PURIFICATION OF A NOVEL PROTEIN (PS20) FROM UROGENITAL SINUS MESENCHYMAL CELLS WITH GROWTH-INHIBITORY PROPERTIES IN-VITRO

Our previous studies have characterized mesenchyme-derived proteins to identify biologically active proteins and novel markers for stromal c ell paracrine action relative to stromal-epithelial interactions. Prev ious reports have characterized properties of a growth inhibitory acti vity (to bladder and prostatic epithelial cells), secreted by U4F feta l rat urogenital sinus mesenchymal cells, not cross-reactive with anti bodies to known cytokines, and provisionally termed UGIF. The present study reports the characterization, purification, and biological prope rties of a 20-21-kDa protein responsible for UGIF activity. The 20-21- kDa protein (termed ps20) was purified to near homogeneity, the amino- terminal sequence was determined, and biological properties were chara cterized in vitro. Amino-terminal sequence analysis indicated no direc t matches or regions of homology with known proteins. Purified ps20 in duced a linear and saturable inhibition of [H-3]thymidine incorporatio n in PC-3 prostatic carcinoma cells (half-maximal activity at 2.6 nM), inhibited cell proliferation (increased population doubling time from 19.8 to 25.8 h), and induced a 210% stimulation in the synthesis of s ecreted proteins. These data suggest that ps20 may be a candidate para crine effector protein and may play a role in stromal-epithelial cell interactions in the prostate gland.