Human transforming growth factor type .beta.2: production by a prostatic adenocarcinoma cell line, purification, and initial characterization

Abstract

Human type beta 2 transforming growth factor (hTGF-beta 2) was purified from tamoxifen-supplemented, serum-free medium conditioned by the human prostatic adenocarcinoma cell line PC-3. The purification of hTGF-beta 2 was monitored in a growth inhibition assay and was achieved by batch purification on methylsilyl-controlled pore glass, followed by gel permeation chromatography and reversed-phase high-performance liquid chromatography. The overall recovery of hTGF-beta 2 was 75% of the initial activity and yielded 22 micrograms of hTGF-beta 2/L of conditioned medium. The concentration of hTGF-beta 2 required for half-maximal inhibition of Mv 1 Lu mink lung epithelial cells (CCl-64) was approximately 5 pM when assayed in the presence of 10% fetal bovine serum. The purified hTGF-beta 2 has a molecular weight of 24,000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and consists of two disulfide-linked, apparently identical polypeptide chains, with a molecular weight of 13,000. The amino-terminal sequence of hTGF-beta 2 was determined. Alignment of the amino acid sequences of hTGF-beta 2 and hTGF-beta reveals statistically significant sequence homology. On the basis of the extensive amino acid sequence homology, we propose the term TGF-beta 2 for this newly isolated polypeptide. The reported results suggest that TGF-beta (TGF-beta 1) and TGF-beta 2 may have evolved from a common progenitor.