IMMUNOHISTOLOGICAL ANALYSIS OF ANGIOGENIC FACTORS OTHER THAN VEGF IN GLIOBLASTOMAS IN RELATION TO THE USE OF BEVACIZUMAB

Abstract Although bevacizumab was shown to improve progression-free survival and performance status of the patients with high-grade gliomas, clinical trials consistently showed lack of benefit in terms of patients’ overall survival. The recurrent tumors are inevitably more aggressive and invasive as compared with the original tumors, and the in-situ observation in actual human specimens is essential to elucidate the mechanism of resistance. In Japan, bevacizumab was approved not only for recurrent but also for newly diagnosed cases. The safety as well as efficacy of resection following neoadjuvant bevacizumab has been reported, and a phase II study is currently ongoing (UMIN-000025579). In the present study, the expression of angiogenic factors other than VEGF (basic fibroblast growth factor (bFGF), placenral growth factor (PlGF), angiopoietin1/2 and ephrinA2) was investigated by immunohistochemistry to be compared among tumors with no previous bevacizumab treatment, those resected following bevacizumab, and those refractory to bevacizumab. Fifty-nine samples from 42 patients were included; 24 of newly diagnosed glioblastomas with no previous bevacizumab (naïve group), 16 resected following neoadjuvant bevacizumab (effective group), and 6 resected after recurrence or autopsied (refractory/autopsied group). 12 were paired samples (8 naïve and refractory, 4 effective and refractory). The expression of PlGF significantly increased in the effective group as compared with the naïve group (p=0.003). In the paired specimens, there was a trend towards increased expression of PlGF in the second specimens (refractory/autopsied group) as compared with the specimens of initial surgery (p=0.083). Angiopoietin1, angiopoietin2 and ephrinA2 were characteristically expressed in the microvessels less than 15μm. The increased expression of PlGF might be associated with the recurrence after bevacizumab.