Tumors In Sprague-Dawley Rats Research Articles

Effect of Preventive Acupunture Combined with CMNS6-1 Electroacupuncture Instrument on Promoting Apoptosis of 7,12-Dimethylbenzene (a) Anthracene-Induced Breast Cancer Model Rats

The purpose of this study was to evaluate the effect of preventive acupuncture combined with CMNS6-1 electroacupuncture on 7,12-dimethylbenzanthracene induced mammary tumors in Sprague-Dawley rats and to explore the effect of preventive acupuncture on mammary tumors from the perspective of apoptosis. 48 w old female Sprague-Dawley rats were randomly divided into control (10), model (10), tamoxifen (10) and preventive acupuncture (10) groups. The model group, tamoxifen group and preventive acupuncture group were administered once intragastrically with 100 mg/kg body weight of 7,12-dimethylbenzanthracene to induce spontaneous breast cancer. On d 1 after modeling, acupuncture plus electrical stimulation was administered to the preventive acupuncture group. Density wave was selected for electrical stimulation with a frequency of 2 Hz/100 Hz and an intensity of 1 mA and three acupoints, "Zu San Li", "San Yin Jiao" and "Tan Zhong", were stimulated for 20 min per treatment, once every other day, three times a week for 16 w. Tamoxifen (3 mg/kg body weight, intragastrically, every day) was started the day after 7,12-dimethylbenzanthracene administration and continued for 16 w, as positive control treatment. Apoptosis of breast tumor tissue cells was detected by terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and expression of caspase-3 and B-cell lymphoma-2 was assessed by immunohistochemistry. During the experiment, no tumors were detected in rats from the control+sham group, all the rats in the 7,12-dimethylbenzanthracene+sham group developed tumors and the cumulative incidence of tumors was 100 %, meanwhile the cumulative incidence of tumors in the 7,12-dimethylbenzanthracene+preventive acupuncture group and the 7,12-dimethylbenzanthracene+tamox group were 60 % and 50 %, respectively. Terminal deoxynucleotidyl transferase dUTP nick-end labeling assay showed that preventive acupuncture could significantly promote apoptosis in breast tumor cells in 7,12-dimethylbenzanthracene induced rat, while increased the expression levels of pro-apoptotic proteins such as caspase-3 and B-cell lymphoma-2 associated X. The expression level of antiapoptotic protein B-cell lymphoma-2 was down-regulated and the ratio of B-cell lymphoma-2/B-cell lymphoma-2 associated X was increased. Preventive acupuncture therapy combined with CMNS6-1 electroacupuncture instrument inhibited 7,12-dimethylbenzanthracene-induced mammary tumorigenesis in rats and the mechanism may be related to the regulation of apoptosis-related protein expression and promotion of tumor cell apoptosis.

Epigenetic silencing of sonic hedgehog elicits antitumor immune response and suppresses tumor growth by inhibiting the hedgehog signaling pathway in metastatic spine tumors in Sprague-Dawley rats.

Patients with metastatic spine tumors may suffer from pain or neurologic deficit, and the disease may be detected in patients with a known malignancy. Sonic hedgehog (SHH) has received special attention due to its role in cancers. Therefore, this study investigated the effects of epigenetic silencing of SHH on antitumor immune response and tumor growth by regulating the hedgehog (Hh) signaling pathway in metastatic spine tumors. Rat models of metastatic spine tumors were successfully established. We first calculated the tumor volume and the inhibition rate of tumor growth to investigate the effect of SHH on tumor growth. Afterwards, immunohistochemistry was used to determine whether proliferation was delayed by SHH depletion, and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to test the changes in the lymphocyte transformation rate in the spleen triggered by SHH silencing. Then, the influence of SHH depletion on immune function was investigated. Later, quantitativereverse transcription polymerase chain reaction and Western blot assay were performed to explore the Hh signaling pathway-related factors. Finally, we added the Hh signaling pathway inhibitor, GDC-0449, to confirm the role of the pathway in tumor progression. Initially, we observed that SHH depletion was a negative factor for tumor growth. Afterwards, it was revealed that epigenetic silencing of SHH served as an inhibitor factor for the function of spleen lymphocyte transformation and inflammation while promoting antitumor immune function. Our preliminary results indicate that epigenetic silencing of SHH elicits an antitumor immune response and suppresses tumor growth by inhibiting the Hh signaling pathway in metastatic spine tumors.

Report of final results regarding brain and heart tumors in Sprague-Dawley rats exposed from prenatal life until natural death to mobile phone radiofrequency field representative of a 1.8 GHz GSM base station environmental emission

BackgroundIn 2011, IARC classified radiofrequency radiation (RFR) as possible human carcinogen (Group 2B). According to IARC, animals studies, as well as epidemiological ones, showed limited evidence of carcinogenicity. In 2016, the NTP published the first results of its long-term bioassays on near field RFR, reporting increased incidence of malignant glial tumors of the brain and heart Schwannoma in rats exposed to GSM – and CDMA – modulated cell phone RFR. The tumors observed in the NTP study are of the type similar to the ones observed in some epidemiological studies of cell phone users. ObjectivesThe Ramazzini Institute (RI) performed a life-span carcinogenic study on Sprague-Dawley rats to evaluate the carcinogenic effects of RFR in the situation of far field, reproducing the environmental exposure to RFR generated by 1.8 GHz GSM antenna of the radio base stations of mobile phone. This is the largest long-term study ever performed in rats on the health effects of RFR, including 2448 animals. In this article, we reported the final results regarding brain and heart tumors. MethodsMale and female Sprague-Dawley rats were exposed from prenatal life until natural death to a 1.8 GHz GSM far field of 0, 5, 25, 50 V/m with a whole-body exposure for 19 h/day. ResultsA statistically significant increase in the incidence of heart Schwannomas was observed in treated male rats at the highest dose (50 V/m). Furthermore, an increase in the incidence of heart Schwann cells hyperplasia was observed in treated male and female rats at the highest dose (50 V/m), although this was not statistically significant. An increase in the incidence of malignant glial tumors was observed in treated female rats at the highest dose (50 V/m), although not statistically significant. ConclusionsThe RI findings on far field exposure to RFR are consistent with and reinforce the results of the NTP study on near field exposure, as both reported an increase in the incidence of tumors of the brain and heart in RFR-exposed Sprague-Dawley rats. These tumors are of the same histotype of those observed in some epidemiological studies on cell phone users. These experimental studies provide sufficient evidence to call for the re-evaluation of IARC conclusions regarding the carcinogenic potential of RFR in humans.

Updated Histologic Classification of Adenomas and Carcinomas in the Colon of Carcinogen-treated Sprague-Dawley Rats.

Recent studies have disclosed novel histological phenotypes of colon tumours in carcinogen-treated rats. The aim of this study was to update the current histological classification of colonic neoplasias in Sprague-Dawley (SD) rats. Archival sections from 398 SD rats having 408 neoplasias in previous experiments were re-evaluated. Of the 408 colonic neoplasias, 11% (44/408) were adenomas without invasive growth and 89% (364/408) invasive carcinomas. Out of the 44 adenomas, 82% were conventional (tubular or villous), 14% traditional serrated (TSA; with unlocked serrations or with closed microtubules) and 5% gut-associated lymphoid tissue (GALT)-associated adenomas. Out of 364 carcinomas, 57% were conventional carcinomas, 26% GALT carcinomas, 8% undifferentiated, 6% signet-ring cell carcinomas, and 4% traditional serrated carcinomas (TSC). Thus, conventional adenomas, conventional carcinomas and GALT-associated carcinomas predominated (p<0.05). The updated classification of colonic tumours in SD rats includes conventional adenomas, TSA, GALT-associated adenomas, conventional carcinomas, TSC, GALT-associated carcinomas, signet-ring cell carcinomas and undifferentiated carcinomas. Several of the histological phenotypes reported here are not included in any of the current classifications of colonic tumours in rodents. This updated classification fulfils the requirements for an animal model of human disease, inasmuch as similar histological phenotypes of colon neoplasias have been documented in humans.

Blood flow, volume and arterio-venous passages in induced mammary tumours of the rat

ObjectiveTo study blood flow, vascular volume and arterio-venous passages in induced mammary tumours of the rat to characterize parameters possibly responsible for tumour hyponutrition. MethodDimethylbenzanthracene-induced mammary tumours in Sprague-Dawley rats were studied. Regional blood flow was studied by use of the radioactive microsphere tracer technique using 141Cerium-labelled 15μm spheres coinjected into the left cardiac ventricle with 125Iodine-labelled 25μm spheres. Blood volume was studied by use of 125Iodine- or 99mTechnetium-labelled human serum albumin, the latter allowing autoradiography of tumour sections for visualization of flow and volume. ResultsTwenty-seven rats with 170 tumours had a mean tumour blood flow of 48 and 67mL×min−1×100g−1 using 15 and 25μm sphere data, respectively, indicating a significant passage through vessels between 15 and 25μm. The lungs showed a “nominal bronchial” blood flow of 260 and 135mL×min−1×100g−1 for the 15 and 25μm spheres, respectively, indicating pulmonary trapping, particularly of small spheres passing the systemic circulation in vessels larger than 15μm. There was a positive correlation between the total tumour blood flow within individual rats and trapped spheres of both dimensions in the lungs, indicating shunts also larger than 25μm.Normal tissues disclosed only small differences in regional blood flow as measured by the two spheres.Blood volume was studied in 20 rats with 120 tumours, with a vascular volume of 3.6mL×100g−1 representing a blood turnover >15 times/min. Blood volume co-localized with perfusion as seen in autoradiographs. ConclusionIn induced rat mammary tumours, a high fraction of blood, 28%, passes arterio-venous vessels between 15 and 25μm and there also exist passages >25μm. These findings indicate that the functional capacity of the tumour vascular bed might be impaired, adding to the abnormal microenvironment of tumours.

Induction of apoptosis and downregulation of ERα in DMBA-induced mammary gland tumors in Sprague-Dawley rats by synthetic 3,5-disubstituted isoxazole derivatives.

Isoxazole derivatives are an important group of chemotherapeutic prototypes. In the current study, we have synthesized few isoxazole derivatives and tested them for their antiproliferative properties in cancer cell lines such as MCF7 and HeLa. The lead compound, 3-(3,4-dimethoxyphenyl)-5-(thiophen-2-yl)isoxazole (2b), showed considerable inhibition of proliferation of MCF7 and HeLa cells with the IC50 values of 19.5 and 39.2µM, respectively. Cell cycle analyses and annexin-FITC staining in 2b-treated breast adenocarcinoma cells (MCF7) showed increased sub-G1 population and apoptosis. Furthermore, we tested the tumor inhibitory effect of 2b and estrogen receptor expression profile in DMBA-induced mammary tumors in Sprague-Dawley rats. The gross morphology of tumor studies was investigated by histopathology and ERα protein expression was evaluated by immunohistochemistry, which showed tumor regression and downregulation of ERα in tumor cells. The present results implicate that compound 2b could be used for the further derivatization for the treatment of breast cancer.

Induction of Human Glioma Tumor in Sprague-Dawley Rats with Intact Immune System.

Glioblastoma (GBM) is an aggressive brain tumor in humans. The median survival rate of patients is one year after the diagnosis. So, development of an animal model is necessary for the advances in the research treatment of GBM. The aim of this study was to investigate the capability of human glioma cells in inducing glioma tumors in rats with intact immune system. U87 cells were implanted in the frontal lobe of rats without suppressing the immune system. We used magnetic resonance imaging (MRI), Hematoxylin-Eosin (H&E) and Immunohistochemical (IHC) staining to assess characteristics of tumor. At the 10th and 14th days of tumor inoculation, MRI images contained the tumor areas in the brain. All tumor-bearing rats developed tumors. The rats retained the morphology and histological characteristics of human glioma. Animals mimic GBM characteristics, such as mitotic activity, invasion, neovascularization, necrosis and pseudopalisading cells. IHC staining revealed tumor growth and progression in the tumor-bearing rats. This model is a standard system for studying the tumor phenotype, genotype, and for evaluating the efficacy of anti-cancer agents. It is a reliable, simple, inexpensive, and easily reproducible model, which may be a way for pre-clinical studies.

Evaluation of potential activity of luseogliflozin on vascular proliferation in the mesenteric lymph node with or without vascular tumors in Sprague-Dawley rats in a carcinogenicity study.

The incidence of mesenteric lymph node vascular tumors can vary in rats, and appropriate assessment of potential risk of tumorigenicity is needed when the incidence is higher in treated groups than in a control group. In a 2-year rat carcinogenicity study of luseogliflozin, a selective sodium-dependent glucose co-transporter 2 inhibitor for the treatment of type 2 diabetes mellitus, there was a slight but statistically significant increase in the total number of hemangiomas and hemangiosarcomas in the mesenteric lymph nodes in males at a high-dose. As part of the risk assessment for luseogliflozin, its effect on the vascular proliferation potential in the mesenteric lymph nodes was examined in a rat carcinogenicity study by performing an image analysis using specimens with double immunohistochemical staining for PCNA and CD34 in control and high-dose males. In addition, immunohistochemical staining for VEGF was performed to detect enhanced angiogenesis. In the high-dose males that did not have a hemangioma/hemangiosarcoma, neither an increased number of PCNA/CD34-positive cells nor changes in the expression pattern of VEGF was observed. On the other hand, in the high-dose males that had a hemangioma/hemangiosarcoma, the number of PCNA-positive cells was increased in the tumor areas, and the number in the hemangioma/hemangiosarcoma was approximately one-half of that in the hemangiosarcoma in the control male. In conclusion, no potential change leading to vascular proliferation/tumors was detected in the mesenteric lymph nodes of high-dose males receiving luseogliflozin.

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.

Seven-Tesla Magnetic Resonance Imaging Accurately Quantifies Intratumoral Uptake of Therapeutic Nanoparticles in the McA Rat Model of Hepatocellular Carcinoma

After inducing McA tumors in Sprague-Dawley rats (McA-SD), the following hypotheses were tested: first, that hypervascular McA tumors grown in Sprague-Dawley rats provide a suitable platform to investigate drug delivery; and second, that high-field MRI can be used to measure intratumoral uptake of DOX-SPIOs. McA cells were implanted into the livers of 18 Sprague-Dawley rats. In successfully inoculated animals, 220-μL DOX-SPIOs were delivered to tumors via the intravenous or intra-arterial route. Pretreatment and posttreatment T2*-weighted images were obtained using 7-T MRI, and change in R2* value (ΔR2*) was obtained from mean signal intensities of tumors in these images. Tumor iron concentration ([Fe]), an indicator of DOX-SPIO uptake, was measured using mass spectroscopy. The primary outcome variable was the Pearson correlation between ΔR2* and [Fe]. Tumors grew successfully in 13 of the 18 animals (72%). Mean (SD) maximum tumor diameter was 0.83 (0.25) cm. The results of phantom studies revealed a strong positive correlation between ΔR2* and [Fe], with r = 0.98 (P < 0.01). The results of in vivo drug uptake studies demonstrated a positive correlation between ΔR2* and [Fe], with r = 0.72 (P = 0.0004). The McA tumors grown in the Sprague-Dawley rats demonstrated uptake of nanoparticle-based therapeutic agents. Magnetic resonance imaging quantification of intratumoral uptake strongly correlated with iron concentrations in pathological specimens, suggesting that MRI may be used to quantify uptake of iron-oxide nanotherapeutics.

Abstract 3694: Complex effects of dietary apigenin on prevention of MPA-accelerated DMBA-induced mammary tumors in Sprague-Dawley rats.

Abstract Epidemiological and laboratory studies support the use of the plant-derived flavonoid apigenin as a potential nutraceutical for preventing a number of different cancers. However the effect of dietary apigenin on prevention of progestin-accelerated breast tumors has hitherto not been explored. Medroxyprogesterone acetate (MPA) is the most commonly used synthetic progestin administered to post-menopausal women for hormone replacement therapy. MPA accelerates the development of breast cancers by reducing tumor latency and increasing tumor incidence and multiplicity in a DMBA-induced breast cancer model, and causes progression of human cancer cells in xenografts (Clin Can Res, 2006, 12:4062; Cancer Res, 2007, 67: 9929). Previously we showed that intraperitoneally administered apigenin effectively treated and prevented the progression of MPA-accelerated breast cancer in both the DMBA-induced, and xenograft mammary cancer models (Cancer Prev Res, 2011, 4: 1316; Horm Canc, 2012, 3: 160). In the present study we used the DMBA model to examine the chemopreventive effect of dietary apigenin against MPA-accelerated tumors. Based on reports in the literature, we examined the effects of feeding 3 different dietary levels of apigenin (0.02%, 0.1% and 0.5% wt/wt) in a phytoestrogen-free diet following treatment with DMBA, and prior to implantation of MPA pellets which accelerate tumor development. The MPA-dependent tumor incidence was lower in the 0.1% dietary apigenin treatment group. Surprisingly, the same dietary level significantly increased tumor multiplicity in those animals that developed tumors. A five-fold increase (0.5%) or reduction (0.02%) in dietary apigenin failed to reduce MPA-dependent tumor incidence and the higher dose (0.5%) substantially increased tumor multiplicity compared with MPA alone. Tumor incidence and multiplicity were unaffected in apigenin-fed animals that were treated with DMBA but supplemented with placebo pellets. There were no morphological or histological differences between tumors from animals fed apigenin-supplemented diets and those given a control diet, either in the presence or absence of MPA.These findings show that apigenin, given in a diet devoid of phytochemicals, exacerbated the effects of MPA on tumor development and multiplicity in a chemically-induced breast cancer model. Consequently, until further research clarifies the effect of dietary apigenin on progestin-accelerated tumors, caution should be exercised when considering the flavonoid as a dietary supplement for preventing hormone-dependent breast cancer. Supported by a COR award from University of Missouri, and research funds from RADIL. Citation Format: Benford Mafuvadze, Matthew Cook, Xu Zhang, Cindy Besch-Williford, Salman M. Hyder. Complex effects of dietary apigenin on prevention of MPA-accelerated DMBA-induced mammary tumors in Sprague-Dawley rats. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3694. doi:10.1158/1538-7445.AM2013-3694

Glargine and Cancer: Can We Now Suggest Closure?

The two publications on the pharmacokinetics of insulin glargine in individuals with type 1 and type 2 diabetes in this issue of Diabetes Care (1,2) provide additional explanatory evidence in support of the definitive findings in the Outcome Reduction with Initial Glargine Intervention (ORIGIN) study in which exposure to insulin glargine for a median duration of 6.2 years did not increase the risk of any cancer (hazard ratio 1.00 [95% CI 0.88–1.13]) or death from cancer (0.94 [0.77–1.15]) (3). Soon after glargine’s long awaited and welcome introduction into clinical practice in 2000, questions were raised about its safety profile. This conception was based on the early finding that insulin glargine had an enhanced affinity to IGF-1 receptors when tested in a human osteosarcoma cell line (Saos/B10) with a preponderance of IGF-1 receptors and associated with increased mitogenicity (proliferation in an existing tumor cell line) (4). These findings were akin to those observed with the AspB10 insulin analog, the development of which had earlier been discontinued because of an increase in both benign and malignant mammary gland tumors in Sprague-Dawley rats after 12 months’ exposure (5,6); thus AspB10 was referred to as the “carcinogenic insulin analog” (7). In contrast, detailed extensive toxicological lifetime carcinogenicity studies of insulin glargine in animals (rodent and nonrodent), albeit at lower doses, revealed no carcinogenicity signal with insulin glargine when compared with human insulin (8,9). The risk was regarded as small by the European Medicines Agency safety working party because of the lack of effect on mammary gland proliferation, absence of mammary carcinoma, and rare tumors during the lifetime studies in animals. The higher insulin receptor affinity and consequent prolonged dephosphorylation due to the increased residence time of AspB10 on insulin receptors (4) along with a predilection for the …

Abstract No. 116: MRI enables measurement of therapeutic nanoparticle uptake in rat N1S1 liver tumors during nano-ablation

Nanoparticles functionalized with chemotherapeutic drugs and MRI contrast agents can serve dual therapeutic and diagnostic applications. Nano-ablation (NA) employs reversible electroporation to temporarily increase cell membrane permeability, offering interventional oncologists a method to enhance drug delivery to tumors. However, it remains unknown if MRI can be combined with NA to predict intratumoral uptake of superparamagnetic iron oxide nanoparticles (SPIOs) injected intravenously. We aimed to test the hypothesis that T2*-w MRI can be used to quantitatively predict intratumoral uptake of SPIOs. Using the N1S1 model of hepatoma, we induced 11 liver tumors in Sprague-Dawley rats. T2*-w MRI was performed using a Bruker 7T ClinScan to determine baseline tumor T2* signal intensity. Two minutes after SPIO injection into the femoral vein, NA was applied to the liver tumor at 1300 V/cm (8 pulses, 100 μs pulse duration) using bipolar electrodes. Animals were euthanized 10 minutes after NA and MRI determined post-procedural tumor T2* signal intensity. We measured the iron concentration of the harvested tissue from treated subjects as a proxy for SPIO uptake using inductively-coupled plasma mass spectroscopy (ICP-MS). Mean tumor iron concentration was correlated with the mean change in tumor T2* (measured in ms) using linear regression, with p<0.05 considered significant. Change in T2*-w MRI signal intensity significantly correlated with tumor SPIO uptake after NA (p=0.014, r=0.71). On average, for each unit of T2* signal intensity change (one millisecond) there was 7.33 μg of iron uptake per mg of tumor tissue. Intratumoral uptake of SPIOs after NA can be successfully quantified with 7T MRI and this uptake correlates with gold standard pathology. Thus, MRI may be used as a non-invasive method to measure the dose of therapeutic nanoparticles taken up by target liver tumors. Before clinical translation, future studies should attempt to replicate these findings using a larger animal model of liver cancer at clinically relevant 1.5T or 3T MRI field strengths.

Spontaneous Renal Tumors Suspected of Being Familial in Sprague-Dawley Rats

Spontaneous renal tubule tumors (RTTs), with a distinctive morphological phenotype, were present in three Sprague-Dawley rats, 1 male and 2 females, out a total of 120 animals of each sex from untreated and placebo control groups in a 2-year carcinogenicity study. One female had one carcinoma, adenoma and hyperplasia, and the other female had five adenomas and many hyperplastic lesions; the male case had one carcinoma. From these cases, a biological continuum of hyperplasia, adenoma and carcinoma could be recognized. The tumors were present in the renal cortex and appeared as solid lobulated growths with occasional central necrosis. The lobules were divided by a small amount of fibrovascular tissue. Occasionally the larger tumors contained a cystic area. Tumor cells appeared distinctive and exhibited variable amounts of eosinophilic/amphophilic and vacuolated cytoplasm. Nuclei were round to oval with a prominent nucleolus. Mitotic figures were uncommon, and no distant metastasis was noted. The tumors were seen as multiple and bilateral lesions in two animals and had no apparent relationship to chronic progressive nephropathy (CPN). Foci of tubule hyperplasia were also noted to contain the same type of cellular morphology. The morphological and biological features of these 3 cases resembled the amphophilic-vacuolar (AV) variant of RTT that has been posited to be of familial origin. This is a report of spontaneous familial renal tumors in Sprague-Dawley rats from Japan.

Abstract 1844: Apigenin prevents development of progestin-accelerated 7,12-dimethylbenz(a) anthracene (DMBA)-induced mammary tumors in Sprague-Dawley rats

Abstract Post-menopausal women undergoing hormone replacement therapy (HRT) containing both progestins (P) and estrogens (E) are at an increased risk of developing breast cancer compared with those taking E alone. The biological mechanisms behind this phenomenon however, remain obscure. We showed that medroxyprogesterone acetate (MPA), a commonly used P, increases the production of the potent angiogenic growth factor VEGF in breast cancer cells that was blocked by the anti-progestin RU-486 suggesting the involvement of progesterone receptors (Int J Cancer, 2001, 92:469). This led to our hypothesis that P increases the angiogenic potential of latent tumorigenic cells in the breast, leading to development of palpable tumors. To prove this hypothesis, we developed in vivo models with human xenografts in mice (Cancer Res., 2007, 67:9929), and DMBA-induced tumors in rats (Clin Can Res, 2006, 12:4062). In both models, MPA accelerated tumor development that was blocked by RU-486. Since RU-486 has severe side-effects, we undertook studies aimed at identifying less toxic naturally-occurring compounds that might prevent P-dependent VEGF induction and tumor acceleration. We recently identified apigenin, a low molecular weight flavonoid commonly found in fruits and vegetables, which inhibited MPA-induced VEGF secretion from human breast cancer cells (Menopause, 2010, 17:1055). In this study we used the DMBA-induced mammary tumor model to determine whether apigenin prevents the development of P-accelerated tumors in vivo. Female Sprague-Dawley rats were treated with DMBA by oral gavage (Day 1). Seven days prior to implantation of 25 mg/60 day release MPA pellets (Day 28), ip administration of apigenin (50 mg/kg daily) began, and continued for 10 days. Animals were palpated for tumors every second day and experiment was terminated 60 days after DMBA treatment was initiated. Apigenin treatment led to a significant delay in the appearance of the first tumor, compared with MPA alone (56 vs 41 days; p&amp;lt;0.05, LIFETEST), as well as a reduction in tumor incidence and tumor multiplicity. Immunohistochemcial analysis with mammary tissue collected immediately after apigenin administration ceased revealed that even though apigenin decreased the overall incidence of MPA-accelerated tumors, it did not block or reverse DMBA-induced mammary tissue hyperplasia, suggesting that the effects of the flavonoid are exerted at a specific stage of tumor development. Further studies showed that apigenin suppressed both VEGF and its receptor, VEGFR-2, in the hyperplastic regions of the mammary gland. Thus apigenin appears to be a compound with useful anti-tumor and anti-angiogenic properties which could be given to post-menopausal women to prevent development of P-accelerated tumors. Support: COR award from the College of Vet Medicine and by research funds from RADIL, Univ. of Missouri. 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 1844. doi:10.1158/1538-7445.AM2011-1844

Synthetic Progestins Differentially Promote or Prevent 7,12-Dimethylbenz(a)anthracene–Induced Mammary Tumors in Sprague-Dawley Rats

Recent clinical trials show that combined oral dosing with estrogen and progestin increases the incidence of breast cancer in postmenopausal women. Similarly, in a rat model system of mammary carcinogenesis, the synthetic progestin medroxyprogesterone acetate (MPA) decreases latency and increases incidence of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors. The goal of this study was to compare the effects of four clinically relevant progestins, MPA, norgestrel (N-EL), norethindrone (N-ONE), and megestrol acetate (MGA), on DMBA-induced mammary carcinogenesis in the rat. The experimental protocol involved implantation of 60-day release progestin pellets four weeks after rats were treated with DMBA. In contrast to the effect of MPA, N-ONE, and N-EL, but not MGA, blocked DMBA-dependent carcinogenesis and a dose-dependent effect on tumor growth was shown for N-EL; MGA did not alter tumor growth. Histopathologic studies showed extensive hyperplastic lesions in mammary tissue of progestin-treated animals. Furthermore, following treatment with N-EL or N-ONE, immunohistochemical staining for vascular endothelial growth factor in hyperplastic mammary tissue was lower than in animals treated with DMBA plus MPA or DMBA alone. Expression of vascular endothelial growth factor receptor-1, estrogen receptor alpha, and progesterone receptor was also lower in hyperplastic mammary tissue in N-EL-, N-ONE-, and MGA-treated animals. Interestingly, N-EL stimulated progression of existing mammary tumors in DMBA/MPA-treated rats, suggesting stage-specific effects of N-EL in this model. Because N-EL and N-ONE prevent tumor growth in the early stages of DMBA-induced mammary carcinogenesis in rats, these progestins may have potential as chemopreventive agents in women with no history of breast disease or family history of breast cancer.

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.

Sonodynamic therapy on chemically induced mammary tumor: pharmacokinetics, tissue distribution and sonodynamically induced antitumor effect of gallium–porphyrin complex ATX-70

Sonodynamically induced antitumor effect of a gallium porphyrin complex, ATX-70 was evaluated on a chemically induced mammary tumor in Sprague-Dawley rats. The timing of 24 h after the administration of ATX-70 was chosen for ultrasonic exposure, based on pharmacokinetic analysis of ATX-70 concentrations in the tumor, plasma, skin, and muscle. At an ATX-70 dose not less than 2.5 mg/kg and at a free-field ultrasonic intensity not less than 3 W/cm(2), the synergistic effect between ATX-70 administration and ultrasonic exposure on the tumor growth inhibition was significant. These results suggest that ATX-70 is a potential sonosensitizer for sonodynamic treatment of spontaneous mammary tumors.

Exercise-induced stress enhances mammary tumor growth in rats: Beneficial effect of the hormone melatonin

We hypothesized that intense exercise training (forced swimming for 30 min, 5 days/week) may enhance the progression of mammary carcinogenesis through the involvement of stress hormones, such as catecholamines and prolactin, which can promote breast cancer. After the appearance of the DMBA-induced tumors in Sprague-Dawley rats, the effect was evaluated of exercise-induced stress (with or without administration of the hormone melatonin) on the survival time, tumor multiplicity, and tumor growth until the death of the animals. In a second set of experiments, after one month of exercise, the NK cells count in blood, and the plasma concentrations of catecholamines and prolactin were determined. Although no significant change was found in either the survival time of the rats or the tumor multiplicity, exercise significantly increased the tumor growth rate. Stress was confirmed by the enhanced adrenaline and prolactin concentrations in the blood of the exercised rats. Exercise-induced stress did not change the percentage of NK cells in the tumor-bearing rats. Melatonin counteracted the increased tumor growth, returning the prolactin and adrenaline concentrations to their optimal physiological levels in the exercised tumor-bearing rats, thus confirming an "anti-stress" role of this hormone. In conclusion, intense exercise-induced stress enhances mammary carcinogenesis through the involvement of adrenaline and prolactin. The results also confirmed a role of melatonin as a therapeutic aid against breast cancer in general, and in particular during situations of stress.

Access to Exercise

The incidence of spontaneous tumors in Sprague-Dawley rats has ranged from 45–71% with female rats having double the percentage compared with males. Mammary tumors account for most of the tumors. Tumors may induce cancer and other life-shortening diseases, making the study of tumor development and prevention a thriving area of research. It is unknown how the gene-environment interaction influences spontaneous tumor development. Animals that reside solely in a standard cage are extremely sedentary and this trait may enhance tumerigenesis. On the other hand, animals with access to physical activity may inhibit tumor development. PURPOSE: This study compared tumorigenesis-related gene expression and the number, size, and age-associated incidence of spontaneous mammary tumors in female Sprague-Dawley rats with different access to physical activity: 1) none outside a standard cage, (SED) 2) twice-weekly physical activity in a large box (PA), and 3) regular running wheel exercise (EX). METHODS: 108 female rats were divided into three treatment groups and investigated and compared for tumor growth and development. Affymetrix microarray and RMA expression analysis identified genes with significant >2 fold changes in gene expression. Real-time quantitative reverse transcriptase polymerase chain reaction (qPCR) was used for microarray verification. RESULTS: Palpable tumors began to develop in all groups at around 59 weeks. SED animals had tumors that were greater in number and size compared with PA and EX. At 98 weeks, 14 EX rats had 36 tumors, 22 PA rats had 52 tumors, and 23 SED rats had 66 tumors. At 98 weeks, the SED group had the lowest percentage of tumor free survival compared with PA and EX. Transforming growth factor alpha (TGF?) and Rab40c (a member of the RAS oncogene family) were 2 fold greater in expression in EX than in SED (p <0.05). CONCLUSION: Animals that resided solely in cages with no access to physical activity outside a cage, demonstrated greater number and size of spontaneous mammary tumors while access to physical activity and exercise for almost two years reduced spontaneous tumorigenesis in female rats. Surprisingly, TGFα and Rab40c, both of which are associated with tumorigenesis and carcinogenesis, were up-regulated in the exercised animals.