The contribution of p53 in the dynamics of cell cycle response to DNA damage interpreted by a mathematical model

Area of Science:

• Cell Biology
• Molecular Biology
• Pharmacology

Background:

• The tumor suppressor p53 is crucial for cellular responses to DNA damage, but its precise role in cell cycle arrest and death across different phases (G1, S, G2M) following drug treatment remains incompletely understood.
• Understanding these dynamics is vital for developing effective cancer therapies that leverage or overcome p53-mediated pathways.

Purpose of the Study:

• To comprehensively analyze the complex cell cycle effects and cytotoxic responses to chemotherapy drugs in a p53-proficient versus p53-deficient cancer cell line.
• To delineate the distinct contributions of p53-dependent and p53-independent mechanisms to cytostasis and cell death across all phases of the cell cycle.

Main Methods:

• Employed a mixed experimental-simulation approach combining time-course measurements using various techniques with computer simulations of cell cycle progression.
• Utilized p53-proficient (HCT-116) and p53-deficient colon carcinoma cell lines to compare drug responses.
• Quantified p53 levels and evaluated cell cycle controls in G1, S, and G2M phases following treatment with cisplatin and doxorubicin.

Main Results:

• Confirmed p53's role in cell cycle arrest and killing across all phases, but also identified significant p53-independent cytostatic and cytotoxic activities for both drugs.
• In G1, p53 mediated a medium/long-term block, distinct from a short-term p53-independent block. p53 presence reduced the delay in S phase traversal.
• In G2M, a strong p53-independent block coexisted with a weaker, persistent p53-dependent block. Cytotoxic concentrations revealed both p53-dependent (earlier, apoptotic) and p53-independent cell death.

Conclusions:

• The study provides a reconciled framework for understanding p53's multifaceted role in cell cycle regulation and drug response, integrating previously contradictory findings.
• Both p53-dependent and independent pathways significantly contribute to the cytostatic and cytotoxic effects of cisplatin and doxorubicin.
• The findings highlight the complexity of p53 signaling in cancer chemotherapy and suggest potential therapeutic strategies targeting these distinct pathways.