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Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1
Published on: February 25, 2016
CDK1 inhibition sensitizes normal cells to DNA damage in a cell cycle dependent manner
Remko Prevo1, Giacomo Pirovano1, Rathi Puliyadi1
1a Department of Oncology, Cancer Research UK/MRC Oxford Institute for Radiation Oncology, Gray Laboratories , University of Oxford , Oxford , UK.
Abstract:
Cyclin-dependent kinase 1 (CDK1) orchestrates the transition from the G2 phase into mitosis and as cancer cells often display enhanced CDK1 activity, it has been proposed as a tumor specific anti-cancer target. Here we show that the effects of CDK1 inhibition are not restricted to tumor cells but can also reduce viability in non-cancer cells and sensitize them to radiation in a cell cycle dependent manner. Radiosensitization by the specific CDK1 inhibitor, RO-3306, was determined by colony formation assays in three tumor lines (HeLa, T24, SQ20B) and three non-cancer lines (HFL1, MRC-5, RPE). Initial results showed that CDK1 inhibition radiosensitized tumor cells, but did not sensitize normal fibroblasts and epithelial cells in colony formation assays despite effective inhibition of CDK1 signaling. Further investigation showed that normal cells were less sensitive to CDK1 inhibition because they remained predominantly in G1 for a prolonged period when plated in colony formation assays. In contrast, inhibiting CDK1 a day after plating, when the cells were going through G2/M phase, reduced their clonogenic survival both with and without radiation. Our finding that inhibition of CDK1 can damage normal cells in a cell cycle dependent manner indicates that targeting CDK1 in cancer patients may lead to toxicity in normal proliferating cells. Furthermore, our finding that cell cycle progression becomes easily stalled in non-cancer cells under normal culture conditions has general implications for testing anti-cancer agents in these cells.
Insights
Cyclin-dependent kinase 1 (CDK1) inhibition harms normal cells, not just cancer cells. This cell cycle-dependent toxicity impacts normal cell viability and radiosensitivity, suggesting potential side effects for cancer patients.
Area of Science:
- Oncology
- Cell Biology
- Cancer Therapeutics
Background:
- Cyclin-dependent kinase 1 (CDK1) is crucial for cell cycle progression into mitosis.
- Enhanced CDK1 activity is observed in cancer cells, making it a potential anti-cancer target.
- CDK1 inhibitors are being investigated for cancer treatment, but their effects on normal cells are not fully understood.
Purpose of the Study:
- To investigate the impact of CDK1 inhibition on both tumor and non-cancer cells.
- To determine if CDK1 inhibition sensitizes non-cancer cells to radiation therapy.
- To elucidate the cell cycle-dependent effects of CDK1 inhibition on cell viability and radiosensitivity.
Main Methods:
- Colony formation assays were used to assess cell viability and radiosensitivity.
- Three tumor cell lines (HeLa, T24, SQ20B) and three non-cancer cell lines (HFL1, MRC-5, RPE) were utilized.
- The specific CDK1 inhibitor RO-3306 was employed to assess CDK1 signaling inhibition.
Main Results:
- CDK1 inhibition radiosensitized tumor cells.
- Normal cells showed reduced sensitivity to CDK1 inhibition when plated under standard conditions, primarily due to prolonged G1 phase arrest.
- Inhibiting CDK1 in normal cells during G2/M phase significantly reduced their clonogenic survival, with or without radiation.
Conclusions:
- CDK1 inhibition can negatively affect normal proliferating cells in a cell cycle-dependent manner, indicating potential toxicity in cancer patients.
- Normal cells exhibit cell cycle stalling, which has implications for evaluating anti-cancer agents.
- Targeting CDK1 requires careful consideration of its cell cycle-dependent effects on both cancerous and non-cancerous cells.
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