KRAS genotypic changes of circulating tumor cells during treatment of patients with metastatic colorectal cancer

PLoS One. 2014 Aug 19;9(8):e104902. doi: 10.1371/journal.pone.0104902. eCollection 2014.


Introduction: Circulating tumor cells (CTCs) could represent a non-invasive source of cancer cells used for longitudinal monitoring of the tumoral mutation status throughout the course of the disease. The aims of the present study were to investigate the detection of KRAS mutations in CTCs from patients with metastatic colorectal cancer (mCRC) and to compare their mutation status during treatment or disease progression with that of the corresponding primary tumors.

Materials and methods: Identification of the seven most common KRAS mutations on codons 12 and 13 was performed by Peptide Nucleic Acid (PNA)-based qPCR method. The sensitivity of the assay was determined after isolation of KRAS mutant cancer cells spiked into healthy donors' blood, using the CellSearch Epithelial Cell kit. Consistent detection of KRAS mutations was achieved in samples containing at least 10 tumor cells/7.5 ml of blood.

Results: The clinical utility of the assay was assessed in 48 blood samples drawn from 31 patients with mCRC. All patients had PIK3CA and BRAF wild type primary tumors and 14 KRAS mutant tumors. CTCs were detected in 65% of specimens obtained from 74% of patients. KRAS mutation analysis in CTC-enriched specimens showed that 45% and 16.7% of patients with mutant and wild type primary tumors, respectively, had detectable mutations in their CTCs. Assessing KRAS mutations in serial blood samples revealed that individual patient's CTCs exhibited different mutational status of KRAS during treatment.

Conclusions: The current findings support the rationale for using the CTCs as a dynamic source of tumor cells which, by re-evaluating their KRAS mutation status, could predict, perhaps more accurately, the response of mCRC patients to targeted therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / drug therapy
  • Adenocarcinoma / genetics*
  • Adenocarcinoma / secondary
  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Monoclonal / administration & dosage
  • Antibodies, Monoclonal, Humanized / administration & dosage
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use
  • Bevacizumab
  • Colorectal Neoplasms / drug therapy
  • Colorectal Neoplasms / genetics*
  • Colorectal Neoplasms / pathology
  • Female
  • Fluorouracil / administration & dosage
  • Genotype
  • HCT116 Cells
  • Humans
  • Male
  • Middle Aged
  • Mutation, Missense
  • Neoplastic Cells, Circulating*
  • Panitumumab
  • Proto-Oncogene Proteins / genetics*
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins / genetics*


  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • KRAS protein, human
  • Proto-Oncogene Proteins
  • Bevacizumab
  • Panitumumab
  • Proto-Oncogene Proteins p21(ras)
  • ras Proteins
  • Fluorouracil

Grant support

This work was supported by research grants from the Cretan Association for Biomedical Research (CABR), the Hellenic Society of Medical Oncology (HeSMO) and the Operational Programme "Competitiveness & Entrepreneurship", National Strategic Reference Framework 2007-2013, National Action: "Cooperation", OncoSeed Diagnostics: Biology of Circulating Tumour Cells, Distant Metastasis & Development of Liquid Biopsy Methods; General Secretariat of Research and Technology of Greece. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.