title: Tubulin-targeted drug action: functional significance of class ii and class IVb beta-tubulin in vinca alkaloid sensitivity.
abstract: Aberrant expression of beta-tubulin isotypes is frequently described in tumor tissues and tubulin-binding agent (TBA)-resistant cell lines. There is limited understanding of the role of specific beta-tubulin isotypes in cellular sensitivity to TBAs, and to gain insights into the functional role of betaII- and betaIVb-tubulin, we examined these isotypes in lung cancer cell lines NCI-H460 (H460) and Calu-6. Drug-treated clonogenic assays revealed that small interfering RNA-mediated knockdown of either betaII- or betaIVb-tubulin hypersensitized the lung cancer cell lines to Vinca alkaloids, with the effects more pronounced following betaIVb-tubulin knockdown. In contrast, there was no change in paclitaxel sensitivity following knockdown of either isotype. Cell cycle analysis revealed a greater propensity for the betaII- and betaIVb-tubulin knockdown cells to undergo G2-M cell cycle block following 5 nmol/L vincristine treatment, with the betaIVb knockdown cells being more sensitive than the betaII-tubulin knockdown cells compared with control. In contrast to betaII-tubulin knockdown, betaIVb-tubulin knockdown cells showed a significant increase in the sub-G1 population (cell death) following treatment with both 5 and 40 nmol/L of vincristine compared with controls. Importantly, betaIVb-tubulin knockdown in H460 cells caused a significant dose-dependent increase in Annexin V staining in response to vincristine but not paclitaxel. Therefore, increased sensitivity to induction of apoptosis is one mechanism underlying the Vinca alkaloid hypersensitivity. This study provides direct evidence that betaII- or betaIVb-tubulins have functionally distinct roles and expression of these isotypes may serve as strong predictors of Vinca alkaloid response and resistance.
authors.affiliation: Children's Cancer Institute Australia for Medical Research, Randwick, New South Wales, Australia.
authors.forename: Pei Pei
authors.initials: PP
authors.lastname: Gan
authors.forename: Maria
authors.initials: M
authors.lastname: Kavallaris
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D016503:Drug Delivery Systems / Q000379:methods; D016195:G2 Phase / Q000187:drug effects; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D017239:Paclitaxel / Q000493:pharmacokinetics / Q000494:pharmacology; D020033:Protein Isoforms; D034622:RNA Interference; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection; D014404:Tubulin / Q000096:biosynthesis / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D014747:Vinblastine / Q000031:analogs & derivatives / Q000493:pharmacokinetics / Q000494:pharmacology; D014748:Vinca Alkaloids / Q000493:pharmacokinetics / Q000494:pharmacology*; D014750:Vincristine / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014404:Tubulin; D014748:Vinca Alkaloids; C111217:vinflunine; D014750:Vincristine; D014747:Vinblastine; D017239:Paclitaxel