Cytochromes P450 and
Skin Cancer: Role of Local Endocrine Pathways
Author(s):
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.
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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.
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