c-Kit mediates chemoresistance and tumor-initiating capacity of ovarian cancer cells through activation of Wnt/β-catenin-ATP-binding cassette G2 signaling

Aberrant angiogenic signaling pathways: Accomplices in ovarian cancer progression and treatment

Ovarian cancer is one of the most common malignant tumors in women, and treatment options are limited. Despite efforts to adjust cancer treatment models and develop new methods, including tumor microenvironment (TME) therapy, more theoretical support is needed. Increasing attention is being given to antiangiogenic measures for TME treatment. Another important concept in ovarian cancer TME is angiogenesis, where tumor cells obtain nutrients and oxygen from surrounding tissues through blood vessels to support further expansion and metastasis. Many neovascularization signaling pathways become imbalanced and hyperactive during this process. Inhibiting these abnormal pathways can yield ideal therapeutic effects in patients, even by reversing drug resistance. However, these deep TME signaling pathways often exhibit crosstalk and correlation. Understanding these interactions may be an important strategy for further treating ovarian cancer. This review summarizes the latest progress and therapeutic strategies for these angiogenic signaling pathways in ovarian cancer.

Cancer stem cells: advances in knowledge and implications for cancer therapy

Cancer stem cells (CSCs), a small subset of cells in tumors that are characterized by self-renewal and continuous proliferation, lead to tumorigenesis, metastasis, and maintain tumor heterogeneity. Cancer continues to be a significant global disease burden. In the past, surgery, radiotherapy, and chemotherapy were the main cancer treatments. The technology of cancer treatments continues to develop and advance, and the emergence of targeted therapy, and immunotherapy provides more options for patients to a certain extent. However, the limitations of efficacy and treatment resistance are still inevitable. Our review begins with a brief introduction of the historical discoveries, original hypotheses, and pathways that regulate CSCs, such as WNT/β-Catenin, hedgehog, Notch, NF-κB, JAK/STAT, TGF-β, PI3K/AKT, PPAR pathway, and their crosstalk. We focus on the role of CSCs in various therapeutic outcomes and resistance, including how the treatments affect the content of CSCs and the alteration of related molecules, CSCs-mediated therapeutic resistance, and the clinical value of targeting CSCs in patients with refractory, progressed or advanced tumors. In summary, CSCs affect therapeutic efficacy, and the treatment method of targeting CSCs is still difficult to determine. Clarifying regulatory mechanisms and targeting biomarkers of CSCs is currently the mainstream idea.

Wnt signaling and tumors (Review)

Wnt signaling is a highly conserved evolutionary pathway that plays a key role in regulation of embryonic development, as well as tissue homeostasis and regeneration. Abnormalities in Wnt signaling are associated with tumorigenesis and development, leading to poor prognosis in patients with cancer. However, the pharmacological effects and mechanisms underlying Wnt signaling and its inhibition in cancer treatment remain unclear. In addition, potential side effects of inhibiting this process are not well understood. Therefore, the present review outlines the role of Wnt signaling in tumorigenesis, development, metastasis, cancer stem cells, radiotherapy resistance and tumor immunity. The present review further identifies inhibitors that target Wnt signaling to provide a potential novel direction for cancer treatment. This may facilitate early application of safe and effective drugs targeting Wnt signaling in clinical settings. An in-depth understanding of the mechanisms underlying inhibition of Wnt signaling may improve the prognosis of patients with cancer.

Blocking Oncostatin M receptor abrogates STAT3 mediated integrin signaling and overcomes chemoresistance in ovarian cancer

Chemotherapy such as cisplatin is widely used to treat ovarian cancer either before or after surgical debulking. However, cancer relapse due to chemotherapy resistance is a major challenge in the treatment of ovarian cancer. The underlying mechanisms related to chemotherapy resistance remain largely unclear. Therefore, identification of effective therapeutic strategies is urgently needed to overcome therapy resistance. Transcriptome-based analysis, in vitro studies and functional assays identified that cisplatin-resistant ovarian cancer cells express high levels of OSMR compared to cisplatin sensitive cells. Furthermore, OSMR expression associated with a module of integrin family genes and predominantly linked with integrin αV (ITGAV) and integrin β3 (ITGB3) for cisplatin resistance. Using ectopic expression and knockdown approaches, we proved that OSMR directly regulates ITGAV and ITGB3 gene expression through STAT3 activation. Notably, targeting OSMR using anti-OSMR human antibody inhibited the growth and metastasis of ovarian cancer cells and sensitized cisplatin treatment. Taken together, our results underscore the pivotal role of OSMR as a requirement for cisplatin resistance in ovarian cancer. Notably, OSMR fostered the expression of a distinct set of integrin genes, which in turn resulted into a crosstalk between OSMR and integrins for signaling activation that is critical for cisplatin resistance. Therefore, targeting OSMR emerges as a promising and viable strategy to reverse cisplatin-resistance in ovarian cancer.

Comparative Analysis of Primary Ovarian Cancer Cells and Established Cell Lines as a New Tool for Studies on Ovarian Cancer Cell Complexity

Primary cancer cells reflect the genetic background and phenotype of a tumor. Immortalized cells with higher proliferation activity have an advantage over primary cells. The aim of the study was to immortalize the primary ovarian cancer (OvCa) cells using the plasmid-carrying human telomerase reverse transcriptase (hTERT) gene and compare their phenotype and biological activity with the primary cells. The primary OvCa3 A and OvCa7 A cells were isolated from the ascitic fluid of two high-grade serous ovarian cancer patients and were characterized using immunocytochemical methods, flow cytometry, real-time RT-PCR, Western blot, metabolic activity, and migratory potential. Both immortalized ovarian cancer cell lines mirrored the phenotype of primary cancer cells, albeit with modifications. The OvCa3 A hTERT cells kept the mesenchymal stem cell phenotype of CD73/CD90/CD105-positivity and were CD133-negative, whereas the cell population of OvCa7 A hTERT lost CD73 expression, but almost 90% of cells expressed the CD133 characteristic for the CSCs phenotype. Immortalized OvCa cells differed in gene expression level with respect to Sox2 and Oct4, which was associated with stemness properties. The OvCa7 A hTERT cells showed higher metabolic and migratory activity and ALDH1 expression than the corresponding primary OvCa cells. Both primary and immortalized cell lines were able to form spheroids. The newly established unique immortalized cell line OvCa7 A hTERT, with the characteristic of a serous ovarian cancer malignancy feature, and with the accumulation of the p53, Pax8, and overexpression of the CD133 and CD44 molecules, may be a useful tool for research on therapeutic approaches, especially those targeting CSCs in ovarian cancer and in preclinical 2D and 3D models.

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.

Essential role of PLD2 in hypoxia-induced stemness and therapy resistance in ovarian tumors

BACKGROUND

Hypoxia in solid tumors is an important source of chemoresistance that can determine poor patient prognosis. Such chemoresistance relies on the presence of cancer stem cells (CSCs), and hypoxia promotes their generation through transcriptional activation by HIF transcription factors.

METHODS

We used ovarian cancer (OC) cell lines, xenograft models, OC patient samples, transcriptional databases, induced pluripotent stem cells (iPSCs) and Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq).

RESULTS

Here, we show that hypoxia induces CSC formation and chemoresistance in ovarian cancer through transcriptional activation of the PLD2 gene. Mechanistically, HIF-1α activates PLD2 transcription through hypoxia response elements, and both hypoxia and PLD2 overexpression lead to increased accessibility around stemness genes, detected by ATAC-seq, at sites bound by AP-1 transcription factors. This in turn provokes a rewiring of stemness genes, including the overexpression of SOX2, SOX9 or NOTCH1. PLD2 overexpression also leads to decreased patient survival, enhanced tumor growth and CSC formation, and increased iPSCs reprograming, confirming its role in dedifferentiation to a stem-like phenotype. Importantly, hypoxia-induced stemness is dependent on PLD2 expression, demonstrating that PLD2 is a major determinant of de-differentiation of ovarian cancer cells to stem-like cells in hypoxic conditions. Finally, we demonstrate that high PLD2 expression increases chemoresistance to cisplatin and carboplatin treatments, both in vitro and in vivo, while its pharmacological inhibition restores sensitivity.

CONCLUSIONS

Altogether, our work highlights the importance of the HIF-1α-PLD2 axis for CSC generation and chemoresistance in OC and proposes an alternative treatment for patients with high PLD2 expression.

ATP-Binding Cassette Subfamily G Member 2 in Acute Myeloid Leukemia: A New Molecular Target?

Despite the progress in the knowledge of disease pathogenesis and the identification of many molecular markers as potential targets of new therapies, the cure of acute myeloid leukemia remains challenging. Disease recurrence after an initial response and the development of resistance to old and new therapies account for the poor survival rate and still make allogeneic stem cell transplantation the only curative option. Multidrug resistance (MDR) is a multifactorial phenomenon resulting from host-related characteristics and leukemia factors. Among these, the overexpression of membrane drug transporter proteins belonging to the ABC (ATP-Binding Cassette)-protein superfamily, which diverts drugs from their cellular targets, plays an important role. Moreover, a better understanding of leukemia biology has highlighted that, at least in cancer, ABC protein's role goes beyond simple drug transport and affects many other cell functions. In this paper, we summarized the current knowledge of ABCG2 (formerly Breast Cancer Resistance Protein, BCRP) in acute myeloid leukemia and discuss the potential ways to overcome its efflux function and to revert its ability to confer stemness to leukemia cells, favoring the persistence of leukemia progenitors in the bone marrow niche and justifying relapse also after therapy intensification with allogeneic stem cell transplantation.

MMP-2 Responsive Peptide Hydrogel-Based Nanoplatform for Multimodal Tumor Therapy

Introduction

Responsive drug delivery systems hold great promise for tumor treatment as they focus on therapeutic agents directly, thus minimizing systemic toxicities and drug leakage. In this study, we covalently bound a matrix metalloproteinases-2 (MMP-2) enzyme-sensitive peptide to a tissue-penetrating peptide to rationally design a MMP-2 responsive multifunctional peptide hydrogel platform (aP/IR@FMKB) for cancer photothermal-chemo-immunotherapy. The constructed aP/IR@FMKB with bufalin (BF) loaded in trimethyl chitosan nanoparticles (TB NPs), photothermal agent IR820, and immune checkpoint inhibitor aPD-L1 by self-assembly could be dissociated in the presence of MMP-2 enzyme, triggering content release.

Methods

TB NPs, IR820, and aPD-L1 were encapsulated by intermolecular self-assembly and enzyme-sensitive nanogels (aP/IR@FMKB) were constructed. The in vitro cytotoxicity of the blank gels and their ability to induce immunogenic cell death (ICD) in aP/IR@FMKB were evaluated using 4T1 cells. The promotion of deep tumor penetration and enzyme responsiveness was analyzed using a 3D cell model. The retention and antitumor activity at the tumor sites were examined using the primary tumor model. To assess the antitumor effect of aP/IR@FMKB induced by the immune response and its mechanism of action, recurrent tumor and distal tumor models were constructed.

Results

This hydrogel system demonstrated exceptional photothermal performance and displayed prolonged local retention. Furthermore, the induction of ICD through IR820 and TB NPs sensitized the PD-L1 blockade, resulting in a remarkable 3.5-fold and 5.2-fold increase in the frequency of intratumor-infiltrating CD8+ T-cells in the primary tumor and distal tumor, respectively. Additionally, this system demonstrated remarkable efficacy in suppressing primary, distal, and recurrent tumors, underscoring its potential as a highly potent therapeutic strategy.

Conclusion

This innovative design of the responsive hydrogel can effectively modulate the tumor immune microenvironment while also demonstrating sensitivity to the PD-1/PD-L1 blockade. This significant finding highlights the promising potential of this hydrogel in the field of multimodal tumor therapy.

The Role of Cancer Stem Cell Markers in Ovarian Cancer

Ovarian cancer is the most lethal gynaecological cancer and the eighth most common female cancer. The early diagnosis of ovarian cancer remains a clinical problem despite the significant development of technology. Nearly 70% of patients with ovarian cancer are diagnosed with stages III-IV metastatic disease. Reliable diagnostic and prognostic biomarkers are currently lacking. Ovarian cancer recurrence and resistance to chemotherapy pose vital problems and translate into poor outcomes. Cancer stem cells appear to be responsible for tumour recurrence resulting from chemotherapeutic resistance. These cells are also crucial for tumour initiation due to the ability to self-renew, differentiate, avoid immune destruction, and promote inflammation and angiogenesis. Studies have confirmed an association between CSC occurrence and resistance to chemotherapy, subsequent metastases, and cancer relapses. Therefore, the elimination of CSCs appears important for overcoming drug resistance and improving prognoses. This review focuses on the expression of selected ovarian CSC markers, including CD133, CD44, CD24, CD117, and aldehyde dehydrogenase 1, which show potential prognostic significance. Some markers expressed on the surface of CSCs correlate with clinical features and can be used for the diagnosis and prognosis of ovarian cancer. However, due to the heterogeneity and plasticity of CSCs, the determination of specific CSC phenotypes is difficult.

High-grade serous ovarian carcinoma, the "Achiles' hill" for clinicians and molecular biologists: a molecular insight

High-grade serous ovarian carcinoma (HGSOC), the deadliest ovarian cancer, alone accounts for 90% of all its subtypes. Characterized by hallmark mutation of TP53, HGSOC show diverse molecular etiology. HGSOC can arise from both ovarian epithelium as well as the fimbrial epithelium of the fallopian tube. Ovulation induced reactive oxygen species, follicular fluid associated growth factor induced stemness, deregulation of hormone receptors like ER, FSHR, AR and hormones like FSH, LH, prolonged ovulation cycle, use of oral contraceptives are agonists of HGSOC while parity, breastfeeding provide protective effect from HGSOC development. Apart from a generic TP53 mutation, mutation of BRCA1/2, RAD51, BRIP1, PALB2, CHEK2, RAD50 etc., were reportedly associated with development of HGSOC. Epigenetic events like methylation of RASSF1A of RAS signaling pathway,OR51L1, OR51I1, OR51F1 etc. has been reported in HGSOC. Micro-RNAs like miR-1290, miR 27-a-3p miR23a, miR205 were reportedly upregulated in HGSOC. Amongst its cognate subtypes viz. differentiated, immunoreactive, mesenchymal, and proliferative, mesenchymal, and proliferative show worst prognosis. A system biology approach showed five major altered pathways in HGSOC, namely, RB, PI3K/RAS, NOTCH, HRR and FOXM1 signaling. For chemonaive patients, drugs that helps in efflux of reduced glutathione or prevent the redox coupling of GSH-GSSG, like Cisplatin, could be considered as the best therapeutic choice for HGSOC. For patients with BRCA1/2 mutations, PARP inhibitors alone or with Bevacizumab can be effective. Immune checkpoint inhibitors could be effective against immunoreactive subtypes. Identification of genes deregulated in chemoresistance could provide better insights in dealing with the disease.

Environmental-relevant bisphenol A exposure promotes ovarian cancer stemness by regulating microRNA biogenesis

Bisphenol A (BPA) is a ubiquitous environmental xenobiotic impacting millions of people worldwide. BPA has long been proposed to promote ovarian carcinogenesis, but the detrimental mechanistic target remains unclear. Cancer stem cells (CSCs) are considered as the trigger of tumour initiation and progression. Here, we show for the first time that nanomolar (environmentally relevant) concentration of BPA can markedly increase the formation and expansion of ovarian CSCs concomitant. This effect is observed in both oestrogen receptor (ER)-positive and ER-defective ovarian cancer cells, suggesting that is independent of the classical ERs. Rather, the signal is mediated through alternative ER G-protein-coupled receptor 30 (GPR30), but not oestrogen-related receptor α and γ. Moreover, we report a novel role of BPA in the regulation of Exportin-5 that led to dysregulation of microRNA biogenesis through miR-21. The use of GPR30 siRNA or antagonist to inhibit GPR30 expression or activity, respectively, resulted in significant inhibition of ovarian CSCs. Similarly, the CSCs phenotype can be reversed by expression of Exportin-5 siRNA. These results identify for the first time non-classical ER and microRNA dysregulation as novel mediators of low, physiological levels of BPA function in CSCs that may underlie its significant tumour-promoting properties in ovarian cancer.

SLC1A5 regulates cell proliferation and self-renewal through β-catenin pathway mediated by redox signaling in arsenic-treated uroepithelial cells

Arsenic exposure increases the risk of bladder cancer in humans, but its underlying mechanisms remain elusive. The alanine, serine, cysteine-preferring transporter 2 (ASCT2, SLC1A5) is frequently overexpressed in cancer cells. The aim of this study was to evaluate the effects of arsenic on SLC1A5, and to determine the role of SLC1A5 in the proliferation and self-renewal of uroepithelial cells. F344 rats were exposed to 87 mg/L NaAsO₂ or 200 mg/L DMA^V for 12 weeks. The SV-40 immortalized human uroepithelial (SV-HUC-1) cells were cultured in medium containing 0.5 μM NaAsO₂ for 40 weeks. Arsenic increased the expression levels of SLC1A5 and β-catenin both in vivo and in vitro. SLC1A5 promoted cell proliferation and self-renewal by activating β-catenin, which in turn was dependent on maintaining GSH/ROS homeostasis. Our results suggest that SLC1A5 is a potential therapeutic target for arsenic-induced proliferation and self-renewal of uroepithelial cells.

Deciphering Common Traits of Breast and Ovarian Cancer Stem Cells and Possible Therapeutic Approaches

Breast cancer (BC) and ovarian cancer (OC) are among the most common and deadly cancers affecting women worldwide. Both are complex diseases with marked heterogeneity. Despite the induction of screening programs that increase the frequency of earlier diagnosis of BC, at a stage when the cancer is more likely to respond to therapy, which does not exist for OC, more than 50% of both cancers are diagnosed at an advanced stage. Initial therapy can put the cancer into remission. However, recurrences occur frequently in both BC and OC, which are highly cancer-subtype dependent. Therapy resistance is mainly attributed to a rare subpopulation of cells, named cancer stem cells (CSC) or tumor-initiating cells, as they are capable of self-renewal, tumor initiation, and regrowth of tumor bulk. In this review, we will discuss the distinctive markers and signaling pathways that characterize CSC, their interactions with the tumor microenvironment, and the strategies they employ to evade immune surveillance. Our focus will be on identifying the common features of breast cancer stem cells (BCSC) and ovarian cancer stem cells (OCSC) and suggesting potential therapeutic approaches.

The role of DNA methylation in ovarian cancer chemoresistance: A narrative review

Background and Aims

Ovarian cancer (OC) is the most lethal gynecological cancer. In 2018, it was responsible for over 180,000 deaths worldwide. The high mortality rate is the culmination of a lack of early diagnosis and high rates of chemotherapy resistance, which is synonymous with disease recurrence. Over the last two decades, an increasingly significant role of epigenetic mechanisms, in particular DNA methylation, has emerged. This review will discuss several of the most significant genes whose hypo/hypermethylation profiles are associated with chemoresistance. Aside from functionally elucidating and evaluating these epimutations, this review will discuss recent trials of DNA methyltransferase inhibitors (DNMTi). Finally, we will propose future directions that could enhance the feasibility of utilizing these candidate epimutations as clinical biomarkers.

Methods

To perform this review, a comprehensive literature search based on our keywords was conducted across the online databases PubMed and Google Scholar for identifying relevant studies published up until August 2022.

Results

Epimutations affecting MLH1, MSH2, and Ras-association domain family 1 isoform A (DNA damage repair and apoptosis); ATP-binding cassette subfamily B member 1 and methylation-controlled J (drug export); secreted frizzled-related proteins (Wnt/β-catenin signaling), neurocalcin delta (calcium and G protein-coupled receptor signaling), and zinc finger protein 671 all have potential as biomarkers for chemoresistance. However, specific uncertainties relating to these epimutations include histotype-specific differences, intrinsic versus acquired chemoresistance, and the interplay with complete surgical debulking. DNMTi for chemoresistant OC patients has shown some promise; however, issues surrounding their efficacy and dose-limiting toxicities remain; a personalized approach is required to maximize their effectiveness.

Conclusion

Establishing a panel of aberrantly methylated chemoresistance-related genes to predict chemoresponsiveness and patients' suitability to DNMTi could significantly reduce OC recurrence, while improving DNMTi therapy viability. To achieve this, a large-scale prospective genome-wide DNA methylation profile study that spans different histotypes, includes paired samples (before and after chemotherapy), and integrates transcriptomic and methylomic analysis, is warranted.

Neo-vascularization-based therapeutic perspectives in advanced ovarian cancer

The process of angiogenesis is well described for its potential role in the development of normal ovaries, and physiological functions as well as in the initiation, progression, and metastasis of ovarian cancer (OC). In advanced stages of OC, cancer cells spread outside the ovary to the pelvic, abdomen, lung, or multiple secondary sites. This seriously limits the efficacy of therapeutic options contributing to fatal clinical outcomes. Notably, a variety of angiogenic effectors are produced by the tumor cells to initiate angiogenic processes leading to the development of new blood vessels, which provide essential resources for tumor survival, dissemination, and dormant micro-metastasis of tumor cells. Multiple proangiogenic effectors and their signaling axis have been discovered and functionally characterized for potential clinical utility in OC. In this review, we have provided the current updates on classical and emerging proangiogenic effectors, their signaling axis, and the immune microenvironment contributing to the pathogenesis of OC. Moreover, we have comprehensively reviewed and discussed the significance of the preclinical strategies, drug repurposing, and clinical trials targeting the angiogenic processes that hold promising perspectives for the better management of patients with OC.

Advances in antitumor research of HIF-1α inhibitor YC-1 and its derivatives

Generally, hypoxia-inducible factor-1α (HIF-1α) is highly expressed in solid tumors, it plays a key role in the occurrence and development of tumors, hindering cancer treatment in various ways. The antitumor activity and pharmacological mechanism of YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1‑benzyl indazole], an HIF-1α inhibitor, and the design and synthesis of its derivatives have attracted tremendous attention in the field of antitumor research. YC-1 is a potential drug candidate and a lead compound for tumor therapy. Hence, the multifaceted mechanism of action of YC-1 and the structure activity relationship (SAR) of its derivatives are important factors to be considered for the development of HIF-1α inhibitors. Therefore, this review aimed to provide a comprehensive overview of the various antitumor mechanisms of YC-1 in antitumor research and an in-depth summary of the SAR for the development of its derivatives. A full understanding and discussion of these aspects are expected to provide potential ideas for developing novel HIF-1α inhibitors and antitumor drugs belonging to the YC-1 class. The review also highlighted the application prospects of the YC-1 class of potential antitumor candidates, and provided some unique insights about these antitumor agents.

Targeting ovarian cancer stem cells: a new way out

Ovarian cancer (OC) is the most lethal gynecological malignancy due to tumor heterogeneity, the lack of reliable early diagnosis methods and the high incidence of chemoresistant recurrent disease. Although there are developments in chemotherapies and surgical techniques to improve the overall survival of OC patients, the 5-year survival of advanced OC patients is still low. To improve the prognosis of OC patients, it is important to search for novel therapeutic approaches. Cancer stem cells (CSCs) are a subpopulation of tumor cells that participate in tumor growth, metastasis and chemoresistance. It is important to study the role of CSCs in a highly heterogeneous disease such as OC, which may be significant to a better understanding of the oncogenetic and metastatic pathways of the disease and to develop novel strategies against its progression and platinum resistance. Here, we summarized the current findings about targeting methods against ovarian cancer stem cells, including related signaling pathways, markers and drugs, to better manage OC patients using CSC-based therapeutic strategies.

Expression level of CD117 (KIT) on ovarian cancer extracellular vesicles correlates with tumor aggressiveness

Ovarian cancer is known to be the most lethal malignancy among all gynecological cancers affecting a large number of women worldwide. The treatment of ovarian cancer is challenging due to the high recurrence rate of the disease and is further complicated by acquired chemoresistance. Most ovarian cancer deaths are the result of the metastatic spread of drug-resistant cells. The theory of cancer stem cells (CSC) suggests that both tumor initiation and progression are driven by a population of undifferentiated capable of self-renewal, tumor initiation and development of chemoresistance. The CD117 mast/stem cell growth factor receptor (KIT) is the most commonly used marker for ovarian CSCs. Here, we analyze the correlation between CD117 expression and histological tumor type in ovarian cancer cell lines (SK-OV-3 and MES-OV) and in small/medium extracellular vesicles (EVs) isolated from the urine of ovarian cancer patients. We have demonstrated that the abundance of CD117 on cells and EVs is correlated with tumor grade and therapy resistance status. Moreover, using small EVs isolated from ovarian cancer ascites, it was shown that recurrent disease is characterized by a much higher abundance of CD117 on EVs than primary tumor.

Anti-Cancer Activity of Cannabis sativa Phytocannabinoids: Molecular Mechanisms and Potential in the Fight against Ovarian Cancer and Stem Cells

Ovarian cancer (OC) is the most lethal gynecological malignancy, with about 70% of cases diagnosed only at an advanced stage. Cannabis sativa, which produces more than 150 phytocannabinoids, is used worldwide to alleviate numerous symptoms associated with various medical conditions. Recently, studies across a range of cancer types have demonstrated that the phytocannabinoids Δ9-trans-tetrahydrocannabinol (THC) and cannabidiol (CBD) have anti-cancer activity in vitro and in vivo, but also the potential to increase other drugs’ adverse effects. THC and CBD act via several different biological and signaling pathways, including receptor-dependent and receptor-independent pathways. However, very few studies have examined the effectiveness of cannabis compounds against OC. Moreover, little is known about the effectiveness of cannabis compounds against cancer stem cells (CSCs) in general and OC stem cells (OCSCs) in particular. CSCs have been implicated in tumor initiation, progression, and invasion, as well as tumor recurrence, metastasis, and drug resistance. Several hallmarks and concepts describe CSCs. OCSCs, too, are characterized by several markers and specific drug-resistance mechanisms. While there is no peer-reviewed information regarding the effect of cannabis and cannabis compounds on OCSC viability or development, cannabis compounds have been shown to affect genetic pathways and biological processes related to CSCs and OCSCs. Based on evidence from other cancer-type studies, the use of phytocannabinoid-based treatments to disrupt CSC homeostasis is suggested as a potential intervention to prevent chemotherapy resistance. The potential benefits of the combination of chemotherapy with phytocannabinoid treatment should be examined in ovarian cancer patients.

Drug resistance in cancer therapy: the Pandora's Box of cancer stem cells

Drug resistance is the main culprit of failure in cancer therapy that may lead to cancer relapse. This resistance mostly originates from rare, but impactful presence of cancer stem cells (CSCs). Ability to self-renewal and differentiation into heterogeneous cancer cells, and harboring morphologically and phenotypically distinct cells are prominent features of CSCs. Also, CSCs substantially contribute to metastatic dissemination. They possess several mechanisms that help them to survive even after exposure to chemotherapy drugs. Although chemotherapy is able to destroy the bulk of tumor cells, CSCs are left almost intact, and make tumor entity resistant to treatment. Eradication of a tumor mass needs complete removal of tumor cells as well as CSCs. Therefore, it is important to elucidate key features underlying drug resistance raised by CSCs in order to apply effective treatment strategies. However, the challenging point that threatens safety and specificity of chemotherapy is the common characteristics between CSCs and normal peers such as signaling pathways and markers. In the present study, we tried to present a comprehensive appraisal on CSCs, mechanisms of their drug resistance, and recent therapeutic methods targeting this type of noxious cells.

Wnt antagonist as therapeutic targets in ovarian cancer

Ovarian cancer is a fatal malignancy in women with a low survival rate that demands new therapeutic paradigms. Cancer cells acquire various exclusive alterations to proliferate, invade, metastasize, and escape cell death, acting independently of growth-inducing or growth-inhibiting signals. The nature of cellular signaling in tumorigenesis is interwoven. Wnt signaling is an evolutionarily conserved signaling cascade that has been shown to regulate ovarian cancer pathogenesis. The molecular mechanism of Wnt signaling underlying the development of ovarian cancer, drug resistance, and relapse is not completely understood. Extracellularly secreted Wnt signaling inhibitors are crucial regulators of ovarian cancer tumorigenesis and malignant properties of cancer stem cells. Wnt inhibitors arbitrated modifications affecting Wnt pathway proteins on the cell membranes, in the cytoplasm, and in the nucleus have been shown to span essential contributions in the initiation, progression, and chemoresistance of ovarian cancer. Although many extrinsic inhibitors developed targeting the downstream components of the Wnt signaling pathway, investigating the molecular mechanisms of endogenous secreted inhibitors might substantiate prognostic or therapeutic biomarkers development. Given the importance of Wnt signaling in ovarian cancer, more systematic studies combined with clinical studies are requisite to probe the precise mechanistic interactions of Wnt antagonists in ovarian cancer. This review outlines the latest progress on the Wnt antagonists and ovarian cancer-specific regulators such as micro-RNAs, small molecules, and drugs regulating these Wnt antagonists in ovarian tumourigenesis.

KDF1 Promoted Proliferation and Metastasis of Epithelial Ovarian Cancer via Wnt/Beta-Catenin Pathway: TCGA-Based Data Mining and Experimental Validation

Objectives: It has been reported that keratinocyte differentiation factor 1 (KDF1) was related to proliferation, differentiation, and cell cycle. However, the role of KDF1 has not been reported in ovarian cancer. The present study investigated the function and the potential mechanism of KDF1 in ovarian cancer.

Methods: We evaluated the prognostic value in ovarian cancer based on data from the Cancer Genome Atlas (TCGA) database. The Kruskal–Wallis test, Wilcoxon signed-rank test, and logistic regression were used to evaluate the relationship between KDF1 expression and clinicopathologic features. The Cox regression and the Kaplan–Meier method were adopted to evaluate prognosis-related factors. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) gene enrichment analysis, and Gene Set Enrichment Analysis (GSEA) were performed to identify the key biological process related to KDF1. Then the expression of KDF1 in ovarian cancer tissues was validated by streptavidin–peroxidase (SP) immunohistochemistry. The proliferation and invasion ability of KDF1 were determined by EdU and Transwell assay, respectively, with KDF1 gene silencing and overexpression. The mRNA expression of KDF1 was determined by qPCR. The protein expression of KDF1 was determined using the Western blot.

Methods: By performing differential expression analysis on the ovarian cancer data of the TCGA database, it was found that KDF1 is highly expressed in ovarian cancer patients and associated with poorer overall survival (OS) and progression-free survival (PFS) of ovarian cancer patients. The highly expressed KDF1 may reduce cell adhesion according to GO, KEGG, and GSEA results. After analysis combining the relevant clinical features, we found that the high expression of KDF1 is an independent prognostic factor of ovarian cancer and associated with platinum resistance and tumor metastasis in ovarian cancer. At the same time, the BioGRID database showed that there might be protein–protein interaction between KDF1 and E-cadherin. Then we further validated that the high expression of KDF1 had a close correlation with the stage and grade of ovarian cancer in ovarian cancer tissue chips. Silencing KDF1 inhibited the proliferation and invasion ability of SKOV3 cells. By contrast, ectopic expression of KDF1 promoted the proliferation and invasion ability of A2780 cells. We also found that KDF1 can interact with E-cadherin and regulate the expression of Wnt5A and β-catenin, hence activating Wnt/β-catenin pathway via in vitro and vivo experiments.

Conclusions: Based on the bioinformatics analysis, in vitro experiments, and an in vivo study, it is indicated that KDF1 played an important role in ovarian cancer progression and might be a therapeutic target for patients with ovarian cancer.

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

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

Downregulated Wnt2B Expression Suppresses Proliferation, Invasion, and Angiogenesis of Ovarian Cancer Cells Through Inhibiting the Wnt/β-Catenin Signaling Pathway

Ovarian cancer (OC) is known to be the most malignant gynecologic cancers. Wnt2B, a member of the Wnt family, plays a critical role in tumor development. However, the effect of Wnt2B on the occurrence and development of OC remains largely uncharacterized. In this study, immunohistochemistry assay indicated that Wnt2B was increased in our study cohort (OC). In addition, the expression of Wnt2B was positively correlated with TNM stages and metastasis of OC patients. Wnt2B markedly mediated the regulation of OC proliferation, invasion, and angiogenesis. Moreover, Wnt2B knockdown inactivated the Wnt/β-catenin signaling pathway. More importantly, the Wnt/β-catenin signaling pathway activator LiCl reversed the effect of Wnt2B knockdown on OC cell proliferation, angiogenesis, and invasion. Our data indicated that Wnt2B silencing could inhibit the proliferation, invasion, and angiogenesis of OC cells through downregulating the activity of Wnt/β-catenin pathway.

The Potential for Natural Products to Overcome Cancer Drug Resistance by Modulation of Epithelial-Mesenchymal Transition

The acquisition of resistance and ultimately disease relapse after initial response to chemotherapy put obstacles in the way of cancer therapy. Epithelial-mesenchymal transition (EMT) is a biologic process that epithelial cells alter to mesenchymal cells and acquire fibroblast-like properties. EMT plays a significant role in cancer metastasis, motility, and survival. Recently, emerging evidence suggested that EMT pathways are very important in making drug-resistant involved in cancer. Natural products are gradually emerging as a valuable source of safe and effective anticancer compounds. Natural products could interfere with the different processes implicated in cancer drug resistance by reversing the EMT process. In this review, we illustrate the molecular mechanisms of EMT in the emergence of cancer metastasis. We then present the role of natural compounds in the suppression of EMT pathways in different cancers to overcome cancer cell drug resistance and improve tumor chemotherapy. HighlightsDrug-resistance is one of the obstacles to cancer treatment.EMT signaling pathways have been correlated to tumor invasion, metastasis, and drug-resistance.Various studies on the relationship between EMT and resistance to chemotherapy agents were reviewed.Different anticancer natural products with EMT inhibitory properties and drug resistance reversal effects were compared.

Cancer Stem Cells: An Ever-Hiding Foe

Cancer stem cells are a population of cells enable to reproduce the original phenotype of the tumor and capable to self-renewal, which is crucial for tumor proliferation, differentiation, recurrence, and metastasis, as well as chemoresistance. Therefore, the cancer stem cells (CSCs) have become one of the main targets for anticancer therapy and many ongoing clinical trials test anti-CSCs efficacy of plenty of drugs. This chapter describes CSCs starting from general description of this cell population, through CSCs markers, signaling pathways, genetic and epigenetic regulation, role of epithelial-mesenchymal transition (EMT) transition and autophagy, cooperation with microenvironment (CSCs niche), and finally role of CSCs in escaping host immunosurveillance against cancer.

TCOF1 upregulation in triple-negative breast cancer promotes stemness and tumour growth and correlates with poor prognosis

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with poor prognosis. By performing multiomic profiling, we recently uncovered super-enhancer heterogeneity between breast cancer subtypes. Our data also revealed TCOF1 as a putative TNBC-specific super-enhancer-regulated gene. TCOF1 plays a critical role in craniofacial development but its function in cancer remains unclear.

METHODS

Overall survival and multivariant Cox regression analyses were conducted using the METABRIC data set. The effect of TCOF1 knockout on TNBC growth and stemness was evaluated by in vitro and in vivo assays. RNA-seq and rescue experiments were performed to explore the underlying mechanisms.

RESULTS

TCOF1 is frequently upregulated in TNBC and its elevated expression correlates with shorter overall survival. TCOF1 depletion significantly inhibits the growth and stemness of basal-like TNBC, but not of mesenchymal-like cells, highlighting the distinct molecular dependency in different TNBC subgroups. RNA-seq uncovers several stem cell molecules regulated by TCOF1. We further demonstrate that KIT is a downstream effector of TCOF1 in mediating TNBC stemness. TCOF1 expression in TNBC is regulated by the predicted super-enhancer.

CONCLUSIONS

TCOF1 depletion potently attenuates the growth and stemness of basal-like TNBC. Expression of TCOF1 may serve as a TNBC prognostic marker and a therapeutic target.

Modeling the Tumor Microenvironment of Ovarian Cancer: The Application of Self-Assembling Biomaterials

Ovarian cancer (OvCa) is one of the leading causes of gynecologic malignancies. Despite treatment with surgery and chemotherapy, OvCa disseminates and recurs frequently, reducing the survival rate for patients. There is an urgent need to develop more effective treatment options for women diagnosed with OvCa. The tumor microenvironment (TME) is a key driver of disease progression, metastasis and resistance to treatment. For this reason, 3D models have been designed to represent this specific niche and allow more realistic cell behaviors compared to conventional 2D approaches. In particular, self-assembling peptides represent a promising biomaterial platform to study tumor biology. They form nanofiber networks that resemble the architecture of the extracellular matrix and can be designed to display mechanical properties and biochemical motifs representative of the TME. In this review, we highlight the properties and benefits of emerging 3D platforms used to model the ovarian TME. We also outline the challenges associated with using these 3D systems and provide suggestions for future studies and developments. We conclude that our understanding of OvCa and advances in materials science will progress the engineering of novel 3D approaches, which will enable the development of more effective therapies.

Tumour Microenvironment Stress Promotes the Development of Drug Resistance

Multi-drug resistance (MDR) is a leading cause of cancer-related death, and it continues to be a major barrier to cancer treatment. The tumour microenvironment (TME) has proven to play an essential role in not only cancer progression and metastasis, but also the development of resistance to chemotherapy. Despite the significant advances in the efficacy of anti-cancer therapies, the development of drug resistance remains a major impediment to therapeutic success. This review highlights the interplay between various factors within the TME that collectively initiate or propagate MDR. The key TME-mediated mechanisms of MDR regulation that will be discussed herein include (1) altered metabolic processing and the reactive oxygen species (ROS)-hypoxia inducible factor (HIF) axis; (2) changes in stromal cells; (3) increased cancer cell survival via autophagy and failure of apoptosis; (4) altered drug delivery, uptake, or efflux and (5) the induction of a cancer stem cell (CSC) phenotype. The review also discusses thought-provoking ideas that may assist in overcoming the TME-induced MDR. We conclude that stressors from the TME and exposure to chemotherapeutic agents are strongly linked to the development of MDR in cancer cells. Therefore, there remains a vast area for potential research to further elicit the interplay between factors existing both within and outside the TME. Elucidating the mechanisms within this network is essential for developing new therapeutic strategies that are less prone to failure due to the development of resistance in cancer cells.

Multidrug efflux transporter ABCG2: expression and regulation

The adenosine triphosphate (ATP)-binding cassette efflux transporter G2 (ABCG2) was originally discovered in a multidrug-resistant breast cancer cell line. Studies in the past have expanded the understanding of its role in physiology, disease pathology and drug resistance. With a widely distributed expression across different cell types, ABCG2 plays a central role in ATP-dependent efflux of a vast range of endogenous and exogenous molecules, thereby maintaining cellular homeostasis and providing tissue protection against xenobiotic insults. However, ABCG2 expression is subjected to alterations under various pathophysiological conditions such as inflammation, infection, tissue injury, disease pathology and in response to xenobiotics and endobiotics. These changes may interfere with the bioavailability of therapeutic substrate drugs conferring drug resistance and in certain cases worsen the pathophysiological state aggravating its severity. Considering the crucial role of ABCG2 in normal physiology, therapeutic interventions directly targeting the transporter function may produce serious side effects. Therefore, modulation of transporter regulation instead of inhibiting the transporter itself will allow subtle changes in ABCG2 activity. This requires a thorough comprehension of diverse factors and complex signaling pathways (Kinases, Wnt/β-catenin, Sonic hedgehog) operating at multiple regulatory levels dictating ABCG2 expression and activity. This review features a background on the physiological role of transporter, factors that modulate ABCG2 levels and highlights various signaling pathways, molecular mechanisms and genetic polymorphisms in ABCG2 regulation. This understanding will aid in identifying potential molecular targets for therapeutic interventions to overcome ABCG2-mediated multidrug resistance (MDR) and to manage ABCG2-related pathophysiology.

A novel anti-c-Kit antibody-drug conjugate to treat wild-type and activating-mutant c-Kit-positive tumors

c‐Kit overexpression and activating mutations, which are reported in various cancers, including gastrointestinal stromal tumor (GIST), small‐cell lung cancer (SCLC), acute myeloid leukemia, acral melanoma, and systemic mastocytosis (SM), confer resistance to tyrosine kinase inhibitors (TKIs). To overcome TKI resistance, an anti‐c‐Kit antibody–drug conjugate was developed in this study to treat wild‐type and mutant c‐Kit‐positive cancers. NN2101, a fully human IgG1, was conjugated to DM1, a microtubule inhibitor, through N‐succinimidyl‐4‐(N‐maleimidomethyl) cyclohexane‐1‐carboxylate (SMCC) (to give NN2101‐DM1). The antitumor activity of NN2101‐DM1 was evaluated in vitro and in vivo using various cancer cell lines. NN2101‐DM1 exhibited potent growth‐inhibitory activities against c‐Kit‐positive cancer cell lines. In a mouse xenograft model, NN2101‐DM1 exhibited potent growth‐inhibitory activities against imatinib‐resistant GIST and SM cells. In addition, NN2101‐DM1 exhibited a significantly higher anti‐cancer effect than carboplatin/etoposide against SCLC cells where c‐Kit does not mediate cancer pathogenesis. Furthermore, the combination of NN2101‐DM1 with imatinib in imatinib‐sensitive GIST cells induced complete remission compared with treatment with NN2101‐DM1 or imatinib alone in mouse xenograft models. These results suggest that NN2101‐DM1 is a potential therapeutic agent for wild‐type and mutant c‐Kit‐positive cancers.

TRIB2 Stimulates Cancer Stem-Like Properties through Activating the AKT-GSK3β-β-Catenin Signaling Axis

Tribbles homolog 2 (TRIB2) is implicated in tumorigenesis and drug resistance in various types of cancers. However, the role of TRIB2 in the regulation of tumorigenesis and drug resistance of cancer stem cells (CSCs) is still elusive. In the present study, we showed increased expression of TRIB2 in spheroid-forming and aldehyde dehydrogenase-positive CSC populations of A2780 epithelial ovarian cancer cells. Short hairpin RNA-mediated silencing of TRIB2 expression attenuates the spheroid-forming, migratory, tumorigenic, and drug-resistant properties of A2780 cells, whereas overexpression of TRIB2 increases the CSC-like characteristics. TRIB2 overexpression induced GSK3β inactivation by augmenting AKT-dependent phosphorylation of GSK3β at Ser9, followed by increasing β-catenin level via reducing the GSK3β-mediated phosphorylation of β-catenin. Treatment of TRIB2-ovexpressed A2780 cells with the phosphoinositide-3-kinase inhibitor LY294002 abrogated TRIB2-stimulated proliferation, migration, drug resistance of A2780 cells. These results suggest a critical role for TRIB2 in the regulation of CSC-like properties by increasing the stability of β-catenin protein via the AKT-GSK3β-dependent pathways.

Therapeutic Strategies for Targeting Ovarian Cancer Stem Cells

Ovarian cancer is a fatal gynecological malignancy. Although first-line chemotherapy and surgical operation are effective treatments for ovarian cancer, its clinical management remains a challenge owing to intrinsic or acquired drug resistance and relapse at local or distal lesions. Cancer stem cells (CSCs) are a small subpopulation of cells inside tumor tissues, and they can self-renew and differentiate. CSCs are responsible for the cancer malignancy involved in relapses as well as resistance to chemotherapy and radiation. These malignant properties of CSCs are regulated by cell surface receptors and intracellular pluripotency-associated factors triggered by internal or external stimuli from the tumor microenvironment. The malignancy of CSCs can be attenuated by individual or combined restraining of cell surface receptors and intracellular pluripotency-associated factors. Therefore, targeted therapy against CSCs is a feasible therapeutic tool against ovarian cancer. In this paper, we review the prominent roles of cell surface receptors and intracellular pluripotency-associated factors in mediating the stemness and malignancy of ovarian CSCs.

Recent advancements in therapeutic targeting of the Warburg effect in refractory ovarian cancer: A promise towards disease remission

Epithelial ovarian cancer, the most lethal gynecological malignancy, is diagnosed at advanced stage, recurs and displays chemoresistance to standard chemotherapeutic regimen of taxane/platinum drugs. Despite development of recent therapeutic approaches including poly-ADP ribose polymerase inhibitors, this fatal disease is diagnosed at advanced stage and heralds strategies for early detection and improved treatment. Recent literature suggests that high propensity of ovarian cancer cells to consume and metabolize glucose via glycolysis even in the presence of oxygen (the 'Warburg effect') can significantly contribute to disease progression and chemoresistance and hence, it has been exploited as novel drug target. This review focuses on the molecular cues of aberrant glycolysis as drivers of chemo-resistance and aggressiveness of recurrent ovarian cancer. Furthermore, we discuss the status quo of small molecule inhibition of aerobic glycolysis and significance of metabolic coupling between cancer cells and tumor microenvironment as novel therapeutic interventions against this lethal pathology.

Whole-transcriptome Analysis of Fully Viable Energy Efficient Glycolytic-null Cancer Cells Established by Double Genetic Knockout of Lactate Dehydrogenase A/B or Glucose-6-Phosphate Isomerase

BACKGROUND/AIM

Nearly all mammalian tumors of diverse tissues are believed to be dependent on fermentative glycolysis, marked by elevated production of lactic acid and expression of glycolytic enzymes, most notably lactic acid dehydrogenase (LDH). Therefore, there has been significant interest in developing chemotherapy drugs that selectively target various isoforms of the LDH enzyme. However, considerable questions remain as to the consequences of biological ablation of LDH or upstream targeting of the glycolytic pathway.

MATERIALS AND METHODS

In this study, we explore the biochemical and whole transcriptomic effects of CRISPR-Cas9 gene knockout (KO) of lactate dehydrogenases A and B [LDHA/B double KO (DKO)] and glucose-6-phosphate isomerase (GPI KO) in the human colon cancer cell line LS174T, using Affymetrix 2.1 ST arrays.

RESULTS

The metabolic biochemical profiles corroborate that relative to wild type (WT), LDHA/B DKO produced no lactic acid, (GPI KO) produced minimal lactic acid and both KOs displayed higher mitochondrial respiration, and minimal use of glucose with no loss of cell viability. These findings show a high biochemical energy efficiency as measured by ATP in glycolysis-null cells. Next, transcriptomic analysis conducted on 48,226 mRNA transcripts reflect 273 differentially expressed genes (DEGS) in the GPI KO clone set, 193 DEGS in the LDHA/B DKO clone set with 47 DEGs common to both KO clones. Glycolytic-null cells reflect up-regulation in gene transcripts typically associated with nutrient deprivation / fasting and possible use of fats for energy: thioredoxin interacting protein (TXNIP), mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2), PPARγ coactivator 1α (PGC-1α), and acetyl-CoA acyltransferase 2 (ACAA2). Other changes in non-ergometric transcripts in both KOs show losses in "stemness", WNT signaling pathway, chemo/radiation resistance, retinoic acid synthesis, drug detoxification, androgen/estrogen activation, and extracellular matrix reprogramming genes.

CONCLUSION

These findings demonstrate that: 1) The "Warburg effect" is dispensable, 2) loss of the LDHAB gene is not only inconsequential to viability but fosters greater mitochondrial energy, and 3) drugs that target LDHA/B are likely to be ineffective without a plausible combination second drug target.

The Cancer Stem Cell Niche in Ovarian Cancer and Its Impact on Immune Surveillance

Ovarian cancer is an aggressive gynaecological cancer with extremely poor prognosis, due to late diagnosis as well as the development of chemoresistance after first-line therapy. Research advances have found stem-like cells present in ovarian tumours, which exist in a dynamic niche and persist through therapy. The stem cell niche interacts extensively with the immune and non-immune components of the tumour microenvironment. Significant pathways associated with the cancer stem cell niche have been identified which interfere with the immune component of the tumour microenvironment, leading to immune surveillance evasion, dysfunction and suppression. This review aims to summarise current evidence-based knowledge on the cancer stem cell niche within the ovarian cancer tumour microenvironment and its effect on immune surveillance. Furthermore, the review seeks to understand the clinical consequences of this dynamic interaction by highlighting current therapies which target these processes.

Cancer stem cells targets and combined therapies to prevent cancer recurrence

Cancer stem cells (CSCs) control the dynamics of tumorigenesis by self-renewal ability and differentiation potential. These properties contribute towards tumor malignancy, metastasis, cellular heterogeneity, and immune escape, which are regulated by multiple signaling pathways. The CSCs are chemoresistant and cause cancer recurrence, generally recognized as a small side-population that eventually leads to tumor relapse. Despite many treatment options available, none can be considered entirely efficient due to a lack of specificity and dose limitation. This review primarily highlights the processes involved in CSCs development and maintenance. Secondly, the current effective therapies based on stem cells, cell-free therapies that involve exosomes and miRNAs, and photodynamic therapy have been discussed. Also, the inhibitors that specifically target various signaling pathways, which can be used in combination to control CSCs kinetics have been highlighted. Conclusively, this comprehensive review is a detailed study of recently developed novel treatment strategies that will facilitate in coming up with better-targeted approaches against CSCs.

The hallmarks of ovarian cancer stem cells and niches: Exploring their harmonious interplay in therapy resistance

The concept of a "cancer stem cell" has evolved over the past decades, and research on cancer stem cell biology has entered into a stage of remarkable progress. Cancer stem cells are a major determining factor contributing to the establishment of phenotypic and functional intratumoral heterogeneity in synchronization with their surrounding "cancer stem cell niches." They serve as the driving force for cancer initiation, metastasis, and therapeutic resistance in various types of malignancies. In verity, reciprocal interplay between ovarian cancer stem cells and their niches involves a complex but ingeniously orchestrated tumor microenvironment within the intraperitoneal milieu and especially contribute to chemotherapy resistance in patients with advanced ovarian cancer. Herein, we review the principles of our current understanding of the biological features of ovarian cancer stem cells, focusing mainly on the precise mechanisms underlying acquired chemotherapy resistance. Furthermore, we highlight the specific roles of various cancer-associated stromal and immune cells in creating possible cancer stem cell niches that regulate ovarian cancer stemness.

MicroRNA-34a: Potent Tumor Suppressor, Cancer Stem Cell Inhibitor, and Potential Anticancer Therapeutic

Overwhelming evidence indicates that virtually all treatment-naive tumors contain a subpopulation of cancer cells that possess some stem cell traits and properties and are operationally defined as cancer cell stem cells (CSCs). CSCs manifest inherent heterogeneity in that they may exist in an epithelial and proliferative state or a mesenchymal non-proliferative and invasive state. Spontaneous tumor progression, therapeutic treatments, and (epi)genetic mutations may also induce plasticity in non-CSCs and reprogram them into stem-like cancer cells. Intrinsic cancer cell heterogeneity and induced cancer cell plasticity, constantly and dynamically, generate a pool of CSC subpopulations with varying levels of epigenomic stability and stemness. Despite the dynamic and transient nature of CSCs, they play fundamental roles in mediating therapy resistance and tumor relapse. It is now clear that the stemness of CSCs is coordinately regulated by genetic factors and epigenetic mechanisms. Here, in this perspective, we first provide a brief updated overview of CSCs. We then focus on microRNA-34a (miR-34a), a tumor-suppressive microRNA (miRNA) devoid in many CSCs and advanced tumors. Being a member of the miR-34 family, miR-34a was identified as a p53 target in 2007. It is a bona fide tumor suppressor, and its expression is dysregulated and downregulated in various human cancers. By targeting stemness factors such as NOTCH, MYC, BCL-2, and CD44, miR-34a epigenetically and negatively regulates the functional properties of CSCs. We shall briefly discuss potential reasons behind the failure of the first-in-class clinical trial of MRX34, a liposomal miR-34a mimic. Finally, we offer several clinical settings where miR-34a can potentially be deployed to therapeutically target CSCs and advanced, therapy-resistant, and p53-mutant tumors in order to overcome therapy resistance and curb tumor relapse.

Heat Shock Protein 90 Triggers Multi-Drug Resistance of Ovarian Cancer via AKT/GSK3β/β-Catenin Signaling

Ovarian cancer is the most lethal gynaecologic tumor, with which multi-drug resistance as the major therapeutic hindrance. Heat shock protein 90 (Hsp90) has been involved in cancer malignant behaviors. However, its role and mechanism in multi-drug resistance of ovarian cancer remains poorly understood. Our results demonstrated that Hsp90 was overexpressed in multi-drug resistant ovarian cancer cells. Hsp90 downregulation by shHsp90 or inhibitor BIIB021 increased the sensitivity of multi-drug resistant ovarian cancer cells to paclitaxel and cisplatin, and augmented the drugs-induced apoptosis. Hsp90 positively regulated the expressions of multi-drug resistance protein 1 (P-gp/MDR1), breast cancer resistance protein (BCRP), Survivin and Bcl-2 expressions closely associated with multi-drug resistance. Moreover, overexpression of Hsp90 promoted β-catenin accumulation, while Hsp90 downregulation decreased the accumulation, nuclear translocation and transcriptional activity of β-catenin. We also identified that β-catenin was responsible for Hsp90-mediated expressions of P-gp, BCRP, Survivin, and Bcl-2. Furthermore, Hsp90 enhanced the AKT/GSK3β signaling, and AKT signaling played a critical role in Hsp90-induced accumulation and transcriptional activity of β-catenin, as well as multi-drug resistance to paclitaxel and cisplatin. In conclusion, Hsp90 enhanced the AKT/GSK3β/β-catenin signaling to induce multi-drug resistance of ovarian cancer. Suppressing Hsp90 chemosensitized multi-drug resistant ovarian cancer cells via impairing the AKT/GSK3β/β-catenin signaling, providing a promising therapeutic strategy for a successful treatment of ovarian cancer.

Identification of hub genes and compounds controlling ovarian cancer stem cell characteristics via stemness indices analysis

Background

Ovarian cancer (OC) is the most lethal gynecological malignancy. It has been reported that cancer stem cells (CSCs) play a crucial role in disseminated metastases in abdominal cavity and chemotherapy resistance of high-grade serous OC. However, the overall gene expression features of OC stem cells have not been clarified.

Methods

Expression datasets of 379 OC samples and 88 normal tissues were downloaded from The Cancer Genome Atlas (TCGA) and the Genotype Tissue Expression (GTEx) project. Differentially expressed genes (DEGs) were screened using the “limma” package in R software. Among the DEGs, modules and hub genes that were highly related to messenger RNA expression-based stemness index (mRNAsi) and epigenetically regulated mRNAsi indices were identified via weighted gene co-expression network analysis (WGCNA). These hub genes were considered to be associated with OC stem cells. The Gene Ontology (GO) project and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis was used to identify the main biological processes that hub genes participated in. Finally, Connectivity Map (CMap) was used to predict compounds that disturb the hub genes.

Results

We identified 2,253 DEGs; of these, 31 had a significantly positive correlation to mRNAsi indices and were upregulated in OC, while 41 of them had a significantly negative correlation with mRNAsi indices and were downregulated in OC. Correlation analysis indicated that hub genes from the same module composed a dense interaction network. GO and KEGG enrichment analysis demonstrated that hub genes primarily play roles in cell division and proliferation. Moreover, the compounds that may disturb hub genes were identified. Of these, 11 compounds, including MS-275, DL-thiorphan, and GW-8510, which have never been studied in OC stem cells, were screened as underlying treatments targeting OC stem cells.

Conclusions

Altogether, 72 hub genes that were closely linked to OC stem cell characteristics were found to mainly participate in cell division and proliferation. Moreover, compounds that disturb these hub gens were identified and can be considered underlying targets for inhibiting OC stem cells.

Targeting the tumour microenvironment in platinum-resistant ovarian cancer

Ovarian cancer typically presents at an advanced stage, and although the majority of cases initially respond well to platinum-based therapies, chemoresistance almost always occurs leading to a poor long-term prognosis. While various cellular autonomous mechanisms contribute to intrinsic or acquired platinum resistance, the tumour microenvironment (TME) plays a central role in resistance to therapy and disease progression by providing cancer stem cell niches, promoting tumour cell metabolic reprogramming, reducing chemotherapy drug perfusion and promoting an immunosuppressive environment. As such, the TME is an attractive therapeutic target which has been the focus of intense research in recent years. This review provides an overview of the unique ovarian cancer TME and its role in disease progression and therapy resistance, highlighting some of the latest preclinical and clinical data on TME-targeted therapies. In particular, it focuses on strategies targeting cancer-associated fibroblasts, tumour-associated macrophages, cancer stem cells and cancer cell metabolic vulnerabilities.

Gel-Free 3D Tumoroids with Stem Cell Properties Modeling Drug Resistance to Cisplatin and Imatinib in Metastatic Colorectal Cancer

Researchers have developed several three-dimensional (3D) culture systems, including spheroids, organoids, and tumoroids with increased properties of cancer stem cells (CSCs), also called cancer-initiating cells (CICs). Drug resistance is a crucial issue involving recurrence in cancer patients. Many studies on anti-cancer drugs have been reported using 2D culture systems, whereas 3D cultured tumoroids have many advantages for assessing drug sensitivity and resistance. Here, we aimed to investigate whether Cisplatin (a DNA crosslinker), Imatinib (a multiple tyrosine kinase inhibitor), and 5-Fluorouracil (5-FU: an antimetabolite) alter the tumoroid growth of metastatic colorectal cancer (mCRC). Gene expression signatures of highly metastatic aggregative CRC (LuM1 cells) vs. low-metastatic, non-aggregative CRC (Colon26 and NM11 cells) were analyzed using microarray. To establish a 3D culture-based multiplexing reporter assay system, LuM1 was stably transfected with the Mmp9 promoter-driven ZsGreen fluorescence reporter gene, which was designated as LuM1/m9 cells and cultured in NanoCulture Plate^®, a gel-free 3D culture device. LuM1 cells highly expressed mRNA encoding ABCG2 (a drug resistance pump, i.e., CSC/CIC marker), other CSC/CIC markers (DLL1, EpCAM, podoplanin, STAT3/5), pluripotent stem cell markers (Sox4/7, N-myc, GATA3, Nanog), and metastatic markers (MMPs, Integrins, EGFR), compared to the other two cell types. Hoechst efflux stem cell-like side population was increased in LuM1 (7.8%) compared with Colon26 (2.9%), both of which were markedly reduced by verapamil treatment, an ABCG2 inhibitor. Smaller cell aggregates of LuM1 were more sensitive to Cisplatin (at 10 μM), whereas larger tumoroids with increased ABCG2 expression were insensitive. Notably, Cisplatin (2 μM) and Imatinib (10 μM) at low concentrations significantly promoted tumoroid formation (cell aggregation) and increased Mmp9 promoter activity in mCRC LuM1/m9, while not cytotoxic to them. On the other hand, 5-FU significantly inhibited tumoroid growth, although not completely. Thus, drug resistance in cancer with increased stem cell properties was modeled using the gel-free 3D cultured tumoroid system. The tumoroid culture is useful and easily accessible for the assessment of drug sensitivity and resistance.

Chemoprotective effect of atorvastatin against benzo(a)pyrene-induced lung cancer via the inhibition of oxidative stress and inflammatory parameters

Background

Lung cancer affects approximately 9% of women and 17% of men worldwide, and has a mortality rate of 17%. Previously published studies have suggested that oxidative stress expansion can lead to lung cancer. The aim of the current study was to analyze the possible inhibitory pathway of atorvastatin against lung cancer cells in an in vivo model.

Methods

The cytotoxic effects of atorvastatin on lung cancer cell lines H460 and A549 were analyzed, as well as cell cycle arrest and cell morphology. Benzo(a)pyrene (BaP) was used for the induction of lung cancer in experimental rats, and atorvastatin (5, 10, and 20 mg/kg body weight) was used for treatment in a dose-dependent manner. Body weight and lung tumors were calculated at regular intervals. Antioxidants, pro-inflammatory cytokines, phase I and II antioxidant enzymes, polyamine enzymes, and apoptosis markers were determined at end of the experimental study.

Results

Cell cycle arrest occurred at the G2/M phase after atorvastatin treatment. Atorvastatin increased cytochrome C expression and caspase activity in a dose-dependent manner, and increased the activity of antioxidative enzymes, such as GPx, SOD, GST, reduced glutathione, and catalase, and reduced the level of nitrate and LPO. It also altered the xanthine oxidase (XO), Lactic Acid Dehydrogenase (LDH), quinone reductase (QR), UDP-glucuronosyltransferase (UDP-GT), adenosine deaminase (ADA), Aryl hydrocarbon hydroxylase (AHH), 5'-nucleotidase, cytochrome P450, cytochrome B5 and NADPH cytochrome C reductase levels. Atorvastatin was found to modulate polyamine enzyme levels, such as histamine, spermine, spermidine, and putrescine, and significantly (P<0.001) reduced the pro-inflammatory cytokine levels, such as tumor necrosis factor-α. Interleukin (IL)-6 and interleukin-1β (IL-1β) increased caspase-3 and caspase-9 levels in a dose-dependent manner.

Conclusions

Our findings indicate that atorvastatin can inhibit lung cancer through apoptosis.

BMP signaling is a therapeutic target in ovarian cancer

BMP signaling has been found to have tumor-promoting as well as tumor-suppressing effects in different types of tumors. In this study, we investigated the effects of BMP signaling and of BMP inhibitors on ovarian cancer (OC) cells in vitro and in vivo. High expression of BMP receptor 2 (BMPR2) correlated with poor overall survival of OC patients in the TCGA dataset. Both BMP2 and BMPR2 enhanced OC cell proliferation, whereas BMP receptor kinase inhibitors inhibited OC cell growth in cell culture as well as in a mouse model. BMP2 also augmented sphere formation, migration, and invasion of OC cells, and induced EMT. High BMP2 expression was observed after chemotherapy of OC patients in the GSE109934 dataset. In accordance, carboplatin, used for the treatment of OC patients, increased BMP2 secretion from OC cells, and induced EMT partially via activation of BMP signaling. Our data suggest that BMP signaling has tumor-promoting effects in OC, and that BMP inhibitors might be useful therapeutic agents for OC patients. Considering that carboplatin treatment augmented BMP2 secretion, the possibility to use a combination of BMP inhibitors and carboplatin in the treatment of OC patients, would be worth exploring.

Integrated analysis of a competing endogenous RNA network reveals an 11-lncRNA prognostic signature in ovarian cancer

Long noncoding RNA (lncRNA) can function as a competing endogenous RNA (ceRNA) involved in tumor initiation and progression. However, the prognostic roles of lncRNAs in the integrated analysis of the ceRNA network in ovarian cancer (OVC) are still lacking. This study aimed to identify lncRNAs associated with the prognosis of OVC. Differential expression analysis and WGCNA were used to screen OVC-specific RNAs. A lncRNA-miRNA-mRNA regulatory network consisting of 201 lncRNAs, 85 miRNA and 146 mRNAs was constructed, and functional enrichment and protein-protein network analyses were performed. Then, the OVC-specific RNAs were submitted to Cox regression analysis. Twelve differentially expressed lncRNAs and mRNAs were identified as significantly associated with OS of OVC patients. Meanwhile, 11 lncRNAs (including C4A-AS1, LINC02408, LINC00488) were established as prognostic risk formulas. The low-risk group had better OS and DFS than the high-risk group (P <0.01). Univariate and multivariate Cox regression analyses revealed the 11-lncRNA risk score as an independent prognostic factor. A prognostic nomogram was developed based on independent prognostic factors. Our data provide evidence that the 11-lncRNA signature could serve as an independent prognostic indicator. This study also suggests that these 11 lncRNAs potentially participate in the progression of OVC.

Hsa_circ_0043278 functions as competitive endogenous RNA to enhance glioblastoma multiforme progression by sponging miR-638

Circular RNAs have a critical function in the pathogenesis of many diseases and can function as competing endogenous RNA or miRNA sponges to inhibit miRNA and therefore upregulate the expression of target genes. However, little is known about the role of has_circRNA_0043278 (circ_0043278) in glioblastoma multiforme (GBM) and its potential downstream miRNA targets. This work validated that circ_0043278 is highly expressed in GMB cell lines and tissues, while knockdown circ_0043278 inhibited GBM cell migration, proliferation, and invasion invitro and tumorigenesis invivo. Dual-luciferase reporter assay determined that circ_0043278 directly sponged miR-638 to upregulate the expression of HOXA9, which can activate downstream Wnt/β-catenin signaling in GBM. Moreover, miR-638 inhibition reversed circ_0043278 silencing-induced impairment of malignant tumor behavior. These results showed that circ-0043278/miRNA-638/ Homeobox A9 (HOXA9) axis had a vital function in promoting GBM progression. Our findings may provide potential new targets for the diagnosis and therapy of GBM.