In vivo orthotopic breast tumor model

Based on surgical breast tumor cell inoculation into the fourth mammary fat pad of immunocompetent mice, our syngeneic orthotopic 4T1 breast tumor-bearing mouse model, which is an aggressive model of human breast carcinoma, has indeed many characteristics that make it a suitable experimental tool for human breast cancer. In addition to their poor immunogenicity – a characteristic shared with human mammary cancers, 4T1 tumor cells are easily implanted into the mammary fat pad thereby allowing for the growth of the primary tumor in the anatomically correct site. Moreover, 4T1 model is capable of spontaneous metastasis to several organs including and not limited to lungs and liver, in a pattern that is analogous to human mammary cancer. Metastases begin while the primary tumor is in place but are heterogenous and not detectable in all animals.
In an interesting way, the model is characterized by the presence of at least two types of tumor-infiltrating immunosuppressive cells – myeloid suppressive cells (MSC) and T regulatory cells (Treg). Such cell populations are known, as a result, to suppress T cell responses and thus promote tumor immune escape and metastasis.
Our orthotopic syngeneic breast tumor model is a well-suited tool for preclinical testing of new anti-cancer therapies that require an intact immune system to elicit activity, e.g. checkpoint inhibitors or targeted therapies, which would directly target cancer cells or aim at suppressing the immunosuppressive cell functions. Interestingly, our model is run with stable Luc-2-expressing 4T1 tumor cells which has the advantage to monitor tumor growth by in vivo bioluminescence imaging (BLI).

In vivo efficacy and anti-tumor immune response profiling

  • Standard efficacy package: Tumor growth and progression are monitored and quantitatively measured by BLI along the study. Tumor growth, body weight and survival are assessed weekly in experimental groups of standardly 10 mice, to test a drug candidate alone and in combination with an immunotherapeutic treatment reference.
  • Upon study initiation, the model is quickly set up. Weekly reports are provided to follow the progressively achieved efficacy profile of treatments in conjunction with the Sponsor, which allows, if needed, to adjust the experimental design.

Illustrative data

Anti-tumor effect of Doxorubicin in the orthotopic syngeneic 4T1 mammary fat pad model
Orthotopic mammary fat pad model is sensitive to Doxorubicin treatment.

Mice are orthotopically inoculated with 4T1 tumor cells and exposed to intravenous injection of Doxorubicin, and tumor growth is monitored overtime. Doxorubicin treatment slows down tumor growth when compared to controls (a),  that translates into a lower tumor and spleen weight at a day of sacrifice (b).

Orthotopic mammary fat pad model is sensitive to Doxorubicin treatment. Mice are orthotopically ...

Orthotopic syngeneic 4T1 mammary fat pad model displays an immunosuppressive tumor microenvironment
Flow cytometry analysis of 4T1 tumors shows the presence of immunosuppressive tumor-infiltrating immune cells.

4T1 tumors are infiltrated by CD4 and CD8 lymphocytes, and by myeloid CD11b+ cells (a).

Myeloid CD11b+ are further analyzed as Gr1- or Gr1+ as represented in (b). Activated CD4 lymphocytes (CD25+) are analyzed for FoxP3 expression to identify Treg cell population (c). Myeloid CD11b+ Gr1+ and Treg cells are all known to display immunosuppressive properties and thus to participate in the tumor immune escape. 

Flow cytometry analysis of 4T1 tumors shows the presence of immunosuppressive tumor-infiltrating ...

Our added-value

  • Longitudinal mice bleeding: blood samples can be collected every week, allowing the evaluation of peripheral markers overtime or at given analysis time-points.
  • A strong expertise in syngeneic tumor models of immune checkpoint inhibition: Explicyte offers a range of in vivo tumor models including orthotopic and subcutaneous models for anti-CTLA-4 and/or anti-PD-1/PD-L1 therapy.