Tunneling nanotubes and intercellular communication: Differences between platinum-resistant and platinum-sensitive ovarian cancer.

Abstract

e22007 Background: Preliminary evidence suggests that cell-to-cell communication may be responsible for the development of chemotherapy resistance in ovarian cancer. We propose tunneling nanotubes (TnTs) – long, thin actin-based cell extensions – as novel candidates to explain direct communication between treatment-refractory malignant ovarian cells. The purpose of this study was to investigate TnT formation between ovarian cancer cells in vitro. Methods: Using platinum-sensitive (A2780) and resistant (C200 and SKOV3, as well as ES2) ovarian cancer cell lines, we tested various conditions to assess factors affecting TnT formation. Scratch assays were utilized as a 2-dimensional simulation of ovarian cancer invasion. To assess TnTs as a conduit for transmission of therapeutic drugs between connected cells, we used doxorubicin, which auto-fluoresces in cell culture. Results: We determined that a hyperglycemic, low-serum, acidic medium stimulated TnT formation between all ovarian cancer cells studied, and more significantly, formed direct connections between A2780 to both C200 and SKOV3 cell lines. Conversely, Everolimus or Metformin decreased TnT formation in all cell lines with continuous exposure up to 96 hours; most prominently for the platinum-sensitive cell line. Time-lapse microscopy was used to assess chronologic formation of TnTs at the advancing front of the scratch wound. Cell proliferation assays were performed and confirmed the decrease in TnTs was not due to decreased cell proliferation. We directly observed fluorescing doxorubicin within the TnTs, suggesting TnTs act as a transport mechanism for cellular communication. Conclusions: TnT formation is stimulated in conditions of cellular stress similar to those experienced in vivo and results in direct connections between cells. Our data suggests that these conduits are a potential means of cellular exchange between platinum-sensitive and resistant ovarian cancer cells. Using currently available agents to target TnTs and disrupt this communication provides a novel approach to understanding and treating the problem of platinum resistance in ovarian cancer.