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TGF beta elicits opposite responses in clonal subpopulations of NRK-49F cells
N Tang1, K Cunningham, M D Enger
1Department of Zoology and Genetics, Iowa State University, Ames 50011.
Abstract:
Clonal subpopulations of NRK-49F cells were isolated and characterized for their responses to transforming growth factor beta (TGF beta). Two fibroblastic clones, N1 and N4, were found to have opposite TGF beta responses. TGF beta inhibits EGF-induced proliferation in growth-arrested, subconfluent monolayer cultures of N1 but not N4 cells. In contrast, TGF beta stimulates DNA synthesis and an increase in cell number in N4 but not N1 cells. The inhibitory effect of TGF beta on DNA synthesis in N1 cells is due not to modulation of the EGF receptor or other early G1 events. EGF-induced myc mRNA accumulation is not inhibited, and the action point for TGF beta inhibition of the entry into S of N1 cells is at the G1-S boundary.
Insights
Transforming growth factor beta (TGF beta) has opposite effects on NRK-49F cell clones. TGF beta inhibits proliferation in N1 cells while stimulating it in N4 cells, revealing distinct cellular responses.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Cellular responses to growth factors are crucial for tissue homeostasis and development.
- Transforming growth factor beta (TGF beta) is a key regulator of cell proliferation, differentiation, and apoptosis.
- Understanding differential cellular responses to TGF beta is vital for comprehending various physiological and pathological processes.
Purpose of the Study:
- To investigate the distinct cellular responses of NRK-49F cell subpopulations to TGF beta.
- To characterize the mechanisms underlying TGF beta's differential effects on cell proliferation and DNA synthesis.
- To identify the specific cell cycle stage targeted by TGF beta in inhibiting proliferation.
Main Methods:
- Isolation and characterization of clonal subpopulations (N1 and N4) from NRK-49F cells.
- Assessment of TGF beta's effects on epidermal growth factor (EGF)-induced proliferation and DNA synthesis.
- Analysis of EGF receptor modulation and myc mRNA accumulation.
- Determination of the cell cycle action point for TGF beta inhibition.
Main Results:
- Two clones, N1 and N4, exhibited opposing responses to TGF beta.
- TGF beta inhibited EGF-induced proliferation in N1 cells but not N4 cells.
- TGF beta stimulated DNA synthesis and cell number increase in N4 cells, but not N1 cells.
- TGF beta's inhibitory effect on N1 cells was not mediated by EGF receptor modulation or early G1 events.
- The inhibitory action of TGF beta on N1 cell entry into S phase occurs at the G1-S boundary.
Conclusions:
- NRK-49F cell clones display divergent responses to TGF beta, highlighting clonal heterogeneity.
- TGF beta exerts differential control over cell cycle progression at the G1-S boundary.
- These findings provide insights into the complex roles of TGF beta in regulating cell growth and division.