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What is a Syngeneic Tumor Mouse Model?

2021-10-08
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The syngeneic tumor mouse model is one of the earliest tumor animal models, and it has a history of at least 50 years. This type of model is to transplant tumor cells or tissues derived from mice into host mice with the same genetic background and immune capabilities.

Medicilon's Syngeneic Mouse Models

The syngeneic mouse model tests the ability of model animals to fight cancer with their perfect immune system, as well as the therapeutic effects of immunotherapy. We can provide various syngeneic models to test the effectiveness of drugs according to our clients’ requirements. Typical orthotopic diseases include breast cancer, lung cancer, colon cancer, kidney cancer, diffuse large B-cell lymphoma (DLBCL), etc., with mice, rats and hamsters as test subjects.

The allograft (ie, tumor) formed in the syngeneic tumor model is protected from rejection because the tissue donor and the transplant recipient have the same genetic background. At the same time, the syngeneic tumor mouse model eliminates the complex process of immune reconstitution in immunodeficient mice. This advantage of maintaining a complete immune system in mice makes syngeneic tumor mouse models suitable for studying tumor microenvironment, tumor metastasis, and especially A powerful tool for evaluating immunomodulatory therapies.

Syngeneic Tumor Mouse Model
Syngeneic Tumor Mouse Model

Types of Syngeneic Tumor Mouse Models

  • Cell-derived allograft

  • GEM-derived allograft

  • immune checkpoint humanized allograft mouse model

  • B-cell deficient allograft mouse model

Syngeneic Tumor Cell Line Transplantation Mouse Model

The mouse model of syngeneic tumor cell line transplantation is to inoculate a histocompatibility tumor cell line, that is, a tumor cell line derived from the same background into immune-sound inbred mice. Compared with the CDX model, the mouse model of mouse tumor cell line transplantation retains the mouse’s complete immune system and can be used to study the performance of cancer immunotherapy in the presence of a functional immune system.

The most commonly used host mice for traditional syngeneic transplantation models are Balb/c and C57BL/6 mice. Balb/c and C57BL/6 have some differences in immunology. For example, Balb/c has a stronger humoral response compared with C57BL/6 mice; in C57BL/6 mice, Th1 immune response and IFNγ production accounted for Dominance, and Balb/c easily triggers Th2 immune response, and so on. A variety of mouse tumor cell lines have been developed, mainly under the background of C57BL/6 and Balb/c. For example, the MC38 colon cancer cell line is derived from C57BL/6 inbred mice, and MC38 cells can be easily transplanted into C57BL/6 mice.

This type of mouse-derived cell line transplantation mouse model has the advantages of simple operation, high efficiency and economy, and can be used for large-scale screening of new immunotherapies or anti-tumor drugs, such as immune checkpoint inhibitors, combination therapy, etc.
The mouse model of syngeneic tumor cell line transplantation can be constructed by subcutaneous injection (heterotopic) transplantation or orthotopic transplantation. The ectopic model obtained by subcutaneous injection of tumor cells has the advantages of simplicity and accuracy, which is convenient for tumor interventional therapy and tumor growth monitoring. However, the ectopic model cannot faithfully reflect the tumor microenvironment because the innate immune cells and stromal cells are different between organ systems. At this time, the in situ model can more accurately reflect the natural tumor microenvironment of the organ undergoing tumorigenesis.

GEM Source Allograft Model

Using genetic engineering methods to modify proto-oncogenes or tumor suppressor genes can establish genetically engineered mice (GEM) mouse models of spontaneous tumors, such as H11-Myc transgenic mice and Kras transgenic mice. Transplanting tumors from these mice into recipient mice with the same genetic background can obtain a spontaneous tumor-derived mouse-derived tumor tissue transplantation mouse model, that is, a GEM-derived allogeneic transplantation model. Using spontaneous tumor mice as transplantation donors can make up for the shortage of murine tumor cell lines to a certain extent.

Similar to the preparation of the PDX model, small pieces of tissue from the orthotopic GEM tumor can be transplanted in situ or subcutaneously into a homologous host with immune function. GEM-derived tumor tissues can be stored for mass preparation to obtain high-throughput mouse models of homologous tumors. As shown in the figure below, (I) genetically engineered mice to form tumors, and the proliferating tumor tissues are directly transplanted subcutaneously or in situ into syngeneic mice with complete immune function. After successful transplantation, GDA tumor-bearing mice can be used to evaluate the treatment of drugs alone or in combination (*), and study the therapeutic effects of drugs on “primary” tumors (II). Survival surgery can also be used to remove the transplanted GDA tumor tissue and focus the treatment on metastatic disease, simulating the first-line treatment of human patients after the removal of the primary tumor. GDA tumor-bearing mice are used for interventional therapy (III) after the discovery of metastatic disease, or prophylactic adjuvant therapy (IV) immediately after surgical resection.

Immune Checkpoint Humanized Syngeneic Transplantation Mouse Model

Since the tumor cells and the recipient immune system in the syngeneic tumor transplantation model are both mouse-derived, the immune checkpoint molecules expressed are somewhat different from those of human homologous proteins, so there may be a certain deviation in the evaluation of drug efficacy. If human immune checkpoint proteins can be expressed in mice by replacing human genes with corresponding mouse genes, the system can be optimized for specific targeted drugs, especially in the application of immune checkpoint inhibitors or combination therapy Vital.

At present, a variety of immune checkpoint humanized tumor cell lines and immune checkpoint humanized recipient mice can be used together. The humanized immune checkpoint syngeneic transplantation model realizes the humanization of core target genes. At the same time, mice have a sound immune system, which enables drugs to recognize human targets while also regulating the immune system to respond. It has obvious advantages in the development of tumor immune drugs, which improves the accuracy of drug evaluation.

B Cell Defect Syngeneic Transplantation Mouse Model

In the drug development stage, immunogenicity is also one of the main factors that interfere with drug efficacy experiments. Because monoclonal antibodies and other protein drugs induce the expression of anti-drug antibodies (ADAs) in wild-type inbred mice. ADAs can neutralize the activity of drugs, affect drug clearance, plasma half-life and tissue distribution, change drug efficacy or pharmacokinetics, so that the effects observed in non-clinical studies may not be the true pharmacological and/or toxic reactions of the drug[ 3-4], which makes the evaluation of drug effectiveness more complicated. Therefore, eliminating immunogenicity in animal models can help screen potential drugs more efficiently.

According to the above principles, mature B-cell-deficient mice can become good recipient mice due to their interrupted B-cell development and no adaptive antibody response. We can target the destruction of Ig heavy chain genes to construct Igh gene-modified mice, so that key stages such as B cell receptor rearrangement and shearing of these mice are inhibited, and B cell development stops at the pre-B cell stage, which leads to failure. Produce antibodies.

Therefore, the B-cell-deficient syngeneic tumor transplantation model based on Igh gene modified mice can be used as an effective screening model for tumor immune drugs. It not only retains the immune cell types important for immunotherapy evaluation, but also does not produce ADAs allergic reactions. Reduce or even avoid the production of immunogenicity, and provide more possibilities for the screening of potentially effective drugs.

Reference:

1.Gould SE, Junttila MR, de Sauvage FJ. Translational value of mouse models in oncology drug development. Nat Med 2015;21:431-9.

2.Day CP, Merlino G, Van Dyke T. Preclinical mouse cancer models: a maze of opportunities and challenges. Cell. 2015 Sep 24;163(1):39-53.

3.Bresnahan E, Lindblad KE, Ruiz de Galarreta M, Lujambio A. Mouse Models of Oncoimmunology in Hepatocellular Carcinoma. Clin Cancer Res. 2020 Oct 15;26(20):5276-5286.

4.Zitvogel L, Pitt JM, Daillère R, Smyth MJ, Kroemer G. Mouse models in oncoimmunology. Nat Rev Cancer. 2016 Dec;16(12):759-773.

5. Lu Qiujun. Evaluation of the immunity of biotech drugs and the challenges they face[J]. Chinese Journal of New Drugs, 2007(03):181-188

6.Aarden L, Ruuls SR, Wolbink G. Immunogenicity of anti-tumor necrosis factor antibodies-toward improved methods of anti-antibody measurement. Curr Opin Immunol. 2008 Aug;20(4):431-5.

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