Current Cancer Drug Targets - Volume 18, Issue 2, 2018

Oncolytic viruses are a promising anti-cancer platform, achieving significant pre-clinical and clinical milestones in recent years. A full arsenal of selective, safe, and effective viruses has been developed with some emerging pre-clinical research focusing on optimizing these therapies in the face of remaining challenges, both in the bloodstream and in the tumour microenvironment. Herein we discuss the recent progress in pre-clinical virotherapy research to address these challenges, with special focus on innovative strategies that seek to complement the current strengths of virotherapy, ensuring an optimal multi-faceted attack on cancer. This review highlights the research areas that we believe provide the most potential to increase the efficacy of this exciting biotherapy platform: cell carriers, tumour vascular destruction, microenvironment modulation, combination therapies, and virus-mediated anti-tumour immune responses.

Adenovirus is one of the most commonly used vectors for gene therapy and it is the first approved virus-derived drug for treatment of cancer. As an oncolytic agent, it can induce lysis of infected cells, but it can also engage the immune system, promoting activation and maturation of antigen- presenting cells (APCs). In essence, oncolysis combined with the associated immunostimulatory actions result in a “personalized in situ vaccine” for each patient. In order to take full advantage of these features, we should try to understand how adenovirus interacts with the immune system, what are the receptors involved in triggering subsequent signals and which kind of responses they elicit. Tackling these questions will give us further insight in how to manipulate adenovirus-mediated immune responses for enhancement of anti-tumor efficacy. In this review, we first highlight how oncolytic adenovirus interacts with the innate immune system and its receptors such as Toll-like receptors, nucleotide-binding and oligomerization domain (NOD)- like receptors and other immune sensors. Then we describe the effect of these interactions on the adaptive immune system and its cells, especially B and T lymphocytes. Finally, we summarize the most significant preclinical and clinical results in the field of gene therapy where researchers have engineered adenovirus to manipulate the host immune system by expressing cytokines and signalingmediators.

Novel treatment modalities are rapidly advancing toward clinical use as many malignant cancers still remain incurable. Adenovirus (Ad) in particular has been extensively researched as a promising alternative to conventional cancer therapy in the past decades. Although Ad has demonstrated promising therapeutic outcome and cancer specificity in preclinical models, its therapeutic efficacy in clinical trials is still insufficient due to several drawbacks such as rapid clearance of viral particles by host immune response, induction of acute inflammatory response, and hepatotoxicity. In this regard, combination of Ad with other cancer treatment modalities, such as chemotherapy, radiotherapy, or immunotherapy, can be an effective strategy to overcome the limitations of Ad. Cancerspecific and effective expression of multifunctional therapeutic genes by Ad can enhance the therapeutic profile of other treatment modalities, making it a logical candidate for combination therapy to combat malignant tumors.

Pancreatic cancer is an aggressive malignant disease and the efficacy of current treatments for unresectable diseases is quite limited despite recent advances. Gene therapy /virotherapy strategies may provide new options for the treatment of various cancers including pancreatic cancer. Oncolytic adenovirus shows an antitumoral effect via its intratumoral amplification and strong cytocidal effect in a variety of cancers and it has been employed for the development of potent oncolytic virotherapy agents for pancreatic cancer. Our ultimate goal is to develop an oncolytic adenovirus enabling the treatment of patients with advanced or spread diseases by systemic injection. Systemic application of oncolytic therapy mandates more efficient and selective gene delivery and needs to embody sufficient antitumor effect even with limited initial delivery to the tumor location. In this review, the current status of oncolytic adenoviruses from the viewpoints of vector design and potential strategies to overcome current obstacles for its clinical application will be described. We will also discuss the efforts to improve the antitumor activity of oncolytic adenovirus, in in vivo animal models, and the combination therapy of oncolytic adenovirus with radiation and chemotherapy.

Oncolytic virotherapy is a novel therapeutic modality for malignant diseases that exploits selective viral replication in cancer cells. Herpes simplex virus (HSV) is a promising agent for oncolytic virotherapy due to its broad cell tropism and the identification of mutations that favor its replication in tumor over normal cells. However, these attenuating mutations also tend to limit the potency of current oncolytic HSV vectors that have entered clinical studies. As an alternative, vector retargeting to novel entry receptors has the potential to achieve tumor specificity at the stage of virus entry, eliminating the need for replication-attenuating mutations. Here, we summarize the molecular mechanism of HSV entry and recent advances in the development of fully retargeted HSV vectors for oncolytic virotherapy. Retargeted HSV vectors offer an attractive platform for the creation of a new generation of oncolytic HSV with improved efficacy and specificity.

The oncolytic viruses now hold a promise of new therapeutic strategy for cancer. Its concept has inspired a wave of commercial research and development activities for the products of this category in China since 1998. The first commercialized oncolytic virus product in the world, Oncorine (H101), developed by Shanghai Sunway Biotech Co., Ltd since 1999, was approved by Chinese SFDA in November, 2005 for nasopharyngeal carcinoma in combination with chemotherapy after the phase III clinical trial, and finally acquired GMP certificate in August, 2006. This review introduces how Oncorine was successfully developed in China, and how the Chinese market responded after it was launched into the market in 2006.

Attenuated Edmonston lineage measles virus (MV-Edm) vaccine strains can preferentially infect and lyse a wide variety of cancer cells. Oncolytic MV-Edm derivatives are genetically engineered to express the human carcinoembryonic antigen (MV-CEA virus) or the human sodium iodide symporter (MV-NIS virus) and are currently being tested in clinical trials against ovarian cancer, glioblastoma multiforme, multiple myeloma, mesothelioma, head and neck cancer, breast cancer and malignant peripheral nerve sheath tumors. This review describes the basic and preclinical data that facilitated the clinical translation of MV-Edm strains, and summarizes the clinical results of this oncolytic platform to date. Furthermore, we discuss the latest clinically relevant MV-Edm vector developments and creative strategies for future translational steps.

Advanced liver cancers and biliary cancers represent diseases with dismal prognosis because of frequent local invasion and metastasis. Effective therapeutic agents for these cancers have not been established. Oncolytic viruses (OVs) constitute a novel class of promising, selective anticancer agents and recent studies have elucidated their unique features. Moreover, clinical trials are demonstrating promising results. Numerous OVs are being tested in preclinical models of hepatocellular carcinoma (HCC). The lead agent Pexa-Vec (pexastimogene devacirepvec, JX-594), a recombinant Wyeth strain vaccinia virus, has demonstrated preliminary evidence of safety and efficacy for HCC in clinical trials. Few other OVs have entered clinical testing. Relatively few preclinical studies and clinical trials exist for biliary cancers. In this review, we introduce various approaches using OVs to treat the intractable hepatobiliary cancers.

Oncolytic viruses, which include both naturally occurring wild-type viruses/attenuated viruses and genetically modified viruses, have recently been developed for use in innovative cancer therapies. Genetically modified oncolytic viruses possess the unique ability to replicate conditionally as a unique gene therapy product. Since oncolytic viruses exhibit prolonged persistence in patients, viral shedding and transmission to third parties should be major concerns for clinical trials along with the clinical safety and efficacy. Accordingly, studies are now underway to establish the safety and efficacy of oncolytic viruses.

Background: Epithelial to mesenchymal transition (EMT) is a major determinant of cancer metastasis and is closely linked with TGF-β1. Intracellular proteins, including E. Cadherin, N. Cadherin and Vimentin are directly related to EMT that affect cell migration and adhesion; on the other hand, non muscle myosin (NM) has a central role in cytokinesis, migration and adhesion. Objective: We aimed to explore the association of EMT and metastasis with TGF-β1 through regulation of non-muscle myosin II-A (NMII-A) and its interaction with Hexosamine Biosynthesis Pathway (HBP). Method: Protein expression changes were assessed by western blotting and immunofluorescent staining while transcription level changes were assessed by qRT-PCR. EMT was assessed by phenotypic analysis, wound healing, proliferation and transwell migration assay in vitro while in vivo studies were conducted in BALB/c nude mice for lung orthotopic and tail vein metastasis models. Results: We demonstrated that regulation of JNK/ P38/PI3K by TGF-β1 led to down expression of NMII-A which promoted EMT and lung cancer metastasis. This down expression of NMII-A conversely upregulated the expression of Core 2 N-acetyl Glucosaminyl Transferase mucin type (C2GnT-M) and further facilitated up-regulation and down-regulation of N-acetylglucosaminyltransferase (GnT) -V and -III respectively; moreover, NMII-A K.D cells showed 3 times more tendency to migrate towards brain in vivo. Conclusion: The study reports a novel pathway through which NMII-A negatively regulates EMT and metastasis via up regulation of C2GnT-M, GnT-V and down expression of GnT-III. These findings of lung cancer may further be required to study other cancer types.