Atypical senescent states: Endoplasmic Reticulum stress induced senescence

Endoplasmic reticulum (ER) stress may also promote a senescent-like response.  The accumulation of unfolded proteins in the ER triggers a stress-signaling pathway that can result in cell cycle arrest mediated by p27 (Han et al. 2013) and the p53/47 isoform (Bourougaa et al. 2010).  Furthermore, ER stress has also been shown to induce an inflammatory response via NFkB activation (Garg et al. 2012) and induce cytokines such as MCP-1, IL-6 and IL-8 (Schroder, 2008), which are capable of attracting and activating immune cells (Sagiv and Krizhanovsky, 2013). ER stress has also been shown to promote cell survival, another feature of cell senescence (Raciti et al. 2012).  Interestingly, a senescent state via activation of ER stress-dependent p21 signaling has been reported in proximal tubular epithelial cells, triggered by receptors for advanced glycation end-products (RAGE) (Liu et al. 2014).  Although, ER stress-induced senescence has the potential induce an immunogenic phenotype in the absence of DNA damage, a full evaluation of the phenotype is required to determine if this is so.