Compositional and structural alterations of proteoglycans in human rectum carcinoma with special reference to versican and decorin.

This study indicated that human normal rectum (HNR) and human rectum carcinoma (HRC) contained three populations of proteoglycans (PGs). About 63% of the HNR PGs, in terms of uronic acid, were heparan sulfate proteoglycans (HSPGs) of M(r) 500,000 with HS side-chains of M(r) 35,000. The other two populations were versican (29%) and decorin (8%) of M(r) 715,000 and 90,000, respectively, bearing mainly dermatan sulfate (DS) (73%) and chondroitin sulfate (CS) (27%) chains of M(r) 24-26,000 and 20-22,000, respectively. In contrast, in terms of uronic acid, HRC contained 2-fold amounts of PGs. The majority of these PGs (87%) were versican and decorin of lower hydrodynamic size (500,000 and 70,000, respectively) than in HNR, with CS as prominent GAG (70%) in both types of PG. The M(r) of CS and DS chains in these PGs was 12-14,000 and 14-16,000, respectively. The remaining portion (13%) of PG was HSPGs of lower hydrodynamic size (300,000) with smaller HS chains (29,000) than HSPGs of HNR. Moreover, the molar concentrations of versican and decorin estimated from PG-derived protein contents represented a significant, but disproportionate increase, about 5-fold and 8-fold, respectively. The sulfation pattern of rectum carcinoma-associated versican and decorin was significantly altered mainly in containing (62%) 6-sulfated disaccharides and a significant proportion (10%) of non-sulfated disaccharides. DS chains of the tumor-associated versican and decorin contained decreased amounts of iduronic acid. On the metabolic level, the abnormally high production of versican and decorin in this malignant tumor suggests a dramatic modification in their biosynthetic steps at both translational and posttranslational levels.