Spatiotemporally controlled induction of gene expression in vivo allows tracking the fate of tumor cells that traffic through the lymphatics

• Published in: International journal of cancer 2020-08, Vol.147 (4), p.1190-1198
• Main Authors: Grau, Nicole, Scherer, Sandra D., Rothley, Melanie, Roßwag, Sven, Thiele, Wilko, Stoecklein, Nikolas H., Cremers, Natascha, Thaler, Sonja, Garvalov, Boyan K., Sleeman, Jonathan P.
• Format: Article
• Language: English
• Subjects: Animals; Cancer; Cell Line, Tumor; Cell Movement - genetics; cell tracking; Gene expression; Gene Expression Regulation, Neoplastic; genetic switch; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; heat‐inducible expression; Humans; Luminescent Proteins - genetics; Luminescent Proteins - metabolism; Lung Neoplasms - genetics; Lung Neoplasms - metabolism; Lung Neoplasms - secondary; lymph node; Lymph nodes; Lymph Nodes - pathology; Lymphatic Metastasis; Lymphatic system; Lymphatic System - pathology; Medical research; Metastases; Metastasis; Neoplasms - genetics; Neoplasms - metabolism; Neoplasms - pathology; Neoplastic Cells, Circulating - metabolism; Neoplastic Cells, Circulating - pathology; Pancreatic cancer; Rats; Red Fluorescent Protein; Spatio-Temporal Analysis; Tumor cells
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.32766

Metastasis is a multistep process, during which circulating tumor cells traffic through diverse anatomical locations. Stable inducible marking of tumor cells in a manner that is tightly spatially and temporally controlled would allow tracking the contribution of cells passing through specific locations to metastatic dissemination. For example, tumor cells enter the lymphatic system and can form metastases in regional lymph nodes, but the relative contribution of tumor cells that traffic through the lymphatic system to the formation of distant metastases remains controversial. Here, we developed a novel genetic switch based on mild transient warming (TW) that allows cells to be marked in a defined spatiotemporal manner in vivo. Prior to warming, cells express only EGFP. Upon TW, the EGFP gene is excised and expression of mCherry is permanently turned on. We employed this system in an experimental pancreatic cancer model and used localized TW to induce the genetic switch in tumor cells trafficking through tumor‐draining lymph nodes. Thereby we found that tumor cells disseminating via the lymphatics make a major contribution to the seeding of lung metastases. The inducible genetic marking system we have developed is a powerful tool for the tracking of metastasizing cells in vivo. What's new? Tracking tumor cells as they move through tissues on their way to colonizing distant organs can provide important insight into the metastatic process. Methods to accurately track tumor cell movement, particularly through the lymphatic system, however, have been lacking. Here, the authors developed a novel system employing a genetic switch from green fluorescent protein expression to red fluorescent protein expression to track tumor cells in an in vivo model. The switch, induced in a spatio‐temporally controlled manner by mild transient warming, permanently marked tumor cells, allowing the cells to be successfully followed through the lymphatics to their final destinations.