PROSTATIC LOCALIZATION OF SPONTANEOUS EARLY INVASIVE-CARCINOMA IN LOBUND-WISTAR RATS

Animal models of human prostate cancer are very limited in number but are of obvious importance to develop. Dr. Morris Pollard (M. Pollard, J. Natl. Cancer Inst., 51: 1235-1241, 1973) has reported that Lobund-W istar rats develop spontaneous metastatic prostatic cancer when they b ecome old(similar to 25% incidence after 25 months). A chemically-indn ced form of the disease has also been described in Lobund-Wistar rats. However, recent reports suggest that most of the chemically induced a denocarcinomas are not prostatic in origin, with most arising in the s eminal vesicle, and thereby raise questions about the origin of the sp ontaneous cancers. We herein report cancer spontaneously arising in th e lateral lobes of the prostates in Lobund-Wistar rats. One of 8 rats killed at 16 months of age showed prostatic carcinoma in situ. Two of 39 rats killed at 20 months displayed early invasive adenocarcinomas w ith no signs of metastases. Because sectioning of the prostates in thi s study was limited to face sections from a single block for each rat, it is highly probable that the true incidence of dysplasias and carci nomas is underestimated by these data. Dysplastic or neoplastic change s were not seen in either the seminal vesicles or other portions of th e prostatic complex. The nuclei of adenocarcinoma cells showed less la beling with antibody to the androgen hormone receptor than did normal cells. These data strongly support the validity of the Pollard model o f spontaneous prostate cancer in Lobund-Wister rats.