Loss of calcitonin receptors: a genetically transmitted defect in rats with high incidence of C-cell tumors

C-cell tumors (medullary thyroid carcinoma) occur in humans and several other mammalian species. This tumor develops spontaneously with a high incidence (50%) in old Wag/Rij (Wistar-derived strain) rats. We have recently shown that calcitonin binding sites, which are present in the Wistar rats, are lost from renal medulla of the Wag/Rij rats before they reach the age of 1 month. In the present work, we investigated the distribution of calcitonin binding sites in the kidneys of first and second generation hybrids of Wistar x Wag/Rij rats. The absence of calcitonin binding sites from the renal medullas of 25% of F2 hybrids indicates that the deficiency is inherited in a Mendelian fashion and opens the way to establishing inbred strains lacking renal medullary calcitonin binding sites.     

Clinical study of a synthetic calcitonin derivative (elcatonin) in patients with metastatic bone tumors

Forty-three cases of metastatic bone tumor were treated with Elcatonin. The agent was injected intramuscularly to each patient at a dose of 40 units twice daily. Twelve patients (28%) experienced pain relief within 4 days after treatment and after 4 weeks, twenty-eight patients (65%) had palliation of pain. In patients with hypercalcemia (4 cases), a decrease of serum Ca was observed one week after administration of Elcatonin. Improved bone scintigram was observed in 37.5% of cases, and radiographic improvement in 20% of cases. These data indicate that Elcatonin is effective for achieving pain relief and in improving the state of invaded bones when administered in combination with conventional treatment modalities for patients with metastatic bone tumors.     

Incidence of spontaneous ileocecal immunocytomas in hybrids of LOU/C rats and rat strains with low spontaneous tumor incidence

Young adult female rats of either the Sprague-Dawley stock or the ACI strain were each given an implant of a compressed pellet of 5 mg diethylstilbestrol (DES) and 15 mg cholestrol 2 days before irradiation with 0.4, 1.3, or 4.0 rads of 0.43-MeV neutrons. These rats were studied, along with appropriate irradiated and nonirradiated controls, until death or for a maximum of 48 weeks. Response differences between the strain and stock included the following: DES produced both pituitary tumors and mammary adenocarcinomas (MAC) in ACI rats only. Neutron radiation increased mammary fibroadenoma (MFA) formation in Srague-Dawley rats only. No interactions between DES and radiation on MAC formation in Sprague-Dawley rats or MFA formation in ACI rats were demonstrated. However, when DES and neutron radiation were combined, DES appeared to inhibit the MFA response to radiation in Sprague-Dawley rats. In contrast, DES appeared to act synergistically with neutron radiation on MAC formation in ACI rats. These results clearly demonstrate rat differences in mammary gland carcinogenesis in response to estrogen, to radiation, or to a combination of both agents.     

A recessive mutation (ter) causing germ cell deficiency and a high incidence of congenital testicular teratomas in 129/Sv-ter mice

The genetic basis of a germ cell deficiency, accompanied by a high incidence of testicular teratomas, was studied in strain 129/Sv-ter mice (formerly designated "129/terSv"). Germ cell deficiency became more severe with advancing age in males, and they were sterile whether or not they had bilateral teratomas. Germ cell-deficient testes were smaller than normal except when the testes had teratomas. In females the ovaries were smaller than normal, but the germ cell deficiency did not progress and most were fertile. The germ cell deficiency resulted from the homozygous state of a recessive mutant gene designated "teratoma (ter)." Matings between females with small ovaries and homozygous normal males produced no germ cell-deficient offspring. When F1 offspring with normal gonads were mated together, germ cell-deficient F2 animals appeared at a frequency close to 1 in 4. When females with small ovaries (ter/ter) were mated with heterozygous males (ter/+), half of the offspring were germ cell deficient. It was concluded that the genetic factor is a single recessive gene. The incidence of teratomas in +/+ strain 129/Sv-ter males was 1.4% (3/216), and all teratomas were unilateral. Seventeen percent (20/117) of heterozygous males had teratomas, of which 18 were unilateral and 2 were bilateral. Ninety-four percent (167/178) of homozygous ter/ter males had teratomas, of which 75% were bilateral. Introduction of the mutant gene ter onto the C57BL/6 genetic background resulted in germ cell deficiency in homozygotes, but it reduced considerably the teratoma incidence in ter/ter males.     

Quantitative transplantation assays of the rat rhabdomyosarcoma BA1112 isografts into the WAG/Rij Y rat and xenotransplantation into the athymic NCr(nu/nu) nude mouse

Quantitative tumor cell transplantation assays have been performed to compare the transplantability of rat rhabdomyosarcoma BA1112 into isologous WAG/Rij Y rats and athymic NCr(nu/nu) nude mice. The end-point was the td₅₀ or the number of viable tumor cells which would transplant the tumors into half of the recipients. At Yale, two sets of 2-fold dilutions were prepared, one was sent to the MGH by Air Express. That afternoon, concurrent assays were performed at Yale using the WAG/Rij Y rat and at MGH using the NCr(nu/nu) mouse. The td₅₀ values were the same for iso- and xenotransplantation. Furthermore, the td₅₀s in rats and mice were unaffected by standard immunization procedures prior to challenge of the td₅₀ assay. The BA1112 (10⁷ trypan blue excluding cells) grew to 10–12 mm and then completely regressed if transplanted into NCr(nu/+) mice which had received 6 Gy whole body irradiation but did not grow in control NCr(nu/+) mice. The times for the BA1112 to grow to 10 mm were the same in normal or preimmunized WAG/Rij Y rats or NCr(nu/nu) mice and in 6 Gy WBI NCr(nu/nu) mice. All of the experimental data show that the xenogenic NCr(nu/nu) mice accept the BA1112 as readily as do the isologous WAG/Rij Y rats.     

Prolactin binding to 7,12-dimethylbenz(a)anthracene-induced mammary tumors and liver in diabetic rats.

Growth rates of 7,12-dimethylbenz(a)anthracene-induced mammary tumors and the specific 125I-labeled prolactin binding to membrane fractions prepared from livers and tumors were studied in rats made diabetic by streptozotocin injection. Growth was inhibited in a majority of tumors and prolactin binding was reduced in both tumors and livers from diabetic animals. Prolactin binding to individual tumors varied over a wide range in both intact and diabetic animals. Scatchard analysis of binding data revealed that the apparent affinity of prolactin binding to liver and tumor membranes was similar (Ka approximately 3.0 X 10(9) M-1) and was not affected by diabetes. We suggest that the reduction in prolactin binding to tumors may render these tissues less responsive to prolactin and thereby explain, at least in part, the observed inhibition of tumor growth in diabetic rats. However, some tumors in diabetic animals regressed despite relatively high levels of prolactin binding activity. Therefore, additional factors most certainly play important roles in the mechanism(s) by which the growth of 7,12-dimethylbenz(a)anthracene-induced tumors is impaired in the diabetic rat.     

Decreased incidence of renal tumors in DMN treated Balb/C mice after orchiectomy

Dimethylnitrosamine (DMN) induced a significant incidence (45.5%) of kidney epithelial tumors in adult male Balb/C mice. The proportion of mice with renal tumors orchiectomized after DMN injection was reduced to 25.6%; whereas the proportion of tumor bearing animals at other sites, such as lung, liver, and lymphatic tissue, increased compared to intact DMN treated animals and controls. This experiment confirms other studies in rats and mice showing that androgens play a role in initiation and progression of nitrosamine induced renal cancer, paralleling the finding of increased male susceptibility in human renal cancer.     

Induction of a high incidence of lung tumors in C57BL/6 mice with multiple ethyl carbamate injections

Murine pulmonary adenomas progress to malignancy with many similarities to human pulmonary adenocarcinoma, the most common form of lung cancer. Inbred mice vary in their susceptibility to lung tumor development, and induced genetic modifications are a powerful tool for understanding this susceptibility. Many transgenic and null mutations relevant to lung cancer pathogenesis were derived on the highly resistant C57BL/B6 (B6) background. Since the inability to reliably induce lung tumors in B6 mice limits these studies, we systematically examined several carcinogenesis protocols in B6 mice. Ten weekly ethyl carbamate (EC) doses caused a nearly 100% lung tumor incidence with a tumor multiplicity >2; multiple EC dosing is thus an alternative to the time-consuming transfer of transgenes and null mutations to susceptible backgrounds.     

Differences in susceptibility to N-butyl-N-(4-hydroxybutyl)nitrosamine-induced urinary bladder carcinogenesis between SD/gShi rats with spontaneous hypospermatogenesis and SD/cShi rats with spontaneous hydronephrosis

Differences in susceptibility to N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced urinary bladder carcinogenesis between two substrains of male Sprague-Dawley rats were examined. One substrain was SD/gShi, which has spontaneous hypospermatogenesis, and the other was SD/cShi, which is a sister strain of SD/gShi, and has normal testis but spontaneous hydronephrosis. SD/gShi rats had a lower incidence of urinary bladder tumors and had lower 5-bromo-2'-deoxyuridine labeling indices in the urinary bladder epithelium than SD/cShi rats when BBN was given. SD/gShi rats had significantly lower urinary concentrations of N-butyl-N-(3-carboxypropyl)nitrosamine (BCPN), which is a metabolite and proximate carcinogen of BBN. In vitro analysis also showed significantly less BCPN formation, using an S9 mix derived from the liver and kidney, in SD/gShi rats than in SD/cShi rats. BCPN formation in vitro was markedly inhibited by non-selective cytochrome P450 (CYP) inhibitors, but not alcohol dehydrogenase inhibitor. However, analysis of CYP proteins including hepatic CYP1A1/2, 2B1/2, 2E1, and 3A2 and renal CYP2E1 and 3A2 revealed no significant variation in levels in either tissue in the groups. There were also no significant intergroup differences in the mutagenicity of carcinogens, including heterocyclic amines and N-nitrosamines, activated by CYP1A1/2 and CYP2E1 and/or CYP2B1/2, respectively. These results suggest that SD/gShi rats are less susceptible to BBN, possibly because less BCPN is produced by CYP isoforms other than those investigated. A contribution of CYP4B1 to the strain difference is also possible.     

Consumption of commercial whole and non-fat milk increases the incidence of 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats

BACKGROUND: Breast cancer has become the most common cancer among women worldwide. Although the consumptions of milk and dairy products were considered to be a risk factor for breast cancer in some epidemiological studies, the results were inconsistent. METHODS: In the present study, female Sprague-Dawley rats received a single oral dose of 5mg 7,12-dimethylbenz(a)anthracene (DMBA). One week later, the animals were divided into four groups: whole milk (WM), artificial whole milk (A-WM), non-fat milk (NFM) or artificial non-fat milk (A-NFM) mixed with commercial powder chow. Rats were palpated weekly to monitor tumor development. At week 20 after DMBA administration, rats were decapitated and the volume and weight of mammary tumor were recorded. RESULTS: Tumor incidence, the cumulative number of tumors and the sums of tumor volume were higher in the WM and NFM groups than in the A-WM and A-NFM groups both at palpation and at autopsy. CONCLUSION: Combining our previous studies, we found the consumption of milk promoted the development of DMBA-induced mammary tumors in rats independent of the fat level.     

Promotion of N-methyl-N-nitrosourea-induced thyroid tumors by iodine deficiency in F344/NCr rats

Six-week-old male F344 rats were each given an injection once iv of N-methyl-N-nitrosourea [(MNU) CAS: 684-93-5] at a dose of 41.2 mg/kg body weight. Two weeks later, groups of rats were placed on iodine-deficient (ID) or iodine-adequate (IA) diets and then sacrificed at 20 and 33 weeks. Other groups received ID or IA diets without MNU. For localizing thyroid-stimulating hormone (TSH) and prolactin, sections of pituitary glands were stained by the avidin-biotin-peroxidase complex technique with the use of anti-rat TSH or prolactin antibody. At 20 weeks, rats receiving MNU and ID diets had a 100% incidence of diffuse follicular goiter and multiple follicular adenomas of the thyroid. Focal proliferative thyroid follicular lesions including focal hyperplasias and adenomas per square centimeter of thyroid gland were significantly increased in rats given MNU and ID diets in comparison with rats given MNU and IA diets. At 33 weeks, all MNU rats on ID diets had a significantly increased incidence of thyroid carcinoma of the follicular or papillary types and diffuse pituitary thyrotroph hyperplasia, hypertrophy, and vacuolar degeneration. Rats fed ID diets without MNU had diffuse follicular goiter but no tumors at any time period. MNU given alone in rats fed IA diets induced a 10% incidence of single thyroid adenomas at 20 weeks and 70% at 33 weeks and a 10% incidence of thyroid carcinoma at 33 weeks. Tumors induced in other organs by MNU were not affected by the ID diets. Thus this experiment provided evidence that ID diets are potent promoters of thyroid tumors in this system, but the ID diet itself without carcinogen was not carcinogenic under the conditions of the study.     

Metabolism of benzo(a)pyrene in animals with high aryl hydrocarbon hydroxylase levels and high rates of spontaneous cancer

Immunogenic, methylcholanthrene-induced sarcomas failed to elicit the production of rapidly cytolytic T lymphocytes in syngeneic mice, although they did elicit the production of more slowly cytotoxic cells. They were, however, susceptible to attack by cytolytic T cells from allo-immune mice and, if infected with ectromelia virus, to attack by similar cells from virus-immune, H-2 compatible mice. It is suggested that the failure to elicit cytolytic T cell production may be due to the lack of an appropriate association between tumour-specific antigens and elements of the major histocompatibility complex.     

Maternal pregnancy hormone levels in an area with a high incidence (Boston, USA) and in an area with a low incidence (Shanghai, China) of breast cancer

Characteristics probably associated with the fetal hormonal milieu have recently been shown to increase (birth size indicators, prematurity, neonatal jaundice) or decrease (pregnancy toxaemia) breast cancer risk in the female offspring. However, it is unknown whether differences in pregnancy hormone levels may contribute to the marked geographical variation in breast cancer incidence. We have compared, in a highly standardized manner, pregnancy hormone levels in a population with high incidence and one with low incidence of breast cancer. Three hundred and four pregnant Caucasian women in Boston and 334 pregnant Chinese women in Shanghai were enrolled from March 1994 to October 1995. Levels of oestradiol, oestriol, prolactin, progesterone, human growth hormone, albumin and sex hormone-binding globulin were measured in maternal blood at weeks 16 and 27 of gestation and compared between the two study sites using non-parametric Wilcoxon''s rank-sum test. Demographical, anthropometrical and pregnancy characteristics were ascertained through interview, and relevant variables concerning delivery and the newborn were abstracted from medical records and paediatric charts. During the first visit, median serum levels of all studied hormones were statistically significant, and in most instances substantially, higher among Chinese women, who have a low incidence of breast cancer, compared with American women, who have a high incidence of breast cancer. An analogous pattern was evident during the second visit, although the relative differences tended to be smaller. Further research is needed to identify lifestyle or other exogenous determinants of pregnancy hormone levels, as well as possible mechanisms by which they may influence carcinogenic processes in the breast and possibly other organs. © 1999 Cancer Research Campaign     

Growth factor binding to 7,12-dimethylbenz(a)anthracene-induced mammary tumors from rats subject to chronic caloric restriction

Caloric restriction (CR) inhibits tumorigenesis in rodents. To understand the basis for this effect the binding of insulin, insulin-like growth factor I/somatomedin C (IGF-I/Sm-C), insulin-like growth factor II/multiplication stimulating activity (IGF-II/MSA), and epidermal growth factor were examined to membrane preparations of 7,12-dimethylbenz(a)anthracene-induced mammary adenocarcinomas and several normal tissues from female Sprague-Dawley rats. Animals were fed ad libitum (AL) or 25% and 40% calorically restricted diets. Large, palpable (LP) and small, less than or equal to 100 mg, nonpalpable (SNP) tumors were evaluated. Growth factor binding to tumors was differentially affected by CR. IGF-I/Sm-C binding was comparable for AL-LP, AL-SNP, and 25% CR-LP tumors, but elevated in 25% CR-SNP tumors. Scatchard analysis revealed high and low affinity IGF-I/Sm-C binding sites, with AL-SNP and 25% CR-SNP tumors exhibiting similar levels of high affinity sites and at a greater concentration than AL-LP and 25% CR-LP tumors. Insulin binding to mammary tumors was low, i.e., 8- to 13-fold lower than IGF-I/Sm-C binding. The 25% CR-LP and SNP tumors bound 2- to 5-fold more insulin than corresponding AL-LP and SNP tumors. Binding of IGF-II/MSA to these tumor preparations was high, approximately 11- to 25-fold greater than insulin binding, and was unaffected by CR or tumor size. The binding of epidermal growth factor was not detected in any tumor preparations. Receptor binding studies were confirmed with covalent cross-linking and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses. Normal tissues exhibited tissue- and growth factor-specific alterations in binding with host CR. Thus, alterations in growth factor binding were not tumor specific, but were less pronounced than in mammary tumors. These findings suggest alterations in IGF-I/Sm-C and insulin binding properties to tumors in relation to CR and tumor size may contribute, in part, to the inhibitory effects of CR on tumorigenesis.     

Antiestrogen-binding sites in 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors: relation to growth

We have detected specific high-affinity binding sites for nonsteroidal antiestrogens in 98% of 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors. Since recent studies have suggested that these binding sites may be involved in the regulation of cell growth and proliferation, we attempted to define a possible relationship between the growth of these hormone-dependent tumors and their antiestrogen-binding site content. Rats bearing such tumors were either treated with haloperidol (to increase prolactin secretion and stimulate tumor growth) or oophorectomized (to reduce circulating estrogen concentration and suppress tumor growth). Compared with controls, haloperidol treatment clearly enhanced tumor growth while oophorectomy induced tumor regression, but neither procedure had any effect on the antiestrogen-binding site concentration. Furthermore, tumors which responded to endocrine manipulation had similar antiestrogen-binding site concentrations as tumors which did not respond. We conclude that (1) the alterations in tumor growth induced by these endocrine manipulations are probably not mediated through a change in antiestrogen-binding site concentration, and (2) the tumor concentration of these binding sites is not under estrogen or prolactin control.