Histology, histochemistry, and acid phosphatase of Noble (Nb) rat prostate adenocarcinomas and treatment of androgen-dependent Nb rat prostate adenocarcinoma

For 17 months, Noble (Nb) rat prostate adenocarcinomas were evaluated in various experimental and therapeutic groups. Histologic evaluation of these tumors revealed them to be stable throughout more than 40 tumor transplant generations. The tumor growth pattern in unmanipulated Nb rats was also stable during that time, with less than 10% variation. The acid phosphatase content was determined with the use of the thymolphthalein method, which revealed production of acid phosphatase by these tumors. In addition in approximately 22% of all Nb rat prostate tumors developed pulmonary metastases. The autonomous tumors resulted in a much higher rate of metastases than did the hormonally dependent tumors: 35% versus 18%, respectively. Histochemical staining revealed acid phosphatase in the normal dorsolateral lobe of the Nb rat prostate gland and also in the prostate tumors. The reaction was more positive in the androgen-dependent tumors than in the autonomous ones. One androgen-dependent tumor, which mimics the humoral response of human prostate carcinoma, was chosen to evaluate treatment modalities, castration and chemotherapy (1,3 bis(2-chloroethyl)-1-nitrosourea, adriamycin, and methotrexate). Results were significant with all modalities (P<0.001); however, chemotherapy was more efficacious than was castration in reducing tumor growth. These parameters helped to establish the Nb rat prostate adenocarcinoma model as appropriate for enhancing knowledge of human tumor biology and response to therapy.