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Synchronized prostate cancer cells for studying androgen regulated events in cell cycle progression from G1 into S
Eugenia Cifuentes1, Richard Croxen, Mani Menon
1Vattikuti Urology Institute, Henry Ford Health Sciences Center, Detroit, Michigan 48202, USA.
Abstract:
Androgen-ablation is a most commonly prescribed treatment for metastatic prostate cancer but it is not curative. Development of new strategies for treatment of prostate cancer is limited partly by a lack of full understanding of the mechanism by which androgen regulates prostate cancer cell proliferation. This is due, mainly, to the limitations in currently available experimental models to distinguish androgen/androgen receptor (AR)-induced events specific to proliferation from those that are required for cell viability. We have, therefore, developed an experimental model system in which both androgen-sensitive (LNCaP) and androgen-independent (DU145) prostate cancer cells can be reversibly blocked in G(0)/G(1) phase of cell cycle by isoleucine deprivation without affecting their viability. Pulse-labeling studies with (3)H-thymidine indicated that isoleucine-deprivation caused LNCaP and DU145 cells to arrest at a point in G(1) phase which is 12-15 and 6-8 h, respectively, before the start of S phase and that their progression into S phase was dependent on serum factors. Furthermore, LNCaP, but not DU145, cells required AR activity for progression from G(1) into S phase. Western blot analysis of the cell extracts prepared at regular intervals following release from isoleucine-block revealed remarkable differences in the expression of cyclin E, p21(Cip1), p27(Kip1), and Rb at the protein level between LNCaP and DU145 cells during progression from G(1) into S phase. However, in both cell types Cdk-2 activity associated with cyclin E and cyclin A showed an increase only when the cells transited from G(1) into S phase. These observations were further corroborated by studies using exponentially growing cells that were enriched in specific phases of the cell cycle by centrifugal elutriation. These studies demonstrate usefulness of the isoleucine-deprivation method for synchronization of androgen-sensitive and androgen-independent prostate cancer cells, and for examining the role of androgen and AR in progression of androgen-sensitive prostate cancer cells from G(1) into S phase.
Insights
A new experimental model using isoleucine deprivation synchronizes prostate cancer cells. This method reveals androgen receptor activity is crucial for androgen-sensitive prostate cancer cell proliferation.
Area of Science:
- Oncology
- Cell Biology
- Molecular Biology
Background:
- Androgen-ablation therapy is a common treatment for metastatic prostate cancer, but it is not curative.
- Understanding androgen's role in prostate cancer cell proliferation is limited by current experimental models.
- Distinguishing androgen/androgen receptor (AR)-induced proliferation from cell viability events is challenging.
Purpose of the Study:
- To develop a novel experimental model for synchronizing prostate cancer cells.
- To investigate the role of androgen and AR in cell cycle progression.
- To differentiate androgen-specific proliferation from cell viability mechanisms.
Main Methods:
- Developed a model using isoleucine deprivation to reversibly block androgen-sensitive (LNCaP) and androgen-independent (DU145) prostate cancer cells in G(0)/G(1) phase.
- Utilized pulse-labeling with (3)H-thymidine to assess cell cycle arrest and progression.
- Employed Western blot analysis and centrifugal elutriation to examine protein expression and cell cycle dynamics.
Main Results:
- Isoleucine deprivation effectively synchronized both LNCaP and DU145 cells in G(1) phase without affecting viability.
- AR activity was essential for LNCaP cell progression from G(1) to S phase, but not for DU145 cells.
- Observed distinct protein expression patterns (cyclin E, p21, p27, Rb) between LNCaP and DU145 cells during cell cycle transition.
Conclusions:
- Isoleucine deprivation is a useful method for synchronizing prostate cancer cells for cell cycle studies.
- This model system facilitates the examination of androgen and AR roles in prostate cancer cell cycle progression.
- The findings highlight differences in cell cycle regulation between androgen-sensitive and androgen-independent prostate cancer cells.