Growth Stimulation Leads to Cellular Senescence When the Cell Cycle Is Blocked. Zoya N Demidenko

Growth Stimulation Leads to Cellular Senescence When the Cell Cycle Is Blocked

Zoya N Demidenko , Mikhail V Blagosklonny
Abstract
We tested a hypothesis that activation of growth-promoting pathways is required for cellular senescence. In the presence of serum, induction of p21 caused senescence, characterized by beta-Galactosidase staining, cell hypertrophy, increased levels of cyclin D1 and active TOR (target of rapamycin, also known as mTOR). Serum starvation and rapamycin inhibited TOR and prevented the expression of some senescent markers, despite high levels of p21 and cell cycle arrest. In the presence of serum, p21-arrested cells irreversibly lost proliferative potential. In contrast, when cells were arrested by p21 in the absence of serum, they retained the capacity to resume proliferation upon termination of p21 induction. In normal human cells such as WI38 fibroblasts and retinal pigment epithelial (RPE) cells, serum starvation caused quiescence, which was associated with low levels of cyclin D1, inactive TOR and slim-cell morphology. In contrast, cellular senescence with high levels of TOR activity was induced by doxorubicin (DOX), a DNA damaging agent, in the presence of serum. Inhibition of TOR partially prevented senescent phenotype caused by DOX. Thus growth stimulation coupled with cell cycle arrest leads to senescence, whereas quiescence (a condition with inactive TOR) prevents senescence.
oncotarget predatory Zoya Demidenko Dr. Zoya N. Demidenko Zoya N. Demidenko , Ph.D. is Executive Manager of the Oncotarget journal . Oncotarget publishes high-impact research papers of general interest and outstanding significance and novelty in all areas of biology and medicine: in translational, basic and clinical research including but not limited to cancer research, oncogenes, oncoproteins and tumor suppressors, signaling pathways as potential targets for therapeutic intervention, shared targets in different diseases (cancer, benign tumors, atherosclerosis, eukaryotic infections, metabolic syndrome and other age-related diseases), chemotherapy, and new therapeutic strategies. After earning her Ph.D. in molecular biology, Zoya was awarded a Fogarty post-doctoral Fellowship from the National Institutes of Health in Bethesda, MD. After successful completion of post-doctoral training, she continued her professional career at George Washington University and Albert Einstein School of Medicine . In 2005 she cofounded the startup company Oncotarget Inc. which is focused on the development of anti-aging and anti-cancer drugs. Her research interests include signal transduction, cell cycle and cellular senescence, and their pharmacological targeting. In 2009 she cofounded the publishing house Impact Journals which specializes in publishing scientific journals. In 2011 she was selected to be a Member of the National Association of Professional Women .
http://www.oncotarget.com/index.php?journal=oncotarget&page=article&op=view&path%5B%5D=2037

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