In order to study the angiogenic activity of individual human tumors, microvessel density and vascular endothelial growth factor (VEGF) expression were determined in 152 human tumors of different localization (lung, ovary, breast, colon/rectum, kidney) using immunohistochemistry. Considerable variability in vascular density has been noted between different tumors with the same histology as well as between tumors of different localization. Kidney and breast carcinomas exhibited significantly higher vessel counts than carcinomas of other localization (p<0.001). In most tumor types (lung, breast, ovarian, nephroblastoma) about two-thirds of the tumors expressed VEGF. In contrast, only 7 out of 20 colorectal carcinomas (35%) and 9 out of 20 kidney carcinomas (45%) and all small cell lung carcinomas (13/13) were positive for VEGF, despite a relatively low vascularity. These results indicate that each single tumor has its own pattern of vascularity and its variable expression of VEGF and that the individual determination of the degree of vascularization together with the assessment of one or more angiogenic peptides may provide valid information on the angiogenic activity of a tumor. This may lead to identification of those patients who are more likely to have benefit from antiangiogenic therapies.

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