Anthracene-induced Mammary Tumors Research Articles

Fraction from Calliandra portoricensis reduces 7, 12 dimethylbenz(a)anthracene-induced mammary tumors in Wistar rats.

Objective: Calliandra portoricensis (CP) is used in Nigeria for the treatment of breast diseases. We investigated the effects of fraction from CP on 7, 12-dimethylbenz(a)anthracene (DMBA)-induced mammary gland tumors. Materials and Methods:Female Wistar rats (40) were allotted into five equal groups. Group 1 served as control, group 2 received DMBA (50 mg/kg), groups 3 and 4 received DMBA and were treated with CP at doses of 50 and 100 mg/kg respectively, and the group 5 received DMBA and vincristine (0.5 mg/kg). DMBA was injected intraperitoneally once while vincristine and CP were given twice and thrice per week, respectively. Results:Administration ofDMBA caused a significant decrease in body weight gain by 52%. In addition, DMBA significantly increased organo-somatic weight of mammary gland by 4.0 folds. Also, DMBA significantly increased inflammatory and oxidative stress markers serum interleukin-1β (IL-1β), lipid peroxidation (LPO) and myeloperoxidase (MPO) by 27, 18 and 435%, respectively. Similarly, mammary NO (nitric oxide) and LPO were increased by 468 and 21%, respectively. In contrast, DMBA decreased the levels of apoptotic markers BAX, caspases 3 and 9 by 20, 15 and 18%, and mammary superoxide dismutase (SOD), catalase (CAT) and glutathione-s-peroxidase (GPx) by 45, 51 and 68%, respectively. Histology revealed gland with malignant epithelial cells and high nucleo-cytoplasm in DMBA-administered rats. Treatment with CP 100 mg/kg decreased LPO, MPO, IL-1β and NO by 28, 35, 78 and 85%, respectively, and ameliorated DMBA-induced cyto-architectural anomalies. Conclusion:Fraction of CP protects mammary gland from DMBA insults via antioxidative and anti-inflammatory mechanisms.

In Vivo Assessment of Anti-Tumor Activity of Methyl 2'-Methyl-1,3-dioxo-1,1',2',3,5',6',7',7a'-octahydrospiro[indene-2,3'-pyrrolizidine]-2' carboxylate (6) on 7,12 dimethylbenz(a) Anthracene-Induced Mammary Tumors in Rat

Objective- Breast cancer is one of the most serious problems in oncology. Alkaloids pyrrolizidine are widely found in nature and exhibited versatile biological activities. The aim of the present study was to assess anti-tumor activity of methyl 1,3-dioxo-1,1',2',3,5',6',7',7a'-octahydrospiro[indene-2,3'-pyrrolizidine]-2'-carboxylate (6) on 7,12 dimethylbenz(a) anthracene (DMBA)-induced mammary tumors in rat. Design- Experimental study. Animals- Twenty-one female Wistar ats Procedures- 7-Week-old female Wistar rats (180 g body weight) were randomized into three groups of seven animals each. DMBA-induced mammary tumors was achived using DMBA dissolved in 1ml of vehicle (0.5 ml of DMSO plus 0.5 ml of saline) and injected by subcutaneous injection beneath the mammary gland on either side. Tumor yield and size were stabilized after 90 days with the initiation of DMBA. Healthy intact animals (NC) were considered as a normal control feeding on pellets and tap water. In group DMBA, the tumor was induced by DMBA. In group DMBA/7d the animals with tumor received 100 µL 6 dissolved in DMSO (0.25 µM) solution intraperitoneally for one week. Synthesis of 6 was accomplished and the structure of new product was assigned by their 1H/13C NMR, IR, CH-COSY and mass spectral data as well as the elemental analysis. Results- The overall tumor analysis showed that 6 treatment significantly inhibited the breast tumor incidence, tumor multiplicity, and tumor size in the DMBA-initiated rat model. 6 treatment significantly inhibited the total volume of tumors per rat. Conclusion and Clinical Relevance-The findings of the present study showed that the 6 treatment was significantly effective in reduction of tumors versus the cancer controls.

Luteolin suppresses development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumors in Sprague-Dawley rats

Postmenopausal women undergoing hormone-replacement therapy containing both progestins and estrogens are at an increased risk of developing breast cancer compared with women taking estrogen alone. We recently demonstrated that medroxyprogesterone acetate, a progestin commonly used for hormone-replacement therapy, accelerates development of mammary carcinogenesis in 7,12-dimethylbenz(a)anthracene‑treated Sprague-Dawley rats. Synthetic antiprogestins used to block the deleterious effects of progestins, are themselves associated with toxic side-effects. In order to circumvent this, we used the aforementioned model to identify less toxic natural compounds that may prevent the development of progestin-accelerated tumors. Luteolin, a naturally-occurring flavonoid commonly found in fruits and vegetables, has previously been shown to possess anticancer properties. In our studies, both low (1 mg/kg) and high (25 mg/kg) doses of luteolin significantly suppressed progestin-dependent increases in tumor incidence, while increasing tumor latency and reducing the occurrence of large (>300 mm3) mammary tumors. However, an intermediate dose of luteolin (10 mg/kg), while suppressing the development of large tumors, did not affect either tumor incidence or latency. Immunohistochemical analysis of tumor tissues revealed that all concentrations of luteolin (1, 10, and 25 mg/kg) significantly reduced levels of VEGF within tumors. The suppressive effects of luteolin on tumor incidence and volume, together with its ability to reduce VEGF and blood vessels, persisted even after treatment was terminated. This suggests that luteolin possesses anti‑angiogenic properties which could mechanistically explain its capacity to control tumor progression. Thus luteolin may be a valuable, non-toxic, naturally-occurring anticancer compound which may potentially be used to combat progestin-accelerated mammary tumors.

Whey Protein Hydrolysate but not Whole Whey Protein Protects Against 7,12-Dimethylbenz(a)anthracene-Induced Mammary Tumors in Rats

Effects of intact and processed bovine milk proteins on development of chemically induced mammary tumors in female rats were compared. AIN-93G diets were made with 20% casein (CAS), casein hydrolysate (CASH), intact whey protein (IWP), or whey protein hydrolysate (WPH). Pregnant Sprague-Dawley rats were fed the diets starting at Gestational Day 4. Offspring were fed the same diet. At 50 days, female offspring (44–49/group) were gavaged with sesame oil containing 80 mg/kg of the mammary carcinogen dimethylbenzanthracene (DMBA) and euthanized 62 days posttreatment. Rats fed WPH had an adenocarcinoma incidence of 17% compared to the rats fed CAS, CASH, and IWP diets (34%, 33%, and 36% respectively) (P < 0.001). Median palpable tumor latency for rats fed WPH was greater (61 days, P < 0.001) compared to CAS (44 days), CASH (42 days) and IWP (45 days). Tumor multiplicity was also lower (1.5 vs. 3.0, P < 0.05) in rats fed WPH than in CAS and CASH fed groups. Results demonstrate that hydrolytic processing of whey protein is required for this diet to be effective in reducing DMBA-induced mammary tumors. The bioactive compounds produced during whey protein processing and mechanisms underlying the anticancer effects of WPH are yet to be identified.

Estrogen deprivation and excess energy supply accelerate 7,12-dimethylbenz(a)anthracene-induced mammary tumor growth in C3H/HeN mice.

BACKGROUND/OBJECTIVESObesity is a risk factor of breast cancer in postmenopausal women. Estrogen deprivation has been suggested to cause alteration of lipid metabolism thereby creating a cellular microenvironment favoring tumor growth. The aim of this study is to investigate the effects of estrogen depletion in combination with excess energy supply on breast tumor development.MATERIALS/METHODSOvariectomized (OVX) or sham-operated C3H/HeN mice at 4 wks were provided with either a normal diet or a high-fat diet (HD) for 16 weeks. Breast tumors were induced by administration of 7,12-dimethylbenz(a)anthracene once a week for six consecutive weeks.RESULTSStudy results showed higher serum concentrations of free fatty acids and insulin in the OVX+HD group compared to other groups. The average tumor volume was significantly larger in OVX+HD animals than in other groups. Expressions of mammary tumor insulin receptor and mammalian target of rapamycin proteins as well as the ratio of pAKT/AKT were significantly increased, while pAMPK/AMPK was decreased in OVX+HD animals compared to the sham-operated groups. Higher relative expression of liver fatty acid synthase mRNA was observed in OVX+HD mice compared with other groups.CONCLUSIONSThese results suggest that excess energy supply affects the accelerated mammary tumor growth in estrogen deprived mice.

PTEN/PIK3CA genes are frequently mutated in spontaneous and medroxyprogesterone acetate-accelerated 7,12-dimethylbenz(a)anthracene-induced mammary tumours of tree shrews

Tree shrew has increasingly become an attractive experimental animal model for human diseases, particularly for breast cancer due to spontaneous breast tumours and their close relationship to primates and by extension to humans. However, neither normal mammary glands nor breast tumours have been well characterised in the Chinese tree shrew (Tupaia belangeri chinensis). In this study, normal mammary glands from four different developmental stages and 18 spontaneous breast tumours were analysed. Haematoxylin and eosin (H&E) staining and immunohistochemistry (IHC) showed that normal mammary gland morphology and structures of tree shrews were quite similar to those found in humans. Spontaneous breast tumours of tree shrews were identified as being intraductal papilloma, papillary carcinoma, and invasive ductal carcinoma with or without lung metastasis. To further analyse breast cancer tumours among tree shrews, 40 3–4month-old female tree shrews were orally administrated 20mg 7,12-dimethylbenz(a)anthracene (DMBA) or peanut oil thrice, and then, 15 of these DMBA administrated tree shrews were implanted with medroxyprogesterone acetate (MPA) pellets. DMBA was shown to induce breast tumours (12%) while the addition of MPA increased the tumour incidence (50%). Of these, three induced breast tumours were intraductal papillary carcinomas and one was invasive ductal carcinoma (IDC). The PTEN/PIK3CA (phosphatase and tensin homologue/phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha), but not TP53 and GATA3, genes are frequently mutated in breast tumours, and the PTEN/PIK3CA gene mutation status correlated with the expression of pAKT in tree shrew breast tumours. These results suggest that tree shrews may be a promising animal model for a subset of human breast cancers with PTEN/PIK3CA gene mutations.

Effects of morin on the pharmacokinetics of etoposide in 7,12-dimethylbenz[a]anthracene-induced mammary tumors in female Sprague-Dawley rats

Etoposide, used for the treatment of breast cancer, is mainly metabolized via hepatic cytochrome P450 (CYP) 3A4 in humans and is also a substrate for p-glycoprotein (P-gp). Morin is known to be able to modulate the activities of metabolic enzymes including CYPs and can act as a potent P-gp inhibitor. The purpose of this study was to investigate the effects of morin on the pharmacokinetics of etoposide in rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors. Etoposide was administered intravenously (2mg/kg) and orally (10 mg/kg) in control and DMBA rats without (DMBA-WOM) and with (DMBA-WM) morin (15mg/kg). Protein and mRNA expression of CYP3A and P-gp was analyzed, and the tissue distribution of etoposide was also measured. Both protein and mRNA expression of CYP3A and P-gp was inhibited by morin in the liver, intestine and breast tumors of DMBA-WM rats. After both intravenous and oral administration of etoposide in DMBA-WM rats, the total area under the plasma concentration-time curve from time zero to infinity (AUC) of etoposide was significantly greater, and the time-averaged total body clearance (CL) of etoposide was significantly slower than those in control and DMBA-WOM rats. The amount of etoposide recovered from each tissue was significantly higher in DMBA-WM rats, especially in the breast tumor, liver and large intestine. No significant differences between control and DMBA-WOM rats were observed. Taken together, greater AUC and slower CL of etoposide in DMBA-WM rats could possibly be due to the inhibition of hepatic CYP3A (intravenous) and mainly due to the inhibition of intestinal CYP3A and P-gp (oral) by morin.

RAP80 Is Critical in Maintaining Genomic Stability and Suppressing Tumor Development

The ubiquitin interaction motif-containing protein RAP80 was recently found to play a key role in DNA damage response (DDR) signaling by facilitating the translocation of several DDR mediators, including BRCA1, to ionizing irradiation (IR)-induced foci. In this study, we examine the effect of the loss of RAP80 on genomic stability and the susceptibility to cancer development in RAP80 null (RAP80(-/-)) mice. RAP80(-/-) mice are viable and did not exhibit any apparent developmental defects. Mouse embryonic fibroblasts (MEF) derived from RAP80(-/-) mice underwent premature senescence compared with wild-type (WT) MEFs, were more sensitive to IR, and exhibited a higher level of spontaneous and IR-induced genomic instability. RAP80(-/-) thymocytes were more sensitive to IR-induced cell death than WT thymocytes. RAP80(-/-) mice were more susceptible to spontaneous lymphoma development and the development of 7,12-dimethylbenz(a)anthracene-induced mammary gland tumors. Moreover, the loss of RAP80 accelerated tumor formation in both p53(-/-) and p53(+/-) mice. Our data indicate that RAP80-deficiency promotes genomic instability and causes an increase in cancer risk consistent with the concept that RAP80 exhibits a tumor suppressor function.

ERα signaling imparts chemotherapeutic selectivity to selenium nanoparticles in breast cancer

The present study focuses on the synthesis of stable selenium nanoparticles (SeNPs) and the elucidation of their mechanism of action in preventing the growth of mammary tumors. Selenious acid and reduced glutathione in the presence of sodium alginate were used as precursors for synthesis of SeNPs. Cell viability and expression of apoptotic markers (pp38, Bax, and cytochrome c) were assessed in MCF-7 and MDA-MB-231 breast cancer cells treated with SeNPs. Reduction in tumor volume was measured in rats with dimethylbenz[a]anthracene-induced mammary tumors. Synthesized SeNPs ranged in size from 40 to 90 nm and were stable up to 3 months of storage. We report that SeNP-induced cell death and expression of pp38, Bax, and cytochrome c were significantly higher in estrogen receptor-α (ERα)–positive cells (MCF-7) but not in ERα-negative cells (MDA-MB-231). Interestingly, animals showing significant decrease in tumor volume (small tumors) had lower levels of ERα as compared with animals showing a nonsignificant decrease in tumor volume (large tumor). This is the first report in our knowledge suggesting that the anticancer activity of SeNPs correlates with the level of ERα in breast cancer cells both in vivo and in vitro. From the Clinical EditorThis study focuses on the synthesis of selenium nanoparticles (SeNPs) with the goal of preventing the growth of breast cancer cells, suggesting that the anticancer activity of SeNPs correlates with the level of ERα in breast cancer cells both in vivo and in vitro.

Apigenin Prevents Development of Medroxyprogesterone Acetate-Accelerated 7,12-Dimethylbenz(a)anthracene-Induced Mammary Tumors in Sprague–Dawley Rats

The use of progestins as a component of hormone replacement therapy has been linked to an increase in breast cancer risk in postmenopausal women. We have previously shown that medroxyprogesterone acetate (MPA), a commonly administered synthetic progestin, increases production of the potent angiogenic factor vascular endothelial growth factor (VEGF) by tumor cells, leading to the development of new blood vessels and tumor growth. We sought to identify nontoxic chemicals that would inhibit progestin-induced tumorigenesis. We used a recently developed progestin-dependent mammary cancer model in which tumors are induced in Sprague-Dawley rats by 7,12-dimethylbenz(a)anthracene (DMBA) treatment. The flavonoid apigenin, which we previously found to inhibit progestin-dependent VEGF synthesis in human breast cancer cells in vitro, significantly delayed the development of, and decreased the incidence and multiplicity of, MPA-accelerated DMBA-induced mammary tumors in this animal model. Whereas apigenin decreased the occurrence of such tumors, it did not block MPA-induced intraductal and lobular epithelial cell hyperplasia in the mammary tissue. Apigenin blocked MPA-dependent increases in VEGF, and suppressed VEGF receptor-2 (VEGFR-2) but not VEGFR-1 in regions of hyperplasia. No differences were observed in estrogen or progesterone receptor (ER/PR) levels, or the number of estrogen receptor-positive cells, within the mammary gland of MPA-treated animals administered apigenin, MPA-treated animals, and placebo treated animals. However, the number of progesterone receptor-positive cells was reduced in animals treated with MPA or MPA and apigenin compared with those treated with placebo. These findings suggest that apigenin has important chemopreventive properties for those breast cancers that develop in response to progestins.

Antineoplastic effect of iodine and iodide in dimethylbenz[a]anthracene-induced mammary tumors: association between lactoperoxidase and estrogen-adduct production

Several groups, including ours, have reported that iodine exhibited antiproliferative and apoptotic effects in various cancer cells only if this element is supplemented as molecular iodine, or as iodide, to cells that are able to oxidize it with the enzyme thyroperoxidase. In this study, we analyzed the effect of various concentrations of iodine and/or iodide in the dimethylbenz[a]anthracene (DMBA) mammary cancer model in rats. The results show that 0.1% iodine or iodide increases the expression of peroxisome proliferator-activated receptor type γ (PPARγ), triggering caspase-mediated apoptosis pathways in damaged mammary tissue (DMBA-treated mammary gland) as well as in frank mammary tumors, but not in normal mammary gland. DMBA treatment induces the expression of lactoperoxidase, which participates in the antineoplastic effect of iodide and could be involved in the pro-neoplastic effect of estrogens, increasing the formation of DNA adducts. In conclusion, our results show that a supplement of 0.1% molecular iodine/potassium iodide (0.05/0.05%) exert antineoplastic effects, preventing estrogen-induced DNA adducts and inducing apoptosis through PPARγ/caspases in pre-cancer and cancerous cells. Since this iodine concentration does not modify the cytology (histology, apoptosis rate) or physiology (triiodothyronine and thyrotropin) of the thyroid gland, we propose that it be considered as an adjuvant treatment for premenopausal mammary cancer.

Abstract 4528: Genotoxic and estrogenic properties of new antiestrogens

Abstract Long-term administration of tamoxifen (TAM) to breast cancer patients and women at high risk of developing this disease gives serious side effects, including endometrial cancer. These side-effects are due to the DNA damaging and/or estrogenic action of the drug. Several antiestrogens have been developed in last three decades, but were dropped out from the clinical trials due to their undesirable effects on the uterus. To avoid this serious side-effect, we have synthesized a new triphenylethylene antiestrogen, E-3-{4-[(E)-4-chloro-1-(4-hydroxyphenyl)-2-phenylbut-1-enyl]-phenyl} acrylic acid (SS1020) and a new benzopyran antiestrogen, 2E-3-{4-[(7-hydroxy-2-oxo-3-phenyl-2H-chromen-4-yl)-methyl]-phenyl}-acrylic acid (SS5020). SS1020 and SS5020 had antitumor potential much higher than that of TAM or other antiestrogens at the human equivalent doses (TAM 0.3-1.0 mg/kg/day), against 7,12-dimethylbenz(a)anthracene-induced mammary tumors in rats or human MCF-7 breast cancer xenograft implanted into athymic nude mice. To evaluate their genotoxic activity, the capability of forming hepatic DNA adducts in rats was determined. When rats were treated orally at a dose molar equivalent to TAM (20 mg/kg/day), a high level (∼1 adduct/105 nucleotides) of DNA adducts was detected in TAM-treated rats whereas no DNA adducts were observed in rats treated with SS1020 or SS5020. To evaluate the estrogenic potential, the uterotrophic activity of our compounds was determined in ovariectomized (OVX) rats at a dose molar equivalent to TAM (10 mg/kg/day), which is 30 times higher than the human equivalent dose of TAM. TAM had high uterotrophic activity while SS1020 and SS5020 did not present significant uterotrophic activity. Therefore, SS1020 and SS5020, lacking estrogenic and genotoxic actions, are expected not to induce reproductive cancers. Interestingly, the antitumor activities of several antiestrogens examined were, rather, increased significantly to the lowering uterotrophic activity evaluated with OVX-rats, but not to their antiproliferative activities against cultured estrogen receptor positive human MCF-7 breast cancer cells. The use of uterotrophic assay, not antiproliferative assay, may be a suitable screening system to exploit antiestrogen alternatives. Non-genotoxic and non-estrogenic SS1020 and SS5020, having strong antitumor potency superior to that of TAM, could be safer alternatives for breast cancer therapy and prevention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4528. doi:10.1158/1538-7445.AM2011-4528

Hydroxytyrosol inhibits growth and cell proliferation and promotes high expression of sfrp4 in rat mammary tumours

Hydroxytyrosol (a phenolic compound derived from virgin olive oil) has demonstrated an anti-tumour effect in several tumour cell lines in addition to other health-related properties. The aim of this study was to investigate, for the first time in an animal model of experimental mammary carcinoma, the anti-cancer ability of hydroxytyrosol and to discover which pathways are modified by hydroxytyrosol. Dimethylbenz[α]anthracene-induced mammary tumours were induced in 28 female Sprague-Dawley rats and ten of them were treated with hydroxytyrosol (0.5 mg/kg b.w. 5 days/week for 6 wk). cDNA microarray and quantitative RT-PCR experiments were performed. Hydroxytyrosol was found to inhibit the experimental mammary tumour growth and proliferation rate, with results comparable to those of doxorubicin but better with regard to the histopathological outcome. It also altered the expression of genes related to apoptosis, cell cycle, proliferation, differentiation, survival and transformation pathways. This study shows that hydroxytyrosol exerts anti-cancer effects in Sprague-Dawley rats with experimental mammary tumours, inhibiting growth and cell proliferation in mammary tumours. Moreover, hydroxytyrosol alters several genes associated with cell proliferation, apoptosis and the Wnt signalling pathway, promoting a high expression of Sfrp4. However, further studies are necessary to better understand the mechanisms of hydroxytyrosol.

Dehydroepiandrosterone intake protects against 7,12-dimethylbenz(a)anthracene-induced mammary tumor development in the obese Zucker rat model

Obesity has been epidemic in the US for over two decades; almost 65% of adults in the US are overweight. Obesity has been linked with the risk of development of various cancers, including breast cancer. Dehydroepiandrosterone (DHEA) is an over-the-counter dietary supplement used as an immunomodulating, anti-depressant, anti-aging, anti-cardiovascular disease, and anti-cancer agent and anti-obesity supplement. The objectives of this study were to investigate the long-term effects of obesity and DHEA treatment on body weight gain and on 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumor development. Forty-three six-week-old obese female Zucker rats were used. Rats were randomly assigned and had ad libitum access to water and a diet of either chow (2016) as a control diet or chow with the addition of DHEA at a concentration of 6 g/kg of chow as a DHEA diet. All rats were orally gavaged at age 50 days with 65 mg DMBA/kg body weight. Rats were weighed and palpated twice weekly for detection of mammary tumors and sacrificed 155 days post-DMBA treatment. Obese rats fed the DHEA diet gained significantly less weight than obese control diet rats (P<0.001). At the end of the experiment, 55% of the control diet group developed mammary tumors, while no tumors were detected in the DHEA diet group (P<0.001). Our results suggest that DHEA treatment can reduce body weight gain and protects against DMBA-induced mammary tumor development in the obese Zucker rat model.

Prepubertal genistein exposure affects erbB2/Akt signal and reduces rat mammary tumorigenesis

Breast cancer is the most common malignancy in women worldwide and pharmaceutical agents have therapeutic and preventive effects in breast cancer. The human epidermal growth factor receptor 2/neu is one of the most important oncogenes in human breast cancer. Prepubertal exposure to endogenous estradiol and a phytoestrogen, genistein (Gen), has been shown to reduce future breast cancer risk. Gen downregulates tyrosine kinase regulated protein expression and reduces prostate cancer. In this study, the effects of prepubertal exposure to Gen on rat mammary carcinogenesis and the erbB2/Akt signal pathway were investigated. Prepubertal female Sprague-Dawley rats were daily exposed to Gen at 125 mg/kg (Gen-1) and 500 mg/kg (Gen-5) from postnatal days 22-28. Subsequently, the rats were given a single dose of 100 mg/kg 7.12-dimethylbenz [a] anthracene on postnatal day 42 to induce mammary tumor. The mRNA expression of erbB2 and amplified in breast cancer 1 (AIB1) was detected by reverse transcription-polymerase chain reaction. The protein levels of proliferating cell nuclear antigen (PCNA), erbB2, phosphotyrosine protein, Akt, and p-Akt were detected by immunohistochemistry and Western blotting. The activity of protein tyrosine kinase (PTK) was detected by liquid scintillation counting. The percentage of rats with mammary tumors in breast cancer model (BCM), Gen-1, and Gen-5 was 71.43, 52.38, and 33.34%, respectively. The incidence of 7.12-dimethylbenz [a] anthracene-induced mammary tumors significantly decreased in Gen-5 compared with that in BCM. The mRNA levels of AIB1 and erbB2 and the protein levels of erbB2, p-Akt, and PCNA protein expression were downregulated for a long time in the mammary tumors in Gen-5 groups. The activity of PTK was also decreased for a long time. However, the total Akt protein expression did not change significantly among BCM, Gen-1, and Gen-5. Prepubertal exposure of Sprague-Dawley female rats to 500 mg/kg Gen can reduce later breast cancer risk and its protective effect is associated with persistent downregulation of the expression of erbB2, p-Akt, AIB1, and PCNA and with low PTK activity in the mammary tumor. Our results suggest that erbB2/Akt signaling plays a role in tumor formation and targeting erbB2/Akt signaling with prepubertal exposure to Gen may provide greater efficacy to the current therapies used to treat tumors.

Curcumin delays development of medroxyprogesterone acetate-accelerated 7,12-dimethylbenz[a]anthracene-induced mammary tumors

Combined hormone therapy (HT) containing estrogen and progestin (medroxyprogesterone acetate [MPA]) leads to increased risk of breast cancer in postmenopausal women, compared with HT regimens containing estrogen alone or placebo. We previously reported that in animal models, progestins can accelerate the development of mammary tumors by increasing vascular endothelial growth factor (VEGF) levels. We furthermore showed that curcumin, an Indian spice derived from the turmeric root, specifically inhibits MPA-induced VEGF secretion from breast cancer cells in vitro. In the present study, we investigated whether curcumin inhibits 7,12-dimethylbenz[a]anthracene (DMBA)-induced, MPA-accelerated tumors in Sprague-Dawley rats. On day 0, virgin female Sprague-Dawley rats (age, 55 d) were given DMBA (20 mg/rat). Sixty-day timed-release pellets containing 25 mg MPA were implanted into the rats on day 30. Curcumin was administered daily at a rate of 200 mg kg-1 day-1 from days 26 to 50, and animals were killed on day 52 (n = 15-19 per group). Treatment with curcumin delayed the first appearance of MPA-accelerated tumors by 7 days, decreased tumor incidence by the end of the experiment, and reduced tumor multiplicity in DMBA-induced MPA-accelerated tumors. Curcumin also prevented many of the gross histological changes seen in the MPA-treated mammary gland. Immunohistochemical analyses of mammary tumors showed that curcumin decreased MPA-induced VEGF induction in hyperplastic lesions, although it did not affect the levels of estrogen and progesterone receptors. We suggest that curcumin be tested as a dietary chemopreventive agent in women already exposed to MPA, in an effort to decrease or delay the risk of breast cancer associated with combined HT.

Effect of genistein therapy on plasma levels of asymmetric dimethylarginine in healthy postmenopausal women: a randomized, placebo-controlled study

The aim of this study was to investigate the effects of pure genistein therapy on asymmetric dimethylarginine in healthy postmenopausal women. Healthy postmenopausal women received pure genistein (n=21) or placebo (n=17) for 6 months, and no statistically significant effects on plasma asymmetric dimethylarginine levels were found with pure genistein treatment.

Regression of progestin-accelerated 7,12-dimethylbenz[a]anthracene-induced mammary tumors in Sprague–Dawley rats by p53 reactivation and induction of massive apoptosis: a pilot study

p53 Reactivation and induction of massive apoptosis (PRIMA-1) is a small-molecule compound that reactivates mutant p53, restoring its normal tumor suppressor function. PRIMA-1 effectively suppresses the growth of homogeneous p53-deficient tumor xenografts in immunosuppressed mice; however, the ability of PRIMA-1 to suppress the growth of mammary tumors in rodents and other species is not well characterized. Here, we examined the ability of PRIMA-1 to suppress the growth of 7,12-dimethylbenz[a]anthracene (DMBA)-induced and progestin-accelerated DMBA-induced mammary tumors in Sprague-Dawley rats. Mammary tumors were induced in female rats with DMBA or DMBA plus progestin treatment. After tumors had reached 5-25 mm(2) in size, PRIMA-1 was administered twice a day for 3 days via tail vein injection (20 or 50 mg/kg). Tumor size was monitored every day following PRIMA-1 for at least 15 days prior to killing. PRIMA-1 caused regression of approximately 40% of progestin-accelerated DMBA-induced mammary tumors, but did not induce regression of native non-progestin-accelerated DMBA-induced tumors. Importantly, PRIMA-1 also suppressed the emergence of any new progestin-accelerated tumors in this model. Immunological studies with an antibody that selectively reacts with mutant p53 suggested that none of the native DMBA-induced tumors expressed mutant p53. By contrast, six out of eight progestin-accelerated DMBA-induced tumors stained for mutant p53 protein. In PRIMA-1-treated tumor-bearing rats, tumor regression correlated with conversion of mutant to wild-type p53 conformation, reduced expression of vascular endothelial growth factor and estrogen receptor, lack of blood vessel perfusion, increased expression of p21, and massively increased expression of anti-angiogenic protein, secreted protein acidic and rich in cysteine. These pre-clinical results suggest that PRIMA-1, as a single agent or in combination with other anti-cancer compounds, has potential as a novel chemotherapeutic treatment for progestin-accelerated human breast cancer.

Milk Inhibits the Regression of 7,12-Dimethylbenz(a)anthracene-Induced Mammary Tumors in Ovariectomized Rats

Epidemiological studies have yielded inconsistent results regarding the relation between the milk consumption and breast cancer risk. In this study, rats were induced mammary tumors by 7,12-dimethylbenz(a)anthracene. When tumors developed to acceptable levels, rats were placed into 1 of 3 treatment groups. Those in the negative control group and the milk group were ovariectomized, whereas those in the positive control group were sham operated. After grouping, tumor incidence remained 100%, and tumor number and volume increased in the positive control group. However, tumors in the 2 ovariectomized groups regressed. Compared with the negative control group, tumor incidence and tumor number and volume per rat in the milk group became significantly higher from Week 6 and Week 4, respectively. Insulin-like growth factor-I levels were borderline significantly higher in the milk group than in the negative control group at autopsy. Although plasma 17β-estradiol levels did not differ significantly, estrogenicity was found in the milk group because uterine weight was significantly heavier in the milk group than in the negative control group. In conclusion, commercial milk inhibited the regression of carcinogen-induced mammary tumors in ovariectomized rats.

Lack of a Significant Effect of Arctiin on Development of 7,12-dimethylbenz(a)anthracene-induced Mammary Tumors in Ovariectomized Sprague-Dawley Rats

: Arctiin, a plant lignan, is metabolized to hormone-like compounds with weak estrogenic and antioxidative activity in experimental animals and man. To clarify its influence on mammary carcinogenesis, female rats were administrated 7,12-dimethylbenz(a)anthracene (DMBA) once, and when the incidence of palpable mammary tumors reached 50%, subjected to ovariectomy (OVX) and divided into tumor-bearing [DMBA-Tumor (+)] and no-tumor-bearing [DMBA-Tumor (−)] groups, subgroups of each then being fed soybean-free diet containing 0, 40, 200, and 1000 ppm of arctiin for 31 wk. The incidence and multiplicity of palpable tumors in the 200 ppm DMBA-Tumor (+) subgroup from week 12 of arctiin treatment tended to be decreased as compared to the 0 ppm subgroup and at terminal sacrifice, the volume of histopathologically defined mammary tumors was decreased in the 40 ppm DMBA-Tumor (−) subgroup, but again without statistical significance. In conclusion, weak inhibitory effects of arctiin on DMBA-induced mammary tumor development were suggested in OVX rats, but any further assessment is needed to obtain conclusive results.