The Emerging Roles and Therapeutic Implications of Epigenetic Modifications in Ovarian Cancer

Extracellular-Vesicle-Associated UBE2NL and HIST2H3PS2 Promote Tumor Aggressiveness and Metastasis in Gynecologic Cancer

Extracellular vesicles (EVs) play pivotal roles in tumor progression and metastasis by mediating intercellular communication within the tumor microenvironment. In this study, we identified two novel EX cargo proteins-UBE2NL and HIST2H3PS2-derived from highly aggressive epithelial ovarian cancer (EOC) cells and mesenchymal-type ovarian stromal progenitor cells (MSC-OCSPCs) but absent in less aggressive SKOV3 cells. Quantitative proteomic profiling via LC-MS/MS and TCGA-integrated analysis revealed that high expression of these genes correlated with advanced tumor stages and poor overall survival in EOC, and high HIST2H3PS2 expression predicted poor survival in endometrial cancer (EC). Functionally, UBE2NL and HIST2H3PS2 overexpression promoted EOC cell invasiveness, which was further enhanced by EX-mediated autocrine and paracrine effects. In contrast, the knockdown of UBE2NL reduced cell invasiveness and prolonged mouse survival in vivo. Moreover, HIST2H3PS2-enriched EXs significantly increased peritoneal dissemination and ascites in murine models. These findings suggest that EX-packaged UBE2NL and HIST2H3PS2 drive tumor aggressiveness and metastasis in gynecologic cancers, highlighting their potential as prognostic biomarkers and therapeutic targets.

Processed Products of Aconitum soongaricum Stapf. Inhibit the Growth of Ovarian Cancer Cells In vivo via Regulating the PI3K/AKT Signal Pathway

INTRODUCTION/OBJECTIVE

The alkaloids of songorine, aconitine, and benzoylaconitine, as the processed products of Aconitum soongaricum Stapf., can significantly inhibit the migration and invasion of ovarian cancer cells in vitro. Herein, we studied the in vivo role and mechanism of these natural products in processed A. soongaricum Stapf.

METHODS

A xenograft tumor model was constructed. Tumor volumes and weights were calculated. HE staining assessed the histopathological changes of tumors. Inflammatory factors were detected using ELISA. Gene and protein expressions of E-cadherin, N-cadherin, PIK3CA, and AKT1 proteins were measured using RT-qPCR and immunohistochemistry. Protein expressions of E-cadherin, N-cadherin, PIK3CA, AKT1, p-PIK3CA, and p- AKT1 proteins were detected using western blot analysis.

RESULTS

Songorine, aconitine, and benzoylaconine significantly inhibited the growth of tumors as evidenced by decreased tumor volume and weight. The extent and scope of tumor cell necrosis were less in the songorine group compared to the vehicle group. Songorine, aconitine, and benzoylaconine significantly reduced IL-6, IL-1β, and TNF-α levels. Furthermore, songorine, aconitine, and benzoylecgonine induced down-regulation of N-cadherin and AKT1 mRNA in comparison to the vehicle group. Meanwhile, songorine, aconitine, and benzoylaconine also significantly reduced N-cadherin, p-PIK3CA, and p-AKT1 proteins, while upregulating E-cadherin protein expression in comparison to the vehicle group. These effects were further enhanced when combined with the PI3K inhibitor LY294002.

CONCLUSION

Songorine, aconitine, and benzoylaconine may inhibit ovarian cancer growth in vivo by blocking the PI3K/AKT signaling pathway. Our findings may provide evidence for the clinical application of the processed products of Aconitum soongaricum Stapf. in ovarian cancer treatment.

Epigenetic Modulation of Estrogen Receptor Signaling in Ovarian Cancer

Ovarian cancer remains one of the leading causes of cancer-related deaths in women. There are several processes that are described to have a causal relationship in ovarian cancer development, progression, and metastasis formation, that occur both at the genetic and epigenetic level. One of the mechanisms involved in its pathogenesis and progression is estrogen signaling. Estrogen receptors (ER) α, ERβ, and G-protein coupled estrogen receptor 1 (GPER1), in concert with various coregulators and pioneer transcription factors, mediate the effects of estrogens primarily by the transcriptional regulation of estrogen responsive genes, thereby exerting pleiotropic effects including the regulation of cellular proliferation and apoptosis. The expression and activity of estrogen receptors and their coregulators have been demonstrated to be regulated by epigenetic mechanisms like histone modifications and DNA methylation. Here, we intend to summarize and to provide an update on the current understanding of epigenetic mechanisms regulating estrogen signaling and their role in ovarian cancer. For this purpose, we reviewed publications on this topic listed in the PubMed database. Finally, we assess to which extent drugs acting on the epigenetic level might be suitable for the treatment of ovarian cancer.

Exosomes in diagnostic and therapeutic applications of ovarian cancer

Ovarian cancer accounts for more deaths than any other female reproductive tract cancer. The major reasons for the high mortality rates include delayed diagnoses and drug resistance. Hence, improved diagnostic and therapeutic options for ovarian cancer are a pressing need. Extracellular vesicles (EVs), that include exosomes provide hope in both diagnostic and therapeutic aspects. They are natural lipid nanovesicles secreted by all cell types and carry molecules that reflect the status of the parent cell. This facilitates their potential use as biomarkers for an early diagnosis. Additionally, EVs can be loaded with exogenous cargo, and have features such as high stability and favorable pharmacokinetic properties. This makes them ideal for tumor-targeted delivery of biological moieties. The International Society of Extracellular Vesicles (ISEV) based on the Minimal Information for Studies on Extracellular Vesicles (MISEV) recommends the usage of the term "small extracellular vesicles (sEVs)" that includes exosomes for particles that are 30-200 nm in size. However, majority of the studies reported in the literature and relevant to this review have used the term "exosomes". Therefore, this review will use the term "exosomes" interchangeably with sEVs for consistency with the literature and avoid confusion to the readers. This review, initially summarizes the different isolation and detection techniques developed to study ovarian cancer-derived exosomes and the potential use of these exosomes as biomarkers for the early diagnosis of this devastating disease. It addresses the role of exosome contents in the pathogenesis of ovarian cancer, discusses strategies to limit exosome-mediated ovarian cancer progression, and provides options to use exosomes for tumor-targeted therapy in ovarian cancer. Finally, it states future research directions and recommends essential research needed to successfully transition exosomes from the laboratory to the gynecologic-oncology clinic.

Pharmacological inhibition of EZH2 using a covalent inhibitor suppresses human ovarian cancer cell migration and invasion

Metastasis is the cause of poor prognosis in ovarian cancer (OC). Enhancer of Zeste homolog 2 (EZH2), a histone-lysine N-methyltransferase enzyme, promotes OC cell migration and invasion by regulating the expression of tissue inhibitor of metalloproteinase-2 (TIMP2) and matrix metalloproteinases-9 (MMP9). Hence, we speculated that EZH2-targeting therapy might suppress OC migration and invasion. In this study, the expression of EZH2, TIMP2, and MMP9 in OC tissues and cell lines was analyzed using The Cancer Genome Atlas (TCGA) database and western blotting, respectively. The effects of SKLB-03220, an EZH2 covalent inhibitor, on OC cell migration and invasion were investigated using wound-healing assays, Transwell assays, and immunohistochemistry. TCGA database analysis confirmed that the EZH2 and MMP9 mRNA expression was significantly higher in OC tissues, whereas TIMP2 expression was significantly lower than that in normal ovarian tissues. Moreover, EZH2 negatively correlated with TIMP2 and positively correlated with MMP9 expression. In addition to the anti-tumor activity of SKLB-03220 in a PA-1 xenograft model, immunohistochemistry results showed that SKLB-03220 markedly increased the expression of TIMP2 and decreased the expression of MMP9. Additionally, wound-healing and Transwell assays showed that SKLB-03220 significantly inhibited the migration and invasion of both A2780 and PA-1 cells in a concentration-dependent manner. SKLB-03220 inhibited H3K27me3 and MMP9 expression and increased TIMP2 expression in PA-1 cells. Taken together, these results indicate that the EZH2 covalent inhibitor SKLB-03220 inhibits metastasis of OC cells by upregulating TIMP2 and downregulating MMP9, and could thus serve as a therapeutic agent for OC.

Novel players in the development of chemoresistance in ovarian cancer: ovarian cancer stem cells, non-coding RNA and nuclear receptors

Ovarian cancer (OC) ranks as the fifth leading factor for female mortality globally, with a substantial burden of new cases and mortality recorded annually. Survival rates vary significantly based on the stage of diagnosis, with advanced stages posing significant challenges to treatment. OC is primarily categorized as epithelial, constituting approximately 90% of cases, and correct staging is essential for tailored treatment. The debulking followed by chemotherapy is the prevailing treatment, involving platinum-based drugs in combination with taxanes. However, the efficacy of chemotherapy is hindered by the development of chemoresistance, both acquired during treatment (acquired chemoresistance) and intrinsic to the patient (intrinsic chemoresistance). The emergence of chemoresistance leads to increased mortality rates, with many advanced patients experiencing disease relapse shortly after initial treatment. This review delves into the multifactorial nature of chemoresistance in OC, addressing mechanisms involving transport systems, apoptosis, DNA repair, and ovarian cancer stem cells (OCSCs). While previous research has identified genes associated with these mechanisms, the regulatory roles of non-coding RNA (ncRNA) and nuclear receptors in modulating gene expression to confer chemoresistance have remained poorly understood and underexplored. This comprehensive review aims to shed light on the genes linked to different chemoresistance mechanisms in OC and their intricate regulation by ncRNA and nuclear receptors. Specifically, we examine how these molecular players influence the chemoresistance mechanism. By exploring the interplay between these factors and gene expression regulation, this review seeks to provide a comprehensive mechanism driving chemoresistance in OC.

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.

The role of circRNAs in regulation of drug resistance in ovarian cancer

Ovarian cancer is one of the female reproductive system tumors. Chemotherapy is used for advanced ovarian cancer patients; however, drug resistance is a pivotal cause of chemotherapeutic failure. Hence, it is critical to explore the molecular mechanisms of drug resistance of ovarian cancer cells and to ameliorate chemoresistance. Noncoding RNAs (ncRNAs) have been identified to critically participate in drug sensitivity in a variety of human cancers, including ovarian cancer. Among ncRNAs, circRNAs sponge miRNAs and prevent miRNAs from regulation of their target mRNAs. CircRNAs can interact with DNA or proteins to modulate gene expression. In this review, we briefly describe the biological functions of circRNAs in the development and progression of ovarian cancer. Moreover, we discuss the underneath regulatory molecular mechanisms of circRNAs on governing drug resistance in ovarian cancer. Furthermore, we mention the novel strategies to overcome drug resistance via targeting circRNAs in ovarian cancer. Due to that circRNAs play a key role in modulation of drug resistance in ovarian cancer, targeting circRNAs could be a novel approach for attenuation of chemoresistance in ovarian cancer.

An epigenetic hypothesis for ovarian cancer prevention by oral contraceptive pill use

BACKGROUND

Ovarian cancer is the second most common gynecological cancer type after uterine cancers. In 2020, according to worldwide statistics, there were more than 313,000 new cases of ovarian cancer. Most concerning with ovarian cancer is the poor overall survival, with only 30% of patients surviving for longer than 5 years after diagnosis. The reason for this poor outcome includes late diagnosis due to non-specific symptoms and a lack of any highly effective biomarkers of the early stages of ovarian carcinogenesis. However, it is important to note that some modifiable lifestyle factors can be preventative [pregnancy, breastfeeding and combined oral contraceptives pill (COCP) use].

RESULTS

There is now increasing data reporting the role of epigenetic changes, which are detectable in ovarian cancer tumors, suggesting the possibility that epigenetics may also play a key role in the mechanism of long-term effective prevention of ovarian cancer. To our knowledge, there is a lack of high-quality data on the molecular mechanisms of ovarian cancer prevention, although several hypotheses have been proposed.

CONCLUSIONS

This review focusses on the evidence for a proposed novel hypothesis-that COCPs act as a chemoprevention through the impact on the epigenome of the cells of origin of ovarian cancer-fallopian tubes epithelium.

Post-translational modifications of histones: Mechanisms, biological functions, and therapeutic targets

Histones are DNA-binding basic proteins found in chromosomes. After the histone translation, its amino tail undergoes various modifications, such as methylation, acetylation, phosphorylation, ubiquitination, malonylation, propionylation, butyrylation, crotonylation, and lactylation, which together constitute the "histone code." The relationship between their combination and biological function can be used as an important epigenetic marker. Methylation and demethylation of the same histone residue, acetylation and deacetylation, phosphorylation and dephosphorylation, and even methylation and acetylation between different histone residues cooperate or antagonize with each other, forming a complex network. Histone-modifying enzymes, which cause numerous histone codes, have become a hot topic in the research on cancer therapeutic targets. Therefore, a thorough understanding of the role of histone post-translational modifications (PTMs) in cell life activities is very important for preventing and treating human diseases. In this review, several most thoroughly studied and newly discovered histone PTMs are introduced. Furthermore, we focus on the histone-modifying enzymes with carcinogenic potential, their abnormal modification sites in various tumors, and multiple essential molecular regulation mechanism. Finally, we summarize the missing areas of the current research and point out the direction of future research. We hope to provide a comprehensive understanding and promote further research in this field.