Proteoglycan changes in the intercellular matrix of human colon carcinoma: an integrated biochemical and stereologic analysis

Abstract

Abnormal forms and concentrations of proteoglycans have been reported for various types of tumors, suggesting that proteoglycans may play a role in neoplasia. The purpose of this study was to test two hypotheses: (1) that the glycosaminoglycan (GAG)-containing proteoglycans of the intercellular matrix of normal and neoplastic colon have different chemical characteristics, and (2) that these characteristics can be associated with distinct morphologic patterns. Chemical analysis of purified GAGs revealed a 12-fold increase in the concentration of chondroitin 4- and 6-sulfate in colonic tumors as compared with the controls; no changes were detected for the other GAGs. Histochemically, this increase in sulfated GAG occurred predominantly in the intercellular matrix of the connective tissue stroma adjacent to the neoplasm. Autoradiographic analysis of samples incubated in vitro with [35S]sulfate revealed that the connective tissue cells surrounding the tumor (but not the tumor cells) were the major sites of sulfated proteoglycan biosynthesis. Ultrastructurally, proteoglycans were identified as ruthenium red-positive granules that were present throughout the intercellular matrix of the connective tissue stroma in both normal and malignant colon. Quantitation of these granules revealed that the neoplasm contained 92 per cent shorter than in granules per cu. cm. of intercellular matrix, but that the average volume of a granule was 79 per cent smaller and the nearest neighbor distance between granules was 19 per cent shorter than in the control. Assuming that the matrix granules represent the major source of proteoglycans, we estimated that a cubic centimeter of matrix granules in the tumor contained 3.66 times more GAGs than the control, even though an average granule in the tumor contained 23 per cent less GAG than did the control. These findings suggest that the increased amounts of sulfated GAGs detected chemically in colon carcinoma can be explained by the presence of a larger number of smaller proteoglycan granules packed more closely together in the intercellular matrix.