fenretinide and Cocarcinogenesis

While all-inclusive complete models for breast cancer development are not available, four concepts are likely to be critical to creation of well-grounded breast cancer prevention efforts: 1) step-by-step progressive development, 2) involving multiple factors, 3) over several years, and 4) during a long period of which the process may be reversible. Interventions to prevent breast cancer must have a comprehensive biological rationale, an absence of serious toxic effects, and long-term acceptability by women. Prophylactic mastectomy may be beneficial in some women, but identification of individuals at very high risk for breast cancer remains elusive. At present, greater attention to four manipulable risk factors is appropriate: radiation, smoking, alcohol, and lactation. Clinical trials are in the process of studying a synthetic retinoid (4-hydroxyphenylretinamide), tamoxifen, and a low-fat diet. Other breast cancer prevention strategies in various phases of preclinical trial evaluation include: pseudopregnancy, an "ideal" combination oral contraceptive, luteinizing hormone-releasing hormone (LHRH) agonist oophorectomy, modification of estrogen metabolism, suppression of ornithine decarboxylase induction, and manipulation of growth factors.

Topics: Adult; Ataxia Telangiectasia; Breast Neoplasms; Cocarcinogenesis; Contraceptives, Oral, Hormonal; Dietary Fats; Estrogens; Female; Fenretinide; Gonadotropin-Releasing Hormone; Humans; Lactation; Mastectomy; Neoplasms, Radiation-Induced; Ornithine Decarboxylase Inhibitors; Premenopause; Prospective Studies; Pseudopregnancy; Randomized Controlled Trials as Topic; Risk Factors; Smoking; Tamoxifen; Temperance; Time Factors

The influence of chemical carcinogen, hormonal stimulation, and chronic dietary administration of the synthetic retinoid, N-(4-hydroxyphenyl)-all-trans-retinamide (4-HPR), on the induction of prostate cancer in male Wistar-Unilever rats was determined. Three different tumor induction regimens were used: (a) a single i.v. dose of 50 mg of N-methyl-N-nitrosourea (MNU) per kg body weight, followed by chronic androgen stimulation via s.c. implantation of two silastic capsules containing 40 mg testosterone each; (b) a single i.v. dose of 50 mg of MNU per kg body weight (no testosterone treatment); and (c) chronic androgen stimulation with implanted testosterone capsules (no MNU treatment). In a fourth series of animals, the incidence of spontaneous prostate tumors was determined in groups of rats receiving neither carcinogen nor hormone stimulation. Within each series, parallel groups of animals were fed a control (vehicle-supplemented) diet or control diet supplemented with 4-HPR beginning 1 day after carcinogen administration; retinoid administration was continuous until termination of the study at 450 days. The incidence of accessory sex gland cancer in rats treated sequentially with MNU + testosterone was >60%, in comparison with cancer incidences of <20% in rats receiving MNU only and <5% in rats treated with testosterone only. No spontaneous accessory sex gland tumors were observed in rats receiving no carcinogen and no testosterone. Tumor induction in the accessory sex glands by MNU + testosterone was relatively specific for the prostate: the incidence of carcinoma of the dorsolateral/anterior prostate was more than 5-fold greater than the incidence of cancer present only in the seminal vesicle. 4-HPR conferred no protection against cancer induction in the prostate by any regimen of MNU and/or testosterone. These results demonstrate the importance of both carcinogen exposure and hormone stimulation on the induction of neoplasia in the prostate of Wistar-Unilever rats.

Topics: Animals; Anticarcinogenic Agents; Body Weight; Carcinogens; Cocarcinogenesis; Fenretinide; Male; Methylnitrosourea; Prostatic Neoplasms; Rats; Rats, Wistar; Testosterone

The activity of the synthetic retinoid, N-(4-hydroxyphenyl)retinamide (4-HPR), as a promoter and as an inhibitor of tumor promotion in mouse skin was investigated using CD-1 and SENCAR mice. Dietary administration of 4-HPR inhibited skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA) in both mouse strains, although protective activity was observed only at high TPA doses. Dietary 4-HPR had no promoting activity in mice receiving initiation and no TPA promotion. These data suggest that retinoid promotion of skin tumorigenesis may be specific to retinoic acid, and is not necessarily characteristic of the entire chemical class.

Topics: Animals; Carcinogens; Cocarcinogenesis; Diet; Drug Antagonism; Female; Fenretinide; Mice; Mice, Inbred Strains; Neoplasms, Multiple Primary; Phorbols; Skin Neoplasms; Species Specificity; Tetradecanoylphorbol Acetate; Tretinoin