A Perspective Review: Analyzing Collagen Alterations in Ovarian Cancer by High-Resolution Optical Microscopy

High-grade serous ovarian cancer (HGSOC) is the predominant subtype of ovarian cancer (OC), occurring in more than 80% of patients diagnosed with this malignancy. Histological and genetic analysis have confirmed the secretory epithelial of the fallopian tube (FT) as a major site of origin of HGSOC. Although there have been significant strides in our understanding of this disease, early stage detection and diagnosis are still rare. Current clinical imaging modalities lack the ability to detect early stage pathogenesis in the fallopian tubes and the ovaries. However, there are several microscopic imaging techniques used to analyze the structural modifications in the extracellular matrix (ECM) protein collagen in ex vivo FT and ovarian tissues that potentially can be modified to fit the clinical setting. In this perspective, we evaluate and compare the myriad of optical tools available to visualize these alterations and the invaluable insights these data provide on HGSOC initiation. We also discuss the clinical implications of these findings and how these data may help novel tools for early diagnosis of HGSOC.

6-Plex mdSUGAR Isobaric-Labeling Guide Fingerprint Embedding for Glycomics Analysis

Glycans are vital biomolecules with diverse functions in biological processes. Mass spectrometry (MS) has become the most widely employed technology for glycomics studies. However, in the traditional data-dependent acquisition mode, only a subset of the abundant ions during MS1 scans are isolated and fragmented in subsequent MS2 events, which reduces reproducibility and prevents the measurement of low-abundance glycan species. Here, we reported a new method termed 6-plex mdSUGAR isobaric-labeling guide fingerprint embedding (MAGNI), to achieve multiplexed, quantitative, and targeted glycan analysis. The glycan peak signature was embedded by a triplicate-labeling strategy with a 6-plex mdSUGAR tag, and using ultrahigh-resolution mass spectrometers, the low-abundance glycans that carry the mass fingerprints can be recognized on the MS1 spectra through an in-house developed software tool, MAGNIFinder. These embedded unique fingerprints can guide the selection and fragmentation of targeted precursor ions and further provide rich information on glycan structures. Quantitative analysis of two standard glycoproteins demonstrated the accuracy and precision of MAGNI. Using this approach, we identified 304 N-glycans in two ovarian cancer cell lines. Among them, 65 unique N-glycans were found differentially expressed, which indicates a distinct glycosylation pattern for each cell line. Remarkably, 31 N-glycans can be quantified in only 1 × 103 cells, demonstrating the high sensitivity of our method. Taken together, our MAGNI method offers a useful tool for low-abundance N-glycan characterization and is capable of determining small quantitative differences in N-glycan profiling. Therefore, it will be beneficial to the field of glycobiology and will expand our understanding of glycosylation.

Mononuclear Cells Negatively Regulate Endothelial Ca2+ Signaling

Endothelial Ca2+ signaling has important roles to play in maintaining pregnancy associated vasodilation in the utero-placenta. Inflammatory cytokines, often elevated in vascular complications of pregnancy, negatively regulate ATP-stimulated endothelial Ca2+ signaling and associated nitric oxide production. However, the role of direct engagement of immune cells on endothelial Ca2+ signaling and therefore endothelial function is unclear. To model immune-endothelial interactions, herein, we evaluate the effects of peripheral blood mononuclear cells (PBMCs) in short-term interaction with human umbilical vein endothelial cells (HUVECs) on agonist-stimulated Ca2+ signaling in HUVECs. We find that mononuclear cells (10:1 and 25:1 mononuclear: HUVEC) cause decreased ATP-stimulated Ca2+ signaling; worsened by activated mononuclear cells possibly due to increased cytokine secretion. Additionally, monocytes, natural killers, and T-cells cause decrease in ATP-stimulated Ca2+ signaling using THP-1 (monocyte), NKL (natural killer cells), and Jurkat (T-cell) cell lines, respectively. PBMCs with Golgi-restricted protein transport prior to interaction with endothelial cells display rescue in Ca2+ signaling, strongly suggesting that secreted proteins from PBMCs mediate changes in HUVEC Ca2+ signaling. We propose that endothelial cells from normal pregnancy interacting with PBMCs may model preeclamptic endothelial-immune interaction and resultant endothelial dysfunction.

Preclinical studies of a PARP targeted, Meitner-Auger emitting, theranostic radiopharmaceutical for metastatic ovarian cancer

Advanced ovarian cancer currently has few therapeutic options. Poly(ADP-ribose) polymerase (PARP) inhibitors bind to nuclear PARP and trap the protein-inhibitor complex to DNA. This work investigates a theranostic PARP inhibitor for targeted radiopharmaceutical therapy of ovarian cancer in vitro and PET imaging of healthy mice in vivo.

METHODS

[77Br]RD1 was synthesized and assessed for pharmacokinetics and cytotoxicity in human and murine ovarian cancer cell lines. [76Br]RD1 biodistribution and organ uptake in healthy mice were quantified through longitudinal PET/CT imaging and ex vivo radioactivity measurements. Organ-level dosimetry following [76/77Br]RD1 administration was calculated using RAPID, an in-house platform for absorbed dose in mice, and OLINDA for equivalent and effective dose in human.

RESULTS

The maximum specific binding (Bmax), equilibrium dissociation constant (Kd), and nonspecific binding slope (NS) were calculated for each cell line. These values were used to calculate the cell specific activity uptake for cell viability studies. The half maximal effective concentration (EC50) was measured as 0.17 (95 % CI: 0.13-0.24) nM and 0.46 (0.13-0.24) nM for PARP(+) and PARP(-) expressing cell lines, respectively. The EC50 was 0.27 (0.21-0.36) nM and 0.30 (0.22-0.41) nM for BRCA1(-) and BRCA1(+) expressing cell lines, respectively. When measuring the EC50 as a function of cellular activity uptake and nuclear dose, the EC50 ranges from 0.020 to 0.039 Bq/cell and 3.3-9.2 Gy, respectively. Excretion through the hepatobiliary and renal pathways were observed in mice, with liver uptake of 2.3 ± 0.4 %ID/g after 48 h, contributing to estimated absorbed dose values in mice of 19.3 ± 0.3 mGy/MBq and 290 ± 10 mGy/MBq for [77Br]RD1 and [76Br]RD1, respectively.

CONCLUSION

[77Br]RD1 cytotoxicity was dependent on PARP expression and independent of BRCA1 status. The in vitro results suggest that [77Br]RD1 cytotoxicity is driven by the targeted Meitner-Auger electron (MAe) radiotherapeutic effect of the agent. Further studies investigating the theranostic potential, organ dose, and tumor uptake of [76/77Br]RD1 are warranted.

Oxidative phosphorylation inhibitors inhibit proliferation of endometriosis cells

In brief

Developing novel therapies to cure and manage endometriosis is a major unmet need that will benefit over 180 million women worldwide. Results from the current study suggest that inhibitors of oxidative phosphorylation may serve as novel agents for the treatment of endometriosis.

Abstract

Current therapeutic strategies for endometriosis focus on symptom management and are not curative. Here, we provide evidence supporting the inhibition of oxidative phosphorylation (OXPHOS) as a novel treatment strategy for endometriosis. Additionally, we report an organotypic organ-on-a-chip luminal model for endometriosis. The OXPHOS inhibitors, curcumin, plumbagin, and the FDA-approved anti-malarial agent, atovaquone, were tested against the endometriosis cell line, 12Z, in conventional as well as the new organotypic model. The results suggest that all three compounds inhibit proliferation and cause cell death of the endometriotic cells by inhibiting OXPHOS and causing an increase in intracellular oxygen radicals. The oxidative stress mediated by curcumin, plumbagin, and atovaquone causes DNA double-strand breaks as indicated by the elevation of phospho-γH2Ax. Mitochondrial energetics shows a significant decrease in oxygen consumption in 12Z cells. These experiments also highlight differences in the mechanism of action as curcumin and plumbagin inhibit complex I whereas atovaquone blocks complexes I, II, and III. Real-time assessment of cells in the lumen model showed inhibition of migration in response to the test compounds. Additionally, using two-photon lifetime imaging, we demonstrate that the 12Z cells in the lumen show decreased redox ratio (NAD(P)H/FAD) and lower fluorescence lifetime of NAD(P)H in the treated cells confirming major metabolic changes in response to inhibition of mitochondrial electron transport. The robust chemotoxic responses observed with atovaquone suggest that this anti-malarial agent may be repurposed for the effective treatment of endometriosis.

Assessing the roles of collagen fiber morphology and matrix stiffness on ovarian cancer cell migration dynamics using multiphoton fabricated orthogonal image-based models

Ovarian cancer remains the deadliest of the gynecological cancers, where this arises from poor screening and imaging tools that can detect early disease, and also limited understanding of the structural and functional aspects of the tumor microenvironment. To gain insight into the underlying cellular dynamics, we have used multiphoton excited fabrication to create Second Harmonic Generation (SHG) image-based orthogonal models from collagen/GelMA that represent both the collagen matrix morphology and stiffness (∼2-8 kPa) of normal ovarian stroma and high grade serous ovarian cancers (HGSOC). These scaffolds are used to study migration/cytoskeletal dynamics of normal (IOSE) and ovarian cancer (OVCA433) cell lines. We found that the highly aligned fiber morphology of HGSOC promotes aspects of motility (motility coefficient, motility, and focal adhesion expression) through a contact guidance mechanism and that stiffer matrix further promotes these same processes through a mechanosensitive mechanism, where these trends were similar for both normal and cancer cells. However, cell specific differences were found on these orthogonal models relative to those providing only morphology, showing the importance of presenting both morphology and stiffness cues. Moreover, we found increased cadherin expression and decreased cell alignment only for cancer cells on scaffolds of intermediate modulus suggesting different stiffness-dependent mechanotransduction mechanisms are engaged. This overall approach affords decoupling the roles of matrix morphology, stiffness and cell genotype and affords hypothesis testing of the factors giving rise to disease progression and metastasis. Further, more established fabrication techniques cannot simultaneously reproduce both the 3D collagen fiber morphology and stiffness. STATEMENT OF SIGNIFICANCE: Ovarian cancer metastasizes when lesions are small, where cells exfoliate from the surface of the ovary and reattach at distal sites in the peritoneum. The adhesion/migration dynamics are not well understood and there is a need for new 3D in vitro models of the extracellular matrix to study the biology. Here we use multiphoton excited crosslinking to fabricate ECM orthogonal models that represent the collagen morphology and stiffness in human ovarian tissues. These are then used to study ovarian cancer cell migration dynamics and we found that contact guidance and a mechanosensitive response and cell genotype all combine to affect the behavior. These models provide insight into disease etiology and progression not readily possible by other fabrication methods.

Ovarian Cancer Ascites Inhibits Transcriptional Activation of NK Cells Partly through CA125

Malignant ascites is a common clinical problem in ovarian cancer. NK cells are present in the ascites, but their antitumor activity is inhibited. The underlying mechanisms of the inhibition have yet to be fully elucidated. Using an Fcγ receptor-mediated NK cell activation assay, we show that ascites from ovarian cancer patients potently inhibits NK cell activation. Part of the inhibitory activity is mediated by CA125, a mucin 16 fragment shed from ovarian cancer tumors. Moreover, transcriptional analyses by RNA sequencing reveal upregulation of genes involved in multiple metabolic pathways but downregulation of genes involved in cytotoxicity and signaling pathways in NK cells purified from ovarian cancer patient ascites. Transcription of genes involved in cytotoxicity pathways are also downregulated in NK cells from healthy donors after in vitro treatment with ascites or with a CA125-enriched protein fraction. These results show that ascites and CA125 inhibit antitumor activity of NK cells at transcriptional levels by suppressing expression of genes involved in NK cell activation and cytotoxicity. Our findings shed light on the molecular mechanisms by which ascites inhibits the activity of NK cells and suggest possible approaches to reactivate NK cells for ovarian cancer immunotherapy.

Multiparameter Flow Cytometry for Detailed Characterization of Peritoneal Immune Cells from Patients with Ovarian Cancer

Multiparameter flow cytometry is a convenient and efficient method for thorough phenotyping of cells, and especially immune cells from various tissues. We have successfully used multiparameter flow cytometry to characterize immune cells from patients with ovarian cancer and leveraged dimensionality reduction and machine learning for optimized visualization and analysis. Herein, we describe our optimized and established protocols for the labeling of cells with fluorophore-conjugated antibody panels, followed by details on data acquisition. Finally, we describe methods for analysis of the flow cytometry data using both FlowJo as well as R package, Cytofkit, for multidimensional data visualization.

The Natural Product β-Escin Targets Cancer and Stromal Cells of the Tumor Microenvironment to Inhibit Ovarian Cancer Metastasis

Simple Summary

β-escin, a component of horse chestnut seed extract, was first identified as an inhibitor of ovarian cancer (OvCa) adhesion/invasion in our high-throughput screening program using a three-dimensional organotypic model assembled from primary human cells and extracellular matrix. The goal of the study presented here is to determine if β-escin and structurally-similar compounds have a therapeutic potential against OvCa metastasis. β-escin and cardiac glycosides inhibit ovarian cancer adhesion/invasion to the omental microenvironment in vivo, and β-escin inhibits ovarian cancer metastasis in the prevention and intervention setting. Additionally, β-escin was found to decrease the stemness of ovarian cancer cells, inhibit extracellular matrix production in the tumor microenvironment, and inhibit HIF1α stability in ovarian cancer cells and the tumor microenvironment. This study reveals that the natural compound β-escin has therapeutic potential because of its ability to prevent OvCa dissemination by targeting both cancer and stromal cells in the OvCa tumor microenvironment.

Abstract

The high mortality of OvCa is caused by the wide dissemination of cancer within the abdominal cavity. OvCa cells metastasize to the peritoneum, which is covered by mesothelial cells, and invade into the underlying stroma, composed of extracellular matrices (ECM) and stromal cells. In a study using a three-dimensional quantitative high-throughput screening platform (3D-qHTS), we found that β-escin, a component of horse chestnut seed extract, inhibited OvCa adhesion/invasion. Here, we determine whether β-escin and structurally similar compounds have a therapeutic potential against OvCa metastasis. Different sources of β-escin and horse chestnut seed extract inhibited OvCa cell adhesion/invasion, both in vitro and in vivo. From a collection of 160 structurally similar compounds to β-escin, we found that cardiac glycosides inhibited OvCa cell adhesion/invasion and proliferation in vitro, and inhibited adhesion/invasion and metastasis in vivo. Mechanistically, β-escin and the cardiac glycosides inhibited ECM production in mesothelial cells and fibroblasts. The oral administration of β-escin inhibited metastasis in both OvCa prevention and intervention mouse models. Specifically, β-escin inhibited ECM production in the omental tumors. Additionally, the production of HIF1α-targeted proteins, lactate dehydrogenase A, and hexokinase 2 in omental tumors was blocked by β-escin. This study reveals that the natural compound β-escin has a therapeutic potential because of its ability to prevent OvCa dissemination by targeting both cancer and stromal cells in the OvCa tumor microenvironment.

Evaluation of Collagen Alterations in Early Precursor Lesions of High Grade Serous Ovarian Cancer by Second Harmonic Generation Microscopy and Mass Spectrometry

Simple Summary

The collagen architecture in the extracellular matrix (ECM) is highly remodeled in high grade serous ovarian cancer (HGSOC). Many of these tumors begin in the fallopian tubes (FT) before metastasizing to the ovaries and it is important to study ECM alterations in carcinogenesis. Here, we used Second Harmonic Generation (SHG) microscopy to classify changes in the collagen fiber morphology in normal FT, and precursor pure p53 signatures and serous tubal intraepithelial carcinoma (STICs) in tissues with no HGSOC. Using a machine learning approach based on image features, we were able to discriminate the tissue groups with good classification accuracy. We additionally performed mass spectrometry analysis of normal and HGSOC tissues to associate the differential expression of collagen isoforms with fiber morphology alterations. This work provides new insights into ECM remodeling in early stage HGSOC and suggests the combined use of SHG microscopy and mass spectrometry as a new diagnostic/prognostic approach.

Abstract

Background: The collagen architecture in high grade serous ovarian cancer (HGSOC) is highly remodeled compared to the normal ovary and the fallopian tubes (FT). We previously used Second Harmonic Generation (SHG) microscopy and machine learning to classify the changes in collagen fiber morphology occurring in serous tubal intraepithelial carcinoma (STIC) lesions that are concurrent with HGSOC. We now extend these studies to examine collagen remodeling in pure p53 signatures, STICs and normal regions in tissues that have no concurrent HGSOC. This is an important distinction as high-grade disease can result in distant collagen changes through a field effect mechanism. Methods: We trained a linear discriminant model based on SHG texture and image features as a classifier to discriminate the tissue groups. We additionally performed mass spectrometry analysis of normal and HGSOC tissues to associate the differential expression of collagen isoforms with collagen fiber morphology alterations. Results: We quantified the differences in the collagen architecture between normal tissue and the precursors with good classification accuracy. Through proteomic analysis, we identified the downregulation of single α-chains including those for Col I and III, where these results are consistent with our previous SHG-based supramolecular analyses. Conclusion: This work provides new insights into ECM remodeling in early ovarian cancer and suggests the combined use of SHG microscopy and mass spectrometry as a new diagnostic/prognostic approach.

Identifying novel ovarian tumor biomarkers through mining of the transcriptome of circulating immune cells: A proof-of-concept study

OBJECTIVE

Treatment of high-grade serous ovarian cancer (HGSOC) will benefit from early detection of cancer. Here, we provide proof-of-concept data supporting the hypothesis that circulating immune cells, because of their early recognition of tumors and the tumor microenvironment, can be considered for biomarker discovery.

METHODS

Longitudinal blood samples from C57BL/6 mice bearing syngeneic ovarian tumors and peripheral blood mononuclear cells (PBMC) from healthy postmenopausal women and newly diagnosed for HGSOC patients were subjected to RNASeq. The results from human immune cells were validated using Affymetrix microarrays. Differentially expressed transcripts in immune cells from tumor-bearing mice and HGSOC patients were compared to matching controls.

RESULTS

A total of 1282 transcripts (798 and 484, up- and downregulated, respectively) were differentially expressed in the tumor-bearing mice as compared with controls. Top 100 genes showing longitudinal changes in gene expression 2, 4, 7, and 18 days after tumor implantation were identified. Analysis of the PBMC from healthy post-menopausal women and HGSOC patients identified 4382 differentially expressed genes and 519 of these were validated through Affymetrix microarray analysis. A total of 384 genes, including IL-1R2, CH3L1, Infitm1, FP42, CXC42, Hdc, Spib, and Sema6b, were differentially expressed in the human and mouse datasets.

CONCLUSION

The PBMC transcriptome shows longitudinal changes in response to the progressing tumor. Several potential biomarker transcripts were identified in HGSOC patients and mouse models. Monitoring their expression in individual PBMC subsets can serve as additional discriminator for the diagnosis of HGSOC.

Affinity-free enrichment and mass spectrometry analysis of the ovarian cancer biomarker CA125 (MUC16) from patient-derived ascites

Developing a mass spectrometry-based assay for the ovarian cancer biomarker CA125 (MUC16) is a desirable goal, because it may enable detection of molecular regions that are not recognized by antibodies and are therefore analytically silent in the current immunoassay. Additionally, the ability to characterize the CA125 proteoforms expressed by individuals may offer clinical insight. Enrichment of CA125 from malignant ascites may provide a high-quality source of this important ovarian cancer biomarker, but a reliable strategy for such enrichment is currently lacking. Beginning with crude ascites isolated from three individual patients with high grade serous ovarian cancer, we enriched for MUC16 using filtration, ion exchange, and size exclusion chromatography and then performed bottom-up proteomics on the isolated proteins. This approach of enrichment and analysis reveals that the peptides detected via mass spectrometry map to the SEA domain and C-loop regions within the tandem repeat domains of CA125 and that peptide abundance correlates with clinical CA125 counts.

Characterization of Cell-Bound CA125 on Immune Cell Subtypes of Ovarian Cancer Patients Using a Novel Imaging Platform

MUC16, a sialomucin that contains the ovarian cancer biomarker CA125, binds at low abundance to leucocytes via the immune receptor, Siglec-9. Conventional fluorescence-based imaging techniques lack the sensitivity to assess this low-abundance event, prompting us to develop a novel "digital" optical cytometry technique for qualitative and quantitative assessment of CA125 binding to peripheral blood mononuclear cells (PBMC). Plasmonic nanoparticle labeled detection antibody allows assessment of CA125 at the near-single molecule level when bound to specific immune cell lineages that are simultaneously identified using multiparameter fluorescence imaging. Image analysis and deep learning were used to quantify CA125 per each cell lineage. PBMC from treatment naïve ovarian cancer patients (N = 14) showed higher cell surface abundance of CA125 on the aggregate PBMC population as well as on NK (p = 0.013), T (p < 0.001) and B cells (p = 0.024) compared to circulating lymphocytes of healthy donors (N = 7). Differences in CA125 binding to monocytes or NK-T cells between the two cohorts were not significant. There was no correlation between the PBMC-bound and serum levels of CA125, suggesting that these two compartments are not in stoichiometric equilibrium. Understanding where and how subset-specific cell-bound surface CA125 takes place may provide guidance towards a new diagnostic biomarker in ovarian cancer.

Oxidative stress induced by the anti-cancer agents, plumbagin, and atovaquone, inhibits ion transport through Na+/K+-ATPase

Oxidative stress inhibits Na⁺/K⁺-ATPase (NKA), the ion channel that maintains membrane potential. Here, we investigate the role of oxidative stress-mediated by plumbagin and atovaquone in the inhibition of NKA activity. We confirm that plumbagin and atovaquone inhibit the proliferation of three human (OVCAR-3, SKOV-3, and TYKNu) and one mouse (ID8) ovarian cancer cell lines. The oxygen radical scavenger, N-acetylcysteine (NAC), attenuates the chemotoxicity of plumbagin and atovaquone. Whole-cell patch clamping demonstrates that plumbagin and atovaquone inhibit outward and the inward current flowing through NKA in SKOV-3 and OVCAR-3. Although both drugs decrease cellular ATP; providing exogenous ATP (5 mM) in the pipet solution used during patch clamping did not recover NKA activity in the plumbagin or atovaquone treated SKOV-3 and OVCAR-3 cells. However, pretreatment of the cells with NAC completely abrogated the NKA inhibitory activity of plumbagin and atovaquone. Exposure of the SKOV-3 cells to either drug significantly decreases the expression of NKA. We conclude that oxidative stress caused by plumbagin and atovaquone degrades NKA, resulting in the inability to maintain ion transport. Therefore, when evaluating compounds that induce oxidative stress, it is important to consider the contribution of NKA inhibition to their cytotoxic effects on tumor cells.

On-Tissue Derivatization with Girard's Reagent P Enhances N-Glycan Signals for Formalin-Fixed Paraffin-Embedded Tissue Sections in MALDI Mass Spectrometry Imaging

Glycosylation is a major protein post-translational modification whose dysregulation has been associated with many diseases. Herein, an on-tissue chemical derivatization strategy based on positively charged hydrazine reagent (Girard's reagent P) coupled with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) was developed for analysis of N-glycans from FFPE treated tissue sections. The performance of the proposed approach was evaluated by analysis of monosaccharides, oligosaccharides, N-glycans released from glycoproteins, as well as MS imaging of N-glycans from human cancer tissue sections. The results demonstrated that the signal-to-noise ratios for target saccharides were notably improved after chemical derivatization, in which signals were enhanced by 230-fold for glucose and over 28-fold for maltooctaose. Improved glycome coverage was obtained for N-glycans derived from glycoproteins and tissue samples after chemical derivatization. Furthermore, on-tissue derivatization was applied for MALDI-MSI of N-glycans from human laryngeal cancer and ovarian cancer tissues. Differentially expressed N-glycans among the tumor region, adjacent normal tissue region, and tumor proximal collagen stroma region were imaged, revealing that high-mannose type N-glycans were predominantly expressed in the tumor region. Overall, our results indicate that the on-tissue labeling strategy coupled with MALDI-MSI shows great potential to spatially characterize N-glycan expression within heterogeneous tissue samples with enhanced sensitivity. This study provides a promising approach to better understand the pathogenesis of cancer related aberrant glycosylation, which is beneficial to the design of improved clinical diagnosis and therapeutic strategies.

Plasmonic Nanoparticle-Based Digital Cytometry to Quantify MUC16 Binding on the Surface of Leukocytes in Ovarian Cancer

Although levels of the circulating ovarian cancer marker (CA125) can distinguish ovarian masses that are likely to be malignant and correlate with severity of disease, serum CA125 has not proved useful in general population screening. Recently, cell culture studies have indicated that MUC16 may bind to the Siglec-9 receptor on natural killer (NK) cells where it downregulates the cytotoxicity of NK cells, allowing ovarian cancer cells to evade immune surveillance. We present evidence that the presence of MUC16 can be locally visualized and imaged on the surface of peripheral blood mononuclear cells (PBMCs) in ovarian cancer via a novel "digital" cytometry technique that incorporates: (i) OC125 monoclonal antibody-conjugated gold nanoparticles as optical nanoprobes, (ii) a high contrast dark-field microscopy system to detect PBMC-bound gold nanoparticles, and (iii) a computational algorithm for automatic counting of these nanoparticles to estimate the quantity of surface-bound MUC16. The quantitative detection of our technique was successfully demonstrated by discriminating clones of the ovarian cancer cell line, OVCAR3, based on low, intermediate, and high expression levels of MUC16. Additionally, PBMC surface-bound MUC16 was tracked in an ovarian cancer patient over a 17 month period; the results suggest that the binding of MUC16 on the surface of immune cells may play an early indicator for recurrent metastasis 6 months before computational tomography-based clinical diagnosis. We also demonstrate that the levels of surface-bound MUC16 on PBMCs from five ovarian cancer patients were greater than those from five healthy controls.

Abstract 4993: Label-free metabolic imaging of T cell response to the tumor microenvironment

Numerous factors including low pH, low glucose, and high lactic acid levels in tumors create an immunosuppressive tumor microenvironment. This immunosuppression is partially due to the metabolic requirements of T cell activation, which are difficult to meet in the tumor microenvironment. The goal of this study is to use label-free optical metabolic imaging (OMI) of the metabolic co-factors NAD(P)H and FAD in CD3-conjugated (activated) and control T cells to monitor metabolic changes of T cells within tumor micro environmental conditions. Single-cell measurements include the optical redox ratio (fluorescence intensity of NAD(P)H divided by FAD), which measures the oxidation-reduction state of the cell, and the mean fluorescence lifetimes (τm) of NAD(P)H and FAD, which measure enzyme-binding activity in the cell. Jurkat T cells were conjugated with CD3 antibody over a two-day incubation period to achieve activation. Control and CD3-conjugated cells were exposed to environments with increasing concentrations of lactic acid (0-20 mM), hydrochloric acid (HCl; pH 6.4- 7.4), and glucose deprivation to mimic the tumor microenvironment. OMI monitored metabolic changes on a single-cell level without confounding factors associated with cell surface marker labeling. Treatment with lactic acid resulted in a significant dose-dependent decrease in the FAD τm and optical redox ratio (p&lt;0.005). Along with changes in metabolism, OMI also resolved impaired mobility of the T cells with increasing lactic acid concentrations. Lactic acid affects both pH and metabolism, so cells were separately exposed to different concentrations of HCl (pH 6.4 - pH 7.4) to monitor pH effects alone. In control cells, the optical redox ratio decreased with decreasing pH (p&lt;0.005). Conversely, in the presence of CD3, the optical redox ratio increased with decreasing pH (p&lt;0.005). CD3 conjugation in glucose deprived environments also resulted in increases in both optical redox ratio and NAD(P)H τm. Cellular viability assays indicate apoptosis only in the lowest pH environment (pH 6.4, p&lt;0.005). These studies indicate that OMI is a promising label-free approach to investigate the effects of the tumor microenvironment on T cell metabolism, activation, and drug response.

Citation Format: Ava VanDommelen, Amani Gillette, Manish S. Patankar, Melissa Skala. Label-free metabolic imaging of T cell response to the tumor microenvironment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4993.

Identification of unique clusters of T, dendritic, and innate lymphoid cells in the peritoneal fluid of ovarian cancer patients

PROBLEM

We hypothesize that activated peritoneal immune cells can be redirected to target ovarian tumors. Here, we obtain fundamental knowledge of the peritoneal immune environment through deep immunophenotyping of T cells, dendritic cells (DC), and innate lymphoid cells (ILC) of ovarian cancer patients.

METHOD OF STUDY

T cells, DC, and ILC from ascites of ovarian cancer patients (n = 15) and peripheral blood of post-menopausal healthy donors (n = 6) were immunophenotyped on a BD Fortessa cytometer using three panels-each composed of 16 antibodies. The data were analyzed manually and by t-SNE/DensVM. CA125 levels were obtained from patient charts.

RESULTS

We observed decreased CD3⁺ T cells and a higher proportion of activated CD4⁺ and effector memory CD4⁺ /CD8⁺ T cells, plasmacytoid DC, CD1c⁺ and CD141⁺ myeloid DC and CD56^Hi NK cells in ascites. t-SNE/DensVM identified eight T cell, 17 DC, and 17 ILC clusters that were unique in the ascites compared to controls. Hierarchical clustering of cell frequency distinctly segregated the T-cell and ILC clusters from controls. Increased CA125 levels were associated with decreased CD8⁺ /CD45RA⁺ /CD45RO^- /CCR7^- T cells.

CONCLUSION

The identified immune clusters serve as the basis for interrogation of the peritoneal immune environment and the development of novel immunologic modalities against ovarian cancer.

Cannabidiol: Assessing preclinical safety in ovarian and endometrial carcinoma cell lines

e24130

Background: Cancer patients use cannabidiol (CBD) for chemotherapy and cancer symptoms, though research of CBD safety and efficacy for these conditions are ongoing and mixed. We sought to determine endometrial (ECC1) and epithelial ovarian cancer (Kuramochi) cell proliferation when exposed to different concentrations of CBD, for the broader goal to establish if CBD can safely be utilized to treat the symptoms of cancer, including those caused by chemotherapy. Methods: ECC1 and Kuramochi cells were kept in media (RPMI with 10% bovine serum and 1% penicillin/streptomycin). We passaged cells when > 90% confluent by adding tryspin-EDTA, incubating at 37C for 3 minutes, then spinning down with media to harvest the cell pellet. Cells were re-suspended in media, counted and apportioned to 96 well plates. Plates were incubated at 37C x 24 hours. CBD (from Cayman Chemical) was suspended in DMSO per manufacturer instruction then used to treat cells x72 hours at different concentrations (2.5-50uM). MTT was added to cells, cells incubated at 37C x 3 hours, media and MTT were removed and DMSO was added. Optical depth (OD) was calculated for plates using SoftMaxPro version 6.2.2. ODs were used to calculate inhibitory concentration for 50% cell death (IC50). Results: Kuramochi and ECC1 demonstrated decreased cell proliferation when exposed to CBD for 72hours. ECC1 IC50 fell between 2.5-5uM. Kuramochi IC50 fell between 15-20uM. Nearly all ECC1 growth was inhibited at concentrations 10uM or greater. Kuramochi proliferation was 15% that of controls at concentrations of 40 and 50uM CBD. Conclusions: ECC1 and Kuramochi cells demonstrated decreased proliferation in the presence of CBD. This bodes well for future studies of concurrent exposure to CBD and cytotoxic chemotherapy. Further preclinical research needed on CBD effects in endometrial and ovarian cancer, as patients turn to CBD for symptomatic relief from cancer and chemotherapy side effects. [Table: see text]

Abstract NT-096: FABCLAVINE, A SECONDARY METABOLITE FROM XENORHABDUS BUDAPESTENSIS AS THERAPY AGAINST OVARIAN CANCER

Ovarian cancer is the fifth most common cause of cancer-related deaths in women in the United States. Most women with ovarian cancer present with advanced disease. Even though initial response to surgery and chemotherapy is generally positive, many patients relapse with chemoresistant disease. We are especially interested in finding natural products that have anti-neoplastic activity against relapsed disease. Here, we report fabclavine, a secondary metabolite from Xenorhabdus budapestensis as novel anti-cancer agent.

Fabclavine was isolated and purified from cell-free supernatants of Xbu cultures. In a two-step procedure, active compounds were first precipitated from the supernatant with acetone and subsequently purified via reverse phase chromatography. Proliferation assays conducted on several ovarian cancer cell lines such as OVCAR3, OVCA433, ID8, IOSE, show that fabclavine inhibits the cancer cell proliferation at nanomolar (250-400 nM) concentration but has no effect on IOSE at that concentration. The ovarian cancer cell line OVCA33 when tested in proliferation assay showed, they are sensitive to fabclavine at a ten-fold lower concentration than cisplatin. Besides proliferation assay in 2D culture, we also tested the effect of fabclavine in 3D culture of ovarian cancer cell lines. The results indicate, fabclavine was equally effective in 3D culture and killed 40-50% of the cells in spheroids. In addition, fabclavine was also tested against cancer stem cells isolated from ovarian cancer patient and grown in 3D culture and it inhibited the growth of stem cells by 45%. Treatment of ovarian cancer cell lines with Fabclavine indicated DNA damage and an increase in cleaved caspase 3 and Annexin V binding, confirming that this agent was killing the OVCAR3, ID8 and OVCA433 cancer cell lines via apoptosis. Further experiments are underway to determine the apoptosis pathway (intrinsic or extrinsic) activated by fabclavine. Here we are describing for the first time a novel agent which is water soluble, active at low concentration and conveniently purified from cell free supernatant of bacterial culture. These properties of fabclavine makes it an excellent molecule to develop as therapy against ovarian tumors.

Citation Format: Arvinder K Kapur, Mayur Kajla, Susan Paskewitz, Pooja Mehta, Geeta Mehta, Manish S Patankar. FABCLAVINE, A SECONDARY METABOLITE FROM XENORHABDUS BUDAPESTENSIS AS THERAPY AGAINST OVARIAN CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-096.

Abstract NT-103: TARGETING OVARIAN TUMORS WITH OXPHOS INHIBITORS

Aerobic glycolysis is an important metabolic adaptation in tumors. However, there is mounting evidence that oxidative phosphorylation (OXPHOS) also contributes to metabolism in cancer cells. Therefore, agents targeting OXPHOS can serve as novel anticancer agents. We will present data on small molecule agents that inhibit the proliferation of ovarian and other cancer cells by inhibiting mitochondrial electron transport. We have focused our attention on citral, plumbagin, curcumin, cinnamaldehyde, piperlongumine, perillaldehyde, nonenal and other naturally occurring agents. All of these molecules share a common molecular epitope, the unsaturated carbonyl that participates in redox reactions. Cancer cells treated with these agents show a marked decrease in oxygen consumption rate and an increase in extracellular acidification. The redox ratio (NADH/FAD) and cellular ATP levels also decrease in response to these small molecule agents. In our search for additional and more potent OXPHOS inhibitors we have discovered that the FDA-approved anti-malarial drug atovaquone is an efficient inhibitor of electron transport in ovarian cancer cells. Chronic administration of atovaquone decreases the growth of ID8 tumors in C57BL/6 mice. Investigation in to the mechanism of action of the unsaturated carbonyl compounds indicates that their initial effect in cancer cells is the immediate and substantial rise in oxygen radicals as a result of OXPHOS inhibition. This increase in reactive oxygen causes extensive oxidative damage leading to DNA strand breaks. Subsequently, we have observed activation of p53-mediated apoptosis. These experiments are suggesting that inhibition of OXPHOS and the subsequent increase in intracellular oxygen radicals can result in the reactivation of the tumor suppressive responses of at least a subset of the p53 mutants. Additionally, our studies also indicate that the oxidative stress occurring as a result of OXPHOS inhibition directly leads to inhibition of ion transport through the Na+/K+-ATPase. As a result of this inhibition, cancer cells are unable to maintain a normal membrane potential. Studies are currently underway to determine if the inability to maintain membrane potential also contributes to apoptotic cancer cell death induced by these unsaturated carbonyl-containing compounds. Oxidative stress caused by these compounds leads to an increase in superoxide dismutase, catalase and glutathione synthesis via the activation of Nrf-2. Inhibition of Nrf-2 results in an increase in the potency of the unsaturated carbonyl compounds. We are therefore examining Nrf-2 increase as a form of chemoresistance mechanism that likely impinges on the anti-cancer activity of the unsaturated carbonyl compounds. These studies are allowing us to develop medicinal chemistry-based approaches to develop novel molecules with increased potency and targetability as OXPHOS inhibitors for the treatment of ovarian cancer.

Citation Format: Arvinder Kapur, Amruta Nayak, Mildred Felder, Allegra Cappucini, Spencer Ericksen, Yousef Alharbi, Bikash Pattnaik, Lisa Barroilhet, and Manish S. Patankar. TARGETING OVARIAN TUMORS WITH OXPHOS INHIBITORS [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-103.

Mass Spectrometry Imaging of N-Glycans from Formalin-Fixed Paraffin-Embedded Tissue Sections Using a Novel Subatmospheric Pressure Ionization Source

N-linked glycosylation, featuring various glycoforms, is one of the most common and complex protein post-translational modifications (PTMs) controlling protein structures and biological functions. It has been revealed that abnormal changes of protein N-glycosylation patterns are associated with many diseases. Hence, unraveling the disease-related alteration of glycosylation, especially the glycoforms, is crucial and beneficial to improving our understanding about the pathogenic mechanisms of various diseases. In past decades, given the capability of in situ mapping of biomolecules and their region-specific localizations, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been widely applied to the discovery of potential biomarkers for many diseases. In this study, we coupled a novel subatmospheric pressure (SubAP)/MALDI source with a Q Exactive HF hybrid quadrupole-orbitrap mass spectrometer for in situ imaging of N-linked glycans from formalin-fixed paraffin-embedded (FFPE) tissue sections. The utility of this new platform for N-glycan imaging analysis was demonstrated with a variety of FFPE tissue sections. A total of 55 N-glycans were successfully characterized and visualized from a FFPE mouse brain section. Furthermore, 29 N-glycans with different spatial distribution patterns could be identified from a FFPE mouse ovarian cancer tissue section. High-mannose N-glycans exhibited elevated expression levels in the tumor region, indicating the potential association of this type of N-glycans with tumor progression.

Abstract 891: Plumbagin and atovaquone inhibit Na+/K+-ATPase through the generation of oxidative stress

Plumbagin and atovaquone are chemotoxic to ovarian, breast and other tumors. Both molecules inhibit oxidative phosphorylation causing a rapid increase in intracellular oxygen radicals and apoptosis. Oxidative stress is also known to inhibit the activity of Na+/K+-ATPase (NKA), the ion channel that maintains the membrane potential. Here, we investigate if the oxidative stress mediated by plumbagin and atovaquone also leads to inhibition of NKA activity. We confirm that plumbagin and atovaquone inhibit proliferation of three human (OVCAR-3, SKOV-3 and TYKNu) and one mouse (ID8) ovarian cancer cell lines. Using SKOV-3 and OVCAR-3 as models for ovarian cancer, we demonstrate that oxygen radical scavenger, N-acetylcysteine (NAC) attenuated the cytotoxicity of plumbagin and atovaquone. Using whole cell patch clamping we demonstrate that plumbagin and atovaquone inhibit outward and inward current flowing through NKA in SKOV-3 and OVCAR-3. Both drugs decrease cellular ATP. Providing exogenous ATP (5 mM) in the pipet solution used during patch clamping did not recover NKA activity in the plumbagin or atovaquone treated SKOV-3 and OVCAR-3 cells. However, pretreatment of the cells with NAC completely abrogated the NKA inhibitory activity of plumbagin and atovaquone. Exposure of the SKOV-3 cells to either of the drugs for 1-2 h resulted in a significant decrease in the expression of NKA. We conclude that oxidative stress caused by plumbagin and atovaquone degrades NKA and hence the membrane potential cannot be optimally maintained. Evaluation of compounds that induce oxidative stress should therefore consider contribution of NKA inhibition to the cytotoxic activity of such agents.

Citation Format: Yousef Alharbi, Arvinder Kapur, Mildred Felder, Lisa Barroilhet, Bikash Pattnaik, Manish S. Patankar. Plumbagin and atovaquone inhibit Na+/K+-ATPase through the generation of oxidative stress [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 891.

Abstract 1251: Potential tumor suppressor function of polo-like kinase 5 in ovarian cancers

Ovarian cancer remains one of the leading causes of cancer-related deaths in women worldwide, with an estimated 295,414 new cases and 184,799 deaths to occur in 2018. In the United States, although this malignancy is not in the top 10 for number of estimated new cases, it is the 5th leading cause of cancer-related deaths in women. This disparity is due to the fact that most ovarian cancers are not diagnosed until late stages when only limited options for treatment are available. Therefore, it is important to uncover novel molecular mechanisms that can be targeted to control this deadly cancer. The polo-like kinases (PLKs 1-5) are a family of serine/threonine kinases that that primarily play key roles in cell cycle progression, and have been linked to cancer pathogenesis. Limited information is available regarding the role of PLK5 in cancer. PLK5 is structurally unique, in that it has been shown to be missing the majority of the kinase domain that the other family members have. Interestingly, although PLK5 is not expressed in many tissues, it has been found to be present in appreciable levels in fallopian tube tissue, which suggests that PLK5 may be important in fallopian tube biology. Contrary to previous dogma, recent research has suggested that most ovarian cancers may actually have their origin in the fallopian tubes. Keeping this in mind, we wanted to explore the role of PLK5 in fallopian cancer. To this end, we performed a quantitative immunostaining of PLK5 in a fallopian tube disease tissue microarray (TMA) containing 5 normal tissues, 10 cases of inflammation, 10 fallopian adenocarcinoma, and 4 adjacent normal tissues. Following staining, the TMA was scanned with the Vectra platform and immunostaining was analyzed using InForm software that allows us to quantitatively measure the PLK5 intensity in each tissue and subcellular compartment. Our data demonstrated that PLK5 protein levels were significantly decreased in fallopian tumors compared to normal fallopian tissue (p = 0.01). Interestingly, although there was no significant difference between inflamed tissue and normal tissue, PLK5 levels were significantly reduced in the fallopian tube adenocarcinomas compared to the inflamed fallopian tissue (p&lt;0.001), suggesting a potential role for PLK5 in fallopian tube carcinogenesis. Further, our data demonstrated that PLK5 was enriched in the nucleus (p&lt;0.001) versus the cytoplasm, which is the opposite of what has been previously published in human neurons and glial cells. Taken together, our data suggests that PLK5 may be a tumor suppressor in fallopian tube cancer, and potentially ovarian cancers, as a majority of them are derived from the fallopian tube epithelium. However, further studies are needed to understand the exact roles played by this kinase in these reproductive tissues.

Citation Format: Mary A. Ndiaye, Shengqin Su, Rebecca M. Baus, Wei Huang, Manish S. Patankar, Nihal Ahmad. Potential tumor suppressor function of polo-like kinase 5 in ovarian cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1251.

MUC16 suppresses human and murine innate immune responses

OBJECTIVE

MUC16, the mucin that contains the CA125 epitopes, suppresses the cytolytic responses of human NK cells and inhibits the efficacy of therapeutic antibodies. Here, we provide further evidence of the regulatory role of MUC16 on human and murine NK cells and macrophages.

METHODS

Target cell cytolysis and doublet formation assays were performed to assess effects of MUC16 on human NK cells. The effect of MUC16 on ovarian tumor growth was determined in a mouse model by monitoring survival and ascites formation. Innate immune cells from spleens and peritoneal cavities of mice were isolated and stimulated in vitro with anti-CD40 antibody, lipopolysaccharide and IFN-γ and their ability to cytolyse MUC16 expressing and non-expressing cells was determined.

RESULTS

We confirm that MUC16 inhibits cytolysis by human NK cells as well as the formation of NK-tumor conjugates. Mice implanted with MUC16-knockdown OVCAR-3 show >2-fold increase in survival compared to controls. Murine NK cells and macrophages are more efficient at lysing MUC16-knockdown cells. In vitro cytotoxicity assays with NK cells and macrophages isolated from mice stimulated with anti-CD40 antibody showed 2-3-fold increased activity against the MUC16-knockdown cells as compared to matching target cells expressing this mucin. Finally, knockdown of MUC16 increased the susceptibility of cancer cells to ADCC by murine splenocytes.

CONCLUSIONS

For the first time, we demonstrate the immunoregulatory effects of MUC16 on murine NK cells and macrophages. Our study implies that the immunoregulatory role of MUC16 on murine NK cells and macrophages should be considered when examining the biology of MUC16 in mouse models.

Abstract A21: Computational methods and novel in vitro model elucidate a therapeutic target against ovarian cancer metastasis

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecologic cancer, and patients with HGSOC are often subject to extensive metastasis. The primary mode of metastasis in HGSOC is transcoelomic, where tumor cells detach and float in the peritoneal fluid before reattaching to the mesothelial-lined peritoneum. Levels of alternatively activated macrophages (AAMs) in ascites in the peritoneal cavity are correlated with disease stage, but it is unclear if AAMs play a role in transcoelomic spread. We hypothesized that AAM-secreted ligands enhance adhesion of ovarian cancer to mesothelial cells, which would support tumor progression. To address this hypothesis, we adapted a novel coculture device from our lab to create an in vitro model of the metastatic microenvironment and partial-least squares regression (PLSR) modeling to identify AAM-secreted ligands that enhanced adhesion.

Methods: The device consists of two parallel culture surfaces (a well within a 24-well tissue culture plate and a glass coverslip) that are separated by a PDMS ring such that only paracrine interactions can occur between cells cultured on the surfaces. LP-9 or LP-3 mesothelial cells were seeded to confluency onto adsorbed collagen I within the PDMS ring and primary monocytes isolated from whole blood were differentiated to the M2 phenotype on the coverslip. Mesothelial cells were then cultured for 24 hours with a primary AAM coverslip, mimicking paracrine signaling between macrophages and the peritoneal mesothelium. As a control, mesothelial cells were cultured with a cell-free coverslip for 24 hours. Cell-Tracker Green-labeled ovarian cancer cells (OVCAR5, CaOV3, or OV-90) were seeded on top of the mesothelial cells and allowed to adhere for 3 hours. Nonadherent cells were washed off and the adherent cells were quantified. Media were collected from the devices and screened for 36 cytokines and matrix metalloproteinases using Bioplex assays. The data were analyzed using PLSR to identify secreted factors that correlated to the observed changes in cell adhesion. To validate the model, adhesion experiments were repeated using blocking antibodies and recombinant proteins. To examine the presence of these factors in patients, ascites fluid from patients with benign conditions or HGSOC were obtained under protocols approved by the Institutional Review Board at UW-Madison.

Results and Conclusions: Coculture of primary AAMs with mesothelial cells increased ovarian cancer cell adhesion by at least 40% in all three cell lines. Bioplex analysis revealed that cytokines such as MIP-1β, MMP-7, and IL-13 were present in the media of AAM cultures. A PLSR model constructed with this data indicated a strong correlation between the ligands measured in the cultures and cell adhesion (R2Y= 0.95, Q2Y= 0.84). MIP-1β correlated strongly with adhesion and contributed highly to the model’s predictive capacity. To validate this model-predicted relationship, we experimentally tested the impact of inhibiting MIP-1β and found that while the baseline adhesion was unaffected, the ability of AAMs to enhance adhesion was lost with all three tumor cell lines. Similarly, treatment of mesothelial cells with MIP-1β alone was sufficient to increase tumor cell adhesion. Additionally, analysis of benign and HGSOC ascites showed elevated levels of MIP-1β in HGSOC patients. Overall, our findings suggest a role of AAMs in the multicellular process of transcoelomic spread of HGSOC, and identify MIP-1β as a potential target in the peritoneal cavity. Ongoing efforts are decoding the mechanisms by which MIP-1β increases adhesion between mesothelial and tumor cells.

Citation Format: Molly J. Carroll, Kaitlin C. Fogg, Harin A. Patel, Anne-Sophie Mancha, Manish S. Patankar, Pamela K. Kreeger. Computational methods and novel in vitro model elucidate a therapeutic target against ovarian cancer metastasis. [abstract]. In: Proceedings of the AACR Conference: Addressing Critical Questions in Ovarian Cancer Research and Treatment; Oct 1-4, 2017; Pittsburgh, PA. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(15_Suppl):Abstract nr A21.

Polarization-resolved second harmonic generation imaging of human ovarian cancer

Remodeling of the extracellular matrix in human ovarian cancer can be manifested in increased collagen concentration, changes in alignment within fibrils/fibers and/or up-regulation of different collagen isoforms. We used pixel-based second harmonic generation (SHG) polarization microscopy analyses to probe these molecular changes in human ovarian tissues [normal stroma, benign tumors, and high-grade serous (HGS) tumors] by: (i) determination of the α-helical pitch angle via the single-axis molecular model, (ii) collagen alignment within fibrils via SHG anisotropy, and (iii) chirality via SHG circular dichroism (SHG-CD). Pixel approaches are required due to the complex structure of the matrix that lacks a high degree of fiber alignment. The largest differences in the helical pitch angle were between normal stroma and benign tumors, consistent with gene expression showing the Col III isoform is up-regulated in the latter. The data were not consistent with up-regulation of Col III in HGS tumors as previous reports have suggested. The different tissues also displayed differing SHG anisotropies and SHG-CD responses, consistent with either Col III incorporation or randomization of Col I alignment within benign and malignant tumors. Additionally, the high-grade tumors displayed higher collagen concentration, where this desmoplasia is consistent with the higher fiber density in these tissues. These results collectively indicate that the fibril assemblies are distinct in all tissues, where these differences likely result from the synthesis of collagen rather than remodeling of existing collagen. Importantly, these analyses are label-free and interrogate subresolution collagen structure on intact tissues, without the need for conventional structural biology tools.

Alternatively-Activated Macrophages Upregulate Mesothelial Expression of P-Selectin to Enhance Adhesion of Ovarian Cancer Cells

Peritoneal metastasis of high-grade serous ovarian cancer (HGSOC) occurs when tumor cells suspended in ascites adhere to mesothelial cells. Despite the strong relationship between metastatic burden and prognosis in HGSOC, there are currently no therapies specifically targeting the metastatic process. We utilized a coculture model and multivariate analysis to examine how interactions between tumor cells, mesothelial cells, and alternatively-activated macrophages (AAM) influence the adhesion of tumor cells to mesothelial cells. We found that AAM-secreted MIP-1β activates CCR5/PI3K signaling in mesothelial cells, resulting in expression of P-selectin on the mesothelial cell surface. Tumor cells attached to this de novo P-selectin through CD24, resulting in increased tumor cell adhesion in static conditions and rolling underflow. C57/BL6 mice treated with MIP-1β exhibited increased P-selectin expression on mesothelial cells lining peritoneal tissues, which enhanced CaOV3 adhesion ex vivo and ID8 adhesion in vivo Analysis of samples from patients with HGSOC confirmed increased MIP-1β and P-selectin, suggesting that this novel multicellular mechanism could be targeted to slow or stop metastasis in HGSOC by repurposing anti-CCR5 and P-selectin therapies developed for other indications.Significance: This study reports novel insights on the peritoneal dissemination occurring during progression of ovarian cancer and has potential for therapeutic intervention.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/13/3560/F1.large.jpg Cancer Res; 78(13); 3560-73. ©2018 AACR.

M2 macrophages induce ovarian cancer cell proliferation via a heparin binding epidermal growth factor/matrix metalloproteinase 9 intercellular feedback loop

In ovarian cancer, a high ratio of anti-inflammatory M2 to pro-inflammatory M1 macrophages correlates with poor patient prognosis. The mechanisms driving poor tumor outcome as a result of the presence of M2 macrophages in the tumor microenvironment remain unclear and are challenging to study with current techniques. Therefore, in this study we utilized a micro-culture device previously developed by our lab to model concentrated paracrine signaling in order to address our hypothesis that interactions between M2 macrophages and ovarian cancer cells induce tumor cell proliferation. Using the micro-culture device, we determined that co-culture with M2-differentiated primary macrophages or THP-1 increased OVCA433 proliferation by 10-12%. This effect was eliminated with epidermal growth factor receptor (EGFR) or heparin-bound epidermal growth factor (HB-EGF) neutralizing antibodies and HBEGF expression in peripheral blood mononuclear cells from ovarian cancer patients was 9-fold higher than healthy individuals, suggesting a role for HB-EGF in tumor progression. However, addition of HB-EGF at levels secreted by macrophages or macrophage-conditioned media did not induce proliferation to the same extent, indicating a role for other factors in this process. Matrix metalloproteinase-9, MMP-9, which cleaves membrane-bound HB-EGF, was elevated in co-culture and its inhibition decreased proliferation. Utilizing inhibitors and siRNA against MMP9 in each population, we determined that macrophage-secreted MMP-9 released HB-EGF from macrophages, which increased MMP9 in OVCA433, resulting in a positive feedback loop to drive HB-EGF release and increase proliferation in co-culture. Identification of multi-cellular interactions such as this may provide insight into how to most effectively control ovarian cancer progression.

Oxidative stress via inhibition of the mitochondrial electron transport and Nrf-2-mediated anti-oxidative response regulate the cytotoxic activity of plumbagin

Plumbagin, an anti-cancer agent, is toxic to cells of multiple species. We investigated if plumbagin targets conserved biochemical processes. Plumbagin induced DNA damage and apoptosis in cells of diverse mutational background with comparable potency. A 3-5 fold increase in intracellular oxygen radicals occurred in response to plumbagin. Neutralization of the reactive oxygen species by N-acetylcysteine blocked apoptosis, indicating a central role for oxidative stress in plumbagin-mediated cell death. Plumbagin docks in the ubiquinone binding sites (Q0 and Qi) of mitochondrial complexes I-III, the major sites for oxygen radicals. Plumbagin decreased oxygen consumption rate, ATP production and optical redox ratio (NAD(P)H/FAD) indicating interference with electron transport downstream of mitochondrial Complex II. Oxidative stress induced by plumbagin triggered an anti-oxidative response via activation of Nrf2. Plumbagin and the Nrf2 inhibitor, brusatol, synergized to inhibit cell proliferation. These data indicate that while inhibition of electron transport is the conserved mechanism responsible for plumbagin's chemotoxicity, activation of Nrf2 is the resulting anti-oxidative response that allows plumbagin to serve as a chemopreventive agent. This study provides the basis for designing potent and selective plumbagin analogs that can be coupled with suitable Nrf2 inhibitors for chemotherapy or administered as single agents to induce Nrf2-mediated chemoprevention.

Abstract MIP-068: TUMOR–PROMOTING EFFECTS OF THE OVARIAN CANCER MUCIN, MUC16, ARE ASSOCIATED WITH SUPPRESSION OF INNATE IMMUNITY

The membrane-spanning mucin MUC16 promotes proliferation and metastasis of ovarian cancer cells. Here, we demonstrate that mice implanted with MUC16-knockdown human ovarian tumors show greater than two-fold increase in survival as compared to controls with tumors that express this mucin. While the lower survival of mice bearing MUC16-positive tumors is reportedly attributable to the ability of MUC16 to increase proliferation and metastasis, we also show that murine NK cells and macrophages are more efficient at lysing MUC16-knockdown cells. Macrophages showed infiltration in the MUC16-knockdown tumors but were restricted to the surrounding stroma in MUC16-positive tumors. In vitro cytotoxicity assays with NK cells and macrophages isolated from mice stimulated with agonistic anti-CD40 antibody showed 2-3-fold increased activity against the MUC16-knockdown cells as compared to matching target cells expressing this mucin. Finally, knockdown of MUC16 increased the susceptibility of cancer cells to ADCC and lysis by KS-IL2, an immunocytokine investigated as a treatment for ovarian cancer. Collectively our results support a role for MUC16 in promoting tumor growth. The ability of murine innate cells to selectively target MUC16-knockdown cells indicates that in vivo experiments investigating the biology of this mucin should be interpreted taking into account its immunomodulating activity as well as its growth promoting properties.

Citation Format: Mildred Felder, Arvinder Kapur, Alexander L. Rakhmilevich, Xiaoyi Qu2, Joseph Connor, and Manish S. Patankar. TUMOR–PROMOTING EFFECTS OF THE OVARIAN CANCER MUCIN, MUC16, ARE ASSOCIATED WITH SUPPRESSION OF INNATE IMMUNITY [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr MIP-068.

Abstract AP15: MODULATION OF OXIDATIVE STRESS AND SUBSEQUENT INDUCTION OF APOPTOSIS AND ENDOPLASMIC RETICULUM STRESS ALLOWS CITRAL TO DECREASE CANCER CELL PROLIFERATION

The monoterpenoid, citral, when delivered through PEG-b-PCL nanoparticles inhibits in vivo growth of 4T1 breast tumors. Here, we show that citral inhibits proliferation of multiple human cancer cell lines. In p53 expressing ECC-1 and OVCAR-3 but not in p53-deficient SKOV-3 cells, citral induces G1/S cell cycle arrest and apoptosis as determined by Annexin V staining and increased cleaved caspase3 and Bax and decreased Bcl-2. In SKOV-3 cells, citral induces the ER stress markers CHOP, GADD45, EDEM, ATF4, Hsp90, ATG5, and phospho-eIF2α. The molecular chaperone 4-phenylbutyric acid attenuates citral activity in SKOV-3 but not in ECC-1 and OVCAR-3 cells. In p53-expressing cells, citral increases phosphorylation of serine-15 of p53. Activation of p53 increases Bax, PUMA, and NOXA expression. Inhibition of p53 by pifithrin-α, attenuates citral-mediated apoptosis. Citral increases intracellular oxygen radicals and this leads to activation of p53. Inhibition of gluthatione synthesis by L-buthionine sulfoxamine increased potency of citral. Pretreatment with N-acetylcysteine decreases phosphorylation of p53 in citral-treated ECC-1 and OVCAR-3. These results define a p53-dependent, and in the absence of p53, ER stress-dependent mode of action of citral. This study indicates that citral in PEG-b-PCL nanoparticle formulation should be considered for treatment of breast and other tumors.

Citation Format: Arvinder Kapur, Mildred Felder, Lucas Fass, Justanjot Kaur, Austin Czarnecki, Kavya Rathi, San Zeng, Kathryn Kalady Osowski, Colin Howell, May P. Xiong, Rebecca J. Whelan, Manish S. Patankar. MODULATION OF OXIDATIVE STRESS AND SUBSEQUENT INDUCTION OF APOPTOSIS AND ENDOPLASMIC RETICULUM STRESS ALLOWS CITRAL TO DECREASE CANCER CELL PROLIFERATION [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr AP15.

Modulation of oxidative stress and subsequent induction of apoptosis and endoplasmic reticulum stress allows citral to decrease cancer cell proliferation

The monoterpenoid, citral, when delivered through PEG-b-PCL nanoparticles inhibits in vivo growth of 4T1 breast tumors. Here, we show that citral inhibits proliferation of multiple human cancer cell lines. In p53 expressing ECC-1 and OVCAR-3 but not in p53-deficient SKOV-3 cells, citral induces G1/S cell cycle arrest and apoptosis as determined by Annexin V staining and increased cleaved caspase3 and Bax and decreased Bcl-2. In SKOV-3 cells, citral induces the ER stress markers CHOP, GADD45, EDEM, ATF4, Hsp90, ATG5, and phospho-eIF2α. The molecular chaperone 4-phenylbutyric acid attenuates citral activity in SKOV-3 but not in ECC-1 and OVCAR-3 cells. In p53-expressing cells, citral increases phosphorylation of serine-15 of p53. Activation of p53 increases Bax, PUMA, and NOXA expression. Inhibition of p53 by pifithrin-α, attenuates citral-mediated apoptosis. Citral increases intracellular oxygen radicals and this leads to activation of p53. Inhibition of glutathione synthesis by L-buthionine sulfoxamine increases potency of citral. Pretreatment with N-acetylcysteine decreases phosphorylation of p53 in citral-treated ECC-1 and OVCAR-3. These results define a p53-dependent, and in the absence of p53, ER stress-dependent mode of action of citral. This study indicates that citral in PEG-b-PCL nanoparticle formulation should be considered for treatment of breast and other tumors.

Abstract B42: Identification of nucleic acid aptamers for ovarian cancer biomarkers using multiple selection modes and high-throughput sequencing

Nucleic acid-based affinity probes that specifically recognize ovarian cancer biomarkers in serum may serve as the basis of novel blood tests, whereas use of these affinity probes to direct payloads to tumor-associated markers may enable theranostic and imaging applications. Herein, we report our ongoing efforts to identify nucleic acid aptamers through the SELEX (Systematic Evolution of Ligands by Exponential Enrichment) process. We use the cell-SELEX method to identify single-stranded DNA aptamers to serve as affinity probes for the ovarian cancer markers MUC16 and mesothelin, using cell lines that express these proteins as the target. Further, we have conducted in-vitro selection using purified CA125 and HE4, in separate experiments, as the targets. In all cases, selective pressures are introduced to evolve the initially randomized population of oligonucleotides into a selected sub-population with affinity for the target of interest. The process concludes with sequencing of the oligonucleotides comprising the selected population on an Illumina platform, a high-throughput technology that reveals the sequence information of tens of millions of oligonucleotides, a dramatic improvement over the 10s to 100s of sequences identified by conventional cloning and sequencing. Mining this abundant sequence information has required the development of bioinformatics tools that identify the most promising aptamers for subsequent testing. We have generated a bioinformatics pipeline, using a combination of existing open-source computational tools and a new script to calculate enrichment. We have made this script available through GitHub. Concluding the aptamer selection process with high-throughput sequencing enables the entirety of the selection process, and not only its endpoint, to be characterized. This characterization enabled us to test the following hypotheses: (1) Enrichment of sequences in response to the selective pressures is more important than the abundance of sequences, particularly if the initial “random” pool is sub-optimally randomized; (2) Aptamers belonging to sequence clusters are more likely to display affinity for their targets than “orphan” sequences; (3) An aptamer that is selected against—decreasing its abundance in response to selective pressure—is an effective negative control. We find that biases in as-synthesized “random” libraries can be significant, both in nucleotide abundance and in sequence over-representation. Enriched sequences are more likely to be effective target binders than abundant sequences that result from synthesis or amplification bias. Sequences that are selected against do not display affinity for the target and therefore are effective controls. We acknowledge support from the National Institutes of Health.

Citation Format: Rebecca J. Whelan, Arvinder Kapur, Mildred Felder, Jamie Shallcross, Manish S. Patankar. Identification of nucleic acid aptamers for ovarian cancer biomarkers using multiple selection modes and high-throughput sequencing. [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 B42.

Abstract POSTER-BIOL-1341: MUC16 (CA125) knockdown as a potential strategy to decrease tumor growth

MUC16 (CA125), a membrane spanning mucin, promotes proliferation and metastasis of ovarian cancer cells. Here, we demonstrate that MUC16 protects cancer cells from cytolysis by NK cells and macrophages. SCID mice implanted with MUC16-positive and MUC16-knockdown human ovarian tumors have a median survival of 75 and 181 days, respectively. Animals bearing MUC16-positive tumors developed ascites fluid and were moribund because of high tumor volume. In contrast, none of the mice with MUC16-knockdown tumors developed ascites. Decreased growth of MUC16-knockdown tumors correlated with increased cytolysis by murine splenocytes from naïve and anti-CD40 antibody treated mice. Murine NK cells showed a 2.5-fold higher preference for MUC16-knockdown cells. Unstimulated and LPS or IFN-γ-activated peritoneal macrophages from SCID mice also preferentially inhibited proliferation of MUC16-knockdown targets. Even in SCID/Beige mice, where cytolysis by resident NK cells is impaired, median survival MUC16-positive tumor-bearing animals was 75 days as compared to 189 days for animals with MUC16-knockdown tumors. All ten SCID/Beige mice with MUC16-knockdown tumors showed significant macrophage infiltration throughout the tumor nests and only two of the ten developed ascites. In contrast, 80% of SCID/Beige mice with MUC16-positive tumors had significant ascites and macrophages were predominantly found in the stroma. Finally, knockdown of MUC16 increased the susceptibility of cancer cells to natural cytotoxic responses of human NK cells, and increased their susceptibility to ADCC and lysis in the presence of immunocytokines. Therefore, strategies that decrease the expression of immunosuppressive MUC16 coupled with NK or macrophage-based immunotherapies should be investigated for the treatment of ovarian cancer.

Citation Format: Mildred Felder, Arvinder Kapur, Alexander L. Rakhmilevich, Xiaoyi Qu, Joseph Connor, Manish S. Patankar. MUC16 (CA125) knockdown as a potential strategy to decrease tumor growth [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1341.

Abstract POSTER-THER-1429: Selection of DNA aptamers for an ovarian cancer cell line using high-throughput sequencing

Humanized antibodies have been extensively investigated as therapeutic as well as diagnostic agents. While the antigen specificity offered by antibodies makes them very attractive for such theranostic applications, their large-scale synthesis can be challenging and expensive. We are therefore investigating alternate strategies to develop agents that can be used for in vivo monitoring as well as for treatment of epithelial ovarian tumors. One approach is to develop Single Stranded DNA aptamers that selectively bind to ovarian cancer cells. The ssDNA aptamers can be synthesized using template-driven or de novo chemical synthetic approaches to manufacture agents at a large scale and low cost. The challenge however, is to develop aptamers that are specific to ovarian cancer cells. In the current study, we report a streamlined approach that incorporates the cell-based Systematic Evolution of Ligands by Exponential Enrichment (cell-SELEX) with DNASeq technology to select aptamers that recognize ovarian cancer cells. An ssDNA aptamer library composed of ~1015 sequences was subjected to ten iterative rounds of selection against the ovarian cancer cell line OVCAR-3. Aptamers from each round were amplified by asymmetric PCR and subjected to high-throughput sequencing. Eight ssDNA aptamers enriched through the selection process were identified by DNASeq and subsequent bioinformatics analysis and their selectivity and affinity for OVCAR-3 cells was determined by flow cytometry. Two of these aptamers (Apt-1 and Apt-8) showed significant binding to OVCAR-3 cells with Kd of 24 and 28 nM, respectively. Secondary structure analysis using mfold indicated that Apt-1 and Apt-8 had defined secondary structures resulting from ordered base pairing of the ssDNA. The inclusion of high-throughput sequencing techniques has therefore allowed rapid identification of theranostic aptamers from an large randomized library of ssDNA sequences. Our ongoing experiments are focused on coupling of the ovarian cancer cell-specific ssDNA aptamers to contrast agents or cytotoxic drugs. The ssDNA aptamers coupled to contrast agents are specifically being investigated for in vivo imaging of ovarian cancer masses in the peritoneum whereas the aptamers coupled to drugs can be used for the treatment of ovarian cancer.

Citation Format: Rebecca J. Whelan, Arvinder Kapur, Mildred Felder, Jamie Shallcross, Jeff Nie, Manish S. Patankar. Selection of DNA aptamers for an ovarian cancer cell line using high-throughput sequencing [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-THER-1429.

Abstract POSTER-THER-1417: Citral is the major component of ginger-derived terpenes to mediate p53-dependent apoptosis in cancer cells

Ginger extracts and ginger powder have been previously studied for their anti-cancer effects. It is generally believed that phenolic compounds present in ginger- especially shogaol and gingerol- are the active components that are cytotoxic to cancer cells. In our previous work we demonstrated that steam distilled extracts of ginger that are primarily composed of terpenes and do not contain any phenolic compounds, can induce cancer cell death with a potency that is significantly higher than gingerol and shogaol. In the current study we conduct a thorough analysis of the steam distilled extract of ginger to identify the bioactive terpene that induces cell death in ovarian cancer cells and also describe the molecular mechanisms leading to apoptosis. First, we screened the major components present in the extract for their ability to induce cancer cell death and determined that terpenes such as α-pinene and camphene are not active in the cell death assays. Instead, the major killing of ovarian and other cancer cells is mediated by the two monoterpene isomers, neral and geranial. Citral is a mixture of neral and geranial and is commercially available. Using citral in our assays we now demonstrate that these isomers can increase the expression of cleaved caspase 3 and apoptosis is also indicated in annexin V labeling assays. Treatment of cancer cells with citral results in a rapid rise in intracellular reactive oxygen species (ROS). In fact, inhibition of ROS by N-acetylcysteine blocks the ability of citral to produce apoptotic cell death. Another major observation is that citral induces rapid phosphorylation of the serine-15 residue of the tumor suppressor p53. Inhibition of ROS attenuates citral-induced phosphorylation of p53. Inhibition of p53 by pifithrin-α, a specific inhibitor, inhibits citral-mediated apoptosis. These experiments indicate that citral triggers ROS in cancer cells causing double stranded DNA breaks. DNA damage activates p53-mediated apoptotic signaling. Indeed, in cancer cells lacking p53 (SKOV3), while the ginger-derived terpene decreases proliferation, apoptosis is not observed. Instead after treatment with citral, SKOV3 cells undergo autophagy as determined by an increase in autophagolysosomes and increased expression of LC3B. We have also studied the mechanisms behind ROS increase in citral-treated cancer cells. Our studies show that immediately after exposure of cancer cells to citral, there is a rapid decrease in the intracellular levels of glutathione. This decrease is likely caused due to the enzymatic as well as non-enzymatic covalent coupling of glutathione and citral. As a result, citral works as a glutathione sink whereby the cancer cells are unable to control ROS. Concluding from these studies, we are using established concepts from medicinal chemistry to develop drug conjugates of citral that have higher bioavailability and can be targeted specifically to ovarian tumors. Even though p53 is mutated in ovarian tumors, not all mutations result in complete loss of function. We are screening for p53 mutations that result in only partial loss of tumor suppressor function. Patients stratified for such mutations will be good candidates for citral-based therapy. Citral has been approved by FDA as a safe food additive and hence can likely serve as an agent for maintenance therapy in ovarian cancer patients.

Citation Format: Arvinder Kapur, Mildred Felder, Lucas Faas, Manish S. Patankar. Citral is the major component of ginger-derived terpenes to mediate p53-dependent apoptosis in cancer cells [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-THER-1417.

Abstract AS11: Mining the circulating immune cell transcriptome for ovarian cancer-specific biomarkers: a proof of concept study

The continuous interplay between cancer cells and immune system leads to significant changes in the function of innate as well as adaptive immune cells. These changes occur through direct contact between the immune cells and the cancer cells as well as through soluble factors released from the tumor microenvironment. Since the immune cells are considered as “first responders” to a site of infection or to aberrant cells and pre-cancerous lesions, it is likely that immune cell function is influenced even at an early stage of tumor development. We have therefore hypothesized that changes in the proteome and transcriptome of circulating immune cells (conveniently obtained via venipuncture) should be studied closely to identify disease-specific biomarkers. Here, we present data from a proof-of-concept study that shows specific differences in the expression of a panel of genes in the immune cell transcriptome in peripheral blood mononuclear cells (PBMCs) obtained from healthy donors and patients with ovarian cancer. In our initial study, we isolated RNA from PBMCs of four healthy women and 5 ovarian cancer patients. Using an Illumina microarray we established that over 122 genes were up-regulated and 64 genes were downregulated in the PBMCs isolated from cancer patients. Gene cluster analysis showed that based on expression, the healthy donor samples clustered separately than the samples from ovarian cancer patients. For the purpose of additional exploration and to also identify genes (microRNA, etc, for example) that are typically not represented in conventional microarrays, we also conducted RNASeq experiments. Bioinformatics analysis showed that in PBMCs from ovarian cancer patients, 507 and 717 genes were upregulated or downregulated, respectively. The RNASeq data strongly validated the results from the microarray analysis. Additional validation on PBMC samples obtained from postmenopausal healthy women and ovarian cancer patients (n=20/cohort) using quantitative PCR is currently underway in our laboratories. Furthermore, we are also employing a murine ovarian cancer model to identify changes in the gene expression patterns in immune cells in tumor bearing versus non-tumor bearing immunecompetent mice. The results from these studies are leading to identification of candidate gene sets that can be used as potential biomarkers form ovarian cancer. These transcript-based biomarkers represent several important immunologic pathways- T cell receptor, cytokine activation and others. Studies are also continuing to determine if these biomarkers are expressed in all or only a subset of the immune cells isolated from ovarian cancer patients.

Citation Format: Shitanshu Uppal, Arvinder Kapur, Erin Medlin, Mildred Felder, Hadi Shojaie, Nicole Gregorich, Manish S. Patankar, Jesus Gonzalez-Bosquet. Mining the circulating immune cell transcriptome for ovarian cancer-specific biomarkers: a proof of concept study [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS11.

Formulation, Characterization, and Antitumor Properties of Trans- and Cis-Citral in the 4T1 Breast Cancer Xenograft Mouse Model

PURPOSE

Citral is composed of a random mixture of two geometric stereoisomers geranial (trans-citral) and neral (cis-citral) yet few studies have directly compared their in vivo antitumor properties. A micelle formulation was therefore developed.

METHODS

Geranial and neral were synthesized. Commercially-purchased citral, geranial, and neral were formulated in PEG-b-PCL (block sizes of 5000:10,000, Mw/Mn 1.26) micelles. In vitro degradation, drug release, cytotoxicity, flow cytometry, and western blot studies were conducted. The antitumor properties of drug formulations (40 and 80 mg/kg based on MTD studies) were evaluated on the 4T1 xenograft mouse model and tumor tissues were analyzed by western blot.

RESULTS

Micelles encapsulated drugs with >50% LE at 5-40% drug to polymer (w/w), displayed sustained release (t1/2 of 8-9 h), and improved drug stability at pH 5.0. The IC50 of drug formulations against 4T1 cells ranged from 1.4 to 9.9 μM. Western blot revealed that autophagy was the main cause of cytotoxicity. Geranial at 80 mg/kg was most effective at inhibiting tumor growth.

CONCLUSIONS

Geranial is significantly more potent than neral and citral at 80 mg/kg (p < 0.001) and western blot of tumor tissues confirms that autophagy and not apoptosis is the major mechanism of tumor growth inhibition in p53-null 4T1 cells.

Abstract 3211: Citral is the major component of ginger-derived terpenes to mediate p53-dependent apoptosis in cancer cells

Steam distillation of ginger yields a mixture of twenty two terpenes. This mixture has anti-proliferative effect on over fifteen different human and mouse cancer cell lines tested in our previous studies. Since the mixture is heterogeneous, it cannot be developed into a therapeutic drug. Hence, we tested individual terpenes from the ginger extract to identify its bioactive component(s). Camphene and alpha-pinene together constitute 10% of the ginger terpene extract and have no effect on cancer cell proliferation. On the other hand, citral a mixture of the two isomers, neral and geranial which constitute 30-50% of the ginger terpene extract, inhibits proliferation of ECC-1, OVCAR-3, OVCAR5, OVCAR 433 with IC50 between 20-50 μM. The decrease in proliferation of the cells is due to induction of apoptosis by citral as measured by monitoring Annexin V and propidium iodide staining and expression of cleaved caspase3. Treatment of cancer cells with citral results in a rapid increase in intracellular Reactive Oxygen Species (ROS). The cellular stress resulting from ROS generation leads to phosphorylation of the Ser-15 residue of p53. Activation of p53 via this phosphorylation event leads to apoptosis in cancer cells. When cells are pre-treated with ROS inhibitor, N-acetyl cysteine (NAC), citral induced apoptosis is inhibited. Similarly inhibition of p53 by pifithrin-α or knockdown of the tumor suppressor by siRNA attenuates the pro-apoptotic response of citral. There is a significant increase in p53 protein expression in cancer cells when treated with Citral This increase in p53 is likely due to an increase in p53 gene expression as determined in our qPCR assays, even though increase due to inhibition of proteasomal degradation of the protein cannot be completely ruled out at this point. An increase in p53 expression in response to citral is associated with an increase in expression of the p53 responsive genes BAX, PUMA and NOXA. All of these experiments demonstrate a novel p53-dependent mechanism for citral to induce apoptosis in cancer cells. Anti-proliferative effects of citral were observed in cancer cells expressing wild-type p53 (ECC-1) as well as in cell lines with R248Q (OVCAR3), ins224 (OVCAR5) p53 mutations. Based on these experimental results we propose that citral should be considered as a novel p53 activating agent that can be used as an adjunct to conventional chemo- and biologic therapies against cancer. Our on-going efforts will identify sensitivity of commonly found p53 mutations to activation by citral and also the specific p53 kinases triggered subsequent to the ROS surge mediated by this terpene.

Citation Format: Lucas Fass, Mildred Felder, Manish S. Patankar, Arvinder K. Kapur. Citral is the major component of ginger-derived terpenes to mediate p53-dependent apoptosis in cancer cells. [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 3211. doi:10.1158/1538-7445.AM2014-3211

Abstract 893: Mining the circulating immune cell transcriptome for ovarian cancer-specific biomarkers: A proof of concept study

The continuous interplay between cancer cells and immune system allows an opportunity to identify cancer-specific biomarkers in immune cells. Here, we compare the transcriptomes of peripheral blood mononuclear cells (PBMCs) obtained from advanced stage ovarian cancer patients and healthy donors in a proof-of-concept study to identify ovarian cancer-specific biomarkers. PBMCs were collected from patients undergoing surgery with the gynecologic oncology service. RNA was extracted from the PBMCs of five patients (training set) with confirmed diagnosis of epithelial ovarian cancer and 4 health donor blood samples. Microarray analysis using Illumina platform was conducted and analyzed using the R statistical package. After data normalization, differentially expressed genes in the two cohorts were identified controlling for false discovery rate at 5 and 10%. The top ten up- and downregulated genes were selected. Gene ontology and pathway analysis led to identification of a Candidate Biomarker Panel (CBP) comprising of five of the ten genes that were most likely to serve as biomarkers for ovarian cancer. Validation of the CBP was achieved using PBMCs isolated from a separate group of six patients and healthy donors (test set) was performed using qPCR and flow cytometry and in vitro culture experiments. Bioinformatics analysis identified 391 genes that were up-regulated and 599 that were down-regulated. A set of five genes with high biomarker potential and were included in the CBP. All of the CBP genes were differentially expressed by 3-5 fold (p&lt;0.03) in the cancer patient PBMCs as compared to healthy donors. Validation results for the CBP were similar between the training set and the test set. Co-culture experiments indicated differential expression of the CBP genes in healthy donor-derived PBMCs co-cultured with cancer cells. Continuous cross-talk between immune cells and abnormal tissues leads to changes in the immune cell transcriptome and proteome in response to a pathologic state. We demonstrate that the transcriptome and proteome of circulating immune cells is a repository for ovarian cancer-specific biomarkers. Our on-going studies are focused on validating the CBP in a larger cohort of samples obtained from healthy donors, ovarian cancer patients and subjects treated for benign gynecologic anomalies.

Citation Format: Shitanshu Uppal, Arvinder Kapur, Mildred Felder, Erin Medlin, Hadi Shojaei, Jesus Gonzalez-Bosquet, Manish S. Patankar. Mining the circulating immune cell transcriptome for ovarian cancer-specific biomarkers: A proof of concept study. [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 893. doi:10.1158/1538-7445.AM2014-893

MUC16 (CA125): tumor biomarker to cancer therapy, a work in progress

Over three decades have passed since the first report on the expression of CA125 by ovarian tumors. Since that time our understanding of ovarian cancer biology has changed significantly to the point that these tumors are now classified based on molecular phenotype and not purely on histological attributes. However, CA125 continues to be, with the recent exception of HE4, the only clinically reliable diagnostic marker for ovarian cancer. Many large-scale clinical trials have been conducted or are underway to determine potential use of serum CA125 levels as a screening modality or to distinguish between benign and malignant pelvic masses. CA125 is a peptide epitope of a 3-5 million Da mucin, MUC16. Here we provide an in-depth review of the literature to highlight the importance of CA125 as a prognostic and diagnostic marker for ovarian cancer. We focus on the increasing body of literature describing the biological role of MUC16 in the progression and metastasis of ovarian tumors. Finally, we consider previous and on-going efforts to develop therapeutic approaches to eradicate ovarian tumors by targeting MUC16. Even though CA125 is a crucial marker for ovarian cancer, the exact structural definition of this antigen continues to be elusive. The importance of MUC16/CA125 in the diagnosis, progression and therapy of ovarian cancer warrants the need for in-depth research on the biochemistry and biology of this mucin. A renewed focus on MUC16 is likely to culminate in novel and more efficient strategies for the detection and treatment of ovarian cancer.

An endogenous aryl hydrocarbon receptor ligand inhibits proliferation and migration of human ovarian cancer cells

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor mediates many biological processes. Herein, we investigated if 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylic acid methyl ester (ITE, an endogenous AhR ligand) regulated proliferation and migration of human ovarian cancer cells via AhR. We found that AhR was widely present in many histotypes of ovarian cancer tissues. ITE suppressed OVCAR-3 cell proliferation and SKOV-3 cell migration in vitro, which were blocked by AhR knockdown. ITE also suppressed OVCAR-3 cell growth in mice. These data suggest that the ITE might potentially be used for therapeutic intervention for at least a subset of human ovarian cancer.

Estradiol 17β and its metabolites stimulate cell proliferation and antagonize ascorbic acid-suppressed cell proliferation in human ovarian cancer cells

Estradiol 17β (E2β) and ascorbic acid (AA) have been implicated in cancer progression. However, little is known about the actions of biologically active metabolites of E2β, 2-hydroxyestradiol (2OHE2), 4-hydroxyestradiol (4OHE2), 2-methoxyestradiol (2ME2), and 4-methoxyestradiol (4ME2) synthesized sequentially by cytochrome P450, family 1, subfamily A (CYP1A1) and B (CYP1B1), polypeptide 1, and catechol-O-methyltransferase (COMT) on ovarian cancer. Herein, we examined the expression of CYP1A1, CYP1B1, COMT, and estrogen receptor α (ERα) and β (ERβ) in human ovarian surface epithelial (IOSE-385) and cancer cell lines (OVCAR-3, SKOV-3, and OVCA-432). We also investigated the roles of E2β, 2OHE2, 4OHE2, 2ME2, and 4ME2 in cell proliferation, and their interactive effects with AA on ovarian cells. We found the expression of CYP1A1, CYP1B1, COMT, ERα, and ERβ in most cell lines tested. Treating cells with physiological concentrations of E2β and its metabolites promoted (13%-42% of the control) IOSE-385 and OVCAR-3 proliferation. The ER blockade inhibited IOSE-385 (∼76%) and OVCAR-3 (∼87%) proliferative response to E2β but not to its metabolites. The ERα blockade inhibited (∼85%) E2β-stimulated OVCAR-3 proliferation, whereas ERβ blockade attenuated (∼83%) E2β-stimulated IOSE-385 proliferation. The AA at ≥250 μmol/L completely inhibited serum-stimulated cell proliferation in all cell lines tested; however, such inhibition in IOSE-385, OVCAR-3, and OVCA-432 was partially (∼10%-20%) countered by E2β and its metabolites. Thus, our findings indicate that E2β and its metabolites promote cell proliferation and antagonize the AA-suppressed cell proliferation in a subset of ovarian cancer cells, suggesting that blocking the actions of E2β and its metabolites may enhance AA's antiovarian cancer activity.

Abstract 2246: Steam distilled ginger extract inhibits endometrial cancer cell proliferation by activating P53 and causing apoptosis

Phenolic compounds present in dry ginger powder or solvent extracts of ginger roots induce cell cycle arrest and apoptosis in skin, breast, prostate, colon, and ovarian cancer cells. Another class of bioactive compounds, the terpenes, can be isolated by steam distillation of the ginger rhizomes. In this study, we examine the anti-cancer properties of Steam Distilled Ginger Extracts (SDGE) on endometrial cancer cells.

SDGE at an IC-50 of 1.5 micrograms/ml inhibited the proliferation of two endometrial cancer cell lines, ECC-1 and Ishikawa. Decreased proliferation of Ishikawa and ECC-1 cells was a direct result of SDGE-induced-apoptosis as demonstrated by Annexin V FITC staining and increased expression of cleaved caspase 3. GC-MS analysis allowed us to identify 22 distinct terpenes in SDGE. Gingerols and other non-terpene phenolic compounds were not present in SDGE. Neral and Geranial constituted 25-35% of the total SDGE terpenes and were found to inhibit endometrial cancer cell proliferation. On the other hand, camphene and α-pinene, which together constitute 10% of SDGE, showed no effect on the proliferation of ECC-1 and Ishikawa cells. SDGE at concentrations as low as 25 nanograms/ml caused a rapid increase in intracellular calcium levels and an approximate decrease of 20% in the mitochondrial membrane potential. Ser-15 of p53 was phosphorylated after a 15 minute treatment of the cancer cells with SDGE (250 nanograms/ml). This activation of p53 was associated with a 90% decrease in Bcl2, whereas no effect was observed on Bax. Pifithrin-α, an inhibitor of p53, attenuated the anti-cancer effects of SDGE that result from apoptosis. In addition, SDGE (1.5 microgram/ml) was unable to induce apoptosis in the p53-negative ovarian cancer cell line, SKOV3. Our data therefore indicates that specific terpenes present in SDGE are highly efficient in controlling the growth of p53-expressing cancer cells. We therefore propose that SDGE and its constituent bioactive terpenes should be further investigated as anti-cancer agents.

Citation Format: Yang Liu, Rebecca J. Whelan, Bikash R. Pattnaik, Kai David Ludwig, Rosalina V. Landeros, Enkateswar Subudhi, Helen Rowland, Nicholas Claussen, Noah Zucker, Shitanshu Uppal, David M. Kushner, Mildred Felder, Manish S. Patankar, Arvinder K. Kapur. Steam distilled ginger extract inhibits endometrial cancer cell proliferation by activating P53 and causing apoptosis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2246. doi:10.1158/1538-7445.AM2013-2246

Abstract B95: MUC16 protects ovarian cancer cells from the cytolytic responses of human and murine natural killer cells and macrophages

MUC16 is a membrane-spanning mucin that frequently is overexpressed by ovarian cancer cells. Knockdown of MUC16 is known to increase apoptosis in both ovarian and breast cancer cells. MUC16 also plays an important role in facilitating metastasis and protecting cancer cells from innate immune responses. Here, we demonstrate that MUC16 protects ovarian cancer cells from cytolysis by NK cells and macrophages. Immunodeficient SCID and SCID/beige mice implanted with MUC16-expressing and MUC16 knockdown tumors have a median survival of 78 and 198 days, respectively. In vitro assays demonstrate that better immune recognition of the MUC16 knockdown ovarian cancer cells contributes to the higher median survival of the tumor-bearing immunocompromised animals. NK cells which were unstimulated, activated in vivo with anti-CD40 antibody, and/or stimulated with lipopolysaccharides preferentially lyse MUC16-knockdown cancer cells in standard chromium release assays. Thus the reduction of MUC16 expression leads to a significant increase of the natural cytotoxic responses of NK cells. In addition, MUC16 protects the cancer cells from Antibody-Dependent Cell-mediated Cytotoxicity (ADCC). ADCC of the MUC16 knockdown cancer cells was studied using the anti-EpCAM antibody KS1/4 and its corresponding immunocytokine huKS-IL2. NK cells from immunocompetent C57BL/6 mice exhibited an increase in the cytolysis of MUC16-knockdown ovarian cancer cells in the presence of either KS1/4 or huKS-IL2. Similar effect was also observed when the ADCC assays were conducted using human NK cells isolated from healthy donors. The immune protection provided by MUC16 not only reduces the effectiveness of NK cells, but also murine macrophages, explaining the longer survival observed in the NK cell deficient SCID-beige mice transplanted with the MUC16-knockdown cancer cells. Immunohistochemical analysis of the tumors from the SCID-beige mice showed increased infiltration of macrophages in the tumor nests of MUC16-knockdown tumors. In contrast, macrophages were primarily detected in the peritumoral stroma of MUC16pos tumors. Murine macrophages from unstimulated and anti-CD40 antibody stimulated animals showed a 3-fold increase in tumoristatic activity against the MUC16-knockdown versus the MUC16pos ovarian cancer cells. The results of our study also demonstrate that siRNA-based strategies to knockdown MUC16 can be coupled with immunotherapeutic approaches, such as the use of activated NK cells or specific immunocytokines, to render ovarian tumors especially vulnerable to innate immune responses. Therefore, our results not only indicate that immune protection is a major biological role of MUC16, but also demonstrate that attenuation of MUC16 expression will likely serve as an important strategy to boost the anticancer efficacy of immunotherapeutic agents.

Citation Format: Mildred Felder, Arvinder Kapur, Alexander Rakhmilevich, Joseph Connor, Manish S. Patankar. MUC16 protects ovarian cancer cells from the cytolytic responses of human and murine natural killer cells and macrophages. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B95.

Terpenoids from Zingiber officinale (Ginger) induce apoptosis in endometrial cancer cells through the activation of p53

Novel strategies are necessary to improve chemotherapy response in advanced and recurrent endometrial cancer. Here, we demonstrate that terpenoids present in the Steam Distilled Extract of Ginger (SDGE) are potent inhibitors of proliferation of endometrial cancer cells. SDGE, isolated from six different batches of ginger rhizomes, consistently inhibited proliferation of the endometrial cancer cell lines Ishikawa and ECC-1 at IC(50) of 1.25 µg/ml. SDGE also enhanced the anti-proliferative effect of radiation and cisplatin. Decreased proliferation of Ishikawa and ECC-1 cells was a direct result of SDGE-induced apoptosis as demonstrated by FITC-Annexin V staining and expression of cleaved caspase 3. GC/MS analysis identified a total of 22 different terpenoid compounds in SDGE, with the isomers neral and geranial constituting 30-40%. Citral, a mixture of neral and geranial inhibited the proliferation of Ishikawa and ECC-1 cells at an IC(50) 10 µM (2.3 µg/ml). Phenolic compounds such as gingerol and shogaol were not detected in SDGE and 6-gingerol was a weaker inhibitor of the proliferation of the endometrial cancer cells. SDGE was more effective in inducing cancer cell death than citral, suggesting that other terpenes present in SDGE were also contributing to endometrial cancer cell death. SDGE treatment resulted in a rapid and strong increase in intracellular calcium and a 20-40% decrease in the mitochondrial membrane potential. Ser-15 of p53 was phosphorylated after 15 min treatment of the cancer cells with SDGE. This increase in p53 was associated with 90% decrease in Bcl2 whereas no effect was observed on Bax. Inhibitor of p53, pifithrin-α, attenuated the anti-cancer effects of SDGE and apoptosis was also not observed in the p53(neg) SKOV-3 cells. Our studies demonstrate that terpenoids from SDGE mediate apoptosis by activating p53 and should be therefore be investigated as agents for the treatment of endometrial cancer.

The mucin MUC16 (CA125) binds to NK cells and monocytes from peripheral blood of women with healthy pregnancy and preeclampsia

PROBLEM

MUC16 (CA125) released from ovarian tumors binds to NK cells and monocytes via the inhibitory receptor Siglec-9. Here, we investigate whether MUC16 also binds to circulating immune cells during pregnancy and in women with preeclampsia.

METHOD OF STUDY

MUC16 binding was monitored by flow cytometry and immunoprecipitation, and RT-PCR was used to monitor indigenous expression in immune cells. Serum CA125 levels were measured by a clinical assay.

RESULTS

MUC16 was equally distributed on Siglec-9(pos) CD16(pos)/CD56(dim) and CD16(neg)/CD56(br) NK cells in the healthy pregnant and preeclampsia groups. While serum CA125 levels and number of NK and monocytes were similar, increased binding of MUC16 was observed on these immune cells in the preeclampsia cohort as compared to the healthy pregnant samples.

CONCLUSION

MUC16 binding to NK cells and monocytes likely contributes to tolerance of the fetal allograft from maternal responses and may also serve as a novel biomarker for preeclampsia.