Resveratrol Reverses Retinoic Acid Resistance of Anaplastic Thyroid Cancer Cells via Demethylating CRABP2 Gene.

Cellular retinoic acid binding protein 2 (CRABP2) mediates retinoic acid/RA anti-cancer pathways. Resveratrol effectively reverses RA tolerance and upregulates CRABP2 expression of anaplastic thyroid cancer cell line THJ-11T. As DNA methylation is responsible for CRABP2 silencing, the CRABP2 methylation status of THJ-11T cells and the demethylating effect of resveratrol on this gene are elucidated. The statuses of CRABP2 expression and methylation and the levels of DNA methyltransferases (DNMTs) DNMT1, DNMT3A, and DNMT3B of THJ-11T cells were examined before and after resveratrol treatment via multiple experimental methods. The human medulloblastoma UW228-2 cell line was cited as the control of CRABP2 methylation and gemcitabine as the demethylator control. RT-PCR, immunocytochemical staining and Western blotting showed that resveratrol significantly increased the CRABP2 expression and RA sensitivity of THJ-11T and UW228-2 cells. Bisulfite sequencing showed five CpG methylation sites at the CRABP2 promoter region of both cell lines, which were partially (3/5) demethylated by resveratrol and totally (5/5) by gemcitabine. DNMT1, DNMT3A, and DNMT3B were reduced in UW228-2 cells and DNMT1 and DNMT3A were reduced in THJ-11T cells after resveratrol treatment in a time-related fashion. Resveratrol is able to erase CRABP2 methylation and can thereby increase the RA sensitivity of THJ-11T and UW228-2 cells. This study demonstrates the additional value of the natural polyphenolic compound resveratrol as a demethylator in cancer treatments.