title: mRNA expression profiles in circulating tumor cells of metastatic colorectal cancer patients.
abstract: BACKGROUND
  The molecular characterization of circulating tumor cells (CTCs) is a promising tool for the repeated and non-invasive evaluation of predictive and prognostic factors. Challenges associated with CTC characterization using the only FDA approved method for CTC enumeration, the CellSearch technique, include the presence of an excess of leukocytes in CTC-enriched blood fractions. Here we aimed to identify colorectal tumor-specific gene expression levels in the blood of patients with and without detectable CTCs according to CellSearch criteria.
  
  
  METHODS
  Blood of 30 healthy donors (HDs) and 142 metastatic colorectal cancer (mCRC) patients was subjected to CellSearch CTC enumeration and isolation. In all samples, 95 mRNAs were measured by reverse transcriptase quantitative PCR (RT-qPCR). HD blood samples and patient samples with three or more CTCs were compared to identify CTC-specific mRNAs. Patient samples without detectable CTCs were separately analyzed.
  
  
  RESULTS
  Thirty-four CTC-specific mRNAs were higher expressed in patients with ≥3 CTCs compared with HDs (Mann-Whitney U-test P < 0.05). Among patients without detectable CTCs, a HD-unlike subgroup was identified which could be distinguished from HDs by the expression of epithelial genes such as KRT19, KRT20 and AGR2. Also, in an independent patient set, a similar HD-unlike group could be identified among the patients without detectable CTCs according to the CellSearch system.
  
  
  CONCLUSIONS
  Extensive molecular characterization of colorectal CTCs is feasible and a subgroup of patients without detectable CTCs according to CellSearch criteria bears circulating tumor load, which may have clinical consequences. This CTC-specific gene panel for mCRC patients may enable the exploration of CTC characterization as a novel means to further individualize cancer treatment.
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Bianca
authors: B
authors: Mostert
authors: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Anieta M
authors: AM
authors: Sieuwerts
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Joan
authors: J
authors: Bolt-de Vries
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Jaco
authors: J
authors: Kraan
authors: Department of Surgery, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Zarina
authors: Z
authors: Lalmahomed
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Anne
authors: A
authors: van Galen
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Petra
authors: P
authors: van der Spoel
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Vanja
authors: V
authors: de Weerd
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Raquel
authors: R
authors: Ramírez-Moreno
authors: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Marcel
authors: M
authors: Smid
authors: Department of Surgery, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Cornelis
authors: C
authors: Verhoef
authors: Department of Surgery, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Jan N M
authors: JN
authors: IJzermans
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Jan W
authors: JW
authors: Gratama
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands; Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: Stefan
authors: S
authors: Sleijfer
authors: Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands.
authors: John A
authors: JA
authors: Foekens
authors: Department of Medical Oncology and Cancer Genomics Netherlands, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands. Electronic address: j.martens@erasmusmc.nl.
authors: John W M
authors: JW
authors: Martens
mesh_terms: D014408:Biomarkers, Tumor / Q000378:metabolism; D002452:Cell Count; D016000:Cluster Analysis; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology*; D005260:Female; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009360:Neoplastic Cells, Circulating / Q000378:metabolism*; D011379:Prognosis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D014408:Biomarkers, Tumor; D012333:RNA, Messenger
keywords: Circulating tumor cells; Gene expression; Liver resection; Metastatic colorectal cancer; Real-time PCR
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