Potent anti-tumor activity of telomerase-dependent and HSV-TK armed oncolytic adenovirus for non-small cell lung cancer in vitro and in vivo

Advances in cell-based delivery of oncolytic viruses as therapy for lung cancer

Lung cancer's intractability is enhanced by its frequent resistance to (chemo)therapy and often high relapse rates that make it the leading cause of cancer death worldwide. Improvement of therapy efficacy is a crucial issue that might lead to a significant advance in the treatment of lung cancer. Oncolytic viruses are desirable combination partners in the developing field of cancer immunotherapy due to their direct cytotoxic effects and ability to elicit an immune response. Systemic oncolytic virus administration through intravenous injection should ideally lead to the highest efficacy in oncolytic activity. However, this is often hampered by the prevalence of host-specific, anti-viral immune responses. One way to achieve more efficient systemic oncolytic virus delivery is through better protection against neutralization by several components of the host immune system. Carrier cells, which can even have innate tumor tropism, have shown their appropriateness as effective vehicles for systemic oncolytic virus infection through circumventing restrictive features of the immune system and can warrant oncolytic virus delivery to tumors. In this overview, we summarize promising results from studies in which carrier cells have shown their usefulness for improved systemic oncolytic virus delivery and better oncolytic virus therapy against lung cancer.

Oncolytic viruses in lung cancer treatment: a review article

Lung cancer has a high morbidity rate worldwide due to its resistance to therapy. So new treatment options are needed to improve the outcomes of lung cancer treatment. This study aimed to evaluate the effectiveness of oncolytic viruses (OVs) as a new type of cancer treatment. In this study, 158 articles from PubMed and Scopus from 1994 to 2022 were reviewed on the effectiveness of OVs in the treatment of lung cancer. The oncolytic properties of eight categories of OVs and their interactions with treatment options were investigated. OVs can be applied as a promising immunotherapy option, as they are reproduced selectively in different types of cancer cells, cause tumor cell lysis and trigger efficient immune responses.

Blood-Derived Exosomal hTERT mRNA in Patients with Lung Cancer: Characterization and Correlation with Response to Therapy

Background: Telomerase (human telomerase reverse transcriptase (hTERT) is considered a hallmark of cancer, being active in cancer cells but repressed in human somatic cells. As such, it has the potential to serve as a valid cancer biomarker. Exosomal hTERT mRNA can be detected in the serum of patients with solid malignancies but not in healthy individuals. We sought to evaluate the feasibility of measuring serum exosomal hTERT transcripts levels in patients with lung cancer. Methods: A prospective analysis of exosomal hTERT mRNA levels was determined in serum-derived exosomes from 76 patients with stage III-IV lung cancer (11 SCLC and 65 NSCLC). An hTERT level above RQ = 1.2 was considered "detectable" according to a previous receiver operating characteristic curve (ROC) curve. Sequential measurements were obtained in 33 patients. Demographic and clinical data were collected retrospectively from patients' charts. Data on response to systemic therapy (chemotherapy, immunotherapy, and tyrosine kinase inhibitors) were collected by the treating physicians. Results: hTERT was detected in 53% (40/76) of patients with lung cancer (89% of SCLC and 46% of NSLCC). The mean hTERT levels were 3.7 in all 76 patients, 5.87 in SCLC patients, and 3.62 in NSCLC patients. In total, 25 of 43 patients with sequential measurements had detectable levels of hTERT. The sequential exosomal hTERT mRNA levels reflected the clinical course in 23 of them. Decreases in hTERT levels were detected in 17 and 5 patients with partial and complete response, respectively. Eleven patients with a progressive disease had an increase in the level of exosomal hTERT, and seven with stable disease presented increases in its exosomal levels. Another patient who progressed on the first line of treatment and had a partial response to the second line of treatment exhibited an increase in exosomal hTERT mRNA levels during the progression and a decrease during the response. Conclusions: Exosomal hTERT mRNA levels are elevated in over half of patients with lung cancer. The potential association between hTERT levels and response to therapy suggests its utility as a promising cancer biomarker for response to therapy. This issue should be further explored in future studies.

Oncolytic Virotherapy: From Bench to Bedside

Oncolytic viruses are naturally occurring or genetically engineered viruses that can replicate preferentially in tumor cells and inhibit tumor growth. These viruses have been considered an effective anticancer strategy in recent years. They mainly function by direct oncolysis, inducing an anticancer immune response and expressing exogenous effector genes. Their multifunctional characteristics indicate good application prospects as cancer therapeutics, especially in combination with other therapies, such as radiotherapy, chemotherapy and immunotherapy. Therefore, it is necessary to comprehensively understand the utility of oncolytic viruses in cancer therapeutics. Here, we review the characteristics, antitumor mechanisms, clinical applications, deficiencies and associated solutions, and future prospects of oncolytic viruses.

Fighting Fire With Fire: Oncolytic Virotherapy for Thoracic Malignancies

Thoracic malignancies are associated with high mortality rates. Conventional therapy for many of the patients with thoracic malignancies is obviated by a high incidence of locoregional recurrence and distant metastasis. Fortunately, developments in immunotherapy provide effective strategies for both local and systemic treatments that have rapidly advanced during the last decade. One promising approach to cancer immunotherapy is to use oncolytic viruses, which have the advantages of relatively high tumor specificity, selective replication-mediated oncolysis, enhanced antigen presentation, and potential for delivery of immunogenic payloads such as cytokines, with subsequent elicitation of effective antitumor immunity. Several oncolytic viruses including adenovirus, coxsackievirus B3, herpes virus, measles virus, reovirus, and vaccinia virus have been developed and applied to thoracic cancers in preclinical murine studies and clinical trials. This review discusses the current state of oncolytic virotherapy in lung cancer, esophageal cancer, and metastatic malignant pleural effusions and considers its potential as an emergent therapeutic for these patients.

Delivery of cancer therapies by synthetic and bio-inspired nanovectors

BACKGROUND

As a complement to the clinical development of new anticancer molecules, innovations in therapeutic vectorization aim at solving issues related to tumor specificity and associated toxicities. Nanomedicine is a rapidly evolving field that offers various solutions to increase clinical efficacy and safety. MAIN: Here are presented the recent advances for different types of nanovectors of chemical and biological nature, to identify the best suited for translational research projects. These nanovectors include different types of chemically engineered nanoparticles that now come in many different flavors of 'smart' drug delivery systems. Alternatives with enhanced biocompatibility and a better adaptability to new types of therapeutic molecules are the cell-derived extracellular vesicles and micro-organism-derived oncolytic viruses, virus-like particles and bacterial minicells. In the first part of the review, we describe their main physical, chemical and biological properties and their potential for personalized modifications. The second part focuses on presenting the recent literature on the use of the different families of nanovectors to deliver anticancer molecules for chemotherapy, radiotherapy, nucleic acid-based therapy, modulation of the tumor microenvironment and immunotherapy.

CONCLUSION

This review will help the readers to better appreciate the complexity of available nanovectors and to identify the most fitting "type" for efficient and specific delivery of diverse anticancer therapies.

Engineering and Characterization of Oncolytic Vaccinia Virus Expressing Truncated Herpes Simplex Virus Thymidine Kinase

Oncolytic viruses are a promising class of anti-tumor agents; however, concerns regarding uncontrolled viral replication have led to the development of a replication-controllable oncolytic vaccinia virus (OVV). The engineering involves replacing the native thymidine kinase (VV-tk) gene, in a Wyeth strain vaccinia backbone, with the herpes simplex virus thymidine kinase (HSV-tk) gene, which allows for viral replication control via ganciclovir (GCV, an antiviral/cytotoxic pro-drug). Adding the wild-type HSV-tk gene might disrupt the tumor selectivity of VV-tk deleted OVVs; therefore, only engineered viruses that lacked tk activity were selected as candidates. Ultimately, OTS-412, which is an OVV containing a mutant HSV-tk, was chosen for characterization regarding tumor selectivity, sensitivity to GCV, and the influence of GCV on OTS-412 anti-tumor effects. OTS-412 demonstrated comparable replication and cytotoxicity to VV^tk- (control, a VV-tk deleted OVV) in multiple cancer cell lines. In HCT 116 mouse models, OTS-412 replication in tumors was reduced by >50% by GCV (p = 0.004); additionally, combination use of GCV did not compromise the anti-tumor effects of OTS-412. This is the first report of OTS-412, a VV-tk deleted OVV containing a mutant HSV-tk transgene, which demonstrates tumor selectivity and sensitivity to GCV. The HSV-tk/GCV combination provides a safety mechanism for future clinical applications of OTS-412.

Molecular imaging-monitored radiofrequency hyperthermia-enhanced intratumoral herpes simplex virus-thymidine kinase gene therapy for rat orthotopic ovarian cancer

Objective: To establish the technique of intratumoral combination therapy of radiofrequency hyperthermia (RFH) with herpes simplex virus-thymidine kinase/ganciclovir (HSV-TK/GCV) gene therapy for rat ovarian cancers.Material and methods: This study consisted of three parts: (1) in vitro experiments to establish the 'proof of principal' that combination of RFH and HSV-TK gene therapy has the synergistic effect on human ovarian cancer cells; (2) creation of bioluminescence imaging-detectable rat ovarian cancer model; and (3) in vivo experiments using this rat model to validate the technical feasibility of the combination therapy. Cells and nude rats were divided into four groups: (i) combination therapy (HSV-TK/GCV + RFH); (ii) RFH; (iii) HSV-TK/GCV; and (iv) phosphate-buffered saline (PBS). Data were analyzed using Dunnett t-test or Kruskal-Wallis test.Results: Cell proliferation assay demonstrated significantly greater reduction in viable cells with the combination therapy [0.52 (0.43, 0.61)] compared to other treatments [RFH 0.90 (0.84, 0.96), HSV-TK/GCV 0.71 (0.53, 0.88), PBS 1 (1, 1); p < .05]. For 24 rat models with bioluminescence imaging-detectable orthotopic ovarian cancer (n = 6 per group), optical imaging demonstrated significantly decreased relative bioluminescence signal with the combination therapy [0.81 (0.52, 1.08)] compared to other treatments [RFH 3.60 (2.34, 4.86), HSV-TK/GCV 2.21 (1.71, 2.71), PBS 3.74 (3.19, 4.29); p < .001]. Ultrasound imaging demonstrated the smallest relative tumor volume with the combination therapy [0.78 (0.45, 1.11) versus 3.50 (2.67, 4.33), 2.10 (0.83, 3.37), 3.70 (1.79, 5.61); p < .05].Conclusion: The feasibility of intratumoral RFH-enhanced HSV-TK/GCV gene therapy was established on a unique rat model with molecular imaging-detectable orthotopic ovarian cancer.

Fighting Cancer with Viruses: Oncolytic Virus Therapy in China

As part of oncolytic virotherapy to treat cancer, oncolytic viruses (OVs) can selectively infect tumor cells to promote oncolysis of cancer cells, local immunological reactions, and systemic antitumor immunity with minimal toxicity to normal tissues. The immunostimulatory properties of OVs provide enormous benefits for the treatment of cancer. A variety of OVs, including genetically engineered and natural viruses, have shown promise in preclinical models and clinical studies. In 2005, the China Food and Drug Administration approved its first OV drug, Oncorine (H101), for treatment of advanced head and neck cancer. To explore new treatment strategies, >200 recombinant or natural OVs are undergoing in-depth investigation in China, and >250 oncolytic virotherapy-related reports from the OV community in China have been published in the past 5 years. These studies investigated a variety of exogenous genes and combination therapeutic strategies to enhance the treatment effects of OVs. To date, five clinical trials covering four OV agents (Oncorine, OrienX010, KH901, and H103) are ongoing, and additional OV agents are awaiting approval for clinical trials in China. Overall, this research emphasizes that combination therapy, especially tumor immunotherapy coupled with effective system administration strategies, can promote the development of oncolytic virotherapies. This article focuses on studies that were carried out in China in order to give an overview of the past, present, and future of oncolytic virotherapy in China.

Epithelial ovarian cancer: feasibility of image-guided intratumoral radiofrequency hyperthermia-enhanced direct gene therapy

The aim of this study was to develop an interventional oncologic technique, "Image-guided intratumoral radiofrequency hyperthermia (RFH)-enhanced herpes simplex virus-thymidine kinase (HSV-TK) gene therapy of ovarian cancer. This study consisted of three portions: (1) serial in-vitro experiments to establish "proof-of-principle" of this novel technique using human ovarian cancer cells; (2) serial in-vivo experiments to validate technical feasibility using animal models with the same orthotopic ovarian cancers; and (3) serial investigations into the underlying bio-molecular mechanisms of this technique. We included four subject groups: (i) combination therapy with RFH+HSV-TK gene therapy; (ii) gene therapy-only; (iii) RFH-only; and (iv) Phosphate-buffered saline (PBS). For in-vitro experiments, confocal microscopy and MTS assays were performed to quantify HSV-TK gene expression and assess cell viability. For in-vivo experiments, bioluminescence optical and ultrasound imaging were used to assess therapeutic effectiveness. These results were correlated with subsequent pathologic/laboratory studies to further elucidate the biologic mechanisms of this technique. In in-vitro experiments, combination therapy resulted in the lowest cell proliferation and greatest increase in HSV-TK gene expression among four subject groups. In in-vivo experiments, combination therapy lead to significant decreases of bioluminescence signals and sizes of tumors in combination therapy by optical and ultrasound imaging. Pathology/laboratory examinations confirmed the significantly increased expression of Bax, Caspase-3, HSP70, IL-2, and CD94 in cancer tissues subjected to combination therapy. "Image-guided intratumoral RFH-enhanced direct gene therapy" is an effective interventional oncologic technique which functions through apoptotic/anti-tumor immunity pathways. This technical development may open new avenues for treating ovarian cancer.

Non-Small-Cell Lung Cancer: Feasibility of Intratumoral Radiofrequency Hyperthermia-enhanced Herpes Simplex Virus Thymidine Kinase Gene Therapy

Purpose To validate the feasibility and efficacy of intratumoral radiofrequency hyperthermia (RFH)-enhanced herpes simplex virus (HSV) thymidine kinase (TK) and ganciclovir (GCV) (hereafter, HSV-TK/GCV) gene therapy for non-small-cell lung cancer (NSCLC). Materials and Methods This study was performed from November 11, 2015, to April 14, 2017, and included (a) in vitro experiments with human NSCLC cells to establish the proof of principle, (b) in vivo experiments using mice with subcutaneous NSCLC to further demonstrate the principle, and (c) in vivo experiments using rats with orthotopic NSCLC to validate the technical feasibility. Cells, nude mice, and nude rats were randomly divided into four groups (six animals per group): (a) combination therapy (HSV-TK/GCV combined with RFH), (b) RFH, (c) HSV-TK/GCV, and (d) phosphate-buffered saline. Data were analyzed by using the Dunnett t test or Kruskal-Wallis test. Results For in vitro experiments, the cell proliferation assay showed significantly diminished viable cells with combination therapy (mean, 0.56; 95% confidence interval [CI]: 0.44, 0.68) versus RFH (mean, 0.89; 95% CI: 0.82, 0.97), HSV-TK/GCV (mean, 0.71; 95% CI: 0.56, 0.86), and phosphate-buffered saline (mean, 1; 95% CI: 1, 1) (P < .05 for all). For in vivo experiments, optical imaging showed significantly decreased relative bioluminescence signal with combination therapy (mean, 0.71 [95% CI: 0.03, 1.39] in mice; 1.29 [95% CI: 0.51, 2.06] in rats) compared with RFH (mean, 2.66 [95% CI: 1.73, 3.59] in mice; 2.26 [95% CI: 1.51, 3.01] in rats), HSV-TK/GCV (mean, 1.37 [95% CI: 0.65, 2.08] in mice; 1.76 [95% CI: 1.20, 2.31] in rats), and phosphate-buffered saline (mean, 3.07 [95% CI: 2.50, 3.65] in mice; 2.94 [95% CI: 2.29, 3.58] in rats) (P < .001 for all). US showed that the smallest relative tumor volumes occurred with combination therapy (mean, 0.60; 95% CI: 0.15, 1.05) versus RFH (mean, 2.43; 95% CI: 1.80, 3.06), HSV-TK/GCV (mean, 1.32; 95% CI: 0.75, 1.89), and phosphate-buffered saline (mean, 2.56; 95% CI: 1.75, 3.38) (P < .05 for all) in the mouse subcutaneous model. Conclusion Intratumoral radiofrequency hyperthermia-enhanced herpes simplex virus thymidine kinase and ganciclovir gene therapy for non-small-cell lung cancer is feasible and can be guided by molecular imaging. © RSNA, 2018.

Armed oncolytic viruses: A kick-start for anti-tumor immunity

Oncolytic viruses (OVs), viruses that specifically result in killing tumor cells, represent a promising class of cancer therapy. Recently, the focus in the OV therapy field has shifted from their direct oncolytic effect to their immune stimulatory effect. OV therapy can function as a "kick start" for the antitumor immune response by releasing tumor associated antigens and release of inflammatory signals. Combining OVs with immune modulators could enhance the efficacy of both immune and OV therapies. Additionally, genetic engineering of OVs allows local expression of immune therapeutics, thereby reducing related toxicities. Different options to modify the tumor microenvironment in combination with OV therapy have been explored. The possibilities and obstacles of these combinations will be discussed in this review.

Assessment of Specificity of an Adenovirus Targeted to HER3/4

Gene therapy with viral vectors, such as adenovirus (Ad), targeted to the human epidermal growth factor receptors 3 and 4 (HER3/4) are potentially useful for cancer therapy. Testing the expression of a reporter gene from these viruses in target cells is essential to determine functionality of the targeted virus. A competition assay with a relevant ligand (heregulin, HRG) can provide convincing evidence that blocking binding to the HER3/4 receptor results in decreased reporter gene expression. Labeling individual viruses with a fluorescent molecule allows examination of the targeted virus in specific steps in the infection. Virus internalization into cell lines can be determined using antibody-labeled receptors, and the virus colocalization with receptors can also be visualized. Characterization of a targeted virus in this fashion is important to demonstrate that the targeting of the virus functions in an expected manner, and provides support for larger-scale testing of the virus. Information acquired in these experiments may also be useful to inform and improve on the design of future targeted viruses.

Viroimmunotherapy of Thoracic Cancers

Thoracic cancers, including non-small cell lung cancer (NSCLC), small cell lung cancer (SCLC), and malignant pleural mesothelioma (MM), cause the highest rate of cancer mortality worldwide. Most of these deaths are as a result of NSCLC; however, prognoses for the other two diseases remain as some of the poorest of any cancers. Recent advances in immunotherapy, specifically immune checkpoint inhibitors, have begun to help a small population of patients with advanced lung cancer. People who respond to these immune therapies generally have a durable response and many see dramatic decreases in their disease. However, response to immune therapies remains relatively low. Therefore, intense research is now underway to rationally develop combination therapies to expand the range of patients who will respond to and benefit from immune therapy. One promising approach is with oncolytic viruses. These oncolytic viruses (OVs) have been found to be selective for or have been engineered to preferentially infect and kill cancer cells. In pre-clinical models of different thoracic cancers, it has been found that these viruses can induce immunogenic cell death, increase the number of immune mediators brought into the tumor microenvironment and broaden the neoantigen-specific T cell response. We will review here the literature regarding the application of virotherapy toward augmenting immune responses in thoracic cancers.

Assessment of α-fetoprotein targeted HSV1-tk expression in hepatocellular carcinoma with in vivo imaging

Tumor-specific enhancer/promoter is applicable for targeting gene expression in tumors and helpful for tumor-targeting imaging and therapy. We aimed to acquire α-fetoprotein (AFP)-producing hepatocellular carcinoma (HCC) specific images using adenovirus containing HSV1-tk gene controlled by AFP enhancer/promoter and evaluate in vivo ganciclovir (GCV)-medicated therapeutic effects on AFP-targeted HSV1-tk expression with (18)F-FDG positron emission tomography (PET). Recombinant adenovirus expressing HSV1-tk under AFP enhancer/promoter was produced (AdAFP-TK) and the expression levels were evaluated by RT-PCR and (125)I-IVDU uptake. GCV-mediated HSV1-tk cytotoxicity was determined by MTT assay. After the mixture of AdAFP-fLuc and AdAFP-TK was administrated, bioluminescent images (BLIs) and (18)F-FHBG PET images were obtained in tumor-bearing mice. In vivo therapeutic effects of AdAFP-TK and GCV in the HuH-7 xenograft model were monitored by (18)F-FDG PET. When infected with AdAFP-TK, cell viability in HuH-7 was reduced, but those in HT-29 and SK-Hep-1 were not significantly decreased at any GCV concentration less than 100 μM. AFP-targeted fLuc and HSV1-tk expression were clearly visualized by BLI and (18)F-FHBG PET images in AFP-producing HCC, respectively. In vivo GCV-mediated tumor growth inhibition by AFP-targeted HSV1-tk expression was monitored by (18)F-FDG PET. Recombinant AdAFP-TK could be applied for AFP-targeted HCC gene therapy and imaging in AFP-producing HCC.

Oncolytic therapy of a recombinant Newcastle disease virus D90 strain for lung cancer

Background

Lung cancer is one of the leading causes of deaths from cancer worldwide. Tumor virotherapy using naturally oncolytic Newcastle disease virus (NDV) has been shown to be safe and effective in preclinical studies and clinical trials. Previously, we have reported the NDV D90 strain that was isolated from natural source has an antiproliferative effect in human lung cancer cell line A549.

Methods and results

In this study, we constructed a reverse genetics system based on the oncolytic NDV D90 strain and generated a recombinant NDV carrying a gene encoding enhanced green fluorescent protein (rNDV-GFP). The rescued virus rNDV-D90 and rNDV-GFP showed the similar characteristics of replication and apoptotic ability in lung cancer A549 cells, which suggested that the recombinant viruses sustained the property of tumor-selective replication and induced apoptosis of tumor cells. The athymic mice bearing implanted lung cancer were treated with the parental D90 virus, the rescued rNDV-D90 and rNDV-GFP via intratumoral injections, respectively. The results showed that the recombinant viruses as well as the parental D90 virus significantly suppressed the loss of body weight and tumor growth.

Conclusions

The study provides a new platform to develop effective therapeutic agents for tumor treatment. The availability of the reverse genetics system for NDV D90 strain will make it possible to develop novel recombinant oncolytic viruses based on the NDV D90 strain for improving the efficacy of tumor treatment.

Pancreatic tumor mass in a xenograft mouse model is decreased by treatment with therapeutic stem cells following introduction of therapeutic genes

Pancreatic cancer is the fourth most common cause of cancer-related mortality. In the present study, we employed 2 types of therapeutic stem cells expressing cytosine deaminase (CD) with or without human interferon-β (IFN‑β), HB1.F3.CD and HB1.F3.CD.IFN-β cells, respectively, to selectively treat pancreatic cancer. The CD gene converts the non-toxic prodrug, 5-flurorocytosine (5-FC), into the toxic agent, 5-fluorouracil (5-FU). In addition, human IFN-β is a potent cytokine that has antitumor effects. To generate a xenograft mouse model, PANC-1 cells (2x10(6)/mouse) cultured in DMEM containing 10% FBS were mixed with Matrigel and were subcutaneously injected into Balb/c nu/nu mice. In the migration assay, the stem cells expressing the CD or IFN-β gene effectively migrated toward the pancreatic cancer cells, suggesting the presence of chemoattractant factors secreted by the pancreatic tumors. In the co-culture and MTT assay, antitumor activity of the therapeutic stem cells was observed in the presence of 5-FC was shown that the growth of PANC-1 cells was inhibited. Furthermore, these effects were confirmed in the xenograft mouse model bearing tumors originating from PANC-1 cells. Analyses by histological and fluorescence microscopy showed that treatment with the stem cells resulted in the inhibition of pancreatic cancer growth in the presence of 5-FC. Taken together, these results indicate that stem cells expressing the CD and/or IFN-β gene can be used to effectively treat pancreatic cancer and reduce the side-effects associated with conventional therapies.

Human telomerase reverse-transcriptase promoter-controlled and herpes simplex virus thymidine kinase-armed adenoviruses for renal cell carcinoma treatment

New treatment strategies are required for renal cell carcinoma (RCC) due to its relative insensitivity to conventional radio- and chemotherapies. The promising strategy of tumor inhibition using human telomerase reverse transcriptase (hTERT)-controlled herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) in the hTERT promoter-driven HSV-TK/GCV suicide gene system was investigated. Tumor volume, weight, relative proliferation rate, and cell-apoptosis levels were examined in mice injected with adenovirus (Ad)-hTERT-HSV-TK and GCV. Increased cell death occurred following treatment with Ads carrying hTERT-HSV-TK/GCV or cytomegalovirus promoter-controlled (CMV)-HSV-TK/GCV for human RCC 786-0 and fibroblast MRC-5 cells. In mice, Ad-hTERT-HSV-TK/GCV more specifically inhibited tumor and RCC xenograft growth than Ad-CMV-HSV-TK/GCV (P < 0.05). Furthermore, Ad-hTERT-HSV-TK/GCV did not significantly damage normal fibroblasts or organ systems (heart, lung, liver, brain, kidney, and spleen). Thus, Ad-hTERT-HSV-TK/GCV is an effective RCC inhibitor in human cells in vitro and in vivo mouse models, indicating potential usefulness in RCC-targeted gene therapy.

Chapter eight--Oncolytic adenoviruses for cancer immunotherapy: data from mice, hamsters, and humans

Adenovirus is one of the most commonly used vectors for gene therapy and two products have already been approved for treatment of cancer in China (Gendicine(R) and Oncorine(R)). An intriguing aspect of oncolytic adenoviruses is that by their very nature they potently stimulate multiple arms of the immune system. Thus, combined tumor killing via oncolysis and inherent immunostimulatory properties in fact make these viruses in situ tumor vaccines. When further engineered to express cytokines, chemokines, tumor-associated antigens, or other immunomodulatory elements, they have been shown in various preclinical models to induce antigen-specific effector and memory responses, resulting both in full therapeutic cures and even induction of life-long tumor immunity. Here, we review the state of the art of oncolytic adenovirus, in the context of their capability to stimulate innate and adaptive arms of the immune system and finally how we can modify these viruses to direct the immune response toward cancer.

Effective combination gene therapy using CEACAM6-shRNA and the fusion suicide gene yCDglyTK for pancreatic carcinoma in vitro

The incidence of pancreatic carcinoma, a gastrointestinal malignancy, is on the increase and effective therapeutic strategies are therefore required. This study aimed to construct a recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK from CEACAM6 targeting shRNA and the fusion suicide gene yCDglyTK for inhibition of SW1990 human pancreatic carcinoma cell growth and invasion. A plasmid containing hU6 promoter and CEACAM6 targeting short hairpin RNA (CEACAM6-shRNA) frame was constructed. It was subcloned to a CEA promoter-driven fusion suicide gene pcDNA3.1(-)yCDglyTK. The recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK was identified by restriction endonuclease analysis and DNA sequencing. The recombinant plasmid was delivered into SW1990 human pancreatic carcinoma cells, the mRNA and protein expression of yCDglyTK and CEACAM6 was examined by RT-PCR, western blot analysis and immunofluorescence. SW1990 cells were treated with the prodrug 5-fluorocytosine (5-FC), and the cell viability was evaluated using the 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide (MTT) assay. The invasiveness and migration of SW1990 cells were evaluated by transwell migration assays. The restriction endonuclease analysis and DNA sequencing confirmed the construction of the recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK. Reverse transcription polymerase chain reaction (RT-PCR) and western blot analysis outcomes showed that yCDglyTK was expressed in SW1990 cells and expression of CEACAM6 in SW1990 cells was significantly knocked down. MTT assay showed that the mean viability of SW1990 cells was significantly reduced after administration of the prodrug 5-FC in vitro. Transwell migration assays showed that invasion and migration action of SW1990 cells was significantly inhibited. In conclusion, recombinant plasmid pcDNA3.1(-) shCEACAM6-yCDglyTK was successfully constructed. The recombinant plasmid may therefore serve as a novel gene therapy approach for pancreatic carcinoma.

The use of oncolytic viruses to overcome lung cancer drug resistance

Intrinsic and acquired drug resistance remains a fundamental obstacle to successful applications of anticancer therapies for lung cancer. Combining conventional therapies with immunotherapeutic approaches is a promising strategy to circumvent lung cancer drug resistance. Genetically modified oncolytic viruses (OVs) kill tumor cells via completely unique mechanisms compared to small molecule chemotherapeutics typically used in lung cancer treatment and can also be used to deliver specific toxic, therapeutic or immunomodulatory genes to tumor cells. Recent pre-clinical and clinical studies with oncolytic vaccine approaches have revealed promising combination strategies that enhance oncolysis of tumor cells and circumvent tumor resistance mechanisms. As clinical trials with oncolytic vaccines progress, and as the knowledge acquired from these studies builds a foundation demonstrating OVs safety and efficacy, novel combination approaches could soon have a major impact on the clinical management of patients diagnosed with lung cancer.

Optimization and preclinical design of genetically engineered viruses for human oncolytic therapy

INTRODUCTION

Oncolytic viruses (OVs) occupy a strategic niche in the dynamic era of biological and gene therapy of human cancers. However, the use of OVs is the subject of close scrutiny due to impediments such as the insufficiency of patient generalizations posed by heterogeneous tumor responses to treatment, inherent or potentially lethal viral pathogenicities, unanticipated host- or immune-related adverse effects, and the emergence of virus-resistant cancer cells. These challenges can be overcome by the design and development of more definitive (optimized, targeted, and individualized) cancer virotherapeutics.

AREAS COVERED

The translation of current knowledge and recent innovations into rational treatment prospects hinges on an iterative loop of variables pertaining to genetically engineered viral oncolytic efficacy and safety profiles, mechanism-of-action data, potencies of synergistic oncolytic viral combinations with conventional tumor, immuno-, chemo-, and radiation treatment modalities, optimization of the probabilities of treatment successes in heterogeneous (virus-sensitive and -resistant) tumor cell populations by mathematical modeling, and lessons learned from preclinical studies and human clinical trials.

EXPERT OPINION

In recent years, it has become increasingly clear that proof-of-principle is critical for the preclinical optimization of oncolytic viruses to target heterogeneous forms of cancer and to prioritize current concerns related to the efficacy and safety of oncolytic virotherapy.

Potential antitumor therapeutic strategies of human amniotic membrane and amniotic fluid-derived stem cells

As stem cells are capable of self-renewal and can generate differentiated progenies for organ development, they are considered as potential source for regenerative medicine and tissue replacement after injury or disease. Along with this capacity, stem cells have the therapeutic potential for treating human diseases including cancers. According to the origins, stem cells are broadly classified into two types: embryonic stem cells (ESCs) and adult stem cells. In terms of differentiation potential, ESCs are pluripotent and adult stem cells are multipotent. Amnion, which is a membranous sac that contains the fetus and amniotic fluid and functions in protecting the developing embryo during gestation, is another stem cell source. Amnion-derived stem cells are classified as human amniotic membrane-derived epithelial stem cells, human amniotic membrane-derived mesenchymal stem cells and human amniotic fluid-derived stem cells. They are in an intermediate stage between pluripotent ESCs and lineage-restricted adult stem cells, non-tumorigenic, and contribute to low immunogenicity and anti-inflammation. Furthermore, they are easily available and do not cause any controversial issues in their recovery and applications. Not only are amnion-derived stem cells applicable in regenerative medicine, they have anticancer capacity. In non-engineered stem cells transplantation strategies, amnion-derived stem cells effectively target the tumor and suppressed the tumor growth by expressing cytotoxic cytokines. Additionally, they also have a potential as novel delivery vehicles transferring therapeutic genes to the cancer formation sites in gene-directed enzyme/prodrug combination therapy. Owing to their own advantageous properties, amnion-derived stem cells are emerging as a new candidate in anticancer therapy.

Human amniotic fluid-derived stem cells expressing cytosine deaminase and thymidine kinase inhibits the growth of breast cancer cells in cellular and xenograft mouse models

As human amniotic fluid-derived stem cells (hAFSCs) are capable of multiple lineage differentiation, extensive self-renewal and tumor targeting, they may be valuable for clinical anticancer therapies. In this study, we used hAFSCs as vehicles for targeted delivery of therapeutic suicide genes to breast cancer cells. hAFSCs were engineered to produce AF2.CD-TK cells in order to express two suicide genes encoding bacterial cytosine deaminase (CD) and herpes simplex virus thymidine kinase (HSV-TK) that convert non-toxic prodrugs, 5-fluorocytosine (5-FC) and mono-phosphorylate ganciclovir (GCV-MP), into cytotoxic metabolites, 5-fluorouracil (5-FU) and triphosphate ganciclovir (GCV-TP), respectively. In cell viability test in vitro, AF2.CD-TK cells inhibited the growth of MDA-MB-231 human breast cancer cells in the presence of the 5-FC or GCV prodrugs, or a combination of these two reagents. When the mixture of 5-FC and GCV was treated together, an additive cytotoxic effect was observed in the cell viability. In animal experiments using female BALB/c nude mouse xenografts, which developed by injecting MDA-MB-231 cells, treatment with AF2.CD-TK cells in the presence of 5-FC and GCV significantly reduced tumor volume and weight to the same extent seen in the mice treated with 5-FU. Histopathological and fluorescent staining assays further showed that AF2.CD-TK cells were located exactly at the site of tumor formation. Furthermore, breast tissues treated with AF2.CD-TK cells and two prodrugs maintained their normal structures (for example, the epidermis and reticular layers) while breast tissue structures in 5-FU-treated mice were almost destroyed by the potent cytotoxicity of the drug. Taken together, these results indicate that AF2.CD-TK cells can serve as excellent vehicles in a novel therapeutic cell-based gene-directed prodrug system to selectively target breast malignancies.

Stem cells with fused gene expression of cytosine deaminase and interferon-β migrate to human gastric cancer cells and result in synergistic growth inhibition for potential therapeutic use

Genetically engineered stem cells (GESTECs) producing suicide enzymes and immunotherapeutic cytokines have therapeutic effects on tumors, and may possibly reduce the side effects of toxic drugs used for treatments. Suicide enzymes can convert non-toxic pro-drugs to toxic metabolites that can reduce tumor growth. Cytosine deaminase (CD) is a suicide enzyme that metabolizes a non-toxic pro-drug, 5-fluorocytosine (5-FC), into the cytotoxic agent, 5-fluorouracil (5-FU). As an immunotherapeutic agent, human interferon-β (IFN-β) has anticancer effects. In this study, we used modified human neural stem cells (HB1.F3) expressing the Escherichia coli (E. coli) CD gene (HB1.F3.CD) or both the CD and human IFN-β genes (HB1.F3.CD.IFN-β) and evaluated their effectiveness on gastric carcinoma cells (AGS); migration of GESTECs to AGS was analyzed as well as formation of 5-FU and IFN-β. Reverse transcription-polymerase chain reaction (RT-PCR) was used to confirm the expression of CD and IFN-β genes in GESTECs along with confirming the production of chemoattractant molecules such as stem cell factor (SCF), CXCR4, c-Kit, vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR2). In addition, by co-culturing GESTECs with AGS in the presence of 5-FC, we were able to confirm that cancer growth was inhibited, along with a synergistic effect when the CD and IFN-β genes (HB1.F3.CD.IFN-β) were co-expressed. Indeed a marked anticancer effect was demonstrated when the CD and IFN-β genes were expressed together compared to expression of the CD gene alone (HB1.F3.CD). According to a modified transwell migration assay, the migration of GESTECs toward AGS was confirmed. In conclusion, these data suggest potential application of GESTECs to gastric cancer therapy, due to a remarkable synergistic effect of CD and IFN-β genes in the presence of 5-FC. Additionally, the tumor-selective migration capability in vitro suggests that GESTECs are a potential anticancer therapy candidate that may result in minimal side effects compared to the conventional chemotherapy.

Targeting telomerase-expressing cancer cells

The role of telomeres and telomerase as a target for cancer therapeutics is an area of continuing interest. This review is intended to provide an update on the field, pointing to areas in which our knowledge remains deficient and exploring the details of the most promising areas being advanced into clinical trials. Topics that will be covered include the role of dysfunctional telomeres in cellular aging and how replicative senescence provides an initial barrier to the emergence of immortalized cells, a hallmark of cancer. As an important translational theme, this review will consider possibilities for selectively targeting telomeres and telomerase to enhance cancer therapy. The role of telomerase as an immunotherapy, as a gene therapy approach using telomerase promoter driven oncolytic viruses and as a small oligonucleotide targeted therapy (Imetelstat) will be discussed.

Assessment of an altered E1B promoter on the specificity and potency of triple-regulated conditionally replicating adenoviruses: implications for the generation of ideal m-CRAs

Although previous studies modified two components of conditionally replicating adenoviruses (CRAs), which selectively replicate in and kill cancer cells, the most accurate ways to achieve increased cancer specificity (that is, safety) without reducing the anticancer (that is, therapeutic) effects are unknown. Here, we generated two types of survivin-responsive m-CRAs (Surv.m-CRAs), Surv.m-CRA-CMVp and Surv.m-CRA-OCp, which use two and three different mechanisms to target cancer, that is, early region 1A (E1A) regulated by the survivin promoter and mutated E1BΔ55K regulated by the ubiquitously active cytomegalovirus promoter and cancer/tissue-specific osteocalcin promoter, respectively, and carefully examined their safety and anticancer effects. Endogenous osteocalcin mRNA was expressed and further enhanced by vitamin D(3) in all osteosarcoma and prostate cancer cell lines and human osteoblasts, but not in human fibroblasts. The osteocalcin promoter activity was weak even with vitamin D(3) treatment in these osteocalcin-expressing cancers, leading to low E1BΔ55K expression after Surv.m-CRA-OCp infection. Nevertheless, Surv.m-CRA-OCp had significantly increased cancer specificity without reduced anticancer effects in both in vitro and in vivo experiments. The unexpected but favorable fact that strong activity of an altered E1B promoter is unnecessary indicates that the majority of cancer/tissue-specific promoters may be used to generate ideal m-CRAs and will advance the development of m-CRA-based cancer therapies.

Is telomerase a viable target in cancer?

The ideal cancer treatment would specifically target cancer cells yet have minimal or no adverse effects on normal somatic cells. Telomerase, the ribonucleoprotein reverse transcriptase that maintains the ends of human chromosome, is an attractive cancer therapeutic target for exactly this reason [1]. Telomerase is expressed in more than 85% of cancer cells, making it a nearly universal cancer marker, while the majority of normal somatic cells are telomerase negative. Telomerase activity confers limitless replicative potential to cancer cells, a hallmark of cancer which must be attained for the continued growth that characterizes almost all advanced neoplasms [2]. In this review we will summarize the role of telomeres and telomerase in cancer cells, and how properties of telomerase are being exploited to create targeted cancer therapies including telomerase inhibitors, telomerase-targeted immunotherapies and telomerase-driven virotherapies. A frank and balanced assessment of the current state of telomerase inhibitors with caveats and potential limitations will be included.

Targeted gene therapy of nasopharyngeal cancer in vitro and in vivo by enhanced thymidine kinase expression driven by human TERT promoter and CMV enhancer

Background/Aim

To explore the therapeutic effects of thymidine kinase (TK) expressed by enhanced vector pGL3-basic- hTERTp-TK-EGFP-CMV driven by human telomerase reverse transcriptase promoter (hTERTp) as well as cytomegalovirus immediate early promoter enhancer (CMV).

Materials/Methods

Enhanced TK-EGFP expression was confirmed by fluorescent microscopy, real time PCR and telomerase activity. Its effects were examined by survival of tumor cells NPC 5-8F and MCF-7, index of xenograft implanted in nude mice and histology.

Results

Compared with non-enhanced vector pGL3-basic-TK-hTERTp-EGFP, TK expressed by the enhanced vector significantly decreased NPC 5-8F and MCF-7 cell survival rates after ganciclovir (GCV) treatment (p < 0.001) and tumor progress in nude mice with NPC xenograft and treated with GCV, without obvious toxicity to mouse liver and kidney.

Conclusion

The enhanced TK expression vector driven by hTERTp with CMV enhancer has brighter clinical potentials in nasopharyngeal carcinoma therapy than the non-enhanced vector.