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Nerve growth factor-induced accumulation of PC12 cells expressing cyclin D1: evidence for a G1 phase block
L A van Grunsven1, A Thomas, J L Urdiales
1Laboratoire de Biologie Moléculaire et Cellulaire, Ecole Normale Supérieure de Lyon, France.
Abstract:
The anti-proliferative effect of nerve growth factor (NGF) on the rat pheochromocytoma cell line PC12 has been previously shown to be accompanied by the accumulation of cells in either the G1 phase with a 2c DNA content, or with a 4c DNA content characteristic for G2/M, as evidenced by flow cytometric analysis of DNA distribution using propidium iodide. Herein, these apparently conflicting results are clarified. The present studies indicate that a simple DNA distribution profile obtained by this technique can confound interpretation of the biological effects of NGF on cell-cycle distribution due to the presence of tetraploid cells. Using cyclin D1 and incorporation of bromodeoxyuridine as markers of respectively, G1 and S phase, we show that PC12 cultures can have a considerable amount of tetraploid cells which, when in the G1 phase, have a 4c DNA content and express cyclin D1. During exposure to NGF, this population increases, reflecting the accumulation of cells in the G1 phase of the cell cycle. The data presented, support the possibility that events affecting the expression or action of G1 regulatory proteins may be involved in the molecular mechanism of the anti-mitogenic effect of NGF.
Insights
Nerve growth factor (NGF) has an anti-proliferative effect on PC12 cells. This study clarifies cell cycle distribution by identifying tetraploid cells, revealing NGF promotes G1 phase accumulation in these cells.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- Nerve growth factor (NGF) exhibits anti-proliferative effects on PC12 cells.
- Previous studies showed conflicting cell cycle distributions (G1/2c or G2/M/4c) after NGF treatment.
- Flow cytometry with propidium iodide can be confounded by tetraploid cells.
Purpose of the Study:
- To clarify the anti-proliferative mechanism of NGF on PC12 cell cycle distribution.
- To investigate the role of tetraploid cells in NGF-induced cell cycle arrest.
- To identify specific cell cycle phases affected by NGF treatment.
Main Methods:
- Utilized flow cytometry for DNA content analysis.
- Employed cyclin D1 as a G1 phase marker.
- Used bromodeoxyuridine incorporation to mark S phase.
- Analyzed rat pheochromocytoma cell line (PC12).
Main Results:
- Identified a significant population of tetraploid PC12 cells.
- Demonstrated that tetraploid cells in G1 phase possess 4c DNA content and express cyclin D1.
- Showed that NGF treatment increases the proportion of cells in G1 phase, including tetraploid cells.
- Confirmed NGF's anti-proliferative effect is linked to G1 phase accumulation.
Conclusions:
- Tetraploid cells complicate the interpretation of NGF's effect on PC12 cell cycle.
- NGF induces accumulation of cells in the G1 phase, particularly affecting the tetraploid population.
- The anti-mitogenic action of NGF may involve regulatory proteins controlling the G1 phase.