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Trabectedin is a marine natural product, approved in Europe for the treatment of soft tissue sarcoma and relapsed ovarian cancer. Clinical and experimental evidence indicates that trabectedin is particularly effective against myxoid liposarcomas where response is associated to regression of capillary networks. Here, we investigated the mechanism of the antiangiogenic activity of trabectedin in myxoid liposarcomas. Trabectedin directly targeted endothelial cells, impairing functions relying on extracellular matrix remodeling (invasion and branching morphogenesis) through the upregulation of the inhibitors of matrix metalloproteinases TIMP-1 and TIMP-2. Increased TIMPs synthesis by the tumor microenvironment following trabectedin treatment was confirmed in xenograft models of myxoid liposarcoma. In addition, trabectedin upregulated tumor cell expression of the endogenous inhibitor thrombospondin-1 (TSP-1, a key regulator of angiogenesis-dependent dormancy in sarcoma), in in vivo models of myxoid liposarcomas, in vitro cell lines and primary cell cultures from patients' myxoid liposarcomas. Chromatin Immunoprecipitation analysis showed that trabectedin displaced the master regulator of adipogenesis C/EBPβ from the TSP-1 promoter, indicating an association between the up-regulation of TSP-1 and induction of adipocytic differentiation program by trabectedin. We conclude that trabectedin inhibits angiogenesis through multiple mechanisms, including directly affecting endothelial cells in the tumor microenvironment--with a potentially widespread activity--and targeting tumor cells' angiogenic activity, linked to a tumor-specific molecular alteration., (© 2014 UICC.)

The dissemination of ovarian carcinoma cells within the abdominal cavity involves interaction of tumor cells with the peritoneal mesothelium. The aim of our study was to investigate whether mesothelial cells might directly affect the spreading of this tumor by inducing motility and invasiveness of human ovarian carcinoma cells. Serum-free supernatants of cultured human mesothelial cells [conditioned medium (CM)] induced chemotaxis and invasiveness of the human ovarian carcinoma cell lines SK-OV-3, OVCAR-5 and A2780 in a Boyden chamber. Checkerboard analysis indicated that the stimulated motility was prevalently directional. Most of the chemotactic activity was retained by a heparin affinity column, indicating that the motility factor(s) is a heparin-binding protein. Using different monoclonal antibodies (MAbs) directed against chemotactic factors that are secreted by mesothelial cells, we found that chemotaxis was partially prevented (64.8% inhibition) by antibodies against fibronectin (FN). CM also induced haptotactic migration of ovarian carcinoma cells, and anti-FN antibodies significantly inhibited haptotaxis. The presence of FN in the CM was confirmed by Western blot analysis. Our findings suggest that mesothelium plays an active role in inducing the intraperitoneal spread of ovarian carcinoma cells, and point to FN as being one of the main mediators of mesothelium-induced ovarian carcinoma cell motility.

All trans-retinoic acid (ATRA) induces complete remission in acute-promyelocytic-leukemia (APL) patients. This study investigated the adhesive properties of APL cells for the endothelium and the extracellular matrix, their motility and the effect of ATRA on these functions. Blasts from 7 APL patients adhered to resting and IL-1-activated endothelium, to the same degree as normal PMN. Adhesion was partially mediated by ICAM-1 and, for IL-1-activated endothelium, by VCAM-1 and E-selectin. These cells showed less adhesiveness for the matrix than PMN, although they maintained the same substrate preference: they adhered to fibronectin and thrombospondin, but not to laminin and type-IV collagen. Exposure to ATRA in vitro (1 microM for 48 to 96 hr) increased the adhesiveness of APL cells; this effect was particularly evident in the case of sub-endothelial matrix and fibronectin. A similar increment in adhesiveness was observed when comparing cells from 2 patients before and after treatment with ATRA. APL cells migrated in response to fMLP and motility was increased by ATRA. In conclusion, APL cells were less adhesive to the matrix than PMN, but treatment with ATRA considerably enhanced their adhesive properties. This could be important in determining the efflux of leukemic cells from the bone marrow and their tissue infiltration during ATRA therapy.

Cells derived from retinoblastomas grow slowly in vitro and only very rarely form tumors in nude mice. Matrigel, a mixture of components normally found in basement membranes, promotes the growth of Y-79 and WERI-Rb1 retinoblastoma (Rb) cells when added to suspension cultures of the 2 Rb cell lines. It also substantially increases cell adhesion in vitro. Y-79 cells, seeded into a Matrigel matrix, form round colonies over a 3-week period similar to those of control, weakly metastatic murine melanoma cells. In vivo, s.c. co-injection of Matrigel with either Y-79 or WERI-Rb 1 cells into nude mice promotes retinoblastoma tumor formation. Transplantation of as few as 1,000 cells allows for xenografting under these conditions, while no tumors were observed in the absence of Matrigel, even at 10 x 10(6) cells/inoculum. The tumors produced have the expected morphology and express an mRNA for a highly specific retina/retinoblastoma marker protein, the interphotoreceptor retinoid-binding protein. Thus, the xenografts obtained maintain the original morphological and molecular characteristics of the injected cells and represent a useful model for in vivo studies of retinoblastoma growth and treatment.

Membrane fluidity, determined by steady-state fluorescence polarization measurements, was correlated with metastatic capacity of murine tumor-cell lines. A correlation was observed in cell lines with different metastatic potential, and was confirmed when their lung-colonizing ability was modulated by alteration of either the membrane lipid composition or the culture conditions. Two cellular functions, motility and basement membrane invasion, were affected by the membrane lipid composition, and might explain the role of membrane fluidity observed in cancer metastasis.