Generation of a conditionally transformed murine embryonic fibroblast cell line using doxycycline-dependent IGF-1R
Ralph Graeser1, Patricia Vrignaud, Norbert Esser
1ProQinase GmbH, Tumor Biology Center, Freiburg, Germany. r.graeser17@gmail.com
Abstract:
The insulin-like growth factor I receptor (IGF1-R) system has long been implicated in cancer and is a promising target for tumor therapy. Besides in vitro screening assays, the discovery of specific inhibitors against IGF-1R requires relevant cellular models, ideally applicable to both in vitro and in vivo studies. With this aim in mind, the authors generated an inducible cell line using the tetracycline-responsive gene expression system to mimic the effects of therapeutic inhibition of the IGF-1R both in vitro and on established tumors in vivo. Inducible overexpression of IGF-1R in murine embryonic fibroblasts was achieved and resulted in the transformation of the cells as verified by their ability to grow in soft agar and in nude mice. Continuous repression of exogenous IGF-1R expression completely prevented outgrowth of the tumors. Furthermore, induced repression of IGF-1R expression in established tumors resulted in regression of the tumors. Interestingly, however, IGF-1R-independent relapse of tumor growth was observed upon prolonged IGF-1R repression. The IGF-1R cell line generated using this approach was successfully employed to test reference small-molecule inhibitors in vitro and an IGF-1R-specific inhibitory antibody, EM164, in vivo. Besides efficacy as a read-out, phospho-AKT could be identified as a pharmacodynamic biomarker, establishing this cell line as a valuable tool for the preclinical development of IGF-1R inhibitors.
Insights
Researchers developed an inducible cell line to study insulin-like growth factor I receptor (IGF1-R) inhibition in cancer. This model demonstrated tumor regression but also revealed IGF1-R-independent relapse, highlighting its value for preclinical drug development.
Area of Science:
- Oncology
- Molecular Biology
- Drug Discovery
Background:
- The insulin-like growth factor I receptor (IGF1-R) is a key target in cancer therapy.
- Developing effective IGF1-R inhibitors requires robust in vitro and in vivo models.
Purpose of the Study:
- To create an inducible cell line for studying IGF1-R inhibition.
- To evaluate this model's utility in preclinical cancer research.
Main Methods:
- Generated a tetracycline-inducible IGF1-R overexpression cell line in murine embryonic fibroblasts.
- Assessed cell transformation, tumor growth in nude mice, and drug responses in vitro and in vivo.
- Utilized phospho-AKT as a pharmacodynamic biomarker.
Main Results:
- Inducible IGF1-R overexpression led to cell transformation and tumor formation.
- Repressing IGF1-R inhibited tumor outgrowth and caused regression in established tumors.
- Observed IGF1-R-independent tumor relapse after prolonged repression.
- Validated the cell line for testing small-molecule inhibitors and the antibody EM164.
Conclusions:
- The developed inducible IGF1-R cell line is a valuable tool for preclinical evaluation of IGF1-R inhibitors.
- The model demonstrated both efficacy and limitations, including IGF1-R-independent relapse.
- Phospho-AKT serves as a useful pharmacodynamic biomarker for IGF1-R targeted therapies.
