title: Robust Thyroid Gene Expression and Radioiodine Uptake Induced by Simultaneous Suppression of BRAF V600E and Histone Deacetylase in Thyroid Cancer Cells.
abstract: BACKGROUND
  Use of BRAF V600E inhibitors to restore thyroid iodide-handling gene expression and radioactive iodine (RAI) avidity is an attractive therapeutic strategy for RAI-refractory thyroid cancer, but recent initial clinical responses were modest. Given histone deacetylation at the sodium/iodide symporter promoter by histone deacetylase (HDAC) as a mechanism, simultaneously targeting BRAF V600E and HDAC could be a more effective strategy.
  
  
  OBJECTIVE
  The objective of the study was to test whether suppressing both BRAF V600E and HDAC could more effectively induce thyroid gene expression and RAI uptake in thyroid cancer cells.
  
  
  METHODS
  We tested the BRAF V600E inhibitor PLX4032 (vemurafenib) and the HDAC inhibitor SAHA (vorinostat), two major anticancer drugs currently approved for clinical use, in inducing thyroid gene expression and RAI uptake in thyroid cancer cells.
  
  
  RESULTS
  PLX4032 alone induced a modest expression of thyroid genes and RAI uptake preferentially in thyroid cancer cells harboring BRAF V600E. SAHA showed an effect in a genetic-independent manner in all the cells. A robust synergistic effect on thyroid gene expression and RAI uptake was observed in BRAF V600E-positive thyroid cancer cells when the two inhibitors were simultaneously used. This was dramatically enhanced further by TSH; triple combination of PLX4032, SAHA, and TSH showed the most robust effect on thyroid gene expression and RAI uptake in cells harboring BRAF V600E. Abundant sodium/iodide symporter protein expression in thyroid cancer cells under these conditions was confirmed by immunofluorescent microscopy.
  
  
  CONCLUSIONS
  Simultaneously suppressing BRAF V600E and HDAC, particularly when cotreated with TSH, induced a far more robust expression of thyroid genes and RAI uptake in thyroid cancer cells than suppressing BRAF V600E alone. Triple combination of PLX4032, SAHA, and TSH is a specific robust regimen to restore RAI avidity in RAI-refractory BRAF V600E-positive thyroid cancer, which warrants clinical trials to confirm.
authors.affiliation: Laboratory for Cellular and Molecular Thyroid Research (W.C., R.L., G.Z., M.X.), Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Department of Nuclear Medicine (H.W.), Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Cheng
authors.affiliation: Laboratory for Cellular and Molecular Thyroid Research (W.C., R.L., G.Z., M.X.), Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Department of Nuclear Medicine (H.W.), Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China.
authors.forename: Rengyun
authors.initials: R
authors.lastname: Liu
authors.affiliation: Laboratory for Cellular and Molecular Thyroid Research (W.C., R.L., G.Z., M.X.), Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Department of Nuclear Medicine (H.W.), Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China.
authors.forename: Guangwu
authors.initials: G
authors.lastname: Zhu
authors.affiliation: Laboratory for Cellular and Molecular Thyroid Research (W.C., R.L., G.Z., M.X.), Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Department of Nuclear Medicine (H.W.), Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: Laboratory for Cellular and Molecular Thyroid Research (W.C., R.L., G.Z., M.X.), Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287; and Department of Nuclear Medicine (H.W.), Xin Hua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai 200092, China.
authors.forename: Mingzhao
authors.initials: M
authors.lastname: Xing
mesh_terms: D000970:Antineoplastic Agents; D045744:Cell Line, Tumor; D015870:Gene Expression / Q000187:drug effects*; D056572:Histone Deacetylase Inhibitors / Q000627:therapeutic use*; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D007457:Iodine Radioisotopes / Q000378:metabolism* / Q000627:therapeutic use; D048493:Proto-Oncogene Proteins B-raf / Q000037:antagonists & inhibitors*; D013449:Sulfonamides / Q000494:pharmacology; D027981:Symporters / Q000235:genetics; D013961:Thyroid Gland / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism* / Q000532:radiotherapy; D013972:Thyrotropin / Q000008:administration & dosage; D000077484:Vemurafenib; D000099209:Sodium-Iodide Symporters
chemical_list: D000970:Antineoplastic Agents; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases; D007211:Indoles; D007457:Iodine Radioisotopes; D048493:Proto-Oncogene Proteins B-raf; D013449:Sulfonamides; D027981:Symporters; D013972:Thyrotropin; D000077484:Vemurafenib; D000099209:Sodium-Iodide Symporters; C482119:BRAF protein, human