Skin is the largest body organ forming a metabolically active barrier between external and internal environments. The metabolic barrier is composed of
cytochromes P450 (CYPs) that regulate its homeostasis through activation or inactivation of biologically relevant molecules. In this review we focus our attention on local steroidogenic and secosteroidogenic systems in relation to
skin cancer, e.g., prevention, attenuation of
tumor progression and
therapy. The local steroidogenic system is composed of locally expressed CYPs involved in local production of
androgens,
estrogens, gluco- and mineralo-
corticosteroids from
cholesterol (initiated by
CYP11A1) or from
steroid precursors delivered to the skin, and of their metabolism and/or inactivation. Cutaneous 7-hydroxylases (CYP7A1, CYP7B1 and CYP39) potentially can produce 7-hydroxy/oxy-
steroids/
sterols with modifying effects on local
tumorigenesis.
CYP11A1 also transforms
7-dehydrocholesterol (7DHC)→22(OH)7DHC→20,22(OH)2-7DHC→7-dehydropregnenolone, which can be further metabolized to other 5,7- steroidal dienes. These 5,7-dienal intermediates are converted by ultraviolet radiation B (UVB) into
secosteroids which show pro-differentiation and anti-
cancer properties. Finally, the skin is the site of activation of
vitamin D3 through two alternative pathways. The classical one involves sequential hydroxylation at positions 25 and 1 to produce active
1,25(OH)2D3, which is further inactivated through hydroxylation at C24. The novel pathway is initiated by
CYP11A1 with predominant production of
20(OH)D3 which is further metabolized to biologically active but non-calcemic D3-hydroxyderivatives. Classical and non-classical (novel)
vitamin D analogs show pro-differentiation, anti-proliferative and anticancer properties. In addition,
melatonin is metabolized by local CYPs. In conclusion cutaneously expressed CYPs have significant effects on skin physiology and pathology trough regulation of its chemical milieu.