title: Valproic acid induces apoptosis and cell cycle arrest in poorly differentiated thyroid cancer cells.
abstract: Poorly differentiated thyroid carcinoma is an aggressive human cancer that is resistant to conventional therapy. Histone deacetylase inhibitors are a promising class of drugs, acting as antiproliferative agents by promoting differentiation, as well as inducing apoptosis and cell cycle arrest. Valproic acid (VPA), a class I selective histone deacetylase inhibitor widely used as an anticonvulsant, promotes differentiation in poorly differentiated thyroid cancer cells by inducing Na(+)/I(-) symporter and increasing iodine uptake. Here, we show that it is also highly effective at suppressing growth in poorly differentiated thyroid cancer cell lines (N-PA and BHT-101). Apoptosis induction and cell cycle arrest are the underlying mechanisms of VPA's effect on cell growth. It induces apoptosis by activating the intrinsic pathway; caspases 3 and 9 are activated but not caspase 8. Cell cycle is selectively arrested in G(1) and is associated with the increased expression of p21 and the reduced expression of cyclin A. Both apoptosis and cell cycle arrest are induced by treatment with 1 mm VPA, a dose that promotes cell redifferentiation and that is slightly above the serum concentration reached in patients treated for epilepsy. These multifaceted properties make VPA of clinical interest as a new approach to treating poorly differentiated thyroid cancer.
authors.affiliation: Dipartimento di Fisiopatologia Clinica, Via Genova 3, 10126 Torino, Italy.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Catalano
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Fortunati
authors.forename: Mariateresa
authors.initials: M
authors.lastname: Pugliese
authors.forename: Lucia
authors.initials: L
authors.lastname: Costantino
authors.forename: Roberta
authors.initials: R
authors.lastname: Poli
authors.forename: Ornella
authors.initials: O
authors.lastname: Bosco
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boccuzzi
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002291:Carcinoma, Papillary; D002453:Cell Cycle / Q000187:drug effects; D018797:Cell Cycle Proteins / Q000235:genetics; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D013964:Thyroid Neoplasms; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D014635:Valproic Acid