulation has become a promising therapeutic approach for the treatment of several types of disease. The emerging field of noncoding RNA-based therapies has now come to the attention of cardiovascular research, in which it could provide valuable advancements in comparison to current pharmacotherapy such as small molecule drugs or antibodies. In this review, we focus on noncoding RNA-based studies conducted mainly in large-animal models, including pigs, rabbits, dogs, and nonhuman primates. The obstacles and promises of targeting long noncoding RNAs and circRNAs as therapeutic modalities in humans are specifically discussed. We also describe novel ex vivo methods based on human cells and tissues, such as engineered heart tissues and living myocardial slices that could help bridging the gap between in vivo models and clinical applications in the future. Finally, we summarize antisense oligonucleotide drugs that have already been approved by the Food and Drug Administration for targeting mRNAs and discuss the progress of noncoding RNA-based drugs in clinical trials. Additional factors, such as drug chemistry, drug formulations, different routes of administration, and the advantages of RNA-based drugs, are also included in the present review. Recently, first therapeutic miRNA-based inhibitory strategies have been tested in heart failure patients as well as healthy volunteers to study effects on wound healing (NCT04045405; NCT03603431). In summary, a combination of novel therapeutic RNA targets, large-animal models, ex vivo studies with human cells/tissues, and new delivery techniques will likely lead to significant progress in the development of noncoding RNA-based next-generation therapeutics for cardiovascular disease.

Abstract P3-10-19: Precise targeting of POLR2A for treating triple negative breast cancer with Chr17p loss

Abstract Triple-negative breast cancer (TNBC) is a molecularly diverse and clinically heterogeneous disease. The challenges for developing novel treatment approaches for TNBC are the paucity of actionable targets, lack of targeted therapies, and poor prognosis of patients. Breast cancer genomics revealed that heterozygous deletion of chromosome 17p (Chr17p) is the most prevalent (53%) event in TNBC. Within the 17p deletion region is the tumor suppressor TP53 (encoding p53), whose deletion or mutation has been long known as a primary tumorigenic driver. However, it remains unclear whether the deletion event, which often includes as many as 200 genes, impacts tumorigenesis beyond TP53 loss alone. While p53 aberrancy promotes proliferation, metabolism and metastatic potential of the TNBC cells, we found that heterozygous deletion of Chr17p is tightly correlated with poor cytotoxicity of tumor infiltrating lymphocytes (TILs) and poor clinical outcomes in patients with TNBC. This result suggests that selective advantage due to Chr17p loss reflects the combined impact of TP53 loss and the reduced dosage of co-deleted genes. Our recent study also identified POLR2A in the TP53-neighboring region as a collateral vulnerability target in the TNBC tumors with Chr17p loss, suggesting that inhibition of POLR2A may be a precision therapy approach for TNBC. As a proof-of-concept, we designed pH-activated nanoparticles (termed as nanobomb) for delivery of POLR2A siRNA, which enhances bioavailability and improves endo/lysosomal escape of the siRNA. In this study (Nature Nanotechnology, 2019)1, we demonstrated that suppressing POLR2A expression with the siRNA-laden nanoparticles led to marked growth reduction of TNBC tumors with 17p loss. Despite recent success of the first FDA-approved RNAi-based therapy for polyneuropathy, the issues of RNAi-based drugs, such as non-specific and incomplete knockdown, can make RNAi unpredictable, slow, and risky, in particular in drug discovery, where speed and reliability of results are crucial factors. To accelerate the translational development of our important finding, we will use α-amanitin, a natural small compound isolated from Amanita phalloides, to specifically inhibit POLR2A (Kd ∼10−9 M). However, free form of α-amanitin causes liver toxicity via the interaction with the hepatocyte-specific OATP1B3 transporter, limiting its clinical applications. To overcome the drug toxicity of α-amanitin, we have been developing α-amanitin-based antibody-drug conjugates (ADC). This approach inhibits the specific uptake of α-amanitin into hepatocytes and increases tumor-specific targeting using tumor-specific monoclonal antibodies. This type of ADC showed significant efficacy in inhibiting the growth of colorectal tumors with heterozygous deletion of TP53 and POLR2A (Nature, 2015)2. Here, we propose that heterozygous deletion of Chr17p not only contributes to TNBC tumorigenesis, but also confers therapeutic vulnerabilities, which can be utilized to develop novel targeted cancer therapy. Refernces 1. Xu,J. et al. Precise targeting of POLR2A as a therapeutic strategy for human triple negative breast cancer. Nat. Nanotechnol. 14, 388-397 (2019). 2. Liu,Y. et al. TP53 loss creates therapeutic vulnerability in colorectal cancer. Nature 520, 697-701 (2015). Citation Format: Xiongbin Lu, Yujing Li, Yifan Sun, Kevin Van der Jeught, Michael Kulke, Pahl Andreas, Xinna Zhang, Xiaoming He, Chi Zhang. Precise targeting of POLR2A for treating triple negative breast cancer with Chr17p loss [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-10-19.

RNA-Based Therapeutics: From Antisense Oligonucleotides to miRNAs.

The first therapeutic nucleic acid, a DNA oligonucleotide, was approved for clinical use in 1998. Twenty years later, in 2018, the first therapeutic RNA-based oligonucleotide was United States Food and Drug Administration (FDA) approved. This promises to be a rapidly expanding market, as many emerging biopharmaceutical companies are developing RNA interference (RNAi)-based, and RNA-based antisense oligonucleotide therapies. However, miRNA therapeutics are noticeably absent. miRNAs are regulatory RNAs that regulate gene expression. In disease states, the expression of many miRNAs is measurably altered. The potential of miRNAs as therapies and therapeutic targets has long been discussed and in the context of a wide variety of infections and diseases. Despite the great number of studies identifying miRNAs as potential therapeutic targets, only a handful of miRNA-targeting drugs (mimics or inhibitors) have entered clinical trials. In this review, we will discuss whether the investment in finding potential miRNA therapeutic targets has yielded feasible and practicable results, the benefits and obstacles of miRNAs as therapeutic targets, and the potential future of the field.

STAT1 and STAT2 Null Cells Are Resistant to RNA-Induced Apoptosis Due to Deficiency in Constitutive and Inducible Apoptosis-Regulating Genes

Although much progress has been made in identifying the signaling pathways that mediate viral RNA-induced apoptosis and activation of interferon-stimulated genes, the role that bacterial RNA plays in regulating these responses has remained undetermined. Herein, we identified bacterial RNA as a novel inducer of the apoptotic cell death. Unlike the parental cells, STAT1 and STAT2 mutants display apoptotic defects which were reversed by restoring the expression of wild type proteins. While STAT1 mutants lacking tyrosine-701 or a functional SH2 domain were effective as the wild-type protein in restoring the apoptotic response, the mutant carrying a point mutation at serine-727 of STAT1 was resistant to bacterial RNA-induced apoptosis. We also determined that the lack of apoptosis in the STAT1 and STAT2 mutants was correlated with the constitutive and inducible activation of apoptosis regulating proteins. Furthermore, we show that bacterial RNA induces transcriptional activation of STAT1, STAT2, IRF1, and ISGF3, which was impaired in STAT1 or STAT2 mutants. These observations suggested that the participation of STATs in regulating the apoptotic response is independent of their downstream functions as cytokine-induced transcriptional activators. In addition to bacterial immunity, the results presented here may also have implications in cellular pathophysiology and RNA-based therapy.

A Light-Triggerable Nanoparticle Library for the Controlled Release of Non-Coding RNAs.

RNA-based therapies offer a wide range of therapeutic interventions including the treatment of skin diseases; however, the strategies to efficiently deliver these biomolecules are still limited due to obstacles related to the cellular uptake and cytoplasmic delivery. Herein, we report the synthesis of a triggerable polymeric nanoparticle (NP) library composed of 160 formulations, presenting physico-chemical diversity and differential responsiveness to light. Six formulations were more efficient (up to 500 %) than commercially available lipofectamine in gene-knockdown activity. These formulations showed differential internalization by skin cells and the endosomal escape was rapid (minutes range). The NPs were effective in the release of siRNA and miRNA. Acute skin wounds treated with the top hit NP complexed with miRNA-150-5p healed faster than wounds treated with scrambled miRNA. Light-activatable NPs offer a new strategy to topically deliver non-coding RNAs.

EBV microRNA-BHRF1-2-5p targets the 3′UTR of immune checkpoint ligands PD-L1 and PD-L2

AbstractEpstein-Barr virus–positive (EBV+) diffuse large B-cell lymphomas (DLBCLs) express high levels of programmed death ligand 1 (PD-L1) and PD-L2. MicroRNA (miR) regulation is an important mechanism for the fine-tuning of gene expression via 3′-untranslated region (3′UTR) targeting, and we have previously demonstrated strong EBV miR expression in EBV+ DLBCL. Whereas the EBV latent membrane protein-1 (LMP1) is known to induce PD-L1/L2, a potential counterregulatory role of EBV miR in the fine-tuning of PD-L1/L2 expression remains to be established. To examine this, a novel in vitro model of EBV+ DLBCL was developed, using the viral strain EBV WIL, which unlike common laboratory strains retains intact noncoding regions where several EBV miRs reside. This enabled interrogation of the relationship among EBV latency genes, cell of origin (COO), PD-L1, PD-L2, and EBV miRs. The model successfully recapitulated the full spectrum of B-cell differentiation, with 4 discrete COO phases: early and late germinal center B cells (GCBs) and early and late activated B cells (ABCs). Interestingly, PD-L1/L2 levels increased markedly during transition from late GCB to early ABC phase, after LMP1 upregulation. EBV miR–BamHI fragment H rightward open reading frame 1 (BHRF1)–2-5p clustered apart from other EBV miRs, rising during late GCB phase. Bioinformatic prediction, together with functional validation, confirmed EBV miR-BHRF1-2-5p bound to PD-L1 and PD-L2 3′UTRs to reduce PD-L1/L2 surface protein expression. Results indicate a novel mechanism by which EBV miR-BHRF1-2-5p plays a context-dependent counterregulatory role to fine-tune the expression of the LMP1-driven amplification of these inhibitory checkpoint ligands. Further identification of immune checkpoint–targeting miRs may enable potential novel RNA-based therapies to emerge.

Novo teams with Dicerna for RNAi drugs

Novo Nordisk will pay Dicerna Pharmaceuticals $225 million, which includes up-front fees and an equity investment, as part of a broad collaboration to develop RNAi-based therapies targeting liver-related diseases. Dicerna’s technology platform hinges on using a substrate for an enzyme called Dicer to deliver a drug into cells, where it can turn off a specific gene. The companies will work on more than 30 liver cell targets, including ones implicated in nonalcoholic steatohepatitis, type 2 diabetes, and obesity.

BRC-mediated RNAi targeting of USE1 inhibits tumor growth in vitro and in vivo

USE1 has been demonstrated to play crucial roles in the development and progression of human lung cancer. However, the antitumor efficacy of RNA interference (RNAi) targeting of USE1 has not yet been evaluated as a possible clinical application. We here synthesized USE1 targeting bubbled RNA-based cargo (BRC) composed of densely packed multimeric pre-siRNAs with specific Dicer cleavage sites to enable efficient siRNA release upon entry to target cells. The physical entanglement and continuous networking of RNAs via hybridization during enzymatic replication serve as a driving force for the self-assembly of BRCs. These molecules effectively suppressed the transcription of their target genes, leading to tumor growth suppression in vitro and in vivo. Moreover, their repeated intravenous administration efficiently inhibited the growth of A549 tumor xenografts. Based on these findings of a reduced cancer cell viability following a USE1 knockdown, we further explored cell cycle arrest and apoptosis pathways. The observed tumor cell growth suppression was found to be controlled by cell cycle arrest and apoptosis signals induced by the USE1 reduction. These results suggest that USE1 BRCs may have future clinical applications as an RNAi-based cancer therapy.

AI at CPhI

We are excited to finally publish the names of the companies that made it into C&EN’s 10 Start-Ups to Watch for 2019 (see page 28). It’s an interesting collection of young firms working on diverse solutions, including new approaches to recycling polystyrene, a water purification system based on β-cyclodextrin, and RNA-based therapies. We can’t guarantee that these organizations will make it big, but they certainly have interesting and creative technologies with the potential to change the world around them. What is more exciting, however, is that many of the companies that made it onto the list for other years are doing really well. According to Senior Correspondent Melody Bomgardner, “Since November 2018, start-ups from the classes of 2015–18 have collectively raised more than $1.2 billion from investors.” Check out the online-only story at cenm.ag/10watn2019. While this editorial package was being assembled, a group of C&EN staff and I were attending

Harnessing therapeutic viruses as a delivery vehicle for RNA-based therapy.

Messenger RNA (mRNA) and microRNA (miRNA)-based therapeutics have become attractive alternatives to DNA-based therapeutics due to recent advances in manufacture, scalability and cost. Also, RNA-based therapeutics are considered safe since there are no risk of inducing genomic changes as well as the potential adverse effects would be only temporary due to the transient nature of RNA-based therapeutics. However, efficient in vivo delivery of RNA-based therapeutics remains a challenge. We have developed a delivery platform for RNA-based therapeutics by exploiting the physicochemical properties of enveloped viruses. By physically attaching cationic liposome/RNA complexes onto the viral envelope of vaccinia virus, we were able to deliver mRNA, self-replicating RNA as well as miRNA inside target cells. Also, we showed that this platform, called viRNA platform, can efficiently deliver functional miRNA mimics into B16.OVA tumour in vivo.

SINEUP non-coding RNAs rescue defective frataxin expression and activity in a cellular model of Friedreich's Ataxia.

Friedreich's ataxia (FRDA) is an untreatable disorder with neuro- and cardio-degenerative progression. This monogenic disease is caused by the hyper-expansion of naturally occurring GAA repeats in the first intron of the FXN gene, encoding for frataxin, a protein implicated in the biogenesis of iron-sulfur clusters. As the genetic defect interferes with FXN transcription, FRDA patients express a normal frataxin protein but at insufficient levels. Thus, current therapeutic strategies are mostly aimed to restore physiological FXN expression. We have previously described SINEUPs, natural and synthetic antisense long non-coding RNAs, which promote translation of partially overlapping mRNAs through the activity of an embedded SINEB2 domain. Here, by in vitro screening, we have identified a number of SINEUPs targeting human FXN mRNA and capable to up-regulate frataxin protein to physiological amounts acting at the post-transcriptional level. Furthermore, FXN-specific SINEUPs promote the recovery of disease-associated mitochondrial aconitase defects in FRDA-derived cells. In summary, we provide evidence that SINEUPs may be the first gene-specific therapeutic approach to activate FXN translation in FRDA and, more broadly, a novel scalable platform to develop new RNA-based therapies for haploinsufficient diseases.

Mechanisms of the Multitasking Endothelial Protein NRG-1 as a Compensatory Factor During Chronic Heart Failure.

Heart failure is a complex syndrome whose phenotypic presentation and disease progression depends on a complex network of adaptive and maladaptive responses. One of these responses is the endothelial release of NRG (neuregulin)-1-a paracrine growth factor activating ErbB2 (erythroblastic leukemia viral oncogene homolog B2), ErbB3, and ErbB4 receptor tyrosine kinases on various targets cells. NRG-1 features a multitasking profile tuning regenerative, inflammatory, fibrotic, and metabolic processes. Here, we review the activities of NRG-1 on different cell types and organs and their implication for heart failure progression and its comorbidities. Although, in general, effects of NRG-1 in heart failure are compensatory and beneficial, translation into therapies remains unaccomplished both because of the complexity of the underlying pathways and because of the challenges in the development of therapeutics (proteins, peptides, small molecules, and RNA-based therapies) for tyrosine kinase receptors. Here, we give an overview of the complexity to be faced and how it may be tackled.

P.49Translating DUX4-targeted RNAi-based gene therapy for FSHD

P.49Translating DUX4-targeted RNAi-based gene therapy for FSHD

A review of potential RNA therapeutics for Machado-Joseph disease

Polyglutamine diseases are a group of neurodegenerative disorders characterized by the expansion of a CAG trinucleotide in a protein-coding gene. The translation of these expanded repeats leads to long polyglutamine tracts that increase the potential of the protein to aggregate itself and other proteins into the pathological amyloid conformation. Machado-Joseph disease (MJD), also known as Spinocerebellar Ataxia 3, is the second most common polyglutamine disease behind Huntington disease. In MJD, the CAG expansion occurs in the ATXN3 gene. Currently there are no FDA-approved therapies to prevent or cure MJD. However, RNA-based therapies that silence the expression of or alter the structure of the mutant protein have the potential to prevent and ameliorate the disease. Here, we will review how RNA interference (RNAi) and antisense oligonucleotides (AONs) could potentially be used to target ATXN3. These technologies could mediate allele-specific silencing of mutant ATXN3 alleles but also allele non-specific silencing for individuals without a targetable polymorphism. Both RNAi and AONs could be used to promote mRNA degradation and translational inhibition; in addition AONs may be used as splicing modulators. The evidence suggests that viral-mediated delivery of RNAi therapies may have longer term potency than liposomal-mediated delivery of RNAi or AON therapies; however, this has not been fully explored in animal models. Nevertheless, there are promising results from studies of MJD and similar neurodegenerative disorders that suggest that RNAi and AON technology may be a viable long-term treatment therapy.

Fusion transcripts: Unexploited vulnerabilities in cancer?

Gene fusions are an important class of mutations in several cancer types and include genomic rearrangements that fuse regulatory or coding elements from two different genes. Analysis of the genetics of cancers harboring fusion oncogenes and the proteins they encode have enhanced cancer diagnosis and in some cases patient treatment. However, the effect of the complex structure of fusion genes on the biogenesis of the resulting chimeric transcripts they express is not well studied. There are two potential RNA‐related vulnerabilities inherent to fusion‐driven cancers: (a) the processing of the fusion precursor messenger RNA (pre‐mRNA) to the mature mRNA and (b) the mature mRNA. In this study, we discuss the effects that the genetic organization of fusion oncogenes has on the generation of translatable mature RNAs and the diversity of fusion transcripts expressed in different cancer subtypes, which can fundamentally influence both tumorigenesis and treatment. We also discuss functional genomic approaches that can be utilized to identify proteins that mediate the processing of fusion pre‐mRNAs. Furthermore, we assert that an enhanced understanding of fusion transcript biogenesis and the diversity of the chimeric RNAs present in fusion‐driven cancers will increase the likelihood of successful application of RNA‐based therapies in this class of tumors.This article is categorized under:RNA Processing > RNA Editing and ModificationRNA Processing > Splicing Regulation/Alternative SplicingRNA in Disease and Development > RNA in Disease

RNA-based therapy for osteogenesis.

Nucleic acid-based therapy has shown great promise in accelerating bone regeneration as well as other diseases. Nucleic acids used in gene therapy mainly are either plasmid DNA (pDNA) or RNAs. Although pDNA therapy has been extensively studied for decades with encouraging preclinical and clinical results, side effects, and low efficiency associated with nuclear trafficking are hard to bypass. Unlike pDNA, RNAs (mRNA, siRNA, miRNA) exert their function in the cytoplasm, thereby being more efficient in hard-to-transfect cells such as primary osteoblasts. RNA interference-based gene silencing represents a negative regulation which knockdown the expression of antagonists that impair osteogenesis process. In contrary, mRNA therapy for osteogenesis represents a positive regulation which delivers mRNA encoding growth factors to accelerate bone regeneration. This review presents a comprehensive summary of the mRNA and siRNA-based therapies and the targets for bone regeneration in case of bone defect and osteoporosis.

Elimination of HER3-expressing breast cancer cells using aptamer-siRNA chimeras.

Breast cancer is the most common cancer in women worldwide. Despite recent developments in breast cancer detection and treatment, 1.38 million women each year are still affected. Breast cancer heterogeneity at the population and single-cell level, complexity and developing different metastases are setting several challenges to develop efficient breast cancer therapies. RNA interference (RNAi) represents an opportunity to silence gene expression and inhibit specific pathways in cancer cells. In order to reap the full advantages of RNAi-based therapy, different pathways that sustain cancer cells growth have been targeted using specific siRNAs. The present study investigated the ability of a set of cytotoxic siRNAs to inhibit growth of breast cancer cells. These siRNAs are targeting eukaryotic elongation factor 2 (EEF2), polo-like kinase 1 (PLK1), G protein-coupled receptor kinase 4 (GRK4) and sphingosine kinase interacting protein (SKIP5). To facilitate their targeted delivery, the human epidermal growth factor receptor-3 (HER3)-specific aptamer A30 was used. The in vitro results described in this work indicate that combining the highly specific HER3 aptamer with cytotoxic siRNAs targeting (EEF2, PLK1, GRK4 and SKIP5) can inhibit its activity and ultimately suppress proliferation of HER3 positive breast cancer cells.

Bone-targeting AAV-mediated silencing of Schnurri-3 prevents bone loss in osteoporosis

RNAi-based bone anabolic gene therapy has demonstrated initial success, but many practical challenges are still unmet. Here, we demonstrate that a recombinant adeno-associated virus 9 (rAAV9) is highly effective for transducing osteoblast lineage cells in the bone. The adaptor protein Schnurri-3 (SHN3) is a promising therapeutic target for osteoporosis, as deletion of shn3 prevents bone loss in osteoporotic mice and short-term inhibition of shn3 in adult mice increases bone mass. Accordingly, systemic and direct joint administration of an rAAV9 vector carrying an artificial-microRNA that targets shn3 (rAAV9-amiR-shn3) in mice markedly enhanced bone formation via augmented osteoblast activity. Additionally, systemic delivery of rAAV9-amiR-shn3 in osteoporotic mice counteracted bone loss and enhanced bone mechanical properties. Finally, we rationally designed a capsid that exhibits improved specificity to bone by grafting the bone-targeting peptide motif (AspSerSer)6 onto the AAV9-VP2 capsid protein. Collectively, our results identify a bone-targeting rAAV-mediated gene therapy for osteoporosis.

Abstract 5098: In silico analysis of the membrane targeting mechanism of the pleckstrin homology domains within the oncogenic Grb2-associated-binding protein family

Abstract Members of the metazoan Grb2-associated-binding (GAB) family of proteins are crucial regulatory elements of receptor tyrosine kinase (RTK) signaling pathways. These scaffold proteins link and amplify plasma membrane receptor signaling to downstream targets by staging protein-protein interactions. Aberrant GAB expression is associated with improper growth and development, and several members of the GAB family have been implicated as oncogenes. GAB1, GAB2, and GAB3 are overexpressed in various cancers including lung, breast, colorectal, nervous system, and ovarian cancers, along with certain leukemias and melanomas. Recent studies suggest a direct relationship between GAB expression levels and tumorigenesis, where induced or silenced expression respectively accelerated or inhibited tumor proliferation. Silencing of GAB1 in colorectal cancers and GAB2 in glioblastoma via miRNA, and GAB3 in gliomas via siRNA inhibits tumor proliferation indicating that GAB proteins can be potentially effective targets in cancer therapy. The most conserved structural moiety in all members of the GAB family is an N-terminally located pleckstrin homology (PH domain) that directs subcellular localization and is crucial for effective protein function. Given the challenges facing RNA-based cancer therapies, more practical therapeutic avenues may be found in disrupting or inhibiting proper PH domain function; however, the mechanism of membrane targeting of all GABs remains to be elucidated. To this end, we have performed a comprehensive computational analysis of the six known GAB family members - chordate GAB1, GAB2, GAB3, and GAB4; Caenorhabditis elegans Suppressor of Clear (SOC1); Drosophila melanogaster Daughter of Sevenless (DOS) and their respective homologs to establish intra-familiar relationships via sequence analysis. Furthermore, in silico homology-based and ab initio modeling techniques were employed to propose suitable structural models of the PH domains and confirm the structural conservation of the fold. The refined theoretical models were docked against phosphoinositide head-groups to establish binding affinities and the mechanism of GAB PH domain localization. Our results suggest that non-specific electrostatics may be a key component for membrane targeting of GAB PH domains acting in concert with interaction through specific conserved residues and reveal an alternative binding pocket in addition to the canonical binding site. Our study is the first step in rational design of potential therapies based on targeting GAB function via the PH domain. Citation Format: Antonio Lopez, Ezza Awan, Areeba Zaheer, Shaneen Singh. In silico analysis of the membrane targeting mechanism of the pleckstrin homology domains within the oncogenic Grb2-associated-binding protein family [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 5098.

Theranostic Nanoparticles for RNA-Based Cancer Treatment.

Certain genetic mutations lead to the development of cancer through unchecked cell growth and division. Cancer is typically treated through surgical resection, radiotherapy, and small-molecule chemotherapy. A relatively recent approach to cancer therapy involves the use of a natural process wherein small RNA molecules regulate gene expression in a pathway known as RNA interference (RNAi). RNA oligomers pair with a network of proteins to form an RNA-induced silencing complex, which inhibits the translation of mRNA into proteins, thereby controlling the expression of gene products. Synthetically produced RNA oligomers may be designed to target and silence specific oncogenes to provide cancer therapy. The primary challenges facing the use of the RNAi pathway for cancer therapy are the safe and efficacious delivery of RNA payloads and their release at pertinent sites within disease-causing cells. Nucleases are abundant in the bloodstream and intracellular environment, and therapeutic RNA sequences often require a suitable carrier to provide protection from degradation prior to reaching their site of action in the body. The use of metal core nanoparticles (NPs) serving as targeted delivery vehicles able to shield and direct RNA payloads to their intended destinations have recently gained favor. Biological barriers present in the body establish a size prerequisite for drug delivery vehicles; to overcome recognition by the body's immune system and to gain access to intracellular environments, drug carriers must be small (< 100 nm). Iron oxide and gold core NPs can be synthesized with a high degree of control to create uniform ultrasmall drug delivery vehicles capable of bypassing key biological barriers. While progress is being made in size control of liposomal and polymer NPs, such advances still lag in comparison to the exquisite tunability and time stability of size engineering achievable with metal core NPs at bulk scales. Further, unlike lipid- and viral-based transfection agents, the biodistribution of metal core NPs can be traced using noninvasive imaging techniques that capitalize on the interaction of electromagnetic radiation and the inorganic atoms at the core of the NPs. Finally, metal core NPs have been shown to match the transfection efficiency of conventional RNA-delivery vehicles while also providing less immunogenicity and minimal side effects through the addition of tumor-targeting ligands on their surface. This Account reviews recent advances in the use of iron oxide and gold NPs for RNAi therapy. An overview of the different types of RNA-based therapies is provided along with a discussion of the advantages and current limitations of the technique. We highlight design considerations for the use of iron oxide and gold NP carriers in RNAi, including a discussion of the importance of size and its role in traversing biological barriers, NP surface modifications required for targeted delivery and RNA payload release, and auxiliary properties supporting imaging functionality for treatment monitoring. Applications of NPs for combination therapies including the pairing of RNAi with chemotherapy, photothermal therapy, immunotherapy, and radiotherapy are explored through examples. Finally, future perspectives are provided with a focus on the current limitations and the potential for clinical translation of iron oxide and gold NPs in RNAi therapy.