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Essential Insights | How to Properly Select a Tumor Animal Model?

Introduction:

In China, approximately 7,710 cancer patients die each day—averaging six per minute. Consequently, cancer research has become a top priority in biomedicine, and tumor animal models play a pivotal role in both oncological research and drug development.

Faced with a variety of tumor animal models, which one can truly and accurately reflect the progression of human cancers?

First, we need to determine what kind of model to build; using different models for the same experiment will yield different results. You can follow the guidelines below to make this determination step by step.

 

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Step 1: Clearly define the experimental objective.

Only by selecting the most appropriate animal model based on the established experimental objectives can one obtain scientifically sound conclusions and desirable outcomes. The applications of tumor animal models are generally categorized into: studies on the mechanisms of tumorigenesis and tumor progression, screening of anti‑tumor drugs, and research related to immunotherapy, among others.

 

Step 2: Understand the classifications and characteristics of common tumor models.

Tumor animal models are generally classified as:

①CDTX (tumor cell line xenograft model)

②PDTX (Patient-Derived Tumor Xenograft Model)

③ Induced tumor animal model

④ Genetically modified tumor models

⑤ Spontaneous tumor animal models;

 

Step 3: Refine Your Selection

It mainly includes the following uncertainties that require further refinement:

(1) Selection of Cell Lines

Select appropriate tumor cell lines based on the tumor type and genotype under investigation. Tumor‑bearing cells should be in good growth condition, free of contamination, and in the logarithmic growth phase. Tumor cell lines exhibit varying tumorigenicity; therefore, choose a cell line with a high tumorigenic rate for your experiments.

For example, there are dozens of breast cancer cell lines; based on their origin, they can be murine or human, and according to their molecular subtype, they can be triple-negative or non-triple-negative. To conduct research that more closely mimics human triple-negative breast cancer, the MDA-MB-231 cell line, which readily forms tumors in vivo, is typically chosen.

(2) Selection of mouse strains

Tumor cell line–based xenograft models are categorized into two types: transplantation of human tumor cell lines or tumor tissues into mice, and transplantation of murine tumor cells into mice. The former is an allogeneic xenograft and thus requires immunocompromised mouse strains (e.g., nude, NOD/scid, NSG), whereas the latter is an autologous xenograft; therefore, mice of the same strain as the tumor cell line should be used (for example, melanoma cell line B16F10 and Lewis lung carcinoma cell line LLC, both derived from C57BL/6 mice, require C57BL/6 recipient mice).

(3) Mouse age, body weight, and sex

Typically 6–8 weeks, with a body weight of 18–22 g (with some variations depending on the model), ensuring minimal inter‑individual variability. Both sexes are generally suitable; however, the choice should be guided by the tumor type and cell line under investigation—for example, female animals are preferred for breast cancer models, while male animals are chosen for prostate cancer models.

(4) Selection of the Injection Site

For example, CDTX models primarily include subcutaneous tumor‑bearing animals, various metastasis models (via tail vein or left ventricular injection), and orthotopic tumor‑bearing models. The choice of model depends on the specific experimental question; for instance, if the focus is solely on tumor growth, a simple subcutaneous model may be sufficient.

 

Step 4: Select a model by considering both the experimental objectives and the characteristics of the models.

For example, CDTX exhibits a high tumor‑formation rate and a short experimental duration, making it commonly used in drug development; in contrast, spontaneous tumor models have a prolonged induction period, with variability in tumor onset, location, and size, and are therefore seldom employed in drug discovery.

Note: Model construction should build upon existing research to avoid redundant efforts.

Typically, academic literature does not provide a highly detailed account of the model‑building process, so you’ll need to seek guidance from more experienced colleagues. Pay close attention to every detail—never let theory outpace practice. When building a model on your own for the first time, it’s best to conduct a preliminary experiment; such pilot studies are crucial.

 

 

Below, we’ll provide a few examples based on the experimental objectives to help you gain a more intuitive understanding:

1. For the purpose of screening anti-tumor drugs, CDTX, PSTX, and similar compounds are typically selected.

a. Tumor cell-line-derived xenograft model (CDTX model)

These primarily include subcutaneous tumor‑bearing models, various metastasis‑bearing models, and orthotopic tumor‑bearing models, among others.

① The subcutaneous tumor-bearing model is primarily used for the screening and evaluation of drugs that inhibit tumor growth (cell proliferation).

② Various metastasis models (including left ventricular injection and tail vein injection) are primarily used for screening and evaluating drugs that inhibit tumor metastasis.

③ Because orthotopic models involve transplanting tumor cells into the corresponding organs of mice, tumors are prone to metastasize (e.g., lung cancer, breast cancer), making these models suitable for screening and evaluating drugs that inhibit both tumor growth and metastasis.

For example: Orthotopic tumor-bearing model in nude mice using human lung cancer A549 cells

As shown in Figure 1, compared with the subcutaneous tumor‑bearing model, the orthotopic growth model more accurately mimics the in vivo microenvironment of tumor cells and provides a more reliable prediction of drug efficacy. The A549 orthotopic model progresses more rapidly than the subcutaneous model, with metastasis occurring within 2–3 weeks and a significantly shorter survival time; consequently, it facilitates the construction of growth curves (also known as Kaplan–Meier curves), which offer a more intuitive assessment of antitumor effects.

Figure 1. Orthotopic lung cancer tumor-bearing model

 

b. Patient-derived tumor xenograft model (PDTX model)

Xenograft tumors are a type of transplantable tumor model, primarily used for screening and evaluating drugs that inhibit tumor growth (cell proliferation). In recent years, there has been growing emphasis on establishing in vivo animal models of human tumors. Because these models utilize tumor tissue derived from patients and closely mimic human tumors in terms of histological morphology and genetic characteristics, they provide a direct means of investigating the biological properties of human cancers and assessing anti‑tumor agents. By selecting an appropriate tumor model based on the target tumor type of the drug under investigation, researchers can effectively evaluate its efficacy.

 

c. Genetically Modified Models

Genetically modified tumor models are created by using techniques such as transgenesis, gene targeting, and conditional gene targeting to knock out or insert specific genes, thereby inducing tumor formation in animals. These models are primarily employed to study the processes of tumorigenesis and tumor progression, as well as their underlying molecular mechanisms. They also find applications in the screening of anti‑cancer drugs. Since oncogenes frequently undergo mutations in humans and represent a major driver of tumorigenesis, the development of anti‑cancer agents that target these oncogenes has emerged as a key research direction. Consequently, corresponding mouse models harboring relevant gene mutations play a crucial role in the preclinical screening of anticancer therapeutics.

For example: Lox-STOP-Lox-KrasG12D Conditional Mouse Model

Ras is frequently mutated in human tumors, and activating mutations in K-ras are one of the causes of lung tumorigenesis. A Lox‑Stop‑Lox‑Kras construct was knocked into the K-ras locus. G12D , Ad-Cre recombinant adenovirus was administered via the nasal cavity of mice to induce K-ras in the lungs. G12D Expression thereby gives rise to lung cancer. Because its underlying mechanisms, histological features, and genetic characteristics closely resemble those of human K‑ras–mutant tumors, this model is well suited for evaluating the antitumor activity of drugs targeting K‑ras mutations [2]. Consequently, for antitumor agents that specifically target particular genes, corresponding genetically engineered models can be employed for screening and assessment.

 

 

II. With the aim of investigating the mechanisms underlying tumor initiation and progression.

For studies on tumor mechanisms, the aforementioned models can also be employed, with a greater emphasis on genetically modified animal models. The experimental endpoints and analytical approaches vary across studies, and it is common practice to validate findings using multiple models in parallel.

For example: For example, in studies investigating the role of REGγ in the development of skin cancer, both tumor cell line xenograft models and genetically modified animal models were employed (Figure 3). By comparing REGγ… + / + and REGγ -／- We investigated the progression of skin tumor formation in mice and the tumor size in a subcutaneous xenograft model using human tumor cells with either wild-type REGγ or REGγ knockdown. Our findings demonstrate that REGγ plays a critical role in the initiation and development of skin tumors, functioning through the Wnt/β-catenin signaling pathway.

Figure 3. Study on the role of REGγ in the development of skin tumors [3]

 

III. For the purpose of conducting research related to immunotherapy.

Among the many cancer therapies available today, immunotherapy has emerged as a particularly promising approach. Emerging tumor‑immunotherapies—such as T‑cell receptor–engineered T cells (TCR‑T), chimeric antigen receptor–engineered T cells (CAR‑T), and immune checkpoint blockade—are continually yielding significant clinical advances. In previous installments, we have provided detailed overviews of these technologies in preclinical tumor models, primarily focusing on studies using severe combined immunodeficiency mice for adoptive cell transfer and syngeneic tumor‑cell line–bearing mouse models for immune checkpoint blockade.

To meet the demands of research, selecting an appropriate animal model from the wide array available has become particularly crucial. This requires tailoring the choice to one’s specific needs and, more often than not, combining multiple models to address a given question.

That’s all for this episode—did it prove helpful to you?

 

References:

[1] Wang J, Hu K, Guo J, et al. Suppression of KRas-mutant cancer through the combined inhibition of KRAS with PLK1 and ROCK[J]. Nature Communications, 2016: 11363-11363.

[2] Michel DuPage, Alison L Dooley & Tyler Jack. Conditional mouse lung cancer models using adenoviral or lentiviral delivery of Cre recombinase .Nat Protoc. 2009;4(7):1064-72.

[3] Lei Li1,2,*, Yongyan Dang2,*, Jishen Zhang1,*, Wangjun Yan1 et al. REGγ is critical for skin carcinogenesis by modulating the Wnt/b-catenin pathway Nature Communications, 2015 Apr 24;6:6875.

 

 

 

Aniphe BioLab can provide you with tumor animal model generation and pharmacological efficacy evaluation services. We will select the most suitable animal models based on your experimental objectives and application scope, and we can also tailor personalized efficacy assessment services to meet your specific needs.

Using small-animal in vivo imaging technology, we can monitor tumor status in real time with high precision. Feel free to call for more information!

 

 

Organizer  |  Aniphe BioLab Marketing Department

Supervising Producer  |  Always

Editor-in-chief  |  Lemon

Editor-in-chief  |  Swallow

 

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