Patrick F. Forde

Releasing pressure in tumors: what do we know so far and where do we go from here? A review.

Tumor interstitial pressure is a fundamental feature of cancer biology. Elevation in tumor pressure affects the efficacy of cancer treatment. It causes heterogenous intratumoral distribution of drugs and macromolecules. It also causes the development of hypoxia within tumor bulk, leading to reduced efficacy of therapeutic drugs and radiotherapy. Tumor pressure has been associated with increased metastatic potential and poor prognosis in some tumors. The formation of increased pressure in solid tumors is multifactorial. Factors known to affect tumor pressure include hyperpermeable tortuous tumor vasculatures, the lack of functional intratumoral lymphatic vessels, abnormal tumor microenvironment, and the solid stress exerted by proliferating tumor cells. Reducing this pressure is known to enhance the uptake and homogenous distribution of many therapies. Pharmacologic and biologic agents have been shown to reduce tumor pressure. These include antiangiogenic therapy, vasodilatory agents, antilymphogenic therapy, and proteolytic enzymes. Physical manipulation has been shown to cause reduction in tumor pressure. These include irradiation, hyperbaric oxygen therapy, hyper- or hypothermic therapy, and photodynamic therapy. This review explores the methods to reduce tumor pressure that may open up new avenues in cancer treatment.

The emerging role of viruses in the treatment of solid tumours

There is increasing optimism for the use of non-pathogenic viruses in the treatment of many cancers. Initial interest in oncolytic virotherapy was based on the observation of an occasional clinical resolution of a lymphoma after a systemic viral infection. In many cancers, by comparison with normal tissues, the competency of the cellular anti-viral mechanism is impaired, thus creating an exploitable difference between the tumour and normal cells, as an unimpeded viral proliferation in cancer cells is eventually cytocidal. In addition to their oncolytic capability, these particular viruses may be engineered to facilitate gene delivery to tumour cells to produce therapeutic effects such as cytokine secretion and anti -tumour immune responses prior to the eventual cytolysis. There is now promising clinical experience with these viral strategies, particularly as part of multimodal studies, and already several clinical trials are in progress. The limitations of standard cancer chemotherapies, including their lack of specificity with consequent collateral toxicity and the development of cross-resistance, do not appear to apply to viral-based therapies. Furthermore, virotherapy frequently restores chemoradiosensitivity to resistant tumours and has also demonstrated efficacy against cancers that historically have a dismal prognosis. While there is cause for optimism, through continued improvements in the efficiency and safety of systemic delivery, through the emergence of alternative viral agents and through favourable clinical experiences, clinical trials as part of multimodal protocols will be necessary to define clinical utility. Significant progress has been made and this is now a major research area with an increasing annual bibliography.

Review of current thermal ablation treatment for lung cancer and the potential of electrochemotherapy as a means for treatment of lung tumours

Lung cancer remains the most common cancer diagnosed worldwide and has one of the lowest survival rates of all cancers. Surgery remains the only curative treatment option but because most patients are either diagnosed at advanced stages or are unfit for surgery, less than a third of all lung cancer patients will undergo a surgical resection. Thermal ablation has emerged as an alternative option in patients who are unfit to undergo surgery. Thermal ablative therapies used in clinical practice to date include Radiofrequency Ablation (RFA), Microwave Ablation (MWA) and Cryoablation This article will focus on the advantages and limitations of thermal ablative therapy and investigates the potential of a relatively new treatment modality, Electrochemotherapy (ECT), as a novel treatment for lung cancer.

Electrochemotherapy for the treatment of ocular basal cell carcinoma; a novel adjunct in the disease management

Basal Cell Carcinoma (BCC) affecting the ocular region is potentially problematic due to its ability to infiltrate aesthetic and functional structures. Due to the paucity of local tissue, resection frequently requires reconstruction with skin grafts or local flaps. Surgical treatment may not be suitable for patients with multiple co-morbidities. Electrochemotherapy (ECT) is a technique where cells are temporarily permeabilized after exposure to a brief electrical field and when combined with normally impermeant chemotherapy drugs can resolve cutaneous cancers - even those previously recalcitrant to chemotherapy or radiotherapy. Its particular advantage is its speed of application and the minimal damage to the surrounding healthy tissue structures. We present a series of 3 patients with BCCs in the peri-ocular region and significant co-morbidities deemed unsuitable for surgical resection, who underwent ECT. The lesions were all primary BCC ranging in size from 0.5 cm(2) to 1 cm(2). Two lesions were on the upper eyelid and one on the lower eyelid. ECT was performed using an 8-needle electrode and a CE approved electroporation generator with intra-lesional Bleomycin. All lesions responded to treatment. All BCCs completely resolved, with acceptable scarring. No side effects were reported from the Bleomycin or the electric pulses. ECT for peri-ocular BCC is an adjunct to surgical excision in the management of surgically problematic lesions. This technique could provide a useful initial treatment option for patients who are medically unfit or where resection and would be associated with significant morbidity.

Local tumour ablative therapies: opportunities for maximising immune engagement and activation.

The relationship between cancer and the immune system is a complex one. The immune system can prevent tumour growth by eliminating cancer cells but this editing process ultimately results in poorly immunogenic cells remaining allowing for unchallenged tumour growth. In light of this, the focus of cancer treatment should be to maximise cancer elimination and the prevention of escape mechanisms. In this review we will examine current and emerging ablative treatment modalities that induce Immunogenic Cell Death (ICD), a special type of cell death that allows for immune cell involvement and the generation of an anti-tumour specific immune response. When paired with immune modulating agents, capable of potentiating the immune response and reversing the immune-suppressive environment created by tumours, we may be looking at the future of anti-cancer therapy.

Enhancement of electroporation facilitated immunogene therapy via T-reg depletion

Regulatory T cells (T-regs) can negatively impact tumor antigen-specific immune responses after infiltration into tumor tissue. However, depletion of T-regs can facilitate enhanced anti-tumor responses, thus augmenting the potential for immunotherapies. Here we focus on treating a highly aggressive form of cancer using a murine melanoma model with a poor prognosis. We utilize a combination of T-reg depletion and immunotherapy plasmid DNA delivered into the B16F10 melanoma tumor model via electroporation. Plasmids encoding murine granulocyte macrophage colony-stimulating factor and human B71 were transfected with electroporation into the tumor and transient elimination of T-regs was achieved with CD25-depleting antibodies (PC61). The combinational treatment effectively depleted T-regs compared to the untreated tumor and significantly reduced lung metastases. The combination treatment was not effective in increasing the survival, but only effective in suppression of metastases. These results indicate the potential for combining T-reg depletion with immunotherapy-based gene electrotransfer to decrease systemic metastasis and potentially enhance survival.

Calcium electroporation induces tumor eradication, long-lasting immunity and cytokine responses in the CT26 colon cancer mouse model

ABSTRACT Electroporation is used in cancer treatment because of its ability to increase local cytotoxicity of e.g. bleomycin (electrochemotherapy) and calcium (calcium electroporation). Calcium electroporation is a novel anticancer treatment that selectively kills cancer cells by necrosis, a cell death pathway that stimulates the immune system due to high release of antigens and “danger signals.” In this exploratory study, we aimed to investigate whether calcium electroporation could initiate an anticancer immune response similar to electrochemotherapy. To this end, we treated immunocompetent balb/c mice with CT26 colon tumors with calcium electroporation, electrochemotherapy, or ultrasound-based delivery of calcium or bleomycin. High treatment efficiency was observed with 100% complete remission in all four groups (12/12 with complete remission in each treatment group). In addition, none of the surviving mice from these groups formed new tumors when re-challenged with CT26 cancer cells 100-d post treatment, whereas mice challenged with different cancer cells (4T1 breast cancer) all developed tumors. Treatment of immunodeficient mice with calcium electroporation and electrochemotherapy showed no long-lasting tumor response. Calcium electroporation and electrochemotherapy was associated with a release of High Mobility Group Box 1 protein (HMGB1) in vitro (p = 0.029) and a significant increase of the overall systemic level of pro-inflammatory cytokines in serum from the treated mice (p < 0.003). These findings indicate that calcium electroporation as well as electrochemotherapy could have a role as immune stimulators in future treatments.

Preclinical evaluation of an endoscopic electroporation system

BACKGROUND AND STUDY AIMS Targeted delivery of specific chemotherapeutic drugs into tumors can be achieved by delivering electrical pulses directly to the tumor tissue. This causes a transient formation of pores in the cell membrane that enables passive diffusion of normally impermeant drugs. A novel device has been developed to enable the endoscopic delivery of this tumor permeabilizing treatment. The aim of the preclinical studies described here was to investigate the efficacy and safety of this nonthermal ablation system in the treatment of gastrointestinal cancer models. METHODS Murine, porcine, and canine gastrointestinal tumors and tissues were used to assess the efficacy and safety of electroporation delivered through the special device in combination with bleomycin. Tumor cell death, volume, and overall survival were recorded. RESULTS Murine tumors treated with electrochemotherapy showed excellent responses, with cell death being induced rapidly, mainly via an apoptotic-type mechanism. Use of the system in canine gastrointestinal cancers demonstrated successful local endoluminal tumor resolution, with no safety or adverse effects noted. CONCLUSIONS Electroporation via the new device in combination with bleomycin offers a nonthermal tumor ablative approach, and presents clinicians with a new option for the management of gastrointestinal cancers.

Non-viral immune electrogene therapy induces potent antitumour responses and has a curative effect in murine colon adenocarcinoma and melanoma cancer models

Antitumour efficacy of electroporated pEEV, coding for granulocyte–macrophage colony-stimulating factor and the B7-1 costimulatory immune molecule (pEEVGmCSF-b7.1) in growing solid tumours, was investigated and compared with a standard plasmid. Application of pEEVGmCSF-b7.1 led to complete tumour regression in 66% of CT26-treated tumours and 100% in the B16F10-treated tumours at day 150 post-treatment. pEEVGmCSF-b7.1 treatment was found to significantly enhance levels of both innate and adaptive immune populations in tumour and systemic sites, which corresponded to significantly increased tissue levels of proinflammatory cytokines including interferon-γ (IFN-γ) and interleukin-12 (IL-12). In contrast, pEEVGmCSF-b7.1 treatment significantly reduced the T-regulatory populations and also the anti-inflammatory cytokine IL-10. Upon further characterisation of functional immune responses, we observed a significant increase in cytotoxic (CD107a+) and IFN-γ-producing natural killer cells and also significantly more in IL-12-producing B cells. Importantly, splenocytes isolated from pEEVGmCSF-b7.1-treated ‘cured’ mice were tumour-specific and afforded significant protection in a tumour rechallenge model (Winn assay). Our data indicate that electroimmunogene therapy with the non-viral pEEVGmCSF-b7.1 is able to induce potent and durable antitumour immune responses that significantly reduce primary and also secondary tumour growth, and thus represents a solid therapeutic platform for pursuing future clinical trials.

Antitumour responses induced by a cell-based Reovirus vaccine in murine lung and melanoma models

BackgroundThe ever increasing knowledge in the areas of cell biology, the immune system and the mechanisms of cancer are allowing a new phase of immunotherapy to develop. The aim of cancer vaccination is to activate the host immune system and some success has been observed particularly in the use of the BCG vaccine for bladder cancer as an immunostimulant. Reovirus, an orphan virus, has proven itself as an oncolytic virus in vitro and in vivo. Over 80 % of tumour cell lines have been found to be susceptible to Reovirus infection and it is currently in phase III clinical trials. It has been shown to induce immune responses to tumours with very low toxicities.MethodsIn this study, Reovirus was examined in two main approaches in vivo, in mice, using the melanoma B16F10 and Lewis Lung Carcinoma (LLC) models. Initially, mice were treated intratumourally (IT) with Reovirus and the immune responses determined by cytokine analysis. Mice were also vaccinated using a cell-based Reovirus vaccine and subsequently exposed to a tumourigenic dose of cells (B16F10 or LLC). Using the same cell-based Reovirus vaccine, established tumours were treated and subsequent immune responses and virus retrieval investigated.ResultsUpregulation of several cytokines was observed following treatment and replication-competent virus was also retrieved from treated tumours. Varying levels of cytokine upregulation were observed and no replication-competent virus was retrieved in vaccine-treated mice. Prolongation of survival and delayed tumour growth were observed in all models and an immune response to Reovirus, either using Reovirus alone or a cell-based vaccine was also observed in all mice.ConclusionThis study provides evidence of immune response to tumours using a cell-based Reovirus vaccine in both tumour models investigated, B16F10 and LLC, cytokine induction was observed with prolongation of survival in almost all cases which may suggest a new method for using Reovirus in the clinic.