MAPK14 and Werner syndrome: These data, together with the effects of p38 inhibition on WS fibroblast growth, suggest that activation of p38 may be responsible for many of the senescence-like features of WS fibroblasts, a situation known as stress-induced premature senescence (SIPS) (Davis and Kipling 2006; Toussaint et al. 2000) and may underlie the accelerated ageing seen in WS individuals.