CYP27B1 and melanoma: Lastly, immunocytochemistry studies on human melanoma samples have shown that high levels of melanin pigmentation are associated with decreased expression of the vitamin D receptor (VDR) [406], the CYP27B1 enzyme that is involved in vitamin D activation [407], and retinoic acid-related orphan receptors (ROR)α and γ [408] on which vitamin D hydroxyderivatives can act as inverse agonists [409].