AAV-mediated gene therapies for glaucoma and uveitis: are we there yet?

Glaucoma and uveitis are non-vascular ocular diseases which are among the leading causes of blindness and visual loss. These conditions have distinct characteristics and mechanisms but share a multifactorial and complex nature, making their management challenging and burdensome for patients and clinicians. Furthermore, the lack of symptoms in the early stages of glaucoma and the diverse aetiology of uveitis hinder timely and accurate diagnoses, which are a cause of poor visual outcomes under both conditions. Although current treatment is effective in most cases, it is often associated with low patient adherence and adverse events, which directly impact the overall therapeutic success. Therefore, long-lasting alternatives with improved safety and efficacy are needed. Gene therapy, particularly utilising adeno-associated virus (AAV) vectors, has emerged as a promising approach to address unmet needs in these diseases. Engineered capsids with enhanced tropism and lower immunogenicity have been proposed, along with constructs designed for targeted and controlled expression. Additionally, several pathways implicated in the pathogenesis of these conditions have been targeted with single or multigene expression cassettes, gene editing and silencing approaches. This review discusses strategies employed in AAV-based gene therapies for glaucoma and non-infectious uveitis and provides an overview of current progress and future directions.

AAV-Based Strategies for Treatment of Retinal and Choroidal Vascular Diseases: Advances in Age-Related Macular Degeneration and Diabetic Retinopathy Therapies

Age-related macular degeneration (AMD) and diabetic retinopathy (DR) are vascular diseases with high prevalence, ranking among the leading causes of blindness and vision loss worldwide. Despite being effective, current treatments for AMD and DR are burdensome for patients and clinicians, resulting in suboptimal compliance and real risk of vision loss. Thus, there is an unmet need for long-lasting alternatives with improved safety and efficacy. Adeno-associated virus (AAV) is the leading vector for ocular gene delivery, given its ability to enable long-term expression while eliciting relatively mild immune responses. Progress has been made in AAV-based gene therapies for not only inherited retinal diseases but also acquired conditions with preclinical and clinical studies of AMD and DR showing promising results. These studies have explored several pathways involved in the disease pathogenesis, as well as different strategies to optimise gene delivery. These include engineered capsids with enhanced tropism to particular cell types, and expression cassettes incorporating elements for a targeted and controlled expression. Multiple-acting constructs have also been investigated, in addition to gene silencing and editing. Here, we provide an overview of strategies employing AAV-mediated gene delivery to treat AMD and DR. We discuss preclinical efficacy studies and present the latest data from clinical trials for both diseases.

Clinical and economic burden of benign and malignant skin lesions in renal transplant recipients

BACKGROUND

Studies evaluating the economic burden of dermatological care in the transplant setting are currently not available in Australia.

AIMS

To evaluate the clinical and economic burden of benign and malignant skin lesions in renal transplant recipients in Central Queensland.

METHODS

A bottom-up approach was used to determine the clinical burden and direct costs from patient-level Medicare data obtained from Service Australia for skin lesions.

RESULTS

Seventy-six percent of the renal transplant population in Central Queensland participated in this study. The median age was 57.0 years (standard deviation ± 13.6) and the majority (61.8%) of participants were men. The mean duration after transplant surgery was 99.9 months (interquartile range, 73.2-126.6 months). During a 2-year follow-up, 22 (40%) patients were diagnosed with benign skin lesions, 21 (38%) with nonmelanoma skin carcinoma (NMSC) and one (2%) with melanoma. There was a total of 231 visits to clinicians for diagnostic and therapeutic skin procedures and the direct costs to Medicare was $48 806 Australian Dollars (AUD) or $30 427 US Dollars (USD). Approximately 86% of the total direct costs was spent for nonNMSC and mean direct costs for NMSC was $763 AUD (or $476 USD).

CONCLUSION

This Medicare data-based study provides further insight into the burgeoning clinical and economic burden of the care for benign and malignant skin lesions in the renal transplantation setting in Australia.

MicroRNAs in cancer metastasis: biological and therapeutic implications

Cancer metastasis is the primary cause of cancer-related deaths. The seeding of primary tumours at a secondary site is a highly inefficient process requiring substantial alterations in the genetic architecture of cancer cells. These alterations include significant changes in global gene expression patterns. MicroRNAs are small, non-protein coding RNAs which play a central role in regulating gene expression. Here, we focus on microRNA determinants of cancer metastasis and examine microRNA dysregulation in metastatic cancer cells. We dissect the metastatic process in a step-wise manner and summarise the involvement of microRNAs at each step. We also discuss the advantages and limitations of different microRNA-based strategies that have been used to target metastasis in pre-clinical models. Finally, we highlight current clinical trials that use microRNA-based therapies to target advanced or metastatic tumours.

Attitudes of eye health practitioners towards diagnostic tests and therapies for dry eye disease in Australasia

INTRODUCTION

The diagnosis of dry eye is challenging for eye health practitioners (EHP) and recently, a variety of new diagnostic tests have emerged. This study assesses the attitudes of EHP to dry eye and testing and compares these with attitudes in 2003.

METHODS

An electronic questionnaire was disseminated to EHP in Australasia between December 2020 to March 2021. Participants rated the likelihood that presenting symptoms/signs were associated with dry eye, the utility of diagnostic tests, the value of test characteristics, and their satisfaction with dry eye diagnostics. Qualitative responses were categorised into positive, negative, or neutral themes.

RESULTS

144 responses were received, with 117 (81.3%) from Australia and 27 (18.7%) from New Zealand. Posterior blepharitis was significantly more likely to be associated with dry eye than other factors (p < 0.01). Clinical history, fluorescein staining and FBUT were judged significantly more useful in diagnosing dry eye compared to other tests (p < 0.01). Test validity was judged significantly more important in choosing a test than other qualities. Qualitative attitudes towards dry eye presentations and diagnostic tests were positive in 42.2% and 24.3%, negative in 32.4% and 41.9%, and neutral in 25.5% and 33.8% respectively.

CONCLUSIONS

The opinions of EHP regarding dry eye tests were variable, but most favour history and corneal staining for diagnosis. Patterns of responses were similar to that reported by Turner et al 16-years ago, however, there is a higher satisfaction with available tests and therapeutic options. There is a need to develop a consensus amongst real-world clinicians regarding an optimum diagnostic pathway for dry eye, particularly in relation to newer diagnostic tests.

Differences in Uveal Melanoma Age-Standardized Incidence Rates in Two Eastern States of Australia Are Driven by Differences in Rurality and Ultraviolet Radiation

Uveal melanoma (UM) is the second-most-common melanoma in humans and has a high age-standardized incidence rate (ASR) in Australia. Regional patterns of UM ASRs in Australia are unknown. The aim of this study was to determine and compare UM ASRs in two geographically disparate eastern states, Queensland (QLD) and Victoria (VIC), by using cancer registry data that was obtained from 2001 to 2013. World-standardized UM ASRs and incidence-rate ratios (IRRs) were calculated. Higher UM ASR was also observed in anterior UM compared to posterior UM ASR. UM ASR remained unchanged from 2001 to 2013 in QLD but decreased in VIC. A south-to-north latitude trend in UM ASR along the east of Australia is weakly evident, and rural populations have higher UM ASRs than major city populations in both states. Differences in ultraviolent radiation (UVR) susceptibility, indigenous populations, social behaviours, chemical exposure, and socioeconomic status could all be contributing to differences in UM rates between QLD and VIC and between rural compared to major city areas. It is possible that a minority of cases in QLD and VIC might be prevented by sun-protective behaviours. This is important, because these findings suggest that QLD, which is already known to have one of the highest cutaneous melanoma (CM) ASRs in the world, also has one of the highest UM ASRs.

Complement Factor H Loss in RPE Cells Causes Retinal Degeneration in a Human RPE-Porcine Retinal Explant Co-Culture Model

Age-related Macular degeneration (AMD) is a degenerative disease of the macula affecting the elderly population. Treatment options are limited, partly due to the lack of understanding of AMD pathology and the lack of suitable research models that replicate the complexity of the human macula and the intricate interplay of the genetic, aging and lifestyle risk factors contributing to AMD. One of the main genetic risks associated with AMD is located on the Complement Factor H (CFH) gene, leading to an amino acid substitution in the Factor H (FH) protein (Y402H). However, the mechanism of how this FH variant promotes the onset of AMD remains unclear. Previously, we have shown that FH deprivation in RPE cells, via CFH silencing, leads to increased inflammation, metabolic impairment and vulnerability toward oxidative stress. In this study, we established a novel co-culture model comprising CFH silenced RPE cells and porcine retinal explants derived from the visual streak of porcine eyes, which closely resemble the human macula. We show that retinae exposed to FH-deprived RPE cells show signs of retinal degeneration, with rod cells being the first cells to undergo degeneration. Moreover, via Raman analyses, we observed changes involving the mitochondria and lipid composition of the co-cultured retinae upon FH loss. Interestingly, the detrimental effects of FH loss in RPE cells on the neuroretina were independent of glial cell activation and external complement sources. Moreover, we show that the co-culture model is also suitable for human retinal explants, and we observed a similar trend when RPE cells deprived of FH were co-cultured with human retinal explants from a single donor eye. Our findings highlight the importance of RPE-derived FH for retinal homeostasis and provide a valuable model for AMD research.

The Effects of Continual Consumption of Origanum vulgare on Liver Transcriptomics

Simple Summary

The use of phytogenic products has entered mainstream use in the livestock industry as an antibiotic alternative. These products, often based on herbs and spices with established antimicrobial properties, are generally considered as safe and natural, however, they are often administered in high doses and frequency. The direct effects of these products on the livestock animals remains under-reported. Using a transcriptomics, we show that supplementing 2% oregano in feed has direct effects on gene expression in the livers of broilers with a potential range of beneficial and negative side effects.

Abstract

Pathogen control is re-emerging as a significant challenge to the health of both humans and animals. The livestock industry is in the process of massively replacing in-feed antibiotics with organic production friendly plant-based products. Nutrigenomics as a science of the effects of food constituents on gene expression is shedding more light on both benefits and detrimental side-effects of feed additive prolonged consumption on the host, indicating the need to understand the feed-host interactions and their influence on the host disease profile. In this study, we investigated the effects of 2% oregano powder supplementation on the liver gene expression in healthy male broilers from the hatch to 6 weeks of age. Deep RNAseq was performed on average 113.3 million paired and quality trimmed sequences per sample and four samples for the control and treatment each. The results demonstrate the severity of oregano effect on liver gene expression with substantial modifications in steroid hormone regulation, fat and carbohydrate metabolism alterations and strong influence on the host disease and function profile. Oregano supplementation was able to interfere with the transcriptional effects of a range of registered drugs and to significantly transcriptionally inhibit a range of cancer disease categories including liver cancer, and to modify fat and carbohydrate metabolism.

Prolonged continual consumption of oregano herb interferes with the action of steroid hormones and several drugs, and effects signaling across the brain-gut axis

Herbs and spices have been used throughout human history for their medicinal qualities. The advent of cheap and readily available medicines have lessened the need for herbs and spices as traditional medicines, however, they are rapidly regaining popularity with rising interest of the general population in health, natural products and nutrition. The need for alternative medicines with antimicrobial properties, such as herbs and spices, has also come to the forefront in light of the recent bans of antibiotic use in the livestock industry, including the poultry industry. This large scale use presents an opportunity to observe nutrigenomic effects of prolonged use of herbs on a substantial number of birds fed high concentrations of these products throughout the production cycle. In this manuscript, we investigated the transcriptional effect of continual prolonged oregano supplementation on chicken ileum gene expression. Based on ileum transcriptomics, we report that continual supplementation with 2% oregano altered microbiota-gut-brain axis signalling, rearranged cancer susceptibility towards reduced steroid hormone-related cancers and altered expression of genes targeted by many registered drugs, thus likely affecting their efficiency and side effects. Transcriptional toxicology analysis indicated significant activation of Ventricular Septal Defect and Congenital Heart Disease categories. Our results, counter the notion that natural products such as oregano have the potential for little to no side-effects as they are "natural". The nutrigenomic approach of understanding benefits and side effects of the food we eat, can revolutionize disease management and therapy and have special significance in designing the diets for individuals or livestock with known disease predispositions.

Stathmin 1 deficiency induces erythro-megakaryocytic defects leading to macrocytic anemia and thrombocythemia in Stathmin 1 knock out mice

Stathmin 1 (STMN1) is a cytosolic phosphoprotein that was discovered as a result of its high level of expression in leukemic cells. It plays an important role in the regulation of mitosis by promoting depolymerization of the microtubules that make up the mitotic spindle and, aging has been shown to impair STMN1 levels and change microtubule stability. We have previously demonstrated that a high level of STMN1 expression during early megakaryopoiesis is necessary for proliferation of megakaryocyte progenitors and that down-regulation of STMN1 expression during late megakaryopoiesis is important for megakaryocyte maturation and platelet production. In this report, we examined the effects of STMN1 deficiency on erythroid and megakaryocytic lineages in the mouse. Our studies show that STMN1 deficiency results in mild thrombocytopenia in young animals which converts into profound thrombocythemia as the mice age. STMN1 deficiency also lead to macrocytic changes in both erythrocytes and megakaryocytes that persisted throughout the life of STMN1 knock-out mice. Furthermore, STMN1 knock-out mice displayed a lower number of erythroid and megakaryocytic progenitor cells and had delayed recovery of their blood counts after chemotherapy. These studies show an important role for STMN1 in normal erythro-megakaryopoietic development and suggests potential implications for disorders affecting these hematopoietic lineages.

Natural product-derived phytochemicals as potential agents against coronaviruses: A review

Coronaviruses are responsible for a growing economic, social and mortality burden, as the causative agent of diseases such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), avian infectious bronchitis virus (IBV) and COVID-19. However, there is a lack of effective antiviral agents for many coronavirus strains. Naturally existing compounds provide a wealth of chemical diversity, including antiviral activity, and thus may have utility as therapeutic agents against coronaviral infections. The PubMed database was searched for papers including the keywords coronavirus, SARS or MERS, as well as traditional medicine, herbal, remedy or plants, with 55 primary research articles identified. The overwhelming majority of publications focussed on polar compounds. Compounds that show promise for the inhibition of coronavirus in humans include scutellarein, silvestrol, tryptanthrin, saikosaponin B₂, quercetin, myricetin, caffeic acid, psoralidin, isobavachalcone, and lectins such as griffithsin. Other compounds such as lycorine may be suitable if a therapeutic level of antiviral activity can be achieved without exceeding toxic plasma concentrations. It was noted that the most promising small molecules identified as coronavirus inhibitors contained a conjugated fused ring structure with the majority being classified as being polyphenols.

Presence and prevalence of UV related genetic mutations in uveal melanoma: similarities with cutaneous melanoma

Ultraviolet (UV) radiation is an accepted etiological factor in cutaneous melanoma (CM), however its role in uveal melanoma (UM) is controversial. Partly as a consequence, CM and UM are often considered to be separate conditions, and advances in the treatment of CM have not led to joint clinical trials or parallel improvements in survival of UM. This study hypothesized that a subset of UM tumors displays evidence of genetic changes consistent with UV-related damage similar to that shown in CM. Analysis of the Broad Institute's Firebrowse depository of 80 UM samples and 343 CM samples, together with the Sanger Institute's Catalogue of Somatic Mutations in Cancer depository of 995 UM and 12,447 CM samples was undertaken to identify the most frequently mutated genes, mutation types, and specific nucleotide variants (SNVs) in each condition. Somatic mutation data were cross-correlated and shared mutations assessed against known effects of UV radiation. The proportion of samples with C>T substitutions (a classic genetic marker of UV-related damage) was higher in UM than CM on both DNA strands (17.0% vs 13.1%, p=0.038). The most frequently encountered cross-correlated mutated genes between UM and CM were, in order, BRAF, NRAS, TP53, CDKN2A, TERT, PTEN, ARID2, and KMT2C, with multiple common BRAF point mutations. Each cross-correlated mutation, and each common point mutation in BRAF, was associated with UV-related mechanistic changes. These findings support the hypothesis that the etiology of a substantial minority of UMs may be more UV dependent than previously recognized.

Characterisation and validation of the 8-fold quadrant dissected human retinal explant culture model for pre-clinical toxicology investigation

One of the major challenges in studying ocular toxicology is a lack of clinically-relevant retinal experimental models. In this study we describe the use of an in vitro human retinal explant strategy to generate a reproducible experimental model with utility in neuro-toxicity retinal studies. A retinal dissection strategy, referred to as the 8 fold quadrant dissection, was developed by dissecting human donor retinas into 4 fragments through the fovea in order to obtain 8 experimentally reproducible retinal explants from a single donor. This quadrant dissection gave rise to equivalent proportions of CD73+ photoreceptors and CD90+ ganglion cells in 8 fragments from a single donor and this remained stable for up to 3 days in culture. Major retinal cell types continued to be observed after 8 weeks in culture, despite breakdown of the retinal layers, suggesting the potential to use this model in long-term studies where observation of individual cell types is possible. The utility of this system was examined in a proof of principle neuro-toxicology study. We showed reproducible induction of toxicity in photoreceptors and retinal ganglion cells by glutamate, cobalt chloride and hydrogen peroxide insults, and observed the therapeutic positive effects of the administration of memantine, formononetin and trolox. The quadrant dissected human retinal explants have the potential to be used in toxicology studies in human ocular diseases.

Localization of human recombinant adenoviral vectors to the mitochondria following transduction of human cell lines

Recently, mitochondria have been shown to have a vital role in the innate immune response to viral infection. In response, viruses such as adenovirus, have developed mechanisms to alter mitochondrial function through direct or indirect interaction with the mitochondria. The interaction of human recombinant adenoviral vectors directly with human mitochondria has not previously been shown. We demonstrate that human recombinant adenoviral vectors co-localize to mitochondria. We show that the adenoviral vectors are present within the membranes of the mitochondria and that they cause ultrastructural changes to the cristae. Further, we show that the adenoviral genome is also present in intact mitochondria. We have posited that the interaction between the adenovirus and the mitochondria may act to inhibit mitochondrial function. We have also posited that the transport of the adenoviral genome to the mitochondria may allow the future use of this vector as a tool for gene therapy of mitochondrial diseases. Keywords: mitochondria; human recombinant adenovirus; gene therapy; viral vectors; mitochondrial DNA; electron microscopy.

Gene therapy and the adeno-associated virus in the treatment of genetic and acquired ophthalmic diseases in humans: Trials, future directions and safety considerations

Voretigene neparvovec-rzyl was recently approved for the treatment of Leber congenital amaurosis, and the use of gene therapy for eye disease is attracting even greater interest. The eye has immune privileged status, is easily accessible, requires a reduced dosage of therapy due to its size and is highly compartmentalized, significantly reducing systemic spread. Adeno-associated virus (AAV), with its low pathogenicity, prolonged expression profile and ability to transduce multiple cell types, has become the leading gene therapy vector. Target diseases have moved beyond currently untreatable inherited dystrophies to common, partially treatable acquired conditions such as exudative age-related macular degeneration and glaucoma, but use of the technology in these conditions imposes added obligations for caution in vector design. This review discusses the current status of AAV gene therapy trials in genetic and acquired ocular diseases, and explores new scientific developments, which could help ensure effective and safe use of the therapy in the future.

Retinal explant culture: A platform to investigate human neuro-retina

The retina is the tissue responsible for light detection, in which retinal neurons convert light energy into electrical signals to be transported towards the visual cortex. Damage of retinal neurons leads to neuronal cell death and retinal pathologies, compromising visual acuity and eventually leading to irreversible blindness. Models of retinal neurodegeneration include 2D systems like cell lines, disassociated cultures and co-cultures, and 3D models like organoids, organotypic retinal cultures and animal models. Of these, ex vivo human retinal cultures are arguably the most suitable models for translational research as they retain complex inter-cellular interactions of the retina and precisely mimic in-situ responses. In this review, we summarize the distinguishing features of the human retina which are important to preserve in experimental culture, the historical development of human retinal culture systems, the factors affecting ex vivo human retinal culture and the applications and challenges associated with current methods of human retinal explant culture.

Spotlight on Bortezomib: potential in the treatment of hepatocellular carcinoma

INTRODUCTION

This study reviews the evidence for the use of Bortezomib (BZB), a first-in-class proteasome inhibitor in advanced Hepatocellular carcinoma (HCC). This review aims to delineate the role of BZB within the management of non-surgical and metastatic HCC, either as an alternative or as an adjunct to the current treatment paradigm.

AREAS COVERED

In addition to BZB pharmacology and mechanism of action, safety and tolerance profiles of the drug obtained from clinical trials are explored. The utility of BZB as a therapeutic agent either alone or in combination with other therapies against HCC, including its application in both preclinical and clinical settings has been reviewed. In particular, we highlight the importance of preclinical evaluation of BZB as a combinatorial agent in synergism with other therapies for the use in the management of HCC.

EXPERT OPINION

There has been much interest surrounding the use of BZB, a first-in-class proteasome inhibitor for HCC therapy. The discernment of outcomes of BZB clinical trials for HCC need to take into consideration the disease-specific factors that can affect survival outcomes including patient selection and aetiological differences. Further preclinical testing of BZB in combination with other therapeutic modalities can be important for eliciting enhanced anti-HCC effects.

Abstract A52: Vaccine cells derived from cancer stem cells expressing interleukin-15 and its receptor inhibit tumor growth

Background: Interleukin-15 (IL-15) is a powerful activator and inducer of NK cells and cytolytic CD8+ T cells. IL-15 also activates and expands CD8+ memory T cells without stimulating immunosuppressive CD4+CD25+ T regulatory cells. As such, IL-15 may be useful as an immunotherapy for cancer. In an effort to enhance antitumor activity and reduce systemic side effects, we studied an approach using a tumor vaccine enriched for cancer stem cells (CSCs) expressing murine (m) IL-15 and its receptor (mIL-15Rα).

Methods: Lentiviral vectors expressing the wild type or optimized (opt) cDNA sequences for mIL-15 and/or mIL-15Rα under the control of the human EF-1 promoter were generated and used to transduce TC1 mouse lung cancer cells. The TC1 cells were cultured under low serum conditions to generate tumor spheroids enriched for CSCs.

Results: The transduced TC1 cells demonstrated the expected mRNA transcripts. On flow cytometry only the cells transduced with mIL15Rα in combination with mIL-15 showed surface expression of mIL-15, while cells transduced with mIL-15 or mIL-15Rα constructs did not. When co-cultured with the transduced tumor spheroids or incubated with supernatants from these TC1 cells, CTLL-2 murine T cells demonstrated proliferation indicating that the cloned cDNAs expressed functional proteins. The vector demonstrating the greatest stimulation of CTLL-2 cells expressed both the mIL-15Rα and mIL-15opt sequences and demonstrated suppressed TC1 tumor growth in vivo.

Conclusion: CSCs expressing mIL-15Rα and mIL-15 stimulated proliferation of T cells in vitro and demonstrated inhibited tumor growth in mice. In vivo tumor vaccination studies are in progress.

Citation Format: Donatien Kamdem Toukam, Jason C. Steel, Christian Carwell, Ihab Eldessouki, John C. Morris. Vaccine cells derived from cancer stem cells expressing interleukin-15 and its receptor inhibit tumor growth [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2017 Oct 1-4; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2018;6(9 Suppl):Abstract nr A52.

MicroRNA199a-Based Post-transcriptional Detargeting of Gene Vectors for Hepatocellular Carcinoma

A gene therapeutic platform needs to be both efficient and safe. The criterion of safety is particularly important for diseases like hepatocellular carcinoma (HCC), which develop in a background of an already compromised liver. Gene vectors can be constructed either by targeting HCC or by detargeting liver and/or other major organs. miRNA-based negative detargeting has gained considerable attention in recent times due to its effectiveness and the ease with which it can be adapted into current gene delivery vectors. In this study, we provide a proof-of-concept using miRNA199a as a negative targeting agent. We introduced vectors harboring reporters with miRNA199a binding sites in cells expressing high endogenous levels of miRNA199a and compared the reporter expression in HCC cells with low endogenous miRNA199a. We observed that the expression of reporters with miRNA199a binding sites is significantly inhibited in miRNA199a-positive cells, whereas minimal effect was observed in miRNA199a-negative HCC cells. In addition, we created a post-transcriptionally regulated suicide gene therapeutic system based on cytosine deaminase (CD)/5-fluorocytosine (5-FC) exploiting miRNA199a binding sites and observed significantly lower cell death for miRNA199a-positive cells. Furthermore, we observed a decrease in the levels of miRNA199 in 3D tumorspheres of miRNA199a-positive Hepa1-6 cells and a reduction in the inhibition of reporter expression after transfection in these 3D models when compared with 2D Hepa1-6 cells. In summary, we provide evidence of miRNA199a-based post-transcriptional detargeting with relevance to HCC gene therapy.

Monitoring Immune Checkpoint Regulators as Predictive Biomarkers in Hepatocellular Carcinoma

The global burden of hepatocellular carcinoma (HCC), one of the frequent causes of cancer-related deaths worldwide, is rapidly increasing partly due to the limited treatment options available for this disease and recurrence due to therapy resistance. Immune checkpoint inhibitors that are proved to be beneficial in the treatment of advanced melanoma and other cancer types are currently in clinical trials in HCC. These ongoing trials are testing the efficacy and safety of a few select checkpoints in HCC. Similar to observations in other cancers, these immune checkpoint blockade treatments as monotherapy may benefit only a fraction of HCC patients. Studies that assess the prevalence and distribution of other immune checkpoints/modulatory molecules in HCC have been limited. Moreover, robust predictors to identify which HCC patients will respond to immunotherapy are currently lacking. The objective of this study is to perform a comprehensive evaluation on different immune modulators as predictive biomarkers to monitor HCC patients at high risk for poor prognosis. We screened publically available HCC patient databases for the expression of previously well described immune checkpoint regulators and evaluated the usefulness of these immune modulators to predict high risk, patient overall survival and recurrence. We also identified the immune modulators that synergized with known immune evasion molecules programmed death receptor ligand-1 (PD-L1), programmed cell death protein-1 (PD-1), and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and correlated with worse patient outcomes. We evaluated the association between the expression of epithelial-to-mesenchymal transition (EMT) markers and PD-L1 in HCC patient tumors. We also examined the relationship of tumor mutational burden with HCC patient survival. Notably, expression of immune modulators B7-H4, PD-L2, TIM-3, and VISTA were independently associated with worse prognosis, while B7-H4, CD73, and VISTA predicted low recurrence-free survival. Moreover, the prognosis of patients expressing high PD-L1 with high B7-H4, TIM-3, VISTA, CD73, and PD-L2 expression was significantly worse. Interestingly, PD-L1 expression in HCC patients in the high-risk group was closely associated with EMT marker expression and prognosticates poor survival. In HCC patients, high tumor mutational burden (TMB) predicted worse patient outcomes than those with low TMB.

MicroRNA-Regulated Gene Delivery Systems for Research and Therapeutic Purposes

Targeted gene delivery relies on the ability to limit the expression of a transgene within a defined cell/tissue population. MicroRNAs represent a class of highly powerful and effective regulators of gene expression that act by binding to a specific sequence present in the corresponding messenger RNA. Involved in almost every aspect of cellular function, many miRNAs have been discovered with expression patterns specific to developmental stage, lineage, cell-type, or disease stage. Exploiting the binding sites of these miRNAs allows for construction of targeted gene delivery platforms with a diverse range of applications. Here, we summarize studies that have utilized miRNA-regulated systems to achieve targeted gene delivery for both research and therapeutic purposes. Additionally, we identify criteria that are important for the effectiveness of a particular miRNA for such applications and we also discuss factors that have to be taken into consideration when designing miRNA-regulated expression cassettes.

Epithelial-to-Mesenchymal Transition: A Mediator of Sorafenib Resistance in Advanced Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most lethal cancers worldwide and its incidence is steadily rising. Currently, sorafenib remains the only approved standard treatment for patients with advanced HCC, as it has proven to increase survival in these patients. However, clinical and preclinical observations indicate that sorafenib treatment may have limited efficacy due to tumor progression from the rapid development of acquired resistance. Elucidation of the underlying mechanisms of evasive resistance to sorafenib is a major challenge in HCC research. In recent years, the role of epithelial-to-mesenchymal transition (EMT) in the advancement of HCC and development of drug resistance has gained increasing attention. EMT is a developmental multistep molecular and cellular reprogramming process that is hijacked by cancer cells to enable aggressiveness. In this review, we provide an overview of the currently available preclinical studies on the EMT mechanisms underlying resistance to sorafenib treatment. Recent studies report enrichment of cancer stem cells (CSCs) after sorafenib treatment. Interestingly, EMT process has been implicated in the generation of CSCs associated with therapy resistance. We discuss how combination of sorafenib with EMT inhibitors could enhance the clinical response to sorafenib, resulting in longer duration of responses, than observed with sorafenib monotherapy. In particular, we discuss how these new insights may facilitate rational development of combination therapies in the future to impact survival of patients with advanced HCC.

Reduction of MHC-I expression limits T-lymphocyte-mediated killing of Cancer-initiating cells

Background

It has been proposed that cancer establishment, maintenance, and recurrence may be attributed to a unique population of tumor cells termed cancer-initiating cells (CICs) that may include characteristics of putative cancer stem cell-like cells. Studies in lung cancer have shown that such cells can be enriched and propagated in vitro by culturing tumor cells in serum-free suspension as tumorspheres. CICs have been characterized for their phenotype, stem cell-like qualities, and their role in establishing tumor and maintaining tumor growth. Less is known about the interaction of CICs with the immune system.

Methods

We established CIC-enriched tumorspheres from murine TC-1 lung cancer cells, expressing human papillomavirus 16 (HPV-16) E6/E7 antigens, and evaluated their susceptibility to antitumor immune responses both in vitro and in vivo.

Results

TC-1 CICs demonstrated reduced expression of surface major histocompatibility complex (MHC)-I molecules compared to non-CICs. We similarly determined decreased MHC-I expression in five of six human lung cancer cell lines cultured under conditions enriching for CICs. In vivo, TC-1 cells enriched for CICs were resistant to human papillomavirus 16 E6/E7 peptide vaccine-mediated killing. We found that vaccinated mice challenged with CIC enriched tumorspheres demonstrated shorter survivals and showed significantly fewer CD8⁺ tumor infiltrating lymphocytes compared to CIC non-enriched challenged mice. Furthermore, cultured cytotoxic T lymphocytes (CTLs) from vaccinated mice demonstrated reduced capacity to lyse TC-1 cells enriched for CICs compared to non-enriched TC-1 cells. Following treatment with IFN-γ, both CIC enriched and non-enriched TC-1 cells expressed similar levels of MHC-I, and the increased MHC-I expression on CICs resulted in greater CTL-mediated tumor lysis and improved tumor-free survival in mice.

Conclusions

These results suggest that the attenuated expression of MHC-I molecules by CICs represents a potential strategy of CICs to escape immune recognition, and that the development of successful immunotherapy strategies targeting CICs may decrease their resistance to T cell-mediated immune detection by enhancing CIC MHC-I expression.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4389-3) contains supplementary material, which is available to authorized users.

Murine hepatocellular carcinoma derived stem cells reveal epithelial-to-mesenchymal plasticity

AIM

To establish a model to enrich and characterize stem-like cells from murine normal liver and hepatocellular carcinoma (HCC) cell lines and to further investigate stem-like cell association with epithelial-to-mesenchymal transition (EMT).

METHODS

In this study, we utilized a stem cell conditioned serum-free medium to enrich stem-like cells from mouse HCC and normal liver cell lines, Hepa 1-6 and AML12, respectively. We isolated the 3-dimensional spheres and assessed their stemness characteristics by evaluating the RNA levels of stemness genes and a cell surface stem cell marker by quantitative reverse transcriptase-PCR (qRT-PCR). Next, we examined the relationship between stem cells and EMT using qRT-PCR.

RESULTS

Three-dimensional spheres were enriched by culturing murine HCC and normal hepatocyte cell lines in stem cell conditioned serum-free medium supplemented with epidermal growth factor, basic fibroblast growth factor and heparin sulfate. The 3-dimensional spheres had enhanced stemness markers such as Klf4 and Bmi1 and hepatic cancer stem cell (CSC) marker Cd44 compared to parental cells grown as adherent cultures. We report that epithelial markers E-cadherin and ZO-1 were downregulated, while mesenchymal markers Vimentin and Fibronectin were upregulated in 3-dimensional spheres. The 3-dimensional spheres also exhibited changes in expression of Snai, Zeb and Twist family of EMT transcription factors.

CONCLUSION

Our novel method successfully enriched stem-like cells which possessed an EMT phenotype. The isolation and characterization of murine hepatic CSCs could establish a precise target for the development of more effective therapies for HCC.

Seek and destroy: targeted adeno-associated viruses for gene delivery to hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer with high incidence globally. Increasing mortality and morbidity rates combined with limited treatment options available for advanced HCC press for novel and effective treatment modalities. Gene therapy represents one of the most promising therapeutic options. With the recent approval of herpes simplex virus for advanced melanoma, the field of gene therapy has received a major boost. Adeno-associated virus (AAV) is among the most widely used and effective viral vectors today with safety and efficacy demonstrated in a number of human clinical trials. This review identifies the obstacles for effective AAV based gene delivery to HCC which primarily include host immune responses and off-target effects. These drawbacks could be more pronounced for HCC because of the underlying liver dysfunction in most of the patients. We discuss approaches that could be adopted to tackle these shortcomings and manufacture HCC-targeted vectors. The combination of transductional targeting by modifying the vector capsid and transcriptional targeting using HCC-specific promoters has the potential to produce vectors which can specifically seek HCC and deliver therapeutic gene without significant side effects. Finally, the identification of novel HCC-specific ligands and promoters should facilitate and expedite this process.

Abstract B001: Preliminary clinical activity and safety of an autologous AdHER2 dendritic cell vaccine in patients with advanced metastatic HER2+ solid tumors

Background: In HER2-expressing mouse tumor models we achieved cure of large established tumors using an adenoviral vector vaccine expressing the HER2 extracellular and transmembrane (ECTM) domains that was mediated by the induction of anti-HER2 antibodies. Here we report clinical translation of this vaccine utilizing a therapeutic autologous adenoviral transduced dendritic cell (DC) vaccine expressing human HER2 EC and TM domains (AdHER2ECTM) in adults with advanced metastatic tumors and muscle-invasive bladder cancer (MIBC) post cystectomy, with with 1-3+ HER2 expression by immunohistochemistry (IHC).

Methods: In this two-part phase I study (NCT01730118) subjects with HER2+ metastatic solid tumors naïve to HER2-targeted therapies received up to 5 doses of the AdHER2 DC vaccine at Weeks 0, 4, 8, 16 and 24. Dose escalation occurred in 3 cohorts of 6 patients utilizing 5, 10 or 20×106 viable AdHER2ECTM transduced DCs per dose, respectively. Cohorts 1-3 have been completed without dose-limiting or cardiac toxicity. Enrollment has been initiated in an Expansion Cohort with further dose escalation to 40×106 viable DCs per vaccine. MIBC patients were enrolled and received vaccination in the adjuvant setting after 12-week safety was documented in ≥ 10 treated patients. Response was assessed using immune-related response criteria (irRC).

Results: A total of 21 patients (7 with colon, 5 ovarian, 3 bladder and 6 other cancers), median age 60 yrs (range, 36-72 yrs) with a median of 3 prior treatment regimens received ≥ 2 vaccine doses (median 4) (range 2-5): 14F, 7M; HER2 IHC: 1+ N = 6, 2+ N = 8, 3+ N = 7. Patients that received all 5 scheduled vaccines in Cohorts 1, 2 and 3 were 0 of 6, 2 of 6 and 4 of 6, respectively. Among patients with metastatic disease, the following responses were observed: Cohort 1: No responses; Cohort 2: 1 partial response (PR) in a gastroesophageal cancer patient (-71% lasting 44 weeks), stable disease (SD) in 2 colon cancer patients lasting 24 and 28 weeks; Cohort 3: 1 complete response (CR) (ongoing at 52 weeks) in an ovarian cancer patient, and 1 SD (ongoing at 36 weeks), also in a patient with ovarian cancer, by irRC. Indeed, in dose Cohorts 2 and 3, 5 of 10 metastatic patients had a CR, PR or SD for an overall disease control rate of 50%. Responses were seen in subjects with all ranges of HER2 expression. MIBC patients remain without disease at 48 and 60 weeks. Adverse events were limited to injection site reactions (all ≤ G2) and no cardiac safety signal has been detected to date with serial monitoring of LVEF by echocardiogram and serum Troponin T levels. Decreases in circulating tumor cells (CTCs) were observed at 12 weeks in 6 of 16 (38%) of patients examined, including 3 of the 5 patients exhibiting disease control. Analyses of anti-HER2 antibody titers and epitope repertoire are ongoing.

Conclusion: AdHER2 DC vaccination is safe, well tolerated and is associated with anti-tumor activity, including decreases in circulating tumor cells.

Citation Format: Lauren V. Wood, Brenda D. Roberson, Piyush Agarwal, Andrea A. Apolo, David Stroncek, Lou M. Weiner, John C. Morris, Jason C. Steel, Masaki Terabe, MIn-Jung Lee, Jane Trepel, Sohee Shim, Jay A. Berzofsky. Preliminary clinical activity and safety of an autologous AdHER2 dendritic cell vaccine in patients with advanced metastatic HER2+ solid tumors [abstract]. In: Proceedings of the Second CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; 2016 Sept 25-28; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(11 Suppl):Abstract nr B001.

Epithelial-to-mesenchymal plasticity of cancer stem cells: therapeutic targets in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) remains one of the most common and lethal malignancies worldwide despite the development of various therapeutic strategies. A better understanding of the mechanisms responsible for HCC initiation and progression is essential for the development of more effective therapies. The cancer stem cell (CSC) model has provided new insights into the development and progression of HCC. CSCs are specialized tumor cells that are capable of self-renewal and have long-term repopulation potential. As they are important mediators of tumor proliferation, invasion, metastasis, therapy resistance, and cancer relapse, the selective targeting of this crucial population of cells has the potential to improve HCC patient outcomes and survival. In recent years, the role of epithelial-to-mesenchymal transition (EMT) in the advancement of HCC has gained increasing attention. This multi-step reprograming process resulting in a phenotype switch from an epithelial to a mesenchymal cellular state has been closely associated with the acquisition of stem cell-like attributes in tumors. Moreover, CSC mediates tumor metastasis by maintaining plasticity to transition between epithelial or mesenchymal states. Therefore, understanding the molecular mechanisms of the reprograming switches that determine the progression through EMT and generation of CSC is essential for developing clinically relevant drug targets. This review provides an overview of the proposed roles of CSC in HCC and discusses recent results supporting the emerging role of EMT in facilitating hepatic CSC plasticity. In particular, we discuss how these important new insights may facilitate rational development of combining CSC- and EMT-targeted therapies in the future.

Lung cancer vaccines: current status and future prospects

Designing a cancer treatment that very specifically targets and kills tumor cells with little to no side effects is the "holy grail" of oncology. Cancer vaccines have this potential. Vaccines utilize the immune system to specifically target and eliminate tumor cells. Historically, vaccination approaches against lung cancer have been disappointing. However, over the past decade, a greater understanding of the immune system and of the antigens expressed by tumors, coupled with advances in immunoadjuvants and improved delivery systems, has led to advances in the use of immunotherapy including vaccines to target lung cancer. Proof of principle phase I/II clinical trials targeting the MAGE-A3 and MUC1 tumor antigens, as well as cell-based vaccines such as belagenpumatucel-L have suggested improved survival, leading to larger scale phase III clinical trials. This review will discuss cancer vaccines in relation to lung cancer and present clinical data supporting their use.

Vaginal type-II mucosa is an inductive site for primary CD8⁺ T-cell mucosal immunity

The structured lymphoid tissues are considered the only inductive sites where primary T-cell immune responses occur. The naïve T cells in structured lymphoid tissues, once being primed by antigen-bearing dendritic cells, differentiate into memory T cells and traffic back to the mucosal sites through the bloodstream. Contrary to this belief, here we show that the vaginal type-II mucosa itself, despite the lack of structured lymphoid tissues, can act as an inductive site during primary CD8(+) T-cell immune responses. We provide evidence that the vaginal mucosa supports both the local immune priming of naïve CD8(+) T cells and the local expansion of antigen-specific CD8(+) T cells, thereby demonstrating a different paradigm for primary mucosal T-cell immune induction.

Oral vaccination with adeno-associated virus vectors expressing the Neu oncogene inhibits the growth of murine breast cancer

Recombinant adeno-associated viruses (AAV) have been used for therapeutic gene transfer. These vectors offer a number of advantages including resistance to the effects of pH, a broad cellular tropism, efficient gene transfer, persistence of gene expression, and little toxicity. AAV vectors; however, at high doses can induce humoral and cellular immune responses. While potentially problematic for replacement gene therapy, this effect may be advantageous for antitumor vaccination. We examined the activity of an oral and intramuscular antitumor vaccination using AAV serotypes 5 and 6 expressing a truncated neu oncogene in a neu-positive murine TUBO breast cancer model. Mice receiving a single oral administration of AAV5-neu or AAV6-neu demonstrated improved survival. Oral vaccination significantly improved survivals compared with intramuscular vaccination. Mice vaccinated with AAV6-neu survived longer than those treated with AAV5-neu. Vaccination with AAV5-neu or AAV6-neu induced both humoral and cellular immune responses against the NEU antigen. These responses were more robust in the mice undergoing oral vaccination compared with mice receiving the intramuscular vaccination. Protection from tumor was long lasting with 80% of the animals treated with oral AAV6-neu surviving a re-challenge with TUBO cells at 120 and 320 days post-vaccination. Further evaluation of AAV-based vectors as tumor vaccines is warranted.

Sphere culture of murine lung cancer cell lines are enriched with cancer initiating cells

Cancer initiating cells (CICs) represent a unique cell population essential for the maintenance and growth of tumors. Most in vivo studies of CICs utilize human tumor xenografts in immunodeficient mice. These models provide limited information on the interaction of CICs with the host immune system and are of limited value in assessing therapies targeting CICs, especially immune-based therapies. To assess this, a syngeneic cancer model is needed. We examined the sphere-forming capacity of thirteen murine lung cancer cell lines and identified TC-1 and a metastatic subclone of Lewis lung carcinoma (HM-LLC) as cell lines that readily formed and maintained spheres over multiple passages. TC-1 tumorspheres were not enriched for expression of CD133 or CD44, putative CIC markers, nor did they demonstrate Hoechst 33342 side population staining or Aldefluor activity compared to adherent TC-1 cells. However, in tumorsphere culture, these cells exhibited self-renewal and long-term symmetric division capacity and expressed more Oct-4 compared to adherent cells. HM-LLC sphere-derived cells exhibited increased Oct-4, CD133, and CD44 expression, demonstrated a Hoechst 33342 side population and Aldefluor activity compared to adherent cells or a low metastatic subclone of LLC (LM-LLC). In syngeneic mice, HM-LLC sphere-derived cells required fewer cells to initiate tumorigenesis compared to adherent or LM-LLC cells. Similarly TC-1 sphere-derived cells were more tumorigenic than adherent cells in syngeneic mice. In contrast, in immunocompromised mice, less than 500 sphere or adherent TC-1 cells and less than 1,000 sphere or adherent LLC cells were required to initiate a tumor. We suggest that no single phenotypic marker can identify CICs in murine lung cancer cell lines. Tumorsphere culture may provide an alternative approach to identify and enrich for murine lung CICs. Furthermore, we propose that assessing tumorigenicity of murine lung CICs in syngeneic mice better models the interaction of CICs with the host immune system.

Interleukin-15 expression in lung cancer

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Background: Interleukin-15 (IL-15) is a pro-inflammatory cytokine that stimulates the differentiation and proliferation of T, B, and NK cells. IL-15 is normally tightly bound by its receptor, IL-15Rα. Dendritic cells and monocytes/macrophages primarily express both IL-15 and IL-15-Rα; however, expression has been detected on epithelial cells including those of the lung. In the lung, IL-15 is thought to play a role in the induction of immune responses to infection. Over expression of IL-15 has been shown to induce NK cell activation and cytotoxic T-lymphocyte (CTL) responses leading to tumor regression. Little is known about IL-15 or IL-15Rα expression in lung cancer. Methods: mRNA from 146 primary lung cancers were analyzed by multiplex qPCR for expression of IL-15, IL-15Rα and b-actin (internal control) and compared to expression in normal lung tissue from 45 patients. Of the 146 patients, 50 were stage I (IA=20, IB=30), 49 stage II (IIA=9, IIB=40), 36 stage III (IIIA=18, IIIB=18), and 11 stage IV. Results: Comparing the expression of IL-15 between normal lung and tumor, we found tumors expressed significantly less IL-15 than normal lung (P<0.001). Lung cancers at any given stage, expressed significantly less IL-15 than that seen in normal lung. When comparing stages, stage IV tumors expressed significantly less IL-15 than tumors of stages I (P=0.021), II (P=0.020), or III (P=0.024). There was no difference in expression between stages I, II or III (P>0.05). When examining the expression of IL-15Rα we found no differences between normal lung and tumor. No differences were seen between normal lung and stages I-IIIA; however, significantly less IL-15Rα expression was noted in stages IIIB and IV compared to normal lung. Between stages, stages I and II had significantly more IL-15Rα expression than stage IV tumors. There were no differences between stages I, II and III. Conclusions: Pro-inflammatory cytokines such as IL-15 may be important for the induction of lung immunity. IL-15 expression is down regulated in lung cancers and this down regulation increases with stage. We posit that the down regulation of IL-15 by lung cancers may aid in their evasion of immune responses allowing progression and dissemination of tumor.

Interleukin-15 biology and its therapeutic implications in cancer

Cancer immunotherapy is designed to stimulate the immune system to reject and destroy tumors. Recently, interleukin-15 (IL-15), a member of the four α-helix bundle family of cytokines, has emerged as a candidate immunomodulator for the treatment of cancer. IL-15 acts through its specific receptor, IL-15Rα, which is expressed on antigen-presenting dendritic cells, monocytes and macrophages. IL-15 exhibits broad activity and induces the differentiation and proliferation of T, B and natural killer (NK) cells. It also enhances the cytolytic activity of CD8(+) T cells and induces long-lasting antigen-experienced CD8(+)CD44(hi) memory T cells. IL-15 stimulates differentiation and immunoglobulin synthesis by B cells and induces maturation of dendritic cells. It does not stimulate immunosuppressive T regulatory cells (Tregs). Thus, boosting IL-15 activity could enhance innate and specific immunity and fight tumors. Here we review aspects of IL-15 biology that make it a promising agent for anticancer therapy. We also discuss preclinical models in which IL-15 has demonstrated antitumor activity and highlight ongoing clinical trials of IL-15 in patients with cancer and HIV infection.

Simultaneous blockade of multiple immune system inhibitory checkpoints enhances antitumor activity mediated by interleukin-15 in a murine metastatic colon carcinoma model

PURPOSE

Interleukin 15 (IL-15) is a promising cytokine for immunotherapy of cancer due to its ability to stimulate the immunity of natural killer, B, and T cells. Its effectiveness, however, may be limited by inhibitory checkpoints and pathways that can attenuate immune responses. Finding strategies to abrogate these negative regulators and enhance the efficacy of IL-15 is a critical challenge.

EXPERIMENTAL DESIGN

In a preclinical study, we evaluated IL-15 combined with antibodies to block the negative immune regulators cytotoxic T-lymphocyte antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) in a metastatic murine CT26 colon carcinoma model.

RESULTS

IL-15 treatment resulted in a significant prolongation of survival in mice with metastatic tumor. Administration of IL-15, however, also increased expression of PD-1 on the surface of CD8(+) T cells including CD8(+)CD44(high) memory phenotype T cells. Moreover, IL-15 also increased the secretion of the immunosuppressive cytokine, IL-10. Combining IL-15 with anti-PD-L1 and anti-CTLA-4 (multiple immune checkpoint blockade) exhibited greater CTL killing and IFNγ secretion. Moreover, this combination resulted in a significant reduction in surface expression of PD-1 on CD8(+) T cells, a decrease in IL-10 secretion, and led to significantly longer survival of tumor-bearing animals compared with mice treated with IL-15 alone or combined singularly with anti-PD-L1 or anti-CTLA-4.

CONCLUSIONS

Combining the immune stimulatory properties of IL-15 with the simultaneous removal of 2 critical immune system inhibitory checkpoints, we showed enhancement of immune responses leading to increased antitumor activity.

Interleukin-15 and its receptor augment dendritic cell vaccination against the neu oncogene through the induction of antibodies partially independent of CD4 help

Interleukin-15 (IL-15) stimulates the diffrentiation and proliferation of T, B, and natural killer cells; enhances CD8(+) cytolytic T-ceII activity; helps maintain CD44(hi)CD8(+) memory T cells; and stimulates immunoglobulin synthesis by B cells. IL-15 is trans-presented to effector cells by its receptor, IL-15Ralpha, expressed on dendritic cells (DC) and monocytes. We examined the antitumor effect of adenoviral-mediated gene transfer of IL-15 and IL-15Ralpha to augment a DC vaccine directed against the NEU (ErbB2) oncoprotein. Transgenic BALB-neuT mice vaccinated in late-stage tumor development with a DC vaccine expressing a truncated NEU antigen, IL-I5, and its receptor (DC(Ad.Neu+Ad_mIL-15+Ad.mlL-15Ralpha)) were protected from mammary carcinomas, with 70% of animals tumor-free at 30 weeks compared with none of the animals vaccinated with NEU alone (DC(Ad.Neu)). The combination of neu, IL-15, and IL-15Ralpha gene transfer leads to a significaintly greater anti-NEU antibody response compared with mice treated with DC(Ad.Neu) or DC(Ad.Neu) combined with either IL-15 (DC(Ad.Neu+Ad.mlL-15)) or lL-15Ralpha (DC(Ad.Neu+Ad.mlL-15Ralpha)). The antitumor effect was antibody mediated and involved modulation of NEU expression and signaIing. Depletion of CD4(+) cells did not abrogate the antitumor effect of the vaccine, nor did it inhibit the induction of anti-NEU aritibodies. Coexpression of IL-15 and IL-15Ralpha in an anticancer vaccine enhanced immune responses against the NEU antigen and may overcome impaired CD4(+) T-helper function.

Induction of allogeneic mixed chimerism by immature dendritic cells and bone marrow transplantation leads to prolonged tolerance to major histocompatibility complex disparate allografts

Mixed chimerism has been shown to lead to prolonged major histocompatibility complex (MHC) disparate allograft survival and immune-specific tolerance; however, traditional conditioning regimes often involve myeloablation, which may pose a significant safety risk. In this study we examined the use of donor C57BL/6 (H-2(b)) immature dendritic cells (imDCs) to tolerize the BALB/c (H-2(d)) recipient to bone marrow transplantation (BMT), allowing the induction of mixed chimerism without immunosuppression or myeloablation. We showed that successful mismatched bone marrow engraftment can be achieved using imDCs given up to 3 days prior to BMT and that mixed chimerism can be established and detected in excess of 100 days post-BMT without evidence of graft-versus-host disease. Furthermore, we showed that imDCs can suppress lymphocyte proliferation in response to mismatched MHC stimulation, leading to increased expression of interleukin (IL)-4 and IL-10 and decreased expression of IL-2 and interferon-gamma (IFN-gamma). The induction of stable chimeras through pre-conditioning of mice with donor imDCs followed by BMT led to tolerance, allowing the long-term survival (> 110 days) of mismatched cardiac allografts and the prolonged survival of mismatched skin allografts without the need for immunosuppression or myeloablation. Transplantation with third-party C3H allografts were rapidly rejected in this model, suggesting that immune-specific tolerance was achieved. The induction of immune-specific tolerance without the need for immunosuppression or myeloablation represents a significant advance in transplant immunology and may provide clinicians with a plausible alternative in combating organ rejection following transplantation.

Therapy of advanced established murine breast cancer with a recombinant adenoviral ErbB-2/neu vaccine

ErbB-2 (HER-2/neu) is a transforming oncogene expressed by a substantial fraction of breast cancers, and monoclonal antibody therapy directed toward this antigen is an established treatment modality. However, not all tumors respond, and with a monoclonal antibody directed to a single epitope, there is always the risk of tumor escape. Furthermore, passive antibody therapy requires continual treatment. Whereas cancer vaccines have prevented the growth of tumors, it has been far more difficult to treat large established tumors. Here, we show that vaccination with a recombinant adenovirus expressing a truncated ErbB-2 antigen can cure large established subcutaneous ErbB-2-expressing breast cancers in mice, and can also cure extensive established lung metastatic disease. We also show that the mechanism of protection involves antibody-mediated blockade of ErbB-2 function, independent of Fc receptors. We conclude that a vaccine inducing antibodies to a functional oncogenic receptor could have tremendous therapeutic potential against cancers overexpressing such molecules.

Immunocompetent syngeneic cotton rat tumor models for the assessment of replication-competent oncolytic adenovirus

Oncolytic adenoviruses as a treatment for cancer have demonstrated limited clinical activity. Contributing to this may be the relevance of preclinical animal models used to study these agents. Syngeneic mouse tumor models are generally non-permissive for adenoviral replication, whereas human tumor xenograft models exhibit attenuated immune responses to the vector. The cotton rat (Sigmodon hispidus) is susceptible to human adenovirus infection, permissive for viral replication and exhibits similar inflammatory pathology to humans with adenovirus replicating in the lungs, respiratory passages and cornea. We evaluated three transplantable tumorigenic cotton rat cell lines, CCRT, LCRT and VCRT as models for the study of oncolytic adenoviruses. All three cells lines were readily infected with adenovirus type-5-based vectors and exhibited high levels of transgene expression. The cell lines supported viral replication demonstrated by the induction of cytopathogenic effect (CPE) in tissue culture, increase in virus particle numbers and assembly of virions seen on transmission electron microscopy. In vivo, LCRT and VCRT tumors demonstrated delayed growth after injection with replicating adenovirus. No in vivo antitumor activity was seen in CCRT tumors despite in vitro oncolysis. Adenovirus was also rapidly cleared from the CCRT tumors compared to LCRT and VCRT tumors. The effect observed with the different cotton rat tumor cell lines mimics the variable results of human clinical trials highlighting the potential relevance of this model for assessing the activity and toxicity of oncolytic adenoviruses.

Increased tumor localization and reduced immune response to adenoviral vector formulated with the liposome DDAB/DOPE

We aimed to increase the efficiency of adenoviral vectors by limiting adenoviral spread from the target site and reducing unwanted host immune responses to the vector. We complexed adenoviral vectors with DDAB-DOPE liposomes to form adenovirus-liposomal (AL) complexes. AL complexes were delivered by intratumoral injection in an immunocompetent subcutaneous rat tumor model and the immunogenicity of the AL complexes and the expression efficiency in the tumor and other organs was examined. Animals treated with the AL complexes had significantly lower levels of beta-galactosidase expression in systemic tissues compared to animals treated with the naked adenovirus (NA) (P<0.05). The tumor to non-tumor ratio of beta-galactosidase marker expression was significantly higher for the AL complex treated animals. NA induced significantly higher titers of adenoviral-specific antibodies compared to the AL complexes (P<0.05). The AL complexes provided protection (immunoshielding) to the adenovirus from neutralizing antibody. Forty-seven percent more beta-galactosidase expression was detected following intratumoral injection with AL complexes compared to the NA in animals pre-immunized with adenovirus.

CONCLUSIONS

Complexing of adenovirus with liposomes provides a simple method to enhance tumor localization of the vector, decrease the immunogenicity of adenovirus, and provide protection of the virus from pre-existing neutralizing antibodies.

Modification of liposomal concentration in liposome/adenoviral complexes allows significant protection of adenoviral vectors from neutralising antibody, in vitro

Adenoviral vectors have been commonly used in gene therapy protocols, however the success of their use is often limited by the induction of host immunity to the vector. Following exposure to the adenoviral vector, adenoviral-specific neutralising antibodies are produced which limits further administration. This study examines the efficacy of complexing liposomes to adenovirus for the protection of the adenovirus from neutralising antibodies in an in vitro setting. Dimethyldioctadecylammonium bromide (DDAB)-dioleoyl-l-phosphatidylethanolamine (DOPE) liposomes were bound at varying concentrations to adenovirus to form AL complexes and tested these complexes' ability to prevent adenoviral neutralisation. It is shown that by increasing the concentration of liposomes in the adenoviral-liposome (AL) complexes we can increase the level of immuno-shielding afforded the adenovirus. It is also shown that the increase in liposomal concentration may lead to drawbacks such as increased cytotoxicity and reductions in expression levels.

Microsphere-liposome complexes protect adenoviral vectors from neutralising antibody without losses in transfection efficiency, in-vitro

Adenoviral vectors have been commonly used in gene therapy protocols but the success of their use is often limited by the induction of host immunity to the vector. Following exposure to the adenoviral vector, adenoviral-specific neutralising antibodies are produced, which limits further administration. This study examines the effectiveness of a novel combination of microspheres and liposomes for the shielding of adenovirus from neutralising antibodies in an in-vitro setting. We show that liposomes are effective in the protection of adenovirus from neutralising antibody and that the conjugation of these complexes to microspheres augments the level of protection. This study further reveals that previously neutralised adenovirus may still be transported into the cell via liposome-cell interactions and is still capable of expressing its genes, making this vector an effective tool for circumvention of the humoral immune response. We also looked at possible side effects of using the complexes, namely increases in cytotoxicity and reductions in transfection efficiency. Our results showed that varying the liposome:adenovirus ratio can reduce the cytotoxicity of the vector as well as increase the transfection efficiency. In addition, in cell lines that are adenoviral competent, transfection efficiencies on par with uncomplexed adenoviral vectors were achievable with the combination vector.

In-vitro evaluation of ion-exchange microspheres for the sustained release of liposomal–adenoviral conjugates

This study looks at the development of a novel combination vector consisting of adenovirus conjugated to liposomes (AL complexes) bound to cation-exchanging microspheres (MAL complexes). With adenovirus having a net negative charge and the liposomes a net positive charge it was possible to modify the net charge of the AL complexes by varying the concentrations of adenovirus to liposomes. The modification of the net charge resulted in altered binding and release characteristics. Of the complexes tested, the 5:1 and 2:1 ratio AL complexes were able to be efficiently bound by the microspheres and exhibited sustained release over 24 h. The 1:1 and 1:2 AL complexes, however, bound poorly to the microspheres and were rapidly released. In addition the MAL complexes also were able to reduce the toxicity of the AL complexes, which was seen with the 10:1 ratio. The AL complexes showed considerably more toxicity alone than in combination with microspheres, highlighting a potential benefit of this vector.

Pre-treatment with a non-therapeutic dose of cisplatin increases solid tumour response to liposomal-p53 gene therapy- An in vivo study

Successful liposomal-mediated gene therapy is often limited by poor transfection efficiencies. One method previously shown to increase the efficiency of liposomal gene delivery is through the administration of a non-therapeutic dose of the chemotherapeutic drug cisplatin prior to lipofection. The currents study aims to utilise this method to deliver lipoplexes containing the p53 tumour suppressor gene with the aim of increasing therapeutic effect of the p53 gene on a solid tumour in vivo. Rats, implanted with solid salivary adenocarcinomas, were pre-treated with a low dose of cisplatin seven days prior to liposomal mediated p53 treatment. Following treatment with p53, tumour growth, p53 expression and levels of apoptosis were examined and compared to animals treated with p53 without cisplatin pre-treatment and a saline control. Tumours that had been pre-treated with cisplatin prior to p53-lipofection were significantly smaller than both the saline control and the non-cisplatin treated tumours. Saline treated tumours increased in size by an average of 164% over a 96-hour period compared to 64% and 101% for the cisplatin and non-cisplatin p53-liposome treated tumours. The cisplatin pre-treated tumours resulted in significantly higher levels of apoptosis surrounding the treatment site and exhibited prolonged p53 expression when compared to the non-cisplatin pre-treated tumours. The results suggest that the use of cisplatin to pre-sensitise tumours to lipofection has significant benefits when used in conjunction with p53.