Comparison of endoscopic submucosal implantation vs. surgical intramuscular implantation of VX2 fragments for establishing a rabbit esophageal tumor model for mimicking human esophageal squamous carcinoma

Cottontail Rabbit Papillomavirus (CRPV) Related Animal Models for Head and Neck Cancer Research: A Comprehensive Review of the Literature

Having suitable animal models is crucial to mimic human disease states and for the successful transfer of experimental data into clinical practice. In the field of papillomavirus research, the domestic rabbit (Oryctolagus cuniculus) has served as an indispensable model organism for almost 100 years. The identification and characterization of the first papillomaviruses in rabbits, their carcinogenic potential and their immunogenicity have contributed significantly to the state of knowledge on the genetics and life cycle of papillomaviruses in general, as well as the development of antiviral strategies such as vaccination procedures. Due to the high species specificity of papillomaviruses, only rabbit papillomaviruses (RPVs) can be used for animal studies on papilloma-based tumor diseases in the rabbit. The major focus of this article is on cottontail rabbit papillomavirus (CRPV)-related rabbit squamous cell carcinoma (RSCC). A brief history outlines the discovery and generation of experimentally used RSCC tumors. A comprehensive overview of the current CRPV-associated VX2 carcinoma-based tumor models with a major focus on human head and neck squamous cell carcinoma (HNSCC) tumor models is provided, and their strengths in terms of transferability to human HNSCC are discussed.

A Review of Self-Expanding Esophageal Stents for the Palliation Therapy of Inoperable Esophageal Malignancies

Esophageal cancer is a very deadly disease, killing more than 15,000 people in the United States annually. Almost 400,000 new cases happen in the worldwide every year. More than 50% esophageal cancer patients are diagnosed at an advanced stage when they need an esophageal stent to open the blocked esophagus for feeding and drinking. Esophageal stents have evolved in stages over the years. Current clinically used stents commonly include stainless steel or nitinol self-expandable metallic stent (SEMS) and self-expandable plastic stent (SEPS). There are many choices of different types of stents and sizes, with fierce competition among manufacturers. However, current stent technology, whether uncovered, partially covered, fully covered SEMS or SEPS, has their own advantages to solve the dysphagia, stricture, and fistula problems, but they also cause some clinical complications. The ideal stent remains elusive. New 3D printing technique may bring new promising potential to manufacturing personalized esophageal stents. Drug-eluting stents could be the new avenue to do more than just pry open a stricture or cover a defect in the esophageal lumen, a possibility of proving local anticancer therapy simultaneously. Additionally, the lack of esophageal cancer animal models also hinders the progress of stent development. This paper reviews these topics for a comprehensive understanding of this field. In a conclusion, the ultimate goal of the future esophageal stent would have multifunction to treat the underlying conditions and restore esophageal function to near normal.

Spatiotemporal Optoacoustic Mapping of Tumor Hemodynamics in a Clinically Relevant Orthotopic Rabbit Model of Head and Neck Cancer

The purpose of this study was to investigate the usefulness of photoacoustic imaging (PAI) for spatiotemporal mapping of tumor hemodynamics in a rabbit model of head and neck carcinoma. Shope cottontail rabbit papilloma virus associated VX2 carcinomas were established in adult male New Zealand White rabbits (n = 9) by surgical transplantation of tumor tissue in the neck. Noninvasive PAI with co-registered ultrasound (US) was performed to longitudinally monitor tumor growth, oxygen saturation (%sO₂), and hemoglobin concentration (HbT). PAI findings were validated with Doppler sonography measures of percent vascularity (PV). Differences in tumor volumes, %sO₂, HbT, and PV values over time were analyzed using repeated-measures analysis of variance with multiple comparisons. Two-tailed Spearman correlation analysis was performed to determine the correlation coefficient (r) for comparisons between %sO₂, HbT, and tumor volume. US revealed a significant (P < .0001) increase in tumor volume over the 3-week period from 549 ± 260 mm³ on day 7 to 5055 ± 438 mm³ at 21 days postimplantation. Consistent with this aggressive tumor growth, PAI revealed a significant (P < .05) and progressive reduction in %sO₂ from day 7 (37.6 ± 7.4%) to day 21 (9.5 ± 2.1%). Corresponding Doppler images also showed a decrease in PV over time. PAI revealed considerable intratumoral spatial heterogeneity with the tumor rim showing two- to three-fold higher %sO₂ values compared to the core. Noninvasive PAI based on endogenous contrast provides a label-free method for longitudinal monitoring of temporal changes and spatial heterogeneity in thick head and neck tumors.

Real-time computed tomography fluoroscopy-guided solitary lung tumor model in a rabbit

Preclinical studies of lung cancer require suitable large-animal models to allow evaluation and development of surgical and interventional techniques. We assessed the feasibility and safety of a novel rabbit lung cancer model of solitary tumors, in which real-time computed tomography fluoroscopy is used to guide inoculation of VX2 carcinoma single-cell suspensions. Thirty-eight rabbits were divided into four groups according to the volume of the VX2 tissue or cell suspension, the volume of lipiodol, the volume of Matrigel, and the injection needle size. The mixtures were percutaneously injected into rabbit lungs under real-time computed tomography fluoroscopy guidance. Two weeks later, VX2 lung carcinomas were confirmed via positron emission tomography/computed tomography, necropsy, and histology. Real-time computed tomography fluoroscopy allowed the precise inoculation of the tumor cell suspensions containing lipiodol, while the use of Matrigel and a small needle prevented leakage of the suspensions into the lung parenchyma. Solitary lung tumors were successfully established in rabbits (n = 22) inoculated with single-cell suspensions (150 μL), lipiodol (150 μL), and Matrigel (150 μL) using a 26-gauge needle. This combination was determined to be optimal. Pneumothorax was observed in only two of the 38 rabbits (5.3%), both of which survived to the end of the study without any intervention. Real-time computed tomography fluoroscopy-guided inoculation of VX2 single-cell suspensions with lipiodol and Matrigel using a small needle is an easy and safe method to establish solitary lung tumors in rabbits.

The effect of paclitaxel-eluting covered metal stents versus covered metal stents in a rabbit esophageal squamous carcinoma model

BACKGROUND

The use of self-expanding metallic stents (SEMSs) is the current treatment of choice for malignant gastrointestinal obstructions. However, these stents can promote only drainage and have no antitumor effect. Some studies have reported that drug-eluting SEMSs may have tumor inhibition potential. The aim of this study was to evaluate the efficiency and safety of paclitaxel-eluting SEMSs (PEMSs) in rabbit esophageal cancer models.

MATERIALS AND METHODS

A PEMS was covered with a paclitaxel-incorporated membrane, in which the concentration of paclitaxel was 10% (wt/vol). The rabbit models were created endoscopically. Then, a PEMS or SEMS was endoscopically inserted into the rabbit esophagus. Two weeks after stent placement, the rabbits were sacrificed, and we evaluated the tumor volume, area of the wall defect, area of the tumor under endoscopic ultrasound (EUS) before and after stent placement, status of the proximal esophageal obstruction, tumor metastasis food-intake and weight loss.

RESULTS

A total of 26 rabbits received stent insertion and survived until sacrifice, and migration occurred in 4 cases, 3 in SEMS group and 1 in PEMS group. For the remaining 22 rabbits, at the sacrificed time, the average tumor volume was 7.00±4.30 cm3 in the SEMS group and 0.94±1.51 cm3 in the PEMS group (P<0.05). The area of the esophageal wall defect was 0.70±0.63 cm2 in the SEMS group and 0.17±0.16 cm2 in the PEMS group (P<0.05). The tumor area under EUS was 4.40±1.47 cm2 in the SEMS group and 1.30±1.06 cm2 in the PEMS group (P<0.05). At the time of stent placement, tumor area under EUS was comparable in the two groups. Other indices did not significantly differ between the two groups.

CONCLUSIONS

SEMS and PEMS are both safe and effective to relieve dysphagia in rabbit esophageal cancer models. A PEMS can serve as an alternative tool for advanced esophageal cancer that may inhibit tumor growth by serving as a drug sustained-release platform. Clinical trials of the stent are warranted in the future.

Laboratory animal models for esophageal cancer

The incidence of esophageal cancer is rapidly increasing especially in developing countries. The major risk factors include unhealthy lifestyle practices such as alcohol consumption, smoking, and chewing tobacco to name a few. Diagnosis at an advanced stage and poor prognosis make esophageal cancer one of the most lethal diseases. These factors have urged further research in understanding the pathophysiology of the disease. Animal models not only aid in understanding the molecular pathogenesis of esophageal cancer but also help in developing therapeutic interventions for the disease. This review throws light on the various recent laboratory animal models for esophageal cancer.

Effect of a paclitaxel-eluting metallic stent on rabbit esophagus

The use of self-expanding metallic stents (SEMS) is the current treatment of choice for malignant gastrointestinal obstructions. A paclitaxel-eluting metallic SEMS (PEMS) may have an antitumor effect on esophageal tissue. PEMS with 10% paclitaxel or conventional SEMS were inserted into the lower esophagus of rabbits. Following the insertion of the stents for 1, 2, 4 and 6 weeks, the rabbits were sacrificed and the status of the stent insertion was examined, as well as any macroscopic or microscopic mucosal changes in the esophageal tissue. All the rabbits survived until death without any complications. No migration following stent insertion occurred. The number of cases with proximal obstruction increased in a time-dependent manner, and no significant difference was observed between the two groups. Gross histological examination showed similar tissue reaction to the stents at 1, 2 and 4 weeks, and inflammatory cell infiltrating was higher in the SEMS group at 1 and 2 weeks. However, inflammatory cell infiltration was markedly higher in the PEMS group at 4 and 6 weeks. Food-intake and weight were similar in the two groups. The results of the present study demonstrated that PEMS may serve as a safe alternative treatment strategy for esophageal obstruction. Furthermore, PEMS may inhibit the tumor growth of the esophageal wall through inflammatory infiltration and targeted drug delivery. A tumor model will be required in the future for evaluating the prognosis of patients with advanced esophageal carcinoma.

Near-infrared fluorescence imaging-guided surgery improves recurrence-free survival rate in novel orthotopic animal model of head and neck squamous cell carcinoma

BACKGROUND

Appropriate animal models are required to test novel therapeutics for head and neck squamous cell carcinoma (HNSCC) such as near-infrared (NIR) imaging-guided surgery.

METHODS

We developed an optimized animal model of orthotopic HNSCC (in female athymic NMRI (Naval Medical Research Institute) nude mice) with a prolonged survival time. Resection of the orthotopic tumors was performed 30 days after implantation with or without the aid of a miniaturized clinical grade NIR optical imaging device, after systemic administration of a fluorescent RGD-based probe that targets αv β3 integrin.

RESULTS

NIR optical imaging-guided surgery increased the recurrence-free survival rate by 50% through the detection of fluorescent cancer residues as small as 185 µm; these fragments could remain unidentified if resection was performed exclusively under unaided visual guidance.

CONCLUSION

NIR optical imaging-guided surgery showed an improved HNSCC tumor resection quality in our optimized orthotopic animal model. © 2015 Wiley Periodicals, Inc. Head Neck 38: E246-E255, 2016.

Study on the diagnosis of rabbit VX2 esophageal cancer and stent-therapy efficacy based on multiphoton microscopy

Histopathology is the gold standard for diagnosis of esophageal carcinoma. Based on two photon excited fluorescence (TPEF) and second harmonic generation (SHG), multiphoton microscopy (MPM) has become a novel optical tool adjunct to current histopathological techniques without any exogenous contrast agents. We thus investigated the potential of using TPEF and SHG techniques for differentiating cancer tissues from cancer tissues after paclitaxel-eluting stent implantation and normal esophageal tissues which are fresh and unstained without dying from the VX2 esophageal carcinoma rabbit models. Comparisons were made between MPM imaging and gold standard sections for each specimen stained with hematoxylin-eosin (H&E). Our results indicated that the MPM imaging technique could identify and distinguish among normal esophageal tissues, cancer tissues, as well as cancer tissues after stent implantation. Therefore, MPM potentially offers a powerful tool to not only diagnose esophageal cancer but also monitor stent-therapy efficacy.