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Fig. 4. Tie-2 staining is increased when tumour cells are present. (A) HUVECs were
cultured on Transwell inserts as for net-like formation and stained with CD31
or with Tie-2. Staining is comparable in cells in monoculture and in
co-culture for CD-31, but Tie-2 staining is visible only in HUVECs cultured
with U87 in the well. (B) Control brain tissue is compared with tissue from
U87 xenografts. CD31 staining is not significantly different in control and
tumour sections, with only endothelial cells in vessel lumina staining
positive. For Tie-2, staining is visible in vessels in control tissue. In U87
xenografts, more structures are Tie-2 positive, possibly caused by an
increased number of microvessels.