Different vascular morphologies displayed a similar pattern of gene expression. High variability of vascular morphology was observed in tumors of large volume. Large lumen-containing vessels ((b, d) vessel lumen size > 25 μm) existed next to much smaller blood vessels that did not contain a visible lumen (a, c). (a, b) Immunohistochemical staining for CD31: pictures represent different regions within the same large tumor (Magnification 100x). (c, d) Cryosections from large tumors were stained with GSL-I IsolectinB4:FITC and the different vascular morphologies were separately isolated by laser microdissection along the depicted lines, magnification 400x. Microdissection of these different vascular phenotypes followed by gene expression profiling did not reveal a differential pattern of mRNA expression of angiogenesis- and vascular stability-regulating genes (e), nor of the Notch family of genes that has recently been identified to be important regulators of both angiogenic sprouting and endothelial-pericyte adhesion (f), but demonstrated that the lumen-containing vessels were associated with significantly higher levels of αSMA mRNA compared to the small vessels without lumen (g). (e)–(g) Mean values + SD of duplicate qPCR measurements of three large tumors. ND: not detectable. *.