Assessment of epidermal growth factor receptor status in glioblastomas

Our previous study showed that a newly designed tracer radioiodinated 6-(3-morpholinopropoxy)-7-ethoxy-4-(3'-iodophenoxy)quinazoline ([(125)I]PYK) is promising for the evaluation of the epidermal growth factor receptor (EGFR) status and prediction of gefitinib treatment of non-small cell lung cancer. EGFR is over-expressed and mutated also in glioblastoma. In the present study, the expressions and mutation of EGFR were tested with [(125)I] PYK in glioblastoma in vitro and in vivo to determine whether this could be used to predict the sensitivity of glioblastoma to gefitinib treatment.

Glioblastoma cell lines with different expression of EGFR were tested. Growth inhibition of cell lines by gefitinib was assessed by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay. Uptake levels of [(125)I]PYK were evaluated in cell lines in vitro. Tumor targeting of [(125)I]PYK was examined by a biodistribution study and imaging by single photon emission computed tomography (SPECT).

High concentrations of gefitinib were needed to suppress EGFR-mediated proliferation. The uptake of [(125)I] PYK in cell lines in vitro was low, and showed no correlation with EGFR expression or mutation status. Biodistribution study and SPECT imaging with [(125)I]PYK for xenografts showed no [(125)I]PYK uptake.

The results showed prediction of gefitinib effectiveness was difficult in glioblastoma by [(125)I]PYK, which might be due to the complicated expression of EGFR status in glioblastoma. Thus, new tracers for sites downstream of the mutant EGFR should be investigated in further studies.