Figure 2.

Morphological and immunohistochemical analyses of highly aggressive and poorly aggressive cutaneous melanoma cells in three-dimensional collagen gels (A–D and F) and in monolayer culture (E). Phase-contrast microscopy (A–C) demonstrates the ability of highly aggressive cutaneous C8161 melanoma cells to form a vasculogenic pattern of cordlike networks (A), similar to those formed de novo by human angioblasts (B). Poorly aggressive cutaneous C81–61 melanoma cells were unable to form networks under similar culture conditions (C). Immunohistochemical staining for VE-cadherin (shown as red chromogenic stain) in a cryostat section of C8161 cells highlights developing vasculogenic networks; the negative control (Inset) receiving no primary antibody showed no nonspecific staining by the secondary antibody (D). Immunostaining for VE-cadherin in C8161 monolayer culture demonstrates the intercellular junctions (E). Transmission electron microscopy of developing vasculogenic networks by C8161 cells reveals the endothelial-like nature of the outermost perimeter cells (F). Alignment of melanosomes within the perimeter network cells is shown in the Inset.