No effect of a high-fat diet on promotion of sex hormone-induced prostate and mammary carcinogenesis in the Noble rat model

Results of international correlation and migrant studies suggest that dietary fat promotes carcinogenesis in hormone-sensitive sites, but this is disputed. In the present study, we used a Noble rat model of sex hormone-induced cancers to examine the effect of a high-fat diet on the incidence and latency of prostate and mammary cancer in male (n 139) and female (n 72) animals respectively. We also measured alpha-tocopherol levels in female breast tissue to determine whether a high intake of polyunsaturated fatty acids depletes antioxidant defence in target tissues, providing a possible potentiating mechanism for carcinogenesis. Results showed a very high incidence of hormone-induced adenocarcinomas of prostate and mammary gland, irrespective of diet. There was no difference in the pattern of carcinogenesis in different prostatic locations, weight of the prostate, or weight gain between male rats on the high-fat diet compared with the control (standard, low-fat) diet. In female rats, the incidence of mammary cancer and the body-weight gain were the same in both dietary groups, and breast alpha-tocopherol was also unaffected by dietary fat intake. Our present results are supportive of recent cohort studies that reported no significant association between intake of fat and the development of human prostate and breast cancer, and do not support a role for dietary fat in promoting sex hormone-induced prostate and mammary carcinogenesis.

Adenovirus-mediated endostatin delivery results in inhibition of mammary gland tumor growth in C3(1)/SV40 T-antigen transgenic mice

We demonstrate the efficacy of systemic administration of a replication-defective adenovirus expressing endostatin (Ad-mEndo) administered during the preinvasive stage of mammary tumor development in C3(1)/T antigen transgenic mice. Mean serum levels of endostatin increased about 8-fold above that of controls and resulted in a significant decrease in tumor growth and an increase in survival. The inhibitory effect of endostatin occurred during or after the progression to invasive carcinoma. Reduced levels of vascular endothelial growth factor mRNA were found in association with high levels of endostatin. Our results demonstrate that the adenoviral induction of high levels of circulating endostatin significantly inhibits mammary tumor growth during the period when the "angiogenic switch" occurs.

Overexpression of parathyroid hormone-related protein causes hypercalcemia but not bone metastases in a murine model of mammary tumorigenesis

Several lines of evidence suggest that production of parathyroid hormone-related protein (PTHrP) by breast cancer cells contributes to the formation of bone metastases. However, it is not clear if PTHrP promotes access of cancer cells to the skeleton or if it simply promotes bone resorption around cells already within bone. To study the effects of PTHrP on the development of bone metastases, we treated mice overexpressing PTHrP in their mammary glands (K14-PTHrP transgenic mice) with 9,10-dimethyl-1,2-benz-anthracene (DMBA), a known mammary carcinogen. After DMBA treatment, K14-PTHrP mice showed a higher incidence of tumor formation and a shorter latency to tumor formation than wild-type littermates. Transgenic tumors expressed the K14-PTHrP transgene and secreted excess amounts of PTHrP. In response, tumor-bearing transgenic mice became hypercalcemic and had elevated circulating levels of PTHrP. Despite the development of visceral metastases, neither transgenic mice nor wild-type controls developed bone metastases. This was true even if tumor cells were introduced into the arterial circulation of immunodeficient mice. Our results are consistent with the emerging notion that the ability of breast cancer cells to produce PTHrP in response to cues from the bone microenvironment may be more important to the development of skeletal metastases than the production of PTHrP by cells within the primary breast cancer.

Lack of promotion of estrogen-dependent mammary gland tumors in vivo by an isopropanolic Cimicifuga racemosa extract

Cimicifuga racemosa (CR) is widely used in the treatment of menopausal symptoms. Mechanistic studies suggest that unlike hormone-replacement therapy, CR does not stimulate estrogen-receptor positive breast cancer cells. To evaluate CR safety, we performed an in vivo investigation of a clinically tested isopropanolic CR extract. Mammary tumors were induced in Sprague Dawley rats (n = 75) by the application of 7,12-dimethylbenz[a]anthracene. Five to nine weeks later, the animals were ovariectomized, allowed to recover, and administered daily doses of CR extract (0.714, 7.14, or 71.4 mg/kg body weight per day) or control substances (estrogen/positive control: 450 microg/kg/day mestranol; or CR vehicle/negative control). The animals were sacrificed 6 weeks later, and tumor number, size, plasma hormone levels, and the weight of estrogen-sensitive organs were analyzed. In contrast to mestranol treatment, CR treatment did not stimulate cancerous growth. There were no significant differences in tumor number or size between the CR groups and the vehicle control. Likewise, prolactin, follicle-stimulating hormone, and luteinizing hormone levels and organ weights and endometrial proliferation were unaffected. The lack of mammary tumor-stimulating effects of this extract is of great significance in establishing the safety of CR extracts for treatment of menopausal symptoms in women with a history of breast cancer in which hormone-replacement therapy is contraindicated.

Suppression of mammary tumorigenesis in transgenic mice by the RXR-selective retinoid, LGD1069

Retinoids have been used in the clinic for the prevention and treatment of human cancers. They regulate several cellular processes including growth, differentiation, and apoptosis. Previously, we demonstrated that a pan-agonist retinoid 9-cis retinoic acid was able to suppress mammary tumorigenesis in the C3(1)-SV40 T-antigen (Tag) transgenic mouse model. However, significant toxicity was seen with this naturally occurring retinoid. We hypothesized that the cancer preventive effects of retinoids could be dissected from the toxic effects by using receptor-selective retinoids. In this study, we used TTNPB, an retinoic acid receptor-selective retinoid, and LGD1069, an retinoid X receptor-selective retinoid, to preferentially activate retinoic acid receptors and retinoid X receptors. In vitro, both compounds were able to inhibit the growth of T47D breast cancer cells. We then determined whether these retinoids prevented mammary tumorigenesis. C3(1)-SV40 Tag mice were treated daily by gastric gavage with vehicle, two different doses of TTNPB (0.3 or 3.0 microg/kg), or two different doses of LGD1069 (10 or 100 mg/kg). Mice were treated from approximately 6-8 weeks to 7-8 months of age. Tumor size and number were measured twice each week, and toxicities were recorded daily. Our data show that LGD1069 suppresses mammary tumorigenesis in C3(1)-SV40 Tag transgenic mice with no observable toxicity, whereas TTNPB had a modest chemopreventive effect, yet was very toxic. Median time to tumor development was 129 days in vehicle-treated mice versus 156 days in mice treated with 100 mg/kg LGD1069 (P = 0.05). In addition, tumor multiplicity was reduced by approximately 50% in mice treated with LGD1069 (2.9 for vehicle, 2.4 for 10 mg/kg LGD1069, and 1.4 for 100 mg/kg, P < or = 0.03). TTNPB-treated mice showed a delayed median time to tumor development (131 days for vehicle versus 154 days for 3.0 microg/kg TTNPB; P < or = 0.05), but no changes were seen in tumor multiplicity. However, toxicity (skin erythema, hair loss) was seen in all of the mice treated with TTNPB. These data demonstrate that receptor-selective retinoids suppress mammary tumorigenesis in transgenic mice and that preventive effects of retinoids can be separated from their toxicity, demonstrating that receptor-selective retinoids are promising agents for the prevention of breast cancer.

Tumor-derived platelet-derived growth factor-BB plays a critical role in osteosclerotic bone metastasis in an animal model of human breast cancer

Breast cancer produces a variety of growth factors to promote its behavior at primary and secondary sites in autocrine/paracrine manners. However, the role of these growth factors in the colonization of cancer cells in bone, which is one of the most common metastatic sites, is poorly understood. To study this, we established an in vivo model in which the MCF-7 human breast cancer cells caused predominant osteosclerotic bone metastases 20-25 weeks after inoculation into the left cardiac ventricle in female nude mice. To make this model more time efficient, we overexpressed the oncogene Neu, which is associated with aggressive behavior in human breast cancers, in MCF-7 cells (MCF-7/Neu). MCF-7/Neu cells grew without estrogen and developed osteosclerotic bone metastases in 10-12 weeks in animals. Of note, MCF-7/Neu-bearing mice showed substantial plasma levels of human platelet-derived growth factor-BB (hPDGF-BB; 855 +/- 347 pg/ml; mean +/- SE, n = 5), indicating hPDGF-BB production by inoculated MCF-7/Neu cells. MCF-7/Neu cells in culture also produced large amounts of hPDGF-BB. Conditioned medium harvested from MCF-7/Neu cells stimulated osteoblastic bone formation in organ cultures of neonatal mouse calvariae, and a neutralizing antibody to hPDGF-BB blocked the osteoblastic bone formation. Stable transfection of the hPDGF-B AS in MCF-7/Neu cells reduced hPDGF-BB production in culture. Mice bearing these MCF-7/Neu cells with antisense showed reduced bone metastases with decreased plasma hPDGF-BB levels (54 +/- 20 and 35 +/- 21 in two different antisense and 696 +/- 312 pg/ml in empty vector; mean +/- SE; n = 5). Introduction of hPDGF-B cDNA in the MDA-MB-231 human breast cancer cells, which consistently formed osteolytic bone metastases, induced osteosclerotic lesions in the osteolytic bone metastases. In conclusion, we show that MCF-7 cells cause osteosclerotic bone metastases and that Neu enhances this capacity of MCF-7 cells. Our data suggest that MCF-7/Neu-derived hPDGF-BB plays a causative role in the development of osteosclerotic bone metastases in this model.

LAS, a novel selective estrogen receptor modulator with chemopreventive and therapeutic activity in the N-nitroso-N-methylurea-induced rat mammary tumor model

The N-nitroso-N-methylurea-induced rat mammary tumor model was used to conduct two types of studies: a prevention study designed to test the ability of the novel selective estrogen receptor modulator lasofoxifene (LAS) to inhibit the development of mammary tumors, and a treatment study designed to test the inhibitory effect of LAS on the growth of established tumors. The prevention study indicated that LAS markedly delayed the emergence of N-nitroso-N-methylurea-induced tumors to an extent similar to that obtained by the established antiestrogen tamoxifen (TAM). At the highest dose administered, both TAM and LAS reduced tumor incidence by 75% and total tumor number by 90% relative to the controls. LAS also reduced the multiplicity of tumors, i.e., the mean number of tumors per rat, and resulted in substantially smaller total tumor burden. In the treatment study, LAS significantly inhibited tumor growth compared with the controls. In addition, whereas none of the untreated tumors regressed completely over the experimental period, 40% of LAS-treated tumors regressed by >50% at the highest dose (10 mg/kg daily). The results of this study in a rat mammary tumor model indicate that LAS has both chemopreventive and chemotherapeutic effects quantitatively comparable with those of TAM.

Rho family GTPases regulate mammary epithelium cell growth and metastasis through distinguishable pathways

BACKGROUND

Relatively few genes have been shown to directly affect the metastatic phenotype of breast cancer epithelial cells in vivo. The Rho family of proteins, incluing the Rho, Rac and Cdc42 subfamilies, are related to the small GTP binding protein Ras and regulated diverse biological processes including gene transcription, cytoskeletal organization, cell proliferation and transformation. The effects of Cdc42, Rac and Rho on the actin cytoskeleton suggested a possible role for Rho proteins in cellular motility and metastasis; however, a formal analysis of the role of Rho proteins in breast cancer cellular growth and metastasis in vivo had not previously been performed.

MATERIALS AND METHODS

We generated a panel of MTLn3 rat mammary adenocarcinoma cells that expressed similar levels of dominant inhibitory mutants of Cdc42-, Rac- and Rho-dependent signaling, to examine the contribution of these GTPases to cell spreading, guided chemotaxis, and metastasis in vivo. The ability of Rho proteins to regulate intravasation into the peripheral blood was determined by implanting MTLn3 cell stable dominant negative lines in nude mice and measuring the formation of breast cancer cell colonies grown from the peripheral blood. Serial sectioning of the lungs was performed to determine the presence of metastasis in mice in which mammary tumors expressing the dominant negative Rho family proteins had grown to a similar size.

RESULTS

Cell spreading of MTLn3 cells was selectively abrogated by N17Rac1. N19RhoA and N17Cdc42 reduced the number of focal contacts (FCs) and disrupted the co-localization of vinculin with phosphotyrosine at FCs. While N17Rac1 and N17Cdc42 preferentially inhibited colony formation in soft agar, all three GTPases affected cell growth in vivo. To distinguish effects on tumorigenicity from intravasation into the bloodstream, implanted tumors were grown to the same size in nude mice. Each dominant inhibitory Rho protein reduced intravasation into the peripheral blood. Lung metastasis of MTLn3 cells was also abrogated by the dominant inhibitory Rho proteins, despite the presence of residual CFU.

CONCLUSIONS

These studies demonstrate for the first time a critical role for the Rho GTPases involving independent signaling pathways to limit mammary tumor cellular growth and metastasis in vivo.

Urea as a recovery marker for quantitative assessment of tumor interstitial solutes with microdialysis

Microdialysis is a technique that enables measurement of extracellular concentrations of unbound analytes. A small probe with a semipermeable membrane is implanted in tissue and constantly perfused. Small analytes in the interstitial fluid diffuse into the perfusate and are collected. Often, microdialysate concentrations of an analyte are only a fraction of the unbound concentrations in the extracellular space attributable to incomplete equilibration between these two compartments. Thus, it is necessary to determine the degree of equilibration between microdialysate and interstitium for each probe to accurately estimate concentrations. In this study, we investigated tissue urea as a solute to continually correct for nonequilibrium conditions. We used this method, along with relative diffusivities of urea and glucose, to monitor glucose levels before and during hyperglycemia as an example of how this method can be applied. No-net-flux experiments were performed on 10 anesthetized female rats with mammary adenocarcinomas. Microdialysis probes 1 cm in length with a molecular weight cutoff of M(r) 100,000 were used. Urea was added to the perfusate in concentrations of 0.83, 2.5, 5.0, and 13.33 mM. Microdialysate samples were collected every 15 min. For each rat, there was a linear relationship between the net urea concentration (outflow-inflow) and the urea concentration in the perfusate (inflow). Net flux should equal zero when perfusate and interstitial concentrations are equal. In an additional series of 13 rats, microdialysate samples were obtained before, during, and after administration of glucose at a dose of 1 g/kg. The interstitial tumor urea concentration was 7.8 +/- 0.3 mM compared with 6.2+/- 0.3 mM in plasma. There was a significant linear relationship between plasma urea (measured directly) and tumor urea (microdialysis measurement). Plasma urea concentrations were constant over time in all of the experiments, including those where hyperglycemia was induced. Hyperglycemia caused 7.7- and 3.6-fold increases in tumor and plasma glucose, respectively. There was no effect of hyperglycemia on tumor blood flow. Urea appears to be a useful low molecular weight relative recovery marker for tumor microdialysis. In combination with the determination of relative diffusivity between urea and the solute of interest, this calibration method may allow for quantitative measurements of tumor metabolites and unbound drugs.

Induction of systemic neutrophil response in mice by photodynamic therapy of solid tumors

Photodynamic therapy (PDT) of solid tumors elicits a strong, acute inflammatory response characterized by a rapid and massive infiltration of activated neutrophils into the tumor. The present study investigated the impact of PDT on the systemic and local (treatment site) kinetics of neutrophil trafficking and activity in mouse SCCVII and EMT6 tumor models. Differential leukocyte counts in the peripheral blood of treated mice revealed a pronounced neutrophilia developing rapidly after Photofrin porfimer sodium (Photofrin)- or tetra(m-tetrahydroxyphenyl)chlorin (mTHPC)-based PDT. Significant neutrophilia was also observed upon PDT treatment of normal dorsal skin but not on the footpad of tumor-free mice. The changes in circulating neutrophil numbers were accompanied by an efflux of these cells from the bone marrow. An increased proportion of cells with high L-selectin (CD62L antigen) expression was found among bone-marrow-residing neutrophils 6-24 h after PDT, and in neutrophils in the peripheral circulation and treated tumors 24 h after therapy. Complement inhibition completely prevented the development of PDT-induced neutrophilia. The results of the present study demonstrate that treatment of solid tumors by PDT induces a strong and protracted increase in systemic neutrophil numbers mediated by complement activation. This reaction reflects rapid and massive mobilization and activation of neutrophils for the destruction of PDT-treated tumor tissue.

Antitumor activity of cytotropic heterogeneous molecular lipids (CHML) on human breast cancer xenograft in nude mice

Cytotropic heterogeneous molecular lipid (CHML), which is a new anticancer agent with US patent number 5,260,067, has recently been shown to suppress tumor cell growth in multiple tumor lines and induce apoptosis in vitro (1). These results indicate that CHML may be an effective antitumor agent. In the present study, using both local injection and intravenous injection, we have investigated the suppressive effect of CHML on human breast caner cells MCF-7 xenograft in nude mice. In the local injection, CHML was introduced into nude mice implanted with human breast cancer xenograft at doses of 25 mg/tumor area (cm2), 35 mg/tumor area (cm2), or 50 mg/tumor area (cm2), once every two days, total 3 times. The inhibition of tumor growth was 81.3%, 93.8% and 100%, respectively. In the intravenous injection, the nude mice bearing MCF-7 xenografts were treated with CHML at 10 mg/kg/day, or 15 mg/kg/day, or 20 mg/kg/day, once a day, total 7 days, the growth inhibition of tumor area was 58.1%, 77.4%, and 83.9%, respectively. At the same time, the toxicity of CHML was determined through examining the number of the white blood cell (WBC) and the activity of the serum glutamic-pyruvic transaminase (SGPT). However, no evident alterations of WBC and SGPT were detected in all animals treated with CHML, suggesting that CHML has little toxicity on nude mice. Taken together, these results indicate that CHML is an effective agent that suppresses breast tumor growth and suggest the possibility of using CHML in the clinical trial in the near future.

Effect of changing tumor oxygenation on glycolytic metabolism in a murine C3H mammary carcinoma assessed by in vivo nuclear magnetic resonance spectroscopy

The rate of conversion of D-[1-(13)C]glucose into [3-(13)C]lactate (apparent glycolytic rate) has been determined in C3H murine mammary carcinomas in vivo using tumor-selective (13)C nuclear magnetic resonance spectroscopy with (1)H-(13)C cross-polarization. Under conditions of acute hypoxia induced by breathing carbon monoxide at 660 ppm, the apparent glycolytic rate was 0.0239 +/- 0.0019 min(-1). The proportion of (13)C label incorporated into [4-(13)C]glutamate (measured in tumor extracts) was 25-fold lower than that incorporated into [3-(13)C]lactate, reflecting a very limited oxidative metabolism during this hypoxic episode. For animals breathing air or carbogen (95% O(2) + 5% CO(2)), the calculated glycolytic rates were correspondingly lower (0.0160 +/- 0.0021 min(-1) and 0.0050 +/- 0.0011 min(-1), respectively). Although (13)C labeling of glutamate at C4 was still an order of magnitude lower than that for lactate at C3 (11-fold for air and 9-fold for carbogen), these ratios did show a greater degree of oxidative metabolism than that seen in animals breathing carbon monoxide at 660 ppm. The marked difference in apparent glycolytic rate for this tumor model between well-oxygenated and hypoxic conditions demonstrates a substantial Pasteur effect (inhibition of glycolysis by oxygen). Dynamic (13)C nuclear magnetic resonance spectroscopy provides a noninvasive estimate of tumor glycolysis that can be used to evaluate the relationship between oxygenation and energy metabolism, and this has potential consequences for the sensitivity of hypoxic cells to treatment and their ability to promote angiogenesis.

Comparison of plasma component levels in four strains of female mice with different mammary tumour potentials

Based on the importance of general metabolic activity to mammary tumourigenesis, plasma component levels were examined at 6 and 10 months of age in female virgin mice of four strains, which in mammary tumour potential, rank in the descending order of SHN, GR/A, SLN and C3H/He. The plasma aspartate aminotransferase level elevated from 6 to 10 months of age in the SHN and GR/A, but not in the SLN and C3H/He strains. The total bilirubin level was higher in the former two strains than the latter two at both 6 and 10 months. The blood urea nitrogen level was highest in SHN. C3H/He had the lowest plasma levels of these components as well as amylase at both ages. The results indicate the signifcance to the mammary tumourigenic potential of plasma levels of certain components related to general metabolic activity.

Prevention of N-methyl-N-nitrosourea-induced mammary carcinogenesis in rats by 1alpha-hydroxyvitamin D(5)

BACKGROUND

Although the active form of vitamin D, i.e., 1,25-dihydroxyvitamin D(3), is a potent cell-differentiating agent, its use in cancer prevention or therapy is precluded because it induces excessive blood calcium levels (hypercalcemia). However, less calcemic or noncalcemic synthetic analogues of vitamin D(3) are poorly effective against mammary carcinogenesis. We synthesized an analogue of vitamin D(5), 1alpha-hydroxy-24-ethylcholecalciferol (1alpha-hydroxyvitamin D(5)), which was less calcemic than 1,25-dihydroxyvitamin D(3) and prevented the development of precancerous lesions in mammary glands. Here, we evaluate its efficacy in an experimental rat mammary carcinogenesis model.

METHODS

Sprague-Dawley rats were treated with 1alpha-hydroxyvitamin D(5) beginning 2 weeks before carcinogen treatment. Animals received an intravenous injection of N-methyl-N-nitrosourea at 80 days of age and continued to receive dietary 1alpha-hydroxyvitamin D(5) for an additional 105 days. Tumor incidence and multiplicity were determined, and plasma concentrations of calcium and phosphorus were measured. The efficacy of 1alpha-hydroxyvitamin D(5) at different stages of carcinogenesis was determined in mouse mammary gland organ culture. All statistical tests were two-sided.

RESULTS

The tumor incidence was reduced from 80% (95% confidence interval [CI] = 51.9%-95.7%) in control rats to 53.3% (95% CI = 26.6%-78.8%) and 46.6% (95% CI = 21.3%-73.4%) in rats treated with 1alpha-hydroxyvitamin D(5) at 25 microg/kg diet and 50 microg/kg diet, respectively. The tumor multiplicity was reduced from 1.6 tumors per rat to 1.2 (95% CI for the difference = -0.45 to 1.25; P=.34) and 0.8 (95% CI for the difference = 0.14-1.46; P =.02), respectively. There was no statistically significant increase in the plasma calcium or phosphorus concentration at either dose level. The vitamin D(5) analogue was effective during both the initiation and the promotion stages of mammary lesion formation in organ culture.

CONCLUSION

Our findings indicate that 1alpha-hydroxyvitamin D(5) reduces the incidence of mammary carcinogenesis in vivo. This analogue appears to be a good candidate for further development as a chemopreventive agent.

An evaluation of near infrared spectroscopy and cryospectrophotometry estimates of haemoglobin oxygen saturation in a rodent mammary tumour model

Haemoglobin oxygen saturation in subcutaneous rat mammary tumours was measured using near infrared spectroscopy (NIRS) in vivo and in rapidly frozen sections from the same tumours using cryospectrophotometry, which reports oxygen saturation in individual blood vessels to depths of 4 mm from the tissue surface. Measurements were performed on tumours while animals breathed either room air or carbogen. In five of nine tumours, the average saturation calculated from cryospectrophotometric measurements agreed with that determined from NIRS to within 13%, and in four of these five tumours agreement was 5% or better. In the remaining four of nine tumours, where agreement was poor, the volume-averaged saturations estimated from NIRS were consistently higher than those calculated from cryospectrophotometry. Monte Carlo simulations demonstrated that the depth of tissue probed by NIRS was significantly greater than that sampled by cryospectrophotometry. Analysis of the frequency of severely hypoxic vessels showed that when NIRS reported a saturation of approximately 70% or higher, the fraction of tumour vessels with saturations less than 10% was limited to 0.06 or less. Sensitivity and specificity analysis suggests that NIRS and NIRS imaging may identify clinically relevant hypoxia, even when its spatial extent is below the resolution limit of the NIRS technique.

Transplacental effects of maternal feeding with high fat diets on lipid exchange and response of the splenic lymphoid system in mice offspring exposed to low doses of carcinogen

We studied whether feeding pregnant female mice with different fats affects lipid exchange and activity of the splenic lymphoid system in offspring exposed to low doses of carcinogen. Female mice were fed diets with either 7% or 15% corn oil or olive oil. The 4-week-old offspring of these mice were transferred to a chow diet, and exposed to a low dose of the carcinogen, dimethylbenz(a)antracene (2 mg/kg). Results of experiments were studied 5 months later. Concentrations of polyunsaturated linoleic and oleic acids were determined in the blood and liver of mothers and offspring. The activity of the splenic immune system in offspring was studied using immunohistochemical methods for evaluating the number of different types of lymphocytes (B and T cells), mitotic and apoptotic indexes and the number of Fas-positive lymphocytes. Serum concentrations of the fatty acids examined were unchanged in the blood of the mothers and their offspring. Concentration of both linoleic and oleic acids was significantly higher in the liver of mothers fed the 15% olive-oil or corn-oil diets. This high level was maintained in linoleic acid in offspring of mothers fed the 15% olive-oil diet. Spleen weight was higher in offspring of mothers fed a 15% corn-oil diet compared to those fed the 7% corn-oil diet. The 15% olive-oil diet slightly decreased the weight of the spleen compared to counterparts fed the 15% corn-oil diet. Immunohistochemical studies showed that the olive diet, partially of 15%, significantly stimulated B-cell blast transformation. The finding reflects the reaction of B lymphocyte-producing splenic zones to the carcinogenic effect, though to a weak extent. T lymphocyte-producing zones did not respond to the diets studied, probably due to the weak carcinogenic effect and lack of tumor appearance. The Fas activity of both B and T cells in the spleen was stimulated by the carcinogen and enhanced by feeding the mothers on the olive-oil diet. Maternal feeding with a diet rich in olive oil before pregnancy results in stimulation of morphological and functional attributes of the splenic immune system of the offspring, particularly related to producing of B lymphocytes.

Role of fibrinogen covalently associated with cell membrane in blood-borne lung tumor colony formation of murine mammary carcinoma cells

The role of fibrinogen covalently associated with cell membrane in blood-borne lung tumor colony formation of murine mammary carcinoma cells in mice was studied. When mice were treated with prednisolone, their plasma fibrinogen levels profoundly increased. Hyperfibrinogenemia, induced by prednisolone treatment or plasma fibrinogen infusion of syngeneic mice, accelerated the coagulation time and significantly increased the number of lung tumor colonies of SCK tumor cells. Hypofibrinogenemia, induced by rabbit antisyngenic mouse fibrinogen immunoglobulin G or heparin infusion, markedly delayed coagulation time and prominently reduced the numbers of blood-borne lung tumor colonies of the tumor cells. SCK mammary carcinoma cells form a coating of fibrinogen on their surfaces in a medium containing fibrinogen. This coating is cross-linked in a manner characteristic of catalysis by tumor cell membrane-bound transglutaminase K. The fibrinogen coating on the surface of these tumor cells functions to protect against autologous lymphokine-activated killer cells. These results provide information on the impact of fibrin stability on blood-borne lung tumor colony formation of SCK mammary carcinoma cells.

Possible mechanisms underlying mammary carcinogenesis in female Wistar rats by nitrofurazone

Mechanisms underlying mammary carcinogenesis in female rat given nitrofurazone (NF) were examined. Experiment I: female Wistar rats were divided into three groups, and given diets containing 0, 500 or 1000 ppm NF for 5 weeks. At terminal sacrifice, body and uterus weights were the same in all groups, although ovary weights in NF-treated animals were significantly higher than in control animals, the increase being dose-dependent. Serum prolactin (PRL) concentrations in NF-treated groups at 17:00 h on the day of proestrus were also dose-dependently higher than that in control group. Experiment II: a two-stage rat mammary carcinogenesis protocol was performed. Rats were divided into four groups, Groups 2 and 4 being treated by 9,10-dimethyl-1,2-benzanthracene (DMBA) at 7-weeks-old. Groups 3 and 4 were given diets containing 1000 ppm of NF between 8 and 27 weeks of age, when all surviving rats were autopsied. DMBA-treated animals demonstrated mammary tumors at high incidences, 91.1 and 90.5%, respectively, in Groups 2 and 4, no tumor development being observed without the initial carcinogen exposure (Groups 1 and 3). The mean tumor weights and the mean numbers of tumors per tumor-bearing rats in Group 4 were increased as compared with Group 2, albeit not significantly. Serum PRL (proestrus day at 17:00 h) and progesterone (PG) (diestrus day at 10:00 h) concentrations in NF-treated animals (Groups 3 and 4) were significantly higher than those in untreated rats (Groups 1 and 2). These results suggest that increases of serum PRL and PG concentrations by NF may be the most important factors regarding its promotion of mammary tumor growth and/or enhancement of mammary carcinogenesis in female rats.

Maximum effect of urokinase plasminogen activator inhibitors in the control of invasion and metastasis of rat mammary cancer

Experimentally induced pulmonary metastases of mammary cancer in the Fisher 344 rat can be suppressed by the inhibition of urokinase plasminogen activator (uPA). The inhibition of uPA with amiloride or B428 has been shown to be dose dependent. Increased dosage levels of inhibitors might be expected to enhance levels of suppression of metastases. The use of each of these inhibitors at equipotent concentrations that exceeded the doses administered in previous studies failed to eliminate pulmonary metastases. These results demonstrate that a maximum limit is attained for the inhibitory capacities on cells during in vitro invasion or in vivo metastasis. At increased levels, uPA inhibitors continue to suppress, but do not eradicate, experimental pulmonary metastases of MATB cell rat mammary cancer.

Inhibition by whole-body hyperthermia with far-infrared rays of the growth of spontaneous mammary tumours in mice

To evaluate possible therapeutic benefits of irradiation with far-infrared rays (FIR) on breast cancer, we examined combined effects of the chronic exposure to FIR at ambient temperature (26.5-27.5 degrees C) and the whole-body hyperthermia induced by FIR (WBH) (35-41 degrees C) on the growth of spontaneous mammary tumours of mice. A high mammary tumour strain of SHN virgin mice born on the normal rack or FIR rack were maintained on the respective racks until mammary tumour appearance. When the mammary tumour size reached approximately 7 mm, some mice in each group received no further treatment (Control and FIR groups, respectively) and the remaining mice received 3 hours of WBH each of 5 consecutive days (C + WBH and FIR + WBH groups, respectively). There was little difference between the control and FIR groups in the tumour growth over 10 days of examination. On the other hand, the tumour growth was inhibited significantly in both C + WBH and FIR + WBH groups and the degree of inhibition was similar. The data confirmed that the chronic exposure to FIR at ambient temperature has little effect on the growth of spontaneous mammary tumours in mice. WBH with FIR, however, strongly inhibited the tumour growth without deleterious side-effects, while chronic FIR irradiation itself again had little effect in this process. This WBH regimen may serve as a useful animal model for long-term studies of a noninvasive treatment of breast cancer.

Wakame seaweed suppresses the proliferation of 7,12-dimethylbenz(a)-anthracene-induced mammary tumors in rats

We examined the anti-tumor proliferation effects of wakame seaweed on 7,12-dimethylbenz(a)-anthracene (DMBA)-induced rat mammary tumor. DMBA was administered to 8-week-old female Sprague-Dawley rats, and rats which developed mammary tumors were assigned randomly to three groups. Commercial rat feed was used in a control group (group I-A), and two feed mixtures were prepared, which contained commercial rat feed blended with wakame at 1.0% (group I-B) and 5.0% (group I-C) by weight. The respective feeds were given to each group for 8 weeks, and changes in mammary tumor size were compared. At the end of the experiment, mammary tumors and thyroid glands were resected to compare their weights. Serum total iodine and thyroxin (T4) levels were measured. Immunohistochemical studies for bromodeoxyuridine (BrdU) labeling, transforming growth factor (TGF)-beta, and apoptosis were carried out in the resected tumor. Significant suppression of tumor growth was observed in groups I-B and I-C compared with I-A. In groups I-B and I-C, the weights of resected mammary tumors were significantly lower and serum total iodine concentration was significantly higher than in I-A. BrdU indices were significantly lower in groups I-B and I-C, compared with I-A. TGF-beta and apoptotic index were inversely related to BrdU. These results suggest that iodine is transported from the serum into mammary tissues and induces apoptosis through the expression of TGF-beta. In conclusion, wakame suppressed the proliferation of DMBA-induced mammary tumors.

Chemoprevention by curcumin during the promotion stage of tumorigenesis of mammary gland in rats irradiated with gamma-rays

We have evaluated the chemopreventive effects of curcumin on diethylstilbestrol (DES)-induced tumor promotion of rat mammary glands initiated with radiation. Sixty-four pregnant rats received whole body irradiation with 2.6 Gy gamma-rays from a 60Co source at day 20 of pregnancy and were divided into two groups after weaning. In the control group of 39 rats fed a basal diet and then implanted with a DES pellet for 1 year, 33 (84.6%) developed mammary tumors. Twenty-five rats were fed diet containing 1% curcumin immediately after weaning and received a DES pellet, as for the control. The administration of dietary curcumin significantly reduced the incidence (28.0%) of mammary tumors. Multiplicity and Iball's index of mammary tumors were also decreased by curcumin. Rats fed the curcumin diet showed a reduced incidence of the development of both mammary adenocarcinoma and ER(+)PgR(+) tumors in comparison with the control group. On long-term treatment with curcumin, body weight and ovarian weight were reduced, but liver weight was increased. Compared with the control rats, the curcumin-fed rats showed a significant reduction in serum prolactin, whereas estradiol-17beta and progesterone concentrations were not significantly different between the two groups. Curcumin did not have any effect on the concentration of free cholesterol, cholesterol ester and triglyceride. Feeding of the curcumin diet caused a significant increase in the concentrations of tetrahydrocurcumin, arachidonic acid and eicosapentaenoic acid and a significant decrease in thiobarbituric acid-reactive substance concentration in serum. Whole mounts of the mammary glands showed that curcumin yielded morphologically indistinguishable proliferation and differentiation from the glands of the control rats. These findings suggest that curcumin has a potent preventive activity during the DES-dependent promotion stage of radiation-induced mammary tumorigenesis.

Evidence that irradiation of far-infrared rays inhibits mammary tumour growth in SHN mice

To evaluate the effect of irradiation of far infrared rays (FIR), the growth of spontaneous mammary tumours of SHN mice was compared among 3 groups: the control was kept until the end of experiment on the normal rack in the absence of FIR and Experimental group I was constantly exposed to FIR. Experimental group Il was raised as the control followed by movement to the FIR rack after mammary tumour appearance. While there was little difference between the control and Experimental group I in mammary tumour growth for 16 days, Experimental group II was significantly lower than the control in this parameter. Furthermore, the percentage of rapidly growing tumours showing greater than 200% of growth rate was apparently lower in Experimental group II. Associated with this, epidermal growth factor receptor expression in mammary tumours, anterior pituitary weight and serum leptin level were significantly decreased in Experimental group II. The findings suggest that whole-body FIR irradiation at ambient temperature could be a possible way of a hyperthermic therapy for tumours.

A comparison of the anticancer activities of dietary beta-carotene, canthaxanthin and astaxanthin in mice in vivo

The anticancer activities of beta-carotene, astaxanthin and canthaxanthin against the growth of mammary tumors were studied in female eight-wk-old BALB/c mice. The mice were fed a synthetic diet containing 0, 0.1 or 0.4% beta-carotene, astaxanthin or canthaxanthin. After 3 weeks, all mice were inoculated with 1 x 10(6) WAZ-2T tumor cells into the mammary fat pad. All animals were killed on 45 d after inoculation with the tumor cells. No carotenoids were detectable in the plasma or tumor tissues of unsupplemented mice. Concentrations of plasma astaxanthin (20 to 28 mumol/L) were greater (P < 0.05) than that of beta-carotene (0.1 to 0.2 mumol/L) and canthaxanthin (3 to 6 mmol/L). However, in tumor tissues, the concentration of canthaxanthin (4.9 to 6.0 nmol/g) was higher than that of beta-carotene (0.2 to 0.5 nmol/g) and astaxanthin (1.2 to 2.7 nmol/g). In general, all three carotenoids decreased mammary tumor volume. Mammary tumor growth inhibition by astaxanthin was dose-dependent and was higher than that of canthaxanthin and beta-carotene. Mice fed 0.4% beta-carotene or canthaxanthin did not show further increases in tumor growth inhibition compared to those fed 0.1% of each carotenoid. Lipid peroxidation activity in tumors was lower (P < 0.05) in mice fed 0.4% astaxanthin, but not in those fed beta-carotene and canthaxanthin. Therefore, beta-carotene, canthaxanthin and especially astaxanthin inhibit the growth of mammary tumors in mice; their anti-tumor activity is also influenced by the supplemental dose.