Hormonal aspects of experimental tumorigenesis

Factors associated with the development of neoplasia

A number of factors have been associated with the development of the phenotypic expression of neoplastic disease. The following article reviews the evidence implicating these factors in carcinogenesis and considers them under the groupings of familial or genetic factors, dietary factors, hormonal factors, age and gender.

Factors affecting spontaneous tumor incidence rates in mice: a literature review

The recent increased use of mice for lifetime oncogenicity testing has resulted in concern for the modulating effects on spontaneous tumor incidence rates by factors other than the test article and the high variability of spontaneous tumor incidence rates in control mice. The various factors shown to affect spontaneous tumor incidence rates in mice must be considered in the planning and conduct of oncogenicity studies with this species if biologically meaningful results are to be achieved. This review reports the results of investigations conducted during the past 50 years to determine the effects of various environmental, dietary, hormonal, viral, and genetic factors on spontaneous tumor incidence rates for mice.

Estrogen receptors in the male

Estrogens in the male are secreted by the testes and derived extragonadally from the aromatization of certain androgens. In some brain regions critical for the control of gonadotropin secretion and behavior, androgens may be aromatized to estrogens within the cells that are regulated. Estrogen may have other physiological roles on the testes to control testosterone secretion and on accessory sex glands to promote both fibromuscular growth and secretion. High doses of estrogen given for treatment of prostatic cancer or modulation of reproductive function not only reduce testosterone secretion but also interact with the liver, changing the secretion of various plasma proteins and causing several undesirable side effects. The hypothalamus, pituitary, testes, accessory sex glands, and liver all contain an apparently identical protein, the estrogen receptor, which may mediate the actions of estrogen.

Effect of hormone therapy on immune response in patients with prostatic cancer

Thirty-one patients with adenocarcinoma of the prostate had laboratory studies done for total proteins, serum immunoglobulins, white blood cell counts, lymphocyte blastogenesis, skin tests, acid phosphatase, and CEA (carcinoembryonic antigen). The 16 patients receiving no hormones had depressed total proteins, lymphocyte and monocyte counts, skin tests, and CEA compared with the 15 patients receiving hromones who had depressed serum immunoglobulins, white blood cell counts, lymphocyte blastogenesis, and acid phosphatase.

Influence of hormones and chemical carcinogen on murine leukaemia

Leukaemogenesis induced with chemical carcinogens and hormones was studied in intact and ovariectomized mice of the ICRC strain which is susceptible to spontaneous development of both breast cancer and leukaemia and the Strong A strain susceptible only to breast cancer and not to leukaemia. In ovariectomized females oestradiol was administered at two dose levels (i) 1 μg oestradiol/day for 30 days, (ii) 10 μg oestradiol/day for 30 days. The effect of oestradiol (1 μg/day) and progesterone (1 mg/day) for 30 days was also studied. In one group, two pituitaries of the syngeneic male mice were implanted subcutaneously on the right inguinal pair of mammary glands. Enhancing effect of 20-MCA on leukaemogenesis was seen in intact strain ICRC mice and not in ovariectomized mice. However, administration of hormones, either oestradiol alone or in combination with progesterone, or by the way of pituitary grafts, to these carcinogen treated ovariectomized females increased the incidence of leukaemia with a shorter latent period. Although 20-MCA could induce leukaemogenesis in Strong A ovariectomized females, further treatment with hormones, either with pituitary graft or with oestradiol, failed to promote leukaemogenesis. The highest leukaemia incidence in strain A ovariectomized females was observed in the group treated with a balanced dose of oestradiol and progesterone. The present experimental findings in the ICRC and Strong A strains suggest specific differential responses of different strains of mice to the action of carcinogen and hormones for the induction of leukaemogenesis.

Studies of the regulatory effects of the sex hormones on antibody formation and stem cell differentiation

The primary and secondary immune responses to thymus-dependent and -independent antigens were evaluated in normal male and female mice and in castrated male mice. Both IgM antibody production in the primary response and IgG antibody production in the secondary response were enhanced in females vs. males of equivalent age. Castration of the male converted this animal to a female in terms of responsiveness to the thymus-dependent group of antigens, while inducing equivalent or even greater enhanced responsiveness over the female to the thymus-independent antigen, polyvinylpyrrolidone. Further characteristics of the changes in lymphoid organs were determined in the castrated animal vs. normal males and females. It was shown that the spleen and thymus became markedly hyperplastic, the organ weights exceeding the female, which in turn were greater than in the male. The enhanced weight of the thymus was shown to be due to increased numbers of cortisone-sensitive cells, the absolute number of cortisone-resistant cells remaining equivalent to normal males and females. Thus, the increased thymic weight of the female also resided in the cortisone-sensitive population. Peripheral lymphocyte counts in castrated animals exceeded both normal males and females. Further experiments in gonadectomized males provided evidence that increased thymic cell activity per se played a role in enhanced response to thymus-dependent antigens, but that a thymic-derived hormone mediated the enhanced effect to the thymus-independent antigen in the castrated animal. The capacity for loss of androgenic hormone-producing tissue to generate enhanced differentiation of stem cells was denoted by experiments in which numbers of spleen colonies and uptake of (59)Fe, employed as an index of hematopoiesis 1 wk after reconstitution of lethally irradiated castrated and normal recipients, were enhanced in gonadectomized male animals. Thus, in summary, changes in sex hormone levels exerted a marked influence on immune responsiveness and stem cell differentiation, by increasing numbers of functioning cells, by promoting cellular differentiation, as well as by promoting cellular function via hormonal effects.

The effects of increased numbers of carcinogenic treatments on the induction of cervico-vaginal and vulval tumours in intact and castrate rats

The effect of 5, 10, 20 or 40 weekly local applications of DMBA on the induction of cervico-vaginal epithelial and sarcomatous tumours and on that of squamous celled vulval neoplasms was investigated in intact and castrate rats. The threshold dose increases in the following order: epithelial cervico-vaginal tumours of castrates, followed by those in intacts and by squamous celled vulval tumours and lastly by sarcomas in castrates and intacts.The incidence of sarcomas levels off at about 25% after 20 doses in spayed rats, but increases to 70% with dose in intacts. All sarcomas appear between 200 and 400 days. The incidence of vulval neoplasms increases and the duration of the induction period decreases with dose.Significantly more cervico-vaginal epithelial tumours occur with 5 to 20 paintings than with further application of DMBA. Their peak value is 60% in castrates and 20% in intacts. Castration promotes the progression of vulval papillomas to carcinomas. The sensitivity to carcinogenic stimulation is thus tissue specific and also subject to modification by hormones.While epithelial tumours are multifocal and pass through well-defined intermediate stages (radication, papillomas, microcarcinomas) to full malignancy, the early stages of sarcoma formation are rarely detected and ill-defined. For epitheliomas and sarcomas "invasion" is a criterion of malignancy only if invading cells have acquired "xenoplasia", i.e. the ability to grow in new environments. This capacity increases progressively and its initial lack accounts for the discrepancy between the incidence of embolism and that of metastatic deposits.

The effect of oestrogens, testosterone and progesterone on the induction of cervico-vaginal tumours in intact and castrate rats

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L'azione Promovente Dell'ormone Follicolare nel Duplice Meccanismo di Carcinogenesi Dell'utero e Vagina di Ratte

In order to study the promoting action of the follicular hormone on the genital system of the female, 48 rats were treated. After 2 previous endovaginal instillations of 0.30 per cent 3,4-benzpyrene, the rats have been divided into 4 groups: the first did not receive further treatment, the second received endovaginal instillations of 0.1 ml of folliculin (Estrene) every 3 days, the third received instillations of 0.1ml of croton oil in olive oil, the fourth 0.1 ml of a 5 per cent solution of croton oil in Estrene. The rats were sacrificed at time intervals, from a minimum of 20 days to a maximum of 250 days.

The whole of the experiments showed that:

a) benzpyrene in the employed dosis did not produce tumour occurrence in the genital organs of the rat.

b) the association of benzpyrene (initiating factor) with croton oil in olive oil (promoting factor) induces only changes of hyperplastic and precarcinomatous type.

c) folliculin, on the other hand, exerts a marked promoting action on cancer appearance. In fact, in animals treated with folliculin, a gradual transformation of the hyperplastic processes in precarcinomatous stages and in true epithelial tumours is observed, restricted to the vagina and the low portion of the uterine cervix; such transformation is directly related to the duration of the folliculin treatment, and the hormonal action is increased by croton oil association. In the upper portion of the cervix, in the horns, salpinx and ovary only alterations dependent on the specific and prolonged action of the follicular hormone are observed.

The Role of the Ovary in the Induction of Tumours by the Local Application of 9,10-Dimethyl-1,2-Benzanthracene to the Genital Tract of Rats

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Granulosa cell tumours in intrasplenic ovarian grafts, with intrahepatic metastases, in guinea-pigs at five years after grafting

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