Related Experiment Video
Updated: Aug 15, 2026

Epigenetic Conversion as a Safe and Simple Method to Obtain Insulin-secreting Cells from Adult Skin Fibroblasts
Published on: March 18, 2016
Spontaneously transformed NRK cells lose their mitogenic response to epidermal growth factor
R J Wegrzyn1, D Defeo-Jones, D C Heimbrook
1Department of Cancer Research, Merck Sharp and Dohme Research Laboratories, West Point, Pennsylvania 19486.
Abstract:
To understand the relationship between growth factor-induced mitogenesis and spontaneous cell transformation, a clonal isolate of epidermal growth factor (EGF)-responsive NRK cells was passed in vitro until morphologically transformed variants arose. Subclones of EGF responsive (Cl-3) and EGF nonresponsive (Cl-10) NRK cells were isolated. Cl-3 cells grew as flat, contact-inhibited monolayers, while Cl-10 cells grew as rounded or spindle-shaped cells that formed dense foci. Cl-10 cells formed colonies in soft agar more efficiently (p less than 0.01) and formed larger tumors in nude mice (p less than 0.05) than Cl-3 cells. Cl-3 cells exhibited a sixfold increase in DNA synthesis in response to 1.0 nM EGF. Cl-10 cells did not increase DNA synthesis on exposure to 100 nM EGF. These different responses to EGF occurred despite similar numbers of receptors and similar receptor.binding affinities for EGF (Cl-3: 7000 receptors, Kd = 0.67 nM; Cl-10: 8000 receptors, Kd = 0.72 nM). No evidence of transforming growth factor-alpha was detected in either of these cell lines using Northern blots, Western blots, or biologic assays. We conclude that NRK cells which undergo spontaneous morphologic transformation and exhibit enhanced anchorage-independent growth lose their mitogenic response to EGF.
Insights
Spontaneously transformed NRK cells lose their growth factor-induced DNA synthesis response. This study investigates the link between cell transformation and epidermal growth factor (EGF) signaling.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Epidermal growth factor (EGF) is crucial for cell proliferation and survival.
- Cell transformation involves changes in cell morphology and growth properties.
- Understanding the interplay between growth factor signaling and cell transformation is vital for cancer research.
Purpose of the Study:
- To investigate the relationship between growth factor-induced mitogenesis and spontaneous cell transformation.
- To characterize EGF-responsive and nonresponsive NRK cell lines.
- To determine the impact of cell transformation on EGF signaling pathways.
Main Methods:
- Isolation and characterization of EGF-responsive (Cl-3) and EGF-nonresponsive (Cl-10) NRK cell subclones.
- Assessment of cell morphology, growth in soft agar, and tumor formation in nude mice.
- Measurement of DNA synthesis in response to EGF.
- Analysis of EGF receptor number and binding affinity.
Main Results:
- EGF-nonresponsive Cl-10 cells exhibited hallmarks of transformation, including altered morphology, enhanced anchorage-independent growth, and increased tumor formation.
- Cl-3 cells showed a significant increase in DNA synthesis upon EGF stimulation, while Cl-10 cells did not.
- Both cell lines possessed similar numbers of EGF receptors with comparable binding affinities.
- No evidence of transforming growth factor-alpha was detected.
Conclusions:
- Spontaneous morphologic transformation in NRK cells leads to a loss of mitogenic response to EGF.
- EGF signaling pathways are altered during cell transformation, independent of receptor number or affinity.
- These findings highlight a dissociation between EGF receptor expression and downstream signaling in transformed cells.
Related Concept Videos
Mitogens and the Cell Cycle
MAPK Signaling Cascades
Renewal of Skin Epidermal Stem Cells
Clinical Applications of Epidermal Stem Cells
Methods of Nuclear Reprogramming

