CDKN1A and Familial prostate cancer: Luminal cells expressed negative regulators of the cell cycle, including the cyclin-dependent kinase inhibitors p21CIP1/WAF1 (CDKN1A) and p27KIP (CDKN1B), the latter having earlier been localised to prostate luminal cells (Harper et al, 1993; Fernandez et al, 1999), and the tumour suppressor genes NBL1 (Enomoto et al, 1994), NDRG1 (Daly-Burns et al, 2007) and PHB, which are downregulated in prostate cancer cells (Gamble et al, 2007).