Abstract 1480: The effect of Metformin on microtentacle formation and stabilization in breast cancer cells.

Abstract

Abstract Metastasis is one of the main causes of mortality in women with breast cancer. Epithelial-to-mesenchymal transition (EMT) has emerged to be a key mediator of breast cancer metastasis. It has previously been shown that EMT can stabilize and increase microtentacles (McTNs) in breast cancer cell lines and enhance their metastatic potential. McTNs are dynamic, microtubule-enriched plasma membrane extensions that are stabilized with the exposure of a carboxy-terminal glutamic acid residue in alpha-tubulin (Glu-tubulin). McTN stabilization has been shown to promote tumor cell aggregation and reattachment in vitro. In this study, we investigated the effect of EMT suppression on McTN formation and stabilization in breast cancer cells by the dimethyl biguanide, Metformin. While it is widely used to treat type 2 diabetes, Metformin has more recently been shown to inhibit EMT in multiple breast cancer cell lines. We show here that Metformin decreased mesenchymal markers, such as N-cadherin and vimentin, in a dose-dependent manner in MDA-MB-231 breast cancer cells. Confocal and fluorescent microscopy was used to visualize and quantify McTN formation in these cells. There was a significant decrease in McTNs in MDA-MB-231 cells treated with 5mM Metformin for 24 hours. We correlated the decrease in the number of McTNs with a decrease in Glu-tubulin protein levels, which suggests that Metformin also inhibits McTN stabilization. The decrease in McTN formation and stabilization was also associated with diminished tumor cell reattachment in vitro. In addition, Metformin was able to protect MDA-MB-231 cells from increased McTN formation induced by the microtubule stabilizing agent, Taxol. Metformin's mechanism of action on breast cancer cells to elicit these cytoskeletal modifications has yet to be elucidated. However, these results suggest a role for Metformin at multiple stages of tumor progression to protect breast cancer patients from clinical spread of disease. Citation Format: Kristi Chakrabarti, Rebecca A. Whipple, Amanda E. Boggs, Monica S. Charpentier, Jana Slovic, Michele I. Vitolo, Stuart S. Martin. The effect of Metformin on microtentacle formation and stabilization in breast cancer cells. [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 1480. doi:10.1158/1538-7445.AM2013-1480