title: Valproic acid enhances tubulin acetylation and apoptotic activity of paclitaxel on anaplastic thyroid cancer cell lines.
abstract: The introduction of paclitaxel into multimodal therapy for anaplastic thyroid carcinoma has failed to improve overall survival. Toxicity rules out the high doses required, especially in older patients. The search for strategies to enhance paclitaxel antineoplastic activity and reduce its side effects is thus advisable. The study aimed to determine whether the histone deacetylase (HDAC) inhibitor valproic acid (VPA) improves the anticancer action of paclitaxel and elucidate the mechanisms underlying the effects of combined treatment. We examined the effect of VPA on the sensitivity to paclitaxel of two anaplastic thyroid carcinoma cell lines (CAL-62 and ARO), and the ability of the drug to determine tubulin acetylation and enhance paclitaxel-induced acetylation. The addition of as little as 0.7 mM VPA to paclitaxel enhances both cytostatic and cytotoxic effects of paclitaxel alone. Increased apoptosis explains the enhancement of the cytotoxic effect. The mechanism underlying this effect is through inhibition of HDAC6 activity, which leads to tubulin hyperacetylation. The results suggest a mechanistic link between HDAC6 inhibition, tubulin acetylation, and the VPA-induced enhancement of paclitaxel effects, and provide the rationale for designing future combination therapies.
authors.affiliation: Department of Clinical Pathophysiology, University of Turin, Via Genova, 3, 10126 Turin, Italy.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Catalano
authors.forename: Roberta
authors.initials: R
authors.lastname: Poli
authors.forename: Mariateresa
authors.initials: M
authors.lastname: Pugliese
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Fortunati
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Boccuzzi
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000123:Acetyltransferases / Q000378:metabolism*; D000972:Antineoplastic Agents, Phytogenic / Q000008:administration & dosage; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D017209:Apoptosis / Q000187:drug effects*; D002277:Carcinoma / Q000188:drug therapy*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D017239:Paclitaxel / Q000008:administration & dosage*; D013964:Thyroid Neoplasms / Q000188:drug therapy*; D014404:Tubulin / Q000378:metabolism*; D014635:Valproic Acid / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D014404:Tubulin; D014635:Valproic Acid; D000123:Acetyltransferases; D017239:Paclitaxel