Tumor microenvironment-induced FOXM1 regulates ovarian cancer stemness.

In ovarian tumors, the omental microenvironment profoundly influences the behavior of cancer cells and sustains the acquisition of stem-like traits, with major impacts on tumor aggressiveness and relapse. Here, we leverage a patient-derived platform of organotypic cultures to study the crosstalk between the tumor microenvironment and ovarian cancer stem cells. We discovered that the pro-tumorigenic transcription factor FOXM1 is specifically induced by the microenvironment in ovarian cancer stem cells, through activation of FAK/YAP signaling.

Cancer-associated mesothelial cell-derived ANGPTL4 and STC1 promote the early steps of ovarian cancer metastasis.

Ovarian cancer (OvCa) preferentially metastasizes in association with mesothelial cell-lined surfaces. We sought to determine if mesothelial cells are required for OvCa metastasis and detect alterations in mesothelial cell gene expression and cytokine secretion upon interaction with OvCa cells. Using omental samples from patients with high-grade serous OvCa and mouse models with Wt1-driven GFP-expressing mesothelial cells, we validated the intratumoral localization of mesothelial cells during human and mouse OvCa omental metastasis.

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

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.

Modeling the Early Steps of Ovarian Cancer Dissemination in an Organotypic Culture of the Human Peritoneal Cavity.

The majority of ovarian cancer patients present clinically with wide-spread metastases throughout the peritoneal cavity, metastasizing to the mesothelium-lined peritoneum and visceral adipose depots within the abdomen. This unique metastatic tumor microenvironment is comprised of multiple cell types, including mesothelial cells, fibroblasts, adipocytes, macrophages, neutrophils, and T lymphocytes. Modeling advancements, including complex 3D systems and organoids, coupled with 2D cocultures, in vivo mouse models, and ex vivo human tissue cultures have greatly enhanced our understanding of the tumor-stroma interactions that are required for successful metastasis of ovarian cancer cells.

Neutrophil elastase selectively kills cancer cells and attenuates tumorigenesis.

Cancer cell genetic variability and similarity to host cells have stymied development of broad anti-cancer therapeutics. Our innate immune system evolved to clear genetically diverse pathogens and limit host toxicity; however, whether/how innate immunity can produce similar effects in cancer is unknown. Here, we show that human, but not murine, neutrophils release catalytically active neutrophil elastase (ELANE) to kill many cancer cell types while sparing non-cancer cells.

Mesothelial Cell HIF1α Expression Is Metabolically Downregulated by Metformin to Prevent Oncogenic Tumor-Stromal Crosstalk.

The tumor microenvironment (TME) plays a pivotal role in cancer progression, and, in ovarian cancer (OvCa), the primary TME is the omentum. Here, we show that the diabetes drug metformin alters mesothelial cells in the omental microenvironment. Metformin interrupts bidirectional signaling between tumor and mesothelial cells by blocking OvCa cell TGF-β signaling and mesothelial cell production of CCL2 and IL-8.

Cancer-derived small extracellular vesicles promote angiogenesis by heparin-bound, bevacizumab-insensitive VEGF, independent of vesicle uptake.

Cancer-derived small extracellular vesicles (sEVs) induce stromal cells to become permissive for tumor growth. However, it is unclear whether this induction solely occurs through transfer of vesicular cargo into recipient cells. Here we show that cancer-derived sEVs can stimulate endothelial cell migration and tube formation independently of uptake.

Quantitative High-Throughput Screening Using an Organotypic Model Identifies Compounds that Inhibit Ovarian Cancer Metastasis.

The tumor microenvironment (TME) is a key determinant of metastatic efficiency. We performed a quantitative high-throughput screen (qHTS) of diverse medicinal chemistry tractable scaffolds (44,420 compounds) and pharmacologically active small molecules (386 compounds) using a layered organotypic, robust assay representing the ovarian cancer metastatic TME. This 3D model contains primary human mesothelial cells, fibroblasts, and extracellular matrix, to which fluorescently labeled ovarian cancer cells are added.

Inhibition of fascin in cancer and stromal cells blocks ovarian cancer metastasis.

Objective: Ovarian cancer (OvCa) metastasis requires the coordinated motility of both cancer and stromal cells. Cellular movement is a dynamic process that involves the synchronized assembly of f-actin bundles into cytoskeletal protrusions by fascin. Fascin directly binds f-actin and is an integral component of filopodia, lamellapodia and stress fibers.

Neutrophils facilitate ovarian cancer premetastatic niche formation in the omentum.

Ovarian cancer preferentially metastasizes to the omentum, a fatty tissue characterized by immune structures called milky spots, but the cellular dynamics that direct this tropism are unknown. Here, we identified that neutrophil influx into the omentum is a prerequisite premetastatic step in orthotopic ovarian cancer models. Ovarian tumor-derived inflammatory factors stimulated neutrophils to mobilize and extrude chromatin webs called neutrophil extracellular traps (NETs).

Fibroblasts Mobilize Tumor Cell Glycogen to Promote Proliferation and Metastasis.

Successful metastasis requires the co-evolution of stromal and cancer cells. We used stable isotope labeling of amino acids in cell culture coupled with quantitative, label-free phosphoproteomics to study the bidirectional signaling in ovarian cancer cells and human-derived, cancer-associated fibroblasts (CAFs) after co-culture. In cancer cells, the interaction with CAFs supported glycogenolysis under normoxic conditions and induced phosphorylation and activation of phosphoglucomutase 1, an enzyme involved in glycogen metabolism.

Organotypic 3D Models of the Ovarian Cancer Tumor Microenvironment.

Ovarian cancer progression involves multifaceted and variable tumor microenvironments (TMEs), from the in situ carcinoma in the fallopian tube or ovary to dissemination into the peritoneal cavity as single cells or spheroids and attachment to the mesothelial-lined surfaces of the omentum, bowel, and abdominal wall. The TME comprises the tumor vasculature and lymphatics (including endothelial cells and pericytes), in addition to mesothelial cells, fibroblasts, immune cells, adipocytes and extracellular matrix (ECM) proteins. When generating 3D models of the ovarian cancer TME, researchers must incorporate the most relevant stromal components depending on the TME in question (e.

Adipocyte-induced CD36 expression drives ovarian cancer progression and metastasis.

Ovarian cancer (OvCa) is characterized by widespread and rapid metastasis in the peritoneal cavity. Visceral adipocytes promote this process by providing fatty acids (FAs) for tumour growth. However, the exact mechanism of FA transfer from adipocytes to cancer cells remains unknown.

A High-Throughput Screening Model of the Tumor Microenvironment for Ovarian Cancer Cell Growth.

The tumor microenvironment plays an important role in the processes of tumor growth, metastasis, and drug resistance. We have used a multilayered 3D primary cell culture model that reproduces the human ovarian cancer metastatic microenvironment to study the effect of the microenvironment on the pharmacological responses of different classes of drugs on cancer cell proliferation. A collection of oncology drugs was screened to identify compounds that inhibited the proliferation of ovarian cancer cells growing as monolayers or forming spheroids, on plastic and on a 3D microenvironment culture model of the omentum metastatic site, and also cells already in preformed spheroids.

Unsaturated Fatty Acids Maintain Cancer Cell Stemness.

Investigation of the metabolic regulation of cancer stem cells is an emerging field that offers promising approaches for identifying and targeting recalcitrant stem cell populations. In this issue of Cell Stem Cell, Li et al. (2017) indicate that increased lipid desaturation is essential to stem-like characteristics in ovarian cancer cells.

Reversal of Chemoresistance in Ovarian Cancer by Co-Delivery of a P-Glycoprotein Inhibitor and Paclitaxel in a Liposomal Platform.

The overexpression of permeability-glycoprotein (P-gp), an ABC transporter involved in the cellular exclusion of chemotherapeutic drugs, is a major factor in paclitaxel-resistant ovarian cancer. However, in clinical trials, co-administration of P-gp inhibitors and anticancer drugs has not resulted in the efficient reversal of drug resistance. To improve administration, we encapsulated the third-generation P-gp inhibitor tariquidar (XR-9576, XR), alone or in combination with paclitaxel (PCT) in liposomes (LP).

Molecular pathways: trafficking of metabolic resources in the tumor microenvironment.

A model of tumor metabolism is proposed that describes how the complementary metabolic functions of the local stroma and the tumor cells contribute to cancer progression. Cancer cells alter the metabolism of cancer-associated fibroblasts to obtain lactate and amino acids, which are utilized for energy production, rapid growth, and resistance to chemotherapy drugs. Cancer cells use glutamine supplied by cancer-associated fibroblasts to replenish tricarboxylic acid cycle intermediates and as a nitrogen source for nucleotide synthesis.

Quantitative high throughput screening using a primary human three-dimensional organotypic culture predicts in vivo efficacy.

The tumour microenvironment contributes to cancer metastasis and drug resistance. However, most high throughput screening (HTS) assays for drug discovery use cancer cells grown in monolayers. Here we show that a multilayered culture containing primary human fibroblasts, mesothelial cells and extracellular matrix can be adapted into a reliable 384- and 1,536-multi-well HTS assay that reproduces the human ovarian cancer (OvCa) metastatic microenvironment.

Mesothelial cells promote early ovarian cancer metastasis through fibronectin secretion.

Ovarian cancer (OvCa) metastasizes to organs in the abdominal cavity, such as the omentum, which are covered by a single layer of mesothelial cells. Mesothelial cells are generally thought to be "bystanders" to the metastatic process and simply displaced by OvCa cells to access the submesothelial extracellular matrix. Here, using organotypic 3D cultures, we found that primary human mesothelial cells secrete fibronectin in the presence of OvCa cells.

Three-dimensional modeling of ovarian cancer.

New models for epithelial ovarian cancer initiation and metastasis are required to obtain a mechanistic understanding of the disease and to develop new therapeutics. Modeling ovarian cancer however is challenging as a result of the genetic heterogeneity of the malignancy, the diverse pathology, the limited availability of human tissue for research, the atypical mechanisms of metastasis, and because the origin is unclear. Insights into the origin of high-grade serous ovarian carcinomas and mechanisms of metastasis have resulted in the generation of novel three-dimensional (3D) culture models that better approximate the behavior of the tumor cells in vivo than prior two-dimensional models.

Urokinase plasminogen activator system-targeted delivery of nanobins as a novel ovarian cancer therapy.

The urokinase system is overexpressed in epithelial ovarian cancer cells and is expressed at low levels in normal cells. To develop a platform for intracellular and targeted delivery of therapeutics in ovarian cancer, we conjugated urokinase plasminogen activator (uPA) antibodies to liposomal nanobins. The arsenic trioxide-loaded nanobins had favorable physicochemical properties and the ability to bind specifically to uPA.

Adipocytes promote ovarian cancer metastasis and provide energy for rapid tumor growth.

Intra-abdominal tumors, such as ovarian cancer, have a clear predilection for metastasis to the omentum, an organ primarily composed of adipocytes. Currently, it is unclear why tumor cells preferentially home to and proliferate in the omentum, yet omental metastases typically represent the largest tumor in the abdominal cavities of women with ovarian cancer. We show here that primary human omental adipocytes promote homing, migration and invasion of ovarian cancer cells, and that adipokines including interleukin-8 (IL-8) mediate these activities.

The first line of intra-abdominal metastatic attack: breaching the mesothelial cell layer.

Iwanicki and colleagues reveal that ovarian cancer spheroids clear mesothelial cells which cover the surface of the abdominal cavity using myosin-generated force.

Targeting the urokinase plasminogen activator receptor inhibits ovarian cancer metastasis.

Purpose: To understand the functional and preclinical efficacy of targeting the urokinase plasminogen activator receptor (u-PAR) in ovarian cancer.

Experimental Design: Expression of u-PAR was studied in 162 epithelial ovarian cancers, including 77 pairs of corresponding primary and metastatic tumors. The effect of an antibody against u-PAR (ATN-658) on proliferation, adhesion, invasion, apoptosis, and migration was assessed in 3 (SKOV3ip1, HeyA8, and CaOV3) ovarian cancer cell lines.