Does the serpin PI-9 protect tumor cells?

no proof that low VEGF levels contribute to neurodegeneration. It is possible that low levels of VEGF are neuroprotective, while high levels cause neuronal sheath edema and ischemic polyneuropathy. 3 VEGF's effects on the endothelial cells are more complicated. VEGF increases vascular permeability and promotes angiogenesis by stimulating endothelial-cell growth. 4 Extensive apoptosis of endothelial cells as suggested by Straume et al could have catastrophic consequences such as bleeding, a known side effect of bevacizumab. Although the data are limited, we hypothesize that endothelial damage stimulates platelet aggregation and release of VEGF that is stored at high levels in the platelets, thus maintaining adequate VEGF levels locally to preserve the newly formed blood vessels. It is worth noting that inhibition of platelet function has resulted in decreased VEGF levels and clinical improvement in POEMS. 5 Understating the cause and source of VEGF overproduction in POEMS will help define the role of bevacizumab, if any, in the treatment of this disorder. In the absence of clinical trials, bevacizumab should be carefully considered in selected POEMS patients as adjuvant to conventional chemotherapy, and when used, patients must be monitored carefully for potential toxicities.