Abstract 4347: Interphase reduction in ZEB1 and tubulin isotypes in breast cancer cells associated with antimitotic drug treatment

Abstract

Abstract We recently demonstrated that paclitaxel treatment (10X IC50) reduces mRNA for the epithelial to mesenchymal protein ZEB1 and β-tubulin isotype classes I, III and IVB in MDA-MB-231 breast cancer cells, commonly used as a model for triple-negative breast cancers [Lobert et al., Biochemistry Aug 13;52(32):5482-9]. This work showed that miR-200c, which regulates ZEB1, contributes to the changes in β-tubulin isotype mRNA. The current question is whether these parallel changes in ZEB1 and β-tubulin isotype mRNA were unique to antimitotic drug treatment. We treated MDA-MB-231 cells with equipotent (3X IC50) concentrations of paclitaxel, vincristine, eribulin or doxorubicin for 24 hours. Flow cytometry demonstrated that 27-30% of cells were in G2/M (paclitaxel, vincristine and eribulin) compared to 25% of control cells. Thus the cells had similar cell cycle profiles and were not blocked in mitosis. At 24 hours, there were no measurable changes in total tubulin protein by Western blotting. As shown previously, paclitaxel treatment significantly reduced ZEB1 and β-tubulin isotype classes I, III and IVB mRNA. Eribulin treatment significantly reduced ZEB1 and β-tubulin isotype classes I and IVB mRNA, but not β-tubulin class III. Vincristine treatment only reduced β-tubulin class I mRNA. These data together indicate that although antimitotic drugs all target tubulin, they alter signaling pathways that do not overlap. Doxorubicin did not reduce ZEB1 or β-tubulin isotypes; nor did it increase levels of miR-200c, suggesting that these changes may require tubulin or microtubules as a mediator of the effects. These data show that signaling during interphase is altered by antimitotic drug treatment, leading to changes in β-tubulin isotype mRNA levels. A reduction in β-tubulin isotype class III mRNA in interphase cells is associated specifically with paclitaxel treatment. Next generation sequencing for micro-RNAs comparing control cells to those treated with paclitaxel under the conditions described above suggests that nineteen micro-RNAs are either up or downregulated, indicating that the efficacy of paclitaxel may in part be due to micro-RNA regulation of mRNA. (supported by funding from UMMC School of Nursing) Note: This abstract was not presented at the meeting. Citation Format: Sharon Lobert, Mary E. Graichen. Interphase reduction in ZEB1 and tubulin isotypes in breast cancer cells associated with antimitotic drug treatment. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4347. doi:10.1158/1538-7445.AM2014-4347