Studies focused on the cellular control of nucleoside diphosphate hexoses, which are precursors for hyaluronic acid (HA) synthesis, and on the regulation of HA synthesis, a glycosaminoglycan that is associated with tumor invasion and metastasis. HA synthetase activity compares closely with the production of HA by 3T3 fibroblasts under a variety of culture conditions indicating that the cellular control of HA production is through the synthesis of new HA synthetase molecules. Furthermore, kinetic studies indicate that one HA synthetase molecule is responsible for the synthesis of molecule of HA. Glucosamine-6-phosphate synthetase is under study as a possible control point for the synthesis of UDP- hexoses as precursors for HA synthesis. A series of 13 glutamine antagonists are being evaluated for differential effects on HA vs. DNA synthesis and as inhibitors of glucosamine-6-phosphate synthetase. Oligosaccharides of various lengths and compositions were prepared and under evaluation for their ability to disrupt the interaction of tumor cells with their extracellular matrix. These oligosaccharides are being evaluated in three systems: (1) their ability to bind to purified HA- binding protein, (2) their effect on cell migration (in vitro metastasis model), and (3) for their ability to block the invasion/metastasis of B16F10 cells in mice (lung invasion model). Studies of the regulation of pyrimidine synthesis in tumors and normal host tissues in the intact mouse were continued. Stable isotopes and GC/MS were used to determine the differential effects of low (therapeutically relevant) doses of PALA on de novo pyrimidine synthesis in liver and intestine. The onset, extent, and duration of inhibition were determined and compared with effects in PALA-sensitive and PALA- insensitive tumors.
