Characterization of the Dunning R3327H prostatic adenocarcinoma: an appropriate animal model for prostatic cancer.

The Dunning R3327H rat prostatic adenocarcinoma appears to be an appropriate animal model for studying prostatic cancer. This report contains a detailed characterization of this tumor at the morphologic, biochemical, and therapeutic levels. Electron micrographic, histologic, and histochemical studies clearly establish the adenocarcinoma nature of this tumor. The histology of the R3327H tumor is similar to well-differentiated human prostatic cancer. The biochemical and enzymatic profile of the tumor indicates its origin from the rat dorsolateral prostate. The cell kinetics and growth rates of this tumor following a variety of hormonal manipulations (castration, estrogens, androgens, and antiandrogens) have established that 70%-90% of the cells in this tumor require androgens for their growth. However, 10%-30% of the cells are capable of growth in the absence of androgens. Both cell types are present in the initial tumor inoculum and these different cell types possess similar growth rates. The predominance of the androgen-sensitive cells accounts for the relatively greater size of the tumor achieved in the intact male animal at a given growth time. After the tumor is well established in an intact animal, subsequent estrogen therapy or castration resulted in a marked diminution in tumro volume. This was followed by a subsequent relapse. In addition, estramustine phosphate was also shown to cause shrinkage in the tumor volume.