Human CYP24 catalyzing the inactivation of calcitriol is post-transcriptionally regulated by miR-125b.
Human vitamin D3 hydroxylase (CYP24) catalyzes the inactivation of 1alpha,25-dihydroxyvitamin D3 (calcitriol), which exerts antiproliferative effects. CYP24 has been reported to be overexpressed in various cancers in which microRNA levels are dysregulated. In silico analysis identified a potential miR-125b recognition element (MRE125b) in the 3'-untranslated region of human CYP24 mRNA. We investigated whether CYP24 is regulated by miR-125b. In luciferase assays using a reporter plasmid containing MRE125b, transfection of the antisense oligonucleotide (AsO) for miR-125b increased the reporter activity in KGN cells, and transfection of precursor miR-125b decreased the reporter activity in MCF-7 cells. The endogenous CYP24 protein level was also increased by AsO for miR-125b in KGN cells and was decreased by precursor miR-125b in MCF-7 cells. These results suggested that human CYP24 is regulated by miR-125b. Immunohistochemical analysis revealed that the CYP24 protein levels in human breast cancer were higher than in adjacent normal tissues, without an accompanying CYP24 mRNA increase. On the other hand, the expression levels of miR-125b in cancer tissues were significantly (P < 0.0005) lower than those in normal tissues. It is noteworthy that the CYP24 protein levels in cancer tissues were inversely associated with the cancer/normal ratios of the miR-125b levels, indicating that the decreased miR-125b levels in breast cancer tissues would be one of the causes of the high CYP24 protein expression. In conclusion, this study clearly demonstrates that miR-125b post-transcriptionally regulates the CYP24, which serves as a possible mechanism for the high CYP24 expression in cancer tissues.
Komagata
Sayaka
S
Drug Metabolism and Toxicology, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
Nakajima
Miki
M
Takagi
Shingo
S
Mohri
Takuya
T
Taniya
Takao
T
Yokoi
Tsuyoshi
T
D020413:3' Untranslated Regions; D001483:Base Sequence; D055162:Biocatalysis; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000201:enzymology / Q000473:pathology; D002117:Calcitriol / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D045744:Cell Line, Tumor; D017931:DNA Primers; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D035683:MicroRNAs / Q000502:physiology*; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism*; D065668:Vitamin D3 24-Hydroxylase
D020413:3' Untranslated Regions; D017931:DNA Primers; C531888:MIRN125 microRNA, human; D035683:MicroRNAs; D012333:RNA, Messenger; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D002117:Calcitriol