Effect of indomethacin on N-(4-(5-nitro-2-firyl)-2-thiazolyl)formamide-induced urinary tract carcinogenesis

The effects of indomethacin on the urinary bladder and renalpelvis in rats treated with N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide(FANFT) were studied. Two hundred female Sprague-Dawley ratswere divided into four groups. Group 1 received control dietwithout added chemicals. Group 2 was treated with indomethacin(1 mg/kg per day) in the drinking water throughout the experiment.Groups 3 and 4 received 0.2% FANFT in the diet for seven weeksfollowed by control diet. In addition to FANFT, Group 4 receivedindomethacin, 1 mg/kg per day, for the entire experiment. Therats were sacrificed after 92 weeks. There were no urothelialtumors in the control group, one renal pelvic tumor in the indomethacingroup, 4 tumors in the FANFT group and 10 urothelial tumorsin the FANFT ⁺ indomethacin group. The difference between Groups3 and 4 was statistically significant (P < 0.05). Moderateand severe hyperplasia of the renal pelvic and papillary epitheliumwas found in 15 of 48 rats in Group 2 (indomethacin only) ascompared with 6 of 49 control rats (P < 0.05). Moderate andsevere hyperplasia was equally frequent in Groups 3 and 4 (14and 17 animals in each group, respectively). Twenty-four ratsin Group 2 had mammary tumors as compared to 12 animals in Group1 (P < 0.01). Five of the tumors in Group 2 were adenocarcinomas.There was no difference between the number of mammary tumorsin Groups 3 and 4 (36 and 32 animals in each group, respectively).The results suggest that indomethacin enhances FANFT-inducedurinary tract carcinogenesis. Indomethacin also seems to exertsome tumorigenic activity in the mammary gland.     

Parous rats regain high susceptibility to chemically induced mammary cancer after treatment with various mammotropic hormones.

Parity in humans and rats provides significant protection against mammary tumor development. This study was carried out to investigate whether treatment of parous rats with mammotropic hormones would affect methyl-nitrosourea (MNU)-induced mammary carcinogenesis. Parous rats were treated with 17beta-estradiol (E2), progesterone (P4) and thyroxine (T4) alone or in combination. E2 (20 microg/60 days) and P4 (20 mg/60 days) were administered by silastic tubing and T4 in the drinking water (3 microg T4/ml). Hormonal treatments commenced 7 days before MNU injection and continued for 33 weeks. Animals were palpated weekly for tumor detection. The effects of the hormonal treatments on the circulating concentrations of E2, P4, growth hormone (GH), prolactin (PRL), T4 and insulin-like growth factor-I (IGF-I) after 7 days of treatment, the time of MNU injection, was assessed. Animals treated with E2 had significantly elevated circulation concentrations of GH, PRL and P4, and serum levels of E2 were more consistent in this group than in the other animal groups. P4 treatment caused elevation in P4 concentration in serum but did not affect the circulating levels of other hormones. The proliferation of the mammary gland at the time of MNU injection was elevated in animal groups treated with E2 either alone or with P4 and T4 and in animals treated with P4 alone, but the mammary gland was most differentiated in untreated parous rats and least in animals treated with E2 either alone or with P4 and T4. Mammary tumor incidence was 10% in parous rats that did not receive any hormonal treatment. Treatments with E2 or P4 alone significantly increased the susceptibility of parous animals to 67 and 50.0%, respectively; a tumor incidence similar to that of untreated AMV rats (64%). Parous rats treated with E2 plus P4 had tumor incidence higher than 90%. T4 administered did not affect mammary carcinogenesis.     

Effect of alpha-naphthyl isothiocyanate on 2-amino-3-methylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis in rats

The modifying effects of alpha-naphthyl isothiocyanate (ANIT) on 2-amino-3-methylimidazo[4,5-b]pyridine (PhIP)-induced mammary carcinogenesis were investigated in female Sprague-Dawley (SD) rats, and the hepatic activities of the phase II detoxifying enzymes glutathione S-transferase (GST) and quinone reductase (QR) were also assayed. Ninety-eight rats were divided into 4 groups. Starting at 6 weeks of age, rats were fed the high-fat diet without ANIT (Groups 1 and 4) or the experimental diet (high-fat diet mixed with 400 ppm ANIT, Groups 2 and 3). At 7 weeks of age, Groups 1 and 2 were given PhIP in corn oil (85 mg/kg body weight, 8 times for 11 days) by intragastric intubation. One week after the last PhIP injection, 5 rats in each group were sacrificed to assay GST and QR activities, and the experimental diets for Groups 2 and 3 were switched to the high-fat diet without ANIT until termination of the experiment. Group 4 served as the vehicle control. All rats were sacrificed at 24 weeks after the start of the experiment. At termination of the experiment, mammary tumours were detected in Groups 1 (PhIP alone) and 2 (PhIP + ANIT) and were shown histologically to be adenocarcinomas; their incidences (multiplicities) were 56.3% (1.66 +/- 2.31/rat) in Group 1 and 6.7% (0.07 +/- 0.25/rat) in Group 2 (p < 0.001). Mean sizes of the tumours were 10.6 +/- 5.3 mm in Group 1 and 6.5 mm in Group 2. No mammary tumours were observed in rats of Groups 3 and 4. In addition, ANIT treatment significantly increased the activities of GST and QR in the livers of rats in Groups 2 and 3 as compared to Groups 1 and 4. These results imply that the isothiocyanate compound ANIT shows potent inhibitory effects on mammary carcinogenesis induced by PhIP in female SD rats when administered during the initiation stage.     

Antitumor effect of pyridoglutethimide, an aromatase inhibitor, on 7,12-dimethylbenz(a)anthracene-induced mammary tumors of rat.

The antitumor effects of pyridoglutethimide (PG; 3-ethyl-3-(4-pyridyl) piperidine -2, 6-dione), a new analogue of aminoglutethimide (AG), were examined in rats with DMBA-induced mammary tumors. On the day following ovariectomy, the DMBA-treated rats were divided into four groups. The rats in each group (n = 25) received testosterone (20 mg/kg/day) or testosterone (20 mg/kg/day) with PG or AG (50 mg/kg/day) daily 6 times per weeks for 4 weeks; tumor volume was measured once weekly. Mammary tumors were dramatically increased after the administration of testosterone. However, in the rats receiving PG or AG simultaneously with testosterone, the tumors were significantly reduced with decrease of serum estradiol levels. Thus PG may suppress the growth of estrogen-dependent mammary tumors.     

Site-dependent modulating effects of conjugated fatty acids from safflower oil in a rat two-stage carcinogenesis model in female Sprague-Dawley rats

Modifying effects of dietary administration of conjugated fatty acids from safflower oil (CFA-S), rich in conjugated linoleic acid, on major organs were examined in the post-initiation stage of a two-stage carcinogenesis model in female rats. Groups of 21 or 22 F344 female rats were treated sequentially with 2,2'-dihydroxy-di-n-propylnitosamine (intragastrically, i.g.), 7,12-dimethylbenz[a]anthracene (i.g.), 1,2-dimethylhydrazine (subcutaneously) and N-butyl-N-(4-hydroxybutyl)nitrosamine (in drinking water) during the first 3 weeks for initiation, and then administered diet containing 1 or 0.1% CFA-S for 33 weeks. Further groups of animals were treated with carcinogens or 1% CFA-S alone, or maintained as non-treated controls. All surviving animals were killed at week 36, and major organs were examined histopathologically for development of pre-neoplastic and neoplastic lesions. The 1 and 0.1% CFA-S treatment significantly decreased the incidence and multiplicity of mammary carcinomas, though a clear dose response was not observed. In the urinary bladder, the incidence of papillary or nodular hyperplasia but not tumors was significantly increased in the 1% CFA-S-treated group. The results indicate that low dose CFA-S may find application as a potent chemopreventor of mammary carcinogenesis.     

Organ-dependent modifying effects of caffeine, and two naturally occurring antioxidants alpha-tocopherol and n-tritriacontane-16,18-dione, on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary and colonic carcinogenesis in female F344 rats.

Modifying effects of caffeine, alpha-tocopherol, and n-tritriacontane-16,18-dione (TTAD) on 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced mammary and colonic carcinogenesis were investigated in female F344 rats. Groups of 20 rats, 6 weeks old, were given 0.02% PhIP (in diet) alone, or together with 0.1% caffeine (in drinking water), 0.5% alpha-tocopherol (in diet) or 0.1% TTAD (in diet) for up to 54 weeks. Groups of 10 females receiving basal diet or one of the test chemicals without PhIP supplementation were also maintained. The final combined incidences (adenomas plus adenocarcinomas) and multiplicity (No./rat) of mammary adenomas and adenocarcinomas were significantly lowered in the PhIP plus caffeine group (10%, 0.10) as compared to the PhIP alone value (40%, (1.50). Incidences of mammary tumors in the PhIP plus alpha-tocopherol or TTAD groups tended to be decreased while their multiplicities were significantly lowered. With regard to colon tumor development, on the other hand, rats given PhIP plus caffeine exhibited an elevated incidence (75% versus 15% in the control), whereas alpha-tocopherol and TTAD had no effect. Surprisingly, metabolic activation of PhIP was inhibited by addition of caffeine in an in vitro assay. The results indicate that caffeine exerts a potent chemopreventive action against PhIP-induced mammary carcinogenesis, but acts as a co-carcinogen for PhIP-induced colonic carcinogenesis.     

Prolactin levels and molecular heterogeneity in rat strains with high and low incidence of DMBA-induced mammary tumors

Summary We compared the following parameters in Long-Evans (LE) and Sprague-Dawley (SD) female rats: 1) mammary tumor incidence after DMBA, 2) plasma prolactin (PRL) during the estrous cycle before and after DMBA, 3) plasma PRL in immature females from 0900 hr on day 29 to 0900 hr on day 30, 4) plasma PRL from 1200 to 1700 hr and before and 10 min after i.p. TRH administration in ovariectomized (OVX) rats treated with 200 µg polyestradiol phosphate (PEP), 5) anterior pituitary (AP) PRL concentration in OVX rats treated with 200µg PEP, and 6) levels and Sephadex G-100 gel filtration patterns of plasma PRL 10 min after i.p. TRH administration in OVX rats treated with 200µg PEP. We observed marked mammary tumor incidence in SD rats from one supplier (S-SD, Spartan) (96%) compared to SD from another supplier (CRSD, Charles River) (40%) or LE rats (10%). Plasma PRL was significantly decreased on metestrus-diestrus and increased on proestrus-estrus in SD (both suppliers) but not in LE rats 90 days after DMBA compared to rats not given DMBA and sacrificed at same stages of the estrous cycle on day 55 of age. Immature LE and SD-CR females exhibited significant late afternoon and early morning prolactin surges on days 29–30 whereas SD-H rats had either no surges or poorly synchronized surges at the same times. Ovariectomized mature females of the tumor-resistant strains had significantly more AP PRL than the tumor-sensitive strain when given PEP, however there were no differences between the strains in estrogen-induced afternoon PRL surges or in TRH-induced PRL release in the mature OVX, PEP-treated rats. On the other hand, Sephadex G-100 gel filtration patterns of plasma PRL in OVX LE and the tumor-resistant SD group treated with PEP and sacrificed 10 min after TRH administration were markedly different when compared with tumorsensitive SD rats. These studies indicate that there are differences in PRL secretion between strains of rats with high and low mammary tumor incidence but not all of these differences are directly related to the variation in tumorigenesis. The most promising parameters appear to be PRL secretion in immature rats and molecular heterogeneity of plasma PRL. These factors are currently under further investigation.A visiting scientist from the Department of Animal Science, Nihon University, Tokyo, Japan.     

Estrous cycle modification of rat mammary tumor induction by a single dose of N-methyl-N-nitrosourea

The potential of individual stages of the rat estrous cycle to alter the incidence and subsequent behavior of mammary carcinomas induced by a single dose of N-methyl-N-nitrosourea on diestrus, proestrus, or estrus was examined. Mean latencies to first tumor appearance in diestrous, proestrous, and estrous groups were 86, 71, and 69 days, respectively (P less than 0.05 diestrus versus proestrus, estrus). Tumor incidence in diestrous rats given injections (73%) was significantly lower than in proestrous (87%) or estrous (89%) animals given injections, as was the mean number of tumors per rat. However, the number of days required for tumors to reach 1 cm in diameter in diestrous animals given injections (13.0) was significantly lower as compared with tumors in rats given injections during proestrus (19.3) or estrus (22.2). In later growth stages, the diestrous tumor doubling time was one-half that of tumors in proestrous rats given injections. Flow cytometric analysis of tumor tissues during midlog and later growth phases did not reveal any significant changes in ploidy or growth fractions between groups. Further, there was no significant difference in tumor cytosol estrogen receptor incidence, affinity (Kd), or content between groups, although tumor cell nuclear receptor for estrogen was higher (38.3 fmol/mg DNA; P less than 0.05) in proestrous rats given injections than in diestrous (21.6) or estrous (21.8) animals given injections. These data support the concept that the prevailing hormonal profile of the estrous cycle at the time of tumor initiation modulates the subsequent induction of mammary tumors. Further, the absence of any observed difference in tumor behavior between proestrous and estrous rats given injections suggests that prolactin does not impose an additive or synergistic effect on the initial stage of tumor induction when mammary gland epithelial cell DNA is previously stimulated by estrogen.     

Organ-dependent Modifying Effects of Caffeine, and Two Naturally Occurring Antioxidants α-Tocopherol and n-Tritriacontane-16,18-dione, on 2-Amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP)-induced Mammary and Colonic Carcinogenesis in Female F344 Rats

Modifying effects of caffeine, α-tocopherol, and n -tritriacontane-16,18-dione (TTAD) on 2-amino-1-methyl-6-phenylimidazo[4,5- b ]pyridine (PhIP)-induced mammary and colonic carcinogenesis were investigated in female F344 rats. Groups of 20 rats, 6 weeks old, were given 0.02% PhIP (in diet) alone, or together with 0.1% caffeine (in drinking water), 0.5%α-tocopherol (in diet) or 0.1% TTAD (in diet) for up to 54 weeks. Groups of 10 females receiving basal diet or one of the test chemicals without PhIP supplementation were also maintained. The final combined incidences (adenomas plus adenocarcinomas) and multiplicity (No./rat) of mammary adenomas and adenocarcinomas were significantly lowered in the PhIP plus caffeine group (10%, 0.10) as compared to the PhIP alone value (40%, 0.50). Incidences of mammary tumors in the PhIP plus α-tocopherol or TTAD groups tended to be decreased while their multiplicities were significantly lowered. With regard to colon tumor development, on the other hand, rats given PhIP plus caffeine exhibited an elevated incidence (75% versus 15% in the control), whereas α-tocopherol and TTAD had no effect. Surprisingly, metabolic activation of PhIP was inhibited by addition of caffeine in an in vitro assay. The results indicate that caffeine exerts a potent chemopreventive action against PhIP-induced mammary carcinogenesis, but acts as a co-carcinogen for PhIP-induced colonic carcinogenesis.     

Effects of age on multiple organ carcinogenesis induced by 3,2'-dimethyl-4-aminobiphenyl in rats, with particular reference to the prostate

The effects of age on multi-organ carcinogenesis induced by 3,2'-dimethyl-4-aminobiphenyl (DMAB) in male F344 rats were examined. Groups of 5-, 35-, and 65-week-old animals were given 4 weekly sc injections of DMAB at a dose of 200 or 150 mg/kg body weight. Prostate carcinomas were induced in 8 to 19% of rats treated, no significant differences in the incidence between different ages being observed. Tumors in the small intestine, skin, pancreas and peritoneum, however, developed more frequently in young than in old animals, whereas higher incidences of testis, preputial and mammary gland lesions were found in the 35- and/or 65-week-old groups. Colon and Zymbal gland carcinogenesis did not reveal any age dependence.     

Effects of Age on Multiple Organ Carcinogenesis Induced by 3,2'-Dimethyl-4-aminobiphenyl in Rats, with Particular Reference to the Prostate

The effects of age on multi-organ carcinogenesis induced by 3,2'-dimethyl-4-aminobiphenyl (DMAB) in male F344 rats were examined. Groups of 5-, 35-, and 65-week-old animals were given 4 weekly sc injections of DMAB at a dose of 200 or 150 mgAg body weight. Prostate carcinomas were induced in 8 to 19% of rats treated, no significant differences in the incidence between different ages being observed. Tumors in the small intestine, skin, pancreas and peritoneum, however, developed more frequently in young than in old animals, whereas higher incidences of testis, preputial and mammary gland lesions were found in the 35- and/or 65-week-old groups. Colon and Zymbal gland carcinogenesis did not reveal any age dependence.     

N-nitroso-N-methylurea-induced mammary tumors in the rat: role of prolactin and a prolactin-lowering drug

Female outbred Sprague-Dawley rats bearing N-nitroso-N-methylurea (NMU)-induced mammary tumors received various endocrine therapies 3 months after the first NMU injection. Rats were divided into 5 groups (15-20 rats/group) and received a 4-week treatment as follows: group 1, controls; group 2, ovariectomized; group 3, 0.5 mg 2-bromoergocryptine (CB-154) injected so twice daily; group 4a, pituitary implant under the kidney capsule; and group 4b, CB-154 injected during the last 2 weeks of the experiment in rats bearing a pituitary implant. Castration of rats with established NMU-induced tumors resulted in a decrease in both tumor number and size, but these parameters again started to increase 3 weeks post castration. CB-154 failed to reduce the tumor number but did arrest the increase in tumor size. In the animals with a pituitary implant, both tumor number and tumor size increased progressively at a greater rate than in control animals, whereas the addition of CB-154 (group 4b) stabilized the tumor growth. Ovariectomy (OVX) resulted in a significant decline of steroid receptor levels. Prolactin (PRL) receptor levels were significantly stimulated by the pituitary implant, and CB-154 prevented this increase. The present studies confirmed that NMU-induced mammary tumors are less hormone-dependent (response to OVX) than 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumors. The role of PRL also appears to be less important, at least for established tumors, for NMU-induced mammary tumors than for DMBA-induced mammary tumors.     

Effects of dietary fat on age-dependent sensitivity to mammary carcinogenesis

Two groups of female Fischer rats were fed either a high-fat, low-carbohydrate (HF) diet or a low-fat, high-carbohydrate (LF) diet throughout the experiments, beginning from weaning. Each group of rats was divided into 4 subgroups and given an i.v. dose (50 mg/kg body wt.) of N-methylnitrosourea (NMU) at 35, 50, 90 or 130 days of age, respectively. Mammary tumor yield showed an age-dependent response in both groups. Although mammary tumor incidence decreased in rats as their age increased, irrespective of whether they were fed a high- or low-fat diet, the tumor incidence was significantly higher in rats fed the high-fat diet at any age. Thus, the combined effect of dietary fat and age-dependent sensitivity on mammary carcinogenesis caused more than a 4-fold difference in mammary tumor incidence rates between the 2 groups of rats.     

Chemoprevention of experimental mammary carcinogenesis by the synthetic organoselenium compound, benzylselenocyanate, in rats

The effect of the dietary organoselenium compound, benzylselenocyanate (BSC) along with its sulphur analogue, benzylthiocynanate (BTC) and sodium selenite (Na2SeO3), on 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary carcinogenesis was examined in female Sprague-Dawley rats during the initiation phase of carcinogenesis. Semipurified diets containing 25 p.p.m. of BSC and 25 p.p.m. BTC, and 4 p.p.m. Selenium as Na2SeO3 in drinking water were given to 5-week-old rats for 3 weeks starting 2 weeks before, during and until 1 week after carcinogen treatment. At 7 weeks of age animals were given a single dose of DMBA (10 mg) in 1 ml olive oil by oral intubation. One week after DMBA treatment, the groups receiving BSC- and BTC-supplemented diets were transferred to the unsupplemented standard diets and the group of rats receiving Na2SeO3 in drinking water was transferred to regular tap water for the duration of the experiment. The results indicate that the rats receiving BSC in their diet showed a highly significant inhibition of tumor incidence and tumor multiplicity as well as a prolonged latency period when compared to the group fed the control diet. Neither BTC nor Na2SeO3 had any effect on the subsequent development of mammary tumors. These results indicate that dietary BSC inhibits mammary tumor incidence during the initiation phase of carcinogenesis and is a considerably more potent inhibitor than its sulphur analogue BTC and inorganic selenium. This is the first report that demonstrates the inhibition of mammary carcinogenesis by a synthetic organoselenium compound.     

Histopathology of breast lesions induced in BUF rats of varying ages by ingestion of N-4-(4'-fluorobiphenyl) acetamide.

Inbred BUF male and female rats 4, 12, 24, and 52 weeks old ingested 0.04 percent N-4-(4'fluorobiphenyl)-acetamide in a semisynthetic diet for 36 weeks. They were killed 12 weeks later. Susceptibility to mammary carcinogenesis was related to the age and sex of the animals. Younger female rats developed more mammary tumors. Approximately half of these mammary tumors were well-differentiated adenocarcinomas; the remainder were either poorly differentiated or anaplastic adenocarcinomas.     

A bitter diterpenoid furanolactone columbin from Calumbae Radix inhibits azoxymethane-induced rat colon carcinogenesis

Chemopreventive effects of conjugated fatty acids derived from safflower oil (CFA-S), which contains large amounts of conjugated linoleic acid, and from perilla oil (CFA-P) with abundant conjugated alpha-linolenic acid were examined in a 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)-induced rat mammary carcinogenesis model. Groups of 20-22 6-week-old female Sprague-Dawley (SD) rats were given eight intragastric injections of PhIP at a dose of 100 mg/kg b.w. during the initial 8 week period. Powdered basal diets containing 0.1% CFA-S or CFA-P were applied during or after PhIP treatment until week 40. In the rats receiving CFA-S or CFA-P together with PhIP treatment, retardation of mammary tumor emergence was observed until week 27. The groups given CFA-S or CFA-P after PhIP treatment, in contrast, demonstrated significant decrease in the final incidences of mammary adenocarcinomas. The indices of proliferating cell nuclear antigen positive cells in mammary adenocarcinomas were significantly reduced with both CFA-S and CFA-P in the post-initiation phase. Formation of aberrant crypt foci in the colon and basophilic foci of the pancreas due to the PhIP treatment group were not affected by CFA-S or CFA-P. In a second short-term experiment, female SD rats were maintained on powdered basal diet containing 0.03% PhIP alone or together with 0.1% CFA-S or CFA-P for 4 weeks. Immunohistochemically, CFA-S and CFA-P were revealed to suppress PhIP-DNA adduct formation in the epithelial cells of mammary gland (duct and alveolar cells), colon and pancreas. These results indicated that CFA-P and CFA-S may retard development of PhIP-induced mammary tumors with inhibition of PhIP-DNA adduct formation, and decreased mammary carcinogenesis in the post-initiation period with inhibition of cell proliferation.     

Inhibitory effect of bioginseng on radiation-induced carcinogenesis in rats

Influence of bioginseng (biotechnological pharmaceutical drug from ginseng radix culture) on radiation-induced carcinogenesis has been studied. LIO female rats were divided into 3 groups. Rats of the first group (n=25) were used as intact control and weren't exposed to any influence. Rats of the second (n=50) and third (n=50) groups were exposed to single total body gamma-irradiation at a dose of 4 Gy. Animals of the 2nd group weren't exposed to any influence after irradiation, while animals of the 3rd group were given bioginseng with tap water (20 ml/l) until the end of study (438 days). In the control group 22,7% of animals developed tumors. In the 2nd group (irradiated control) 70% of animals were bearing multiple tumors one third of which were malignant. Mammary gland tumors were most frequent. Compared to the 2nd group the 3rd group receiving irradiation and bioginseng demonstrated the decrease in tumor incidence by 24.5% and 2,4 rate of decrease in tumors number. For the malign tumors was observed the decrease by 26.8% and 2,9 times, accordingly. For the mammary tumors the decrease was by 23.0% and 2,0 times, for mammary adenocarcinomas by 23.4% and 3,5 times, accordingly. The incidence and number of endocrine and reproductive organs tumors was 20,9% and 5,6 times, accordingly. Therefore, bioginseng effectively inhibits carcinogenesis induced by ionizing radiation in female rats.     

Inhibition of carcinogen-induced rat mammary tumor growth and other estrogen-dependent responses by symmetrical dihalo-substituted analogs of diindolylmethane

90%) by the haloDIMs at concentrations of 5 or 10 microM, and only 4, 4'-dichloroDIM alone increased cell proliferation. With the exception of 5,5'-difluoroDIM, the remaining compounds also inhibited E2-induced growth of MCF-7 human breast cancer cells. DihaloDIMs (100 mg/kg/dayx3) were not estrogenic in the immature female B6C3F1 mouse uterus; however, in animals co-treated with E2 (0.02 microg/mouse), 5,5'-dichloro- and 6,6'-dichloroDIM inhibited uterine progesterone receptor (PR) binding and uterine peroxidase activity, whereas 5,5'-dichloro- and 5,5'-dichloro-2,2'-dimethylDIM inhibited only the latter response. The antitumorigenic activities of the dihaloDIMs were determined by their inhibition of carcinogen-induced mammary tumor growth in female Sprague-Dawley rats. 4,4'-Dichloro-, 5,5'-dibromo- and 6,6'-dichloroDIM, significantly inhibited mammary tumor growth at doses of 1 mg/kg every second day, and no significant changes in organ weights or liver and kidney histopathology were observed. These three compounds were more active than DIM in the same in vivo assay.     

N-nitroso-N-methylurea-induced mammary carcinogenesis: effect of prolactin on expression of Ia antigen by tumor cells

Prolactin (PRL) increases of Ia antigen (Ia Ag) expression in female Sprague-Dawley rats with N-nitroso-N-methylurea [(NMU) CAS: 684-93-5]-induced mammary tumors were studied. The effectiveness of PRL was examined when cancers appeared about 2-3 months after the first NMU administration. Rats with NMU-induced mammary tumors were divided into 3 groups: Group 1 was treated with 30 micrograms ovine PRL (o-PRL) in daily sc injections for 5 days. Group 2 received 0.5 mg 2 alpha-bromoergocryptine (CB-154), a known inhibitor of pituitary gland secretion, daily in sc injections for 6 days. Group 3 was the control group. Ia Ags expressed by NMU-induced mammary tumor cells were then quantified successively by double labeling [protein membrane cells with iodine-131 and anti-Ia monoclonal antibody (MoAb) with iodine-125]; then isolation and quantification of the doubly labeled immune complex were performed by affinity chromatography and chromatofocusing successively. When the specific activity of glycoproteins is known, the amount of glycoproteins that bind specifically to the anti-Ia MoAb can be deduced. In NMU-induced rat mammary tumor controls, about 5% of the purified glycoproteins bound specifically to the MoAb, and the amount increased to 8% for NMU-induced rat mammary tumors treated with 30 micrograms o-PRL daily for 5 days and decreased to 2.5% in NMU-induced rat mammary tumors treated with 0.5 mg CB-154 daily for 6 days. Total PRL receptor levels were measured in all tumors tested. For control NMU-induced rat mammary tumors, total PRL receptor levels were 6.35 +/- 1.40 fmol/mg protein, 7.20 +/- 2.40 fmol/mg protein for NMU-induced rat mammary tumors treated with o-PRL, and 6.81 +/- 2.34 fmol/mg protein for NMU-induced rat mammary tumors treated with CB-154. Our results demonstrated that treatment of NMU-induced rat mammary tumors with PRL increased the amount of Ia Ag expression by tumor cells and should prove very useful to the understanding of the biology of PRL in the tumorogenesis of the mammary gland.     

Mammary tumorigenesis in growth hormone deficient spontaneous dwarf rats; effects of hormonal treatments

This study was carried out to investigate mammary tumorigenesis in growth hormone (GH) deficient spontaneous dwarf rats (SDR). At 50–60 days of age, the rats were divided into five groups. Group 1 received bovine (b) GH (prolonged release formulation) administered at a dose of 40–50 mg/kg body wt. in 50 l weekly injections; group 2 received recombinant human insulin-like growth factor-I (IGF-I) at a dose of 1 mg/kg body wt./day administered via osmotic pumps; animals in group 3 were fitted with subcutaneous silastic capsule containing 30 g 17-estradiol (E2) plus 30 mg progesterone (P4), replaced every 2 months; group 4 received both bGH and E2 plus P4 treatments at the same doses as above, and control animals (group 5) received sham treatments (vegetable oil injection, silastic capsules containing cellulose). After 1week of treatment, all animals were injected intraperitoneally with the carcinogen N-methyl-N-nitrosourea (MNU) at a dose of 50 mg/kg body wt. Other groups of animals, receiving identical hormonal treatment to those exposed to MNU, were treated for 10 days only and then sacrificed for assessment of circulating concentrations of hormones and mammary gland characteristics at the time of carcinogen exposure. The hormonal treatments of the animals exposed to the MNU were continued for an additional 20 weeks and mammary tumor development monitored by weekly palpation and tumors collected as necessary. The rats were weighed weekly. At the end of the treatment period, all animals were sacrificed and remaining tumors were collected. Rats in all groups continued to gain weight throughout the experimental period, but the largest weight gain was see in animals receiving GH either alone or with E2 and P4. Animals treated with IGF-I also gained weight compared to controls, but this weight gain was less than that seen in GH-treated rats. GH treatment alone increased mammary tumor incidence from 4.8% in controls to 100%. Average tumor load and latency in the GH-treated rats were 7.0 ± 0.8 tumors/tumor-bearing rat (mean±SEM) and 57.3 ± 2.7 days (mean±SEM), respectively. As in intact Sprague–Dawley rats, approximately 90% of the tumors that developed in the GH-treated rats were ovarian dependent for growth. IGF-I treatment also increased mammary tumor development to 62.5%. Average tumor load and latency in the IGF-I-treated rats were 1.6 ± 0.4 tumors/tumor-bearing rat (mean±SEM) and 96.2 ± 14.5 days (mean±SEM), respectively. However E2+P4 treatments did not significantly alter tumorigenesis and, surprisingly, simultaneous treatment with E2+P4 and GH obliterated the GH-stimulated increase in tumor development. Prolactin (PRL) did not appear to influence mammary tumorigenesis in the SDRs, as untreated SDRs had significantly elevated serum concentration of PRL as compared with normal Sprague–Dawley (SD) rats, whereas GH-treated SDRs had PRL levels similar to that of normal SD rats. No obvious structural characteristics were associated with high or low susceptibility to mammary tumorigenesis, as assessed by mammary gland whole mounts from the different animal groups sacrificed at the time of carcinogen administration.Enhanced expression of the extracellular signal-regulated kinase 1/2 (ERK1/2), and activation (phosphorylation) of ERK1/2 were associated with an increase in mammary tumorigenesis. Similarly, the expression of the estrogen receptor- (ER) was significantly elevated in animal groups with the highest susceptibility to tumorigenesis, whereas the levels of cyclin D1 expression were not related to mammary tumorigenesis.