Pheochromocytomas and paragangliomas are rare neuroendocrine tumors which develop from chromaffin cells of the adrenal medulla and extra-adrenal sites, leading to excess catecholamine release and hypertension. Many of the tumors are characterized by a high vascularity, suggesting the possible implementation of anti-angiogenic therapies for patients. Here, the efficacy of the tyrosine kinase inhibitors sunitinib and sorafenib was investigated in vivo and in vitro. Oral treatment with either sunitinib or sorafenib (40mg/kg/day) for 14days induced a marked reduction in the volume and weight of PC12 pheochromocytoma cell tumor xenografts in mice. Assessment of tumoral neo-angiogenesis, assessed by morphometric analysis of the vascular network after CD31 immunolabeling, showed that both sunitinib and sorafenib reduced the microvessel area (-85% and -80%, respectively) and length (-80% and -78%, respectively) in treated compared to control tumors. In addition, the number of vessel nodes was significantly lower in treated tumors (-95% and -84%, respectively). Furthermore, cleaved caspase 3 immunolabeling revealed a marked increase in the number of apoptotic cells in tumors from treated animals. Sunitinib and sorafenib could exert a direct effect on PC12 cell viability in vitro. While sunitinib induced a rapid (4h) and pronounced (5-fold) increase in caspase-3/7-dependent apoptosis, sorafenib seems to exert its cytotoxic activity through a different mechanism. Altogether, our data demonstrate that sunitinib and sorafenib have the ability to impair pheochromocytoma development by inhibiting angiogenesis and reducing tumor cell viability. These results strongly suggest that both sunitinib and sorafenib could represent valuable therapeutic tools for pheochromocytoma.

Neurogranin (Ng) is a brain-specific postsynaptic calmodulin-binding protein involved in synaptic activity-dependent plasticity. In the adult olfactory bulb (OB), Ng is expressed by a large population of GABAergic interneurons in the granule cell layer. We show here that, during postnatal development, Ng is also expressed by OB neurons in the superficial external plexiform layer (sEPL) and glomerular layer (GL). These Ng-positive neurons display morphological and neurochemical features of superficial and external tufted cells. Ng expression in these cells is transient during OB development: few elements express Ng at postnatal day (P) 5, increasing in number and reaching a peak at P10, then progressively decreasing. At P30, Ng is rarely detectable in these neurons. Ng expression in developing tufted cells is also modulated at the cellular level: at earlier stages, Ng labeling is distributed throughout the cell body and dendritic arborization in the GL, but, at P20, when the glomerular circuits are fully matured, Ng becomes restricted to the soma and proximal portion of tufted cell apical dendrites. We show that olfactory deprivation at early postnatal stages induces a strong increase in Ng-positive tufted cells from P10 to P20, whereas no changes have been observed following olfactory deprivation in adult mice. These findings demonstrate that Ng expression in sEPL-GL is restricted to developmental stages and indicate its activity-dependent regulation in a time window critical for glomerular circuit development, suggesting a role for Ng in maturation and dendritic remodeling of tufted cells.