Tubulin-targeted drug action: functional significance of class ii and class IVb beta-tubulin in vinca alkaloid sensitivity.
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.
Gan
Pei Pei
PP
Children's Cancer Institute Australia for Medical Research, Randwick, New South Wales, Australia.
Kavallaris
Maria
M
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
D020033:Protein Isoforms; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D014404:Tubulin; D014748:Vinca Alkaloids; C111217:vinflunine; D014750:Vincristine; D014747:Vinblastine; D017239:Paclitaxel