Antiangiogenic activity of trabectedin in myxoid liposarcoma: involvement of host TIMP-1 and TIMP-2 and tumor thrombospondin-1.

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/EBPß 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.

The association between tumour progression and vascularity in myxofibrosarcoma and myxoid/round cell liposarcoma.

Angiogenesis is an important factor in the morphological progression and metastasis of many solid tumours. We studied two homogeneous series of myxofibrosarcoma (MFS) and myxoid/round liposarcoma (MRLS), characterised by distinct vascular patterns and correlated the intratumoral microvessel density (IMD) with morphologic progression in both types of sarcoma. In our study, 43 cases of MFS and 42 cases of MRLS were graded according to established diagnostic criteria. For evaluation of IMD, representative sections were stained immunohistochemically for CD31. After selection of "neovascular hot spots", IMD was calculated by measuring the endothelial surface within twenty 200x fields in relation to the total analysed area. In addition to the correlation of IMD with histological grades of malignancy, a correlation of IMD with the inflammatory infiltrate in MFS was done. To determine whether vascular endothelial growth factor (VEGF) and its receptors, KDR and flt-1, may play a role in the progression of both types of sarcomas, we used mRNA in situ hybridisation (ISH) to study VEGF, KDR and flt-1 expression in selected cases. In addition, the expression of thrombospondin-1, which has been reported to inhibit angiogenesis, and of collagen type I was studied using mRNA ISH. Cases of MFS varied histologically from hypocellular, mainly myxoid, neoplasms (low-grade malignant, 18 cases) to intermediate-grade malignant lesions with increased cellularity and mitotic activity (13 cases), and high-grade malignant cases with marked pleomorphism, high proliferative activity and areas of necrosis in many cases (12 cases). Cases of purely low-grade myxoid liposarcoma (16 cases) were characterised by low-cellularity, mucin pooling and plexiform vasculature. In combined MRLS, these hypocellular areas were admixed with hypercellular, round cell areas (5-80% of the analysed tumour area; 23 cases), and in round cell liposarcoma (three cases) rounded tumour cells predominated (>80% of the analysed tumour area). The average IMD in intermediate and high-grade malignant MFS (4.03 and 4.09, respectively) was significantly higher than in low-grade malignant MFS (2.73). Correlation of vascularity with the inflammatory infiltrate in MFS showed increased IMD only in cases with abundant neutrophils; most of these cases were high-grade malignant neoplasms. In contrast, no statistical correlation between morphological progression and IMD was seen in myxoid liposarcoma (6.08), MRLS (6.57) and round cell liposarcoma (4.07). VEGF mRNA was expressed by tumour cells in all histological grades of MFS and MRLS. VEGF receptor mRNA was weakly expressed by endothelia of newly formed blood vessels in both entities. Interestingly, tumour cells of all analysed cases of MFS strongly expressed collagen type I and thrombospondin-1, while these proteins were not detected in tumour cells of MRLS. In conclusion, morphologic tumour progression in MFS is associated with increased IMD, whereas, in MRLS, no such correlation is seen. Whereas VEGF and VEGF receptor mRNA were expressed in both entities, a characteristic expression profile of collagen type I and thrombospondin-1 in MFS emerged. Further studies are necessary to correlate vascularity and clinical course in MFS and MRLS.

The myxoid/round cell liposarcoma fusion oncogene FUS-DDIT3 and the normal DDIT3 induce a liposarcoma phenotype in transfected human fibrosarcoma cells.

Myxoid/round cell liposarcoma (MLS/RCLS) is the most common subtype of liposarcoma. Most MLS/RCLS carry a t(12;16) translocation, resulting in a FUS-DDIT3 fusion gene. We investigated the role of the FUS-DDIT3 fusion in the development of MLS/RCLS in FUS-DDIT3- and DDIT3-transfected human HT1080 sarcoma cells. Cells expressing FUS-DDIT3 and DDIT3 grew as liposarcomas in severe combined immunodeficient mice and exhibited a capillary network morphology that was similar to networks of MLS/RCLS. Microarray-based comparison of HT1080, the transfected cells, and an MLS/RCLS-derived cell line showed that the FUS-DDIT3- and DDIT3-transfected variants shifted toward an MLS/RCLS-like expression pattern. DDIT3-transfected cells responded in vitro to adipogenic factors by accumulation of fat and transformation to a lipoblast-like morphology. In conclusion, because the fusion oncogene FUS-DDIT3 and the normal DDIT3 induce a liposarcoma phenotype when expressed in a primitive sarcoma cell line, MLS/RCLS may develop from cell types other than preadipocytes. This may explain the preferential occurrence of MLS/RCLS in nonadipose tissues. In addition, development of lipoblasts and the typical MLS/RCLS capillary network could be an effect of the DDIT3 transcription factor partner of the fusion oncogene.

Normal and neoplastic cells of brown adipose tissue express the adhesion molecule CD31.

CONTEXT: CD31 (platelet-endothelial cell adhesion molecule-1; PECAM-1), an adhesion molecule involved in the process of angiogenesis, is used as a marker of normal and neoplastic vascularization. During the assessment of angiogenesis and vascular invasion in a thymic carcinoid tumor, we observed unexpected immunostaining for CD31 in perithymic brown fat nests. OBJECTIVE: To determine whether CD31 is expressed by normal and neoplastic cells of brown fat, a tissue whose thermogenetic activity depends heavily on high perfusion. DESIGN: Formalin-fixed, paraffin-embedded archival tissues were immunostained by the labeled avidin-biotin method using antibodies against CD31 (clones JC70A and 1A10) after retrieval of heat-induced epitopes. Archival tissues included perithymic, periadrenal, axillary, and neck adipose tissue in which were embedded nests of brown fat (n = 15), hibernoma (n = 3), lipoma (n = 6), well-differentiated liposarcoma (n = 4), and myxoid liposarcoma (n = 4). RESULTS: Invariably, multivacuolated and univacuolated adipocytes of normal brown fat and hibernomas were intensely positive for the CD31 antigen. The immunostaining "decorated" cell membranes and the membranes of intracytoplasmic vacuoles. No expression of CD31 was found in normal adipocytes of white fat, in neoplastic cells of lipomas, or in multivacuolated lipoblasts of well-differentiated and myxoid liposarcomas. CONCLUSIONS: The spectrum of cell types that express CD31 is expanded to include normal and neoplastic brown fat cells. We speculate that the expression of CD31 may play a role in the development and maintenance of the vascular network characterizing this specialized adipose tissue. Moreover, CD31 may inhibit the Bax-mediated apoptosis of brown fat cells. For practical purposes, CD31 may be used as an immunohistochemical marker for distinguishing between white and brown fat and for diagnosing hibernoma in paraffin sections.

Myxoid liposarcoma: appearance at MR imaging with histologic correlation.

Although myxoid liposarcoma is a subtype of liposarcoma, it may be difficult to establish the correct diagnosis with magnetic resonance (MR) imaging due to the lack of fat signal intensity. Without the administration of gadolinium contrast material, the tumor may even mimic a cystic tumor. A spectrum of MR imaging abnormalities occur in myxoid liposarcoma, depending on the amount of fat and myxoid material, the degree of cellularity and vascularity, and the presence of necrosis. Most myxoid liposarcomas have lacy or linear, amorphous foci of fat. Some myxoid liposarcomas appear to be cystic at nonenhanced MR imaging, although they enhance like other solid masses at contrast material-enhanced MR imaging. The enhancing areas within the tumor represent increased cellularity and vascularity; the nonenhancing areas represent necrosis, reduced cellularity, and accumulated mucinous material. Gadolinium-enhanced imaging is important in differentiating myxoid liposarcoma from benign cystic tumors. Characterization of the tumor with MR imaging plays an important role in the management of myxoid liposarcoma.