There is growing evidence that it is not only the mutational status of p53 that is important in cancer but also its transcriptional activity,24 and a role for perturbation of p53 stability has been suggested to play a role in PV progression.25 We therefore investigated a key phosphorylation site, serine 212, that has been demonstrated to be critical in the transcriptional activity of p53 in relation to differentiation and self-renewal26 rather than apoptosis. This evidence concerns the gene TP53 and cancer.