Dual Inhibitor AEE788 Reduces Tumor Growth in Preclinical Models of Medulloblastoma.

Medulloblastoma is the most frequent malignant pediatric brain tumor with a dismal prognosis in 30% of cases. We examined the activity of AEE788, a dual inhibitor of human epidermal receptor (HER) 1/2 and vascular endothelial growth factor receptor (VEGFR) 1/2, in medulloblastoma preclinical models. Established lines (Daoy and D283), chemoresistant (Daoy(Pt)), and ectopically HER2-overexpressing (Daoy(HER2)) cells expressed diverse levels of total and activated AEE788 target receptors. In vitro, AEE788 inhibited cell proliferation (IC(50) from 1.7 to 3.8 µM) and prevented epidermal growth factor- and neuregulin-induced HER1, HER2, and HER3 activation. Inhibition of Akt paralleled that of HER receptors. In vivo, AEE788 growth inhibited Daoy, Daoy(Pt), and Daoy(HER2) xenografts by 51%, 45%, and 72%, respectively. Immunohistochemical analysis of mock- and HER2-transfected xenografts revealed that the latter showed, along with high HER2 expression, high VEGFR2 staining in tumor and endothelial cells and increased expression of the endothelial marker CD31. AEE788 reduced the activation of target receptors and angiogenesis. In 21 primary medulloblastoma, HER2 expression significantly correlated (P < .01) with VEGFR2 (r = 0.56) and VEGF (r = 0.61). In conclusion, AEE788 shows similar growth-suppressive activities in chemosensitive and chemoresistant medulloblastoma cells in vitro and in vivo. Ectopic HER2 overexpression sensitizes cells to AEE788 in vivo, but not in vitro, possibly through host-mediated processes. Together with the experimental data, the finding that HER2 positively correlates with VEGFR2 and VEGF in human medulloblastoma specimens indicates HER2-overexpressing medulloblastoma as the subset that most likely might benefit from AEE788 treatment.