<prompt> While advancing there is increased chance of developing cancers. Tumorigenesis in aging is due to:Telomerase reactivationTelomerase inactivationIncreased apoptosisSuppression of proto-oncogenes  <response>: Telomerase is a ribonucleoprotein that is expressed in stem cells and most cancer cells, but not in somatic cells. More than 90 of human cancers express high levels of telomerase that prevent telomere shoening to critical levels and allow indefinite cell proliferation. Ref: Longo D.L. 2012. Chapter 84. Cancer Cell Biology and Angiogenesis. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo Eds, Harrisons Principles of Internal Medicine, 18e. 