Abstract 2555: Class I β-tubulin mutations induce resistance to microtubule destabilizer through stabilization of the microtubule networks

Abstract

Abstract Anti-mitotic compounds such as vincristine, colchicine and paclitaxel have been developed to target microtubules in cancers. Although these compounds have been shown successful in treating various cancers, development of drug-resistance cells limits their efficacies in clinical situations. To determine possible mechanisms that are responsible for drug-resistance to microtubule de-stabilizers, KB-derived drug-resistant KB-L30 cells were developed. KB-L30 cells showed resistance to various microtubule de-stabilizers through multiple-drug resistant (MDR)-independent mechanisms. In contrast, this specific clone showed hyper-sensitized to the microtubule-stabilizer, paclitaxel. Single-strand conformation polymorphism (SSCP) analysis, RT-PCR and DNA sequencing revealed no mutation on exon 1, 2 and 3 of βI-tubulin. Surprisingly, six novel mutation sites were found present in the exon 4 of βI-tubulin gene. Transfection of the βI-tubulin-mutated construct into KB cells demonstrated that these mutations could alter its sensitivity to the microtubule de-stabilizer, BPR0L075, in vitro. On the other hand, western blot analysis revealed increased microtubule assembly and reduced microtubule dynamic instability in KB-L30 cells when compared to its parental KB cells. In addition, computational modeling indicated that a direct relationship exists between tubulin mutations and alteration in the microtubule assembly and dynamic instability in KB-L30 cells. In conclusion, we showed for the first time that mutations in exon 4 of βI-tubulin induced resistance to microtubule de-stabilizers and hyper-sensitivity to microtubule stabilizer through an alteration in the microtubule assembly and dynamics in cancer cells. The results of this study have important implications for the development of future anti-mitotic compounds that are able to target microtubule mutation-induced drug-resistant cancer cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2555.