Tunneling nanotubes (TnTs) represent a novel mechanism by which intercellular components such as proteins, Golgi vesicles, and mitochondria can be transferred from cell to cell in the complex tumor microenvironment. Here, we report data showing that microRNAs (miRNAs) are transferred through TnTs in osteosarcoma (OS) and ovarian cancer as in vitro model systems. miRNA array analysis demonstrated significant upregulation of miR-19a in OS tumors resected from human patients, and differential expression of miR-199a in ovarian cancer cell lines resistant or sensitive to platinum chemotherapy. K7M2 murine OS cells were transfected with miR-19a and cultured with nontransfected K7M2 cells in low-serum, hyperglycemic medium for up to 72 hours to induce TnT formation. miRNA transfer via TnTs was detected by time-lapse microscopic imaging. miR-19a was also transported via TnTs connecting transfected K7M2 cells and nontransfected stromal MC3T3 murine osteoblast cells. Similar findings were observed in studies of TnT-mediated transport of miR-199a among SKOV3 ovarian cancer cells and nonmalignant immortalized ovarian epithelial cells. To quantify TnT-mediated transport of miRNAs, we used modified Boyden chambers to separate miR-19a-transfected K7M2 cells (top chamber) and DiI-labeled MC3T3 cells (bottom chamber) compared with open culture of these cells. Fluorescence-activated cell sorting analysis of cells collected after 48 hours of culture indicated that miR-19a-positive MC3T3 cells were 3-fold higher in open culture; this finding suggests that miR-19a transfer occurred via TnTs, exclusive of other forms of cell-cell communication. These studies demonstrate that TnTs mediate direct transfer of genetic material between tumor and stromal cells.
Bibliographical noteFunding Information:
This research was kindly funded and supported in part by Minnesota Masonic Charities , Minnesota Medical Foundation (Grant number 4101-9225-12 ), Institutional Research Grant #118198-IRG-58-001-52-IRG94 and Research Grant RSG-13-381-01 from the American Cancer Society , the Deborah Powell Center for Women's Health at the University of Minnesota , (Grant number PCWH-2013-002 ) the National Pancreas Foundation (Grant number 00035607 ), Karen Wyckoff Rein in Sarcoma Foundation (Grant number 1914 ), and the UMN Clinical and Translational Science Institute KL2 Scholar Award (to E.L.; Grant number 8UL1TR000114 ). Research reported in this publication was supported by the National Center for Advancing Translational Sciences of the National Institutes of Health Award Number UL1TR000114. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.