gms | German Medical Science

62nd Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Polish Society of Neurosurgeons (PNCH)

German Society of Neurosurgery (DGNC)

7 - 11 May 2011, Hamburg

Suppression of carbonic anhydrase IX expression augments efficacy of radiation and chemotherapy in malignant glioma cells

Meeting Abstract

  • M. Proescholdt - Klinik für Neurochirurgie, Universitätsklinik Regensburg
  • E.M. Störr - Klinik für Neurochirurgie, Universitätsklinik Regensburg
  • A. Lohmeier - Klinik für Neurochirurgie, Universitätsklinik Regensburg
  • A. Brawanski - Klinik für Neurochirurgie, Universitätsklinik Regensburg

Deutsche Gesellschaft für Neurochirurgie. Polnische Gesellschaft für Neurochirurgen. 62. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit der Polnischen Gesellschaft für Neurochirurgen (PNCH). Hamburg, 07.-11.05.2011. Düsseldorf: German Medical Science GMS Publishing House; 2011. DocP 089

DOI: 10.3205/11dgnc310, URN: urn:nbn:de:0183-11dgnc3106

Published: April 28, 2011

© 2011 Proescholdt et al.
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Outline

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Objective: Concomittant radiochemotherapy utilizing external beam radiation and temozolomide (TMZ) is currently the standard postsurgical treatment for glioblastoma. However, despite improvement of radiation technique and the advent of intensified chemotherapy dosage regimen, virtually all patients display recurrent tumor indicating treatment failure. The hypoxia inducible carbonic anhydrase IX (CAIX) is highly expressed in glioblastoma, leading to production of bicarbonate ions and effective buffering of intracellular pH. Since transient acidification of intracellular pH is required for the induction of apoptotic cell death, due to both radio- and chemotherapy, we hypothesized that inhibition of CAIX expression may contribute to an enhanced efficacy of radiation or chemotherapy.

Methods: U251 glioblastoma cells were transfected with a CAIX siRNA construct utilizing lipofectamine 2000 (Invitrogen) as transfection reagent. As control served a non specific sequence siRNA. The cells were incubated in a humified 5% CO2 modular with either 21% oxygen and 25 mM glucose in the culture medium (ctrl.) or 0% oxygen plus 125 mM glucose (glycolysis). Cells were radiated using a linear accelerator with 10 Gy; TMZ treatment was performed at a concentration of 50 µM. Suppression of CAIX expression by siRNA was investigated by quantitative RTPCR and Western Blot. Cell toxicity was measured by a colorimetric assay (AQ assay, Promega), apoptotic cell death was investigated by annexin V labeling.

Results: Transfection with sequence specific siRNA lead to a 90% reduction of both CAIX mRNA and protein expression compared to the non specific control siRNA. Knockdown of CAIX expression caused a significantly higher efficacy of radiation and chemotherapy particularly under glycolytic conditions. In addition, annexin V labeling demonstrated an increased number of apoptotic cells upon CAIX knockdown in both treatment arms compared to the non specific control.

Conclusions: Our data demonstrate that CAIX overexpression, which has been found in more than 90% of all glioblastomas, reduces efficacy of adjuvant treatment such as chemotherapy and radiation treatment. Blocking CAIX activity may therefore be an additional target for glioblastoma treatment.