An Integrated Approach for Monitoring Cell Senescence

Cellular senescence is considered as a crucial mechanism of tumor suppression that helps to prevent the growth of cells at risk for neoplastic transformation. In normal cells, cellular senescence induces an irreversible cell cycle arrest in response to telomere dysfunction, oncogene activation, genotoxic stress and a persistent DNA damage response (DDR). This process is accompanied by dramatic changes in cell morphology as well as in the activity of several signaling pathways. The senescent phenotype is multifaceted. In addition to an obligatory proliferation arrest, senescent cells manifest various senescence markers: mTOR-mediated hypertrophic growth (cell size increase), cell flattening, senescence-associated β galactosidase (SA-β gal) staining, expression of negative cell cycle regulators p53, p21^Waf1 and p16^Ink4a , specific chromatin reorganization including DNA segments with chromatin alterations reinforcing senescence (DNA-SCARS), senescence-associated secretory phenotype (SASP) and other features. Here, we describe the protocols that are used to study histone deacetylase inhibitor (HDACI)-induced cellular senescence in transformed cells with a special emphasis on the morphological features of senescence.