ro-24-5531 and Prostatic-Neoplasms

The magnitude of the problem of prostate cancer, and the failure of conventional chemotherapy and surgery to effect a marked diminution in the total number of deaths from this disease, now indicate that chemoprevention of prostatic carcinogenesis must be seriously considered. We describe the development of a new system for quantitating the process of prostatic carcinogenesis in an experimental animal, and the use of this system to demonstrate that the retinoid, 4-hydroxyphenylretinamide, the deltanoid, Ro24-5531, and the estrogen analog, tamoxifen, all are effective agents for prevention of experimental prostate cancer.

Topics: Animals; Anticarcinogenic Agents; Calcitriol; Disease Models, Animal; Drugs, Investigational; Fenretinide; Male; Neoplasm Staging; Prostatic Neoplasms; Rats; Tamoxifen; Treatment Outcome

We evaluated the ability of dietary N-(4-hydroxyphenyl)retinamide; 1 alpha,25-dihydroxy-16-ene-23-yne-26,27-hexafluorocholecalcifero l (Ro24-5531); and tamoxifen to inhibit the development of androgen-promoted carcinomas of the accessory sex organs of male Lobund-Wistar rats. Invasive carcinomas of the seminal vesicle (SV) and anterior prostate (AP) were induced in Lobund-Wistar rats with three different combinations of initiator [N-nitroso-N-methylurea (NMU)] and promoter [testosterone propionate (TP)]: (a) high-dose NMU (30 mg/kg) + high-dose TP (20 mg via implant every 2 months); (b) high-dose NMU + low-dose TP (10 mg implanted every 2 months); or (c) low-dose NMU (15 mg/kg) + low-dose TP. During the period of TP administration, rats were fed a diet supplemented with either N-(4-hydroxyphenyl)retinamide (1 or 2 mmol/kg diet), Ro24-5531 (1.25 or 2.5 nmol/kg diet), tamoxifen (0.5 or 5 mg/kg diet), or vehicle alone. After sacrifice at 8.5 or 11 months, the prostate-seminal vesicle complex from each rat was processed in toto and histologically staged as to the extent of tumor involvement. In animals given low-dose TP, all three agents were significantly effective at reducing the incidence of invasive carcinomas of the SV and, to a lesser degree, the AP. Of the three agents, tamoxifen given in high dose (5 mg/kg) had the strongest activity, reducing the occurrence of invasive SV carcinomas from 72-83% in controls to 6% (P = 0.0001) and the occurrence of invasive AP carcinomas from 50-72% to 18-22% (P < 0.05).

Topics: Androgens; Animals; Anticarcinogenic Agents; Calcitriol; Carcinogens; Drug Screening Assays, Antitumor; Male; Methylnitrosourea; Neoplasms, Experimental; Neoplasms, Hormone-Dependent; Prostate; Prostatic Neoplasms; Rats; Seminal Vesicles; Tamoxifen; Testosterone