Abstract A75: Circulating tumor cells in human breast cancer exhibit dynamic changes in epithelial and mesenchymal composition

Epithelial mesenchymal transition (EMT) has been postulated to contribute to the dissemination of cancer cells, but supporting histopathological evidence is limited. We used a microfluidic device to isolate circulating tumor cells (CTCs), combined with multiplex RNA-in-situ hybridization (ISH) and RNA sequencing, to quantify and characterize EMT in breast CTCs. Whereas only rare cells in the primary tumor expressed both mesenchymal and epithelial markers, such biphenotypic as well as purely mesenchymal cells were enriched among CTCs, across all histological subtypes of breast cancer. Analysis of treatment responses in 10 patients suggested an association of mesenchymal CTCs with disease progression. In an index patient followed longitudinally, fluctuation in epithelial and mesenchymal states was observed as a function of initial response and subsequent resistance to therapy. Mesenchymal markers were predominant in clusters of tumor cells, many of which had adherent platelets. Finally, RNA sequencing of CTC clusters identified EMT-related signatures, including FOXC1, a known transcriptional regulator of EMT. Together, these data support a role for EMT in the blood-borne dissemination of breast cancer and point to the dynamic nature of this cell fate change. Citation Format: Min Yu, Aditya Bardia, Ben Wittner, Shannon Stott, Malgorzata Smas, David Ting, Steven Isakoff, Jordan Ciciliano, Marissa Wells, Ajay Shah, Kyle Concannon, Maria Donaldson, Lecia Sequist, Elena Brachtel, Dennis Sgroi, Jose Baselga, Sridhar Ramaswamy, Mehmet Toner, Daniel Haber, Shyamala Maheswaran. Circulating tumor cells in human breast cancer exhibit dynamic changes in epithelial and mesenchymal composition. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A75.