title: Immune escape and survival mechanisms in circulating tumor cells of colorectal cancer.
abstract: The prognosis of colorectal cancer is closely linked to the occurrence of distant metastases. Systemic dissemination is most likely caused by circulating tumor cells (CTC). Despite the fundamental role of CTC within the metastatic cascade, technical obstacles have so far prevented detailed genomic and, in particular, phenotypic analyses of CTC, which may provide molecular targets to delay or prevent distant metastases. We show here a detailed genomic analysis of single colorectal cancer-derived CTC by array comparative genomic hybridization (aCGH), mutational profiling, and microsatellite instability (MSI) analysis. Furthermore, we report the first gene expression analysis of manually selected colorectal cancer-derived CTC by quantitative real-time PCR (qRT-PCR) to investigate transcriptional changes, enabling CTC to survive in circulation and form distant metastases. aCGH confirmed the tumor cell identity of CellSearch-isolated colorectal cancer-derived CTC. Mutational and MSI analyses revealed mutational profiles of CTC to be similar, but not identical to the corresponding tumor tissue. Several CTC exhibited mutations in key genes such as KRAS or TP53 that could not be detected in the tumor. Gene expression analyses revealed both a pronounced upregulation of CD47 as a potential immune-escape mechanism and a significant downregulation of several other pathways, suggesting a dormant state of viable CTC. Our results suggest mutational heterogeneity between tumor tissue and CTC that should be considered in future trials on targeted therapy and monitoring of response. The finding of upregulated immune-escape pathways, which may be responsible for survival of CTC in circulation, could provide a promising target to disrupt the metastatic cascade in colorectal cancer. Cancer Res; 74(6); 1694-704. ©2014 AACR.
authors.affiliation: Authors' Affiliations: Department of General, Gastrointestinal and Transplant Surgery; Department of Applied Tumor Biology, Institute of Pathology, University of Heidelberg; German Cancer Research Center, Division of Biostatistics, Heidelberg; Department of Gastrointestinal, Thoracic and Vascular Surgery, Medizinische Fakultät Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; Department of General, Visceral and Paediatric Surgery, Medical Faculty, University Hospital, Heinrich Heine University, Düsseldorf, Germany; and Edwin L. Steele Laboratory for Tumor Biology, Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Steinert
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schölch
authors.forename: Thomas
authors.initials: T
authors.lastname: Niemietz
authors.forename: Naoki
authors.initials: N
authors.lastname: Iwata
authors.forename: Sebastián A
authors.initials: SA
authors.lastname: García
authors.forename: Bianca
authors.initials: B
authors.lastname: Behrens
authors.forename: Anita
authors.initials: A
authors.lastname: Voigt
authors.forename: Matthias
authors.initials: M
authors.lastname: Kloor
authors.forename: Axel
authors.initials: A
authors.lastname: Benner
authors.forename: Ulrich
authors.initials: U
authors.lastname: Bork
authors.forename: Nuh N
authors.initials: NN
authors.lastname: Rahbari
authors.forename: Markus W
authors.initials: MW
authors.lastname: Büchler
authors.forename: Nikolas H
authors.initials: NH
authors.lastname: Stoecklein
authors.forename: Jürgen
authors.initials: J
authors.lastname: Weitz
authors.forename: Moritz
authors.initials: M
authors.lastname: Koch
mesh_terms: D002470:Cell Survival; D015179:Colorectal Neoplasms / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D004252:DNA Mutational Analysis; D019073:HT29 Cells; D006801:Humans; D053842:Microsatellite Instability; D009360:Neoplastic Cells, Circulating / Q000276:immunology / Q000378:metabolism*; D059467:Transcriptome; D019139:Tumor Escape