CTC1 and cancer: Knockdown of either Stn1 or Ctc1 in human cancer cells and in mouse fibroblasts results in substantially elongated telomeric G-overhangs, consistent with its recently demonstrated role in facilitating telomeric C-strand synthesis and negatively regulating telomerase (Surovtseva et al., 2009; Dai et al., 2010; Chen et al., 2012; Wang et al., 2012; Wu et al., 2012).