The roles of cytochrome P450 enzymes in prostate cancer development and treatment.

The active form of vitamin D, 1α,25-dihydroxyvitamin D [1α,25(OH)(2)D], interacts with vitamin D receptor (VDR) and induces antiproliferative, anti-invasive, proapoptotic and pro-differentiation activities in prostate cancer cells. Three cytochrome P-450 (CYP) hydroxylases are responsible for vitamin D synthesis and degradation, including vitamin D-25-hydroxylase (25-OHase) in the liver, and 25(OH)D-1α-hydroxylase (1α-OHase) or CYP27B1, and 25(OH)D-24-hydroxylase (24-OHase) or CYP24A1 in the kidneys. However, it is now recognized that CYP27B1 and CYP24A1 are also expressed in many tissues and cells, including the prostate. Although at least six CYP enzymes have been identified with 25-OHase activity, the two major ones are CYP27A1 and CYP2R1, and both are expressed in the prostate, with CYP2R1 as the predominate type. This indicates that prostate tissue has the ability to activate and inactivate vitamin D in an autocrine/paracrine fashion. Recent evidence indicates that 25-hydroxyvitamin D [25(OH)D] and its analogs can bind to VDR as agonists, without converting them to 1α,25(OH)(2)D or the corresponding 1α-hydroxylated metabolites, to modulate gene expressions that will lead to cell growth arrest and other antitumor activities. This finding suggests that the circulating levels of 25(OH)D, and the autocrine synthesis of 25(OH)D may play an important role in regulating the growth of prostate cancer. Thus, in addition to 1α,25(OH)(2)D analogs, the presence of CYP2R1, CYP27B1 and CYP24A1 in the prostate suggests that the analogs of vitamin D and 25(OH)D, especially those that are resistant to CYP24A1 degradation, can be developed and used for the prevention and treatment of prostate cancer.