Apoptotic tubular cells are implicated in the progression of renal fibrosis due to their release of pro-fibrotic and pro-inflammatory mediators (Mao et al., 2008) The lack of effect of increased extracellular phosphate concentrations on apoptotic activity (as assessed by caspase 3/7 activity measurements) was unexpected. The gene discussed is CASP3; the disease is renal fibrosis.