To understand how elevated TRF2 levels might affect telomere maintenance, we overexpressed full-length, untagged wild-type TRF2 (Fig. 1b) in HT1080 human fibrosarcoma cells to approximately sevenfold of endogenous level using a lentiviral expression system and analysed the effects on telomeres. The gene discussed is TERF2; the disease is fibrosarcoma.