Alteration of cell-associated heparan sulfate proteoglycan in tumor-bearing rats

Alteration of cell-associated heparan sulfate proteoglycan (HSPG) under tumor-bearing conditions was evaluated using microsomal membranes prepared from the liver of ascites Tawa sarcoma-bearing and age-matched control rats. Cell-associated HSPGs have been fractionated into two populations displaying different modes of membrane association; one is a NaCl-soluble HSPG and the other is recovered only after detergent treatment of the membranes. The former is thought to represent HSPG from the peripheral membrane and the latter, HSPG from the intercalated membrane. We extracted the cell-associated HSPGs from liver microsomal membranes with a NaCl solution followed by a deoxycholate (DCA) solution. Both were isolated by gel filtration and cetylpyridinium chloride precipitation. Glycosaminoglycans (GAGs) were isolated from the tumor cells and tumorous ascitic fluids by standard procedures. Using electrophoresis on a cellulose acetate membrane, it was confirmed that the cell-associated HSPGs contained no GAG chains other than HS, and that these HSPGs did not include PGs from tumor cells since hyaluronic acid predominates in tumor cells while chondroitin sulfate is present in ascitic fluids. The HSPG extracted with the DCA solution was markedly reduced under tumor-bearing conditions, with slight increase in the NaCl-soluble HSPG. The results suggests that this condition strongly influences the type of cell-associated HSPG related to the intracellular cytoskeleton.