title: The synergistic combination of the farnesyl transferase inhibitor lonafarnib and paclitaxel enhances tubulin acetylation and requires a functional tubulin deacetylase.
abstract: Farnesyl transferase (FT) inhibitors (FTI) are anticancer agents developed to target oncogenic Ras proteins by inhibiting Ras farnesylation. FTIs potently synergize with paclitaxel and other microtubule-stabilizing drugs; however, the mechanistic basis underlying this synergistic interaction remains elusive. Here we show that the FTI lonafarnib affects the microtubule cytoskeleton resulting in microtubule bundle formation, increased microtubule stabilization and acetylation, and suppression of microtubule dynamics. Notably, treatment with the combination of low doses of lonafarnib with paclitaxel markedly enhanced tubulin acetylation (a marker of microtubule stability) as compared with either drug alone. This synergistic effect correlated with FT inhibition and was accompanied by a synergistic increase in mitotic arrest and cell death. Mechanistically, we show that the combination of lonafarnib and paclitaxel inhibits the in vitro deacetylating activity of the only known tubulin deacetylase, histone deacetylase 6 (HDAC6). In addition, the lonafarnib/taxane combination is synergistic only in cells lines expressing the wild-type HDAC6, but not a catalytic-mutant HDAC6, revealing that functional HDAC6 is required for the synergy of lonafarnib with taxanes. Furthermore, tubacin, a specific HDAC6 inhibitor, synergistically enhanced tubulin acetylation in combination with paclitaxel, similar to the combination of lonafarnib and paclitaxel. Taken together, these data suggest a relationship between FT inhibition, HDAC6 function, and cell death, providing insight into the putative molecular basis of the lonafarnib/taxane synergistic antiproliferative combination.
authors.affiliation: Winship Cancer Institute, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: Adam I
authors.initials: AI
authors.lastname: Marcus
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou
authors.forename: Aurora
authors.initials: A
authors.lastname: O'Brate
authors.forename: Ernest
authors.initials: E
authors.lastname: Hamel
authors.forename: Jason
authors.initials: J
authors.lastname: Wong
authors.forename: Michael
authors.initials: M
authors.lastname: Nivens
authors.forename: Adel
authors.initials: A
authors.lastname: El-Naggar
authors.forename: Tso-Pang
authors.initials: TP
authors.lastname: Yao
authors.forename: Fadlo R
authors.initials: FR
authors.lastname: Khuri
authors.forename: Paraskevi
authors.initials: P
authors.lastname: Giannakakou
mesh_terms: D000107:Acetylation / Q000187:drug effects; D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors*; D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D051231:Farnesyltranstransferase; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000378:metabolism; D051379:Mice; D008870:Microtubules / Q000187:drug effects; D008938:Mitosis / Q000187:drug effects; D041681:NIH 3T3 Cells; D017239:Paclitaxel / Q000008:administration & dosage / Q000494:pharmacology*; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology*; D011725:Pyridines / Q000008:administration & dosage / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism*; D003986:Dibenzocycloheptenes
chemical_list: D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase; D000073864:Histone Deacetylase 6; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases; D017239:Paclitaxel; D010880:Piperidines; D011725:Pyridines; D014404:Tubulin; C433811:HDAC6 protein, human; C499033:Hdac6 protein, mouse; C115354:lonafarnib; D003986:Dibenzocycloheptenes