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.