Epigenetics of ovarian cancer: From the lab to the clinic

Drug Repositioning for Ovarian Cancer Treatment: An Update

Ovarian cancer (OC) is one of the most prevalent malignancies in female reproductive organs, and its 5-year survival is below 45%. Despite the advances in surgical and chemotherapeutic options, OC treatment is still a challenge, and new anticancer agents are urgently needed. Drug repositioning has gained significant attention in drug discovery, representing a smart way to identify new clinical applications for drugs whose human safety and pharmacokinetics have already been established, with great time and cost savings in pharmaceutical development endeavors. This review offers an update on the most promising drugs repurposable for OC treatment and/or prevention.

Hsa_circ_0000119 promoted ovarian cancer development via enhancing the methylation of CDH13 by sponging miR-142-5p

Ovarian cancer is the leading cause of gynecological cancer-related death in women, and is difficult to treat. The aim of our study is to explore the role and action mechanism of hsa_circ_0000119 in ovarian cancer, thus to analyze whether the circular RNA is a potential target for the treatment of the disease. In this present study, our data shows that hsa_circ_0000119 and DNA methyltransferase 1 (DNMT1) was increased, while miR-142-5p was decreased in ovarian cancer. Overexpression of hsa_circ_0000119 promoted tumor growth, while silencing of hsa_circ_0000119 resulted in an opposite effects. Decreasing of hsa_circ_0000119 also notably inhibited the proliferation, migration, and invasion of the ovarian cancer cells. Moreover, the data proves that hsa_circ_0000119 negatively regulated miR-142-5p and cadherin 13 (CDH13) expression, but positively regulated DNMT1 expression. miR-142-5p could interact with hsa_circ_0000119 and DNMT1 3'-UTR. Silencing of DNMT1 could reverse the inhibition of hsa_circ_0000119 to miR-142-5p and CDH13 expression. Importantly, higher level of CDH13 promoter methylation existed in the ovarian tumors than that in matched normal tissues. DNA methyltransferase inhibitor could increase the expression of CDH13 in ovarian cancer cells. In addition, our results also prove that increasing of CDH13 or miR-142-5p effectively reversed the inhibition of hsa _circ_0000119 to the cell malignant phenotypes. Overall, our data demonstrate that hsa_circ_0000119 facilitated ovarian cancer development through increasing CDH13 expression via promoting DNMT1 expression by sponging miR-142-5p. Our data demonstrate the potential role of hsa_circ_0000119 in the treatment of ovarian cancer.

Review the progression of ovarian clear cell carcinoma from the perspective of genomics and epigenomics

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian cancer with unique molecular characteristics, specific biological and clinical behavior, poor prognosis and high resistance to chemotherapy. Pushed by the development of genome-wide technologies, our knowledge about the molecular features of OCCC has been considerably advanced. Numerous studies are emerging as groundbreaking, and many of them are promising treatment strategies. In this article, we reviewed studies about the genomics and epigenetics of OCCC, including gene mutation, copy number variations, DNA methylation and histone modifications.

Potential of histone deacetylase inhibitors for the therapy of ovarian cancer

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemotherapy increase patient mortality. Accumulating evidence demonstrates that histone modifications play a key role in cancerization and progression. Histone deacetylases is associated with chromatin condensed structure and transcriptional repression and play a role in chromatin remodeling and epigenetics. Histone deacetylases are promising targets for therapeutic interventions intended to reverse aberrant epigenetic associated with cancer. Therefore, histone deacetylases inhibitors could be used as anti-cancer drugs. Preclinical studies have shown promising outcomes of histone deacetylases inhibitors in ovarian cancer while clinical trials have had mixed results and limited success as monotherapy. Therefore, combination therapy with different anticancer drugs for synergistic effects and newly selective histone deacetylases inhibitors development for lower toxicity are hot issues now. In this review, we summarize the latest studies on the classification and mechanisms of action of histone deacetylase and the clinical application of their inhibitors as monotherapy or combination therapy in ovarian cancer.

Elevated SYNC Expression Is Associated with Gastric Tumorigenesis and Infiltration of M2-Polarized Macrophages in the Gastric Tumor Immune Microenvironment

Aims: To assess the expression and epigenetic regulation of Syncoilin, intermediate filament protein (SYNC) in gastric cancer tissues, and to determine its associations with clinicopathological features; immune infiltration of macrophages in tumors; and patient survival. Materials and Methods: Clinicopathological features, expression profiles, and methylation data of the SYNC gene were obtained from multi-institutional real-world public datasets. A total of 1601 samples from patients with gastric cancer were examined. The associations between clinicopathological features and SYNC expression levels were assessed by the chi-square test; survival was assessed using the Kaplan-Meier analysis. The infiltration levels of M1, 2-polarized tumor-associated macrophages (TAMs) in a gastric tumor immune microenvironment were quantified using deconvolution, and the correlation between SYNC expression level and M1, 2-polarized macrophages' infiltration was examined using the Pearson correlation test. SYNC gene methylation data were analyzed to investigate epigenetic control of its expression. Results: SYNC expression was elevated in gastric cancer tissues (p < 0.01), and was associated with a poorer overall survival (p < 0.01) and poorer postprogression survival (p = 0.01). Higher SYNC levels were significantly associated with more aggressive clinicopathological features in gastric cancer patients (p < 0.05). SYNC was also associated with the infiltration of M2-polarized TAMs in the gastric tumor immune microenvironment (p < 0.001). Hypomethylation was shown to be associated with SYNC's upregulation (p < 0.05). Conclusion: SYNC is highly expressed in gastric cancer tissues and has the potential to be a therapeutic target and to serve as a prognostic marker.

Current paradigms in epigenetic anticancer therapeutics and future challenges

Any alteration at the genetic or epigenetic level, may result in multiplex of diseases including tumorigenesis which ultimately results in the cancer development. Restoration of the normal epigenome by reversing the epigenetic alterations have been reported in tumors paving the way for development of an effective epigenetic treatment in cancer. However, delineating various epigenetic events has been a challenging task so far despite substantial progress in understanding DNA methylation and histone modifications during transcription of genes. Many inhibitors in the form of epigenetic drugs mostly targeting chromatin and histone modifying enzymes including DNA methyltransferase (DNMT) enzyme inhibitors and a histone deacetylases (HDACs) inhibitor, have been in use subsequent to the approval by FDA for cancer treatment. Similarly, other inhibitory drugs, such as FK228, suberoylanilide hydroxamic acid (SAHA) and MS-275, have been successfully tested in clinical studies. Despite all these advancements, still we see a hazy view as far as a promising epigenetic anticancer therapy is concerned. The challenges are to have more specific and effective inhibitors with negligible side effects. Moreover, the alterations seen in tumors are not well understood for which one has to gain deeper insight into the tumor pathology as well. Current review focusses on such epigenetic alterations occurring in cancer and the effective strategies to utilize such alterations for potential therapeutic use and treatment in cancer.

High ELK3 expression is associated with the VEGF-C/VEGFR-3 axis and gastric tumorigenesis and enhances infiltration of M2 macrophages

Aim: To assess the expression and effect of ELK3 in gastric cancer, along with its associations with the VEGF-C/VEGFR-3 axis, IC₅₀ of the VEGFR-3 inhibitor axitinib and immune infiltration of M2-polarized macrophages in gastric cancer, and to analyze the possible epigenetic regulation mechanism. Materials & methods: Expression profiles and methylation data from 1645 samples were obtained and examined from multi-institutional public datasets. The associations were assessed by multiple analysis methods. Results: Elevated ELK3 is associated with the VEGF-C/VEGFR-3 axis and tumorigenesis, reduces the effect of axitinib in vitro, enhances immune infiltration of M2 macrophages and affects clinical outcomes. Hypomethylation contributes to the upregulation of ELK3 in gastric cancer. Conclusions: ELK3 is a potential therapeutic target which reduces the effect of axitinib and enhances infiltration of M2-polarized macrophages.

METTL3-mediated maturation of miR-126-5p promotes ovarian cancer progression via PTEN-mediated PI3K/Akt/mTOR pathway

Methyltransferase-like 3 (METTL3) functions as an RNA methyltransferase that controls the modification of N(6)-methyladenosine (m6A) to influence the biosynthesis, decay, and translation of mRNAs. This study aims to investigate the regulation of METTL3-mediated promotion of microRNA-126-5p (miR-126-5p) in the progression of ovarian cancer and to identify the mechanisms in relation to phosphatase and tensin homolog (PTEN) and the PI3K/Akt/mTOR pathway. We found high expression of miR-126-5p in ovarian cancer samples compared to paired adjacent samples, and also in ovarian cancer cell lines. Gain-of-function experiments demonstrated that overexpression of miR-126-5p promoted ovarian cancer cell proliferation, migration, and invasion, and inhibited their apoptosis. Luciferase reporter assay identified that miR-126-5p could directly bind to PTEN. By targeting PTEN, miR-126-5p could activate the PI3K/Akt/mTOR pathway. Furthermore, the RNA methyltransferase METTL3 promoted the maturation of miR-126-5p via the m6A modification of pri-miR-126-5p. Finally, in vitro and in vivo experiments substantiated that silencing of METTL3 impeded the progression and tumorigenesis of ovarian cancer by impairing the miR-126-5p-targeted inhibition of PTEN and thus blocking the PI3K/Akt/mTOR pathway. Coherently, knockdown of METTL3 inhibited the effect of miR-126-5p to upregulate PTEN, and thus prevents PI3K/Akt/mTOR pathway activation, thereby suppressing the development of ovarian cancer. These findings highlight potential targets for the future ovarian cancer treatment as well as tumorigenic mechanisms mediated by m6A modification.

Advanced Evanescent-Wave Optical Biosensors for the Detection of Nucleic Acids: An Analytic Perspective

Evanescent-wave optical biosensors have become an attractive alternative for the screening of nucleic acids in the clinical context. They possess highly sensitive transducers able to perform detection of a wide range of nucleic acid-based biomarkers without the need of any label or marker. These optical biosensor platforms are very versatile, allowing the incorporation of an almost limitless range of biorecognition probes precisely and robustly adhered to the sensor surface by covalent surface chemistry approaches. In addition, their application can be further enhanced by their combination with different processes, thanks to their integration with complex and automated microfluidic systems, facilitating the development of multiplexed and user-friendly platforms. The objective of this work is to provide a comprehensive synopsis of cutting-edge analytical strategies based on these label-free optical biosensors able to deal with the drawbacks related to DNA and RNA detection, from single point mutations assays and epigenetic alterations, to bacterial infections. Several plasmonic and silicon photonic-based biosensors are described together with their most recent applications in this area. We also identify and analyse the main challenges faced when attempting to harness this technology and how several innovative approaches introduced in the last years manage those issues, including the use of new biorecognition probes, surface functionalization approaches, signal amplification and enhancement strategies, as well as, sophisticated microfluidic solutions.

ALDH1A2 Is a Candidate Tumor Suppressor Gene in Ovarian Cancer

Aldehyde dehydrogenase 1 family member A2 (ALDH1A2) is a rate-limiting enzyme involved in cellular retinoic acid synthesis. However, its functional role in ovarian cancer remains elusive. Here, we found that ALDH1A2 was the most prominently downregulated gene among ALDH family members in ovarian cancer cells, according to complementary DNA microarray data. Low ALDH1A2 expression was associated with unfavorable prognosis and shorter disease-free and overall survival for ovarian cancer patients. Notably, hypermethylation of ALDH1A2 was significantly higher in ovarian cancer cell lines when compared to that in immortalized human ovarian surface epithelial cell lines. ALDH1A2 expression was restored in various ovarian cancer cell lines after treatment with the DNA methylation inhibitor 5-aza-2'-deoxycytidine. Furthermore, silencing DNA methyltransferase 1 (DNMT1) or 3B (DNMT3B) restored ALDH1A2 expression in ovarian cancer cell lines. Functional studies revealed that forced ALDH1A2 expression significantly impaired the proliferation of ovarian cancer cells and their invasive activity. To the best of our knowledge, this is the first study to show that ALDH1A2 expression is regulated by the epigenetic regulation of DNMTs, and subsequently that it might act as a tumor suppressor in ovarian cancer, further suggesting that enhancing ALDH1A2-linked signaling might provide new opportunities for therapeutic intervention in ovarian cancer.

Elevated SLC6A6 expression drives tumorigenesis and affects clinical outcomes in gastric cancer

AIM

To assess SLC6A6 expression in gastric cancer, its correlation with patients' clinicopathological features and survival, and the possible epigenetic regulation mechanism.

METHODS

Expression profiles and methylation data were obtained from the Gene Expression Omnibus database and the Cancer Genome Atlas. The SLC6A6's protein level were obtained from the Human Protein Atlas. Correlations between SLC6A6 expression and clinicopathological features were assessed using the χ² test, and survival by the Kaplan-Meier analysis. By analyzing methylation data, the mechanisms of SLC6A6 dysregulation were investigated.

RESULTS

SLC6A6 expression was higher in gastric cancer, and indicated poor prognosis. Low-methylation levels were significantly related to high SLC6A6 expression.

CONCLUSION

SLC6A6 may be a potential prognostic marker and therapeutic target. Hypomethylation contributes to SLC6A6 upregulation in gastric cancer.

Genomics to immunotherapy of ovarian clear cell carcinoma: Unique opportunities for management

Ovarian clear cell carcinoma (OCCC) is distinctive from other histological types of epithelial ovarian cancer, with genetic/epigenetic alterations, a specific immune-related molecular profile, and epidemiologic associations with ethnicity and endometriosis. These findings allow for the exploration of unique and specific treatments for OCCC. Two major mutated genes in OCCC are PIK3CA and ARID1A, which are frequently coexistent with each other. Other genes' alterations also contribute to activation of the PI3K (e.g. PIK3R1 and PTEN) and dysregulation of the chromatin remodeling complex (e.g. ARID1B, and SMARKA4). Although the number of focal copy number variations is small in OCCC, amplification is recurrently detected at chromosome 20q13.2 (including ZNF217), 8q, and 17q. Both expression and methylation profiling highlight the significance of adjustments to oxidative stress and inflammation. In particular, up-regulation of HNF-1β resulting from hypomethylation contributes to the switch from anaerobic to aerobic glucose metabolism. Additionally, up-regulation of HNF-1β activates STAT3 and NF-κB signaling, and leads to immune suppression via production of IL-6 and IL-8. Immune suppression may also be induced by the increased expression of PD-1, Tim-3 and LAG3. Mismatch repair deficient (microsatellite instable) tumors as found in Lynch syndrome also induce immune suppression in some OCCC. In a recent phase II clinical trial in heavily-treated platinum-resistant ovarian cancer, two out of twenty cases with a complete response to the anti-PD-1 antibody, nivolumab, were OCCC subtypes. Thus, the immune-suppressive state resulting from both genetic alterations and the unique tumor microenvironment may be associated with sensitivity to immune checkpoint inhibitors in OCCC. In this review, we highlight recent update and progress in OCCC from both the genomic and immunologic points of view, addressing the future candidate therapeutic options.

Epigenetic Crosstalk between the Tumor Microenvironment and Ovarian Cancer Cells: A Therapeutic Road Less Traveled

Metastatic dissemination of epithelial ovarian cancer (EOC) predominantly occurs through direct cell shedding from the primary tumor into the intra-abdominal cavity that is filled with malignant ascitic effusions. Facilitated by the fluid flow, cells distribute throughout the cavity, broadly seed and invade through peritoneal lining, and resume secondary tumor growth in abdominal and pelvic organs. At all steps of this unique metastatic process, cancer cells exist within a multidimensional tumor microenvironment consisting of intraperitoneally residing cancer-reprogramed fibroblasts, adipose, immune, mesenchymal stem, mesothelial, and vascular cells that exert miscellaneous bioactive molecules into malignant ascites and contribute to EOC progression and metastasis via distinct molecular mechanisms and epigenetic dysregulation. This review outlines basic epigenetic mechanisms, including DNA methylation, histone modifications, chromatin remodeling, and non-coding RNA regulators, and summarizes current knowledge on reciprocal interactions between each participant of the EOC cellular milieu and tumor cells in the context of aberrant epigenetic crosstalk. Promising research directions and potential therapeutic strategies that may encompass epigenetic tailoring as a component of complex EOC treatment are discussed.

Epigenetics in ovarian cancer: premise, properties, and perspectives

Malignant ovarian tumors bear the highest mortality rate among all gynecological cancers. Both late tumor diagnosis and tolerance to available chemical therapy increase patient mortality. Therefore, it is both urgent and important to identify biomarkers facilitating early identification and novel agents preventing recurrence. Accumulating evidence demonstrates that epigenetic aberrations (particularly histone modifications) are crucial in tumor initiation and development. Histone acetylation and methylation are respectively regulated by acetyltransferases-deacetylases and methyltransferases-demethylases, both of which are implicated in ovarian cancer pathogenesis. In this review, we summarize the most recent discoveries pertaining to ovarian cancer development arising from the imbalance of histone acetylation and methylation, and provide insight into novel therapeutic interventions for the treatment of ovarian carcinoma.

High Expression of PLOD1 Drives Tumorigenesis and Affects Clinical Outcome in Gastrointestinal Carcinoma

BACKGROUND

PLOD1 (procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1) is important for extracellular matrix formation and is involved in various diseases, including cancer; however, its role in gastrointestinal cancer is unclear. In this study, the expression of PLOD1 in gastrointestinal carcinoma and its relationships with patient survival were examined.

MATERIALS AND METHODS

Sample expression profiles were downloaded from the Gene Expression Omnibus database and methylation data were obtained from the Cancer Genome Atlas. Correlations between PLOD1 expression and clinicopathological features were analyzed by chi-square tests. Patient survival was evaluated by a Kaplan-Meier analysis.

RESULTS

PLOD1 expression was upregulated in gastric cancer and colorectal cancer compared with that in normal tissues. High PLOD1 levels indicated a poor prognosis. The high methylation group had a significantly lower level of PLOD1 expression.

CONCLUSION

These results indicated that PLOD1 is highly expressed in gastrointestinal carcinoma and is a potential prognostic marker and therapeutic target. The data also indicate that hypomethylation contributes to PLOD1 upregulation in gastric and colon cancers.

Disruption of NSD1 in Head and Neck Cancer Promotes Favorable Chemotherapeutic Responses Linked to Hypomethylation

Human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) represents a distinct classification of cancer with worse expected outcomes. Of the 11 genes recurrently mutated in HNSCC, we identify a singular and substantial survival advantage for mutations in the gene encoding Nuclear Set Domain Containing Protein 1 (NSD1), a histone methyltransferase altered in approximately 10% of patients. This effect, a 55% decrease in risk of death in NSD1-mutated versus non-mutated patients, can be validated in an independent cohort. NSD1 alterations are strongly associated with widespread genome hypomethylation in the same tumors, to a degree not observed for any other mutated gene. To address whether NSD1 plays a causal role in these associations, we use CRISPR-Cas9 to disrupt NSD1 in HNSCC cell lines and find that this leads to substantial CpG hypomethylation and sensitivity to cisplatin, a standard chemotherapy in head and neck cancer, with a 40% to 50% decrease in the IC₅₀ value. Such results are reinforced by a survey of 1,001 cancer cell lines, in which loss-of-function NSD1 mutations have an average 23% decrease in cisplatin IC₅₀ value compared with cell lines with wild-type NSD1Significance: This study identifies a favorable subtype of HPV-negative HNSCC linked to NSD1 mutation, hypomethylation, and cisplatin sensitivity. Mol Cancer Ther; 17(7); 1585-94. ©2018 AACR.

Endometriosis Malignant Transformation: Epigenetics as a Probable Mechanism in Ovarian Tumorigenesis

Endometriosis, defined as the presence of ectopic endometrial glands and stroma outside the uterine cavity, is a chronic, hormone-dependent gynecologic disease affecting millions of women across the world, with symptoms including chronic pelvic pain, dysmenorrhea, dyspareunia, dysuria, and subfertility. In addition, there is well-established evidence that, although endometriosis is considered benign, it is associated with an increased risk of malignant transformation, with the involvement of various mechanisms of development. More and more evidence reveals an important contribution of epigenetic modification not only in endometriosis but also in mechanisms of endometriosis malignant transformation, including DNA methylation and demethylation, histone modifications, and miRNA aberrant expressions. In this present review, we mainly summarize the research progress about the current knowledge regarding the epigenetic modifications of the relations between endometriosis malignant transformation and ovarian cancer in an effort to identify some risk factors probably associated with ectopic endometrium transformation.

High SLC4A11 expression is an independent predictor for poor overall survival in grade 3/4 serous ovarian cancer

In this study, we aimed to examine the expression of SLC4A11 in ovarian cancer and in normal ovarian tissues, its prognostic value and the possible mechanism of its dysregulation. Bioinformatic analysis was performed by using data from the GEO datasets, the Cancer Genome Atlas-Ovarian Cancer (TCGA-OV) and the Human Protein Atlas (HPA). Results showed that SLC4A11 was upregulated in ovarian cancer compared with normal ovarian epithelial tissues. In patients with primary serous ovarian cancer in TCGA-OV, the cases with lymphatic invasion (N = 133) had significantly higher SLC4A11 expression than those without lymphatic invasion (N = 77) (p = 0.0069). High SLC4A11 expression was consistently associated with worse overall survival (OS). Univariate and multivariate analysis confirmed that high SLC4A11 expression was an independent prognostic factor for poor OS in grade 3/4 (G3/G4) tumors (HR = 1.416, 95%CI: 1.098–1.824, p = 0.007). 320 out of 578 (55.4%) ovarian cancer cases had SLC4A11 amplification. High methylation group had a significantly lower level of SLC4A11 expression. Based on these findings, we infer that high SLC4A11 expression is an independent predictor for poor OS in grade 3/4 serous ovarian cancer. Both DNA amplification and hypomethylation contribute to its upregulation in ovarian cancer.

Silencing of LSD1 gene modulates histone methylation and acetylation and induces the apoptosis of JeKo-1 and MOLT-4 cells

Lysine-specific demethylase 1 (LSD1) has been identified and biochemically characterized in epigenetics; however, the pathological roles of its dysfunction in mantle cell lymphoma (MCL) and T-cell acute lymphoblastic leukemia remain to be elucidated. In this study, we evaluated LSD1, and histone H3 lysine 4 (H3K4)me1 and H3K4me2 expression in patients with MCL and silenced LSD1 in JeKo‑1 and MOLT‑4 cells, in order to define its role in JeKo‑1 and MOLT‑4 cell proliferation and apoptosis. We retrospectively analyzed the protein expression of LSD1, and mono- and dimethylated H3K4 (H3K4me1 and H3K4me2), and cyclin D1 and Ki67 in 30 cases of MCL by immunohistochemistry. The correlation of LSD1, H3K4me1 and H3K4me2 with Ki67 was determined by statistical analysis. LSD1 was silenced by small interfering RNA (siRNA). Cell apoptosis and cell proliferation were detected by flow cytometry and 3-(4,5-dimethylthiazol‑2-yl)‑2,5-diphenyltetrazolium bromide (MTT) assay. The protein expression levels of LSD1, histone methylated H3K4, histone acetylated H3, cyclin D1, apoptotic proteins, p15 and DNA methyltransferase 1 (DNMT1) were examined by western blot analysis. We demonstrated that LSD1 was upregulated, and that H3K4me1 and H3K4me2 were downregulated in the cases with MCL, compared to those with proliferative lymphadenitis (p<0.05). LSD1 positively correlated with Ki67 in MCL [Cohen's kappa (κ)=0.667, p<0.01]. There was no significant correlation between H3K4me1 and H3K4me2, and Ki67 (κ=-0.182, p>0.05, κ=-0.200, p>0.05). The silencing of LSD1 decreased the levels of the apoptosis-related proteins, Bcl-2, pro-caspase-3 and C-myc, and decreased those of DNMT1 and increased p15, and resulted in the loss of cell viability and the induction apoptosis. The silencing of LSD1 increased the expression of H3K4me1 and H3K4me2, and histone acetylated H3 in the JeKo‑1 and MOLT‑4 cells. LSD1 siRNA also decreased cyclin D1 expression in the JeKo‑1 cells. On the whole, our findings demonstrate that the overexpression of LSD1 may be associated with the pathogenesis in MCL. We demonstrated that the silencing of LSD1 is capable of removing the mono- and dimethyl groups from H3K4, and upregulating the histone acetylation of H3 in JeKo‑1 and MOLT‑4 cells. The silencing of LSD1 inhibited cell growth and induced cell apoptosis. Of note, in JeKo‑1 cells, the silencing of LSD1 decreased cyclin D1 expression, which is one of the genes that contribute to the pathogenesis of MCL. LSD1 may thus be a possible therapeutic target in MCL and acute lymphoblastic leukemia MOLT‑4 cells.

Aberrant Hypomethylation of Solute Carrier Family 6 Member 12 Promoter Induces Metastasis of Ovarian Cancer

PURPOSE

Ovarian cancer (OC) is the most fatal of gynecological malignancies with a high rate of recurrence. We aimed to evaluate the expression of solute carrier family 6, member 12 (SLC6A12) and methylation of its promoter CpG sites in a xenograft mouse model of metastatic OC, and to investigate the regulatory mechanisms that promote aggressive properties during OC progression.

MATERIALS AND METHODS

Expression of SLC6A12 mRNA was determined by reverse-transcription quantitative polymerase chain reaction (RT-qPCR), and DNA methylation status of its promoter CpGs was detected by quantitative methylation-specific PCR. The metastatic potential of SLC6A12 was evaluated by in vitro migration/invasion transwell assays. Gene expression and DNA methylation of SLC6A12 and clinical outcomes were further investigated from publicly available databases from curatedOvarianData and The Cancer Genome Atlas.

RESULTS

SLC6A12 expression was 8.1-14.0-fold upregulated and its DNA methylation of promoter CpG sites was 41-62% decreased in tumor metastases. After treatment with DNA methyltransferase inhibitor and/or histone deacetylase inhibitor, the expression of SLC6A12 was profoundly enhanced (~8.0-fold), strongly supporting DNA methylation-dependent epigenetic regulation of SLC6A12. Overexpression of SLC6A12 led to increased migration and invasion of ovarian carcinoma cells in vitro, approximately 2.0-fold and 3.3-fold, respectively. The meta-analysis showed that high expression of SLC6A12 was significantly associated with poor overall survival [hazard ratio (HR)=1.07, p value=0.016] and that low DNA methylation levels of SLC6A12 at specific promoter CpG site negatively affected patient survival.

CONCLUSION

Our findings provide novel evidence for the biological and clinical significance of SLC6A12 as a metastasis-promoting gene.

Genetic and epigenetic heterogeneity of epithelial ovarian cancer and the clinical implications for molecular targeted therapy

Epithelial ovarian cancer (EOC) is the most lethal gynaecological malignancy, and tumoural heterogeneity (TH) has been blamed for treatment failure. The genomic and epigenomic atlas of EOC varies significantly with tumour histotype, grade, stage, sensitivity to chemotherapy and prognosis. Rapidly accumulating knowledge about the genetic and epigenetic events that control TH in EOC has facilitated the development of molecular-targeted therapy. Poly (ADP-ribose) polymerase (PARP) inhibitors, designed to target homologous recombination, are poised to change how breast cancer susceptibility gene (BRCA)-related ovarian cancer is treated. Epigenetic treatment regimens being tested in clinical or preclinical studies could provide promising novel treatment approaches and hope for improving patient survival.

MiR-486-3p targeting ECM1 represses cell proliferation and metastasis in cervical cancer

MicroRNAs (miRNAs) regulate gene expression and are involved in cervical cancer. But the molecular mechanism is still unclear. Here, miRNA profile of cervical cancer was performed and demonstrated that miR-486-3p decreased in specimens of cervical cancer patients. In addition, our clinical data show that decreased miR-486-3p was associated with metastasis in cervical cancer patients. ECM1 was predicted and velified as a target gene of miR-486-3p. Overexpression of miR-486-3p inhibited cell growth and metastasis by targeting ECM1. In a conclusion, these findings suggest that miR-486-3p is a tumor suppressor miRNA and induction of miR-486-3p is a potential strategy to inhibit cervical cancer progression.

DNA methylation changes in epithelial ovarian cancer histotypes

Survival after a diagnosis of ovarian cancer has not improved, and despite histological differences, treatment is similar for all cases. Understanding the molecular basis for ovarian cancer risk and prognosis is fundamental, and to this end much has been gleaned about genetic changes contributing to risk, and to a lesser extent, survival. There's considerable evidence for genetic differences between the four pathologically defined histological subtypes; however, the contribution of epigenetics is less well documented. In this report, we review alterations in DNA methylation in ovarian cancer, focusing on histological subtypes, and studies examining the roles of methylation in determining therapy response. As epigenetics is making its way into clinical care, we review the application of cell free DNA methylation to ovarian cancer diagnosis and care. Finally, we comment on recurrent limitations in the DNA methylation literature for ovarian cancer, which can and should be addressed to mature this field.

Contributions of the Epidermal Growth Factor Receptor to Acquisition of Platinum Resistance in Ovarian Cancer Cells

Acquisition of platinum resistance following first line platinum/taxane therapy is commonly observed in ovarian cancer patients and prevents clinical effectiveness. There are few options to prevent platinum resistance; however, demethylating agents have been shown to resensitize patients to platinum therapy thereby demonstrating that DNA methylation is a critical contributor to the development of platinum resistance. We previously reported the Epidermal Growth Factor Receptor (EGFR) is a novel regulator of DNA methyltransferase (DNMT) activity and DNA methylation. Others have shown that EGFR activation is linked to cisplatin treatment and platinum resistance. We hypothesized that cisplatin induced activation of the EGFR mediates changes in DNA methylation associated with the development of platinum resistance. To investigate this, we evaluated EGFR signaling and DNMT activity after acute cisplatin exposure. We also developed an in vitro model of platinum resistance to examine the effects of EGFR inhibition on acquisition of cisplatin resistance. Acute cisplatin treatment activates the EGFR and downstream signaling pathways, and induces an EGFR mediated increase in DNMT activity. Cisplatin resistant cells also showed increased DNMT activity and global methylation. EGFR inhibition during repeated cisplatin treatments generated cells that were more sensitive to cisplatin and did not develop increases in DNA methylation or DNMT activity compared to controls. These findings suggest that activation of EGFR during platinum treatment contributes to the development of platinum resistance. Furthermore, EGFR inhibition may be an effective strategy at attenuating the development of platinum resistance thereby enhancing the effectiveness of chemotherapeutic treatment in ovarian cancer.

Cisplatin-, Doxorubicin-, and Docetaxel-Induced Cell Death Promoted by the Aqueous Extract of Solanum nigrum in Human Ovarian Carcinoma Cells

Chemotherapy is a major clinical treatment for managing patients with advanced and recurrent ovarian cancer. However, the clinical performance of chemotherapy is limited, and adverse effects have been observed. Integrating chemotherapy with current chemotherapeutic drugs and novel antitumor ingredients might improve the clinical performance of current chemotherapy for ovarian cancer. The aqueous extract of Solanum nigrum leaves (AE-SN), a key ingredient in many traditional Chinese medicine formulae, has exhibited tumor suppression efficacy in numerous human cancer cells but not in ovarian cancer cells. In this study, tumor suppression efficacy was determined using the ES-2, SKOV-3, and OVCAR-3 human ovarian cancer cell lines. The half-maximal inhibitory concentrations of the AE-SN in ES-2 and SKOV-3 cells were 1.052 and 1.779 mg/mL, respectively. AE-SN treatment increased the accumulation of mammalian microtubule-associated protein 1 light chain 3 A/B, an autophagic cell marker, in all the tested cell lines; however, it activated the cleavage of caspase-3, an apoptotic marker, only in SKOV-3 cells. Furthermore, the AE-SN also promoted tumor suppression efficiency of cisplatin, doxorubicin, and docetaxel in the tested ovarian cancer cells. In addition, AE-SN-enhanced cell death was associated with AE-SN-induced caspase-3 cleavage in SKOV-3 cells. In conclusion, the AE-SN exhibited tumor suppression efficacy and improved the tumor suppression efficiency of cisplatin, doxorubicin, and docetaxel in human ovarian cancer cells. Therefore, the AE-SN is a candidate antitumor ingredient that can be used in developing future integrated chemotherapy for managing ovarian cancer.

The H3K9 methyltransferase G9a is a marker of aggressive ovarian cancer that promotes peritoneal metastasis

BACKGROUND

Ovarian cancer (OCa) peritoneal metastasis is the leading cause of cancer-related deaths in women with limited therapeutic options available for treating it and poor prognosis, as the underlying mechanism is not fully understood.

METHOD

The clinicopathological correlation of G9a expression was assessed in tumor specimens of ovarian cancer patients. Knockdown or overexpression of G9a in ovarian cancer cell lines was analysed with regard to its effect on adhesion, migration, invasion and anoikis-resistance. In vivo biological functions of G9a were tested by i.p. xenograft ovarian cancer models. Microarray and quantitative RT-PCR were used to analyze G9a-regulated downstream target genes.

RESULTS

We found that the expression of histone methyltransferase G9a was highly correlated with late stage, high grade, and serous-type OCa. Higher G9a expression predicted a shorter survival in ovarian cancer patients. Furthermore, G9a expression was higher in metastatic lesions compared with their corresponding ovarian primary tumors. Knockdown of G9a expression suppressed prometastatic cellular activities including adhesion, migration, invasion and anoikis-resistance of ovarian cancer cell lines, while G9a over-expression promoted these cellular properties. G9a depletion significantly attenuated the development of ascites and tumor nodules in a peritoneal dissemination model. Importantly, microarray and quantitative RT-PCR analysis revealed that G9a regulates a cohort of tumor suppressor genes including CDH1, DUSP5, SPRY4, and PPP1R15A in ovarian cancer. Expression of these genes was also inversely correlated with G9a expression in OCa specimens.

CONCLUSION

We propose that G9a contributes to multiple steps of ovarian cancer metastasis and represents a novel target to combat this deadly disease.

Epigenetic determinants of ovarian clear cell carcinoma biology

Targeted approaches have revealed frequent epigenetic alterations in ovarian cancer, but the scope and relation of these changes to histologic subtype of disease is unclear. Genome-wide methylation and expression data for 14 clear cell carcinoma (CCC), 32 non-CCC and four corresponding normal cell lines were generated to determine how methylation profiles differ between cells of different histological derivations of ovarian cancer. Consensus clustering showed that CCC is epigenetically distinct. Inverse relationships between expression and methylation in CCC were identified, suggesting functional regulation by methylation, and included 22 hypomethylated (UM) genes and 276 hypermethylated (HM) genes. Categorical and pathway analyses indicated that the CCC-specific UM genes were involved in response to stress and many contain hepatocyte nuclear factor (HNF) 1-binding sites, while the CCC-specific HM genes included members of the estrogen receptor alpha (ERalpha) network and genes involved in tumor development. We independently validated the methylation status of 17 of these pathway-specific genes, and confirmed increased expression of HNF1 network genes and repression of ERalpha pathway genes in CCC cell lines and primary cancer tissues relative to non-CCC specimens. Treatment of three CCC cell lines with the demethylating agent Decitabine significantly induced expression for all five genes analyzed. Coordinate changes in pathway expression were confirmed using two primary ovarian cancer datasets (p < 0.0001 for both). Our results suggest that methylation regulates specific pathways and biological functions in CCC, with hypomethylation influencing the characteristic biology of the disease while hypermethylation contributes to the carcinogenic process.

Histones and their modifications in ovarian cancer - drivers of disease and therapeutic targets

Epithelial ovarian cancer has the highest mortality of the gynecological malignancies. High grade serous epithelial ovarian cancer (SEOC) is the most common subtype, with the majority of women presenting with advanced disease where 5-year survival is around 25%. Platinum-based chemotherapy in combination with paclitaxel remains the most effective treatment despite platinum therapies being introduced almost 40 years ago. Advances in molecular medicine are underpinning new strategies for the treatment of cancer. Major advances have been made by international initiatives to sequence cancer genomes. For SEOC, with the exception of TP53 that is mutated in virtually 100% of these tumors, there is no other gene mutated at high frequency. There is extensive copy number variation, as well as changes in methylation patterns that will influence gene expression. To date, the role of histones and their post-translational modifications in ovarian cancer is a relatively understudied field. Post-translational histone modifications play major roles in gene expression as they direct the configuration of chromatin and so access by transcription factors. Histone modifications include methylation, acetylation, and monoubiquitination, with involvement of enzymes including histone methyltransferases, histone acetyltransferases/deacetylases, and ubiquitin ligases/deubiquitinases, respectively. Complexes such as the Polycomb repressive complex also play roles in the control of histone modifications and more recently roles for long non-coding RNA and microRNAs are emerging. Epigenomic-based therapies targeting histone modifications are being developed and offer new approaches for the treatment of ovarian cancer. Here, we discuss histone modifications and their aberrant regulation in malignancy and specifically in ovarian cancer. We review current and upcoming histone-based therapies that have the potential to inform and improve treatment strategies for women with ovarian cancer.

Importance of promoter methylation of GATA4 gene in epithelial ovarian cancer

AIMS

Ovarian cancer is the most lethal gynecological malignancy, with typically late diagnosis. Altered DNA methylation of tumor suppressor gene promoters probably plays a relevant role in ovarian carcinogenesis and frequently occurs as an early event in the development of different types of cancer including ovarian carcinoma. GATA4 methylation has been reported in a variety of human cancers. The aim of this study was to investigate promoter methylation of the GATA4 gene in ovarian cancer by comparison with that in normal ovarian tissue.

METHODS

To search for promoter methylation of the GATA4 gene we used MSP (methylation-specific PCR) to compare the methylation status in 67 tissue samples of ovarian cancer with that in 40 control samples.

RESULTS

In our study, methylation-specific PCR revealed GATA4 promoter methylation in 21 of 67 specimens with ovarian cancer (31.3%), and in none of the control ovarian tissue samples.

CONCLUSION

These results confirm that methylation in the GATA4 promoter region could play an important role in ovarian carcinogenesis, and show new loci which are highly methylated only in ovarian cancer samples and which are associated predominantly with the endometrioid type of ovarian carcinoma.

Epigenetic therapies as a promising strategy for overcoming chemoresistance in epithelial ovarian cancer

Over the past decades, prognosis of advanced stage epithelial ovarian cancer remains very poor, despite the development of new chemotherapeutic drugs, as well as molecular targeted agents. Late presentation and frequent chemoresistance account for the poor prognosis. Emerging studies have shown that many genetic changes, especially p53 mutation, are associated with the chemoresistance. However, recent failure of the clinical trials using p53 gene-therapy makes researchers discuss the possible reasons for the failure. Epigenetic changes are considered one of the substantial reasons. Successful restoration of the aberrant epigenetic changes may be a promising strategy for overcoming chemoresistance in epithelial ovarian cancer. Herein, we will summarize the rationale for epigenetic therapy of cancer and current status of epigenetic studies in relation to chemoresistance in epithelial ovarian cancer.

A potential diagnostic marker for ovarian cancer: Involvement of the histone acetyltransferase, human males absent on the first

Human males absent on the first (hMOF), a human ortholog of the Drosophila MOF protein, is responsible for histone H4 lysine 16 (H4K16) acetylation in human cells. The depletion of hMOF leads to a global reduction in histone H4K16 acetylation in human cells, genomic instability, cell cycle defects, reduced transcription of certain genes, defective DNA damage repair and early embryonic lethality. Studies have shown that abnormal hMOF gene expression is involved in a number of primary cancers. The present study examined the involvement of hMOF expression and histone H4K16 acetylation in clinically diagnosed primary ovarian cancer tissues. Clinically diagnosed frozen primary ovarian cancer tissues were used for polymerase chain reaction (PCR), quantitative PCR (qPCR), western blotting and immunohistochemical staining approaches. A PCR analysis of mRNA expression in 47 samples revealed a downregulation of hMOF mRNA in 81% of patients, whereas only 13% of patients demonstrated upregulation. qPCR was used to validate the frequent downregulation of hMOF expression in the primary ovarian cancer tissues. As expected, the analysis of hMOF expression in 57 samples revealed that hMOF mRNA expression was significantly downregulated (>2-fold decrease) in 65% of patients, while a <2-fold reduction of hMOF was observed in 10.5% of patients. Furthermore, the expression of hMOF-regulated human leukocyte antigen (HLA) complex 5, (HCP5), was also found to be downregulated in >87% of patients with a decrease in hMOF. hMOF and its regulated gene, HCP5, are frequently downregulated in human ovarian cancer, suggesting that hMOF may be involved in the pathogenesis of the disease.

Loss of HOXD10 expression induced by upregulation of miR-10b accelerates the migration and invasion activities of ovarian cancer cells

Small and large non-coding RNAs (ncRNAs) contribute to the acquisition of aggressive tumor behavior in diverse human malignancies. Two types of ncRNAs, miRNA‑10b (miR-10b) and homemobox (HOX) transcript antisense RNA (HOTAIR), can suppress the translation of the HOXD10 gene, an mRNA encoding a transcriptional repressor that inhibits the expression of cell migration/invasion-associated genes. Using epithelial ovarian cancer cell lines and primary tumors, we investigated whether miR‑10b and/or HOTAIR can regulate the expression of HOXD10, and whether it permits gain of pro‑metastatic gene products, matrix metallopeptidase 14 (MMP14) and ras homolog family member C (RHOC). Overexpression of miR-10b induced a decrease in HOXD10 protein expression, and upregulated the migration and invasion abilities in ovarian cancer cell lines (P<0.05). In these cells, a significant increase of MMP14 and RHOC protein was observed. No significant upregulation of the HOXD10 protein was observed in cells with the treatment of HOTAIR-siRNA. Positive signals for HOXD10 and MMP14 proteins were observed in 47 (69%) and 25 (37%) of 68 patients with epithelial ovarian cancers. An inverse correlation between HOXD10 and MMP14 immunoreactivities was observed (P<0.05), and miR-10b expression was also inversely correlated with HOXD10 protein expression (P<0.05). These results suggested that downregulation of HOXD10 expression by miR-10b overexpression may induce an increase of pro-metastatic gene products, such as MMP14 and RHOC, and contribute to the acquisition of metastatic phenotypes in epithelial ovarian cancer cells.

Epigenetic silencing of BLU through interfering apoptosis results in chemoresistance and poor prognosis of ovarian serous carcinoma patients

Epithelial ovarian carcinoma is usually present at the advanced stage, during which the patients generally have poor prognosis. Our study aimed to evaluate the correlation of gene methylation and the clinical outcome of patients with advanced-stage, high-grade ovarian serous carcinoma. The methylation status of eight candidate genes was first evaluated by methylation-specific PCR and capillary electrophoresis to select three potential genes including DAPK, CDH1, and BLU (ZMYND10) from the exercise group of 40 patients. The methylation status of these three genes was further investigated in the validation group consisting of 136 patients. Patients with methylated BLU had significantly shorter progression-free survival (PFS; hazard ratio (HR) 1.48, 95% CI 1.01-2.56, P=0.013) and overall survival (OS; HR 1.83, 95% CI 1.07-3.11, P=0.027) in the multivariate analysis. Methylation of BLU was also an independent risk factor for 58 patients undergoing optimal debulking surgery for PFS (HR 2.37, 95% CI 1.03-5.42, P=0.043) and OS (HR 3.96, 95% CI 1.45-10.81, P=0.007) in the multivariate analysis. A possible mechanism of BLU in chemoresistance was investigated in ovarian cancer cell lines by in vitro apoptotic assays. In vitro studies have shown that BLU could upregulate the expression of BAX and enhance the effect of paclitaxel-induced apoptosis in ovarian cancer cells. Our study suggested that methylation of BLU could be a potential prognostic biomarker for advanced ovarian serous carcinoma.

Epigenetic analysis of the Notch superfamily in high-grade serous ovarian cancer

OBJECTIVES

Gene methylation and other epigenetic modifications of gene regulation have been implicated in the growth of ovarian cancer, but the clinical significance of such modifications in the Notch pathway in high-grade serous ovarian cancer (HGS-OvCa) is not well understood. We used The Cancer Genome Atlas (TCGA) data to study the clinical relevance of epigenetic modifications of Notch superfamily genes.

METHODS

We analyzed the interaction of DNA methylation and miRNAs with gene expression data for Notch superfamily members with the Spearman rank correlation test and explored potential relationships with overall survival (OS) with the log-rank test. We downloaded clinical data, level 3 gene expression data, and level 3 DNA methylation data for 480 patients with stage II-IV HGS-OvCa from the TCGA data portal. Patients were randomly divided into training and validation cohorts for survival analyses. In each set, patients were grouped into percentiles according to methylation and microRNA (miRNA) or messenger RNA (mRNA) levels. We used several algorithms to predict miRNA-mRNA interaction.

RESULTS

There were significant inverse relationships between methylation status and mRNA expression for PPARG, CCND1, and RUNX1. For each of these genes, patients with a lower methylation level and higher expression level had significantly poorer OS than did patients with a higher methylation level and lower expression level. We also found a significant inverse relationship between miRNAs and mRNA expression for CCND1, PPARG, and RUNX1. By further analyzing the effect of miRNAs on gene expression and OS, we found that patients with higher levels of CCND1, PPARG, and RUNX1 expression and lower expression levels of their respective miRNAs (502-5p, 128, and 215/625) had significantly poorer OS.

CONCLUSIONS

Epigenetic alterations of multiple Notch target genes and pathway interacting genes (PPARG, CCND1, and RUNX1) may relate to activation of this pathway and poor survival of patients with HGS-OvCa.

Anticancer efficacy of cisplatin and trichostatin A or 5-aza-2'-deoxycytidine on ovarian cancer

BACKGROUND

To evaluate the anticancer efficacy of the combination of epigenetic modifiers and cisplatin in human ovarian cancer.

METHODS

The effect of trichostatin A (TSA) and 5-aza-2'-deoxycytidine alone or in combination with low-dose cisplatin was evaluated on human ovarian cancer cell lines in vitro. We measured drug interaction by MTS assay, migration by transwell assay, expression of epithelial to mesenchymal transition (EMT) markers (Twist, Snail, Slug, E-cadherin, and N-cadherin), pluripotency markers (Oct4, Sox2, and Nanog), and epigenetic markers (DNMT3A, LSD1 and H3K4me2, H3K4me3, H3K9me2, and H3K9me3) by western blot, and the impact on and characteristics of spheroid growth when exposed to these drugs. Mouse xenografts were used to evaluate the anticancer effect of sequential drug treatment.

RESULTS

Combination treatment had greater efficacy than single drugs and significantly suppressed cell viability, migration, and spheroid formation and growth. Sequential treatment of cisplatin (1 mg kg(-1)) followed by TSA (0.3 mg kg(-1)) significantly suppressed tumorigenicity of HEY xenografts through inhibition of EMT and decreased pluripotency of ovarian cancer cells.

CONCLUSION

Epigenetic modifiers potentiate the anticancer efficacy of low-dose cisplatin in ovarian cancer through regulation of EMT and pluripotency, and may provide a promising treatment for ovarian cancer patients.

Lack of significance of the BRCA2 promoter methylation status in different genotypes of the MTHFR a1298c polymorphism in ovarian cancer cases in Iran

OBJECTIVE

Promoter methylation, which can be regulated by MTHFR activity, is associated with silencing of genes. In this study we evaluated the methylation status (type) of the BRCA2 promoter in ovarian cancer patients carrying different genotypes of the MTHFR gene (A or C polymorphisms at position 1298).

METHODS

The methylation type of the BRCA2 promoter was evaluated using bisulfate-modified DNA in methylation- specific PCR and the MTHFRa1278c polymorphism was assessed by PCR-RFLP.

RESULTS

Analysis of the BRCA2 promoter methylation type of cases showed that 7 out of 60 cases (11.7%) were methylated while the remaining 53 (88.3%) were unmethylated. In methylated cases, one out of the 7 cases had a CC genotype and the remaining 6 methylated cases had an AC genotype. The AA genotype was absent. In unmethylated cases, 34, 18, and one out of these had AC, AA and CC genotype, respectively.

CONCLUSION

There was no significant relationship between the methylation types of the BRCA2 promoter in different genotypes of MTHFRa1298c polymorphism in ovarian cancer; p=0.255. There was no significant relation between the methylation types of the BRCA2 promoter in different genotypes of the MTHFRa1298c polymorphism in ovarian cancer.

Establishment of primary cultures from ovarian tumor tissue and ascites fluid

We have refined the technique for isolating and propagating cultures of primary epithelial ovarian cancer (EOC) cells derived from solid tumors and ascites. Both protocols involve a simple yet rapid method for the growth and propagation of EOC tumor and ascites cells in a basal culture medium without the addition of growth factors. Isolation of tumor EOC cells involves the mechanical disruption of the tumor tissue with the help of a cell scraper, while ascites-derived EOC cells are mixed with growth medium and placed directly into culture with very little manipulation. We further describe a partial trypsinization method to eliminate fibroblast contamination from primary EOC cells derived from solid tumors. These methods allow for the direct application of many molecular, cellular, and functional analyses within a few weeks of initial isolation, with the added potential of retrospective analyses of archived cells and tissues. Thus, we have included steps for long-term cryopreservation of early-passage EOC cells. Initial isolation of EOC cells can be completed within 1 h, and primary cells are further expanded in culture for several weeks.

Combination of AT-101/cisplatin overcomes chemoresistance by inducing apoptosis and modulating epigenetics in human ovarian cancer cells

We investigated the effects of AT-101/cisplatin combination treatment on the expression levels of apoptotic proteins and epigenetic events such as DNA methyltransferase (DNMT) and histone deacetylase (HDAC) enzyme activities in OVCAR-3 and MDAH-2774 ovarian cancer cells. XTT cell viability assay was used to evaluate cytotoxicity. For showing apoptosis, both DNA Fragmentation and caspase 3/7 activity measurements were performed. The expression levels of apoptotic proteins were assessed by human apoptosis antibody array. DNMT and HDAC activities were evaluated by ELISA assay and mRNA levels of DNMT1 and HDAC1 genes were quantified by qRT-PCR. Combination of AT-101/cisplatin resulted in strong synergistic cytotoxicity and apoptosis in human ovarian cancer cells. Combination treatment reduced some pivotal anti-apoptotic proteins such as Bcl-2, HIF-1A, cIAP-1, XIAP in OVCAR-3 cells, whereas p21, Bcl-2, cIAP-1, HSP27, Clusterin and XIAP in MDAH-2774 cells. Among the pro-apoptotic proteins, Bad, Bax, Fas, phospho-p53 (S46), Cleaved caspase-3, SMAC/Diablo, TNFR1 and Cytochrome c were induced in OVCAR-3 cells, whereas, Bax, TRAILR2, FADD, p27, phospho-p53 (S46), Cleaved caspase-3, Cytochrome c, SMAC/Diablo and TNFR1 were induced in MDAH-2774 cells. Combination treatment also inhibited both DNMT and HDAC activities and also mRNA levels in both ovarian cancer cells. AT-101 exhibits great potential in sensitization of human ovarian cancer cells to cisplatin treatment in vitro, suggesting that the combination of AT-101 with cisplatin may hold great promise for development as a novel chemotherapeutic approach to overcome platinum-resistance in human ovarian cancer.

Promoter methylation of the SALL2 tumor suppressor gene in ovarian cancers

The SALL2 gene product and transcription factor p150 were first identified in a search for tumor suppressors targeted for inactivation by the oncogenic mouse polyoma virus. SALL2 has also been identified as a cellular quiescence factor, essential for cells to enter and remain in a state of growth arrest under conditions of serum deprivation. p150 is a transcriptional activator of p21(Cip1/Waf1) and BAX, sharing important growth arrest and proapoptotic properties with p53. It also acts as a repressor of c-myc. Restoration of SALL2 expression in cells derived from a human ovarian carcinoma (OVCA) suppresses growth of the cells in immunodeficient mice. Here we examine the pattern of p150 expression in the normal human ovary, in OVCA-derived cell lines and in primary ovarian carcinomas. Immunohistochemical staining showed that p150 is highly expressed in surface epithelial cells of the normal human ovary. Expression is exclusively from the P2 promoter governing the E1A splice variant of p150. The P2 promoter is CpG-rich and susceptible to methylation silencing. p150 expression was restored in OVCA cell lines following growth in the presence of 5-azacytidine. In a survey of 210 cases of OVCA, roughly 90% across major and minor histological types failed to show expression of the protein. Immunological and biochemical approaches were used to show hypermethylation of the SALL2 P2 promoter in OVCA-derived cell lines and in a majority of primary tumors. These results bring together molecular biological and clinical evidence in support of a role of SALL2 as a suppressor of ovarian cancers.

Epigenetic silencing of DKK2 and Wnt signal pathway components in human ovarian carcinoma

Wnt/β-Catenin signaling dysregulation is involved in tumorigenesis. Furthermore, epigenetic modification of the Dickkopf (DKK) family (DKK1-DKK4) has been shown to be important in Wnt signaling regulation. In this study, the role of DKK2, a Wnt antagonist, in epithelial ovarian cancer (EOC) was evaluated by examining the expression and methylation of DKK2 in SKOV3 and ES-2 ovarian cancer cell lines and 78 tissues collected from patients (50 ovarian carcinoma, 20 benign tumor and 8 normal ovarian tissues). DKK2 is highly downregulated in EOCs; however, DKK2 expression levels are higher in both normal tissues and benign tumors. In most cases of ovarian carcinoma, DKK2 is methylated, compared with the more common unmethylated form present in benign tumors and normal ovarian tissues. Additionally, DKK2 may be epigenetically silenced by methylation in higher grades and stages of EOC. Functional analysis revealed that overexpression of DKK2 suppressed malignant cell growth and invasion in SKOV3 and ES-2 cell lines. The expression of the downstream genes of Wnt signaling, including β-catenin, c-Myc and cyclin D1, was decreased in DKK2-transfected cells compared with mock cells. The expression of matrix metalloproteinase-2 and focal adhesion kinase were also decreased in DKK2 transfectants, supporting findings indicating inhibition of cell migration and invasion. This report provides novel indications that DKK2 is a unique hypermethylated target gene in EOC and that DKK2 may contribute to tumorigenesis in EOC through the Wnt/β-catenin signaling mechanisms.

Increased DNA methyltransferase activity and DNA methylation following Epidermal Growth Factor stimulation in ovarian cancer cells

Ovarian cancer progression is correlated with accumulation of aberrant CpG island methylation. In ovarian cancer, ascites fluid contains numerous Epidermal-Growth-Factor-Receptor (EGFR) activators, which could result in a tumor microenvironment of constant EGFR activation. Signaling pathways downstream of EGFR, such as Ras, regulate DNA methylation. We hypothesized that chronic EGFR activation could alter DNA methylation. We found that EGFR activation increased DNA methyltransferase (DNMT) activity acutely, as well as after long-term EGF treatment or expression of a mutationally activated EGFR. Furthermore, this increase in DNMT activity was dependent on EGFR catalytic activity and resulted in increased global DNA methylation. Additionally, treatment with the DNMT inhibitor/hypomethylating agent 5-Aza-2'-deoxycytidine (AZA) inhibited the EGF induced increase of both DNMT activity and global methylation. These data support a role for EGFR in the process of accumulated DNA methylation during ovarian cancer progression and suggest that epigenetic therapy may be beneficial for the treatment of ovarian cancer.

Virion protein 16 induces demethylation of DNA integrated within chromatin in a novel mammalian cell model

DNA methylation and demethylation play important roles in mediating epigenetic regulation. So far, the mechanism of DNA demethylation remains elusive and controversial. Here, we constructed a plasmid, named with pCBS-luc, that contained an artificial CpG island, eight Gal4 DNA-binding domain binding site, an SV40 promoter, and a firefly luciferase reporter gene. The linearized pCBS-luc plasmid was methylated in vitro by DNA methyltransferase, and transfected into the HEK293 cells. The stable HEK293 transfectants with methylated pCBS-luc (me-pCBS-luc) were selected and obtained. The methylation status of the selected stable cell lines were confirmed by bisulfite sequencing polymerase chain reaction amplification. The methylation status could be maintained even after 15 passages. The virion protein 16 (VP16) was reported to enhance DNA demethylation around its binding sites of the promoter region in Xenopus fertilized eggs. Using our me-pCBS-luc model, we found that VP16 also had the ability to activate the expression of methylated luciferase reporter gene and induce DNA demethylation in chromatin DNA in mammalian cells. Altogether, we constructed a cell model stably integrated with the me-pCBS-luc reporter plasmid, and in this model we found that VP16 could lead to DNA demethylation. We believe that this cell model will have many potential applications in the future research on DNA demethylation and dynamic process of chromatin modification.

Epigenetic biomarkers in cancer epidemiology

Biochemical, epigenetic, genetic, and imaging biomarkers are used to identify people at high risk for developing cancer. In cancer epidemiology, epigenetic biomarkers offer advantages over other types of biomarkers because they are expressed against a person's genetic background and environmental exposure, and because epigenetic events occur early in cancer development. This chapter describes epigenetic biomarkers that are being used to study the epidemiology of different types of cancer. Because epigenetic alterations can be reversed by chemicals and activate gene expression, epigenetic biomarkers potentially have numerous clinical applications in cancer intervention and treatment and significant implications in public health. This review discusses cancer biomarkers, the characteristics of an ideal biomarker for cancer, and technologies for biomarker detection.

Sensitization of tumor cells by targeting histone deacetylases

Epigenetic mechanisms may contribute to drug resistance by interfering with tumor growth regulatory pathways and pro-apoptotic programs. Since gene expression is regulated by acetylation status of histones, a large variety of histone deacetylase (HDAC) inhibitors have been studied as antitumor agents. On the basis of their pro-apoptotic activity, HDAC inhibitors have been combined with conventional antitumor agents or novel target-specific agents to increase susceptibility to apoptosis and drug sensitivity of cancer cells. Several combination strategies including HDAC inhibitors have been explored in preclinical studies. Promising therapeutic effects have been reported in combination with DNA damaging agents, taxanes, targeted agents, death receptor agonists and hormonal therapies. Some histone deacetylases, such as HDAC6, can also modulate the function of non-histone proteins involved in critical regulatory processes which may be relevant as therapeutic targets. Given the pleiotropic effects of most of the available inhibitors, the mechanisms of the sensitization are not completely elucidated. A better understanding of the involved mechanisms will provide a rational basis to improve the therapeutic outcome of the available antitumor agents.