Accelerated preclinical testing using transplanted tumors from genetically engineered mouse breast cancer models.
ABSTRACT The use of genetically engineered mouse (GEM) models for preclinical testing of anticancer therapies is hampered by variable tumor latency, incomplete penetrance, and complicated breeding schemes. Here, we describe and validate a transplantation strategy that circumvents some of these difficulties.
Tumor fragments from tumor-bearing MMTV-PyMT or cell suspensions from MMTV-PyMT, -Her2/neu, -wnt1, -wnt1/p53(+/-), BRCA1/p53(+/-), and C3(1)T-Ag mice were transplanted into the mammary fat pad or s.c. into naïve syngeneic or immunosuppressed mice. Tumor development was monitored and tissues were processed for histopathology and gene expression profiling. Metastasis was scored 60 days after the removal of transplanted tumors.
PyMT tumor fragments and cell suspensions from anterior glands grew faster than posterior tumors in serial passages regardless of the site of implantation. Microarray analysis revealed genetic differences between these tumors. The transplantation was reproducible using anterior tumors from multiple GEM, and tumor growth rate correlated with the number of transplanted cells. Similar morphologic appearances were observed in original and transplanted tumors. Metastasis developed in >90% of mice transplanted with PyMT, 40% with BRCA1/p53(+/-) and wnt1/p53(+/-), and 15% with Her2/neu tumors. Expansion of PyMT and wnt1 tumors by serial transplantation for two passages did not lead to significant changes in gene expression. PyMT-transplanted tumors and anterior tumors of transgenic mice showed similar sensitivities to cyclophosphamide and paclitaxel.
Transplantation of GEM tumors can provide a large cohort of mice bearing mammary tumors at the same stage of tumor development and with defined frequency of metastasis in a well-characterized molecular and genetic background.
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ABSTRACT: The prevalence of obesity, an established risk and progression factor for postmenopausal breast cancer, remains high in US women. Activation of Akt/mammalian target of rapamycin (mTOR) signaling plays a key role in the obesity-breast cancer link. However, the impact of weight normalization in obese postmenopausal women on breast tumorigenesis and/or Akt/mTOR activation is poorly characterized. To model this, ovariectomized female C57BL/6 mice were fed a control diet (n = 20), a calorie restriction (CR) regimen (n = 20), or a diet-induced obesity (DIO) diet (n = 30). At week 17, DIO mice were switched to control diet, resulting in formerly obese (FOb) mice with weights identical to the controls by week 20. MMTV-Wnt-1 mammary tumor cells were injected at 20 wk into each mouse. Two weeks post-injection, vehicle or the mTOR inhibitor RAD001 at 10 or 15 mg/kg body weight (n = 10/diet group) was administered by gavage twice/week until termination. Relative to controls, CR mice had decreased (and DIO mice had increased) serum insulin-like growth factor-1 (IGF-1) and phosphorylation of Akt/mTOR pathway components. RAD001 decreased tumor growth in the CR, control, and FOb mice. Wnt-1 tumor cells treated in vitro with serum from mice from each group established that diet-dependent circulating factors contribute to tumor growth and invasiveness. These findings suggest weight normalization in obese mice does not immediately reverse tumor progression or Akt/mTOR activation. Treatment with RAD001 blocked mammary tumor development and mTOR activation observed in the FOb mice, suggesting combination of lifestyle and pharmacologic strategies may be effective for breaking the obesity-breast cancer link. © 2012 Wiley Periodicals, Inc.Molecular Carcinogenesis 01/2012; · 4.27 Impact Factor
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ABSTRACT: Most mammals develop their mammary glands in pairs of which the two counterparts are symmetrically displaced away from the ventral midline. Based on this symmetry and the same functional outcome as a milk-producing organ, the mammary glands are easily presumed to be mere copies of one another. Based on our analysis of published data with inclusion of new results related to mammary development and pathology in mice, we argue that this presumption is incorrect: Between and within pairs, mammary glands differ from one another, and tumor incidence and biology depend on the position along the anterior-posterior and the left-right axis as well. This insight has implications for experimental designs with mouse models and for data extrapolation between mammary glands within and between species. We suggest that improved documentation of location-specific mammary gland features will lead to more insights into the molecular mechanisms of mammary gland development and cancer biology in both mice and humans.Journal of Mammary Gland Biology and Neoplasia 05/2013; · 7.52 Impact Factor
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ABSTRACT: Adiponectin is an adipokine that can suppress the proliferation of various human carcinoma cells. Although its anti-tumor activities have been suggested by many clinical investigations and animal studies, the underlying mechanisms are not fully characterized. In MMTV-polyomavirus middle T antigen (MMTV-PyVT) transgenic mice models, reduced- or complete loss-of-adiponectin expression promotes mammary tumor development. The present study demonstrated that while tumor development in control MMTV-PyVT mice is associated with a progressively decreased circulating cholesterol concentration, adiponectin deficient MMTV-PyVT mice showed significantly elevated total- and low density lipoprotein (LDL)-cholesterol levels. Cholesterol contents in tumors derived from adiponectin deficient mice were dramatically augmented. High fat high cholesterol diet further accelerated the tumor development in adiponectin deficient PyVT mice. The protein levels of LDL receptor (LDLR) were found to be upregulated in adiponectin-deficient tumor cells. In human breast carcinoma cells, treatment with LDL-cholesterol or overexpressing LDLR elevates nuclear beta-catenin activity and facilitates tumor cell proliferation. On the other hand, adiponectin decreased LDLR protein expression in breast cancer cells and inhibited LDL-cholesterol-induced tumor cell proliferation. Both in vivo and in vitro evidence demonstrated a stimulatory effect of adiponectin on autophagy process, which mediated the down-regulation of LDLR. Adiponectin-induced reduction of LDLR was blocked by treatment with a specific inhibitor of autophagy, 3-methyladenine. In conclusion, the study demonstrates that adiponectin elicits tumor suppressive effects by modulating cholesterol homeostasis and LDLR expression in breast cancer cells, which is at least in part attributed to its role in promoting autophagic flux.Oncotarget 10/2013; · 6.64 Impact Factor