Aggregation of feline lymphoma cells by hyaluronic acid.

Abstract

AbstractAddition of media from cultured human sarcoma or glioma cells to cultures of suspended feline lymphoma cells (established line FL 74) induced visible aggregation of the lymphoma cells within a few minutes. A number of other normal and malignant cells, including a series of human lymphoid cells, failed to aggregate under identical conditions. The aggregation process showed no temperature dependence, within a range of 4° C to 37° C, and did not require divalent metal ions. The cell‐aggregating factor was heat‐stable and resistant to digestion with trypsin. It was identified as hyaluronic acid on the basis of its macromolecular and polyelectrolyte properties in conjunction with its susceptibility to various enzymes. A standard preparation of hyaluronic acid induced aggregation of suspended FL 74 cells at concentrations of 30 ng /ml or more. Chondroitin sulphate, chondroitin sulphate proteoglycan, dermatan sulphate, heparan sulphate and heparin did not aggregate the cells, nor did partially depolymerized hyaluronic acid. Pretreatment of the FL 74 target cells with trypsin abolished their clumping ability, implying the presence of a trypsin‐sensitive receptor at the cell surface. Trypsinized and washed cells regained their aggregation properties with hyaluronic acid within a 24 h period in continued culture. The interaction of hyaluronic acid with its receptor was studied by inhibition experiments, in which FL 74 cells were subjected to hyaluronic acid after preincubation with various oligosaccharides. Tetra‐ and hexasaccharides, derived from either hyaluronic acid or chondroitin sulphate, were able to prevent aggregation of the cells by polymeric hyaluronic acid.