Concomitant use of Ad5/35 chimeric oncolytic adenovirus with TRAIL gene and taxol produces synergistic cytotoxicity in gastric cancer cells

Oncolytic virus: A catalyst for the treatment of gastric cancer

Gastric cancer (GC) is a leading contributor to global cancer incidence and mortality. According to the GLOBOCAN 2020 estimates of incidence and mortality for 36 cancers in 185 countries produced by the International Agency for Research on Cancer (IARC), GC ranks fifth and fourth, respectively, and seriously threatens the survival and health of people all over the world. Therefore, how to effectively treat GC has become an urgent problem for medical personnel and scientific workers at this stage. Due to the unobvious early symptoms and the influence of some adverse factors such as tumor heterogeneity and low immunogenicity, patients with advanced gastric cancer (AGC) cannot benefit significantly from treatments such as radical surgical resection, radiotherapy, chemotherapy, and targeted therapy. As an emerging cancer immunotherapy, oncolytic virotherapies (OVTs) can not only selectively lyse cancer cells, but also induce a systemic antitumor immune response. This unique ability to turn unresponsive 'cold' tumors into responsive 'hot' tumors gives them great potential in GC therapy. This review integrates most experimental studies and clinical trials of various oncolytic viruses (OVs) in the diagnosis and treatment of GC. It also exhaustively introduces the concrete mechanism of invading GC cells and the viral genome composition of adenovirus and herpes simplex virus type 1 (HSV-1). At the end of the article, some prospects are put forward to determine the developmental directions of OVTs for GC in the future.

Oncolytic virotherapy in upper gastrointestinal tract cancers

Upper gastrointestinal tract malignancies are among the most challenging cancers with regard to response to treatment and prognosis. Cancers of the esophagus, stomach, pancreas, liver, and biliary tree have dismal 5-year survival, and very modest improvements in this rate have been made in recent times. Oncolytic viruses are being developed to address these malignancies, with a focus on high safety profiles and low off-target toxicities. Each viral platform has evolved to enhance oncolytic potency and the clinical response to either single-agent viral therapy or combined viral treatment with radiotherapy and chemotherapy. A panel of genomic alterations, chimeric proteins, and pseudotyped capsids are the breakthroughs for vector success. This article revisits developments for each viral platform to each tumor type, in an attempt to achieve maximum tumor selectivity. From the bench to clinical trials, the scope of this review is to highlight the beginnings of translational oncolytic virotherapy research in upper gastrointestinal tract malignancies and provide a bioengineering perspective of the most promising platforms.

Tumor necrosis factor-related apoptosis inducing ligand overexpression and Taxol treatment suppresses the growth of cervical cancer cells in vitro and in vivo

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is a member of tumor necrosis factor (TNF) superfamily and functions to promote apoptosis by binding to cell surface death receptor (DR)4 and DR5. Cancer cells are more sensitive than normal cells to TRAIL-induced apoptosis, and TRAIL-based therapeutic strategies have shown promise for the treatment of cancer. The present study investigated whether enforced overexpression of TRAIL in cervical cancer cells promoted cell death in the presence or absence of Taxol, an important first-line cancer chemotherapeutic drug. Hela human cervical cancer cells were transfected with a TRAIL expression plasmid, and the effects of the combination treatment with Taxol on apoptosis was investigated in vitro and in tumor xenografts in vivo. The results indicated that Taxol treatment and TRAIL overexpression enhanced apoptosis compared with either treatment alone. The present data indicate that Taxol may enhance the pro-apoptotic effects of TRAIL overexpression in HeLa cells by increasing cleaved caspase-3 and DR5 expression levels and decreasing Bcl-2 expression levels. Furthermore, the findings suggest a possible novel treatment option for cervical cancer and uncovers a potential mechanism of the enhancing effects of Taxol on TRAIL-induced apoptosis.

Oncolytic viral therapy for pancreatic cancer

Outcomes of pancreatic adenocarcinoma (PDA) remain dismal despite extensive clinical investigation. Combination chemotherapy provides modest improvements in survival above best supportive care, and immunotherapy has thus far not proven effective. Nevertheless, growing insight into antitumor immunity and the tumor microenvironment has inspired the discovery of novel agents targeting PDA. Oncolytic viruses represent an emerging class of immunotherapeutic agents that have undergone extensive preclinical investigation and warrant further investigation in well-designed clinical trials.

Enhanced growth suppression of TERT-positive tumor cells by oncolytic adenovirus armed with CCL20 and CD40L

Conditionally replicating adenoviruses (CRAds) selectively replicate in cancer cells and induce cell lysis, which represents a potential platform for cancer immunotherapy. The chemokine CCL20 exerts antitumor activity via chemoattraction of immature dendritic cells (DCs) and lymphocytes. However, the activation and maturation status of DCs is a limiting factor in the DCs -based immunity response. CD40L induces the phenotypic maturation of DCs, mediates DCs cytokine secretion, and increases the expression of FasL, which mediates apoptosis. We constructed a CCL20/CD40L co-expression CRAds (Ad-CCL20-CD40L) based on the AdEasy system. Ad-CCL20-CD40L was constructed from three plasmids, pGTE-CD40L, pShuttle-CMV-CCL20 and AdEasy-1, and was homologously recombined and propagated in the Escherichia coli strain BJ5183 and the packaging cell line HEK-293, respectively. Ad-CCL20-CD40L selectively replicates in TERT-positive tumor cells because the pGTE-CD40L plasmid contains the telomerase reverse transcriptase promoter (TERTp). Our results showed that Ad-CCL20-CD40L induced oncolytic effects and tumor-specific cytotoxicity of cytotoxic T lymphocytes (CTLs) in vitro. This study suggests that Ad-CCL20-CD40L can induce the antitumor immune response and that this platform can be modified to generate novel CRAds with other transgenes.

C-Jun N-terminal kinases are required for oncolytic adenovirus-mediated autophagy

Oncolytic adenoviruses, such as Delta-24-RGD, are replication-competent viruses that are genetically engineered to induce selective cancer cell lysis. In cancer cells, Delta-24-RGD induces massive autophagy, which is required for efficient cell lysis and adenoviral spread. Understanding the cellular mechanisms underlying the regulation of autophagy in cells treated with oncolytic adenoviruses may provide new avenues to improve the therapeutic effect. In this work, we showed that cancer cells infected with Delta-24-RGD undergo autophagy despite the concurrent activation of the AKT/mTOR pathway. Moreover, adenovirus replication induced sustained activation of JNK proteins in vitro. ERK1/1 phosphorylation remained unchanged during adenoviral infection, suggesting specificity of JNK activation. Using genetic ablation and pharmacological inactivation of JNK, we unequivocally demonstrated that cells infected with Delta-24-RGD required JNK activation. Thus, genetic co-ablation of JNK1 and JNK2 genes or inhibition of JNK kinase function rendered Delta-24-RGD–treated cells resistant to autophagy. Accordingly, JNK activation induced phosphorylation of Bcl-2 and prevented the formation of Bcl-2/Beclin 1 autophagy suppressor complexes. Using an orthotopic model of human glioma xenograft, we showed that treatment with Delta-24-RGD induced phosphorylation and nuclear translocation of JNK, as well as phosphorylation of Bcl-2. Collectively, our data identified JNK proteins as an essential mechanistic link between Delta-24-RGD infection and autophagy in cancer cells. Activation of JNK without inactivation of the AKT/mTOR pathway constitutes a distinct molecular signature of autophagy regulation that differentiates Delta-24-RGD adenovirus from the mechanism used by other oncolytic viruses to induce autophagy and provides a new rationale for the combination of oncolytic viruses and chemotherapy.

Armed therapeutic viruses - a disruptive therapy on the horizon of cancer immunotherapy

For the past 150 years cancer immunotherapy has been largely a theoretical hope that recently has begun to show potential as a highly impactful treatment for various cancers. In particular, the identification and targeting of immune checkpoints have given rise to exciting data suggesting that this strategy has the potential to activate sustained antitumor immunity. It is likely that this approach, like other anti-cancer strategies before it, will benefit from co-administration with an additional therapeutic and that it is this combination therapy that may generate the greatest clinical outcome for the patient. In this regard, oncolytic viruses are a therapeutic moiety that is well suited to deliver and augment these immune-modulating therapies in a highly targeted and economically advantageous way over current treatment. In this review, we discuss the blockade of immune checkpoints, how oncolytic viruses complement and extend these therapies, and speculate on how this combination will uniquely impact the future of cancer immunotherapy.

Anticancer gene transfer for cancer gene therapy

Gene therapy vectors are among the treatments currently used to treat malignant tumors. Gene therapy vectors use a specific therapeutic transgene that causes death in cancer cells. In early attempts at gene therapy, therapeutic transgenes were driven by non-specific vectors which induced toxicity to normal cells in addition to the cancer cells. Recently, novel cancer specific viral vectors have been developed that target cancer cells leaving normal cells unharmed. Here we review such cancer specific gene therapy systems currently used in the treatment of cancer and discuss the major challenges and future directions in this field.

Chimeric 5/35 adenovirus-mediated Dickkopf-1 overexpression suppressed tumorigenicity of CD44⁺ gastric cancer cells via attenuating Wnt signaling

BACKGROUND

Gastric cancer stem cells (CSCs), which require activation of Wnt signaling to maintain their self-renewal and tumorigenicity, are proposed to be critical targets for effective therapy of gastric carcinomas. Gene therapies that are delivered by adenovirus of serotype 5 (Ad5) or chimeric 5/35(Ad5/35) adenovirus have shown promise for treating various cancers. Here we aimed to develop a gene therapy strategy that targeted gastric CSCs (CD44⁺ cells).

METHODS

CD44⁺ cells were isolated by fluorescence activated cell sorting from both primary gastric cancer cells and cell lines. Expression of adenovirus receptors was examined in CD44⁺ and CD44⁻ cells. A potent Wnt antagonist Dickkopf-1 (DKK1) was delivered into CD44⁺ cells using Ad5/35 (Ad5/35-DKK1). The therapeutic outcomes were evaluated.

RESULTS

Expression of Coxsakievirus adenovirus receptor for Ad5 was significantly reduced, while abundance of CD46, the receptor for Ad5/35, was slightly higher in CD44⁺ cells. Accordingly, CD44⁺ cells were sensitive to Ad5/35 infection, but not to Ad5. Ad5/35-DKK1 introduced DKK1 into CD44⁺ cells and deactivated endogenous Wnt/β-catenin signaling efficiently. Overexpression of DKK1 inhibited survival, anchorage-independent colony formation, and invasion of CD44⁺ cells, which were restored by a GSK-3 specific inhibitor BIO-acetoxime. More importantly, introduction of DKK1 abrogated the tumorigenicity of CD44⁺ cells in vivo. However, Ad5/35-DKK1 only showed minimal cytotoxicity to normal tissue-derived cells, L-02 and GES-1.

CONCLUSIONS

We developed, for the first time, a novel Ad5/35-DKK1-based approach to abrogate Wnt signaling in CSCs and demonstrated that gastric CSC-targeting gene therapy was effective in preclinical experiments.

Bugs and drugs: oncolytic virotherapy in combination with chemotherapy

Single agent therapies are rarely successful in treating cancer, particularly at metastatic or end stages, and survival rates with monotherapies alone are generally poor. The combination of multiple therapies to treat cancer has already driven significant improvements in the standard of care treatments for many types of cancers. The first combination treatments exploited for cancer therapy involved the use of several cytotoxic chemotherapy agents. Later, with the development of more targeted agents, the use of novel, less toxic drugs, in combination with the more classic cytotoxic drugs has proven advantageous for certain cancer types. Recently, the combination of oncolytic virotherapy with chemotherapy has shown that the use of these two therapies with very distinct anti-tumor mechanisms may also lead to synergistic interactions that ultimately result in increased therapeutic effects not achievable by either therapy alone. The mechanisms of synergy between oncolytic viruses (OVs) and chemotherapeutic agents are just starting to be elucidated. It is evident, however, that the success of these OV-drug combinations depends greatly on the particular OV, the drug(s) selected, and the cancer type targeted. This review summarizes the different OV-drug combinations investigated to date, including the use of second generation armed OVs, which have been studied with the specific purpose of generating synergistic interactions with particular chemotherapy agents. The known mechanisms of synergy between these OV-drug combinations are also summarized. The importance of further investigating these mechanisms of synergy will be critical in order to maximize the therapeutic efficacy of OV-drug combination therapies in the future.

Combining conditionally replicating adenovirus-mediated gene therapy with chemotherapy: a novel antitumor approach

Despite significant improvements in diagnosis and innovations in the therapy of specific cancers, effective treatment of neoplastic diseases still presents major challenges. Recent studies have shown that conditionally replicating adenoviruses (CRAds) not only have the ability to destroy cancer cells but may also be potential vectors for the expression of therapeutic genes. Several studies in animal models have demonstrated that the combination of CRAds-mediated gene therapy and chemotherapy has greater therapeutic benefit than either treatment modality alone. In this review, an overview of specifications for a novel antitumor approach combining CRAd-gene therapy and chemotherapy is provided and recent progress in this field is discussed.

Current advances in adenovirus nanocomplexes: more specificity and less immunogenicity

An often overlooked issue in the field of adenovirus (Ad)-mediated cancer gene therapy is its limited capacity for effective systemic delivery. Although primary tumors can be treated effectively with intralesional injection of conventional Ad vectors, systemic metastasis is difficult to cure. Systemic administration of conventional naked Ads leads to acute accumulation of Ad particles in the liver, induction of neutralizing antibody, short blood circulation half-life, non-specific biodistribution in undesired organs, and low selective accumulation in the target disease site. Versatile strategies involving the modification of viral surfaces with polymers and nanomaterials have been designed for the purpose of maximizing Ad anti-tumor activity and specificity by systemic administration. Integration of viral and non-viral nanomaterials will substantially advance both fields, creating new concepts in gene therapeutics. This review focuses on current advances in the development of smart Ad hybrid nanocomplexes based on various design-based strategies for optimal Ad systemic administration.

Improving gene transfer in human renal carcinoma cells: Utilization of adenovirus vectors containing chimeric type 5 and type 35 fiber proteins

The transduction efficacy of adenovirus serotype 5 (Ad5) vector in human renal carcinoma cells is generally low due to the down-regulated expression of Coxsackie and adenovirus receptor (CAR) in target cells. By contrast, the infectivity of adenovirus serotype 35 vectors depends on the binding rate to CD46 receptor, independent of CAR. In this study, we examined whether an adenovirus vector containing chimeric type 5 and type 35 fiber proteins (Ad5/F35) increases transduction efficiency compared to Ad5 vector in human renal carcinoma cells in vitro. The expression of CAR was much lower in the human renal carcinoma cells than in control HEK293 cells. By contrast, the expression of CD46 was similar and perhaps at a higher level in the human renal carcinoma cells than in the HEK293 cells. The transduction efficacy of Ad5/F35 vector was dramatically higher compared to that of Ad5 in human renal carcinoma cells, and was correlated to the expression of CD46. Thus, Ad5/35 vector may be useful for the development of novel gene therapy approaches to renal cell carcinoma.

Oncolytic Viruses for Cancer Therapy: Overcoming the Obstacles

Targeted therapy of cancer using oncolytic viruses has generated much interest over the past few years in the light of the limited efficacy and side effects of standard cancer therapeutics for advanced disease. In 2006, the world witnessed the first government-approved oncolytic virus for the treatment of head and neck cancer. It has been known for many years that viruses have the ability to replicate in and lyse cancer cells. Although encouraging results have been demonstrated in vitro and in animal models, most oncolytic viruses have failed to impress in the clinical setting. The explanation is multifactorial, determined by the complex interactions between the tumor and its microenvironment, the virus, and the host immune response. This review focuses on discussion of the obstacles that oncolytic virotherapy faces and recent advances made to overcome them, with particular reference to adenoviruses.

Silencing MRP4 by small interfering RNA reverses acquired DDP resistance of gastric cancer cell

A cisplatin (DDP) resistant cell line (SGC7901/DDP) from a Chinese gastric cancer cell line (SGC7901) was established by step-increasing DDP treatment, and the resultant cell line showed an over 21.9-fold increased resistance to DDP. To identify the mechanism of DDP resistance, the differential gene expression panel was examined by Affymetrix microarray. Among the identified differential genes, 681 genes expression were increased and 1139 genes were decreased. To confirm these gene changes furtherly, one of the upregulated gene, MRP4 was identified with increased mRNA and protein level of SGC7901/DDP by RT-PCR and Western-blot analysis compared with its parental cell line. By using the small interfering RNA (RNAi) to decrease the MRP4 expression, the DDP resistance phenotype of SGC7901/DDP was reversed. These data suggest that MRP4 is a DDP resistance candidate gene of SGC7901 gastric cancer cell line.