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Differential growth factor expression in transformed mouse NIH-3T3 cells
F Ciardiello1, E M Valverius, G L Colucci-D'Amato
1Laboratory of Tumor Immunology and Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892.
Abstract:
The expression of growth factor-specific mRNA transcripts and the presence of biologically active growth factors in the conditioned medium and in the cell extracts from mouse NIH-3T3 cells transformed by different oncogenes (Ki-ras, mos, src, fms, fes, met, and trk), by a DNA tumor virus (SV40), or by a chemical carcinogen (N-nitrosomethylurea) were studied. In contrast to NIH-3T3 cells or simian virus 40 (SV40)-transformed 3T3 cells, all the other transformed NIH-3T3 cell lines expressed a 4.5 kb transforming growth factor-alpha (TGF alpha)-specific mRNA transcript and secreted immunoreactive and biologically active TGF alpha ranging from 100 to 225 ng/10(8) cells/48 h. In addition, in the transformed cell lines that were secreting elevated levels of biologically active TGF alpha, there was a 75-95% reduction in the total number of epidermal growth factor receptors on these cells. A 2.6 kb TGF beta mRNA transcript and TGF beta protein in the conditioned medium (30-140 ng/10(8) cells/48 h) was also detected in those lines expressing TGF alpha. Basic fibroblast growth factor-like activity (11-50 ng/10(8) cells) was detected in the cell lysates from NIH-3T3 cells transformed with N-nitrosomethylurea or with trk, where expression of specific 6.9 and 3.9 kb mRNA transcripts for basic fibroblast growth factor could also be found. B chain (c-sis) expression of platelet-derived growth factor was present only in trk-transformed NIH-3T3 cells in which specific c-sis 6.5 and 4.6 kb transcripts were identified. In contrast, platelet-derived growth factor A chain expression of 2.9 and 2.3 kb transcripts was found in ras-, met-, mos-, and fms-transformed NIH-3T3 cells. These results suggest that the expression of different sets of growth factors is controlled in part by structurally distinct groups of transforming genes.
Insights
Transformed mouse cells express specific growth factor mRNA and proteins, including transforming growth factor-alpha (TGF alpha), TGF beta, and platelet-derived growth factor. This suggests distinct transforming genes control different growth factor sets.
Area of Science:
- Molecular biology
- Cell biology
- Oncology
Background:
- Cell transformation by oncogenes, viruses, or carcinogens alters cellular functions.
- Growth factors play crucial roles in cell growth, differentiation, and cancer.
- Understanding growth factor expression in transformed cells is key to cancer research.
Purpose of the Study:
- To investigate the expression of growth factor-specific mRNA and biologically active growth factors in mouse NIH-3T3 cells transformed by various agents.
- To determine the relationship between specific oncogenes and the production of different growth factors.
- To examine the impact of altered growth factor expression on epidermal growth factor receptor levels.
Main Methods:
- Analysis of mRNA transcripts for various growth factors (TGF alpha, TGF beta, basic FGF, PDGF A and B chains).
- Detection and quantification of biologically active growth factors in conditioned medium and cell extracts.
- Measurement of epidermal growth factor receptor levels on transformed cell surfaces.
Main Results:
- Transformed NIH-3T3 cells, except for SV40-transformed cells, expressed TGF alpha mRNA and secreted active TGF alpha.
- Elevated TGF alpha levels correlated with a significant reduction in epidermal growth factor receptors.
- TGF beta, basic FGF, and platelet-derived growth factor (PDGF) variants were detected in specific transformed cell lines, with distinct mRNA expression patterns.
Conclusions:
- Different transforming genes are associated with the expression of specific sets of growth factors.
- Altered growth factor profiles in transformed cells may contribute to their aberrant behavior.
- The study highlights the complex interplay between genetic alterations and growth factor dysregulation in cancer development.