Recently identified drug resistance biomarkers in ovarian cancer

Identification of Specific Cell Subpopulations and Marker Genes in Ovarian Cancer Using Single-Cell RNA Sequencing

Objective

Ovarian cancer is the deadliest gynaecological cancer globally. In our study, we aimed to analyze specific cell subpopulations and marker genes among ovarian cancer cells by single-cell RNA sequencing (RNA-seq).

Methods

Single-cell RNA-seq data of 66 high-grade serous ovarian cancer cells were employed from the Gene Expression Omnibus (GEO). Using the Seurat package, we performed quality control to remove cells with low quality. After normalization, we detected highly variable genes across the single cells. Then, principal component analysis (PCA) and cell clustering were performed. The marker genes in different cell clusters were detected. A total of 568 ovarian cancer samples and 8 normal ovarian samples were obtained from The Cancer Genome Atlas (TCGA) database. Differentially expressed genes were identified according to ∣log2fold change (FC) | >1 and adjusted p value <0.05. To explore potential biological processes and pathways, functional enrichment analyses were performed. Furthermore, survival analyses of differentially expressed marker genes were performed.

Results

After normalization, 6000 highly variable genes were identified across the single cells. The cells were divided into 3 cell populations, including G1, G2M, and S cell cycles. A total of 1,124 differentially expressed genes were identified in ovarian cancer samples. These differentially expressed genes were enriched in several pathways associated with cancer, such as metabolic pathways, pathways in cancer, and PI3K-Akt signaling pathway. Furthermore, marker genes, STAT1, ANP32E, GPRC5A, and EGFL6, were highly expressed in ovarian cancer, while PMP22, FBXO21, and CYB5R3 were lowly expressed in ovarian cancer. These marker genes were positively associated with prognosis of ovarian cancer.

Conclusion

Our findings revealed specific cell subpopulations and marker genes in ovarian cancer using single-cell RNA-seq, which provided a novel insight into the heterogeneity of ovarian cancer.

Translational Physiology of Anti-Müllerian Hormone: Clinical Applications in Female Fertility Preservation and Cancer Treatment

Background

Whilst the ability of AMH to induce the regression of the Müllerian ducts in the male fetus is well appreciated, AMH has additional biological actions in relation to steroid biosynthesis and ovarian follicle dynamics. An understanding of the physiology of AMH illuminates the potential therapeutic utility of AMH to protect the ovarian reserve during chemotherapy and in the treatment of female malignancies. The translation of the biological actions of AMH into clinical applications is an emerging focus of research, with promising preliminary results.

Objective and Rationale

Studies indicate AMH restrains primordial follicle development, thus administration of AMH during chemotherapy may protect the ovarian reserve by preventing the mass activation of primordial follicles. As AMH induces regression of tissues expressing the AMH receptor (AMHRII), administration of AMH may inhibit growth of malignancies expressing AMHR II. This review evaluates the biological actions of AMH in females and appraises human clinical applications.

Search Methods

A comprehensive search of the Medline and EMBASE databases seeking articles related to the physiological functions and therapeutic applications of AMH was conducted in July 2021. The search was limited to studies published in English.

Outcomes

AMH regulates primordial follicle recruitment and moderates sex steroid production through the inhibition of transcription of enzymes in the steroid biosynthetic pathway, primarily aromatase and 17α-hydroxylase/17,20-lyase. Preliminary data indicates that administration of AMH to mice during chemotherapy conveys a degree of protection to the ovarian reserve. Administration of AMH at the time of ovarian tissue grafting has the potential to restrain uncontrolled primordial follicle growth during revascularization. Numerous studies demonstrate AMH induced regression of AMHR II expressing malignancies. As this action occurs via a different mechanism to traditional chemotherapeutic agents, AMH has the capacity to inhibit proliferation of chemo-resistant ovarian cancer cells and cancer stem cells.

Wider Implications

To date, AMH has not been administered to humans. Data identified in this review suggests administration of AMH would be safe and well tolerated. Administration of AMH during chemotherapy may provide a synchronistic benefit to women with an AMHR II expressing malignancy, protecting the ovarian reserve whilst the cancer is treated by dual mechanisms.

A Novel ZIP4-HDAC4-VEGFA Axis in High-Grade Serous Ovarian Cancer

Simple Summary

Despite tremendous research efforts, epithelial ovarian cancer (EOC) remains one of the most difficult cancers to detect early and treat successfully for >5-year survival. We have recently shown that ZIP4, a zinc transporter, is a novel cancer stem cell (CSC) marker and a therapeutic target for EOC. The current work focuses on developing new strategies to target ZIP4 and inhibit its CSC activities in EOC. We found that cells expressing high levels of ZIP4 were supersensitive to a group of inhibitors called HDACis. One of the major targets of these inhibitors is a protein called HDAC4. We revealed the new molecular bases for the ZIP4-HDAC4 axis and tested the efficacies of targeting this axis in the lab and in mouse models. Our study provides a new mechanistic-based targeting strategy for EOC.

Abstract

We have recently identified ZIP4 as a novel cancer stem cell (CSC) marker in high-grade serous ovarian cancer (HGSOC). While it converts drug-resistance to cisplatin (CDDP), we unexpectedly found that ZIP4 induced sensitization of HGSOC cells to histone deacetylase inhibitors (HDACis). Mechanistically, ZIP4 selectively upregulated HDAC IIa HDACs, with little or no effect on HDACs in other classes. HDAC4 knockdown (KD) and LMK-235 inhibited spheroid formation in vitro and tumorigenesis in vivo, with hypoxia inducible factor-1 alpha (HIF1α) and endothelial growth factor A (VEGFA) as functional downstream mediators of HDAC4. Moreover, we found that ZIP4, HDAC4, and HIF1α were involved in regulating secreted VEGFA in HGSOC cells. Furthermore, we tested our hypothesis that co-targeting CSC via the ZIP4-HDAC4 axis and non-CSC using CDDP is necessary and highly effective by comparing the effects of ZIP4-knockout/KD, HDAC4-KD, and HDACis, in the presence or absence of CDDP on tumorigenesis in mouse models. Our results showed that the co-targeting strategy was highly effective. Finally, data from human HGSOC tissues showed that ZIP4 and HDAC4 were upregulated in a subset of recurrent tumors, justifying the clinical relevance of the study. In summary, our study provides a new mechanistic-based targeting strategy for HGSOC.

Signaling within the epithelial ovarian cancer tumor microenvironment: the challenge of tumor heterogeneity

Epithelial ovarian cancer (EOC) is a leading cause of cancer death in women. Standard of care treatment has remained platinum-containing cytotoxic chemotherapy for over three decades. Among the central challenges in treating ovarian CA are disease recurrence and the development of chemoresistance. Survival is uniformly poor for patients with chemoresistant recurrent disease and effective therapeutic options are limited. As such, delineating the mechanisms of chemoresistance and developing targeted therapies to prevent chemoresistance from occurring are of vital importance to improving survival for patients with EOC. Attempts to characterize mechanisms of chemoresistance have implicated numerous cellular pathways, but a rift remains between pre-clinical findings and translation to improving patient survival. More recently, the interplay among different cell types within the tumor microenvironment has become central to understanding how chemoresistance may develop and may be sustained. An improved understanding of how tumor cell-intrinsic and -extrinsic pathways converge during the development of chemoresistance may improve the likelihood of successful clinical translation. This review focuses on the roles of the EOC tumor microenvironment and tumor cell heterogeneity in the development of chemoresistance. We review recent studies into mechanisms of chemoresistance as they relate to tumor microenvironment and development of novel therapeutic approaches that exploit these mechanisms to prevent or reverse chemoresistance. This review attempts to cast these latest discoveries in a clinical context by summarizing trends in ongoing clinical trials for patients with EOC.

Mutation analysis and genomic imbalances of cells found in effusion fluids from patients with ovarian cancer

Ovarian carcinomas and carcinosarcomas often cause malignant effusions, an accumulation within serous cavities of fluid containing cancer cells. Few studies have focused on the molecular alterations and genetic mechanisms behind effusion formation. The present study investigated the mutation status of TP53, PIK3CA, KRAS, HRAS, NRAS and BRAF in effusion fluids from 103 patients with ovarian cancer. In addition, array Comparative Genomic Hybridization (aCGH) analysis was performed on 20 effusions from patients with high-grade serous carcinoma (10 cases positive for TP53 mutation and 10 with TP53 wild-type). TP53 mutations, two of which were novel: c.826_830delCCTGT and c.475_476GC>TT, were identified in 44% of the cases. Mutations in KRAS, HRAS, and PIK3CA were identified in two, two and four cases, respectively. None of the effusions analysed showed NRAS or BRAF mutations. The aCGH analysis revealed highly imbalanced genomes similar to those described in primary ovarian carcinomas. No specific profile was indicated to distinguish tumors with TP53 mutations from those without. The molecular profiling of cells found in effusion fluids from patients with ovarian cancer thus showed considerable molecular heterogeneity. TP53 seems to be the most frequently mutated gene in these cells and may serve a leading role in the metastatic process.

Role of the Exosome Secretion Machinery in Ovarian Carcinoma: In Vitro and In Vivo Models

Objective. We recently reported on the expression and clinical role of molecules that mediate exosome secretion in high-grade serous carcinoma. In the present study, the biological role of these molecules was analyzed. Methods. OVCAR8 and ES-2 ovarian carcinoma cells were studied using a combination of CRISPR/Cas9 technology and two 3D in vitro models—spheroids emulating effusions and alginate scaffolds representing solid lesions. Isolation of exosomes was validated by electron microscopy. TSAP6, NSMASE2, RAB27A, and RAB27B mRNA and protein levels were analyzed using qRT-PCR and Western blotting, respectively. Tumor aggressiveness was studied in vitro using scratch assay, invasion assay, and matrix metalloproteinase (MMP) activity assay and in vivo using a mouse model. Results. In OVCAR8 cells, mRNA expression of TSAP6 and RAB27A was significantly higher in spheroids compared to scaffolds, whereas the opposite was true for NSMASE2 mRNA. In ES-2 cells, TSAP6 and RAB27B mRNA expression was significantly higher in spheroids versus scaffolds. In addition, nSMase2 and TSAP6 protein expression was significantly higher in scaffolds compared to spheroids. CRISPR-edited cells with silencing of NSMASE2, TSAP6, and RAB27A/B had reduced migration, invasion, and MMP activity. Additionally, knockout (KO) of these molecules resulted in significantly diminished exosome secretion. In vivo assay showed that when injected to mice, OVCAR8 RAB27A/B KO cells, as opposed to control OVCAR8 cells, did not form ascites or visible tumor lesions and had reduced MMP expression. Conclusion. The present study provides evidence that different models for culturing ovarian carcinoma cells affect the expression of molecules mediating exosome secretion and that these molecules have a tumor-promoting role. Silencing these molecules may consequently have therapeutic relevance in this cancer.

Expression of the cancer stem cell marker SSEA1 is associated with poor survival in metastatic high-grade serous carcinoma

The objective of the present study was to perform a quantitative analysis of cancer stem cell (CSC) marker expression in ovarian carcinoma effusions. The clinical role of SSEA1 in metastatic high-grade serous carcinoma (HGSC) was additionally analyzed. CD133, Nanog, SOX2, Oct3/4, SSEA1, and SSEA4 protein expressions were quantitatively analyzed using flow cytometry (FCM) in 24 effusions. SSEA1 expression by immunohistochemistry was analyzed in 384 HGSC effusions. Highly variable expression of CSC markers by FCM was observed, ranging from 0 to 78% of Ber-EP4-positive cells in the case of CD133, with the largest number of negative specimens seen for SSEA4. SSEA1 expression by immunohistochemistry was found in HGSC cells in 336/384 (89%) effusions, most commonly focally (< 5% of cells). SSEA1 was overexpressed in post-chemotherapy disease recurrence specimens compared with chemo-naïve HGSC effusions tapped at diagnosis (p = 0.029). In univariate survival analysis, higher SSEA1 expression was significantly associated with poor overall survival (p = 0.047) and progression-free survival (p = 0.018), though it failed to retain its prognostic role in Cox multivariate survival analysis in which it was analyzed with clinical parameters (p = 0.059 and p = 0.111 for overall and progression-free survival, respectively). In conclusion, CSC markers are variably expressed in ovarian carcinoma effusions. SSEA1 expression is associated with disease progression and poor survival in metastatic HGSC. Silencing this molecule may have therapeutic relevance in this cancer.

NCALD affects drug resistance and prognosis by acting as a ceRNA of CX3CL1 in ovarian cancer

Drug resistance, an impenetrable barrier in the treatment of ovarian cancer (OC), is often associated with poor outcomes. Hence, it is urgent to discover new factors controlling drug resistance and survival. The association between neurocalcin delta (NCALD) and cancer drug resistance is poorly understood. Here, we reveal that NCALD messenger RNA expression, probably regulated by DNA methylation and microRNAs, was significantly downregulated in at least three independent microarrays covering 633 ovarian carcinomas and 16 normal controls, which includes the Cancer Genome Atlas (TCGA) ovarian cohort. In the sub-groups of the TCGA cohort, NCALD was suppressed in 90 platinum-resistant tissues vs in 197 sensitive tissues. It is consistent with the quantitative reverse transcription polymerase chain reaction results revealing gene downregulation in carboplatin-resistant SKOV3 and HeyA8 OC cells as compared with that in controls. Low expression of NCALD predicted poor overall survival (OS) in sub-groups of 1656 patients, progression-free survival (PFS) in 1435 patients, and post-progression survival (PPS) in 782 patients according to Kaplan-Meier plotter covering 1815 OC patients. Comprehensive bioinformatic analyses strongly implicated NCALD in the regulation of drug resistance, probably via competing for endogenous RNA (ceRNA) interactions with CX3CL1 and tumor immune-microenvironment. NCALD acted as a ceRNA for CX3CL1 in 21 different cancers includes OC according to Starbase. These two genes negatively correlated with tumor purity and positively correlated with infiltration levels of neutrophils and dendritic cells in OC. The combined low expression of NCALD and CX3CL1 showed better prognosis potential for OS, PFS, and PPS in the 1815 OC patients than any of the individually tested genes. In summary, NCALD acts as a ceRNA for CX3CL1, and its downregulation may affect drug resistance and prognosis in OC. Thus, NCALD could be a new therapeutic target for anticancer therapy and a new biomarker for survival prediction in OC.

SOX2 and SOX9 are markers of clinically aggressive disease in metastatic high-grade serous carcinoma

OBJECTIVE

The aim of this study was to analyze the expression, biological role and clinical relevance of cancer stem cell markers in high-grade serous carcinoma (HGSC).

METHODS

mRNA expression by qRT-PCR of NANOG, OCT4, SOX2, SOX4, SOX9, LIN28A and LIN28B was analyzed in 134 HGSC specimens (84 effusions, 50 surgical specimens). Nanog, OCT3/4, SOX2 and SOX9 protein expression by immunohistochemistry was analyzed in 52 HGSC effusions. Nanog protein expression in exosomes from 80 HGSC effusions was studied by Western Blotting. OVCAR3 cells underwent CRISPR/Cas9 Nanog knockout (KO), and the effect of Nanog KO on migration, invasion, proliferation and proteolytic activity was analyzed in OVCAR3 and OVCAR8 cells.

RESULTS

OCT4 mRNA was overexpressed in effusions compared to solid specimens (p = 0.046), whereas SOX9 was overexpressed in the ovarian tumors compared to effusions and solid metastases (p = 0.003). Higher SOX2 and SOX9 expression was associated with primary (intrinsic) chemoresistance (p = 0.009 and p = 0.02, respectively). Higher SOX9 levels were associated with shorter overall survival in univariate (p = 0.04) and multivariate (p = 0.049) analysis. OCT3/4, SOX2 and SOX9 proteins were found in HGSC cells, whereas Nanog was detected only in exosomes. Higher SOX2 protein expression was associated with shorter overall survival in univariate analysis (p = 0.049). OVCAR cells exposed to OVCAR3 NANOG KO exosomes had reduced migration, invasion and MMP9 activity.

CONCLUSIONS

SOX2 and SOX9 mRNA levels in HGSC effusions may be markers of clinically aggressive disease. Nanog is secreted in HGSC exosomes in effusions and modulates tumor-promoting cellular processes in vitro.

Increased STAT1 Expression in High Grade Serous Ovarian Cancer Is Associated With a Better Outcome

OBJECTIVE

Recently it has been demonstrated that constitutively activated signal transducer and activator of transcription 1 (STAT1) gene expression may act as a biomarker of ovarian cancer chemotherapy response. In this study, our objective was to validate the use of STAT1 immunohistochemistry as a prognostic biomarker for disease outcome using a cohort derived from Latin America.

METHODS

We evaluated a cohort of Brazilian high-grade serous ovarian cancer, comprising 65 patients with outcome data covering more than 5 years to determine the prognostic and predictive value of STAT1 expression levels. High-grade serous ovarian cancer tumors were used to construct a tissue microarray. Exploratory analyses were conducted on clinical, histopathological, and STAT1 expression data that included descriptive statistics and Pearson correlative analyses. Survival curves for disease-free survival and overall survival were obtained by the Kaplan-Meier method, and the significance of homogeneity between the classes was assessed by log-rank statistics (Mantel-Cox).

RESULTS

High expression of STAT1 in tumors was significantly associated with improved disease-free survival (P = 0.0256) and overall survival (P = 0.0193). Proportional hazards regression analysis showed STAT1 expression had an independent effect on both disease-free survival (P = 0.0358) and overall survival (P = 0.0469).

CONCLUSIONS

These findings from a Brazilian cohort of patients with ovarian cancer reinforce the association of high STAT1 expression with better response to chemotherapy, providing additional validation of this protein as both a prognostic and predictive biomarker. Collectively, these results together with other recently published studies increase the feasibility of using the STAT1 pathway for the development of novel immunomodulator drugs that could enhance response to treatment.

Developing a Prognostic Gene Panel of Epithelial Ovarian Cancer Patients by a Machine Learning Model

Epithelial ovarian cancer patients usually relapse after primary management. We utilized the support vector machine algorithm to develop a model for the chemo-response using the Cancer Cell Line Encyclopedia (CCLE) and validated the model in The Cancer Genome Atlas (TCGA) and the GSE9891 dataset. Finally, we evaluated the feasibility of the model using ovarian cancer patients from our institute. The 10-gene predictive model demonstrated that the high response group had a longer recurrence-free survival (RFS) (log-rank test, p = 0.015 for TCGA, p = 0.013 for GSE9891 and p = 0.039 for NTUH) and overall survival (OS) (log-rank test, p = 0.002 for TCGA and p = 0.016 for NTUH). In a multivariate Cox hazard regression model, the predictive model (HR: 0.644, 95% CI: 0.436⁻0.952, p = 0.027) and residual tumor size < 1 cm (HR: 0.312, 95% CI: 0.170⁻0.573, p < 0.001) were significant factors for recurrence. The predictive model (HR: 0.511, 95% CI: 0.334⁻0.783, p = 0.002) and residual tumor size < 1 cm (HR: 0.252, 95% CI: 0.128⁻0.496, p < 0.001) were still significant factors for death. In conclusion, the patients of high response group stratified by the model had good response and favourable prognosis, whereas for the patients of medium to low response groups, introduction of other drugs or clinical trials might be beneficial.

Soluble AXL is ubiquitously present in malignant serous effusions

OBJECTIVE

The objective of this study was to analyze the expression level and clinical role of soluble AXL (sAXL) in cancers affecting the serosal surfaces, with focus on ovarian carcinoma.

METHODS

sAXL protein expression by ELISA was analyzed in 572 effusion supernatants, including 424 peritoneal, 147 pleural and 1 pericardial specimens.

RESULTS

sAXL was overexpressed in peritoneal effusions compared to pleural and pericardial specimens (p < 0.001). sAXL levels were additionally significantly higher in effusions from patients with ovarian carcinoma, malignant mesothelioma and breast carcinoma compared to specimens from patients with other cancers (predominantly carcinomas of lung, gastrointestinal or uterine corpus/cervix origin) or benign reactive effusions (p < 0.001). sAXL was further overexpressed in high-grade serous carcinoma (HGSC; n = 373) compared to low-grade serous carcinoma (LGSC; n = 32; p = 0.036). In HGSC, sAXL levels were significantly lower in post-chemotherapy effusions compared to primary diagnosis pre-chemotherapy specimens (p = 0.002). sAXL levels in HGSC were unrelated to chemoresponse at diagnosis, progression-free survival or overall survival. Levels were similarly unrelated to survival in LGSC and breast carcinoma.

CONCLUSIONS

sAXL is widely expressed in malignant effusions, particularly in ovarian and breast carcinoma and in malignant mesothelioma. sAXL is overexpressed in HGSC compared to LGSC and its levels are lower following exposure to chemotherapy. However, sAXL levels are not informative of chemoresponse or survival.

Expression and clinical role of the dipeptidyl peptidases DPP8 and DPP9 in ovarian carcinoma

Dipeptidyl peptidase 9 (DPP9) was recently identified as fusion gene in ovarian high-grade serous carcinoma (HGSC). The aim of this study was to analyze the expression and clinical relevance of DPP8 and DPP9 in ovarian carcinoma, with focus on HGSC. mRNA expression by qRT-PCR of DPP8 and DPP9 was analyzed in 232 carcinomas, including 114 effusions and 118 surgical specimens (89 ovarian, 29 solid metastases). DPP8 and DPP9 protein expression was analyzed in 92 effusions. DPP8 and DPP9 mRNA was overexpressed in effusions compared to solid lesions in analysis of all histotypes (p < 0.001 both), as well as in analysis limited to HGSC (p < 0.001 for DPP9, p = 0.002 for DPP8). DPP9 mRNA was additionally overexpressed in HGSC compared to other histotypes (p = 0.021). DPP8 and DPP9 protein was expressed in carcinoma cells in 31/92 (37%) and 81/92 (88%) effusions, respectively. DPP8 protein expression in HGSC effusions was significantly related to better (complete) chemoresponse at diagnosis (p = 0.005). DPP8 and DPP9 mRNA and protein expression was unrelated to survival in analysis of the entire effusion cohort. However, higher DPP9 mRNA levels were significantly related to longer overall survival in pre-chemotherapy effusions (p = 0.049). In conclusion, DPP8 and DPP9 mRNA is frequently expressed in ovarian carcinoma, whereas DPP9 is more frequently expressed at the protein level. DPP8 and DPP9 may be related to less aggressive disease in advanced-stage HGSC.

Activity and clinical relevance of autotaxin and lysophosphatidic acid pathways in high-grade serous carcinoma

The aim of this study was to analyze the expression, biological role and clinical relevance of autotaxin (ATX), the enzyme synthetizing lysophosphatidic acid (LPA), and LPA receptors (LPAR) in high-grade serous carcinoma (HGSC). mRNA expression by qRT-PCR of LPAR1-6 was analyzed in 155 HGSC specimens (88 effusions, 67 solid lesions). ATX mRNA expression was analyzed in 97 specimens. ATX, ERK, and AKT protein expression was studied by Western blotting. LPAR2 mRNA was overexpressed in HGSC cells in effusions compared to solid lesions, with opposite findings for LPAR3 and LPAR6 mRNA and ATX protein. Higher LPAR1 levels were significantly related to longer overall survival (OS) in pre-chemotherapy effusions (p = 0.027). Conversely, higher expression of LPAR1, LPAR2, and LPAR5 in post-chemotherapy effusions was significantly associated with shorter OS (p = 0.037, p = 0.025 and p = 0.021, respectively) and progression-free survival (PFS) (p < 0.001, p = 0.007 and p < 0.001, respectively) in univariate survival analysis. LPAR1 mRNA expression was an independent prognosticator of OS in patients with pre-chemotherapy effusions and PFS in patients with post-chemotherapy effusions (p = 0.013 both). In conclusion, LPAR mRNA and ATX protein levels are anatomic site-dependent in HGSC and the former are informative of disease outcome.

Physical interaction of STAT1 isoforms with TGF-β receptors leads to functional crosstalk between two signaling pathways in epithelial ovarian cancer

BACKGROUND

The signal transducer and activator of transcription (STAT) and transforming growth factor-β (TGF-β) signaling pathways play important roles in epithelial ovarian cancer (EOC). However, the mechanism of crosstalk between two pathways is not completely understood.

METHODS

The expression of STAT1 protein was detected by tissue microarray and immunoblotting (IB). The interaction of STAT1 isoforms with TGF-β receptors was confirmed by immunoprecipitation and IB. The effect of TGF-β signaling on STAT1 activation was examined in EOC and non-tumorous HOSEpiC cells treated with TGF-β1 in the presence or absence of the inhibitor of TGF-β type I receptor. The gain-of-function and loss-of-function approaches were applied for detecting the role of STAT1 on EOC cell behaviours.

RESULTS

The high level of STAT1 was observed in patients with high-grade serous EOC. STAT1 expression was higher in ovarian cancer cells than noncancerous cells. TGF-β1 activated the STAT1 pathway by inducing the phosphorylation of STAT1α on S727 residue. The full-length STAT1α and the truncated STAT1β directly interacted with TGF-β receptors (ALK1/ALK5 and TβRII), which was mediated by TGF-β1. STAT1α and STAT1β blocked the activation of the TGF-β1 signaling pathway in EOC cells by reducing Smad2 phosphorylation. STAT1 overexpression induced EOC cell proliferation, migration, and invasion; whereas its inhibition enhanced TGF-β1-induced phospho-Smad2 and suppressed EOC cell proliferation, migration, and invasion.

CONCLUSIONS

Our data unveil a novel insight into the molecular mechanism of crosstalk between the STAT1 and TGF-β signaling pathways, which affected the cancer cell behavior. Suppression of STAT1 may be a potential therapeutic strategy for targeting ovarian cancer.

Transducin-Like Enhancer of Split 3 (TLE3) Expression Is Associated with Taxane Sensitivity in Nonserous Ovarian Carcinoma in a Three-Cohort Study

Background: Chemoresistance is a major challenge in ovarian cancer treatment, resulting in poor survival rates. Identifying markers of treatment response is imperative for improving outcome while minimizing unnecessary side effects. We have previously demonstrated that expression of transducin-like enhancer of split 3 (TLE3) is associated with favorable progression-free survival in taxane-treated ovarian cancer patients with nonserous histology. The purpose of this study was to perform an independent evaluation of the association of TLE3 expression with response to taxane-based chemotherapy in nonserous ovarian cancer, to validate its role as a potential therapeutic response marker for taxane-based chemotherapy.Methods: We performed immunohistochemical staining of TLE3 on ovarian cancer specimens from the Australian Ovarian Cancer Study, the Westmead Gynaecological Oncology Biobank, and Memorial Sloan Kettering Cancer Center. Progression-free survival and overall survival were assessed to validate an association between TLE3 expression and response to taxane therapy that we previously observed in a smaller study.Results: Expression of TLE3 was associated with favorable outcome only in patients who had received paclitaxel as part of their treatment regimen for both 3-year progression-free survival (n = 160; HR, 0.56; P = 0.03) and 5-year overall survival (HR, 0.53; P = 0.04). Further analysis revealed that the predictive association between TLE3 expression and outcome was strongest in tumors with clear cell histology.Conclusions: The association between high TLE3 expression and a favorable response to taxane-containing chemotherapy regimens was validated in patients with nonserous ovarian cancer.Impact: TLE3 expression may serve as a marker of chemosensitivity in taxane-treated patients with nonserous histologies. Cancer Epidemiol Biomarkers Prev; 27(6); 680-8. ©2018 AACR.

Raman micro-spectroscopy applied to treatment resistant and sensitive human ovarian cancer cells

Despite the many advances intended to enhance the response to treatment, the survival rate of patients with ovarian cancer has only marginally improved in the past few decades. One major cause for this, is the lack of diagnostics for platinum-resistant disease. The goal of this study was to determine whether Raman micro-spectroscopy in conjunction with multivariate statistical analysis could discriminate between chemically fixed cisplatin-resistant (A2780cp) and cisplatin-sensitive (A2780s) human ovarian carcinoma cells. Raman spectra collected from individual cells were pre-processed and subsequently analyzed with Principal Component Analysis - Linear Discriminant Analysis (PCA-LDA). Statistically significant differences (P <  0.0001) were observed between the Raman spectra of A2780s and A2780cp cells. A diagnostic accuracy of 82% was obtained using the PCA-LDA classifier model for the discrimination between the A2780s and A2780cp cells. The loading plot analysis suggests that relative increases in proteins and glutathione in the cisplatin-resistant cells compared to the cisplatin-sensitive cells are most likely the major source of discrimination between the two types of cells. These results support the potential application of Raman spectroscopy in the identification of chemo-resistant tumors prior to treatment.

Formoxanthone C, isolated from Cratoxylum formosum ssp. pruniflorum, reverses anticancer drug resistance by inducing both apoptosis and autophagy in human A549 lung cancer cells

Multidrug resistance (MDR) cancer toward cancer chemotherapy is one of the obstacles in cancer therapy. Therefore, it is of interested to use formoxanthone C (1,3,5,6-tetraoxygenated xanthone; XanX), a natural compound, which showed cytotoxicity against MDR human A549 lung cancer (A549RT-eto). The treatment with XanX induced not only apoptosis- in A549RT-eto cells, but also autophagy-cell death. Inhibition of apoptosis did not block XanX-induced autophagy in A549RT-eto cells. Furthermore, suppression of autophagy by beclin-1 small interfering RNAs (siRNAs) did not interrupt XanX-induced apoptosis, indicating that XanX can separately induce apoptosis and autophagy. Of interest, XanX treatment reduced levels of histone deacetylase 4 (HDAC4) protein overexpressed in A549RT-etocells. The co-treatment with XanX and HDAC4 siRNA accelerated both autophagy and apoptosis more than that by XanX treatment alone, suggesting survival of HDAC4 in A549RT-eto cells. XanX reverses etoposide resistance in A549RT-eto cells by induction of both autophagy and apoptosis, and confers cytotoxicity through down-regulation of HDAC4.

MicroRNA-27b functions as a new inhibitor of ovarian cancer-mediated vasculogenic mimicry through suppression of VE-cadherin expression

Aggressive cancer cells gain robust tumor vascular mimicry (VM) capability that promotes tumor growth and metastasis. VE-cadherin is aberrantly overexpressed in vasculogenic cancer cells and regarded as a master gene of tumor VM. Although microRNAs (miRNAs) play an important role in modulating tumor angiogenesis and cancer metastasis, the miRNA that targets VE-cadherin expression in cancer cells to inhibit tumor cell-mediated VM is enigmatic. In this study, we found that miR-27b levels are negatively co-related to VE-cadherin expression in ovarian cancer cells and tumor cell-mediated VM, and demonstrated that miR-27b could bind to the 3'-untranslated region (3'UTR) of VE-cadherin mRNA. Overexpression of miR-27b in aggressive ovarian cancer cell lines Hey1B and ES2 significantly diminished intracellular VE-cadherin expression; convincingly, the inhibitory effect of miR-27b could be reversed by miR-27b specific inhibitor. Intriguingly, miR-27b not only effectively suppressed ovarian cancer cell migration and invasion, but also markedly inhibited formation of ovarian cancer cell-mediated capillary-like structures in vitro and suppressed generation of functional tumor blood vessels in mice. Together, our study suggests that miR-27b functions as a new inhibitor of ovarian cancer cell-mediated VM through suppression of VE-cadherin expression, providing a new potential drug candidate for antitumor VM and anti-ovarian cancer therapy.

Impact of the putative cancer stem cell markers and growth factor receptor expression on the sensitivity of ovarian cancer cells to treatment with various forms of small molecule tyrosine kinase inhibitors and cytotoxic drugs

Increased expression and activation of human epidermal growth factor receptor (EGFR) and HER-2 have been reported in numerous cancers. The aim of this study was to determine the sensitivity of a large panel of human ovarian cancer cell lines (OCCLs) to treatment with various forms of small molecule tyrosine kinase inhibitors (TKIs) and cytotoxic drugs. The aim was to see if there was any association between the protein expression of various biomarkers including three putative ovarian cancer stem cell (CSC) markers (CD24, CD44, CD117/c-Kit), P-glycoprotein (P-gp), and HER family members and response to treatment with these agents. The sensitivity of 10 ovarian tumour cell lines to the treatment with various forms of HER TKIs (gefitinib, erlotinib, lapatinib, sapitinib, afatinib, canertinib, neratinib), as well as other TKIs (dasatinib, imatinib, NVP-AEW541, crizotinib) and cytotoxic agents (paclitaxel, cisplatin and doxorubicin), as single agents or in combination, was determined by SRB assay. The effect on these agents on the cell cycle distribution, and downstream signaling molecules and tumour migration were determined using flow cytometry, western blotting, and the IncuCyte Clear View cell migration assay respectively. Of the HER inhibitors, the irreversible pan-TKIs (canertinib, neratinib and afatinib) were the most effective TKIs for inhibiting the growth of all ovarian cancer cells, and for blocking the phosphorylation of EGFR, HER-2, AKT and MAPK in SKOV3 cells. Interestingly, while the majority of cancer cells were highly sensitive to treatment with dasatinib, they were relatively resistant to treatment with imatinib (i.e., IC50 >10 µM). Of the cytotoxic agents, paclitaxel was the most effective for inhibiting the growth of OCCLs, and of various combinations of these drugs, only treatment with a combination of NVP-AEW541 and paclitaxel produced a synergistic or additive anti-proliferative effect in all three cell lines examined (i.e., SKOV3, Caov3, ES2). Finally, of the TKIs, only treatment with afatinib, neratinib and dasatinib were able to reduce the migration of HER-2 overexpressing SKOV3 cells. We did not find any significant association between the expression of putative ovarian CSC marker, HER family members, c-MET, ALK, and IGF-IR and the response to the irreversible HER TKIs. Our results support the need for further investigations of the therapeutic potential of these irreversible HER family blockers in ovarian cancer, and the therapeutic potential of dasatinib when used in combination with the inhibitors of the HER family members in ovarian cancer.

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.