EL4 xenograft model (subcutaneous and metastatic)
Malignant lymphoma is one of the prevalent hematological cancers. The prognosis and response to current treatment regimens is poor for patients with aggressive non-Hodgkin’s lymphoma (NHL). Thus, novel treatment approaches are required for NHL patients. The EL4 murine tumor cell line was derived from a chemically induced lymphoma by Dr. Peter Gorer in 1945. EL4 has been extensively studied in immunological research. Preclinical studies of xenograft models are instrumental in finding new therapies for lymphoma patients. A 2009 study by Gao et al. published in Chinese Journal of Cancer, investigated the antitumor effect of arsenic trioxide (As2O3), using the murine T-cell lymphoma cell line EL4 and the EL4 xenograft model. According to the article, As2O3 inhibited the proliferation of EL4 cells both in vivo and in vitro and could be used as a suitable model for treating advanced/refractory lymphomas. The EL4 cell line (mouse lymphoma) is used to create the CDX (Cell Line Derived Xenograft) EL4 xenograft mouse model. The EL4 xenograft model offered by Altogen Labs enables the study of monoclonal antibodies such as rituximab.
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Basic study design
- EL4 cells used are maintained at a phase of exponential growth.
- The EL4 cells are collected, counted and viability is determined using a trypan blue exclusion assay (min 98% cell viability). Cell suspension concentration is adjusted to the appropriate density.
- All mice (NOD/SCID or athymic BALB/C, 10-12 week old) receive a subcutaneous injection into a hind leg that contains one million cells (volume of 100 uL) of the matrigel-EL4 cell suspension.
- Injection sites are palpated up to three times a week. After establishment, tumors are measured utilizing digital calipers. The study begins when tumors reach an average size of 80-120 mm3.
- Animals are then randomized into appropriate treatment cohorts and the administration of test compound is performed.
- Mouse weights recorded up to 3 times a week and tumors are measured daily.
- The mice are euthanized as tumor size reaches the predetermuined study size limit or 2,000 mm3.
- All necropsies and tissue collections are performed according to the study design.
- Tumors are excised and weighed; additional documentation is performed by digital imaging.
- Gross necropsies are performed; tissues are collected for downstream analysis. Tumors and tissues shall be snap frozen, stabilized in RNAlater, prepared for histology or prepared for gene expression analysis.
CDX models are mouse xenografts used in pre-clinical therapeutic studies. However, as primary tumors proliferate they invade surrounding tissue, become circulatory, survive in circulation, implant in foreign parenchyma and proliferate in the distant tissue. This result leads to an extremely high percentage of death in cancer patients due to metastasis. Metastatic tumor mouse models are utilized to develop novel therapeutic agents that target metastasis (anti-metastatic therapeutics).
To create a metastatic model, the cell line of interest is transfected with vectors containing green fluorescent protein (GFP) or luciferase. Maintained under antibiotic selection, only cells containing the integrated vector will survive. The new cell line clones are capable of stably expressing the gene of interest and are used in metastatic mouse model studies. Although each new cell line clone may contain its own inherent difficulties, the new cell line contains the ability to track internal tumor progression via bioluminescence (luciferase fluorescence after injecting luciferin) or fluorescence (GFP). Internal orthotopic and metastatic tumor growth (not palpable) can now be measured throughout the study, enabling a researcher to gain more insight and additional data in contrast to relying on end of study tumor weight measurements.
Case Study: U87-luc Xenograft Model
An example of Altogen Labs utilizing a luciferase expressing cell line to monitor orthotopic tumor growth is exhibited below. The same ideology of tumor observation is incorporated in metastatic tumor models.
Luciferase expressing U87-luc cells were implanted and tumors allowed to grow. Tumor growth was monitored in a Night Owl (Berthold Technologies) imaging system 10 minutes after an intraperitoneal (IP) injection of the luciferin substrate. As seen in the example below, luciferase expression (measured as photons emitted) in the U87-luc model grants the researcher a visual image and quantifiable metric for orthotopic or metastatic tumor progression.
Figure 1. Luciferase expression in U87-luc orthotopic model. Control and implanted glioma mouse model fluorescence was analyzed 10 minutes after intraperitoneal luciferin injection.
View full details of the case study by clicking here.
Xenograft animal models are used to assess the effectiveness of drugs against specific types of cancer. New medicines are tested on staged tumor growths that have been engrafted via subcutaneous or orthotopic inoculation in an immunocompromised mouse or rat model. All clinically approved anti-cancer agents have been evaluated with conventional preclinical in vivo models. Xenograft studies can be highly complex, starting with the selection of the appropriate animal model, choice of tumorigenic cell line, administration method, dosing, analysis of tumor growth rates and tumor analysis (histology, mRNA and protein expression levels).
Altogen Labs provides an array of laboratory services using over 30 standard Cell Line Derived Xenograft (CDX) models and over 20 PDX models. Researchers investigating the role of specific proteins or gene products in regulating tumor growth can benefit from development of protein overexpression (genetically engineered to ectopically express proteins, tumor suppressors, or oncogenes) and RNAi cell lines with long term gene silencing. Altogen Labs provides quantitative gene expression analysis of mRNA expression (RT-PCR) and protein expression analysis using the WES system (ProteinSimple).
The dosing of the experimental compound of interest is initiated, for a staged study, when the mean tumor size reaches a specified volume (typically 50-100 mm3). In an unstaged study, the dosing of the compound of interest is initiated immediately after xenografting. Mice are dosed once or twice a day for 28 days (or other desired study duration) via the chosen route of administration. Tumor volume (mm3) is calculated via the “(W x W x L) / 2” formula, where W is tumor width and L is tumor length.
Animal handling and maintenance at the Altogen Labs facility is IACUC-regulated and GLP-compliant. Following acclimatization to the vivarium environment, mice are sorted according to body mass. The animals are examined daily for tumor appearance and clinical signs. We provide detailed experimental procedures, health reports and data (all-inclusive report is provided to the client that includes methods, results, discussion and raw data along with statistical analysis). Additional services available include collection of tissue, histology, isolation of total protein or RNA and analysis of gene expression. Our animal facilities have the flexibility to use specialized food or water systems for inducible gene expression systems.
Following options are available for the EL4 xenograft model:
- EL4 Tumor Growth Delay (TGD; latency)
- EL4 Tumor Growth Inhibition (TGI)
- Dosing frequency and duration of dose administration
- Dosing route (intravenous, intratracheal, continuous infusion, intraperitoneal, intratumoral, oral gavage, topical, intramuscular, subcutaneous, intranasal, using cutting-edge micro-injection techniques and pump-controlled IV injection)
- EL4 tumor immunohistochemistry
- Alternative cell engraftment sites (orthotopic transplantation, tail vein injection and left ventricular injection for metastasis studies, injection into the mammary fat pad, intraperitoneal injection)
- Blood chemistry analysis
- Toxicity and survival (optional: performing a broad health observation program)
- Gross necropsies and histopathology
- Positive control group employing cyclophosphamide, at a dosage of 50 mg/kg administered by intramuscular injection to the control group daily for the study duration
- Lipid distribution and metabolic assays
- Imaging studies: Fluorescence-based whole body imaging, MRI