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Background Context: Metastases to the spine are a common source of severe pain in cancer patients. The secondary effects of spinal metastases include pain, bone fractures, hypercalcemia, and neurological deficits. As the disease progresses, pain severity can increase until it becomes refractory to medical treatments and leads to a decreased quality of life for patients. A key obstacle in the study of pain-induced spinal cancer is the lack of reliable and reproducible spine cancer animal models. In the present study, we developed a reproducible and reliable rat model of spinal cancer using human-derived tumor tissue to evaluate neurological decline using imaging and behavioral techniques., Purpose: The present study outlines the development and characterization of an orthotopic model of human breast cancer to the spine in immunocompromised rats., Study Design/setting: This is a basic science study., Methods: Female immunocompromised rats were randomized into three groups: tumor (n=8), RBC3 mammary adenocarcinoma tissue engrafted in the L5 vertebra body; sham (n=6), surgery performed but not tumor engrafted; and control (n=6), naive rats, no surgery performed. To evaluate the neurological impairment due to tumor invasion, functional assessment was done in all rodents at day 40 after tumor engraftment using locomotion gait analysis and pain response to a mechanical stimulus (Randall-Selitto test). Bioluminescence (BLI) was used to evaluate tumor growth in vivo and cone beam computed tomography (CBCT) was performed to evaluate bone changes due to tumor invasion. The animals were euthanized at day 45 and their spines were harvested and processed for hematoxylin and eosin (H&E) staining., Results: Tumor growth in the spine was confirmed by BLI imaging and corroborated by histological analysis. Cone beam computed tomography images were characterized by a decrease in the bone intensity in the lumbar spine consistent with tumor location on BLI. On H&E staining of tumor-engrafted animals, there was a near-complete ablation of the ventral and posterior elements of the L5 vertebra with severe tumor invasion in the bony components displacing the spinal cord. Locomotion gait analysis of tumor-engrafted rats showed a disruption in the normal gait pattern with asignificant reduction in length (p=.02), duration (p=.002), and velocity (p=.002) of right leg strides and only in duration (p=.0006) and velocity (p=.001) of left leg strides, as compared with control and sham rats. Tumor-engrafted animals were hypersensitive to pain stimulus shown as a significantly reduced response in time (p=.02) and pressure (p=.01) applied when compared with control groups., Conclusions: We developed a system for the quantitative analysis of pain and locomotion in an animal model of metastatic human breast cancer of the spine. Tumor-engrafted animals showed locomotor and sensory deficits that are in accordance with clinical manifestation in patients with spine metastasis. Pain response and locomotion gait analysis were performed during follow-up. The Randall-Selitto test was a sensitive method to evaluate pain in the rat's spine. We present a model for the study of bone-associated cancer pain secondary to cancer metastasis to the spine, as well as for the study of new therapies and treatments to lessen pain from metastatic cancer to the neuroaxis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Object: The goal of this study was to optimize local delivery of magnetic nanoparticles in a rat model of metastatic breast cancer in the spine for tumor hyperthermia while minimizing systemic exposure., Methods: A syngeneic mammary adenocarcinoma was implanted into the L-6 vertebral body of 69 female Fischer rats. Suspensions of 100-nm starch-coated iron oxide magnetic nanoparticles (micromod Partikeltechnologie GmbH) were injected into tumors 9 or 13 days after implantation. For nanoparticle distribution studies, tissues were harvested from a cohort of 36 rats, and inductively coupled plasma mass spectrometry and histopathological studies with Prussian blue staining were used to analyze the samples. Intratumor heating was tested in 4 anesthetized animals with a 20-minute exposure to an alternating magnetic field (AMF) at a frequency of 150 kHz and an amplitude of 48 kA/m or 63.3 kA/m. Intratumor and rectal temperatures were measured, and functional assessments of AMF-exposed animals and histopathological studies of heated tumor samples were examined. Rectal temperatures alone were tested in a cohort of 29 rats during AMF exposure with or without nanoparticle administration. Animal studies were completed in accordance with the protocols of the University Animal Care and Use Committee., Results: Nanoparticles remained within the tumor mass within 3 hours of injection and migrated into the bone at 6, 12, and 24 hours. Subarachnoid accumulation of nanoparticles was noted at 48 hours. No evidence of lymphoreticular nanoparticle exposure was found on histological investigation or via inductively coupled plasma mass spectrometry. The mean intratumor temperatures were 43.2°C and 40.6°C on exposure to 63.3 kA/m and 48 kA/m, respectively, with histological evidence of necrosis. All animals were ambulatory at 24 hours after treatment with no evidence of neurological dysfunction., Conclusions: Locally delivered magnetic nanoparticles activated by an AMF can generate hyperthermia in spinal tumors without accumulating in the lymphoreticular system and without damaging the spinal cord, thereby limiting neurological dysfunction and minimizing systemic exposure. Magnetic nanoparticle hyperthermia may be a viable option for palliative therapy of spinal tumors.

Background Context: Cancer is a major global public health problem responsible for one in every four deaths in the United States. Prostate cancer alone accounts for 29% of all cancers in men and is the sixth leading cause of death in men. It is estimated that up to 30% of patients with cancer will develop metastatic disease, the spine being one of the most frequently affected sites in patients with prostate cancer., Purpose: To study this condition in a preclinical setting, we have created a novel animal model of human metastatic prostate cancer to the spine and have characterized it histologically, functionally, and via bioluminescence imaging., Study Design: Translational science investigation of animal model of human prostate cancer in the spine., Methods: Luciferase-positive human prostate tumor cells PC3 (PC3-Luc) were injected in the flank of athymic male rats. PC3-Luc tumor samples were then implanted into the L5 vertebral body of male athymic rats (5 weeks old). Thirty-two rats were randomized into three surgical groups: experimental, control, and sham. Tumor growth was assessed qualitatively and noninvasively via bioluminescence emission, upon luciferin injection. To determine the functional impact of tumor growth in the spine, rats were evaluated for gait abnormalities during gait locomotion using video-assisted gait analysis. Rats were euthanized 22 days after tumor implantation, and spines were subjected to histopathological analyses., Results: Twenty days after tumor implantation, the tumor-implanted rats showed distinct signs of gait disturbances: dragging tail, right- or left-hind limb uncoordination, and absence of toe clearance during forward limb movement. At 20 days, all rats experienced tumor growth, evidenced by bioluminescent signal. Locomotion parameters negatively affected in tumor-implanted rats included stride length, velocity, and duration. At necropsy, all spines showed evidence of tumor growth, and the histological analysis found spinal cord compression and peritumoral osteoblastic reaction characteristic of bony prostate tumors. None of the rats in the sham or control groups demonstrated any evidence of bioluminescence signal or signs of gait disturbances., Conclusions: In this project, we have developed a novel animal model of metastatic spine cancer using human prostate cancer cells. Tumor growth, evaluated via bioluminescence and corroborated by histopathological analyses, affected hind limb locomotion in ways that mimic motor deficits present in humans afflicted with metastatic spine disease. Our model represents a reliable method to evaluate the experimental therapeutic approaches of human tumors of the spine in animals. Gait locomotion and bioluminescence analyses can be used as surrogate noninvasive methods to evaluate tumor growth in this model., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Object: Metastatic spine disease is prevalent in cancer victims; 10%-30% of the 1.2 million new patients diagnosed with cancer in the US exhibit spinal metastases. Unfortunately, treatments are limited for these patients, as disseminated disease is often refractory to chemotherapy and is difficult to treat with surgical intervention alone. New animal models that accurately recapitulate the human disease process are needed to study the behavior of metastases in real time., Methods: In this study the authors report on a cell line that reliably generates bony metastases following intracardiac injection and can be tracked in real time using optical bioluminescence imaging. This line, RBC3, was derived from a metastatic breast adenocarcinoma lesion arising in the osseous spine of a rat following intracardiac injection of MDA-231 human breast cancer cells., Results: Upon culture and reinjection of RBC3, a statistically significantly increased systemic burden of metastatic tumor was noted. The resultant spine lesions were osteolytic, as demonstrated by small animal CT scanning., Conclusions: This cell line generates spinal metastases that can be tracked in real time and may serve as a useful tool in the study of metastatic disease in the spine.

Object: Recombinant human bone morphogenetic proteins (rhBMPs) are FDA-approved for specific spinal fusion procedures, but their use is contraindicated in spine tumor resection beds because of an unclear interaction between tumor tissue and such growth factors. Interestingly, a number of studies have suggested that BMPs may slow the growth of adenocarcinomas in vitro, and these lesions represent the majority of bony spine tumors. In this study, the authors hypothesized that rhBMP-2 placed in an intraosseous spine tumor in the rat could suppress tumor and delay the onset of paresis in such animals., Methods: Twenty-six female nude athymic rats were randomized into an experimental group (Group 1) or a positive control group (Group 2). Group 1 (tumor + 15 μg rhBMP-2 sponge, 13 rats) underwent transperitoneal exposure and implantation of breast adenocarcinoma (CRL-1666) into the L-6 spine segment, followed by the implantation of a bovine collagen sponge impregnated with 15 μg of rhBMP-2. Group 2 (tumor + 0.9% NaCl sponge, 13 rats) underwent transperitoneal exposure and tumor implantation in the lumbar spine but no local treatment with rhBMP-2. An additional 8 animals were randomized into 2 negative control groups (Groups 3 and 4). Group 3 (15 μg rhBMP-2 sponge, 4 rats) and Group 4 (0.9% NaCl sponge, 4 rats) underwent transperitoneal exposure of the lumbar spine along with the implantation of rhBMP-2- and saline-impregnated bovine collagen sponges, respectively. Neither of the negative control groups was implanted with tumor. The Basso-Beattie-Bresnahan (BBB) scale was used to monitor daily motor function regression and the time to paresis (BBB score ≤ 7)., Results: In comparison with the positive control animals (Group 2), the experimental animals (Group 1) had statistically significant longer mean (25.8 ± 12.2 vs 13 ± 1.4 days, p ≤ 0.001) and median (20 vs 13 days) times to paresis. In addition, the median survival time was significantly longer in the experimental animals (20 vs 13.5 days, p ≤ 0.0001). Histopathological analysis demonstrated bone growth and tumor inhibition in the experimental animals, whereas bone destruction and cord compression were observed in the positive control animals. Neither of the negative control groups (Groups 3 and 4) demonstrated any evidence of neurological deterioration, morbidity, or cord compromise on either gross or histological analysis., Conclusions: This study shows that the local administration of rhBMP-2 (15 μg, 10 μl of 1.5-mg/ml solution) in a rat spine tumor model of breast cancer not only fails to stimulate local tumor growth, but also decreases local tumor growth and delays the onset of paresis in rats. This preclinical experiment is the first to show that the local placement of rhBMP-2 in a spine tumor bed may slow tumor progression and delay associated neurological decline.