The Theory Of Aging : A Robust Tumor Suppressive Mechanism That Inhibits The Proliferation Of Damaged

969 Words Jun 7th, 2016 4 Pages
Senescence is a robust tumor suppressive mechanism that inhibits the proliferation of damaged as well as initiated cells in response to a diverse range of stresses. The observations that human benign cancer precursor lesions are comprised of senescent cells further provide evidence that senescence is a physiological mechanism that prevents cancer progression in humans, possibly at an early stage. Senescence is clearly not fail-safe, since cells in pre-cursor lesions occasionally progress towards advance stages of cancer (Michaloglou et al., 2005). However, what remains unclear is if cells in these pre-cursor lesions escape senescence by acquiring changes that help them overcome the restrictive barriers of proliferation or if cancer progression is due to expansion of a small fraction of mitotically active cells that have never entered senescence.

Although the theory of aging was first introduced by August Weisman in the 19th century, it was Hayflick and Moorehead who first demonstrated that normal somatic cells have a limited proliferative capacity (Hayflick & Moorhead, 1961). They showed that normal fibroblasts when serially passaged cease proliferation after approximately 50 population doublings and enter an irreversible state of growth arrest (Hayflick, 1965). Although the progression and onset of senescence varied among organisms, it was later observed that almost all cells, with the exception of immortal cells, underwent growth arrest after a finite number…

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