Development of an Orthotopic Human Pancreatic Cancer Xenograft Model Using Ultrasound Guided Injection of Cells

Abstract

Mice have been employed as models of cancer for over a century, providing significant advances in our understanding of this multifaceted family of diseases. In particular, orthotopic tumor xenograft mouse models are emerging as the preference for cancer research due to increased clinical relevance over subcutaneous mouse models. In the current study, we developed orthotopic pancreatic cancer xenograft models in mice by a minimally invasive method, ultrasound guided injection (USGI) comparable to highly invasive surgical orthotopic injection (SOI) methods. This optimized method prevented injection complications such as recoil of cells through the injection canal or leakage of cells out of the pancreas into the peritoneal cavity. Tumor growth was monitored in vivo and quantified by ultrasound imaging weekly, tumors were also detected by in vivo fluorescence imaging using a tumor targeted molecular probe. The mean tumor volumes for the USGI and SOI models after 2 weeks of tumor growth were 205 mm3 and 178 mm3 respectively. By USGI of human pancreatic cancer cell lines, human orthotopic pancreatic cancer xenografts were established. Based on ultrasound imaging, the orthotopic human pancreatic cancer xenograft take rate was 100% for both human pancreatic cancer cell lines used, MiaPaCa-2 and Su86.86, with mean tumor volumes of 28 mm3and 30 mm3. We demonstrated that this USGI method is feasible, reproducible, facile, minimally invasive and improved compared to the highly-invasive SOI method for establishing orthotopic pancreatic tumor xenograft models suitable for molecular imaging.

Pharmacological Ascorbate Radiosensitizes Pancreatic Cancer

“…In the orthotopic pancreatic cancer model, 6-week-old athymic nude mice were injected with the human pancreatic cancer cell line MIA PaCa-2, which had previously been stably transfected with firefly luciferase. Ultrasound guidance was used to identify the pancreas as described ( 21 ) and 400,000 cells suspended in 20 μL of a 1:1 mixture of PBS and matrigel were injected into the pancreas under direct visualization. Bioluminescence-imaging microscopy was used to identify mice with established tumors within the pancreas and tumor-containing mice were randomly assigned and treatment was initiated.…”

Orthotopic pancreatic tumors detected by optoacoustic tomography using Syndecan-1

“…These models offer multiple advantages over subcutaneous models, including improved tumor-host interactions, a complex tumor microenvironment, and the development of relevant metastases. (22) However, given their deeper location, monitoring tumors in these models becomes complicated by the problems of signal scattering, attenuation, and lack of anatomic detail. While these problems are reduced when using subcutaneous xenografts, these models do not simulate the tumor microenvironment of a primary tumor and can be poorly predictive of tumor behavior and response to therapy.…”

“…While these problems are reduced when using subcutaneous xenografts, these models do not simulate the tumor microenvironment of a primary tumor and can be poorly predictive of tumor behavior and response to therapy. (22, 23) Furthermore, although subcutaneous tumors have historically been the most widely-used murine tumor model, fluorescent signal from these tumors can be misleading. Although imaging may show homogenous signal throughout tumors, subsequent histology or tomographic images demonstrate poor penetration of probe into tumors, with accumulation limited largely to the periphery.…”

Folic acid-tagged protein nanoemulsions loaded with CORM-2 enhance the survival of mice bearing subcutaneous A20 lymphoma tumors

“…The subcutaneous model presents advantages such as visual confirmation that mice used in an experiment have tumors prior to therapy; and assessment to tumor response or growth over time. 30 Subcutaneous models may however be promiscuous of small particle penetration. 32 Thus the effectiveness of targeting and effect over disease progression should be further supported, in future experiments in vivo, in an orthotopic fat-pad model or a disseminated lymphoma model to avoid this issue.…”

“…The subcutaneous model has additional advantages, such as providing visual confirmation that mice do have tumors prior to therapy and easy assessment of tumor response or growth over time. 30 Figure 3, A shows a considerable tumor growth inhibition when mice were treated with FA-functionalized nanoemulsions loaded with CORM-2, whilst empty FA-functionalized nanoemulsions were shown to have no effect. The treatment with FA-functionalized nanoemulsions containing CORM-2 substantially increased mice survival (Figure 3, B).…”