Fig. 3

The changing activity of mutational processes during cancer evolution. Mutational forces that operate on the cancer genome are active over different timescales, with varying intensities. A schematic timeline indicates how they correspond to events in a patient’s lifetime. Spontaneous deamination (purple) is operative from the fertilized egg, and is thought to remain relatively constant over time. Exposures to mutagens may also be constant, such as UV light (blue), or transient, such as smoking (red). Tumor-specific processes, such as APOBEC-mediated mutagenesis, become dominant as the tumor develops (yellow) and, finally, the mutational imprint of chemotherapy (green) may be observed in the final few years before sequencing. SNV single nucleotide variant, WGD whole genome duplication