BETA-IG-H3 - A TRANSFORMING GROWTH FACTOR-BETA-RESPONSIVE GENE ENCODING A SECRETED PROTEIN THAT INHIBITS CELL ATTACHMENT IN-VITRO AND SUPPRESSES THE GROWTH OF CHO CELLS IN NUDE-MICE

beta ig-h3 is a novel gene first discovered by differential screening of a cDNA library made from A549 human lung adenocarcinoma cells treat ed with transforming growth factor-beta 1 (TGF-beta 1). It encodes a 6 83-amino-acid protein containing a secretory signal sequence and four homologous internal domains. Here we show that treatment of several ty pes of cells, including human melanoma cells, human mammary epithelial cells, human keratinocytes, and human fibroblasts, with TGF-P resulte d in a significant increase in beta ig-h3 RNA. A portion of the beta i g-h3 coding sequence was expressed in bacteria, and antisera against t he bacterially produced protein was raised in rabbits. This antisera w as used to demonstrate that several cell lines secreted a 68-kD beta I G-H3 protein after treatment with TGF-beta. Transfection of beta IG-H3 expression plasmids into Chinese hamster ovary (CHO) cells led to a m arked decrease in the ability of these cells to form tumors in nude mi ce. The beta ig-H3 protein was purified from media conditioned by reco mbinant CHO cells, characterized by immunoblotting and protein sequenc ing and shown to function in an anti-adhesion assay in that it inhibit ed the attachment of A549, HeLa, and WI-38 cells to plastic in serum-f ree media. Sequencing of cDNA clones encoding murine Pig-HS indicated 90.6% conservation at the amino acid level between the murine and huma n proteins. Finally, the beta ig-h3 gene was localized to human chromo some 5q31, a region frequently deleted in preleuakemic myelodysplasia and leukemia. The corresponding mouse beta ig-h3 gene was mapped to mo use chromosome 13 region B to C1, which confirms a region of conservat ion on human chromosome 5 and mouse chromosome 13. We suggest that thi s protein be named p68(beta ig-h3).