Mitochondrial transfer from cancer associated fibroblasts increases migration in aggressive breast cancer

Cancer associated fibroblasts (CAFs) have distinct roles within the tumor microenvironment, which may impact the mode and efficacy of tumor cell migration. CAFs are known to increase invasion of less-aggressive breast cancer cells through matrix remodeling and leader-follower dynamics. Here, we demonstrate that CAFs communicate with breast cancer cells through the formation of contact-dependent tunneling nanotubes (TNTs) that allow for the exchange of cargo between cell types. The transferring of CAF mitochondria is an integral cargo component, and CAF mitochondria are sufficient to increase the 3D migration of cancer cells. This cargo transfer results in an increase in mitochondrial ATP production in cancer cells while having negligible impact on glycolytic ATP production. Manually increasing mitochondrial oxidative phosphorylation (OXPHOS) by providing extra substrates for OXPHOS fails to enhance cancer cell migration unless glycolysis is maintained at a constant level. Together, these data indicate that tumor-stromal crosstalk via TNTs and the associated metabolic symbiosis is a finely controlled mechanism by which tumor cells co-opt their microenvironment to promote cancer progression and may become a potential therapeutic target.

Abstract 1711: Mechanical strain induces phenotypic changes in breast cancer cells and promotes immunosuppression in the tumor microenvironment

Introduction: Breast cancer (BCa) occurs with a complex, three-dimensional microenvironment that involves heterogeneous biochemical and biophysical cues. Understanding how mechanical properties within the tumor microenvironment (TME) regulate breast cancer phenotype and immunosuppression is of great interest.

Materials and Methods: BCa cells (MCF-7, MDA-MB-231 or 4T1.2) cultured to confluence on collagen coated FlexCell culture plates were subjected to 10% uniaxial cyclic/oscillatory strain at 0.3 Hz, or 10% constant strain, or no strain for 48 hours. They were isolated for analysis of proliferation (MTT assay and cell count by trypan blue), and migration (transwell and wound healing assay). Exosomes from conditioned media were isolated by differential centrifugation or using the Total Exosome Isolation kit. The purified exosomes were quantified by NanoSight and characterized by ImageStream. 5 × 105 4T1.2 cells or PKH67-labeled strained or control cells were injected into the mammary fat pad of BALB/c mice. Tumor volume was measured at the indicated time points after injection. Tumor-infiltrating immune cells and the internalization of exosomes were analyzed by flow cytometry on day 14 post implantation. In some experiments, on day 6 after tumor injection, 7.5 × 108 PHK67-labeled tumor cell-derived exosomes or PBS were injected into the tumor nodule. Tumor tissues were harvested for analysis of the internalization of exosomes by immune cells and tumor cells on days 2 and 8 after exosome injection.

Results: We show that mechanical strain enhanced the proliferation and migration of BCa cells in vitro. Exosome concentrations produced by triple negative breast cancer (TNBC) cells were increased following exposure to oscillatory strain. Phenotyping exosomes by ImageStream showed that the percentages of CD81+PD-L1+ and CD63+PD-L1+ exosomes were increased after exposure to oscillatory strain. Using a syngeneic orthotopic mouse model of TNBC, we showed that preconditioning with mechanical strain increased tumor growth. The percentages of tumor-infiltrating monocytic myeloid-derived suppressor cells (M-MDSC) and recruited macrophages were increased while CD8+ T cells decreased in the TME of mice implanted with 4T1.2 cells preconditioned with oscillatory strain. Further, exosome internalizations by M-MDSC and recruited macrophages were elevated when tumor cells were preconditioned with oscillatory strain. Moreover, exosomes internalization by immune cells and tumor cells in TME were identified by PKH67 positive signals on days 2 and 8 after injection of PKH67-labeled exosomes into tumor nodules by flow cytometry analyses and confocal microscope imaging.

Conclusions: Our data indicate that exposure to mechanical strain promotes invasive and pro-tumorigenic phenotypes in BCa, alters exosome production by BCa and induces immunosuppression in the TME.

Citation Format: Yong Wang, Kayla F. Goliwas, Paige E. Severino, Kenneth Hough, Derek Van Vessem, Hong Wang, Sultan Tousif, Roy P. Koomullil, Andra R. Frost, Selvarangan Ponnazhagen, Joel L. Berry, Jessy S. Deshane. Mechanical strain induces phenotypic changes in breast cancer cells and promotes immunosuppression in the tumor microenvironment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1711.

Identification of Distinct Heterogenic Subtypes and Molecular Signatures Associated with African Ancestry in Triple Negative Breast Cancer Using Quantified Genetic Ancestry Models in Admixed Race Populations

Triple negative breast cancers (TNBCs) are molecularly heterogeneous, and the link between their aggressiveness with African ancestry is not established. We investigated primary TNBCs for gene expression among self-reported race (SRR) groups of African American (AA, n = 42) and European American (EA, n = 33) women. RNA sequencing data were analyzed to measure changes in genome-wide expression, and we utilized logistic regressions to identify ancestry-associated gene expression signatures. Using SNVs identified from our RNA sequencing data, global ancestry was estimated. We identified 156 African ancestry-associated genes and found that, compared to SRR, quantitative genetic analysis was a more robust method to identify racial/ethnic-specific genes that were differentially expressed. A subset of African ancestry-specific genes that were upregulated in TNBCs of our AA patients were validated in TCGA data. In AA patients, there was a higher incidence of basal-like two tumors and altered TP53, NFB1, and AKT pathways. The distinct distribution of TNBC subtypes and altered oncologic pathways show that the ethnic variations in TNBCs are driven by shared genetic ancestry. Thus, to appreciate the molecular diversity of TNBCs, tumors from patients of various ancestral origins should be evaluated.

Abstract 1177: Mechanical strain induces phenotypic changes in breast cancer cells and promotes immunosuppression in the tumor microenvironment

Introduction: Cells within the breast tumor mass are met with a variety of biophysical or mechanical signals that is associated with elevated compression or solid stress within the tumor interior, tension at the tumor periphery, and altered interstitial fluid pressure. Understanding how the mechanical stress within the tumor microenvironment (TME) regulates cancer cell phenotype is of interest, yet the response of breast cancer (BCa) cells to these forces is largely unknown. Our study aims to identify the impact of mechanical stress on BCa cell phenotype by mimicking the tension at the tumor periphery.

Materials and Methods: BCa cells (MCF-7 or 4T1.2) were cultured to confluence on collagen coated FlexCell culture plates. These plates were then subjected to 10% uniaxial cyclic/oscillatory strain at 0.3 Hz, or 10% constant strain, or no strain for 48 hours. Strained or control cells were isolated for analysis of proliferation (MTT assay), and migration (8.0 μm pore transwell). Exosomes from conditioned media were isolated via differential centrifugation and purified exosomes were characterized by ImageStream. 5x105 4T1.2 cells or PKH-labeled strained or control cells were injected into the mammary fat pad of BALB/c mice. Tumor volume was measured over 14 days. Tumor-infiltrating immune cells and the uptake of exosomes were analyzed by flow cytometry on day-14 post implantation.

Results: We determined significant increases in proliferation and migration of 4T1.2 and MCF-7 cells in vitro following exposure to oscillatory forces. The populations of CD63+, CD63+CD24+ and CD63+PD-L1+ exosomes were increased when 4T1.2 cells were exposed to oscillatory strain compared to unstrained control cells. Further, we investigated how oscillatory forces affect tumor growth and tumor-immune cell interactions in vivo by using a syngeneic, orthotopic mouse model of BCa. Mice implanted with 4T1.2 cells that were pre-exposed to oscillatory forces showed a significant increase in primary tumor growth at 8 and 11 days post tumor challenge. The percentages of tumor-infiltrating monocytic myeloid-derived suppressor cells (M-MDSC) and recruited macrophages were increased in the TME of mice implanted with 4T1.2 cells that were pre-exposed to oscillatory forces, while the granulocytic MDSC subset was not significantly different between the two groups. A marginal decrease in the percentage of CD8+ T cells was noted in the TME of mice implanted with strained 4T1.2 when compared to controls, suggesting immune suppression in the TME. Furthermore, exosome uptakes by M-MDSC and recruited macrophages were increased in the TME of mice implanted with PKH-labeled 4T1.2 cells, exposed to oscillatory strain.

Conclusion: Together, these data indicate that exposure to mechanical stress changes BCa cell phenotype to an invasive and protumorigenic phenotype that promotes immunosuppressive effects in the TME.

Citation Format: Yong Wang, Paige E. Severino, Kayla Goliwas, Kenneth Hough, Derek Van Vessem, Hong Wang, Andra R. Frost, Selvarangan Ponnazhagen, Joel L. Berry, Jessy S. Deshane. Mechanical strain induces phenotypic changes in breast cancer cells and promotes immunosuppression in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1177.

Abstract A05: Evaluation of in vitro three dimensional breast cancer surrogates using histologic morphology and non-invasive imaging to monitor growth and viability throughout culture

Introduction: Tumor dimensionality creates a dynamic three dimensional (3D) architecture that is influenced by the associated microenvironment, including stromal cells and the extracellular matrix. These paracrine interactions impact therapeutic efficacy and can alter drug response in vivo , yet most current in vitro models do not accurately recapitulate the dimensionality or the stromal microenvironment of human tumors. In vitro models that are more recapitulative of the human tumor microenvironment have broad applicability in evaluation of signaling pathways driving cancer progression, therapeutic efficacy, and mechanisms involved in therapeutic resistance and tumor recurrence. There is a great need to adapt traditional analytical methods, developed for two dimensional cell culture, for use in 3D tissue models. Herein, a novel perfusion bioreactor system is used to support the multi-week growth and development of 3D breast carcinoma tissue surrogates (measuring 1.0 cm in maximum dimension) consisting of breast carcinoma epithelial cell lines and cancer associated fibroblasts (CAF) in a supportive extracellular matrix. Further, non-invasive imaging techniques, commonly employed to evaluate in vivo animal model systems, were used to measure growth of the surrogates overtime.

Methods: 3D breast carcinoma surrogates were generated by incorporating MDA-MB-231 cells (tagged with GFP and luciferase) or MCF-7 cells (tagged with GFP and luciferase), with or without CAF, into an extracellular matrix. Surrogates were cultured in a perfusion bioreactor system for up to 3 weeks. Cell growth was measured on histologic sections of surrogates by counting the number of nucleated cells per surrogate cross-sectional area (cell density). Growth and viability were also determined in the same surrogates over time by using non-invasive fluorescence and luminescence imaging (IVIS 100 system).

Results: The use of a flow perfusion bioreactor system resulted in a marked increase in the cell density of surrogates compared to non-perfused surrogates (perfused: 93.3 nucleated cells/area vs. non-perfused: 32.1 nucleated cells/area) at 21 days culture. Fluorescence and luminescence imaging of surrogates, containing increasing concentrations of breast cancer epithelial cells, were imaged at day 0 to confirm a correlation between signal intensity and cell number using each imaging modality (GFP: R2=0.97, p<0.01, Luciferase: R2=0.99, p=0.053 ). Next, fluorescence imaging of the same 3D breast carcinoma surrogates (containing breast carcinoma cells and CAF) overtime was completed at days 0, 7, and 14 of culture and showed an increase in signal (7.9 fold higher signal at day 14 compared to day 0) indicating growth throughout culture. Similar results were seen with imaging of the luciferase signal where the signal was 28.2 fold higher at day 14 compared to day 0.

Conclusions: The presence of perfusion allows the growth and development of a recapitulative breast carcinoma surrogate with a size similar to human breast carcinomas at the time of detection and with an appropriate tumor microenvironment. Non-invasive imaging methods have successfully been adapted to evaluate growth of the breast carcinoma surrogates throughout multi-week culture.

Future Directions: The use of these perfused breast carcinoma surrogates and imaging modalities in the evaluation of established and candidate cancer therapeutics will be assessed.

Citation Format: Kayla F. Goliwas, Jillian R. Richter, Lauren E. Marshall, Joel L. Berry, Andra R. Frost. Evaluation of in vitro three dimensional breast cancer surrogates using histologic morphology and non-invasive imaging to monitor growth and viability throughout culture. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr A05.

Computational and Experimental Analysis of Fluid Transport Through Three-Dimensional Collagen-Matrigel Hydrogels

A preclinical testing model for cancer therapeutics that replicates in vivo physiology is needed to accurately describe drug delivery and efficacy prior to clinical trials. To develop an in vitro model of breast cancer that mimics in vivo drug/nutrient delivery as well as physiological size and bio-composition, it is essential to describe the mass transport quantitatively. The objective of the present study was to develop in vitro and computational models to measure mass transport from a perfusion system into a 3D extracellular matrix (ECM). A perfusion-flow bioreactor system was used to control and quantify the mass transport of a macromolecule within an ECM hydrogel with embedded through-channels. The material properties, fluid mechanics, and structure of the construct quantified in the in vitro model were input into, and served as validation of, the computational fluid dynamics (CFD) simulation. Results showed that advection and diffusion played a complementary role in mass transport. As the CFD simulation becomes more complex with embedded blood vessels and cancer cells, it will become more recapitulative of in vivo breast cancers. This study is a step toward development of a preclinical testing platform that will be more predictive of patient response to therapeutics than two-dimensional cell culture.

A recapitulative three-dimensional model of breast carcinoma requires perfusion for multi-week growth

Breast carcinomas are complex, three-dimensional tissues composed of cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix. In vitro models that more faithfully recapitulate this dimensionality and stromal microenvironment should more accurately elucidate the processes driving carcinogenesis, tumor progression, and therapeutic response. Herein, novel in vitro breast carcinoma surrogates, distinguished by a relevant dimensionality and stromal microenvironment, are described and characterized. A perfusion bioreactor system was used to deliver medium to surrogates containing engineered microchannels and the effects of perfusion, medium composition, and the method of cell incorporation and density of initial cell seeding on the growth and morphology of surrogates were assessed. Perfused surrogates demonstrated significantly greater cell density and proliferation and were more histologically recapitulative of human breast carcinoma than surrogates maintained without perfusion. Although other parameters of the surrogate system, such as medium composition and cell seeding density, affected cell growth, perfusion was the most influential parameter.

Preparation and Analysis of In Vitro Three Dimensional Breast Carcinoma Surrogates

Three dimensional (3D) culture is a more physiologically relevant method to model cell behavior in vitro than two dimensional culture. Carcinomas, including breast carcinomas, are complex 3D tissues composed of cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix (ECM). Yet most in vitro models of breast carcinoma consist only of cancer epithelial cells, omitting the stroma and, therefore, the 3D architecture of a tumor in vivo. Appropriate 3D modeling of carcinoma is important for accurate understanding of tumor biology, behavior, and response to therapy. However, the duration of culture and volume of 3D models is limited by the availability of oxygen and nutrients within the culture. Herein, we demonstrate a method in which breast carcinoma epithelial cells and stromal fibroblasts are incorporated into ECM to generate a 3D breast cancer surrogate that includes stroma and can be cultured as a solid 3D structure or by using a perfusion bioreactor system to deliver oxygen and nutrients. Following setup and an initial growth period, surrogates can be used for preclinical drug testing. Alternatively, the cellular and matrix components of the surrogate can be modified to address a variety of biological questions. After culture, surrogates are fixed and processed to paraffin, in a manner similar to the handling of clinical breast carcinoma specimens, for evaluation of parameters of interest. The evaluation of one such parameter, the density of cells present, is explained, where ImageJ and CellProfiler image analysis software systems are applied to photomicrographs of histologic sections of surrogates to quantify the number of nucleated cells per area. This can be used as an indicator of the change in cell number over time or the change in cell number resulting from varying growth conditions and treatments.

Abstract 989: Regulation of metastatic potential through adiponectin-stimulated induction of autophagy

Each year, an unacceptable number of deaths occur in women because of the lack of curative approaches for metastatic breast cancer. Some of the key regulators of breast cancer progression are molecules within the tumor microenvironment including adipokines, a broad array of autocrine-, endocrine-, and paracrine-acting bioactive molecules secreted by adipocytes. Adiponectin is one of the most abundant adipokines and, while multiple widely cited epidemiological studies have indicated that low levels of circulating plasma adiponectin portend poorer prognosis, recent work has reported that elevated adiponectin expression in breast tissue is, in fact, correlated with more advanced disease. Thus, the purpose of this work is to better understand how adiponectin in breast tissue acts directly on tumor cells to regulate the early steps of breast cancer metastasis. Our hypothesis is that adiponectin alters metastatic potential of breast cancer cells via induction of autophagy. To begin to test this premise, we discerned the effect of globular versus full-length adiponectin on invasive and migratory phenotypes of a human metastatic breast cancer cell line (MDA-MB-231). In transwell assays with and without Matrigel, globular adiponectin increased invasion (91%; p < 0.001) and migration (222%; p < 0.05) compared to untreated cells, whereas full length adiponectin had no significant effect. Rapamycin, an established autophagy inducer, elicited effects similar to globular adiponectin (increase of 210%; p < 0.001 in invasion and 238%; p < 0.05 in migration). Likewise, three-dimensional growth in Matrigel revealed that cells treated with globular adiponectin and rapamycin developed extended spikes indicative of a more invasive phenotype, whereas those treated with full-length adiponectin maintained a less invasive grape-like structure. Neither adiponectin isoform altered proliferation. Biochemical assays of autophagic induction supported these observations, demonstrating increases in LC3B-II expression (immunoblot) and in the number of intracellular LC3B puncta (immunofluorescence) upon treatment with globular, but not full-length, adiponectin. Together, these results suggest a plausible model linking a specific adiponectin isoform with induction of autophagy to stimulate breast cancer metastasis. Our findings will advance the field by revealing distinct, novel roles for key microenvironmental regulatory molecules, potentially opening up new avenues for therapeutic development. This work is timely considering recent interest in adiponectin and adiponectin receptor agonists as therapeutic strategies. In addition, noting that an aberrant level of adiponectin is a putative mechanism linking obesity to poor breast cancer prognosis and metastasis, our results may provide mechanistic insight to guide lifestyle interventions that will reduce breast cancer's heavy morbidity and mortality burden.

Citation Format: Emily Falk Libby, Jianzhong Liu, Monica J. Lewis, Andra R. Frost, Wendy Demark-Wahnefried, Douglas R. Hurst. Regulation of metastatic potential through adiponectin-stimulated induction of autophagy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 989. doi:10.1158/1538-7445.AM2015-989

Abstract 4004: Prognostic value of miRNAs in breast cancer varies with patient race and molecular subtype

Background: MicroRNAs (miRNAs) may serve as biomarkers for breast cancer (BC) diagnosis and prognosis. Since their clinical value based on race/ethnicity and molecular subtypes has not been studied, we evaluated the prognostic significance of a panel of miRNAs in luminal and triple-negative BCs (TNBCs) of African Americans (AAs) and non-Hispanic Caucasians (CAs).

Methods: TaqMan® assays were used to quantify levels of miR-21, miR-106a, miR-206, miR-155, miR-210, and miR-335 in 151 BCs and corresponding normal tissues of 80 AAs (luminal = 24 and TNBCs = 56) and 71 CAs (luminal = 27 and TNBC = 44). Fold changes in levels between tumor-normal pairs were used to categorize the tumors into high- and low-expression groups. The levels of miRNAs were correlated with molecular subtype, patient race/ethnicity, and overall survival by Kaplan-Meier univariate and Cox regression multivariate analyses. Further, the added predictive value of these miRNAs to a baseline prediction model consisting of standard clinical risk factors was evaluated at 2-, 5-, and 8-years post-surgery based on positive predictive curves.

Results: In BC tissues, miR-21, miR-106a, miR-155, miR-206, and miR-210 were up-regulated, and miR-335 was down-regulated. For the combined population, univariate and multivariate analyses showed that high levels of miR-21 (adjusted HR = 2.91, 95% CI: 1.27-6.62) and miR-106a (adjusted HR = 2.49, 95% CI: 1.04-5.97) and down-regulation of miR-335 (adjusted HR = 2.97, 95% CI: 1.35-5.54) were associated with poor survival. In multivariate analyses by race, high miR-21 (HR = 7.35, 95% CI: 2.46-21.98) and low miR-335 (HR = 14.13, 95% CI: 2.93-68.13) were indicators of poor survival in only CA patients. Additionally, expression levels of miR-21 aided in identifying risk of death in CA patients with either molecular subtype. In CAs, differences in the area under the positive predictive curve (ΔAUC) between the models with and without miR-21 were 0.077 (95% CI = 0.007-0.154) and 0.053 (95% CI = 0.002-0.128) at 5 and 8 years after surgery, respectively. In TNBCs of both racial groups, addition of miR-106a increased predictive accuracy at 5 (ΔAUC = 0.026, 95% CI = 0.001-0.068) and 8 years (ΔAUC = 0.022, 95% CI = 0-0.061) post-surgery. No miRNA was helpful in identifying patients at high risk of death due to luminal BCs or to AA ethnicity.

Conclusions: High levels of miR-106a and miR-21 and low levels of miR-335 are independent prognostic markers of BCs. Furthermore, miR-21 has added predictive value above the standard clinical risk factors for CAs and miR-106a has added predictive value for TNBCs. In evaluation of the clinical utility of miRNAs, patient race and molecular types of BCs should be considered. This work was supported by a pilot grant from UAB Breast SPORE grant of the National Institutes of Health/National Cancer Institute (5P50CA089019).

Citation Format: Balananda-Dhurjati Kumar Putcha, Trafina Jadhav, Michael P. Behring, Sejong Bae, Andra R. Frost, Isam-Eldin Eltoum, Li Chen, Heidi L. Weiss, William E. Grizzle, Upender Manne. Prognostic value of miRNAs in breast cancer varies with patient race and molecular subtype. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4004. doi:10.1158/1538-7445.AM2015-4004

Abstract 331: A novel perfusion bioreactor system maintains long-term viability of a three dimensional in vitro breast carcinoma surrogate

Background: Breast carcinomas are complex, three-dimensional (3D) tissues composed of breast cancer epithelial cells and stromal components, including fibroblasts and extracellular matrix (ECM). Most in vitro models of carcinoma consist only of cancer epithelial cells, omitting the stroma and, therefore, the 3D architecture of a tumor in vivo. While more accurate 3D modeling allows for enhanced recapitulation of tumor biology and behavior, 3D culture is acknowledged to be challenging with cell viability decreasing dramatically overtime due to lack of available nutrients. Here-in, a novel perfusion bioreactor system supplies medium through 400 uM-diameter channels to maintain survival of a 3D breast cancer surrogate consisting of MDA-MB-231 (231) breast cancer epithelial cells, breast cancer fibroblasts (CAF) and ECM. For optimization of ECM in the breast cancer surrogates, collagen I concentration and species were varied and the effect on 3D morphology and cell viability was assessed. Methods: To assess the effect of collagen concentration on 3D morphology and cell viability, 231 cells and CAF (2:1 ratio) were incorporated into 1.9, 4, 6, or 8 mg/ml (bovine or rat tail) collagen I mixed with 10% basement membrane (BM, i.e. GFR Matrigel) and cultured for 7 days in 8-well chamber slides (non-perfused, solid 3D cultures). H&E stained histologic sections were prepared after fixation and paraffin embedding of the cultures. Cell aggregation, as a measure of 3D morphology, and viability were assessed on histologic sections by image analysis (ImageJ) and autofluorescence, respectively. To compare cell viability in solid 3D culture to surrogates in the perfusion bioreactor system, 231 cells and CAF (2:1 ratio) were incorporated into an ECM composed of 6 mg/ml bovine collagen I mixed with 10% BM and grown in solid 3D culture or in the bioreactor system. The conditions were compared at 7, 14, and 21 days. Results: Collagen I concentration and species had no significant effect on the extent of cell aggregation. However, cell viability was significantly greater in 6 and 8 mg/ml (69.6% and 67.0% alive, respectively) than 1.9 mg/ml (31.9% alive) bovine collagen (ANOVA, p≤0.05). A similar increase in viability with increasing concentration was not seen with rat-tail collagen. Therefore, 6 mg/ml bovine collagen I was used in cancer surrogates in the perfusion bioreactor system. Cell viability was increased in the perfused surrogate (87.9% alive) in comparison to solid cultures (69.6% alive, t-Test, p = 0.03) at 7 days. There was no significant decrease in viability at 14 and 21 days in perfused surrogates (93.8% and 76.7% alive, respectively). Conclusions: Bovine collagen I concentration affects viability of breast cancer cells in 3D. The perfusion bioreactor system promotes cell viability allowing for multi-week culture of breast carcinoma surrogates.

Citation Format: Kayla F. Goliwas, Lauren E. Marshall, Kun Yuan, Joel L. Berry, Andra R. Frost. A novel perfusion bioreactor system maintains long-term viability of a three dimensional in vitro breast carcinoma surrogate. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 331. doi:10.1158/1538-7445.AM2015-331

The presence of primary cilia in cancer cells does not predict responsiveness to modulation of smoothened activity

Primary cilia are microtubule-based organelles that regulate smoothened-dependent activation of the GLI transcription factors in canonical hedgehog signaling. In many cancers, primary cilia are markedly decreased or absent. The lack of primary cilia may inhibit or alter canonical hedgehog signaling and, thereby, interfere in the cellular responsiveness to modulators of smoothened activity. Clinical trials of smoothened antagonists for cancer treatment have shown the best response in basal cell carcinomas, with limited response in other solid tumors. To determine whether the presence or absence of primary cilia in cancer cells will predict their responsiveness to modulation of smoothened activity, we compared the ability of an agonist and/or inhibitor of smoothened (SAG and SANT1, respectively) to modulate GLI-mediated transcription, as measured by GLI1 mRNA level or GLI-luciferase reporter activity, in non-cancer cells with primary cilia (ovarian surface epithelial cells and breast fibroblasts), in cancer cells that cannot assemble primary cilia (MCF7, MDA-MB-231 cell lines), and in cancer cells with primary cilia (SKOV3, PANC1 cell lines). As expected, SAG and SANT1 resulted in appropriate modulation of GLI transcriptional activity in ciliated non-cancer cells, and failed to modulate GLI transcriptional activity in cancer cells without primary cilia. However, there was also no modulation of GLI transcriptional activity in either ciliated cancer cell line. SAG treatment of SKOV3 induced localization of smoothened to primary cilia, as assessed by immunofluorescence, even though there was no increase in GLI transcriptional activity, suggesting a defect in activation of SMO in the primary cilia or in steps later in the hedgehog pathway. In contrast to SKOV3, SAG treatment of PANC1 did not cause the localization of smoothened to primary cilia. Our data demonstrate that the presence of primary cilia in the cancer epithelial cells lines tested does not indicate their responsiveness to smoothened activation or inhibition.

Flow-perfusion bioreactor system for engineered breast cancer surrogates to be used in preclinical testing

There is a need for preclinical testing systems that predict the efficacy, safety and pharmacokinetics of cancer therapies better than existing in vitro and in vivo animal models. An approach to the development of predictive in vitro systems is to more closely recapitulate the cellular and spatial complexity of human cancers. One limitation of using current in vitro systems to model cancers is the lack of an appropriately large volume to accommodate the development of this complexity over time. To address this limitation, we have designed and constructed a novel flow-perfusion bioreactor system that can support large-volume, engineered tissue comprised of multicellular cancer surrogates by modifying current microfluidic devices. Key features of this technology are a three-dimensional (3D) volume (1.2 cm³ ) that has greater tissue thickness than is utilized in existing microfluidic systems and the ability to perfuse the volume, enabling the development of realistic tumour geometry. The constructs were fabricated by infiltrating porous carbon foams with an extracellular matrix (ECM) hydrogel and engineering through-microchannels. The carbon foam structurally supported the hydrogel and microchannel patency for up to 161 h. The ECM hydrogel was shown to adhere to the carbon foam and polydimethylsiloxane flow chamber, which housed the hydrogel-foam construct, when surfaces were coated with glutaraldehyde (carbon foam) and nitric acid (polydimethylsiloxane). Additionally, the viability of breast cancer cells and fibroblasts was higher in the presence of perfused microchannels in comparison to similar preparations without microchannels or perfusion. Therefore, the flow-perfusion bioreactor system supports cell viability in volume and stromal contexts that are physiologically-relevant. Copyright © 2015 John Wiley & Sons, Ltd.

Wnt5a suppresses tumor formation and redirects tumor phenotype in MMTV-Wnt1 tumors

Wnt5a is a non-canonical signaling Wnt that has been implicated in tumor suppression. We previously showed that loss of Wnt5a in MMTV-PyVmT tumors resulted in a switch in tumor phenotype resulting in tumors with increased basal phenotype and high Wnt/β-catenin signaling. The object of this study was to test the hypothesis that Wnt5a can act to inhibit tumors formed by activation of Wnt/β-catenin signaling. To this end, we characterized tumor and non-tumor mammary tissue from MMTV-Wnt1 and double transgenic MMTV-Wnt1;MMTV-Wnt5a mice. Wnt5a containing mice demonstrated fewer tumors with increased latency when compared to MMTV-Wnt1 controls. Expression of markers for basal-like tumors was down-regulated in the tumors that formed in the presence of Wnt5a indicating a phenotypic switch. Reduced canonical Wnt signaling was detected in double transgenic tumors as a decrease in active β-catenin protein and a decrease in Axin2 mRNA transcript levels. In non-tumor tissues, over-expression of Wnt5a in MMTV-Wnt1 mammary glands resulted in attenuation of phenotypes normally observed in MMTV-Wnt1 glands including hyperbranching and increased progenitor and basal cell populations. Even though Wnt5a could antagonize Wnt/β-catenin signaling in primary mammary epithelial cells in culture, reduced Wnt/β-catenin signaling was not detected in non-tumor MMTV-Wnt1;Wnt5a tissue in vivo. The data demonstrate that Wnt5a suppresses tumor formation and promotes a phenotypic shift in MMTV-Wnt1 tumors.

Abstract PR5: Prognostic value of miRNAs in breast cancer: Molecular type and patient race

Background: MicroRNAs (miRNAs) are a class of conserved, non-coding RNAs that are dysregulated in various cancers, including breast cancers. The potential of miRNAs to serve as biomarkers for breast cancer diagnosis and prognosis is being explored, but their clinical value based on race/ethnicity and molecular subtypes (luminal and triple negative breast cancers, TNBCs) has not been examined. Thus, we evaluated expression levels of a panel of miRNAs in luminal (A and B) breast cancers and TNBCs of African Americans (Blacks) and non-Hispanic Caucasians (Whites). We further evaluated the prognostic value of miRNAs based on molecular type of breast cancer and patient race.

Methods: TaqMan® miRNA assays were used to quantify expression of miR-181a, miR181b, miR-21, miR-106a, miR-155, miR-210, miR-335, miR-206, and miR-126 in 105 breast cancers (luminal=51 and TNBCs=54) and their corresponding benign/normal tissues. Cancer tissuefrom 48 Blacks (luminal=23 and TNBCs=25) and 57 Whites (luminal=28 and TNBC=29) were analyzed. Fold change in the expression levels between tumor-normal pairs were determined using the 2-∆∆Ct method. A cutoff value for each miRNA was determined by utilizing the Cutoff Finder software application [PLoS ONE 7(12):e51862, 2012]. The cutoff values were used to categorize the tumors into two groups (High expression or positive and low expression or negative). The expression status of tumors was correlated with patient overall survival by univariate Kaplan-Meier analysis.

Results: Since the survival probabilities of Blacks and Whites with TNBCs (log rank, p=0.899) were similar, TNBCs from both racial groups were pooled. Similarly, no survival differences were noted in patients of both racial groups with luminal breast cancers (log rank, p=0.178). Therefore, luminal cancers of Blacks and Whites were also pooled together to perform survival analyses based on miRNA expression levels. MiRNA expression profiling studies indicated that, in both the racial groups, miR-181a, miR-181b, miR-21, miR-106a, miR-155, and miR-210 were up-regulated in luminal cancers and TNBCs. In contrast, miR-335, miR-206, and miR-126 were down-regulated in both molecular types. When the prognostic value of miRNAs was evaluated in each molecular type separately, it was found that over-expression of miR-106a (p=0.037) and miR-210 (p=0.039) were associated with poor prognosis of TNBCs. However, none of the evaluated miRNAs were useful in assessing the prognosis of patients with luminal cancers.

Conclusions: These findings suggest that increased expression of miR-106a and miR-210 were poor prognostic indicators of TNBCs collected from both Black and White patients. Additionally, our results suggest that in the evaluation of clinical utility of miRNAs molecular types of breast cancer should be considered. This study was funded in part by the National Cancer Institute of the National Institute of Health UAB/TU/MSM Partnership grant (U54 CA118948).

This abstract is also presented as Poster C21.

Citation Format: Balananda-Dhurjati Kumar Putcha, Trafina Jadhav, Shantel Hebert-Magee, Jeehyun Helen Bae, Andra R. Frost, Isam-Eldin Eltoum, Sejong Bae, Upender Manne. Prognostic value of miRNAs in breast cancer: Molecular type and patient race. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr PR5. doi:10.1158/1538-7755.DISP13-PR5

Abstract 2022: Importance of ECM and media permeation in 3D modeling of breast cancer

Background: Three dimensional (3D) culture is a more physiologically relevant method to model cell behavior in vitro than two dimensional culture. 3D modeling of cancer is of particular importance in drug development where predicting in vivo effectiveness is challenging. Not only is the 3D structure important for proper modeling of cancer but the response from the surrounding microenvironment, including the extracellular matrix (ECM) and fibroblasts, is also necessary to accurately predict drug response. A major hindrance to 3D culture is loss of cell viability due to nutrient limitation. Herein, we demonstrate the ability of our novel bioreactor system to prolong viability of 3D cultures and the importance of ECM composition in breast cancer modeling. Methods: To gain further understanding of the effect of different ECM on the 3D arrangement of breast cancer cells and breast fibroblasts, three different variations of ECM were tested: 1) 100% basement membrane (BM, reduced growth factor Matrigel) diluted to 9-12 μg/ml, 2) an equal volume of BM and Collagen I (50% BM + 50% Collagen I), and 3) 10% BM in Collagen I. MDA-MB-231 (231) breast cancer cells were grown in each ECM in monoculture or co-culture with breast fibroblasts (ratio of 2:1) for 3 or 7 days. The formation of cell aggregates, as seen in most infiltrating carcinomas of the breast, was assessed by image analysis. To improve viability, 250 μM channels penetrated the 3D co-cultures (consisting of 231 cells and fibroblasts (2:1) mixed into 10% BM/Collagen I) in our perfusion bioreactor system. Proliferation, measured by Ki-67 immunostaining, was compared over time in solid co-cultures and perfused and non-perfused co-cultures after 3 or 7 days. Results: In 3D monocultures, significantly greater cell aggregation was seen with 100% BM compared to 50% and 10% BM at both 3 and 7 days (p<0.002, ANOVA). A similar result was seen in 3D co-cultures with fibroblasts (p<0.002, ANOVA). 3D cultures without channels (solid) demonstrated a reduced Ki-67 labeling index over time (65% at 1 day, 35% at 3 days, and 8.5% at 7 days). Whereas, 3D co-cultures with channels, both perfused and non-perfused, had a more constant Ki-67 labeling index over time (49.6% at 3 days and 37.3% at 7 days with perfusion and 37.4% at 3 days and 34.4% at 7 days without perfusion). Conclusions: Using 3D co-culture with fibroblasts and ECM to model breast cancer recapitulates in vivo tumor-stromal interactions in breast carcinomas better than monocultures in 2D. The formulation of ECM affected cell arrangement, with the presence of BM promoting cell aggregation. The use of our perfusion bioreactor system improved cell proliferation in comparison to solid 3D cultures, which did not sustain growth over time. We anticipate that further refinement of our 3D culture system will allow more accurate investigation of tumor-stromal interactions and drug testing in breast cancer.

Citation Format: Kayla F. Goliwas, Lauren E. Marshall, Kun Yuan, Joel Berry, Andra R. Frost. Importance of ECM and media permeation in 3D modeling of breast cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2022. doi:10.1158/1538-7445.AM2014-2022

The presence of a cytopathologist increases the diagnostic accuracy of endoscopic ultrasound-guided fine needle aspiration cytology for pancreatic adenocarcinoma: a meta-analysis

OBJECTIVE

A meta-analysis has not been previously performed to evaluate critically the diagnostic accuracy of endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) of solely pancreatic ductal adenocarcinoma and address factors that have an impact on variability of accuracy. The aim of this study was to determine whether the presence of a cytopathologist, variability of the reference standard and other sources of heterogeneity significantly impacts diagnostic accuracy.

METHODS

We conducted a comprehensive search to identify studies, in which the pooled sensitivity, specificity, likelihood ratios for a positive or negative test (LR+, LR-) and summary receiver-operating curves (SROC) could be determined for EUS-FNA of the pancreas for ductal adenocarcinoma using clinical follow-up, and/or surgical biopsy or excision as the reference standard.

RESULTS

We included 34 distinct studies (3644 patients) in which EUS-FNA for a solid pancreatic mass was evaluated. The pooled sensitivity and specificity for EUS-FNA for pancreatic ductal adenocarcinoma was 88.6% [95% confidence interval (CI): 87.2-89.9] and 99.3% (95% CI: 98.7-99.7), respectively. The LR+ and LR- were 33.46 (95% CI: 20.76-53.91) and 0.11 (95% CI: 0.08-0.16), respectively. The meta-regression model showed rapid on-site evaluation (ROSE) (P = 0.001) remained a significant determinant of EUS-FNA accuracy after correcting for study population number and reference standard.

CONCLUSION

EUS-FNA is an effective modality for diagnosing pancreatic ductal adencarcinoma in solid pancreatic lesions, with an increased diagnostic accuracy when using on-site cytopathology evaluation.

Abstract 1406: Tgfbr1 haploinsufficiency is a potent modifier of breast cancer risk

Background: We previously identified a hypomorphic TGF-β type 1 receptor variant (TGFBR1*6A) that is associated with cancer risk and has impaired TGF-β signaling capability. Two recent large meta-analyses of case control studies have found a significant association between TGFBR1*6A and risk of several types of cancer, including breast cancer (ORs 1.16,1.01-1.34; 1.15,1.01-1.31). To investigate the effects of constitutively decreased TGFBR1 signaling on cancer development, we developed a novel mouse model of Tgfbr1 haploinsufficiency to mimic the decreased TGFBR1 signaling observed in individuals with higher risk of cancer. Using this model, we demonstrated that Apcmin;Tgfbr1+/- mice develop more than twice as many intestinal tumors as Apcmin controls. The aim of the current study was to assess the effects of Tgfbr1 haploinsufficiency on breast carcinogenesis by crossing Tgfbr1+/- mice with the MMTV-c-Neu mouse model.

Methods: Fully congenic (100%) FVB/N-Tgfbr1+/- mice were crossed with FVB/N-Neu mice, and female virgin progeny were kept for analysis. Mammary glands were collected from 10, 12, and 40 week-old Neu and Neu;Tgfbr1+/- mice. Mice assessed for tumor development were sacrificed 80 days after the initial tumor palpation or at the earliest sign of morbidity. Whole lungs, tumor tissue, and primary tumor cells were collected for additional analysis. Long-term evaluation of 2-year-old Tgfbr1+/+ and Tgfbr1+/- mice was also conducted to directly assess the impact of Tgfbr1 haploinsufficiency on mammary gland and lung development.

Results: Mammary gland whole mounts revealed that Neu;Tgfbr1+/- mice have more ductal branching at all time points compared to Neu mice. In the assessment of breast tumor development, Neu;Tgfbr1+/- mice were observed to have a significantly shorter tumor latency period (171 days) compared to Neu mice (220 days) (p=0.004). Seventy percent of Neu;Tgfbr1+/- mice (14/20) developed surface lung metastases, while 36.4% were observed in Neu mice (8/22), a borderline significant difference (p=0.061). The TGF-β-mediated growth inhibition of Neu;Tgfbr1+/- primary tumor cells was 32.2% lower than that of Neu tumor cells (p=0.007). Neu;Tgfbr1+/- tumor cells and tissue had significantly reduced Smad2/3 phosphorylation and total Cdkn1b (p27Kip1) expression compared to Neu mice. Long-term evaluation of Tgfbr1+/- and wild-type mice revealed no signs of mammary gland hyperplasia or differences in lung fibrosis in either group.

Conclusion: This study is the first in vivo evidence that Tgfbr1 haploinsufficiency promotes breast carcinogenesis by increasing breast cancer proliferation. The relevance of this data to human breast cancer warrants additional investigations into the effects of decreased TGFBR1 signaling on tumor development and progression and identifies potential targets for prevention and treatment.

Citation Format: Michael J. Pennison, Diana S. Rosman-Balzer, Lakisha Moore-Smith, Jacquelyn W. Zimmerman, Trenton R. Schoeb, Andra R. Frost, Ming Zhang, Peter M. Siegel, Boris C. Pasche. Tgfbr1 haploinsufficiency is a potent modifier of breast cancer risk. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1406. doi:10.1158/1538-7445.AM2013-1406

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Abstract 1816: Blocking synthesis of oncogenic proteins in breast tumor cells through pharmacologic inhibition of the IRES

Many genes involved in the control of cell proliferation and survival, i.e. those most important to cancer biology, are now known to be regulated specifically at the translational (RNA to protein) level. An intriguing translation-regulatory element is the internal ribosomal entry site (IRES), which provides a mechanism by which oncogene-associated mRNAs can be translated independently of the global controls on protein synthesis. Tumor cells may rely on IRES-mediated translation of key oncogenic proteins to promote their own survival and proliferation under adverse conditions or exposure to cytotoxic chemotherapy. We have previously shown that the mRNA for type 1 insulin-like growth factor receptor (IGF1R) contains an IRES immediately upstream of the initiation codon. We have characterized the RNA-binding proteins that regulate the IRES, and elucidated the mechanism by which the IRES recruits the 40S ribosome. We have accumulated evidence that IGF1R IRES activity may be aberrantly upregulated in human breast cancer cells and tissues. Based on these observations, we hypothesized that IRES-mediated translation of key oncogenic proteins could be a rational target in cancer therapeutics with pharmacologic potential. Using T47D breast cancer cells genetically engineered to produce firefly luciferace under control of the IGF1R IRES, and a similar construct from which the IRES has been deleted as a control, a high throughput screen of 135000 compounds was performed. Four promising lead compounds with distinct chemical scaffolds have been identified and further validated in dose response titrations. Their specificity in blocking IRES-mediated translation was shown in reticulocyte lysates using a bicistronic construct containing the IGF1R IRES. The compounds inhibited de novo synthesis of IGF1R in T47D and SUM159 breast cancer cells with an IC50 on Western blots between <2 and 10 µg/mL. Consistent with the importance of IGF1R in tumor cell survival, the IRES inhibitors induced massive apoptosis in the same cell lines with a toxic concentration-90 in the range of <1 - 8 µg/mL. In contrast, normal human mammary epithelial cells tolerated prolonged exposure to IGF1R IRES inhibitors. A high degree of synergism (3+ to 4+) was observed when the IRES inhibitor was combined with a cytotoxic chemotherapeutic agent (doxorubicin), with combination indices of 0.153 - 0.334 and dose reduction indices for doxorubicin of 5.0-14.9. Furthermore, these compounds were shown to completely block the clonogenic survival and the formation of mammospheres in both ER positive and negative breast cancer cell lines, suggesting that cancer stem cells are sensitive to IRES inhibition. The pharmacologic inhibition of IRES-mediated translation is a novel strategy to modulate oncogene expression and could represent a new paradigm in cancer therapeutics.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1816. doi:1538-7445.AM2012-1816

Targeting ErbB3-mediated stromal-epithelial interactions in pancreatic ductal adenocarcinoma

Background:

We sought to investigate the role of ErbB3-mediated signalling on the interaction between pancreatic cancer-associated fibroblasts (CAF) and carcinoma cells in an effort to disrupt tumourigenic pancreatic ductal adenocarcinoma (PDAC) stromal–epithelial cross-communication.

Methods:

Primary CAF cultures were established from human PDAC surgical specimens. AsPC-1 pancreatic cancer cell murine subcutaneous xenografts were developed in the presence and absence of CAF and were subsequently treated with epidermal growth factor receptor (EGFR) inhibitors (erlotinib) and ErbB3 inhibitors (MM-121, monoclonal ErbB3 antibody).

Results:

Cancer-associated fibroblasts were found to secrete neuregulin-1 (NRG-1), which promoted proliferation via phosphorylation of ErbB3 and AKT in AsPC-1 PDAC cells. This signalling cascade was effectively inhibited both in vitro and in vivo by specific ErbB3 blockade with MM-121, with greater degree of tumourigenesis inhibition when combined with erlotinib. The CAF–AsPC-1 pancreatic cancer xenografts reached significantly greater tumour volume than those xenografts lacking CAF and were resistant to the anti-tumour effects of EGFR inhibition with erlotinib.

Conclusion:

Cancer-associated fibroblasts-derived NRG-1 promote PDAC tumourigenesis via ErbB3-AKT signalling and overcomes single-agent EGFR inhibition. Disruption of this stromally mediated tumourigenic mechanism is best obtained through combined EGFR-ErbB3 inhibition with both erlotinib and MM-121. We have identified the NRG-1/ErbB3 axis as an attractive molecular target for the interruption of tumourigenic stromal–epithelial interactions within the PDAC microenvironment.

Gli1 enhances migration and invasion via up-regulation of MMP-11 and promotes metastasis in ERα negative breast cancer cell lines

Gli1 is an established oncogene and its expression in Estrogen Receptor (ER) α negative and triple negative breast cancers is predictive of a poor prognosis; however, the biological functions regulated by Gli1 in breast cancer have not been extensively evaluated. Herein, Gli1 was over-expressed or down-regulated (by RNA interference and by expression of the repressor form of Gli3) in the ERα negative, human breast cancer cell lines MDA-MB-231 and SUM1315. Reduced expression of Gli1 in these two cell lines resulted in a decrease in migration and invasion. Gli1 over-expression increased the migration and invasion of MDA-MB-231 cells with a corresponding increase in expression of MMP-11. Silencing MMP-11 in MDA-MB-231 cells that over-expressed Gli1 abrogated the Gli1-induced enhancement of migration and invasion. Sustained suppression of Gli1 expression decreased growth of MDA-MB-231 in vitro by increasing apoptosis and decreasing proliferation. In addition, silencing of Gli1 reduced the numbers and sizes of pulmonary metastases of MDA-MB-231 in an in vivo experimental metastasis assay. In summary, Gli1 promotes the growth, survival, migration, invasion and metastasis of ERα negative breast cancer. Additionally, MMP-11 is up-regulated by Gli1 and mediates the migration and invasion induced by Gli1 in MDA-MB-231.

Gli3 mediates cell survival and sensitivity to cyclopamine in pancreatic cancer

Activation of the hedgehog (HH) pathway plays a critical role in the development and continued growth of pancreatic adenocarcinoma (PAC). Cyclopamine, a HH pathway inhibitor, has been shown to suppress PAC cell proliferation in vitro and in vivo. However, the molecular basis of response to cyclopamine has not been fully elucidated nor have genes that predict sensitivity to this compound been identified. To better understand these features of HH pathway inhibition, we evaluated the biological and molecular effects of cyclopamine in vitro. The viability of 9 human PAC cell lines following cyclopamine exposure was determined using MTS assay. Proliferation and induction of apoptosis in treated cells were examined by bromo-deoxyuridine incorporation, caspase activation, and mitochondrial membrane potential. Gene expression before and after cyclopamine treatment was determined using Taqman real-time quantitative polymerase chain reaction (RTQ-PCR) and Taqman low-density array (TLDA). Among the cell lines examined, cyclopamine IC50 values ranged from 8.79 to >30 µM. Response to cyclopamine included reduced cell proliferation and induction of apoptosis with and without mitochondrial membrane depolarization. Regression analysis revealed that GLI3 expression significantly correlated with cyclopamine resistance (r = 0.80; p = 0.0102). Knockdown of GLI3 using siRNAs increased sensitivity to cyclopamine. In addition, GLI3 siRNAs decreased PAC cell viability and reduced expression of genes involved in HH signaling (Patched 1 and GLI1) and cell proliferation, similar to cyclopamine. These effects were not observed in PAC cells with undetectable GLI3 expression. These data suggest that Gli3 mediates cell survival and sensitivity to cyclopamine in pancreatic cancer.

Epithelial transformation by KLF4 requires Notch1 but not canonical Notch1 signaling

The transcription factors Notch1 and KLF4 specify epithelial cell fates and confer stem cell properties. Suggesting a functional relationship, each gene can act to promote or suppress tumorigenesis in a context-dependent manner, and alteration of KLF4 or Notch pathway genes in mice gives rise to similar phenotypes. Activation of a conditional allele of KLF4 in RK3E epithelial cells rapidly induces expression of Notch1 mRNA and the active, intracellular form of Notch1. KLF4-induced transformation was suppressed by knockdown of endogenous Notch1 using siRNA or an inhibitor of gamma-secretase. Chromatin immunoprecipitation assay shows that KLF4 binds to the proximal Notch1 promoter in human mammary epithelial cells, and siRNA-mediated suppression of KLF4 in human mammary cancer cells results in reduced expression of Notch1. Furthermore, KLF4 and Notch1 expression are correlated in primary human breast tumors (N = 89; Pearson analysis, r > 0.5, p < 0.0001). Like KLF4, Notch1 was previously shown to induce transformation of rat cells immortalized with adenovirus E1A, similar to RK3E cells. We therefore compared the signaling requirements for Notch1- or KLF4-induced malignant transformation of RK3E. As expected, transformation by Notch1 was suppressed by dominant-negative CSL or MAML1, inhibitors of canonical Notch1 signaling. However, these inhibitors did not suppress transformation by KLF4. Therefore, while KLF4-induced transformation requires Notch1, canonical Notch1 signaling is not required, and Notch1 may signal through a distinct pathway in cells with increased KLF4 activity. These results suggest that KLF4 could contribute to breast tumor progression by activating synthesis of Notch1 and by promoting signaling through a non-canonical Notch1 pathway.

Primary cilia are decreased in breast cancer: analysis of a collection of human breast cancer cell lines and tissues

Primary cilia (PC) are solitary, sensory organelles that are critical for several signaling pathways. PC were detected by immunofluorescence of cultured cells and breast tissues. After growth for 7 days in vitro, PC were detected in ∼70% of breast fibroblasts and in 7-19% of epithelial cells derived from benign breast (184A1 and MCF10A). In 11 breast cancer cell lines, PC were present at a low frequency in four (from 0.3% to 4% of cells), but were absent in the remainder. The cancer cell lines with PC were all of the basal B subtype, which is analogous to the clinical triple-negative breast cancer subtype. Furthermore, the frequency of PC decreased with increasing degree of transformation/progression in the MCF10 and MDA-MB-435/LCC6 isogenic models of cancer progression. In histologically normal breast tissues, PC were frequent in fibroblasts and myoepithelial cells and less common in luminal epithelial cells. Of 26 breast cancers examined, rare PC were identified in cancer epithelial cells of only one cancer, which was of the triple-negative subtype. These data indicate a decrease or loss of PC in breast cancer and an association of PC with the basal B subtype. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Northwestern profiling of potential translation-regulatory proteins in human breast epithelial cells and malignant breast tissues: evidence for pathological activation of the IGF1R IRES

Genes involved in the control of cell proliferation and survival (those genes most important to cancer pathogenesis) are often specifically regulated at the translational level, through RNA-protein interactions involving the 5'-untranslated region of the mRNA. IGF1R is a proto-oncogene strongly implicated in human breast cancer, promoting survival and proliferation of tumor cells, as well as metastasis and chemoresistance. Our lab has focused on the molecular mechanisms regulating IGF1R expression at the translational level. We previously discovered an internal ribosome entry site (IRES) within the 5'-untranslated region of the human IGF1R mRNA, and identified and functionally characterized two individual RNA-binding proteins, HuR and hnRNP C, which bind the IGF1R 5'-UTR and differentially regulate IRES activity. Here we have developed and implemented a high-resolution northwestern profiling strategy to characterize, as a group, the full spectrum of sequence-specific RNA-binding proteins potentially regulating IGF1R translational efficiency through interaction with the 5'-untranslated sequence. The putative IGF1R IRES trans-activating factors (ITAFs) are a heterogeneous group of RNA-binding proteins including hnRNPs originating in the nucleus as well as factors tightly associated with ribosomes in the cytoplasm. The IGF1R ITAFs can be categorized into three distinct groups: (a) high molecular weight external ITAFs, which likely modulate the overall conformation of the 5'-untranslated region of the IGF1R mRNA and thereby the accessibility of the core functional IRES; (b) low molecular weight external ITAFs, which may function as general chaperones to unwind the RNA, and (c) internal ITAFs which may directly facilitate or inhibit the fundamental process of ribosome recruitment to the IRES. We observe dramatic changes in the northwestern profile of non-malignant breast cells downregulating IGF1R expression in association with acinar differentiation in 3-D culture. Most importantly, we are able to assess the RNA-binding activities of these putative translation-regulatory proteins in primary human breast surgical specimens, and begin to discern positive correlations between individual ITAFs and the malignant phenotype. Together with our previous findings, these new data provide further evidence that pathological dysregulation of IGF1R translational control may contribute to development and progression of human breast cancer, and breast metastasis in particular.

Dual effects of TGF-beta on ERalpha-mediated estrogenic transcriptional activity in breast cancer

Background

TGF-β resistance often develops in breast cancer cells that in turn overproduce this cytokine to create a local immunosuppressive environment that fosters tumor growth and exacerbates the invasive and metastatic behavior of the tumor cells themselves. Smads-mediated cross-talk with the estrogen receptor has been implied to play an important role in development and/or progression of breast cancer. We investigated how TGF-β regulates ERα-induced gene transcription and potential mechanisms of frequent TGF-β resistance in breast cancer.

Methods

Effect of TGF-β on ERα-mediated gene transcription was investigated in breast cancer cell lines using transient transfection, real-time PCR, sequential DNA precipitation, and small interfering RNA assays. The expression of Smads on both human breast cancer cell lines and ERα-positive human breast cancer tissue was evaluated by immunofluorescence and immunohistochemical assays.

Results

A complex of Smad3/4 mediates TGF-β inhibition of ERα-mediated estrogenic activity of gene transcription in breast cancer cells, and Smad4 is essential and sufficient for such repression. Either overexpression of Smad3 or inhibition of Smad4 leads to the "switch" of TGF-β from a repressor to an activator. Down-regulation and abnormal cellular distribution of Smad4 were associated with some ERα-positive infiltrating human breast carcinoma. There appears a dynamic change of Smad4 expression from benign breast ductal tissue to infiltrating ductal carcinoma.

Conclusion

These results suggest that aberrant expression of Smad4 or disruption of Smad4 activity lead to the loss of TGF-β suppression of ERα transactivity in breast cancer cells.

Gli1 promotes cell survival and is predictive of a poor outcome in ERalpha-negative breast cancer

Gli1 is a transcription factor and oncogene with documented roles in the progression of several cancer types, including cancers of the skin and pancreas. The contribution of Gli1 to the progression of breast cancer is less established. In order to investigate the functional impact of Gli1 in breast cancer, expression of Gli1 and its contribution to cell growth was assessed in breast cancer cell lines. These in vitro results were compared to expression of Gli1, determined by immunohistochemistry, in 171 breast cancers. In these cancers, the association of Gli1 with expression of estrogen receptor alpha (ERalpha) and progesterone receptor (PR), ErbB2, p53, the rate of proliferation, and clinicopathologic parameters and outcome was assessed. Expression of Gli1 and ERalpha mRNA was strongly correlated in ERalpha-positive cell lines (r = 0.999). Treatment with estrogen increased expression of Gli1 in 2 of 3 ERalpha-positive cell lines; this increase was prevented by treatment with the ERalpha-specific antagonist MPP. Silencing of Gli1 by shRNA markedly reduced the survival of two ERalpha-negative cell lines, but caused only a modest reduction in ERalpha-positive cell lines. In breast cancer tissues, cancers with nuclear localization of Gli1 had a higher ERalpha (P=0.027) and lower p53 expression (P=0.017) than those without nuclear localization of Gli1. However, nuclear localization of Gli1 was predictive of a poorer cancer-specific survival in ERalpha-negative, including triple negative, cancers (P = 0.005), but not ERalpha-positive cancers. In conclusion, we demonstrate a positive association between expression of Gli1 and ERalpha; however, our data indicate a greater functional effect of Gli1 in ERalpha-negative cancers.

A shift from nuclear to cytoplasmic breast cancer metastasis suppressor 1 expression is associated with highly proliferative estrogen receptor-negative breast cancers

BACKGROUND/AIMS

To determine breast cancer metastasis suppressor 1 (BRMS1) expression in breast cancers and the efficacy of BRMS1 as a prognostic indicator, BRMS1 expression was assessed in two sets of breast cancer tissues.

METHODS

Epithelial cells from 36 frozen samples of breast cancers and corresponding normal breast were collected by laser capture microdissection and assessed for BRMS1 by quantitative RT-PCR and immunohistochemistry. BRMS1 was also evaluated by immunohistochemistry in a tissue microarray of 209 breast cancers and correlated with indicators of prognosis [estrogen receptor (ER), progesterone receptor (PR), ErbB2, p53, p27(Kip1), Bcl2 and Ki-67].

RESULTS

BRMS1 mRNA and protein were higher in 94 and 81%, respectively, of breast cancers than in corresponding normal epithelium. BRMS1 localization was predominantly nuclear, but 60-70% of cancers also exhibited cytoplasmic immunostaining. Breast cancers with lower nuclear than cytoplasmic BRMS1 (nuclear score - cytoplasmic score < or =0; 11% of cancers) had lower ER, lower PR and higher Ki-67 expression. There was also a trend toward poorer overall survival in this group of cancers, but this was only of borderline significance (p = 0.073). In Cox proportional hazards models, loss of nuclear BRMS1 was not a significant predictor of overall survival.

CONCLUSIONS

Loss of nuclear BRMS1 was associated with ER-negative cancers and a high rate of proliferation, but was not an independent indicator of prognosis.

Loss of TGF-beta or Wnt5a results in an increase in Wnt/beta-catenin activity and redirects mammary tumour phenotype

Introduction

The tumour-suppressive effects of transforming growth factor-beta (TGF-β) are well documented; however, the mechanistic basis of these effects is not fully understood. Previously, we showed that a non-canonical member of the Wingless-related protein family, Wnt5a, is required for TGF-β-mediated effects on mammary development. Several lines of evidence support the hypothesis that Wnt5a acts as a tumour suppressor. In addition, it has been shown that Wnt5a can antagonise canonical Wnt/β-catenin signalling in various cell types. Here we test the hypothesis that TGF-β and Wnt5a can antagonise Wnt/β-catenin signalling and redirect mammary tumour phenotype. The results provide a new mechanism for the tumour-suppressive effects of TGF-β.

Methods

Wnt/β-catenin signalling was measured in tumours with altered TGF-β (dominant-negative TGF-β type II receptor, DNIIR) or Wnt5a (Wnt5a^-/-) signalling as the accumulation of nuclear β-catenin using both confocal microscopy and cell fractionation. RT-PCR was used to measure the expression of Wnt/β-catenin target genes. Sca1 expression was determined by western blot and keratin (K) 6- and K14-positive populations were determined by immunohistochemistry.

Results

Loss of TGF-β or Wnt5a signalling resulted in stabilisation of nuclear β-catenin and expression of Wnt/β-catenin target genes suggesting that TGF-β and Wnt5a act to inhibit Wnt/β-catenin signalling in mammary epithelium. Increased expression of Sca-1 was observed in developing DNIIR and Wnt5a-/- mammary glands. DNIIR and Wnt5a-/- tumours demonstrated an expanded population of K6- and K14-expressing cells typically seen in Wnt/β-catenin-induced tumours.

Conclusions

The key findings here are that: TGF-β and Wnt5a regulate Wnt/β-catenin activity; and loss of TGF-β and Wnt5a redirect the phenotype of tumours so that they resemble tumours induced by activation of Wnt/β-catenin. The findings suggest a new mechanism for the tumour-suppressive effects of TGF-β.

Identification of molecular distinctions between normal breast-associated fibroblasts and breast cancer-associated fibroblasts

Stromal fibroblasts influence the behavior of breast epithelial cells. Fibroblasts derived from normal breast (NAF) inhibit epithelial growth, whereas fibroblasts from breast carcinomas (CAF) have less growth inhibitory capacity and can promote epithelial growth. We sought to identify molecules that are differentially expressed in NAF versus CAF and potentially responsible for their different growth regulatory abilities. To determine the contribution of soluble molecules to fibroblast–epithelial interactions, NAF were grown in 3D, transwell or direct contact co-cultures with MCF10AT epithelial cells. NAF suppressed proliferation of MCF10AT in both direct contact and transwell co-cultures, but this suppression was significantly greater in direct co-cultures, indicating involvement of both soluble and contact factors. Gene expression profiling of early passage fibroblast cultures identified 420 genes that were differentially expressed in NAF versus CAF. Of the eight genes selected for validation by real-time PCR, FIBULIN 1, was overexpressed in NAF, and DICKKOPF 1, NEUREGULIN 1, PLASMINOGEN ACTIVATOR INHIBITOR 2, and TISSUE PLASMINOGEN ACTIVATOR were overexpressed in CAF. A higher expression of FIBULIN 1 in normal- than cancer-associated fibroblastic stroma was confirmed by immunohistochemistry of breast tissues. Among breast cancers, stromal expression of Fibulin 1 protein was higher in estrogen receptor α-positive cancers and low stromal expression of Fibulin 1 correlated with a higher proliferation of cancer epithelial cells. In conclusion, expression profiling of NAF and CAF cultures identified many genes with potential relevance to fibroblast–epithelial interactions in breast cancer. Furthermore, these early passage fibroblast cultures can be representative of gene expression in stromal fibroblasts in vivo.

Prevention of KLF4-mediated tumor initiation and malignant transformation by UAB30 rexinoid

The transcription factor KLF4 acts in post-mitotic epithelial cells to promote differentiation and functions in a context-dependent fashion as an oncogene. In the skin KLF4 is co-expressed with the nuclear receptors RARgamma and RXRalpha, and formation of the skin permeability barrier is a shared function of these three proteins. We utilized a KLF4-transgenic mouse model of skin cancer in combination with cultured epithelial cells to examine functional interactions between KLF4 and retinoic acid receptors. In cultured cells, activation of a conditional, KLF4-estrogen receptor fusion protein by 4-hydroxytamoxifen resulted in rapid upregulation of transcripts for nuclear receptors including RARgamma and RXRalpha. We tested retinoids in epithelial cell transformation assays, including an RAR-selective agonist (all-trans RA), an RXR-selective agonist (9-cis UAB30, rexinoid), and a pan agonist (9-cis RA). Unlike for several other genes, transformation by KLF4 was inhibited by each retinoid, implicating distinct nuclear receptor heterodimers as modulators of KLF4 transforming activity. When RXRalpha expression was suppressed by RNAi in cultured cells, transformation was promoted and the inhibitory effect of 9-cis UAB30 was attenuated. Similarly as shown for other mouse models of skin cancer, rexinoid prevented skin tumor initiation resulting from induction of KLF4 in basal keratinocytes. Rexinoid permitted KLF4 expression and KLF4-induced cell cycling, but attenuated the KLF4-induced misexpression of cytokeratin 1 in basal cells. Neoplastic lesions including hyperplasia, dysplasia and squamous cell carcinoma-like lesions were prevented for up to 30 days. Taken together, the results identify retinoid receptors including RXRalpha as ligand-dependent inhibitors of KLF4-mediated transformation or tumorigenesis.

Vascular endothelial growth factor reduces tamoxifen efficacy and promotes metastatic colonization and desmoplasia in breast tumors

Clinical studies have shown that decreased tamoxifen effectiveness correlates with elevated levels of vascular endothelial growth factor (VEGF)-A(165) in biopsy samples of breast cancers. To investigate the mechanisms underlying tamoxifen resistance and metastasis, we engineered the estrogen receptor (ER)-positive MCF-7 human breast cancer cell line to express VEGF to clinically relevant levels in a doxycycline-regulated manner. Induction of VEGF expression in orthotopically implanted xenografts that were initially tamoxifen responsive and noninvasive resulted in tamoxifen-resistant tumor growth and metastasis to the lungs. Lung metastases were also observed in a VEGF-dependent manner following tail vein injection of tumor cells. At both primary and metastatic sites, VEGF-overexpressing tumors exhibited extensive fibroblastic stromal content, a clinical feature called desmoplasia. VEGF-induced metastatic colonies were surrounded by densely packed stromal cells before detectable angiogenesis, suggesting that VEGF is involved in the initiation of desmoplasia. Because expression of VEGF receptors R1 and R2 was undetectable in these tumor cells, the observed VEGF effects on reduction of tamoxifen efficacy and metastatic colonization are most likely mediated by paracrine signaling that enhances tumor/stromal cell interactions and increases the level of desmoplasia. This study reveals new roles for VEGF in breast cancer progression and suggests that combination of antiestrogens and VEGF inhibitors may prolong tamoxifen sensitivity and prevent metastasis in patients with ER-positive tumors.

Sulfotransferase 2B1b in human breast: differences in subcellular localization in African American and Caucasian women

Breast cancer (BC) is the most commonly diagnosed cancer among American women; however, the development of post-menopausal BC is significantly lower in African Americans as compared to Caucasians. Hormonal stimulation is important in BC development and differences in the conversion of dehydroepiandrosterone (DHEA) into estrogens may be involved in the lower incidence of post-menopausal BC in African American women. DHEA sulfation by sulfotransferase 2B1b (SULT2B1b) is important in regulating the conversion of DHEA into estrogens in tissues. SULT2B1b is localized in both cytosol and nuclei of some tissues including cancerous and associated-normal breast tissue. Immunohistochemical staining was used to evaluate the total expression and subcellular localization of SULT2B1b in African American and Caucasian breast tissues. Cell fractionation, immunoblot analysis and sulfation assays were used to characterize the subcellular expression and activity of SULT2B1b in BC tissues and T-47D breast adenocarcinoma cells. Immunohistochemical analysis of SULT2B1b showed that African Americans had a significantly greater amount of SULT2B1b in epithelial cells of associated-normal breast tissue as compared to Caucasians. Also, more SULT2B1b in African American associated-normal breast epithelial cells was localized in the nuclei than in Caucasians. Equivalent levels of SULT2B1b were detected in breast adenocarcinoma tissues from both African American and Caucasian women. Nuclei isolation and immunoblot analysis of both BC tissue and human T-47D breast adenocarcinoma cells demonstrated that SULT2B1b is present in nuclei and cytoplasm.

Epigenetic silencing contributes to the loss of BRMS1 expression in breast cancer

Breast Cancer Metastasis Suppressor 1 (BRMS1) suppresses metastasis of human breast cancer, ovarian cancer and melanoma in athymic mice. Studies have also shown that BRMS1 is significantly downregulated in some breast tumors, especially in metastatic disease. However, the mechanisms which regulate BRMS1 expression are currently unknown. Upon examination of the BRMS1 promoter region by methylation specific PCR (MSP) analysis, we discovered a CpG island (-3477 to -2214), which was found to be hypermethylated across breast cancer cell lines. A panel of 20 patient samples analyzed showed that 45% of the primary tumors and 60% of the matched lymph node metastases, displayed hypermethylation of BRMS1 promoter. Furthermore, we found a direct correlation between the methylation status of the BRMS1 promoter in the DNA isolated from tissues, with the loss of BRMS1 expression assessed by immunohistochemistry. There are several studies investigating the mechanism by which BRMS1 suppresses metastasis; however thus far there is no study that reports the cause(s) of loss of BRMS1 expression in aggressive breast cancer. Here we report for the first time that BRMS1 is a novel target of epigenetic silencing; and aberrant methylation in the BRMS1 promoter may serve as a cause of loss of its expression.

An engineering approach to modelling, decision support and control for sustainable systems

Engineering research and development contributes to the advance of sustainable agriculture both through innovative methods to manage and control processes, and through quantitative understanding of the operation of practical agricultural systems using decision models. This paper describes how an engineering approach, drawing on mathematical models of systems and processes, contributes new methods that support decision making at all levels from strategy and planning to tactics and real-time control. The ability to describe the system or process by a simple and robust mathematical model is critical, and the outputs range from guidance to policy makers on strategic decisions relating to land use, through intelligent decision support to farmers and on to real-time engineering control of specific processes. Precision in decision making leads to decreased use of inputs, less environmental emissions and enhanced profitability-all essential to sustainable systems.

Laser capture microdissection

Laser capture microdissection (LCM) offers a rapid and precise method of isolating and removing specified cells from complex tissues for subsequent analysis of their RNA, DNA, or protein content, thereby allowing assessment of the role of the cell type in the normal physiologic or disease process being studied. In this unit, protocols for the preparation of mammalian frozen tissues, fixed tissues, and cytologic specimens for LCM, including hematoxylin and eosin staining, are presented, as well as a protocol for the performance of LCM utilizing the PixCell I or II Laser Capture Microdissection System manufactured by Arcturus Engineering. Also provided is a protocol for tissue processing and paraffin embedding, and recipes for lysis buffers for the recovery of nucleic acids and proteins. The Commentary section addresses the types of specimens that can be utilized for LCM and approaches to staining of specimens for cell visualization. Emphasis is placed on the preparation of tissue or cytologic specimens as this is critical to effective LCM.

Hedgehog signaling in mammary gland development and breast cancer

The Hedgehog pathway is critical for many developmental processes, including the formation of several epidermal appendages. In the mammary gland strict regulation of the Hedgehog pathway is required for normal development. Alterations in Hedgehog signaling result in defects in both the embryonic and postnatal mammary gland. Activation of Hedgehog signaling either by mutation or misexpression of pathway members can lead to the development and/or progression of cancers in multiple organs. This review addresses the current understanding and controversies of Hedgehog signaling in mammary gland development and its potential role in promoting breast carcinogenesis and cancer progression.

Human breast fibroblasts inhibit growth of the MCF10AT xenograft model of proliferative breast disease

Stromal fibroblasts are important for normal breast homeostasis and regulation of epithelial growth; however, this regulatory function is altered during carcinogenesis. To study the role of fibroblasts in the development of breast cancer, fibroblasts derived from normal breast (NAFs) were incorporated into the MCF10AT xenograft model of progressive proliferative breast disease. The persistence of human NAFs in xenografts was established by intracellular labeling and tyramide-coupled fluorescent in situ hybridization. Overall, the number of MCF10AT epithelial structures was decreased, and the rate of epithelial cell apoptosis was increased in xenografts containing NAFs. However, these changes were primarily in low-grade epithelial structures, corresponding to normal or mildly hyperplastic ductal epithelium. The level and rate of apoptosis of high-grade epithelial structures, corresponding to in situ and invasive carcinoma, were not consistently altered by NAFs. In addition, there was variability in the growth-inhibitory capacity of NAFs derived from different individuals. NAFs induced changes in the morphology of high-grade MCF10AT structures and in xenograft stroma, including the composition of extracellular matrix, and increased angiogenesis and lymphocytic infiltration. These findings imply that NAFs can inhibit the growth of normal and hyperplastic epi-thelium but are less able to regulate the more transformed epithelial cells that arise during carcino-genesis.

Requirement of KISS1 secretion for multiple organ metastasis suppression and maintenance of tumor dormancy

BACKGROUND

The KISS1 protein suppresses metastasis of several tumor models without blocking orthotopic tumor growth, but the mechanism remains elusive. For its role in human sexual maturation, KISS1 protein is secreted and processed to kisspeptins, which bind to the G protein-coupled receptor GPR54. We tested the hypothesis that KISS1 secretion is required for metastasis suppression via GPR54.

METHODS

KISS1 containing an internal FLAG epitope with (KFM) or without (KFMdeltaSS) a signal sequence was transfected into C8161.9 human melanoma cells, which do not express endogenous KISS1. Whole-cell lysates and conditioned medium from C8161.9(KFM) and C8161.9(KFMdeltaSS) cells were collected and analyzed for kisspeptins by immunoprecipitation and enzyme-linked immunosorbent assay. GPR54 levels were measured using real-time reverse transcription-polymerase chain reaction. The ability of conditioned medium from C8161.9(KFM) and C8161.9(KFMdeltaSS) cells to stimulate calcium mobilization in GPR54-expressing Chinese hamster ovary cells (CHO-G) and in C8161.9 cells was evaluated. Metastasis was monitored in athymic mice (groups of 10 per experiment) that were injected with C8161.9(KFM) or C8161.9(KFMdeltaSS) cells labeled with enhanced green fluorescent protein. Survival of mice injected with C8161.9 or C8161.9(KFM) cells was analyzed by Kaplan-Meier methods.

RESULTS

Full-length KFM and KFMdeltaSS were detected in whole-cell lysates of C8161.9(KFM) and C8161.9(KFMdeltaSS) cells, respectively, but kisspeptins were detected only in conditioned medium of C8161.9(KFM) cells. In vivo, C8161.9(KFM), but not C8161.9(KFMdeltaSS), cells were suppressed for metastasis to lung, eye, kidney, and bone, with corresponding differences in mouse survival (median > 120 versus 42 days). C8161.9(KFM) cells seeded mouse lungs but did not form macroscopic metastases. Conditioned medium from C8161.9(KFM), but not C8161.9(KFMdeltaSS), cells stimulated calcium mobilization in CHO-G cells. GPR54 expression was low in C8161.9 cells, which were not stimulated by conditioned medium from C8161.9(KFM) cells.

CONCLUSIONS

KISS1 secretion was required for multiple organ metastasis suppression and for maintenance of disseminated cells in a dormant state. The absence of GPR54 expression in C8161.9 cells (whose metastatic spread was suppressed by KFM) suggests that metastasis suppression is not mediated through this receptor. The results imply the existence of another KISS1 receptor and/or paracrine signaling. The findings raise the possibility that soluble KISS1, kisspeptins, or mimetics could be used to maintain tumor dormancy, rendering treatment of already disseminated tumor cells (i.e., micrometastases) a legitimate target.

Loss of breast cancer metastasis suppressor 1 protein expression predicts reduced disease-free survival in subsets of breast cancer patients

PURPOSE

This study aims to determine the effect of loss of breast cancer metastasis suppressor 1 (BRMS1) protein expression on disease-free survival in breast cancer patients stratified by estrogen receptor (ER), progesterone receptor (PR), or HER2 status, and to determine whether loss of BRMS1 protein expression correlated with genomic copy number changes.

EXPERIMENTAL DESIGN

A tissue microarray immunohistochemical analysis was done on tumors of 238 newly diagnosed breast cancer patients who underwent surgery at the Cleveland Clinic between January 1, 1995 and December 31, 1996, and a comparison was made with 5-year clinical follow-up data. Genomic copy number changes were determined by array-based comparative genomic hybridization in 47 breast cancer cases from this population and compared with BRMS1 staining.

RESULTS

BRMS1 protein expression was lost in nearly 25% of cases. Patients with tumors that were PR negative (P=0.006) or HER2 positive (P=0.039) and <50 years old at diagnosis (P=0.02) were more likely to be BRMS1 negative. No overall correlation between BRMS1 staining and disease-free survival was observed. A significant correlation, however, was seen between loss of BRMS1 protein expression and reduced disease-free survival when stratified by either loss of ER (P=0.008) or PR (P=0.029) or HER2 overexpression (P=0.026). Overall, there was poor correlation between BRMS1 protein staining and copy number status.

CONCLUSIONS

These data suggest a mechanistic relationship between BRMS1 expression, hormone receptor status, and HER2 growth factor. BRMS1 staining could potentially be used in patient stratification in conjunction with other prognostic markers. Further, mechanisms other than genomic deletion account for loss of BRMS1 gene expression in breast tumors.

Human cytosolic sulfotransferase 2B1: isoform expression, tissue specificity and subcellular localization

Sulfation is an important Phase II conjugation reaction involved in the synthesis and metabolism of steroids in humans. Two different isoforms (2B1a and 2B1b) are encoded by the sulfotransferase (SULT) 2B1 gene utilizing different start sites of transcription resulting in the incorporation of different first exons. SULT2B1a and SULT2B1b are 350 and 365 amino acids in length, respectively, and the last 342 aa are identical. Message for both SULT2B1 isoforms is present in human tissues although SULT2B1b message is generally more abundant. However, to date only SULT2B1b protein has been detected in human tissues or cell lines. SULT2B1b is localized in the cytosol and/or nuclei of human cells. A unique 3'-extension of SULT2B1b is required for nuclear localization in human BeWo placental choriocarcinoma cells. Nuclear localization is stimulated by forskolin treatment in BeWo cells and serine phosphorylation has been identified in the 3'-extension. SULT2B1b is selective for the sulfation of 3beta-hydroxysteroids such as dehydroepiandrosterone and pregnenolone, and may also have a role in cholesterol sulfation in human skin. The substrate specificity, nuclear localization, and tissue localization of SULT2B1b suggest a role in regulating the responsiveness of cells to adrenal androgens via their direct inactivation or by preventing their conversion to more potent androgens and estrogens.

O-GlcNAc integrates the proteasome and transcriptome to regulate nuclear hormone receptors

Mechanisms controlling nuclear hormone receptors are a central question to mammalian developmental and disease processes. Herein, we show that a subtle increase in O-GlcNAc levels inhibits activation of nuclear hormone receptors. In vivo, increased levels of O-GlcNAc impair estrogen receptor activation and cause a decrease in mammary ductal side-branching morphogenesis associated with loss of progesterone receptors. Increased O-GlcNAc levels suppress transcriptional expression of coactivators and of the nuclear hormone receptors themselves. Surprisingly, increased O-GlcNAc levels are also associated with increased transcription of genes encoding corepressor proteins NCoR and SMRT. The association of the enzyme O-GlcNAc transferase with these corepressors contributes to specific regulation of nuclear hormone receptors by O-GlcNAc. Overall, transcriptional inhibition is related to the integrated effect of O-GlcNAc by direct modification of critical elements of the transcriptome and indirectly through O-GlcNAc modification of the proteasome.

Multiple gene expression analyses in paraffin-embedded tissues by TaqMan low-density array: Application to hedgehog and Wnt pathway analysis in ovarian endometrioid adenocarcinoma

Recent studies have shown the hedgehog and Wnt families of signaling proteins to be associated with tumor initiation, growth, and survival. However, these pathways remain unexplored in ovarian endometrioid adenocarcinoma (OEA). Here, we describe a novel TaqMan low-density array to examine the expression of 26 and 20 genes in the hedgehog and Wnt pathways, respectively, in six matched snap-frozen and formalin-fixed, paraffin-embedded (FPE) OEA specimens. Expression values were normalized to uninvolved ovarian epithelium. Gene expression in matched frozen and FPE tissues demonstrated significant concordance (r = 0.92, P < 0.0001). However, comparison of amplified and unamplified RNA from frozen OEA tissues revealed an altered molecular profile in amplified RNA. Amplification of RNA from FPE tissues was not successful. The expression of Desert hedgehog (DHH), Indian hedgehog (IHH), Hedge-hog interacting protein (HHIP), Wnt10B, Wnt9B, and Wnt inhibitory factor (WIF1) were tumor-specific with no detectable expression in normal ovarian epithelium. In addition, several genes were significantly (P < 0.025) down-regulated in OEA, including cyclin E2, Porcupine, c-Myc, and Axin 2 (4.8-, 3.6-, 2.9-, and 1.9-fold, respectively). TaqMan low-density array provides an effective multivariate technique for examining gene expression in RNA isolated from either snap-frozen or archival FPE tissues and can identify tumor-specific genes, possibly leading to novel treatments.

Osteopontin knockdown suppresses tumorigenicity of human metastatic breast carcinoma, MDA-MB-435

Elevated expression of osteopontin (OPN), a secreted phosphoglycoprotein, is frequently associated with many transformed cell lines. Various studies suggest that OPN may contribute to tumor progression as well as metastasis in multiple tumor types. High levels of OPN have been reported in patients with metastatic cancers, including breast. We found that the expression of OPN corroborates with the aggressive phenotype of the breast cancer cells i.e. the expression of OPN is acquired as the breast cancer cells become more aggressive. To assess the role(s) of OPN in breast carcinoma, expression of endogenous OPN was knocked down in metastatic MDA-MB-435 human breast carcinoma cells using RNA interference. We targeted multiple regions of the OPN transcript for RNA interference, along with 'scrambled' and 'non-targeting siRNA pool' controls to distinguish between target-specific and potential off-target effects including interferon-response gene (PeIF2-alpha) induction. The OPN knockdown by shRNA suppressed tumor take in immunocompromised mice. The 'silenced' cells also showed significantly lower invasion and migration in modified Boyden chamber assays and reduced ability to grow in soft agar. Thus, in addition to the widely reported roles of OPN in late stages of tumor progression, these results provide functional evidence that OPN contributes to breast tumor growth as well.

Hedgehog signaling and response to cyclopamine differ in epithelial and stromal cells in benign breast and breast cancer

The hedgehog pathway regulates epithelial-mesenchymal interactions, differentiation, proliferation and survival during development. Stimulation of hedgehog signaling induces carcinogenesis or promotes cell survival in cancers of multiple organs. Using real-time, quantitative PCR, laser capture microdissection, and immunohistochemistry, distinctive patterns of expression of the hedgehog pathway members patched 1 (PTCH1), smoothened, GLI1, GLI2 and the 3 hedgehog ligands were identified for epithelial cells and stromal fibroblasts in benign breast and breast cancer. Hedgehog ligands were expressed at higher levels in some cancer epithelial cell lines compared to noncancerous epithelial cells. Correspondingly, expression of GLI1, a transcription factor and transcriptional product of hedgehog signaling, was increased 8-fold in cancer epithelial cell lines; however, PTCH1, also a transcriptional target of hedgehog signaling in many cell types, was not increased. GLI1 protein and mRNA, and PTCH1 and sonic hedgehog (SHH) proteins were elevated in 3 of 10 breast cancers; however, PTCH1 transcripts were not consistently increased. Hedgehog-mediated transcription, as indicated by a reporter of GLI-dependent promoter activity and by expression of GLI1 transcripts, was reduced by the hedgehog pathway inhibitor cyclopamine in both MDA-MB-435 cancer epithelial cells and MCF10AT epithelial cells, a cell line derived from benign breast. However, cyclopamine reduced viability of cancer epithelial cell lines, including MDA-MB-435, but did not specifically affect fibroblasts or epithelial cells from benign breast, including MCF10AT. Treatment with sonic hedgehog ligand diminished the cyclopamine-induced reduction in GLI-dependent promoter activity in MCF10AT and MDA-MB-435 and viability of MDA-MB-435. These results demonstrate modulation of GLI-mediated transcription in both cancer and benign-derived epithelial cells by cyclopamine and sonic hedgehog, and further suggest that hedgehog signaling contributes to the survival of only the cancer epithelial cells. Determination as to whether the increase in GLI1 and SHH expression in breast cancer indicates a significant increase in hedgehog signaling will require further evaluation.

Kinetics of metastatic breast cancer cell trafficking in bone

PURPOSE

In vivo studies have focused on the latter stages of the bone metastatic process (osteolysis), whereas little is known about earlier events, e.g., arrival, localization, and initial colonization. Defining these initial steps may potentially identify the critical points susceptible to therapeutic intervention.

EXPERIMENTAL DESIGN

MDA-MB-435 human breast cancer cells engineered with green fluorescent protein were injected into the cardiac left ventricle of athymic mice. Femurs were analyzed by fluorescence microscopy, immunohistochemistry, real-time PCR, flow cytometry, and histomorphometry at times ranging from 1 hour to 6 weeks.

RESULTS

Single cells were found in distal metaphyses at 1 hour postinjection and remained as single cells up to 72 hours. Diaphyseal arrest occurred rarely and few cells remained there after 24 hours. At 1 week, numerous foci (2-10 cells) were observed, mostly adjacent to osteoblast-like cells. By 2 weeks, fewer but larger foci (> or =50 cells) were seen. Most bones had a single large mass at 4 weeks (originating from a colony or coalescing foci) which extended into the diaphysis by 4 to 6 weeks. Little change (<20%) in osteoblast or osteoclast numbers was observed at 2 weeks, but at 4 to 6 weeks, osteoblasts were dramatically reduced (8% of control), whereas osteoclasts were reduced modestly (to approximately 60% of control).

CONCLUSIONS

Early arrest in metaphysis and minimal retention in diaphysis highlight the importance of the local milieu in determining metastatic potential. These results extend the Seed and Soil hypothesis by demonstrating both intertissue and intratissue differences governing metastatic location. Ours is the first in vivo evidence that tumor cells influence not only osteoclasts, as widely believed, but also eliminate functional osteoblasts, thereby restructuring the bone microenvironment to favor osteolysis. The data may also explain why patients receiving bisphosphonates fail to heal bone despite inhibiting resorption, implying that concurrent strategies that restore osteoblast function are needed to effectively treat osteolytic bone metastases.