A CELL-SURFACE PROTEOGLYCAN MEDIATES HUMAN ADENOCARCINOMA HT-29 CELL-ADHESION TO HUMAN ANGIOGENIN

Human angiogenin is an excellent substrate for the adhesion of HT-29 h uman colon adenocarcinoma cells. These cells adhere more quickly to hu man angiogenin than to fibronectin, laminin, collagen I, and collagen IV. Anti-angiogenin antibodies and the angiogenesis inhibitors platele t factor-4 and placental ribonuclease inhibitor prevent adhesion of HT -29 cells to angiogenin. Calcium and magnesium ions are not required f or adhesion and Arg Gly-Asp-Ser has no effect, indicating that the int eraction is integrin-independent. Instead, adhesion seems to involve a heparan/chondroitin sulfate proteoglycan. Treatment of the cells with heparinase or heparitinase decreases HT-29 cell adhesion onto angioge nin but not onto collagen I. Moreover, cell adhesion is decreased by t he presence of heparin or chondroitin sulfates and by preincubation of the cells with inhibitors of proteoglycan synthesis or secretion. In addition, angiogenin binds tightly to heparin-Sepharose, requiring 0.7 8 M NaCl for elution. Angiogenin-affinity chromatography of a S-35-, H -3-labeled HT-29 cell fraction enriched in cell-surface proteoglycans yields a single, heparinase-sensitive component of apparent molecular mass >200 kDa, as detected by autoradiography after SDS-polyacrylamide gel electrophoresis. These results suggest that angiogenin could be a n effective substrate for tumor cell adhesion during metastasis and ma y provide a basis for the design of inhibitors of this process.