Abstract 3603: Zidovudine (AZT)-induced aneuploidy, mediated by Stathmin 1 (STMN1), involves a loss of polymerized β-tubulin

The nucleoside reverse transcriptase inhibitor AZT induces multiple manifestations of genotoxicity, among which aneuploidy, observed as micronuclei containing whole chromosomes, has been reported (Borojerdi et al., Mut Res, 2009). We have seen a loss of β-tubulin polymerization in about 23% of normal human mammary epithelial cells (NHMECs) exposed for 24 hr to 200 μM AZT, and demonstrated down-regulation of hsa-miR-770-5p, a microRNA known to target STMN1, in the same AZT-exposed cells. STMN1 prevents microtubule polymerization, resulting in destabilization of the mitotic spindle and chromosome misalignment. We therefore hypothesized that, if AZT exposure downregulates hsa-miR-770-5p, there should be increased expression of STMN1, which would result in loss of microtubule polymerization leading to aneuploidy. In this study we exposed cells of the human breast line MCF-10A to 100 μM AZT continuously for 1 to 3 passages (P). By Western Blot we showed that total STMN1 was 3.5-fold increased at P1, in AZT-exposed cells, compared to the unexposed controls. Using the same STMN1 antiserum, by immunohistochemistry (IHC), we observed that some cells stained heavily for STMN1, while others had virtually no staining, and that the overall STMN1 fluorescence was increased in AZT-exposed cells, compared to unexposed controls. When tubulin polymerization was evaluated by IHC, using β-tubulin antiserum, 10.1% of AZT-exposed cells showed a loss of tubulin polymerization, while only 0.7% of unexposed cells showed the same effect (p=0.004). The data suggest that AZT induced aneuploidy may be mediated by inhibition of hsa-miR-770-5p, upregulation of STMN1, impaired polymerization of β-tubulin, aberrant mitotic spindle formation and consequent chromosome misalignment resulting in aneuploidy. If confirmed, this will constitute a novel mechanism of AZT-induced genotoxicity that may or may not be related to AZT-DNA incorporation. Ongoing experiments will explore these relationships further by localizing STMN1 and β-tubulin in specific cells, and examining the same cultures for spindle aberrations at mitosis. Citation Format: Andrea V. Rivera, Vanesa C. Sanchez, Miriam C. Poirier, Ofelia A. Olivero. Zidovudine (AZT)-induced aneuploidy, mediated by Stathmin 1 (STMN1), involves a loss of polymerized β-tubulin. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3603. doi:10.1158/1538-7445.AM2013-3603