Non-viral Gene Therapy for Melanoma Using Lysenin from Eisenia Foetida

Earthworms, long utilized in traditional medicine, serve as a source of inspiration for modern therapeutics. Lysenin, a defensive factor in the coelom fluid of the earthworm Eisenia fetida, has multiple bioactivities. However, the inherent toxicity of Lysenin as a pore-forming protein (PFP) restricts its application in therapy. Here, a gene therapy strategy based on Lysenin for cancer treatment is presented. The formulation consists of polymeric nanoparticles complexed with the plasmid encoding Lysenin. After transfection in vitro, melanoma cells can express Lysenin, resulting in necrosis, autophagy, and immunogenic cell death. The secretory signal peptide alters the intracellular distribution of the expressed product of Lysenin, thereby potentiating its anticancer efficacy. The intratumor injection of Lysenin gene formulation can efficiently kill the transfected melanoma cells and activate the antitumor immune response. Notably, no obvious systemic toxicity is observed during the treatment. Non-viral gene therapy based on Lysenin derived from Eisenia foetida exhibits potential in cancer therapy, which can inspire future cancer therapeutics.

CRISPR editing to mimic porphyria combined with light: A new preclinical approach for prostate cancer

Thanks to its very high genome-editing efficiency, CRISPR-Cas9 technology could be a promising anticancer weapon. Clinical trials using CRISPR-Cas9 nuclease to ex vivo edit and alter immune cells are ongoing. However, to date, this strategy still has not been applied in clinical practice to directly target cancer cells. Targeting a canonical metabolic pathway essential to good functioning of cells without potential escape would represent an attractive strategy. We propose to mimic a genetic metabolic disorder in cancer cells to weaken cancer cells, independent of their genomic abnormalities. Mutations affecting the heme biosynthesis pathway are responsible for porphyria, and most of them are characterized by an accumulation of toxic photoreactive porphyrins. This study aimed to mimic porphyria by using CRISPR-Cas9 to inactivate UROS, leading to porphyrin accumulation in a prostate cancer model. Prostate cancer is the leading cancer in men and has a high mortality rate despite therapeutic progress, with a primary tumor accessible to light. By combining light with gene therapy, we obtained high efficiency in vitro and in vivo, with considerable improvement in the survival of mice. Finally, we achieved the preclinical proof-of-principle of performing cancer CRISPR gene therapy.

GSH/pH Dual Activatable Cross-linked and Fluorinated PEI for Cancer Gene Therapy Through Endogenous Iron De-Hijacking and in Situ ROS Amplification

Ferroptosis-related cancer therapy is limited by insufficient Fe2+ /Fe3+ redox pair and hydrogen peroxide (H2 O2 ) for producing lethal hydroxyl radicals (·OH). Although exogenous iron or ROS-producing drugs can enhance ferroptosis, exploiting endogenous iron (labile iron pool, LIP) stored in ferritin and promoting ROS generation may be safer. Herein, a metal/drug-free nanomedicine is developed for responsive LIP release and H2 O2 generation on the mitochondria membranes, amplifying hydroxyl radical production to enhance ferroptosis-mediated antitumor effects. A glutathione(GSH)/pH dual activatable fluorinated and cross-linked polyethyleneimine (PEI) with dialdehyde polyethylene glycol layer nanocomplex loaded with MTS-KR-SOD (Mitochondria-targeting-sequence-KillerRed-Superoxide Dismutase) and CRISPR/Cas9-CA IX (Carbonic anhydrase IX (CA IX)) plasmids (FP@MC) are developed for enhanced ferroptosis through endogenous iron de-hijacking and in situ ROS amplification. Two plasmids are constructed to knockdown CA IX and translate KillerRed-SOD recombinant protein specifically on mitochondria membranes, respectively. The CA IX knockdown acidifies the intracellular environment, leading the release of LIP from ferritin as a "flare" to initiate endogenous chemodynamic therapy. Meanwhile, MTS-KR-SOD generates H2 O2 when irradiated by a 590 nm laser to assist chemodynamic therapy, leading to ROS amplification for mitochondria damage and lipid peroxide accumulation. The combined therapeutic effects aggravate cancer ferroptosis and suppress tumor growth, providing a new paradigm for amplifying ROS and iron ions to promote ferroptosis-related cancer therapy.

Adenovirus VA RNAs impair maturation of primary microRNA

BACKGROUND

Adenovirus expresses two non-coding virus-associated (VA) RNAs: VA I RNA and VA II RNA. Adenovirus-expressed VA RNAs interfere with the microRNA (miRNA) pathway by competing with precursor miRNAs. The processing pattern of primary miRNA (pri-miRNA) and factors to affect its processing are not exactly known when using adenovirus for the delivery of pri-miRNA.

METHODS

To observe pri-miRNA processing, plasmid construct encoding pri-miRNA was co-transfected with VA I/II RNA expression plasmid, or recombinant adenovirus encoding pri-miRNA was generated and infected. Levels of miRNAs, VA I RNA and VA II RNA were analyzed by a quantitative real-time PCR (RT-PCR). VA I-II full-length RNA was analyzed by a RT-PCR. RNA immunoprecipitation analysis to pull-down the VA I-II full-length RNA binding with Drosha was conducted with Drosha antibody.

RESULTS

pri-miRNA was normally processed into mature miRNA when it was expressed in cells using plasmid. However, miRNA maturation was impaired when pri-miRNA was delivered and expressed using adenovirus. Of note, pri-miRNA processing was observed to be blocked by VA RNA expression. Such blocked processing could be recovered by introducing antisense RNA of VA RNA, anti-3'VA RNA. In addition, VA RNAs were transcribed into VA I-II full-length RNA, which was found to bind and sequester Drosha.

CONCLUSIONS

Adenovirus infection downregulated the processing of pri-miRNAs in cells, and such downregulation could be derived from VA I-II full-length RNAs in pri-miRNA-like form through competitively binding to Drosha protein. These results indicated that the expression of adenovirus VA RNAs should be inhibited for successful delivery and expression of pri-miRNA or shRNA in cells using adenovirus.

Design and Biological Evaluation of Piperazine-Bearing Nitrobenzamide Hypoxia/GDEPT Prodrugs: The Discovery of CP-506

Off-target aerobic activation of PR-104A by human aldo-keto reductase 1C3 (AKR1C3) has confounded the development of this dual hypoxia/gene therapy prodrug. Previous attempts to design prodrugs resistant to AKR1C3 activation have resulted in candidates that require further optimization. Herein we report the evaluation of a lipophilic series of PR-104A analogues in which a piperazine moiety has been introduced to improve drug-like properties. Octanol-water partition coefficients (LogD7.4) spanned >2 orders of magnitude. 2D antiproliferative and 3D multicellular clonogenic assays using isogenic HCT116 and H1299 cells confirmed that all examples were resistant to AKR1C3 metabolism while producing an E. coli NfsA nitroreductase-mediated bystander effect. Prodrugs 16, 17, and 20 demonstrated efficacy in H1299 xenografts where only a minority of tumor cells express NfsA. These prodrugs and their bromo/mesylate counterparts (25-27) were also evaluated for hypoxia-selective cell killing in vitro. These results in conjunction with stability assays recommended prodrug 26 (CP-506) for Phase I/II clinical trial.

Gene therapy in cancer

Gene therapy, recently frequently investigated, is an alternative treatment method that introduces therapeutic genes into a cancer cell or tissue to cause cell death or slow down the growth of the cancer. This treatment has various strategies such as therapeutic gene activation or silencing of unwanted or defective genes; therefore a wide variety of genes and viral or nonviral vectors are being used in studies. Gene therapy strategies in cancer can be classified as inhibition of oncogene activation, activation of tumor suppressor gene, immunotherapy, suicide gene therapy and antiangiogenic gene therapy. In this review, we explain gene therapy, gene therapy strategies in cancer, approved gene medicines for cancer treatment and future of gene therapy in cancer. Today gene therapy has not yet reached the level of replacing conventional therapies. However, with a better understanding of the mechanism of cancer to determine the right treatment and target, in the future gene therapy, used as monotherapy or in combination with another existing treatment options, is likely to be used as a new medical procedure that will make cancer a controllable disease.

Visible Light-Guided Gene Delivery with Nonviral Supramolecular Block Copolymer Vectors

To achieve efficient gene delivery in vitro or in vivo, nonviral vectors should have excellent biostability across cellular and tissue barriers and also smart stimuli responsiveness toward controlled release of therapeutic genes into the cell nucleus. However, it remains a key challenge to effectively combine the biostability of covalent polymers with the stimuli responsiveness of noncovalent polymers into one nonviral vehicle. In this work, we report the construction of a kind of cationic supramolecular block copolymers (SBCs) through noncovalent polymerization of β-cyclodextrin/azobenzene-terminated pentaethylenehexamine (DMA-Azo-PEHA-β-CD) in aqueous media using β-CD-monosubstituted poly(ethylene glycol) (PEG-β-CD) as a supramolecular initiator. The resultant SBC exhibits superior biostability, biocompatibility, and light/pH dual-responsive characteristics, and it also demonstrates efficient plasmid DNA condensation capacity and the ability to rapidly release plasmid DNA into cells driven by visible light (450 nm). Eventually, this SBC-based delivery system demonstrates visible light-induced enhancement of gene delivery in both COS-7 and HeLa cells. We anticipate that this work provides a facile and robust strategy to enhance gene delivery in vitro or in vivo via visible light-guided manipulation of genes, further achieving safe, highly efficient, targeting gene therapy for cancer.

Biological and therapeutic viewpoints towards role of miR-218 in human cancers: Revisiting molecular interactions and future clinical translations

Understanding the exact pathogenesis of cancer is difficult due to heterogenous nature of tumor cells and multiple factors that cause its initiation and development. Treatment of cancer is mainly based on surgical resection, chemotherapy, radiotherapy and their combination, while gene therapy has been emerged as a new kind of therapy for cancer. Post-transcriptional regulation of genes has been of interest in recent years and among various types of epigenetic factors that can modulate gene expression, short non-coding RNAs known as microRNAs (miRNAs) have obtained much attention. The stability of mRNA decreases by miRNAs to repress gene expression. miRNAs can regulate tumor malignancy and biological behavior of cancer cells and understanding their function in tumorigenesis can pave the way towards developing new therapeutics in future. One of the new emerging miRNAs in cancer therapy is miR-218 that increasing evidence highlights its anti-cancer activity, while a few studies demonstrate its oncogenic function. The miR-218 transfection is promising in reducing progression of tumor cells. miR-218 shows interactions with molecular mechanisms including apoptosis, autophagy, glycolysis and EMT, and the interaction is different. miR-218 induces apoptosis, while it suppresses glycolysis, cytoprotective autophagy and EMT. Low expression of miR-218 can result in development of chemoresistance and radio-resistance in tumor cells and direct targeting of miR-218 as a key player is promising in cancer therapy. LncRNAs and circRNAs are nonprotein coding transcripts that can regulate miR-218 expression in human cancers. Moreover, low expression level of miR-218 can be observed in human cancers such as brain, gastrointestinal and urological cancers that mediate poor prognosis and low survival rate.

Design and Characterization of Mutated Variants of the Oncotoxic Parvoviral Protein NS1

Oncotoxic proteins such as the non-structural protein 1 (NS1), a constituent of the rodent parvovirus H1 (H1-PV), offer a novel approach for treatment of tumors that are refractory to other treatments. In the present study, mutated NS1 variants were designed and tested with respect to their oncotoxic potential in human hepatocellular carcinoma cell lines. We introduced single point mutations of previously described important residues of the wild-type NS1 protein and a deletion of 114 base pairs localized within the N-terminal domain of NS1. Cell-viability screening with HepG2 and Hep3B hepatocarcinoma cells transfected with the constructed NS1-mutants led to identification of the single-amino acid NS1-mutant NS1-T585E, which led to a 30% decrease in cell viability as compared to NS1 wildtype. Using proteomics analysis, we could identify new interaction partners and signaling pathways of NS1. We could thus identify new oncotoxic NS1 variants and gain insight into the modes of action of NS1, which is exclusively toxic to human cancer cells. Our in-vitro studies provide mechanistic explanations for the observed oncolytic effects. Expression of NS1 variants had no effect on cell viability in NS1 unresponsive control HepG2 cells or primary mouse hepatocytes. The availability of new NS1 variants in combination with a better understanding of their modes of action offers new possibilities for the design of innovative cancer treatment strategies.

Evaluation of Malarial Var2CSA-Displaying Baculovirus Vector in Transduction Efficiency in Human Cancer Cells

Baculovirus vectors (BVs) are able to use for gene transduction in mammalian cells and are recognized as growing viral vectors for cancer gene therapy applications. The transduction efficiency of BVs varies among cancer cell types. To improve the transduction efficiency of BVs in human cancer cells, BV displaying malarial variant surface antigen 2-chondroitin sulfate A (var2CSA) molecules was developed in this study. Var2CSA plays a critical role in the sequestration of Plasmodium falciparum-infected erythrocytes in the placenta. Moreover, var2CSA binds to cancer cells via placenta-like chondroitin sulfate A (CSA), but not to non-cancer cells. Var2CSA BV showed significantly higher gene transduction than control BV in HepG2 and Huh7 cells, human hepatic cancer cells as well as AsPC-1 cells, human pancreatic cancer cells. The transduction efficiency of var2CSA BV was significantly inhibited by the anti-gp64 antibody, free heparin, and CSA. The results of this study suggest that var2CSA BV would be an improved vector for cancer gene therapies, especially in the treatment of hepatic and pancreatic cancers.

Bacteriophage-Mediated Cancer Gene Therapy

Bacteriophages have long been considered only as infectious agents that affect bacterial hosts. However, recent studies provide compelling evidence that these viruses are able to successfully interact with eukaryotic cells at the levels of the binding, entry and expression of their own genes. Currently, bacteriophages are widely used in various areas of biotechnology and medicine, but the most intriguing of them is cancer therapy. There are increasing studies confirming the efficacy and safety of using phage-based vectors as a systemic delivery vehicle of therapeutic genes and drugs in cancer therapy. Engineered bacteriophages, as well as eukaryotic viruses, demonstrate a much greater efficiency of transgene delivery and expression in cancer cells compared to non-viral gene transfer methods. At the same time, phage-based vectors, in contrast to eukaryotic viruses-based vectors, have no natural tropism to mammalian cells and, as a result, provide more selective delivery of therapeutic cargos to target cells. Moreover, numerous data indicate the presence of more complex molecular mechanisms of interaction between bacteriophages and eukaryotic cells, the further study of which is necessary both for the development of gene therapy methods and for understanding the cancer nature. In this review, we summarize the key results of research into aspects of phage-eukaryotic cell interaction and, in particular, the use of phage-based vectors for highly selective and effective systemic cancer gene therapy.

Hepatocellular Carcinoma Is a Natural Target for Adeno-Associated Virus (AAV) 2 Vectors

Simple Summary

Gene therapy is a novel approach to treat diseases by introducing corrective genetic information into target cells. Adeno-associated virus vectors are the most frequently applied gene delivery tools for in vivo gene therapy and are also studied as part of innovative anticancer strategies. Here, we report on the natural preference of AAV2 vectors for hepatocellular carcinoma (HCC) compared to nonmalignant liver cells in mice and human tissue. This preference in transduction is due to the improved intracellular processing of AAV2 vectors in HCC, resulting in significantly more vector genomes serving as templates for transcription in the cell nucleus. Based on this natural tropism for HCC, novel therapeutic strategies can be designed or existing therapeutic approaches can be strengthened as they currently result in only a minor improvement of the poor prognosis for most liver cancer patients.

Abstract

Although therapeutic options are gradually improving, the overall prognosis for patients with hepatocellular carcinoma (HCC) is still poor. Gene therapy-based strategies are developed to complement the therapeutic armamentarium, both in early and late-stage disease. For efficient delivery of transgenes with antitumor activity, vectors demonstrating preferred tumor tropism are required. Here, we report on the natural tropism of adeno-associated virus (AAV) serotype 2 vectors for HCC. When applied intravenously in transgenic HCC mouse models, similar amounts of vectors were detected in the liver and liver tumor tissue. In contrast, transduction efficiency, as indicated by the level of transgene product, was moderate in the liver but was elevated up to 19-fold in mouse tumor tissue. Preferred transduction of HCC compared to hepatocytes was confirmed in precision-cut liver slices from human patient samples. Our mechanistic studies revealed that this preference is due to the improved intracellular processing of AAV2 vectors in HCC, resulting, for example, in nearly 4-fold more AAV vector episomes that serve as templates for gene transcription. Given this background, AAV2 vectors ought to be considered to strengthen current—or develop novel—strategies for treating HCC.

Evaluating a Targeted Cancer Therapy Approach Mediated by RNA trans-Splicing In Vitro and in a Xenograft Model for Epidermolysis Bullosa-Associated Skin Cancer

Conventional anti-cancer therapies based on chemo- and/or radiotherapy represent highly effective means to kill cancer cells but lack tumor specificity and, therefore, result in a wide range of iatrogenic effects. A promising approach to overcome this obstacle is spliceosome-mediated RNA trans-splicing (SMaRT), which can be leveraged to target tumor cells while leaving normal cells unharmed. Notably, a previously established RNA trans-splicing molecule (RTM44) showed efficacy and specificity in exchanging the coding sequence of a cancer target gene (Ct-SLCO1B3) with the suicide gene HSV1-thymidine kinase in a colorectal cancer model, thereby rendering tumor cells sensitive to the prodrug ganciclovir (GCV). In the present work, we expand the application of this approach, using the same RTM44 in aggressive skin cancer arising in the rare genetic skin disease recessive dystrophic epidermolysis bullosa (RDEB). Stable expression of RTM44, but not a splicing-deficient control (NC), in RDEB-SCC cells resulted in expression of the expected fusion product at the mRNA and protein level. Importantly, systemic GCV treatment of mice bearing RTM44-expressing cancer cells resulted in a significant reduction in tumor volume and weight compared with controls. Thus, our results demonstrate the applicability of RTM44-mediated targeting of the cancer gene Ct-SLCO1B3 in a different malignancy.

CRISPR-to-Kill (C2K)-Employing the Bacterial Immune System to Kill Cancer Cells

Simple Summary

Reasoning that multiple DNA breaks will trigger programmed cell death, we generated lentiviral CRISPR-to-kill (C2K) vectors targeting highly repetitive SINE sequences for cancer gene therapy. In proof-of-concept experiments, C2K-Alu-vectors selectively killed human, but not murine cell lines, and efficiently inhibited the growth of patient-derived glioblastoma cell lines resistant to high-dose irradiation. In combination with tumor-targeting approaches, the C2K system might represent a promising tool for cancer gene therapy.

Abstract

CRISPR/Cas9 was described as a bacterial immune system that uses targeted introduction of DNA double-strand breaks (DSBs) to destroy invaders. We hypothesized that we can analogously employ CRISPR/Cas9 nucleases to kill cancer cells by inducing maximal numbers of DSBs in their genome and thus triggering programmed cell death. To do so, we generated CRISPR-to-kill (C2K) lentiviral particles targeting highly repetitive Short Interspersed Nuclear Element-Alu sequences. Our Alu-specific sgRNA has more than 15,000 perfectly matched target sites within the human genome. C2K-Alu-vectors selectively killed human, but not murine cell lines. More importantly, they efficiently inhibited the growth of cancer cells including patient-derived glioblastoma cell lines resistant to high-dose irradiation. Our data provide proof-of-concept for the potential of C2K as a novel treatment strategy overcoming common resistance mechanisms. In combination with tumor-targeting approaches, the C2K system might therefore represent a promising tool for cancer gene therapy.

Trends and Frontiers of Research on Cancer Gene Therapy From 2016 to 2020: A Bibliometric Analysis

Background: With rapid development in molecular biology techniques and a greater understanding of cancer pathogenesis, the growing attention has been concentrated on cancer gene therapy, with numerous articles on this topic published in recent 5 years. However, there is lacking a bibliometric analysis of research on cancer gene therapy. Therefore, the aim of the present study was to conduct a bibliometric analysis to provide the trends and frontiers of research on cancer gene therapy during 2016-2020. Methods: We utilized CiteSpace 5.7.R5 software to conduct a bibliometric analysis of publications on cancer gene therapy published during 2016-2020. The bibliometric records were obtained from the Web of Science Core Collection. Results: A total of 4,392 papers were included in the bibliometric analysis. Materials Science and Nanoscience and Nanotechnology took an increasing part in the field of cancer gene therapy. Additionally, WANG W was the most productive author, while ZHANG Y ranked top in terms of citations. Harvard Medical School and Sichuan University ranked top in the active institutions. P NATL ACAD SCI USA was identified as the core journal in the field of cancer gene therapy. "Ovarian cancer" was found to be the latest keyword with the strongest burst. The keyword analysis suggested that the top three latest clusters were labeled "gene delivery," "drug delivery," and "gene therapy." In the reference analysis, cluster#2 labeled "gene delivery" held a dominant place considering both the node volume and mean year. Conclusion: The academic attention on cancer gene therapy was growing at a dramatically high speed. Materials Science and Nanoscience and Nanotechnology might become promising impetus for the development of this field. "Gene delivery" was thought to best reflect the research frontier on cancer gene therapy. The top-cited articles on gene delivery were focused on several novel non-viral vectors due to their specialty compared with viral vectors. "Ovarian cancer" was likely to be the potential research direction. These findings would help medical workers conduct further investigations on cancer gene therapy.

[Combination of ARE and HRE cis- Regulatory Elements Elevates the Activity of Tumor-Specific hTERT Promoter]

Tumor-specific promoters and cis-regulatory genetic elements are used for transcriptional control of therapeutic transgene expression in cancer gene therapy. HRE (hypoxia response element) and ARE (anti-oxidant response elements) cis-regulatory elements are targets for HIF1 and Nrf2 transcriptional factors, respectively, and mediate activation of gene transcription in a response to hypoxia and oxidative stress, characteristic of most solid tumors. Due to these features HREs and AREs are used in genetic constructs for cancer gene therapy to provide tumor-specific therapeutic transgene expression or replication of oncolytic adenovi-ruses. In this work on the basis of the tumor-specific promoter hTERT we have constructed hybrid promoters carrying combinations of HRE and ARE. We showed that upon imitation of hypoxia in human lung cancer cell lines the activity of the hybrid promoter HRE-ARE-hTERT is substantially higher compared to promoters carrying only ARE or HRE. Using in vitro suicide cancer gene therapy with the CD: UPRT/5-FC (cytosine deaminase; uracil phosphoribosyl transferase/5-fluorocytosine) enzyme-prodrug system as a model we showed an enhancement of the cytotoxic effect on human lung cancer cells upon imitation of hypoxia when cytosine deaminase: uracil phosphoribosyl transferase was expressed under the control of the HRE-ARE-hTERT promoter compared to HRE-hTERT and ARE-hTERT promoters. The novel hybrid promoter HRE-ARE-hTERT could be used for transcriptional targeting of therapeutic transgene expression or oncolytic adenovirus replication upon development of novel anti-cancer gene therapeutics.

Tumor protein p53 mutation in archived tumor samples from a 12-year survivor of stage 4 pancreatic ductal adenocarcinoma may predict long-term survival with DeltaRex-G: A case report and literature review

DeltaRex-G is a replication-incompetent amphotropic murine leukemia virus-based retroviral vector that displays a collagen-matrix-targeting decapeptide on its surface envelope protein, gp70, and encodes a cytocidal ‘dominant negative’, i.e. a truncated construct of the executive cyclin G1 (CCNG1) oncogene. DeltaRex-G inhibits the CCNG1 function of promoting cell competence and survival through the commanding CCNG1/cyclin-dependent kinase (CDK)/Myc/mouse double minute 2 homolog (Mdm2)/p53 axis. In 2009, DeltaRex-G was granted Fast Track designation from the US Food and Drug Administration for the treatment of pancreatic cancer. In 2019, the results of a phase 1/2 study that used DeltaRex-G as monotherapy for stage 4 chemotherapy-resistant pancreatic ductal adenocarcinoma (PDAC) were published. A unique participant of the aforementioned phase 1/2 study is now an 84-year-old Caucasian woman with chemoresistant PDAC who was treated with DeltaRex-G, 3x10¹¹ colony forming units (cfu)/dose, 3 times/week for 4 weeks with a 2-week rest period, for 1.5 years. During the treatment period, the patient's tumors in the liver, lymph node and peritoneum exhibited progressive decreases in size, which were accompanied by a reduction and normalization of serum carbohydrate antigen 19-9 levels, and the patient achieved complete remission after 8 months of DeltaRex-G therapy with minimal side effects (grade 2 fatigue). Henceforth, the patient has been in remission for 12 years with no evidence of disease, no late therapy-related adverse events, and no further cancer therapy following DeltaRex-G treatment. The present study reports a mutation of tumor protein p53 (TP53) (G199V) found retrospectively in the patient's archived tumor samples. TP53 is a well-characterized tumor suppressor gene, and a critical regulatory component of the executive CCNG1/CDK/Myc/Mdm2/p53 axis, which regulates proliferative cell competence, DNA fidelity and survival. Studies are underway to determine whether TP53 mutations in pancreatic cancer can help identify a subset of patients with advanced metastatic cancer with an otherwise poor prognosis who would respond favorably to DeltaRex-G, which would broaden the treatment options for patients with otherwise lethal PDAC.

Malignant tissues produce divergent antibody glycosylation of relevance for cancer gene therapy effectiveness

Gene therapy approaches now allow for the production of therapeutic antibodies by healthy or cancerous human tissues directly in vivo, and, with an increasing number of gene delivery methods available, the cell type for expression can be chosen. Yet, little is known about the biophysical changes introduced by expressing antibodies from producer cells or tissues targeted by gene therapy approaches, nor about the consequences for the type of glycosylation. The effects of different glycosylation on therapeutic antibodies have been well studied by controlling their glycan compositions in non-human mammalian production cells, i.e., Chinese hamster ovary cells. Therefore, we investigated the glycosylation state of clinically approved antibodies secreted from cancer tissues frequently targeted by in vivo gene therapy, using native mass spectrometry and glycoproteomics. We found that antibody sialylation and fucosylation depended on the producer tissue and the antibody isotype, allowing us to identify optimal producer cell types according to the desired mode of action of the antibody. Furthermore, we discovered that high amounts (>20%) of non-glycosylated antibodies were produced in cells sensitive to the action of the produced antibodies. Different glycosylation in different producer cells can translate into an altered potency of in-vivo produced antibodies, depending on the desired mode of action, and can affect their serum half-lives. These results increase our knowledge about antibodies produced from cells targeted by gene therapy, enabling development of improved cancer gene therapy vectors that can include in vivo glycoengineering of expressed antibodies to optimize their efficacies, depending on the desired mode of action.

Combinatorial Approaches for Cancer Treatment Using Oncolytic Viruses: Projecting the Perspectives through Clinical Trials Outcomes

Recent cancer immunotherapy breakthroughs have fundamentally changed oncology and revived the fading hope for a cancer cure. The immune checkpoint inhibitors (ICI) became an indispensable tool for the treatment of many malignant tumors. Alongside ICI, the application of oncolytic viruses in clinical trials is demonstrating encouraging outcomes. Dozens of combinations of oncolytic viruses with conventional radiotherapy and chemotherapy are widely used or studied, but it seems quite complicated to highlight the most effective combinations. Our review summarizes the results of clinical trials evaluating oncolytic viruses with or without genetic alterations in combination with immune checkpoint blockade, cytokines, antigens and other oncolytic viruses as well. This review is focused on the efficacy and safety of virotherapy and the most promising combinations based on the published clinical data, rather than presenting all oncolytic virus variations, which are discussed in comprehensive literature reviews. We briefly revise the research landscape of oncolytic viruses and discuss future perspectives in virus immunotherapy, in order to provide an insight for novel strategies of cancer treatment.

Harnessing the Natural Biology of Adeno-Associated Virus to Enhance the Efficacy of Cancer Gene Therapy

Adeno-associated virus (AAV) was first characterized as small “defective” contaminant particles in a simian adenovirus preparation in 1965. Since then, a recombinant platform of AAV (rAAV) has become one of the leading candidates for gene therapy applications resulting in two FDA-approved treatments for rare monogenic diseases and many more currently in various phases of the pharmaceutical development pipeline. Herein, we summarize rAAV approaches for the treatment of diverse types of cancers and highlight the natural anti-oncogenic effects of wild-type AAV (wtAAV), including interactions with the cellular host machinery, that are of relevance to enhance current treatment strategies for cancer.

Tumor-Associated Macrophage and Tumor-Cell Dually Transfecting Polyplexes for Efficient Interleukin-12 Cancer Gene Therapy

Interleukin 12 (IL12) is a potent pro-inflammatory chemokine with multifunction, including promoting cytotoxic T-cell-mediated killing of cancer cells. IL12-based cancer gene therapy can overcome IL12's life-threatening adverse effects, but its clinical translation has been limited by the lack of systemic gene-delivery vectors capable of efficiently transfecting tumors to produce sufficient local IL12. Macrophages inherently excrete IL12, and tumor-associated macrophages (TAMs) are the major tumor component taking up a large fraction of the vectors arriving in the tumor. It is thus hypothesized that a gene vector efficiently transfecting both cancer cells and TAMs would make the tumor to produce sufficient IL12; however, gene transfection of TAMs is challenging due to their inherent strong degradation ability. Herein, an IL12 gene-delivery vector is designed that efficiently transfects both cancer cells and TAMs to make them as a factory for IL12 production, which efficiently activates anticancer immune responses and remodels the tumor microenvironment, for instance, increasing the M1/M2 ratio by more than fourfold. Therefore, the intravenously administered vector retards tumor growth and doubles survival in three animal models' with negligible systemic toxicities. This work reports the first nonviral IL12 gene delivery system that effectively makes use of both macrophages and tumor cells.

Barriers and Strategies of Cationic Liposomes for Cancer Gene Therapy

Cationic liposomes (CLs) have been regarded as the most promising gene delivery vectors for decades with the advantages of excellent biodegradability, biocompatibility, and high nucleic acid encapsulation efficiency. However, the clinical use of CLs in cancer gene therapy is limited because of many uncertain factors in vivo. Extracellular barriers such as opsonization, rapid clearance by the reticuloendothelial system and poor tumor penetration, and intracellular barriers, including endosomal/lysosomal entrapped network and restricted diffusion to the nucleus, make CLs not the ideal vector for transferring extrinsic genes in the body. However, the obstacles in achieving productive therapeutic effects of nucleic acids can be addressed by tailoring the properties of CLs, which are influenced by lipid compositions and surface modification. This review focuses on the physiological barriers of CLs against cancer gene therapy and the effects of lipid compositions on governing transfection efficiency, and it briefly discusses the impacts of particle size, membrane charge density, and surface modification on the fate of CLs in vivo, which may provide guidance for their preclinical studies.

Efficient Colorectal Cancer Gene Therapy with IL-15 mRNA Nanoformulation

Immunogene therapy is a novel method for the treatment of colorectal cancer. Cytokine IL-15 has exhibited therapeutic anticancer potential due to its immune-stimulation property. However, conventional IL-15-based cancer gene therapy studies have been performed using the plasmid DNA form, which has potential shortcomings including weak delivery efficiency and backbone effect. In this study, an IL-15 immunogene therapy study for colon cancer using in vitro transcript mRNA is described. A protamine/liposome system (CLPP) is developed to provide efficient condensation and delivery capacity for in vivo mRNA transportation. They demonstrated that the prepared CLPP system could deliver the IL-15-encoding mRNA into C26 cells with high efficacy. The secretory expressed IL-15 cytokine by the C26 cells successfully produced lymphocyte stimulation and triggered anticancer cytotoxicity upon cancer cells in vitro. Local or systemic administration of the CLPP/mIL-15 complex exhibited obvious inhibition effects on multiple C26 murine colon cancer models with inhibition rates of up to 70% in the C26 abdominal cavity metastasis tumor model, 55% in the subcutaneous model, and 69% in the pulmonary metastasis model, demonstrating high efficacy and safety. These results successfully demonstrated the high therapeutic potential of the CLPP/mIL-15 complex for colorectal cancer immunogene therapy.

Acylation of the antimicrobial peptide CAMEL for cancer gene therapy

Obtaining ideal gene delivery vectors is still a major goal in cancer gene therapy. CAMEL, a short hybrid antimicrobial peptide, can kill cancer cells by membrane lysis. In this study, we constructed a series of non-viral vectors by attaching fatty acids with different chain lengths to the N-terminus of CAMEL. Our results showed that the cellular uptake and transfection efficiency of acyl-CAMEL started to significantly increase from a chain length of 12 carbons. C18-CAMEL was screened for gene delivery because it had the highest transfection efficiency. Surprisingly, C18-CAMEL/plasmid complexes displayed strong endosomal escape activity after entering cells via endocytosis. Importantly, C18-CAMEL could deliver p53 plasmids to cancer cells and significantly inhibited cell proliferation by the expression of p53. In addition, the C18-CAMEL/p53 plasmid complexes and the MDM2 inhibitor nutlin-3a showed significantly synergistic anticancer activity against MCF-7 cells expressing wild-type p53. Conclusively, our study demonstrated that conjugation of stearic acid to antimicrobial peptides is a simple and successful approach for constructing efficient and economical non-viral vectors for cancer gene therapy.

Apoptin as a Tumor-Specific Therapeutic Agent: Current Perspective on Mechanism of Action and Delivery Systems

Cancer remains one of the leading causes of death worldwide in humans and animals. Conventional treatment regimens often fail to produce the desired outcome due to disturbances in cell physiology that arise during the process of transformation. Additionally, development of treatment regimens with no or minimum side-effects is one of the thrust areas of modern cancer research. Oncolytic viral gene therapy employs certain viral genes which on ectopic expression find and selectively destroy malignant cells, thereby achieving tumor cell death without harming the normal cells in the neighborhood. Apoptin, encoded by Chicken Infectious Anemia Virus' VP3 gene, is a proline-rich protein capable of inducing apoptosis in cancer cells in a selective manner. In normal cells, the filamentous Apoptin becomes aggregated toward the cell margins, but is eventually degraded by proteasomes without harming the cells. In malignant cells, after activation by phosphorylation by a cancer cell-specific kinase whose identity is disputed, Apoptin accumulates in the nucleus, undergoes aggregation to form multimers, and prevents the dividing cancer cells from repairing their DNA lesions, thereby forcing them to undergo apoptosis. In this review, we discuss the present knowledge about the structure of Apoptin protein, elaborate on its mechanism of action, and summarize various strategies that have been used to deliver it as an anticancer drug in various cancer models.

Single-Stranded DNA-Packaged Polyplex Micelle as Adeno-Associated-Virus-Inspired Compact Vector to Systemically Target Stroma-Rich Pancreatic Cancer

Despite the rigidity of double-stranded DNA (dsDNA), its packaging is used to construct nonviral gene carriers due to its availability and the importance of its double-helix to elicit transcription. However, there is an increasing demand for more compact-sized carriers to facilitate tissue penetration, which may be easily fulfilled by using the more flexible single-stranded DNA (ssDNA) as an alternative template. Inspired by the adeno-associated virus (AAV) as a prime example of a transcriptionally active ssDNA system, we considered a methodology that can capture unpaired ssDNA within the polyplex micelle system (PM), an assembly of DNA and poly(ethylene glycol)-b-poly(l-lysine) (PEG-PLys). A micellar assembly retaining unpaired ssDNA was prepared by unpairing linearized pDNA with heat and performing polyion complexation on site with PEG-PLys. The PM thus formed had a compact and spherical shape, which was distinguishable from the rod-shaped PM formed from dsDNA, and still retained its ability to activate gene expression. Furthermore, we demonstrated that its capacity to encapsulate DNA was much higher than AAV, thereby potentially allowing the delivery of a larger variety of protein-encoding DNA. These features permit the ssDNA-loaded PM to easily penetrate the size-restricting stromal barrier after systemic application. Further, they can elicit gene expression in tumor cell nests of an intractable pancreatic cancer mouse model to achieve antitumor effects through suicide gene therapy. Thus, single-stranded DNA-packaged PM is appealing as a potential gene vector to tackle intractable diseases, particularly those with target delivery issues due to size-restriction barriers.

Mesenchymal stromal cells producing TNFα lack inhibitory effect against A375 experimental lung metastases

Cell-based anticancer therapy using mesenchymal stromal cells (MSCs) engineered to express therapeutic genes has a potential to target the cancer cells in vivo. Metastatic dissemination of melanoma remains a serious problem in the treatment. In our previous work we used MSCs overexpressing gene for tumor necrosis factor α (TNFα; MSCs/TNFα), and we achieved inhibition of melanoma xenograft growth when engineered MCSs/TNFα were coinjected with tumor cells subcutaneously. The TNFα as a pleiotropic cytokine induces apoptosis of tumor cells, creates "tumor resistant" microenvironment, enhances immune response and can have tumor destructive capacity in selected tumor types, especially in tumors of mesodermal origin.In this study we investigated the possibility of intravenously administered MCSs/TNFα to inhibit metastatic spread of A375 melanoma cells in the lungs. We confirmed elevated expression of TNFα transgene in the lung tissue 20 days after MCSs/TNFα intravenous infusion. We also documented that constitutive expression of TNFα transgene is able to neutralize the supportive effect of MSCs on melanoma cells growth. Metastatic spread of A375 melanoma cells in the lung was inhibited approximately to 50% after MCSs/TNFα i.v. administration in comparison to control group with parental MSCs supporting tumor growth. In conclusion, engineered MCSs/TNFα administered intravenously did not demonstrate significant antitumor effect against experimental melanoma lung metastases in this model settings.

The First Approved Gene Therapy Product for Cancer Ad-p53 (Gendicine): 12 Years in the Clinic

Gendicine (recombinant human p53 adenovirus), developed by Shenzhen SiBiono GeneTech Co. Ltd., was approved in 2003 by the China Food and Drug Administration (CFDA) as a first-in-class gene therapy product to treat head and neck cancer, and entered the commercial market in 2004. Gendicine is a biological therapy that is delivered via minimally invasive intratumoral injection, as well as by intracavity or intravascular infusion. The wild-type (wt) p53 protein expressed by Gendicine-transduced cells is a tumor suppressor that is activated by cellular stress, and mediates cell-cycle arrest and DNA repair, or induces apoptosis, senescence, and/or autophagy, depending upon cellular stress conditions. Based on 12 years of commercial use in >30,000 patients, and >30 published clinical studies, Gendicine has exhibited an exemplary safety record, and when combined with chemotherapy and radiotherapy has demonstrated significantly higher response rates than for standard therapies alone. In addition to head and neck cancer, Gendicine has been successfully applied to treat various other cancer types and different stages of disease. Thirteen published studies that include long-term survival data showed that Gendicine combination regimens yield progression-free survival times that are significantly longer than standard therapies alone. Although the p53 gene is mutated in >50% of all human cancers, p53 mutation status did not significantly influence efficacy outcomes and long-term survival rate for Ad-p53-treated patients. To date, Shenzhen SiBiono GeneTech has manufactured 41 batches of Gendicine in compliance with CFDA QC/QA requirements, and 169,571 vials (1.0 × 10¹² vector particles per vial) have been used to treat patients. No serious adverse events have been reported, except for vector-associated transient fever, which occurred in 50-60% of patients and persisted for only a few hours. The manufacturing accomplishments and clinical experience with Gendicine, as well as the understanding of its cellular mechanisms of action and implications, could provide valuable insights for the international gene therapy community and add valuable data to promote further developments and advancements in the gene therapy field.

Oncolytic Virus-Mediated RAS Targeting in Rhabdomyosarcoma

Aberrant activation of the receptor tyrosine kinase-mediated RAS signaling cascade is the primary driver of embryonal rhabdomyosarcoma (ERMS), a pediatric cancer characterized by a block in myogenic differentiation. To investigate the cellular function of activated RAS signaling in regulating the growth and differentiation of ERMS cells, we genetically ablated activated RAS oncogenes with high-efficiency genome-editing technology. Knockout of NRAS in CRISPR-inducible ERMS xenograft models resulted in near-complete tumor regression through a combination of cell death and myogenic differentiation. Utilizing this strategy for therapeutic RAS targeting in ERMS, we developed a recombinant oncolytic myxoma virus (MYXV) engineered with CRISPR/Cas9 gene-editing capability. Treatment of pre-clinical human ERMS tumor xenografts with an NRAS-targeting version of this MYXV significantly reduced tumor growth and increased overall survival. Our data suggest that targeted gene-editing cancer therapies have promising translational applications, especially with improvements to gene-targeting specificity and oncolytic vector technology.

Genetically engineered mesenchymal stromal cells in cancer gene therapy

Based on our experimental data, we aimed to emphasise the perspectives of the use of mesenchymal stromal cells (MSC) in the cancer gene therapy. On the other hand, we would like to point out factors which should be taken into consideration at their clinical use. In this review we define MSC as unique targets for targeted therapy. We proved the efficacy of experimental therapeutic approach utilising enzymatic conversion of non-toxic prodrug into chemotherapeutic by engineered MSC, and we observed significant cytotoxic effect in many preclinical models including metastatic disease. Treatment was enabled by affinity of MSC to tumour tissue and subsequent delivery of therapeutic molecule into the tumour. We also observed decreased efficacy of cell-mediated gene therapy on chemoresistant tumour cells. Moreover MSC can exert a supportive effect on tumour cells as well as to decrease the efficacy of conventional treatment. Besides obvious unique benefits connected to the use of MSC we pointed also to possible risks associated with their clinical application (Ref. 24).

Cell cycle checkpoint control: The cyclin G1/Mdm2/p53 axis emerges as a strategic target for broad-spectrum cancer gene therapy - A review of molecular mechanisms for oncologists

Basic research in genetics, biochemistry and cell biology has identified the executive enzymes and protein kinase activities that regulate the cell division cycle of all eukaryotic organisms, thereby elucidating the importance of site-specific protein phosphorylation events that govern cell cycle progression. Research in cancer genomics and virology has provided meaningful links to mammalian checkpoint control elements with the characterization of growth-promoting proto-oncogenes encoding c-Myc, Mdm2, cyclins A, D1 and G1, and opposing tumor suppressor proteins, such as p53, pRb, p16^INK4A and p21^WAF1, which are commonly dysregulated in cancer. While progress has been made in identifying numerous enzymes and molecular interactions associated with cell cycle checkpoint control, the marked complexity, particularly the functional redundancy, of these cell cycle control enzymes in mammalian systems, presents a major challenge in discerning an optimal locus for therapeutic intervention in the clinical management of cancer. Recent advances in genetic engineering, functional genomics and clinical oncology converged in identifying cyclin G1 (CCNG1 gene) as a pivotal component of a commanding cyclin G1/Mdm2/p53 axis and a strategic locus for re-establishing cell cycle control by means of therapeutic gene transfer. The purpose of the present study is to provide a focused review of cycle checkpoint control as a practicum for clinical oncologists with an interest in applied molecular medicine. The aim is to present a unifying model that: i) clarifies the function of cyclin G1 in establishing proliferative competence, overriding p53 checkpoints and advancing cell cycle progression; ii) is supported by studies of inhibitory microRNAs linking CCNG1 expression to the mechanisms of carcinogenesis and viral subversion; and iii) provides a mechanistic basis for understanding the broad-spectrum anticancer activity and single-agent efficacy observed with dominant-negative cyclin G1, whose cytocidal mechanism of action triggers programmed cell death. Clinically, the utility of companion diagnostics for cyclin G1 pathways is anticipated in the staging, prognosis and treatment of cancers, including the potential for rational combinatorial therapies.

Mesenchymal stem cells expressing interleukin-18 inhibit breast cancer in a mouse model

Development of an improved breast cancer therapy has been an elusive goal of cancer gene therapy for a long period of time. Human mesenchymal stem cells derived from umbilical cord (hUMSCs) genetically modified with the interleukin (IL)-18 gene (hUMSCs/IL-18) were previously demonstrated to be able to suppress the proliferation, migration and invasion of breast cancer cells in vitro. In the present study, the effect of hUMSCs/IL-18 on breast cancer in a mouse model was investigated. A total of 128 mice were divided into 2 studies (the early-effect study and the late-effect study), with 4 groups in each, including the PBS-, hUMSC-, hUMSC/vector- and hUMSC/IL-18-treated groups. All treatments were injected along with 200 µl PBS. Following therapy, the tumor size, histological examination, and expression of lymphocytes, Ki-67, cluster of differentiation 31 and cytokines [interleukin (IL)-18, IL-12, interferon (IFN)-γ and TNF-α] in each group were analyzed. Proliferation of cells (assessed by measuring tumor size and Ki-67 expression) and metastasis, (by determining pulmonary and hepatic metastasis) of breast cancer cells in the hUMSC/IL-18 group were significantly decreased compared with all other groups. hUMSCs/IL-18 suppressed tumor cell proliferation by activating immunocytes and immune cytokines, decreasing the proliferation index of proliferation marker protein Ki-67 of tumor cells and inhibiting tumor angiogenesis. Furthermore, hUMSCs/IL-18 were able to induce a more marked and improved therapeutic effect in the tumor sites, particularly in early tumors. The results of the present study indicate that hUMSCs/IL-18 were able to inhibit the proliferation and metastasis of breast cancer cells in vivo, possibly leading to an approach for a novel antitumor therapy in breast cancer.

Selective eradication of cancer cells by delivery of adenovirus-based toxins

Background and objective

KRAS mutation is an early event in colorectal cancer carcinogenesis. We previously reported that a recombinant adenovirus, carrying a pro-apoptotic gene (PUMA) under the regulation of Ets/AP1 (RAS-responsive elements) suppressed the growth of cancer cells harboring hyperactive KRAS. We propose to exploit the hyperactive RAS pathway, rather than to inhibit it as was previously tried and failed repeatedly. We aim to improve efficacy by substituting PUMA with a more potent toxin, the bacterial MazF-MazE toxin-antitoxin system, under a very tight regulation.

Results

A massive cell death, in a dose-dependent manner, reaching 73% at MOI 10 was seen in KRAS cells as compared to 22% in WT cells. Increase expression of MazE (the anti-toxin) protected normal cells from any possible internal or external leakage of the system and confirmed the selectivity, specificity and safety of the targeting system. Considerable tumor shrinkage (61%) was demonstrated in vivo following MazEF-encoding adenovirus treatment without any side effects.

Design

Efficient vectors for cancer-directed gene delivery were constructed; “pAdEasy-Py4-SV40mP-mCherry-MazF”“pAdEasy-Py4-SV40mP-mCherry-MazF-IRES-TetR-CMVmp-MazE-IRES-EGFP“,“pAdEasy-ΔPy4-SV40mP-mCherry-MazF-IRES-TetR-CMVmp-MazE-IRES-EGFP “and “pAdEasy-mCherry”. Virus particles were produced and their potency was tested. Cell death was measured qualitatively by using the fluorescent microscopy and colony formation assay, and was quantified by MTT. FACS analysis using annexin V and RedDot2 dyes was performed for measuring apoptotic and dead cells, respectively. In vivo tumor formation was measured in a xenograft model.

Conclusions

A proof of concept for a novel cancer safe and effective gene therapy exploiting an aberrant hyperactive pathway is achievable.

Efficient Therapeutic Protein Expression Using Retroviral Replicating Vector with 2A Peptide in Cancer Models

Toca 511, a retroviral replicating vector (RRV), uses an internal ribosomal entry site (IRES) to express an optimized yeast cytosine deaminase (yCD2), which converts 5-fluorocytosine to 5-fluorouracil. This configuration is genetically stable in both preclinical mouse models and human clinical trials. However, the use of IRES (∼600 bp) restricts choices of therapeutic transgenes due to limits in RRV genome size. This study replaced IRES with 2A peptides derived from picornaviruses with or without a GSG linker. The data show that GSG-linked 2A (g2A) peptide resulted in higher polyprotein separation efficiency than non-GSG linked 2A peptide. The study also shows that RRV can tolerate insertion of two separate 2A peptides to allow expression of two transgenes without compromising the assembly and function of the virus in addition to insertion of a single 2A peptide to confirm genetic stability with yCD2, green fluorescent protein, and HSV-1 thymidine kinase. In a parallel comparison of the RRV-IRES-yCD2 and RRV-g2A-yCD2 configurations, the study shows the yCD2 protein expressed from RRV-g2A-yCD2 has higher activity, resulting in a higher survival benefit in an intracranial tumor mouse model. These data enable a wider range of potential product candidates that could be developed using the RRV platform.

Systemic tumor-targeted sodium iodide symporter (NIS) gene therapy of hepatocellular carcinoma mediated by B6 peptide polyplexes

BACKGROUND

Nonviral polymer-based gene transfer represents an adaptable system for tumor-targeted gene therapy because various design strategies of shuttle systems, together with the mechanistic concept of active tumor targeting, lead to improved gene delivery vectors resulting in higher tumor specificity, efficacy and safety.

METHODS

Using the sodium iodide symporter (NIS) as a theranostic gene, nonviral gene delivery vehicles based on linear polyethylenimine (LPEI), polyethylene glycol (PEG) and coupled to the synthetic peptide B6 (LPEI-PEG-B6), which specifically binds to tumor cells, were investigated in a hepatocellular carcinoma xenograft model for tumor selectivity and transduction efficiency.

RESULTS

In vitro incubation of three different tumor cell lines with LPEI-PEG-B6/NIS resulted in significant increase in iodide uptake activity compared to untargeted and empty vectors. After establishment of subcutaneous HuH7 tumors, NIS-conjugated nanoparticles were injected intravenously followed by analysis of radioiodide biodistribution using ¹²³ I-scintigraphy showing significant perchlorate-sensitive iodide accumulation in tumors of LPEI-PEG-B6/NIS-treated mice (8.0 ± 1.5% ID/g ¹²³ I; biological half-life of 4 h). After four cycles of repetitive polyplex/¹³¹ I applications, a significant delay of tumor growth was observed, which was associated with markedly improved survival in the therapy group.

CONCLUSIONS

These results clearly demonstrate that systemic in vivo NIS gene transfer using nanoparticle vectors coupled to B6 tumor targeting ligand is capable of inducing tumor-specific radioiodide uptake. This promising gene therapy approach opens the exciting prospect of NIS-mediated radionuclide therapy in metastatic cancer, together with the possibility of combining several targeting ligands to enhance selective therapeutic efficacy in a broad field of cancer types with various receptor expression profiles.

siRNA Delivery Using a Cationic-Lipid-Based Highly Selective Human DNA Ligase I Inhibitor

The present article illustrates the serendipitous discovery of a cationic-lipid-based human DNA ligase (hLig) I inhibitor and the development of siRNA delivering, a hLigI-targeted cationic-lipid-based nonviral vector. We have tested a small in-house library of structurally similar cationic lipo-anisamides for antiligase activity, and amongst tested, N-dodecyl-N-(2-(4-methoxybenzamido)ethyl)-N-methyldodecan-1-ammonium iodide (C12M) selectively and efficiently inhibited the enzyme activity of hLigI, compared to other human ligases (hLigIIIβ and hLigIV/XRCC4) and bacterial T4 DNA ligase. Furthermore, upon hydration with equimolar cholesterol, C12M produced antiligase cationic liposomes, which transfected survivin siRNA and showed significant inhibition of tumor growth.

Construction of a combinatorial library of chimeric tumor-specific promoters

Gene therapy is a fast-developing field of molecular medicine. New, effective, and cancer-specific promoters are in high demand by researchers seeking to treat cancer through expression of therapeutic genes. Here, we created a combinatorial library of tumor-specific chimeric promoter modules for identifying new promoters with desired functions. The library was constructed by randomly combining promoter fragments from eight human genes involved in cell proliferation control. The pool of chimeric promoters was inserted into a lentiviral expression vector upstream of the CopGFP reporter gene, transduced into A431 cells, and enriched for active promoters by cell sorting. The enriched library contained a remarkably high proportion of active and tumor-specific promoters. This approach to generating combinatorial libraries of chimeric promoters may serve as a useful tool for selecting highly specific and effective promoters for cancer research and gene therapy.

A 3D-Engineered Conformal Implant Releases DNA Nanocomplexs for Eradicating the Postsurgery Residual Glioblastoma

Gene therapy has great promise for glioblastoma treatment; however, it remains a great challenge to efficiently deliver genes to the brain. The incomplete resection of glioblastoma always leads to poor prognosis. Here, a 3D‐engineered conformal implant for eradicating the postsurgery residual glioblastoma is designed. This implant is constructed by 3D‐printing technology to match the tumor cavity and release an oncolytic virus‐inspired DNA nanocomplex to kill glioblastoma cells through apoptosis induction. Meanwhile, a 3D‐engineered subcutaneous glioblastoma xenograft is built to mimic the resection tumor cavity in mice. Insertion of the implant into the glioblastoma resection cavity efficiently delays tumor recurrence and significantly prolongs overall survival. This study provides a proof‐of‐concept of glioblastoma therapy using a conformal implant that releases oncolytic DNA nanocomplexs. This strategy can lead to the development of future precision therapy for eradicating postsurgery residual tumors.

Mutagenic Analysis of an Adeno-Associated Virus Variant Capable of Simultaneously Promoting Immune Resistance and Robust Gene Delivery

In addition to the ability to boost gene delivery efficiency in many therapeutically relevant cells, the capability of circumventing neutralizing antibody (NAb) inactivation is a key prerequisite that gene carriers must fulfill for their extensive applications as therapeutic agents in many gene therapy trials, especially for cancer treatments. This study revealed that a genetically engineered adeno-associated virus (AAV) variant, AAVr3.45, inherently possesses dual beneficial properties as a gene carrier: (i) efficiently delivering therapeutic genes to many clinically valuable cells (e.g., stem or cancer cells) and (ii) effectively bypassing immunoglobulin (IgG) neutralization. Detailed interpretation of the structural features of AAVr3.45, which was previously engineered from AAV2, demonstrated that the LATQVGQKTA peptide at the heparan sulfate proteoglycan binding domain, especially the presence of cationic lysine on the peptide, served as a key motif for dramatically enhancing its gene delivery capabilities, ultimately broadening its tropisms for many cancer cell lines. Furthermore, the substitution of valine on the AAV2 capsid at the amino acid 719 site to methionine functioned as a coordinator for promoting viral resistance against IgG inactivation. The NAb-resistant characteristics of AAVr3.45 were possibly associated with the LATQVGQKTA sequence itself, indicating that its synergistic cooperation with the point mutation (V719M) is required for maximizing its ability to evade NAb inactivation. The potential of AAVr3.45 as a cancer gene therapy agent was confirmed by provoking apoptosis in breast adenocarcinoma by efficiently delivering a pro-apoptotic gene, BIM (Bcl-2-like protein 11), under high titers of human IgG. Thus, the superior aspects of the NAb-resistant AAVr3.45 as a potential therapeutic agent for systemic injection approaches, especially for cancer gene therapy, were highlighted in this study.

Enhanced Vector Design for Cancer Gene Therapy with Hierarchical Enhancement of Therapeutic Transgene Expression

A set of vectors for Cre recombinase-dependent expression of the hybrid suicidal FCU1 transgene was constructed, including a two-plasmid system wherein the FCU1 and Cre transgenes reside in separate vectors, and single-plasmid variants in which a single plasmid bears both transgenes. To improve the safety profile and specificity in cancer gene therapy applications, as well as to ensure stable propagation of plasmids in bacterial cells, the Cre/LoxP system components were optimized. A bicistronic vector with the Cre expression cassette placed between the LoxP sites unidirectionally with FCU1 cDNA resulted in higher therapeutic efficiency compared with the double-plasmid system in an enzyme-prodrug suicide cancer gene therapy scheme. Therefore, the feasibility of a single-plasmid approach in the development of cancer gene therapy with hierarchical enhancement of therapeutic transgene expression has been demonstrated.

Combining Oncolytic Virotherapy with p53 Tumor Suppressor Gene Therapy

Oncolytic virus (OV) therapy utilizes replication-competent viruses to kill cancer cells, leaving non-malignant cells unharmed. With the first U.S. Food and Drug Administration-approved OV, dozens of clinical trials ongoing, and an abundance of translational research in the field, OV therapy is poised to be one of the leading treatments for cancer. A number of recombinant OVs expressing a transgene for p53 (TP53) or another p53 family member (TP63 or TP73) were engineered with the goal of generating more potent OVs that function synergistically with host immunity and/or other therapies to reduce or eliminate tumor burden. Such transgenes have proven effective at improving OV therapies, and basic research has shown mechanisms of p53-mediated enhancement of OV therapy, provided optimized p53 transgenes, explored drug-OV combinational treatments, and challenged canonical roles for p53 in virus-host interactions and tumor suppression. This review summarizes studies combining p53 gene therapy with replication-competent OV therapy, reviews preclinical and clinical studies with replication-deficient gene therapy vectors expressing p53 transgene, examines how wild-type p53 and p53 modifications affect OV replication and anti-tumor effects of OV therapy, and explores future directions for rational design of OV therapy combined with p53 gene therapy.

A Novel Hybrid Promoter ARE-hTERT for Cancer Gene Therapy

describe a novel hybrid tumor-specific promoter, ARE-hTERT, composed of the human TERT gene promoter (hTERT) and the antioxidant response element (ARE) from the human GCLM gene promoter. The hybrid promoter retains the tumor specificity of the basal hTERT promoter but is characterized by an enhanced transcriptional activity in cancer cells with abnormal activation of the Nrf2 transcription factor and upon induction of oxidative stress. In the in vitro enzyme-prodrug cancer gene therapy scheme, ARE-hTERT promoter-driven expression of CD : UPRT (yeast cytosine deaminase : uracil phosphoribosyltransferase) chimeric protein induced a more pronounced death of cancer cells either upon treatment with 5-fluorouracil (5FC) alone or when 5FC was combined with chemotherapeutic drugs as compared to the hTERT promoter. The developed hybrid promoter can be considered a better alternative to the hTERT promoter in cancer gene therapy schemes.

Oncolytic Adenovirus Complexes Coated with Lipids and Calcium Phosphate for Cancer Gene Therapy

Oncolytic adenovirus (Onco^Ad) is a promising therapeutic agent for treating cancer. However, the therapeutic potential of Onco^Ad is hindered by hepatic sequestration and the host immune response in vivo. Here, we constructed a PEG/Lipids/calcium phosphate (CaP)-Onco^Ad (PLC-Onco^Ad) delivery system for ZD55-IL-24, an oncolytic adenovirus that carries the IL-24 gene. The negatively charged PLC-ZD55-IL-24 were disperse and resisted serum-induced aggregation. Compared to naked ZD55-IL-24, the systemic administration of PLC-ZD55-IL-24 in BALB/c mice resulted in reduced liver sequestration and systemic toxicity and evaded the innate immune response. In addition, masking the surface of Onco^Ad protected it from neutralization by pre-existing neutralizing antibody. PLC-Onco^Ad achieved efficient targeted delivery in Huh-7-bearing nude mice, and intravenous administration of a high dose of PLC-ZD55-IL-24 increased therapeutic efficacy without inducing toxicity. The developed PLC-Onco^Ad delivery system represents a promising improvement for oncolytic adenovirus-based cancer gene therapy in vivo.

Esterase-Activated Charge-Reversal Polymer for Fibroblast-Exempt Cancer Gene Therapy

Selective gene expression in tumors via responsive dissociation of polyplexes triggered by intracellular signals is demonstrated. An esterase-responsive charge-reversal polymer mediates selective gene expression in the cancer cells high in esterases over fibroblasts low in esterase activity. Its gene therapy with the TRAIL suicide gene effectively induces apoptosis of HeLa cells but does not activate fibroblasts to secrete WNT16B, enabling potent cancer gene therapy with few side effects.

Enzyme/Prodrug Systems for Cancer Gene Therapy

The use of enzyme/prodrug system has gained attention because it could help improve the efficacy and safety of conventional cancer chemotherapies. In this approach, cancer cells are first transfected with a gene that can express an enzyme with ability to convert a non-toxic prodrug into its active cytotoxic form. As a result, the activated prodrug could kill the transfected cancer cells. Despite the significant progress of different suicide gene therapy protocols in preclinical studies and early clinical trials, none has reached the clinic due to several shortcomings. These include slow prodrug-drug conversion rate, low transfection/transduction efficiency of the vectors and nonspecific toxicity/immunogenicity related to the delivery systems, plasmid DNA, enzymes and/or prodrugs. This mini review aims at providing an overview of the most widely used enzyme/prodrug systems with emphasis on reporting the results of the recent preclinical and clinical studies.

RNAi Screening of the Glucose-Regulated Chaperones in Cancer with Self-Assembled siRNA Nanostructures

The emerging field of RNA nanotechnology has been used to design well-programmed, self-assembled nanostructures for applications in chemistry, biology, and medicine. At the forefront of its utility in cancer is the unrestricted ability to self-assemble multiple siRNAs within a single nanostructure formulation for the RNAi screening of a wide range of oncogenes while potentiating the gene therapy of malignant tumors. In our RNAi nanotechnology approach, V- and Y-shape RNA templates were designed and constructed for the self-assembly of discrete, higher-ordered siRNA nanostructures targeting the oncogenic glucose regulated chaperones. The GRP78-targeting siRNAs self-assembled into genetically encoded spheres, triangles, squares, pentagons and hexagons of discrete sizes and shapes according to TEM imaging. Furthermore, gel electrophoresis, thermal denaturation, and CD spectroscopy validated the prerequisite siRNA hybrids for their RNAi application. In a 24 sample siRNA screen conducted within the AN3CA endometrial cancer cells known to overexpress oncogenic GRP78 activity, the self-assembled siRNAs targeting multiple sites of GRP78 expression demonstrated more potent and long-lasting anticancer activity relative to their linear controls. Extending the scope of our RNAi screening approach, the self-assembled siRNA hybrids (5 nM) targeting of GRP-75, 78, and 94 resulted in significant (50-95%) knockdown of the glucose regulated chaperones, which led to synergistic effects in tumor cell cycle arrest (50-80%) and death (50-60%) within endometrial (AN3CA), cervical (HeLa), and breast (MDA-MB-231) cancer cell lines. Interestingly, a nontumorigenic lung (MRC5) cell line displaying normal glucose regulated chaperone levels was found to tolerate siRNA treatment and demonstrated less toxicity (5-20%) relative to the cancer cells that were found to be addicted to glucose regulated chaperones. These remarkable self-assembled siRNA nanostructures may thus encompass a new class of potent siRNAs that may be useful in screening important oncogene targets while improving siRNA therapeutic efficacy and specificity in cancer.

Delivery of nucleic acids for cancer gene therapy: overcoming extra- and intra-cellular barriers

The therapeutic potential of cancer gene therapy has been limited by the difficulty of delivering genetic material to target sites. Various biological and molecular barriers exist which need to be overcome before effective nonviral delivery systems can be applied successfully in oncology. Herein, various barriers are described and strategies to circumvent such obstacles are discussed, considering both the extracellular and intracellular setting. Development of multifunctional delivery systems holds much promise for the progression of gene delivery, and a growing body of evidence supports this approach involving rational design of vectors, with a unique molecular architecture. In addition, the potential application of composite gene delivery platforms is highlighted which may provide an alternative delivery strategy to traditional systemic administration.

Metastatic Ovarian Cancer Can Be Efficiently Treated by Genetically Modified Mesenchymal Stromal Cells

Due to late diagnosis, often recurrence, formation of metastases and resistance to commonly used chemotherapeutics human ovarian carcinoma represents a serious disease with high mortality. Adipose tissue-derived mesenchymal stromal cells (AT-MSC) can serve as vehicles for therapeutic genes and we engineered AT-MSC to express either Herpes simplex virus thymidine kinase (HSVtk-MSC), which phosphorylates ganciclovir (GCV) to its toxic metabolites or yeast fused cytosine deaminase::uracil phosphoribosyltransferase (CD::UPRT-MSC), which converts 5-fluorocytosine (5-FC) to highly toxic 5-fluorouracil (5-FU). Here, we reported different responses of cytotoxicity mediated by CD::UPRT-MSC/5-FC treatment on human ovarian carcinoma cell lines-SKOV-3 and A2780 used in adherent or three-dimensional (3D) cell culture and we proved high potential of 3D model to predict results in our in vivo experiments. Both tumor cell lines showed similarly high chemosensitivity to the used treatment in adherent culture, but 3D model revealed severe discrepancy-only 36% of SKOV-3 cells but even 90% of A2780 cells were eliminated. This result served as a prognostic marker-we were able to achieve significantly decreased tumor volumes of subcutaneous xenografts of A2780 cells in nude mice and we prolonged tumor-free survival in 33% of animals bearing highly metastatic ovarian carcinoma after CD::UPRT-MSC/5-FC treatment.

Role of nanotechnology and gene delivery systems in TRAIL-based therapies

Since its identification as a member of the tumour necrosis factor (TNF) family, TRAIL (TNF-related apoptosis-inducing ligand) has emerged as a new avenue in apoptosis-inducing cancer therapies. Its ability to circumvent the chemoresistance of conventional therapeutics and to interact with cancer stem cells (CSCs) self-renewal pathways, amplified its potential as a cancer apoptotic agent. Many recombinant preparations of this death ligand and monoclonal antibodies targeting its death receptors have been tested in monotherapy and combinational clinical trials. Gene therapy is a new approach for cancer treatment which implies viral or non-viral functional transgene induction of apoptosis in cancer cells or repair of the underlying genetic abnormality on a molecular level. The role of this approach in overcoming the traditional barriers of radiation and chemotherapeutics systemic toxicity, risk of recurrence, and metastasis made it a promising platform for cancer treatment. The recent first Food Drug Administration (FDA) approved oncolytic herpes virus for melanoma treatment brings forth the potency of the cancer gene therapy approach in the future. Many gene delivery systems have been studied for intratumoural TRAIL gene delivery alone or in combination with chemotherapeutic agents to produce synergistic cancer cytotoxicity. However, there still remain many obstacles to be conquered for this different gene delivery systems. Nanomedicine on the other hand offers a new frontier for clinical trials and biomedical research. The FDA approved nanodrugs motivates horizon exploration for other nanoscale designed particles’ implications in gene delivery. In this review we aim to highlight the molecular role of TRAIL in apoptosis and interaction with cancer stem cells (CSCs) self-renewal pathways. Finally, we also aim to discuss the different roles of gene delivery systems, mesenchymal cells, and nanotechnology designs in TRAIL gene delivery.

Cellular heterogeneity mediates inherent sensitivity-specificity tradeoff in cancer targeting by synthetic circuits

Synthetic gene circuits are emerging as a versatile means to target cancer with enhanced specificity by combinatorial integration of multiple expression markers. Such circuits must also be tuned to be highly sensitive because escape of even a few cells might be detrimental. However, the error rates of decision-making circuits in light of cellular variability in gene expression have so far remained unexplored. Here, we measure the single-cell response function of a tunable logic AND gate acting on two promoters in heterogeneous cell populations. Our analysis reveals an inherent tradeoff between specificity and sensitivity that is controlled by the AND gate amplification gain and activation threshold. We implement a tumor-mimicking cell-culture model of cancer cells emerging in a background of normal ones, and show that molecular parameters of the synthetic circuits control specificity and sensitivity in a killing assay. This suggests that, beyond the inherent tradeoff, synthetic circuits operating in a heterogeneous environment could be optimized to efficiently target malignant state with minimal loss of specificity.