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Growth arrest states of RNA virus- and chemically transformed mouse cells
Abstract:
Moloney virus- and benzo(a)pyrene-transformed cells, like the mouse BALB/c 3T3 cell line from which they are derived, arrest with a G1 DNA content in serum-deficient medium. The arrested cells are stimulated to proliferate by readdition of serum. The stimulated Moloney virus-transformed cells show identical kinetics of entry into S phase and also synthesize the same marker proteins as do growth-stimulated quiescent (G0) BALB/c 3T3 cells. In contrast, the benzo(a)pyrene-transformed cells enter S phase about 2 hr earlier and show a lower level of marker protein synthesis. Studies with cycloheximide indicate that protein synthesis is required for all three lines to resume DNA synthesis. Thus, it appears that transformed tumorigenic cells can have kinetic and biochemical growth properties very similar to those of their nontumorigenic parental cells.
Insights
Transformed cells arrested in G1 phase can re-enter the cell cycle upon serum readdition. Some transformed cells exhibit similar growth kinetics and protein synthesis to normal cells, suggesting similarities between tumorigenic and non-tumorigenic cells.
Area of Science:
- Cell Biology
- Cancer Research
- Molecular Biology
Background:
- Mouse BALB/c 3T3 cells, and cells transformed by Moloney virus or benzo(a)pyrene, arrest in the G1 phase of the cell cycle when deprived of serum.
- Serum reintroduction stimulates proliferation in these arrested cells.
Purpose of the Study:
- To compare the cell cycle kinetics and protein synthesis of serum-stimulated transformed cells with their normal counterparts.
- To investigate the role of protein synthesis in the resumption of DNA synthesis in these cell lines.
Main Methods:
- Cell culture and serum deprivation/readdition protocols.
- Analysis of DNA content to determine cell cycle phase.
- Monitoring of cell proliferation and entry into S phase.
- Assessment of marker protein synthesis.
- Inhibition studies using cycloheximide.
Main Results:
- Moloney virus-transformed cells displayed kinetics of S phase entry and marker protein synthesis similar to quiescent BALB/c 3T3 cells.
- Benzo(a)pyrene-transformed cells entered S phase earlier and synthesized lower levels of marker proteins compared to normal cells.
- Protein synthesis, as indicated by cycloheximide studies, is essential for all three cell lines to resume DNA synthesis.
Conclusions:
- Tumorigenic transformed cells can exhibit growth properties kinetically and biochemically resembling their non-tumorigenic parental cells.
- The findings suggest that significant overlap exists in the cell cycle regulation mechanisms between normal and certain transformed cells.