Vitamin D Signaling Expression Markers in Thyroid Tumors

Introduction

• 25(OH)D deficiency has been associated with higher thyroid cancer risk; however, it is unclear if it mechanistically affects biologic behavior and aggressiveness. ^1,2
• Studies have demonstrated an association between vitamin D receptor (VDR) polymorphisms and thyroid cancer.³
• BRAFV600E is the most common mutation seen in PTC.⁴
• CYP27B1 encodes 1α-hydroxylase which converts 25(OH)D to 1,25(OH)₂D.
• CYP24A1 encodes for 25-hydroxyvitamin D3-24-hydroxylase which converts 25(OH)D and 1,25(OH)₂D to inactive metabolites.
• Increased expression of VDR (CYP24A1) is seen in PTC as well as tumors that have BRAFV600E mutations.⁵
• It is unclear how Vitamin D Activity relates to tumor aggressiveness and disease progression.

Study Aim

The aim of this study was to characterize VDR, VD regulatory enzymes, and VD pathway target gene expression in thyroid nodules sent for Afirma Genomic Sequencing Classifier (GSC) molecular testing.

Methods

• Characterize vitamin D expression and genes involved in its synthesis in Afirma GSC-(B)enign and GSC-(S)uspicious (B)ethesda III/IV nodules and Bethesda V/VI malignant nodules.
• Further characterize expression according to BRAFV600E+ vs BRAFwt and other molecular variants.
• CAMP, CD14, ORM1, CLMN
• This score is the average expression level of the 4 vitamin D target genes.
• The Afirma thyroid nodule molecular database (DB) was analyzed to:
• The mRNA expression levels of four vitamin D target genes were evaluated.
• A Vitamin D Activity Score was developed as a measure of VD signaling and correlated with Afirma result, expressed variant and fusion status, and ERK signaling.

Conclusion

• Bethesda III/IV-GSC-S and Bethesda V/VI malignant nodules have reduced VD signaling compared with GSC-benign nodules.
• BRAF-like alterations have lower VD signaling than RAS-like alterations.
• Novel VD Activity score was lowest in BRAFV600E+ GSC-S and malignant nodules when compared to those negative for BRAFV600E.
• VD Activity score is inversely correlated with ERK signaling.
• VD Activity score may be a novel marker predicting tumor behavior, especially in nodules that do not express canonical mutations.