Ovarian cancer spheroids use myosin-generated force to clear the mesothelium

Identification of potential cell surface targets in patient-derived cultures toward photoimmunotherapy of high-grade serous ovarian cancer

Tumor-targeted, activatable photoimmunotherapy (taPIT) has shown promise in preclinical models to selectively eliminate drug-resistant micrometastases that evade standard treatments. Moreover, taPIT has the potential to resensitize chemo-resistant tumor cells to chemotherapy, making it a complementary modality for treating recurrent high-grade serous ovarian cancer (HGSOC). However, the established implementation of taPIT relies on the overexpression of EGFR in tumor cells, which is not universally observed in HGSOCs. Motivated by the need to expand taPIT applications beyond EGFR, we conducted mRNA-sequencing and proteomics to identify alternative cell surface targets for taPIT in patient-derived HGSOC cell cultures with weak EGFR expression and lacking expression of other cell surface proteins commonly reported in the literature as overexpressed in ovarian cancers, such as FOLR1 and EpCAM. Our findings highlight TFRC and LRP1 as promising alternative targets. Notably, TFRC was overexpressed in 100% (N = 5) of the patient-derived HGSOC models tested, whereas only 60% of models had high EpCAM expression, suggesting that future larger cohort studies should include TFRC. While this study focuses on target identification, future work will expand the approaches developed here to larger HGSOC biopsy repositories and will also develop and evaluate antibody-photosensitizer conjugates targeting these proteins for taPIT applications.

Durotaxis and extracellular matrix degradation promote the clustering of cancer cells

Early stages of metastasis depend on the collective behavior of cancer cells and their interaction with the extracellular matrix (ECM). Cancer cell clusters are known to exhibit higher metastatic potential than single cells. To explore clustering dynamics, we developed a calibrated computational model describing how motile cancer cells biochemically and biomechanically interact with the ECM during the initial invasion phase, including ECM degradation and mechanical remodeling. The model reveals that cluster formation time, size, and shape are influenced by ECM degradation rates and cellular compliance to external stresses (durotaxis). The results align with experimental observations, demonstrating distinct cell trajectories and cluster morphologies shaped by biomechanical parameters. The simulations provide valuable insights into cancer invasion dynamics and may suggest potential therapeutic strategies targeting early-stage invasive cells.

Basal cell adhesion molecule (BCAM) promotes mesothelial-to-mesenchymal transition and tumor angiogenesis through paracrine signaling

BACKGROUND

High expression of basal cell adhesion molecule (BCAM) is a hallmark of ovarian cancer (OC) progression. BCAM facilitates transcoelomic dissemination by promoting mesothelial cell clearance at peritoneal attachment sites of tumor cell spheroids. We investigated how BCAM mediates this effect and potentially drives other pro-metastatic functions.

METHODS

The impact of BCAM on the tumor cell secretome and the mesothelial cell phenotype was analyzed by affinity proteomics, bulk and single-cell RNA sequencing, life-cell and multiphoton microscopy, biochemical and functional in vitro assays as well as a murine tumor model. BCAM manipulation involved ectopic overexpression, inducible expression and treatment with soluble BCAM.

RESULTS

All forms of BCAM enhanced the secretion of cytokines that impact cell motility, mesenchymal differentiation and angiogenesis, including AREG, CXCL family members, FGF2, TGFB2, and VEGF. Notably, their levels in OC ascites were correlated with BCAM expression, and recombinant BCAM-induced cytokines triggered mesothelial-mesenchymal transition (MMT). Mesothelial cells undergoing MMT exhibited enhanced motility away from attaching tumor spheroids, leading to mesothelial clearance at spheroid attachment sites. BCAM-mediated MMT-associated transcriptional changes were also observed in subpopulations of omental mesothelial cells from OC patients, and were associated with poor survival. Consistent with the secretome data, BCAM induced endothelial tube formation in vitro and markedly promoted tumor angiogenesis in a mouse model.

CONCLUSION

We have identified previously unknown functions of the BCAM-induced secretome potentially impacting distinct stages of OC metastasis. While BCAM's impact on MMT may facilitate initiation of micrometastases, neo-angiogenesis is essential for tumor growth. Taken together with the observed clinical adverse association, our findings underscore the potential of BCAM as a therapeutic target.

A Peptide Derived from Nectin-4 Increases Cisplatin Cytotoxicity in Cell Lines and Cells from Ovarian Cancer Patients' Ascites

BACKGROUND/OBJECTIVES

New approaches to the treatment of women with ovarian cancer are desperately needed, since most women develop resistance to chemotherapy and the 5-year survival rate remains low. The hypothesis guiding this study was that the inhibition of cell adhesion could be used as a novel strategy to increase the chemosensitivity of ovarian cancer cells.

METHODS

The Nectin-4 peptide N4-P10 was used to inhibit the formation of cell-cell aggregates (spheroids) using cell lines and cells isolated from ovarian cancer patients' ascites. Cell lines were pre-treated with peptide N4-P10 or control scrambled peptides and monitored for spheroid formation with live-cell imaging by digital time-lapse photography. Cells were then tested for the cytotoxicity of the chemotherapeutic agent, cisplatin.

RESULTS

Peptide N4-P10 blocked aggregation in cell lines with different levels of Nectin-4 expression and different spheroid morphologies. The cytotoxicity of cisplatin increased in cells pre-treated with peptide N4-P10. Similarly, when single cells were isolated from the ascites of ovarian cancer patients, peptide N4-P10 blocked cell aggregation and increased the cytotoxicity of cisplatin.

CONCLUSIONS

These results suggest that targeting the cell-cell adhesive property of cancer cells could serve as a new approach to augment the cytotoxic effect of chemotherapy and potentially reduce disease recurrence in ovarian cancer patients.

PIN1 Prolyl Isomerase Promotes Initiation and Progression of Bladder Cancer through the SREBP2-Mediated Cholesterol Biosynthesis Pathway

SIGNIFICANCE

This study provides deeper insights into the regulatory role of the phospho-dependent prolyl isomerase PIN1 in bladder cancer. The identification of the link between PIN1 and SREBP2-mediated transcription and cholesterol biosynthesis offers the potential for developing novel therapeutic strategies for bladder cancer.

Cisplatin resistance alters ovarian cancer spheroid formation and impacts peritoneal invasion

Epithelial ovarian cancer (EOC) is an aggressive and lethal gynaecologic malignancy due to late diagnosis and acquired resistance to chemotherapeutic drugs, such as cisplatin. EOC metastasis commonly occurs through the extensive dissemination of multicellular aggregates, formed of cells originally shed from the primary ovarian tumour, within the peritoneal cavity. However, little is known about how cisplatin resistance (CR) alters the biophysical properties of EOC multicellular aggregates and how this impacts metastasis. In this interdisciplinary study, light and atomic force microscopy was used, alongside quantitative gene and protein expression analysis, to reveal distinct differences in the biophysical properties of CR spheroids, which correlated with altered protein expression of plasminogen activator inhibitor-1 (PAI-1) and Tenascin-C. CR SKOV3 spheroids (IC50: 25.5 µM) had a significantly greater area and perimeter and were less spherical, with a reduced Young's modulus, (p < 0.01) compared to parental (P) SKOV3 spheroids (IC50: 5.4 µM). Gene expression arrays revealed upregulation of genes associated with cell adhesion, extracellular matrix (ECM) and epithelial-to-mesenchymal transition (EMT) in CR spheroids, while immunofluorescence assays demonstrated increased protein expression of PAI-1 (p < 0.05; implicated in cell adhesion) and reduced protein expression of Tenascin-C (p < 0.01; implicated in elasticity) in CR spheroids compared to P spheroids. Furthermore, the CR spheroids demonstrated altered interactions with a surface that mimics the peritoneal lining post mesothelial clearance (Matrigel). CR spheroids were significantly less adhesive with reduced disaggregation on Matrigel surfaces, compared to P spheroids (p < 0.05), while CR cells were more invasive compared to P cells. The combined characterisation of the biophysical and biological roles of EOC multicellular aggregates in drug resistance and metastasis highlight key proteins which could be responsible for altered metastatic progression that may occur in patients that present with cisplatin resistance.

Exploiting Cancer Dormancy Signaling Mechanisms in Epithelial Ovarian Cancer Through Spheroid and Organoid Analysis

Epithelial ovarian cancer (EOC) exhibits a unique mode of metastasis, involving spheroid formation in the peritoneum. Our research on EOC spheroid cell biology has provided valuable insights into the signaling plasticity associated with metastasis. We speculate that EOC cells modify their biology between tumour and spheroid states during cancer dormancy, although the specific mechanisms underlying this transition remain unknown. Here, we present novel findings from direct comparisons between cultured EOC spheroids and organoids. Our results indicated that AMP-activated protein kinase (AMPK) activity was significantly upregulated and protein kinase B (Akt) was downregulated in EOC spheroids compared to organoids, suggesting a clear differential phenotype. Through RNA sequencing analysis, we further supported these phenotypic differences and highlighted the significance of cell cycle regulation in organoids. By inhibiting the G2/M checkpoint via kinase inhibitors, we confirmed that this pathway is essential for organoids. Interestingly, our results suggest that specifically targeting aurora kinase A (AURKA) may represent a promising therapeutic strategy since our cells were equally sensitive to Alisertib treatment as both spheroids and organoids. Our findings emphasize the importance of studying cellular adaptations of EOC cells, as there may be different therapeutic targets depending on the step of EOC disease progression.

Reversible downregulation of MYC in a spheroid model of metastatic epithelial ovarian cancer

Upon detachment from the primary tumour, epithelial ovarian cancer cells can form multicellular aggregates, also referred to as spheroids, that have the capacity to establish metastases at distant sites. These structures exhibit numerous adaptations that may facilitate metastatic transit and promote tumorigenic potential. One such adaptation is the acquisition of dormancy, characterized by decreased proliferation and molecular features of quiescence. One of the most frequently dysregulated genes in cancer is MYC, which encodes a transcription factor that promotes cell proliferation. In this study, we demonstrate that MYC protein abundance and associated gene expression is significantly decreased in EOC spheroids compared to adherent cells. This downregulation occurs rapidly upon cell detachment and is proteasome-dependent. Moreover, MYC protein abundance and associated gene expression is restored upon spheroid reattachment to an adherent culture surface. Overall, our findings suggest that suppression of MYC activity is a common feature of EOC spheroids and may contribute to the reversible acquisition of dormancy.

Beyond tumor‑associated macrophages involved in spheroid formation and dissemination: Novel insights for ovarian cancer therapy (Review)

Ovarian cancer (OC) is the most common and deadly malignant tumor of the female reproductive system. When OC cells detach from the primary tumor and enter the ascitic microenvironment, they are present as individual cells or multicellular spheroids in ascites. These spheroids, composed of cancer and non‑malignant cells, are metastatic units and play a crucial role in the progression of OC. However, little is known about the mechanism of spheroid formation and dissemination. Tumor‑associated macrophages (TAMs) in the center of spheroids are key in spheroid formation and metastasis and provide a potential target for OC therapy. The present review summarizes the key biological features of spheroids, focusing on the role of TAMs in spheroid formation, survival and peritoneal metastasis, and the strategies targeting TAMs to provide new insights in treating OC.

Leader cells promote immunosuppression to drive ovarian cancer progression in vivo

Over 75% of patients with ovarian cancer present with late-stage disease, often accompanied by extensive metastasis. The metastatic cascade is driven by a sub-population of transcriptionally plastic cells known as "leader cells" (LCs), which play a critical role in collective invasion yet remain poorly understood. LCs are marked by the expression of keratin-14 (KRT14), which determines their migratory and invasive capacity in ovarian cancer. This study demonstrates that KRT14+ LCs promote tumor progression through immunosuppression and immune privilege in vivo. In the ID8 syngeneic epithelial ovarian cancer mouse model, tumor-specific loss of KRT14+ LCs impairs tumor progression and metastatic spread without affecting cellular proliferation. Immune profiling shows reduced immunosuppressive regulatory T cells (Tregs) and M2 macrophages and improved CD8+ T cell/Treg ratios in LC knockout (LCKO) mice. Conversely, forced LC overexpression accelerates metastasis and increases the secretion of immunosuppressive chemokines, such as CCL22 and CCL5, highlighting the role of KRT14+ LCs in immune suppression and metastatic progression.

LKB1 and STRADα Promote Epithelial Ovarian Cancer Spheroid Cell Invasion

Late-stage epithelial ovarian cancer (EOC) involves the widespread dissemination of malignant disease throughout the peritoneal cavity, often accompanied by ascites. EOC metastasis relies on the formation of multicellular aggregates, called spheroids. Given that Liver Kinase B1 (LKB1) is required for EOC spheroid viability and LKB1 loss in EOC cells decreases tumor burden in mice, we investigated whether the LKB1 complex controls the invasive properties of human EOC spheroids. LKB1 signalling was antagonized through the CRISPR/Cas9 genetic knockout of LKB1 and/or the RNAi-dependent targeting of STE20-related kinase adaptor protein (STRAD, an LKB1 activator). EOC spheroids expressing nuclear GFP (green) or mKate2 (red) constructs were embedded in Matrigel for real-time live-cell invasion monitoring. Migration and invasion were also assessed in spheroid culture using Transwell chambers, spheroid reattachment, and mesothelial clearance assays. The loss of LKB1 and STRAD signalling decreased cell invasion through Matrigel and Transwell membranes, as well as mesothelial cell clearance. In the absence of LKB1, zymographic assays identified a loss of matrix metalloproteinase (MMP) activity, whereas spheroid reattachment assays found that coating plates with fibronectin restored their invasive potential. A three-dimensional EOC organoid model demonstrated that organoid area was greatly reduced by LKB1 loss. Overall, our data indicated that LKB1 and STRAD facilitated EOC metastasis by promoting MMP activity and fibronectin expression. Given that LKB1 and STRAD are crucial for EOC metastasis, targeting LKB1 and/or STRAD could disrupt the dissemination of EOC, making inhibitors of the LKB1 pathway an alternative therapeutic strategy for EOC patients.

Recombinant humanized type III collagen inhibits ovarian cancer and induces protective anti-tumor immunity by regulating autophagy through GSTP1

Ovarian cancer (OC) is one of the leading causes of death from malignancy in women and lacks safe and efficient treatment. The novel biomaterial, recombinant humanized collagen type III (rhCOLIII), has been reported to have various biological functions, but its role in OC is unclear. This study aimed to reveal the function and mechanism of action of rhCOLIII in OC. We developed an injectable recombinant human collagen (rhCOL)-derived material with a molecular weight of 45 kDa, with a stable triple helix structure, high biocompatibility, water solubility and biosafety. The anti-tumor activity of rhCOLIII was comprehensively evaluated through in vitro and in vivo experiments. In vitro, our results showed that rhCOLIII inhibited the proliferation, migration, and invasion of ovarian cancer cells (OCCs), and induced apoptosis. In addition, rhCOLIII not only inhibited autophagy of OCCs but also increased the expression of MHC-1 molecule within OCCs. To further elucidate the mechanism of rhCOLIII in OC, we conducted joint analysis of RNA-Seq and proteomics, and found that rhCOLIII exerted anti-tumor function and autophagy inhibition by downregulating Glutathione S-transferase P1 (GSTP1). Furthermore, various rescue experiments were designed to demonstrate that rhCOLIII suppressed autophagy and proliferation of OCCs by mediating GSTP1. In vivo, we found that rhCOLIII could inhibit tumor growth and promote CD8+ T cell infiltration. Our results indicate that rhCOLIII has great anti-tumor potential activity in OC, and induces protective anti-tumor immunity by regulating autophagy through GSTP1. These findings illustrate the potential therapeutic prospects of rhCOLIII for OC treatment.

The expression level of VEGFR2 regulates mechanotransduction, tumor growth and metastasis of high grade serous ovarian cancer cells

Recent data shows that alterations in the expression and/or activation of the vascular endothelial growth factor receptor 2 (VEGFR2) in high grade serous ovarian cancer (HGSOC) modulate tumor progression. However, controversial results have been obtained, showing that in some cases VEGFR2 inhibition can promote tumorigenesis and metastasis. Thus, it is urgent to better define the role of the VEGF/VEGFR2 system to understand/predict the effects of its inhibitors administered as anti-angiogenic in HGSOC. Here, we modulated the expression levels of VEGFR2 and analyzed the effects in two cellular models of HGSOC. VEGFR2 silencing (or its pharmacological inhibition) promote the growth and invasive potential of OVCAR3 cells in vitro and in vivo. Consistent with this, the low levels of VEGFR2 in OV7 cells are associated with more pronounced proliferative and motile phenotypes when compared to OVCAR3 cells, and VEGFR2 overexpression in OV7 cells inhibits cell growth. In vitro data confirmed that VEGFR2 silencing in OVCAR3 cells favors the acquisition of an invasive phenotype by loosening cell-ECM contacts, reducing the size and the signaling of focal adhesion contacts (FAs). This is translated into a reduced FAK activity at FAs, ECM-dependent alterations of mechanical forces through FAs and YAP nuclear translocation. Together, the data show that low expression, silencing or inhibition of VEGFR2 in HGSOC cells alter mechanotransduction and lead to the acquisition of a pro-proliferative/invasive phenotype which explains the need for a more cautious use of anti-VEGFR2 drugs in ovarian cancer.

Ascites microenvironment conditions the peritoneal pre-metastatic niche to promote the implantation of ovarian tumor spheroids: Involvement of fibrinogen/fibrin and αV and α5β1 integrins

At least one-third of patients with epithelial ovarian cancer (OC) present ascites at diagnosis and almost all have ascites at recurrence especially because of the propensity of the OC cells to spread in the abdominal cavity leading to peritoneal metastasis. The influence of ascites on the development of pre-metastatic niches, and on the biological mechanisms leading to cancer cell colonization of the mesothelium, remains poorly understood. Here, we show that ascites weakens the mesothelium by affecting the morphology of mesothelial cells and by destabilizing their distribution in the cell cycle. Ascites also causes destabilization of the integrity of mesothelium by modifying the organization of cell junctions, but it does not affect the synthesis of N-cadherin and ZO-1 by mesothelial cells. Moreover, ascites induces disorganization of focal contacts and causes actin cytoskeletal reorganization potentially dependent on the activity of Rac1. Ascites allows the densification and reorganization of ECM proteins of the mesothelium, especially fibrinogen/fibrin, and indicates that it is a source of the fibrinogen and fibrin surrounding OC spheroids. The fibrin in ascites leads to the adhesion of OC spheroids to the mesothelium, and ascites promotes their disaggregation followed by the clearance of mesothelial cells. Both αV and α5β1 integrins are involved. In conclusion ascites and its fibrinogen/fibrin composition affects the integrity of the mesothelium and promotes the integrin-dependent implantation of OC spheroids in the mesothelium.

Enhancing PKA-dependent mesothelial barrier integrity reduces ovarian cancer transmesothelial migration via inhibition of contractility

Cancer-mesothelial cell interactions are critical for multiple solid tumors to colonize the surface of peritoneal organs. Understanding mechanisms of mesothelial barrier dysfunction that impair its protective function is critical for discovering mesothelial-targeted therapies to combat metastatic spread. Here, we utilized a live cell imaging-based assay to elucidate the dynamics of ovarian cancer spheroid transmesothelial migration and mesothelial-generated mechanical forces. Treatment of mesothelial cells with the adenylyl cyclase agonist forskolin strengthens cell-cell junctions, reduces actomyosin fibers, contractility-driven matrix displacements, and cancer spheroid transmigration in a protein kinase A (PKA)-dependent mechanism. We also show that inhibition of the cytoskeletal regulator Rho-associated kinase in mesothelial cells phenocopies the anti-metastatic effects of forskolin. Conversely, upregulation of contractility in mesothelial cells disrupts cell-cell junctions and increases the clearance rates of ovarian cancer spheroids. Our findings demonstrate the critical role of mesothelial cell contractility and mesothelial barrier integrity in regulating metastatic dissemination within the peritoneal microenvironment.

ROR2/Wnt5a Signaling Regulates Directional Cell Migration and Early Tumor Cell Invasion in Ovarian Cancer

Adhesion to and clearance of the mesothelial monolayer are key early events in metastatic seeding of ovarian cancer. ROR2 is a receptor tyrosine kinase that interacts with Wnt5a ligand to activate noncanonical Wnt signaling and has been previously shown to be upregulated in ovarian cancer tissue. However, no prior study has evaluated the mechanistic role of ROR2 in ovarian cancer. Through a cellular high-throughput genetic screen, we independently identified ROR2 as a driver of ovarian tumor cell adhesion and invasion. ROR2 expression in ovarian tumor cells serves to drive directed cell migration preferentially toward areas of high Wnt5a ligand, such as the mesothelial lined omentum. In addition, ROR2 promotes ovarian tumor cell adhesion and clearance of a mesothelial monolayer. Depletion of ROR2, in tumor cells, reduces metastatic tumor burden in a syngeneic model of ovarian cancer. These findings support the role of ROR2 in ovarian tumor cells as a critical factor contributing to the early steps of metastasis. Therapeutic targeting of the ROR2/Wnt5a signaling axis could provide a means of improving treatment for patients with advanced ovarian cancer.

IMPLICATIONS

This study demonstrates that ROR2 in ovarian cancer cells is important for directed migration to the metastatic niche and provides a potential signaling axis of interest for therapeutic targeting in ovarian cancer.

Ovarian tumor cell-derived JAGGED2 promotes omental metastasis through stimulating the Notch signaling pathway in the mesothelial cells

The primary site of metastasis for epithelial ovarian cancer (EOC) is the peritoneum, and it occurs through a multistep process that begins with adhesive contacts between cancer cells and mesothelial cells. Despite evidence that Notch signaling has a role in ovarian cancer, it is unclear how exactly it contributes to ovarian cancer omental metastasis, as well as the cellular dynamics and intrinsic pathways that drive this tropism. Here we show that tumor cells produced the Notch ligand Jagged2 is a clinically and functionally critical mediator of ovarian cancer omental metastasis by activating the Notch signaling in single-layered omental mesothelial cells. In turn, Jagged2 promotes tumor growth and therapeutic resistance by stimulating IL-6 release from mesothelial cells. Additionally, Jagged2 is a potent downstream mediator of the omental metastasis cytokine TGF-β that is released during omental destruction. Importantly, therapeutic inhibition of Jagged2-mediated omental metastasis was significantly improved by directly disrupting the Notch pathway in omental mesothelial cells. These findings highlight the key role of Jagged2 to the functional interplay between the TGF-β and the Notch signaling pathways during the metastatic process of ovarian cancer cells to the omentum and identify the Notch signaling molecule as a precision therapeutic target for ovarian cancer metastasis.

Reciprocal crosstalk between Th17 and mesothelial cells promotes metastasis-associated adhesion of ovarian cancer cells

BACKGROUND

IL-17A and TNF synergistically promote inflammation and tumorigenesis. Their interplay and impact on ovarian carcinoma (OC) progression are, however, poorly understood. We addressed this question focusing on mesothelial cells, whose interaction with tumor cells is known to play a pivotal role in transcoelomic metastasis formation.

METHODS

Flow-cytometry and immunohistochemistry experiments were employed to identify cellular sources of IL-17A and TNF. Changes in transcriptomes and secretomes were determined by bulk and single cell RNA sequencing as well as affinity proteomics. Functional consequences were investigated by microscopic analyses and tumor cell adhesion assays. Potential clinical implications were assessed by immunohistochemistry and survival analyses.

RESULTS

We identified Th17 cells as the main population of IL-17A- and TNF producers in ascites and detected their accumulation in early omental metastases. Both IL-17A and its receptor subunit IL-17RC were associated with short survival of OC patients, pointing to a role in clinical progression. IL-17A and TNF synergistically induced the reprogramming of mesothelial cells towards a pro-inflammatory mesenchymal phenotype, concomitantly with a loss of tight junctions and an impairment of mesothelial monolayer integrity, thereby promoting cancer cell adhesion. IL-17A and TNF synergistically induced the Th17-promoting cytokines IL-6 and IL-1β as well as the Th17-attracting chemokine CCL20 in mesothelial cells, indicating a reciprocal crosstalk that potentiates the tumor-promoting role of Th17 cells in OC.

CONCLUSIONS

Our findings reveal a novel function for Th17 cells in the OC microenvironment, which entails the IL-17A/TNF-mediated induction of mesothelial-mesenchymal transition, disruption of mesothelial layer integrity and consequently promotion of OC cell adhesion. These effects are potentiated by a positive feedback loop between mesothelial and Th17 cells. Together with the observed clinical associations and accumulation of Th17 cells in omental micrometastases, our observations point to a potential role in early metastases formation and thus to new therapeutic options.

A Recipe for Successful Metastasis: Transition and Migratory Modes of Ovarian Cancer Cells

One of the characteristic features of ovarian cancer is its early dissemination. Metastasis and the invasiveness of ovarian cancer are strongly dependent on the phenotypical and molecular determinants of cancer cells. Invasive cancer cells, circulating tumor cells, and cancer stem cells, which are responsible for the metastatic process, may all undergo different modes of transition, giving rise to mesenchymal, amoeboid, and redifferentiated epithelial cells. Such variability is the result of the changing needs of cancer cells, which strive to survive and colonize new organs. This would not be possible if not for the variety of migration modes adopted by the transformed cells. The most common type of metastasis in ovarian cancer is dissemination through the transcoelomic route, but transitions in ovarian cancer cells contribute greatly to hematogenous and lymphatic dissemination. This review aims to outline the transition modes of ovarian cancer cells and discuss the migratory capabilities of those cells in light of the known ovarian cancer metastasis routes.

Mesothelial cells with mesenchymal features enhance peritoneal dissemination by forming a protumorigenic microenvironment

Malignant ascites accompanied by peritoneal dissemination contain various factors and cell populations as well as cancer cells; however, how the tumor microenvironment is shaped in ascites remains unclear. Single-cell proteomic profiling and a comprehensive proteomic analysis are conducted to comprehensively characterize malignant ascites. Here, we find defects in immune effectors along with immunosuppressive cell accumulation in ascites of patients with gastric cancer (GC) and identify five distinct subpopulations of CD45(-)/EpCAM(-) cells. Mesothelial cells with mesenchymal features in CD45(-)/EpCAM(-) cells are the predominant source of chemokines involved in immunosuppressive myeloid cell (IMC) recruitment. Moreover, mesothelial-mesenchymal transition (MMT)-induced mesothelial cells strongly express extracellular matrix (ECM)-related genes, including tenascin-C (TNC), enhancing metastatic colonization. These findings highlight the definite roles of the mesenchymal cell population in the development of a protumorigenic microenvironment to promote peritoneal dissemination.

HDAC1/2 control mesothelium/ovarian cancer adhesive interactions impacting on Talin-1-α5β1-integrin-mediated actin cytoskeleton and extracellular matrix protein remodeling

BACKGROUND

Peritoneal metastasis, which accounts for 85% of all epithelial ovarian carcinoma (EOC) metastases, is a multistep process that requires the establishment of adhesive interactions between cancer cells and the peritoneal membrane. Interrelations between EOC and the mesothelial stroma are critical to facilitate the metastatic process. No data is available so far on the impact of histone acetylation/deacetylation, a potentially relevant mechanism governing EOC metastasis, on mesothelial cells (MCs)-mediated adhesion.

METHODS

Static adhesion and peritoneal clearance experiments were performed pretreating mesenchymal-like MCs and platinum-sensitive/resistant EOC cell lines with MS-275-a Histone deacetylase (HDAC)1-3 pharmacological inhibitor currently used in combination trials. Results were acquired by confocal microscopy and were analyzed with an automated Opera software. The role of HDAC1/2 was validated by genetic silencing. The role of α4-, α5-α1 Integrins and Fibronectin-1 was validated using specific monoclonal antibodies. Quantitative proteomic analysis was performed on primary MCs pretreated with MS-275. Decellularized matrices were generated from either MS-275-exposed or untreated cells to study Fibronectin-1 extracellular secretion. The effect of MS-275 on β1 integrin activity was assessed using specific monoclonal antibodies. The role of Talin-1 in MCs/EOC adhesion was analyzed by genetic silencing. Talin-1 ectopic expression was validated as a rescue tool from MS-275-induced phenotype. The in vivo effect of MS-275-induced MC remodeling was validated in a mouse model of peritoneal EOC dissemination.

RESULTS

Treatment of MCs with non-cytotoxic concentrations of MS-275 caused a consistent reduction of EOC adhesion. Proteomic analysis revealed several pathways altered upon MC treatment with MS-275, including ECM deposition/remodeling, adhesion receptors and actin cytoskeleton regulators. HDAC1/2 inhibition hampered actin cytoskeleton polymerization by downregulating actin regulators including Talin-1, impairing β1 integrin activation, and leading to abnormal extracellular secretion and distribution of Fibronectin-1. Talin-1 ectopic expression rescued EOC adhesion to MS-275-treated MCs. In an experimental mouse model of metastatic EOC, MS-275 limited tumor invasion, Fibronectin-1 secretion and the sub-mesothelial accumulation of MC-derived carcinoma-associated fibroblasts.

CONCLUSION

Our study unveils a direct impact of HDAC-1/2 in the regulation of MC/EOC adhesion and highlights the regulation of MC plasticity by epigenetic inhibition as a potential target for therapeutic intervention in EOC peritoneal metastasis.

TRAIL-dependent apoptosis of peritoneal mesothelial cells by NK cells promotes ovarian cancer invasion

A crucial requirement for metastasis formation in ovarian high-grade serous carcinoma (HGSC) is the disruption of the protective peritoneal mesothelium. Using co-culture systems of primary human cells, we discovered that tumor-associated NK cells induce TRAIL-dependent apoptosis in mesothelial cells via death receptors DR4 and DR5 upon encounter with activated T cells. Upregulation of TRAIL expression in NK cells concomitant with enhanced cytotoxicity toward mesothelial cells was driven predominantly by T-cell-derived TNFα, as shown by affinity proteomics-based analysis of the T cell secretome in conjunction with functional studies. Consistent with these findings, we detected apoptotic mesothelial cells in the peritoneal fluid of HGSC patients. In contrast to mesothelial cells, HGSC cells express negligible levels of both DR4 and DR5 and are TRAIL resistant, indicating cell-type-selective killing by NK cells. Our data point to a cooperative action of T and NK in breaching the mesothelial barrier in HGSC patients.

The senescent mesothelial matrix accentuates colonization by ovarian cancer cells

Ovarian cancer is amongst the most morbid of gynecological malignancies due to its diagnosis at an advanced stage, a transcoelomic mode of metastasis, and rapid transition to chemotherapeutic resistance. Like all other malignancies, the progression of ovarian cancer may be interpreted as an emergent outcome of the conflict between metastasizing cancer cells and the natural defense mounted by microenvironmental barriers to such migration. Here, we asked whether senescence in coelom-lining mesothelia, brought about by drug exposure, affects their interaction with disseminated ovarian cancer cells. We observed that cancer cells adhered faster on senescent human and murine mesothelial monolayers than on non-senescent controls. Time-lapse epifluorescence microscopy showed that mesothelial cells were cleared by a host of cancer cells that surrounded the former, even under sub-confluent conditions. A multiscale computational model predicted that such colocalized mesothelial clearance under sub-confluence requires greater adhesion between cancer cells and senescent mesothelia. Consistent with the prediction, we observed that senescent mesothelia expressed an extracellular matrix with higher levels of fibronectin, laminins and hyaluronan than non-senescent controls. On senescent matrix, cancer cells adhered more efficiently, spread better, and moved faster and persistently, aiding the spread of cancer. Inhibition assays using RGD cyclopeptides suggested the adhesion was predominantly contributed by fibronectin and laminin. These findings led us to propose that the senescence-associated matrisomal phenotype of peritoneal barriers enhances the colonization of invading ovarian cancer cells contributing to the metastatic burden associated with the disease.

Proteomic characterization of epithelial ovarian cancer delineates molecular signatures and therapeutic targets in distinct histological subtypes

Clear cell carcinoma (CCC), endometrioid carcinoma (EC), and serous carcinoma (SC) are the major histological subtypes of epithelial ovarian cancer (EOC), whose differences in carcinogenesis are still unclear. Here, we undertake comprehensive proteomic profiling of 80 CCC, 79 EC, 80 SC, and 30 control samples. Our analysis reveals the prognostic or diagnostic value of dysregulated proteins and phosphorylation sites in important pathways. Moreover, protein co-expression network not only provides comprehensive view of biological features of each histological subtype, but also indicates potential prognostic biomarkers and progression landmarks. Notably, EOC have strong inter-tumor heterogeneity, with significantly different clinical characteristics, proteomic patterns and signaling pathway disorders in CCC, EC, and SC. Finally, we infer MPP7 protein as potential therapeutic target for SC, whose biological functions are confirmed in SC cells. Our proteomic cohort provides valuable resources for understanding molecular mechanisms and developing treatment strategies of distinct histological subtypes.

Matriptase drives dissemination of ovarian cancer spheroids by a PAR-2/PI3K/Akt/MMP9 signaling axis

The transmembrane serine protease matriptase is a key regulator of both barrier-disruptive and protective epithelial cell-cell interactions. Elevated matriptase is a consistent feature of epithelial ovarian cancers (OvCa), where multicellular spheroids shed from the primary tumor into the peritoneal cavity are critical drivers of metastasis. Dynamic cell-to-cell adhesive contacts are required for spheroid formation and maintenance. Here, we show that overactive matriptase, reflected in an increased ratio of matriptase to its inhibitor hepatocyte growth factor activator inhibitor 1 (HAI-1), disrupts cell-cell contacts to produce loose prometastatic spheroids that display increased mesothelial cell adhesion and submesothelial invasion. We show that these activities are dependent on the matriptase activation of a protease-activated receptor-2 (PAR-2) signaling pathway involving PI3K/Akt and MMP9-induced disruption of cell-cell adhesion by the release of the soluble E-cadherin ectodomain. These data reveal a novel pathological connection between matriptase activation of PAR-2 and disruption of cell-cell adhesion, and support the clinical investigation of this signaling axis as a therapeutic strategy for aggressive metastatic OvCa.

Stromal DDR2 Promotes Ovarian Cancer Metastasis through Regulation of Metabolism and Secretion of Extracellular Matrix Proteins

Ovarian cancer is the leading cause of gynecologic cancer-related deaths. The propensity for metastasis within the peritoneal cavity is a driving factor for the poor outcomes associated with this disease, but there is currently no effective therapy targeting metastasis. In this study, we investigate the contribution of stromal cells to ovarian cancer metastasis and identify normal stromal cell expression of the collagen receptor, discoidin domain receptor 2 (DDR2), that acts to facilitate ovarian cancer metastasis. In vivo, global genetic inactivation of Ddr2 impairs the ability of Ddr2-expressing syngeneic ovarian cancer cells to spread throughout the peritoneal cavity. Specifically, DDR2 expression in mesothelial cells lining the peritoneal cavity facilitates tumor cell attachment and clearance. Subsequently, omentum fibroblast expression of DDR2 promotes tumor cell invasion. Mechanistically, we find DDR2-expressing fibroblasts are more energetically active, such that DDR2 regulates glycolysis through AKT/SNAI1 leading to suppressed fructose-1,6-bisphosphatase and increased hexokinase activity, a key glycolytic enzyme. Upon inhibition of DDR2, we find decreased protein synthesis and secretion. Consequently, when DDR2 is inhibited, there is reduction in secreted extracellular matrix proteins important for metastasis. Specifically, we find that fibroblast DDR2 inhibition leads to decreased secretion of the collagen crosslinker, LOXL2. Adding back LOXL2 to DDR2 deficient fibroblasts rescues the ability of tumor cells to invade. Overall, our results suggest that stromal cell expression of DDR2 is an important mediator of ovarian cancer metastasis.

IMPLICATIONS

DDR2 is highly expressed by stromal cells in ovarian cancer that can mediate metastasis and is a potential therapeutic target in ovarian cancer.

Glucocorticoid Receptor Activation in Lobular Breast Cancer Is Associated with Reduced Cell Proliferation and Promotion of Metastases

Estrogen receptor-positive (ER+) invasive lobular breast cancer (ILC) comprises about ~15% of breast cancer. ILC's unique genotypic (loss of wild type E-cadherin expression) and phenotypic (small individual round cancer cells that grow in discontinuous nests) are thought to contribute to a distinctive pattern of metastases to serosal membranes. Unlike invasive ductal carcinoma (IDC), ILC metastases often intercalate into the mesothelial layer of the peritoneum and other serosal surfaces. While ER activity is a known driver of ILC proliferation, very little is known about how additional nuclear receptors contribute to ILC's distinctive biology. In ER+ IDC, we showed previously that glucocorticoid receptor (GR) activity inhibits pro-proliferative gene expression and cell proliferation. Here we examined ER+ ILC models and found that GR activation similarly reduces S-phase entry gene expression and ILC proliferation. While slowing tumor growth rate, our data also suggest that GR activation results in an enhanced metastatic phenotype through increasing integrin-encoding gene expression, extracellular matrix protein adhesion, and mesothelial cell clearance. Moreover, in an intraductal mouse mammary gland model of ILC, we found that GR expression is associated with increased bone metastases despite slowed primary mammary tumor growth. Taken together, our findings suggest GR-mediated gene expression may contribute to the unusual characteristics of ILC biology.

MicroRNAs Can Influence Ovarian Cancer Progression by Dysregulating Integrin Activity

Ovarian cancer is a deadly disease that affects thousands of women worldwide. Integrins, transmembrane receptors that mediate cell adhesion and signaling, play important roles in ovarian cancer progression, metastasis, and drug resistance. Dysregulated expression of integrins is implicated in various cellular processes, such as cell migration, invasion, and proliferation. Emerging evidence suggests that microRNAs (miRNAs) can regulate integrin expression and function, thus affecting various physiological and pathological processes, including ovarian cancer. In this article, we review the current understanding of integrin-mediated cellular processes in ovarian cancer and the roles of miRNAs in regulating integrins. We also discuss the therapeutic potential of targeting miRNAs that regulate integrins for the treatment of ovarian cancer. Targeting miRNAs that regulate integrins or downstream signaling pathways of integrins may provide novel therapeutic strategies for inhibiting integrin-mediated ovarian cancer progression.

Cancer-mesothelial and cancer-macrophage interactions in the ovarian cancer microenvironment

The metastatic ovarian cancer microenvironment is characterized by an intricate interaction network between cancer cells and host cells. This complex heterotypic cancer-host cell crosstalk results in an environment that promotes cancer cell metastasis and treatment resistance, leading to poor patient prognosis and survival. In this review, we focus on two host cell types found in the ovarian cancer microenvironment: mesothelial cells and tumor-associated macrophages. Mesothelial cells make up the protective lining of organs in the abdominal cavity. Cancer cells attach and invade through the mesothelial monolayer to form metastatic lesions. Crosstalk between mesothelial and cancer cells can contribute to metastatic progression and chemotherapy resistance. Tumor-associated macrophages are the most abundant immune cell type in the ovarian cancer microenvironment with heterogeneous subpopulations exhibiting protumor or antitumor functions. Macrophage reprogramming toward a protumor or antitumor state can be influenced by chemotherapy and communication with cancer cells, resulting in cancer cell invasion and treatment resistance. A better understanding of cancer-mesothelial and cancer-macrophage crosstalk will uncover biomarkers of metastatic progression and therapeutic targets to restore chemotherapy sensitivity.

Mechanical factors driving cancer progression

A fundamental step of tumor metastasis is tumor cell migration away from the primary tumor site. One mode of migration that is essential but still understudied is collective invasion, the process by which clusters of cells move in a coordinated fashion. In recent years, there has been growing interest to understand factors regulating collective invasion, with increasing number of studies investigating the biomechanical regulation of collective invasion. In this review we discuss the dynamic relationship between tumor microenvironment cues and cell response by first covering mechanical factors in the microenvironment and second, discussing the mechanosensing pathways utilized by cells in collective clusters to dynamically respond to mechanical matrix cues. Finally, we discuss model systems that have been developed which have increased our understanding of the mechanical factors contributing to tumor progression.

Positional influence on cellular transcriptional identity revealed through spatially segmented single-cell transcriptomics

Single-cell RNA sequencing (scRNA-seq) is a powerful technique for describing cell states. Identifying the spatial arrangement of these states in tissues remains challenging, with the existing methods requiring niche methodologies and expertise. Here, we describe segmentation by exogenous perfusion (SEEP), a rapid and integrated method to link surface proximity and environment accessibility to transcriptional identity within three-dimensional (3D) disease models. The method utilizes the steady-state diffusion kinetics of a fluorescent dye to establish a gradient along the radial axis of disease models. Classification of sample layers based on dye accessibility enables dissociated and sorted cells to be characterized by transcriptomic and regional identities. Using SEEP, we analyze spheroid, organoid, and in vivo tumor models of high-grade serous ovarian cancer (HGSOC). The results validate long-standing beliefs about the relationship between cell state and position while revealing new concepts regarding how spatially unique microenvironments influence the identity of individual cells within tumors.

Engineering tools for quantifying and manipulating forces in epithelia

The integrity of epithelia is maintained within dynamic mechanical environments during tissue development and homeostasis. Understanding how epithelial cells mechanosignal and respond collectively or individually is critical to providing insight into developmental and (patho)physiological processes. Yet, inferring or mimicking mechanical forces and downstream mechanical signaling as they occur in epithelia presents unique challenges. A variety of in vitro approaches have been used to dissect the role of mechanics in regulating epithelia organization. Here, we review approaches and results from research into how epithelial cells communicate through mechanical cues to maintain tissue organization and integrity. We summarize the unique advantages and disadvantages of various reduced-order model systems to guide researchers in choosing appropriate experimental systems. These model systems include 3D, 2D, and 1D micromanipulation methods, single cell studies, and noninvasive force inference and measurement techniques. We also highlight a number of in silico biophysical models that are informed by in vitro and in vivo observations. Together, a combination of theoretical and experimental models will aid future experiment designs and provide predictive insight into mechanically driven behaviors of epithelial dynamics.

Intraperitoneal metastasis of ovarian cancer: new insights on resident macrophages in the peritoneal cavity

Ovarian cancer metastasis occurs primarily in the peritoneal cavity. Orchestration of cancer cells with various cell types, particularly macrophages, in the peritoneal cavity creates a metastasis-favorable environment. In the past decade, macrophage heterogeneities in different organs as well as their diverse roles in tumor settings have been an emerging field. This review highlights the unique microenvironment of the peritoneal cavity, consisting of the peritoneal fluid, peritoneum, and omentum, as well as their own resident macrophage populations. Contributions of resident macrophages in ovarian cancer metastasis are summarized; potential therapeutic strategies by targeting such cells are discussed. A better understanding of the immunological microenvironment in the peritoneal cavity will provide a stepping-stone to new strategies for developing macrophage-based therapies and is a key step toward the unattainable eradication of intraperitoneal metastasis of ovarian cancer.

Insights into high-grade serous carcinoma pathobiology using three-dimensional culture model systems

Epithelial ovarian cancer (EOC) research has become more complex as researchers try to fully understand the metastatic process. Especially as we delve into the concept of tumour dormancy, where cells transition between proliferative and dormant states to survive during disease progression. Thus, the in vitro models used to conduct this research need to reflect this vast biological complexity. The innovation behind the many three-dimensional (3D) spheroid models has been refined to easily generate reproducible spheroids so that we may understand the various molecular signaling changes of cells during metastasis and determine therapeutic efficacy of treatments. This ingenuity was then used to develop the 3D ex vivo patient-derived organoid model, as well as multiple co-culture model systems for EOC research. Although, researchers need to continue to push the boundaries of these current models for in vitro and even in vivo work in the future. In this review, we describe the 3D models already in use, where these models can be developed further and how we can use these models to gain the most knowledge on EOC pathogenesis and discover new targeted therapies.

Research progress of Astragalus membranaceus in treating peritoneal metastatic cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Peritoneal metastasis is a manifestation of advanced cancer often associated with a poor prognosis and poor response to treatment. Astragalus membranaceus (Fisch.) Bunge is a commonly used medicinal material in traditional Chinese medicine with various biological activities. In patients with cancer, Astragalus membranaceus has demonstrated anti-tumor effects, immune regulation, postoperative recurrence and metastasis prevention, and survival prolongation.

AIM OF THE STUDY

Peritoneal metastasis results from tumor cell and peritoneal microenvironment co-evolution. We aimed to introduce and discuss the specific mechanism of action of Astragalus membranaceus in peritoneal metastasis treatment to provide a new perspective for treatment and further research.

MATERIALS AND METHODS

We consulted reports on the anti-peritoneal metastases effects of Astragalus membranaceus from PubMed, Web of Science, China National Knowledge Infrastructure, and Wanfang databases, as well as Google Scholar. Meanwhile, we also obtained data from published medical works and doctoral and master's theses. Then, we focused on the research progress of Astragalus membranaceus in peritoneal metastatic cancer treatment. Plant names are provided in accordance with "The Plant List" (www.theplantlist.org).

RESULTS

To date, more than 200 compounds have been isolated from Astragalus membranaceus. Among them, Astragalus polysaccharides, saponins, and flavonoids are the main bioactive components, and their effects on cancer have been extensively studied. In this review, we systematically summarize the effects of Astragalus membranaceus on the peritoneal metastasis microenvironment and related mechanisms, including maintaining the integrity of peritoneal mesothelial cells, restoring the peritoneal immune microenvironment, and inhibiting the formation of tumor blood vessels, matrix metalloproteinase, and dense tumor spheroids.

CONCLUSIONS

Our analysis demonstrates that Astragalus membranaceus could be a potential therapeutic for preventing the occurrence of peritoneal metastasis. However, it might be too early to recommend its use owing to the paucity of reliable in vivo experiment, clinical data, and evidence of clinical efficacy. In addition, previous studies of Astragalus membranaceus report inconsistent and contradictory findings. Therefore, detailed in vitro, in vivo, and clinical studies on the mechanism of Astragalus membranaceus in peritoneal metastatic cancer treatment are warranted.

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. Removing mesothelial cells ex vivo from human and mouse omenta or in vivo using diphtheria toxin-mediated ablation in Msln-Cre mice significantly inhibited OvCa cell adhesion and colonization. Human ascites induced angiopoietin-like 4 (ANGPTL4) and stanniocalcin 1 (STC1) expression and secretion by mesothelial cells. Inhibition of STC1 or ANGPTL4 via RNAi obstructed OvCa cell-induced mesothelial cell to mesenchymal transition while inhibition of ANGPTL4 alone obstructed OvCa cell-induced mesothelial cell migration and glycolysis. Inhibition of mesothelial cell ANGPTL4 secretion via RNAi prevented mesothelial cell-induced monocyte migration, endothelial cell vessel formation, and OvCa cell adhesion, migration, and proliferation. In contrast, inhibition of mesothelial cell STC1 secretion via RNAi prevented mesothelial cell-induced endothelial cell vessel formation and OvCa cell adhesion, migration, proliferation, and invasion. Additionally, blocking ANPTL4 function with Abs reduced the ex vivo colonization of 3 different OvCa cell lines on human omental tissue explants and in vivo colonization of ID8p53-/-Brca2-/- cells on mouse omenta. These findings indicate that mesothelial cells are important to the initial stages of OvCa metastasis and that the crosstalk between mesothelial cells and the tumor microenvironment promotes OvCa metastasis through the secretion of ANGPTL4.

A 3D multi-cellular tissue model of the human omentum to study the formation of ovarian cancer metastasis

Reliable and predictive experimental models are urgently needed to study metastatic mechanisms of ovarian cancer cells in the omentum. Although models for ovarian cancer cell adhesion and invasion were previously investigated, the lack of certain omental cell types, which influence the metastatic behavior of cancer cells, limits the application of these tissue models. Here, we describe a 3D multi-cellular human omentum tissue model, which considers the spatial arrangement of five omental cell types. Reproducible tissue models were fabricated combining permeable cell culture inserts and bioprinting technology to mimic metastatic processes of immortalized and patient-derived ovarian cancer cells. The implementation of an endothelial barrier further allowed studying the interaction between cancer and endothelial cells during hematogenous dissemination and the impact of chemotherapeutic drugs. This proof-of-concept study may serve as a platform for patient-specific investigations in personalized oncology in the future.

Extracellular Matrix in High-Grade Serous Ovarian Cancer: Advances in Understanding of Carcinogenesis and Cancer Biology

High-grade serous ovarian cancer (HGSOC) is notoriously known as the "silent killer" of post-menopausal women as it has an insidious progression and is the deadliest gynaecological cancer. Although a dual origin of HGSOC is now widely accepted, there is growing evidence that most cases of HGSOC originate from the fallopian tube epithelium. In this review, we will address the fallopian tube origin and involvement of the extracellular matrix (ECM) in HGSOC development. There is limited research on the role of ECM at the earliest stages of HGSOC carcinogenesis. Here we aim to synthesise current understanding on the contribution of ECM to each stage of HGSOC development and progression, beginning at serous tubal intraepithelial carcinoma (STIC) precursor lesions and proceeding across key events including dissemination of tumourigenic fallopian tube epithelial cells to the ovary, survival of these cells in peritoneal fluid as multicellular aggregates, and colonisation of the ovary. Likewise, as part of the metastatic series of events, serous ovarian cancer cells survive travel in peritoneal fluid, attach to, migrate across the mesothelium and invade into the sub-mesothelial matrix of secondary sites in the peritoneal cavity. Halting cancer at the pre-metastatic stage and finding ways to stop the dissemination of ovarian cancer cells from the primary site is critical for improving patient survival. The development of drug resistance also contributes to poor survival statistics in HGSOC. In this review, we provide an update on the involvement of the ECM in metastasis and drug resistance in HGSOC. Interplay between different cell-types, growth factor gradients as well as evolving ECM composition and organisation, creates microenvironment conditions that promote metastatic progression and drug resistance of ovarian cancer cells. By understanding ECM involvement in the carcinogenesis and chemoresistance of HGSOC, this may prompt ideas for further research for developing new early diagnostic tests and therapeutic strategies for HGSOC with the end goal of improving patient health outcomes.

The interaction of β-arrestin1 with talin1 driven by endothelin A receptor as a feature of α5β1 integrin activation in high-grade serous ovarian cancer

Dissemination of high-grade serous ovarian cancer (HG-SOC) in the omentum and intercalation into a mesothelial cell (MC) monolayer depends on functional α5β1 integrin (Intα5β1) activity. Although the binding of Intα5β1 to fibronectin drives these processes, other molecular mechanisms linked to integrin inside-out signaling might support metastatic dissemination. Here, we report a novel interactive signaling that contributes to Intα5β1 activation and accelerates tumor cells toward invasive disease, involving the protein β-arrestin1 (β-arr1) and the activation of the endothelin A receptor (ETAR) by endothelin-1 (ET-1). As demonstrated in primary HG-SOC cells and SOC cell lines, ET-1 increased Intβ1 and downstream FAK/paxillin activation. Mechanistically, β-arr1 directly interacts with talin1 and Intβ1, promoting talin1 phosphorylation and its recruitment to Intβ1, thus fueling integrin inside-out activation. In 3D spheroids and organotypic models mimicking the omentum, ETAR/β-arr1-driven Intα5β1 signaling promotes the survival of cell clusters, with mesothelium-intercalation capacity and invasive behavior. The treatment with the antagonist of ETAR, Ambrisentan (AMB), and of Intα5β1, ATN161, inhibits ET-1-driven Intα5β1 activity in vitro, and tumor cell adhesion and spreading to intraperitoneal organs and Intβ1 activity in vivo. As a prognostic factor, high EDNRA/ITGB1 expression correlates with poor HG-SOC clinical outcomes. These findings highlight a new role of ETAR/β-arr1 operating an inside-out integrin activation to modulate the metastatic process and suggest that in the new integrin-targeting programs might be considered that ETAR/β-arr1 regulates Intα5β1 functional pathway.

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

Background

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

Methods

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

Results

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

Discussion

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

Challenges and Opportunities Modeling the Dynamic Tumor Matrisome

We need novel strategies to target the complexity of cancer and, particularly, of metastatic disease. As an example of this complexity, certain tissues are particularly hospitable environments for metastases, whereas others do not contain fertile microenvironments to support cancer cell growth. Continuing evidence that the extracellular matrix (ECM) of tissues is one of a host of factors necessary to support cancer cell growth at both primary and secondary tissue sites is emerging. Research on cancer metastasis has largely been focused on the molecular adaptations of tumor cells in various cytokine and growth factor environments on 2-dimensional tissue culture polystyrene plates. Intravital imaging, conversely, has transformed our ability to watch, in real time, tumor cell invasion, intravasation, extravasation, and growth. Because the interstitial ECM that supports all cells in the tumor microenvironment changes over time scales outside the possible window of typical intravital imaging, bioengineers are continuously developing both simple and sophisticated in vitro controlled environments to study tumor (and other) cell interactions with this matrix. In this perspective, we focus on the cellular unit responsible for upholding the pathologic homeostasis of tumor-bearing organs, cancer-associated fibroblasts (CAFs), and their self-generated ECM. The latter, together with tumoral and other cell secreted factors, constitute the "tumor matrisome". We share the challenges and opportunities for modeling this dynamic CAF/ECM unit, the tools and techniques available, and how the tumor matrisome is remodeled (e.g., via ECM proteases). We posit that increasing information on tumor matrisome dynamics may lead the field to alternative strategies for personalized medicine outside genomics.

In Vitro Models of Ovarian Cancer: Bridging the Gap between Pathophysiology and Mechanistic Models

Ovarian cancer (OC) is a disease of major concern with a survival rate of about 40% at five years. This is attributed to the lack of visible and reliable symptoms during the onset of the disease, which leads over 80% of patients to be diagnosed at advanced stages. This implies that metastatic activity has advanced to the peritoneal cavity. It is associated with both genetic and phenotypic heterogeneity, which considerably increase the risks of relapse and reduce the survival rate. To understand ovarian cancer pathophysiology and strengthen the ability for drug screening, further development of relevant in vitro models that recapitulate the complexity of OC microenvironment and dynamics of OC cell population is required. In this line, the recent advances of tridimensional (3D) cell culture and microfluidics have allowed the development of highly innovative models that could bridge the gap between pathophysiology and mechanistic models for clinical research. This review first describes the pathophysiology of OC before detailing the engineering strategies developed to recapitulate those main biological features.

Basal cell adhesion molecule promotes metastasis-associated processes in ovarian cancer

BACKGROUND

Basal cell adhesion molecule (BCAM) is a laminin α5 (LAMA5) binding membrane-bound protein with a putative role in cancer. Besides full-length BCAM1, an isoform lacking most of the cytoplasmic domain (BCAM2), and a soluble form (sBCAM) of unknown function are known. In ovarian carcinoma (OC), all BCAM forms are abundant and associated with poor survival, yet BCAM's contribution to peritoneal metastatic spread remains enigmatic.

METHODS

Biochemical, omics-based and real-time cell assays were employed to identify the source of sBCAM and metastasis-related functions of different BCAM forms. OC cells, explanted omentum and a mouse model of peritoneal colonisation were used in loss- and gain-of-function experiments.

RESULTS

We identified ADAM10 as a major BCAM sheddase produced by OC cells and identified proteolytic cleavage sites proximal to the transmembrane domain. Recombinant soluble BCAM inhibited single-cell adhesion and migration identically to membrane-bound isoforms, confirming its biological activity in OC. Intriguingly, this seemingly anti-tumorigenic potential of BCAM contrasts with a novel pro-metastatic function discovered in the present study. Thus, all queried BCAM forms decreased the compactness of tumour cell spheroids by inhibiting LAMA5 - integrin β1 interactions, promoted spheroid dispersion in a three-dimensional collagen matrix, induced clearance of mesothelial cells at spheroid attachment sites in vitro and enhanced invasion of spheroids into omental tissue both ex vivo and in vivo.

CONCLUSIONS

Membrane-bound BCAM as well as sBCAM shed by ADAM10 act as decoys rather than signalling receptors to modulate metastasis-related functions. While BCAM appears to have tumour-suppressive effects on single cells, it promotes the dispersion of OC cell spheroids by regulating LAMA5-integrin-β1-dependent compaction and thereby facilitating invasion of metastatic target sites. As peritoneal dissemination is majorly mediated by spheroids, these findings offer an explanation for the association of BCAM with a poor clinical outcome of OC, suggesting novel therapeutic options.

The metastatic capacity of high-grade serous ovarian cancer cells changes along disease progression: inhibition by mifepristone

BACKGROUND

Simplistic two-dimensional (2D) in vitro assays have long been the standard for studying the metastatic abilities of cancer cells. However, tri-dimensional (3D) organotypic models provide a more complex environment, closer to that seen in patients, and thereby provide a more accurate representation of their true capabilities. Our laboratory has previously shown that the antiprogestin and antiglucocorticoid mifepristone can reduce the growth, adhesion, migration, and invasion of various aggressive cancer cells assessed using 2D assays. In this study, we characterize the metastatic capabilities of high-grade serous ovarian cancer cells generated along disease progression, in both 2D and 3D assays, and the ability of cytostatic doses of mifepristone to inhibit them.

METHODS

High-grade serous ovarian cancer cells collected from two separate patients at different stages of their disease were used throughout the study. The 2D wound healing and Boyden chamber assays were used to study migration, while a layer of extracellular matrix was added to the Boyden chamber to study invasion. A 3D organotypic model, composed of fibroblasts embedded in collagen I and topped with a monolayer of mesothelial cells was used to further study cancer cell adhesion and mesothelial displacement. All assays were studied in cells, which were originally harvested from two patients at different stages of disease progression, in the absence or presence of cytostatic doses of mifepristone.

RESULTS

2D in vitro assays demonstrated that the migration and invasive rates of the cells isolated from both patients decreased along disease progression. Conversely, in both patients, cells representing late-stage disease demonstrated a higher adhesion capacity to the 3D organotypic model than those representing an early-stage disease. This adhesive behavior is associated with the in vivo tumor capacity of the cells. Regardless of these differences in adhesive, migratory, and invasive behavior among the experimental protocols used, cytostatic doses of mifepristone were able to inhibit the adhesion, migration, and invasion rates of all cells studied, regardless of their basal capabilities over simplistic or organotypic metastatic in vitro model systems. Finally, we demonstrate that when cells acquire the capacity to grow spontaneously as spheroids, they do attach to a 3D organotypic model system when pre-incubated with conditioned media. Of relevance, mifepristone was able to cause dissociation of these multicellular structures.

CONCLUSION

Differences in cellular behaviours were observed between 2 and 3D assays when studying the metastatic capabilities of high-grade serous ovarian cancer cells representing disease progression. Mifepristone inhibited these metastatic capabilities in all assays studied.

Extracellular Matrix Modulates Outgrowth Dynamics in Ovarian Cancer

Ovarian carcinoma (OC) forms outgrowths that extend from the outer surface of an afflicted organ into the peritoneum. OC outgrowth formation is poorly understood due to the limited availability of cell culture models examining the behavior of cells that form outgrowths. Prompted by immunochemical evaluation of extracellular matrix (ECM) components in human tissues, laminin and collagen-rich ECM-reconstituted cell culture models amenable to studies of cell clusters that can form outgrowths are developed. It is demonstrated that ECM promotes outgrowth formation in fallopian tube non-ciliated epithelial cells (FNE) expressing mutant p53 and various OC cell lines. Outgrowths are initiated by cells that underwent outward translocation and retained the ability to intercalate into mesothelial cell monolayers. Electron microscopy, optical coherence tomography, and small amplitude oscillatory shear experiments reveal that increased ECM levels led to increased fibrous network thickness and high shear elasticity of the microenvironment. These physical characteristics are associated with outgrowth suppression. The low ECM microenvironment mimicks the viscoelasticity of malignant peritoneal fluid (ascites) and supports cell proliferation, cell translocation, and outgrowth formation. These results highlight the importance of the ECM microenvironment in modulating OC growth and can provide additional insights into the mode of dissemination of primary and recurrent ovarian tumors.

Agent-based modeling predicts RAC1 is critical for ovarian cancer metastasis

Experimental and computational studies pinpoint rate-limiting step(s) in metastasis governed by Rac1. Using ovarian cancer cell and animal models, Rac1 expression was manipulated, and quantitative measurements of cell-cell and cell-substrate adhesion, cell invasion, mesothelial clearance, and peritoneal tumor growth discriminated the tumor behaviors most highly influenced by Rac1. The experimental data were used to parameterize an agent-based computational model simulating peritoneal niche colonization, intravasation, and hematogenous metastasis to distant organs. Increased ovarian cancer cell survival afforded by the more rapid adhesion and intravasation upon Rac1 overexpression is predicted to increase the numbers of and the rates at which tumor cells are disseminated to distant sites. Surprisingly, crowding of cancer cells along the blood vessel was found to decrease the numbers of cells reaching a distant niche irrespective of Rac1 overexpression or knockdown, suggesting that sites for tumor cell intravasation are rate limiting and become accessible if cells intravasate rapidly or are displaced due to diminished viability. Modeling predictions were confirmed through animal studies of Rac1-dependent metastasis to the lung. Collectively, the experimental and modeling approaches identify cell adhesion, rapid intravasation, and survival in the blood as parameters in the ovarian metastatic cascade that are most critically dependent on Rac1.

A catalog of numerical centrosome defects in epithelial ovarian cancers

Centrosome amplification, the presence of more than two centrosomes in a cell is a common feature of most human cancer cell lines. However, little is known about centrosome numbers in human cancers and whether amplification or other numerical aberrations are frequently present. To address this question, we have analyzed a large cohort of primary human epithelial ovarian cancers (EOCs) from 100 patients. We found that rigorous quantitation of centrosome number in tumor samples was extremely challenging due to tumor heterogeneity and extensive tissue disorganization. Interestingly, even if centrosome clusters could be identified, the incidence of centrosome amplification was not comparable to what has been described in cultured cancer cells. Surprisingly, centrosome loss events where a few or many nuclei were not associated with centrosomes were clearly noticed and overall more frequent than centrosome amplification. Our findings highlight the difficulty of characterizing centrosome numbers in human tumors, while revealing a novel paradigm of centrosome number defects in EOCs.

Evaluation of the potential of ultrasound-mediated drug delivery for the treatment of ovarian cancer through preclinical studies

Ovarian cancer (OC) has the greatest mortality rate among gynecological cancers, with a five-year survival rate of &lt;50%. Contemporary adjuvant chemotherapy mostly fails in the case of OCs that are refractory, metastatic, recurrent, and drug-resistant. Emerging ultrasound (US)-mediated technologies show remarkable promise in overcoming these challenges. Absorption of US waves by the tissue results in the generation of heat due to its thermal effect causing increased diffusion of drugs from the carriers and triggering sonoporation by increasing the permeability of the cancer cells. Certain frequencies of US waves could also produce a cavitation effect on drug-filled microbubbles (MBs, phospholipid bilayers) thereby generating shear force and acoustic streaming that could assist drug release from the MBs, and promote the permeability of the cell membrane. A new class of nanoparticles that carry therapeutic agents and are guided by US contrast agents for precision delivery to the site of the ovarian tumor has been developed. Phase-shifting of nanoparticles by US sonication has also been engineered to enhance the drug delivery to the ovarian tumor site. These technologies have been used for targeting the ovarian cancer stem cells and protein moieties that are particularly elevated in OCs including luteinizing hormone-releasing hormone, folic acid receptor, and vascular endothelial growth factor. When compared to healthy ovarian tissue, the homeostatic parameters at the tissue microenvironment including pH, oxygen levels, and glucose metabolism differ significantly in ovarian tumors. US-based technologies have been developed to take advantage of these tumor-specific alterations for precision drug delivery. Preclinical efficacy of US-based targeting of currently used clinical chemotherapies presented in this review has the potential for rapid human translation, especially for formulations that use all substances that are deemed to be generally safe by the U.S. Food and Drug Administration.

Peritoneal carcinomatosis with intraperitoneal immunotherapy: current treatment options and perspectives

INTRODUCTION

Peritoneal carcinomatosis (PC) is an advanced malignancy that is not sensitive to systemic conventional chemotherapy. Treatment options for PC are usually palliative rather than curative. Cytoreductive surgery and hyperthermic intraperitoneal (IP) chemotherapy are associated with limited efficacy in patients with PC. However, the peritoneum can produce effective immunity by inducing T-lymphocyte recruitment and proliferation, and the unique immune environment of the peritoneum provides the rationale for IP immunotherapy in PC.

AREAS COVERED

The authors retrieved relevant documents of IP immunotherapy for PC from PubMed and Medline. This review elaborates on the knowledge of the peritoneal immune microenvironment and IP immunotherapy for PC covering immune stimulators, radioimmunotherapy, catumaxomab, cancer vaccines, chimeric antigen receptor (CAR)-T cells, and immune checkpoint inhibitors.

EXPERT OPINION

The prognosis of PC is poor. However, the peritoneal cavity is a unique immune compartment with abundant immune cells which can produce effective immunity. IP immunotherapy may be a promising strategy in patients with PC.

Glycosphingolipids are mediators of cancer plasticity through independent signaling pathways

The molecular repertoire promoting cancer cell plasticity is not fully elucidated. Here, we propose that glycosphingolipids (GSLs), specifically the globo and ganglio series, correlate and promote the transition between epithelial and mesenchymal cells. The epithelial character of ovarian cancer remains stable throughout disease progression, and spatial glycosphingolipidomics reveals elevated globosides in the tumor compartment compared with the ganglioside-rich stroma. CRISPR-Cas9 knockin mediated truncation of endogenous E-cadherin induces epithelial-to-mesenchymal transition (EMT) and decreases globosides. The transcriptomics analysis identifies the ganglioside-synthesizing enzyme ST8SIA1 to be consistently elevated in mesenchymal-like samples, predicting poor outcome. Subsequent deletion of ST8SIA1 induces epithelial cell features through mTOR^S2448 phosphorylation, whereas loss of globosides in ΔA4GALT cells, resulting in EMT, is accompanied by increased ERK^Y202/T204 and AKT^S124. The GSL composition dynamics corroborate cancer cell plasticity, and further evidence suggests that mesenchymal cells are maintained through ganglioside-dependent, calcium-mediated mechanisms.