TLR2 enhances ovarian cancer stem cell self-renewal and promotes tumor repair and recurrence

Risk factors for blood transfusion in patients undergoing hysterectomy for stage I endometrial cancer

PURPOSE

To highlight the risk factors contributing to blood transfusion among patients undergoing surgical intervention for Stage I Endometrial Cancer (EC).

METHOD

Using the American College of Surgeons National Surgical Quality Improvement Program database, a nationally validated database dedicated to improving surgical care, females over the age of 18 who underwent surgery for EC stage I between the years 2016-2022 were queried. The cohort was then characterized based on those who received blood transfusion 72 h postoperatively.

RESULTS

27,183 patients with endometrial cancer who received surgical management were identified. 668 (2.5%) of those patients received blood transfusions. A multivariate logistic model found that a medical factor low preoperative Hct % (aOR 22.4, 95% CI[17.7, 28.3]; p < 0.001) and surgical factors such as 180 min or more of operative time (aOR 3.38, 95% CI[2.77, 4.14]; p < 0.001), larger uteri of 250-500 g (aOR 1.93, 95% CI[1.48, 2.49]; p < 0.001) and ≥ 500 g (aOR 2.35, 95% CI[1.77, 3.12]; p < 0.001), and abdominal approach compared to laparoscopic (aOR 6.36,95% CI[4.95, 8.18]; p < 0.001) were significantly associated with receiving blood transfusion.

CONCLUSION

Many significant risk factors were found to be associated with blood transfusions in patients with Stage I endometrial cancer. These findings allow surgeons to proactively prepare adequate measures for patients who may require blood transfusions when they undergo surgery for endometrial cancer.

Selective targeting of IRAK1 attenuates low molecular weight hyaluronic acid-induced stemness and non-canonical STAT3 activation in epithelial ovarian cancer

Advanced epithelial ovarian cancer (EOC) survival rates are dishearteningly low, with ~25% surviving beyond 5 years. Evidence suggests that cancer stem cells contribute to acquired chemoresistance and tumor recurrence. Here, we show that IRAK1 is upregulated in EOC tissues, and enhanced expression correlates with poorer overall survival. Moreover, low molecular weight hyaluronic acid, which is abundant in malignant ascites from patients with advanced EOC, induced IRAK1 phosphorylation leading to STAT3 activation and enhanced spheroid formation. Knockdown of IRAK1 impaired tumor growth in peritoneal disease models, and impaired HA-induced spheroid growth and STAT3 phosphorylation. Finally, we determined that TCS2210, a known inducer of neuronal differentiation in mesenchymal stem cells, is a selective inhibitor of IRAK1. TCS2210 significantly inhibited EOC growth in vitro and in vivo both as monotherapy, and in combination with cisplatin. Collectively, these data demonstrate IRAK1 as a druggable target for EOC.

Immune checkpoints as potential theragnostic biomarkers for epithelial ovarian cancer

BACKGROUND

Epithelial ovarian cancer (EOC) is the leading cause of death associated with gynecologic tumors. EOC is asymptomatic in early stages, so most patients are not diagnosed until late stages, highlighting the need to develop new diagnostic biomarkers. Mediators of the tumoral microenvironment may influence EOC progression and resistance to treatment.

AIM

To analyze immune checkpoints to evaluate them as theranostic biomarkers for EOC.

PATIENTS AND METHODS

Serum levels of 16 immune checkpoints were determined in EOC patients and healthy controls using the MILLIPLEX MAP® Human Immuno-Oncology Checkpoint Protein Magnetic Bead Panel.

RESULTS

Seven receptors: BTLA, CD40, CD80/B7-1, GITRL, LAG-3, TIM-3, TLR-2 are differentially expressed between EOC and healthy controls. Serum levels of immune checkpoints in EOC patients are positively significantly correlated with levels of their ligands, with a higher significant correlation between CD80 and CTLA4 than between CD28 and CD80. Four receptors, CD40, HVEM, PD-1, and PD-L1, are positively associated with the development of resistance to Taxol-platinum-based chemotherapy. All of them have an acceptable area under the curve (>0.7).

CONCLUSION

This study has yielded a first panel of seven immune checkpoints (BTLA, CD40, CD80/B7-1, GITRL, LAG-3, TIM-3, TLR-2) associated with a higher risk of EOC and a second panel of four immune checkpoints (CD40, HVEM, PD-1, PD-L1) that may help physicians to identify EOC patients who are at high risk of developing resistance to EOC chemotherapy.

Inflammatory auxo-action in the stem cell division theory of cancer

Acute inflammation is a beneficial response to the changes caused by pathogens or injuries that can eliminate the source of damage and restore homeostasis in damaged tissues. However, chronic inflammation causes malignant transformation and carcinogenic effects of cells through continuous exposure to pro-inflammatory cytokines and activation of inflammatory signaling pathways. According to the theory of stem cell division, the essential properties of stem cells, including long life span and self-renewal, make them vulnerable to accumulating genetic changes that can lead to cancer. Inflammation drives quiescent stem cells to enter the cell cycle and perform tissue repair functions. However, as cancer likely originates from DNA mutations that accumulate over time via normal stem cell division, inflammation may promote cancer development, even before the stem cells become cancerous. Numerous studies have reported that the mechanisms of inflammation in cancer formation and metastasis are diverse and complex; however, few studies have reviewed how inflammation affects cancer formation from the stem cell source. Based on the stem cell division theory of cancer, this review summarizes how inflammation affects normal stem cells, cancer stem cells, and cancer cells. We conclude that chronic inflammation leads to persistent stem cells activation, which can accumulate DNA damage and ultimately promote cancer. Additionally, inflammation not only facilitates the progression of stem cells into cancer cells, but also plays a positive role in cancer metastasis.

SHCBP1 contributes to the proliferation and self‑renewal of cervical cancer cells and activation of the NF‑κB signaling pathway through EIF5A

Cervical cancer (CC) is the most common human papillomavirus-related disease. Continuous activation of the NF-κB signaling pathway has been observed in CC. SHC binding and spindle associated 1 (SHCBP1) contributes to tumorigenesis and activation of the NF-κB pathway in multiple cancer types, while its function in CC remains unclear. In the present study, three Gene Expression Omnibus datasets were used to identify differentially expressed genes (DEGs) in CC. Loss- and gain-of-function experiments were performed using stable SHCBP1-silenced and SHCBP1-overexpressing CC cells. To further explore the molecular mechanism of SHCBP1 in CC, small interfering RNA targeting eukaryotic translation initiation factor 5A (EIF5A) was transfected into stable SHCBP1-overexpressing CC cells. The results demonstrated that SHCBP1 was an upregulated DEG in CC tissues compared with healthy control cervical tissues. Functional experiments revealed the pro-proliferative and pro-stemness role of SHCBP1 in CC cells (CaSki and SiHa cells), in vitro. Furthermore, the NF-κB signaling pathway in CC cells was activated by SHCBP1. Increases in cell proliferation, stemness and activation of NF-κB, induced by SHCBP1 overexpression in CC cells, were reversed by EIF5A knockdown. Taken together, the results indicated that SHCBP1 serves an important role in regulation of CC cell proliferation, self-renewal and activation of NF-κB via EIF5A. The present study demonstrated a potential molecular mechanism underlying the progression of CC.

Toll-Like Receptors and the Response to Radiotherapy in Solid Tumors: Challenges and Opportunities

Toll-like receptors (TLRs) are indispensable for the activation, maintenance and halting of immune responses. TLRs can mediate inflammation by recognizing molecular patterns in microbes (pathogen-associated molecular patterns: PAMPs) and endogenous ligands (danger-associated molecular patterns: DAMPs) released by injured or dead cells. For this reason, TLR ligands have attracted much attention in recent years in many cancer vaccines, alone or in combination with immunotherapy, chemotherapy and radiotherapy (RT). TLRs have been shown to play controversial roles in cancer, depending on various factors that can mediate tumor progression or apoptosis. Several TLR agonists have reached clinical trials and are being evaluated in combination with standard of care therapies, including RT. Despite their prolific and central role in mediating immune responses, the role of TLRs in cancer, particularly in response to radiation, remains poorly understood. Radiation is recognized as either a direct stimulant of TLR pathways, or indirectly through the damage it causes to target cells that subsequently activate TLRs. These effects can mediate pro-tumoral and anti-tumoral effects depending on various factors such as radiation dose and fractionation, as well as host genomic features. In this review, we examine how TLR signaling affects tumor response to RT, and we provide a framework for the design of TLR-based therapies with RT.

Tp53 haploinsufficiency is involved in hotspot mutations and cytoskeletal remodeling in gefitinib-induced drug-resistant EGFRL858R-lung cancer mice

Tumor heterogeneity is the major factor for inducing drug resistance. p53 is the major defender to maintain genomic stability, which is a high proportion mutated in most of the cancer types. In this study, we established in vivo animal models of gefitinib-induced drug-resistant lung cancer containing EGFR^L858R and EGFR^L858R*Tp53^+/- mice to explore the molecular mechanisms of drug resistance by studying the genomic integrity and global gene expression. The cellular morphology of the lung tumors between gefitinib-induced drug-resistant mice and drug-sensitive mice were very different. In addition, in drug-resistant mice, the expression of many cytoskeleton-related genes were changed, accompanied by decreased amounts of actin filaments and increased amounts of microtubule, indicating that significant cytoskeletal remodeling is induced in gefitinib-induced drug-resistant EGFR^L858R and EGFR^L858R*Tp53^+/- lung cancer mice. The gene expression profiles and involved pathways were different in gefitinib-sensitive, gefitinib-resistant and Tp53^+/--mice. Increases in drug resistance and nuclear size (N/C ratio) were found in EGFR^L858R*Tp53^+/- drug-resistant mice. Mutational hotspot regions for drug resistance via Tp53^+/+- and Tp53^+/--mediated pathways are located on chromosome 1 and chromosome 11, respectively, and are related to prognosis of lung cancer cohorts. This study not only builds up a gefitinib-induced drug-resistant EGFR^L858R lung cancer animal model, but also provides a novel mutation profile in a Tp53^+/+- or Tp53^+/--mediated manner and induced cytoskeleton remodeling during drug resistance, which could contribute to the prevention of drug resistance during cancer therapy.

The emerging roles of TLR and cGAS signaling in tumorigenesis and progression of ovarian cancer

Ovarian cancer is fatal to women and has a high mortality rate. Although on-going efforts are never stopped in identifying diagnostic and intervention strategies, the disease is so far unable to be well managed. The most important reason for this is the complexity of pathogenesis for OC, and therefore, uncovering the essential molecular biomarkers accompanied with OC progression takes the privilege for OC remission. Inflammation has been reported to participate in the initiation and progression of OC. Both microenvironmental and tumor cell intrinsic inflammatory signals contribute to the malignancy of OC. Inflammation responses can be triggered by various kinds of stimulus, including endogenous damages and exogenous pathogens, which are initially recognized and orchestrated by a series of innate immune system related receptors, especially Toll like receptors, and cyclic GMP-AMP synthase. In this review, we will discuss the roles of innate immune system related receptors, including TLRs and cGAS, and responses both intrinsic and exogenetic in the development and treatment of OC.

Dysregulated FOXM1 signaling in the regulation of cancer stem cells

Since the introduction of the cancer stem cell (CSC) paradigm, significant advances have been made in understanding the functional and biological plasticity of these elusive components in malignancies. Endowed with self-renewing abilities and multilineage differentiation potential, CSCs have emerged as cellular drivers of virtually all facets of tumor biology, including metastasis, tumor recurrence/relapse, and drug resistance. The functional and biological characteristics of CSCs, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation are regulated by an array of extracellular factors, signaling pathways, and pluripotent transcriptional factors. Besides the well-characterized regulatory role of transcription factors OCT4, SOX2, NANOG, KLF4, and MYC in CSCs, evidence for the central role of Forkhead box transcription factor FOXM1 in the establishment, maintenance, and functions of CSCs is accumulating. Conventionally identified as a master regulator of the cell cycle, a comprehensive understanding of this molecule has revealed its multifarious oncogenic potential and uncovered its role in angiogenesis, invasion, migration, self-renewal, and drug resistance. This review compiles the large body of literature that has accumulated in recent years that provides evidence for the mechanisms by which FOXM1 expression promotes stemness in glioblastoma, breast, colon, ovarian, lung, hepatic, and pancreatic carcinomas. We have also compiled the data showing the association of stem cell mediators with FOXM1 using TCGA mRNA expression data. Further, the prognostic importance of FOXM1 and other stem cell markers is presented. The delineation of FOXM1-mediated regulation of CSCs can aid in the development of molecularly targeted pharmacological approaches directed at the selective eradication of CSCs in several human malignancies.

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.

Microbial Colonization and Inflammation as Potential Contributors to the Lack of Therapeutic Success in Oral Squamous Cell Carcinoma

This review discusses the microenvironment of evolving and established conventional oral squamous cell carcinoma, by far the most common oral cancer. The focus of this paper is mainly on the more recent data that describe the role of microorganisms, host-microbial interactions, and in particular, the contributions of cell-surface toll-like receptors on immune system cells and on normal and malignant epithelial cells to their functions that support carcinogenesis. Because carcinomas arising at various host surfaces share much in common, additional information available from studies of other carcinomas is included in the discussion. Accumulating evidence reveals the complex toll-like receptor-mediated tumor-supporting input into many aspects of carcinogenesis via malignant cells, stromal immune cells and non-immune cells, complicating the search for effective treatments.

Stemness, Inflammation and Epithelial-Mesenchymal Transition in Colorectal Carcinoma: The Intricate Network

In global cancer statistics, colorectal carcinoma (CRC) ranks third by incidence and second by mortality, causing 10.0% of new cancer cases and 9.4% of oncological deaths worldwide. Despite the development of screening programs and preventive measures, there are still high numbers of advanced cases. Multiple problems compromise the treatment of metastatic colorectal cancer, one of these being cancer stem cells—a minor fraction of pluripotent, self-renewing malignant cells capable of maintaining steady, low proliferation and exhibiting an intriguing arsenal of treatment resistance mechanisms. Currently, there is an increasing body of evidence for intricate associations between inflammation, epithelial–mesenchymal transition and cancer stem cells. In this review, we focus on inflammation and its role in CRC stemness development through epithelial–mesenchymal transition.

TNF-α Regulated Endometrial Stroma Secretome Promotes Trophoblast Invasion

Successful implantation requires the coordinated migration and invasion of trophoblast cells from out of the blastocyst and into the endometrium. This process relies on signals produced by cells in the maternal endometrium. However, the relative contribution of stroma cells remains unclear. The study of human implantation has major technical limitations, therefore the need of in vitro models to elucidate the molecular mechanisms. Using a recently described 3D in vitro models we evaluated the interaction between trophoblasts and human endometrial stroma cells (hESC), we assessed the process of trophoblast migration and invasion in the presence of stroma derived factors. We demonstrate that hESC promotes trophoblast invasion through the generation of an inflammatory environment modulated by TNF-α. We also show the role of stromal derived IL-17 as a promoter of trophoblast migration through the induction of essential genes that confer invasive capacity to cells of the trophectoderm. In conclusion, we describe the characterization of a cellular inflammatory network that may be important for blastocyst implantation. Our findings provide a new insight into the complexity of the implantation process and reveal the importance of inflammation for embryo implantation.

Extracellular Vesicles and Cancer Stem Cells in Tumor Progression: New Therapeutic Perspectives

Tumor burden is a complex microenvironment where different cell populations coexist and have intense cross-talk. Among them, a heterogeneous population of tumor cells with staminal features are grouped under the definition of cancer stem cells (CSCs). CSCs are also considered responsible for tumor progression, drug resistance, and disease relapse. Furthermore, CSCs secrete a wide variety of extracellular vesicles (EVs) with different cargos, including proteins, lipids, ssDNA, dsDNA, mRNA, siRNA, or miRNA. EVs are internalized by other cells, orienting the microenvironment toward a protumorigenic and prometastatic one. Given their importance in tumor growth and metastasis, EVs could be exploited as a new therapeutic target. The inhibition of biogenesis, release, or uptake of EVs could represent an efficacious strategy to impair the cross-talk between CSCs and other cells present in the tumor microenvironment. Moreover, natural or synthetic EVs could represent suitable carriers for drugs or bioactive molecules to target specific cell populations, including CSCs. This review will discuss the role of CSCs and EVs in tumor growth, progression, and metastasis and how they affect drug resistance and disease relapse. Furthermore, we will analyze the potential role of EVs as a target or vehicle of new therapies.

Ovarian Cancer and Cancer Stem Cells-Cellular and Molecular Characteristics, Signaling Pathways, and Usefulness as a Diagnostic Tool in Medicine and Oncology

Simple Summary

Ovarian cancer is still a high-risk, metastatic disease, often diagnosed at a late stage. Difficulties in its treatment are associated with high resistance to chemotherapy and recurrence. Responsible for the malignant features of cancer are considered to be cancer stem cells (CSCs), which generate new cells by modifying various signaling pathways. Signaling pathways are crucial for the regulation of epithelial-mesenchymal transition, metastasis, and self-renewal of CSCs. New therapies based on the use of inhibitors that block CSC growth and proliferation signals are being investigated. The current histological classification of ovarian tumors, their epidemiology, and the recent knowledge of ovarian CSCs, with particular emphasis on their molecular basis, are important considerations.

Abstract

Despite the increasing development of medicine, ovarian cancer is still a high-risk, metastatic disease that is often diagnosed at a late stage. In addition, difficulties in its treatment are associated with high resistance to chemotherapy and frequent relapse. Cancer stem cells (CSCs), recently attracting significant scientific interest, are considered to be responsible for the malignant features of tumors. CSCs, as the driving force behind tumor development, generate new cells by modifying different signaling pathways. Moreover, investigations on different types of tumors have shown that signaling pathways are key to epithelial-mesenchymal transition (EMT) regulation, metastasis, and self-renewal of CSCs. Based on these established issues, new therapies are being investigated based on the use of inhibitors to block CSC growth and proliferation signals. Many reports indicate that CSC markers play a key role in cancer metastasis, with hopes placed in their targeting to block this process and eliminate relapses. Current histological classification of ovarian tumors, their epidemiology, and the most recent knowledge of ovarian CSCs, with particular emphasis on their molecular background, are important aspects for consideration. Furthermore, the importance of signaling pathways involved in tumor growth, development, and metastasis, is also presented.

Toll-like Receptor 2 as a Marker Molecule of Advanced Ovarian Cancer

Ovarian cancer is a global problem that affects women of all ages. Due to the lack of effective screening tests and the usually asymptomatic course of the disease in the early stages, the diagnosis is too late, with the result that less than half of the patients diagnosed with ovarian cancer (OC) survive more than five years after their diagnosis. In this study, we examined the expression of TLR2 in the peripheral blood of 50 previously untreated patients with newly diagnosed OC at various stages of the disease using flow cytometry. The studies aimed at demonstrating the usefulness of TLR2 as a biomarker in the advanced stage of ovarian cancer. In this study, we showed that TLR2 expression levels were significantly higher in women with more advanced OC than in women in the control group. Our research sheds light on the prognostic potential of TLR2 in developing new diagnostic approaches and thus in increasing survival in patients with confirmed ovarian cancer.

Exosomal SNHG16 secreted by CSCs promotes glioma development via TLR7

Background

Glioma is one of the most common central nervous system malignant tumors, accounting for 45~60% of adult intracranial tumors. However, the clinical treatment of glioma is limited. It is of great significance to seek new therapeutic methods for glioma via gene therapy.

Methods

Long non-coding RNA (lncRNA) SNHG16 expression level was measured by microarray and qRT-PCR assay; ISH was used to identify the location of SNHG16. Cancer stem cells (CSCs) were separated from glioma tissues and identified using immunofluorescence. Exosomes were isolated from CSCs and cancer cells and identified by TEM and western blot. MTT, wound healing, transwell, and colony formation assay were performed to explore the role of SNHG16 or si-SNHG16 from CSCs on progression of glioma cells. RIP was used to verify the interaction between SNHG16 and TLR7. The experiment of Xenograft used for exploring the function of SNHG16/ TLR7/MyD88/NFκB/c-Myc on growth on glioma in vivo.

Results

Microarray assay showed long non-coding RNA (lncRNA) SNHG16 was upregulated in glioma. Followed qRT-PCR also showed an increase of SNHG16 in glioma tissues; high expression of SNHG16 indicated a poor prognosis in glioma patients. Interestingly, SNHG16 was packaged into exosomes and derived from CSCs. Functional analysis showed exo-SNHG16 secreted by CSCs promoted the progression of glioma cell lines SHG44 and U251. Furthermore, SNHG16 interacted with TLR7 and activated NFκB/c-Myc signaling in glioma cells. And the silencing of TLR7 inhibited the progression of SHG44 and U251 cells by exo-SNHG16 from CSCs. In vivo tumorigenesis experiments showed that exo-SNHG16 induced glioma progression by activating TLR7/MyD88/NFκB/c-Myc signaling.

Conclusion

Our study suggested CSC-derived exo-SNHG16 promoted cancer progression by activating TLR7/MyD88/NFκB/c-Myc signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02393-8.

The MEK1/2 Pathway as a Therapeutic Target in High-Grade Serous Ovarian Carcinoma

High-grade serous ovarian carcinoma (HGSOC) is the deadliest of gynecological cancers due to its high recurrence rate and acquired chemoresistance. RAS/MEK/ERK pathway activation is linked to cell proliferation and therapeutic resistance, but the role of MEK1/2-ERK1/2 pathway in HGSOC is poorly investigated. We evaluated MEK1/2 pathway activity in clinical HGSOC samples and ovarian cancer cell lines using immunohistochemistry, immunoblotting, and RT-qPCR. HGSOC cell lines were used to assess immediate and lasting effects of MEK1/2 inhibition with trametinib in vitro. Trametinib effect on tumor growth in vivo was investigated using mouse xenografts. MEK1/2 pathway is hyperactivated in HGSOC and is further stimulated by cisplatin treatment. Trametinib treatment causes cell cycle arrest in G1/0-phase and reduces tumor growth rate in vivo but does not induce cell death or reduce fraction of CD133+ stem-like cells, while increasing expression of stemness-associated genes instead. Transient trametinib treatment causes long-term increase in a subpopulation of cells with high aldehyde dehydrogenase (ALDH)1 activity that can survive and grow in non-adherent conditions. We conclude that MEK1/2 inhibition may be a promising approach to suppress ovarian cancer growth as a maintenance therapy. Promotion of stem-like properties upon MEK1/2 inhibition suggests a possible mechanism of resistance, so a combination with CSC-targeting drugs should be considered.

Toll-Like Receptor 2 at the Crossroad between Cancer Cells, the Immune System, and the Microbiota

Toll-like receptor 2 (TLR2) expressed on myeloid cells mediates the recognition of harmful molecules belonging to invading pathogens or host damaged tissues, leading to inflammation. For this ability to activate immune responses, TLR2 has been considered a player in anti-cancer immunity. Therefore, TLR2 agonists have been used as adjuvants for anti-cancer immunotherapies. However, TLR2 is also expressed on neoplastic cells from different malignancies and promotes their proliferation through activation of the myeloid differentiation primary response protein 88 (MyD88)/nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) pathway. Furthermore, its activation on regulatory immune cells may contribute to the generation of an immunosuppressive microenvironment and of the pre-metastatic niche, promoting cancer progression. Thus, TLR2 represents a double-edge sword, whose role in cancer needs to be carefully understood for the setup of effective therapies. In this review, we discuss the divergent effects induced by TLR2 activation in different immune cell populations, cancer cells, and cancer stem cells. Moreover, we analyze the stimuli that lead to its activation in the tumor microenvironment, addressing the role of danger, pathogen, and microbiota-associated molecular patterns and their modulation during cancer treatments. This information will contribute to the scientific debate on the use of TLR2 agonists or antagonists in cancer treatment and pave the way for new therapeutic avenues.

Differences and similarities between cancer and somatic stem cells: therapeutic implications

Over the last decades, the cancer survival rate has increased due to personalized therapies, the discovery of targeted therapeutics and novel biological agents, and the application of palliative treatments. Despite these advances, tumor resistance to chemotherapy and radiation and rapid progression to metastatic disease are still seen in many patients. Evidence has shown that cancer stem cells (CSCs), a sub-population of cells that share many common characteristics with somatic stem cells (SSCs), contribute to this therapeutic failure. The most critical properties of CSCs are their self-renewal ability and their capacity for differentiation into heterogeneous populations of cancer cells. Although CSCs only constitute a low percentage of the total tumor mass, these cells can regrow the tumor mass on their own. Initially identified in leukemia, CSCs have subsequently been found in cancers of the breast, the colon, the pancreas, and the brain. Common genetic and phenotypic features found in both SSCs and CSCs, including upregulated signaling pathways such as Notch, Wnt, Hedgehog, and TGF-β. These pathways play fundamental roles in the development as well as in the control of cell survival and cell fate and are relevant to therapeutic targeting of CSCs. The differences in the expression of membrane proteins and exosome-delivered microRNAs between SSCs and CSCs are also important to specifically target the stem cells of the cancer. Further research efforts should be directed toward elucidation of the fundamental differences between SSCs and CSCs to improve existing therapies and generate new clinically relevant cancer treatments.

Deubiquitinating Enzyme-Mediated Signaling Networks in Cancer Stem Cells

Cancer stem cells (CSCs) have both the capacity for self-renewal and the potential to differentiate and contribute to multiple tumor properties, such as recurrence, metastasis, heterogeneity, multidrug resistance, and radiation resistance. Thus, CSCs are considered to be promising therapeutic targets for cancer therapy. The function of CSCs can be regulated by ubiquitination and deubiquitination of proteins related to the specific stemness of the cells executing various stem cell fate choices. To regulate the balance between ubiquitination and deubiquitination processes, the disassembly of ubiquitin chains from specific substrates by deubiquitinating enzymes (DUBs) is crucial. Several key developmental and signaling pathways have been shown to play essential roles in this regulation. Growing evidence suggests that overactive or abnormal signaling within and among these pathways may contribute to the survival of CSCs. These signaling pathways have been experimentally shown to mediate various stem cell properties, such as self-renewal, cell fate decisions, survival, proliferation, and differentiation. In this review, we focus on the DUBs involved in CSCs signaling pathways, which are vital in regulating their stem-cell fate determination.

Therapeutic Targeting of Signaling Pathways Related to Cancer Stemness

The theory of cancer stem cells (CSCs) proposes that the different cells within a tumor, as well as metastasis deriving from it, are originated from a single subpopulation of cells with self-renewal and differentiation capacities. These cancer stem cells are supposed to be critical for tumor expansion and metastasis, tumor relapse and resistance to conventional therapies, such as chemo- and radiotherapy. The acquisition of these abilities has been attributed to the activation of alternative pathways, for instance, WNT, NOTCH, SHH, PI3K, Hippo, or NF-κB pathways, that regulate detoxification mechanisms; increase the metabolic rate; induce resistance to apoptotic, autophagic, and senescence pathways; promote the overexpression of drug transporter proteins; and activate specific stem cell transcription factors. The elimination of CSCs is an important goal in cancer therapeutic approaches because it could decrease relapses and metastatic dissemination, which are main causes of mortality in oncology patients. In this work, we discuss the role of these signaling pathways in CSCs along with their therapeutic potential.

Stem cell programs in cancer initiation, progression, and therapy resistance

Over the past few decades, substantial evidence has convincingly revealed the existence of cancer stem cells (CSCs) as a minor subpopulation in cancers, contributing to an aberrantly high degree of cellular heterogeneity within the tumor. CSCs are functionally defined by their abilities of self-renewal and differentiation, often in response to cues from their microenvironment. Biological phenotypes of CSCs are regulated by the integrated transcriptional, post-transcriptional, metabolic, and epigenetic regulatory networks. CSCs contribute to tumor progression, therapeutic resistance, and disease recurrence through their sustained proliferation, invasion into normal tissue, promotion of angiogenesis, evasion of the immune system, and resistance to conventional anticancer therapies. Therefore, elucidation of the molecular mechanisms that drive cancer stem cell maintenance, plasticity, and therapeutic resistance will enhance our ability to improve the effectiveness of targeted therapies for CSCs. In this review, we highlight the key features and mechanisms that regulate CSC function in tumor initiation, progression, and therapy resistance. We discuss factors for CSC therapeutic resistance, such as quiescence, induction of epithelial-to-mesenchymal transition (EMT), and resistance to DNA damage-induced cell death. We evaluate therapeutic approaches for eliminating therapy-resistant CSC subpopulations, including anticancer drugs that target key CSC signaling pathways and cell surface markers, viral therapies, the awakening of quiescent CSCs, and immunotherapy. We also assess the impact of new technologies, such as single-cell sequencing and CRISPR-Cas9 screening, on the investigation of the biological properties of CSCs. Moreover, challenges remain to be addressed in the coming years, including experimental approaches for investigating CSCs and obstacles in therapeutic targeting of CSCs.

Ovarian cancer stem cells: ready for prime time?

INTRODUCTION

The role of cancer stem cells (CSC) remains controversial and increasingly subject of investigation as a potential oncogenetic platform with promising therapeutic implications. Understanding the role of CSCs in a highly heterogeneous disease like epithelial ovarian cancer (EOC) may potentially lead to the better understanding of the oncogenetic and metastatic pathways of the disease, but also to develop novel strategies against its progression and platinum resistance.

METHODS

We have performed a review of all relevant literature that addresses the oncogenetic potential of stem cells in EOC, their mechanisms, and the associated therapeutic targets.

RESULTS

Cancer stem cells (CSCs) have been reported to be implicated not only in the development and pathways of intratumoral heterogeneity (ITH), but also potentially modulating the tumor microenvironment, leading to the selection of sub-clones resistant to chemotherapy. Furthermore, it appears that the enhanced DNA repair abilities of CSCs are connected with their endurance and resistance maintaining their genomic integrity during novel targeted treatments such as PARP inhibitors, allowing them to survive and causing disease relapse functioning as a tumor seeds.

CONCLUSIONS

It appears that CSCs play a major role in the underlying mechanisms of oncogenesis and development of relapse in EOC. Part of promising future plans would be to not only use them as therapeutic targets, but also extent their value on a preventative level through engineering mechanisms and prevention of EOC in its origin.

Toll-Like Receptors Signaling in the Tumor Microenvironment

The involvement of inflammation in cancer progression is well-established. The immune system can play both tumor-promoting and -suppressive roles, and efforts to harness the immune system to help fight tumor growth are at the forefront of research. Of particular importance is the inflammatory profile at the site of the tumor, with respect to both the leukocyte population numbers, the phenotype of these cells, as well as the contribution of the tumor cells themselves. In this regard, the pro-inflammatory effects of pattern recognition receptor expression and activation in the tumor microenvironment have emerged as a relevant issue both for therapy and to understand tumor development.Pattern recognition receptors (PRRs) were originally recognized as components of immune cells, particularly innate immune cells, as detectors of pathogens. PRR signaling in immune cells activates them, inducing robust antimicrobial responses. In particular, toll-like receptors (TLRs) constitute a family of membrane-bound PRRs which can recognize pathogen-associated molecular patterns (PAMPs) carried by bacteria, virus, and fungi. In addition, PRRs can recognize products generated by stressed cells or damaged tissues, namely damage-associated molecular patterns or DAMPS. Taking into account the role of the immune system in fighting tumors together with the presence of immune cells in the microenvironment of different types of tumors, strategies to activate immune cells via PRR ligands have been envisioned as an anticancer therapeutic approach.In the last decades, it has been determined that PRRs are present and functional on nonimmune cells and that their activation in these cells contributes to the inflammation in the tumor microenvironment. Both tumor-promoting and antitumor effects have been observed when tumor cell PRRs are activated. This argues against nonspecific activation of PRR ligands in the tumor microenvironment as a therapeutic approach. Therefore, the use of PRR ligands for anticancer therapy might benefit from strategies that specifically deliver these ligands to immune cells, thus avoiding tumor cells in some settings. This review focuses on these aspects of TLR signaling in the tumor microenvironment.

Toll-like Receptors from the Perspective of Cancer Treatment

Toll-like receptors (TLRs) represent a family of pattern recognition receptors that recognize certain pathogen-associated molecular patterns and damage-associated molecular patterns. TLRs are highly interesting to researchers including immunologists because of the involvement in various diseases including cancers, allergies, autoimmunity, infections, and inflammation. After ligand engagement, TLRs trigger multiple signaling pathways involving nuclear factor-κB (NF-κB), interferon-regulatory factors (IRFs), and mitogen-activated protein kinases (MAPKs) for the production of various cytokines that play an important role in diseases like cancer. TLR activation in immune as well as cancer cells may prevent the formation and growth of a tumor. Nonetheless, under certain conditions, either hyperactivation or hypoactivation of TLRs supports the survival and metastasis of a tumor. Therefore, the design of TLR-targeting agonists as well as antagonists is a promising immunotherapeutic approach to cancer. In this review, we mainly describe TLRs, their involvement in cancer, and their promising properties for anticancer drug discovery.

Cancer stem cells and nanotechnological approaches for eradication

Cancer stem cells (CSCs) are currently known as the main cause of tumor recurrence. After chemotherapy is completed, CSCs proliferate and then differentiate to generate new tumor tissues. Similar to normal stem cells, this non-uniformly distributed cell population in the tumor tissue has self-renewal capacity and is responsible for survival of the tumor and difference in its genetic and metabolic characteristics. Followed by gene instability in CSCs, new phenotypic markers are aberrantly expressed in CSCs subpopulation. Hence, some of the surface markers and metabolic pathways that are upregulated in CSCs may be applied as specific targets for development of diagnostic and therapeutic approaches. In this review article, the distinctive properties of CSCs including signal pathways implicated in self-renewal and surface markers were discussed. Moreover, targeting CSCs based on their specific properties using nanodrugs was reviewed.

NF-κB Signaling in Ovarian Cancer

The NF-κB signaling pathway is a master and commander in ovarian cancer (OC) that promotes chemoresistance, cancer stem cell maintenance, metastasis and immune evasion. Many signaling pathways are dysregulated in OC and can activate NF-κB signaling through canonical or non-canonical pathways which have both overlapping and distinct roles in tumor progression. The activation of canonical NF-κB signaling has been well established for anti-apoptotic and immunomodulatory functions in response to the tumor microenvironment and the non-canonical pathway in cancer stem cell maintenance and tumor re-initiation. NF-κB activity in OC cells helps to create an immune-evasive environment and to attract infiltrating immune cells with tumor-promoting phenotypes, which in turn, drive constitutive NF-κB activation in OC cells to promote cell survival and metastasis. For these reasons, NF-κB is an attractive target in OC, but current strategies are limited and broad inhibition of this major signaling pathway in normal physiological and immunological functions may produce unwanted side effects. There are some promising pre-clinical outcomes from developing research to target and inhibit NF-κB only in the tumor-reinitiating cancer cell population of OC and concurrently activate canonical NF-κB signaling in immune cells to promote anti-tumor immunity.

Expanded Expression of Toll-Like Receptor 2 in Proliferative Verrucous Leukoplakia

Proliferative verrucous leukoplakia (PVL) is a premalignant condition of the oral mucosa with > 70% chance of progression to squamous cell carcinoma (SCC), while lacking the common risks and behavior seen in non-PVL oral squamous carcinogenesis. PVL follows a multi-stage slow, relentless and usually multifocal expansion of surface epithelial thickening that over time takes on a verrucous architecture, eventually leading to verrucous carcinoma and/or dysplasia followed by "conventional" SCC, a process that takes years and is notoriously difficult to manage. As mucosal surfaces and carcinomas arising at these sites, are colonized by microorganisms, host receptors for microbial products have received attention as potential contributors to carcinogenesis. Studies show that microbial pattern recognition toll-like receptor (TLR)2 in various epithelial cells is upregulated in premalignant lesions and in malignant cells and can activate oncogenic pathways. Because of the highly progressive nature of PVL, we examined TLR2 expression in well-characterized PVL samples by immunohistochemistry. We found that, similar to epithelial dysplasia and SCC, PVL keratinocytes throughout the epithelial thickness showed diffuse TLR2 expression even in early stage lesions prior to onset of dysplasia. In contrast, oral mucosal samples in the absence of hyperorothokeratosis or dysplasia, expressed TLR2 primarily in the basal and parabasal layers. Given the high rates of PVL transformation and the previously established pro-cancer role of high TLR2 expression in malignant oral squamous cells, it is important to determine how its' expression and functions are regulated in the oral squamous epithelium, and what is the specific TLR2 role in carcinogenesis.

A Pan-ALDH1A Inhibitor Induces Necroptosis in Ovarian Cancer Stem-like Cells

Ovarian cancer is typified by the development of chemotherapy resistance. Chemotherapy resistance is associated with high aldehyde dehydrogenase (ALDH) enzymatic activity, increased cancer "stemness," and expression of the stem cell marker CD133. As such, ALDH activity has been proposed as a therapeutic target. Although it remains controversial which of the 19 ALDH family members drive chemotherapy resistance, ALDH1A family members have been primarily linked with chemotherapy resistant and stemness. We identified two ALDH1A family selective inhibitors (ALDH1Ai). ALDH1Ai preferentially kills CD133+ ovarian cancer stem-like cells (CSCs). ALDH1Ai induce necroptotic CSC death, mediated, in part, by the induction of mitochondrial uncoupling proteins and reduction in oxidative phosphorylation. ALDH1Ai is highly synergistic with chemotherapy, reducing tumor initiation capacity and increasing tumor eradication in vivo. These studies link ALDH1A with necroptosis and confirm the family as a critical therapeutic target to overcome chemotherapy resistance and improve patient outcomes.

Exosomal FMR1-AS1 facilitates maintaining cancer stem-like cell dynamic equilibrium via TLR7/NFκB/c-Myc signaling in female esophageal carcinoma

Background

Though esophageal cancer is three to four times more common among males than females worldwide, this type of cancer still ranks in the top incidence among women, even more than the female specific cancer types. The occurrence is currently attributed to extrinsic factors, including tobacco use and alcohol consumption. However, limited attention has been given to gender-specific intrinsic genetic factors, especially in female.

Methods

We re-annotated a large cohort of microarrays on 179 ESCC patients and identified female-specific differently expressed lncRNAs. The associations between FMR1-AS1 and the risk and prognosis of ESCC were examined in 206 diagnosed patients from eastern China and validated in 188 additional patients from southern China. The effects of FMR1-AS1 on the malignant phenotypes on female ESCC cells were detected in vitro and in vivo. ChIRP-MS, reporter gene assays and EMSA were conducted to identify the interaction and regulation among FMR1-AS1, TLR7 and NFκB.

Results

We found FMR1-AS1 expression is exclusively altered and closely associated with the level of sXCI in female ESCC patients, and its overexpression may correlate to poor clinical outcome. ChIRP-MS data indicate that FMR1-AS1 could be packaged into exosomes and released into tumor microenvironment. Functional studies demonstrated that FMR1-AS1 could bind to endosomal toll-like receptor 7 (TLR7) and activate downstream TLR7-NFκB signaling, promoting the c-Myc expression, thus inducing ESCC cell proliferation, anti-apoptosis and invasion ability. Exosome incubation and co-xenograft assay indicate that FMR1-AS1 exosomes may secreted from ESCC CSCs, transferring stemness phenotypes to recipient non-CSCs in tumor microenvironment. Furthermore, we also found a correlation between the serum levels of FMR1-AS1 and the overall survival (OS) of the female ESCC patients.

Conclusions

Our results highlighted exosomal FMR1-AS1 in maintaining CSC dynamic interconversion state through the mechanism of activating TLR7-NFκB signaling, upregulating c-Myc level in recipient cells, which may be taken as an attractive target approach for advancing current precision cancer therapeutics in female patients.

Electronic supplementary material

The online version of this article (10.1186/s12943-019-0949-7) contains supplementary material, which is available to authorized users.

Therapeutic potential of toll-like receptors in treatment of gynecological cancers

Toll-like receptors (TLRs) play an important role in the innate and adaptive immune system. They are expressed in various regions of the female reproductive tract, and their regulation may be involved in the pathogenesis of gynecological lesions. There is growing evidence that ligands for several TLRs are potentially anticancer agents, some of which have already been approved by the FDA, and these compounds are now undergoing clinical evaluation. There is a rationale for using these ligands as adjuvants in the treatment or prevention of gynecological cancer. Some TLR agonists that are of potential interest in the treatment of gynecological lesions include imiquimod, motolimod, cervarix, and CpG-oligodeoxynucleotides (ODNs). In this review, we outline the different functions of TLRs in gynecological cancer with particular emphasis on the value of TLR agonists as a potential therapeutic target in the treatment of gynecological cancer. © 2019 IUBMB Life, 71(5):549-564, 2019.

Toll-like receptor 2 and Toll-like receptor 4 exhibit distinct regulation of cancer cell stemness mediated by cell death-induced high-mobility group box 1

BACKGROUND

High-mobility group box 1 (HMGB1), a common extracellular damage associated molecular pattern molecule, is overexpressed in several solid tumors including pancreatic carcinoma. We previously observed that radiotherapy induced dying cells secrete HMGB1 and accelerate pancreatic carcinoma progression through an unclear mechanism.

METHODS

Using the Millicell system as an in vitro co-culture model, we performed quantitative reverse transcriptase-polymerase chain reaction, western blot and sphere forming ability analyses to access the effect of dying-cell-derived HMGB1 on CD133+ cancer cell stemness in vitro and in vivo. Interactions between HMGB1 and Toll-like receptor 2(TLR2)/TLR4 were studied by co- immunoprecipitation. Western blot and short-hairpin RNA-based knockdown assays were conducted to detect HMGB1 and TLR2/TLR4 signaling activity.

FINDINGS

Radiation-associated, dying-cell-derived HMGB1 maintained stemness and contributed to CD133+ cancer stem cell self-renewal in vitro and in vivo. In overexpressing and silencing experiments, we demonstrated that the process was activated by TLR2 receptor, whereas TLR4 antagonized HMGB1-TLR2 signaling. Wnt/β-catenin signaling supported the HMGB1-TLR2 mediated stemness of CD133+ cancer cells.

INTERPRETATION

Our results show how irradiation-induced cell death might enhance the stemness of resident cancer cells, and indicate HMGB1-TLR2 signaling as a potential therapeutic target for preventing pancreatic cancer recurrence.

Ovarian cancer stem cells: What progress have we made?

Ovarian cancer (OvCa) is the most lethal gynecological malignancy in the United States primarily due to lack of a reliable early diagnostic, high incidence of chemo-resistant recurrent disease as well as profuse tumor heterogeneity. Cancer stem cells (CSCs) continue to gain attention, as they are known to resist chemotherapy, self-renew and re-populate the bulk tumor with undifferentiated and differentiated cells. Moreover, CSCs appear to readily adapt to environmental, immunologic and pharmacologic cues. The plasticity and ability to inactivate or activate signaling pathways promoting their longevity has been, and continues to be, the challenge faced in developing successful CSC targeted therapies. Identifying and understanding unique ovarian CSC markers and the pathways they utilize could reveal new therapeutic opportunities that may offer alternative adjuvant treatment options. Herein, we will discuss the current state of ovarian CSC characterization, their contribution to disease resistance, recurrence and shed light on clinical trials that may target the CSC population.

Adipocyte microenvironment promotes Bclxl expression and confers chemoresistance in ovarian cancer cells

Resistance to mitochondria-initiated apoptosis is a hallmark of chemoresistant cancer stem cells including CD44+/MyD88+ epithelial ovarian cancer (EOC) stem cells. This is controlled by members of the Bcl₂ family of proteins, which function as rheostats of mitochondrial stability. We observed a differential expression profile of Bcl₂ family members comparing the chemoresistant EOC stem cells and the chemosensitive CD44-/MyD88- EOC cells. Chemoresistant EOC stem cells surprisingly express higher levels of the pro-apoptotic members Bak and Bax compared to the chemosensitive EOC cells. In addition, whereas chemosensitive EOC cells preferentially express Bcl₂, chemoresistant EOC stem cells preferentially express Bcl_xl. In the EOC stem cells, 40% knock-down of Bcl_xl expression was sufficient to induce the full activation of caspases and this can be reversed by concurrent knock-down of Puma. More importantly, we demonstrate that Bcl_xl expression levels in EOC cells is dynamic and can be regulated by microenvironments that are enriched with the pro-inflammatory cytokine IL-6 such as the cancer stem cell and adipocyte niches. Adipocyte-induced upregulation of Bcl_xl correlated with acquisition of chemoresistance and thus demonstrates how a specific microenvironment can regulate the expression of apoptotic proteins and confer chemoresistance.

Surface markers of cancer stem-like cells of ovarian cancer and their clinical relevance

Cancer stem-like cells (CSLCs) are defined as cancer cells with stem cell characteristics. Although CSLCs constitute no more than a few percent of the tumor mass, they play important roles in cancer chemo-resistance, metastasis and disease recurrence. Ovarian cancer (OC) is considered the most aggressive gynecological malignancy in which the role of CSLCs is of major significance, although it remains to be specified. The studies describing ovarian CSLC phenotype vary in the definition of the molecular pattern of expression of the main markers such as CD133, CD44, CD117, and CD24. Stem-like features of OC have been shown to correlate with the clinical course of the disease and permit diagnosis, prognosis and treatment outcome to be improved. Identification of CSLC markers could provide hallmarks which, related to the chemo-resistance of the disease, will facilitate treatment selection. This review describes recent advances in research on stem-like cell status in OC, mainly focusing on surface markers of CSLCs and their clinical relevance.

NSAID-activated gene 1 mediates pro-inflammatory signaling activation and paclitaxel chemoresistance in type I human epithelial ovarian cancer stem-like cells

Epithelial ovarian cancer (EOC) remains the most lethal gynecologic malignancy in developed countries. Chronic endogenous sterile pro-inflammatory responses are strongly linked to EOC progression and chemoresistance to anti-cancer therapeutics. In the present study, the activity of epithelial NF-κB, a key pro-inflammatory transcription factor, was enhanced with the progress of EOC. This result was mechanistically linked with an increased expression of NSAID-Activated Gene 1 (NAG-1) in MyD88-positive type I EOC stem-like cells, compared with that in MyD88-negative type II EOC cells. Elevated NAG-1 as a potent biomarker of poor prognosis in the ovarian cancer was positively associated with the levels of NF-κB activation, chemokines and stemness markers in type I EOC cells. In terms of signal transduction, NAG-1-activated SMAD-linked and non-canonical TGFβ-activated kinase 1 (TAK-1)-activated pathways contributed to NF-κB activation and the subsequent induction of some chemokines and cancer stemness markers. In addition to effects on NF-κB-dependent gene regulation, NAG-1 was involved in expression of EGF receptor and subsequent activation of EGF receptor-linked signaling. The present study also provided evidences for links between NAG-1-linked signaling and chemoresistance in ovarian cancer cells. NAG-1 and pro-inflammatory NF-κB were positively associated with resistance to paclitaxel in MyD88-positive type I EOC cells. Mechanistically, this chemoresistance occurred due to enhanced activation of the SMAD-4- and non-SMAD-TAK-1-linked pathways. All of the present data suggested NAG-1 protein as a crucial mediator of EOC progression and resistance to the standard first-line chemotherapy against EOC, particularly in MyD88-positive ovarian cancer stem-like cells.

Immunoregulatory functions and the therapeutic implications of GARP-TGF-β in inflammation and cancer

GARP (glycoprotein-A repetitions predominant) is a type I transmembrane cell surface docking receptor for latent transforming growth factor-β (TGF-β) that is abundantly expressed on regulatory T lymphocytes and platelets. GARP regulates the availability of membrane-bound latent TGF-β and modulates its activation. For this reason, GARP expression on immune and non-immune cells is involved in maintaining peripheral tolerance. It plays an important role in preventing inflammatory diseases such as allergy and graft versus host disease (GvHD). GARP is also frequently hijacked by cancer cells to promote oncogenesis. This review summarizes the most important features of GARP biology described to date including gene regulation, protein expression and mechanism in activating latent TGF-β, and the function of GARP in regulatory T cell biology and peripheral tolerance, as well as GARP’s increasingly recognized roles in platelet-mediated cancer immune evasion. The promise for GARP-targeted strategy as a novel immunotherapy of cancer is also highlighted.

Targeting cancer stem cells in the clinic: Current status and perspectives

Resistance to chemotherapy and cancer relapse are major clinical challenges attributed to a sub population of cancer stem cells (CSCs). The concept of CSCs has been the subject of intense research by the oncology community since evidence for their existence was first published over twenty years ago. Emerging data indicates that they are also able to evade novel therapies such as targeted agents, immunotherapies and anti-angiogenics. The inability to appropriately identify and isolate CSCs is a major hindrance to the field and novel technologies are now being utilized. Agents that target CSC-associated cell surface receptors and signaling pathways have generated promising pre-clinical results and are now entering clinical trial. Here we discuss and evaluate current therapeutic strategies to target CSCs.

NFκB Promotes Ovarian Tumorigenesis via Classical Pathways That Support Proliferative Cancer Cells and Alternative Pathways That Support ALDH+ Cancer Stem-like Cells

Understanding the mechanisms supporting tumor-initiating cells (TIC) is vital to combat advanced-stage recurrent cancers. Here, we show that in advanced ovarian cancers NFκB signaling via the RelB transcription factor supports TIC populations by directly regulating the cancer stem-like associated enzyme aldehyde dehydrogenase (ALDH). Loss of RelB significantly inhibited spheroid formation, ALDH expression and activity, chemoresistance, and tumorigenesis in subcutaneous and intrabursal mouse xenograft models of human ovarian cancer. RelB also affected expression of the ALDH gene ALDH1A2 Interestingly, classical NFκB signaling through the RelA transcription factor was equally important for tumorigenesis in the intrabursal model, but had no effect on ALDH. In this case, classical signaling via RelA was essential for proliferating cells, whereas the alternative signaling pathway was not. Our results show how NFκB sustains diverse cancer phenotypes via distinct classical and alternative signaling pathways, with implications for improved understanding of disease recurrence and therapeutic response. Cancer Res; 77(24); 6927-40. ©2017 AACR.

MyD88 is an essential component of retinoic acid-induced differentiation in human pluripotent embryonal carcinoma cells

We have previously reported that myeloid differentiation primary response gene 88 (MyD88) is downregulated during all-trans retinoic acid (RA)-induced differentiation of pluripotent NTera2 human embryonal carcinoma cells (hECCs), whereas its maintained expression is associated with RA differentiation resistance in nullipotent 2102Ep hECCs. MyD88 is the main adapter for toll-like receptor (TLR) signalling, where it determines the secretion of chemokines and cytokines in response to pathogens. In this study, we report that loss of MyD88 is essential for RA-facilitated differentiation of hECCs. Functional analysis using a specific MyD88 peptide inhibitor (PepInh) demonstrated that high MyD88 expression in the self-renewal state inhibits the expression of a specific set of HOX genes. In NTera2 cells, MyD88 is downregulated during RA-induced differentiation, a mechanism that could be broadly replicated by MyD88 PepInh treatment of 2102Ep cells. Notably, MyD88 inhibition transitioned 2102Ep cells into a stable, self-renewing state that appears to be primed for differentiation upon addition of RA. At a molecular level, MyD88 inhibition combined with RA treatment upregulated HOX, RA signalling and TLR signalling genes. These events permit differentiation through a standard downregulation of Oct4-Sox2-Nanog mechanism. In line with its role in regulating secretion of specific proteins, conditioned media experiments demonstrated that differentiated (MyD88 low) NTera2 cell media was sufficient to differentiate NTera2 cells. Protein array analysis indicated that this was owing to secretion of factors known to regulate angiogenesis, neurogenesis and all three branches of TGF-β Superfamily signalling. Collectively, these data offer new insights into RA controlled differentiation of pluripotent cells, with notable parallels to the ground state model of embryonic stem cell self-renewal. These data may provide insights to facilitate improved differentiation protocols for regenerative medicine and differentiation-therapies in cancer treatment.

NF-κB Participates in the Stem Cell Phenotype of Ovarian Cancer Cells

BACKGROUND

NF-κB is a transcription factor involved in cancer stem cells maintenance of many tumors. Little is known about the specific stem-associated upstream regulators of this pathway in ovarian cancer. The Aim of the study was to analyze the role of the canonical and non-canonical NF-κB pathways in stem cells of ovarian cancer cell lines.

METHODS

Stem cells were isolated using sorting cytometry. Western blot and RT-PCR were used to quantify protein and messenger RNA levels. Loss and gain of function assays were performed using siRNAs and dominant-negative proteins, respectively. NF-κB binding activity was measured with a reporter gene assay. The stem phenotype was estimated with clonogenic assays using soft agar, colony formation, ovospheres formation and in vivo tumorigenicity assays.

RESULTS

The CD44+ subpopulation of SKOV3 ovarian cancer cell line presented higher mRNA levels of key stemness genes, an increased tumorigenic capacity and higher expression of the RelA, RelB and IKKα. When the canonical pathway was inhibited by means of a dominant-negative version of IkBα, the stem cell population was reduced, as shown by a reduced CD44+ subpopulation, a decrease in the expression of the stemness genes and a reduction of the stem phenotype. In addition, IKKα, the main upstream non-canonical kinase, was highly expressed in the CSC population. Accordingly, when IKKα was inhibited using shRNAs, the expression of the stemness genes was reduced.

CONCLUSIONS

This report is the first to show the importance of several elements of both NF-κB pathway in maintaining the ovarian cancer stem cell population.

An Overview of Lipid Droplets in Cancer and Cancer Stem Cells

For decades, lipid droplets have been considered as the main cellular organelles involved in the fat storage, because of their lipid composition. However, in recent years, some new and totally unexpected roles have been discovered for them: (i) they are active sites for synthesis and storage of inflammatory mediators, and (ii) they are key players in cancer cells and tissues, especially in cancer stem cells. In this review, we summarize the main concepts related to the lipid droplet structure and function and their involvement in inflammatory and cancer processes.

Microbial infection, inflammation and epithelial ovarian cancer

Ovarian cancer is the most common, and life-threatening, type of female gynecological cancer. The etiology of ovarian cancer remains unclear, and there are currently no effective screening or treatment methods for the disease. Microbial infection serves a marked function in inducing carcinogenesis. A number of studies have identified pelvic inflammatory disease as a risk factor for epithelial ovarian cancer. Thus, it is hypothesized that microbial infection may contribute to ovarian cancer. In the present review, the microorganisms that have been identified to be associated with ovarian cancer and the underlying molecular mechanisms involved are discussed. Infection-induced chronic inflammation is considered an important process for carcinogenesis, cancer progression and metastasis. Therefore, the pathological process and associated inflammatory factors are reviewed in the present paper.