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.