Therapeutic targeting of the RB1 pathway in retinoblastoma with the oncolytic adenovirus VCN-01

Safety of intravitreal chemotherapy in the management of retinoblastoma: A systematic review of the literature

Intravitreal chemotherapy is used as a salvage therapy for retinoblastoma with persistent or recurrent vitreous seeding after primary treatment. To assess the safety of this technique, we conducted a systematic review of all studies reporting ocular toxicity data. Forty-eight trials involving 2751 eyes were included. The most common complications were cataract, retinal toxicity, and vitreous hemorrhage. However, severe and permanent adverse events were limited, while the risk of extraocular dissemination, a significant concern, was practically eliminated through preventive techniques. Globe salvage rates ranged from 29 % to 100 %. In conclusion, intravitreal chemotherapy seems to improve prognosis of eyes with advanced disease, with an acceptable safety profile. Nevertheless, most relevant studies are retrospective, and no randomized trials have been performed. Recognizing the challenges regarding the conduct of randomized studies for such a rare pediatric cancer, we believe that multicenter trials through international collaborations can significantly enhance the available information.

Exploring treatment options in cancer: Tumor treatment strategies

Traditional therapeutic approaches such as chemotherapy and radiation therapy have burdened cancer patients with onerous physical and psychological challenges. Encouragingly, the landscape of tumor treatment has undergone a comprehensive and remarkable transformation. Emerging as fervently pursued modalities are small molecule targeted agents, antibody-drug conjugates (ADCs), cell-based therapies, and gene therapy. These cutting-edge treatment modalities not only afford personalized and precise tumor targeting, but also provide patients with enhanced therapeutic comfort and the potential to impede disease progression. Nonetheless, it is acknowledged that these therapeutic strategies still harbour untapped potential for further advancement. Gaining a comprehensive understanding of the merits and limitations of these treatment modalities holds the promise of offering novel perspectives for clinical practice and foundational research endeavours. In this review, we discussed the different treatment modalities, including small molecule targeted drugs, peptide drugs, antibody drugs, cell therapy, and gene therapy. It will provide a detailed explanation of each method, addressing their status of development, clinical challenges, and potential solutions. The aim is to assist clinicians and researchers in gaining a deeper understanding of these diverse treatment options, enabling them to carry out effective treatment and advance their research more efficiently.

Long non-coding RNA MIMT1 promotes retinoblastoma proliferation via sponging miR-153-5p to upregulate FGF2

With the rapid development of biotechnology, long non-coding RNAs (lncRNAs) have shown promising potential for cancer treatment and may become novel therapeutic targets. This study aimed to explore the roles of lncRNAs in retinoblastoma (RB). It involves analysing differentially expressed lncRNAs in RB and normal tissues from the GSE111168 and GSE125903 datasets, further validating them in RB cells. Our findings determined that lncRNA MIMT1 was upregulated in RB cell lines and tissues. In WERI-Rb1 and Y79 cells, silencing MIMT1 significantly inhibited cell proliferation, whereas MIMT1 overexpression enhanced cell proliferation. Furthermore, in vivo xenograft experiments demonstrated that MIMT1 knockdown suppressed tumour volume and weight. Subsequent mechanistic investigations showed that MIMT1 upregulates fibroblast expression of FGF2 by binding to miR-153-5p, ultimately promoting RB cell proliferation. This suggest that MIMT1 functions as an oncogene in RB and potentially serves as a molecular marker for diagnostic and prognostic assessments. Thus, the MIMT1/miR-153-5p/FGF2 pathway is a promising therapeutic target for RB treatment.

Retinoblastoma: An update on genetic origin, classification, conventional to next-generation treatment strategies

The most prevalent paediatric vision-threatening medical condition, retinoblastoma (RB), has been a global concern for a long time. Several conventional therapies, such as systemic chemotherapy and focal therapy, have been used for curative purposes; however, the search for tumour eradication with the least impact on surrounding tissues is still ongoing. This review focuses on the genetic origin, classification, conventional treatment modalities, and their combination with nano-scale delivery systems for active tumour targeting. In addition, the review also delves into ongoing clinical trials and patents, as well as emerging therapies such as gene therapy and immunotherapy for the treatment of RB. Understanding the role of genetics in the development of RB has refined its treatment strategy according to the genetic type. New approaches such as nanostructured drug delivery systems, galenic preparations, nutlin-3a, histone deacetylase inhibitors, N-MYC inhibitors, pentoxifylline, immunotherapy, gene therapy, etc. discussed in this review, have the potential to circumvent the limitations of conventional therapies and improve treatment outcomes for RB. In summary, this review highlights the importance and need for novel approaches as alternative therapies that would ultimately displace the shortcomings associated with conventional therapies and reduce the enucleation rate, thereby preserving global vision in the affected paediatric population.

Advances and challenges in gene therapy strategies for pediatric cancer: a comprehensive update

Pediatric cancers represent a tragic but also promising area for gene therapy. Although conventional treatments have improved survival rates, there is still a need for targeted and less toxic interventions. This article critically analyzes recent advances in gene therapy for pediatric malignancies and discusses the challenges that remain. We explore the innovative vectors and delivery systems that have emerged, such as adeno-associated viruses and non-viral platforms, which show promise in addressing the unique pathophysiology of pediatric tumors. Specifically, we examine the field of chimeric antigen receptor (CAR) T-cell therapies and their adaptation for solid tumors, which historically have been more challenging to treat than hematologic malignancies. We also discuss the genetic and epigenetic complexities inherent to pediatric cancers, such as tumor heterogeneity and the dynamic tumor microenvironment, which pose significant hurdles for gene therapy. Ethical considerations specific to pediatric populations, including consent and long-term follow-up, are also analyzed. Additionally, we scrutinize the translation of research from preclinical models that often fail to mimic pediatric cancer biology to the regulatory landscapes that can either support or hinder innovation. In summary, this article provides an up-to-date overview of gene therapy in pediatric oncology, highlighting both the rapid scientific progress and the substantial obstacles that need to be addressed. Through this lens, we propose a roadmap for future research that prioritizes the safety, efficacy, and complex ethical considerations involved in treating pediatric patients. Our ultimate goal is to move from incremental advancements to transformative therapies.

Advancements in Nanosystems for Ocular Drug Delivery: A Focus on Pediatric Retinoblastoma

The eye's complex anatomical structures present formidable barriers to effective drug delivery across a range of ocular diseases, from anterior to posterior segment pathologies. Emerging as a promising solution to these challenges, nanotechnology-based platforms-including but not limited to liposomes, dendrimers, and micelles-have shown the potential to revolutionize ophthalmic therapeutics. These nanocarriers enhance drug bioavailability, increase residence time in targeted ocular tissues, and offer precise, localized delivery, minimizing systemic side effects. Focusing on pediatric ophthalmology, particularly on retinoblastoma, this review delves into the recent advancements in functionalized nanosystems for drug delivery. Covering the literature from 2017 to 2023, it comprehensively examines these nanocarriers' potential impact on transforming the treatment landscape for retinoblastoma. The review highlights the critical role of these platforms in overcoming the unique pediatric eye barriers, thus enhancing treatment efficacy. It underscores the necessity for ongoing research to realize the full clinical potential of these innovative drug delivery systems in pediatric ophthalmology.

An anti-GD2 aptamer-based bifunctional spherical nucleic acid nanoplatform for synergistic therapy targeting MDM2 for retinoblastoma

Retinoblastoma (RB) is a type of pediatric solid tumor in the fundus. The lack of precision therapies combined with the difficulty of delivering small interfering RNA (siRNA) into the eyes means that there is currently no nucleic acid-based therapy for RB in clinical practice. Here, we reported on anti-GD2 and glutathione-responsive spherical nucleic acids (SNAs), loaded with siRNA and the inhibitor NVP-CGM097, which jointly blocked the oncogenic factor n in RB cells (Y79 and WERI-RB-1). The SNAs were formed through the self-assembly of bifunctional cholesterol amphiphiles containing aptamers that specifically targeted GD2-positive RB cells, allowing for the formation of an SNA with a dense DNA shell. The aptamer/siRNA component functioned both as a carrier and a payload, enhancing the specific recognition and delivery of both components and constituting an active agent for MDM2 regulation. Following SNA endocytosis by RB cells, siRNA and NVP-CGM097 were released from the SNA particles by glutathione, which synergistically blocked the MDM2-p53 pathway, increasing p53 protein content and inducing cell apoptosis. This study showed a potent antitumor effect following intravitreal injection of SNAs in Y79 tumor-bearing mice through clinical manifestation and tumor pathological analysis. In hematological analysis and hepatotoxicity assays, SNAs were safer for mice than melphalan, the favored drug for treating RB in clinical practice. Our results illustrated the potential of intravitreally injected SNAs as a precision medicine for treating RB.

Evidence in Focus: The Sparse Landscape of Randomized Trials on Retinoblastoma Treatment

Background

Retinoblastoma, although rare, is one of the most common intraocular malignancies worldwide. Its prognosis has improved significantly in the past few decades, thanks to modern treatments, like systemic, intra-arterial, and intravitreal chemotherapy. However, regarding survival, there are significant differences between high- and low-income countries, eye salvage is still a challenge worldwide, and treatment-related toxicity needs to be carefully and sufficiently managed.

Summary

To appraise the strength of supporting evidence, we performed a systematic review of randomized controlled trials investigating any therapeutic protocol for retinoblastoma. Four trials with 174 participants (188 eyes) were eligible, all pertaining to different intravenous chemotherapy regimens. Vincristine, etoposide, and carboplatin (VEC) appear superior to a 5-drug combination for stage III retinoblastoma. Moreover, etoposide and carboplatin as neoadjuvant chemotherapy followed by thermochemotherapy seem to offer better local control than vincristine and carboplatin. However, increasing carboplatin dose in the VEC protocol failed to improve treatment efficacy.

Key Messages

Retinoblastoma is a success story of modern medicine. However, only intravenous chemotherapy has been studied through randomized trials, while evidence for the most novel retinoblastoma treatments has mainly stemmed from observational studies. International collaborations for multicenter randomized trials could overcome difficulties and increase certainty and precision in the field.

Management of retinoblastoma: are we there yet?

Since the introduction of intraarterial chemotherapy (IAC) in the last decade, there has been a paradigm shift in the management of retinoblastoma (RB), especially in developed countries. Despite improved globe salvage outcomes with IAC compared with systemic intravenous chemotherapy, IAC has certain limitations, such as poor accessibility and affordability, especially for middle- and low-income countries; the need for expertise; local ocular complications; and possible increased risk of systemic metastasis. This review discusses the important limitations of the current treatment strategy of using IAC, as well as the prospects of new therapeutic targets or routes of drug delivery that may lead to further improvements in the management of RB.

Therapy for Vitreous Seeding Caused by Retinoblastoma. A Review

Retinoblastoma is the most common primary malignant intraocular tumor in children. Seeding, specifically the dispersion of the tumor into the adjacent compartments, represents a major parameter determining the degree of retinoblastoma according to the International Classification of Retinoblastoma. In this article we focused on vitreous seeding, one of the main limiting factors in the successful "eye preservation treatment" of retinoblastoma. This article presents an overview of the history of vitreous seeding of retinoblastoma, established treatment procedures and new-research modalities. The introduction of systemic chemotherapy in the treatment of retinoblastoma at the end of the 1990s represented a significant breakthrough, which enabled the progressive abandonment of radiotherapy with its attendant side effects. However, the attained concentrations of chemotherapeutics in the vitreous space during systemic chemotherapy are not sufficient for the treatment of vitreous seeding, and the toxic effects of systemic chemotherapy are not negligible. A significant change came with the advent of chemotherapy in situ, with the targeted administration of chemotherapeutic drugs, namely intra-arterial and intravitreal injections, contributing to the definitive eradication of external radiotherapy and a reduction of systemic chemotherapy. Although vitreous seeding remains the most common reason for the failure of intra-arterial chemotherapy, this technique has significantly influenced the original treatment regimen of children with retinoblastoma. However, intravitreal chemotherapy has made the greatest contribution to increasing the probability of preservation of the eyeball and visual functions in patients with advanced findings. Novel local drug delivery modalities, gene therapy, oncolytic viruses and immunotherapy from several ongoing preclinical and clinical trials may represent promising approaches in the treatment of vitreous retinoblastoma seeding, though no clinical trials have yet been completed for routine use.

The Use of rAAV2-RB1-Mediated Gene Therapy in Retinoblastoma

Purpose

Retinoblastoma (RB) is a life-threatening malignancy that arises from the retina and is activated upon homozygous inactivation of the tumor suppressor RB1. Gene therapy targeting RB1 is an effective strategy to treat RB. However, it is difficult to target the RB1 gene by site-specific repair, with up to 3366 gene mutation sites identified in RB1. Thus, it is necessary to construct a promising and efficacious gene therapeutic strategy for patients with RB.

Methods

To recover the function of the RB1 protein, we constructed a recombinant adeno-associated virus 2 (rAAV2) expressing RB1 that can restore RB1 function and significantly inhibit RB progression. To confirm the clinical feasibility of rAAV2-RB1, the RB1 protein was validated in vitro and in vivo after transfection. To further evaluate the clinical efficacy, RB patient-derived xenograft models were established and applied. The biosafety of rAAV2-RB1 was also validated in immunocompetent mice.

Results

rAAV2-RB1 was a rAAV2 expressing the RB1 protein, which was validated in vitro and in vivo. In vitro, rAAV2-RB1 was effectively expressed in patient-derived RB cells. In mice, intravitreal administration of rAAV2-RB1 in a population-based patient-derived xenograft trial induced limited tumor growth. Moreover, after transfection of rAAV2-RB1 in immunocompetent mice, rAAV2-RB1 did not replicate and was expressed in other important organs, except retinas, inducing minor local side effects.

Conclusions

Our study suggested a promising efficacy gene therapeutic strategy, which might provide a chemotherapy-independent treatment option for RB.

Oncolytic adenovirus as pancreatic cancer-targeted therapy: Where do we go from here?

Pancreatic cancer remains one of the deadliest cancers with extremely high mortality rate, and the number of cases is expected to steadily increase with time. Pancreatic cancer is refractory to conventional cancer treatment options, like chemotherapy and radiotherapy, and commercialized immunotherapeutics, owing to its immunosuppressive and desmoplastic phenotype. Due to these reasons, development of an innovative treatment option that can overcome these challenges posed by the pancreatic tumor microenvironment (TME) is in an urgent need. The present review aims to summarize the evolution of oncolytic adenovirus (oAd) engineering and usage as therapeutics (either monotherapy or combination therapy) over the last decade to overcome these hurdles to instigate a potent antitumor effect against desmoplastic and immunosuppressive pancreatic cancer.

Translational screening platform to evaluate chemotherapy in combination with focal therapy for retinoblastoma

Retinoblastoma is the most common pediatric eye cancer. It is currently treated with a limited number of drugs, adapted from other pediatric cancer treatments. Drug toxicity and relapse of the disease warrant new therapeutic strategies for these young patients. In this study, we developed a robust tumoroid-based platform to test chemotherapeutic agents in combination with focal therapy (thermotherapy) - a treatment option widely used in clinical practice - in accordance with clinically relevant trial protocols. The model consists of matrix-embedded tumoroids that retain retinoblastoma features and respond to repeated chemotherapeutic drug exposure similarly to advanced clinical cases. Moreover, the screening platform includes a diode laser (810 nm, 0.3 W) to selectively heat the tumoroids, combined with an on-line system to monitor the intratumoral and surrounding temperatures. This allows the reproduction of the clinical settings of thermotherapy and combined chemothermotherapy treatments. When testing the two main drugs currently used in clinics to treat retinoblastoma in our model, we observed results similar to those clinically obtained, validating the utility of the model. This screening platform is the first system to accurately reproduce clinically relevant treatment methods and should lead to the identification of more efficient drugs to treat retinoblastoma.

In-depth understanding of higher-order genome architecture in orphan cancer

The human genome is intertwined, folded, condensed, and gradually constitutes the 3D architecture, thereby affecting transcription and widely involving in tumorigenesis. Incidence and mortality rates for orphan cancers increase due to poor early diagnosis and lack of effective medical treatments, which are now getting attention. In-depth understanding in tumorigenesis has fast-tracked over the last decade, however, the further role and mechanism of 3D genome organization in variant orphan tumorigenesis remains to be fully understood. We summarize for the first time that higher-order genome organization can provide novel insights into the occurrence mechanisms of orphan cancers, and discuss probable future research directions for drug development and anti-tumor therapies.

Oncolytic virotherapy evolved into the fourth generation as tumor immunotherapy

BACKGROUND

Oncolytic virotherapy (OVT) is a promising anti-tumor modality that utilizes oncolytic viruses (OVs) to preferentially attack cancers rather than normal tissues. With the understanding particularly in the characteristics of viruses and tumor cells, numerous innovative OVs have been engineered to conquer cancers, such as Talimogene Laherparepvec (T-VEC) and tasadenoturev (DNX-2401). However, the therapeutic safety and efficacy must be further optimized and balanced to ensure the superior safe and efficient OVT in clinics, and reasonable combination therapy strategies are also important challenges worthy to be explored.

MAIN BODY

Here we provided a critical review of the development history and status of OVT, emphasizing the mechanisms of enhancing both safety and efficacy. We propose that oncolytic virotherapy has evolved into the fourth generation as tumor immunotherapy. Particularly, to arouse T cells by designing OVs expressing bi-specific T cell activator (BiTA) is a promising strategy of killing two birds with one stone. Amazing combination of therapeutic strategies of OVs and immune cells confers immense potential for managing cancers. Moreover, the attractive preclinical OVT addressed recently, and the OVT in clinical trials were systematically reviewed.

CONCLUSION

OVs, which are advancing into clinical trials, are being envisioned as the frontier clinical anti-tumor agents coming soon.

Retinoblastoma: A review of the molecular basis of tumor development and its clinical correlation in shaping future targeted treatment strategies

Retinoblastoma is a retinal cancer that affects children and is the most prevalent intraocular tumor worldwide. Despite tremendous breakthroughs in our understanding of the fundamental mechanisms that regulate progression of retinoblastoma, the development of targeted therapeutics for retinoblastoma has lagged. Our review highlights the current developments in the genetic, epigenetic, transcriptomic, and proteomic landscapes of retinoblastoma. We also discuss their clinical relevance and potential implications for future therapeutic development, with the aim to create a frontline multimodal therapy for retinoblastoma.

Oncolytic virotherapies for pediatric tumors

INTRODUCTION

Many pediatric patients with malignant tumors continue to suffer poor outcomes. The current standard of care includes maximum safe surgical resection followed by chemotherapy and radiation which may be associated with considerable long-term morbidity. The emergence of oncolytic virotherapy (OVT) may provide an alternative or adjuvant treatment for pediatric oncology patients.

AREAS COVERED

We reviewed seven virus types that have been investigated in past or ongoing pediatric tumor clinical trials: adenovirus (AdV-tk, Celyvir, DNX-2401, VCN-01, Ad-TD-nsIL-12), herpes simplex virus (G207, HSV-1716), vaccinia (JX-594), reovirus (pelareorep), poliovirus (PVSRIPO), measles virus (MV-NIS), and Senecavirus A (SVV-001). For each virus, we discuss the mechanism of tumor-specific replication and cytotoxicity as well as key findings of preclinical and clinical studies.

EXPERT OPINION

Substantial progress has been made in the past 10 years regarding the clinical use of OVT. From our review, OVT has favorable safety profiles compared to chemotherapy and radiation treatment. However, the antitumor effects of OVT remain variable depending on tumor type and viral agent used. Although the widespread adoption of OVT faces many challenges, we are optimistic that OVT will play an important role alongside standard chemotherapy and radiotherapy for the treatment of malignant pediatric solid tumors in the future.

Development and application of oncolytic viruses as the nemesis of tumor cells

Viruses and tumors are two pathologies that negatively impact human health, but what occurs when a virus encounters a tumor? A global consensus among cancer patients suggests that surgical resection, chemotherapy, radiotherapy, and other methods are the primary means to combat cancer. However, with the innovation and development of biomedical technology, tumor biotherapy (immunotherapy, molecular targeted therapy, gene therapy, oncolytic virus therapy, etc.) has emerged as an alternative treatment for malignant tumors. Oncolytic viruses possess numerous anti-tumor properties, such as directly lysing tumor cells, activating anti-tumor immune responses, and improving the tumor microenvironment. Compared to traditional immunotherapy, oncolytic virus therapy offers advantages including high killing efficiency, precise targeting, and minimal side effects. Although oncolytic virus (OV) therapy was introduced as a novel approach to tumor treatment in the 19th century, its efficacy was suboptimal, limiting its widespread application. However, since the U.S. Food and Drug Administration (FDA) approved the first OV therapy drug, T-VEC, in 2015, interest in OV has grown significantly. In recent years, oncolytic virus therapy has shown increasingly promising application prospects and has become a major research focus in the field of cancer treatment. This article reviews the development, classification, and research progress of oncolytic viruses, as well as their mechanisms of action, therapeutic methods, and routes of administration.

Translational considerations for immunotherapy clinical trials in pediatric neuro-oncology

While immunotherapy for pediatric cancer has made great strides in recent decades, including the FDA approval of agents such as dinutuximab and tisgenlecleucel, these successes have rarely impacted children with pediatric central nervous system (CNS) tumors. As our understanding of the biological underpinnings of these tumors evolves, new immunotherapeutics are undergoing rapid clinical translation specifically designed for children with CNS tumors. Most recently, there have been notable clinical successes with oncolytic viruses, vaccines, adoptive cellular therapy, and immune checkpoint inhibition. In this article, the immunotherapy working group of the Pacific Pediatric Neuro-Oncology Consortium (PNOC) reviews the current and future state of immunotherapeutic CNS clinical trials with a focus on clinical trial development. Based on recent therapeutic trials, we discuss unique immunotherapy clinical trial challenges, including toxicity considerations, disease assessment, and correlative studies. Combinatorial strategies and future directions will be addressed. Through internationally collaborative efforts and consortia, we aim to direct this promising field of immuno-oncology to the next frontier of successful application against pediatric CNS tumors.

The predictive capacity of in vitro preclinical models to evaluate drugs for the treatment of retinoblastoma

Retinoblastoma is a rare childhood cancer of the eye. Of the small number of drugs are used to treat retinoblastoma, all have been repurposed from drugs developed for other conditions. In order to find drugs or drug combinations better suited to the improved treatment of retinoblastoma, reliable predictive models are required, which facilitate the challenging transition from in vitro studies to clinical trials. In this review, the research performed to date on the development of 2D and 3D in vitro models for retinoblastoma is presented. Most of this research was undertaken with a view to better biological understanding of retinoblastoma, and we discuss the potential for these models to be applied to drug screening. Future research directions for streamlined drug discovery are considered and evaluated, and many promising avenues identified.

Nitric oxide suppression by secreted frizzled-related protein 2 drives retinoblastoma

Retinoblastoma is a cancer of the infant retina primarily driven by loss of the Rb tumor suppressor gene, which is undruggable. Here, we report an autocrine signaling, mediated by secreted frizzled-related protein 2 (SFRP2), which suppresses nitric oxide and enables retinoblastoma growth. We show that coxsackievirus and adenovirus receptor (CXADR) is the cell-surface receptor for SFRP2 in retinoblastoma cells; that CXADR functions as a "dependence receptor," transmitting a growth-inhibitory signal in the absence of SFRP2; and that the balance between SFRP2 and CXADR determines nitric oxide production. Accordingly, high SFRP2 RNA expression correlates with high-risk histopathologic features in retinoblastoma. Targeting SFRP2 signaling by SFRP2-binding peptides or by a pharmacological inhibitor rapidly induces nitric oxide and profoundly inhibits retinoblastoma growth in orthotopic xenograft models. These results reveal a cytokine signaling pathway that regulates nitric oxide production and retinoblastoma cell proliferation and is amenable to therapeutic intervention.

Enhancing the immune effect of oHSV-1 therapy through TLR3 signaling in uveal melanoma

PURPOSE

Uveal melanoma (UM) is the most common primary intraocular malignant tumor in adults, with patients having a low overall survival rate. Oncolytic viruses (OVs) have been shown effective as monotherapy or combined with immunotherapy in the treatment of UM. Oncolytic herpes simplex type I virus (oHSV-1) was found to alter gene expression and immune function in UMs. We investigated whether a combination treatment would be more effective in treating UM and reactive immune cells.

METHODS

RNA sequencing analysis were used to identify the effect of oHSV-1 infection in UM cells and protein changes were validated by western blot. Cell viability assays were performed through UM cell lines (MUM2B, 92.1, and MP41) and retinal pigment epithelial cell line (ARPE-19) to identify the efficacy and safety of the combination treatment. Western blot, qRT-PCR, cell viability assay and immunocytochemistry were performed to discover the reactivation of immune cells (U937 and HMC3).

RESULTS

Through RNA sequencing analysis and in vitro molecular biology assays, this study tested the ability of oHSV-1 combined with the TLR3 agonist poly(I:C) to re-activate the TLR3 meditated NF-ƙB signaling pathway and further increase the anti-tumor activity of UM cells and macrophages, including the stimulation of macrophage polarization and proliferation.

CONCLUSIONS

These findings indicate that the treatment of UM with a combination of oHSV-1 and poly(I:C) generates immune responses and enhances anti-tumoral activity, suggesting the need for further investigations and clinical trials of this combination.

Retinoblastoma: From genes to patient care

Retinoblastoma is the most common paediatric neoplasm of the retina, and one of the earliest model of cancer genetics since the identification of the master tumour suppressor gene RB1. Tumorigenesis has been shown to be driven by pathogenic variants of the RB1 locus, but also genomic and epigenomic alterations outside the locus. The increasing knowledge on this "mutational landscape" is used in current practice for precise genetic testing and counselling. Novel methods provide access to pre-therapeutic tumour DNA, by isolating cell-free DNA from aqueous humour or plasma. This is expected to facilitate assessment of the constitutional status of RB1, to provide an early risk stratification using molecular prognostic markers, to follow the response to the treatment in longitudinal studies, and to predict the response to targeted therapies. The aim of this review is to show how molecular genetics of retinoblastoma drives diagnosis, treatment, monitoring of the disease and surveillance of the patients and relatives. We first recap the current knowledge on retinoblastoma genetics and its use in every-day practice. We then focus on retinoblastoma subgrouping at the era of molecular biology, and the expected input of cell-free DNA in the field.

Emerging therapeutic targets for retinoblastoma

INTRODUCTION

Retinoblastoma (Rb) is an early childhood intraocular tumor of the retina and is managed by multimodal therapeutic approaches. Recent advanced targeted delivery of chemotherapeutic drugs to the eye has improved the possibility of globe salvage. However, enucleation is inevitable for advanced and recurrent Rb. The cumulative knowledge of identification of newer molecular biology tools, exosomal cargo, role of cancer stem cells (CSCs), and its microenvironment in the progression of the diseases warrants a relook at the traditional treatment protocol and explore the feasibility of targeted therapies.

AREAS COVERED

This review covers Rb pathobiology, novel molecular-targeted therapeutics, and strategies targeting Rb CSCs and provides an update on potential therapeutic targets such as second messengers and exosomal cargo.

EXPERT OPINION

The emergence of early diagnosis and multimodality treatment protocols have significantly improved the clinical outcome of children with advanced Rb; however, the problem of tumor recurrence has not yet been overcome. Improved understanding of the molecular pathways, identification, and characterization of CSCs opens up new targeted therapy approaches. The contemporary evidence from other fields shows promising evidence that combining conservative treatment modalities with targeting therapies specific for CSCs in clinical practice is essential for achieving high globe salvage rate in Rb patients.

Emerging New Therapeutics for Retinoblastoma

Background: Over the last few decades, chemotherapy has become the main treatment of retinoblastoma, delivered through various routes: intravenous, intra-arterial, and intravitreal. Despite its efficacy, chemotherapy-related toxicity (ocular and systemic) and recurrences due to resistant tumor clones are common, highlighting the need for novel therapeutic agents. Summary: Recent advances in our understanding of the molecular drivers of Rb1 tumorigenesis and mechanisms of tumor resistance have afforded opportunities to explore novel targets such as the MDMX-p53 pathway (nutlin-3), histone deacetylase inhibitors, spleen tyrosine kinase inhibitors, and genetic and immune modulatory drugs. In this review, we discuss the limitations of current therapeutic strategies, candidate cellular pathways, current evidence for newer targeted drugs, and offer a look toward the future. Key Messages: Advances in the understanding of the molecular drivers of the RB pathway have provided opportunities to explore novel drugs with targeted effects, improved bioavailability, and reduced chemotoxicity.

MDM2 inhibitors-mediated disruption of mitochondrial metabolism: A novel therapeutic strategy for retinoblastoma

MDM2 is the principal inhibitor of p53, and MDM2 inhibitors can disrupt the physical interaction between MDM2 and p53. The half-life of p53 is very short in normal cells and tissues, and an uncontrolled increase in p53 levels has potential harmful effects. It has been shown that p53 is frequently mutated in most cancers; however, p53 mutations are rare in retinoblastoma. Therefore, therapeutic strategies aimed at increasing the expression levels of wild-type p53 are attractive. In this minireview, we discuss the potential use of nutlin-3, the prototype small molecule inhibitor that disrupts the MDM2-p53 interaction, for the treatment of retinoblastoma. Although p53 has pleiotropic biological effects, the functions of p53 depend on its sub-cellular localization. In the nucleus, p53 induces the transcription of a vast array of genes, while in mitochondria, p53 regulates mitochondrial metabolism. This review also discusses the relative contribution of p53-mediated gene transcription and mitochondrial perturbation for retinoblastoma treatment.

Development and characterization of DNA aptamer against Retinoblastoma by Cell-SELEX

Retinoblastoma (RB) is the most common paediatric intraocular tumour. The management of RB has improved the survival and vision with recent advances in the treatment. Improved therapeutic approaches focussing on targeting tumours and minimizing the treatment-associated side effects are being developed. In this study, we generated a ssDNA aptamer against RB by cell-SELEX and high-throughput sequencing using Weri-RB1 cell line as the target, and Muller glial cell line Mio-M1 as the control. Three aptamers were selected based on the number of repetitions in NGS and phylogenetic relationship and evaluated by flow cytometry to assess their binding affinity and selectivity. The dissociation constant, Kd values of three selected aptamers were found to be in the nanomolar range. Aptamer VRF-CSRB-01 with the best binding affinity and a Kd value of 49.41 ± 7.87 nM was further characterized. The proteinase and temperature treatment indicated that VRF-CSRB-01 targets surface proteins, and has a good binding affinity and excellent selectivity under physiological conditions. The aptamer VRF-CSRB-01 was stable over 72 h in serum and 96 h in cerebral spinal fluid and vitreous. With the high affinity, specificity, stability and specific recognition of clinical RB tumours, VRF-CSRB-01 aptamer holds potential for application in diagnosis and targeting RB.

Follow-up of intraocular retinoblastoma through the quantitative analysis of conserved nuclear DNA sequences in aqueous humor from patients

Fundoscopy is the standard method for diagnosis and follow-up of intraocular retinoblastoma, but it is sometimes insufficient to discern whether tumors are inactivated following treatments. In this work, we hypothesized that the amount of conserved nuclear DNA sequences in the cell-free DNA (cfDNA) fraction of the aqueous humor (AH) might complement fundoscopy for retinoblastoma follow-up. To address our hypothesis, we developed highly sensitive droplet digital polymerase chain reaction (ddPCR) methods to quantify highly conserved DNA sequences of nucleus-encoded genes (GAPDH and B4GALNT1) and of a mitochondrial gene, MT-ATP6. We obtained AH samples during intravitreal treatments. We analyzed 42 AH samples from 25 patients with intraocular retinoblastoma and 11 AH from controls (non-cancer patients). According to clinical criteria, we grouped patients as having progression-free or progressive retinoblastoma. cfDNA concentration in the AH was similar in both retinoblastoma groups. Copy counts for nucleus-derived sequences of GAPDH and B4GALNT1 were significantly higher in the AH from patients with progressive disease, compared to the AH from progression-free patients and control non-cancer patients. The presence of mitochondrial DNA in the AH explained that both retinoblastoma groups had similar cfDNA concentration in AH. The optimal cut-off point for discriminating between progressive and progression-free retinoblastomas was 108 GAPDH copies per reaction. Among patients having serial AH samples analyzed during their intravitreal chemotherapy, GAPDH copies were high and decreased below the cut-off point in those patients responding to chemotherapy. In contrast, one non-responder patient remained with values above the cut-off during follow-up, until enucleation. We conclude that the measurement of conserved nuclear gene sequences in AH allows follow-up of intraocular retinoblastoma during intravitreal treatment. The method is applicable to all patients and could be relevant for those in which fundoscopy evaluation is inconclusive.

Nanotechnology for Pediatric Retinoblastoma Therapy

Retinoblastoma is a rare, sometimes hereditary, pediatric cancer. In high-income countries this disease has a survival rate approaching 100%, while in low- and middle-income countries the prognosis is fatal for about 80% of cases. Depending on the stage of the disease, different therapeutic protocols are applied. In more advanced forms of the disease, surgical removal of the entire globe and its intraocular contents (enucleation) is, unfortunately, necessary, whereas in other cases, conventional chemotherapy is normally used. To overcome the side-effects and reduced efficacy of traditional chemotherapic drugs, nanodelivery systems that ensure a sustained drug release and manage to reach the target site have more recently been developed. This review takes into account the current use and advances of nanomedicine in the treatment of retinoblastoma and discusses nanoparticulate formulations that contain conventional drugs and natural products. In addition, future developments in retinoblastoma treatment are discussed.

Novel insights into RB1 mutation

Since the discovery of the retinoblastoma susceptibility gene (RB1) decades ago, RB1 has been regarded as a prototype tumor suppressor gene providing a paradigm for tumor genetic research. Constant research has updated the understanding of RB1-related pathways and their impact on tumor and nontumor diseases. Mutation of RB1 gene has been observed in multiple types of malignant tumors including prostate cancer, lung cancer, breast cancer, and almost every familial and sporadic case of retinoblastoma. Even if well-known and long-investigated, the application potential of RB1 mutation has not been fully tapped. In this review, we focus on the mechanism underlying RB1 mutation during oncogenesis. Therapeutically, we have further discussed potential clinical strategies by targeting RB1-mutated cancers. The unsolved problems and prospects of RB1 mutation are also discussed.

Cancer vaccines: the next immunotherapy frontier

After several decades, therapeutic cancer vaccines now show signs of efficacy and potential to help patients resistant to other standard-of-care immunotherapies, but they have yet to realize their full potential and expand the oncologic armamentarium. Here, we classify cancer vaccines by what is known of the included antigens, which tumors express those antigens and where the antigens colocalize with antigen-presenting cells, thus delineating predefined vaccines (shared or personalized) and anonymous vaccines (ex vivo or in situ). To expedite clinical development, we highlight the need for accurate immune monitoring of early trials to acknowledge failures and advance the most promising vaccines.

Treatment of Retinoblastoma: What Is the Latest and What Is the Future

The management of retinoblastoma, the most common intraocular malignancy in children, has changed drastically over the last decade. Landmark developments in local drug delivery, namely, safer techniques for intravitreal chemotherapy injection and ophthalmic artery chemosurgery, have resulted in eye globe salvages that were not previously attainable using systemic chemotherapy or external beam irradiation. Novel drugs, oncolytic viruses, and immunotherapy are promising approaches in the treatment of intraocular retinoblastoma. Importantly, emerging studies of the pattern of tumor dissemination and local drug delivery may provide the first steps toward new treatments for metastatic disease. Here, we review recent advances in retinoblastoma treatment, especially with regard to local drug delivery, that have enabled successful conservative management of intraocular retinoblastoma. We also review emerging data from preclinical and clinical studies on innovative approaches that promise to lead to further improvement in outcomes, namely, the mechanisms and potential uses of new and repurposed drugs and non-chemotherapy treatments, and discuss future directions for therapeutic development.

VCN-01 disrupts pancreatic cancer stroma and exerts antitumor effects

Background

Pancreatic ductal adenocarcinoma (PDAC) is characterized by dense desmoplastic stroma that limits the delivery of anticancer agents. VCN-01 is an oncolytic adenovirus designed to replicate in cancer cells with a dysfunctional RB1 pathway and express hyaluronidase. Here, we evaluated the mechanism of action of VCN-01 in preclinical models and in patients with pancreatic cancer.

Methods

VCN-01 replication and antitumor efficacy were evaluated alone and in combination with standard chemotherapy in immunodeficient and immunocompetent preclinical models using intravenous or intratumoral administration. Hyaluronidase activity was evaluated by histochemical staining and by measuring drug delivery into tumors. In a proof-of-concept clinical trial, VCN-01 was administered intratumorally to patients with PDAC at doses up to 1×10¹¹ viral particles in combination with chemotherapy. Hyaluronidase expression was measured in serum by an ELISA and its activity within tumors by endoscopic ultrasound elastography.

Results

VCN-01 replicated in PDAC models and exerted antitumor effects which were improved when combined with chemotherapy. Hyaluronidase expression by VCN-01 degraded tumor stroma and facilitated delivery of a variety of therapeutic agents such as chemotherapy and therapeutic antibodies. Clinically, treatment was generally well-tolerated and resulted in disease stabilization of injected lesions. VCN-01 was detected in blood as secondary peaks and in post-treatment tumor biopsies, indicating virus replication. Patients had increasing levels of hyaluronidase in sera over time and decreased tumor stiffness, suggesting stromal disruption.

Conclusions

VCN-01 is an oncolytic adenovirus with direct antitumor effects and stromal disruption capabilities, representing a new therapeutic agent for cancers with dense stroma.

Trial registration number

EudraCT number: 2012-005556-42 and NCT02045589.

LRG1 as a novel therapeutic target in eye disease

Retinal and choroidal diseases are major causes of blindness and visual impairment in the developed world and on the rise due to an ageing population and diabetes epidemic. Standard of care is centred around blockade of vascular endothelial growth factor (VEGF), but despite having halved the number of patients losing sight, a high rate of patient non-response and loss of efficacy over time are key challenges. Dysregulation of vascular homoeostasis, coupled with fibrosis and inflammation, are major culprits driving sight-threatening eye diseases. Improving our knowledge of these pathological processes should inform the development of new drugs to address the current clinical challenges for patients. Leucine-rich α-2 glycoprotein 1 (LRG1) is an emerging key player in vascular dysfunction, inflammation and fibrosis. Under physiological conditions, LRG1 is constitutively expressed by the liver and granulocytes, but little is known about its normal biological function. In pathological scenarios, such as diabetic retinopathy (DR) and neovascular age-related macular degeneration (nvAMD), its expression is ectopically upregulated and it acquires a much better understood pathogenic role. Context-dependent modulation of the transforming growth-factor β (TGFβ) pathway is one of the main activities of LRG1, but additional roles have recently been emerging. This review aims to highlight the clinical and pre-clinical evidence for the pathogenic contribution of LRG1 to vascular retinopathies, as well as extrapolate from other diseases, functions which may be relevant to eye disease. Finally, we will provide a current update on the development of anti-LRG1 therapies for the treatment of nvAMD.

Monitoring Retinoblastoma by Machine Learning of Aqueous Humor Metabolic Fingerprinting

The most common intraocular pediatric malignancy, retinoblastoma (RB), accounts for ≈10% of cancer in children. Efficient monitoring can enhance living quality of patients and 5-year survival ratio of RB up to 95%. However, RB monitoring is still insufficient in regions with limited resources and the mortality may even reach over 70% in such areas. Here, an RB monitoring platform by machine learning of aqueous humor metabolic fingerprinting (AH-MF) is developed, using nanoparticle enhanced laser desorption/ionization mass spectrometry (LDI MS). The direct AH-MF of RB free of sample pre-treatment is recorded, with both high reproducibility (coefficient of variation < 10%) and sensitivity (low to 0.3 pmol) at sample volume down to 40 nL only. Further, early and advanced RB patients with area-under-the-curve over 0.9 and accuracy over 80% are differentiated, through machine learning of AH-MF. Finally, a metabolic biomarker panel of 7 metabolites through accurate MS and tandem MS (MS/MS) with pathway analysis to monitor RB is identified. This work can contribute to advanced metabolic analysis of eye diseases including but not limited to RB and screening of new potential metabolic targets toward therapeutic intervention.

Emerging systemic delivery strategies of oncolytic viruses: A key step toward cancer immunotherapy

Oncolytic virotherapy (OVT) is a novel type of immunotherapy that induces anti-tumor responses through selective self-replication within cancer cells and oncolytic virus (OV)-mediated immunostimulation. Notably, talimogene laherparepvec (T-Vec) developed by the Amgen company in 2015, is the first FDA-approved OV product to be administered via intratumoral injection and has been the most successful OVT treatment. However, the systemic administration of OVs still faces huge challenges, including in vivo pre-existing neutralizing antibodies and poor targeting delivery efficacy. Recently, state-of-the-art progress has been made in the development of systemic delivery of OVs, which demonstrates a promising step toward broadening the scope of cancer immunotherapy and improving the clinical efficacy of OV delivery. Herein, this review describes the general characteristics of OVs, focusing on the action mechanisms of OVs as well as the advantages and disadvantages of OVT. The emerging multiple systemic administration approaches of OVs are summarized in the past five years. In addition, the combination treatments between OVT and traditional therapies (chemotherapy, thermotherapy, immunotherapy, and radiotherapy, etc.) are highlighted. Last but not least, the future prospects and challenges of OVT are also discussed, with the aim of facilitating medical researchers to extensively apply the OVT in the cancer therapy.

Downregulation of MIAT reduces the proliferation and migratory and invasive abilities of retinoblastoma cells by sponging miR-665 and regulating LASP1

Long non-coding RNAs (lncRNAs) can function as onco-lncRNAs in several types of human cancer, including retinoblastoma (Rb). The present study investigated the potential role and regulatory mechanism of the lncRNA myocardial infarction-associated transcript (MIAT) in Rb. To do so, the expression levels of MIAT, microRNA (miR)-665, and LIM and SH3 protein 1 (LASP1) in Rb tissues from patients or Rb cells were analysed using reverse transcription quantitative PCR. The interactions between miR-665 and MIAT/LASP1 were confirmed by the dual-luciferase reporter assay. MTT, Transwell (to assess migration and invasion) and western blotting assays were used to explore the functions of the MIAT/miR-665/LASP1 axis on Rb progression in vitro. The results of the present study indicated that MIAT targeted miR-665. In Rb tissues and cell lines, high expression of MIAT was observed, whereas miR-665 was downregulated in Rb tissues. Furthermore, the proliferation and migratory and invasive abilities of Rb Y79 and HXO-RB44 cells were decreased following MIAT downregulation or miR-665 overexpression. In addition, LASP1 was identified as a target gene of miR-665. Both the decreased expression of miR-665 and the elevated expression of LASP1 reversed the suppressive effects of MIAT knockdown on the proliferation and migratory and invasive abilities of Y79 cells. Furthermore, MIAT silencing attenuated the development of Rb by regulating the miR-665/LASP1 axis. Taken together, these findings suggested that MIAT may be considered as a possible therapeutic target for Rb.

Prevalence, clinical features and prognosis of malignant solid tumors in infants: a 14-year study

The onset of malignant solid tumors in infants is insidious and difficult to diagnose on time. The purpose of our study is to provide a theoretical basis for clinical diagnosis by retrospective analysis of the data in the past 14 years. Here, we retrospectively collected the clinical data of infants aged 0-12 months with malignant solid tumors in Beijing Tongren Hospital Affiliated to Capital Medical University from May 2005 to May 2019. The epidemiology, clinical characteristics, treatments and prognosis were statistically analyzed. A total of 496 infants (294 males and 202 females) with malignant solid tumors were analyzed. The main period of onset was 1-11 months. The most common tumor was retinoblastoma (RB, 51.8%), followed by hepatoblastoma (HB, 26.6%), neuroblastoma (NB, 10.5%), rhabdomyosarcoma (RMS, 3.4%), malignant renal tumors (3.2%), infantile fibrosarcoma (IFS, 1.6%), malignant teratoma (1.2%), Ewing's sarcoma (ES, 0.8%), medulloblastoma (MB, 0.4%) and inflammatory myofibroblastic tumor (IMT, 0.4%). The median follow-up time was 32 months (range 2-162 months). The 1-year, 3-year, and 5-year overall survival of all patients were 97.3%, 89.2%, and 81.1%, respectively, and event-free survival was 94.7%, 84.8%, and 75.8%, respectively. In conclusion, as a special group, malignant solid tumors in infants are complex, heterogeneous, and relatively rare. The prognosis of RB, HB, NB, RMS, malignant renal tumors, IFS, malignant teratoma, ES, MB, and IMT, were excellent duo to timely diagnosis and rational treatment.

Concepts in Oncolytic Adenovirus Therapy

Oncolytic adenovirus therapy is gaining importance as a novel treatment option for the management of various cancers. Different concepts of modification within the adenovirus vector have been identified that define the mode of action against and the interaction with the tumour. Adenoviral vectors allow for genetic manipulations that restrict tumour specificity and also the expression of specific transgenes in order to support the anti-tumour effect. Additionally, replication of the virus and reinfection of neighbouring tumour cells amplify the therapeutic effect. Another important aspect in oncolytic adenovirus therapy is the virus induced cell death which is a process that activates the immune system against the tumour. This review describes which elements in adenovirus vectors have been identified for modification not only to utilize oncolytic adenovirus vectors into conditionally replicating adenoviruses (CRAds) that allow replication specifically in tumour cells but also to confer specific characteristics to these viruses. These advances in development resulted in clinical trials that are summarized based on the conceptual design.

Oncolytic Adenovirus: Prospects for Cancer Immunotherapy

Immunotherapy has moved to the forefront of modern oncologic treatment in the past few decades. Various forms of immunotherapy currently are emerging, including oncolytic viruses. In this therapy, viruses are engineered to selectively propagate in tumor cells and reduce toxicity for non-neoplastic tissues. Adenovirus is one of the most frequently employed oncolytic viruses because of its capacity in tumor cell lysis and immune response stimulation. Upregulation of immunostimulatory signals induced by oncolytic adenoviruses (OAds) might significantly remove local immune suppression and amplify antitumor immune responses. Existing genetic engineering technology allows us to design OAds with increasingly better tumor tropism, selectivity, and antitumor efficacy. Several promising strategies to modify the genome of OAds have been applied: capsid modifications, small deletions in the pivotal viral genes, insertion of tumor-specific promoters, and addition of immunostimulatory transgenes. OAds armed with tumor-associated antigen (TAA) transgenes as cancer vaccines provide additional therapeutic strategies to trigger tumor-specific immunity. Furthermore, the combination of OAds and immune checkpoint inhibitors (ICIs) increases clinical benefit as evidence shown in completed and ongoing clinical trials, especially in the combination of OAds with antiprogrammed death 1/programed death ligand 1 (PD-1/PD-L1) therapy. Despite remarkable antitumor potency, oncolytic adenovirus immunotherapy is confronted with tough challenges such as antiviral immune response and obstruction of tumor microenvironment (TME). In this review, we focus on genomic modification strategies of oncolytic adenoviruses and applications of OAds in cancer immunotherapy.

Multi-omics profiling of primary small cell carcinoma of the esophagus reveals RB1 disruption and additional molecular subtypes

Primary small cell carcinoma of the esophagus (PSCCE) is a lethal neuroendocrine carcinoma. Previous studies proposed a genetic similarity between PSCCE and esophageal squamous cell carcinoma (ESCC) but provided little evidence for differences in clinical course and neuroendocrine differentiation. We perform whole-exome sequencing, RNA sequencing and immunohistochemistry profiling on 46 PSCCE cases. Integrated analyses enable the discovery of multiple mechanisms of RB1 disruption in 98% (45/46) of cases. The transcriptomic landscape of PSCCE closely resembles small cell lung cancer (SCLC) but differs from ESCC or esophageal adenocarcinoma (EAC). Distinct gene expression patterns regulated by ASCL1 and NEUROD1 define two molecular subtypes, PSCCE-A and PSCCE-N, which are highly similar to SCLC subtypes. A T cell excluded phenotype is widely observed in PSCCE. In conclusion, PSCCE has genomic alterations, transcriptome features and molecular subtyping highly similar to SCLC but distinct from ESCC or EAC. These observations are relevant to oncogenesis mechanisms and therapeutic vulnerability.

Primary small cell carcinoma of the oesophagus has a poor prognosis, and has not been fully characterised molecularly. Here, the authors study the disease using multi-omics technology and find frequent RB1 disruptions and similarities to small cell lung cancer, opening potential therapeutic avenues.

Retinoblastoma tumor cell proliferation is negatively associated with an immune gene expression signature and increased immune cells

This study focuses on gene expression differences between early retinal states that ultimately lead to normal development, late onset retinoblastoma, or rapid bilateral retinoblastoma tumors. The late-onset and early-onset retinoblastoma tumor cells are remarkably similar to normally proliferating retinal progenitor cells, but they fail to properly express differentiation markers associated with normal development. Further, early-onset retinoblastoma tumor cells express a robust immune gene expression signature followed by accumulation of dendritic, monocyte, macrophage, and T-lymphocyte cells in the retinoblastoma tumors. This characteristic was not shared by either normal retinae or late-onset retinoblastomas. Comparison of our data with other human and mouse retinoblastoma tumor gene expression significantly confirmed, that the immune signature is present in tumors from each species. Strikingly, we observed that the immune signature in both mouse and human tumors was most highly evident in those with the lowest proliferative capacity. We directly assessed this relationship in human retinoblastoma tumors by co-analyzing proliferation and immune cell recruitment by immunohistochemistry, uncovering a significant inverse relationship between increased immune-cell infiltration in tumors and reduced tumor cell proliferation. Directly inhibiting proliferation with a PI3K/mTOR inhibitor significantly increased the number of CD45+ immune cells in the retina. This work establishes an in vivo model for the rapid recruitment of immune cells to tumorigenic neural tissue.

Evolving Status of Clinical Immunotherapy with Oncolytic Adenovirus

Cancer immunotherapy targeting immune checkpoint inhibitors shows efficacy in several human cancers, but "cold tumors" that lack immune cells are typically unresponsive. Among the potential therapeutic approaches that could "heat" or promote lymphocyte infiltration of cold tumors, oncolytic viruses have attracted interest for their lytic and immunogenic mechanisms of action. In this article, we review the use of oncolytic adenoviruses in cancer immunotherapy, with a particular focus on preclinical and clinical data of oncolytic adenovirus-triggered immune responses against tumor antigens. We also discuss parameters to consider in clinical trial design and the combination of oncolytic adenoviruses with conventional treatments or other immunotherapies.

Hyaluronidase expression within tumors increases virotherapy efficacy and T cell accumulation

Oncolytic viruses (OVs) preferentially infect and selectively replicate in cancer cells. OVs have been tested in clinical trials as monotherapy or in combination with chemotherapy, radiotherapy, and immunotherapy. However, the dense extracellular matrix hampers the intratumoral spreading and efficacy of OVs. Previously we described VCN-01, an oncolytic adenovirus expressing a soluble version of human sperm hyaluronidase (hyal) PH20, which exhibited enhanced intratumoral distribution and antitumor activity in different models. Here, we present two oncolytic adenoviruses designed to increase the secretion of PH20 compared to VCN-01. ICO15K-40SAPH20, encoding PH20 under an Ad40 splice acceptor, and ICO15K-E1aPH20 expressing PH20 fused to the E1A gene by P2A peptide. We demonstrate that increased hyal activity improves antitumor efficacy in both a sensitive immunodeficient model and an immunocompetent model. Moreover, we show that hyal activity impacts T cell accumulation in tumors, highlighting the value of a hyaluronidase-expressing virus for combinations with other immunotherapies in cancers involving dense stroma.

Oncolytic virotherapy reverses the immunosuppressive tumor microenvironment and its potential in combination with immunotherapy

It has been intensively reported that the immunosuppressive tumor microenvironment (TME) results in tumor resistance to immunotherapy, especially immune checkpoint blockade and chimeric T cell antigen therapy. As an emerging therapeutic agent, oncolytic viruses (OVs) can specifically kill malignant cells and modify immune and non-immune TME components through their intrinsic properties or genetically incorporated with TME regulators. Strategies of manipulating OVs against the immunosuppressive TME include serving as a cancer vaccine, expressing proinflammatory factors and immune checkpoint inhibitors, and regulating nonimmune stromal constituents. In this review, we summarized the mechanisms and applications of OVs against the immunosuppressive TME, and strategies of OVs in combination with immunotherapy. We also introduced future directions to achieve efficient clinical translation including optimization of preclinical models that simulate the human TME and achieving systemic delivery of OVs.

Teratogenic Toxicity Evaluation of Bladder Cancer-Specific Oncolytic Adenovirus on Mice

BACKGROUND

In our previous studies, we had demonstrated the efficiency and specificity of constructed bladder tissue-specific adenovirus Ad-PSCAE-UPII-E1A-AR (APU-EIA-AR) on bladder cancer. The virus biodistribution and body toxicity in nude mice have also been investigated. However, the safety of the bladder cancer-specific oncolytic adenovirus on fetal mice and F1 mice should be under intense investigation.

OBJECTIVE

In order to evaluate the teratogenic toxicity of bladder cancer-specific oncolytic adenovirus APU-EIA-AR on mice, in this study, we investigated the fetal mice weight, fetal body length and tail length, fetal skeleton development, as well as the F1 mice weight, growth curve, and major organ pathology. These teratogenic toxicity data of bladder tissue-specific adenovirus Ad-PSCAE- UPII-E1A-AR (AD) would provide safe information prior to embarking on clinical trials.

METHODS

On the sixth day of being fertilized, the pregnant mice began to be intramuscularly administrated with AD (1×10⁷VP, 1×10⁸VP, 1×10⁹VP) every other day for ten days. The pregnant mice were then divided into two groups. One group was euthanized on the seventeenth day; the fetal mice were taken out, and the bone structure of the infants was observed. The other group was observed until natural childbirth. The Filial Generation (F1) is fed for 30 days; the variations in the growth progress and development were assessed. The mice were then euthanized; The tissues from major organs were harvested and observed under the microscope.

RESULTS

In the process of teratogenic toxicity test, the Placenta weight, fetal mice weight, body length, and a tail length of mice fetal in adenovirus treated group did not reveal any alteration. Meanwhile, comparing with the PBS group, there is no obvious change in the skeleton of fetal mice treated with adenovirus. During the development process of F1 mice treated with adenovirus, the changes in mice weight show statistical significance. However, in the progress of the growth curve, this difference is not very obvious. Furthermore, the pathological section showed no obvious alteration in major organs.

CONCLUSION

Our study demonstrated that bladder cancer-specific adenovirus Ad-PSCAE-UPII- E1A-AR appears safe in pregnant mice without any discernable effects on fetal mice and F1 development. Hence, it is relatively safe for tumor gene therapy.

Oncolytic adenovirus with hyaluronidase activity that evades neutralizing antibodies: VCN-11

Tumor targeting and intratumoral virus spreading are key features for successful oncolytic virotherapy. VCN-11 is a novel oncolytic adenovirus, genetically modified to express hyaluronidase (PH20) and display an albumin-binding domain (ABD) on the hexon. ABD allows the virus to self-coat with albumin when entering the bloodstream and evade neutralizing antibodies (NAbs). Here, we validate VCN-11 mechanism of action and characterize its toxicity. VCN-11 replication, hyaluronidase activity and binding to human albumin to evade NAbs was evaluated. Toxicity and efficacy of VCN-11 were assessed in mice and hamsters. Tumor targeting, and antitumor activity was analyzed in the presence of NAbs in several tumor models. VCN-11 induced 450 times more cytotoxicity in tumor cells than in normal cells. VCN-11 hyaluronidase production was confirmed by measuring PH20 activity in vitro and in virus-infected tumor areas in vivo. VCN-11 evaded NAbs from different sources and tumor targeting was demonstrated in the presence of high levels of NAbs in vivo, whereas the control virus without ABD was neutralized. VCN-11 showed a low toxicity profile in athymic nude mice and Syrian hamsters, allowing treatments with high doses and fractionated administrations without major toxicities (up to 1.2x10¹¹vp/mouse and 7.5x10¹¹vp/hamster). Fractionated intravenous administrations improved circulation kinetics and tumor targeting. VCN-11 antitumor efficacy was demonstrated in the presence of NAbs against Ad5 and itself. Oncolytic adenovirus VCN-11 disrupts tumor matrix and displays antitumor effects even in the presence of NAbs. These features make VCN-11 a safe promising candidate to test re-administration in clinical trials.

Oncolytic Virotherapy in Solid Tumors: The Challenges and Achievements

Oncolytic virotherapy (OVT) is a promising approach in cancer immunotherapy. Oncolytic viruses (OVs) could be applied in cancer immunotherapy without in-depth knowledge of tumor antigens. The capability of genetic modification makes OVs exciting therapeutic tools with a high potential for manipulation. Improving efficacy, employing immunostimulatory elements, changing the immunosuppressive tumor microenvironment (TME) to inflammatory TME, optimizing their delivery system, and increasing the safety are the main areas of OVs manipulations. Recently, the reciprocal interaction of OVs and TME has become a hot topic for investigators to enhance the efficacy of OVT with less off-target adverse events. Current investigations suggest that the main application of OVT is to provoke the antitumor immune response in the TME, which synergize the effects of other immunotherapies such as immune-checkpoint blockers and adoptive cell therapy. In this review, we focused on the effects of OVs on the TME and antitumor immune responses. Furthermore, OVT challenges, including its moderate efficiency, safety concerns, and delivery strategies, along with recent achievements to overcome challenges, are thoroughly discussed.