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Hepatocyte growth factor (HGF) and its receptor Met are responsible for a wide variety of cellular responses, both physiologically during embryo development and tissue homeostasis, and pathologically, particularly during tumor growth and dissemination. In cancer, Met can act as an oncogene on tumor cells, as well as a pro-angiogenic factor activating endothelial cells and inducing new vessel formation. Molecules interfering with Met activity could be valuable therapeutic agents. Here we have investigated the antiangiogenic properties of a synthetic peptide mimicking the docking site of the Met carboxyl-terminal tail, which was delivered into the cells by fusion with the internalization sequences from Antennapedia or HIV-Tat. We showed that these peptides inhibit ligand-dependent endothelial cell proliferation, motility, invasiveness and morphogenesis in vitro to an even greater extent and with much less toxicity than the Met inhibitor PHA-665752, which correlated with interference of HGF-dependent downstream signaling. In vivo, the peptides inhibited HGF-induced angiogenesis in the matrigel sponge assay and impaired xenograft tumor growth and vascularization in Kaposi's sarcoma. These data show that interference with the Met receptor intracellular sequence impairs HGF-induced angiogenesis, suggesting the use of antidocking site compounds as a therapeutic strategy to counteract angiogenesis in cancer as well as in other diseases. [ABSTRACT FROM AUTHOR]

The biguanide metformin is used in type 2 diabetes management and has gained significant attention as a potential cancer preventive agent. Angioprevention represents a mechanism of chemoprevention, yet conflicting data concerning the antiangiogenic action of metformin have emerged. Here, we clarify some of the contradictory effects of metformin on endothelial cells and angiogenesis, using in vitro and in vivo assays combined with transcriptomic and protein array approaches. Metformin inhibits formation of capillary-like networks by endothelial cells; this effect is partially dependent on the energy sensor adenosine-monophosphateactivated protein kinase (AMPK) as shown by small interfering RNA knockdown. Gene expression profiling of human umbilical vein endothelial cells revealed a paradoxical modulation of several angiogenesis-associated genes and proteins by metformin, with short-term induction of vascular endothelial growth factor (VEGF), cyclooxygenase 2 and CXC chemokine receptor 4 at the messenger RNA level and downregulation of ADAMTS1. Antibody array analysis shows an essentially opposite regulation of numerous angiogenesis-associated proteins in endothelial and breast cancer cells including interleukin-8, angiogenin and TIMP- 1, as well as selective regulation of angiopioetin-1, -2, endoglin and others. Endothelial cell production of the cytochrome P450 member CYP1B1 is upregulated by tumor cell supernatants in an AMPK-dependent manner, metformin blocks this effect. Metformin inhibits VEGF-dependent activation of extracellular signal-regulated kinase 1/2, and the inhibition of AMPK activity abrogates this event. Metformin hinders angiogenesis in matrigel pellets in vivo, prevents the microvessel density increase observed in obese mice on a high-fat diet, downregulating the number of white adipose tissue endothelial precursor cells. Our data show that metformin has an antiangiogenic activity in vitro and in vivo associated with a contradictory short-term enhancement of proangiogenic mediators, as well as with a differential regulation in endothelial and breast cancer cells. [ABSTRACT FROM AUTHOR]

Although extensively studied, the exact nature of Kaposi's sarcoma (KS), the most common tumors in AIDS patients worldwide, is still controversial. KS is a highly vascularised tumor, apparently induced by HHV8 infection of vascular precursors, endothelial cells, circulating endothelial and/or haematopoietic progenitors. Cell lines derived from KS biopsies show similar characteristics: a mixture of mesenchymal and vascular markers. Given the growing interest in cancer stem cells as a new perspective in cancer treatment, we decided to isolate and characterize the potential stem sub-populations in KS cultures and to study whether the interaction of these cells with the microenvironment may influence their tumorigenicity.Two KS cell lines (KS-IMM and SLK), cultured out of biopsy material from KS patients, were used to asses stemness capability of this tumor.KS cells were karyotypically characterized, analyzed by functional genomics with Affymetrix arrays and then grown in specific serum-free stem cell medium. Cell proliferation assay showed an anchorage-independent growth capability of KS and SLK cell lines forming spheroid structures. With increasing passages, these KS-derived spheroids showed an increase in proliferation potential and sphere forming efficiency.Surface expression markers on spheroids were evaluated through flow cytometry and compared to parental cell lines. Consistent increase in CD34 and CD326 and decrease in CD133 and CD144 were found in cells derived from KS-IMM spheroid compared to parental cells, while only ABCG2 is consistently decreased in SLK spheroids. Preliminary results suggest the existence of a KS subpopulation showing stemness features. [ABSTRACT FROM AUTHOR]