Modelling genetic and clinical heterogeneity in epithelial ovarian cancers

Cancer-Associated Fibroblasts: Mechanisms of Tumor Progression and Novel Therapeutic Targets

Simple Summary

The tumor microenvironment plays an important role in determining the biological behavior of several of the more aggressive malignancies. Among the various cell types evident in the tumor “field”, cancer-associated fibroblasts (CAFs) are a heterogenous collection of activated fibroblasts secreting a wide repertoire of factors that regulate tumor development and progression, inflammation, drug resistance, metastasis and recurrence. Insensitivity to chemotherapeutics and metastatic spread are the major contributors to cancer patient mortality. This review discusses the complex interactions between CAFs and the various populations of normal and neoplastic cells that interact within the dynamic confines of the tumor microenvironment with a focus on the involved pathways and genes.

Abstract

Cancer-associated fibroblasts (CAFs) are a heterogenous population of stromal cells found in solid malignancies that coexist with the growing tumor mass and other immune/nonimmune cellular elements. In certain neoplasms (e.g., desmoplastic tumors), CAFs are the prominent mesenchymal cell type in the tumor microenvironment, where their presence and abundance signal a poor prognosis in multiple cancers. CAFs play a major role in the progression of various malignancies by remodeling the supporting stromal matrix into a dense, fibrotic structure while secreting factors that lead to the acquisition of cancer stem-like characteristics and promoting tumor cell survival, reduced sensitivity to chemotherapeutics, aggressive growth and metastasis. Tumors with high stromal fibrotic signatures are more likely to be associated with drug resistance and eventual relapse. Clarifying the molecular basis for such multidirectional crosstalk among the various normal and neoplastic cell types present in the tumor microenvironment may yield novel targets and new opportunities for therapeutic intervention. This review highlights the most recent concepts regarding the complexity of CAF biology including CAF heterogeneity, functionality in drug resistance, contribution to a progressively fibrotic tumor stroma, the involved signaling pathways and the participating genes.

Ovarian-Cancer-Associated Extracellular Vesicles: Microenvironmental Regulation and Potential Clinical Applications

Ovarian cancer (OC) is one of the most diagnosed gynecological cancers in women. Due to the lack of effective early stage screening, women are more often diagnosed at an advanced stage; therefore, it is associated with poor patient outcomes. There are a lack of tools to identify patients at the highest risk of developing this cancer. Moreover, early detection strategies, therapeutic approaches, and real-time monitoring of responses to treatment to improve survival and quality of life are also inadequate. Tumor development and progression are dependent upon cell-to-cell communication, allowing cancer cells to re-program cells not only within the surrounding tumor microenvironment, but also at distant sites. Recent studies established that extracellular vesicles (EVs) mediate bi-directional communication between normal and cancerous cells. EVs are highly stable membrane vesicles that are released from a wide range of cells, including healthy and cancer cells. They contain tissue-specific signaling molecules (e.g., proteins and miRNA) and, once released, regulate target cell phenotypes, inducing a pro-tumorigenic and immunosuppressive phenotype to contribute to tumor growth and metastasis as well as proximal and distal cell function. Thus, EVs are a “fingerprint” of their cell of origin and reflect the metabolic status. Additionally, via the capacity to evade the immune system and remain stable over long periods in circulation, EVs can be potent therapeutic agents. This review examines the potential role of EVs in the different aspects of the tumor microenvironment in OC, as well as their application in diagnosis, delivery of therapeutic agents, and disease monitoring.

Transcription factors in epithelial ovarian cancer: histotype-specific drivers and novel therapeutic targets

Transcription factors (TFs) are major contributors to cancer risk and somatic development. In preclinical and clinical studies, direct or indirect inhibition of TF-mediated oncogenic gene expression profiles have proven to be effective in many tumor types, highlighting this group of proteins as valuable therapeutic targets. In spite of this, our understanding of TFs in epithelial ovarian cancer (EOC) is relatively limited. EOC is a heterogeneous disease composed of five major histologic subtypes; high-grade serous, low-grade serous, endometrioid, clear cell and mucinous. Each histology is associated with unique clinical etiologies, sensitivity to therapies, and molecular signatures - including diverse transcriptional regulatory programs. While some TFs are shared across EOC subtypes, a set of TFs are expressed in a histotype-specific manner and likely explain part of the histologic diversity of EOC subtypes. Targeting TFs present with unique opportunities for development of novel precision medicine strategies for ovarian cancer. This article reviews the critical TFs in EOC subtypes and highlights the potential of exploiting TFs as biomarkers and therapeutic targets.

Collagen-rich omentum is a premetastatic niche for integrin α2-mediated peritoneal metastasis

The extracellular matrix (ECM) plays critical roles in tumor progression and metastasis. However, the contribution of ECM proteins to early metastatic onset in the peritoneal cavity remains unexplored. Here, we suggest a new route of metastasis through the interaction of integrin alpha 2 (ITGA2) with collagens enriched in the tumor coinciding with poor outcome in patients with ovarian cancer. Using multiple gene-edited cell lines and patient-derived samples, we demonstrate that ITGA2 triggers cancer cell adhesion to collagen, promotes cell migration, anoikis resistance, mesothelial clearance, and peritoneal metastasis in vitro and in vivo. Mechanistically, phosphoproteomics identify an ITGA2-dependent phosphorylation of focal adhesion kinase and mitogen-activated protein kinase pathway leading to enhanced oncogenic properties. Consequently, specific inhibition of ITGA2-mediated cancer cell-collagen interaction or targeting focal adhesion signaling may present an opportunity for therapeutic intervention of metastatic spread in ovarian cancer.

Ovarian Cancer Risk Variants Are Enriched in Histotype-Specific Enhancers and Disrupt Transcription Factor Binding Sites

Quantifying the functional effects of complex disease risk variants can provide insights into mechanisms underlying disease biology. Genome-wide association studies have identified 39 regions associated with risk of epithelial ovarian cancer (EOC). The vast majority of these variants lie in the non-coding genome, where they likely function through interaction with gene regulatory elements. In this study we first estimated the heritability explained by known common low penetrance risk alleles for EOC. The narrow sense heritability (hg2) of EOC overall and high-grade serous ovarian cancer (HGSOCs) were estimated to be 5%-6%. Partitioned SNP heritability across broad functional categories indicated a significant contribution of regulatory elements to EOC heritability. We collated epigenomic profiling data for 77 cell and tissue types from Roadmap Epigenomics and ENCODE, and from H3K27Ac ChIP-seq data generated in 26 ovarian cancer and precursor-related cell and tissue types. We identified significant enrichment of risk single-nucleotide polymorphisms (SNPs) in active regulatory elements marked by H3K27Ac in HGSOCs. To further investigate how risk SNPs in active regulatory elements influence predisposition to ovarian cancer, we used motifbreakR to predict the disruption of transcription factor binding sites. We identified 469 candidate causal risk variants in H3K27Ac peaks that are predicted to significantly break transcription factor (TF) motifs. The most frequently broken motif was REST (p value = 0.0028), which has been reported as both a tumor suppressor and an oncogene. Overall, these systematic functional annotations with epigenomic data improve interpretation of EOC risk variants and shed light on likely cells of origin.

CNC-Milled Superhydrophobic Macroporous Monoliths for 3D Cell Culture

High-strength macroporous monoliths can be obtained by the simple mixing of boehmite nanofiber aqueous acetate dispersions with methyltrimethoxysilane. On the boehmite nanofiber-polymethylsilsesquioxane monoliths, we can fabricate structures smaller than a millimeter in size by computer numerical control (CNC) milling, resulting in a machined surface that is superhydrophobic and biocompatible. Using this strategy, we fabricated a superhydrophobic multiwell plate that holds water droplets to produce 3D cell culture environments for various cell types. We expect these superhydrophobic monoliths to have future applications in 3D tissue construction.

STAT3 signaling in ovarian cancer: a potential therapeutic target

Accumulating evidence has shown that Signal Transducer and Activator of Transcription 3 (STAT3) is thought to be a promising target for cancer therapy as STAT3 is frequently overexpressed in a wide range of cancer cells as well as clinical specimens, promoting tumor progression. It is widely accepted that STAT3 regulates a variety of cellular processes, such as tumor cell growth, survival, invasion, cancer stem cell-like characteristic, angiogenesis and drug-resistance. In this review, we focus on the role of STAT3 in tumorigenesis in ovarian cancer and discuss the existing inhibitors of STAT3 signaling that can be promisingly developed as the strategies for ovarian cancer therapy.

Genome-wide association studies identify susceptibility loci for epithelial ovarian cancer in east Asian women

OBJECTIVE

Genome-wide association studies (GWASs) for epithelial ovarian cancer (EOC) have focused largely on populations of European ancestry. We aimed to identify common germline variants associated with EOC risk in Asian women.

METHODS

Genotyping was performed as part of the OncoArray project. Samples with >60% Asian ancestry were included in the analysis. Genotyping was performed on 533,631 SNPs in 3238 Asian subjects diagnosed with invasive or borderline EOC and 4083 unaffected controls. After imputation, genotypes were available for 11,595,112 SNPs to identify associations.

RESULTS

At chromosome 6p25.2, SNP rs7748275 was associated with risk of serous EOC (odds ratio [OR] = 1.34, P = 8.7 × 10-9) and high-grade serous EOC (HGSOC) (OR = 1.34, P = 4.3 × 10-9). SNP rs6902488 at 6p25.2 (r2 = 0.97 with rs7748275) lies in an active enhancer and is predicted to impact binding of STAT3, P300 and ELF1. We identified additional risk loci with low Bayesian false discovery probability (BFDP) scores, indicating they are likely to be true risk associations (BFDP <10%). At chromosome 20q11.22, rs74272064 was associated with HGSOC risk (OR = 1.27, P = 9.0 × 10-8). Overall EOC risk was associated with rs10260419 at chromosome 7p21.3 (OR = 1.33, P = 1.2 × 10-7) and rs74917072 at chromosome 2q37.3 (OR = 1.25, P = 4.7 × 10-7). At 2q37.3, expression quantitative trait locus analysis in 404 HGSOC tissues identified ESPNL as a putative candidate susceptibility gene (P = 1.2 × 10-7).

CONCLUSION

While some risk loci were shared between East Asian and European populations, others were population-specific, indicating that the landscape of EOC risk in Asian women has both shared and unique features compared to women of European ancestry.

Heterotypic CAF-tumor spheroids promote early peritoneal metastatis of ovarian cancer

The study provides insights in HGSOC by identifying that ascitic CAFs selectively recruit ITGA5^high ascitic tumor cells to form heterotypic spheroids named metastatic units (MUs), which actively engage in peritoneal metastasis, discriminates HGSOC from LGSOC, and act as therapeutic targets in hampering OC metastasis.

High-grade serous ovarian cancer (HGSOC) is hallmarked by early onset of peritoneal dissemination, which distinguishes it from low-grade serous ovarian cancer (LGSOC). Here, we describe the aggressive nature of HGSOC ascitic tumor cells (ATCs) characterized by integrin α5^high (ITGA5^high) ATCs, which are prone to forming heterotypic spheroids with fibroblasts. We term these aggregates as metastatic units (MUs) in HGSOC for their advantageous metastatic capacity and active involvement in early peritoneal dissemination. Intriguingly, fibroblasts inside MUs support ATC survival and guide their peritoneal invasion before becoming essential components of the tumor stroma in newly formed metastases. Cancer-associated fibroblasts (CAFs) recruit ITGA5^high ATCs to form MUs, which further sustain ATC ITGA5 expression by EGF secretion. Notably, LGSOC is largely devoid of CAFs and the resultant MUs, which might explain its metastatic delay. These findings identify a specialized MU architecture that amplifies the tumor–stroma interaction and promotes transcoelomic metastasis in HGSOC, providing the basis for stromal fibroblast-oriented interventions in hampering OC peritoneal propagation.

Tumor metabolism regulating chemosensitivity in ovarian cancer

Elevated metabolism is a key hallmark of multiple cancers, serving to fulfill high anabolic demands. Ovarian cancer (OVCA) is the fifth leading cause of cancer deaths in women with a high mortality rate (45%). Chemoresistance is a major hurdle for OVCA treatment. Although substantial evidence suggests that metabolic reprogramming contributes to anti-apoptosis and the metastasis of multiple cancers, the link between tumor metabolism and chemoresistance in OVCA remains unknown. While clinical trials targeting metabolic reprogramming alone have been met with limited success, the synergistic effect of inhibiting tumor-specific metabolism with traditional chemotherapy warrants further examination, particularly in OVCA. This review summarizes the role of key glycolytic enzymes and other metabolic synthesis pathways in the progression of cancer and chemoresistance in OVCA. Within this context, mitochondrial dynamics (fission, fusion and cristae structure) are addressed regarding their roles in controlling metabolism and apoptosis, closely associated with chemosensitivity. The roles of multiple key oncogenes (Akt, HIF-1α) and tumor suppressors (p53, PTEN) in metabolic regulation are also described. Next, this review summarizes recent research of metabolism and future direction. Finally, we examine clinical drugs and inhibitors to target glycolytic metabolism, as well as the rationale for such strategies as potential therapeutics to overcome chemoresistant OVCA.

Bioprinted 3D vascularized tissue model for drug toxicity analysis

To develop biomimetic three-dimensional (3D) tissue constructs for drug screening and biological studies, engineered blood vessels should be integrated into the constructs to mimic the drug administration process in vivo. The development of perfusable vascularized 3D tissue constructs for studying the drug administration process through an engineered endothelial layer remains an area of intensive research. Here, we report the development of a simple 3D vascularized liver tissue model to study drug toxicity through the incorporation of an engineered endothelial layer. Using a sacrificial bioprinting technique, a hollow microchannel was successfully fabricated in the 3D liver tissue construct created with HepG2/C3A cells encapsulated in a gelatin methacryloyl hydrogel. After seeding human umbilical vein endothelial cells (HUVECs) into the microchannel, we obtained a vascularized tissue construct containing a uniformly coated HUVEC layer within the hollow microchannel. The inclusion of the HUVEC layer into the scaffold resulted in delayed permeability of biomolecules into the 3D liver construct. In addition, the vascularized construct containing the HUVEC layer showed an increased viability of the HepG2/C3A cells within the 3D scaffold compared to that of the 3D liver constructs without the HUVEC layer, demonstrating a protective role of the introduced endothelial cell layer. The 3D vascularized liver model presented in this study is anticipated to provide a better and more accurate in vitro liver model system for future drug toxicity testing.

Connective tissue growth factor as a novel therapeutic target in high grade serous ovarian cancer

Ovarian cancer is the most common cause of death among women with gynecologic cancer. We examined molecular profiles of fibroblasts from normal ovary and high-grade serous ovarian tumors to identify novel therapeutic targets involved in tumor progression. We identified 2,300 genes that are significantly differentially expressed in tumor-associated fibroblasts. Fibroblast expression of one of these genes, connective tissue growth factor (CTGF), was confirmed by immunohistochemistry. CTGF protein expression in ovarian tumor fibroblasts significantly correlated with gene expression levels. CTGF is a secreted component of the tumor microenvironment and is being pursued as a therapeutic target in pancreatic cancer. We examined its effect in in vitro and ex vivo ovarian cancer models, and examined associations between CTGF expression and clinico-pathologic characteristics in patients. CTGF promotes migration and peritoneal adhesion of ovarian cancer cells. These effects are abrogated by FG-3019, a human monoclonal antibody against CTGF, currently under clinical investigation as a therapeutic agent. Immunohistochemical analyses of high-grade serous ovarian tumors reveal that the highest level of tumor stromal CTGF expression was correlated with the poorest prognosis. Our findings identify CTGF as a promoter of peritoneal adhesion, likely to mediate metastasis, and a potential therapeutic target in high-grade serous ovarian cancer. These results warrant further studies into the therapeutic efficacy of FG-3019 in high-grade serous ovarian cancer.

Intact LKB1 activity is required for survival of dormant ovarian cancer spheroids

Metastatic epithelial ovarian cancer (EOC) cells can form multicellular spheroids while in suspension and disperse directly throughout the peritoneum to seed secondary lesions. There is growing evidence that EOC spheroids are key mediators of metastasis, and they use specific intracellular signalling pathways to control cancer cell growth and metabolism for increased survival. Our laboratory discovered that AKT signalling is reduced during spheroid formation leading to cellular quiescence and autophagy, and these may be defining features of tumour cell dormancy. To further define the phenotype of EOC spheroids, we have initiated studies of the Liver kinase B1 (LKB1)-5′-AMP-activated protein kinase (AMPK) pathway as a master controller of the metabolic stress response. We demonstrate that activity of AMPK and its upstream kinase LKB1 are increased in quiescent EOC spheroids as compared with proliferating adherent EOC cells. We also show elevated AMPK activity in spheroids isolated directly from patient ascites. Functional studies reveal that treatment with the AMP mimetic AICAR or allosteric AMPK activator A-769662 led to a cytostatic response in proliferative adherent ovarian cancer cells, but they fail to elicit an effect in spheroids. Targeted knockdown of STK11 by RNAi to reduce LKB1 expression led to reduced viability and increased sensitivity to carboplatin treatment in spheroids only, a phenomenon which was AMPK-independent. Thus, our results demonstrate a direct impact of altered LKB1-AMPK signalling function in EOC. In addition, this is the first evidence in cancer cells demonstrating a pro-survival function for LKB1, a kinase traditionally thought to act as a tumour suppressor.

Functional mechanisms underlying pleiotropic risk alleles at the 19p13.1 breast-ovarian cancer susceptibility locus

A locus at 19p13 is associated with breast cancer (BC) and ovarian cancer (OC) risk. Here we analyse 438 SNPs in this region in 46,451 BC and 15,438 OC cases, 15,252 BRCA1 mutation carriers and 73,444 controls and identify 13 candidate causal SNPs associated with serous OC (P=9.2 × 10(-20)), ER-negative BC (P=1.1 × 10(-13)), BRCA1-associated BC (P=7.7 × 10(-16)) and triple negative BC (P-diff=2 × 10(-5)). Genotype-gene expression associations are identified for candidate target genes ANKLE1 (P=2 × 10(-3)) and ABHD8 (P<2 × 10(-3)). Chromosome conformation capture identifies interactions between four candidate SNPs and ABHD8, and luciferase assays indicate six risk alleles increased transactivation of the ADHD8 promoter. Targeted deletion of a region containing risk SNP rs56069439 in a putative enhancer induces ANKLE1 downregulation; and mRNA stability assays indicate functional effects for an ANKLE1 3'-UTR SNP. Altogether, these data suggest that multiple SNPs at 19p13 regulate ABHD8 and perhaps ANKLE1 expression, and indicate common mechanisms underlying breast and ovarian cancer risk.

Anti-gastric cancer activity in three-dimensional tumor spheroids of bufadienolides

Multicellular spheroids of cancer cells have been increasingly used to screen anti-tumor compounds, owing to their in vivo like microenvironment and structure as well as compatibility to high-throughput/high-content screening. Here we report the potency and efficacy of a family of bufadienolides to inhibit the growth of gastric cancer cell line HGC-27 in three-dimensional (3D) spheroidal models. Examining the morphological and growth patterns of several cell lines in round-bottomed ultra-low attachment microplate suggested that HGC-27 cells formed reproducibly multicellular spheroidal structures. Profiling of 15 natural bufadienolides isolated from toad skin indicated that 8 14-hydroxy bufadienolides displayed inhibitory activity of the growth of HGC-27 spheroids in a dose-dependent manner. Notably, compared to clinical drugs taxol and epirubicin, active bufadienolides were found to penetrate more effectively into the HGC-27 spheroids, but with a narrower effective concentration range and a shorter lasting inhibitory effect. Furthermore, compared to two-dimensional (2D) cell monolayer assays, active bufadienolides exhibited weaker efficacy and different potency in 3D spheroid model, demonstrating the great potential of 3D multicellular cell spheroid models in anti-cancer drug discovery and development.

Epithelial-Mesenchymal Transition (EMT) Gene Variants and Epithelial Ovarian Cancer (EOC) Risk

Epithelial-mesenchymal transition (EMT) is a process whereby epithelial cells assume mesenchymal characteristics to facilitate cancer metastasis. However, EMT also contributes to the initiation and development of primary tumors. Prior studies that explored the hypothesis that EMT gene variants contribute to epithelial ovarian carcinoma (EOC) risk have been based on small sample sizes and none have sought replication in an independent population. We screened 15,816 single-nucleotide polymorphisms (SNPs) in 296 genes in a discovery phase using data from a genome-wide association study of EOC among women of European ancestry (1,947 cases and 2,009 controls) and identified 793 variants in 278 EMT-related genes that were nominally (P < 0.05) associated with invasive EOC. These SNPs were then genotyped in a larger study of 14,525 invasive-cancer patients and 23,447 controls. A P-value <0.05 and a false discovery rate (FDR) <0.2 were considered statistically significant. In the larger dataset, GPC6/GPC5 rs17702471 was associated with the endometrioid subtype among Caucasians (odds ratio (OR) = 1.16, 95% CI = 1.07-1.25, P = 0.0003, FDR = 0.19), whereas F8 rs7053448 (OR = 1.69, 95% CI = 1.27-2.24, P = 0.0003, FDR = 0.12), F8 rs7058826 (OR = 1.69, 95% CI = 1.27-2.24, P = 0.0003, FDR = 0.12), and CAPN13 rs1983383 (OR = 0.79, 95% CI = 0.69-0.90, P = 0.0005, FDR = 0.12) were associated with combined invasive EOC among Asians. In silico functional analyses revealed that GPC6/GPC5 rs17702471 coincided with DNA regulatory elements. These results suggest that EMT gene variants do not appear to play a significant role in the susceptibility to EOC.

Common variants at the CHEK2 gene locus and risk of epithelial ovarian cancer

Genome-wide association studies have identified 20 genomic regions associated with risk of epithelial ovarian cancer (EOC), but many additional risk variants may exist. Here, we evaluated associations between common genetic variants [single nucleotide polymorphisms (SNPs) and indels] in DNA repair genes and EOC risk. We genotyped 2896 common variants at 143 gene loci in DNA samples from 15 397 patients with invasive EOC and controls. We found evidence of associations with EOC risk for variants at FANCA, EXO1, E2F4, E2F2, CREB5 and CHEK2 genes (P ≤ 0.001). The strongest risk association was for CHEK2 SNP rs17507066 with serous EOC (P = 4.74 x 10(-7)). Additional genotyping and imputation of genotypes from the 1000 genomes project identified a slightly more significant association for CHEK2 SNP rs6005807 (r (2) with rs17507066 = 0.84, odds ratio (OR) 1.17, 95% CI 1.11-1.24, P = 1.1×10(-7)). We identified 293 variants in the region with likelihood ratios of less than 1:100 for representing the causal variant. Functional annotation identified 25 candidate SNPs that alter transcription factor binding sites within regulatory elements active in EOC precursor tissues. In The Cancer Genome Atlas dataset, CHEK2 gene expression was significantly higher in primary EOCs compared to normal fallopian tube tissues (P = 3.72×10(-8)). We also identified an association between genotypes of the candidate causal SNP rs12166475 (r (2) = 0.99 with rs6005807) and CHEK2 expression (P = 2.70×10(-8)). These data suggest that common variants at 22q12.1 are associated with risk of serous EOC and CHEK2 as a plausible target susceptibility gene.

Common Genetic Variation in Circadian Rhythm Genes and Risk of Epithelial Ovarian Cancer (EOC)

Disruption in circadian gene expression, whether due to genetic variation or environmental factors (e.g., light at night, shiftwork), is associated with increased incidence of breast, prostate, gastrointestinal and hematologic cancers and gliomas. Circadian genes are highly expressed in the ovaries where they regulate ovulation; circadian disruption is associated with several ovarian cancer risk factors (e.g., endometriosis). However, no studies have examined variation in germline circadian genes as predictors of ovarian cancer risk and invasiveness. The goal of the current study was to examine single nucleotide polymorphisms (SNPs) in circadian genes BMAL1, CRY2, CSNK1E, NPAS2, PER3, REV1 and TIMELESS and downstream transcription factors KLF10 and SENP3 as predictors of risk of epithelial ovarian cancer (EOC) and histopathologic subtypes. The study included a test set of 3,761 EOC cases and 2,722 controls and a validation set of 44,308 samples including 18,174 (10,316 serous) cases and 26,134 controls from 43 studies participating in the Ovarian Cancer Association Consortium (OCAC). Analysis of genotype data from 36 genotyped SNPs and 4600 imputed SNPs indicated that the most significant association was rs117104877 in BMAL1 (OR = 0.79, 95% CI = 0.68-0.90, p = 5.59 × 10-4]. Functional analysis revealed a significant down regulation of BMAL1 expression following cMYC overexpression and increasing transformation in ovarian surface epithelial (OSE) cells as well as alternative splicing of BMAL1 exons in ovarian and granulosa cells. These results suggest that variation in circadian genes, and specifically BMAL1, may be associated with risk of ovarian cancer, likely through disruption of hormonal pathways.

Identification of novel candidate biomarkers of epithelial ovarian cancer by profiling the secretomes of three-dimensional genetic models of ovarian carcinogenesis

Epithelial ovarian cancer (EOC) is still considered the most lethal gynecological malignancy and improved early detection of ovarian cancer is crucial to improving patient prognoses. To address this need, we tested whether candidate EOC biomarkers can be identified using three-dimensional (3D) in vitro models. We quantified changes in the abundance of secreted proteins in a 3D genetic model of early-stage EOC, generated by expressing CMYC and KRAS(G) (12) (V) in TERT-immortalized normal ovarian epithelial cells. Cellular proteins were labeled in live cells using stable isotopic amino acid analogues, and secreted proteins identified and quantified using liquid chromatography-tandem mass spectrometry. Thirty-seven and 55 proteins were differentially expressed by CMYC and CMYC+KRAS(G) (12) (V) expressing cells respectively (p < 0.05; >2-fold). We evaluated expression of the top candidate biomarkers in ∼210 primary EOCs: CHI3L1 and FKBP4 are both expressed by >96% of primary EOCs, and FASN and API5 are expressed by 86 and 75% of cases. High expression of CHI3L1 and FKBP4 was associated with worse patient survival (p = 0.042 and p = 0.002, respectively). Expression of LGALS3BP was positively associated with recurrence (p = 0.0001) and suboptimal debulking (p = 0.018) suggesting that these proteins may be novel prognostic biomarkers. Furthermore, within early stage tumours (I/II), high expression of API5, CHI3L1 and FASN was associated with high tumour grade (p = 3 × 10(-4) , p = 0.016, p = 0.010, respectively). We show in vitro cell biology models of early-stage cancer development can be used to identify novel candidate biomarkers for disease, and report the identification of proteins that represent novel potential candidate diagnostic and prognostic biomarkers for this highly lethal disease.

Cell-type-specific enrichment of risk-associated regulatory elements at ovarian cancer susceptibility loci

Understanding the regulatory landscape of the human genome is a central question in complex trait genetics. Most single-nucleotide polymorphisms (SNPs) associated with cancer risk lie in non-protein-coding regions, implicating regulatory DNA elements as functional targets of susceptibility variants. Here, we describe genome-wide annotation of regions of open chromatin and histone modification in fallopian tube and ovarian surface epithelial cells (FTSECs, OSECs), the debated cellular origins of high-grade serous ovarian cancers (HGSOCs) and in endometriosis epithelial cells (EECs), the likely precursor of clear cell ovarian carcinomas (CCOCs). The regulatory architecture of these cell types was compared with normal human mammary epithelial cells and LNCaP prostate cancer cells. We observed similar positional patterns of global enhancer signatures across the three different ovarian cancer precursor cell types, and evidence of tissue-specific regulatory signatures compared to non-gynecological cell types. We found significant enrichment for risk-associated SNPs intersecting regulatory biofeatures at 17 known HGSOC susceptibility loci in FTSECs (P = 3.8 × 10(-30)), OSECs (P = 2.4 × 10(-23)) and HMECs (P = 6.7 × 10(-15)) but not for EECs (P = 0.45) or LNCaP cells (P = 0.88). Hierarchical clustering of risk SNPs conditioned on the six different cell types indicates FTSECs and OSECs are highly related (96% of samples using multi-scale bootstrapping) suggesting both cell types may be precursors of HGSOC. These data represent the first description of regulatory catalogues of normal precursor cells for different ovarian cancer subtypes, and provide unique insights into the tissue specific regulatory variation with respect to the likely functional targets of germline genetic susceptibility variants for ovarian cancer.

PTEN deletion potentiates invasion of colorectal cancer spheroidal cells through 3D Matrigel

PTEN (phosphatase and tensin homolog), a tumour suppressor negatively regulating the PI3K signalling pathway, is the second most frequently mutated gene in human cancers. Decreased PTEN expression is correlated with colorectal cancer metastases and poor patient survival. Three dimensional (3D) multicellular spheroid models have been postulated to bridge the gap between 2D cell models and animal models for cancer research and drug discovery. However, little is known about the impact of PTEN deletion on the invasion of colon cancer spheroidal cells through a 3D extracellular matrix, and current techniques are limited in their ability to study in vitro 3D cell models in real-time. Here, we investigated the migration and invasion behaviours of the colon cancer cell line HCT116 and its PTEN-/- isogenic cell line using three different in vitro assays, wound healing, transwell invasion, and label-free single cell 3D(2) invasion assays enabled by a resonant waveguide grating (RWG) biosensor. Light microscopic and RWG imaging showed that PTEN deletion influences the spheroid formation of HCT116 cells at high seeding density, and accelerates the spontaneous transfer from the spheroid to substrate surfaces. In vitro migration and invasion assays showed that PTEN knockout increases the 2D migration speed of HCT116 cells, and the invasion rate of individual cells through Matrigel or cells in the spheroid through 3D Matrigel; moreover, the PI3K inhibitor treatment drastically reduces the invasiveness of both cell lines. This study suggests that PTEN knockout potentiates the invasiveness of colorectal cancer spheroidal cells through a 3D extracellular matrix, and the label-free single cell assay is a powerful tool for investigating cancer cell invasion, in particular using 3D cell models.

Personalized in vitro cancer modeling - fantasy or reality?

With greater technological advancements and understanding of pathophysiology, “personalized medicine” has become a more realistic goal. In the field of cancer, personalized medicine is the ultimate objective, as each cancer is unique and each tumor is heterogeneous. For many decades, researchers have relied upon studying the histopathology of tumors in the hope that it would provide clues to understanding the pathophysiology of cancer. Current preclinical research relies heavily upon two-dimensional culture models. However, these models have had limited success in recreating the complex interactions between cancer cells and the stroma environment in vivo. Thus, there is increasing impetus to shift to three-dimensional models, which more accurately reflect this phenomenon. With a more accurate in vitro tumor model, drug sensitivity can be tested to determine the best treatment option based on the tumor characteristics. Many methods have been developed to create tumor models or “tumoroids,” each with its advantages and limitations. One significant problem faced is the replication of angiogenesis that is characteristic of tumors in vivo. Nonetheless, if three-dimensional models could be standardized and implemented as a preclinical research tool for therapeutic testing, we would be taking a step towards making personalized cancer medicine a reality.

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. The 3D models aim to recapitulate the tumor microenvironment, which has a critical role in the pathogenesis of ovarian cancer. Ultimately, findings using models that accurately reflect human ovarian cancer biology are likely to translate into improved clinical outcomes. In this review we discuss the design of new 3D culture models of ovarian cancer primarily using human cells, key studies in which these models have been applied, current limitations, and future applications.

Label-free single cell kinetics of the invasion of spheroidal colon cancer cells through 3D Matrigel

This article reports label-free, real-time, and single-cell quantification of the invasion of spheroidal colon cancer cells through three-dimensional (3D) Matrigel using a resonant waveguide grating (RWG) imager. This imager employs a time-resolved swept wavelength interrogation scheme to monitor cell invasion and adhesion with a temporal resolution up to 3 s and a spatial resolution of 12 μm. As the model system, spheroids of human colorectal adenocarcinoma HT-29 cells are generated by culturing the cells in 96-well round-bottom ultralow attachment plates. 3D Matrigel is formed by its gelation in 384-well RWG biosensor microplates. The invasion and adhesion of spheroidal HT29 cells is initiated by placing individual spheroids onto the Matrigel-coated biosensors. The time series RWG images are obtained and used to extract the optical signatures arising from the adhesion after the cells are dissociated from the spheroids and invade through the 3D Matrigel. Compound profiling shows that epidermal growth factor accelerates cancer cell invasion, while vandetanib, a multitarget kinase inhibitor, dose-dependently inhibits invasion. This study demonstrates that the label-free imager can monitor in real-time the invasion of spheroidal cancer cells through 3D matrices.

Culture models to define key mediators of cancer matrix remodeling

High grade serous epithelial ovarian cancer (HG-SOC) is one of the most devastating gynecological cancers affecting women worldwide, with a poor survival rate despite clinical treatment advances. HG-SOC commonly metastasizes within the peritoneal cavity, primarily to the mesothelial cells of the omentum, which regulate an extracellular matrix rich in collagens type I, III, and IV along with laminin, vitronectin, and fibronectin. Cancer cells depend on their ability to penetrate and invade secondary tissue sites to spread, however a detailed understanding of the molecular mechanisms underlying these processes remain largely unknown. Given the high metastatic potential of HG-SOC and the associated poor clinical outcome, it is extremely important to identify the pathways and the components of which that are responsible for the progression of this disease. In vitro methods of recapitulating human disease processes are the critical first step in such investigations. In this context, establishment of an in vitro “tumor-like” micro-environment, such as 3D culture, to study early disease and metastasis of human HG-SOC is an important and highly insightful method. In recent years, many such methods have been established to investigate the adhesion and invasion of human ovarian cancer cell lines. The aim of this review is to summarize recent developments in ovarian cancer culture systems and their use to investigate clinically relevant findings concerning the key players in driving human HG-SOC.

Detailed analysis of promoter-associated RNA

The detailed analysis of noncoding RNA is an upcoming necessity due to a plethora of recently identified components of this class of molecules. The investigation of their structure, directionality, intracellular localization, interaction with other cellular elements is useful to understand the role they play in transcriptional regulation. In this chapter, we describe some techniques, meant to determine very important features of promoter-associated RNAs, in order to clarify their functionality.

In vitro three-dimensional modeling of fallopian tube secretory epithelial cells

Background

Fallopian tube secretory epithelial cells (FTSECs) have been implicated as a cell-of-origin for high-grade serous epithelial ovarian cancer. However, there are relatively few in vitro models of this tissue type available for use in studies of FTSEC biology and malignant transformation. In vitro three-dimensional (3D) cell culture models aim to recreate the architecture and geometry of tissues in vivo and restore the complex network of cell-cell/cell-matrix interactions that occur throughout the surface of the cell membrane.

Results

We have established and characterized 3D spheroid culture models of primary FTSECs. FTSEC spheroids contain central cores of hyaline matrix surrounded by mono- or multi-layer epithelial sheets. We found that 3D culturing alters the molecular characteristics of FTSECs compared to 2D cultures of the same cells. Gene expression profiling identified more than a thousand differentially expressed genes between 3D and 2D cultures of the same FTSEC lines. Pathways significantly under-represented in 3D FTSEC cultures were associated with cell cycle progression and DNA replication. This was also reflected in the reduced proliferative indices observed in 3D spheroids stained for the proliferation marker MIB1. Comparisons with gene expression profiles of fresh fallopian tube tissues revealed that 2D FTSEC cultures clustered with follicular phase tubal epithelium, whereas 3D FTSEC cultures clustered with luteal phase samples.

Conclusions

This 3D model of fallopian tube secretory epithelial cells will advance our ability to study the underlying biology and etiology of fallopian tube tissues and the pathogenesis of high-grade serous epithelial ovarian cancer.

Detection of the BRAF V600E mutation in serous ovarian tumors: a comparative analysis of immunohistochemistry with a mutation-specific monoclonal antibody and allele-specific PCR

Mutations of components of the mitogen-activated protein kinase pathway, mainly BRAF, are common in serous ovarian borderline tumors, whereas high-grade serous ovarian carcinomas rarely show this feature. With the advent of specific kinase inhibitors active against BRAF-mutated cancers, rapid and sensitive detection of the BRAF V600E, by far the most common mutation of this gene, is of great practical relevance. Currently, BRAF mutations are detected by DNA-based techniques. Recently, a monoclonal antibody (VE1) specific for the BRAF V600E protein suitable for archival tissues has been described. In this study, we compared detection of the V600E mutation in serous ovarian tumors by VE1 immunostaining and by allele-specific polymerase chain reaction. All 141 cases of high-grade serous ovarian cancer showed negative or rarely weak, diffuse background VE1 immunostaining, and BRAF wild type was confirmed by molecular analysis in all tested cases. In contrast, 1 (14%) of 7 low-grade serous carcinomas and 22 (71%) of 31 serous borderline tumors revealed moderate to strong VE1 positivity. Immunostaining was clearly evaluable in all cases with sufficient tumor cells, and only rare cases with narrow cytoplasm were difficult to interpret. The V600E mutation was confirmed by allele-specific polymerase chain reaction and sequencing in all VE1-positive cases. Two VE1-positive cases with low epithelial cell content required repeat microdissection to confirm the presence of the mutation. Immunohistochemistry with the VE1 antibody is a specific and sensitive tool for detection of the BRAF V600E mutation in serous ovarian tumors and may provide a practical screening test, especially in tumor samples with low epithelial content.

Heterotypic three-dimensional in vitro modeling of stromal-epithelial interactions during ovarian cancer initiation and progression

Epithelial ovarian cancers (EOCs) are the leading cause of death from gynecological malignancy in Western societies. Despite advances in surgical treatments and improved platinum-based chemotherapies, there has been little improvement in EOC survival rates for more than four decades. Whilst stage I tumors have 5-year survival rates >85%, survival rates for stage III/IV disease are <40%. Thus, the high rates of mortality for EOC could be significantly decreased if tumors were detected at earlier, more treatable, stages. At present, the molecular genetic and biological basis of early stage disease development is poorly understood. More specifically, little is known about the role of the microenvironment during tumor initiation; but known risk factors for EOCs (e.g. age and parity) suggest that the microenvironment plays a key role in the early genesis of EOCs. We therefore developed three-dimensional heterotypic models of both the normal ovary and of early stage ovarian cancers. For the normal ovary, we co-cultured normal ovarian surface epithelial (IOSE) and normal stromal fibroblast (INOF) cells, immortalized by retrovrial transduction of the catalytic subunit of human telomerase holoenzyme (hTERT) to extend the lifespan of these cells in culture. To model the earliest stages of ovarian epithelial cell transformation, overexpression of the CMYC oncogene in IOSE cells, again co-cultured with INOF cells. These heterotypic models were used to investigate the effects of aging and senescence on the transformation and invasion of epithelial cells. Here we describe the methodological steps in development of these three-dimensional model; these methodologies aren't specific to the development of normal ovary and ovarian cancer tissues, and could be used to study other tissue types where stromal and epithelial cell interactions are a fundamental aspect of the tissue maintenance and disease development.