TERF1 and cancer: Thus, in contrast to the theory that telomere length itself serves to induce the process of replicative senescence, the more immediate event promoting the senescence phenotype appears to be TRF2:TRF1 ratio‐mediated telomere structure, which may explain how many cancer cells appear to flourish with significantly shorter telomeres than normal somatic cells (Xu and Blackburn 2007) while displaying significant genomic instability.