Cancer Stem Cells and Their Microenvironment: Biology and Therapeutic Implications

Regulation of cancer stem cells by CXCL1, a chemokine whose secretion is controlled by MCM2

BACKGROUND

A high expression pattern of minichromosome maintenance 2 (MCM2) has been observed in various cancers. MCM2 is a protein involved in the cell cycle and plays a role in cancer growth and differentiation by binding to six members of the MCM subfamily. The MCM protein family includes MCM2 through MCM7.

METHODS

MCM2 has shown high expression in both lung cancer stem cells (LCSCs) and glioma stem cells (GSCs). We investigated the characteristics of CSCs and the regulation of the epithelial-to-mesenchymal transition (EMT) phenomenon in LCSCs and GSCs by MCM2. Additionally, we explored secreted factors regulated by MCM2.

RESULTS

There was a significant difference in survival rates between lung cancer patients and brain cancer patients based on MCM2 expression. MCM2 was found to regulate both markers and regulatory proteins in LCSCs. Moreover, MCM2 is thought to be involved in cancer metastasis by regulating cell migration and invasion, not limited to lung cancer but also identified in glioma. Among chemokines, chemokine (C-X-C motif) ligand 1 (CXCL1) was found to be regulated by MCM2.

CONCLUSIONS

MCM2 not only participates in the cell cycle but also affects cancer cell growth by regulating the external microenvironment to create a favorable environment for cells. MCM2 is highly expressed in malignant carcinomas, including CSCs, and contributes to the malignancy of various cancers. Therefore, MCM2 may represent a crucial target for cancer therapeutics.

Cancer stem cells and angiogenesis

Cancer remains the primary cause of mortality in developed nations. Although localized tumors can be effectively addressed through surgery, radiotherapy, and other targeted methods, drug efficacy often wanes in the context of metastatic diseases. As a result, significant efforts are being made to develop drugs capable of not only inhibiting tumor growth but also impeding the metastasis of malignant tumors, with a focus on hindering their migration to adjacent organs. Cancer stem cells metastasize via blood and lymphatic vessels, exhibiting a high mutation rate, significant variability, and a predisposition to drug resistance. In contrast, endothelial cells, being less prone to mutation, are less likely to give rise to drug-resistant clones. Furthermore, the direct contact of circulating anti-angiogenic drugs with vascular endothelial cells expedites their therapeutic impact. Hence, anti-angiogenesis targeted therapy assumes a pivotal role in cancer treatment. This paper provides a succinct overview of the molecular mechanisms governing the interaction between cancer stem cells and angiogenesis.

Tumor Microenvironment: A Niche for Cancer Stem Cell Immunotherapy

Tumorigenic Cancer Stem Cells (CSCs), often called tumor-initiating cells (TICs), represent a unique subset of cells within the tumor milieu. They stand apart from the bulk of tumor cells due to their exceptional self-renewal, metastatic, and differentiation capabilities. Despite significant progress in classifying CSCs, these cells remain notably resilient to conventional radiotherapy and chemotherapy, contributing to cancer recurrence. In this review, our objective is to explore novel avenues of research that delve into the distinctive characteristics of CSCs within their surrounding tumor microenvironment (TME). We will start with an overview of the defining features of CSCs and then delve into their intricate interactions with cells from the lymphoid lineage, namely T cells, B cells, and natural killer (NK) cells. Furthermore, we will discuss their dynamic interplay with myeloid lineage cells, including macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs). Moreover, we will illuminate the crosstalk between CSCs and cells of mesenchymal origin, specifically fibroblasts, adipocytes, and endothelial cells. Subsequently, we will underscore the pivotal role of CSCs within the context of the tumor-associated extracellular matrix (ECM). Finally, we will highlight pre-clinical and clinical studies that target CSCs within the intricate landscape of the TME, including CAR-T therapy, oncolytic viruses, and CSC-vaccines, with the ultimate goal of uncovering novel avenues for CSC-based cancer immunotherapy.

Therapeutic Targeting of Glioblastoma and the Interactions with Its Microenvironment

Glioblastoma (GBM) is the most common primary malignant brain tumour, and it confers a dismal prognosis despite intensive multimodal treatments. Whilst historically, research has focussed on the evolution of GBM tumour cells themselves, there is growing recognition of the importance of studying the tumour microenvironment (TME). Improved characterisation of the interaction between GBM cells and the TME has led to a better understanding of therapeutic resistance and the identification of potential targets to block these escape mechanisms. This review describes the network of cells within the TME and proposes treatment strategies for simultaneously targeting GBM cells, the surrounding immune cells, and the crosstalk between them.

Molecular targets, therapeutic agents and multitasking nanoparticles to deal with cancer stem cells: A narrative review

There is increasing evidence that malignant tumors are initiated and maintained by a sub-population of tumor cells that have similar biological properties to normal adult stem cells. This very small population of Cancer Stem Cells (CSC) comprises tumor initiating cells responsible for cancer recurrence, drug resistance and metastasis. Conventional treatments such as chemotherapy, radiotherapy and surgery, in addition to being potentially toxic and non-specific, may paradoxically increase the population, spread and survival of CSCs. Next-generation sequencing and omics technologies are increasing our understanding of the pathways and factors involved in the development of CSCs, and can help to discover new therapeutic targets against CSCs. In addition, recent advances in nanomedicine have provided hope for the development of optimal specific therapies to eradicate CSCs. Moreover, the use of artificial intelligence and nano-informatics can elucidate new drug targets, and help to design drugs and nanoparticles (NPs) to deal with CSCs. In this review, we first summarize the properties of CSCs and describe the signaling pathways and molecular characteristics responsible for the emergence and survival of CSCs. Also, the location of CSCs within the tumor and the effect of host factors on the creation and maintenance of CSCs are discussed. Newly discovered molecular targets involved in cancer stemness and some novel therapeutic compounds to combat CSCs are highlighted. The optimum properties of anti-CSC NPs, including blood circulation and stability, tumor accumulation and penetration, cellular internalization, drug release, endosomal escape, and aptamers designed for specific targeting of CSCs are covered. Finally, some recent smart NPs designed for therapeutic and theranostic purposes to overcome CSCs are discussed.

Bladder cancer: therapeutic challenges and role of 3D cell culture systems in the screening of novel cancer therapeutics

Bladder cancer (BC) is the sixth most common worldwide urologic malignancy associated with elevated morbidity and mortality rates if not well treated. The muscle-invasive form of BC develops in about 25% of patients. Moreover, according to estimates, 50% of patients with invasive BC experience fatal metastatic relapses. Currently, resistance to drug-based therapy is the major tumble to BC treatment. The three-dimensional (3D) cell cultures are clearly more relevant not only as a novel evolving gadget in drug screening but also as a bearable therapeutic for different diseases. In this review, various subtypes of BC and mechanisms of drug resistance to the commonly used anticancer therapies are discussed. We also summarize the key lineaments of the latest cell-based assays utilizing 3D cell culture systems and their impact on understanding the pathophysiology of BC. Such knowledge could ultimately help to address the most efficient BC treatment.

Profiling and targeting cancer stem cell signaling pathways for cancer therapeutics

Tumorigenic cancer stem cells (CSCs) represent a subpopulation of cells within the tumor that express genetic and phenotypic profiles and signaling pathways distinct from the other tumor cells. CSCs have eluded many conventional anti-oncogenic treatments, resulting in metastases and relapses of cancers. Effectively targeting CSCs' unique self-renewal and differentiation properties would be a breakthrough in cancer therapy. A better characterization of the CSCs' unique signaling mechanisms will improve our understanding of the pathology and treatment of cancer. In this paper, we will discuss CSC origin, followed by an in-depth review of CSC-associated signaling pathways. Particular emphasis is given on CSC signaling pathways' ligand-receptor engagement, upstream and downstream mechanisms, and associated genes, and molecules. Signaling pathways associated with regulation of CSC development stand as potential targets of CSC therapy, which include Wnt, TGFβ (transforming growth factor-β)/SMAD, Notch, JAK-STAT (Janus kinase-signal transducers and activators of transcription), Hedgehog (Hh), and vascular endothelial growth factor (VEGF). Lastly, we will also discuss milestone discoveries in CSC-based therapies, including pre-clinical and clinical studies featuring novel CSC signaling pathway cancer therapeutics. This review aims at generating innovative views on CSCs toward a better understanding of cancer pathology and treatment.

Mycochemicals against Cancer Stem Cells

Since ancient times, mushrooms have been considered valuable allies of human well-being both from a dietary and medicinal point of view. Their essential role in several traditional medicines is explained today by the discovery of the plethora of biomolecules that have shown proven efficacy for treating various diseases, including cancer. Numerous studies have already been conducted to explore the antitumoural properties of mushroom extracts against cancer. Still, very few have reported the anticancer properties of mushroom polysaccharides and mycochemicals against the specific population of cancer stem cells (CSCs). In this context, β-glucans are relevant in modulating immunological surveillance against this subpopulation of cancer cells within tumours. Small molecules, less studied despite their spread and assortment, could exhibit the same importance. In this review, we discuss several pieces of evidence of the association between β-glucans and small mycochemicals in modulating biological mechanisms which are proven to be involved with CSCs development. Experimental evidence and an in silico approach are evaluated with the hope of contributing to future strategies aimed at the direct study of the action of these mycochemicals on this subpopulation of cancer cells.

Cancer stem cells: an insight into the development of metastatic tumors and therapy resistance

The term "cancer stem cells" (CSCs) refers to cancer cells that exhibit traits parallel to normal stem cells, namely the potential to give rise to every type of cell identified in a tumor microenvironment. It has been found that CSCs usually develops from other neoplastic cells or non-cancerous somatic cells by acquiring stemness and malignant characteristics through particular genetic modifications. A trivial number of CSCs, identified in solid and liquid cancer, can give rise to an entire tumor population with aggressive anticancer drug resistance, metastasis, and invasiveness. Besides, cancer stem cells manipulate their intrinsic and extrinsic features, regulate the metabolic pattern of the cell, adjust efflux-influx efficiency, modulate different signaling pathways, block apoptotic signals, and cause genetic and epigenetic alterations to retain their pluripotency and ability of self-renewal. Notably, to keep the cancer stem cells' ability to become malignant cells, mesenchymal stem cells, tumor-associated fibroblasts, immune cells, etc., interact with one another. Furthermore, CSCs are characterized by the expression of particular molecular markers that carry significant diagnostic and prognostic significance. Because of this, scientific research on CSCs is becoming increasingly imperative, intending to understand the traits and behavior of cancer stem cells and create more potent anticancer therapeutics to fight cancer at the CSC level. In this review, we aimed to elucidate the critical role of CSCs in the onset and spread of cancer and the characteristics of CSCs that promote severe resistance to targeted therapy.

Role of hypoxia and epithelial-mesenchymal transition in the formation and maintenance of oral cancer stem cells in oral squamous cell carcinomas and metastatic lymph node: An immunohistochemical analysis

Background

Inspite of having advanced treatment modalities the overall survival rate in oral squamous cell carcinoma (OSCC) remains poor. This is considered to be mainly due to local recurrence and distant metastasis. Various studies have concentrated on the role of oral cancer stem cells (OCSCs) in the progression and metastasis of OSCC. However, the role of tumor microenvironment components has been less delved into. Hence clarity on cell biology and metastatic potential OCSCs is essential for the development of more effective anti-cancer treatment.

Aim

To establish the role of OCSCs in different grades of OSCC and metastatic lymph nodes through the expression of cluster of differentiation 44 (CD44). To demonstrate and correlate the role of hypoxia and Epithelial mesenchymal transition (EMT) in the various grades and metastatic lymph nodes in the formation and maintenance of OCSCs by employing Hypoxia-inducible factor-1 Alpha (HIF 1α) and Snail respectively.

Method and Material

A total of 36 cases of OSCC, 12 from each grade and 12 normal oral mucosal tissues were included in the study. Immunohistochemical staining was performed for the demonstration of CD44, HIF1α, and Snail.

Statistics

Descriptive analysis, Chi-square, and Spearman's rank correlation were used to analyze frequency and proportion, to compare expression and correlate between lesion proper and lymph node in each group respectively.

Results

Significant expression of CD44, HIF1 α, and Snail among advancing grades of OSCC and their metastatic lymph node were observed. A positive correlation was seen between them.

Conclusions

The prognosis of OSCC can be improved by better understanding and targeting the molecules involved in the formation and maintenance of OCSCs.

Immunotargeting of Cancer Stem Cells

The generally accepted view is that CSCs hijack the signaling pathways attributed to normal stem cells that regulate the self-renewal and differentiation processes. Therefore, the development of selective targeting strategies for CSC, although clinically meaningful, is associated with significant challenges because CSC and normal stem cells share many important signaling mechanisms for their maintenance and survival. Furthermore, the efficacy of this therapy is opposed by tumor heterogeneity and CSC plasticity. While there have been considerable efforts to target CSC populations by the chemical inhibition of the developmental pathways such as Notch, Hedgehog (Hh), and Wnt/β-catenin, noticeably fewer attempts were focused on the stimulation of the immune response by CSC-specific antigens, including cell-surface targets. Cancer immunotherapies are based on triggering the anti-tumor immune response by specific activation and targeted redirecting of immune cells toward tumor cells. This review is focused on CSC-directed immunotherapeutic approaches such as bispecific antibodies and antibody-drug candidates, CSC-targeted cellular immunotherapies, and immune-based vaccines. We discuss the strategies to improve the safety and efficacy of the different immunotherapeutic approaches and describe the current state of their clinical development.

Cancer stem cells (CSCs): key player of radiotherapy resistance and its clinical significance

Cancer stem cells (CSCs) are self-renewing and slow-multiplying micro subpopulations in tumour microenvironments. CSCs contribute to cancer's resistance to radiation (including radiation) and other treatments. CSCs control the heterogeneity of the tumour. It alters the tumour's microenvironment cellular singling and promotes epithelial-to-mesenchymal transition (EMT). Current research decodes the role of extracellular vesicles (EVs) and CSCs interlink in radiation resistance. Exosome is a subpopulation of EVs and originated from plasma membrane. It is secreted by several active cells. It involed in cellular communication and messenger of healthly and multiple pathological complications. Exosomal biological active cargos (DNA, RNA, protein, lipid and glycan), are capable to transform recipient cells' nature. The molecular signatures of CSCs and CSC-derived exosomes are potential source of cancer theranostics development. This review discusse cancer stem cells, radiation-mediated CSCs development, EMT associated with CSCs, the role of exosomes in radioresistance development, the current state of radiation therapy and the use of CSCs and CSCs-derived exosomes biomolecules as a clinical screening biomarker for cancer. This review gives new researchers a reason to keep an eye on the next phase of scientific research into cancer theranostics that will help mankind.

Cancer Stem Cell Relationship with Pro-Tumoral Inflammatory Microenvironment

Inflammatory processes and cancer stem cells (CSCs) are increasingly recognized as factors in the development of tumors. Emerging evidence indicates that CSCs are associated with cancer properties such as metastasis, treatment resistance, and disease recurrence. However, the precise interaction between CSCs and the immune microenvironment remains unexplored. Although evasion of the immune system by CSCs has been extensively studied, new research demonstrates that CSCs can also control and even profit from the immune response. This review provides an overview of the reciprocal interplay between CSCs and tumor-infiltrating immune cells, collecting pertinent data about how CSCs stimulate leukocyte reprogramming, resulting in pro-tumor immune cells that promote metastasis, chemoresistance, tumorigenicity, and even a rise in the number of CSCs. Tumor-associated macrophages, neutrophils, Th17 and regulatory T cells, mesenchymal stem cells, and cancer-associated fibroblasts, as well as the signaling pathways involved in these pro-tumor activities, are among the immune cells studied. Although cytotoxic leukocytes have the potential to eliminate CSCs, immune evasion mechanisms in CSCs and their clinical implications are also known. We intended to compile experimental findings that provide direct evidence of interactions between CSCs and the immune system and CSCs and the inflammatory milieu. In addition, we aimed to summarize key concepts in order to comprehend the cross-talk between CSCs and the tumor microenvironment as a crucial process for the effective design of anti-CSC therapies.

Notch signaling sculpts the stem cell niche

Adult stem cells depend on their niches for regulatory signaling that controls their maintenance, division, and their progeny differentiation. While communication between various types of stem cells and their niches is becoming clearer, the process of stem cell niche establishment is still not very well understood. Model genetic organisms provide simplified systems to address various complex questions, for example, how is a stem cell niche formed? What signaling cascades induce the stem cell niche formation? Are the mechanisms of stem cell niche formation conserved? Notch signaling is an evolutionarily conserved pathway first identified in fruit flies, crucial in fate acquisition and spatiotemporal patterning. While the core logic behind its activity is fairly simple and requires direct cell-cell interaction, it reaches an astonishing complexity and versatility by combining its different modes of action. Subtleties such as equivalency between communicating cells, their physical distance, receptor and ligand processing, and endocytosis can have an effect on the way the events unfold, and this review explores some important general mechanisms of action, later on focusing on its involvement in stem cell niche formation. First, looking at invertebrates, we will examine how Notch signaling induces the formation of germline stem cell niche in male and female Drosophila. In the developing testis, a group of somatic gonadal precursor cells receive Delta signals from the gut, activating Notch signaling and sealing their fate as niche cells even before larval hatching. Meanwhile, the ovarian germline stem cell niche is built later during late larval stages and requires a two-step process that involves terminal filament formation and cap cell specification. Intriguingly, double security mechanisms of Notch signaling activation coordinated by the soma or the germline control both steps to ensure the robustness of niche assembly. Second, in the vast domains of mammalian cellular signaling, there is an emerging picture of Notch being an active player in a variety of tissues in health and disease. Notch involvement has been shown in stem cell niche establishment in multiple organs, including the brain, muscle, and intestine, where the stem cell niches are essential for the maintenance of adult stem cells. But adult stem cells are not the only cells looking for a home. Cancer stem cells use Notch signaling at specific stages to gain an advantage over endogenous tissue and overpower it, at the same time acquiring migratory and invasive abilities to claim new tissues (e.g., bone) as their territory. Moreover, in vitro models such as organoids reveal similar Notch employment when it comes to the developing stem cell niches. Therefore, a better understanding of the processes regulating stem cell niche assembly is key for the fields of stem cell biology and regenerative medicines.

The roles of Linc-ROR in the regulation of cancer stem cells

Cancer stem cells (CSCs) are considered to be a kind of tumor cell population characterized by self-renewal, easy to metastasize and drug resistance, which play an indispensable role in the occurrence, development, metastasis and drug resistance of tumors, and their existence is an important reason for high metastasis and recurrence of tumors. Long non-coding RNAs (LncRNAs), which are more than 200 nucleotides in length, have a close relationship with the malignant progression of cancer.In recent years, abundant studies have reavling that LncRNAs are beneficial to the regulation of various cancer stem cells. Linc-ROR, as a newly discovered intergenic non-protein-coding RNA in recent years, is considered to be a key regulator affecting the development of human tumors. Dysregulation of Linc-ROR is related to stemness phenotype and functional regulation of cancer stem cells. For that, Linc-ROR has the potential to be used as a diagnostic biomarker for cancer patients and can serve as a clinically meaningful potential therapeutic target. In this review, we generalize the existing research results on the important role of Linc-ROR in regulation of CSCs.

Cofilin Acts as a Booster for Progression of Malignant Tumors Represented by Glioma

Cofilin, as a depolymerization factor of actin filaments, has been widely studied. Evidences show that cofilin has a role in actin structural reorganization and dynamic regulation. In recent years, several studies have demonstrated a regulatory role for cofilin in the migration and invasion mediated by cell dynamics and epithelial to mesenchymal transition (EMT)/EMT-like process, apoptosis, radiotherapy resistance, immune escape, and transcriptional dysregulation of malignant tumor cells, particularly glioma cells. On this basis, it is practical to evaluate cofilin as a biomarker for predicting tumor metastasis and prognosis. Targeting cofilin regulating kinases, Lin11, Isl-1 and Mec-3 kinases (LIM kinases/LIMKs) and their major upstream molecules inhibits tumor cell migration and invasion and targeting cofilin-mediated mitochondrial pathway induces apoptosis of tumor cells represent effective options for the development of novel anti-malignant tumor drug, especially anti-glioma drugs. This review explores the structure, general biological function, and regulation of cofilin, with an emphasis on the critical functions and prospects for clinical therapeutic applications of cofilin in malignant tumors represented by glioma.

Ferroptosis and Its Potential Role in Glioma: From Molecular Mechanisms to Therapeutic Opportunities

Glioma is the most common intracranial malignant tumor, and the current main standard treatment option is a combination of tumor surgical resection, chemotherapy and radiotherapy. Due to the terribly poor five-year survival rate of patients with gliomas and the high recurrence rate of gliomas, some new and efficient therapeutic strategies are expected. Recently, ferroptosis, as a new form of cell death, has played a significant role in the treatment of gliomas. Specifically, studies have revealed key processes of ferroptosis, including iron overload in cells, occurrence of lipid peroxidation, inactivation of cysteine/glutathione antiporter system Xc- (xCT) and glutathione peroxidase 4 (GPX4). In the present review, we summarized the molecular mechanisms of ferroptosis and introduced the application and challenges of ferroptosis in the development and treatment of gliomas. Moreover, we highlighted the therapeutic opportunities of manipulating ferroptosis to improve glioma treatments, which may improve the clinical outcome.

Breast cancer liver metastasis: Pathogenesis and clinical implications

Breast cancer is the most common malignant disease in female patients worldwide and can spread to almost every place in the human body, most frequently metastasizing to lymph nodes, bones, lungs, liver and brain. The liver is a common metastatic location for solid cancers as a whole, and it is also the third most common metastatic site for breast cancer. Breast cancer liver metastasis (BCLM) is a complex process. Although the hepatic microenvironment and liver sinusoidal structure are crucial factors for the initial arrest of breast cancer and progression within the liver, the biological basis of BCLM remains to be elucidated. Importantly, further understanding of the interaction between breast cancer cells and hepatic microenvironment in the liver metastasis of breast cancer will suggest ways for the development of effective therapy and prevention strategies for BCLM. In this review, we provide an overview of the recent advances in the understanding of the molecular mechanisms of the hepatic microenvironment in BCLM formation and discuss current systemic therapies for treating patients with BCLM as well as potential therapeutic development based on the liver microenvironment-associated signaling proteins governing BCLM.

Effects of microenvironment in osteosarcoma on chemoresistance and the promise of immunotherapy as an osteosarcoma therapeutic modality

Osteosarcoma (OS) is one of the most common primary malignant tumors originating in bones. Its high malignancy typically manifests in lung metastasis leading to high mortality. Although remarkable advances in surgical resection and neoadjuvant chemotherapy have lengthened life expectancy and greatly improved the survival rate among OS patients, no further breakthroughs have been achieved. It is challenging to treat patients with chemoresistant tumors and distant metastases. Recent studies have identified a compelling set of links between hypoxia and chemotherapy failure. Here, we review the evidence supporting the positive effects of hypoxia in the tumor microenvironment (TME). In addition, certain anticancer effects of immune checkpoint inhibitors have been demonstrated in OS preclinical models. Continued long-term observation in clinical trials is required. In the present review, we discuss the mutualistic effects of the TME in OS treatment and summarize the mechanisms of immunotherapy and their interaction with TME when used to treat OS. We also suggest that immunotherapy, a new comprehensive and potential antitumor approach that stimulates an immune response to eliminate tumor cells, may represent an innovative approach for the development of a novel treatment regimen for OS patients.

Clinicopathological significances of PLOD2, epithelial-mesenchymal transition markers, and cancer stem cells in patients with esophageal squamous cell carcinoma

BACKGROUND

To examine the expression level of procollagen-lysine2-oxoglutarate 5-dioxygenase 2 (PLOD2) in esophageal squamous cell carcinoma (ESCC) and analyze its correlation with clinicopathological parameters, in order to explore the mechanism of PLOD2 in regulating invasion and metastasis of ESCC.

METHODS

Immunohistochemistry was used to detect the expression level of PLOD2 in tumor tissues and paired adjacent tissues of 172 patients with ESCC, and the relationship between PLOD2 expression and clinicopathological parameters was analyzed. The deposition of collagen fibers in tumor was detected by Sirius red staining. The correlation between tumor stem cells and epithelial-mesenchymal transition (EMT) markers ZEB1 was analyzed by multivariate logistic regression.

RESULTS

The expression level of PLOD2 in tumor tissues of patients with ESCC (70.35%, 121/172) was significantly higher than that in paired adjacent tissues (29.65%, 51/172; P < .01). The positive expression rate of PLOD2 in ESCC was related to T classification, lymph node metastasis, and pathological tumor node metastasis of a tumor. The expression rates of ZEB1, CD44, and CD133 in ESCC were correlated with T classification, lymph node metastasis and pathological tumor node metastasis. Scarlet red staining showed that collagen fiber deposition in ESCC tissues with high expression of PLOD2 was significantly higher than that in tissues with low expression of PLOD2 (P < .01). A positive correlation was observed between the expression of PLOD2 and CD133, PLOD2 and CD44, and PLOD2 and N-cadherin (P < .01). Moreover, a negative correlation was noted between the expression of PLOD2 and E-cadherin (P < .01). The combined expression of PLOD2 and ZEB1 were independent prognostic factors for the total survival time of patients with ESCC.

CONCLUSION

PLOD2 is highly expressed in ESCC and is closely related to tumor invasion and metastasis. The mechanism of PLOD2 for promoting invasion and metastasis of ESCC may be related to activation of the EMT signaling pathway to promote EMT and tumor stem cell transformation.

FZD7 accelerates hepatic metastases in pancreatic cancer by strengthening EMT and stemness associated with TGF-β/SMAD3 signaling

Background

Metastasis of malignant tumors accelerates systemic failure and hastens the deaths of pancreatic cancer patients. During the metastatic process, the physical translocation of cancer cells from the primary lesion to distant organs and is crucial. CSCs properties, such as self-renewal and multiple-direction differentiation capacity are essential for colonization in the microenvironment of distant organs and metastatic lesion formation. It is widely believed that EMT can cause cancer cells to penetrate blood vessels by undergoing phenotypic and cytoskeletal changes, so that they can infiltrate surrounding tissue and disseminate from the primary tumor to the blood circulation, where they are termed circulating tumor cells (CTCs), while CTCs often exhibit stemness properties. Accumulating evidence demonstrates that some EMT-related transcription factors are essential for CSCs self-renewal, so cancer cells that have undergone EMT typically acquire increased stemness properties. Abnormal activation of the WNT signaling pathway can drive a series of gene transcripts to promote EMT in multiple types of cancer, and among different Frizzled receptors of WNT signaling pathway, FZD7 expression is associated with distant organ metastasis, advanced clinical stages, and poor clinical prognosis. Objective of this study is to demonstrate that high FZD7 expression in pancreatic cancer can accelerate hepatic metastases and elucidate the related molecular mechanisms.

Methods

The expression of Frrizled receptor 7 (FZD7) in pancreatic ductal adenocarcinoma (PDAC) and relating survival rate were analyzed by bioinformatics, histochemistry assay and follow-up study. In vitro, FZD7 expression was silenced by lentiviral vectors carrying short hair RNA (shRNA) or upregulated by overexpression plasmid. Then, Wound-healing and Transwell experiment was used to analyze the abilities of migration and invasion; the levels of epithelial-to-mesenchymal transition (EMT) relating phenotype proteins, stemness relating phenotype proteins, and signaling molecular proteins were measured by Western-blot; cell stemness was evaluated by sphere forming ability of cells in suspension culture and detecting the proportion of CD24⁺CD44⁺ cells with flow cytometry. TGF-β1 was used to induce EMT, and observe the effect of shRNA silencing FZD7 on which.

Results

High level of FZD7 expression in pancreatic cancer samples was associated with earlier hepatic metastasis. In vitro upregulation FZD7 can enable pancreatic cancer cells to obtain stronger migration and invasion ability and higher mesenchymal phenotype, and vice versa; the proportion of cancer stem cell (CSC) was also positively correlated with the level of FZD7; cells forming spheres in suspension culture showed stronger migration and invasion ability and higher level of mesenchymal phenotype than normal adherent cultured cells; the level of FZD7 was positively correlated with the level of activated β-catenin. Silencing FZD7 expression can attenuate EMT induced by TGF-β1 stimulating, and TGF-β1 stimulating can also upregulate stemness phenotype expression, such as ABCG2, CD24, and CD44 by mediating of FZD7.

Conclusions

High FZD7 expression in pancreatic cancer can accelerates hepatic metastases by promoting EMT and strengthening cell stemness, and FZD7 can work through the canonical Wingless-type (WNT) signaling pathway and participate in TGF-β/SMAD3 signaling pathway also.

Engineering Next-Generation CAR-T Cells: Overcoming Tumor Hypoxia and Metabolism

T cells engineered to express chimeric antigen receptors (CARs) have shown remarkable success in treating B-cell malignancies, reflected by multiple US Food and Drug Administration-approved CAR-T cell products currently on the market. However, various obstacles have thus far limited the use of approved products and constrained the efficacy of CAR-T cell therapy against solid tumors. Overcoming these obstacles will necessitate multidimensional CAR-T cell engineering approaches and better understanding of the intricate tumor microenvironment (TME). Key challenges include treatment-related toxicity, antigen escape and heterogeneity, and the highly immunosuppressive profile of the TME. Notably, the hypoxic and nutrient-deprived nature of the TME severely attenuates CAR-T cell fitness and efficacy, highlighting the need for more sophisticated engineering strategies. In this review, we examine recent advances in protein- and cell-engineering strategies to improve CAR-T cell safety and efficacy, with an emphasis on overcoming immunosuppression induced by tumor metabolism and hypoxia.

Cell plasticity, senescence, and quiescence in cancer stem cells: Biological and therapeutic implications

Cancer stem cells (CSCs) are a distinct population of cells within tumors with capabilities of self-renewal and tumorigenicity. CSCs play a pivotal role in cancer progression, metastasis, and relapse and tumor resistance to cytotoxic therapy. Emerging scientific evidence indicates that CSCs adopt several mechanisms, driven by cellular plasticity, senescence and quiescence, to maintain their self-renewal capability and to resist tumor microenvironmental stress and treatments. These pose major hindrances for CSC-targeting anti-cancer therapies: cell plasticity maintains stemness in CSCs and renders tumor cells to acquire stem-like phenotypes, contributing to tumor heterogeneity and CSC generation; cellular senescence induces genetic reprogramming and stemness activation, leading to CSC-mediated tumor progression and metastasis; cell quienscence facilitates CSC to overcome their intrinsic vulnerabilities and therapeutic stress, inducing tumor relapse and therapy resistance. These mechanisms are subjected to spatiotemporal regulation by hypoxia, CSC niche, and extracellular matrix in the tumor microenvironment. Here we integrate the recent advances and current knowledge to elucidate the mechanisms involved in the regulation of plasticity, senescence and quiescence of CSCs and the potential therapeutic implications for the future.

Dissecting Tumor Growth: The Role of Cancer Stem Cells in Drug Resistance and Recurrence

Simple Summary

Cancer is one of the most debated problems all over the world. Cancer stem cells are considered responsible of tumor initiation, metastasis, drug resistance, and recurrence. This subpopulation of cells has been found into the tumor bulk and showed the capacity to self-renew, differentiate, up to generate a new tumor. In the last decades, several studies have been set on the molecular mechanisms behind their specific characteristics as the Wnt/β-catenin signaling, Notch signaling, Hedgehog signaling, transcription factors, etc. The most powerful part of CSCs is represented by the niches as “promoter” of their self-renewal and “protector” from the common oncological treatment as chemotherapy and radiotherapy. In our review article we highlighted the primary mechanisms involved in CSC tumorigenesis for the setting of further targets to control the metastatic process.

Abstract

Emerging evidence suggests that a small subpopulation of cancer stem cells (CSCs) is responsible for initiation, progression, and metastasis cascade in tumors. CSCs share characteristics with normal stem cells, i.e., self-renewal and differentiation potential, suggesting that they can drive cancer progression. Consequently, targeting CSCs to prevent tumor growth or regrowth might offer a chance to lead the fight against cancer. CSCs create their niche, a specific area within tissue with a unique microenvironment that sustains their vital functions. Interactions between CSCs and their niches play a critical role in regulating CSCs’ self-renewal and tumorigenesis. Differences observed in the frequency of CSCs, due to the phenotypic plasticity of many cancer cells, remain a challenge in cancer therapeutics, since CSCs can modulate their transcriptional activities into a more stem-like state to protect themselves from destruction. This plasticity represents an essential step for future therapeutic approaches. Regarding self-renewal, CSCs are modulated by the same molecular pathways found in normal stem cells, such as Wnt/β-catenin signaling, Notch signaling, and Hedgehog signaling. Another key characteristic of CSCs is their resistance to standard chemotherapy and radiotherapy treatments, due to their capacity to rest in a quiescent state. This review will analyze the primary mechanisms involved in CSC tumorigenesis, with particular attention to the roles of CSCs in tumor progression in benign and malignant diseases; and will examine future perspectives on the identification of new markers to better control tumorigenesis, as well as dissecting the metastasis process.

Matrix Stiffness Potentiates Stemness of Liver Cancer Stem Cells Possibly via the Yes-Associated Protein Signal

A hepatocellular carcinoma tissue has mechanical heterogeneity, where the stiffness gradually increases from the core to the invasion front. Furthermore, there is evidence that stem cells from liver cancer (LCSCs) preferentially enrich the invasion front, exhibiting the stiffest modulus in the tumor. LCSCs have the features of stem/progenitor cells and play a vital part in liver cancer development. However, whether matrix stiffness affects LCSC stemness remains unclear. Here, we established a three-dimensional hydrogel for culturing LCSCs to simulate the stiffness of the core and the invasion front of a liver cancer tissue. The results showed that a stiffer matrix (72.2 ± 0.90 kPa) significantly potentiated LCSC stemness as compared with a soft matrix (7.7 ± 0.41 kPa). Moreover, Yes-associated protein signaling might mediate this promotion. Together, our findings illustrate the relationship between matrix stiffness and LCSC stemness, which may aid the production of novel treatment approaches against liver cancer.

Cancer extracellular vesicles, tumoroid models, and tumor microenvironment

Cancer extracellular vesicles (EVs), or exosomes, promote tumor progression through enhancing tumor growth, initiating epithelial-to-mesenchymal transition, remodeling the tumor microenvironment, and preparing metastatic niches. Three-dimensionally (3D) cultured tumoroids / spheroids aim to reproduce some aspects of tumor behavior in vitro and show increased cancer stem cell properties. These properties are transferred to their EVs that promote tumor growth. Moreover, recent tumoroid models can be furnished with aspects of the tumor microenvironment, such as vasculature, hypoxia, and extracellular matrix. This review summarizes tumor tissue culture and engineering platforms compatible with EV research. For example, the combination experiments of 3D-tumoroids and EVs have revealed multifunctional proteins loaded in EVs, such as metalloproteinases and heat shock proteins. EVs or exosomes are able to transfer their cargo molecules to recipient cells, whose fates are often largely altered. In addition, the review summarizes approaches to EV labeling technology using fluorescence and luciferase, useful for studies on EV-mediated intercellular communication, biodistribution, and metastatic niche formation.

Role of Tumor Microenvironment in Cancer Stem Cells Resistance to Radiotherapy

Cancer is a chronic disorder that involves several elements of both the tumor and the host stromal cells. At present, the complex relationship between the various factors presents in the tumor microenvironment (TME) and tumor cells, as well as immune cells located within the TME, is still poorly known. Within the TME, the crosstalk of these factors and immune cells essentially determines how a tumor reacts to the treatment and how the tumor can ultimately be destroyed, remain dormant, or develop and metastasize. Also, in TME, reciprocal crosstalk between cancer-associated fibroblasts (CAFs), extracellular matrix (ECM), hypoxia-inducible factor (HIF) intensifies the proliferation capacity of cancer stem cells (CSCs). CSCs are subpopulation of cells that reside within the tumor bulk and have the capacity to self-renew, differentiate, and repair DNA damage. These characteristics make CSCs develop resistance to a variety of treatments, such as radiotherapy (RT). RT is a frequent and often curative treatment for local cancer which mediates tumor elimination by cytotoxic actions. Also, cytokines and growth factors that are released into TME, have been involved in the activation of tumor radioresistance and the induction of different immune cells, altering local immune responses. In this review, we discuss the pivotal role of TME in resistance of CSCs to RT.

Tumor-propagating side population cells are a dynamic subpopulation in undifferentiated pleomorphic sarcoma

Sarcomas contain a subpopulation of tumor-propagating cells (TPCs) with enhanced tumor-initiating and self-renewal properties. However, it is unclear whether the TPC phenotype in sarcomas is stable or a dynamic cell state that can derive from non-TPCs. In this study, we utilized a mouse model of undifferentiated pleomorphic sarcoma (UPS) to trace the lineage relationship between sarcoma side population (SP) cells that are enriched for TPCs and non-SP cells. By cotransplanting SP and non-SP cells expressing different endogenous fluorescent reporters, we show that non-SP cells can give rise to SP cells with enhanced tumor-propagating potential in vivo. Lineage trajectory analysis using single-cell RNA sequencing from SP and non-SP cells supports the notion that non-SP cells can assume the SP cell phenotype de novo. To test the effect of eradicating SP cells on tumor growth and self-renewal, we generated mouse sarcomas in which the diphtheria toxin receptor is expressed in the SP cells and their progeny. Ablation of the SP population using diphtheria toxin did not impede tumor growth or self-renewal. Altogether, we show that the sarcoma SP represent a dynamic cell state and targeting TPCs alone is insufficient to eliminate tumor progression.

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.

Potential Strategies to Improve the Effectiveness of Drug Therapy by Changing Factors Related to Tumor Microenvironment

A tumor microenvironment (TME) is composed of various cell types and extracellular components. It contains tumor cells and is nourished by a network of blood vessels. The TME not only plays a significant role in the occurrence, development, and metastasis of tumors but also has a far-reaching impact on the effect of therapeutics. Continuous interaction between tumor cells and the environment, which is mediated by their environment, may lead to drug resistance. In this review, we focus on the key cellular components of the TME and the potential strategies to improve the effectiveness of drug therapy by changing their related factors.

CD11b+CTLA4+ myeloid cells are a key driver of tumor evasion in colorectal cancer

Background

Tumor metastasis is the major cause of death of colorectal cancer (CRC), and metastatic CRC remains incurable in many cases despite great advances in genetic and molecular profiling, and clinical development of numerous drugs, including immune checkpoint inhibitors. Thus, more effective treatments are urgently needed for the patients in clinical settings.

Methods

We used mouse CRC metastasis models that murine Colon26 cells were subcutaneously and intravenously implanted and attempted to elucidate the tumor biological and immunological mechanisms underlying cancer metastasis. Then, we evaluated in vivo antitumor efficacy induced by agents targeting the identified molecular mechanisms using the mouse models. We validated the clinical relevancy of the findings using peripheral blood mononuclear cells obtained from stage IV metastatic CRC patients.

Results

CD11b⁺CTLA4⁺ myeloid cells were systemically expanded in the metastatic settings and facilitated tumor progression and metastasis directly via generating lipid droplets in tumor cells and indirectly via inducing immune exhaustion. These events were mediated by IL1B produced via the CTLA4 signaling from the increased myeloid cells. Blocking CTLA4 and IL1B with the specific mAbs significantly suppressed tumor progression and metastasis in the mouse models resistant to anti-PD1 therapy, and the therapeutic efficacy was optimized by blocking cyclooxygenases with aspirin.

Conclusions

The CD11b⁺CTLA4⁺ cells are a key driver of tumor evasion, and targeting the CTLA4-IL1B axis could be a promising strategy for treating metastatic CRC. The triple combination regimen with anti-CTLA4/IL1B mAbs and aspirin may be useful in clinical settings.

Nanoparticles for Targeted Drug Delivery to Cancer Stem Cells: A Review of Recent Advances

Cancer stem cells (CSCs) are a subpopulation of cells that can initiate, self-renew, and sustain tumor growth. CSCs are responsible for tumor metastasis, recurrence, and drug resistance in cancer therapy. CSCs reside within a niche maintained by multiple unique factors in the microenvironment. These factors include hypoxia, excessive levels of angiogenesis, a change of mitochondrial activity from aerobic aspiration to aerobic glycolysis, an upregulated expression of CSC biomarkers and stem cell signaling, and an elevated synthesis of the cytochromes P450 family of enzymes responsible for drug clearance. Antibodies and ligands targeting the unique factors that maintain the niche are utilized for the delivery of anticancer therapeutics to CSCs. In this regard, nanomaterials, specifically nanoparticles (NPs), are extremely useful as carriers for the delivery of anticancer agents to CSCs. This review covers the biology of CSCs and advances in the design and synthesis of NPs as a carrier in targeting cancer drugs to the CSC subpopulation of cancer cells. This review includes the development of synthetic and natural polymeric NPs, lipid NPs, inorganic NPs, self-assembling protein NPs, antibody-drug conjugates, and extracellular nanovesicles for CSC targeting.

Cholesterol Metabolism as a Potential Therapeutic Target and a Prognostic Biomarker for Cancer Immunotherapy

Checkpoint-based immunotherapies, such as programmed cell death-1 (PD-1)/programmed cell death ligand-1 (PD-L1) inhibitors, have shown promising clinical outcomes in many types of cancers. Unfortunately, the response rate of immune checkpoint inhibitors is low. It is very important to discover novel therapeutic targets and prognostic biomarkers. Cholesterol metabolism has been demonstrated to be related to the occurrence and development of a variety of tumors and may provide a new breakthrough in the development of immunotherapy. First of all, cholesterol metabolism in the tumor microenvironment affects the function of tumor-infiltrating immune cells. In addition, intracellular cholesterol homeostasis is an important regulator of immune cell function. Furthermore, drugs that act on cholesterol metabolism affect the efficacy of immunotherapy. What is more, peripheral blood cholesterol level can be a biomarker to predict the efficacy of immunotherapy. In this review, we aimed to explore the potential role of cholesterol metabolism on immunotherapy. By summarizing the major findings of recent preclinical and clinical studies on cholesterol metabolism in immunotherapy, we suggested that cholesterol metabolism could be a potential therapeutic target and a prognostic biomarker for immunotherapy.

Autologous stem cell therapy in knee osteoarthritis: a systematic review of randomised controlled trials

OBJECTIVE

Stem cell therapy is increasingly used for knee osteoarthritis (KOA). We aimed to review the evidence of autologous mesenchymal stem cell therapy on pain, function and severity on imaging in KOA.

DESIGN

Systematic review of randomised controlled trials (RCTs).

ELIGIBILITY CRITERIA

RCTs evaluating autologous mesenchymal stem cell (MSC) therapy on patient-reported outcome measures and disease severity.

DATA SOURCES

Seven databases were searched until 31 December 2020.

RISK OF BIAS AND DATA SYNTHESIS

Risk of bias was assessed using the ROB V.2. We used Grading of Recommendations Assessment, Development and Evaluation to appraise the certainty of the evidence. Data were synthesised descriptively.

RESULTS

Fourteen RCTs were included. A total of 408 patients with KOA received MSC therapy derived from bone marrow, adipose tissue or activated peripheral blood. After 1 year, 19 of 26 (73%) clinical outcome measures improved with MSCs compared with control. In the MSC group, patients improved by 1.8-4.4 points on the Visual Analogue Scale (0-10) and 18-32 points of the Knee Osteoarthritis Outcome Score (0-100). Four studies showed better disease severity on imaging after MSC compared with control at 1 year. Ten of 14 (71%) RCTs were at high risk of bias on all outcomes. No serious adverse events were reported after MSC therapy during a maximum of 4 years follow-up.

CONCLUSION

We found a positive effect of autologous MSC therapy compared with control treatments on patient-reported outcome measures, and disease severity. The certainty of this evidence was low to very low.

PROSPERO REGISTRATION NUMBER

CRD42019120506.

TLR4 expression and functionality are downregulated in glioblastoma cells and in tumor-associated macrophages: A new mechanism of immune evasion?

Glioblastoma (GB) is the most common and aggressive form of primary brain tumor, in which the presence of an inflammatory environment, composed mainly by tumor-associated macrophages (TAMs), is related to its progression and development of chemoresistance. Toll-Like Receptors (TLRs) are key components of the innate immune system and their expression in both tumor and immune-associated cells may impact the cell communication in the tumor microenvironment (TME), further modeling cancer growth and response to therapy. Here, we investigated the participation of TLR4-mediated signaling as a mechanism of induced-immune escape in GB. Initially, bioinformatics analysis of public datasets revealed that TLR4 expression is lower in GB tumors when compared to astrocytomas (AST), and in a subset of TAMs. Further, we confirmed that TLR4 expression is downregulated in chemoresistant GB, as well as in macrophages co-cultured with GB cells. Additionally, TLR4 function is impaired in those cells even following stimulation with LPS, an agonist of TLR4. Finally, experiments performed in a cohort of clinical primary and metastatic brain tumors indicated that the immunostaining of TLR4 and CD45 are inversely proportional, and confirmed the low TLR4 expression in GBs. Interestingly, the cytoplasmic/nuclear pattern of TLR4 staining in cancer tissues suggests additional roles of this receptor in carcinogenesis. Overall, our data suggest the downregulation of TLR4 expression and activity as a strategy for GB-associated immune escape. Additional studies are necessary to better understand TLR4 signaling in TME in order to improve the benefits of immunotherapy based on TLR signaling.

Interplay of autophagy and cancer stem cells in hepatocellular carcinoma

Liver cancer is the sixth most common cancer and the fourth leading cause of cancer deaths in the world. The most common type of liver cancers is hepatocellular carcinoma (HCC). Autophagy is the cellular digestion of harmful components by sequestering the waste products into autophagosomes followed by lysosomal degradation for the maintenance of cellular homeostasis. The impairment of autophagy is highly associated with the development and progression of HCC although autophagy may be involved in tumour-suppressing cellular events. In regards to its protecting role, autophagy also shelters the cells from anoikis- a programmed cell death in anchorage-dependent cells detached from the surrounding extracellular matrix which facilitates metastasis in HCC. Liver cancer stem cells (LCSCs) have the ability for self-renewal and differentiation and are associated with the development and progression of HCC by regulating stemness, resistance and angiogenesis. Interestingly, autophagy is also known to regulate normal stem cells by promoting cellular survival and differentiation and maintaining cellular homeostasis. In this review, we discuss the basal autophagic mechanisms and double-faceted roles of autophagy as both tumour suppressor and tumour promoter in HCC, as well as its association with and contribution to self-renewal and differentiation of LCSCs.

Biomaterial-based platforms for cancer stem cell enrichment and study

Cancer stem cells (CSCs) are a relatively rare subpopulation of tumor cell with self-renewal and tumorigenesis capabilities. CSCs are associated with cancer recurrence, progression, and chemoradiotherapy resistance. Establishing a reliable platform for CSC enrichment and study is a prerequisite for understanding the characteristics of CSCs and discovering CSC-related therapeutic strategies. Certain strategies for CSC enrichment have been used in laboratory, particularly fluorescence-activated cell sorting (FACS) and mammosphere culture. However, these methods fail to recapitulate the in vivo chemical and physical conditions in tumors, thus potentially decreasing the malignancy of CSCs in culture and yielding unreliable research results. Accumulating research suggests the promise of a biomaterial-based three-dimensional (3D) strategy for CSC enrichment and study. This strategy has an advantage over conventional methods in simulating the tumor microenvironment, thus providing a more effective and predictive model for CSC laboratory research. In this review, we first briefly discuss the conventional methods for CSC enrichment and study. We then summarize the latest advances and challenges in biomaterial-based 3D CSC platforms. Design strategies for materials, morphology, and chemical and physical cues are highlighted to provide direction for the future construction of platforms for CSC enrichment and study.

The Role of KDM2B and EZH2 in Regulating the Stemness in Colorectal Cancer Through the PI3K/AKT Pathway

Background: The incidence of colorectal cancer (CRC) has been increasing worldwide in recent years. Targeting cancer stem cells (CSCs) in CRC remains a difficult challenge. KDM2B and EZH2 play important role in the maintenance of CSCs' self-renewal capacity and tumorigenic ability; however, the biological functions of those genes in CRC remain unclear. In this study, we aimed to define the contribution of the expression of KDM2B in the features of CRC and establish the relationship between KDM2B and EZH2 in colorectal CSCs.

Methods: The expression of KDM2B and EZH2 in the specimens of CRC and CRC cell lines were analyzed by immunohistochemistry, Western blot, and immunofluorescence. The underlying mechanisms of altered expressions of KDM2B and EZH2 and their impact on the biologic features of CRC and stemness in CRC were investigated.

Results: The KDM2B gene was highly expressed in CRC tissues, and its overexpression positively correlated with tumor stages and tumor/node/metastasis (TNM) classification. The downregulation of KDM2B retarded cell proliferation, induced DNA damage, reduced spheroid formation, and decreased CRC stem cell markers: CD44, CD133, and ALDH-1. Moreover, the downregulation of KDM2B decreased the expression of EZH2 and both regulated cell migration, invasion, and stemness in the CRC cell line. Additionally, the interaction between KDM2B and EZH2 significantly increased the components of the PI3K/AKT pathway including AKT and PI3K. The high expression of KDM2B positively correlated with EZH2 in CRC tissues.

Conclusion: This study shows that the downregulation of KDM2B and EZH2 can regulate CRC cell stemness, and their interaction may serve as a novel prognostic marker and therapeutic target for patients with CRC.

LncRNAs and microRNAs as Essential Regulators of Stemness in Breast Cancer Stem Cells

Breast cancer is an aggressive disease with a high incidence in women worldwide. Two decades ago, a controversial hypothesis was proposed that cancer arises from a subpopulation of “tumor initiating cells” or “cancer stem cells-like” (CSC). Today, CSC are defined as small subset of somatic cancer cells within a tumor with self-renewal properties driven by the aberrant expression of genes involved in the maintenance of a stemness-like phenotype. The understanding of the underlying cellular and molecular mechanisms involved in the maintenance of CSC subpopulation are fundamental in the development and persistence of breast cancer. Nowadays, the hypothesis suggests that genetic and epigenetic alterations give rise to breast cancer stem cells (bCSC), which are responsible for self-renewal, tumor growth, chemoresistance, poor prognosis and low survival in patients. However, the prominence of bCSC, as well as the molecular mechanisms that regulates and promotes the malignant phenotypes, are still poorly understood. The role of non-coding RNAs (ncRNAs), such as long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) acting as oncogenes or tumor suppressor genes has been recently highlighted by a plethora of studies in breast cancer. These ncRNAs positively or negatively impact on different signaling pathways that govern the cancer hallmarks associated with bCSC, making them attractive targets for therapy. In this review, we present a current summary of the studies on the pivotal roles of lncRNAs and microRNAs in the regulation of genes associated to stemness of bCSC.

Mesenchymal stem cells and oncolytic viruses: joining forces against cancer

The development of oncolytic viruses (OVs) has increased significantly in the past 20 years, with many candidates entering clinical trials and three of them receiving approval for some indications. Recently, OVs have also gathered interest as candidates to use in combination with immunotherapies for cancer due to their immunogenic properties, which include immunogenic cell death and the possibility to carry therapeutic transgenes in their genomes. OVs transform non-immunogenic 'cold' tumors into inflamed immunogenic 'hot' tumors, where immunotherapies show the highest efficacy. However, in monotherapy or in combination with immunotherapy, OVs face numerous challenges that limit their successful application, in particular upon systemic administration, such as liver sequestration, neutralizing interactions in blood, physical barriers to infection, and fast clearance by the immune system. In this regard, the use of mesenchymal stem cells (MSCs) as cells carrier for OV delivery addresses many of these obstacles acting as virus carriers and factories, expressing additional transgenes, and modulating the immune system. Here, I review the current progress of OVs-loaded MSCs in cancer, focusing on their interaction with the immune system, and discuss new strategies to improve their therapeutic efficacy.

Cancer Stem Cells-Key Players in Tumor Relapse

Tumor relapse and treatment failure are unfortunately common events for cancer patients, thus often rendering cancer an uncurable disease. Cancer stem cells (CSCs) are a subset of cancer cells endowed with tumor-initiating and self-renewal capacity, as well as with high adaptive abilities. Altogether, these features contribute to CSC survival after one or multiple therapeutic approaches, thus leading to treatment failure and tumor progression/relapse. Thus, elucidating the molecular mechanisms associated with stemness-driven resistance is crucial for the development of more effective drugs and durable responses. This review will highlight the mechanisms exploited by CSCs to overcome different therapeutic strategies, from chemo- and radiotherapies to targeted therapies and immunotherapies, shedding light on their plasticity as an insidious trait responsible for their adaptation/escape. Finally, novel CSC-specific approaches will be described, providing evidence of their preclinical and clinical applications.

Recent advances in drug delivery systems for targeting cancer stem cells

Cancer stem cells (CSCs) are a subpopulation of cancer cells with functions similar to those of normal stem cells. Although few in number, they are capable of self-renewal, unlimited proliferation, and multi-directional differentiation potential. In addition, CSCs have the ability to escape immune surveillance. Thus, they play an important role in the occurrence and development of tumors, and they are closely related to tumor invasion, metastasis, drug resistance, and recurrence after treatment. Therefore, specific targeting of CSCs may improve the efficiency of cancer therapy. A series of corresponding promising therapeutic strategies based on CSC targeting, such as the targeting of CSC niche, CSC signaling pathways, and CSC mitochondria, are currently under development. Given the rapid progression in this field and nanotechnology, drug delivery systems (DDSs) for CSC targeting are increasingly being developed. In this review, we summarize the advances in CSC-targeted DDSs. Furthermore, we highlight the latest developmental trends through the main line of CSC occurrence and development process; some considerations about the rationale, advantages, and limitations of different DDSs for CSC-targeted therapies were discussed.

Expression of Class III Beta-Tubulin Is Associated with Invasive Potential and Poor Prognosis in Thyroid Carcinoma

Although American Thyroid Association guidelines offer a risk stratification scheme for thyroid cancer patients, there is a continuous need for more sophisticated biomarkers that can predict disease progression. In this study, we aim to evaluate the prognostic value of class III beta-tubulin (TUBB3) and uncover the relationship between TUBB3 and invasive potential in thyroid carcinoma. Immunohistochemistry (IHC) for TUBB3 and E-cadherin was performed on a total of 254 cases of thyroid cancer specimens. Tumor budding at the invasive margin was evaluated. In vitro functional studies were also performed; the protein and mRNA levels of TUBB3 were compared among the five cell types at baseline, with transwell invasion and after blocking of TUBB3 by shRNA. IHC revealed that the levels of TUBB3 were higher in conventional papillary carcinomas (cPTCs) and anaplastic thyroid carcinomas (ATCs). In univariate analysis, high tumor budding and TUBB3 expression were associated with inferior progression-free survival in cPTC. The results of a Western blot and RT-PCR agreed with the IHC finding. The results were further validated through data from The Cancer Genome Atlas database. Our results suggest that high expression of TUBB3 in thyroid carcinoma could predict invasive potential and possibly be linked with epithelial–mesenchymal transition.

Platelet-activating factor induces the stemness of ovarian cancer cells via the PAF/PAFR signaling pathway

BACKGROUND

Cancer stem cells (CSCs) play an important role in tumor recurrence, metastasis, and chemoresistance. CSCs can shift between non-CSC and CSC states in certain tumor microenvironments. The mechanisms of this shift are not well understood. We previously demonstrated that platelet-activating factor (PAF), a lipid mediator of inflammation in the tumor microenvironment, can promote ovarian cancer progression and induce chemoresistance via PAF/PAFR-mediated inflammatory signaling pathways. Here, we investigated the role of PAF/PAFR signaling in the stemness of ovarian cancer cell.

METHODS

The effects of PAF and PAFR antagonists on the stemness of SKOV3 and A2780 cells were evaluated using sphere-formation assays, FACS analysis and real-time PCR in vitro and a SKOV3 tumor-formation experiment in nude mice in vivo. The potential mechanism of the PAF effect on the stemness of ovarian cancer cells was evaluated by human cytokine antibody microarray analysis.

RESULTS

PAF can promote spheroid formation and inhibit the transition of quiescent ovarian cancer cells into the cell cycle. The percentage of cancer stem cells increased significantly, and the expression of stemness genes increased in PAF-treated group. These effects could be blocked by PAFR inhibitors. Ginkgolide B (GB) inhibited tumor growth and decreased the CSC percentage in vivo. Human cytokine antibody microarray analysis showed that some stemness-maintaining proteins increased in PAF-treated group.

CONCLUSION

Our results suggest that PAF can regulate the stemness of ovarian cancer cells through the PAF/PAFR pathway, suggesting a new target for the treatment of ovarian cancer.

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.

The oncogenic potential of NANOG: An important cancer induction mediator

Cancer stem cells (CSCs) are a unique population in the tumor, but they only comprise 2%-5% of the tumor bulk. Although CSCs share several features with embryonic stem cells, CSCs can give rise to the tumor cells. CSCs overexpress embryonic transcription factor NANOG, which is downregulated in differentiated tissues. This transcription factor confers CSC's stemness, unlimited self-renewal, metastasis, invasiveness, angiogenesis, and drug-resistance with the assistance of WNT, OCT4, SOX2, Hedgehog, BMI-1, and other complexes. NANOG facilitates CSCs development via multiple pathways, like angiogenesis and lessening E-cadherin expression levels, which paves the road for metastasis. Moreover, NANOG represses apoptosis and leads to drug-resistance. This review aims to highlight the pivotal role of NANOG and the pertained pathways in CSCs. Also, this current study intends to demonstrate that targeting NANOG can dimmish the CSCs, sensitize the tumor to chemotherapy, and eradicate the cancer cells.

A novel hypoxic tumor microenvironment signature for predicting the survival, progression, immune responsiveness and chemoresistance of glioblastoma: a multi-omic study

The hypoxic tumor microenvironment (TME) was reported to promote the aggressive phenotype, progression, recurrence, and chemoresistance of glioblastoma (GBM). We developed and validated a hypoxia gene signature for individualized prognostic prediction in GBM patients. In total, 259 GBM-specific hypoxia-related genes (HRGs) were obtained in hypoxic cultured GBM cells compared with normoxic cells. By applying the k-means algorithm, TCGA GBM patients were divided into two subgroups, and the patients in Cluster 1 exhibited high HRG expression patterns, older age, and poor prognosis, which was validated in the CGGA cohort. Cox regression analyses were performed to generate an HRG-based risk score model consisting of five HRGs, which could reliably discriminate the overall survival (OS) and progression-free survival (PFS) of high- and low-risk patients in both the TCGA training and CGGA validation cohorts. Then, nomograms with the hypoxia signature for OS and PFS prediction were constructed for individualized survival prediction, better treatment decision-making, and follow-up scheduling. Finally, functional enrichment, immune infiltration, immunotherapy response prediction and chemotherapy resistance analyses demonstrated the vital roles of the hypoxic TME in the development, progression, multitherpy resistance of GBM. The hypoxia gene signature could serve as a promising prognostic predictor and potential therapeutic target to combat chemoresistant GBM.