How might telomere-related factors contribute to oncogenesis?
These observations and speculations about telomere function lead to the following predictions regarding the possible contributions of telomere malfunction to disease, including cancer (Table 1). The most obvious contribution is when telomere length is maintained or even increased by the aberrant activation of a TMM, allowing the nascent cancer cells to breach the senescence barrier. A more subtle contribution (for which there is as yet no evidence) might be excessive telomerase or ALT-like activity in otherwise normal tissue compartments at some stage of development resulting in increased reserves of telomere length that permit abnormal clonal expansion when oncogenic mutations happen to occur. Increased telomere shortening is observed in a number of human conditions, including Down syndrome, Werner syndrome, ataxia telangiectasia, and dyskeratosis congenita. For most of these conditions, the relationship between the genetic abnormality and the telomere defect is unknown. In principle,
