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Thoas Fioretos

Thoas Fioretos

Research team manager

Thoas Fioretos

Leukemic stem cell quantification in newly diagnosed chronic myeloid leukemia patients predicts response to nilotinib therapy


  • Noortje Thielen
  • Johan Richter
  • Matthias Baldauf
  • Gisela Barbany
  • Thoas Fioretos
  • Francis Giles
  • Bjørn Tore Gjertsen
  • Andreas Hochhaus
  • Gerrit Jan Schuurhuis
  • Sieghart Sopper
  • Leif Stenke
  • Sarah Thunberg
  • Dominik Wolf
  • Gert Ossenkoppele
  • Kimmo Porkka
  • Jeroen Janssen
  • Satu Mustjoki

Summary, in English

PURPOSE: Leukemic stem cells (LSCs) may harbor important resistance to tyrosine kinase inhibitors in chronic myeloid leukemia (CML). We identified Philadelphia chromosome (Ph) positive CD34+CD38- bone marrow cells (here denoted LSCs) and addressed their response-predictive value in CML patients (n=48) subjected to nilotinib in the ENEST1st trial (NCT01061177).

EXPERIMENTAL DESIGN: Two flow cytometry-based cell sorting methods were employed with multiparameter-directed CD45- (MPFC) and BCR-ABL1 probe-linked (FISH) identification of Ph-positive cells, respectively.

RESULTS: We observed a positive correlation between the proportion of LSCs at diagnosis and established prognostic markers (blast count, spleen size, Sokal score, hemoglobin). Conversely, a high LSC burden predicted for an inferior molecular response at 3 (MPFC, FISH), 6 (MPFC), 9 (FISH) and 15 months (FISH). During nilotinib therapy, the proportion of LSCs decreased rapidly. At 3 months, a median of only 0.3% LSCs remained among CD34+CD38- cells, and in 33% of the patients the LSC clone was not detectable anymore (FISH). The response kinetics was similar in LSC fractions as it was in the progenitor and unseparated bone marrow cell fractions.

CONCLUSION: The proportion of LSCs at diagnosis, as analyzed by two independent methodologies, reflects the biology of the disease and appeared as a prognostic and response-predictive marker in CML patients subjected to first-line nilotinib therapy.


  • Division of Molecular Medicine and Gene Therapy
  • Division of Clinical Genetics
  • BioCARE: Biomarkers in Cancer Medicine improving Health Care, Education and Innovation
  • StemTherapy: National Initiative on Stem Cells for Regenerative Therapy

Publishing year







Clinical Cancer Research





Document type

Journal article


American Association for Cancer Research


  • Cell and Molecular Biology




  • ISSN: 1078-0432