Proteoglycan synthesis by normal and neoplastic human transitional epithelial cells

Glycosaminoglycans in human retinoblastoma cells: heparan sulfate, a modulator of the pigment epithelium-derived factor-receptor interactions

BACKGROUND

Pigment epithelium-derived factor (PEDF) has binding affinity for cell-surface receptors in retinoblastoma cells and for glycosaminoglycans. We investigated the effects of glycosaminoglycans on PEDF-receptor interactions.

RESULTS

125I-PEDF formed complexes with protease-resistant components of medium conditioned by human retinoblastoma Y-79 cells. Using specific glycosaminoglycan degrading enzymes in spectrophotometric assays and PEDF-affinity chromatography, we detected heparin and heparan sulfate-like glycosaminoglycans in the Y-79 conditioned media, which had binding affinity for PEDF. The Y-79 conditioned media significantly enhanced the binding of 125I-PEDF to Y-79 cell-surface receptors. However, enzymatic and chemical depletion of sulfated glycosaminoglycans from the Y-79 cell cultures by heparitinase and chlorate treatments decreased the degree of 125I-PEDF binding to cell-surface receptors.

CONCLUSIONS

These data indicate that retinoblastoma cells secrete heparin/heparan sulfate with binding affinity for PEDF, which may be important in efficient cell-surface receptor binding.

Effect of transforming growth factor-beta1, insulin-like growth factor-I, and hepatocyte growth factor on proteoglycan production and regulation in canine melanoma cell lines

OBJECTIVE

To identify extracellular proteoglycans produced by canine melanoma cell lines and analyze the effect of transforming growth factor-beta1 (TGF-beta1), insulin-like growth factor-I (IGF-I), and hepatocyte growth factor (HGF) on these proteoglycans.

SAMPLE POPULATION

3 canine melanoma cell lines (ie, CML-1, CML-6M, and CML-10c2).

PROCEDURE

Extracellular proteoglycans were analyzed by use of metabolic labeling and western immunoblot analysis. The effect of TGF-beta1 on cell proliferation was determined by incorporation of 5-bromo-2'-deoxyuridine.

RESULTS

The CML-1 and CML-6M melanoma cell lines produced 2 main extracellular proteoglycans. One of them was identified as versican, a proteoglycan found in undifferentiated human melanoma cell lines. The CML-10c2 cells produced a small amount of extracellular proteoglycans. Addition of TGF-beta1 (1.25 to 6.25 ng/ml) increased the release of sulfated proteoglycans into the medium. The TGF-beta1 had mainly a posttranslational effect, because it increased the molecular mass of the sulfated bands. Addition of IGF-I (50 ng/ml) slightly increased production of proteoglycans in the CML-6M cell line, whereas HGF (50 ng/ml) did not have any effect on proteoglycan production.

CONCLUSIONS AND CLINICAL RELEVANCE

The proteoglycan content and response toTGF-beta1 treatment for CML-1 and CML-6M canine melanoma cell lines are similar to that for undifferentiated human melanoma cell lines. In contrast, CML-10c2 cells produced a low amount of proteoglycans with high molecular weight. Because these extracellular proteoglycans are involved in the control of cell adhesion, proliferation, and migration, they may play an important role in the progression of melanomas in dogs.

What destroys the joint in rheumatoid arthritis?

The immunological disturbance in rheumatoid arthritis (RA) gives rise to a nonspecific inflammatory reaction mediated by cells and cytokines. This immunological nonbacterial synovitis, however, does not destroy the articular cartilage. The destruction of joint structures is the effect of tumor-like aggressive synoviogenic cell elements (TLP). These TLP formations are not observed in any other type of arthritis. TLP formations are strictly avascular and short-lived. After they have decayed, a collagenous pannus remains. Invasion and destruction of joint structures are brought about by several types of proteases, synthesized and secreted by highly active TLP cells. The TLP formations possess more than twice the affinity for adjacent bone than for the articular cartilage. In these formations, four oncogenes could be identified. In the course of RA disease, TLP formations can recur. Thus, the joint damage can summate with time. The oncological character of the aggressive process in RA demands new therapeutical considerations to protect RA patients from destruction of their joints.

Enterocytic differentiation correlates with changes in the fine structure and sulfation of perlecan in HT29 human colon carcinoma cells

Undifferentiated HT29 and differentiated HT29G-human colon carcinoma cells have been used to study the changes in proteoglycan production and structure associated with enterocytic cell differentiation. Differentiated cells incorporate twice as much sulfate than undifferentiated cells when labeled with [35S]sulfate. Both cell lines produce a heparan sulfate proteoglycan which was purified by ion-exchange. The heparan sulfate proteoglycan from differentiated HT29G- cells is larger and more homogeneous in size than that produced by undifferentiated HT29 cells. No differences in the core protein structure were observed. The detailed structural analysis of the heparan sulfate chains revealed that the structure of these chains follows the standard rules for these glycosaminoglycans with N-sulfated domains and N-acetylated domains. The main finding was that differentiated HT29G- cells have a degree of higher sulfation than HT29 cells. These differences were found to affect primarily 6-O-sulfated positions.