Abstract PD01-08: Differences in estrogen receptor signaling in non-malignant primary ER-positive breast epithelial cells and breast cancer

Background: The estrogen receptor (ER) is expressed in ∼70% of sporadic breast cancer and activates genes driving cell proliferation and tumorigenesis. We have previously performed genome-wide analysis of ER binding sites in MCF-7 breast cancer cells, and identified distinct mechanisms of ER signaling. We have also previously used EpCAM and CD49f as markers to enrich for viable ER-positive (ER+) cells obtained from non malignant breast tissue. Here, we seek to elucidate differences in ER signaling between non-malignant and ER+ breast cancer cells.

Methods: Primary breast epithelial cells were obtained from patients undergoing reduction mammoplasties and surgical excision of ER+ breast cancer. After dissociation of breast reductions into a single-cell suspension, ER+ mature luminal (ML; EpCAM+CD49f−) and luminal progenitor (LP; EpCAM+CD49f+) subpopulations were obtained by flow cytometry. Following estrogen stimulation, RNA was extracted for gene microarray analysis. ER chromatin immunoprecipitation and DNA sequencing (ChIP-seq) was performed. These results were compared to MCF-7 breast cancer cells.

Results: Reduction mammoplasty and ER+ breast cancer tissues were analyzed, and compared to MCF-7 cells. Gene expression profiles were different between non-malignant tissue and ER+ breast cancer cells following estrogen stimulation, with a 2–3 fold higher number of ER regulated genes in ER+ breast cancer compared to ER+ non malignant cells, and few overlapping estrogen regulated genes. Genes that promotes cell cycling and cell proliferation were downregulated in non-malignant tissue, but were upregulated in breast cancer cells (P < 10–5). CYP1A1, a major estradiol metabolizing enzyme, was upregulated in normal cells but downregulated in ER+ breast cancer cells. Motif analysis of ER ChIP-seq data in normal and ER+ breast cancer tissues demonstrated an enrichment of ER motifs in the overlapping sites and an enrichment of FOXA1 motifs in ER+ breast cancer cells and TCF12 motifs in non-malignant ER+ epithelial cells.

Conclusions: There are contrasting differences in ER signaling between normal mammary and breast cancer cells, with estrogen having anti-proliferative effects in normal luminal cells compared to pro-proliferative effects in breast cancer. ER ChIP-Seq has identified TCF12 as a major co-factor in non-malignant breast tissue whilst FOXA1 is a major co-factor in ER+ breast cancer. Our data provides evidence for key alterations in ER-signaling during tumorigenesis, and identifies potential mechanisms to target cancer specific ER signaling.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD01-08.

Fluid structure interaction simulation of left ventricular flow dynamics under left ventricular assist device support

For patient's receiving mechanical circulatory support, malfunction of the left ventricular assist device (LVADs) as well as mal-positioning of the cannula imposes serious threats to their life. It is therefore important to characterize the flow pattern and pressure distribution within the ventricle in the presence of an LVAD. In this paper, we present a 2D axisymmetric fluid structure interaction model of the passive left ventricle (LV) incorporating an LVAD cannula to simulate the effect of the LVAD cannula placement on the vortex dynamics. Results showed that larger recirculation area was formed at the cannula tip with increasing cannula insertion depth, and this is believed to reduce the risk of thrombus formation. Furthermore, we also simulated suction events (collapse of the LV) by closing the inlet. Vortex patterns were significantly altered under this condition, and the greatest LV wall displacement was observed at the part of the myocardium closest to the cannula tip.

PD08-02: Targeting BCL-2 Expressing Breast Tumors with BH3-Mimetics – A New Class of Drugs in Breast Cancer?

Background: Impairment of apoptosis is a hallmark of cancer and can result in resistance to chemotherapy. Tumor resistance to apoptosis is frequently acquired through deregulated expression of BCL-2 family members or inactivation of the p53 tumor suppressor pathway. Over-expression of the pro-survival protein BCL-2 is common in breast cancer (where it is readily detected by immunostaining), and has been shown to be an important prognostic marker. A potential role for BCL-2 as a therapeutic target in breast cancer, however, has not been explored. Recently, small molecules termed ‘BH3-mimetics’ have been developed that mimic the action of pro-apoptotic BH3-only proteins. These bind and neutralize pro-survival proteins including BCL-2. Here we have derived a panel of primary breast tumor xenografts (that include basal-like breast tumors) to study the efficacy of the BH3-mimetic ABT-737 combined with docetaxel in targeting BCL-2-positive breast cancer.

Methods and Results: We first studied the expression of BCL-2, pro-survival family members BCL-XL and MCL-1, and the pro-apoptotic protein BIM in tissue microarrays of 197 primary breast tumors, which were subtyped on the basis of ER, PR, HER2, CK5/6 and EGFR expression. BCL-2 was overexpressed in luminal (83.3%), HER2−positive (50.0%), basal-like (18.5%) and ‘marker-null’ (41.4%) breast cancers. BCL-2-positive tumors generally co-expressed BCL-XL (96.2%), MCL-1 (94.7%) and BIM (93.5%). To determine whether the BH3-mimetic ABT-737 (which neutralizes BCL-2, BCL-XL and BCL-W) was effective in targeting BCL-2-expressing breast tumors, we generated a panel of 28 primary breast tumor xenografts in immunocompromised NOG mice. Five xenograft lines (838T, 24T, 315T, 13T and 806T) were selected for further analysis. Four were basal-like, and one (315T) was a luminal B tumor, as determined by gene profiling. Mice bearing tumor xenografts were treated with ABT-737 (50 mg/kg i.p. d1-10), docetaxel (10 mg/kg i.p. d1) or a combination in q21d cycles. Tumor response and overall survival were significantly improved by combination therapy, but only for tumors that expressed elevated levels of BCL-2. Treatment with ABT-737 alone was ineffective, suggesting that ABT-737 sensitized tumors to docetaxel. Combination therapy was accompanied by a marked increase in apoptosis and dissociation of BIM from BCL-2, indicating that a perturbation of BIM complexes may contribute to the activation of the apoptotic cascade. Notably, ABT-737 appeared effective in targeting BCL-2-expressing basal-like tumor xenografts (838T and 24T) harboring p53 mutations.

Discussion: Primary breast tumor xenograft models that recapitulate the phenotype of the primary tumor have been developed as useful ‘proof-of-principle', pre-clinical models. Here we provide the first in vivo evidence that BH3-mimetics can be used to sensitize primary BCL-2-expressing breast tumors to taxane chemotherapy. Our results suggest that elevated BCL-2 expression constitutes a predictive response marker in breast cancer. These findings provide a rationale for the development of clinical protocols using the oral analogue ABT-263 (navitoclax) as an adjunct to taxane chemotherapy in BCL-2-expressing basal-like and luminal breast cancer.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD08-02.

P2-10-09: Detecting Breast Cancer with Dynamic Diffuse Optical Tomographic Imaging

Background: Over the last decade diffuse optical tomography (DOT) has emerged as a novel medical imaging modality. Near-infrared light is used to non-invasively probe biological tissue, and three-dimensional (3D) maps of blood-dependent parameters can be obtained. Several studies are underway to show the clinical utility of DOT for imaging brain disease, joint disease, and breast cancer. Here we present the largest clinical study to date that uses hemodynamic effects caused by a simple breath hold to identify breast tumors using DOT.

Methods: We have designed and built a DOT breast imaging system that can acquire full 3D data sets within a fraction of a second. The system affords the ability to study fast hemodynamic effects in both breasts simultaneously. Using non-compressive imaging heads we measured the oxygenated and deoxygenated hemoglobin levels in the breasts of 15 patients whose mammogram showed a mass >1 cm (4 benign, 11 malignant) and 3 healthy controls. Data was acquired over the course of a 30-second breath hold and 30 seconds thereafter. In addition, a baseline measurement of 30 seconds prior to the breath hold was obtained. A multi-wavelength image reconstruction algorithm was used to create 3D maps of hemoglobin-dependent parameters (Δ[HbO2] and Δ[Hb]) in the breast every 0.58 seconds, over the course of the 90-second experiment. An image analysis algorithm identified regions of peak percentage change in [Hb] and [HbO2] in the breast and then computed the average hemoglobin levels in those regions.

Results: We observed an increase in the hemoglobin levels in all breasts during the breath hold. Upon resuming breathing, these hemoglobin levels returned to baseline. Tumor bearing breasts showed a statistically significant slower return to baseline than healthy breasts. In particular, we found that tumors can be detected by a substantially larger Δ[Hb] value as compared to normal tissue in images acquired 15 seconds following the end of the breath hold. In 10 of 11 patients the malignant tumor was identified using this technique, suggesting sensitivity over 90%. No regions of increased Δ[Hb] were seen in the healthy breasts, or in the breasts with benign masses. The peak percentage change in [Hb] at the 15 second post-breath hold time point was 10.0 ± 6.0% (n=11) in the malignant tumors compared to 1.4 ± 0.5% (n=3) (p=0.001) in healthy patients and 4.8 ± 1.9% in benign masses (n=4)(p=0.03).

Discussion: A breath hold impedes venous return to the heart, which causes pooling of blood in the breast. This is observed as an increase in [Hb] and [HbO2] using DOT. Tumor vasculature is known to be more disorganized, tortuous, and leakier than normal vasculature. Therefore, once the breath hold is released and blood is allowed to drain from the breast, blood accumulated in the tumor during the breath hold will drain more slowly than blood in healthy tissue. This study has shown that DOT allows us to visualize these hemodynamic effects and use them to detect tumors with a simple breath hold and compression-free imaging head. Future studies need to explore the detection limits and general clinical utility of this technique for screening, differentiating malignant from benign masses, and treatment monitoring.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P2-10-09.

Partial trisomy 3p and partial monosomy 11q associated with atrial septal defect, cleft palate, and developmental delay: a case report

Unbalanced translocation involving both chromosome 3p duplication and 11q deletion in the same patient is extremely rare; only 1 live-born case was reported previously. This karyotype was also detected during prenatal diagnosis of 2 different pregnancies in a Taiwanese family which were both terminated. In all 3 cases, only standard karyotyping was done to detect the abnormal karyotypes. Here, we report a 4-year-old boy with cleft palate, atrial septal defect, and hypotonia with gross and fine motor delay. Oligonucleotide-based array comparative genomic hybridization showed copy number gain from 3pter to 3p24.2 (approximately 24.5 Mb) and copy number loss from 11q25 to 11qter (approximately 5.8 Mb). This de novo unbalanced translocation event involving a terminal 3p duplication and a terminal 11q deletion provides candidate genes for further investigation of dosage effect leading to the patient's multiple phenotypic abnormalities. Genotype-phenotype correlation is difficult to make in this case due to the large number of genes involved. However, the description of such cases together with precise gene-level mapping of chromosomal breakpoints will add to further refinement of candidate genes to be investigated for terminal imbalances in 3p and 11q when more similar cases are reported.

In vivo validation of pulsatile flow and differential pressure estimation models in a left ventricular assist device

Implantation of sensors to measure hemodynamic parameters such as pulsatile pump flow and differential pressure (head) in an implantable rotary pump (IRBP) requires regular in situ calibration due to measurement drift. In addition, risks associated with sensor failure and thrombus formation makes the long-term implantation in patients problematic. In our laboratory, two stable and novel dynamical models for non-invasive pulsatile flow and head estimation were proposed and tested in vitro using mock circulatory loop experiments with varying hematocrit (HCT). Noninvasive measurements of power and pump speed were used as inputs to the flow model while the estimated flow was used together with the pump rotational speed as inputs to the head estimation model. In this paper, we evaluated the performance of the proposed models using in vivo experimental data obtained from greyhound dogs (N=5). Linear regression analysis between estimated and measured pulsatile flows resulted in a highly significant correlation (R(2) = 0.946) and mean absolute error (e) of 0.810 L/min, while for head, R(2) = 0.951 and e = 10.13 mmHg were obtained.

Abstract P4-04-03: Transcriptome Analyses of Mouse and Human Mammary Cell Subpopulations Reveals Multiple Conserved Genes and Pathways

INTRODUCTION: Molecular characterization of the normal epithelial cell types that reside in the mammary gland is an important step toward understanding pathways that regulate self-renewal, lineage commitment, and differentiation along the hierarchy. We previously reported distinct stages in human mammary epithelial cell development and linked them to breast tumor subtypes previously defined by gene expression profiling. Here we determined the gene expression signatures of four distinct subpopulations isolated from the mouse mammary gland. The epithelial cell signatures were used to interrogate mouse models of mammary tumorigenesis and to compare with their normal human counterpart subsets to identify conserved genes and networks.

METHODS: RNA was prepared from freshly sorted mouse mammary cell subpopulations (mammary stem cell (MaSC)-enriched, committed luminal progenitor, mature luminal and stromal cell) and used for gene expression profiling analysis on the Illumina platform. Gene signatures were derived and compared with those previously reported for the analogous normal human mammary cell subpopulations. The mouse and human epithelial subset signatures were then subjected to Ingenuity Pathway Analysis (IPA) to identify conserved pathways.

RESULTS: The four mouse mammary cell subpopulations exhibited distinct gene signatures. Comparison of these signatures with the molecular profiles of different mouse models of mammary tumorigenesis revealed that tumors arising in MMTV-Wnt-1 and p53-/- mice were enriched for MaSC-subset genes, whereas the gene profiles of MMTV-Neu and MMTV-PyMT tumors were most concordant with the luminal progenitor cell signature. Comparison of the mouse mammary epithelial cell signatures with their human counterparts revealed substantial conservation of genes, whereas IPA highlighted a number of conserved pathways in the three epithelial subsets.

CONCLUSIONS: The conservation of genes and pathways across species further validates the use of the mouse as a model to study mammary gland development and highlights pathways that are likely to govern cell-fate decisions and differentiation. It is noteworthy that many of the conserved genes in the MaSC population have been considered as epithelialmesenchymal transition (EMT) signature genes. Therefore, the expression of these genes in tumor cells may reflect basal epithelial cell characteristics and not necessarily cells that have undergone an EMT. Comparative analyses of normal mouse epithelial subsets with murine tumor models have implicated distinct cell types in contributing to tumorigenesis in the different models.

Figures available in online version.

Novel surgical technique for insertion of pleuroperitoneal shunts for bilateral chylous effusions in Ex preterm infant at term corrected age

Neonatal chylothorax is a relatively uncommon condition. Here we describe the case of an extremely preterm infant with bilateral chylous effusions which were resistant to conventional medical management and were ultimately managed with the insertion of pleuroperitoneal shunts using a novel surgical technique. Subsequently the infant recovered and the shunts could be removed. We report this case to highlight that such shunts can be inserted even in tiny preterm infants with minimally invasive techniques, and be extremely successful in managing chylothorax, pending spontaneous recovery.

Noninvasive deadbeat control of an implantable rotary blood pump: a simulation study

A deadbeat controller has been proposed for the control of pulsatile pump flow in an implantable rotary blood pump (IRBP). A lumped parameter model of the cardiovascular system, in combination with the stable dynamical models of pulsatile flow and differential pressure (head) estimation for the IRBP was used to evaluate the controller. Pump speed and current were used as the only measured variables of the control system. The control algorithm was tested using both constant and sinusoidal reference pump flow input, under healthy and heart failure conditions. Results showed that the controller is able to track the reference input with minimal error in the presence of model uncertainty.