Conception-calibrated male pediatric tumor mitotic clocks

Area of Science:

• Oncology
• Genetics
• Epigenetics

Background:

• Molecular clocks are crucial for reconstructing cancer development but face challenges due to uncertainties in cancer age.
• Pediatric cancers offer a unique advantage for calibrating these clocks due to their narrow age ranges.

Purpose of the Study:

• To develop and validate novel mitotic clocks for estimating tumor age and epimutation rates in pediatric cancers.
• To apply these clocks to understand tumor evolution and remission dynamics.

Main Methods:

• Development of mitotic clocks based on rapidly fluctuating CpG (fCpG) DNA methylation on the X chromosome in male pediatric cancers.
• Application of a two-state Markov model to estimate mitotic age and epimutation rates.
• Analysis of acute lymphoblastic leukemia, acute myeloid leukemia, neuroblastoma, and embryonal brain tumors.

Main Results:

• High concordance between modeled and observed methylation data across diverse pediatric cancers.
• Estimation of epimutation rates at approximately 10^-3 per division.
• Determination of tumor mitotic ages ranging from 30 to several hundred cell divisions.
• Inference of relapse dynamics, suggesting seeding by small numbers of dormant residual cancer cells.

Conclusions:

• Calibrated fCpG mitotic clocks provide a robust quantitative framework for studying human tumor evolution.
• These clocks can uncover hidden aspects of tumor development and remission in pediatric cancers.
• The findings highlight the utility of exploiting unique biological constraints for advancing cancer research.