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Suppression of tumorigenicity in Ras-transformed fibroblasts by alpha 2(I) collagen
H Travers1, N S French, J D Norton
1Cancer Research Campaign, Department of Gene Regulation, Paterson Institute for Cancer Research, Christie Hospital National Health Service Trust, Manchester, United Kingdom.
Abstract:
Transformed fibroblasts exhibit reduced adhesion to substrata, a characteristic attributable in part to reduced expression/increased degradation of extracellular matrix (EM) proteins such as type I collagen. To directly assess the role of EM proteins in cellular transformation, a vKRas-transformed mouse fibroblast cell line was transfected with an alpha 2(I) collagen expression construct. Stable transfectants displaying a partial restoration of type I collagen expression showed a flatter morphology with increased adherence to the substratum. These clones also exhibited a reduced ability to clone in soft agar, slower growth kinetics, and suppression of tumorigenicity in nude mice. Restoration of type I collagen is correlated with down-regulation of ras oncogene-responsive NVL3 VL30 gene expression. These results suggest that in addition to suppressing tumorigenicity by promoting cellular adhesion and cytoskeletal organization, EM proteins such as type I collagen may also act to subvert oncoprotein signaling pathways associated with the malignant phenotype.
Insights
Restoring type I collagen in transformed fibroblasts reduced their cancerous traits, including tumor formation. This extracellular matrix protein also appears to interfere with cancer-promoting gene activity.
Area of Science:
- Cell Biology
- Cancer Research
- Biochemistry
Background:
- Transformed fibroblasts show decreased adhesion due to reduced extracellular matrix (ECM) proteins like type I collagen.
- This reduced adhesion is a key characteristic linked to cellular transformation.
Purpose of the Study:
- To investigate the direct role of ECM proteins, specifically type I collagen, in mitigating cellular transformation.
- To understand how restoring type I collagen affects cancer-related phenotypes.
Main Methods:
- Transfection of a v-Kras-transformed mouse fibroblast cell line with an alpha 2(I) collagen expression construct.
- Analysis of stable transfectants for morphology, adherence, soft agar cloning, growth kinetics, and tumorigenicity in nude mice.
- Correlation of type I collagen restoration with ras oncogene-responsive gene expression.
Main Results:
- Stable transfectants with partially restored type I collagen exhibited flatter morphology and increased substratum adherence.
- These clones showed reduced soft agar cloning ability, slower growth, and suppressed tumorigenicity.
- Type I collagen restoration correlated with down-regulation of NVL3 VL30 gene expression.
Conclusions:
- Restoring type I collagen can suppress tumorigenicity by improving cellular adhesion and cytoskeletal organization.
- Extracellular matrix proteins like type I collagen may disrupt oncoprotein signaling pathways driving the malignant phenotype.
- Type I collagen plays a significant role in regulating fibroblast transformation and tumor suppression.