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A cancer stem cell population in malignant brain tumors takes an essential part in brain tumor initiation, growth, and recurrence. Growth factors, such as epidermal growth factor, fibroblast growth factor-2, vascular endothelial growth factor, platelet-derived growth factor, and hepatocyte growth factor, are shown to support the proliferation of neural stem cells and also may play key roles in gliomagenesis. However, the responsible growth factor(s), which controls maintenance of brain tumor stem cells, is not yet uncovered. We have established three cancer stem cell lines from human gliomas. These cells were immunoreactive with the neuronal progenitor markers, nestin and CD133, and established tumors that closely resembled the features of original tumor upon transplantation into mouse brain. Three cell lines retained their self-renewal ability and proliferation only in the presence of epidermal growth factor (>2.5 ng/ml). In sharp contrast, other growth factors, including fibroblast growth factor-2, failed to support maintenance of these cells. The tyrosine kinase inhibitors of epidermal growth factor signaling (AG1478 and gefitinib) suppressed the proliferation and self-renewal of these cells. Gefitinib inhibited phosphorylation of epidermal growth factor receptor as well as Akt kinase and extracellular signal-regulated kinase 1/2. Flow cytometric analysis revealed that epidermal growth factor concentration-dependently increased the population of CD133-positive cells. Gefitinib significantly reduced CD133-positive fractions and also induced their apoptosis. These results indicate that maintenance of human brain tumor stem cells absolutely requires epidermal growth factor and that tyrosine kinase inhibitors of epidermal growth factor signaling potentially inhibit proliferation and induce apoptosis of these cells.

Objective-Although the majority of cases of Alzheimer disease (AD) are known to be attributable to the sporadic (nongenetic) form of the disease, the mechanism underlying its cause and progression still remains unclear. Methods and Results-We found that vascular ␤-amyloid (A␤), A␤40, inhibited the proliferative activity of human brain vascular endothelial cells (HBECs) without toxic effects on them. This peptide also inhibited tube formation and migration of HBECs. Moreover, A␤40 inhibited ex vivo hippocampal revascularization, reendothelialization, and the differentiation of adult endothelial progenitor cells. Importantly, A␤40 suppressed the proliferative activity of HBECs through the induction of "self-digesting" autophagy. This induction involved the intracellular regulation of class 3 phosphatidylinositol 3-kinase (PI3K) as well as Akt signaling in HBECs. Furthermore, tissue culture of murine brain sections from GFP-LC3 transgenic mice revealed that A␤40 not only reduced the vessel density in hippocampal lesions, but also induced autophagy in neurovascular ECs. Key Words: amyloid Ⅲ autophagy Ⅲ cerebrovascular disorders Ⅲ endothelium N early 100 years ago, Alolis Alzheimer first described a possible vascular disorder as well as neuronal lesions in Alzheimer disease (AD) patients. 1 AD is characterized by a progressive neuronal disorder that causes dementia and is recognized as a major cause of death in the elderly population. [1][2][3] The number of individuals with AD is currently 4.5 million in the United States and is predicted to triple by the year 2050 in industrial countries. However, no treatment can stop AD today. Like diabetes, 2 distinct conditions exist in AD: rare early-onset inherited familial cases, which account for only about 5% of cases, and nongenetic sporadic cases, which account for more than 90% of AD. 4 The typical features of AD are A␤-containing plaques and -containing neurofibrillary tangles in the diseased brain. A␤42, a minor product of amyloid precursor protein (APP), has been extensively focused on in rare familial AD, not because it composes plaque but because its overproduction is associated with genetic abnormality of the APP, presenilin-1, and presenilin-2 genes. In contrast, A␤40 (A␤1-40), whose overproduction is not associated with presenilin mutations, predominantly exists around vessels and accumulates as a major component of vascular amyloid deposits, 5 suggesting possible involvement of A␤40 in neurovascular dysfunction in sporadic AD. However, it is still unclear how A␤40 is involved in the pathogenesis of AD. Conclusions-OurIn the field of vascular biology, it is realized that vascular formation is essential not only for embryonic organ development but also for adult tissue regeneration. 6,7 Together with the recent interpretations that sporadic AD is thought to be associated with vascular disease such as cardiovascular disease, stroke, and atherosclerosis, 8 we hypothesized that A␤40 might induce phenotypic alterations in neurovascular ECs, which then causes neurovas...