title: Inhibition of non-neuronal alpha7-nicotinic receptor reduces tumorigenicity in A549 NSCLC xenografts.
abstract: Nicotinic acetylcholine receptors (nAChR) are expressed on bronchial epithelial and non-small cell lung cancer cells and are involved in cell growth regulation. Nicotine (classical nAChR agonist) induced cell proliferation, whereas nAChR antagonists, d- tubocurarine or alpha-cobratoxin (alpha-CbT), induced cell death. In the current study, we further explored the antitumor potential mechanisms and activities of alpha-CbT. NOD/SCID mice were grafted intraperitoneally or orthotopically and treated with alpha-CbT. alpha-CbT treatment [0.04 ng/kg or 0.12 ng/kg] induced a strong reduction in tumor size ( approximately 90%) in comparison with mice treated with the vehicle alone. Tumor inhibition was related to severe induction of apoptosis. Moreover, neoangiogenesis was strongly inhibited (reduction of cells positive to vascular endothelial growth factor and CD31). Biochemical analyses of the cells, isolated by the primary lung tumor in alpha-CbT-treated mice, showed apoptosis features characterized by: (i) inhibition of BAD phosphorylation at Ser(112) and Ser(136); (ii) BAD dissociation from 14-3-3; (iii) BAD association with BCL-XL; and (iv) cleavage of caspase-9. Moreover, these cells were unable to grow in soft agar and develop tumor, when reinjected into mice. The small interfering RNA-mediated silencing of the alpha7-nAChR gene confirmed that alpha-CbT specifically inhibited the alpha7-nAChR-mediated survival pathway in A549 cells. Furthermore, the specificity of alpha-CbT is reinforced by the lack of effect of short chain toxin (Erabutoxin-a). Once more, the no effect of the low-affinity R33E-modified alpha-CbT strengthened the specificity of this inhibition. Although alpha7-nAChR antagonists, such as alpha-CbT, are unlikely to be a primary therapy, it may provide lead compounds for the design of clinically useful drugs.
authors.affiliation: Lung Cancer Unit, National Cancer Research Institute, Genoa, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Paleari
authors.forename: Fausto
authors.initials: F
authors.lastname: Sessa
authors.forename: Alessia
authors.initials: A
authors.lastname: Catassi
authors.forename: Denis
authors.initials: D
authors.lastname: Servent
authors.forename: Gilles
authors.initials: G
authors.lastname: Mourier
authors.forename: Guido
authors.initials: G
authors.lastname: Doria-Miglietta
authors.forename: Emanuela
authors.initials: E
authors.lastname: Ognio
authors.forename: Michele
authors.initials: M
authors.lastname: Cilli
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Dominioni
authors.forename: Massimo
authors.initials: M
authors.lastname: Paolucci
authors.forename: Andrea
authors.initials: A
authors.lastname: Calcaterra
authors.forename: Alfredo
authors.initials: A
authors.lastname: Cesario
authors.forename: Stefano
authors.initials: S
authors.lastname: Margaritora
authors.forename: Pierluigi
authors.initials: P
authors.lastname: Granone
authors.forename: Patrizia
authors.initials: P
authors.lastname: Russo