Heparin-binding growth factor(s) derived from head and neck squamous cell carcinomas induce endothelial cell proliferations.

BACKGROUND: Tumor growth is dependent on the expansion and proliferation of the host vascular system into the primary neoplasm (angiogenesis). The development of an intact vascular system requires migration and proliferation of endothelial cells and assembly into microvessels. Previous studies in our laboratory demonstrated that head and neck squamous cell carcinomas (HNSCC) are angiogenic in vivo. To clarify the mechanism of HNSCC-induced angiogenesis, the present study sought to determine if HNSCCs produced endothelial cell mitogens in vitro. METHODS: Production of PGE-2, TGF-beta, FGF-2 (basic-FGF [fibroblast growth factor]), and vascular endothelial cell growth factor (VEGF) were quantitated by enzyme-linked immunoabsorbant assay (ELISA) in five HNSCC lines. Cell free supernatants of 5 HNSCC lines were tested in a nonradioactive proliferation assay using human umbilical vein endothelial cells (HUVECs). RESULTS: All lines demonstrated enhanced endothelial cell proliferation in a dose-dependent fashion. Fractionation of these supernatants by heparin column chromatography significantly reduced endothelial cell proliferation in the five lines tested (range, 31.7% to 46.23% reduction; mean, 38.14+/-6.02%). Pretreatment with antibody to VEGF but not transforming growth factor (TGF)-beta inhibited endothelial cell proliferation. CONCLUSIONS: These studies indicate HNSCCs produce factor(s) which stimulate endothelial cell proliferation and that VEGF may be involved in HNSCC-induced endothelial cell mitogenesis.

Effect of link protein and free hyaluronic acid binding region on spacing of proteoglycans in aggregates.

Aging of articular cartilage results in accumulation of aggrecan fragments of various sizes that retain their ability to aggregate even though they may have relatively few glycosaminoglycan chains. Residual binding of partially degraded aggrecan may prevent binding of newly synthesized aggrecan subunits that have greater numbers of glycosaminoglycan chains. This study was undertaken to determine the effects of various relative molar ratios of intact aggrecan, link proteins, and hyaluronic acid binding region fragments on the structure of reconstituted aggregates. High molar ratios of link proteins relative to aggrecan decreased the spacing between adjacent aggrecan subunits; low molar ratios of hyaluronic acid binding region relative to aggrecan (4:1 or less) had no significant effect on spacing, and high molar ratios resulted in an increase in the spacing and a decrease in the percentage of aggrecan subunits found in aggregates. These data suggest that the density of aggrecan subunits on the aggregate is determined primarily by steric hindrance of the glycosaminoglycan chains of the aggrecan subunits and that, to a limited extent, partial degradation of aggrecan in an aggregate allows attachment of more aggrecan subunits.

Chemical stabilization of cartilage matrix.

Severe destruction of articular cartilage in osteoarthritis manifests clinically when repair processes cannot keep up with the catabolic processes. Loss of proteoglycans, which give the tissue its ability to undergo reversible deformation, precedes and probably contributes significantly to breakdown of the matrix in the most superficial layers of articular cartilage. In this study, we have examined the ability of dithiobis[succinimidyl propionate], a bifunctional reagent with a 1.2-nm span that cross-links proteins at lysine amino acid, and poly-L-lysine of high molecular weight (average MW 360,000) to reduce passive loss of proteoglycans and collagen from thin slices (40 and 200 microns) of bovine nasal and human patellar cartilage incubated for 7 days in buffer at 4 degrees C. We present evidence that treatment of thin slices of cartilage with either of these agents is effective in reducing the loss of proteoglycans and collagen from the cartilage matrix and we define conditions (length of treatment and concentrations required) under which the stabilization of the cartilage matrix is optimized. Chemical stabilization of cartilage matrix may become an important modality of treatment in osteoarthritis by protecting the environment around chondrocytes during the repair process.