Article abstract

Nature Methods 7, 224 - 228 (2010)
Published online: 21 February 2010 | Retracted online: 8 September 2013 | doi:10.1038/nmeth.1430

There is a Retraction (October 2013) associated with this Article.

Retracted: Marker-independent identification of glioma-initiating cells

Virginie Clément1, Denis Marino1, Cristina Cudalbu2, Marie-France Hamou3, Vladimir Mlynarik2, Nicolas de Tribolet1, Pierre-Yves Dietrich4, Rolf Gruetter2, Monika E Hegi3 & Ivan Radovanovic1

Tumor-initiating cells with stem cell properties are believed to sustain the growth of gliomas, but proposed markers such as CD133 cannot be used to identify these cells with sufficient specificity. We report an alternative isolation method purely based on phenotypic qualities of glioma-initiating cells (GICs), avoiding the use of molecular markers. We exploited intrinsic autofluorescence properties and a distinctive morphology to isolate a subpopulation of cells (FL1+) from human glioma or glioma cultures. FL1+ cells are capable of self-renewal in vitro, tumorigenesis in vivo and preferentially express stem cell genes. The FL1+ phenotype did not correlate with the expression of proposed GIC markers. Our data propose an alternative approach to investigate tumor-initiating potential in gliomas and to advance the development of new therapies and diagnostics.

  1. Division of Neurosurgery, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.
  2. Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland.
  3. Laboratory of Brain Tumor Biology and Genetics, Department of Neurosurgery, University Hospital Lausanne and University of Lausanne, Lausanne, Switzerland.
  4. Department of Oncology, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.

Correspondence to: Ivan Radovanovic1 e-mail:

* In the version of this article initially published, we described a method to identify tumor-initiating cells from human primary gliomasphere cell cultures or directly from fresh human glioma specimens. We used FACS analysis to describe a tumor-initiating cell subpopulation that displayed a specific morphology (high forward scatter, low side scatter) and had high fluorescence in the FL1 channel of the FACS (excitation at 488 nm, emission at 520 nm). We have since become aware that the majority of the primary gliomasphere lines (7 of 10) used in this paper were contaminated with HEK cells expressing GFP. We had used these sphere cultures to illustrate the selection method, to measure self-renewal, to assess the expression of stemness genes and to test for tumorigenicity.

As assessed by microsatellite analysis of 15 short tandem repeats, seven of the primary sphere cultures used in this paper and all of the three lines used for tumorigenicity experiments did not match their parental tissue, and their genetic profile was consistent with that of HEK cells. We further observed expression of GFP mRNA with reverse-transcription PCR in 7 of the 10 gliomasphere lines. Two of these lines (GSM-1 and OA-III-1) were traceable by microsatellite analysis to their parental tissue at low passages (2–9) but not at higher passages (>20), a result showing that contamination occurred during passage of the cells in the laboratory.

We also described experiments done with cells prospectively isolated from freshly resected glioma tissues; we believe that these experiments remain valid. We discussed in the paper that these cells were rare and did not have the same high fluorescence as gliomasphere cultures. We speculated that glioma cells acquire high fluorescence under in vitro conditions. This led to our misinterpretation of the progressive increase in fluorescence of two of the gliomasphere cultures that were in fact being progressively overgrown by contaminating GFP-expressing HEK cells.

All together, when we exclude HEK-contaminated cultures, we must conclude that glioma-initiating cells do not have high autofluorescence levels or acquire them during culture. Selection of a tumorigenic fraction may be possible on the basis of morphological characteristics. However, because an important part of the study was done on contaminated cells, we wish to retract the paper. We deeply apologize to the scientific community for erroneously reporting an artifactual phenomenon as well as for the delay in detecting, characterizing and reporting the error.

Cross-contamination of cell cultures is likely to be a frequent problem. Routine tracing of cell lines by microsatellite analysis has been advocated before publishing work with cell lines. Our experience shows that this advice holds true also for primary cells passaged in culture.


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