Tissue-directed Implantation Using Ultrasound Visualization for Development of Biologically Relevant Metastatic Tumor Xenografts

Development of a Simple and Reproducible Cell-derived Orthotopic Xenograft Murine Model for Neuroblastoma

BACKGROUND/AIM

Neuroblastoma is a common childhood cancer with poor survival for children with high-risk disease, and ongoing research to improve outcomes is needed. Patient-derived xenografts (PDX) and genetically engineered mouse models (GEMM) are reliable models for oncologic research; however, they are resource-intensive, expensive, and require significant expertise to develop and maintain. We developed an orthotopic xenograft murine model of neuroblastoma that utilizes cryopreserved banks of human neuroblastoma cell lines, requires minimal equipment, and is easily reproducible.

MATERIALS AND METHODS

The neuroblastoma cell line NB1643 was obtained from the Children's Oncology Group (COG) Childhood Cancer Repository. Nod-SCID-gamma (NSG) mice underwent orthotopic injection of 2x106 NB1643 cells suspended in 10 μl of collagen hydrogel directly into the adrenal gland via an open retroperitoneal surgical approach. Mice were monitored by ultrasound and in vivo imaging system (IVIS) until the tumor reached the volume of the ipsilateral kidney. Tumor identity was confirmed by necropsy and histologic analysis.

RESULTS

A total of 55 mice underwent surgery. Eight died due to anesthetic or surgical complications. 39/47 (78%) survivors grew primary adrenal tumors. Average anesthesia time was 30 min. Ultrasound and IVIS successfully characterized tumor growth in all mice. Average time to target tumor size was 5 weeks (range=3-9). Gross pathologic and histologic analysis confirmed adrenal tumors consistent with neuroblastoma in all mice with adrenal masses.

CONCLUSION

A cell-derived orthotopic xenograft murine model can be successfully used to create an in vivo model of neuroblastoma. This model can be utilized in environments where PDX or GEMM models are not feasible.

Ultrasound and Photoacoustic Imaging of the Kidney: Basic Concepts and Protocols

Noninvasive, robust, and reproducible methods to image kidneys are provided by different imaging modalities. A combination of modalities (multimodality) can give better insight into structure and function and to understand the physiology of the kidney. Magnetic resonance imaging can be complemented by a multimodal imaging approach to obtain additional information or include interventional procedures. In the clinic, renal ultrasound has been essential for the diagnosis and management of kidney disease and for the guidance of invasive procedures for a long time. Adapting ultrasound to preclinical requirements and for translational research, the combination with photoacoustic imaging expands the capabilities to obtain anatomical, functional, and molecular information from animal models. This chapter describes the basic concepts of how to image kidneys using different and most appropriate modalities.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.

Utilization of Ultrasound Guided Tissue-directed Cellular Implantation for the Establishment of Biologically Relevant Metastatic Tumor Xenografts

Preclinical testing of anticancer therapies relies on relevant xenograft models that mimic the innate tendencies of cancer. Advantages of standard subcutaneous flank models include procedural ease and the ability to monitor tumor progression and response without invasive imaging. Such models are often inconsistent in translational clinical trials and have limited biologically relevant characteristics with low proclivity to produce metastasis, as there is a lack of a native microenvironment. In comparison, orthotopic xenograft models at native tumor sites have been shown to mimic the tumor microenvironment and replicate important disease characteristics such as distant metastatic spread. These models often require tedious surgical procedures with prolonged anesthetic time and recovery periods. To address this, cancer researchers have recently utilized ultrasound-guided injection techniques to establish cancer xenograft models for preclinical experiments, which allows for rapid and reliable establishment of tissue-directed murine models. Ultrasound visualization also provides a noninvasive method for longitudinal assessment of tumor engraftment and growth. Here, we describe the method for ultrasound-guided injection of cancer cells, utilizing the adrenal gland for NB and renal sub capsule for ES. This minimally invasive approach overcomes tedious open surgery implantation of cancer cells in tissue-specific locations for growth and metastasis, and abates morbid recovery periods. We describe the utilization of both established cell lines and patient derived cell lines for orthotopic injection. Pre-made commercial kits are available for tumor dissociation and luciferase tagging of cells. Injection of cell suspension using image-guidance provides a minimally invasive and reproducible platform for the creation of preclinical models. This method is utilized to create reliable preclinical models for other cancers such as bladder, liver and pancreas exemplifying its untapped potential for numerous cancer models.