John O. Larkin

Electrochemotherapy: Aspects of Preclinical Development and Early Clinical Experience

Objective:To develop an optimized, reproducible system of electrochemotherapy, and to investigate its clinical application in patients with cutaneous or subcutaneous recurrences of inoperable or progressive disease recalcitrant to current anticancer treatments. Background:Electrochemotherapy is the application of electric pulses to tumor tissue, rendering the cell membranes permeable to otherwise impermeant or poorly permeant anticancer drugs. This facilitates a potent local cytotoxic effect. Study Design:The optimal parameters for electrical pulses and bleomycin concentration were obtained in vitro and then applied to tumors derived from 4 histologically distinct human cancer cell lines (7860, PC3, OE19, MCF-7) established in athymic nude mice. Comparison was made with tumors that received bleomycin alone, electric pulses alone, and untreated controls. The optimized electrochemotherapy was then applied to patients with cutaneous or subcutaneous tumors, of any histologic type, recurrent or metastatic and unresponsive to standard chemotherapy and/or radiotherapy regimens. Tumors were assessed at monthly intervals to determine response to the treatment. Results:In vivo: Using the optimal parameters ascertained in vitro, all tumors treated by electrochemotherapy with bleomycin (n = 24) had significantly regressed (P < 0.001, all 4 lines) compared with control tumors (n = 72). Twelve tumors completely regressed (50%) following a single application, with 12 partial regressions (50%). Clinical: In 30 patients (111 tumors), none of the treated tumors progressed. Sixty percent of tumors (66 of 111) showed complete regression, 22% (24 of 111) partial response, and 18% (21 of 111) no change. Electrochemotherapy was more effective in smaller tumors (<3 cm), 71% (64 of 90) showing complete regression, 20% (18 of 90) partial response, and 9% (8 of 90) no change. Conclusions:Electrochemotherapy parameters optimized in vitro are applicable in vivo. This treatment is effective in athymic nude mice for all histologic types indicating a nonimmunologic mode of action. In clinical application, electrochemotherapy is an effective, safe, and reproducible therapy. Patients with cutaneous or subcutaneous tumors previously refractory to surgical intervention, systemic chemotherapy, and/or radiotherapy responded successfully irrespective of histologic type.

Local gene therapy of solid tumors with GM-CSF and B7-1 eradicates both treated and distal tumors.

Gene therapy-induced expression of immunostimulatory molecules at tumor cell level may evoke antitumor immune mechanisms by recruiting and enhancing viability of antigen-processing cells and specific tumoricidal lymphocytes. The antitumor efficacy of a plasmid, coding for granulocyte–macrophage colony-stimulating factor (GM-CSF) and the B7-1 costimulatory immune molecule, delivered into growing solid tumors by electroporation was investigated. Murine fibrosarcomas (JBS) growing in Balb/C mice (⩽100 mm3) were transfected with GM-CSF/B7-1-expressing plasmid. Complete tumor regression occurred in greater than 60% of treated animals. This response was systemic, durable and tumor specific, with all responding animals resistant to repeat tumor challenge. Using a liver metastatic model, effective cure of distal metastases was achieved following treatment of the primary subcutaneous tumor. This treatment strategy could be applicable in the clinical setting for effective elimination of both primary tumors and associated metastatic disease.

Sonoporation Mediated Immunogene Therapy of Solid Tumors

Development of gene-based therapies for the treatment of inherited and acquired diseases, including cancer, has seen renewed interest in the use of nonviral vectors coupled to physical delivery modalities. Low-frequency ultrasound (US), with a well-established record in a clinical setting, has the potential to deliver DNA efficiently, accurately and safely. Optimal in vivo parameters for US-mediated delivery of naked plasmid DNA were established using the firefly luciferase reporter gene construct. Optimized parameters were used to administer a therapeutic gene construct, coding for granulocyte-macrophage colony-stimulating factor (GM-CSF) and B7-1 costimulatory molecule, to growing murine fibrosarcoma tumors. Tumor progression and animal survival was monitored throughout the study and the efficacy of the US-mediated gene therapy determined and compared with an electroporation-based approach. Optimal parameters for US-mediated delivery of plasmid DNA to tumors were deduced to be 1.0 W/cm(2) at 20% duty cycle for 5 min (60 J/cm(2)). In vivo US-mediated gene therapy resulted in a 55% cure rate in tumor-bearing animals. The immunological response invoked was cell mediated, conferring resistance against re-challenge and resistance to tumor challenge after transfer of splenocytes to naïve animals. US treatment was noninjurious to treated tissue, whereas therapeutic efficacy was comparable to an electroporation-based approach. US-mediated delivery of an immune-gene construct to growing tumors was therapeutically effective. Sonoporation has the potential to be a major factor in the development of nonviral gene delivery approaches.

Non-viral in vivo immune gene therapy of cancer: combined strategies for treatment of systemic disease

Many patients with various types of cancers have already by the time of presentation, micrometastases in their tissues and are left after treatment in a minimal residual disease state [Am J Gastroenterol 95(12), 2000]. To prevent tumour recurrence these patients require a systemic based therapy, but current modalities are limited by toxicity or lack of efficacy. We have previously reported that immune reactivity to the primary tumour is an important regulator of micrometastases and determinant of prognosis. This suggests that recruitment of specific anti-tumour mechanisms within the primary tumour could be used advantageously for tumour control as either primary or neo-adjuvant treatments. Recently, we have focused on methods of stimulating immune eradication of solid tumours and minimal residual disease using gene therapy approaches. Gene therapy is now a realistic prospect and a number of delivery approaches have been explored, including the use of viral and non-viral vectors. Non-viral vectors have received significant attention since, in spite of their relative delivery inefficiency, they may be safer and have greater potential for delivery of larger genetic units. By in vivo electroporation of the primary tumour with plasmid expressing GM-CSF and B7-1, we aim to stimulate immune eradication of the treated tumour and associated metastases. In this symposium report, we describe an effective gene based approach for cancer immunotherapy by inducing cytokine and immune co-stimulatory molecule expression by the growing cells of the primary tumour using a plasmid electroporation gene delivery strategy. We discuss the potential for enhancement of this therapy by its application as a neoadjuvant to surgical excision and by its use in combination with suppressor T cell depletion.

Management of the acute scrotum in a district general hospital: 10-year experience.

The acutely painful scrotum is a common urologic emergency. The primary objective of management is to avoid testicular loss. This requires a high index of clinical suspicion and prompt surgical intervention. In our series conducted between January 1996 and December 2005, 119 patients (age range: 4–62 years) underwent emergency operative exploration for acute scrotal pain. The most common finding was torted cyst of Morgagni (63/119, 52.9%), followed by testicular torsion (41/119, 34.4%). The majority of testicular torsions occurred in the pubertal group (22/41, 53.6%). Only one patient in this group had an unsalvageable testis necessitating orchidectomy, a testicular loss rate in torsion of 2.4%. There were no postoperative wound infections or scrotal haematomas. Testicular salvage depends critically on early surgical intervention, so the delay incurred in diagnostic imaging may extend the period of ischaemia. Furthermore, all radiological investigations have a certain false-negative rate. We advocate immediate surgical exploration of the acute scrotum. We report a low orchidectomy rate (2.4%) in testicular torsion.

Immune gene therapy as a neoadjuvant to surgical excision to control metastatic cancers

We investigated if the range of efficacy of a gene-based immunotherapy of solid tumours against systemic disease could be extended when used as a neoadjuvant to surgery. Hundred percent mice whose subcutaneous tumours were surgically removed 4 days post-electroporation with GM-CSF and B7-1 plasmid were systemically resistance to tumour rechallenge. In mice bearing both subcutaneous and hepatic tumours, neoadjuvant treatment of the primary tumour resulted in significant reduction in, or elimination of, hepatic tumour growth, with a significant increase in survival, indicating that control of the primary tumour by immunotherapy was not a prerequisite for containment of systemic disease.

The Development of Novel Flexible Electrode Arrays for the Electrochemotherapy of Solid Tumour Tissue. (Potential for Endoscopic Treatment of Inaccessible Cancers)

Therapeutic “ electroporation” involves application of electric fields to target cells/tissues, thereby rendering their cell membranes transiently porous, thus making feasible the cellular uptake and efficacy of previously impermeant and ineffective therapeutic agents. The objectives of this research are a) the development of flexible electrode arrays for incorporation into microsystem endoscopic devices, and b) the assessment of their efficacy in delivering selected genetic and pharmaceutical anticancer therapies. Gold electrodes were fabricated on flexible polyimide substrates following predictive modeling and simulation of electric fields using FEMLAB software. Subsequent assessment of electroporation efficiency in-vitro involved 1) enumeration of viable tumour cells after delivery of electric pulses and exposure to low concentrations of bleomycin, otherwise known as electrochemotherapy 2) Efficacy of gene delivery by detection of emitted green fluorescence by cells after electroporation with the pEGFP plasmid and 3) In-vivo efficacy of electrochemotherapy in a variety of human solid tumour masses in nude mouse models (xenografts). The flexible electrode system was found to be successful for electrical delivery of plasmids and drugs in-vitro and in-vivo. We found in-vivo complete regression of prostate, colon, oesophageal, and renal cancers with reduced growth rates for fibrosarcoma and breast cell lines. These flexible electrodes are suitable for electrochemotherapy or gene therapy to solid tumours masses and may be fabricated for application to the treatment of some cancers in humans by transcutaneous or endoscopic delivery systems.

Thoracoscopic repair of instrumental perforation of the oesophagus: first report

BackgroundPerforation of the oesophagus is a life-threatening condition requiring early recognition and repair to prevent mediastinitis and death. Primary closure with mediastinal drainage is recognised as the treatment of choice for patients presenting within 24 hours. Many are frail, however, and unsuitable for major surgery. Aim To report the first case of thoracoscopic repair of the oesophagus for oesophageal perforation following instrumentation.MethodsFlexible endoscopy revealed a 10cm perforation in the right lower oesophagus. With the gastroscope in the oesophagus, four thoracoports were introduced. Using suction and irrigation, the pleural cavity was suctioned free of debris and a 10cm longitudinal tear of the right lateral aspect of the oesophagus was repaired using interrupted polyglactin sutures through all layers.ResultsThe patient tolerated the procedure well and made an uncomplicated recovery. Conclusion The uncomplicated recovery of this frail patient without need for blood transfusions or assisted ventilation supports the notion that the thoracoscopic approach may have significant advantages. With increased experience and technical refinements there should be less reluctance to refer these patients for earlier definitive surgical repair.

Oral tolerance to cancer can be abrogated by T regulatory cell inhibition

Oral administration of tumour cells induces an immune hypo-responsiveness known as oral tolerance. We have previously shown that oral tolerance to a cancer is tumour antigen specific, non-cross-reactive and confers a tumour growth advantage. We investigated the utilisation of regulatory T cell (Treg) depletion on oral tolerance to a cancer and its ability to control tumour growth. Balb/C mice were gavage fed homogenised tumour tissue – JBS fibrosarcoma (to induce oral tolerance to a cancer), or PBS as control. Growth of subcutaneous JBS tumours were measured; splenic tissue excised and flow cytometry used to quantify and compare systemic Tregs and T effector (Teff) cell populations. Prior to and/or following tumour feeding, mice were intraperitoneally administered anti-CD25, to inactivate systemic Tregs, or given isotype antibody as a control. Mice which were orally tolerised prior to subcutaneous tumour induction, displayed significantly higher systemic Treg levels (14% vs 6%) and faster tumour growth rates than controls (p<0.05). Complete regression of tumours were only seen after Treg inactivation and occurred in all groups - this was not inhibited by tumour feeding. The cure rates for Treg inactivation were 60% during tolerisation, 75% during tumour growth and 100% during inactivation for both tolerisation and tumour growth. Depletion of Tregs gave rise to an increased number of Teff cells. Treg depletion post-tolerisation and post-tumour induction led to the complete regression of all tumours on tumour bearing mice. Oral administration of tumour tissue, confers a tumour growth advantage and is accompanied by an increase in systemic Treg levels. The administration of anti-CD25 Ab decreased Treg numbers and caused an increase in Teffs. Most notably Treg cell inhibition overcame established oral tolerance with consequent tumor regression, especially relevant to foregut cancers where oral tolerance is likely to be induced by the shedding of tumour tissue into the gut.

Immunogenetherapy of solid tumours using electroporation to deliver GMCSF/B7-1 combination piasmid

ConclusionImmunogene-therapy of solid tumours, by electroporation with GMCSF/B7-1 plasmid induces effective local and systemic durable anti-tumoral immune responses; applicable to primary tumours and associated minimal residual disease.