Molecular analysis of a recurrent glioblastoma treated with bevacizumab

Abstract

We treated a case of recurrent glioblastoma (GBM) with bevacizumab and assessed its effect biologically. A 55-year-old man with a left frontal lobe GBM was experiencing recurrence 7months postoperation. We administered bevacizumab concomitant with temozolomide (TMZ). Follow-up magnetic resonance imaging (MRI) showed dramatic but temporal tumor reduction; however, the patient died of re-recurrent disease 6months after beginning bevacizumab. We obtained an autopsy and analyzed the detailed molecular change. In the autopsy specimen, the quantity of microvessels was significantly reduced. Vascular endothelial growth factor receptor (VEGFR) 1 and VEGFR2 were downregulated, most likely due to a negative feedback mechanism by blocking of VEGF signaling. Matrix metalloproteinase (MMP)-2 and membrane-type 1 MMP were upregulated, resulting in the higher activation of MMP-2 in the autopsy specimen. MIB-1 staining index and phosphorylation levels of p44/42-mitogen-activated protein kinase did not change, whereas phosphorylated protein kinase B (Akt) was decreased in the autopsy specimen, suggesting compensation and/or amplification of other proliferative signaling pathways such as suppression of apoptosis signaling. Consequently, bevacizumab might inhibit the VEGF autocrine loop, which then causes a change in molecular expression related not only to enhancement of tumor invasion but also maintenance of tumor proliferation.