The clinical role of epithelial-mesenchymal transition and stem cell markers in advanced-stage ovarian serous carcinoma effusions

P-cadherin overexpression is associated with early transformation of the Fallopian tube epithelium and aggressiveness of tubo-ovarian high-grade serous carcinoma

Tubo-ovarian high-grade serous carcinoma (HGSC) with proficient homologous recombination (HR) DNA repair (HRP) accounts for approximately 50% of cases and is associated with platinum-resistance and poor prognosis. We hypothesize that the acquisition of hybrid phenotypes displaying both epithelial and mesenchymal (E/M) features may be involved in the malignant transformation and tumour dissemination in this subgroup. Therefore, we analysed, by digital pathology, the expression and prognostic significance of 3 classic cadherins (E-cadherin, epithelial marker; N-cadherin, mesenchymal marker; and P-cadherin, candidate marker of hybrid E/M) in 577 formalin-fixed paraffin-embedded human samples representing the putative stepwise serous carcinogenesis in the Fallopian tube epithelium (FTE). We observed a non-canonical N-to-P-cadherin switch along the carcinogenic progression, with a statistically significant overexpression of P-cadherin in pre-malignant and malignant samples, compared to the control FTE. Interestingly, this overexpression was most pronounced in precursor lesions and HGSC cells from malignant ascites. Tumours with high P-cadherin expression were significantly associated with worse overall survival, especially in the subgroup without BRCA1/2 mutations. Transient P-cadherin knock-down resulted in in vitro significant reduction of functional hybrid E/M hallmarks, namely decreased anoikis resistance, reduced collective migration and invasion in a representative platinum-resistant HRP cell line. Taken together, our results suggest that P-cadherin overexpression is an early event in the serous carcinogenesis and may be involved in hybrid E/M activation in HRP-HGSC, further supporting this adhesion molecule as a promising biomarker for this poor prognostic subgroup.

Snail transcription factors as key regulators of chemoresistance, stemness and metastasis of ovarian cancer cells

Ovarian cancer is one of the deadliest gynecological malignancies among women. The reason for this outcome is the frequent acquisition of cancer cell resistance to platinum-based drugs and unresponsiveness to standard therapy. It has been increasingly recognized that the ability of ovarian cancer cells to adopt more aggressive behavior (mainly through the epithelial-to-mesenchymal transition, EMT), as well as dedifferentiation into cancer stem cells, significantly affects drug resistance acquisition. Transcription factors in the Snail family have been implicated in ovarian cancer chemoresistance and metastasis. In this article, we summarize published data that reveal Snail proteins not only as key inducers of the EMT in ovarian cancer but also as crucial links between the acquisition of ovarian cancer stem properties and spheroid formation. These Snail-related characteristics significantly affect the ovarian cancer cell response to treatment and are related to the acquisition of chemoresistance.

SOX11 and Epithelial-Mesenchymal Transition in Metastatic Serous Ovarian Cancer

BACKGROUND

Ovarian cancer is the leading cause of death from gynecological malignancies, with serous carcinoma being the most common histopathologic subtype. Epithelial-mesenchymal transition (EMT) correlates with increased metastatic potential, whereas the transcription factor SRY-box transcription factor 11 (SOX11) is overexpressed in diverse malignancies.

METHODS

In the present study, we aimed to evaluate the potential role of the immunohistochemical expression of SOX11 in 30 serous ovarian carcinomas in association with E-cadherin and vimentin expression as well as with patients' clinicopathological data.

RESULTS

Most of the examined cases showed concurrent expression of E-cadherin and vimentin, whereas SOX11 was expressed in a minority of the cases (26.7%). Interestingly, the positive cases more frequently had a metastatic disease at the time of diagnosis compared with the negative cases (p = 0.09), an association, however, of marginal significance. Moreover, there was a negative correlation between E-cadherin and SOX11 expression (p = 0.0077) and a positive correlation between vimentin and SOX11 expression (p = 0.0130).

CONCLUSIONS

The present work, for the first time, provides preliminary evidence of a possible implication of SOX11 overexpression in the promotion of EMT in metastatic serous ovarian cancer, thereby endorsing tumor metastasis.

"DEPHENCE" system-a novel regimen of therapy that is urgently needed in the high-grade serous ovarian cancer-a focus on anti-cancer stem cell and anti-tumor microenvironment targeted therapies

Ovarian cancer, especially high-grade serous type, is the most lethal gynecological malignancy. The lack of screening programs and the scarcity of symptomatology result in the late diagnosis in about 75% of affected women. Despite very demanding and aggressive surgical treatment, multiple-line chemotherapy regimens and both approved and clinically tested targeted therapies, the overall survival of patients is still unsatisfactory and disappointing. Research studies have recently brought some more understanding of the molecular diversity of the ovarian cancer, its unique intraperitoneal biology, the role of cancer stem cells, and the complexity of tumor microenvironment. There is a growing body of evidence that individualization of the treatment adjusted to the molecular and biochemical signature of the tumor as well as to the medical status of the patient should replace or supplement the foregoing therapy. In this review, we have proposed the principles of the novel regimen of the therapy that we called the "DEPHENCE" system, and we have extensively discussed the results of the studies focused on the ovarian cancer stem cells, other components of cancer metastatic niche, and, finally, clinical trials targeting these two environments. Through this, we have tried to present the evolving landscape of treatment options and put flesh on the experimental approach to attack the high-grade serous ovarian cancer multidirectionally, corresponding to the "DEPHENCE" system postulates.

FAP is critical for ovarian cancer cell survival by sustaining NF-κB activation through recruitment of PRKDC in lipid rafts

Fibroblast activation protein (FAP) is tumor-specific and plays an important role in tumorigenecity. However, agents against its enzymatic activity or extracellular presence were unsuccessful in the clinic for undefined reasons. Here we show that FAP expression is higher in advanced ovarian cancer and is only detected in invasive ovarian cancer cells. Silencing FAP induces apoptosis and FAP's enzymatic activity is dispensable for cell survival. To elucidate the cause of apoptosis, we find that NF-κB activity is diminished when FAP is depleted and BIRC5 (survivin) acts downstream of FAP-NF-κB axis to promote cell survival. To uncover the link between FAP and NF-κB activation, we reveal that PRKDC (DNA-PK, DNA-dependent protein kinase) forms complex with FAP and is required for NF-κB activation and cell survival. Remarkably, FAP-PRKDC interaction occurs only in lipid rafts, and depleting FAP prevents lipid raft localization of PRKDC. Given the known ability of PRKDC to direct NF-κB activation, these results suggest that FAP recruits PRKDC in lipid rafts for NF-κB activation. FAP's non-enzymatic role and functioning from lipid rafts for cell survival also offer an explanation on the failure of past FAP-targeted therapies. Finally, we demonstrate that EpCAM aptamer-delivered FAP siRNA impeded intraperitoneal xenograft development of ovary tumors.

Target Selection for T-Cell Therapy in Epithelial Ovarian Cancer: Systematic Prioritization of Self-Antigens

Adoptive T cell-receptor therapy (ACT) could represent a promising approach in the targeted treatment of epithelial ovarian cancer (EOC). However, the identification of suitable tumor-associated antigens (TAAs) as targets is challenging. We identified and prioritized TAAs for ACT and other immunotherapeutic interventions in EOC. A comprehensive list of pre-described TAAs was created and candidates were prioritized, using predefined weighted criteria. Highly ranked TAAs were immunohistochemically stained in a tissue microarray of 58 EOC samples to identify associations of TAA expression with grade, stage, response to platinum, and prognosis. Preselection based on expression data resulted in 38 TAAs, which were prioritized. Along with already published Cyclin A1, the TAAs KIF20A, CT45, and LY6K emerged as most promising targets, with high expression in EOC samples and several identified peptides in ligandome analysis. Expression of these TAAs showed prognostic relevance independent of molecular subtypes. By using a systematic vetting algorithm, we identified KIF20A, CT45, and LY6K to be promising candidates for immunotherapy in EOC. Results are supported by IHC and HLA-ligandome data. The described method might be helpful for the prioritization of TAAs in other tumor entities.

NANOG regulates epithelial–mesenchymal transition via AMPK / mTOR signalling pathway in ovarian cancer SKOV ‐3 and A2780 cells

NANOG engages with tumour initiation and metastasis by regulating the epithelial–mesenchymal transition (EMT) in epithelial ovarian cancer (EOC). However, its role in association with pAMPKα, and its clinical significance in EOC have not been elucidated even though AMPK is known to degrade NANOG in various human cancers. Hence, we investigated the role of pAMPKα and its association with NANOG as potential prognostic biomarkers in EOC. Both NANOG and pAMPKα expression were significantly overexpressed in EOCs comparing nonadjacent normal epithelial tissues, benign tissues, and borderline tumours. NANOG overexpression was significantly associated with poor disease‐free survival (DFS) and overall survival (OS), whereas pAMPKα overexpression was associated with good DFS and OS. Importantly, multivariate analysis revealed that the combination of high NANOG and low pAMPKα expression was a poor independent prognostic factor for DFS and was associated with platinum resistance. In ovarian cancer cell lines, siRNA‐mediated NANOG knockdown diminished migration and invasion properties by regulating the EMT process via the AMPK/mTOR signalling pathway. Furthermore, treatment with AMPK activator suppressed expression of stemness factors such as NANOG, Oct4 and Sox2. Collectively, these findings established that the combination of high NANOG and low pAMPKα expression was associated with EOC progression and platinum resistance, suggesting a potential prognostic biomarker for clinical management in EOC patients.

Pigment epithelium-derived factor promotes peritoneal dissemination of ovarian cancer through induction of immunosuppressive macrophages

Peritoneal dissemination of ovarian cancer (OC) correlates with poor prognosis, but the mechanisms underlying the escape of OC cells from the intraperitoneal immune system have remained unknown. We here identify pigment epithelium–derived factor (PEDF) as a promoting factor of OC dissemination, which functions through induction of CD206⁺ Interleukin-10 (IL-10)–producing macrophages. High PEDF gene expression in tumors is associated with poor prognosis in OC patients. Concentrations of PEDF in ascites and serum are significantly higher in OC patients than those with more benign tumors and correlated with early recurrence of OC patients, suggesting that PEDF might serve as a prognostic biomarker. Bromodomain and extraterminal (BET) inhibitors reduce PEDF expression and limit both OC cell survival and CD206⁺ macrophage induction in the peritoneal cavity. Our results thus implicate PEDF as a driver of OC dissemination and identify a BET protein–PEDF–IL-10 axis as a promising therapeutic target for OC.

Endogenously expressed pigment epithelium–derived factor (PEDF) promotes increased survival of ovarian cancer cells in the peritoneal cavity by inducing IL-10 expression in CD206 ⁺ peritoneal macrophages.

Multiomics characterization implicates PTK7 in ovarian cancer EMT and cell plasticity and offers strategies for therapeutic intervention

Most patients with ovarian cancer (OC) are diagnosed at a late stage when there are very few therapeutic options and a poor prognosis. This is due to the lack of clearly defined underlying mechanisms or an oncogenic addiction that can be targeted pharmacologically, unlike other types of cancer. Here, we identified protein tyrosine kinase 7 (PTK7) as a potential new therapeutic target in OC following a multiomics approach using genetic and pharmacological interventions. We performed proteomics analyses upon PTK7 knockdown in OC cells and identified novel downstream effectors such as synuclein-γ (SNCG), SALL2, and PP1γ, and these findings were corroborated in ex vivo primary samples using PTK7 monoclonal antibody cofetuzumab. Our phosphoproteomics analyses demonstrated that PTK7 modulates cell adhesion and Rho-GTPase signaling to sustain epithelial-mesenchymal transition (EMT) and cell plasticity, which was confirmed by high-content image analysis of 3D models. Furthermore, using high-throughput drug sensitivity testing (525 drugs) we show that targeting PTK7 exhibited synergistic activity with chemotherapeutic agent paclitaxel, CHK1/2 inhibitor prexasertib, and PLK1 inhibitor GSK461364, among others, in OC cells and ex vivo primary samples. Taken together, our study provides unique insight into the function of PTK7, which helps to define its role in mediating aberrant Wnt signaling in ovarian cancer.

Cancer Stem Cells in Ovarian Cancer-A Source of Tumor Success and a Challenging Target for Novel Therapies

Ovarian cancer is the most lethal neoplasm of the female genital organs. Despite indisputable progress in the treatment of ovarian cancer, the problems of chemo-resistance and recurrent disease are the main obstacles for successful therapy. One of the main reasons for this is the presence of a specific cell population of cancer stem cells. The aim of this review is to show the most contemporary knowledge concerning the biology of ovarian cancer stem cells (OCSCs) and their impact on chemo-resistance and prognosis in ovarian cancer patients, as well as to present the treatment options targeted exclusively on the OCSCs. The review presents data concerning the role of cancer stem cells in general and then concentrates on OCSCs. The surface and intracellular OCSCs markers and their meaning both for cancer biology and clinical prognosis, signaling pathways specifically activated in OCSCs, the genetic and epigenetic regulation of OCSCs function including the recent studies on the non-coding RNA regulation, cooperation between OCSCs and the tumor microenvironment (ovarian cancer niche) including very specific environment such as ascites fluid, the role of shear stress, autophagy and metabolic changes for the function of OCSCs, and finally mechanisms of OCSCs escape from immune surveillance, are described and discussed extensively. The possibilities of anti-OCSCs therapy both in experimental settings and in clinical trials are presented, including the recent II phase clinical trials and immunotherapy. OCSCs are a unique population of cancer cells showing a great plasticity, self-renewal potential and resistance against anti-cancer treatment. They are responsible for the progression and recurrence of the tumor. Several completed and ongoing clinical trials have tested different anti-OCSCs drugs which, however, have shown unsatisfactory efficacy in most cases. We propose a novel approach to ovarian cancer diagnosis and therapy.

Prognostic value of E-Cadherin and its tumor suppressor role in Saudi women with advanced epithelial ovarian cancer

The extracellular matrix (ECM) disruption and cytoskeleton reorganization are crucial events in tumor proliferation and invasion. E-Cadherin (E-CAD) is a member of cell adhesion molecules involved in cell-cell junctions and ECM stability. The loss of E-CAD expression is associated with cancer progression and metastasis. This retrospective study aimed to assess E-CAD protein expression in ovarian cancer (OC) tissues and to evaluate its prognostic value. Patients and Methods: 143 formalin-fixed and paraffin-embedded (FFPE) blocks of primary advanced stages OC were retrieved and used to construct Tissue microarrays. Automated immunohistochemistry technique was performed to evaluate E-CAD protein expression patterns in OC. Results: E-CAD protein expression was significantly correlated with OC histological subtype (p < 0.0001), while borderline significant correlations were observed with both tumor grade (p = 0.06) and stage (p = 0.07). Interestingly, Kaplan-Meier survival analysis showed that OC patients with membranous E-CAD expression survived longer than those with no E-CAD expression mainly those at advanced stages (p < 0.009). Further in silico analysis confirms the key roles of E-CAD in OC molecular functions. Conclusion: we reported a prognosis value of membranous E-CAD in advanced stage OC patients. Further validation using larger cohorts is recommended to extract clinically relevant outcomes towards better OC management and individualized oncology.

A Keratin 7 and E-Cadherin Signature Is Highly Predictive of Tubo-Ovarian High-Grade Serous Carcinoma Prognosis

During tubo-ovarian high-grade serous carcinoma (HGSC) progression, tumoral cells undergo phenotypic changes in their epithelial marker profiles, which are essential for dissemination processes. Here, we set out to determine whether standard epithelial markers can predict HGSC patient prognosis. Levels of E-CADH, KRT7, KRT18, KRT19 were quantified in 18 HGSC cell lines by Western blot and in a Discovery cohort tissue microarray (TMA) (n = 101 patients) using immunofluorescence. E-CADH and KRT7 levels were subsequently analyzed in the TMA of the Canadian Ovarian Experimental Unified Resource cohort (COEUR, n = 1158 patients) and in public datasets. Epithelial marker expression was highly variable in HGSC cell lines and tissues. In the Discovery cohort, high levels of KRT7 and KRT19 were associated with an unfavorable prognosis, whereas high E-CADH expression indicated a better outcome. Expression of KRT7 and E-CADH gave a robust combination to predict overall survival (OS, p = 0.004) and progression free survival (PFS, p = 5.5 × 10⁻⁴) by Kaplan–Meier analysis. In the COEUR cohort, the E-CADH-KRT7 signature was a strong independent prognostic biomarker (OS, HR = 1.6, p = 2.9 × 10⁻⁴; PFS, HR = 1.3, p = 0.008) and predicted a poor patient response to chemotherapy (p = 1.3 × 10⁻⁴). Our results identify a combination of two epithelial markers as highly significant indicators of HGSC patient prognosis and treatment response.

Revisiting chemoresistance in ovarian cancer: Mechanism, biomarkers, and precision medicine

Among the gynecological cancers, ovarian cancer is the most lethal. Its therapeutic options include a combination of chemotherapy with platinum-based compounds and cytoreductive surgery. Most ovarian cancer patients exhibit an initial response to platinum-based therapy, however, platinum resistance has led to up to 80% of this responsive cohort becoming refractory. Ovarian cancer recurrence and drug resistance to current chemotherapeutic options is a global challenge. Chemo-resistance is a complex phenomenon that involves multiple genes and signal transduction pathways. Therefore, it is important to elucidate on the underlying molecular mechanisms involved in chemo-resistance. This inform decisions regarding therapeutic management and help in the identification of novel and effective drug targets. Studies have documented the individual biomarkers of platinum-resistance in ovarian cancer that are potential therapeutic targets. This review summarizes the molecular mechanisms of platinum resistance in ovarian cancer, novel drug targets, and clinical outcomes.

Expression of palladin is associated with disease progression in metastatic high-grade serous carcinoma

OBJECTIVE

To analyse the expression and clinical role of the actin-associated molecule palladin in serous effusions.

METHODS

PALLD mRNA expression was analysed by quantitative reverse transcription polymerase chain reaction in 83 high-grade serous carcinoma (HGSC) effusions. Fifteen malignant mesothelioma (MM) effusions and 18 surgical HGSC specimens from the ovary were studied for comparative purposes. Palladin protein expression by immunohistochemistry was analysed in another series consisting of 261 HGSC effusions.

RESULTS

PALLD mRNA was significantly overexpressed in HGSC compared to MM effusions (P < .001). Palladin expression by immunohistochemistry was found in HGSC cells in 106/261 (41%) effusions, most commonly focally (<5% of cells). PALLD expression was additionally higher in ovarian HGSC specimens compared to HGSC effusions (P < .001). However, immunohistochemistry showed only stromal expression of this protein in surgical specimens. PALLD mRNA expression in HGSC effusions was unrelated to clinicopathological parameters, chemotherapy response or survival. Palladin protein expression was higher in post-chemotherapy, mainly disease recurrence, specimens compared to chemo-naïve effusions tapped at diagnosis (P = .018), although it was unrelated to other clinicopathological parameters or survival.

CONCLUSION

PALLD mRNA is overexpressed in HGSC compared to MM effusions, and its protein product is overexpressed in post-chemotherapy compared to pre-chemotherapy HGSC effusions, suggesting upregulation along tumour progression. The presence of this molecule in HGSC effusions, at the mRNA or the protein level, is unrelated to disease outcome.

Targeting Notch signaling pathway as an effective strategy in overcoming drug resistance in ovarian cancer

Ovarian cancer, as one of the most common types of gynecological malignancies, has an increasing rate of incidence worldwide. Despite huge amounts of recent efforts in designing novel therapeutic strategies for complete removal of tumors and increasing overall survival of patients, chemotherapy is still the preferred therapy for ovarian cancer. However, chemotherapy is also challenged by development of drug resistance. Therefore, elucidating the underlying mechanisms of drug reissuance is an urgent need in ovarian cancer. Numerous studies have shown the implication of the Notch signaling pathway in the development of various human malignancies. Therefore, this study will provide a brief overview of the published evidence in support of Notch targeting in reverting multidrug resistance as a safer and novel approach for the improvement of ovarian cancer treatment.

Overcoming cisplatin resistance by targeting the MTDH-PTEN interaction in ovarian cancer with sera derived from rats exposed to Guizhi Fuling wan extract

Background

The well-known traditional Chinese herbal formula Guizhi Fuling Wan (GFW) was recently reported to improve the curative effects of chemotherapy for ovarian cancer with few clinical side effects. The present study aimed to investigate the reversal mechanism of sera derived from rats exposed to Guizhi Fuling Wan extract (GFWE) in cisplatin-resistant human ovarian cancer SKOV3/DDP cells; the proteins examined included phosphatase and tensin homolog (PTEN) and metadherin (MTDH), and the possible protein interaction between PTEN and MTDH was explored.

Methods

GFWE was administered to healthy Wistar rats, and the sera were collected after five days. The PubMed and CNKI databases were searched for literature on the bioactive blood components in the sera. The systemsDock website was used to predict potential PTEN/MTDH interactions with the compounds. RT-qPCR, western blotting, and immunofluorescence analyses were used to analyze the mRNA and protein levels of MTDH and PTEN. Laser confocal microscopy and coimmunoprecipitation (co-IP) were used to analyze the colocalization and interaction between MTDH and PTEN.

Results

Sixteen bioactive compounds were identified in GFWE sera after searching the PubMed and CNKI databases. The systemsDock website predicted the potential PTEN/MTDH interactions with the compounds. RT-qPCR, western blotting, and immunofluorescence analyses showed decreased MTDH expression and increased PTEN expression in the sera. Laser confocal microscopy images and coimmunoprecipitation (co-IP) analyses demonstrated that a colocalization and interaction occurred between MTDH and PTEN, and the addition of the sera changed the interaction status.

Conclusions

GFWE restored sensitivity to cisplatin by inhibiting MTDH expression, inducing PTEN expression, and improving the interaction between MTDH and PTEN in SKOV3/DDP cells, and these proteins and their interaction may serve as potential targets for cancer treatment. The sera may represent a new source of anticancer compounds that could help to manage chemoresistance more efficiently and safely.

L1 Cell Adhesion Molecule Confers Radioresistance to Ovarian Cancer and Defines a New Cancer Stem Cell Population

Many solid tumors, including ovarian cancer, contain small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and play a role in disease recurrence. We demonstrated that the L1 cell adhesion molecule (L1CAM) is a new CSC target in ovarian cancer, triggering radioresistance. Using fluorescence-activated cell sorting, specific cell populations expressing L1CAM alone or in combination with the established CSC marker CD133 were isolated from three ovarian cancer cell lines. Double-positive L1CAM+/CD133+ cells displayed higher spherogenic and clonogenic properties in comparison to L1CAM-/CD133- cells. Furthermore, L1CAM+/CD133+ cells retained highest clonogenic capacity after irradiation and exhibited up-regulation of some CSC-specific genes, enhanced tumor-initiating capacity, self-renewal and higher tumor take rate in nude mice when compared with other cell populations. Superior radioresistance by L1CAM expression was confirmed by deletion of L1CAM using CRISPR-Cas9 technology. Moreover, we found expression signatures associated with epithelial-to-mesenchymal transition phenotype in L1CAM deleted cells. These results indicate that L1CAM in combination with CD133 defines a new cancer cell population of ovarian tumor-initiating cells with the implication of targeting L1CAM as a novel therapeutic approach for ovarian CSCs.

NCAM1/FGF module serves as a putative pleuropulmonary blastoma therapeutic target

Pleuropulmonary blastoma (PPB) is a rare pediatric lung neoplasm that recapitulates developmental pathways of early embryonic lungs. As lung development proceeds with highly regulated mesenchymal-epithelial interactions, a DICER1 mutation in PPB generates a faulty lung differentiation program with resultant biphasic tumors composed of a primitive epithelial and mesenchymal stroma with early progenitor blastomatous cells. Deciphering of PPB progression has been hampered by the difficulty of culturing PPB cells, and specifically progenitor blastomatous cells. Here, we show that in contrast with in-vitro culture, establishment of PPB patient-derived xenograft (PDX) in NOD-SCID mice selects for highly proliferating progenitor blastoma overexpressing critical regulators of lung development and multiple imprinted genes. These stem-like tumors were sequentially interrogated by gene profiling to show a FGF module that is activated alongside Neural cell adhesion molecule 1 (NCAM1). Targeting the progenitor blastoma and these transitions with an anti-NCAM1 immunoconjugate (Lorvotuzumab mertansine) inhibited tumor growth and progression providing new paradigms for PPB therapeutics. Altogether, our novel in-vivo PPB xenograft model allowed us to enrich for highly proliferating stem-like cells and to identify FGFR and NCAM1 as two key players that can serve as therapeutic targets in this poorly understood and aggressive disease.

Oncological role of HMGA2 (Review)

The high mobility group A2 (HMGA2) protein is a non‑histone architectural transcription factor that modulates the transcription of several genes by binding to AT‑rich sequences in the minor groove of B‑form DNA and alters the chromatin structure. As a result, HMGA2 influences a variety of biological processes, including the cell cycle process, DNA damage repair process, apoptosis, senescence, epithelial‑mesenchymal transition and telomere restoration. In addition, the overexpression of HMGA2 is a feature of malignancy, and its elevated expression in human cancer predicts the efficacy of certain chemotherapeutic agents. Accumulating evidence has suggested that the detection of HMGA2 can be used as a routine procedure in clinical tumour analysis.

Presence and role of stem cells in ovarian cancer

Ovarian cancer is the deadliest gynecological malignancy. It is typically diagnosed at advanced stages of the disease, with metastatic sites disseminated widely within the abdominal cavity. Ovarian cancer treatment is challenging due to high disease recurrence and further complicated pursuant to acquired chemoresistance. Cancer stem cell (CSC) theory proposes that both tumor development and progression are driven by undifferentiated stem cells capable of self-renewal and tumor-initiation. The most recent evidence revealed that CSCs in terms of ovarian cancer are not only responsible for primary tumor growth, metastasis and relapse of disease, but also for the development of chemoresistance. As the elimination of this cell population is critical for increasing treatment success, a deeper understanding of ovarian CSCs pathobiology, including epithelial-mesenchymal transition, signaling pathways and tumor microenvironment, is needed. Finally, before introducing new therapeutic agents for ovarian cancer, targeting CSCs, accurate identification of different ovarian stem cell subpopulations, including the very small embryonic-like stem cells suggested as progenitors, is necessary. To these ends, reliable markers of ovarian CSCs should be identified. In this review, we present the current knowledge and a critical discussion concerning ovarian CSCs and their clinical role.

Inhibition of PI3K/Akt/mTOR signaling pathway alleviates ovarian cancer chemoresistance through reversing epithelial-mesenchymal transition and decreasing cancer stem cell marker expression

Background

Ovarian cancer is the most common malignant tumor of the female reproductive tract. Chemoresistance is a major challenge for current ovarian cancer therapy. However, the mechanism underlying epithelial ovarian cancer (EOC) chemoresistance is not completely uncovered. The phosphatidylinositol-3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling is an important intracellular pathway in regulating cell cycle, quiescence, and proliferation. The aim of this study is to investigate the role of PI3K/Akt/mTOR signaling pathway and its association with epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) marker expression in EOC chemoresistance.

Methods

The expressions of EMT and CSC markers were detected by immunofluorescence, western blot, and quantitative real-time PCR. BEZ235, a dual PI3K/mTOR inhibitor, was employed to investigate the role of PI3K/Akt/ mTOR signaling in regulating EMT and CSC marker expression. Students’ t test and one-way ANOVA with Tukey’s post-hoc test were used to compare the data from different groups.

Results

We found that EMT and CSC marker expression were significantly enhanced in chemoresistant EOC cells, which was accompanied by the activation of PI3K/Akt/mTOR signaling. Compared with single cisplatin treatment, combined treatment with BEZ235 and cisplatin significantly disrupted the colony formation ability, induced higher ROS level and more apoptosis in chemoresistant EOC cells. Furthermore, the combination approach effectively inhibited PI3K/Akt/mTOR signaling pathway, reversed EMT, and decreased CSC marker expression in chemoresistant EOC cells compared with cisplatin mono-treatment.

Conclusions

Our results first demonstrate that EMT and enhanced CSC marker expression triggered by activated PI3K/Akt/mTOR signaling are involved in the chemoresistance of EOC, and BEZ235 in combination with cisplatin might be a promising treatment option to reverse EOC chemoresistance.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5824-9) contains supplementary material, which is available to authorized users.

Biomarkers of platinum resistance in ovarian cancer: what can we use to improve treatment

Ovarian cancer has poor survival rates due to a combination of diagnosis at advanced disease stages and disease recurrence as a result of platinum chemotherapy resistance. High-grade serous ovarian cancer (HGSOC), the most common ovarian cancer subtype, is conventionally treated with surgery and paclitaxel/carboplatin combination chemotherapy. Initial response rates are 60-80%, but eventually the majority of patients become platinum-resistant with subsequent relapses. Extensive research on individual biomarkers of platinum resistance has revealed many potential targets for the development new treatments. While this is ongoing, there are also epigenetic, DNA repair, genome and immune changes characterised in platinum-resistant HGSOC that can be targeted with current therapies. This review discusses biomarkers of platinum chemotherapy resistance in ovarian cancer with a focus on biomarkers that are targetable with alternative treatment combinations to those currently used. After decades of research focused on elucidating the biological cause of platinum resistance, future research needs to focus on using this knowledge to overcome resistance for patients with ovarian cancer.

Patient-derived ovarian cancer xenografts re-growing after a cisplatinum treatment are less responsive to a second drug re-challenge: a new experimental setting to study response to therapy

Even if ovarian cancer patients are very responsive to a cisplatinum-based therapy, most will relapse with a resistant disease. New experimental animal models are needed to explore the mechanisms of resistance, to better tailor treatment and improve patient prognosis. To address these aims, seven patient-derived high-grade serous/endometrioid ovarian cancer xenografts were characterized for the antitumor response after one and two cycles of cisplatinum and classified as Very Responsive, Responsive, and Low Responsive to drug treatment. Xenografts re-growing after the first drug cycle were much less responsive to the second one. The expression of epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) genes was investigated in cisplatinum-treated and not-treated tumors. We found that different EMT (TCF3, CAMK2N1, EGFR, and IGFBP4) and CSCs (SMO, DLL1, STAT3, and ITGA6) genes were expressed at higher levels in Low Responsive than in Responsive and Very Responsive xenografts. The expression of STAT3 was found to be associated with lower survival (HR = 13.7; p = 0.013) in the TCGA patient data set. MMP9, CD44, DLL4, FOXP1, MERTK, and PTPRC genes were found more expressed in tumors re-growing after cisplatinum treatment than in untreated tumors. We here describe a new in vivo ovarian carcinoma experimental setting that will be instrumental for specific trials of combination therapy to counteract cisplatinum resistance in order to improve the prognosis of ovarian patients.

Splicing factor ratio as an index of epithelial-mesenchymal transition and tumor aggressiveness in breast cancer

Epithelial-to-mesenchymal transition (EMT) has been shown to be associated with tumor progression and metastasis. During this process in breast cancer, a crucial role is played by alternative splicing systems. To identify a new early prognostic marker of metastasis, we evaluated EMT-related gene expression in breast cell lines, and in primary tumor tissue from 31 patients with early breast cancer, focusing our attention on EMT-related splicing factors ESRP1, ESRP2 and RBFOX2. Results showed that the expression patterns of these genes were indicative of the onset of EMT in in-vitro models, but not in tissue samples. However, the ratio between ESRP1 or ESRP2 and RBFOX2 significantly decreased during EMT and positively correlated with the EMT-specific phenotype in cell models, representing a promising prognostic markers. Low ESRP1/RBFOX2 ratio value was associated with a higher risk of metastasis (p < 0.005) in early breast cancer patients, regardless other clinical features. A cut-off of ratio of 1.067 was determined by ROC curve analysis (AUC 0.8375; 95% CI 0.6963-0.9787). Our study show evidence that a decrease in this ratio correlates with cancer progression. The results provide a rationale for using ESRP1/RBFOX2 ratio as a new prognostic biomarker for the early prediction of metastatic potential in breast cancer.

Targeting epithelial-mesenchymal transition and cancer stem cells for chemoresistant ovarian cancer

Chemoresistance is the main challenge for the recurrent ovarian cancer therapy and responsible for treatment failure and unfavorable clinical outcome. Understanding mechanisms of chemoresistance in ovarian cancer would help to predict disease progression, develop new therapies and personalize systemic therapy. In the last decade, accumulating evidence demonstrates that epithelial-mesenchymal transition and cancer stem cells play important roles in ovarian cancer chemoresistance and metastasis. Treatment of epithelial-mesenchymal transition and cancer stem cells holds promise for improving current ovarian cancer therapies and prolonging the survival of recurrent ovarian cancer patients in the future. In this review, we focus on the role of epithelial-mesenchymal transition and cancer stem cells in ovarian cancer chemoresistance and explore the therapeutic implications for developing epithelial-mesenchymal transition and cancer stem cells associated therapies for future ovarian cancer treatment.

Ovarian Cancers: Genetic Abnormalities, Tumor Heterogeneity and Progression, Clonal Evolution and Cancer Stem Cells

Four main histological subtypes of ovarian cancer exist: serous (the most frequent), endometrioid, mucinous and clear cell; in each subtype, low and high grade. The large majority of ovarian cancers are diagnosed as high-grade serous ovarian cancers (HGS-OvCas). TP53 is the most frequently mutated gene in HGS-OvCas; about 50% of these tumors displayed defective homologous recombination due to germline and somatic BRCA mutations, epigenetic inactivation of BRCA and abnormalities of DNA repair genes; somatic copy number alterations are frequent in these tumors and some of them are associated with prognosis; defective NOTCH, RAS/MEK, PI3K and FOXM1 pathway signaling is frequent. Other histological subtypes were characterized by a different mutational spectrum: LGS-OvCas have increased frequency of BRAF and RAS mutations; mucinous cancers have mutation in ARID1A, PIK3CA, PTEN, CTNNB1 and RAS. Intensive research was focused to characterize ovarian cancer stem cells, based on positivity for some markers, including CD133, CD44, CD117, CD24, EpCAM, LY6A, ALDH1. Ovarian cancer cells have an intrinsic plasticity, thus explaining that in a single tumor more than one cell subpopulation, may exhibit tumor-initiating capacity. The improvements in our understanding of the molecular and cellular basis of ovarian cancers should lead to more efficacious treatments.

Small RNAs and the competing endogenous RNA network in high grade serous ovarian cancer tumor spread

High grade serous ovarian cancer (HGSOC) is among the most deadly malignancies in women, frequently involving peritoneal tumor spread. Understanding molecular mechanisms of peritoneal metastasis is essential to develop urgently needed targeted therapies. We described two peritoneal tumor spread types in HGSOC apparent during surgery: miliary (numerous millet-sized implants) and non-miliary (few big, bulky implants). The former one is defined by a more epithelial-like tumor cell characteristic with less immune cell reactivity and with significant worse prognosis, even if corrected for typical clinicopathologic factors.

23 HGSOC patients were enrolled in this study. Isolated tumor cells from fresh tumor tissues of ovarian and peritoneal origin and from ascites were used for ribosomal RNA depleted RNA and small RNA sequencing. RT-qPCR was used to validate results and an independent cohort of 32 patients to validate the impact on survival. Large and small RNA sequencing data were integrated and a new gene-miRNA set analysis method was developed.

Thousands of new small RNAs (miRNAs and piwi-interacting RNAs) were predicted and a 13 small RNA signature was developed to predict spread type from formalin-fixed paraffin-embedded tissues. Furthermore, integrative analyses of RNA sequencing and small RNA sequencing data revealed a global upregulation of the competing endogenous RNA network in tumor tissues of non-miliary compared to miliary spread, i.e. higher expression of circular RNAs and long non-coding RNAs compared to coding RNAs but unchanged abundance of small RNAs. This global deregulated expression pattern could be co-responsible for the spread characteristic, miliary or non-miliary, in ovarian cancer.

CD56 (Neural Cell Adhesion Molecule) Expression in Ovarian Carcinomas: Association With High-Grade and Advanced Stage But Not With Neuroendocrine Differentiation

OBJECTIVE

Neural cell adhesion molecule (CD56) has been proposed as a potential marker for neuroendocrine differentiation in carcinomas, together with synaptophysin and chromogranin A. However, CD56 immunoreactivity by itself can be found in a broad variety of tumors, including ovarian neoplasms. CD56 has recently been suggested as a potential target for antibody-based therapy. However, for ovarian carcinoma, there is only limited data available regarding the pattern of CD56 immunoreactivity, coexpression of neuroendocrine markers, and correlation with histological types and clinical parameters.

METHODS

In our study, we therefore evaluated CD56 staining by immunohistochemistry on a tissue micrroarray with 206 ovarian carcinomas, including 151 high-grade serous, 7 low-grade serous, 32 endometrioid, 11 clear cell, 5 mucinous, as well as 33 atypically proliferating serous tumors/serous borderline tumors.

RESULTS

At least focal CD56 immunoreactivity was observed in 65% of carcinomas of all histological types. Moderate staining with at least 10% positive cells was found in 44 (28%) high-grade serous carcinomas (HGSOCs), 2 (29%) low-grade serous and 3(9%) endometrioid carcinomas. Strong immunoreactivity was limited to 10 (7%) HGSOCs. There was no correlation with the expression of chromogranin or synaptophysin. Serous borderline tumors showed only weak and focal staining in 11 (33%). Expression of CD56 overall was significantly associated with high-grade and advanced stage. In the subgroup of HGSOCs, CD56 expression was associated with reduced overall survival (median 30 vs. 47 months, P = 0.039, log rank, univariate analysis).

CONCLUSIONS

CD56 (neural cell adhesion molecule) is frequently expressed in ovarian carcinomas and is significantly associated with HGSOC and advanced tumor stage. Due to its lack of correlation with neuroendocrine differentiation, CD56 expression is of limited diagnostic value, but may rather serve as a marker for tumor progression or as a potential therapeutic target.

E-cadherin: A determinant molecule associated with ovarian cancer progression, dissemination and aggressiveness

Ovarian cancer (OC) is the fifth cancer death cause in women worldwide. The malignant nature of this disease stems from its unique dissemination pattern. Epithelial-to-mesenchymal transition (EMT) has been reported in OC and downregulation of Epithelial cadherin (E-cadherin) is a hallmark of this process. However, findings on the relationship between E-cadherin levels and OC progression, dissemination and aggressiveness are controversial. In this study, the evaluation of E-cadherin expression in an OC tissue microarray revealed its prognostic value to discriminate between advanced- and early-stage tumors, as well as serous tumors from other histologies. Moreover, E-cadherin, Neural cadherin (N-cadherin), cytokeratins and vimentin expression was assessed in TOV-112, SKOV-3, OAW-42 and OV-90 OC cell lines grown in monolayers and under anchorage-independent conditions to mimic ovarian tumor cell dissemination, and results were associated with cell aggressiveness. According to these EMT-related markers, cell lines were classified as mesenchymal (M; TOV-112), intermediate mesenchymal (IM; SKOV-3), intermediate epithelial (IE; OAW-42) and epithelial (E; OV-90). M- and IM-cells depicted the highest migration capacity when grown in monolayers, and aggregates derived from M- and IM-cell lines showed lower cell death, higher adhesion to extracellular matrices and higher invasion capacity than E- and IE-aggregates. The analysis of E-cadherin, N-cadherin, cytokeratin 19 and vimentin mRNA levels in 20 advanced-stage high-grade serous human OC ascites showed an IM phenotype in all cases, characterized by higher proportions of N- to E-cadherin and vimentin to cytokeratin 19. In particular, higher E-cadherin mRNA levels were associated with cancer antigen 125 levels more than 500 U/mL and platinum-free intervals less than 6 months. Altogether, E-cadherin expression levels were found relevant for the assessment of OC progression and aggressiveness.

E-cadherin: A determinant molecule associated with ovarian cancer progression, dissemination and aggressiveness

Ovarian cancer (OC) is the fifth cancer death cause in women worldwide. The malignant nature of this disease stems from its unique dissemination pattern. Epithelial-to-mesenchymal transition (EMT) has been reported in OC and downregulation of Epithelial cadherin (E-cadherin) is a hallmark of this process. However, findings on the relationship between E-cadherin levels and OC progression, dissemination and aggressiveness are controversial. In this study, the evaluation of E-cadherin expression in an OC tissue microarray revealed its prognostic value to discriminate between advanced- and early-stage tumors, as well as serous tumors from other histologies. Moreover, E-cadherin, Neural cadherin (N-cadherin), cytokeratins and vimentin expression was assessed in TOV-112, SKOV-3, OAW-42 and OV-90 OC cell lines grown in monolayers and under anchorage-independent conditions to mimic ovarian tumor cell dissemination, and results were associated with cell aggressiveness. According to these EMT-related markers, cell lines were classified as mesenchymal (M; TOV-112), intermediate mesenchymal (IM; SKOV-3), intermediate epithelial (IE; OAW-42) and epithelial (E; OV-90). M- and IM-cells depicted the highest migration capacity when grown in monolayers, and aggregates derived from M- and IM-cell lines showed lower cell death, higher adhesion to extracellular matrices and higher invasion capacity than E- and IE-aggregates. The analysis of E-cadherin, N-cadherin, cytokeratin 19 and vimentin mRNA levels in 20 advanced-stage high-grade serous human OC ascites showed an IM phenotype in all cases, characterized by higher proportions of N- to E-cadherin and vimentin to cytokeratin 19. In particular, higher E-cadherin mRNA levels were associated with cancer antigen 125 levels more than 500 U/mL and platinum-free intervals less than 6 months. Altogether, E-cadherin expression levels were found relevant for the assessment of OC progression and aggressiveness.

E-cadherin: A determinant molecule associated with ovarian cancer progression, dissemination and aggressiveness

Ovarian cancer (OC) is the fifth cancer death cause in women worldwide. The malignant nature of this disease stems from its unique dissemination pattern. Epithelial-to-mesenchymal transition (EMT) has been reported in OC and downregulation of Epithelial cadherin (E-cadherin) is a hallmark of this process. However, findings on the relationship between E-cadherin levels and OC progression, dissemination and aggressiveness are controversial. In this study, the evaluation of E-cadherin expression in an OC tissue microarray revealed its prognostic value to discriminate between advanced- and early-stage tumors, as well as serous tumors from other histologies. Moreover, E-cadherin, Neural cadherin (N-cadherin), cytokeratins and vimentin expression was assessed in TOV-112, SKOV-3, OAW-42 and OV-90 OC cell lines grown in monolayers and under anchorage-independent conditions to mimic ovarian tumor cell dissemination, and results were associated with cell aggressiveness. According to these EMT-related markers, cell lines were classified as mesenchymal (M; TOV-112), intermediate mesenchymal (IM; SKOV-3), intermediate epithelial (IE; OAW-42) and epithelial (E; OV-90). M- and IM-cells depicted the highest migration capacity when grown in monolayers, and aggregates derived from M- and IM-cell lines showed lower cell death, higher adhesion to extracellular matrices and higher invasion capacity than E- and IE-aggregates. The analysis of E-cadherin, N-cadherin, cytokeratin 19 and vimentin mRNA levels in 20 advanced-stage high-grade serous human OC ascites showed an IM phenotype in all cases, characterized by higher proportions of N- to E-cadherin and vimentin to cytokeratin 19. In particular, higher E-cadherin mRNA levels were associated with cancer antigen 125 levels more than 500 U/mL and platinum-free intervals less than 6 months. Altogether, E-cadherin expression levels were found relevant for the assessment of OC progression and aggressiveness.

Hic-5 regulates epithelial to mesenchymal transition in ovarian cancer cells in a TGFβ1-independent manner

The molecular basis of epithelial ovarian cancer (EOC) dissemination is still poorly understood. We have previously identified the hydrogen peroxide-inducible clone-5 (Hic-5) gene as hypomethylated in high-grade (HG) serous EOC tumors, compared to normal ovarian tissues. Hic-5 is a focal adhesion scaffold protein and has been primarily studied for its role as a key mediator of TGF-β–induced epithelial-to-mesenchymal transition (EMT) in epithelial cells of both normal and malignant origin; however, its role in EOC has been never investigated.

Here we demonstrate that Hic-5 is overexpressed in advanced EOC, and that Hic-5 is upregulated upon TGFβ1 treatment in the EOC cell line with epithelial morphology (A2780s), associated with EMT induction. However, ectopic expression of Hic-5 in A2780s cells induces EMT independently of TGFβ1, accompanied with enhancement of cellular proliferation rate and migratory/invasive capacity and increased resistance to chemotherapeutic drugs. Moreover, Hic-5 knockdown in the EOC cells with mesenchymal morphology (SKOV3) was accompanied by induction of mesenchymal-to-epithelial transition (MET), followed by a reduction of their proliferative, migratory/invasive capacity, and increased drugs sensitivity in vitro, as well as enhanced tumor cell colonization and metastatic growth in vivo. The modulation of Hic-5 expression in EOC cells resulted in altered regulation of numerous EMT-related canonical pathways and was indicative for a possible role of Hic-5 in controlling EMT through a RhoA/ROCK mediated mechanism.

To our knowledge, this is the first report examining the role of Hic-5 in EOC, and its role in maintaining the mesenchymal phenotype of EOC cells independently of exogenous TGFβ1 treatment.

Ovarian cancer stem cells: still an elusive entity?

The cancer stem cell (CSC) model proposes that tumor development and progression are fueled and sustained by undifferentiated cancer cells, endowed with self-renewal and tumor-initiating capacity. Ovarian carcinoma, based on its biological features and clinical evolution, appears as a prototypical example of CSC-driven disease. Indeed, ovarian cancer stem cells (OCSC) would account not only for the primary tumor growth, the peritoneal spread and the relapse, but also for the development of chemoresistance, thus having profound implication for the treatment of this deadly disease. In the last decade, an increasing body of experimental evidence has supported the existence of OCSC and their pathogenic role in the disease. Nevertheless, the identification of OCSC and the definition of their phenotypical and functional traits have proven quite challenging, mainly because of the heterogeneity of the disease and of the difficulties in establishing reliable biological models. A deeper understanding of OCSC pathobiology will shed light on the mechanisms that underlie the clinical behaviour of OC. In addition, it will favour the design of innovative treatment regimens that, on one hand, would counteract the resistance to conventional chemotherapy, and, on the other, would aim at the eradication of OC through the elimination of its CSC component.

Critical role of HMGA proteins in cancer cell chemoresistance

The high-mobility group A (HMGA) proteins are frequently overexpressed in human malignancies and correlate with the presence of metastases and reduced patient survival. Here, we highlight the main studies evidencing a critical role of HMGA in chemoresistance, mainly by activating Akt signaling, impairing p53 activity, and regulating the expression of microRNAs that target genes involved in the susceptibility of cancer cells to antineoplastic agents. Therefore, these studies account for the association of HMGA overexpression with patient poor outcome, indicating the impairment of HMGA as a fascinating perspective for effectively improving cancer therapy.

Epithelial-mesenchymal transition of ovarian cancer cells is sustained by Rac1 through simultaneous activation of MEK1/2 and Src signaling pathways

Epithelial-mesenchymal transition (EMT) is regarded as a crucial contributing factor to cancer progression. Diverse factors have been identified as potent EMT inducers in ovarian cancer. However, molecular mechanism sustaining EMT of ovarian cancer cells remains elusive. Here we show that the presence of SOS1/EPS8/ABI1 complex is critical for sustained EMT traits of ovarian cancer cells. Consistent with the role of SOS1/EPS8/ABI1 complex as a Rac1-specific guanine nucleotide exchange factor, depleting Rac1 results in the loss of most of mesenchymal traits in mesenchymal-like ovarian cancer cells, whereas expressing constitutively active Rac1 leads to EMT in epithelial-like ovarian cancer cells. With the aid of clinically tested inhibitors targeting various EMT-associated signaling pathways, we show that only combined treatment of mitogen-activated extracellular signal-regulated kinase 1/2 (MEK1/2) and Src inhibitors can abolish constitutively active Rac1-led EMT and mesenchymal traits displayed by mesenchymal-like ovarian cancer cells. Further experiments also reveal that EMT can be induced in epithelial-like ovarian cancer cells by co-expressing constitutively active MEK1 and Src rather than either alone. As the activities of Erk and Src are higher in ovarian cancer cells with constitutively active Rac1, we conclude that Rac1 sustains ovarian cancer cell EMT through simultaneous activation of MEK1/2 and Src signaling pathways. Importantly, we demonstrate that combined use of MEK1/2 and Src inhibitors effectively suppresses development of intraperitoneal xenografts and prolongs the survival of ovarian cancer-bearing mice. This study suggests that cocktail of MEK1/2 and Src inhibitors represents an effective therapeutic strategy against ovarian cancer progression.

Putative stem cells and epithelial-mesenchymal transition revealed in sections of ovarian tumor in patients with serous ovarian carcinoma using immunohistochemistry for vimentin and pluripotency-related markers

Background

The mechanism of aggressive character of ovarian cancer and unsuccessful treatment of women with this deadly disease has been recently explained by the theory of cancer stem cells (CSCs). It has been reported that ovarian carcinogenesis and progression of disease is associated with epithelial-mesenchymal transition (EMT). EMT, a physiological cell process during embryonic development and later in life during regeneration, could, when induced in pathological condition, generate CSCs-like cells. Until now EMT in the ovarian tissue has been mainly studied in cell cultures in vitro. The aim of this study was to focus on in situ morphological changes in the ovarian surface epithelium of tumor tissue in women with epithelial ovarian cancer after we applied the antibodies for markers of EMT vimentin and pluripotency-related markers NANOG, SOX2 and SSEA-4.

Methods

We analyzed ovarian tissue sections of 20 women with high grade serous ovarian carcinoma. After eosin and hematoxylin staining, used in standard practice, immunohistochemistry was performed for vimentin and markers of pluripotency: NANOG, SSEA-4 and SOX2. We focused on the ovarian surface epithelium in order to observe morphological changes in tumor tissue.

Results

Among epithelial cells of the ovarian surface epithelium in women with serous ovarian carcinoma we observed a population of small NANOG-positive cells with diameters of up to 5 μm and nuclei, which filled almost the entire cell volumes. These small NANOG-positive cells were in some cases concentrated in the regions with morphologically changed epithelial cells. In these regions, a population of bigger round cells with diameters of 10–15 μm with large nuclei, and positively stained for vimentin, NANOG and other markers of pluripotnecy, were released from the surface epithelium. These cells are proposed as CSCs, and possibly originate from small stem cells among epithelial cells. They formed typical cell clusters, invaded the tissue by changing their round shape into a mesenchymal-like phenotype, and contributed to the manifestation of ovarian cancer.

Conclusions

Our findings show morphological changes in the ovarian surface epithelium in tumor slides of high grade serous ovarian carcinoma and provide a new population of putative CSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-017-0306-7) contains supplementary material, which is available to authorized users.

Comparative assessment of lipid based nano-carrier systems for dendritic cell based targeting of tumor re-initiating cells in gynecological cancers

We aimed to identify an optimum nano-carrier system to deliver tumor antigen to dendritic cells (DCs) for efficient targeting of tumor reinitiating cells (TRICs) in gynecological malignancies. Different lipid based nano-carrier systems i.e. liposomes, ethosomes and solid lipid nanoparticles (SLNPs) were examined for their ability to activate DCs in allogeneic settings. Out of these three, the most optimized formulation was subjected for cationic and mannosylated surface modification and pulsed with DCs for specific targeting of tumor cells. In both allogeneic and autologous trials, SLNPs showed a strong ability to activate DCs and orchestrate specific immune responses for targeting TRICs in gynecological malignancies. Our findings suggest that the mannosylated form of SLNPs is a suitable molecular vector for DC based therapeutics. DCs pulsed with mannosylated SLNPs may be utilized as adjuvant therapy for specific removal of TRICs to benefit patients from tumor recurrence.

Integrative Analysis of Subcellular Quantitative Proteomics Studies Reveals Functional Cytoskeleton Membrane-Lipid Raft Interactions in Cancer

Lipid rafts are dynamic membrane microdomains that orchestrate molecular interactions and are implicated in cancer development. To understand the functions of lipid rafts in cancer, we performed an integrated analysis of quantitative lipid raft proteomics data sets modeling progression in breast cancer, melanoma, and renal cell carcinoma. This analysis revealed that cancer development is associated with increased membrane raft-cytoskeleton interactions, with ∼40% of elevated lipid raft proteins being cytoskeletal components. Previous studies suggest a potential functional role for the raft-cytoskeleton in the action of the putative tumor suppressors PTRF/Cavin-1 and Merlin. To extend the observation, we examined lipid raft proteome modulation by an unrelated tumor suppressor opioid binding protein cell-adhesion molecule (OPCML) in ovarian cancer SKOV3 cells. In agreement with the other model systems, quantitative proteomics revealed that 39% of OPCML-depleted lipid raft proteins are cytoskeletal components, with microfilaments and intermediate filaments specifically down-regulated. Furthermore, protein-protein interaction network and simulation analysis showed significantly higher interactions among cancer raft proteins compared with general human raft proteins. Collectively, these results suggest increased cytoskeleton-mediated stabilization of lipid raft domains with greater molecular interactions as a common, functional, and reversible feature of cancer cells.

CD24 is highly useful in differentiating high-grade serous carcinoma from benign and malignant mesothelial cells

CD24 was previously shown to be overexpressed in high-grade serous carcinoma (HGSC) effusions compared to malignant mesothelioma (MM) in gene expression array analysis. The present study validated this observation in a large series consisting of both effusions and surgical specimens. Effusions (n = 206; 100 HGSC, 16 ovarian carcinomas of other histological types, 54 breast carcinomas, 36 MM) and surgical specimens (n = 182; 117 ovarian carcinomas, 65 MM) were analyzed for CD24 expression using immunohistochemistry. CD24 was expressed in 105/116 (91%) ovarian carcinoma and 16/54 (30%) breast carcinoma effusions, while it was uniformly absent in MM (0/36; 0%; P < .001). Reactive mesothelial cells were CD24-negative in all carcinoma specimens. Comparative analysis of 117 solid primary (n = 43) and metastatic (n = 74) ovarian carcinomas and 65 solid MM specimens showed CD24 expression in 46% (54/117) of the former compared to 3% (2/65) of the latter (P < .001). Comparative analysis of ovarian carcinomas at different anatomic sites showed significantly higher CD24 expression in effusions compared to solid ovarian and metastatic lesions (P < .001), with similar results when analysis was limited to HGSC (P < .001). In conclusion, CD24 is a highly sensitive and specific marker of ovarian carcinoma in the differential diagnosis from MM and reactive mesothelium in effusions. CD24 is similarly a specific marker in surgical specimens, though with lower sensitivity. The overexpression of CD24 in ovarian carcinoma effusions compared to solid lesions may be due to the acquisition of cancer stem cell characteristics.

CD44 Splice Variant v8-10 as a Marker of Serous Ovarian Cancer Prognosis

CD44 is a transmembrane hyaluronic acid receptor gene that encodes over 100 different tissue-specific protein isoforms. The most ubiquitous, CD44 standard, has been used as a cancer stem cell marker in ovarian and other cancers. Expression of the epithelial CD44 variant containing exons v8-10 (CD44v8-10) has been associated with more chemoresistant and metastatic tumors in gastrointestinal and breast cancers, but its role in ovarian cancer is unknown; we therefore investigated its use as a prognostic marker in this disease. The gene expression profiles of 254 tumor samples from The Cancer Genome Atlas RNAseqV2 were analyzed for the presence of CD44 isoforms. A trend for longer survival was observed in patients with high expression of CD44 isoforms that include exons v8-10. Immunohistochemical (IHC) analysis of tumors for presence of CD44v8-10 was performed on an independent cohort of 210 patients with high-grade serous ovarian cancer using a tumor tissue microarray. Patient stratification based on software analysis of staining revealed a statistically significant increase in survival in patients with the highest levels of transmembrane protein expression (top 10 or 20%) compared to those with the lowest expression (bottom 10 and 20%) (p = 0.0181, p = 0.0262 respectively). Expression of CD44v8-10 in primary ovarian cancer cell lines was correlated with a predominantly epithelial phenotype characterized by high expression of epithelial markers and low expression of mesenchymal markers by qPCR, Western blot, and IHC. Conversely, detection of proteolytically cleaved and soluble extracellular domain of CD44v8-10 in patient ascites samples was correlated with significantly worse prognosis (p<0.05). Therefore, presence of transmembrane CD44v8-10 on the surface of primary tumor cells may be a marker of a highly epithelial tumor with better prognosis while enzymatic cleavage of CD44v8-10, as detected by presence of the soluble extracellular domain in ascites fluid, may be indicative of a more metastatic disease and worse prognosis.

Plakoglobin Reduces the in vitro Growth, Migration and Invasion of Ovarian Cancer Cells Expressing N-Cadherin and Mutant p53

Aberrant expression of cadherins and catenins plays pivotal roles in ovarian cancer development and progression. Plakoglobin (PG, γ-catenin) is a paralog of β-catenin with dual adhesive and signaling functions. While β-catenin has known oncogenic function, PG generally acts as a tumor/metastasis suppressor. We recently showed that PG interacted with p53 and that its growth/metastasis inhibitory function may be mediated by this interaction. Very little is known about the role of PG in ovarian cancer. Here, we investigated the in vitro tumor/metastasis suppressor effects of PG in ovarian cancer cell lines with mutant p53 expression and different cadherin profiles. We showed that the N-cadherin expressing and E-cadherin and PG deficient ES-2 cells were highly migratory and invasive, whereas OV-90 cells that express E-cadherin, PG and very little/no N-cadherin were not. Exogenous expression of PG or E-cadherin or N-cadherin knockdown in ES-2 cells (ES-2-E-cad, ES-2-PG and ES-2-shN-cad) significantly reduced their migration and invasion. Also, PG expression or N-cadherin knockdown significantly decreased ES-2 cells growth. Furthermore, PG interacted with both cadherins and with wild type and mutant p53 in normal ovarian and ES-2-PG cell lines, respectively.

Small putative NANOG, SOX2, and SSEA-4-positive stem cells resembling very small embryonic-like stem cells in sections of ovarian tissue in patients with ovarian cancer

BACKGROUND

In previous studies it has been found that in cell cultures of human adult ovaries there is a population of small stem cells with diameters of 2-4 μm, which are present mainly in the ovarian surface epithelium and are comparable to very small embryonic-like stem cells (VSELs) from bone marrow. These cells are not observed by histopathologists in the ovarian tissue due to their small size and unknown clinical significance. Because these cells express a degree of pluripotency, they might be involved in the manifestation of ovarian cancer. Therefore we studied the ovarian tissue sections in women with borderline ovarian cancer and serous ovarian carcinoma to perhaps identify the small putative stem cells in situ.

METHODS

In 27 women with borderline ovarian cancer and 20 women with high-grade serous ovarian carcinoma the ovarian tissue sections were stained, per standard practice, with eosin and hematoxylin staining and on NANOG, SSEA-4 and SOX2 markers, related to pluripotency, using immunohistochemistry. We focused on the presence and localization of small putative stem cells with diameters of up to 5 μm and with the nuclei spread over nearly the full cell volume.

RESULTS

In ovarian sections of both borderline ovarian cancer and serous ovarian carcinoma patients we were able to identify the presence of small round cells complying with the above criteria. Some of these small cells were NANOG-positive, were located among epithelial cells in the ovarian surface epithelium and as a single cell or groups of cells/clusters in typical "chambers", were found only in the presence of ovarian cancer and not in healthy ovaries and are comparable to those in fetal ovaries. We envision that these small cells could be related to NANOG-positive tumor-like structures and oocyte-like cells in similar "chambers" found in sections of cancerous ovaries, which could support their stemness and pluripotency. Further immunohistochemistry revealed a similar population of SSEA-4 and SOX2-positive cells.

CONCLUSIONS

We may conclude that putative small stem cells expressing markers, related to pluripotency, are present in the ovarian tissue sections of women with borderline ovarian cancer and high-grade serous ovarian carcinoma thus indicating their potential involvement in ovarian cancer.

Expression of zinc finger E-box-binding homeobox factor 1 in epithelial ovarian cancer: A clinicopathological analysis of 238 patients

A growing body of evidence indicates that aberrant activation of epithelial-to-mesenchymal transition (EMT) plays a key role in tumor cell invasion and metastasis. Zinc finger E-box-binding homeobox factor 1 (ZEB1), as a crucial mediator of EMT, contributes to the malignant progression of various epithelial tumors. To determine whether ZEB1 is involved in the progression of ovarian cancer, we immunohistochemically evaluated the expression of ZEB1 in 238 cases of epithelial ovarian cancer (EOC) and analyzed its associations with clinicopathological parameters. Positive expression of ZEB1 was observed in 32.8% (78/238) of EOCs and it was found to be significantly associated with advanced tumor stage (P=0.001). The survival analysis indicated that the expression of ZEB1 was associated with a poor 5-year progression-free survival (PFS) (P=0.021). A similar tendency was also observed between the expression of ZEB1 and 5-year overall survival, although it did not reach statistical significance (P=0.118). Moreover, the multivariate analysis demonstrated that ZEB1 expression was an independent risk factor for 5-year PFS in ovarian cancer. Taken together, our data provide evidence that ZEB1 may play a crucial role in promoting aggressive ovarian carcinoma progression. Therefore, ZEB1 may serve as an effectively predictive marker and a potential target for therapeutic intervention in EOC.

Expression of EphB6 in ovarian serous carcinoma is associated with grade, TNM stage and survival

BACKGROUND

Ovarian serous carcinoma (OSC) is the most common ovarian epithelial malignancy. Despite new medical and surgical advances, the overall 5-year survival for OSC remains poor. There is an important need to determine diagnostic and prognostic markers for this disease. Eph receptors are the largest known family of receptor tyrosines characterised in humans. These receptors are involved in the development and progression of various diseases including cancer. EphB6 contains kinase domains that are altered in several conserved amino acids and is catalytically inactive. The aim of the present study was to correlate the immunohistological expression of EphB6 in a cohort of patients with epithelial ovarian tumours with clinicopathological parameters and survival.

METHODS

In this study we examined the expression of EphB6 protein in 55 cases of OSC, 24 cases of benign ovarian serous tumours, 37 cases of serous borderline tumours and 20 cases with normal fallopian tubes by immunohistochemical staining with a polyclonal anti-EphB6 antibody. The relationship between EphB6 expression and pathological parameters was analysed. Kaplan-Meier survival function was used to analyse the prognosis.

RESULTS

High expression of EphB6 was observed in 100% (20/20) of normal fallopian tube samples, 100% (24/24) of benign epithelial ovarian tumours, 78% (29/37) of ovarian serous borderline tumours and 18% (10/55) of OSCs (p < 0.001). The expression of EphB6 was significantly associated with grade (p < 0.001) and TNM stage (p = 0.017). EphB6 expression was reversely related to Ki-67 (p = 0.021). The survival analysis showed that patients with negative or weak expression of EphB6 protein had a poorer outcome than those with positive expression (p = 0.046).

CONCLUSIONS

Our results show that EphB6 is a new biomarker for distinguishing high- and low-grade OSC, and may be a potential prognostic marker in OSCs.

Akt2/ZEB2 may be a biomarker for exfoliant cells in ascitic fluid in advanced grades of serous ovarian carcinoma

Ovarian cancers present a mild clinical course when diagnosed early but an aggressive pathway when diagnosed in the peri- and postmenopausal periods. However, the predictability of tumor progression is stochastic and is difficult to predict. In the present study, we hypothesized to examine the key pathways that are dysregulated to promote epithelial-mesenchymal transition in serous ovarian carcinoma. Examination of these steps would help to identify ascitic fluid with cells poised for metastasis or otherwise. We focused on examining the Akt2 expression, mainly because of its report as being overamplified in the aggressive variants of ovarian cancer, as well as TGFbeta-sensitivity of Akt2 that forms the key basis for metastasis initiation of most kinds of carcinoma. We obtained primary ovarian carcinoma samples as well as ascitic fluid and distantly metastatic ovarian carcinoma to examine the expression of Akt2. The results of the study demonstrated that in malignant exfoliated ovarian cancer cells, Smad4 expression was tremendously increased in the nuclei, suggesting nuclear translocation of Smad, which thereafter may have activated ZEB2, and thereafter genomically affected the expression of E-cadherin, myosin II, and vimentin, key components for initiating and sustaining metastasis. All of these may have been stimulated by increased cellular expression of Akt2 in metastatic variants of the serous ovarian carcinoma. The reliance on Akt2 and TGF beta signaling may also potentiate the case for Akt inhibitors or small molecule inhibitors of TGFbeta signaling like doxycycline as adjunct chemotherapy in serous ovarian carcinoma, especially the metastatic variants.