Assessing the safety of an Ephedrae Herba aqueous extract in rats: A repeat dose toxicity study.

Ephedrae Herba (EH) has been used in Asian traditional herbal medicine to cure bronchial asthma, cold, flu, chills, fever, headache, nasal congestion, and cough. In this study, we evaluated the subchronic toxicity of an Ephedrae Herba aqueous extract (EHAE) in male and female F344 rats. The EHAE was administered orally daily at doses of 0, 125, 250, 500, and 1000 mg/kg bw/day for 13 weeks. Toxicological assessment was performed to determine mortality, clinical signs, and changes in body weight, food consumption, ophthalmological, urinary, hematological, and serum biochemical parameters, macroscopic and microscopic evaluations, and organ weights. We found that oral administration of EHAE to F344 rats for 13 weeks resulted in histopathological changes in the kidneys and salivary glands. In the kidneys, increased incidence and severity of tubular basophilia were observed in females administered 1000 mg/kg bw/day of the extract. In the salivary glands, acinar cell hypertrophy was observed in males administered 500 mg/kg bw/day and in both sexes administered 1000 mg/kg bw/day of the extract. All test article-treated groups of males and females administered ≥250 mg/kg bw/day showed increased absolute and relative salivary gland weights. Therefore, the NOAEL (No Observed Adverse Effect Level) was determined as 125 mg/kg bw/day for both sexes of rats under the present experimental conditions.

Cytotoxicity and sub-acute toxicity in Crl:CD (SD) rats of traditional herbal formula Ojeok-san.

BACKGROUND: Although Ojeok-san (OJS), an oriental herbal formula, has been used in Asian countries including Korea, China and Japan to treat the common cold and illnesses including fatigue and gastrointestinal disorders, there is little information of its safety and toxicity in vivo and in vitro. METHODS: In the present study, we investigated oral toxicity of OJS over 4 weeks through repeated administration to Crl:CD (SD) rats and its cytotoxicity against various cells as a part of safety evaluation. Animals were given a daily gavage treatment of OJS in daily dosages of 0, 500, 1000 or 2000 mg/kg for 4 weeks. Cytotoxicity assay was conducted at various concentrations in 23 different cell lines including neuroblastoma, glioblastoma, hepatocarcinoma, melanoma, leukemia, colon cancer, breast cancer, keratinocytes, phechromocytoma, prostate cancer, bronchial epithelial cells, and gastric adenocarcinoma. RESULTS: OJS did not induce significant changes in mortality, food consumption, organ weights, hematology, serum biochemistry, and urinalysis, except for decrease in number of white blood cells over 1000 mg/kg/day female group. Thus, the no observed adverse effect level (NOAEL) is more than 2000 mg/kg/day for male and 500 mg/kg/day for female rats. In addition, OJS had no cytotoxicity against all tested cells. CONCLUSIONS: Collectively, our data indicate that OJS may be a safe drug although additional studies in the near future will be required before clinical trials can be taken.

Subacute Oral Toxicity of Yukmijiwhang-Tang in Crl:CD Sprague-Dawley Rats and Its Cytotoxicity.

Background. The traditional herbal formula Yukmijiwhang-tang (YMJ) consists of six medicinal herbs and has been used to treat dysuria, diabetic mellitus, and neurosis in Korea, China, and Japan. Here we report safety information on its subacute toxicity and the cytotoxicity. Methods. YMJ extract was administered to SD rats at various dosages for 4 weeks. We monitored clinical signs, mortality, body and organ weights, food intake, and hematological and serum biochemistry factors. For cytotoxicity testing, each cell line was treated with various concentrations of YMJ for 24 h. Results. YMJ treatment had no significant effects on changes in clinical signs, body weight, or food intake in male or female rats. In male rats, YMJ treatment decreased the absolute weights of the epididymides and serum Na levels. In female rats, YMJ significantly reduced the prothrombin time (PT) and serum creatine level. However, the changes were not severe and were considered to be in the normal physiological range for rats. The no-observed-adverse-effect-level (NOAEL) was estimated to be 2000 mg/kg/day. YMJ extract did not exert any cytotoxicity against 23 tested cell lines. Conclusions. Our data provide scientific evidence on the safety of YMJ for potential development as a prescription drug.

Protective effect of Bojungikki-tang, a traditional herbal formula, against alcohol-induced gastric injury in rats.

ETHNOPHARMACOLOGICAL EVIDENCE: Oxidative stress plays an important role in the pathogenesis of ethanol-induced acute gastric mucosal injury. Bojungikki-tang (Hochuekkito in Japanese, Bu-zhong-yi-qi-tang in Chinese) is a traditional herbal formula used in Korea, Japan, and China to treat allergic diseases and gastrointestinal disorders. However, the mechanism responsible for its actions has not been investigated experimentally. AIM OF THE STUDY: The aims of this study were to investigate whether Bojungikki-tang water extract (BJITE) has protective effects against ethanol-induced acute gastric injury in rats and to perform an acute toxicity study to evaluate its safety. MATERIALS AND METHODS: In this rat model, gastric mucosal injury was imposed by oral administration of 5 mL/kg body weight of absolute ethanol. BJITE at one of two doses (200 or 400 mg/kg body weight) was administered by gavage 2 h before ethanol administration. Gastric tissues were collected and analyzed to assess the gastric injury index, and content or activity of catalase, superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), glutathione-S-transferase (GST), glutathione reductase (GR), and glutathione peroxidase (GPx). RESULTS: Acute administration of ethanol significantly increased the gastric injury index concomitantly with an increase in MDA and GSH content, and a decrease in the activities of catalase, GST, GR, GPx, and SOD. Pretreatment with 200 or 400 mg/kg BJITE attenuated ethanol-induced gastric mucosal injury; this was accompanied by an increase in the content or activity of PGE(2), catalase, GSH, GST, GR, GPx, and SOD, and a decrease in MDA content. In the acute toxicity study, no adverse effects of BJITE were observed at doses up to 2000 mg/kg body weight. CONCLUSION: These results indicate that BJITE can partly protect the gastric mucosa from ethanol-induced acute gastric injury and suggest that these protective effects might be induced by increasing the antioxidant status. We suggest that BJITE can be developed as an effective drug for the treatment of acute gastric injury.

In vitro and in vivo evaluation of the genotoxicity of Gumiganghwal-tang, a traditional herbal prescription.

ETHNOPHARMACOLOGICAL RELEVANCE: Gumiganghwal-tang (GGT, known as Kumi-Kyokatsu-to in Japanese) is a traditional herbal prescription made from nine different herbs that is used for the treatment of the common cold, pain, and inflammatory diseases. AIM OF THE STUDY: This study evaluated the potential genotoxicity of an aqueous GGT extract using three standard battery of tests as part of a safety evaluation. MATERIALS AND METHODS: We prepared GGT using a water extraction method and subsequently extracted six compounds from GGT by high performance liquid chromatography. GGT extract genotoxicity was assayed using three standard tests including the in vitro bacterial reverse mutation test, the in vitro chromosomal aberration test with Chinese hamster lung cells, and the in vivo micronucleus test using ICR mouse bone marrow recommended by the Korean Food and Drug Administration. RESULTS: The bacterial reverse mutation assay showed that GGT extract doses ranging from 333.3 up to 5000mg/plate induced a greater than 2-fold increase in the number of revertant TA1537 strain colonies exhibiting metabolic activation (with S-9 mix), when compared with the vehicle control. The chromosomal aberration test showed that GGT extract induced an increase in the number of chromosomal aberrations after treatment for 6h with the S-9 mix and 22h without the S-9 mix, when compared with vehicle control. In contrast, the micronucleus test showed that GGT extract did not significantly increase the number of micronucleated polychromatic erythrocytes (MNPCEs) in ICR mouse bone marrow. CONCLUSIONS: Based on these results, it was concluded that GGT extract acted as a genotoxic material in our experimental conditions. We did not identify the compounds responsible for the induction of genotoxic effects, but it was significant that we provided a basic genotoxicity profile for GGT.

Antisense inhibition of coagulation factor XI prolongs APTT without increased bleeding risk in cynomolgus monkeys.

A strategy to produce sufficient anticoagulant properties with reduced risk of bleeding may be possible through inhibition of factor XI (FXI), a component of the intrinsic coagulation cascade. The objective of this work was to determine the safety profile of ISIS 416858, a 2'-methoxyethoxy (2'-MOE) antisense oligonucleotide inhibitor of FXI, with focus on assessment of bleeding risk. Cynomolgus monkeys administered ISIS 416858 (4, 8, 12, and 40 mg/kg/wk, subcutaneous) for up to 13 weeks produced a dose-dependent reduction in FXI (mRNA in liver and plasma activity) and a concomitant increase in activated partial thromboplastin time (APTT). ISIS 416858 (20 or 40 mg/kg/wk) reduced plasma FXI activity by 80% at 4 weeks of treatment that resulted in a 33% increase in APTT by 13 weeks with no effects on PT, platelets, or increased bleeding following partial tail amputation or gum and skin laceration. The dose-dependent presence of basophilic granules in multiple tissues in ISIS 416858-treated animals was an expected histologic change for a 2'-MOE antisense oligonucleotide, and no toxicity was attributed to hepatic FXI reduction. Basophilic granules reflect cellular drug uptake and subsequent visualization on hematoxylin staining. These results suggest that ISIS 416858 has an acceptable preclinical safety profile and is a promising clinical candidate to treat thrombotic disease.

Toxicological evaluation of Gumiganghwaltang aqueous extract in Crl:CD (SD) rats: 13 weeks oral gavage studies.

Gumiganghwaltang is a traditional oriental herbal medicine that has been commonly used to treat colds and inflammatory diseases. Aqueous extract of Gumiganghwaltang (GMGHT) was administrated daily by oral gavage to male and female rats for 13 weeks. A dose of 2000 mg/kg/day was selected as a maximum, and doses of 1000 and 500 mg/kg/day were determined as medium and low doses, respectively. No treatment-related clinical signs or mortality were observed in the treatment group. We observed no clear treatment-related effects with regard to body weight, food consumption, ophthalmology, hematology, or urinalysis data. The serum biochemistry values for sodium and chloride in the treated male and female groups (1000 mg/kg/day) were lower than in those treated with the vehicle control. However, these changes lacked dose dependence, and no abnormalities were found in corresponding pathological findings. Our results indicated that the no-observed-adverse-effect-level (NOAEL) for GMGHT was determined to be a dietary dose of over 2000 mg/kg/day for both sexes under the present experimental conditions.

A 4-week Repeated Dose Oral Toxicity and Cytotoxicity Study of Gumiganghwaltang in Crl:CD (SD) Rats.

Gumiganghwaltang (GGT) is a traditional oriental herbal prescription commonly used to treat colds and inflammatory diseases in Korea. This study reports the first evaluation of the oral toxicity and cytotoxicity effects of repeat doses of GGT. GGT was orally administered daily at doses of 0, 500, 1000, and 2000 mg/kg for 4 weeks. Analysis of body weight gain, mortality, clinical observations, urinalysis, blood biochemistry, hematology, organ weight, and histopathological data revealed no significant differences between the V.CONTROL and GGT-treated groups. In addition, we investigated the cytotoxicity of GGT against LNCaP, RBL-1, and BEAS-2B cell lines, and splenocytes. Based on the results, we conclude that GGT orally administered to rats is safe with no drug-related toxicity, even at the highest dose, in 4-week repeated dose studies. Thus, this concentration is considered the non-observable effect dose in rats.

Genotoxicity assessment of a herbal formula, Ojeok-san.

ETHNOPHARMACOLOGICAL RELEVANCE: Ojeok-san (OJS, wuji powder, goshaku-san), a widely used herbal formula in traditional Korean medicine, is used to treat illnesses such as the common cold, fatigue and gastrointestinal disorders; however there is insufficient background information about its safety. To establish safety information for OJS, we evaluated its genotoxicity. MATERIALS AND METHODS: The ability of OJS to induce reverse mutations was evaluated in Salmonella typhimurium (TA100, TA1535, TA98 and TA1537) and Escherichia coli (WP2uvrA) in the presence or absence of the metabolic activation system (S-9 mix). Chromosomal aberrations were evaluated in response to OJS, and viability and metaphase were analyzed in Chinese hamster lung (CHL) cells in the presence or absence of S-9 mix. A micronucleus test was performed using bone marrow cells from male ICR mice. OJS was orally administered twice at a 24h interval at a dose of 500, 1000 and 2000 mg/kg in mice. RESULTS: There were no increases in the number of revertant colonies at any concentrations of OJS regardless of S-9 mix in all tester strains compared to the vehicle control. OJS did not significantly increase the number of structural aberration in CHL cells in the presence or absence of S-9 mix. The oral administration of OJS at doses up to 2000 mg/kg caused no significant increase in the number of micronucleated polychromatic erythrocytes (MNPCEs) and in the mean value for the ratio of PCE to total erythrocytes (PCE/(PCE+NCE)). NCE is normochromatic erythrocyte. OJS did not increase the incidence of MNPCEs in bone marrow. CONCLUSIONS: These results suggest that OJS is toxicologically safe on genotoxicity studies.

Evaluation of genotoxicity of Yukmijihwang-tang, a herbal formula.

Yukmijihwang-tang (Liu wei di huang tang, Rokumigan; YMJ) has been used for body enrichment; however, little toxicological evaluation of YMJ has been performed to assure its safety for clinical treatment. To increase the safety information for YMJ, its genotoxicity was evaluated. There was no increase in the number of revertant colonies in four strains of Salmonella typhimurium or one strain of Escherichia coli at any concentration of YMJ studied, regardless of the including when dosed with YMJ metabolized with and S-9 microsomal fraction. YMJ significantly increased structural aberrations in Chinese hamster lung (CHL) cells at the high concentrations (2500 and 5000 µg/ml) in the presence or absence of metabolic activation by the S-9 microsomal fraction. Oral administration of YMJ at doses up to 2000 mg/kg did not increase the incidence of micronucleated polychromatic erythrocytes in bone marrow. These results suggest that YMJ is not genotoxic at the proper dose.

Genotoxicity assessment of Pyungwi-san (PWS), a traditional herbal prescription.

ETHNOPHARMACOLOGICAL RELEVANCE: Pyungwi-san (PWS, Heii-san in Japanese) is a mixture of six herbs and is traditionally used in Northeast Asia (especially Korea and Japan) for the treatment of gastrointestinal disorder, such as dyspepsia and inappetance induced by gastric dilatation and gastrointestinal catarrh. AIM OF THE STUDY: Although PWS is a widely used herbal prescription in Korea and Japan, little information is available in the literature on the safety and toxicity of PWS. As part of a safety evaluation of PWS, the present study evaluated the potential genotoxicity of PWS using a standard battery of test. MATERIALS AND METHODS: We prepared PWS using a water extraction method and simultaneously extracted three compounds from PWS using high performance liquid chromatography. The PWS extract that was obtained was assayed for genotoxicity using the standard three tests recommended by the Korea Food and Drug Administration. These tests included the bacterial reverse mutation test (Ames test), the chromosomal aberration test using China hamster lung cells, and the micronucleus test using ICR mice. RESULTS: The Ames test showed that the PWS extract did not induce an increase in the number of revertant colonies compared with vehicle control at any dose in all of tester strains. In the micronucleus test, no significant increase was observed in micronucleated polychromatic erythrocytes (MNPCEs) at any dose of PWS extract compared with vehicle control. Conversely, chromosomal aberration test showed that the PWS extract at a dosage of 4500 µg/mL induced an increase in the number of chromosomal aberrations in the 6 h group with metabolic activation compared with the vehicle control. CONCLUSION: PWS extract exhibits genotoxicity, based on the results of the chromosomal aberration test. Thus, further detailed experiments will be needed to identify the ingredient responsible for inducing this genotoxicity and to determine its mechanism.

Two new lignans from the roots of Pulsatilla koreana.

Two new lignans, (2 R,3 R)-2 ß-(4''-hydroxy-3''-methoxybenzyl)-3 α-(4'-hydroxy-3'-methoxybenzyl)-γ-butyrolactone 2-O-( ß-D-glucopyranoside) (1) and (1 S,2 R,3 S)-dimethyl-1,2,3,4-tetrahydro-3,6,7-trihydroxy-1-(3',4'-dihydroxyphenyl)naphthalene-2,3-dicarboxylate (2) together with nine known compounds (3-11) were isolated from the ethyl acetate fraction of the roots of Pulsatilla koreana. Their chemical structures were established based on physicochemical and spectroscopic data analyses. All isolates were investigated for their inhibition effects against the classical pathway of the complement system. Among them, compound 6 showed significant inhibitory activity with an IC (50) value of 75.9 µM, compounds 8 and 9 had moderate effects with IC (50) values of 182.2 and 166.5 µM, respectively.

Dammarane-type glycosides from Gynostemma pentaphyllum and their effects on IL-4-induced eotaxin expression in human bronchial epithelial cells.

Two new dammarane-type glycosides, 2alpha,3beta,12beta,20S-tetrahydroxydammar-24-ene-3-O-[beta-d-glucopyranosyl(1-->4)-beta-d-glucopyranosyl]-20-O-[beta-d-xylopyranosyl-(1-->6)-beta-d-glucopyranoside] (1) and 2alpha,3beta,12beta,20S-tetrahydroxydammar-24-ene-3-O-beta-d-glucopyranosyl-20-O-[beta-d-6-O-acetylglucopyranosyl-(1-->2)-beta-d-glucopyranoside] (2), were isolated from a MeOH extract of the leaves of Gynostemma pentaphyllum. Their structures were elucidated by 1D and 2D NMR spectroscopic interpretation as well as by chemical studies. The isolated compounds showed potential inhibitory effects on eotaxin expression in BEAS-2B bronchial epithelial cells.

2-methoxyestradiol induces mammary gland differentiation through amphiregulin-epithelial growth factor receptor-mediated signaling: molecular distinctions from the mammary gland of pregnant mice.

Levels of 2-methoxyestradiol (2ME(2)), an endogenous metabolite of estradiol, are highly elevated during late stages of pregnancy when mammary glands have differentiated with the formation of alveolar structures producing milk proteins. Based upon our previous demonstration that 2ME(2) induces mammary ductal dilation associated with expression of mammary differentiation markers when administered to transgenic mice that spontaneously develop mammary cancer, we studied the effects of 2ME(2) on normal mammary gland development. The results of this study demonstrate that 2ME(2) can induce a partial differentiation of normal mammary glands in virgin mice, as evidenced by the appearance of limited numbers of alveolar cells and significantly increased expression of the differentiation markers beta-casein and whey acidic protein. 2ME(2)-induced differentiation is associated with inhibition of expression of inhibitor of differentiation 1 (Id-1) in normal mammary epithelial cells through elements in the 5'-flanking region of the Id-1 gene. Microarray analysis revealed that 2ME(2)-induced differentiation of the mammary gland shares some significant similarities in gene expression with that of mammary glands from late-stage pregnancy, including elevated expression of many milk protein differentiation markers. However, several genes are differentially regulated between 2ME(2)-treated mammary glands and differentiated mammary glands through pregnancy. Significantly, amphiregulin, ATF3, serpine2, and SOX6 were up-regulated in 2ME(2)-treated mammary glands but not in mammary glands from pregnant mice. Using the SCp2 differentiation cell line system, we demonstrate that 2ME(2) induces differentiation through the down-regulation of Id-1 and up-regulation of amphiregulin. Administration of amphiregulin to SCp2 cells induced differentiation, whereas inhibition of 2ME(2)-induced expression of amphiregulin by small interfering RNA blocked differentiation. Estrogen receptor-negative SCp2 cells differentiate in response to 2ME(2), but not estradiol, suggesting that 2ME(2) operates through an estrogen receptor-independent mechanism. These data demonstrate that 2ME(2) can induce a partial differentiation of the mammary gland through mechanisms that differ from those normally used during pregnancy.

Distinct tumor stage-specific inhibitory effects of 2-methoxyestradiol in a breast cancer mouse model associated with Id-1 expression.

2-Methoxyestradiol (2ME(2)), a metabolite of 17-beta-estradiol, inhibits angiogenesis and has additional antitumor activities. We have analyzed the tumor stage-specific effects of 2ME(2) in the C3(1)/Tag transgenic mouse model for breast cancer, which spontaneously develops estrogen receptor-negative mammary tumors following a predictable progression of lesion formation. When given either as a therapeutic agent in established tumors (late intervention study) or in mice with pre-invasive mammary lesions (early intervention study), tumor growth was reduced by 60% compared with untreated controls and was associated with an induction of apoptosis. In a prevention study, a significant reduction in mammary intraepithelial neoplasia (MIN) lesions was observed in animals beginning treatment at 6 weeks of age, before the appearance of histopathologic abnormalities. However, although 2ME(2) reduced the number of MIN lesions in the prevention study, a paradoxical increase in tumor multiplicity and growth rate was observed. This was associated with unusual cystic tumor formation, in which significant central necrosis was observed, surrounded by an outer region of proliferative tumor cell growth. The characteristics of the cystic tumor formation in mice treated with 2ME(2) at early ages are consistent with an impaired angiogenic response as observed in mice deficient for inhibitor of differentiation (Id-1). We further show that Id-1 expression is negatively regulated by 2ME(2), which may be an additional mechanism for the antiangiogenic effect of 2ME(2). Although 2ME(2) significantly reduced tumor growth at late stages, these results also suggest that altered tumor morphology and accelerated tumor growth may occur if 2ME(2) is administered in a prevention setting for prolonged periods.

Prostate cancer and the genomic revolution: Advances using microarray analyses.

The emerging technology of microarray analysis allows the establishment of molecular portraits of prostate cancer and the discovery of novel genes involved in the carcinogenesis process. Many novel genes have already been identified using this technique, and functional analyses of these genes are currently being tested. The combination of microarray analysis with other recently developed high-throughput techniques, such as proteomics, tissue arrays, and gene promoter-methylation, especially using tissue microdissection methods, will provide us with more comprehensive insights into how prostate cancer develops and responds to gene-targeted therapies. Animal models of prostate cancer are being characterized by high throughput techniques to better define the similarities and differences between those models and the human disease, and to determine whether particular models may be useful for specific targeted therapies in pre-clinical studies. Although profiling of mRNA expression provides important information of gene expression, the development of proteomic technologies will allow for an even more precise global insight into cellular signaling and structural alterations during prostate carcinogenesis. Not only will the "omic" revolution change basic science, but it will lead to a new era of molecular medicine.

Inhibition of VEGF receptors significantly impairs mammary cancer growth in C3(1)/Tag transgenic mice through antiangiogenic and non-antiangiogenic mechanisms.

Cancer growth and progression is often critically influenced by the production of vascular endothelial growth factor (VEGF), a key mediator of angiogenesis. VEGF produced by tumor cells stimulates endothelial cell growth through the binding and activation of the KDR/Flk-1 receptor (VEGFR-2) on endothelial cells. Recently, some human breast cancer epithelial cells have been shown to express VEGF receptors, suggesting a potential autocrine-mediated growth stimulation of a subset of cancers by VEGF. We demonstrate that mammary tumors in the C3(1)/Tag transgenic model express VEGF and VEGF receptors and tumor growth is stimulated by this autocrine mechanism. GW654652, an indazolylpyrimidine, is a VEGFRs tyrosine kinase inhibitor that dramatically reduces both angiogenesis and tumor cell growth in this model, as demonstrated using both in vitro and in vivo assays. GW654652 significantly decreased cell proliferation and induced apoptosis in human umbilical vein endothelial cells and M6 mammary tumor cells derived from C3(1)/Tag (Tag: simian virus 40 T-antigen) transgenic mice. A 75% reduction in VEGF-induced angiogenesis was observed with GW654652 using the chick chorioallantoic membrane assay, whereas GW654652 produced an approximately 85% reduction in angiogenesis as assessed by the Matrigel plug assay. A profound inhibitory effect on tumor growth in the C3(1)/Tag transgenic model of human breast cancer was observed with oral administration of GW654652 as measured by delayed tumor onset, decreased multiplicity, reduced tumor volume, and extended animal survival. The antitumor effects of GW654652 were associated with reduced tumor vascularization and no apparent toxicity. Tumor growth, however, rapidly advanced following cessation of treatment. This is the first demonstration that a VEGF receptor inhibitor, GW654652, has a strong inhibitory effect on angiogenesis and tumor progression in a transgenic model of mammary cancer, suggesting that this is a useful approach for preclinical testing of such agents.

Application of gene expression profiling for validating models of human breast cancer.

While classical histopathologic approaches are invaluable in classifying tumors and understanding aspects of cellular interactions, genomic approaches provide a means to molecularly dissect tumorigenesis. The relationship of gene expression to the development of neoplasia remains an area of intensive research. With the advent of large-scale genomic platforms, alterations in gene expression can be related to the morphological development of cancer. The feasibility of using large-scale genomic analysis platforms has dramatically changed the landscape of biological sciences, as cellular processes must be considered in the context of complex networks. Alterations in gene expression must now be understood in a systems approach in which the relationships between genes expression changes are studied by considering the interplay of multiple regulatory networks. Ultimately, such changes must be understood at the protein level. We have begun to apply this technology to determine changes in gene expression that differentiate various types of mammary cancers that arise in mouse models that have been initiated by different genetic alterations. Ultimately, a molecular catalogue of similarities and differences between rodent and human tumors can be created which will serve to validate or credential particular models for specific experimental purposes, such as preclinical testing. These approaches have led to new insights into molecular pathways involved in oncogenesis, new classifications of human breast cancer, and the identification of new genes that may be relevant to understanding and treating human cancer.

Genomic approaches to understanding mammary tumor progression in transgenic mice and responses to therapy.

Scores of genetically engineered mice have been generated in the quest to understand mechanisms of breast cancer development and progression. More recently, there has been a growing trend for using such models for testing various therapeutic strategies and agents. The application of these mouse models for these purposes requires that they be characterized in ways that demonstrate they possess important similarities to human breast cancer. In particular, detailed comparisons of the features of the models to human breast cancer must include attention to the histological phenotypes, chromosomal and molecular alterations, and the predictive value of the models for preclinical testing. Whereas these models have become important tools for the study of breast cancer, the great majority of existing mouse mammary cancer models develop tumors that are estrogen receptor negative, with relatively few models demonstrating metastatic spread to the lungs, and none developing metastases to bone. This review focuses on recent studies using genomic approaches to further understand the oncogenic processes occurring in mouse models of mammary cancer and to compare these changes with those identified in human breast cancer. Gene expression profiling is being applied to help define pharmacological responses that occur in vivo. Detailed genomic analyses will provide important information for selecting models for specific experimental purposes, contribute to the understanding of oncogene-specific expression signatures and potential therapeutic targets, and further define mechanisms of chemoprevention and chemotherapy.