We're looking for a nice marker to detect tumor cells within glioma tissue. The tissue will be dissociated into a cell suspension. After that, we want to stain the suspension with a mixture of antibody-conjugates for flow-cytometric analysis to get an idea of the cellular composition of the tumor...
Can anyone suggest a marker (either extra- or intracellular) that is only/mostly expressed by tumor cells?
Hi. There is no universal marker or even handful of markers that will distinguish all glioma cells from normal brain. If that were the case I think we would have much more effective therapies. Perhaps you could target mutated proteins that are specific to some gliomas but the problem is that many of these events are mostly clonal and sometimes specific to tumour histology, grade or location. Also, by glioma do you mean all gliomas; i.e. pylocytic astrocytoma, diffuse glioma, anaplastic astrocytoma, GBM, oligodendroglioma, oligoastrocytoma, PXA, ganglioglioma, etc, etc.? Some low grade gliomas could be differentiated by BRAF V600E mutations (http://jco.ascopubs.org/content/31/14/e233.full). Low grade gliomas or secondary glioblastoma could be identified by IDH1/IDH2 mutations (http://www.ncbi.nlm.nih.gov/pubmed/23532369). Some glioblastomas could be identified by EGFRvIII expression (http://www.ncbi.nlm.nih.gov/pubmed/8586461) or mutations and/or overexpression in other RTKs. Some gliomas would have lack of staining for certain markers if they have mutations, for example ATRX which would be present in normal cells. Then there are markers which most gliomas may express but will likely be expressed in some normal tissue as well; GFAP (but present in normal astrocytes), SOX2 (http://www.fasebj.org/cgi/content/meeting_abstract/22/1_MeetingAbstracts/706.18), OLIG2 (http://www.ncbi.nlm.nih.gov/pubmed/15198128). Then you also have glioma stem cell markers such as CD133, CD15 etc., but then you would miss those tumour cells not expressing these markers. Many paediatric midline gliomas (brainstem/thalamic) and some supratentorial high-grades would have histone H3 mutations. This is just the tip of the iceberg. GL.
Thanks Pawel. I hope that the indicated publications will help us.
The point is that we don't know YET which glioma exactly it is. We get that information a few days after the tissue was removed. Of course, a combination of markers would also be possible...We'll see!
@Christopher
Thanks for the adding a great answer to this discussion. Although I most definitely agree that GFAP is not a good marker to differentiate tumour cells from normal brain cells, I'm a little surprised that only fewer than 5% of the samples you describe were positive for GFAP. There is vast literature describing GFAP immunopositivity having correlation with the WHO grading scheme of neuroglial tumours and indeed it is used regularly in the clinic as a tool in histopathological diagnosis. Yes, GFAP is not a high grade glioma biomarker, because low-grade gliomas, like diffuse astrocytomas (grade II) also express GFAP. Although by no means is this relationship universal, and GFAP immunopositivity can be varied in different glial tumours - weak, strong, diffuse etc., a complete absence of GFAP immunopositivity in a GBM would at least warrant an investigation into a differential diagnosis of a more primitive/embryonal entity, perhaps a PNET and I do not believe this is the case for >95% of high grade glioma patients.
Thanks Christopher!!!! Nice discussion already. I will comment here as soon as we have collected a few samples...
Galectin-1 could be interesting (see the attached articles).
Best regards
Robert
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