Abstract 1464: EMT-induced tubulin detyrosination can be inhibited with parthenolide, reducing microtentacles and the lung retention of circulating breast tumor cells

Abstract

Abstract Epithelial-to-mesenchymal transition (EMT) is associated with increased breast tumor metastasis, although the specific mechanism by which EMT increases metastasis remains somewhat unclear. We have previously demonstrated that detached human breast tumor cells generate unique microtentacle (McTN) extensions of their plasma membrane that are supported by coordinated vimentin intermediate filaments and detyrosinated microtubules. Microtentacles are specifically induced by EMT and promote the reattachment of tumor cells to each other and endothelial cell layers. We report here that immunohistochemical staining of tumor sections from patients with ductal carcinoma in situ and invasive ductal carcinoma indicates that detyrosination of α-tubulin occurs at invasive fronts where tumor cells are moving through the stromal microenvironment. Costaining with the EMT marker, Twist, demonstrates that tubulin detyrosination occurs specifically within cells that are undergoing EMT. Exogenous expression of either Twist or Snail in immortalized human mammary epithelial cells leads to a downregulation of the tubulin tyrosine ligase (TTL) enzyme that catalyzes the readdition of tyrosine to α-tubulin. This provides a novel molecular mechanism for the increase in detyrosinated microtubules observed in cells undergoing EMT. Addition of the sesquiterpene lactone, Parthenolide, to breast tumor cells reversed this EMT-induced increase in detyrosinated tubulin. Treatment of either breast tumor cells or nontumorigenic MCF10A mammary epithelial cells with 10μM Parthenolide also led to reductions in microtentacles, without affecting cell viability. Given the role of microtentacles in adhesion to endothelial layers, whole-animal bioluminescence imaging was used to track circulating tumor cells following tail vein injection. Pretreating metastatic MDA-MB-231 cells with Parthenolide prior to tail vein injection caused up to a 75% decrease in the lung retention of circulating tumor cells. These data support a model where the tubulin detyrosination that supports microtentacles promotes the ability of circulating tumor cells to reattach in distant capillary beds. Furthermore, the tubulin detyrosination that occurs in cells undergoing EMT at invasive tumor fronts could prime these cells for metastatic success once entering the circulation. These findings provide a possible explanation for why increased levels of detyrosinated tubulin are associated with poor patient survival in breast cancer and a new potential mechanism for how EMT could promote tumor metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1464.