Related Experiment Videos
Defective G1-S cell cycle checkpoint function sensitizes cells to microtubule inhibitor-induced apoptosis
Z A Stewart1, D Mays, J A Pietenpol
1Department of Biochemistry, Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Abstract:
Defective cell cycle checkpoint function has been linked to enhanced sensitivity of tumor cells to certain genotoxic agents. To determine whether loss of the G1-S checkpoint function would sensitize tumor cells to microtubule inhibitor (MTI)-induced apoptosis, we examined the effect of the MTIs, Taxol and vincristine, on the cell cycle kinetics and survival of two isogenic cell lines, HCT116 p21+/+ and HCT116 p21-/-, which differ only at the p21 locus. p21-deficient cells displayed a dose-dependent, enhanced chemosensitivity to MTIs in both monolayer and soft agar assays as well as in mice xenograft tumors. The increased sensitivity of the p21-deficient cells to MTIs correlated with prolonged cyclin B1/Cdc2 activity and the occurrence of endoreduplication. Furthermore, sensitivity of p53-deficient cells to MTI-induced apoptosis was significantly reduced by induction of ectopic p21 protein. The results suggest that the status of G1-S checkpoint function in tumor cells may be an important determinant in the efficacy of MTIs used clinically.
Insights
Loss of the G1-S cell cycle checkpoint function enhances tumor cell sensitivity to microtubule inhibitors (MTIs). p21-deficient cells show increased chemosensitivity to MTIs, impacting clinical efficacy.
Area of Science:
- Cell Biology
- Cancer Research
- Pharmacology
Background:
- Defective cell cycle checkpoints can increase tumor cell sensitivity to genotoxic agents.
- The G1-S checkpoint plays a critical role in cell cycle regulation and DNA damage response.
Purpose of the Study:
- To investigate if loss of G1-S checkpoint function sensitizes tumor cells to microtubule inhibitor (MTI)-induced apoptosis.
- To evaluate the role of p21 in MTI sensitivity and cell death pathways.
Main Methods:
- Utilized isogenic HCT116 cell lines (p21+/+ and p21-/-) to assess MTI effects.
- Examined cell cycle kinetics, apoptosis, and survival in monolayer, soft agar, and xenograft models.
- Investigated the impact of ectopic p21 expression in p53-deficient cells.
Main Results:
- p21-deficient cells exhibited dose-dependent enhanced chemosensitivity to MTIs (Taxol, vincristine).
- Increased MTI sensitivity correlated with prolonged cyclin B1/Cdc2 activity and endoreduplication.
- Restoration of p21 expression reduced MTI-induced apoptosis sensitivity in p53-deficient cells.
Conclusions:
- G1-S checkpoint status is a key determinant of tumor cell response to MTIs.
- p21 deficiency significantly sensitizes cells to MTIs, suggesting therapeutic implications.
- Targeting or understanding G1-S checkpoint function could optimize MTI-based cancer therapies.