Prostate cancer(PCa)is the second most common malignancy in men1 and ifloca-lized or confined to the gland at diagnosis,the choice of treatment includes surgery,radiation or watchful waiting.If and when the disease spreads,androgen blockade is effective but inevitably relapse occurs,resulting in incurable castrate-resistant PCa.Understanding the etiology of PCa will underpin the development of better treatment options In particular,the identity of the cell type(s)that are the origin of PCa(or cancer-initiating cells)will enable them to become therapeutic targets that could lead to newer and more sophisticated treatment options.These cells of origin are defined as epithelial cells in the normal prostate,susceptible to malignant transformation and therefore capable of initiating tumourigenesis.However,their identity is unknown.