DIRECT ACTION OF A PROTEIN-BOUND POLYSACCHARIDE, PSK, ON TRANSFORMING-GROWTH-FACTOR-BETA

We investigated the action of a protein-bound polysaccharide, PSK, on transforming growth factor-beta (TGF-beta). (1) In in vitro-mixed cult ure of peripheral blood mononuclear cells (PBMC) from healthy human an d mitomycin C-treated human colon cancer cells, PSK or polyclonal anti body to TGF-beta significantly enhanced incorporation of H-3-thymidine into PBMC, and apparently decreased TGF-beta(1) levels of acid-treate d culture supernatant. (2) PSK or the antibody interfered with the qua ntitation by enzyme immunoassay of TGF-beta(1) in acid-treated superna tant of the mixed culture. (3) PSK was suggested to form a complex wit h I-125-human recombinant TGF-beta(1) standard, when changes in molecu lar weight of radioactivities were assessed by gel filtration. Recombi nant human TGF-beta(1) inhibited growth of mink lung epithelial cell l ine Mv1Lu and promoted collagen synthesis in rat kidney fibroblast cel l line NRK49F, but the complex did not have such activities. (4) In ad dition to TGF-beta(1), PSK bound with TGF-beta(2) and platelet-derived growth factor; however, PSK did not bind with 22 other species of cyt okines and growth factors. (5) Protein moiety of PSK is suggested to p lay an important role in the expression of the activity. These results suggest that PSK modulates the biological activity of TGF-beta(1) by binding to its active form. (C) 1998 Elsevier Science B.V. All rights reserved.