Hormones and hormonomimetic compounds in the etiology of cancer

Uterine adenocarcinoma in N-ethyl-N'-nitro-N-nitrosoguanidine-treated rats with high-dose exposure to p-tert-octylphenol during adulthood

Since many risk factors are associated with the development of uterine adenocarcinomas in humans, the etiology is unclear in most cases, although it has been pointed out that estrogen may play essential roles. To clarify the effects of exposure to p-tert-octylphenol (OP), an environmental xenoestrogen, on uterine carcinogenesis, adult Donryu rats were initiated with a single intrauterine treatment of N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) at 11 weeks of age and exposed thereafter to 100 mg / kg OP by s.c. injection until 15 months of age. Adult ovariectomized (OVX) rats were also treated in a similar way. OP had no effect on occurrence of persistent estrus in middle age, although uterotrophic effects were obvious in OVX rats. At the termination, development of uterine adenocarcinomas was significantly increased in animals exposed to OP during adulthood. No tumors, but a few focal hyperplasias, developed in OVX rats. These findings suggest that OP has tumor-promoting effects on ENNG-treated endometrium of rats, possibly due to direct action on the uterus, as indicated by the uterotrophic effect when a high dose of OP was given. The results provide clues to the mechanisms of influence of hormonal disrupters on uterine carcinogenesis.

Pharmacology and toxicology of ethinyl estradiol and norethindrone acetate in experimental animals

For over 30 years various combinations of synthetic estrogens and progestins have been used in oral contraceptive formulations. Ethinyl estradiol (EE) and norethindrone acetate (NA) are common synthetic hormones used in oral contraceptives such as Loestrin, Brevicon, Ortho-Novum, Norlestrin, and Norinyl. In recent years these oral contraceptives have been considered for development in other therapeutic indications. Given the use of these agents for other clinical indications with different and larger target populations, an updated comprehensive review of the toxicology literature of estrogens and progestins is warranted. This review will summarize available data on the pharmacology and toxicology of estrogens and progestins with an emphasis on the specific synthetic hormones EE and NA. Ethinyl estradiol and norethindrone acetate alone or in combination, possess low acute and chronic toxicity. In some studies, EE and/or NA increased the incidence of specific tumors in susceptible strains of rodents and dogs, but not monkeys. These agents are not teratogenic when given in combination. Alone EE and NA have clastogenic properties. Overall, the animal data demonstrates that long-term exposure to EE and NA formulations pose very little health risks to humans.

Effects of reproduction on spontaneous development of endometrial adenocarcinomas and mammary tumors in Donryu rats

Effects of reproduction on spontaneous development of uterine endometrial adenocarcinomas and mammary tumors in Donryu rats were investigated. While the incidence of endometrial adenocarcinomas in Donryu rats was not influenced by a single reproductive experience (SRE), it showed a tendency to decrease in animals having three reproductive experiences (TRE), compared to the nulliparous case (NRE). In addition, both SRE and TRE animals showed delayed occurrence and decreased incidences and mean numbers of mammary tumors, along with reduced incidences of proliferative lesions in the pituitary gland and mucinous epithelium in the vagina. The appearance-time and incidences of persistent estrus in TRE rats were delayed and low, respectively, compared to the SRE and NRE values. The hormonal environment was altered in both groups, the prolactin level in TRE especially being decreased. These results suggest that suppression of the occurrence of endometrial adenocarcinomas and mammary tumors in rats experiencing reproduction is associated with change in the hormonal milieu.

High-yield induction of uterine endometrial adenocarcinomas in Donryu rats by a single intra-uterine administration of N-ethyl-N'-nitro-N-nitrosoguanidine via the vagina

A total of 130 female Donryu rats (10-week-old) were divided into two groups; 80 animals in the experimental group were given a single intra-uterine administration of 20 mg/kg N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) dissolved in polyethylene glycol (PEG) via the vagina without laparotomy, and 50 animals in the control group received PEG alone in the same manner. Small numbers of animals in both groups were killed at 3, 6, 9 and 12 months after ENNG treatment for sequential histological and endocrinological examination, and at 12.5 experimental months (15 months of age) all survivors were killed. At the termination, endometrial adenocarcinomas were present in 49% of the experimental group, compared to 0% in the control group. Severe endometrial hyperplasias were also found only in the experimental group and sequential histological examination showed first appearance of hyperplasia at 6 months and adenocarcinoma at 9 months. No tumors other than uterine carcinomas were induced by ENNG and the carcinogen treatment did not affect the endocrine environment of rats, persistent estrus appearing at 6 months after the start and increasing with age in both groups. The estradiol-17 beta:progesterone (E:P) ratio was also increased after 6 months, with further elevation at 12 months to about 8 times higher than the level at 6 months. These results indicate that an increased E:P ratio might act as a promoter of development of endometrial proliferative lesions initiated by ENNG in this rat strain. The study indicates that the present simple method using Donryu rats provides a good animal model for endometrial adenocarcinoma development in women.

Psychosocial factors as strong predictors of mortality from cancer, ischaemic heart disease and stroke: the Yugoslav prospective study

We investigated the relation of psychosocial risk factors to mortality in a prospective study of 1353 inhabitants of Crvenka, 619 of whom died between 1966 and 1976. All 38 lung cancer deaths occurred in those with high scores for rationality and antiemotionality (R/A), a factor related to suppression of aggression. Compared with lower R/A, high R/A was also associated with a relative risk of mortality of 29 for other cancer, 4.3 for ischaemic heart disease and 6.5 for stroke. Standardising for R/A reduced the smoking/lung cancer association, virtually eliminated the smoking/other cancer and smoking/heart disease relationships and reduced the association of heart disease with blood cholesterol, blood sugar and hypertension. Long lasting hopelessness was also independently associated with cancer as was anger with heart disease, though not so strongly as for R/A. Psychosocial variables are important predictors of mortality and decisively modify the effect of physical risk factors such as smoking.

Collagen gel culture system and analysis of estrogen effects on mammary carcinogenesis

The results obtained to date from studies dealing with the role of hormones, including estrogen, on growth of mammary epithelial cells inside the collagen gel are described. The collagen gel matrix culture system appears to be a suitable system to obtain in vivo-like effects of hormones on mammary cell in vitro. The results thus far indicate that prolactin along with progesterone or cortisol can stimulate mammary cell proliferation. Thus far, estrogen has not been found to be mitogenic in our in vitro system.