title: Increased CYP24A1 expression is associated with BRAF(V600E) mutation and advanced stages in papillary thyroid carcinoma.
abstract: OBJECTIVE
  1α, 25(OH)2 D3 (calcitriol), the active form of vitamin D, has been shown to exert antiproliferative effects in many cancers. Overexpression of CYP24A1, the primary vitamin D-inactivating enzyme, is also observed in a variety of human cancers, thus potentially neutralizing the antitumour effect of 1α, 25(OH)2 D3. This study investigates the expression of CYP24A1 and the effect of BRAF(V600E) on its expression in thyroid cancer.
  
  
  METHODS
  We investigated 60 papillary thyroid carcinoma (PTC) specimens for CYP24A1 expression and its association with BRAF mutation and disease progression. CYP24A1 expression was measured by real-time RT-PCR, and BRAF(V600E) mutation was detected by PCR-DNA sequencing analysis. The interaction between BRAF(V600E) and CYP24A1 expression was determined by Western blot analysis and real-time RT-PCR.
  
  
  RESULTS
  CYP24A1 expression was increased in PTC as compared to benign multinodular goitre. The expression was further increased in stage III and IV tumours. There is a strong correlation between CYP24A1 overexpression and BRAF(V600E) mutation (P < 0·01). In thyroid cancer cell lines expressing BRAF(V600E) , CYP24A1 expression was significantly higher when compared to those without BRAF(V600E) expression. BRAF(V600E) transgene expression in CAL62 cell line can induce CYP24A1 expression. Furthermore, BRAF(V600E) inhibitor PLX4720 can significantly down-regulate CYP24A1 expression and enhance the antiproliferative effects of calcitriol in thyroid cancer cell lines.
  
  
  CONCLUSIONS
  CYP24A1 overexpression is a poor prognostic indicator for PTC and may reflect BRAF(V600E) mutation and MARK activation. The crosstalk between vitamin D and MAPK signalling pathways results in resistance to calcitriol-mediated antitumour effects, and the resistance can be reversed by BRAF(V600E) inhibitor PLX4720.
authors.affiliation: Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
authors.forename: Minjing
authors.initials: M
authors.lastname: Zou
authors.forename: Faisal S
authors.initials: FS
authors.lastname: BinHumaid
authors.forename: Ali S
authors.initials: AS
authors.lastname: Alzahrani
authors.forename: Essa Y
authors.initials: EY
authors.lastname: Baitei
authors.forename: Futwan A
authors.initials: FA
authors.lastname: Al-Mohanna
authors.forename: Brian F
authors.initials: BF
authors.lastname: Meyer
authors.forename: Yufei
authors.initials: Y
authors.lastname: Shi
mesh_terms: D002277:Carcinoma / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D002291:Carcinoma, Papillary / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D018450:Disease Progression; D006801:Humans; D066298:In Vitro Techniques; D009154:Mutation / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D065668:Vitamin D3 24-Hydroxylase / Q000235:genetics*
chemical_list: C585549:CYP24A1 protein, human; D065668:Vitamin D3 24-Hydroxylase; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf