Peter K. Shires

Real-time ultrasound imaging of irreversible electroporation in a porcine liver model adequately characterizes the zone of cellular necrosis

BACKGROUND   Irreversible electroporation (IRE) is a largely non-thermal method for the ablation of solid tumours. The ability of ultrasound (US) to measure the size of the IRE ablation zone was studied in a porcine liver model. METHODS   Three normal pig livers were treated in vivo with a total of 22 ablations using IRE. Ultrasound was used within minutes after ablation and just prior to liver harvest at either 6 h or 24 h after the procedure. The area of cellular necrosis was measured after staining with nitroblue tetrazolium and the percentage of cell death determined by histomorphometry. RESULTS   Visible changes in the hepatic parenchyma were apparent by US after all 22 ablations using IRE. The mean maximum diameter of the ablation zone measured by US during the procedure was 20.1 ± 2.7 mm. This compared with a mean cellular necrosis zone maximum diameter of 20.3 ± 2.9 mm as measured histologically. The mean percentage of dead cells within the ablation zone was 77% at 6 h and 98% at 24 h after ablation. CONCLUSIONS   Ultrasound is a useful modality for measuring the ablation zone within minutes of applying IRE to normal liver tissue. The area of parenchymal change measured by US correlates with the area of cellular necrosis.

Electromagnetic Energy Sources in Surgery

The biophysics, mechanism of actions, applications, benefits and complications of electromagnetic (EM) energy-based surgical instruments, and their current use are reviewed. Understanding the mechanism of action, tissue effects, and appropriate applications of EM devices is critical to achieving an optimal surgical outcome. Although a more diverse range of EM devices are used in human medicine, current use in veterinary medicine is limited to conventional electrosurgery and CO(2) lasers.

Abstract 4753: Ablation of N1-S1 hepatocellular carcinoma in rat livers with nanosecond pulsed electric fields and induction of protective immunity.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Nanosecond pulsed electric fields (nsPEFs) could be used to ablate local tumor masses through minimally invasive or open surgery delivery, but further pre-clinical studies are needed. NsPEFs not only induces permanent permeabilization of cells, but also impacts intracellular organelles and result in apoptosis and other forms of cell death in vitro and in vivo. Hepatocellular carcinoma (HCC) is the third most common cancer cause of mortality worldwide. A diagnosis of HCC carries a guarded prognosis, especially when metastasis is documented. Presently, reliable, curative treatments without recurrence for very early, early, and intermediate HCC stages are still in urgent need of attention. In these studies, we specifically test the efficacy of nsPEFs in an orthotopic HCC rat tumor model. Orthotropic insertion of stably transfected (mcherry and/or luciferase) N1-S1 cells in Sprague Dawley rat livers was used as a model for treating HCC. Cells were treated with pulses with 100 ns duration and electric field strengths of 50 kV/cm. Different pulse numbers were applied. Recent results suggest that treatments of 300 or 500 pulses were more effective when separated by a 6 minute interval than when applied as a continuous, uninterrupted single treatment. However over time and treatment of more than 20 animals, 1000 nanosecond pulses treatment consistently showed successful ablation by effectively inducing tumor cell death. A single treatment of 1000 nsPEFs successfully induces cell apoptosis by activating caspase-9, caspase-3, but not caspase-8 in some cells, indicating induction of intrinsic apoptosis mechanisms as well as caspase-independent cell death, like that observed in vitro with human Jurkat cells. More importantly, rats successfully treated with 1000 pulses showed protective responses to a second N1-S1 intra-hepatic challenge injection of N1-S1 cells, suggesting a host immune response, which is under exploration. As an ideal potential therapy for HCC, nsPEFs treatment did not show any damaging impact on liver blood flow. These studies demonstrate for the first time, successful intra-hepatic treatment of HCC with a potential induction of immunogenic cell death and a host immune response after nsPEF ablation. Citation Format: Ru Chen, Nova Sain, Tye Harlow, Peter Shires, Gary Long, Ricahrd Heller, Stephen Beebe. Ablation of N1-S1 hepatocellular carcinoma in rat livers with nanosecond pulsed electric fields and induction of protective immunity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4753. doi:10.1158/1538-7445.AM2013-4753

Abstract 5387: Exploring effects of nanosecond and microsecond pulsed electric field ablation in a rat orthotopic hepatocellular carcinoma model

Hepatocellular carcinoma (HCC) is the third most common cancer in the world. A diagnosis of HCC carries a guarded prognosis, especially when metastasis is documented. Reliable, curative treatment for very early, early, and intermediate stages is still an inconsistent ideal. Nanosecond (ns), or microsecond (μs) pulsed electric fields (PEFs) that produce irreversible electroporation (IRE) could be used to ablate local tumor masses through minimal invasive or open surgery delivery. Both nsPEFs and μsPEFs induce permanent permeabilization of cells resulting in cell death without any thermal effect. NsPEFs can also impact intracellular organelles and induce apoptosis. Previous studies indicated under certain condition, there was a protective tumor response following nsPEFs treatment in mouse subcutaneous HCC model. In these studies, we specifically test the efficacy of nsPEFs and μsPEFs in an orthotopic HCC rat tumor model. N1S1 cells stably transfected with luciferase were used to generate tumors. Orthotropic insertion of transfected N1S1 HCC cells in Sprague Dawley rat livers was used as the model. Different pulses numbers, rise times and pulse durations were applied. The effect on treated tumor tissue suggests that a single treatment of 500 or 1000 100ns pulses with either slow (50ns) or fast (10ns) rise times and 50 kV/cm can eliminate HCC tumors. Continuous delivery of eighty 100μs microsecond pulses at 2.5 kV/cm dramatically reverses lesion enlargement. 1000 pulses of 100 ns PEFs with fast rise times provoke an innate immune response. Immune responses in this orthotopic HCC model are still under investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5387. doi:1538-7445.AM2012-5387