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P.1482 left column bottom paragraph: "Not only does DNA damage initiate cancer, but cells may also induce DNA injury for protection against cancer. With every round of DNA replication, a number of protective telomeric repeats are lost at the ends of chromosomes because the telomerase enzyme that adds new repeats is silenced in most somatic cells [primary source]. Clonal outgrowth of a precancerous cell results in critically short telomeres that behave similarly to double-strand breaks, awakening the DNA damage-response system and triggering cell-cycle arrest and cell death. To grow, tumors must overcome this barrier, which explains why reactivated telomerase can be found in approximately 90% of all cancers [primary source]." |