HyCHEED System for Maintaining Stable Temperature Control during Preclinical Irreversible Electroporation Experiments at Clinically Relevant Temperature and Pulse Settings

Electric permeabilization of cell membranes is the main mechanism of irreversible electroporation (IRE), an ablation technique for treatment of unresectable cancers, but the pulses also induce a significant temperature increase in the treated volume. To investigate the therapeutically thermal contribution, a preclinical setup is required to apply IRE at desired temperatures while maintaining stable temperatures. This study’s aim was to develop and test an electroporation device capable of maintaining a pre-specified stable and spatially homogeneous temperatures and electric field in a tumor cell suspension for several clinical-IRE-settings. A hydraulically controllable heat exchange electroporation device (HyCHEED) was developed and validated at 37 °C and 46 °C. Through plate electrodes, HyCHEED achieved both a homogeneous electric field and homogenous-stable temperatures; IRE heat was removed through hydraulic cooling. IRE was applied to 300 μL of pancreatic carcinoma cell suspension (Mia PaCa-2), after which cell viability and specific conductivity were determined. HyCHEED maintained stable temperatures within ±1.5 °C with respect to the target temperature for multiple IRE-settings at the selected temperature levels. An increase of cell death and specific conductivity, including post-treatment, was found to depend on electric-field strength and temperature. HyCHEED is capable of maintaining stable temperatures during IRE-experiments. This provides an excellent basis to assess the contribution of thermal effects to IRE and other bio-electromagnetic techniques.

Evaluation of in vitro Cytotoxic Effects of Especifico Pessoa Phytotherapic Tincture on Ehrlich Tumor Cells and Mice Spleen Cells

Especifico Pessoa (EP) is traditionally used for the treatment of snakebite envenoming. The traditional use of EP and its properties have been reported. In this study, we evaluated the in vitro cytotoxic effects of EP on Ehrlich tumor and mice spleen cells. Cytotoxicity assay was carried out by using Trypan blue exclusion method. Spleen cell suspension was prepared (n=2) with RPMI medium and tumor cell suspension was prepared from ascitic fluid of Ehrlich tumor-bearing mice (n=1); both the suspensions contained 4 x 106 cells mL-1. Pure EP or EP diluted in RPMI (1:2; 1:4) was used. The results were expressed as percentage of cell viability and demonstrate that EP is toxic to Ehrlich cells at all concentrations (Control: 96.42 ± 3.40; Pure: 1.55 ± 2.91; 1:2: 4.85 ± 5.04; 1:4: 13.39 ± 5.08), but nontoxic to spleen cells in at the lowest dilution (Control: 72.86 ± 13.79; Pure: 13.52 ± 6,36; 1:2: 41.36 ± 13.51; 1:4: 56.59 ± 8.62). Therefore, the results demonstrate that EP has cytotoxic effects, depending on the dose and the cell line evaluated.

TMOD-24. DEVELOPMENT OF A NOVEL IN VIVO MODEL OF LUNG-TO-BRAIN METASTASIS PROGRESSION

Brain metastases (BM) are the most common neoplasm to affect the adult central nervous system, occurring ten times more frequently than primary brain tumor. BM develop in 40–50% of advanced lung adenocarcinoma (LUAD), and the lack of durable response to chemotherapy, immunotherapy, or targeted therapy will result in death within a year of BM diagnosis. Despite the high burden of disease, dismal prognosis, and the increase in incidence over time, the biological underpinnings of BM remain poorly understood due to both the difficulty of obtaining a sizable collection of metastatic tissue samples as well as a lack of clinically relevant models. As such, it is possible that the inability to properly study this disease may result in metastasis driver-genes remaining undiscovered. Typical models of BM utilize direct implantation of tumor cells into the mouse brain, or inoculation into the blood via intracardiac/intracarotid injections; these routes are invasive and cannot fully recapitulate the entirety of the metastatic cascade. Here we present a novel, non-invasive method to develop primary lung tumors and brain metastases. A 10µL tumor cell suspension in phosphate-buffered saline was applied to the nostrils of lightly anesthetized mice, allowing direct deposit of cells into the lungs. Mice were monitored with bioluminescence imaging bi-weekly and culled at 2.5–3 months post-inoculation. Lungs and brains were also removed and imaged, where tumors in both organs were observed. Further research is necessary to elucidate either the linear or parallel progression of tumor formation within this model. Nonetheless, our technique presents a novel preclinical tool to interrogate the metastatic process, allowing validation of genetic drivers as well as therapeutic screening.

Reliable Establishment of Human Sarcoma Xenografts in the Nude Rat

Purpose.The ability to establish consistent human tumor xenografts in experimental animals is a crucial part of preclinical investigations.The goal of this study was to develop a method of establishing a human tumor xenograft in the leg of a nude rat for evaluation of new surgical and molecular methods of treatments of human extremity sarcoma.Methods and results.Initial attempts to produce sarcoma nodules by subcutaneous injection of a human leiomyosarcoma tumor cell suspension (SKLMS-1) resulted in tumor nodule formation in only four of 10 sites (40%).The xenograft method was modified to include younger nude rats of a different source and substrain (HSD:rnu/rnu, 5–9 weeks old), treated with 500 cGy whole-body irradiation, and the transplantation of tumor cells or small tumor fragments which had been embedded in Matrigel.These changes improved the tumor take rate per site to 52/52 (100%).Tumor nodules demonstrated rapid and progressive growth and histological features consistent with the original human sarcoma.Discussion.Successful human leiomyosarcoma establishment in these nude rats permits the investigation of sarcoma biology and treatment with surgical procedures for which a mouse model would be inadequate. In this study we identified modifications in technique which enhanced the xenografting of a leiomyosarcoma cell line in nude rats; these techniques may increase tumor take rates for other tumor types as well.

Hematogeneous Pulmonary Metastasis

The purpose of this study was to develop an experimental model of pulmonary metastases using VX-2 tumor, and to describe sequential radiologic and pathologic findings with special attention to the interstitial changes around the metastatic nodules. Through ear veins of 25 rabbits, VX-2 tumor cell suspension was injected with 0.8-mm scalp needles. Chest radiographs were taken every other day after tumor injection. The rabbits were sacrificed at scheduled times from 3 to 30 days after tumor injection. The inflated and fixed lungs were examined with visual inspection, low-kV radiography, high resolution CT (HRCT), microradiography of the sliced lung and with histopathologic studies. Hematogeneous pulmonary metastases occurred in 24 of 25 rabbits. In addition to the metastatic nodules, perinodular and peribronchovascular infiltrations were seen on low-kV radiography, HRCT, microradiography and histologic studies.

A reproducible model of metastatic brain and ocular tumor by hematogenous inoculation of the VX2 tumor in rabbits

✓ A metastatic brain-tumor model has been developed in rabbits by infusing the VX2 carcinoma into the internal carotid artery to simulate hematogenous dissemination of tumor. In a series of 25 New Zealand White rabbits, multiple metastases arose in the hemisphere of 24 (96%) and in the eye of 22 (92%); in all instances ocular metastases were ipsilateral to the site of infusion. Ocular metastases were visible in the anterior chamber in 80% of animals 3 to 12 days after the infusion of VX2 tumor cell suspension. All rabbits deteriorated neurologically or died by Day 15 after the inoculation. Multiple metastases were demonstrated by magnetic resonance imaging as early as 5 to 7 days after infusion of the tumor cells and were confirmed at autopsy. This technique models hematogenous metastases to the brain and eye and is useful in evaluating the response of metastases to chemotherapy and radiation therapy directed to the brain and eye.

Intramedullary canine spinal cord tumor model

✓ The development of a transplantable model brain tumor in the neonatal dog, the adaptation of the tumor to tissue culture, and the successful growth of the tumor in adult mongrel dogs has been adapted to producing similar tumors in the thoracic spinal cord of the adult dog. Ten adult dogs, weighing 4 to 25.4 kg each, were subjected to formal laminectomy. The tumor cell suspension was injected by hand with a Hamilton syringe at two or three sites over a distance of 1 cm; each site received an injection volume to 0.02 to 0.05 cc of the cell suspension after the dura had been opened. Immediately after injection the field was copiously irrigated and the puncture area sealed with a single drop of ethyl cyanoacrylate. Tumor cells for injection were obtained by thawing ampules stored at −195°C in a mixture of 10% dimethyl sulfoxide and RPMI 1640 culture medium. Cells were resuspended in Hank's balanced salt solution and 15% fetal calf serum on ice. Solutions had 90% cell viability, and animals received a dose in the range of 3 to 13 × 106 cells. Eight animals developed tumors and became paraparetic on the 9th to 14th postinjection day. Metrizamide myelography in three animals revealed complete blocks; two animals underwent spinal computerized tomography (CT) and demonstrated syringohydromyelia. Histology revealed the tumors to be highly vascular primitive neoplasms that invaded the surrounding cord. This spinal cord tumor model is large enough to be operated on, studied by CT and myelography, and subjected to pharmacological, electrophysiological, and blood flow study.