Two-dimensional gel electrophoresis of membrane proteins from the R3327 prostate adenocarcinoma.

The Dunning rat prostate adenocarcinoma (R3327) is a reliable model that shares many similarities with the human tumor. Two sublines of the tumor, G and H, represent opposite extremes in histology and growth rate. Purified membrane fractions from G and H solid tumors were isolated by sucrose gradient. Tumor and normal prostate membrane proteins were labeled with 125I, incubated with G and H antisera, and precipitated by adsorption of antibody-antigen complexes to staphylococcal Protein A. Proteins were resolubilized and electrophoresed on two-dimensional gels, and the gels were autoradiographed. A total of eight labeled proteins were precipitated from the G and H tumors in the presence of G antisera. Of these, seven were homologous. One high-molecular-weight protein (Protein b) present on the G tumor was absent from the H tumor. The H tumor contained another high-molecular-weight protein (i) that was not found on the G tumor or on normal prostate. Normal prostate revealed a pattern similar to the G tumor except that Protein b appeared to be quantitatively reduced. Precipitation in the presence of H antisera showed similar patterns except that Protein b was not detected in the G tumor and was greatly reduced in the normal prostate. Therefore, despite variable growth characteristics, there were few changes in membrane proteins between the solid tumors and between the tumors and normal prostate. Iodination of surface proteins of cultured cells from normal prostate and the G and H sublines also showed a high degree of homology. No consistent differences between cultured cell lines were noted.