Figure 4.

Glomeruloid angiogenesis. A: Experimental brain metastases stained for laminin (green fluorescence) and CD31 (blue fluorescence), 28 days following intracarotid inoculation of the A2058 human melanoma cell line. Glomeruloid bodies are connected to each other by a capillary that is very small in diameter (arrows). The outlines of the metastases are clearly visible because of the strong laminin positivity of the tumor cells (arrowheads). B: Schematic representation of glomeruloid body formation. Following extravasation, the tumor cells (green) adhere firmly to the abluminal surface of the capillary basement membrane (gray). In the first step, because of the contractile force of the tumor cell a loop develops on the capillary. Proliferating tumor cells pull the capillary inward, resulting in the development of further loops and reduction of the diameter of the capillary segment lying outside the glomeruloid body. The last drawing shows the cross-section of a fully developed glomeruloid body built by ECs (red), pericytes (brown), and tumor cells (green). Extreme large cytoplasmic projections of the tumor cells adhere to different segments of the capillary.