WiDr xenograft model
Xenotransplantation is a well-known research tool for assessing the effectiveness of drugs against colon cancer. The WiDr cell line was established from the HT-29 cell line, taken from a colon adenocarcinoma of a 44-year-old Caucasian female. WiDr is tumorigenic in nude mice and expresses carcinoembryonic antigen (CEA), colon-specific antigen (CSAp), transforming growth factor beta and epidermal growth factor (EGF). In addition to being negative for colon antigen 3 expression, this cell line is positive for keratin by immunoperoxidase staining and expresses p53 antigen. A 2008 WiDr xenograft study published in International Journal of Oncology, provides evidence that histone deacetylase (HDAC) inhibitors have antitumor activity in vitro and in vivo. Thus, a cyclic-peptide-based HDAC inhibitor YM753 inhibits the tumor growth in vivo through the sustained accumulation of acetylated histones in the tumor tissue. The WiDr cell line is used to create the CDX (Cell Line Derived Xenograft) WiDr xenograft mouse model. The WiDr xenograft model is known to contain high expression levels of EGFR, thus making it an ideal model to study EGFR-TKIs. The EGFR status of this model is exceptionally beneficial when studying combinatorial effects (e.g. gefitinib, irinotecan). Also, antitumor efficacy has been shown using HDAC inhibitors (e.g. YM753).
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Basic study design
- WiDr cells are collected with trypsin-EDTA. Viable cells are counted using trypan blue exclusion. The mice (athymic BALB/C or NOD/SCID, 10 to 12 weeks) are injected subcutaneously in the flank of a hind leg. One million cells are inoculated into the mice (vol = 100 uL of the matrigel plus WiDr suspension).
- The injection are continuously observed until tumors are established. Tumors are measured until they reach an average of 50-150 mm3. Animals are sorted into treatment cohorts and the in-life portion of the study begins.
- Injections of test material is performed following the dosing schedule. Tumors are continually measured and body weights recorded.
- At the end of the study, necropsies and tissue collections are followed according to the study design. Tumors are excised and weighed. All tissues collected can be placed in RNAlater, snap frozen or added to 10% NBF for histology.
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 acclimation 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 WiDr xenograft model:
- WiDr Tumor Growth Delay (TGD; latency)
- WiDr 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)
- WiDr 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