Selective pressures for and against genetic instability in cancer: a time-dependent problem

Area of Science:

• Cancer Biology
• Evolutionary Medicine
• Mathematical Oncology

Background:

• Genetic instability in tumors presents a trade-off, promoting cancerous mutations while increasing cell death.
• Tumor progression is influenced by competing selective pressures: the need for genetic variability and the need to minimize deleterious mutations.

Purpose of the Study:

• To investigate how changing selective pressures shape the optimal mutation rate strategy in cancer cells.
• To model the optimal mutation rate for common multistage carcinogenesis patterns: oncogene activation and tumor-suppressor gene inactivation.

Main Methods:

• Formulation of an optimal control problem for cancer cell mutation rates.
• Development of a method to determine optimal time-dependent mutation strategies.
• Analysis of two-step (tumor-suppressor gene inactivation) and one-step (oncogene activation) carcinogenesis models.

Main Results:

• The optimal cancer cell strategy often involves initiating with a high mutation rate and subsequently transitioning to a stable state.
• This dynamic strategy aligns with biological observations of genetic instability in early cancers and stability in later stages.
• Identified specific parameter ranges favoring constant stability or instability throughout tumor growth.

Conclusions:

• Cancer cells dynamically adjust their mutation rates as a survival and progression strategy.
• The optimal mutation rate strategy is context-dependent, influenced by the stage of carcinogenesis and specific genetic alterations.
• Findings support the adaptive nature of cancer evolution and provide insights into potential therapeutic targets.