Tissue sections from aggressive human intraocular (uveal) and metastatic cutaneous melanomas generally lack evidence of significant necrosis and contain patterned networks of interconnected loops of extracellular matrix. The matrix that forms these loops or networks may be solid or hollow. Red blood cells have been detected within the hollow channel components of this patterned matrix histologically, and these vascular channel networks have been detected in human tumors angiographically. Endothelial cells were not identified within these matrix-embedded channels by light microscopy , by transmission electron microscopy , or by using an immunohistochemical panel of endothelial cell markers (Factor VIIIrelated antigen , Ulex , CD31 , CD34 , and KDR[Flk-1]). Highly invasive primary and metastatic human melanoma cells formed patterned solid and hollow matrix channels (seen in tissue sections of aggressive primary and metastatic human melanomas) in threedimensional cultures containing Matrigel or dilute Type I collagen , without endothelial cells or fibroblasts. These tumor cell-generated patterned channels conducted dye , highlighting looping patterns visualized angiographically in human tumors. Neither normal melanocytes nor poorly invasive melanoma cells generated these patterned channels in vitro under identical culture conditions , even after the addition of conditioned medium from metastatic pattern- It is generally assumed that tumors require a blood supply for growth and metastasis. 1 The development of the tumor microcirculation compartment includes both the production of new blood vessels (angiogenesis) and their remodeling. 2 In fact, the number of vessels 3 and the patterning of the microcirculation 4 by remodeling events are used as histological markers of tumor progression. Although attention has been focused on factors that stimulate and suppress tumor angiogenesis, the molecular mechanisms underlying tumor remodeling remain enigmatic. It is therefore critical to investigate remodeling of the intratumoral microvasculature in various tumor models.Melanoma is among the better characterized tumor models with respect to prognostic staging of disease progression. The rising incidence of cutaneous melanoma makes this tumor an important public health problem. Melanoma of the interior of the eye, uveal melanoma, although much less common than cutaneous melanoma, poses a threat to vision and significant morbidity; nearly 50% of patients with uveal melanoma die from metastatic melanoma. 5 Cutaneous melanoma may disseminate through lymphatics or blood vessels. In contrast, the interior of the eye lacks lymphatics, and uveal melanoma, which develops in one of the most capillary-rich tissues of the body, is a paradigm for pure hematogeneous dissemination of cancer. 6 Therefore, the development of a tumor microcirculation in uveal melanoma is a rate-limiting step for hematological metastasis and serves as an important model for study of the cellular and molecular infrastruc-

We recently have introduced the term vasculogenic mimicry to describe the unique ability of aggressive melanoma tumor cells to form tubular structures and patterned networks in three-dimensional culture, which ''mimics'' embryonic vasculogenic networks formed by differentiating endothelial cells. In the current study, we address the biological significance of several endothelial-associated molecules (revealed by microarray analysis) with respect to expression and function in highly aggressive and poorly aggressive human cutaneous melanoma cell lines (established from the same patient). In a comparative analysis, CD31 was not expressed by any of the melanoma cell lines, whereas TIE-1 (tyrosine kinase with Ig and epidermal growth factor homology domains-1) was strongly expressed

During development, the formation and remodeling of primary vascular networks occurs by vasculogenesis and angiogenesis. Recently, the term "vasculogenic mimicry" has been used by our laboratory and collaborators to reflect the embryonic-like ability of aggressive, but not nonaggressive, melanoma tumor cells to form a pattern of matrix-rich networks (containing channels) surrounding spheroids of tumor cells in three-dimensional culture, concomitant with their expression of vascular cell markers. Ovarian cancer is usually diagnosed as advanced stage disease in most patients when widespread metastases have already been established within the peritoneal cavity. In this study, we explored whether invasive ovarian carcinoma cells could engage in molecular vasculogenic mimicry reflected by their plasticity, compared with their normal cell counterparts. The data revealed that the invasive ovarian cancer cells, but not normal ovarian surface epithelial cells, formed patterned networks containing solid and hollow matrix channels when grown in three-dimensional cultures containing Matrigel or type I collagen, in the absence of endothelial cells or fibroblasts. Immunohistochemical analysis showed that matrix metalloproteinases (MMP)-1, -2, and -9, and MT1-MMP were discretely localized to these networks, and the formation of the networks was inhibited by treatment with MMP inhibitors. Furthermore, the RNase protection assay revealed the expression of multiple vascular cell-associated markers by the invasive ovarian cancer cells. In patient tumor sections from high-stage, high-grade ovarian cancers, 7 to 10% of channels containing red blood cells were lined by tumor cells. By comparison, all vascular areas in benign tumors and low-stage cancers were endothelial lined. These results may offer new insights and molecular markers for consideration in ovarian cancer diagnosis and treatment strategies based on molecular vascular mimicry by aggressive tumor cells.

No abstract

No abstract

In vitro morphogenesis of epithelial cells to form tube-like structures is regulated by hepatocyte growth factor-scatter factor (HGF/SF). The placenta is a rich source of HGF/SF, and its absence in mice has been shown to lead to impaired placental growth and embryonic death. There is no information in the literature regarding in vitro morphogenesis of human cytotrophoblasts or the effect of HGF/SF on this process. In this study, cytotrophoblasts were isolated from human placentae obtained from all three trimesters of gestation and cultured on the recombinant basement membrane matrix (Matrigel). Under these conditions, cytotrophoblasts participated in morphogenetic events including formation of spheroid-like structures, radial linear processes with branching, and invaded Matrigel and formed large, tube-like structures. The presence of a developing lumen was documented in the linear projections arising from spheroids and in the tube-like structures by both confocal and transmission electron microscopy. Immunohistochemistry was used to characterize the phenotype of the cells, and staining with anti-cytokeratin and anti-E-cadherin antibodies confirmed the presence of cytotrophoblasts in both the spheroids and tube-like structures. Recombinant HGF (rHGF) significantly increased the invasive activity of cytotrophoblasts isolated from the first and second (P < 0.001) and third trimesters (P < 0.01). In addition, rHGF significantly increased the percentage of spheroids with branching processes in the first and second trimesters (P < 0.05). Anti-HGF antibody inhibited both these effects in a dose-dependent manner, indicating the specificity of the above findings. This study provides new evidence indicating that HGF/SF regulates invasion and branching morphogenesis of cytotrophoblasts throughout gestation, with maximum effects in the first and second trimester. These findings may help to elucidate the importance of the reduced expression of HGF/SF identified in placentae from women with preeclampsia or intrauterine growth restriction and suggest that HGF/SF may serve as an important candidate in therapeutic intervention strategies.

The morphology of the microcirculation of uveal melanomas is a reliable market of tumor progression. Scanning electron microscopy of cast corrosion preparations can generate three-dimensional views of these vascular patterns, but this technique sacrifices the tumor parenchyma. Formalin-fixed wet tissue sections 100-150 microns thick from uveal melanomas were stained with the lectin Ulex europaeus agglutinin I (UEAI) and proliferating cell nuclear antigen (PCNA) to demonstrate simultaneously the tumor blood vessels and proliferating tumor cells. Indocarbocyanine (Cy3) was used as a fluorophore for UEAI and indodicarbocyanine (Cy5) was used for PCNA. Double labeled sections were examined with a laser scanning confocal microscope. Images of both stains were digitized at the same 5-microns intervals and each of the two images per interval was combined digitally to form one image. These combined images were visualized through voxel processing to study the relationship between melanoma cells expressing PCNA and various microcirculatory patterns. This technique produces images comparable to scanning electron microscopy of cast corrosion preparations while permitting simultaneous localization of melanoma cells expressing PCNA. The microcirculatory tree can be viewed from any perspective and the relationship between tumor cells and the tumor blood vessels can be studied concurrently in three dimensions. This technique is an alternative to cast corrosion preparations.

No abstract