GPT and cancer: While telomerase-positive cancers have been subject to the majority of preclinical studies and clinical trials [144], developing effective treatments against ALT-positive cancers is crucial for two reasons—ALT occurs with overwhelming majority of some classes of solid tumours which have extremely poor prognosis, and telomerase-positive cancers can switch to an ALT-positive one either sporadically or due to selection imposed inadvertently by therapeutic interventions [145,146].