Anti-breast cancer potential of Anonidium mannii (Oliv.) Engl. & Diels barks ethanolic extract: UPLC-ESI-QTOF-MS detection of anticancer alkaloids

ETHNOPHARMACOLOGICAL RELEVANCE

Breast cancer is a serious threat in low-income as well as developed countries. To face this, many herbal preparations are prescribed by traditional healers in Cameroon, among which is Anonidium mannii commonly called "wild soursop".

AIM

This study was undertaken to assess the anti-tumor effect of A. mannii ethanolic extract on cancer cell growth and against DMBA-induced mammary tumors in rats.

MATERIALS AND METHODS

The well characterized MTT bioassay was used to assess the cytotoxic potential of A. mannii ethanolic extract in liver (HepG2), prostate (DU145 & PC3) and breast (MCF-7) cancer cell lines. Considering the fact that breast cells were the most sensitive to the extract, a 7,12-dimethylbenz(a)anthracene (DMBA)-induced breast tumor rat model was used to assess the possible anticancer effect of A. mannii extract. Indeed, rats were treated with either tamoxifen (3.3 mg/kg BW) or A. mannii extract (16.5, 50 and 150 mg/kg BW) or vehicle (2% ethanol) for 20 weeks. Tumor incidence, tumor mass and volume, oxidative stress status in tumor as well as tumor histoarchitecture were evaluated.

RESULTS

A 24 h incubation of tested cells with the A. mannii extract significantly slowed cell growth in a concentration-dependent manner with an interesting effect in breast cells (IC50 ~61.5 μg/mL). As compared to the DMBA rats, those treated with A. mannii extract (50 and 150 mg/kg) showed reduced breast tumor incidence (28%), tumor burden (95.34% at 50 mg/kg and 99.14% at 150 mg/kg) and tumor volume (~92%). A. mannii extract counteracted the high proliferation of terminal mammary ducts induced by DMBA, mainly at 50 mg/kg. Furthermore, the extract decreased MDA and nitrite levels but increased SOD activity in the mammary gland. High Performance Liquid Chromatography coupled with Mass Spectrometry (HPLC-MS) analysis detected potential anticancer and antioxidant alkaloids in A. manni extract, which are close to those found in Annona muricata.

CONCLUSION

These results provide evidence on the in vitro and in vivo anticancer effects of A. mannii, and therefore support its use in traditional medicine system to fight against cancer.

Cancer-derived exosomal miR-7641 promotes breast cancer progression and metastasis

BACKGROUND

Intercellular communication is crucial for breast cancer progression and metastasis. However, the role of cancer-derived exosomes and their crucial microRNA (miRNA) cargoes mediating intercellular communication requires further investigation.

METHODS

Cancer-derived exosomes were isolated using differential centrifugation and differentially expressed miRNAs were determined by microarrays and qRT-PCR analysis. Cell proliferation, wound-healing, Transwell invasion, and tumor xenograft assays were used for functional research. Plasma exosomal RNA was isolated to verify its role as a prognostic biomarker.

RESULTS

We found that the tumor-promoting capacity of the exosomes was positively related to their cells of origin. MiR-7641 was identified to be the most differentially expressed miRNA, both at endogenous and secretory levels in high-metastatic cancer cells. MiR-7641 could promote tumor cell progression and metastasis, and that these functions of miR-7641 could alter recipient cells via transportation of exosomes. Additionally, exosomal miR-7641 could promote tumor growth in vivo; and its levels were significantly elevated in the plasma of patients with distant metastasis. Bioinformatics analysis has suggested that miR-7641 is correlated with breast cancer survival, and several important cellular and biological processes are closely targeted by miR-7641.

CONCLUSION

The findings indicate miR-7641 to be an important component of the cancer exosomes in promoting tumor progression and metastasis via intercellular communication. Additionally, exosomal miR-7641 may serve as a promising non-invasive diagnostic biomarker and potential targetable candidate in breast cancer treatment. Video Abstract.

Nutritional combinatorial impact on the gut microbiota and plasma short-chain fatty acids levels in the prevention of mammary cancer in Her2/neu estrogen receptor-negative transgenic mice

Breast cancer is the second leading cause of cancer-related mortality in women. Various nutritional compounds possess anti-carcinogenic properties which may be mediated through their effects on the gut microbiota and its production of short-chain fatty acids (SCFAs) for the prevention of breast cancer. We evaluated the impact of broccoli sprouts (BSp), green tea polyphenols (GTPs) and their combination on the gut microbiota and SCFAs metabolism from the microbiota in Her2/neu transgenic mice that spontaneously develop estrogen receptor-negative [ER(-)] mammary tumors. The mice were grouped based on the dietary treatment: control, BSp, GTPs or their combination from beginning in early life (BE) or life-long from conception (LC). We found that the combination group showed the strongest inhibiting effect on tumor growth volume and a significant increase in tumor latency. BSp treatment was integrally more efficacious than the GTPs group when compared to the control group. There was similar clustering of microbiota of BSp-fed mice with combination-fed mice, and GTPs-fed mice with control-fed mice at pre-tumor in the BE group and at pre-tumor and post-tumor in the LC group. The mice on all dietary treatment groups incurred a significant increase of Adlercreutzia, Lactobacillus genus and Lachnospiraceae, S24-7 family in the both BE and LC groups. We found no change in SCFAs levels in the plasma of BSp-fed, GTPs-fed and combination-fed mice of the BE group. Marked changes were observed in the mice of the LC group consisting of significant increases in propionate and isobutyrate in GTPs-fed and combination-fed mice. These studies indicate that nutrients such as BSp and GTPs differentially affect the gut microbial composition in both the BE and LC groups and the key metabolites (SCFAs) levels in the LC group. The findings also suggest that temporal factors related to different time windows of consumption during the life-span can have a promising influence on the gut microbial composition, SCFAs profiles and ER(-) breast cancer prevention.

PGRMC1 in animal breast cancer tissue and blood is associated with increased tumor growth with norethisterone in contrast to progesterone and dydrogesterone: four-arm randomized placebo-controlled xenograft study

Progesterone receptor membrane component 1 (PGRMC1) is mediating strong breast cancer cell proliferation induced by certain synthetic progestogens which we have shown within already published in vitro studies. Aim was now to use an animal model, to compare tumor growth using progesterone and its isomer dydrogesterone with norethisterone, which elicited in our in vitro studies the strongest proliferating effect. For the first time, we wanted to investigate if growth can be correlated both with blood concentrations and tissue expression of PGRMC1 to identify if PGRMC1 could be a new tumor marker. Prospective, randomized, blinded, placebo-controlled four-arm study (45-50 days); PGRMC1-transfected or empty-vector T47D- and MCF7-xenotransplants were each treated with estradiol (E2) +placebo; E2 + progesterone; E2 + norethisterone; E2 + dydrogesterone; blood PGRMC1 assessed by a novel ELISA, tissue expression by immunohistochemistry. PGRMC1-transfected tumors further increased with E2 + norethisterone but not with E2-dydrogesterone or E2-progesterone. In both PGRMC1-xenograft groups (T47D, MCF7) with E2/norethisterone, the blood concentrations and tissue expression of PGRMC1 were higher than in all other 14 groups (p < .05), with positive significant correlation between blood PGRMCI concentrations and tissue PGRMC1 expression. In the presence of PGRMC1, certain progestogens could increase the growth of breast tumor, which now also should be tested in clinical studies.

Mixed lineage kinase 3 inhibition induces T cell activation and cytotoxicity

Mixed lineage kinase 3 (MLK3), also known as MAP3K11, was initially identified in a megakaryocytic cell line and is an emerging therapeutic target in cancer, yet its role in immune cells is not known. Here, we report that loss or pharmacological inhibition of MLK3 promotes activation and cytotoxicity of T cells. MLK3 is abundantly expressed in T cells, and its loss alters serum chemokines, cytokines, and CD28 protein expression on T cells and its subsets. MLK3 loss or pharmacological inhibition induces activation of T cells in in vitro, ex vivo, and in vivo conditions, irrespective of T cell activating agents. Conversely, overexpression of MLK3 decreases T cell activation. Mechanistically, loss or inhibition of MLK3 down-regulates expression of a prolyl-isomerase, Ppia, which is directly phosphorylated by MLK3 to increase its isomerase activity. Moreover, MLK3 also phosphorylates nuclear factor of activated T cells 1 (NFATc1) and regulates its nuclear translocation via interaction with Ppia, and this regulates T cell effector function. In an immune-competent mouse model of breast cancer, MLK3 inhibitor increases Granzyme B-positive CD8+ T cells and decreases MLK3 and Ppia gene expression in tumor-infiltrating T cells. Likewise, the MLK3 inhibitor in pan T cells, isolated from breast cancer patients, also increases cytotoxic CD8+ T cells. These results collectively demonstrate that MLK3 plays an important role in T cell biology, and targeting MLK3 could serve as a potential therapeutic intervention via increasing T cell cytotoxicity in cancer.

Comparative pharmacokinetics of six coumarins in normal and breast cancer bone-metastatic mice after oral administration of Wenshen Zhuanggu Formula

ETHNOPHARMACOLOGICAL RELEVANCE

Wenshen Zhuanggu Formula (WSZG) is a traditional Chinese medicine (TCM) prescription used in clinics for adjuvant treatment of breast cancer bone metastases in Longhua Hospital in China. WSZG has been reported to decrease the risk of bone metastases and alleviate the severity of bone lesions in a breast cancer xenograft model.

AIM OF THE STUDY

The present study aimed at investigating the pharmacokinetic behaviors of six coumarins in normal and breast cancer bone-metastatic mice following oral administration of WSZG extract.

MATERIALS AND METHODS

A bone-metastatic mouse model was established by intracardiac injection of MDA-MB-231BO breast cancer cells, and WSZG extract (1.60 g/kg) was given orally to the model and normal mice for 4 weeks. Then, the blood pharmacokinetic parameters of six bioactive components from WSZG (psoralen, isopsoralen, bergapten, xanthotoxin, osthole, and imperatorin) were analyzed by liquid chromatography tandem mass spectrometry.

RESULTS

There were significant differences in pharmacokinetic behaviors between normal and pathological states. Compared with normal mice, the model mice showed significantly increased AUC_0-t and AUC_0-∞ of the bioactive compounds (P < 0.05) and significantly decreased total blood clearance (CL_Z/F) (P < 0.05).

CONCLUSIONS

The different pharmacokinetic behaviors might be partly ascribed to intestinal functional disorders and imbalance of gastrointestinal microbiota under the morbid state. The findings provide some valuable information to evaluate the clinical efficacy and safety of this TCM formula.

Dietary Supplementation with Methylseleninic Acid Inhibits Mammary Tumorigenesis and Metastasis in Male MMTV-PyMT Mice

Male breast cancer, which makes up approximately 1% of all breast cancers, is an aggressive disease with poor prognosis. We investigated the effects of dietary supplementation with selenium in the form of methylseleninic acid [(MSeA) 2.5 mg selenium/kg] on mammary tumorigenesis in male MMTV-PyMT mice. The mammary tumor latency was 14.6 weeks for the MSeA-fed group and 13.8 weeks for the controls fed the AIN93G diet (p < 0.05). Dietary supplementation with MSeA, versus the control, resulted in a 72% reduction in tumor progression, a 46% reduction in both final volume and weight of mammary tumors, and a 70% reduction in the number of lung metastases. Mammary tumorigenesis in MMTV-PyMT mice, versus non-tumor-bearing wild-type mice, resulted in significant increases in concentrations of plasminogen activator inhibitor-1, urokinase plasminogen activator, monocyte chemotactic protein-1, and vascular endothelial growth factor, but not aromatase and estrogen, in the plasma. Concentrations of all variables mentioned above in both plasma and mammary tumors were lower in MSeA-fed mice. Mammary tumorigenesis reduced plasma levels of adiponectin compared to non-tumor-bearing controls. Adiponectin concentrations in mammary tumors, but not in plasma, were higher in MSeA-fed mice than in controls. In summary, dietary supplementation with selenium in the form of MSeA inhibits mammary tumorigenesis and its pulmonary metastasis in male MMTV-PyMT mice.

Membrane Mucin Muc4 promotes blood cell association with tumor cells and mediates efficient metastasis in a mouse model of breast cancer

Mucin-4 (Muc4) is a large cell surface glycoprotein implicated in the protection and lubrication of epithelial structures. Previous studies suggest that aberrantly expressed Muc4 can influence the adhesiveness, proliferation, viability and invasiveness of cultured tumor cells, as well as the growth rate and metastatic efficiency of xenografted tumors. Although it has been suggested that one of the major mechanisms by which Muc4 potentiates tumor progression is via its engagement of the ErbB2/HER2 receptor tyrosine kinase, other mechanisms exist and remain to be delineated. Moreover, the requirement for endogenous Muc4 for tumor growth progression has not been previously explored in the context of gene ablation. To assess the contribution of endogenous Muc4 to mammary tumor growth properties, we first created a genetically engineered mouse line lacking functional Muc4 (Muc4ko), and then crossed these animals with the NDL (Neu DeLetion mutant) model of ErbB2-induced mammary tumorigenesis. We observed that Muc4ko animals are fertile and develop normally, and adult mice exhibit no overt tissue abnormalities. In tumor studies, we observed that although some markers of tumor growth such as vascularity and cyclin D1 expression are suppressed, primary mammary tumors from Muc4ko/NDL female mice exhibit similar latencies and growth rates as Muc4wt/NDL animals. However, the presence of lung metastases is markedly suppressed in Muc4ko/NDL mice. Interestingly, histological analysis of lung lesions from Muc4ko/NDL mice revealed a reduced association of disseminated cells with platelets and white blood cells. Moreover, isolated cells derived from Muc4ko/NDL tumors interact with fewer blood cells when injected directly into the vasculature or diluted into blood from wild type mice. We further observed that blood cells more efficiently promote the viability of non-adherent Muc4wt/NDL cells than Muc4ko/NDL cells. Together, our observations suggest that Muc4 may facilitate metastasis by promoting the association of circulating tumor cells with blood cells to augment tumor cell survival in circulation.

Vitamin D mitigates the adverse effects of obesity on breast cancer in mice

Obesity is an established risk factor for postmenopausal breast cancer (BCa), insulin resistance, and vitamin D deficiency, and all contribute to increased synthesis of mammary estrogens, the drivers of estrogen receptor-positive (ER+) BCa growth. As both dietary vitamin D and calcitriol treatments inhibit breast estrogen synthesis and signaling, we hypothesized that vitamin D would be especially beneficial in mitigating the adverse effects of obesity on ER+BCa. To assess whether obesity exerted adverse effects on BCa growth and whether vitamin D compounds could reduce these unfavorable effects, we employed a diet-induced obesity (DIO) model in ovariectomized C57BL/6 mice. Breast tumor cells originally from syngeneic Mmtv-Wnt1 transgenic mice were then implanted into the mammary fat pads of lean and obese mice. DIO accelerated the initiation and progression of the mammary tumors. Treatments with either calcitriol or dietary vitamin D reduced the adverse effects of obesity causing a delay in tumor appearance and inhibiting continued tumor growth. Beneficial actions of treatments with vitamin D or calcitriol on BCa and surrounding adipose tissue included repressed Esr1, aromatase, and Cox2 expression; decreased tumor-derived estrogen and PGE2; reduced expression of leptin receptors; and increased adiponectin receptors. We demonstrate that vitamin D treatments decreased insulin resistance, reduced leptin, and increased adiponectin signaling and also regulated the LKB1/AMPK pathway contributing to an overall decrease in local estrogen synthesis in the obese mice. We conclude that calcitriol and dietary vitamin D, acting by multiple interrelated pathways, mitigate obesity-enhanced BCa growth in a postmenopausal setting.

[Associativity of microRnA levels in blood serum to quantity and functional activity of haemo - and lymphopoiesis cells in experimental breast cancer]

The work purpose was to reveal an existence of an associativity of the microRNA levels in blood serum to quantitative and functional indices of cells haemo - and lymphopoiesis at the experimental breast cancer induced by N -methyl - N- nitrosourea in the remote period after surgery and carrying out neoadjuvant polychemotherapy. At animals there were investigated levels of microRNA-21, microRNA-221, microRNA-222 and microRNA-429 in serum, also investigated quantitative and functional parameters of cells from bone marrow, from lymph of a chest channel and from spleen. Statistically significant distinctions on the microRNA level in blood serum and an existence of interrelations of microRNA levels with quantitative and functional indices of haemo- and lymphopoiesis cells were revealed.

Raman spectroscopy of serum: A study on 'pre' and 'post' breast adenocarcinoma resection in rat models

Risk of recurrence is a major problem in breast cancer management. Currently available prognostic markers have several disadvantages including low sensitivity and specificity, highlighting the need for new prognostic techniques. One of the candidate techniques is serum-based Raman spectroscopy (RS). In this study, feasibility of using RS to distinguish 'pre' from 'post' breast tumor resection serum in rats was explored. Spectral analysis suggests change in proteins and amino acid profiles in 'post' compared to 'pre-surgical' group. Principal-Component-Linear-Discriminant-Analysis shows 87% and 91% classification efficiency for 'pre' and 'post-surgical' groups respectively. Thus, the study further supports efficacy of RS for theranostic applications.

Macrophages support splenic erythropoiesis in 4T1 tumor-bearing mice

Anemia is a common complication of cancer; a role of spleen in tumor-stress erythropoiesis has been suggested. However, the molecular mechanisms involved in the splenic erythropoiesis following tumor maintenance remain poorly understood. Here we show that tumor development blocks medullar erythropoiesis by granulocyte colony-stimulating factor (G-CSF) and then causes anemia in murine 4T1 breast tumor-bearing mice. Meanwhile, tumor-stress promotes splenic erythropoiesis. Splenectomy worsened tumor-induced anemia, and reduced tumor volume and tumor weight, indicating the essential role of spleen in tumor-stress erythropoiesis and tumor growth. Tumor progression of these mice led to increased amounts of bone morphogenetic protein 4 (BMP4) in spleen. The in vivo role of macrophages in splenic erythropoiesis under tumor-stress conditions was investigated. Macrophage depletion by injecting liposomal clodronate decreased the expression of BMP4, inhibited splenic erythropoiesis, aggravated the tumor-induced anemia and suppressed tumor growth. Our results provide insight that macrophages and BMP4 are positive regulators of splenic erythropoiesis in tumor pathological situations. These findings reveal that during the tumor-stress period, the microenvironment of the spleen is undergoing changes, which contributes to adopt a stress erythropoietic fate and supports the expansion and differentiation of stress erythroid progenitors, thereby replenishing red blood cells and promoting tumor growth.

Detection and quantitation of circulating tumor cell dynamics by bioluminescence imaging in an orthotopic mammary carcinoma model

Circulating tumor cells (CTCs) have been detected in the bloodstream of both early-stage and advanced cancer patients. However, very little is know about the dynamics of CTCs during cancer progression and the clinical relevance of longitudinal CTC enumeration. To address this, we developed a simple bioluminescence imaging assay to detect CTCs in mouse models of metastasis. In a 4T1 orthotopic metastatic mammary carcinoma mouse model, we demonstrated that this quantitative method offers sensitivity down to 2 CTCs in 0.1-1mL blood samples and high specificity for CTCs originating from the primary tumor, independently of their epithelial status. In this model, we simultaneously monitored blood CTC dynamics, primary tumor growth, and lung metastasis progression over the course of 24 days. Early in tumor development, we observed low numbers of CTCs in blood samples (10-15 cells/100 µL) and demonstrated that CTC dynamics correlate with viable primary tumor growth. To our knowledge, these data represent the first reported use of bioluminescence imaging to detect CTCs and quantify their dynamics in any cancer mouse model. This new assay is opening the door to the study of CTC dynamics in a variety of animal models. These studies may inform clinical decision on the appropriate timing of blood sampling and value of longitudinal CTC enumeration in cancer patients.

Copper and resveratrol attenuates serum catalase, glutathione peroxidase, and element values in rats with DMBA-induced mammary carcinogenesis

In this paper, a hypothesis was assessed whether or not the intoxication with copper and supplementation with copper plus resveratrol would result in changes in the activities of catalase and glutathione peroxidase and moreover if the characteristic changes would appear in concentrations of copper, iron, calcium, magnesium, and zinc in the serum of rats with chemically induced carcinogenesis. Female Sprague-Dawley rats were divided into study groups which, apart from the standard diet, were treated with copper (42.6 mg Cu/kg food as CuSO4·5H2O) or copper plus resveratrol (0.2 mg/kg body) via gavage for a period from 40 days until 20 weeks of age. In cancer groups, the rats were treated with a dose of 80 mg/body weight of 7,12-dimethyl-1,2-benz[a]anthracene (DMBA) given in rapeseed oil at 50 and 80 days of age to induce mammary carcinogenesis. The control groups included the rats kept in the same conditions and fed with the same diet as the animals from the study groups, but not DMBA-treated. The activity of catalase significantly decreased in groups of rats with mammary carcinogenesis that were supplemented with copper (p < 0.05) or copper plus resveratrol (p < 0.001) in comparison with the control groups that received the same diets. In cancer groups of nonsupplemented rats, the increase of glutathione peroxidase activity was observed. The process of carcinogenesis and the applied supplementation significantly altered the concentrations of trace elements in serum, in particular as concerns iron and copper. The mean serum iron levels in rats with breast cancer were significantly lower than those in the control groups (p < 0.001). The mean serum copper levels significantly decreased in the groups of rats with mammary carcinogenesis that were supplemented with copper or copper plus resveratrol in comparison with the control groups that received the same diets (p < 0.001). The characteristic changes in iron content and the zinc/copper and zinc/iron ratios in blood may be used as one of the prognostic factors in breast cancer research.

Mammary tumor growth and pulmonary metastasis are enhanced in a hyperlipidemic mouse model

Dyslipidemia has been associated with an increased risk for developing cancer. However, the implicated mechanisms are largely unknown. To explore the role of dyslipidemia in breast cancer growth and metastasis, we used the apolipoprotein E (ApoE) knockout mice (ApoE(-/-)), which exhibit marked dyslipidemia, with elevated circulating cholesterol and triglyceride levels in the setting of normal glucose homeostasis and insulin sensitivity. Non-metastatic Met-1 and metastatic Mvt-1 mammary cancer cells derived from MMTV-PyVmT/FVB-N transgenic mice and c-Myc/vegf tumor explants respectively, were injected into the mammary fat pad of ApoE(-/-) and wild-type (WT) females consuming a high-fat/high-cholesterol diet and tumor growth was evaluated. ApoE(-/-) mice exhibited increased tumor growth and displayed a greater number of spontaneous metastases to the lungs. Furthermore, intravenous injection of Mvt-1 cells resulted in a greater number of pulmonary metastases in the lungs of ApoE(-/-) mice compared with WT controls. To unravel the molecular mechanism involved in enhanced tumor growth in ApoE(-/-) mice, we studied the response of Mvt-1 cells to cholesterol in vitro. We found that cholesterol increased Akt(S473) phosphorylation in Mvt-1 cells as well as cellular proliferation, whereas cholesterol depletion in the cell membrane abrogated Akt(S473) phosphorylation induced by exogenously added cholesterol. Furthermore, in vivo administration of BKM120, a small-molecule inhibitor of phosphatidylinositol 3-kinase (PI3K), alleviated dyslipidemia-induced tumor growth and metastasis in Mvt-1 model with a concomitant decrease in PI3K/Akt signaling. Collectively, we suggest that the hypercholesterolemic milieu in the ApoE(-/-) mice is a favorable setting for mammary tumor growth and metastasis.

Serum inhibits the immunosuppressive function of myeloid-derived suppressor cells isolated from 4T1 tumor-bearing mice

As more groups investigate the role of myeloid-derived suppressor cells (MDSCs) in promoting the growth of primary tumors and distant tumor metastases, it is imperative to ensure the accurate detection and quantification of MDSC immunosuppression ex vivo. MDSCs are defined by their ability to suppress immune responses. Although different in vitro culture conditions have been used to study MDSCs, the effect of different culture conditions on MDSC immunosuppression is unknown. We therefore isolated MDSCs from the lungs and spleens of 4T1 murine mammary tumor-bearing mice and assayed MDSC-mediated suppression of T cell responses under different culture conditions. We found that 4T1-induced MDSCs effectively suppressed T cell proliferation under serum-free conditions, but not when fetal calf serum (FCS) was present. FCS neither altered the immunosuppressive activities of other myeloid cell types (i.e., peritoneal or tumor-associated macrophages) nor modified the susceptibility of T cells to myeloid cell-mediated suppression, but instead acted directly on 4T1-induced MDSCs to significantly reduce their immunosuppressive function. Importantly, we found that bovine serum albumin was a major contributor to the antagonistic effects of FCS on 4T1-induced MDSC immunosuppression by inhibiting reactive oxygen species production from MDSCs. This work reveals that in vitro culture conditions influence the immunosuppressive properties of MDSCs and highlights the importance of testing different culture conditions on MDSC phenotype to ensure that MDSC immunosuppression is not being masked. These data have important implications for the accurate detection and identification of MDSCs, as well as for determining the influence of MDSC-mediated immunosuppression on primary and metastatic tumor growth.

Effects of energy restriction and wheel running on mammary carcinogenesis and host systemic factors in a rat model

Limiting energy availability via diet or physical activity has health benefits; however, it is not known whether these interventions have similar effects on the development of cancer. Two questions were addressed as follows: (i) Does limiting energy availability by increasing physical activity have the same effect on mammary carcinogenesis as limiting caloric intake? and (ii) Are host systemic factors, implicated as risk biomarkers for breast cancer, similarly affected by these interventions? Female Sprague Dawley rats were injected with 50-mg 1-methyl-1-nitrosourea per kg body weight at 21 days of age and randomized to one of five groups (30 rats per group) as follows: (i) sham running wheel control; (ii) restricted fed to 85% of the sham control; (iii and iv) voluntary running in a motorized activity wheel (37 m/min) to a maximum of 3,500 m/d or 1,750 m/d; and (v) sedentary ad libitum fed control with no access to a running wheel. The three energetics interventions inhibited the carcinogenic response, reducing cancer incidence (P = 0.01), cancer multiplicity (P < 0.001), and cancer burden (P < 0.001) whereas prolonging cancer latency (P = 0.004) although differences among energetics interventions were not significant. Of the plasma biomarkers associated with the development of cancer, the energetics interventions reduced bioavailable insulin-like growth factor-1 (IGF-1), insulin, interleukin-6, serum amyloid protein, TNF-α, and leptin and increased IGF-binding protein 3 (IGFBP-3) and adiponectin. Plasma-fasting glucose, C-reactive protein, estradiol, and progesterone were unaffected. The plasma biomarkers of greatest value in predicting the carcinogenic response were adiponectin > IGF-1/IGFBP-3 > IGFBP-3 > leptin > IGF-1.

Potential role of melatonin in DNA damage caused by nitrosourea-induced mammary carcinogenesis

Mammary carcinogenesis was induced in female Sprague-Dawley rats by exposure to N-methyl-N-nitrosourea (NMU). Animals were kept under constant light conditions to arrest endogenous melatonin synthesis and were fed the same melatonin dosage, since nitrosourea exposure may also induce cellular injury, especially with extensive proliferative activity. The pro-apoptotic effects of the biogenic amine, melatonin, on rat whole blood leukocytes were assessed by alkaline single cell gel electrophoresis (comet) assay. Potential induction of stress due to animal immobilization and its additional effect on DNA damage was studied. The parameters relevant to the degree of DNA damage in groups with chemocarcinogen treatment demonstrated no significant effects as a result of the immobilization. A significant increase in DNA damage after melatonin treatment in NMU-induced carcinogenesis confirms its involvement in the activation of apoptosis.

Declining melatonin levels and MT1 receptor expression in aging rats is associated with enhanced mammary tumor growth and decreased sensitivity to melatonin

Serum melatonin (MLT) levels have been reported to diminish significantly by the 5th and 6th decades of life as the incidence of breast cancer increases. Given MLT's anti-cancer activity, we hypothesize that age-related decline in pineal MLT production leads to enhanced breast cancer development and growth as women age. In this study, we sought to determine whether the growth of tissue-isolated mammary tumors in young, adult, and old female Buffalo rats relates to the age-related changes in MLT and its MT1 receptor. Significant decreases in the peak nighttime serum MLT levels were observed in old as compared to adult and young rats. Significantly diminished nighttime and early morning levels of MT1-melatonin receptors were observed in uteri from old rats compared to adult and young rats. Growth rates in transplanted, tissue-isolated, carcinogen-induced mammary tumors are significantly increased in old rats as compared to adult or young rats. The growth-suppressive actions of exogenous MLT are diminished in old rats compared to adult and young rats. This decrease in tumor response correlates with reduced expression of the MT1 receptor in old as compared to young and adult rats. Thus, enhanced mammary tumor growth is associated with old age and diminished levels of MLT and MT1 receptor during old age, resulting in reduced sensitivity to exogenous MLT. Finally, our studies demonstrate that the tissue-isolated tumor model is viable model system in which to study the role of aging on breast cancer growth.

In vivo near-infrared spectroscopy and magnetic resonance imaging monitoring of tumor response to combretastatin A-4-phosphate correlated with therapeutic outcome

PURPOSE

To develop a combination treatment consisting of combretastatin A-4-phosphate (CA4P) with radiation based on tumor oxygenation status.

METHODS AND MATERIALS

In vivo near-infrared spectroscopy (NIRS) and diffusion-weighted (DW) magnetic resonance imaging (MRI) were applied to noninvasively monitor changes in tumor blood oxygenation and necrosis induced by CA4P (30 mg/kg) in rat mammary 13762NF adenocarcinoma, and the evidence was used to optimize combinations of CA4P and radiation treatment (a single dose of 5 Gy).

RESULTS

NIRS showed decreasing concentrations of tumor vascular oxyhemoglobin and total hemoglobin during the first 2 h after CA4P treatment, indicating significant reductions in tumor blood oxygenation and perfusion levels (p < 0.001). Twenty-four hours later, in response to oxygen inhalation, significant recovery was observed in tumor vascular and tissue oxygenation according to NIRS and pimonidazole staining results, respectively (p < 0.05). DW MRI revealed significantly increased water diffusion in tumors measured by apparent diffusion coefficient at 24 h (p < 0.05), suggesting that CA4P-induced central necrosis. In concordance with the observed tumor oxygen dynamics, we found that treatment efficacy depended on the timing of the combined therapy. The most significant delay in tumor growth was seen in the group of tumors treated with radiation while the rats breathed oxygen 24 h after CA4P administration.

CONCLUSIONS

Noninvasive evaluation of tumor oxygen dynamics allowed us to rationally enhance the response of syngeneic rat breast tumors to combined treatment of CA4P with radiation.

Effect of chronic and intermittent calorie restriction on serum adiponectin and leptin and mammary tumorigenesis

The effect of chronic (CCR) and intermittent (ICR) caloric restriction on serum adiponectin and leptin levels was investigated in relation to mammary tumorigenesis. 10-wks old MMTV-TGF-α female mice were assigned to ad libitum fed (AL; AIN-93M diet), ICR (3-week 50% caloric restriction, AIN-93M-mod diet, 2× protein, fat, vitamins, and minerals followed by 3-wks 100% AL consumption of AIN-93M), and CCR (calorie and nutrient intake matched for each 6-wks ICR cycle, ∼ 75% of AL) groups. Mice were sacrificed at 79 (end of restriction) or 82 (end of refeeding) wks of age. Serum was obtained in cycles 1, 3, 5, 8, 11, and terminal. Mammary tumor incidence was 71.0%, 35.4%, and 9.1% for AL, CCR, and ICR mice, respectively. Serum adiponectin levels were similar among groups with no impact of either CCR or ICR. Serum leptin level rose in AL mice with increasing age but was significantly reduced by long-term CCR and ICR. The ICR protocol was also associated with an elevated adiponectin/leptin ratio. In addition, ICR-restricted mice had increased mammary tissue AdipoR1 expression and decreased leptin and ObRb expression compared with AL mice. Mammary fat pads from tumor-free ICR-mice had higher adiponectin expression than AL and CCR mice whereas all tumor-bearing mice had weak adiponectin signal in mammary fat pad. Although we did not show an association of either adiponectin or leptin with individual mice in relation to mammary tumorigenesis, we did find that reduced serum leptin and elevated adiponectin/leptin ratio were associated with the protective effect of intermittent calorie restriction.

Alcohol consumption, obesity, estrogen treatment and breast cancer

Alcohol consumption increases breast cancer risk in postmenopausal women in a dose-dependent manner. The objective of the present study was to determine if the effect of alcohol on mammary cancer is modified by body weight and exogenous estrogen. Ovariectomized mice of various body weights, receiving estrogen or placebo supplementation, and consuming water or alcohol were injected with mammary cancer cells. Alcohol intake resulted in insulin sensitivity and increased tumor growth in obese mice. Exogenous estrogen alone inhibited tumor growth. The combination of estrogen and alcohol overcame the inhibitory effects of estrogen on tumor growth in obese mice. Alcohol consumption increased the circulating estrogen and leptin levels. In conclusion, alcohol and estrogen treatment can modify mammary tumor growth, possibly through the regulation of estrogen and leptin, especially in obese mice.

Ovarian renin--angiotensin system-regulating aminopeptidases are involved in progesterone overproduction in rats with mammary tumours induced by N-methyl nitrosourea

A local renin-angiotensin system (RAS) has been found in ovary. This ovarian RAS may regulate ovarian steroidogenesis. Ample studies show that the ovarian hormones estradiol (E2) and progesterone (P) are strongly implicated in the development of breast cancer.

MATERIALS AND METHODS

The aim of the present work was to elucidate if alterations in ovarian RAS, analyzed through their proteolytic regulatory enzymes aminopeptidase A (APA), B (APB) and N (APN), could be responsible for an altered steroidogenesis in rats with mammary tumours induced by N-methyl nitrosourea (NMU).

RESULTS

We describe here a highly significant increase of serum P levels in NMU-treated rats, concomitantly with an increase in ovarian aspartyl and glutamyl aminopeptidase activities (named together as APA activity). Moreover, we did not find changes in APB or APN activities, suggesting an increased metabolism from Ang II to Ang III and a decreased catabolism of Ang III.

CONCLUSION

The relationship between ovarian RAS and P overproduction in a rat model of mammary carcinogenesis indicates ovarian RAS as a new potential target in breast cancer therapy.

Antitumor and antiangiogenic activity of soy phytoestrogen on 7,12-dimethylbenz[alpha]anthracene-induced mammary tumors following ovariectomy in Sprague-Dawley rats

Soy phytoestrogen is often used as hormone replacement therapy to alleviate the symptoms of menopause in postmenopausal women. Since estrogen has been considered as an important risk factor for the development of breast carcinoma, we need to know whether it is safe for these postmenopausal women with breast cancer to take soy foods that are rich in phytoestrogen. In the present study, we investigated the efficacy of soy phytoestrogen on tumor proliferation, apoptosis, and angiogenesis in mammary tumors that had already formed in ovariectomized rats. We found that soy phytochemical extraction inhibited proliferation and induced apoptosis in vitro and in vivo, and it demonstrated better antitumor effects than single phytoestrogen. Soy phytochemical extraction also produced surprisingly good antiangiogenic effects, which were evidenced by lower microvascular density, reduced plasma vascular endothelial growth factor, and increased plasma endostatin levels. Our findings suggest that soy phytochemical extraction exerts significant antitumor and antiangiogenic activity in a postmenopausal animal model with breast cancer.

Chemopreventive effects of anastrozole in a premenopausal breast cancer model

BACKGROUND

Monotherapy with aromatase inhibitors has no established role in premenopausal breast cancer in women and is an area of future exploration.

MATERIALS AND METHODS

In this study, chemopreventive effects of anastrozole in the model of N-methyl-N-nitrosourea-induced premenopausal mammary carcinogenesis in female rats were evaluated. Anastrozole was dietarily administered at two concentrations: 0.05 mg/kg (ANA 0.05) and 0.5 mg/kg (ANA 0.5). Basic parameters of experimental carcinogenesis and side-effects on selected organs after anastrozole treatment in animals were assessed.

RESULTS

In the ANA 0.5 group, anastrozole suppressed tumor incidence by 40% (p<0.05) and tumor frequency by 57% (p<0.01), as well as lengthening the latency period by 10 days (p=0.084) compared to control animals. Adverse effects of anastrozole on the genital system (uterus and vagina) and lipid and bone metabolism in rats were not found. Anastrozole did not alter serum concentrations of estradiol, testosterone or dehydroepiandrosterone in animals. An increase in the body weight gain of rats in the ANA 0.5 group compared with the controls (p<0.01) was observed.

CONCLUSION

This study is the first about the antineoplastic effects of anastrozole in a model of premenopausal mammary carcinogenesis in female rats.

[Different expression of liver-specific insulin-like growth factor I gene in breast cancer; expression with mice]

OBJECTIVE

To investigate the possible relationship between liver-specific insulin-like growth factor I (IGF-1) and the pathogenesis of breast cancer.

METHODS

Fifty non-IGF-1 deficient (LID) mice were randomly divided into 2 equal groups: Group I, fed with dimethyl-benzanthracene (DMBA) for 8 weeks to cause mammary cancer, and Group III, fed with DMBA and ginsenoside Rg for 28 d; and 50 LID mice were randomly divided into 2 equal groups too Group II, fed with DMBA for 8 weeks, and Group IV, fed with DMBA and ginsenoside Rg for 28 d. The mice were killed after the cessation of DMBA use. The serum IGF-1 expression was detected with method Six Gene chips were used to detect the gene expression in the breast cancer tissues.

RESULTS

The breast cancer rates were 66.67% in Group I and 33.33% in Group II, 36.00% in Group III, and 12.00% in Group IV. The tumor size was (0.79 +/- 0.20) cm in Group I, (0.37 +/- 0.08) cm in Group III , (0.32 +/- 0.08) cm in Group II, and (0.15 +/- 0.05) cm Group IV. The IGF-1 level of Group II was (41.33 +/- 7.52) ng/ml, 1/4 as high as that of Group I [(166.51 +/- 12.32) ng/ml], and the IGF-1 level of Group IV was (33.48 +/- 6.73) ng/ml, 1/4 as high as that of Group III [(155.84 +/- 11.34) ng/ml]. Compared with those of the control mice, the breast cancers of the LID mice had longer latency, lower incidence, and slower growth rate. The differential gene expression in different serum IGF-1 levels involved binding, metabolism, apoptosis, cell cycle, signal transduction, immune response, transcription regulation and interpretation regulation and so on. Among these genes, Col11, Egln3, Glycam1, Irf6, Lgals7, Perp, Rag1, and Rbm35a genes were closely related to the incidence of breast cancer.

CONCLUSION

IGF-1 plays a role as a risk factor in the onset and development of breast cancer by affecting the expression of many differentially expressed genes.

The antitumor effect of lowered doses of cytostatics combined with new analogs of vitamin D in mice

Active and less toxic vitamin D analogs could be useful for clinical applications. In the present study, the antitumor effects of two new synthetic analogs of vitamin D, namely PRI-2202 (24R calcipotriol) and PRI-2205 (5, 6-trans calcipotriol), were evaluated. Since the analogs PRI-2202 and PRI-2205 administered alone inhibited tumor growth only slightly, they were applied in a combined therapy with cytostatics. The in vitro results showed that the synergistic effect between vitamin D analogs and cytostatics was more pronounced when low concentrations of the latter were used. Due to this fact low doses of cytostatics were applied in the in vivo combined treatment schedules. The studies were performed in mouse mammary cancer 4T1 and Lewis lung cancer (LLC) models. Mice bearing subcutaneous tumors were treated with vitamin D analogs and cytostatics in different combinations. Statistically significant inhibition of tumor growth by the combined treatment was observed in 4TI mammary cancer treated with cyclophosphamide and in LLC lung cancer-bearing animals treated with cisplatin. In contrast, no improved therapeutic effect of the combined treatment with low doses of doxorubicin and cyclophosphamide was observed in mice bearing LLC tumors. Moreover, the combined treatment with cisplatin led to increased toxicity, which did not depend on the calcemic activity of the vitamin D analogs. The general conclusion of this work is that combination of vitamin D analogs with cytostatics applied in low doses is not effective in vivo, despite the encouraging in vitro results. Nevertheless, combined treatment with vitamin D analogs was more effective than the treatment with cytostatics applied alone, when higher doses of cytostatics were used.

Temporal factors alter effects of social housing conditions on responses to chemotherapy and hormone levels in a Shionogi mammary tumor model

OBJECTIVE

To identify possible hormonal factors involved in the differential responses to chemotherapy observed in our tumor model, we investigated if the timing among tumor cell injection, rehousing, and chemotherapy administration differentially affects levels of corticosterone (CORT), growth hormone (GH), and testosterone and tumor and host responses to chemotherapy.

METHODS

Mice were reared either individually (I) or in groups (G). At 2 to 4 months, mice were injected with tumor cells and retained in their original housing conditions or rehoused into different experimental groups (GG, IG, II, GI) either immediately (experiment 1) or 14 days later (experiment 2); chemotherapy was administered when tumors weighed approximately 0.8 g.

RESULTS

In experiment 1, IG and GG mice had better responses to chemotherapy than GI mice. Chemotherapy increased CORT levels in II mice and decreased GH levels in GI mice compared with those of their drug vehicle-treated counterparts. Under the temporal conditions of experiment 2, IG and GG mice lost the advantage seen in experiment 1 in terms of tumor and host responses to chemotherapy. Before chemotherapy administration, CORT levels in IG mice and GH levels in GI mice were higher than those in mice in all other housing conditions. At 1 day after chemotherapy, CORT levels were higher for chemotherapy-treated than for drug vehicle-treated IG mice, and at 5 days post chemotherapy, GH levels were higher in GI than in IG mice.

CONCLUSIONS

Temporal relationships among tumor cell injection, rehousing, and chemotherapy administration critically influence responses to chemotherapy; these effects may be mediated, in part, by alterations in hormone levels.

Strain and tumour specific variations in the effect of hypoxia on osteopontin levels in experimental models

PURPOSE

To investigate the relationship between tumour hypoxia and serum and tumour osteopontin (OPN) levels.

MATERIALS AND METHODS

Experiments were performed in CDF1 or C3H/Km mice implanted with a C3H mammary carcinoma (CDF1) or SCCVII squamous cell carcinoma (C3H/Km), respectively. Mice were either untreated or gassed with 10% oxygen for 1-72 h. Serum and tumour OPN levels were measured with an ELISA and tumour OPN mRNA levels using RT-PCR. Tumour oxygenation was estimated using the Eppendorf histograph with the percentage of pO(2) values <or=5 mm Hg (HF5) as the endpoint.

RESULTS

OPN levels were 50-fold higher in the serum of non-tumour bearing CDF1 mice compared to C3H/Km mice. A tumour related increase in serum OPN levels was observed in CDF1 but not in C3H/Km mice. Low oxygen breathing increased HF5 in both tumour models and in the C3H mammary carcinoma model both serum and tumour OPN decreased after prolonged hypoxia (24h and more). When 12h of hypoxia was followed by 24h reoxygenation there was a twofold increase in serum OPN levels. No changes were observed in the SCCVII model. No changes in tumour OPN mRNA expression were observed during hypoxia and reoxygenation in these tumour models.

CONCLUSION

Clear strain and tumour specific differences in the effect of hypoxia on OPN levels have been observed in two different mouse tumour models. These data emphasize the complexity in the relationship between poor oxygenation (and/or reoxygenation) of tumours and serum levels of OPN.

Accelerated tumor formation in a fatless mouse with type 2 diabetes and inflammation

Epidemiologic studies show a positive association between obesity and cancer risk. In addition to increased body adiposity and secretion of fat-derived hormones, obesity is also linked to insulin resistance, type 2 diabetes, and chronic inflammation. We used the fatless A-ZIP/F-1 transgenic mouse to dissociate the relative role of each of these underlying factors in the development of cancer. These mice are unique in that they do not have white fat but do develop type 2 diabetes. In two cancer models, the classic two-stage skin carcinogenesis protocol and the C3(1)/T-Ag transgenic mouse mammary tumor model, A-ZIP/F-1 mice displayed higher tumor incidence, tumor multiplicity, and decreased tumor latency than wild-type mice. We examined circulating levels of adipokines, growth factors, and cytokines. As expected, adipokines (i.e., leptin, adiponectin, and resistin) were undetectable or found at very low levels in the blood of fatless mice. However, insulin, insulin-like growth factor-I, growth hormone, vascular endothelial growth factor, and proinflammatory Th2 cytokines, such as interleukin (IL)-1beta, IL-4, and IL-6, were elevated in A-ZIP/F-1 mice. Additionally, we examined multiple phosphorylated proteins (i.e., protein kinase B/Akt and ErbB2/HER-2 kinase) associated with cancer development. Results show that many of these phosphorylated proteins were activated specifically in the A-ZIP/F-1 skin but not in the wild-type skin. These findings suggest that adipokines are not required for the promotion of tumor development and thus contradict the epidemiologic data linking obesity to carcinogenesis. We postulate that insulin resistance and inflammation are responsible for the positive correlation with cancer observed in A-ZIP/F-1 mice.

Monitoring metabolite gradients in the blood, liver, and tumor after induced hyperglycemia in rats with R3230 flank tumors using microdialysis and bioluminescence imaging

Hypoxia is a common cause of reduced tumor response to treatment such as irradiation. The purpose of this study was to establish a method in a rat model that is clinically applicable to monitor the efficiency of glucose transport to both tumor and normal tissue following the induction of hyperglycemia. Female Fischer 344 rats bearing subcutaneous R3230 rat mammary adenocarcinomas received glucose (1 g/kg in 200 mg/ml Normosol) injected in the femoral vein with an infusion pump at a rate of 0.1 ml/min. Microdialysis sampling was performed on all animals. The perfusion marker Hoechst 33342 was injected intravenously at a dose of 5 mg/kg ten minutes prior to sacrifice. After the last blood sample was collected, the tumor and liver were removed and snap frozen for bioluminescence imaging and the rat was sacrificed. Imaging bioluminescence was performed on cryosections of the tumor and liver of the animal to monitor local metabolite gradients and concentrations of glucose in relation to the perfused vasculature, as determined by injected Hoechst 33342. Microdialysis and bioluminescence show comparable data when monitoring the changes of blood, liver, and tumor glucose concentrations as a result of induced hyperglycemia.

Muscarinic receptors autoantibodies purified from mammary adenocarcinoma-bearing mice sera stimulate tumor progression

The ability of tumor cells to stimulate adaptive immunity, particularly by inducing anti-tumor antibodies (Abs), has been extensively reviewed. LM3 is a tumorigenic cell line derived from a murine mammary metastatic adenocarcinoma that spontaneously overexpressed mAchR. Here we investigate the ability of Abs purified from the sera of LM3 tumor-bearing mice, directed against muscarinic acetylcholine receptors (mAchR) to modulate tumor cells' proliferation and angiogenesis. We observed that IgG from early tumor bearers (ETB), 14-day LM3 tumor, and from late tumor bearers (LTB), 28-day LM3 tumor, displaced tritiated quinuclidinyl benzilate binding to LM3 tumor cells, confirming Abs interaction with cholinoceptors, while IgG from normal mice did not modify the antagonist binding to mAchR at any concentration tested. In addition, Abs from ETB and LTB immunoblotted a protein of 70 kDa on murine tumor cells and on heart homogenates that was also recognized by a specific anti-M(2) receptor monoclonal antibody. We also observed that IgG purified from ETB-stimulated LM3 cells' proliferation in a more effective manner than the muscarinic agonist carbachol (CARB) did. IgG from LTB-potentiated LM3 cells induced angiogenesis by increasing the number of blood vessels and VEGF-A production in peritumoral skin "via" mAchR, in an agonist similar manner. All effects were blocked by preincubating cells with the non-selective antagonist atropine. In conclusion, autoAbs purified from LM3 tumor-bearing mice sera exert different pro-tumor actions depending on the stage of tumor development: in ETB, they stimulate tumor cells' proliferation, while in LTB they potentiate tumor neovascularization.

Effect of glibenclamide on N-nitroso-N-methylurea-induced mammary tumors in diabetic and nondiabetic rats

The objective of this study was to evaluate the antitumor effect of glibenclamide (Gli) alone or in combination with tamoxifen (Tam) on experimental mammary tumors induced by N-nitroso-N-methylurea (NMU) in nondiabetic and diabetic rats. For experimental diabetes induction, Sprague-Dawley rats were injected with streptozotocin (STZ) on the second day of life. For experimental mammary tumor induction, nondiabetic and diabetic rats were injected IP with NMU at 50, 80, and 110 days of life. Nondiabetic and diabetic rats bearing mammary tumors were treated with 0.06 mg/day of Gli orally, Tam 1 mg/kg/day SC, or with the combined treatment (Gli + Tam). After 20 days of treatment, different responses were observed. In nondiabetic rats, 64% of tumors were responsive to Gli treatment (they regressed or remained stable), whereas 57% of tumors under treatment with Tam exhibited a response. Results of the combined Gli + Tam treatment indicated that all tumors were responsive: 58% regressed and 42% remained stable. Diabetic rats receiving Gli treatment did not show response to this treatment, while 65% of the tumors of Tam-treated diabetic rats showed regression. Histopathologic observation indicated an important intratumor secretion in all tumors of Gli-, Tam-, or Gli + Tam-treated rats. No secondary toxic effect was observed after treatment at any assayed doses. In conclusion, the present data demonstrate the in vivo antitumor action of Gli treatment on the experimental mammary tumors employed, indicating that Gli exerted a direct effect on tumor cells in nondiabetic rats. The combined Gli + Tam treatment potentiated the antitumor effect of each drug alone. Future research will examine the molecular aspects of these findings.

Insulin-regulated aminopeptidase/placental leucil Aminopeptidase (IRAP/P-lAP) and angiotensin IV-forming activities are modified in serum of rats with breast cancer induced by N-methyl-nitrosourea

BACKGROUND

In previous reports, changes in oxytocinase activity in human breast cancer tissue and in the serum of N-methyl-nitrosourea (NMU)-induced rat mammary tumors were described. Insulin-regulated aminopeptidase (IRAP) has been identified with oxytocinase and has also been referred to as placental leucine aminopeptidase (P-LAP).

MATERIALS AND METHODS

The IRAP/P-LAP activity in rat serum was assayed to analyze the putative role that IRAP/P-LAP may play in regulating mammary gland carcinogenesis induced by NMU. Furthermore, as it has been recently described that IRAP/P-LAP is the angiotensin IV (Ang IV) receptor AT4, the activities of Ang IV-forming aminopeptidase N (APN) and aminopeptidase B (APB) were also assayed.

RESULTS

Changes in serum IRAP/P-LAP and Ang IV-forming APB activities were found in rats with mammary tumors induced by NMU. Both activities were greatly increased, although the Ang IV-forming APN activity was not modified.

CONCLUSION

These changes in aminopeptidase activities may reflect the local functional status of their substrates, which can be selectively activated or inhibited in the affected tissue as a result of specific conditions brought about by the tumor. Thus, these enzymatic activities may be involved in the promotion and progression of breast cancer through oxytocin (OT), vasopressin (AVP) and/or renin-angiotensin system (RAS) misregulation.

Dual-color imaging of nuclear-cytoplasmic dynamics, viability, and proliferation of cancer cells in the portal vein area

We used dual-color in vivo cellular imaging to visualize trafficking, nuclear-cytoplasmic dynamics, and the viability of cancer cells after their injection into the portal vein of mice. For these studies, we used dual-color fluorescent cancer cells that express green fluorescent protein (GFP) linked to histone H2B in the nucleus and retroviral red fluorescent protein (RFP) in the cytoplasm. Human HCT-116-GFP-RFP colon cancer and mouse mammary tumor (MMT) cells were HCT-116-GFP-RFP in the portal vein of nude mice. The cells were observed intravitally in the liver at the single-cell level using the Olympus OV100 whole-mouse imaging system. Most HCT-116-GFP-RFP cells remained in sinusoids near peripheral portal veins. Only a small fraction of the cancer cells invaded the lobular area. Extensive clasmocytosis (destruction of the cytoplasm) of the HCT-116-GFP-RFP cells occurred within 6 hours. The number of apoptotic cells rapidly increased within the portal vein within 12 hours of injection. Apoptosis was readily visualized in the dual-color cells by their altered nuclear morphology. The data suggest rapid death of HCT-116-GFP-RFP cells in the portal vein. In contrast, dual-color MMT-GFP-RFP cells injected into the portal vein mostly survived in the liver of nude mice 24 hours after injection. Many surviving MMT-GFP-RFP cells showed invasive figures with cytoplasmic protrusions. The cells grew aggressively and formed colonies in the liver. However, when the host mice were pretreated with cyclophosphamide, the HCT-116-GFP-RFP cells also survived and formed colonies in the liver after portal vein injection. These results suggest that a cyclophosphamide-sensitive host cellular system attacked the HCT-116-GFP-RFP cells but could not effectively kill the MMT-GFP-RFP cells.

A novel method for viral gene delivery in solid tumors

Intratumoral infusion is the most commonly used method for viral gene delivery in clinical trials for cancer treatment. However, a potential problem in this approach is that viral vectors may disseminate from tumor to normal tissues during and after the infusion. To reduce the dissemination, we developed a novel method based on a biocompatible polymer, poloxamer 407, which could significantly increase the viscosity of virus suspension when the temperature was changed from 4 degrees C to 37 degrees C. With this method, we could significantly increase transgene expression in solid tumors and reduce virus dissemination by 2 orders of magnitude after intratumoral infusion of adenoviral vectors. The mechanism of reduction was likely to be that the viscous poloxamer solution blocked convection of viral vectors in the interstitial space and the lumen of microvessels in the vicinity of the infusion site. This method has a potential to be used in the clinic for enhancing efficacy and reducing toxicity in viral gene therapy.

Therapeutic Index by Combination of Adriamycin and Docetaxel Depends on Dosing Time in Mice

Although the combination of adriamycin and docetaxel showed a better cure rate against metastatic breast cancer, severe myelosuppression and cardiotoxicity were dose-limiting factors. The purpose of this study was to establish a suitable dosing schedule, based on a chronopharmacologic approach, to relieve severe adverse effects. In experiment 1, adriamycin or docetaxel was injected i.p. at 2, 6, 10, 14, 18, or 22 hours after light onset (HALO) to estimate toxicities. In experiment 2, the dosing time dependency of toxicity and pharmacokinetics were assessed in the combination of adriamycin and docetaxel. In addition, G2-M phase in myelocyte cells was determined in nontreated mice. Adverse effects caused by adriamycin were shown to be the worst at 2 HALO and the best at 14 HALO. On the other hand, docetaxel-induced adverse effects were more severe at 14 HALO than at 2 HALO. In the combination study, the D(2)-A(1)4 group, in which docetaxel was administered at 2 HALO followed by adriamycin at 14 HALO, showed the most toxicity relief of all the treated groups. In the pharmacokinetic study, the dosing time dependency of toxicities was not related to the daily variation of pharmacokinetics of adriamycin and docetaxel. A significant 24-hour rhythm of G2-M phase distribution was found in myelocyte cells of nontreated mice. The daily variation of leukopenia caused by docetaxel corresponded to the 24-hour rhythm of G2-M phase distribution. These findings reveal that the therapeutic index of the combined chemotherapy can be improved by administering adriamycin and docetaxel at the time when the most adverse effects are relieved in each drug.

Spatial heterogeneity and oxygen dependence of glucose consumption in R3230Ac and fibrosarcomas of the Fischer 344 rat

To examine the oxygen-dependence of glucose consumption in solid tumors, we monitored gradients of glucose, lactate, and hypoxia in R3230Ac and FSA tumors growing in Fischer 344 rats. Bioluminescence imaging, detection of Hoechst 33342, and immunostaining of the hypoxia marker EF5 [2-8-N-(2,2,3,3,3-pentafluoropropyl)acetamide] were done in serial tumor slices. Glucose and lactate levels were also determined in liver and blood. Cells were further tested for glucose consumption and lactate production in vitro. In both tumor types, EF5 staining indicated similar maximum levels of hypoxia; the most intense staining occurred in perinecrotic regions. Glucose concentrations were highest in liver, declined from blood to tumor edge, further into vital tumor regions, and were lowest close to necrosis. Glucose was significantly lower in FSA than in R3230Ac tumors. Glucose concentrations in R3230Ac tumors were consistently higher in nonhypoxic than in hypoxic areas, with maximum values equal to systemic blood levels. Glucose in FSA tumors was close to zero, regardless of the presence or absence of hypoxia. Lactate did not differ significantly between the tumor types. FSA cells in culture showed a trend towards higher aerobic glucose consumption versus R3230Ac. Both cell lines increased their lactate production to similar levels under hypoxia. We conclude that both R3230Ac and FSA tumors retain the Pasteur effect, i.e., hypoxia triggers increased glycolysis. However, our results imply that increased aerobic glucose utilization leads to low glucose levels in FSA and a situation where supply limits uptake. This explains the repeatedly observed correlation between tumor blood flow and 18F-deoxyglucose uptake.

Tamoxifen inhibition of estrogen receptor-alpha-negative mouse mammary tumorigenesis

Tamoxifen reduces the relative risk of breast cancer developing from specific premalignant lesions. Many breast cancers that arise after tamoxifen treatment are estrogen receptor-alpha (ER-alpha)-negative, although premalignant lesions such as atypical ductal hyperplasia are highly ER-alpha-positive. The p53 null mouse mammary epithelial transplant model is characterized by ER-alpha-positive premalignant lesions that give rise to both ER-alpha-positive and ER-alpha-negative tumors. Given this progression from ER-alpha-positive to ER-alpha-negative lesions, we tested the ability of tamoxifen to block or delay mammary tumorigenesis in several versions of this model. In groups 1 and 2, p53 null normal mammary epithelial transplants were maintained in virgin mice. In groups 3 to 5, the p53 null and mammary transplants were maintained in mice continuously exposed to high levels of progesterone. In groups 6 and 7, transplants of the premalignant outgrowth line PN8a were maintained in virgin mice. Tamoxifen blocked estrogen signaling in these mice as evidenced by decreases in progesterone-induced lateral branching and epithelial proliferation in the mammary epithelium. Tamoxifen did not alter the elevated levels of progesterone in the blood while significantly reducing the circulating level of prolactin. Tamoxifen reduced tumor incidence in p53 null normal mammary epithelial transplants maintained in virgin mice from 55% to 5% and in progesterone-stimulated mice from 81% to 21%. The majority of the resultant tumors were ER-alpha-negative. Tamoxifen also significantly delayed tumorigenesis in the ER-alpha-positive high premalignant line PN8a from 100% to 75%. These results show that tamoxifen delays the emergence of ER-alpha-negative tumors if given early in premalignant progression.

Diet-Induced Obesity and Mammary Tumor Development in MMTV-neu Female Mice

Obesity is a risk factor for postmenopausal breast cancer and is associated with shortened latency and/or increased mammary tumor (MT) incidence in animals. Elevated body weight is usually associated with hormone-responsive tumors. In agreement with these data we previously showed that latency of hormone-responsive MTs in MMTV-TGF-alpha mice with diet-induced obesity was significantly shortened. Here, we used the same protocol to determine the impact of diet-induced obesity on estrogen receptor-negative MT development in MMTV-neu (strain 202) mice. Mice were fed a low-fat diet (n=20) or a high-fat diet (n=54) from 10 wk of age. Body weight at 19 wk of age was used to assign high-fat mice to obesity-prone, overweight, and obesity-resistant groups. Mice were euthanized due to MT size or at 85 wk of age. Final body weights of obesity-prone mice were heaviest, and those of obesity-resistant and low-fat groups were similar. Fat pad weights were heaviest in obesity-prone mice followed by overweight and obesity-resistant groups, and lightest in low-fat mice. Serum IGF-I levels were similar for low-fat and high-fat mice, whereas leptin was higher in high-fat mice (P <0.0001). MT latency, incidence, metastasis, and burden were similar for all groups. These findings support that obesity is not a risk factor for development of estrogen-negative breast cancer.

Angiogenic and antiangiogenic balance regulates concomitant antitumoral resistance

Concomitant antitumoral resistance (CAR), the phenomenon by which the growth of distant secondary tumor implants or metastases in some tumor-bearing hosts is inhibited by the presence of a primary tumor, has been previously ascribed to an antiangiogenic process. Here, we investigated vascular endothelial growth factor (VEGF) and endostatin serum levels in nude or BALB/c mice bearing human lung tumors (Calu-6 and H460) or murine mammary tumors (M3MC, M-234p and M-234m), respectively. In these experimental models we previously found an association between in vivo generation of CAR and in vitro conversion of plasminogen into angiostatin. Serum endostatin level in CAR+ Calu-6-bearing mice was significantly higher than in CAR- H460 counterpart. Sera from mammary tumor-bearing mice showed similar levels of endostatin, regardless of their ability to induce CAR. Conversely, serum VEGF levels in mice bearing CAR+ tumors were lower than those found in CAR- tumor-bearing hosts. Immunostaining with an anti-CD31 antibody revealed that secondary tumors subjected to CAR were significantly less vascularized than primary tumors, while this difference was not observed in CAR- tumors. In vitro studies showed an inhibitory effect of sera from CAR-inducing tumors on endothelial cell proliferation as compared to normal sera, whereas sera from non-CAR-inducing tumors did not alter endothelial proliferation and, in some instances, even caused stimulation of endothelial proliferation. These data suggest that the antiangiogenic mechanism operating in concomitant antitumoral resistance is the result of an increase in the ratio of antiangiogenic/proangiogenic regulators. The levels of the factors involved in this phenomenon can vary in the different tumor models, but the trend favoring the inhibition of angiogenesis is always conserved.

Histone H1 modulates immune status in experimental breast cancer

BACKGROUND

Breast cancer chemotherapy aims at employing cytotoxic agents that swing the balance between tumor cell invasion and host immune cells in favor of the latter. This study aimed at assessing the effect of exogenous histone H1 in maintaining the immune status of animals in experimental breast cancer taking advantage of its tumor-suppressive activity.

METHODS

Histone H1 was injected intratumorally as a single injection in tumor-bearing animals. Tumor response was assessed from changes in tumor volume, survival time and the immune status of animals from total and differential blood cell counts, levels of circulating immune complexes, thromboxane B2 and IgA in serum. Immune response was assessed from the macrophage count in the tumor and peritoneal exudates after activation.

RESULTS

Histone H1 treatment significantly inhibited tumor growth, enhanced mean survival time and significantly improved the immune response and status.

CONCLUSION

These results indicate that histone H1 plays a vital role in maintaining the immune status.

Interleukin-1 alpha promotes tumor growth and cachexia in MCF-7 xenograft model of breast cancer

Progression of breast cancer involves cross-talk between epithelial and stromal cells. This cross-talk is mediated by growth factors and cytokines secreted by both cancer and stromal cells. We previously reported expression of interleukin (IL)-1 alpha in a subset of breast cancers and demonstrated that IL-1 alpha is an autocrine and paracrine inducer of prometastatic genes in in vitro systems. To understand the role of IL-1 alpha in breast cancer progression in vivo, we studied the growth of MCF-7 breast cancer cells overexpressing a secreted form of IL-1 alpha (MCF-7IL-1 alpha) in nude mice. MCF-7IL-1 alpha cells formed rapidly growing estrogen-dependent tumors compared to parental cells. Interestingly, IL-1 alpha expression alone was not sufficient for metastasis in vivo although in vitro studies showed induction of several prometastatic genes and matrix metalloproteinase activity in response to cross-talk between IL-1 alpha-expressing cancer cells and fibroblasts. Animals implanted with MCF-7IL-1 alpha cells were cachetic, which correlated with increased leptin serum levels but not other known cachexia-inducing cytokines such as IL-6, tumor necrosis factor, or interferon gamma. Serum triglycerides, but not blood glucose were lower in animals with MCF-7IL-1 alpha cell-derived tumors compared to animals with control cell-derived tumors. Cachexia was associated with atrophy of epidermal and adnexal structures of skin; a similar phenotype is reported in triglyceride-deficient mice and in ob/ob mice injected with leptin. Mouse leptin-specific transcripts could be detected only in MCF-7IL-1 alpha cell-derived tumors, which suggests that IL-1 alpha increases leptin expression in stromal cells recruited into the tumor microenvironment. Despite increased serum leptin levels, animals with MCF-7IL-1 alpha cell-derived tumors were not anorexic suggesting only peripheral action of tumor-derived leptin, which principally targets lipid metabolism. Taken together, these results suggest that cancer cell-derived cytokines, such as IL-1 alpha, induce cachexia by affecting leptin-dependent metabolic pathways.

Suppression of mammary gland tumorigenesis in diabetic rats

The aim of this study was to compare mammary gland tumorigenesis in diabetic and non-diabetic rats. Streptozotocin and N-nitroso-N-methylurea were used to induce diabetes and mammary tumors, respectively. A suppression of mammary carcinogenesis in diabetic rats was shown by a longer latency period, a lower number of tumors per animal and a smaller final tumor volume. An 84% of the lesions developed in diabetic animals were benign tumors. Eighty day-old diabetic rats had significantly lower plasma levels of total-IGF-I and insulin versus non-diabetic rats. We postulate that the decrease in the total IGF-I and insulin levels during the promotion phase of carcinogenesis in this model plays an important role in retarding the tumor development in diabetic animals and in favoring the development of benign mammary lesions.

Human recombinant erythropoietin significantly improves tumor oxygenation independent of its effects on hemoglobin

Tumor oxygenation is known to be an important predictive/prognostic marker in a variety of tumors, including cervix, head/neck, sarcoma, non-small cell of the lung, and breast. Tumor oxygenation is influenced by many interactions, including oxygen delivery (angiogenesis, permeability, and HgB) and consumption (metabolic and growth rates). This study randomized 30 nonanemic, female Fischer 344 rats into three treatment arms to examine the effects of recombinant human erythropoietin (EPO) on R3230 rodent mammary carcinoma oxygenation. The three treatment arms were: (a) placebo; (b) EPO after tumor implantation (2000 units/kg/SQdose, M/W/F for six doses); and (c) EPO before tumor implantation (2000 units/kg/SQdose, M/W/F for six doses). Tumors were implanted in the hindflank, and in vivo oxygenation was measured at day 22 after implantation using the Oxylite system (Oxford Optronix, Oxford, England). An average of 180 measurements/animal were performed. On day 22, median tumor volume was 399 mm(3) (range: 65-950 mm(3)), and no differences in tumor volume were seen between treatment arms. Mean hematocrit was equal between arms at therapy initiation but were significantly higher for both arms receiving EPO at day 22 (placebo versus Arm B versus Arm C; Wilcoxon P = 0.052). EPO-treated tumors had significantly less hypoxic measurements when compared with either the placebo or those receiving EPO before implantation. These data confirm that tumor oxygenation in nonanemic individuals may be improved through the administration of EPO, and this improvement appears to be independent of HgB effects.

Acceleration of tumor growth and peri-tumoral blood clotting by imatinib mesylate (Gleevec)

Imatinib mesylate (Gleevec) inhibits the BCR-ABL tyrosine kinase in chronic granulocytic leukemia. Previous studies have demonstrated that imatinib mesylate also inhibits the survival and functions of normal mast cells by interfering with the receptor tyrosine kinase for stem cell factor (SCF), c-kit, which is expressed by mast cells. Because mast cells extensively surround many types of cancer and contain powerful anticoagulants such as heparin, we investigated the effects of imatinib mesylate on blood clotting and tumor growth within subcutaneous implants of a mammary adenocarcinoma cell line (4T1) in BALB/c mice. After 5 days of oral treatment with 10 mg/kg of the drug, the average mass of the tumors in treated mice (198 +/- 42 mg, n = 5) was significantly (p < 0.05) greater than the average mass of the tumors from untreated (control) mice (60 +/- 23 mg, n = 5). Moreover, the tumors in the treated mice were frequently surrounded by large lakes of clotted blood that were not evident in tumors from the control mice. Accelerated growth and blood clotting were also observed in tumor-bearing mice treated with heparinase I enzyme to destroy endogenous mast cell heparin and in NDST-2 knockout mice in which there is a targeted disruption in the gene coding for mast cell heparin synthesis. We conclude that imatinib mesylate accelerated the growth and peri-tumoral blood clotting of implants of mammary adenocarcinoma in mice. These results suggest that imatinib mesylate may have significant effects on mast cells infiltrating tumors, in addition to its other biologic activities. Our results also indicate that the mechanism of this effect may be related to the anticoagulant properties of mast cell heparin.

Reduced circulating insulin-like growth factor I levels delay the onset of chemically and genetically induced mammary tumors

Insulin-like growth factors (IGFs) play a crucial role in regulating cell proliferation and differentiation. The aim of this study was to examine the potential relationship between serum IGF-I levels and breast cancer risk. To do this, we studied liver-specific IGF-I gene-deleted (LID) mice, in which circulating IGF-I levels are 25% of that in control mice. Mammary tumors were induced in two ways: (a) by exposing mice to the carcinogen 7,12-dimethybenz (a)anthracene; and (b) by crossing LID mice with C3(1)/SV40 large T-antigen transgenic mice. In both models, LID mice exhibited a delayed latency period of mammary tumor development. In the 7,12-dimethybenz (a)anthracene-induced mammary tumor model, the incidence of palpable mammary tumors was significantly lower in LID mice (26% versus 56% in controls), and the onset of the tumors was delayed (74 +/- 1.2 days in LID mice versus 59.5 +/- 1.1 days in controls). Histological analysis showed extensive squamous metaplasia in late-stage mammary tumors of control mice, whereas late-stage tumors from LID mice exhibited extensive hyperplasia, but little metaplasia. In control mice, the onset of C3(1)/SV40-large T-antigen-induced mammary tumors occurred at 21.6 +/- 1.8 weeks of age, whereas in LID mice the average age of onset was 30.2 +/- 1.7 weeks. In addition, 60% of the mice in the control group developed two or more mammary tumors per mouse, whereas in the LID mice only 30% developed more than one mammary tumor per mouse. Our data demonstrate that circulating IGF-I levels play a significant role as a risk factor in the onset and development of mammary tumors in two well-established animal models of breast cancer.

Synthesis, toxicity and biodistribution of two 5,15-di[3,5-(nido-carboranylmethyl)phenyl]porphyrins in EMT-6 tumor bearing mice

The total synthesis of a 5,15-di[3,5-(o-carboranylmethyl)phenyl]porphyrin 5, its zinc(II) complex 6, and the corresponding nido-carboranylporphyrins 7 and 8 are reported. The molecular structures of porphyrin 6 and of potassium nido-carborane were obtained and are described. The biodistribution of nido-carboranylporphyrins 7 and 8 in BALB/c mice bearing EMT-6 mammary tumors are presented and compared. Both compounds are effective tumor localizers and delivered therapeutic concentrations of boron to tumors (mean+/-standard deviation): 32.5+/-7.1 and 54.3+/-14 microg/g for 7 and 8, respectively, 2 days after the last of 3 injections of a total boron dose of 23 mg/kg body weight. The zinc(II) complex 8 was found to deliver 1.2-1.7 times higher amounts of boron to tumors than 7, with lower tumor-to-blood boron concentration ratios (9.8/1 and 4.7/1 for 7 and 8, respectively, 2 days after injections). The tumor-to-brain boron concentration ratios were >100/1 for both porphyrins 2 days after administration. Both nido-carboranylporphyrins 7 and 8 were well-tolerated at the concentrations used (75 and 78 mg/kg body weight, respectively) and no morbidity or mortality were observed in these studies.

Assessment of the protective effect of amifostine on radiation-induced pulmonary toxicity

The objective of this study was to assess the radioprotective effects of amifostine in the rat model of radiation-induced lung injury using fractionated doses of radiation, to determine whether amifostine given before irradiation protects tumor from radiation cytotoxicity, and to determine whether changes in plasma levels of transforming growth factor (TGF)-beta correlate with radioprotective effect of amifostine. R3230 AC mammary adenocarcinoma was transplanted on the right posterior chest wall of female Fisher-344 rats. Both tumor-bearing and non-tumor-bearing animals were irradiated to the tumor or right lung using 4 MV photons and fractionated dose of 35 Gy/5 fractions/5 days. Animals with tumors and those without were randomized into 4 groups, respectively (8 to 10 rats per group), to receive (1) radiation alone; (2) radiation + amifostine; (3) amifostine alone; (4) sham radiation. Amifostine (150 mg/kg) was given intraperitoneally 30 minutes before each fraction of irradiation. The tumor size was measured twice a week. Breathing rate was assessed every 2 weeks. TGF-beta levels in plasma were assessed monthly after treatment. Six months after irradiation, animals were euthanized and lung tissue was processed for hydroxyproline content analysis. A significant increase in breathing frequency started 9 weeks after irradiation in animals that received radiation only. In the radiation + amifostine group, there was both a delay and a significantly lower peak in breathing frequency (P < .001). Hydroxyproline content was higher in the radiation-alone group than in rats given amifostine prior to radiation (P < .05). The TGF-beta levels in plasma showed an increase from 1 to 3 months after radiation, peaking at 2 months in the rats with (2.80 +/- 0.23) or without (5.32 +/- 1.21) amifostine compared to sham irradiation. TGF-beta levels were significantly lower at 1 to 3 months in rats receiving amifostine plus radiation versus those receiving radiation alone. Tumor growth delay and regrowth rate after radiation were not different between radiation-alone and radiation + amifostine groups. This study confirms the protective effect of amifostine in reducing radiation-induced pulmonary toxicity. No tumor protection was demonstrated after fractionated radiotherapy. The reduction in pulmonary injury with amifostine in paralleling lower plasma levels of TGF-beta, suggesting that monitoring plasma levels of this cytokine may reflect the efficacy of an intervention aimed at preventing radiation-induced lung injury.

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.