Obesity modulates the cellular and molecular microenvironment in the peritoneal cavity: implication for ovarian cancer risk

Introduction

Abdominal obesity increases the risk of developing ovarian cancer but the molecular mechanisms of how obesity supports ovarian cancer development remain unknown. Here we investigated the impact of obesity on the immune cell and gene expression profiles of distinct abdominal tissues, focusing on the peritoneal serous fluid (PSF) and the omental fat band (OFB) as critical determinants for the dissemination of ovarian metastases and early metastatic events within the peritoneal cavity.

Methods

Female C57BL/6 mice were fed a low-fat (LFD) or a high-fat diet (HFD) for 12 weeks until the body weights in the HFD group were significantly higher and the mice displayed an impaired glucose tolerance. Then the mice were injected with the murine ovarian cancer cells (MOSE-LTICv) while remaining on their diets. After 21 days, the mice were sacrificed, tumor burden was evaluated and tissues were harvested. The immune cell composition of abdominal tissues and changes in gene expression in the PSF and OFB were evaluated by flow cytometry and qPCR RT2-profiler PCR arrays and confirmed by qRT-PCR, respectively. Other peritoneal adipose tissues including parametrial and retroperitoneal white adipose tissues as well as blood were also investigated.

Results

While limited effects were observed in the other peritoneal adipose tissues, feeding mice the HFD led to distinct changes in the immune cell composition in the PSF and the OFB: a depletion of B cells but an increase in myeloid-derived suppressor cells (MDSC) and mono/granulocytes, generating pro-inflammatory environments with increased expression of cyto- and chemokines, and genes supporting adhesion, survival, and growth, as well as suppression of apoptosis. This was associated with a higher peritoneal tumor burden compared to mice fed a LFD. Changes in cellular and genetic profiles were often exacerbated by the HFD. There was a large overlap in genes that were modulated by both the HFD and the cancer cells, suggesting that this 'genetic fingerprint' is important for ovarian metastases to the OFB.

Discussion

In accordance with the 'seed and soil' theory, our studies show that obesity contributes to the generation of a pro-inflammatory peritoneal environment that supports the survival of disseminating ovarian cancer cells in the PSF and the OFB and enhances the early metastatic adhesion events in the OFB through an increase in extracellular matrix proteins and modulators such as fibronectin 1 and collagen I expression as well as in genes supporting growth and invasion such as Tenacin C. The identified genes could potentially be used as targets for prevention strategies to lower the ovarian cancer risk in women with obesity.

Genetic and Functional Modifications Associated with Ovarian Cancer Cell Aggregation and Limited Culture Conditions

The aggregation of cancer cells provides a survival signal for disseminating cancer cells; however, the underlying molecular mechanisms have yet to be elucidated. Using qPCR gene arrays, this study investigated the changes in cancer-specific genes as well as genes regulating mitochondrial quality control, metabolism, and oxidative stress in response to aggregation and hypoxia in our progressive ovarian cancer models representing slow- and fast-developing ovarian cancer. Aggregation increased the expression of anti-apoptotic, stemness, epithelial-mesenchymal transition (EMT), angiogenic, mitophagic, and reactive oxygen species (ROS) scavenging genes and functions, and decreased proliferation, apoptosis, metabolism, and mitochondrial content genes and functions. The incorporation of stromal vascular cells (SVF) from obese mice into the spheroids increased DNA repair and telomere regulatory genes that may represent a link between obesity and ovarian cancer risk. While glucose had no effect, glutamine was essential for aggregation and supported proliferation of the spheroid. In contrast, low glucose and hypoxic culture conditions delayed adhesion and outgrowth capacity of the spheroids independent of their phenotype, decreased mitochondrial mass and polarity, and induced a shift of mitochondrial dynamics towards mitophagy. However, these conditions did not reduce the appearance of polarized mitochondria at adhesion sites, suggesting that adhesion signals that either reversed mitochondrial fragmentation or induced mitobiogenesis can override the impact of low glucose and oxygen levels. Thus, the plasticity of the spheroids' phenotype supports viability during dissemination, allows for the adaptation to changing conditions such as oxygen and nutrient availability. This may be critical for the development of an aggressive cancer phenotype and, therefore, could represent druggable targets for clinical interventions.

Mitochondrial plasticity supports proliferative outgrowth and invasion of ovarian cancer spheroids during adhesion

Background

Ovarian cancer cells aggregate during or after exfoliation from the primary tumor to form threedimensional spheroids. Spheroid formation provides a survival advantage during peritoneal dissemination in nutrient and oxygen-depleted conditions which is accompanied by a suppressed metabolic phenotype and fragmented mitochondria. Upon arrival to their metastatic sites, spheroids adhere to peritoneal organs and transition to a more epithelial phenotype to support outgrowth and invasion. In this study, we investigated the plasticity of mitochondrial morphology, dynamics, and function upon adhesion.

Methods

Using our slow-developing (MOSE-L) and fast-developing (MOSE-LTICv) ovarian cancer models, we mimicked adhesion and reoxygenation conditions by plating the spheroids onto tissue culture dishes and changing culture conditions from hypoxia and low glucose to normoxia with high glucose levels after adhesion. We used Western Blot, microscopy and Seahorse analyses to determine the plasticity of mitochondrial morphology and functions upon adhesion, and the impact on proliferation and invasion capacities.

Results

Independent of culture conditions, all spheroids adhered to and began to grow onto the culture plates. While the bulk of the spheroid was unresponsive, the mitochondrial morphology in the outgrowing cells was indistinguishable from cells growing in monolayers, indicating that mitochondrial fragmentation in spheroids was indeed reversible. This was accompanied by an increase in regulators of mitobiogenesis, PGC1a, mitochondrial mass, and respiration. Reoxygenation increased migration and invasion in both cell types but only the MOSE-L responded with increased proliferation to reoxygenation. The highly aggressive phenotype of the MOSE-LTICv was characterized by a relative independence of oxygen and the preservation of higher levels of proliferation, migration and invasion even in limiting culture conditions but a higher reliance on mitophagy. Further, the outgrowth in these aggressive cells relies mostly on proliferation while the MOSE-L cells both utilize proliferation and migration to achieve outgrowth. Suppression of proliferation with cycloheximide impeded aggregation, reduced outgrowth and invasion via repression of MMP2 expression and the flattening of the spheroids.

Discussion

Our studies indicate that the fragmentation of the mitochondria is reversible upon adhesion. The identification of regulatory signaling molecules and pathways of these key phenotypic alterations that occur during primary adhesion and invasion is critical for the identification of druggable targets for therapeutic intervention to prevent aggressive metastatic disease.

Abstract 1687: Cyto R1 Platform enriches samples’ viability for single-cell sequencing and downstream assays

Single-cell level investigations such as DNA and RNA sequencing, protein analyses, and phenotypic studies require an input sample with a high rate of viability (>90%). If too many dead cells are present in the input, degraded proteins and ambient DNA or RNA can increase background noise that may lead to missing identification of crucial targets. Since the cost for single-cell sequencing experiments still remains high, it is critical to ensure the input sample is optimized for high viability to ensure cost-effective and reproducible data. Current bead assays or other sample viability enrichment techniques used in preparation for single-cell analyses typically result in a significant sample loss, sometimes sacrificing 80% of the starting sample, and these preparation steps require multiple passes (> 45 minutes time) and costly kits. These beads or kits can be biased and change the cell population, subject cells to unwanted stresses, and diminish sample integrity with the time needed for preparations. Here, we investigate sample cell viability enrichment on the Cyto R1 Platform, a label-free, cell enrichment, sorting, and recovery platform. At the core, the Cyto R1 uses Cyto Chips, microfluidic technologies with electrical fields, to phenotypically enrich and sort various cells based upon cells’ unique physical structures and subcellular features. Thus, the Cyto R1 ensures native cell recovery without any unwanted cell tagging to maximize sample integrity. In this work, a variety of single cell solutions derived from T cell lymphoma tumors, ascites fluid, and organ tissues were enriched for viable cells to obtain a final sample viability over 90%. Additionally, we aimed to achieve a minimum of 50,000 viable cells, a common target for single-cell sequencing, in as rapid a timeframe as possible. In one sample origin tested, murine T cell lymphomas, the average starting viability was 65 ± 6.5%, and the final viability after enrichment on the Cyto R1 Platform was 95.8 ± 1.8%. Similarly, murine ascites cell mixtures were enriched from average viabilities below 55% up to 91.6 ± 4.2%. For all samples tested, >50,000 viable cells were obtained in under 30 minutes. This work demonstrates that the Cyto R1 can effectively and efficiently enrich a variety of starting samples for high viability (>90%) as required for downstream assays and single-cell sequencing.

Citation Format: Alexandra R. Hyler, Alicia M. Cole, Ridi Barua, Amiran K. Dzutsev, Eva M. Schmelz. Cyto R1 Platform enriches samples’ viability for single-cell sequencing and downstream assays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1687.

Quantitative Biophysical Metrics for Rapid Evaluation of Ovarian Cancer Metastatic Potential

Ovarian cancer is routinely diagnosed long after the disease has metastasized through the fibrous sub-mesothelium. Despite extensive research in the field linking ovarian cancer progression to increasingly poor prognosis, there are currently no validated cellular markers or hallmarks of ovarian cancer that can predict metastatic potential. To discern disease progression across a syngeneic mouse ovarian cancer progression model, here, we fabricated extracellular-matrix mimicking suspended fiber networks: crosshatches of mismatch diameters for studying protrusion dynamics, aligned same diameter networks of varying inter-fiber spacing for studying migration, and aligned nanonets for measuring cell forces. We found that migration correlated with disease, while force-disease biphasic relationship exhibited f-actin stress-fiber network dependence. However, unique to suspended fibers, coiling occurring at tips of protrusions and not the length or breadth of protrusions displayed strongest correlation with metastatic potential. To confirm that our findings were more broadly applicable beyond the mouse model, we repeated our studies in human ovarian cancer cell lines and found that the biophysical trends were consistent with our mouse model results. Altogether, we report complementary high throughput and high content biophysical metrics capable of identifying ovarian cancer metastatic potential on time scale of hours. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].

Targeting Cbx3/HP1γ Induces LEF-1 and IL-21R to Promote Tumor-Infiltrating CD8 T-Cell Persistence

Immune checkpoint blockade (ICB) relieves CD8⁺ T-cell exhaustion in most mutated tumors, and TCF-1 is implicated in converting progenitor exhausted cells to functional effector cells. However, identifying mechanisms that can prevent functional senescence and potentiate CD8⁺ T-cell persistence for ICB non-responsive and resistant tumors remains elusive. We demonstrate that targeting Cbx3/HP1γ in CD8⁺ T cells augments transcription initiation and chromatin remodeling leading to increased transcriptional activity at Lef1 and Il21r. LEF-1 and IL-21R are necessary for Cbx3/HP1γ-deficient CD8⁺ effector T cells to persist and control ovarian cancer, melanoma, and neuroblastoma in preclinical models. The enhanced persistence of Cbx3/HP1γ-deficient CD8⁺ T cells facilitates remodeling of the tumor chemokine/receptor landscape ensuring their optimal invasion at the expense of CD4⁺ Tregs. Thus, CD8⁺ T cells heightened effector function consequent to Cbx3/HP1γ deficiency may be distinct from functional reactivation by ICB, implicating Cbx3/HP1γ as a viable cancer T-cell-based therapy target for ICB resistant, non-responsive solid tumors.

Differential effects of nanosecond pulsed electric fields on cells representing progressive ovarian cancer

Nanosecond pulsed electric fields (nsPEFs) may induce differential effects on tumor cells from different disease stages and could be suitable for treating tumors by preferentially targeting the late-stage/highly aggressive tumor cells. In this study, we investigated the nsPEF responses of mouse ovarian surface epithelial (MOSE) cells representing progressive ovarian cancer from benign to malignant stages and highly aggressive tumor-initiating-like cells. We established the cell-seeded 3D collagen scaffolds cultured with or without Nocodazole (eliminating the influence of cell proliferation on ablation outcome) to observe the ablation effects at 3 h and 24 h after treatment and compared the corresponding thresholds obtained by numerically calculated electric field distribution. The results showed that nsPEFs induced larger ablation areas with lower thresholds as the cell progress from benign, malignant to a highly aggressive phenotype. This differential effect was not affected by the different doubling times of the cells, as apparent by similar ablation induction after a synergistic treatment of nsPEFs and Nocodazole. The result suggests that nsPEFs could induce preferential ablation effects on highly aggressive and malignant ovarian cancer cells than their benign counterparts. This study provides an experimental basis for the research on killing malignant tumor cells via electrical treatments and may have clinical implications for treating tumors and preventing tumor recurrence after treatment.

A novel ultralow conductivity electromanipulation buffer improves cell viability and enhances dielectrophoretic consistency

Cell separation has become a critical diagnostic, research, and treatment tool for personalized medicine. Despite significant advances in cell separation, most widely used applications require the use of multiple, expensive antibodies to known markers in order to identify subpopulations of cells for separation. Dielectrophoresis (DEP) provides a biophysical separation technique that can target cell subpopulations based on phenotype without labels and return native cells for downstream analysis. One challenge in employing any DEP device is the sample being separated must be transferred into an ultralow conductivity medium, which can be detrimental in retaining cells' native phenotypes for separation. Here, we measured properties of traditional DEP reagents and determined that after just 1-2 h of exposure and subsequent culture, cells' viability was significantly reduced below 50%. We developed and tested a novel buffer (Cyto Buffer) that achieved 6 weeks of stable shelf-life and demonstrated significantly improved viability and physiological properties. We then determined the impact of Cyto Buffer on cells' dielectric properties and morphology and found that cells retained properties more similar to that of their native media. Finally, we vetted Cyto Buffer's usability on a cell separation platform (Cyto R1) to determine combined efficacy for cell separations. Here, more than 80% of cells from different cell lines were recovered and were determined to be >70% viable following exposure to Cyto Buffer, flow stimulation, electromanipulation, and downstream collection and growth. The developed buffer demonstrated improved opportunities for electrical cell manipulation, enrichment, and recovery for next generation cell separations.

Progression-Mediated Changes in Mitochondrial Morphology Promotes Adaptation to Hypoxic Peritoneal Conditions in Serous Ovarian Cancer

Ovarian cancer is the deadliest gynecological cancer in women, with a survival rate of less than 30% when the cancer has spread throughout the peritoneal cavity. Aggregation of cancer cells increases their viability and metastatic potential; however, there are limited studies that correlate these functional changes to specific phenotypic alterations. In this study, we investigated changes in mitochondrial morphology and dynamics during malignant transition using our MOSE cell model for progressive serous ovarian cancer. Mitochondrial morphology was changed with increasing malignancy from a filamentous network to single, enlarged organelles due to an imbalance of mitochondrial dynamic proteins (fusion: MFN1/OPA1, fission: DRP1/FIS1). These phenotypic alterations aided the adaptation to hypoxia through the promotion of autophagy and were accompanied by changes in the mitochondrial ultrastructure, mitochondrial membrane potential, and the regulation of reactive oxygen species (ROS) levels. The tumor-initiating cells increased mitochondrial fragmentation after aggregation and exposure to hypoxia that correlated well with our previously observed reduced growth and respiration in spheroids, suggesting that these alterations promote viability in non-permissive conditions. Our identification of such mitochondrial phenotypic changes in malignancy provides a model in which to identify targets for interventions aimed at suppressing metastases.

Self-aligned microfluidic contactless dielectrophoresis device fabricated by single-layer imprinting on cyclic olefin copolymer

The trapping and deflection of biological cells by dielectrophoresis (DEP) at field non-uniformities in a microfluidic device is often conducted in a contactless dielectrophoresis (cDEP) mode, wherein the electrode channel is in a different layer than the sample channel, so that field penetration through the interceding barrier causes DEP above critical cut-off frequencies. In this manner, through physical separation of the electrode and sample channels, it is possible to spatially modulate electric fields with no electrode-induced damage to biological cells in the sample channel. However, since this device requires interlayer alignment of the electrode to sample channel and needs to maintain a thin interceding barrier (~ 15 μm) over the entire length over which DEP is needed (~ 1 cm), variations in alignment and microstructure fidelity cause wide variations in cDEP trapping level and frequency response across devices. We present a strategy to eliminate interlayer alignment by fabricating self-aligned electrode and sample channels, simultaneously with the interceding barrier layer (14-μm width and 50-μm depth), using a single-layer imprint and bond process on cyclic olefin copolymer. Specifically, by designing support structures, we preserve fidelity of the high aspect ratio insulating posts in the sample channel and the interceding barrier between the sample and electrode channels over the entire device footprint (~ 1 cm). The device operation is validated based on impedance measurements to quantify field penetration through the interceding barrier and by DEP trapping measurements. The presented fabrication strategy can eventually improve cDEP device manufacturing protocols to enable more reproducible DEP performance. Graphical abstract.

Characterization of sequentially-staged cancer cells using electrorotation

The identification and separation of cells from heterogeneous populations is critical to the diagnosis of diseases. Label-free methodologies in particular have been developed to manipulate individual cells using properties such as density and morphology. The electrical properties of malignant cells, including the membrane capacitance and cytoplasmic conductivity, have been demonstrated to be altered compared to non-malignant cells of similar origin. Here, we exploit these changes to characterize individual cells in a sequentially-staged in vitro cancer model using electrorotation (EROT)—the rotation of a cell induced by a rotating electric field. Using a microfabricated device, a dielectrophoretic force to suspend cells while measuring their angular velocity resulting from an EROT force applied at frequencies between 3 kHz to 10 MHz. We experimentally determine the EROT response for cells at three stages of malignancy and analyze the resultant spectra by considering models that include the effect of the cell membrane alone (single-shell model) and the combined effect of the cell membrane and nucleus (double-shell model). We find that the cell membrane is largely responsible for a given cell’s EROT response between 3 kHz and 10 MHz. Our results also indicate that membrane capacitance, membrane conductance, and cytoplasmic conductivity increase with an increasingly malignant phenotype. Our results demonstrate the potential of using electrorotation as a means making of non-invasive measurements to characterize the dielectric properties of cancer cells.

Separation of Macrophages and Fibroblasts Using Contactless Dielectrophoresis and a Novel ImageJ Macro

Background: This study presents a label-free method of separating macrophages and fibroblasts, cell types critically associated with tumors. Materials and Methods: Contactless dielectrophoresis (DEP) devices were used to separate fibroblasts from macrophages by selectively trapping one population. An ImageJ macro was developed to determine the percentage of each population moving or stationary at a given point in time in a video. Results: At 350V_rms, 20 kHz, and 1.25 μL/min, more than 90% of fibroblasts were trapped while less than 20% of macrophages were trapped. Conclusions: Contactless DEP was used to study macrophage and fibroblast separation as a proof-of-concept study for separating cells in the tumor microenvironment. The associated ImageJ macro could be used in other microfluidic cell separation studies.

N-(3-oxododecanoyl)-L-homoserine lactone interactions in the breast tumor microenvironment: Implications for breast cancer viability and proliferation in vitro

It is well documented that the tumor microenvironment profoundly impacts the etiology and progression of breast cancer, yet the contribution of the resident microbiome within breast tissue remains poorly understood. Tumor microenvironmental conditions, such as hypoxia and dense tumor stroma, predispose progressive phenotypes and therapy resistance, however the role of bacteria in this interplay remains uncharacterized. We hypothesized that the effect of individual bacterial secreted molecules on breast cancer viability and proliferation would be modulated by these tumor-relevant stressors differentially for cells at varying stages of progression. To test this, we incubated human breast adenocarcinoma cells (MDA-MB-231, MCF-DCIS.com) and non-malignant breast epithelial cells (MCF-10A) with N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL), a quorum-sensing molecule from Pseudomonas aeruginosa that regulates bacterial stress responses. This molecule was selected because Pseudomonas was recently characterized as a significant fraction of the breast tissue microbiome and OdDHL is documented to impact mammalian cell viability. After OdDHL treatment, we demonstrated the greatest decrease in viability with the more malignant MDA-MB-231 cells and an intermediate MCF-DCIS.com (ductal carcinoma in situ) response. The responses were also culture condition (i.e. microenvironment) dependent. These results contrast the MCF-10A response, which demonstrated no change in viability in any culture condition. We further determined that the observed trends in breast cancer viability were due to modulation of proliferation for both cell types, as well as the induction of necrosis for MDA-MB-231 cells in all conditions. Our results provide evidence that bacterial quorum-sensing molecules interact with the host tissue environment to modulate breast cancer viability and proliferation, and that the effect of OdDHL is dependent on both cell type as well as microenvironment. Understanding the interactions between bacterial signaling molecules and the host tissue environment will allow for future studies that determine the contribution of bacteria to the onset, progression, and therapy response of breast cancer.

A feasibility study for enrichment of highly aggressive cancer subpopulations by their biophysical properties via dielectrophoresis enhanced with synergistic fluid flow

A common problem with cancer treatment is the development of treatment resistance and tumor recurrence that result from treatments that kill most tumor cells yet leave behind aggressive cells to repopulate. Presented here is a microfluidic device that can be used to isolate tumor subpopulations to optimize treatment selection. Dielectrophoresis (DEP) is a phenomenon where particles are polarized by an electric field and move along the electric field gradient. Different cell subpopulations have different DEP responses depending on their bioelectrical phenotype, which, we hypothesize, correlate with aggressiveness. We have designed a microfluidic device in which a region containing posts locally distorts the electric field created by an AC voltage and forces cells toward the posts through DEP. This force is balanced with a simultaneous drag force from fluid motion that pulls cells away from the posts. We have shown that by adjusting the drag force, cells with aggressive phenotypes are influenced more by the DEP force and trap on posts while others flow through the chip unaffected. Utilizing single-cell trapping via cell-sized posts coupled with a drag-DEP force balance, we show that separation of similar cell subpopulations may be achieved, a result that was previously impossible with DEP alone. Separated subpopulations maintain high viability downstream, and remain in a native state, without fluorescent labeling. These cells can then be cultured to help select a therapy that kills aggressive subpopulations equally or better than the bulk of the tumor, mitigating resistance and recurrence.

Alternating electric fields (TTFields) in combination with paclitaxel are therapeutically effective against ovarian cancer cells in vitro and in vivo

Long-term survival rates for advanced ovarian cancer patients have not changed appreciably over the past four decades; therefore, development of new, effective treatment modalities remains a high priority. Tumor Treating Fields (TTFields), a clinically active anticancer modality utilize low-intensity, intermediate frequency, alternating electric fields. The goal of this study was to evaluate the efficacy of combining TTFields with paclitaxel against ovarian cancer cells in vitro and in vivo. In vitro application of TTFields on human ovarian cancer cell lines led to a significant reduction in cell counts as compared to untreated cells. The effect was found to be frequency and intensity dependent. Further reduction in the number of viable cells was achieved when TTFields treatment was combined with paclitaxel. The in vivo effect of the combined treatment was tested in mice orthotopically implanted with MOSE-L_TICv cells. In this model, combined treatment led to a significant reduction in tumor luminescence and in tumor weight as compared to untreated mice. The feasibility of effective local delivery of TTFields to the human abdomen was examined using finite element mesh simulations performed using the Sim4life software. These simulations demonstrated that electric fields intensities inside and in the vicinity of the ovaries of a realistic human computational phantom are about 1 and 2 V/cm pk-pk, respectively, which is within the range of intensities required for TTFields effect. These results suggest that prospective clinical investigation of the combination of TTFields and paclitaxel is warranted.

Abstract B79: Translational study of tumor treating fields in combination with paclitaxel in ovarian cancer

Tumor Treating Fields (TTFields), a clinically active anticancer modality, are based on low intensity intermediate frequency alternating electric fields that exert their cytotoxicity by disrupting mitosis. The present study examines whether concomitant paclitaxel and TTFields have a beneficial impact on ovarian cancer growth both in vitro and in vivo. Moreover, on the basis of the preclinical observations, an open-label pilot clinical study evaluating the effect of the combined modalities in 30 patients with recurrent ovarian cancer was initiated.

Preclinical studies: To investigate the inhibitory effect of TTFields on ovarian cancer cell growth in vitro and determine optimal therapeutic frequency of TTFields in ovarian cancer, human ovarian cancer cell lines were treated with TTFields (100-400 kHz) for 72 hours using the inovitro system (Novocure, Haifa, Israel). To assess whether adding TTFields to paclitaxel increases the response of ovarian cancer cells to paclitaxel, we treated these cell lines with paclitaxel alone and in combination with TTFields. In vivo efficacy of the combined treatment was tested in female C57Bl/6 mice, orthotopically implanted with MOSE-L FFL luciferase positive cells. The feasibility of effective regional delivery of TTFields therapy to the ovaries, pelvis and abdomen of human subjects was examined using Finite Element Mesh (FEM) simulations performed using the Sim4life software. The FEM simulations demonstrated effective distribution of fields at intensities of 1-2 V/cm, which is above the minimal threshold required for TTFields response.

The INNOVATE Trial (NCT02244502): Based on positive preclinical studies demonstrating the combined efficacy of TTFields and paclitaxel in different ovarian cancer models, a pilot clinical trial was initiated to evaluate this therapeutic combination in recurrent ovarian carcinoma patients. In this prospective, pilot, single arm study, 30 patients will receive bi-directional TTFields at 200 kHz applied to the ovaries and surrounding intra-abdominal tissues using 4 transducer arrays located on the surface of the lower abdominal region. In addition, patients will receive concomitant paclitaxel at a standard regimen and dose. The combined treatment will be administered until further radiological progression. Inclusion criteria include ECOG score of 0-1 and no serious co-morbidities. The trial's primary endpoint is adverse events frequency and severity. The study will also collect preliminary efficacy data through the analysis of progression-free survival, 1-year survival rate and overall survival. Compliance data will be analyzed as an additional secondary endpoint. The INNOVATE study started to enroll patients in October 2014, and is currently accruing patients in Switzerland, Belgium and Spain. So far the trial has enrolled half of the planned 30 patients.

In summary, we present the first preclinical evidence in ovarian cancer of the combined efficacy of paclitaxel and TTFields, a new anticancer treatment modality. Our results suggest that it may represent a novel, effective therapeutic strategy against ovarian cancer. Pilot clinical testing is ongoing.

Citation Format: Mijal Munster, Roni Blat, Paul C. Roberts, Eva M. Schmelz, Moshe Giladi, Rosa S. Schneiderman, Yaara Porat, Zeev Bomzon, Noa Urman, Aviran Itzhaki, Tali Voloshin, Shay Cahal, Eilon D. Kirson, Uri Weinberg, Yoram Palti. Translational study of tumor treating fields in combination with paclitaxel in ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B79.

Enhanced contactless dielectrophoresis enrichment and isolation platform via cell-scale microstructures

We designed a new microfluidic device that uses pillars on the same order as the diameter of a cell (20 μm) to isolate and enrich rare cell samples from background. These cell-scale microstructures improve viability, trapping efficiency, and throughput while reducing pearl chaining. The area where cells trap on each pillar is small, such that only one or two cells trap while fluid flow carries away excess cells. We employed contactless dielectrophoresis in which a thin PDMS membrane separates the cell suspension from the electrodes, improving cell viability for off-chip collection and analysis. We compared viability and trapping efficiency of a highly aggressive Mouse Ovarian Surface Epithelial (MOSE) cell line in this 20 μm pillar device to measurements in an earlier device with the same layout but pillars of 100 μm diameter. We found that MOSE cells in the new device with 20 μm pillars had higher viability at 350 VRMS, 30 kHz, and 1.2 ml/h (control 77%, untrapped 71%, trapped 81%) than in the previous generation device (untrapped 47%, trapped 42%). The new device can trap up to 6 times more cells under the same conditions. Our new device can sort cells with a high flow rate of 2.2 ml/h and throughput of a few million cells per hour while maintaining a viable population of cells for off-chip analysis. By using the device to separate subpopulations of tumor cells while maintaining their viability at large sample sizes, this technology can be used in developing personalized treatments that target the most aggressive cancerous cells.

Interleukin-12 Immunomodulation Delays the Onset of Lethal Peritoneal Disease of Ovarian Cancer

The omental fat band (OFB) is the predominant site for metastatic seeding of ovarian cancer. Previously, we highlighted the influx and accumulation of neutrophils and macrophages in the OFB following syngeneic ovarian cancer cell seeding as an important factor in the development of a protumorigenic cascade. Here we investigated localized immunomodulation as a means of promoting a successful protective response. As an important TH1-type immunomodulator, interleukin (IL)-12 has previously been investigated clinically as an anticancer therapeutic. However, systemic IL-12 administration was associated with serious side effects, galvanizing the development of immune or accessory cells engineered to express secreted or membrane-bound IL-12 (mbIL-12). Using an mbIL-12-expressing cell variant, we demonstrate that localized IL-12 in the tumor microenvironment significantly delays disease development. The mbIL-12-mediated decrease in tumor burden was associated with a significant reduction in neutrophil and macrophage infiltration in the OFB, and correlated with a reduced expression of neutrophil and macrophage chemoattractants (CXCL1, -2, -3 and CCL2, -7). Vaccination with mitotically impaired tumor cells did not confer protection against subsequent tumor challenge, indicating that IL-12 did not impact the immunogenicity of the cancer cells. Our findings are in agreement with previous reports suggesting that IL-12 may hold promise when delivered in a targeted and sustained manner to the omental microenvironment. Furthermore, resident cells within the omental microenvironment may provide a reservoir that can be activated and mobilized to prevent metastatic seeding within the peritoneum and, therefore, may be targets for chemotherapeutics.

Abstract 5365: Alternating electric fields (TTFields) in combination with paclitaxel are therapeutically effective against ovarian cancer cells in vitro and in vivo

Tumor Treating Fields (TTFields) are low intensity intermediate frequency alternating electric fields that disrupt mitosis. Our previous in vitro studies suggest that ovarian cancer cells are highly sensitive to TTFields treatment.

The goal of the present study was to evaluate the efficacy of the combined treatment of TTFields and paclitaxel against ovarian cancer cells in vitro and in vivo.

For in vitro studies, TTFields (1.75 V/cm) were applied for 72 hours using the inovitro system. The in vivo efficacy of the combined treatment was tested in C57Bl/6 mice, orthotopically injected with MOSE-L FFL luciferase positive cells. Finite Element Mesh (FEM) simulations were performed using the Sim4life software package (ZMT, Zurich, Switzerland) for the calculations of the electric fields intensities around the ovaries.

Our results demonstrate that in vitro application of 200 kHz TTFields led to a significant reduction in both the number of viable cells (44.6%) and the clonogenic potential (23.8%) as compared to untreated cells (p<0.001). Further reduction in the number of viable cells was achieved when TTFields were combined with paclitaxel. In vivo, the combined treatment of TTFields and Paclitaxel led to a significant reduction in tumor luminescence (40%, p<0.01) and in the tumor weight (55%, p<0.05) as compared to untreated tumor bearing mice. FEM simulations demonstrated that electric fields intensities inside and in the vicinity of the ovaries of a real human anatomy model are about 1 and 2 V/cm RMS which is above the minimal threshold required for TTFields response.

Taken together these results demonstrate that the combined treatment of TTFields and paclitaxel could serve as an effective treatment against ovarian cancer. A clinical trial testing the efficacy of the combined modalities is now underway.

Citation Format: Mijal Munster, Christopher P. Roberts, Eva M. Schmelz, Moshe Giladi, Roni Blat, Rosa S. Schneiderman, Yaara Porat, Zeev Bomzon, Noa Urman, Aviran Itzhaki, Tali Voloshin Sela, Shay Cahal, Eilon D. Kirson, Uri Weinberg, Yoram Palti. Alternating electric fields (TTFields) in combination with paclitaxel are therapeutically effective against ovarian cancer cells in vitro and in vivo. [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 5365. doi:10.1158/1538-7445.AM2015-5365

Abstract LB-155: Ovarian cancer-induced changes in the intestinal microbiota as potential biomarkers for early detection

Early detection of cancer can drastically increase the survival rate of the patient. While tremendous efforts were devoted to developing early detection tools, especially cancers in the peritoneal cavity such as ovarian cancer are often detected late after the exfoliated cancer cells have spread throughout the peritoneal cavity and have formed metastases, leading to a high mortality. However, early detection can increase the 5-year survival rate of afflicted women from less than 30% to more than 80%, highlighting the importance of developing early detection tools. Ideally, these tools should be specific for ovarian cancer but include most histological sub-types, and be non-invasive. An attractive source of biomarkers lies within the complex gut microbiome- whose membership and functionality are tightly associated with the health of its host. Changes to the gut microbiota, a concept referred to as dysbiosis, are associated with disease in humans. Here we describe changes in the intestinal microbiota as a function of the presence of ovarian cancer metastases in the peritoneal cavity. We postulate that these might serve as useful markers for earlier detection of ovarian cancer or other peritoneal-associated cancers.

Citation Format: Eva M. Schmelz, Paul C. Roberts, Monica A. Ponder. Ovarian cancer-induced changes in the intestinal microbiota as potential biomarkers for early detection. [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 LB-155. doi:10.1158/1538-7445.AM2014-LB-155

Ovarian tumor-initiating cells display a flexible metabolism

An altered metabolism during ovarian cancer progression allows for increased macromolecular synthesis and unrestrained growth. However, the metabolic phenotype of cancer stem or tumor-initiating cells, small tumor cell populations that are able to recapitulate the original tumor, has not been well characterized. In the present study, we compared the metabolic phenotype of the stem cell enriched cell variant, MOSE-LFFLv (TIC), derived from mouse ovarian surface epithelial (MOSE) cells, to their parental (MOSE-L) and benign precursor (MOSE-E) cells. TICs exhibit a decrease in glucose and fatty acid oxidation with a concomitant increase in lactate secretion. In contrast to MOSE-L cells, TICs can increase their rate of glycolysis to overcome the inhibition of ATP synthase by oligomycin and can increase their oxygen consumption rate to maintain proton motive force when uncoupled, similar to the benign MOSE-E cells. TICs have an increased survival rate under limiting conditions as well as an increased survival rate when treated with AICAR, but exhibit a higher sensitivity to metformin than MOSE-E and MOSE-L cells. Together, our data show that TICs have a distinct metabolic profile that may render them flexible to adapt to the specific conditions of their microenvironment. By better understanding their metabolic phenotype and external environmental conditions that support their survival, treatment interventions can be designed to extend current therapy regimens to eradicate TICs.

Bioactive sphingolipid metabolites modulate ovarian cancer cell structural mechanics

Cancer progression is associated with an increased deformability of cancer cells and reduced resistance to mechanical forces, enabling motility and invasion. This is important for metastases survival and outgrowth and as such could be a target for chemopreventive strategies. In this study, we determined the differential effects of exogenous sphingolipid metabolites on the elastic modulus of mouse ovarian surface epithelial cells as they transition to cancer. Treatment with ceramide or sphingosine-1-phosphate in non-toxic concentrations decreased the average elastic modulus by 21% (p≤ 0.001) in transitional and 15% (p≤ 0.02) in aggressive stages while exerting no appreciable effect on non-malignant cells. In contrast, sphingosine treatment on average increased the elastic modulus by 33% (p≤ 0.0002) in aggressive cells while not affecting precursor cells. These results indicate that tumor-supporting sphingolipid metabolites act by making cells softer, while the anti-cancer metabolite sphingosine partially reverses the decreased elasticity associated with cancer progression. Thus, sphingosine may be a valid alternative to conventional chemotherapeutics in ovarian cancer prevention or treatment.

The parity-associated microenvironmental niche in the omental fat band is refractory to ovarian cancer metastasis

Ovarian cancer is an insidious and aggressive disease of older women, typically undiscovered before peritoneal metastasis due to its asymptomatic nature and lack of early detection tools. Epidemiologic studies suggest that child-bearing (parity) is associated with decreased ovarian cancer risk, although the molecular mechanisms responsible for this phenomenon have not been delineated. Ovarian cancer preferentially metastasizes to the omental fat band (OFB), a secondary lymphoid organ that aids in filtration of the peritoneal serous fluid (PSF) and helps combat peritoneal infections. In the present study, we assessed how parity and age impact the immune compositional profile in the OFB of mice, both in the homeostatic state and as a consequence of peritoneal implantation of ovarian cancer. Using fluorescence-activated cell sorting analysis and quantitative real-time PCR, we found that parity was associated with a significant reduction in omental monocytic subsets and B1-B lymphocytes, correlating with reduced homeostatic expression levels of key chemoattractants and polarization factors (Ccl1, Ccl2, Arg1, and Cxcl13). Of note, parous animals exhibited significantly reduced tumor burden following intraperitoneal implantation compared with nulliparous animals. This was associated with a reduction in tumor-associated neutrophils and macrophages, as well as in the expression levels of their chemoattractants (Cxcl1 and Cxcl5) in the OFB and PSF. These findings define a preexisting "parity-associated microenvironmental niche" in the OFB that is refractory to metastatic tumor seeding and outgrowth. Future studies designed to manipulate this niche may provide a novel means to mitigate peritoneal dissemination of ovarian cancer.

Roles of bioactive sphingolipid metabolites in ovarian cancer cell biomechanics

Bioactive sphingolipid metabolites have emerged as important lipid second messengers in the regulation of cell growth, death, motility and many other events. These processes are important in cancer development and progression; thus, sphingolipid metabolites have been implicated in both cancer development and cancer prevention. Despite recent considerable progress in understanding the multi-faceted functions of these bioactive metabolites, little is known about their influence on the biomechanical property of cells. The biomechanical properties of cancer cells change during progression with aggressive and invasive cells being softer compared to their benign counterparts. In this paper, we investigated the effects of exogenous sphingolipid metabolites on the Young's modulus and cytoskeletal organization of cells representing aggressive ovarian cancer. Our findings demonstrate that the elasticity of aggressive ovarian cancer cells decreased ∼15% after treatment with ceramide and sphingosine-1-phosphate. In contrast, sphingosine treatment caused a ∼30% increase in the average elasticity which was associated with a more defined actin cytoskeleton organization. This indicates that sphingolipid metabolites differentially modulate the biomechanic properties of cancer cells which may have a critical impact on cancer cell survival and progression, and the use of sphingolipid metabolites as chemopreventive or chemo-therapeutic agents.

Sphingolipid metabolites modulate dielectric characteristics of cells in a mouse ovarian cancer progression model

Currently, conventional cancer treatment regimens often rely upon highly toxic chemotherapeutics or target oncogenes that are variably expressed within the heterogeneous cell population of tumors. These challenges highlight the need for novel treatment strategies that (1) are non-toxic yet able to at least partially reverse the aggressive phenotype of the disease to a benign or very slow-growing state, and (2) act on the cells independently of variably expressed biomarkers. Using a label-independent rapid microfluidic cell manipulation strategy known as contactless dielectrophoresis (cDEP), we investigated the effect of non-toxic concentrations of two bioactive sphingolipid metabolites, sphingosine (So), with potential anti-tumor properties, and sphingosine-1-phosphate (S1P), a tumor-promoting metabolite, on the intrinsic electrical properties of early and late stages of mouse ovarian surface epithelial (MOSE) cancer cells. Previously, we demonstrated that electrical properties change as cells progress from a benign early stage to late malignant stages. Here, we demonstrate an association between So treatment and a shift in the bioelectrical characteristics of late stage MOSE (MOSE-L) cells towards a profile similar to that of benign MOSE-E cells. Particularly, the specific membrane capacitance of MOSE-L cells shifted toward that of MOSE-E cells, decreasing from 23.94 ± 2.75 to 16.46 ± 0.62 mF m(-2) after So treatment, associated with a decrease in membrane protrusions. In contrast, S1P did not reverse the electrical properties of MOSE-L cells. This work is the first to indicate that treatment with non-toxic doses of So correlates with changes in the electrical properties and surface roughness of cells. It also demonstrates the potential of cDEP to be used as a new, rapid technique for drug efficacy studies, and for eventually designing more personalized treatment regimens.

Investigating dielectric properties of different stages of syngeneic murine ovarian cancer cells

In this study, the electrical properties of four different stages of mouse ovarian surface epithelial (MOSE) cells were investigated using contactless dielectrophoresis (cDEP). This study expands the work from our previous report describing for the first time the crossover frequency and cell specific membrane capacitance of different stages of cancer cells that are derived from the same cell line. The specific membrane capacitance increased as the stage of malignancy advanced from 15.39 ± 1.54 mF m(-2) for a non-malignant benign stage to 26.42 ± 1.22 mF m(-2) for the most aggressive stage. These differences could be the result of morphological variations due to changes in the cytoskeleton structure, specifically the decrease of the level of actin filaments in the cytoskeleton structure of the transformed MOSE cells. Studying the electrical properties of MOSE cells provides important information as a first step to develop cancer-treatment techniques which could partially reverse the cytoskeleton disorganization of malignant cells to a morphology more similar to that of benign cells.

In vitro model of spontaneous mouse OSE transformation

An in vitro syngeneic model of neoplastic progression of murine ovarian surface epithelial (MOSE) cells represents a valid and significant model that allows for investigations into early mechanisms that impact tumorigenesis. Importantly, MOSE cells representing different stages of neoplastic transformation can be implanted back into immunocompetent mice to investigate host microenvironmental interactions that impact peritoneal dissemination and suppress immune surveillance mechanisms. Here we describe the isolation of MOSE cells that undergo spontaneous transformation upon repeated passage in cell culture. We also provide detailed in vitro assays for 3-D culturing of MOSE cells for characterizing anchorage-independent and invasive growth properties of these cells. Cell lines derived from this model have provided numerous insights into genetic, epigenetic, and biomechanical changes associated with neoplastic progression, as well as the immune responses associated with peritoneal dissemination of ovarian cancer cells.

Dielectrophoretic differentiation of mouse ovarian surface epithelial cells, macrophages, and fibroblasts using contactless dielectrophoresis

Ovarian cancer is the leading cause of death from gynecological malignancies in women. The primary challenge is the detection of the cancer at an early stage, since this drastically increases the survival rate. In this study we investigated the dielectrophoretic responses of progressive stages of mouse ovarian surface epithelial (MOSE) cells, as well as mouse fibroblast and macrophage cell lines, utilizing contactless dielectrophoresis (cDEP). cDEP is a relatively new cell manipulation technique that has addressed some of the challenges of conventional dielectrophoretic methods. To evaluate our microfluidic device performance, we computationally studied the effects of altering various geometrical parameters, such as the size and arrangement of insulating structures, on dielectrophoretic and drag forces. We found that the trapping voltage of MOSE cells increases as the cells progress from a non-tumorigenic, benign cell to a tumorigenic, malignant phenotype. Additionally, all MOSE cells display unique behavior compared to fibroblasts and macrophages, representing normal and inflammatory cells found in the peritoneal fluid. Based on these findings, we predict that cDEP can be utilized for isolation of ovarian cancer cells from peritoneal fluid as an early cancer detection tool.

Abstract 1496: Changes in white adipose tissue progenitor populations with ovarian cancer

Ovarian cancer is the fourth leading cause of cancer death in women and has the highest mortality rate of all gynecological malignancies. Among the greatest risk factors are age, reproductive history, hormone therapy, and more recently suggested, obesity. Currently, the mechanism for how obesity contributes to ovarian cancer is unknown, but there is potential for adipose tissue-associated cells to be key players in this pathogenesis. The stromal vascular fraction (SVF) of white adipose tissue is a rich source of various stem and progenitor cell populations, which can be recruited by cancer cells to enhance cancer progression and metastatic potential. Studies have shown that there is an increase in progenitor populations within the adipose tissue with obesity and age, two risk factors for ovarian cancer. While it has been shown that SVF cells can contribute to cancer, it has not been determined what impact cancer progression has on adipose tissue. It is plausible that ovarian cancer has systemic effects, which may influence cell populations within adipose tissue to promote metastases. Our lab has developed a spontaneously transformed murine ovarian surface epithelial (MOSE) cell model that becomes increasingly more aggressive with repeated passaging. Late passage cells rapidly form tumors when injected into mice, while earlier passage cells do not. Using this model, we investigated the effects of ovarian cancer on systemic changes in progenitor populations. Firefly luciferase-expressing MOSE-L TICv cells, a highly aggressive, metastatic tumor-initiating cell variant were injected into the peritoneal cavity of C57BL/6 mice and stem/progenitor populations and various immune cell populations within the perigonadal white adipose tissue, blood, ascites, and omentum were immunophenotyped by flow cytometry. Changes in gene expression profiles were also analyzed using quantitative real-time PCR. Interestingly, peritoneal dissemination changed the profile and composition of progenitor populations in the various tissues, suggesting that ovarian cancer does have a more widespread impact, affecting the blood and perigonadal adipose tissue. Additionally, co-culture studies demonstrate that MOSE cells and SVF associated cells positively interact enhancing tumor spheroid growth and provide survival signals. This suggests a synergistic relationship between the MOSE and SVF cells. These discoveries may provide a mechanistic link for the detrimental impact of obesity on ovarian cancer progression.

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 1496. doi:1538-7445.AM2012-1496

Abstract 401: Early immune modulatory events during ovarian cancer outgrowth in the omental fat band

Ovarian cancer is the fourth most deadly cancer in women. Typically originating in the layer of epithelial cells surrounding the ovary, cancer cells exfoliate, disseminating throughout the peritoneal cavity. The omental fat band (OFB) has been described as a secondary lymphoid organ, composed of heavily vascularized fatty tissue interspersed with immune cell aggregates. The OFB is also the site of preferential tumor cell adhesion and invasion within the peritoneal cavity, and is removed at the time of surgical debulking in ovarian cancer patients as a preventative measure. Animal studies have shown that ovarian cancer cells home to the omentum as early as 20 minutes post-injection, however the early signaling events that contribute to immune evasion and neoplastic outgrowth have not been fully elucidated. Our lab has developed a spontaneously transformed murine ovarian surface epithelial (MOSE) cell model that, following long-term passaging mimics the progressive stages of ovarian cancer from non-tumorigenic MOSE-E (early) cells to MOSE-L (late) cells which readily disseminate and establish tumors throughout the peritoneum after injection. We have developed two cell variants of the MOSE-L cell line, which differ in their in vivo aggressiveness. The heterogeneous EGFP-expressing MOSE-L IVP2 cell line results in a slowly developing disease state with administration of 1 x 106 cells. In contrast, the MOSE-L firefly luciferase-expressing (FFL) TICv is a highly aggressive tumor-initiating cell variant that results in rapidly disseminating disease with as few as 100 implantable cells. Here we have utilized these cell lines to evaluate early and late changes within the OFB immune microenvironment in order to shed light on both beneficial anti-tumorigenic immune signals, as opposed to signals involved in immune evasion, tumor cell seeding/outgrowth and establishment of aggressive disease states. Specifically, MOSE-E, EGFP∼MOSE-L IVP2 and MOSE-L FFL TICv cells were injected intraperitoneally (IP) into C57BL/6 mice and at 24 h or 4 wks post-injection subsets of mice were euthanized and blood, peritoneal washings, OFB, spleens, perigonadal fat depots were collected for further analysis. Here we describe changes to the OFB and peritoneal serous exudate as a function of tumor cell dissemination using flow cytometry for immunophenotyping and quantitative real-time PCR for gene expression profiling. Preliminary results confirm that ovarian tumor initiating cells preferentially invade the omentum early during cancer metastasis, and are capable of escaping innate immune surveillance mechanisms. In contrast, MOSE-E cells readily home to the OFB early, but are cleared within 7 days. The completion of this study should provide new insights into the initial immunomodulatory events associated with early ovarian cancer seeding and outgrowth within the OFB, a tissue crucial in early ovarian cancer metastasis.

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 401. doi:1538-7445.AM2012-401

Selective concentration of human cancer cells using contactless dielectrophoresis

This work is the first to demonstrate the ability of contactless dielectrophoresis (cDEP) to isolate target cell species from a heterogeneous sample of live cells. Since all cell types have a unique molecular composition, it is expected that their dielectrophoretic (DEP) properties are also unique. cDEP is a technique developed to improve upon traditional and insulator-based DEP devices by replacing embedded metal electrodes with fluid electrode channels positioned alongside desired trapping locations. Through the placement of the fluid electrode channels and the removal of contact between the electrodes and the sample fluid, cDEP mitigates issues associated with sample/electrode contact. MCF10A, MCF7, and MDA-MB-231 human breast cells were used to represent early, intermediate, and late-staged breast cancer, respectively. Trapping frequency responses of each cell type were distinct, with the largest difference between the cells found at 20 and 30 V. MDA-MB-231 cells were successfully isolated from a population containing MCF10A and MCF7 cells at 30 V and 164 kHz. The ability to selectively concentrate cells is the key to development of biological applications using DEP. The isolation of these cells could provide a workbench for clinicians to detect transformed cells at their earliest stage, screen drug therapies prior to patient treatment, increasing the probability of success, and eliminate unsuccessful treatment options.

Selective growth inhibition of human breast cancer cells by graviola fruit extract in vitro and in vivo involving downregulation of EGFR expression

The epidermal growth factor receptor (EGFR) is an oncogene frequently overexpressed in breast cancer (BC), and its overexpression has been associated with poor prognosis and drug resistance. EGFR is therefore a rational target for BC therapy development. This study demonstrated that a graviola fruit extract (GFE) significantly downregulated EGFR gene expression and inhibited the growth of BC cells and xenografts. GFE selectively inhibited the growth of EGFR-overexpressing human BC (MDA-MB-468) cells (IC(50) = 4.8 μg/ml) but had no effect on nontumorigenic human breast epithelial cells (MCF-10A). GFE significantly downregulated EGFR mRNA expression, arrested cell cycle in the G0/G1 phase, and induced apoptosis in MDA-MB-468 cells. In the mouse xenograft model, a 5-wk dietary treatment of GFE (200 mg/kg diet) significantly reduced the protein expression of EGFR, p-EGFR, and p-ERK in MDA-MB-468 tumors by 56%, 54%, and 32.5%, respectively. Overall, dietary GFE inhibited tumor growth, as measured by wet weight, by 32% (P < 0.01). These data showed that dietary GFE induced significant growth inhibition of MDA-MB-468 cells in vitro and in vivo through a mechanism involving the EGFR/ERK signaling pathway, suggesting that GFE may have a protective effect for women against EGFR-overexpressing BC.

Abstract 2359: Regulation of cytoskeleton organization by sphingosine in a mouse cell model of ovarian cancer progression

Ovarian cancer is the fifth leading cause of cancer deaths among women mainly because of late detection of the disease due the lack of symptoms and reliable biomarkers. Approximately 90% of ovarian cancers are derived from the surface epithelium of the ovary. To further investigate the events that lead to progression of epithelial ovarian cancer, we previously developed a cell model of ovarian cancer. Mouse ovarian surface epithelial (MOSE) cells that have undergone spontaneous transformation in cell culture were categorized into distinct morphological and phenotypical stages based on passage history: early passage cells (MOSE-E) represent a pre-neoplastic, non-tumorigenic phenotype whereas late passage cells (MOSE-L) exhibit a highly aggressive malignant phenotype both in vitro and in vivo. In depth studies of genetic changes during MOSE cell progression in our labs have identified the cytoskeleton and its regulatory genes as critical early progression events. These changes in gene expression led to an increasingly dysregulated cytoskeleton which may affect the intracellular localization of signaling intermediates, and, thereby, important downstream signaling events involved in cancer progression. Sphingosine (SO), a bioactive metabolite of complex sphingolipids, has been shown to have chemopreventive activity against cancer, including cancer of the colon, breast and ovarian. In the present study, we have investigated the hypothesis that SO prevents or reverses the observed aberrant cytoskeleton organization, and thereby affects the cells metastatic potential. In MOSE-L cells, SO treatment did not significantly influence the gene expression or protein levels of several cytoskeleton components or regulatory proteins. However, immunostaining of SO-treated MOSE-L cells revealed a reversal of the aberrant cytoskeleton organization and mislocalization of regulatory proteins, many of which are associated with cell migration. This corresponds to observations that SO reduces cell motility in MOSE cells. Our data indicates that cytoskeleton re-organization induced by exogenous SO treatment may be involved in the regulation of signaling pathways that reduce proliferation, migration and invasion of the MOSE cells.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2359. doi:10.1158/1538-7445.AM2011-2359

Abstract 986: Metabolic changes in ovarian cancer progression and mediation by sphingosine: The MOSE model

It is well established that tumor cells have an altered metabolic phenotype. Otto Warburg first demonstrated increased rates of glycolysis and decreased rates of oxidative phosphorylation in late-stage malignant cancer cells. It is however, unclear as to when, during the malignant progression of cancer cells, this switch takes place, what processes are involved, and the potential of these changes to serve as therapeutic targets for clinical intervention trials. Because of the late diagnosis that is associated with ovarian cancer, it is particularly imperative to identify when cellular changes are occurring to develop more efficacious detection and treatment strategies. We used our recently developed and characterized mouse ovarian surface epithelial (MOSE) cancer cells, spontaneously transformed in cell culture and progressed over time from a benign to a highly malignant phenotype both in vitro and in vivo, to study metabolic changes in the distinct disease stages. As ovarian cancer progresses from early to late stages, there were marked decreases in complete oxidation of both glucose and fatty acids. This was concurrent with increases in lactate excretion and 3H-deoxyglucose uptake by the late-stage cancer cells compared to the benign cells. Together, these metabolic changes shift the cells towards a more glycolytic phenotype. Additional studies revealed that these changes were accompanied by increases in pyruvate dehydrogenase activity and citrate synthase activity, indicating an increase in de novo fatty acid and cholesterol synthesis. Treatment of the MOSE cells with 1.5 μM sphingosine, a potent growth inhibitory and cytotoxic sphingolipid metabolite, partially reversed the glycolytic phenotype, decreasing citrate synthase activity and increasing citric acid cycle flux. The Seahorse Bioscience XF Analyzer was used to determine if the observed metabolic changes during MOSE progression are the result of mitochondrial function impairment. Both basal and uncoupled oxygen consumption rates (OCR) decreased as cancer progressed. OCR changes were partially restored after sphingosine treatment. The decreases in mitochondria OCR were supported by decreases in gene and protein expression of mitochondrial fusion and fission proteins as determined by real-time PCR and Western blotting. Taken together, our data confirm metabolic changes during progression and identify the stage specificity of these changes. These results validate the use of the MOSE cell model as an effective model for studying metabolic changes in cancer cell progression and the use of sphingosine as a chemotherapeutic agent to mediate these metabolic changes.

Supported by NIH CA118846 to EMS and PCR.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 986. doi:10.1158/1538-7445.AM2011-986

Changes in gene expression and cellular architecture in an ovarian cancer progression model

BACKGROUND

Ovarian cancer is the fifth leading cause of cancer deaths among women. Early stage disease often remains undetected due the lack of symptoms and reliable biomarkers. The identification of early genetic changes could provide insights into novel signaling pathways that may be exploited for early detection and treatment.

METHODOLOGY/PRINCIPAL FINDINGS

Mouse ovarian surface epithelial (MOSE) cells were used to identify stage-dependent changes in gene expression levels and signal transduction pathways by mouse whole genome microarray analyses and gene ontology. These cells have undergone spontaneous transformation in cell culture and transitioned from non-tumorigenic to intermediate and aggressive, malignant phenotypes. Significantly changed genes were overrepresented in a number of pathways, most notably the cytoskeleton functional category. Concurrent with gene expression changes, the cytoskeletal architecture became progressively disorganized, resulting in aberrant expression or subcellular distribution of key cytoskeletal regulatory proteins (focal adhesion kinase, α-actinin, and vinculin). The cytoskeletal disorganization was accompanied by altered patterns of serine and tyrosine phosphorylation as well as changed expression and subcellular localization of integral signaling intermediates APC and PKCβII.

CONCLUSIONS/SIGNIFICANCE

Our studies have identified genes that are aberrantly expressed during MOSE cell neoplastic progression. We show that early stage dysregulation of actin microfilaments is followed by progressive disorganization of microtubules and intermediate filaments at later stages. These stage-specific, step-wise changes provide further insights into the time and spatial sequence of events that lead to the fully transformed state since these changes are also observed in aggressive human ovarian cancer cell lines independent of their histological type. Moreover, our studies support a link between aberrant cytoskeleton organization and regulation of important downstream signaling events that may be involved in cancer progression. Thus, our MOSE-derived cell model represents a unique model for in depth mechanistic studies of ovarian cancer progression.

Suppression of intestinal inflammation and inflammation-driven colon cancer in mice by dietary sphingomyelin: importance of peroxisome proliferator-activated receptor γ expression

Inflammation of the gastrointestinal tract increases the risk of developing colon cancer especially in younger adults. Dietary compounds are not only associated with the etiology of inflammation and colon cancer but also in their prevention. Sphingolipid metabolites have been shown to play a role in the initiation and perpetuation of inflammatory responses. In the present study, we investigated the suppression of dextran sodium sulfate-induced colitis and azoxymethane-induced colon cancer by dietary sphingomyelin (SM) in mice that lack functional peroxisome proliferator-activated receptor γ (PPAR-γ) in intestinal epithelial and immune cells. Dietary SM decreased disease activity and colonic inflammatory lesions in mice of both genotypes but more efficiently in mice expressing PPAR-γ. The increased survival and suppression of tumor formation in the SM-fed mice appeared to be independent of PPAR-γ expression in immune and epithelial cells. Using a real-time polymerase chain reaction array, we detected an up-regulation in genes involved in Th1 (interferon γ) and Th17 (interleukin [IL]-17 and IL-23) responses despite the reduced inflammation scores. However, the genes involved in Th2 (IL-4, IL-13 and IL-13ra2) and Treg (IL-10rb) anti-inflammatory responses were up-regulated in a PPAR-γ-dependent manner. In line with the PPAR-γ dependency of our in vivo findings, treatment of RAW macrophages with sphingosine increased the PPAR-γ reporter activity. In conclusion, dietary SM modulated inflammatory responses at the early stages of the disease by activating PPAR-γ, but its anticarcinogenic effects followed a PPAR-γ-independent pattern.

Evaluation of the influence of growth medium composition on cell elasticity

Recently, there has been an increasing interest in using the biomechanical properties of cells as biomarkers to discriminate between normal and cancerous cells. However, few investigators have considered the influence of the growth medium composition when evaluating the biomechanical properties of the normal and diseased cells. In this study, we investigated the variation in Young's modulus of non-malignant MCF10A and malignant MDA-MB-231 breast cells seeded in five different growth media under controlled experimental conditions. The average Young's modulus of MDA-MB-231 cells was significantly lower (p<0.0001) than the mean Young's modulus of MCF10A cells when compared in identical medium compositions. However, we found that growth medium composition affected the elasticity of MCF10A and MDA-MB-231 cells. The average Young's modulus of both cell lines decreased by 10-18% when the serum was reduced from 10% to 5% and upon addition of epidermal growth factor (EGF, 20 ng/ml) to the medium. Though these elasticity changes might have some biological impact, none was statistically significant. However, the elasticity of MCF10A was significantly more responsive than MDA-MB-231 cells to the medium composition supplemented with EGF, cholera toxin (CT), insulin (INS) and hydrocortisone (HC), which are recommended for routine cultivation of MCF10A cells (M5). MCF10A cells were significantly softer (p<0.002) when grown in medium M5 compared to a standard MDA-MB-231 medium (M1). The investigation of the effects of culture medium composition on the elastic properties of cells highlights the need to take these effects into consideration when interpreting elasticity measurements in cells grown in different media.

Folate deficiency provides protection against colon carcinogenesis in DNA polymerase beta haploinsufficient mice

Aging and DNA polymerase beta deficiency (beta-pol(+/-)) interact to accelerate the development of malignant lymphomas and adenocarcinoma and increase tumor bearing load in mice. Folate deficiency (FD) has been shown to induce DNA damage repaired via the base excision repair (BER) pathway. We anticipated that FD and BER deficiency would interact to accelerate aberrant crypt foci (ACF) formation and tumor development in beta-pol haploinsufficient animals. FD resulted in a significant increase in ACF formation in wild type (WT) animals exposed to 1,2-dimethylhydrazine, a known colon and liver carcinogen; however, FD reduced development of ACF in beta-pol haploinsufficient mice. Prolonged feeding of the FD diet resulted in advanced ACF formation and liver tumors in wild type mice. However, FD attenuated onset and progression of ACF and prevented liver tumorigenesis in beta-pol haploinsufficient mice, i.e. FD provided protection against tumorigenesis in a BER-deficient environment in all tissues where 1,2-dimethylhydrazine exerts its damage. Here we show a distinct down-regulation in DNA repair pathways, e.g. BER, nucleotide excision repair, and mismatch repair, and decline in cell proliferation, as well as an up-regulation in poly(ADP-ribose) polymerase, proapoptotic genes, and apoptosis in colons of FD beta-pol haploinsufficient mice.

Abstract 2875: Regulation of gene expression by sphingosine in a mouse cell model of ovarian cancer progression

Approximately 90% of ovarian cancers are derived from the surface epithelium of the ovary. To study and further understand the early events that lead to epithelial ovarian cancer, we previously developed the syngeneic mouse ovarian surface epithelial (MOSE) model; MOSE cells have undergone spontaneous transformation in cell culture and were categorized into distinct stages by their phenotype, with early passages (MOSE-E) representing a pre-neoplastic, non-tumorigenic phenotype to late passages (MOSE-L) that demonstrate a highly aggressive malignant phenotype both in vitro and in vivo. Sphingosine, a bioactive metabolite of complex sphingolipids, has been shown to have chemopreventive properties in cancer, including colon and ovarian. In these studies we have investigated the hypothesis that sphingosine can prevent or reverse the aberrant gene expression in MOSE-L cells. Using a complete mouse genome microarray, we have identified 1412 genes that were significantly changed in the late malignant MOSE-L versus non-tumorigenic MOSE-E cells. Upon treatment of MOSE-L cells with non-toxic concentrations of sphingosine, microarray analysis revealed the down-regulation of 172 of 701 upregulated genes and up-regulation of 176 of 711 down-regulated genes in MOSE-L cells. Gene ontology analyses showed that these genes were overrepresented in specific categories with up-regulated genes involved in lipid and steroid metabolism, ER, and innate immune response while down regulated genes are involved in cell cycle, cytoskeleton and its regulation, and chromosome stability. A comparison of upregulated genes in MOSE-L cells treated with 5’-azaDC and sphingosine identified genes that are potentially epigenetically silenced by promoter methylation as cells transition from pre-neoplastic to malignant. Also, in addition to changes in gene expression, sphingosine reversed aberrant cytoskeleton organization. Taken together, this indicates that sphingosine acts as a chemopreventive agent by regulating multiple pathways including gene expression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2875.

Abstract 5684: B-catenin-dependent and independent changes in gene expression induced by sphingolipids

Dietary supplementation with sphingolipids inhibits colon tumorigenesis in carcinogen-treated CF1 mice and in multiple intestinal neoplasia (Min) mice that produce intestinal tumors spontaneously. In both cancer models the regulation of β-catenin by sphingolipid metabolites is an important early event. Stabilization and nuclear translocation of β-catenin and its interaction with T-cell factor (TCF)/lymphoid enhancer factor (LEF) play important roles to activate the transcription of genes associated with cancer development and progression. Sphingosine and ceramides, major digestion products of complex sphingolipids in the diet, down-regulate β-catenin transcriptional activity in a dose- and time-dependent manner. Our data indicate that sphingosine and ceramides suppress SW480 human colon cancer cell growth in a concentration-dependent manner. In the present study, we investigated the dependency of sphingosine- and ceramide-induced changes in gene expression on β-catenin transcriptional activity by comparing control and β-catenin siRNA treated cells. We observed changes in the expression of genes involved in signal transduction, transcription factors, cell cycle control and DNA damage repair, cell adhesion, cell invasion and metastasis, angiogenesis, and apoptosis and cell senescence. Most genes were regulated by all metabolites; however, some genes were only targeted by specific metabolites. Furthermore, only a small number of genes regulated by the sphingolipid metabolites relied completely on the activation of the β-catenin transcriptional activity. Further experiments are currently being performed to confirm the function of β-catenin on the regulation of these genes.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5684.

Conjugated linoleic acid ameliorates inflammation-induced colorectal cancer in mice through activation of PPARgamma

Conjugated linoleic acid (CLA) exerts a protective effect on experimental inflammatory bowel disease and shows promise as a chemopreventive agent against colorectal cancer (CRC) in mice, although the mechanisms by which it exerts its beneficial effects against malignancies in the gut are not completely understood. Mice lacking PPARgamma in immune and epithelial cells and PPARgamma-expressing littermates were fed either control or CLA-supplemented (1 g CLA/100 g) diets to determine the role of PPARgamma in inflammation-induced CRC. To induce tumor formation and colitis, mice were treated with azoxymethane and then challenged with 2% dextran sodium sulfate, respectively. Dietary CLA ameliorated disease activity, decreased colitis, and prevented adenocarcinoma formation in the PPARgamma-expressing floxed mice but not in the tissue-specific PPARgamma-null mice. Dietary CLA supplementation significantly decreased the percentages of macrophages in the mesenteric lymph nodes (MLN) regardless of the genotype and increased regulatory T cell numbers in MLN of PPARgamma-expressing, but not in the tissue-specific, PPARgamma-null mice. Colonic tumor necrosis factor-alpha mRNA expression was significantly suppressed in CLA-fed, PPARgamma-expressing mice. This study suggests CLA ameliorates colitis and prevents tumor formation in part through a PPARgamma-dependent mechanism.

Regulation of beta-catenin and connexin-43 expression: targets for sphingolipids in colon cancer prevention

Sphingolipid metabolites are generated throughout the intestinal tract after hydrolysis of orally administered complex sphingolipids and significantly suppress colon cancer in carcinogen-treated CF1 mice. In the present study, the mechanisms of tumor suppression by dietary sphingolipids were investigated. Changes in select genes that are critical in early stages of colon cancer were analyzed in the colonic mucosa of dimethylhydrazine-treated CF1 mice fed AIN76A diet with or without 0.05% sphingomyelin (SM). Supplementation with SM did not significantly alter mRNA levels of most of the selected genes. However, a downregulation of beta-catenin (p = 0.007) and increased protein levels of connexin-43 (p = 0.017) and Bcl-2 (p = 0.033) were observed in SM-fed animals. This suggests that sphingolipids may be regulating specific post-transcriptional events to reverse aberrant expression of individual proteins. Since the dysregulation of beta-catenin metabolism and its transcriptional activity in addition to a decreased intercellular communication has been causally linked to the development of colon cancer while a low Bcl-2 expression is associated with a worse prognosis in colon cancer, the reversal of these early changes may be important events in the prevention of colon cancer by orally administered sphingolipids, and may provide specific molecular biomarkers for sphingolipid efficacy in vivo.

Regression of early and intermediate stages of colon cancer by targeting multiple members of the EGFR family with EGFR-related protein

A role of the epidermal growth factor receptor (EGFR) family has been suggested in colon cancer etiology, progression, and/or severity. Our recently identified pan-erbB inhibitor EGFR-related protein (ERRP) targets EGFRs by attenuating their activation and subsequent signaling leading to cellular growth inhibition. In the present study, we evaluated the therapeutic effectiveness of ERRP on early and intermediate stages of colon cancer by examining regression of chemically induced aberrant crypt foci (ACF) in the colon of CF1 mice and intestinal adenomas in APC(Min+/-) (Min) mice. After formation of ACF or adenomas, the mice were injected (i.p.) with ERRP (50 microg/mouse) for 10 consecutive days. This treatment significantly reduced the number of ACF from 25.0 +/- 3.0 (controls) to 14.9 +/- 1.6 (ERRP-treated; P = 0.011) and also reduced their size (P < 0.01). In Min mice, ERRP caused the regression of adenomas throughout the small intestine (P < 0.05) and reduced their size (P < 0.001). This could partly be attributed to inhibition of proliferation and stimulation of apoptosis in the intestinal mucosa and was associated with decreased activation of several EGFR family members, suppression of downstream effector nuclear factor kappaB and down-regulation of cyclooxygenase-2. ERRP-induced attenuation of EGFR activation could be due to increased sequestration of the ligand(s) by ERRP, rendering them unavailable for binding to and activation of the receptor. In conclusion, our data show that ERRP is effective in regressing both early and intermediate intestinal lesions and could be an effective therapeutic agent for colon cancer.