Figure 2: Angiotropism of human melanoma cells in the murine brain tumor.

The left panels show representative images of the progression of C8161-induced tumor (green) in coronal sections at one week (A), two weeks (B) and four weeks (C) after injection. The right panels show a magnification of the hatched inset areas from the corresponding left panels. Insets on the right are images of vessels (red) in the absence of the green channels (i.e. the tumor melanoma cells). (A) Note initial sprouting of melanoma cells (green) beyond the solid tumor mass as single cells and spreading along the abluminal surfaces of the microvessels (red). This might be termed “the advancing front” of the tumor. On can discern empty vascular lumina with no evidence of intravascular localization of tumor cells. (B) Comparable image of GFP-labeled melanoma cells associated with microvascular channels at two weeks. The GFP-labeled melanoma cells are spreading along the abluminal surfaces of the microvessels some distance away from the tumor mass. (C) At four weeks, the spreading of melanoma cells has continued some distance beyond from the tumor mass while remaining confined to the external surfaces of endothelial cells. White arrows indicate direction of tumor progression. Scale bars, 100 mm.