Fig. 1
From: Mechanisms of human telomerase reverse transcriptase (hTERT) regulation: clinical impacts in cancer
Telomere length dynamics in different cells over time. Telomeres shorten over time. Germ cells and embryonic stem cells have long telomeres that are maintained by telomerase activity. Stem cells have shorter telomeres and somatic cells even shorter. After multiple cell divisions these cells achieve a senescence state (M1). At M2 stage cells enter crisis due to their short telomeres that lead to chromosomal and genomic instability resulting in apoptosis. Cancer cells escape from crisis through telomerase activation, reacquire longer telomeres and unlimited self-renewal capacity