A systematic comparison of the anti-tumoural activity and toxicity of the three Adv-TKs

Critical View of Novel Treatment Strategies for Glioblastoma: Failure and Success of Resistance Mechanisms by Glioblastoma Cells

According to the invasive nature of glioblastoma, which is the most common form of malignant brain tumor, the standard care by surgery, chemo- and radiotherapy is particularly challenging. The presence of glioblastoma stem cells (GSCs) and the surrounding tumor microenvironment protects glioblastoma from recognition by the immune system. Conventional therapy concepts have failed to completely remove glioblastoma cells, which is one major drawback in clinical management of the disease. The use of small molecule inhibitors, immunomodulators, immunotherapy, including peptide and mRNA vaccines, and virotherapy came into focus for the treatment of glioblastoma. Although novel strategies underline the benefit for anti-tumor effectiveness, serious challenges need to be overcome to successfully manage tumorigenesis, indicating the significance of developing new strategies. Therefore, we provide insights into the application of different medications in combination to boost the host immune system to interfere with immune evasion of glioblastoma cells which are promising prerequisites for therapeutic approaches to treat glioblastoma patients.

Truncated Bid Regulates Cisplatin Response via Activation of Mitochondrial Apoptosis Pathway in Ovarian Cancer

Refractoriness to conventional chemotherapy is a major challenge in the treatment of advanced ovarian cancer (OC). There is increasing evidence that mitochondrial priming correlates with cisplatin response in various cancers. Notably, Bim and Bid, two of the proapoptotic BH3-only proteins, are recognized as the most effective inducers of mitochondrial priming in OC. In this study, we constructed two tumor-specific oncolytic adenoviruses (Ads) coding for Bim (Ad-Bim) or truncated Bid (Ad-tBid), respectively, and performed gain-of-function assays in nine OC cell lines. Ad-tBid exhibited significant antitumor efficacy than the controls. On addition of Ad-tBid pretreatment, mito-primed cells displayed more sensitivity to cisplatin both in vitro and ex vivo. We also found that Ad-tBid induced mitochondrial apoptosis in a Bak-dependent manner. Furthermore, a combined cisplatin plus Ad-tBid therapy markedly inhibited tumor growth in a subcutaneous xenotransplanted tumor model. In mice bearing peritoneal disseminated OC, intraperitoneal administration of Ad-tBid potentiated the antitumor effect of cisplatin. Our findings suggest that Ad-tBid enhances cisplatin response in OC cells, establishing the potential treatment of advanced OC via a combination of cisplatin and Ad-tBid.

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.

Immunotherapy and gene therapy as novel treatments for cancer

The immune system interacts closely with tumors during the disease development and progression to metastasis. The complex communication between the immune system and the tumor cells can prevent or promote tumor growth. New therapeutic approaches harnessing protective immunological mechanisms have recently shown very promising results. This is performed by blocking inhibitory signals or by activating immunological effector cells directly. Immune checkpoint blockade with monoclonal antibodies directed against the inhibitory immune receptors CTLA-4 and PD-1 has emerged as a successful treatment approach for patients with advanced melanoma. Ipilimumab is an anti-CTLA-4 antibody which demonstrated good results when administered to patients with melanoma. Gene therapy has also shown promising results in clinical trials. Particularly, Herpes simplex virus (HSV)-mediated delivery of the HSV thymidine kinase (TK) gene to tumor cells in combination with ganciclovir (GCV) may provide an effective suicide gene therapy for destruction of glioblastomas, prostate tumors and other neoplasias by recruiting tumor-infiltrating lymphocytes into the tumor. The development of new treatment strategies or combination of available innovative therapies to improve cell cytotoxic T lymphocytes trafficking into the tumor mass and the production of inhibitory molecules blocking tumor tissue immune-tolerance are crucial to improve the efficacy of cancer therapy.

Alpha-N-acetyl-neuraminide alpha-2,8-sialyltransferase 1 can support immune responses toward tumors overexpressing ganglioside D3 in mice

An immunotherapeutic strategy is discussed supporting anti-tumor activity toward malignancies overexpressing ganglioside D3. GD3 can be targeted by NKT cells when derived moieties are presented in the context of CD1d. NKT cells can support anti-tumor responses by secreting inflammatory cytokines and through cytotoxicity toward CD1d+GD3+ tumors. To overexpress GD3, we generated expression vector DNA and an adenoviral vector encoding the enzyme responsible for generating GD3 from its ubiquitous precursor GM3. We show that DNA encoding α-N-acetyl-neuraminide α-2,8-sialyltransferase 1 (SIAT8) introduced by gene gun vaccination in vivo leads to overexpression of GD3 and delays tumor growth. Delayed tumor growth is dependent on CD1d expression by host immune cells, as shown in experiments engaging CD1d knockout mice. A trend toward greater NKT cell populations among tumor-infiltrating lymphocytes is associated with SIAT8 vaccination. A single adenoviral vaccination introduces anti-tumor activity similarly to repeated vaccination with naked DNA. Here, greater NKT tumor infiltrates were accompanied by marked overexpression of IL-17 in the tumor, later switching to IL-4. Our results suggest that a single intramuscular adenoviral vaccination introduces overexpression of GD3 by antigen-presenting cells at the injection site, recruiting NKT cells that provide an inflammatory anti-tumor environment. We propose adenoviral SIAT8 (AdV-SIAT8) can slow the growth of GD3 expressing tumors in patients.

Adenovirus-mediated delivery of herpes simplex virus thymidine kinase administration improves outcome of recurrent high-grade glioma

BACKGROUND

This randomized, open-label, multicenter, phase II clinical trial was conducted to assess the anti-tumor efficacy and safety of replication-deficient adenovirus mutant thymidine kinase (ADV-TK) in combination with ganciclovir administration in patients with recurrent high-grade glioma (HGG).

PATIENTS AND METHODS

53 patients with recurrent HGG were randomly allocated to receive intra-arterial cerebral infusion of ADV-TK or conventional treatments. The primary end point was 6-month progression-free survival (PFS-6). Secondary end points included progression-free survival (PFS), overall survival (OS), safety, and clinical benefit. This trial is registered with Clinicaltrials.gov, NCT00870181.

RESULTS

In ADV-TK group, PFS-6 was 54.5%, the median PFS was 29.6 weeks, the median OS was 45.4 weeks, and better survivals were achieved when compared with control group. The one-year PFS and OS were 22.7% and 44.6% in ADV-TK group respectively, and clinical benefit was 68.2%. There are 2 patients alive for more than 4 years without progression in ADV-TK group. In the subgroup of glioblastoma received ADV-TK, PFS-6 was 71.4%, median PFS was 34.9 weeks, median OS was 45.7 weeks respectively, much better than those in control group. The one-year PFS and OS were 35.7% and 50.0% in ADV-TK group respectively. ADV-TK/ganciclovir gene therapy was well tolerated, and no treatment-related severe adverse events were noted.

CONCLUSION

Our study demonstrated a notable improvement of PFS-6, PFS and OS in ADV-TK treated group, and the efficacy and safety appear to be comparable to other reported treatments used for recurrent HGG. ADV-TK gene therapy is therefore a valuable therapeutic option for recurrent HGG.

Oncolytic viruses: From bench to bedside with a focus on safety

Oncolytic viruses are a relatively new class of anti-cancer immunotherapy agents. Several viruses have undergone evaluation in clinical trials in the last decades, and the first agent is about to be approved to be used as a novel cancer therapy modality. In the current review, an overview is presented on recent (pre)clinical developments in the field of oncolytic viruses that have previously been or currently are being evaluated in clinical trials. Special attention is given to possible safety issues like toxicity, environmental shedding, mutation and reversion to wildtype virus.