Circulating tumor cells exhibit stem cell characteristics in an orthotopic mouse model of colorectal cancer

Abstract

// Sebastian Schölch 1, * , Sebastián A. García 1, * , Naoki Iwata 2, * , Thomas Niemietz 3 , Alexander M. Betzler 1 , Lahiri K. Nanduri 1 , Ulrich Bork 1 , Christoph Kahlert 1 , May-Linn Thepkaysone 1 , Anka Swiersy 1 , Markus W. Büchler 3 , Christoph Reissfelder 1 , Jürgen Weitz 1 , Nuh N. Rahbari 1 1 Department of Gastrointestinal, Thoracic and Vascular Surgery, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany 2 Department of Gastroenterological Surgery, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan 3 Department of General, Gastrointestinal and Transplantation Surgery, University Hospital Heidelberg, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany * These author contributed equally to this work Correspondence to: Sebastian Schölch, email: sebastian.schoelch@uniklinikum-dresden.de Keywords: circulating tumor cells, colorectal cancer, mouse model, stem cells, metastasis Received: October 20, 2015      Accepted: March 14, 2016      Published: March 25, 2016 ABSTRACT The prognosis of colorectal cancer (CRC) is closely linked to the occurrence of distant metastases, which putatively develop from circulating tumor cells (CTCs) shed into circulation by the tumor. As far more CTCs are shed than eventually metastases develop, only a small subfraction of CTCs harbor full tumorigenic potential. The aim of this study was to further characterize CRC-derived CTCs to eventually identify the clinically relevant subfraction of CTCs. We established an orthotopic mouse model of CRC which reliably develops metastases and CTCs. We were able to culture the resulting CTCs in vitro , and demonstrated their tumor-forming capacity when re-injected into mice. The CTCs were then subjected to qPCR expression profiling, revealing downregulation of epithelial and proliferation markers. Genes associated with cell-cell adhesion (claudin-7, CD166) were significantly downregulated, indicating a more metastatic phenotype of CTCs compared to bulk tumor cells derived from hepatic metastases. The stem cell markers DLG7 and BMI1 were significantly upregulated in CTC, indicating a stem cell-like phenotype and increased capacity of tumor formation and self-renewal. In concert with their in vitro and in vivo tumorigenicity, these findings indicate stem cell properties of mouse-derived CTCs. In conclusion, we developed an orthotopic mouse model of CRC recapitulating the process of CRC dissemination. CTCs derived from this model exhibit stem-cell like characteristics and are able to form colonies in vitro and tumors in vivo . Our results provide new insight into the biology of CRC-derived CTCs and may provide new therapeutic targets in the metastatic cascade of CRC.