Molecular tumour clocks

Multistep tumour progression predicts that cancer arises through a series of mutations and cell divisions. This process has been difficult to document in humans because direct physical observations over time are impractical. Phylogenetic approaches, properly translated to cancer, offer opportunities to unravel the occult historical trail of mutations and clonal expansions inherent to multistep progression. Microsatellite loci in mutator phenotype tumours can function as molecular tumour clocks because they acquire single repeat unit additions or deletions at high frequencies. Differences in the number of somatic microsatellite mutations may indicate their relative ages.