Intercellular communication is a fundamental mechanism for maintaining cell homeostasis, facilitating the evolution of multicellular organisms. Classical modes of intercellular communication primarily focus on paracrine and endocrine signaling mechanisms or direct cellular exchange of cytoplasmic contents through gap-junctions. Recently, a novel mechanism of cellular communication was discovered that allows for direct transfer of intercellular contents through thin nanotubular projections forming continuous connections between cells. These structures, referred to as tunneling nanotubes (TNTs), have been found in a variety of eukaryotic and prokaryotic cell types. TNTs mediate transfer of a diverse array of intercellular contents including organelles, proteins, and pathogens. Here we report, TNTs allow for intercellular communication between metastatic breast cancer cells and the endothelium, introducing a potentially novel mechanism for breast cancer progression. Human endothelial cells were allowed to undergo tubulogenesis in a 3D matrigel matrix. To the preformed endothelial vessels, metastatic breast cancer MDA-MB-231 cells were added. The resulting phenotype was characterized using both fluorescent and electron microscopy. Interestingly, when added to the human endothelial cells, the metastatic breast cancer cells preferentially align and incorporate within the endothelial vessels, invading the tubular structures, instead of forming the expected mammary bodies. The physical proximity between the cell types facilitates the formation of TNTs that originate from the metastatic breast cancer cells to form continuous membrane connections with the endothelial vessels. To test for transfer of intercellular contents, the metastatic breast cancer cells were loaded with fluorescently labeled small molecules. Transfer of intercellular contents was quantified using both fluorescent microscopy and flow cytometry. The TNTs were found to transfer a variety of intercellular contents from the metastatic cells to the endothelium including green fluorescent protein, CFSE, and quantum dots. Between 20-40% of the isolated endothelial cell population received transfer of intercellular contents from the metastatic cells. Communication via the TNTs occurred quickly, with the membrane structures forming 4-6hrs post seeding, and intercellular transfer beginning at 6hrs and peaking at approximately 16-20hrs. In conclusion, TNTs provide a novel mechanism for communication between the tumor compartment and the angiogenic component, introducing a new paradigm of cancer progression where tumor cells can directly manipulate the surrounding cell populations to facilitate cancer pathology.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4222. doi:1538-7445.AM2012-4222