In normal conditions, telomerase expression is limited to embryonic and other stem cell-like cells and is silenced in somatic cells [428], whereas TERT gene and TERT promoter alterations (discussed in more detail in articles such as [373]) are frequently detected in various cancers, resulting in telomere length protection, implicated as a key factor in tumor cell propagation and tumorigenesis [429]. The gene discussed is TERT; the disease is neoplasm.