Replies to post #476 on Entremed (ENMD)

[docaaron1]

Jento, C-peptide: I have to admit that this discussion is a bit over my head. I take it that the significance of this mouse endothelial BM study is that it conflicts with the usefulness of the following study and “appears” to make it obsolete. I said appears because the mice to man model does not hold up in this case due to mice not needing to call on BM endothelial cells until they are much older. Do I understand the discussion correctly?

Endostatin inhibits the vascular endothelial growth factor-induced mobilization of endothelial progenitor cells.

Schuch G, Heymach JV, Nomi M, Machluf M, Force J, Atala A, Eder JP Jr, Folkman J, Soker S.

Department of Urology, Children's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.

Circulating endothelial cells (CECs) are present in peripheral blood and have been shown to contribute to normal and pathological neovascularization. Antiangiogenic molecules can inhibit neovascularization in tumors and other sites, but their effect on CECs has not yet been determined. We hypothesize that angiogenic factors will increase the number of CECs, and conversely, antiangiogenic treatment will reduce these numbers. Mice treated with high levels of vascular endothelial growth factor (VEGF) showed increased numbers of Flk-1-positive cells in peripheral blood and endothelial cell colonies compared with vehicle-treated controls. These changes were accompanied by increased bone marrow neovascularization. In contrast, mice that received VEGF and endostatin had significantly lower numbers of CECs and reduced bone marrow vascularization. Endostatin-induced apoptosis was probably responsible for the decreased number of CECs. Systemic delivery of a VEGF antagonist, soluble Flt-1, also inhibited the VEGF-induced increase in CECs. These results were further confirmed in a Tie2/LacZ mouse model, in which endostatin reduced the number of beta-galactosidase-expressing peripheral blood mononuclear cells. We propose that endothelial progenitor cells are a novel target for endostatin and suggest that the relative numbers of CECs can serve as a surrogate marker for the biological activity of antiangiogenic treatment.

PMID: 14678995 [PubMed - indexed for MEDLINE]