Mammary Tumors In HER-2 Research Articles

The аntitumor effect of 2-[3-(2-chloroethyl)-3-nitrosoureido]-1,3-propanediol (chlonisol) on the growth of spontaneous mammary tumors in HER-2/neu transgenic mice

Background. Current treatment of HER2-positive metastatic breast cancer (BC) is based on the use of anti-HER2 blockers as pathogenic drugs, as well as the search for the optimal combination of anticancer drugs with different mechanisms of action. The potential activity of chlonisol in HER2+ ВС is of great interesting. The aim of the study was to evaluate the antitumor effect of 2-[3-(2-chloroethyl)-3-nitrosouriedo]-1,3-propanediol (chlonisol) on the growth of spontaneous mammary tumors in HER-2/neu transgenic FVB/N mice. Material and Methods. A prospective study used 5-month-old female mice with HER2-positive mammary tumors. Of these animals, ten pairs with almost the same size of tumors were formed (respectively, for the control group and the chlonisol treatment group). Chlonisol was administered at a dose of 20 mg/kg intraperitoneally, once. The animals were followed up for 30 days. Results. In all ten pairs of mice, chlonisol showed a significant antitumor effect, up to a complete temporary regression of the tumor. When summing the comparative results of all ten pairs of animals, the inhibition of tumor growth (ITG) in the chlonisol treatment group was 90-97 % (p<0.0001), and the area under the kinetic curve of tumor growth was 13.6 times less than in the control group (p<0.0001), thus indicating a significant effect. Conclusion. Chlonisol has a high therapeutic activity by inhibiting the growth of spontaneous HER2-positive breast tumors in FVB/N mice.

Abstract 3616: Potential therapeutic use of Estrogen Receptor β agonist in the prevention and progression of breast cancer using HER-2/neu mouse model

Abstract Breast cancer is the most common cancer among women worldwide. Hormone-mediated therapy to treat estrogen receptor alpha (ERα) positive breast cancers include the use of ER antagonist, Tamoxifen, aromatase inhibitors and other compounds that degrade ERα. Unlike ERα, ERβ has been shown to have tumor-suppressive function in various cancers, including breast cancer. Recent studies have identified, synthesized, and tested the clinical safety of ERβ-selective agonists. Given the tumor-suppressive properties of ERβ, it may be possible to use these compounds to induce or activate the ERβ and test their role in the chemoprevention and blocking the progression of breast cancer. We have investigated the therapeutic utility of ERβ agonists in the prevention and progression of breast cancer using MMTV-HER2/neu mice transgenic mouse model. MMTV-HER2/neu mice develop premalignant lesions at 4-5 months, and tumors starting at month 7 due to overexpression of the HER2/neu proto-oncogene. MMTV-HER2/neu mice were treated with an ERβ agonist, LY500307 examined the prevention and progression of mammary cancers in these mice. When compared to controls, ERβ agonist-treated mice exhibited a significant decrease in the development of preneoplastic changes. Differential gene expression analysis revealed a significant change in the expression of a number of genes in response to LY500307 treatment. Pathway analysis identified an enrichment for chemokines signaling pathways, particularly TNF, in blocking the development of preneoplastic changes resulting from treatment with ERβ agonists. Our studies also show a decrease in the formation of mammary tumors in HER-2/neu mice with preexisting preneoplastic changes when treated with LY500307. This study suggests that ERβ agonist treatment may be a valuable therapeutic option for the prevention in women at increased risk of breast cancer and in blocking the progression of hormone receptor positive breast tumors. Citation Format: Kumaraguruparan Ramasamy, Cathy Samayoa, Naveen K. Krishnegowda, Ratna K. Vadlamudi, Rajeshwar R. Tekmal. Potential therapeutic use of Estrogen Receptor β agonist in the prevention and progression of breast cancer using HER-2/neu mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3616. doi:10.1158/1538-7445.AM2017-3616

Abstract CT086: Omega-3 fatty acids and ERPR(-) and HER-2/neu(+) breast cancer prevention

Abstract Background: Breast cancer is a family of diseases, each with distinctive biologic behaviors and clinical outcomes. Refining therapy for specific breast cancer subtypes improves survival and limits toxicity. The application of these concepts to prevention has been limited and is a novel aspect of this clinical trial. Our pre-clinical research demonstrated that diets enriched in fish oil decreased the incidence and multiplicity of estrogen receptor negative, progesterone receptor negative (ERPR-), HER-2/neu positive (HER2+) mammary tumors in HER-2/neu transgenic mice, with decreased mammary atypia, Ki67 and COX-2 expression (Yee et al, 2005, 2012). Of interest is whether human breast cancers with poor prognostic features of negative hormone receptor status ± HER-2/neu overexpression might be uniquely responsive to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the long chain ω-3 fatty acids (FAs) found in fish oil. This study aims to determine biological changes associated with a low vs high dose of ω-3 FAs over 12 months in women at high risk for recurrent breast cancer. Doses were based on our dose finding study of ω-3 FAs in high risk women that showed superiority of ? 2.52 g EPA+DHA/day vs 0.84 g/day to increase serum and breast adipose tissue EPA+DHA content over 6 months (Yee et al, 2010). The objectives of the trial are to develop novel mammary epithelial, adipose tissue markers of exposure and response to ω-3 FAs that can be carried forward into definitive intervention trials of ω-3 FAs for breast cancer prevention. Methods: This is a double blinded randomized trial of high dose (∼5.4 g EPA+DHA) or low dose (∼0.9 g EPA+DHA in fatty acid mix of the typical American diet) of ω-3 FAs provided in 5 capsules/day for 12 months. Cellular samples of breast epithelial and adipose tissue are obtained by fine needle aspiration (FNA) to determine the effects of ω-3 FAs on mammary tissue biomarkers of ω-3 exposure, DNA methylation patterns, and intermediate anti-carcinogenic endpoints related to inflammation. Sample size of 40 participants per arm was justified to provide at least 80% power to detect a difference of interest (e.g. 1.5 fold) for each primary endpoint (six in total) based on two-sided t test with Bonferroni adjustment for multiplicity (α = 0.05/6 = 0.008, CV = 50%). This study focuses on women survivors of high risk breast cancer subtypes, namely triple negative or ERPR(-),HER2(+) disease, who are currently without long term adjuvant options. Eligibility criteria include prior diagnosis of ERPR(-) Stage 0 to III breast cancer, ?5 years from completion of standard therapy. Ineligibility criteria include current malignancy, inability to undergo breast FNA, chronic use of ω-3 FAs/fish oil, NSAIDs or full dose aspirin. The trial opened in September 2014 with first enrollment 9/16/14. 43% of planned participants have enrolled as of January 2016. The trial is continuing as planned. This study is registered at ClinicalTrials.gov (NCT02295059) and supported by the National Cancer Institute (1R01CA164019-01A1). Citation Format: Lisa D. Yee, Joanne L. Lester, Shana R. Straka, Sarah Woelke, Jia-Yu Ke, Rulong Shen, Pearlly Yan, Jianying Zhang, Martha A. Belury, Steven K. Clinton. Omega-3 fatty acids and ERPR(-) and HER-2/neu(+) breast cancer prevention. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr CT086.

Effect of annatto-tocotrienols supplementation on the development of mammary tumors in HER-2/neu transgenic mice

Tocotrienols (T3), the lesser known isomers of vitamin E, have been reported to possess anticancer activity both in in vitro and in vivo experimental models of rodents transplanted with parental tumors or treated with carcinogens. We investigated the effects of dietary supplementation with annatto-T3 (90% δ-T3 and 10% γ-T3) on the spontaneous development of mammary tumors in HER-2/neu transgenic mice. Underlying mechanisms of the antitumor effect were evaluated by studying apoptosis, senescent-like growth arrest, immune modulation, oxidative effect and the expression of HER-2/neu in tumoral mammary glands of transgenic mice and in vitro in human and mice tumor cell lines. Annatto-T3 supplementation delayed the development of mammary tumors, reducing the number and size of mammary tumor masses and those of lung metastases. In annatto-T3-supplemented mice, both apoptosis and senescent-like growth arrest of tumor cells were increased in mammary glands while no immune modulation was observed. In vitro, a dose-dependent inhibition of cell growth, increased apoptosis and senescent-like growth arrest and a time-dependent accumulation of reactive oxygen species were observed in tumor cells treated with annatto-T3 or purified δ-T3. Annatto-T3 reduced both HER-2/neu mRNA and p185(HER-2/neu) protein in tumors and in tumor cell lines. The results show that the antitumor effect of annatto-T3 supplementation in HER-2/neu transgenic mice is mainly related to the direct induction of oxidative stress, senescent-like growth arrest and apoptosis of tumor cells rather than to an immune modulation.

Effect of annatto-tocotrienols supplementation on the Development of Mammary Tumors in HER-2/neu Transgenic Mice

Tocotrienols (T3), the lesser known isomers of vitamin E, have been reported to possess anticancer activity both in in vitro and in vivo experimental models of rodents transplanted with parental tumors or treated with carcinogens. We investigated the effects of dietary supplementation with annatto-T3 (90% δ-T3 and 10% γ-T3) on the spontaneous development of mammary tumors in HER-2/neu transgenic mice. Underlying mechanisms of the antitumor effect were evaluated by studying apoptosis, senescent-like growth arrest, immune modulation, oxidative effect and the expression of HER-2/neu in tumoral mammary glands of transgenic mice and in vitro in human and mice tumor cell lines. Annatto-T3 supplementation delayed the development of mammary tumors, reducing the number and size of mammary tumor masses and those of lung metastases. In annatto-T3-supplemented mice, both apoptosis and senescent-like growth arrest of tumor cells were increased in mammary glands while no immune modulation was observed. In vitro, a dose-dependent inhibition of cell growth, increased apoptosis and senescent-like growth arrest and a time-dependent accumulation of reactive oxygen species were observed in tumor cells treated with annatto-T3 or purified δ-T3. Annatto-T3 reduced both HER-2/neu mRNA and p185(HER-2/neu) protein in tumors and in tumor cell lines. The results show that the antitumor effect of annatto-T3 supplementation in HER-2/neu transgenic mice is mainly related to the direct induction of oxidative stress, senescent-like growth arrest and apoptosis of tumor cells rather than to an immune modulation.

Infiltrating CD11b+CD11c+ cells have the potential to mediate inducible nitric oxide synthase‐dependent cell death in mammary carcinomas of HER‐2/neu transgenic mice

The development of autochtonous mammary tumors in HER-2/neu transgenic mice is facilitated by immune tolerance to the neu-transgene. However, appropriate vaccination strategies can initiate immune system-mediated antitumor response by a process that requires IFN-gamma. We investigated the role of inducible nitric oxide synthase (iNOS) induction by IFN-gamma to promote tumor cell apoptosis. Tumors from FVBN202 mice expressing the normal neu gene under the control of the MMTV-LTR were treated in slice cultures with IFN-gamma for up to 24 hr. Apoptosis was induced, which depended on iNOS enzymatic activity. iNOS expression was predominantly found in infiltrating CD11b(+)CD11c(+) myeloid cells and at much lower levels in the tumor epithelium. By contrast, IFN-gamma treatment of explant cultures of tumor epithelial cells was not sufficient to efficiently induce iNOS, emphasizing an important role of the integrity of tumor tissue architecture, which was preserved in the slice cultures. This notion was further supported by the upregulation of iNOS costimulatory cytokines TNF-alpha and IL-1beta in slice cultures but not in explants and the capability of purified CD11b(+)CD11c(+) cells to enhance iNOS expression of tumor cells in cocultures. The findings suggest that tumor-infiltrating myeloid cells in immuno-tolerant HER-2/neu transgenic mice possess tumor killing ability via induction of iNOS and underline the capacity of antitumor strategies designed to stimulate infiltrating myeloid cells.

In Vivo Effect of α-Bisabolol, a Nontoxic Sesquiterpene Alcohol, on the Induction of Spontaneous Mammary Tumors in HER-2/neu Transgenic Mice

Breast cancer represents the most commonly diagnosed invasive malignancy in pre- and postmenopausal women in both developed and underdeveloped countries. Taking into account that treatment options, including surgery, have not been able to deal with the growing incidence of breast malignancy, it is required to develop mechanism-based novel agents for its prevention. Wide interest in some natural compounds as antiinflammatory agents and as alternative to the traditional medicines is increasing because they do not provoke any adverse effects and are effective in multiple organs, alpha-Bisabolol (BISA), a small oily sesquiterpene alcohol, was reported as chemopreventive agent in induced rat mammary carcinogenesis. The aim of the present study is to investigate the role played by two doses of BISA (via intramammary infusion) on the induction and development of mammary tumor in HER-2/neu transgenic mice as well as the BISA effect after tumor surgical resection. The main data show that (a) optimal dosage of BISA is 10 mg/mouse rather than 3.6 mg/mouse with no adverse effects (e.g., alopecia); (b) the number of the palpable tumor masses decreases in mice treated with 10 mg/mouse of BISA; (c) mice after surgical resection of the primary tumor and treatment with BISA (10 mg) are free from tumor for more weeks, after the surgical treatment; (d) using array analysis, some genes implicated in carcinogenesis mechanisms (NF-kappaBia, Map2k, Mapkl4, and HER2/ neu), angiogenesis process (Fgf), and inhibition of apoptosis (Birc5) are differently regulated after BISA treatment, with a downregulation of the HER2/neu as well as of Fgf and Birc5 genes; (e) the NK cell cytotoxicity increases in tumor-treated mice, especially after the removal of the first tumor mass. Such effectiveness could be important to achieve goals for a possible combination of BISA to conventional therapies in breast cancer and to tumor surgical removal (adjuvant therapy), as suggested for other sesquiterpene analogs.

The role of immature myeloid suppressor cells (IMSCs) in transgenic mammary tumor chemoprevention and therapy by Celecoxib (49.21)

Abstract Immune manipulation can control tumor initiation and growth while tumor growth may suppress host immunity. In our studies of tumor–host interactions, we observed a tumor associated expansion of IMSCs and suppression of T cell number and tumor infiltration. Further, the cyclooxygenase-2 (COX-2) inhibitor, Celecoxib had chemopreventative and as shown for the first time, therapeutic activity for mammary tumors in HER-2/neu transgenic BALB/c mice. Tumor growth was associated with a significant decrease in T cells and a significant increase in IMSCs (CD11b+Gr1+). In addition type 1 cytokine transcripts were depressed, while transcription levels of COX-2, arginase-1 (ARG1), nitric oxide synthetase-2 (NOS2), granulocyte (G) and G-monocyte colony stimulating factor, and vascular endothelial growth factor-alpha (VEGF-a) were increased in the preneoplastic lesions, tumors, and spleens and to a greater extent tumor infiltrating leukocytes. Celecoxib chemoprevention reduced the changes in IMSC and T cell numbers and cytokine and enzyme transcription levels. We posit that the increase in IMSCs may be due to the increased levels of COX-2, VEGF-a and growth factor(s), while the loss of T cell numbers and function maybe due to the heightened levels of ARG1 and NOS2. Further, as Celecoxib administration does not increase T cell infiltration of tumors or decrease IMSC infiltration, the changes in cytokine and growth factor levels maybe critical to the improved clinical outcomes. Together, these studies suggest an important role for IMSCs and its regulation by Celecoxib in cancer induction, and therapeutic intervention. Supported in part by funding from NIH grant 5 RO1 AT001739, Eppley Cancer Center and Nebraska DHHS LB506.

Effect of the Silybin-Phosphatidylcholine Complex (IdB 1016) on the Development of Mammary Tumors in HER-2/neu Transgenic Mice

Silybin, a main component of the milk thistle of Silybum marianum, has been reported to possess anticancer activity. We investigated the effects of IdB 1016, a complex of silybin with phosphatidylcholine, on the development of mammary tumors appearing spontaneously in HER-2/neu transgenic mice. The mechanisms involved in the antitumor effect of IdB 1016 were evaluated by studying the apoptosis, senescent-like growth arrest, intratumoral leukocyte infiltrate, and the expression of HER-2/neu and p53 in tumoral mammary glands from transgenic mice and in human breast SKBR3 tumor cells. The administration of IdB 1016 delayed the development of spontaneous mammary tumors, reduced the number and size of mammary tumor masses, and diminished lung metastasization in HER-2/neu transgenic mice. In tumoral mammary glands from IdB 1016-treated mice, a down-regulation of HER-2/neu gene expression was associated with an increased senescent-like growth arrest of tumor cells, and an increased infiltrate of neutrophils, CD4, and CD8 T cells. Both senescent-like growth arrest and apoptosis were significantly increased and were associated with a reduced p185(HER-2/neu) protein and an increased p53 mRNA in SKBR3 in vitro treated with IdB 1016 in comparison with control cells. The results show the antitumor effect of IdB 1016 in the development of spontaneous mammary tumors in HER-2/neu transgenic mice. The effect of IdB 1016 might be related to the down-regulation of HER-2/neu expression and the induction of senescent-like growth arrest and apoptosis through a p53-mediated pathway in tumor cells.

Effect of metformin on life span and on the development of spontaneous mammary tumors in HER-2/neu transgenic mice

Studies in mammals have led to the suggestion that hyperglycemia and hyperinsulinemia are important factors both in aging and in the development of cancer. Insulin/insulin-like growth factor 1 (IGF-1) signaling molecules that have been linked to longevity include DAF-2 and InR and their homologues in mammals, and inactivation of the corresponding genes is followed by increased life span in nematodes, fruit flies and mice. It is possible that the life-prolonging effects of calorie restriction are due to decreasing IGF-1 levels. A search of pharmacological modulators of insulin/IGF-1 signaling pathway (which mimetic effects of life span extending mutations or calorie restriction) could be a perspective direction in regulation of longevity. The chronic treatment of female transgenic HER-2/neu mice with metformin (100 mg/kg in drinking water) slightly decreased the food consumption but failed in reducing the body weight or temperature, slowed down the age-related rise in blood glucose and triglycerides level, as well as the age-related switch-off of estrous function, prolonged the mean life span by 8% ( p<0.05), the mean life span of last 10% survivors by 13.1%, and the maximum life span by 1 month in comparison with control mice. The demographic aging rate represented by the estimate of respective Gompertz's parameter was decreased 2.26 times. The metformin-treatment significantly decreased the incidence and size of mammary adenocarcinomas in mice and increased the mean latency of the tumors.

Metformin Decelerates Aging and Development of Mammary Tumors in HER-2/neu Transgenic Mice

Transgenic FVB/N female mice carrying HER-2/neu mammary cancer gene received metformin (1200 mg/liter) with drinking water 5 days a week starting from the age of 2 months until natural death. Metformin slightly reduced food consumption, but did not change water consumption and dynamics of weight gain. Mean life span of mice increased by 8% (p<0.05), in 10% long-living mice it was prolonged by 13.1%, and the maximum life span was prolonged by 1 month under the effect of metformin in comparison with the control. The rate of populational aging decreased by 2.26 times. The total incidence of mammary adenocarcinoma and their multiplicity did not change under the effect of metformin, while the latency of tumor development increased and the mean diameter of tumors decreased. Hence, we first demonstrated a geroprotective effect of metformin and its suppressive effect towards the development of mammary tumors.

Effect of resveratrol on the development of spontaneous mammary tumors in HER‐2/neu transgenic mice

Resveratrol (Res) has been reported to possess cancer chemopreventive activity on the basis of its in vitro effects on tumor cells and in vivo experimental models of rodents transplanted with parental tumors or treated with carcinogens. We investigated the effects of Res on the development of mammary tumors appearing spontaneously in HER-2/neu transgenic mice at an early age. The mechanisms involved in the Res antitumor effect were evaluated by studying the immune effectiveness, tumor apoptosis and expression of mRNA and protein for HER-2/neu in tumoral mammary glands from Res-treated mice and in tumor cell lines. Res supplementation delayed the development of spontaneous mammary tumors (p < 0.001), reduced the mean number and size of mammary tumors (p < 0.0001) and diminished the number of lung metastases in HER-2/neu transgenic mice. The effects of Res were associated with downregulation of HER-2/neu gene expression and increased apoptosis both in tumoral mammary glands and in murine (N202) and human (SKBr3) tumor cell lines. Neither the basal, the IL-2-induced NK activity nor the lymphocyte number and proliferation was modified in Res-supplemented compared to control mice. Our results demonstrate that Res supplementation delays the development and reduces the metastasizing capacity of spontaneous mammary tumors in HER-2/neu transgenic mice. The antitumor effect of Res might be related to the downregulation of HER-2/neu expression and the induction of apoptosis in tumor cells.

Mammary tumors in HER-2/NEU mice are characterized by low content of estrogen receptors-alpha and absence of progesterone receptors.

Transgenic mice carrying erbB2(HER-2)neu gene are characterized by high incidence of mammary adenocarcinoma. The content of estrogen receptor was no more than 10 fmol/mg protein in 8 of 14 studied tumors, while the content of progesterone receptors was even lower in all 14 studied tumors. Based on these data, we distinguish two subtypes of HER-2/neu-adenocarcinomas in mice: ER+,PR- and ER-,PR-, which can be used for the development of new approaches to the treatment of receptor-negative mammary gland tumors.

The effect of melatonin treatment regimen on mammary adenocarcinoma development in HER-2/neu transgenic mice.

The effect of various regimens of treatment with melatonin on the development of mammary tumors in HER2/neu transgenic mice was investigated. Female HER-2/neu mice starting from the age of 2 months were kept under standard light/dark regimen and as given melatonin with tap water (20 mg/l) during the night time 5 times monthly (interrupted treatments) or constantly to natural death. Intact mice served as controls. Treatment with melatonin slowed down age-related disturbances in estrous function most in the group exposed to interrupted treatment with the hormone. Constant treatment with melatonin decreased incidence and size of mammary adenocarcinomas, and incidence of lung metastases, compared to controls. The number of mice bearing 4 and more tumors was reduced in the group with constant melatonin treatment. Interrupted treatment with melatonin promote mammary carcinogenesis in HER-2/neu transgenic mice. The data demonstrate the regimen-dependent inhibitory effect of melatonin on the development of spontaneous mammary tumors in HER-2/neu mice but not on overall survival with implication about the likely cause of the effect. Polycystic kidney disease is common in this transgenic line. Adverse effect of melatonin on the life span in our study may be unique to the transgenic model used and may not be relevant to the suppressive effect of melatonin in delay of mammary cancer.

Inhibitory effect of the peptide epitalon on the development of spontaneous mammary tumors in HER-2/neu transgenic mice.

Female FVB/N HER-2/neu transgenic mice from the age of 2 months were subcutaneously injected with saline, the peptide Epitalon(R) (Ala-Glu-Asp-Gly) or with the peptide Vilon(R) (Lys-Glu) in a single dose of 1 microg/mouse for 5 consecutive days every month. Epitalon treatment reduced the cumulative number and the maximum size of tumors (p < 0.05). Furthermore, the number of mice bearing 1 mammary tumor was increased, whereas the number of mice bearing 2 or more mammary tumors was reduced in Epitalon-treated in comparison to saline-treated animals (p < 0.05). The size but not the number of lung metastases was reduced in Epitalon-treated compared to saline-treated mice (p < 0.05). The treatment with Vilon produced significant negative effects when compared to the control group, with an increased incidence of mammary cancer development (p < 0.05), a shorter mean latent period of tumors (p < 0.05) and an increased cumulative number of tumors (p < 0.05). A 3.7-fold reduction in the expression of HER-2/neu mRNA was found in mammary tumors from HER-2/neu transgenic mice treated with Epitalon compared to control animals. The expression of mRNA for HER-2/neu was also partially reduced in Vilon-treated mice, but it remained significantly higher in Vilon- than in Epitalon-treated animals (1.9-fold increase). The data demonstrate the inhibitory effect of Epitalon in the development of spontaneous mammary tumors in HER-2/neu mice, suggesting that a downregulation of HER-2/neu gene expression in mammary adenocarcinoma may be responsible, at least in part, for the antitumor effect of the peptide.

DNA vaccination with full-length or truncated neu induces protective immunity against the development of spontaneous mammary tumors in HER-2/neu transgenic mice.

Genetic immunization against tumor antigens is an effective way to induce an immune response able to oppose cancer progression. Overexpression of HER-2/neu can lead to neoplastic transformation and has been found in many human primary breast cancers. We constructed DNA expression vectors encoding the full-length neu oncogene of rat cDNA (pCMV-NeuNT), the neu extracellular domain (pCMV-ECD), or the neu extracellular and transmembrane domains (pCMV-ECD-TM). We evaluated whether i.m. injection of these plasmids induces protection against the development of mammary tumors occurring spontaneously in FVB/N neu-transgenic mice. We found that pCMV-ECD-TM induced the best protection, whereas both pCMV-ECD and pCMV-NeuNT were less effective. The coinjection with a bicistronic vector for murine IL-12 increased the efficacy of pCMV-ECD and pCMV-NeuNT plasmids, and led to the same protection obtained with pCMV-ECD-TM alone. Anti-neuECD antibodies were detected in pCMV-ECD-TM vaccinated mice and, after coinjection with pCMV-IL12 plasmids, they appeared also in animals immunized with pCMV-ECD. Our data demonstrate the effectiveness of DNA vaccination using truncated Neu plasmids in inducing antitumor protection in a spontaneous mammary tumor model.