Expression of c-Src and phospho-Src in epithelial ovarian carcinoma

Deciphering Biophysical Modulation in Ovarian Cancer Cells

It has been long known that the oncogenic extracellular environment plays an indispensable role in developing and nurturing cancer cell progression and in resistance to standard treatments. However, by how much the biophysical components of tumour extracellular environment contribute to these processes is uncertain. In particular, the topographic environment is scarcely explored. The biophysical modulation of cell behaviour is primarily facilitated through mechanotransduction-associated mechanisms, including focal adhesion and Rho/ROCK signalling. Dysregulation of these pathways is commonly observed in ovarian cancer and, therefore, biophysical modulation of these mechanisms may be of great importance to ovarian cancer development and progression. In this work, aspects of the biophysical environment were explored using a bioimprinting technique. The study showed that topography-mediated substrate sensing delayed cell attachment, however, cell-cell interactions overrode the effect of topography in some cell lines, such as OVCAR-5. Also, 3D topographical cues were shown to modulate the inhibition of focal adhesion and Rho signalling, which resulted in higher MAPK activity in cells on the bioimprints. It was revealed that c-Src is vital to the biophysical modulation of cell proliferation and inhibition of c-Src could downregulate biophysically modulated MAPK activity. This study provides evidence that the biophysical extracellular environment affects key intracellular mechanisms associated with tumourigenicity in ovarian cancer cells.

Mechanisms of Taxane Resistance

The taxane family of chemotherapy drugs has been used to treat a variety of mostly epithelial-derived tumors and remain the first-line treatment for some cancers. Despite the improved survival time and reduction of tumor size observed in some patients, many have no response to the drugs or develop resistance over time. Taxane resistance is multi-faceted and involves multiple pathways in proliferation, apoptosis, metabolism, and the transport of foreign substances. In this review, we dive deeper into hypothesized resistance mechanisms from research during the last decade, with a focus on the cancer types that use taxanes as first-line treatment but frequently develop resistance to them. Furthermore, we will discuss current clinical inhibitors and those yet to be approved that target key pathways or proteins and aim to reverse resistance in combination with taxanes or individually. Lastly, we will highlight taxane response biomarkers, specific genes with monitored expression and correlated with response to taxanes, mentioning those currently being used and those that should be adopted. The future directions of taxanes involve more personalized approaches to treatment by tailoring drug-inhibitor combinations or alternatives depending on levels of resistance biomarkers. We hope that this review will identify gaps in knowledge surrounding taxane resistance that future research or clinical trials can overcome.

Extracellular biophysical environment: Guilty of being a modulator of drug sensitivity in ovarian cancer cells

The roles of the extracellular biophysical environment in cancer are barely studied. This study considers the possibility that cell-like topography of a cancer cell environment may influence chemo-responses. Here, a novel bioimprinting technique was employed to produce cell-like topography on the polystyrene substrates used for cell culture. In this work, we have shown that extracellular biophysical cues generated from the topography alter the chemosensitivity of ovarian cancer cells. The three-dimensionality of the bioimprinted surface altered the cell-surface interaction, which consequently modulated intracellular signalling and chemoresponses. Sensitivity to platinum was altered more than that to paclitaxel. The effect was largely mediated through the integrin/focal adhesion system and the Rho/ROCK pathway. Moreover, the results provided evidence that biophysical cues also modulate MAPK signalling associated with chemo-resistance in ovarian cancer. Therefore, the novel findings from of this study revealed for the first time that the effects of the biophysical environment, such as substrate topography, influences ovarian cancer cell responses to clinical drugs. These observations suggest that a full clinical understanding of ovarian cancer will include biophysical aspects of tumour microenvironment.

A Cell-Autonomous Oncosuppressive Role of Human RNASET2 Affecting ECM-Mediated Oncogenic Signaling

RNASET2 is an extracellular ribonuclease endowed with a marked antitumorigenic role in several carcinomas, independent from its catalytic activity. Besides its antitumorigenic role by the recruitment to the tumor mass of immune cells from the monocyte/macrophage lineage, RNASET2 is induced by cellular stress and involved in actin cytoskeleton remodeling affecting cell interactions with the extracellular matrix (ECM). Here, we aimed to investigate the effects of RNASET2 expression modulation on cell phenotype and behavior in epithelial ovarian cancer (EOC) cellular models. In silico analysis on two publicly available datasets of gene expression from EOC patients (n = 392) indicated that increased RNASET2 transcript levels are associated with longer overall survival. In EOC biopsies (n = 101), analyzed by immunohistochemistry, RNASET2 was found heterogeneously expressed among tumors with different clinical⁻pathological characteristics and, in some cases, its expression localized to tumor-associated ECM. By characterizing in vitro two models of EOC cells in which RNASET2 was silenced or overexpressed, we report that RNASET2 expression negatively affects growth capability by conferring a peculiar cell phenotype upon the interaction of EOC cells with the ECM, resulting in decreased src activation. Altogether, these data suggest that drugs targeting activated src might represent a therapeutic approach for RNASET2-expressing EOCs.

Paclitaxel-Induced Src Activation Is Inhibited by Dasatinib Treatment, Independently of Cancer Stem Cell Properties, in a Mouse Model of Ovarian Cancer

Approximately seventy percent of ovarian cancer patients succumb to the disease within the first 5 years of diagnosis, even after successful surgery and effective chemotherapy treatment. A small subset of chemotherapy resistant cancer stem cells (CSCs) cause relapse of ovarian cancers. This study investigated the association between paclitaxel-mediated Src activation (p-Src) and CSC populations in driving ovarian cancer progression. We demonstrate that patients with high-stage serous ovarian carcinomas have significantly elevated levels of p-Src, compared to patient with low-stage and benign ovarian tumours. Additionally, p-Src was significantly enhanced in ascites-derived tumour cells obtained from recurrent patients, compared to chemonaïve patients. Paclitaxel treatment increased Src activation in ovarian cancer cells, causing enrichment of CSC marker expression in the surviving cells in vitro and in xenografts of nude mice. Dasatinib in combination with paclitaxel significantly suppressed p-Src in ovarian cancer cell lines and xenografts but had no effect on the expression of CSC markers. However, combination of paclitaxel and Dasatinib showed lower trend in invasion in liver and pancreas, compared to paclitaxel-only treatment. The tumours treated with combination therapy also had significantly lower infiltration of mononuclear cells. Robust recurrent tumour growth was observed in all mice groups after termination of treatments. The above results suggest that Dasatinib-mediated inhibition of p-Src may not be crucial for paclitaxel-induced CSC-mediated recurrence in ovarian cancer.

Multiomics Analysis of Tumor Microenvironment Reveals Gata2 and miRNA-124-3p as Potential Novel Biomarkers in Ovarian Cancer

Ovarian cancer is a common and, yet, one of the most deadly human cancers due to its insidious onset and the current lack of robust early diagnostic tests. Tumors are complex tissues comprised of not only malignant cells but also genetically stable stromal cells. Understanding the molecular mechanisms behind epithelial-stromal crosstalk in ovarian cancer is a great challenge in particular. In the present study, we performed comparative analyses of transcriptome data from laser microdissected epithelial, stromal, and ovarian tumor tissues, and identified common and tissue-specific reporter biomolecules-genes, receptors, membrane proteins, transcription factors (TFs), microRNAs (miRNAs), and metabolites-by integration of transcriptome data with genome-scale biomolecular networks. Tissue-specific response maps included common differentially expressed genes (DEGs) and reporter biomolecules were reconstructed and topological analyses were performed. We found that CDK2, EP300, and SRC as receptor-related functions or membrane proteins; Ets1, Ar, Gata2, and Foxp3 as TFs; and miR-16-5p and miR-124-3p as putative biomarkers and warrant further validation research. In addition, we report in this study that Gata2 and miR-124-3p are potential novel reporter biomolecules for ovarian cancer. The study of tissue-specific reporter biomolecules in epithelial cells, stroma, and tumor tissues as exemplified in the present study offers promise in biomarker discovery and diagnostics innovation for common complex human diseases such as ovarian cancer.

Genome-wide methylation profiling of ovarian cancer patient-derived xenografts treated with the demethylating agent decitabine identifies novel epigenetically regulated genes and pathways

Background

In high-grade serous ovarian cancer (HGSOC), intrinsic and/or acquired resistance against platinum-containing chemotherapy is a major obstacle for successful treatment. A low frequency of somatic mutations but frequent epigenetic alterations, including DNA methylation in HGSOC tumors, presents the cancer epigenome as a relevant target for innovative therapy. Patient-derived xenografts (PDXs) supposedly are good preclinical models for identifying novel drug targets. However, the representativeness of global methylation status of HGSOC PDXs compared to their original tumors has not been evaluated so far. Aims of this study were to explore how representative HGSOC PDXs are of their corresponding patient tumor methylome and to evaluate the effect of epigenetic therapy and cisplatin on putative epigenetically regulated genes and their related pathways in PDXs.

Methods

Genome-wide analysis of the DNA methylome of HGSOC patients with their corresponding PDXs, from different generations, was performed using Infinium 450 K methylation arrays. Furthermore, we analyzed global methylome changes after treatment of HGSOC PDXs with the FDA approved demethylating agent decitabine and cisplatin. Findings were validated by bisulfite pyrosequencing with subsequent pathway analysis. Publicly available datasets comprising HGSOC patients were used to analyze the prognostic value of the identified genes.

Results

Only 0.6–1.0 % of all analyzed CpGs (388,696 CpGs) changed significantly (p < 0.01) during propagation, showing that HGSOC PDXs were epigenetically stable. Treatment of F3 PDXs with decitabine caused a significant reduction in methylation in 10.6 % of CpG sites in comparison to untreated PDXs (p < 0.01, false discovery rate <10 %). Cisplatin treatment had a marginal effect on the PDX methylome. Pathway analysis of decitabine-treated PDX tumors revealed several putative epigenetically regulated pathways (e.g., the Src family kinase pathway). In particular, the C-terminal Src kinase (CSK) gene was successfully validated for epigenetic regulation in different PDX models and ovarian cancer cell lines. Low CSK methylation and high CSK expression were both significantly associated (p < 0.05) with improved progression-free survival and overall survival in HGSOC patients.

Conclusions

HGSOC PDXs resemble the global epigenome of patients over many generations and can be modulated by epigenetic drugs. Novel epigenetically regulated genes such as CSK and related pathways were identified in HGSOC. Our observations encourage future application of PDXs for cancer epigenome studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13073-016-0361-5) contains supplementary material, which is available to authorized users.

A Synthetic Lethality Screen Using a Focused siRNA Library to Identify Sensitizers to Dasatinib Therapy for the Treatment of Epithelial Ovarian Cancer

Molecular targeted therapies have been the focus of recent clinical trials for the treatment of patients with recurrent epithelial ovarian cancer (EOC). The majority have not fared well as monotherapies for improving survival of these patients. Poor bioavailability, lack of predictive biomarkers, and the presence of multiple survival pathways can all diminish the success of a targeted agent. Dasatinib is a tyrosine kinase inhibitor of the Src-family kinases (SFK) and in preclinical studies shown to have substantial activity in EOC. However, when evaluated in a phase 2 clinical trial for patients with recurrent or persistent EOC, it was found to have minimal activity. We hypothesized that synthetic lethality screens performed using a cogently designed siRNA library would identify second-site molecular targets that could synergize with SFK inhibition and improve dasatinib efficacy. Using a systematic approach, we performed primary siRNA screening using a library focused on 638 genes corresponding to a network centered on EGFR, HER2, and the SFK-scaffolding proteins BCAR1, NEDD9, and EFS to screen EOC cells in combination with dasatinib. We followed up with validation studies including deconvolution screening, quantitative PCR to confirm effective gene silencing, correlation of gene expression with dasatinib sensitivity, and assessment of the clinical relevance of hits using TCGA ovarian cancer data. A refined list of five candidates (CSNK2A1, DAG1, GRB2, PRKCE, and VAV1) was identified as showing the greatest potential for improving sensitivity to dasatinib in EOC. Of these, CSNK2A1, which codes for the catalytic alpha subunit of protein kinase CK2, was selected for additional evaluation. Synergistic activity of the clinically relevant inhibitor of CK2, CX-4945, with dasatinib in reducing cell proliferation and increasing apoptosis was observed across multiple EOC cell lines. This overall approach to improving drug efficacy can be applied to other targeted agents that have similarly shown poor clinical activity.

Dasatinib enhances antitumor activity of paclitaxel in ovarian cancer through Src signaling

Src family tyrosine kinase (SFK) activation is associated with ovarian cancer progression. Therefore, SFKs are targets for the development of potential treatments of ovarian cancer. Dasatinib is a tyrosine kinase inhibitor that targets SFK activity, and is used for the treatment of B cell and Abelson lymphomas. At the present time, the potential effect of dasatinib on ovarian cancer is not clear. The aim of the present study was to investigate the antitumor activity of dasatinib, alone and in combination with paclitaxel, in ovarian cancer in vitro and in vivo. In the present study, the expression of Src and phospho‑Src-Y416 (p‑Src) was measured in six ovarian cancer cell lines using western blotting and immunohistochemistry. In addition, cell viability and apoptosis were measured using an MTT assay and annexin V‑fluorescein isothiocyanate staining. An ovarian cancer murine xenograft model was established, in order to evaluate the antitumor effect of dasatinib alone and in combination with paclitaxel in ovarian cancer. High levels of p‑Src protein expression were observed in all cell lines, as compared with healthy cells, which indicated activation of the Src signaling pathway. p‑Src expression increased in ovarian cancer cells following paclitaxel treatment. Dasatinib treatment demonstrated anti‑ovarian cancer properties, by downregulating p‑Src expression and by inducing cancer cell apoptosis. Combined treatment with dasatinib and paclitaxel markedly inhibited proliferation and promoted apoptosis of ovarian cancer cells, compared with control cells. Combined dasatinib and paclitaxel treatment exhibited antitumor activities in vivo and in vitro (combination indices, 0.25‑0.93 and 0.31‑0.75; and tumor growth inhibitory rates, 76.7% and 58.5%, in A2780 and HO8910 cell lines, respectively), compared with paclitaxel treatment alone. Dasatinib monotherapy demonstrated anti‑ovarian cancer activities. The effects of dasatinib and paclitaxel treatments on ovarian cancer cells appeared to be mediated by the Src pathway.

An ovarian cancer model with positive ER: Reversion of ER antagonist resistance by Src blockade

Approximately 60% of ovarian cancers are positive for the estrogen receptor (ER); however, ER-targeted treatment is disappointing due to drug resistance as compared with breast cancer. In estrogen-sensitive cancers, estrogen activates Src to phosphorylate p27 promoting its degradation and increasing cell cycle progression. Since Src is frequently activated in ovarian cancers, we investigated whether combined Src and ER blockade by saracatinib and fulvestrant would circumvent anti-estrogen resistance. In 20 out of 40 enrolled patients with immunohistochemically ER-positive ovarian cancer, phosphorylated Src (p-Src) at the site of 416 tyrosine was expressed with a propensity for metastasis and a poorer disease-free survival (DFS) at 3 years following ER antagonist treatment. The effects of ER and Src blockade on cell cycle were assayed in estrogen receptor α (ERα)-positive ovarian cancer. We observed that Src activity was fairly greater in anti-estrogen-resistant ovarian cancer cells than that in the anti-estrogen-sensitive cell line. Estrogen activated Src via ER-Src binding and ER translocation from cytoplasm to nucleus. Mitogenesis was mediated via ERα, not ERβ. Combined saracatinib and fulvestrant increased p27 and inhibited cell cycle progression. Furthermore, dual therapy induced autophagy and inhibited ovarian cancer xenograft growth more effectively than monotherapy. Saracatinib facilitated the therapeutic effects of fulvestrant by antagonizing the estrogen-mediated Src activation. These are supportive of further preclinical assessment of combined fulvestrant and saracatinib in patients with ovarian cancer.