Emerging role of nanog in tumorigenesis and cancer stem cells

Mechanisms of Breast Cancer Stem Cell Specification and Self-Renewal Mediated by Hypoxia-Inducible Factor 1

Many advanced human cancers contain regions of intratumoral hypoxia, with O2 gradients extending to anoxia. Hypoxia-inducible factors (HIFs) are activated in hypoxic cancer cells and drive metabolic reprogramming, vascularization, invasion, and metastasis. Hypoxia induces breast cancer stem cell (BCSC) specification by inducing the expression and/or activity of the pluripotency factors KLF4, NANOG, OCT4, and SOX2. Recent studies have identified HIF-1-dependent expression of PLXNB3, NARF, and TERT in hypoxic breast cancer cells. PLXNB3 binds to and activates the MET receptor tyrosine kinase, leading to activation of the SRC non-receptor tyrosine kinase and subsequently focal adhesion kinase, which promotes cancer cell migration and invasion. PLXNB3-MET-SRC signaling also activates STAT3, a transcription factor that mediates increased NANOG gene expression. Hypoxia-induced NARF binds to OCT4 and serves as a coactivator by stabilizing OCT4 binding to the KLF4, NANOG, and SOX2 genes and by stabilizing the interaction of OCT4 with KDM6A, a histone demethylase that erases repressive trimethylation of histone H3 at lysine 27, thereby increasing KLF4, NANOG, and SOX2 gene expression. In addition to increasing pluripotency factor expression by these mechanisms, HIF-1 directly activates expression of the TERT gene encoding telomerase, the enzyme required for maintenance of telomeres, which is required for the unlimited self-renewal of BCSCs. HIF-1 binds to the TERT gene and recruits NANOG, which serves as a coactivator by promoting the subsequent recruitment of USP9X, a deubiquitinase that inhibits HIF-1α degradation, and p300, a histone acetyltransferase that mediates acetylation of H3K27, which is required for transcriptional activation.

A thorough and current study of miR-214-related targets in cancer

Cancer is a complex genetic anomaly involving coding and non-coding transcript structural and expressive irregularities. A class of tiny non-coding RNAs known as microRNAs (miRNAs) regulates gene expression at the post-transcriptional level by binding only to messenger RNAs (mRNAs). Due to their capacity to target numerous genes, miRNAs have the potential to play a significant role in the development of tumors by controlling several biological processes, including angiogenesis, drug resistance, metastasis, apoptosis, proliferation, and drug resistance. According to several recent studies, miRNA-214 has been linked to the emergence and spread of tumors. The human genome's q24.3 arm contains the DNM3 gene, which is about 6 kb away and includes the microRNA-214. Its primary purpose was the induction of apoptosis in cancerous cells. The multifaceted and complex functions of miR-214 as a modulator in neoplastic conditions have been outlined in the current review.

High-Resolution In Situ High-Content Imaging of 3D-Bioprinted Single Breast Cancer Spheroids for Advanced Quantification of Benzo(a)pyrene Carcinogen-Induced Breast Cancer Stem Cells

Cancer stem cells (CSCs), also known as tumor-initiating cells, are critically correlated with carcinogenesis and are strongly affected by the environmental factors. Environmental carcinogens, such as benzo(a)pyrene (BaP), are associated with the overproduction of CSCs in various types of cancers, including breast cancer. In this report, we present a sophisticated 3D breast cancer spheroid model for the direct identification and quantitative determination of CSCs induced by carcinogens within intact 3D spheroids. To this end, hydrogel microconstructs containing MCF-7 breast cancer cells were bioprinted within direct-made diminutive multi-well chambers, which were utilized for the mass cultivation of spheroids and in situ detection of CSCs. We found that the breast CSCs caused by BaP-induced mutations were higher in the biomimetic MCF-7 breast cancer spheroids than that in standard 2D monolayer cultures. Precisely controlled MCF-7 cancer spheroids could be generated by serially cultivating MCF-7 cells within the printed hydrogel microconstructs, which could be further utilized for high-resolution in situ high-content 3D imaging analysis to spatially identify the emergence of CSCs at the single spheroid level. Additionally, potential therapeutic agents specific to breast CSCs were successfully evaluated to verify the effectiveness of this model. This bioengineered 3D cancer spheroid system provides a novel approach to investigating the emergence of CSC induced by a carcinogen for environmental hazard assessment in a reproducible and scalable format.

Plexin-B3 expression stimulates MET signaling, breast cancer stem cell specification, and lung metastasis

Intratumoral hypoxia is a microenvironmental feature that promotes breast cancer progression and is associated with cancer mortality. Plexin B3 (PLXNB3) is highly expressed in estrogen receptor-negative breast cancer, but the underlying mechanisms and consequences have not been thoroughly investigated. Here, we report that PLXNB3 expression is increased in response to hypoxia and that PLXNB3 is a direct target gene of hypoxia-inducible factor 1 (HIF-1) in human breast cancer cells. PLXNB3 expression is correlated with HIF-1α immunohistochemistry, breast cancer grade and stage, and patient mortality. Mechanistically, PLXNB3 is required for hypoxia-induced MET/SRC/focal adhesion kinase (FAK) and MET/SRC/STAT3/NANOG signaling as well as hypoxia-induced breast cancer cell migration, invasion, and cancer stem cell specification. PLXNB3 knockdown impairs tumor formation and lung metastasis in orthotopic breast cancer mouse models.

Transcriptional factors targeting in cancer stem cells for tumor modulation

Cancer Stem Cells (CSCs) are now considered the primary "seeds" for the onset, development, metastasis, and recurrence of tumors. Despite therapeutic breakthroughs, cancer remains the leading cause of death worldwide. This is because the tumor microenvironment contains a key population of cells known as CSCs, which promote tumor aggression. CSCs are self-renewing cells that aid tumor recurrence by promoting tumor growth and persisting in patients after many traditional cancer treatments. According to reports, numerous transcription factors (TF) play a key role in maintaining CSC pluripotency and its self-renewal property. The understanding of the functions, structures, and interactional dynamics of these transcription factors with DNA has modified the hypothesis, paving the way for novel transcription factor-targeted therapies. These TFs, which are crucial and are required by cancer cells, play a vital function in the etiology of human cancer. Such CSC TFs will help with gene expression profiling, which provides crucial data for predicting the prognosis of patients. To overcome anti-cancer medication resistance and completely eradicate cancer, a potent therapy combining TFs-based CSC targets with traditional chemotherapy may be developed. In order to develop therapies that could eliminate CSCs, we here concentrated on the effect of TFs and other components of signalling pathways on cancer stemness.

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.

The metabolic addiction of cancer stem cells

Cancer stem cells (CSC) are the minor population of cancer originating cells that have the capacity of self-renewal, differentiation, and tumorigenicity (when transplanted into an immunocompromised animal). These low-copy number cell populations are believed to be resistant to conventional chemo and radiotherapy. It was reported that metabolic adaptation of these elusive cell populations is to a large extent responsible for their survival and distant metastasis. Warburg effect is a hallmark of most cancer in which the cancer cells prefer to metabolize glucose anaerobically, even under normoxic conditions. Warburg's aerobic glycolysis produces ATP efficiently promoting cell proliferation by reprogramming metabolism to increase glucose uptake and stimulating lactate production. This metabolic adaptation also seems to contribute to chemoresistance and immune evasion, a prerequisite for cancer cell survival and proliferation. Though we know a lot about metabolic fine-tuning in cancer, what is still in shadow is the identity of upstream regulators that orchestrates this process. Epigenetic modification of key metabolic enzymes seems to play a decisive role in this. By altering the metabolic flux, cancer cells polarize the biochemical reactions to selectively generate "onco-metabolites" that provide an added advantage for cell proliferation and survival. In this review, we explored the metabolic-epigenetic circuity in relation to cancer growth and proliferation and establish the fact how cancer cells may be addicted to specific metabolic pathways to meet their needs. Interestingly, even the immune system is re-calibrated to adapt to this altered scenario. Knowing the details is crucial for selective targeting of cancer stem cells by choking the rate-limiting stems and crucial branch points, preventing the formation of onco-metabolites.

Role of prostate cancer stem-like cells in the development of antiandrogen resistance

Androgen deprivation therapy (ADT) is the standard of care treatment for advance stage prostate cancer. Treatment with ADT develops resistance in multiple ways leading to the development of castration-resistant prostate cancer (CRPC). Present research establishes that prostate cancer stem-like cells (CSCs) play a central role in the development of treatment resistance followed by disease progression. Prostate CSCs are capable of self-renewal, differentiation, and regenerating tumor heterogeneity. The stemness properties in prostate CSCs arise due to various factors such as androgen receptor mutation and variants, epigenetic and genetic modifications leading to alteration in the tumor microenvironment, changes in ATP-binding cassette (ABC) transporters, and adaptations in molecular signaling pathways. ADT reprograms prostate tumor cellular machinery leading to the expression of various stem cell markers such as Aldehyde Dehydrogenase 1 Family Member A1 (ALDH1A1), Prominin 1 (PROM1/CD133), Indian blood group (CD44), SRY-Box Transcription Factor 2 (Sox2), POU Class 5 Homeobox 1(POU5F1/Oct4), Nanog and ABC transporters. These markers indicate enhanced self-renewal and stemness stimulating CRPC evolution, metastatic colonization, and resistance to antiandrogens. In this review, we discuss the role of ADT in prostate CSCs differentiation and acquisition of CRPC, their isolation, identification and characterization, as well as the factors and pathways contributing to CSCs expansion and therapeutic opportunities.

Nanog, as a key cancer stem cell marker in tumor progression

Cancer stem cells (CSCs) are a small population of malignant cells that induce tumor onset and development. CSCs share similar features with normal stem cells in the case of self-renewal and differentiation. They also contribute to chemoresistance and metastasis of cancer cells, leading to therapeutic failure. To identify CSCs, multiple cell surface markers have been characterized, including Nanog, which is found at high levels in different cancers. Recent studies have revealed that Nanog upregulation has a substantial association with the advanced stages and poor prognosis of malignancies, playing a pivotal role through tumorigenesis of multiple human cancers, including leukemia, liver, colorectal, prostate, ovarian, lung, head and neck, brain, pancreatic, gastric and breast cancers. Nanog through different signaling pathways, like JAK/STAT and Wnt/β-catenin pathways, induces stemness, self-renewal, metastasis, invasiveness, and chemoresistance of cancer cells. Some of these signaling pathways are common in various types of cancers, but some have been found in one or two cancers. Therefore, this review aimed to focus on the function of Nanog in multiple cancers based on recent studies surveying the suitable approaches to target Nanog and inhibit CSCs residing in tumors to gain favorable results from cancer treatments.

Hypoxia-inducible factors: cancer progression and clinical translation

Hypoxia-inducible factors (HIFs) are master regulators of oxygen homeostasis that match O2 supply and demand for each of the 50 trillion cells in the adult human body. Cancer cells co-opt this homeostatic system to drive cancer progression. HIFs activate the transcription of thousands of genes that mediate angiogenesis, cancer stem cell specification, cell motility, epithelial-mesenchymal transition, extracellular matrix remodeling, glucose and lipid metabolism, immune evasion, invasion, and metastasis. In this Review, the mechanisms and consequences of HIF activation in cancer cells are presented. The current status and future prospects of small-molecule HIF inhibitors for use as cancer therapeutics are discussed.

Recent Advances of m6A Demethylases Inhibitors and Their Biological Functions in Human Diseases

N6-methyladenosine (m6A) is a post-transcriptional RNA modification and one of the most abundant types of RNA chemical modifications. m6A functions as a molecular switch and is involved in a range of biomedical aspects, including cardiovascular diseases, the central nervous system, and cancers. Conceptually, m6A methylation can be dynamically and reversibly modulated by RNA methylation regulatory proteins, resulting in diverse fates of mRNAs. This review focuses on m6A demethylases fat-mass- and obesity-associated protein (FTO) and alkB homolog 5 (ALKBH5), which especially erase m6A modification from target mRNAs. Recent advances have highlighted that FTO and ALKBH5 play an oncogenic role in various cancers, such as acute myeloid leukemias (AML), glioblastoma, and breast cancer. Moreover, studies in vitro and in mouse models confirmed that FTO-specific inhibitors exhibited anti-tumor effects in several cancers. Accumulating evidence has suggested the possibility of FTO and ALKBH5 as therapeutic targets for specific diseases. In this review, we aim to illustrate the structural properties of these two m6A demethylases and the development of their specific inhibitors. Additionally, this review will summarize the biological functions of these two m6A demethylases in various types of cancers and other human diseases.

CRISPR/Cas9-mediated knockout of PIM3 suppresses tumorigenesis and cancer cell stemness in human hepatoblastoma cells

Hepatoblastoma remains one of the most difficult childhood tumors to treat and is alarmingly understudied. We previously demonstrated that Proviral Insertion site in Maloney murine leukemia virus (PIM) kinases, specifically PIM3, are overexpressed in human hepatoblastoma cells and function to promote tumorigenesis. We aimed to use CRISPR/Cas9 gene editing with dual gRNAs to introduce large inactivating deletions in the PIM3 gene and achieve stable PIM3 knockout in the human hepatoblastoma cell line, HuH6. PIM3 knockout of hepatoblastoma cells led to significantly decreased proliferation, viability, and motility, inhibited cell-cycle progression, decreased tumor growth in a xenograft murine model, and increased animal survival. Analysis of RNA sequencing data revealed that PIM3 knockout downregulated expression of pro-migratory and pro-invasive genes and upregulated expression of genes involved in apoptosis and differentiation. Furthermore, PIM3 knockout decreased hepatoblastoma cancer cell stemness as evidenced by decreased tumorsphere formation, decreased mRNA abundance of stemness markers, and decreased cell surface expression of CD133, a marker of hepatoblastoma stem cell-like cancer cells. Reintroduction of PIM3 into PIM3 knockout cells rescued the malignant phenotype. Successful CRISPR/Cas9 knockout of PIM3 kinase in human hepatoblastoma cells confirmed the role of PIM3 in promoting hepatoblastoma tumorigenesis and cancer cell stemness.

Chicory: Understanding the Effects and Effectors of This Functional Food

Industrial chicory has been the subject of numerous studies, most of which provide clinical observations on its health effects. Whether it is the roasted root, the flour obtained from the roots or the different classes of molecules that enter into the composition of this plant, understanding the molecular mechanisms of action on the human organism remains incomplete. In this study, we were interested in three molecules or classes of molecules present in chicory root: fructose, chlorogenic acids, and sesquiterpene lactones. We conducted experiments on the murine model and performed a nutrigenomic analysis, a metabolic hormone assay and a gut microbiota analysis, associated with in vitro observations for different responses. We have highlighted a large number of effects of all these classes of molecules that suggest a pro-apoptotic activity, an anti-inflammatory, antimicrobial, antioxidant, hypolipidemic and hypoglycemic effect and also an important role in appetite regulation. A significant prebiotic activity was also identified. Fructose seems to be the most involved in these activities, contributing to approximately 83% of recorded responses, but the other classes of tested molecules have shown a specific role for these different effects, with an estimated contribution of 23-24%.

Nanog mediated by FAO/ACLY signaling induces cellular dormancy in colorectal cancer cells

Dormant cancer cells drive recurrence and drug resistance, which lead to poor prognosis in colorectal cancer (CRC). The mechanisms that regulate the entry of cancer cells into dormancy remain to be extensively studied. Nanog is a master transcription factor to maintain the self-renewal and pluripotency of stem cells. Since dormant cancer cells are similar to quiescent cancer stem cells, the correlation between dormant state and Nanog in CRC is worth to be explored. Serum deprivation is a common method to establish experimental cellular dormancy model. Here, we verified that serum deprivation-induced CRC cells to enter a cellular dormancy state, characterized by no proliferation, no death, no senescence, resistance to chemotherapy, high expression of dormant markers, metabolic suppression, and recovery to active status. Interestingly, we further identified that Nanog was upregulated in dormant CRC cells. Nanog knockdown could destroy the dormant state of serum-deprived CRC cells while Nanog overexpression could induce dormancy in CRC cells. Mechanistically, Nanog was regulated through a fatty acid oxidation (FAO)/ATP citrate lyase (ACLY)-dependent pathway. FAO increased ACLY expression to promote the synthesis of acetyl-CoA, which was transferred by P300 to accelerate H3K27 acetylation of Nanog promoter. Then, Nanog upregulation increased the transcription of P21 and P27, which promoted the dormancy of CRC cells. Our findings revealed that Nanog could induce cellular dormancy in CRC cells and unlocked a specific mechanism to govern the process.

[Vascular endothelial growth factor promotes cancer stemness of triple-negative breast cancer via MAPK/ERK pathway]

OBJECTIVE

To investigate the role of vascular endothelial growth factor (VEGF) in regulating triple-negative breast cancer (TNBC) stem cells and the possible pathways involved in this regulatory mechanism.

METHODS

The Oncomine database, UALCAN database and Human Protein Atlas (HPA) database were used to analyze the expression of VEGF in breast cancer and its association with the molecular subtypes and prognosis of breast cancer. Sphere formation assay was carried out to examine the effects of hVEGF₁₆₅ on sphere formation ability of TNBC MDA-MB-231 cell line; Western blotting and RT-qPCR were performed to detect the expression of the tumor stem cell markers including CD44, c-Myc, Nanog, and ALDH1 and the activation of the related pathways.

RESULTS

Data from the online databases all showed a significant increase of VEGF expression in breast cancer tissues than in the adjacent tissues (P < 0.0001), and its expression level was associated with the molecular subtypes of breast cancer. Specifically, the expression of VEGF was markedly higher in TNBC than in other subtypes of breast cancer. Survival analysis showed that breast cancer patients with a high VEGF expression had a significantly shortened overall survival (P < 0.0001). In the cell experiments, the sphere formation ability of MDA-MB-231 cells was significantly enhanced after treatment with hVEGF₁₆₅ (P=0.0029). Compared with the monolayer cells, MDA-MB-231 spheres showed significantly increased expressions of VEGF, NRP-1, CD44, Nanog and c-Myc. Treatment with hVEGF₁₆₅ resulted in significant time-dependent up-regulation of the expressions of CD44, c-Myc, Nanog and ALDH1 and down-regulation of CD24 expression in the cells. The results of Western blotting demonstrated that treatment with hVEGF₁₆₅ caused significant activation of the ERK/MAPK pathway in MDA-MB-231 cells.

CONCLUSION

VEGF promotes cancer stemness of triple-negative breast cancer possibly through the ERK/MAPK pathway.

NANOG Promotes Cell Proliferation, Invasion, and Stemness via IL-6/STAT3 Signaling in Esophageal Squamous Carcinoma

Background: Cancer cells have properties similar to those of stem cells, including high proliferation and self-renewal ability. NANOG is the key regulatory gene that maintains the self-renewal and pluripotency characteristics of embryonic stem cells. We previously reported that knockdown of the pluripotent stem cell factor NANOG obviously reduced the proliferation and drug-resistance capabilities of esophageal squamous cell carcinoma (ESCC). In this study, we gained insights into the potential regulatory mechanism of NANOG, particularly in ESCC. Methods: NANOG was ectopically expressed in the Eca-109 cell line via pcDNA3.1 vector transfection. The mRNA expression of different genes was detected using quantitative real-time polymerase chain reaction, and protein quantification was performed by western blotting. The enzyme-linked immunosorbent assay was used to detect the expression of interleukin 6 (IL-6). The capabilities of proliferation, migration, and invasion were investigated using cell count and Transwell assays. The tumor sphere-forming assay was used to investigate the sphere formation capacity of cancer stem cells. Results: The expression of NANOG promoted the cell proliferation and sphere formation capacity of cancer stem cells in a dose-dependent manner. IL-6-mediated activation of signal transducer and activator of transcription 3 (STAT3) was closely related to the expression of NANOG in ESCC. Consistently, the target genes of STAT3, including CCL5, VEGFA, CCND1, and Bcl-xL, were upregulated upon the overexpression of NANOG. Conclusion: These results revealed that the expression of NANOG promotes cell proliferation, invasion, and stemness via IL-6/STAT3 signaling in ESCC.

A direct negative feedback loop of miR-4721/FOXA1/Nanog promotes nasopharyngeal cell stem cell enrichment and metastasis

Objective

The recurrence and metastasis of nasopharyngeal cancer (NPC) may be mainly attributed to the persistence of cancer stem cells (CSCs); however, the linkage mechanism has yet to be fully elucidated.

Methods

The levels of miR-4721, FOXA1, and Nanog expression in NPC were detected by in situ hybridization and immunohistochemistry. In vivo and in vitro metastasis assays confirmed miR-4721 promotes cell migration and invasion. Tumor spheroid formation assay, side population (SP) assay, and ALDEFLUOR assay verified miR-4721 regulates cancer stem cell-like properties. Luciferase reporter assay showed that miR-4721 directly regulates FOXA1 and FOXA1 effects the promoter activity of miR-4721 and Nanog. Chromatin immunoprecipitation (ChIP) analysis and electrophoresis mobility shift assay (EMSA) revealed that FOXA1 combined the promoter region of human miR-4721 and Nanog and the possible mechanism was also analyzed.

Results

In this study, a new mechanism of NPC tumorigenesis related to miR-4721 was verified. We found that miR-4721, FOXA1 and Nanog control their expressions through a negative feedback loop and then activate the downstream regulator of stem cell signaling to promote the enrichment and metastasis of NPC stem cells.

Conclusion

These findings elucidate that the feedback loop of miR-4721/FOXA1/Nanog can regulate stemness and metastasis in NPC and may provide an experimental theoretical basis for metastasis and treatment resistance in NPC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03059-y.

miR-219-5p targets TBXT and inhibits breast cancer cell EMT and cell migration and invasion

miR-219-5p has been reported to act as either a tumor suppressor or a tumor promoter in different cancers by targeting different genes. In the present study, we demonstrated that miR-219-5p negatively regulated the expression of TBXT, a known epithelial–mesenchymal transition (EMT) inducer, by directly binding to TBXT 3′-untranslated region. As a result of its inhibition on TBXT expression, miR-219-5p suppressed EMT and cell migration and invasion in breast cancer cells. The re-introduction of TBXT in miR-219-5p overexpressing cells decreased the inhibitory effects of miR-219 on EMT and cell migration and invasion. Moreover, miR-219-5p decreased breast cancer stem cell (CSC) marker genes expression and reduced the mammosphere forming capability of cells. Overall, our study highlighted that TBXT is a novel target of miR-219-5p. By suppressing TBXT, miR-219-5p plays an important role in EMT and cell migration and invasion of breast cancer cells.

The role of FOSL1 in stem-like cell reprogramming processes

Cancer stem-like cells (CSCs) have self-renewal abilities responsible for cancer progression, therapy resistance, and metastatic growth. The glioblastoma stem-like cells are the most studied among CSC populations. A recent study identified four transcription factors (SOX2, SALL2, OLIG2, and POU3F2) as the minimal core sufficient to reprogram differentiated glioblastoma (GBM) cells into stem-like cells. Transcriptomic data of GBM tissues and cell lines from two different datasets were then analyzed by the SWItch Miner (SWIM), a network-based software, and FOSL1 was identified as a putative regulator of the previously identified minimal core. Herein, we selected NTERA-2 and HEK293T cells to perform an in vitro study to investigate the role of FOSL1 in the reprogramming mechanisms. We transfected the two cell lines with a constitutive FOSL1 cDNA plasmid. We demonstrated that FOSL1 directly regulates the four transcription factors binding their promoter regions, is involved in the deregulation of several stemness markers, and reduces the cells' ability to generate aggregates increasing the extracellular matrix component FN1. Although further experiments are necessary, our data suggest that FOSL1 reprograms the stemness by regulating the core of the four transcription factors.

MicroRNAs as the critical regulators of Doxorubicin resistance in breast tumor cells

BACKGROUND

Chemotherapy is one of the most common treatment options for breast cancer (BC) patients. However, about half of the BC patients are chemotherapeutic resistant. Doxorubicin (DOX) is considered as one of the first line drugs in the treatment of BC patients whose function is negatively affected by multi drug resistance. Due to the severe side effects of DOX, it is very important to diagnose the DOX resistant BC patients. Therefore, assessment of molecular mechanisms involved in DOX resistance can improve the clinical outcomes in BC patients by introducing the novel therapeutic and diagnostic molecular markers. MicroRNAs (miRNAs) as members of the non-coding RNAs family have pivotal roles in various cellular processes including cell proliferation and apoptosis. Therefore, aberrant miRNAs functions and expressions can be associated with tumor progression, metastasis, and drug resistance. Moreover, due to miRNAs stability in body fluids, they can be considered as non-invasive diagnostic markers for the DOX response in BC patients.

MAIN BODY

In the present review, we have summarized all of the miRNAs that have been reported to be associated with DOX resistance in BC for the first time in the world.

CONCLUSIONS

Since, DOX has severe side effects; it is required to distinguish the non DOX-responders from responders to improve the clinical outcomes of BC patients. This review highlights the miRNAs as pivotal regulators of DOX resistance in breast tumor cells. Moreover, the present review paves the way of introducing a non-invasive panel of prediction markers for DOX response among BC patients.

EIF5A2 enhances stemness of epithelial ovarian cancer cells via a E2F1/KLF4 axis

BACKGROUND

Ovarian cancer stem cells (OCSC), endowed with tumor-initiating and self-renewal capacity, would account not only for the tumor growth, the peritoneal metastasis, and the relapse, but also for the acquisition of chemotherapy resistance. Nevertheless, figuring out their phenotypical and functional traits has proven quite challenging, mainly because of the heterogeneity of ovarian cancer. A deeper understanding of OCSC mechanisms will shed light on the development of the disease. Therefore, we aim to explore it for the design of innovative treatment regimens which aim at the eradication of ovarian cancer through the elimination of the CSC component.

METHODS

In this study, immunohistochemistry assay and western blot assay were used to detect protein expression in the primary tumor and peritoneal multi-cellular aggregates/spheroids (MCAs/MCSs). OCSCs induced from cell line SKOV3 and HO-8910 were enriched in a serum-free medium (SFM). The effect of EIF5A2 on CSC-like properties was detected by sphere-forming assays, re-differentiation assays, quantitative real-time polymerase chain reaction, western blotting, flow cytometry, cell viability assays, immunofluorescence staining, and in vivo xenograft experiments. RNA-sequencing (RNA-seq) was used to reveal the mechanism by which EIF5A2 positively modulates the stem-like properties of ovarian cancer cells.

RESULTS

Expression of EIF5A2 was significantly higher in peritoneal MCAs/MCSs compared to matched primary tumors, and EIF5A2 was also unregulated in ovarian cancer cell line-derived spheroids. Knockdown of EIF5A2 reduced the expression of the stem-related markers (ALDH1A1 and OCT-4), inhibited self-renewal ability, improved the sensitivity to chemotherapeutic drugs, and inhibited tumorigenesis in vivo. Mechanistic studies revealed that EIF5A2 knockdown reduced the expression of KLF4, which could partially rescue stem-like properties abolished by EIF5A2 knockdown or strengthened by EIF5A2 overexpression, through the transcription factor E2F1, which directly bind to KLF4 promoter.

CONCLUSION

Our results imply that EIF5A2 positively regulates stemness in ovarian cancer cells via E2F1/KLF4 pathway and may serve as a potential target in CSCs-targeted therapy for ovarian cancer.

Intratumoral Hypoxia and Mechanisms of Immune Evasion Mediated by Hypoxia-Inducible Factors

Activation of the innate and adaptive immune systems represents a promising strategy for defeating cancer. However, during tumor progression, cancer cells battle to shift the balance from immune activation to immunosuppression. Critical sites of this battle are regions of intratumoral hypoxia, and a major driving force for immunosuppression is the activity of hypoxia-inducible factors, which regulate the transcription of large batteries of genes in both cancer and stromal cells that block the infiltration and activity of cytotoxic T lymphocytes and natural killer cells, while stimulating the infiltration and activity of regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages. Targeting hypoxia-inducible factors or their target gene products may restore anticancer immunity and improve the response to immunotherapies.

Scaffold-based 3D cellular models mimicking the heterogeneity of osteosarcoma stem cell niche

The failure of the osteosarcoma conventional therapies leads to the growing need for novel therapeutic strategies. The lack of specificity for the Cancer Stem Cells (CSCs) population has been recently identified as the main limitation in the current therapies. Moreover, the traditional two-dimensional (2D) in vitro models, employed in the drug testing and screening as well as in the study of cell and molecular biology, are affected by a poor in vitro-in vivo translation ability. To overcome these limitations, this work provides two tumour engineering approaches as new tools to address osteosarcoma and improve therapy outcomes. In detail, two different hydroxyapatite-based bone-mimicking scaffolds were used to recapitulate aspects of the in vivo tumour microenvironment, focusing on CSCs niche. The biological performance of human osteosarcoma cell lines (MG63 and SAOS-2) and enriched-CSCs were deeply analysed in these complex cell culture models. The results highlight the fundamental role of the tumour microenvironment proving the mimicry of osteosarcoma stem cell niche by the use of CSCs together with the biomimetic scaffolds, compared to conventional 2D culture systems. These advanced 3D cell culture in vitro tumour models could improve the predictivity of preclinical studies and strongly enhance the clinical translation.

MUC1-C Activates the BAF (mSWI/SNF) Complex in Prostate Cancer Stem Cells

The Brg/Brahma-associated factor (BAF, mSWI/SNF) chromatin remodeling complex is of importance in development and has been linked to prostate oncogenesis. The oncogenic MUC1-C protein promotes lineage plasticity in the progression of neuroendocrine prostate cancer (NEPC), however, there is no known association between MUC1-C and BAF. We report here that MUC1-C binds directly to the E2F1 transcription factor and that the MUC1-C→E2F1 pathway induces expression of embryonic stem cell-specific BAF (esBAF) components BRG1, ARID1A, BAF60a, BAF155, and BAF170 in castrate-resistant prostate cancer (CRPC) and NEPC cells. In concert with this previously unrecognized pathway, MUC1 was associated with increased expression of E2F1 and esBAF components in NEPC tumors as compared with CRPC, supporting involvement of MUC1-C in activating the E2F1→esBAF pathway with progression to NEPC. MUC1-C formed a nuclear complex with BAF and activated cancer stem cell (CSC) gene signatures and the core pluripotency factor gene network. The MUC1-C→E2F1→BAF pathway was necessary for induction of both the NOTCH1 effector of CSC function and the NANOG pluripotency factor, and collectively, this network drove CSC self-renewal. These findings indicate that MUC1-C promotes NEPC progression by integrating activation of E2F1 and esBAF with induction of NOTCH1, NANOG, and stemness. SIGNIFICANCE: These findings show that MUC1-C, which promotes prostate cancer progression, activates a novel pathway that drives the BAF remodeling complex, induces NOTCH1 and NANOG, and promotes self-renewal of prostate cancer stem cells.

Human Pluripotent Stem Cells-Based Therapies for Neurodegenerative Diseases: Current Status and Challenges

Neurodegenerative diseases are characterized by irreversible cell damage, loss of neuronal cells and limited regeneration potential of the adult nervous system. Pluripotent stem cells are capable of differentiating into the multitude of cell types that compose the central and peripheral nervous systems and so have become the major focus of cell replacement therapies for the treatment of neurological disorders. Human embryonic stem cell (hESC) and human induced pluripotent stem cell (hiPSC)-derived cells have both been extensively studied as cell therapies in a wide range of neurodegenerative disease models in rodents and non-human primates, including Parkinson's disease, stroke, epilepsy, spinal cord injury, Alzheimer's disease, multiple sclerosis and pain. In this review, we discuss the latest progress made with stem cell therapies targeting these pathologies. We also evaluate the challenges in clinical application of human pluripotent stem cell (hPSC)-based therapies including risk of oncogenesis and tumor formation, immune rejection and difficulty in regeneration of the heterogeneous cell types composing the central nervous system.

Association of High Expression Levels of SOX2, NANOG, and OCT4 in Gastric Cancer Tumor Tissues with Progression and Poor Prognosis

BACKGROUND

Expression of the essential regulator genes, SOX2, NANOG, and OCT4, so-called as stemness factors, is prerequisite for the tumorigenic capability of cancer stem cells (CSCs) and their potential role in the formation and progression of various human cancers.

METHODS

In this study, the expression levels of SOX2, NANOG, and OCT4 were quantified by a qRT-PCR method in 100 gastric cancer tumor tissues vs the paired adjacent normal tissues. Then, the relationship between the expression of the three genes in gastric cancer tumor tissues and the clinicopathological characteristics and overall survival of patients was investigated.

RESULTS

Higher expression levels of SOX2, NANOG, and OCT4 were found in gastric cancer tumor tissues compared with those in paired adjacent normal tissues (P = 0.0001). Overexpression of the mentioned genes in gastric cancer tumor tissues was resolved to be significantly associated with tumor size (P < 0.05), TNM stage (P = 0.001), tumor grade (P < 0.01), and shortened overall survival time (P = 0.0001).

CONCLUSIONS

These findings indicted that the stemness factors SOX2, NANOG, and OCT4 are significantly overexpressed in gastric cancer and may serve as potential biomarkers of gastric cancer progression and prognosis.

SNORA72 Activates the Notch1/c-Myc Pathway to Promote Stemness Transformation of Ovarian Cancer Cells

Cancer stem cells (CSCs) are responsible for the migration and recurrence of cancer progression. Small nucleolar RNAs (snoRNAs) play important roles in tumor development. However, how snoRNAs contribute to the regulation of the stemness of ovarian CSCs (OCSCs) remains unclear. In the present study, we found that SNORA72 was significantly upregulated in OVCAR-3 spheroids (OS) and CAOV-3 spheroids (CS) with the OCSC characteristics attained by serum-free culture in a suspension of OVCAR-3 (OV) and CAOV-3 (CA) cells. The overexpression of SNORA72 increased self-renewal abilities and migration abilities in OV and CA cells and upregulated the expressions of the stemness markers Nanog, Oct4, and CD133. In addition, the ectopic expression of SNORA72 can elevate the messenger RNA (mRNA) and protein expression levels of Notch1 and c-Myc in parental cells. The opposite results were observed in SNORA72-silenced OCSCs. Moreover, we found that Notch1 knockdown inversed the migration abilities and self-renewal abilities raised by overexpressing SNORA72. In summary, stemness transformation of ovarian cancer cells can be activated by SNORA72 through the Notch1/c-Myc pathway. This study introduces a novel therapeutic strategy for improving the treatment efficiency of ovarian cancer.

Nanog mediates tobacco smoke-induced enhancement of renal cancer stem cell properties

Nanog plays an important role in the regulation of cancer stem cells (CSCs) which participate in tumorgenesis and progression. In renal cancer, tobacco smoke (TS) is considered a major risk factor. However, the molecular mechanism by which TS induces the development of renal CSC properties remains largely unknown. In this study, we showed that the level of Nanog was elevated in renal cell carcinoma (RCC) patients with a smoking history, and that Nanog overexpression promoted the traits of CSCs in renal cancer. We further demonstrated that a 8-week exposure of TS enhanced the formation of renal tumorspheres, increased the population of CD133-positive cells, and stimulated the expression of Nanog and CSC markers. In addition, TS was found to play a role in accelerating the cell growth transition from G1 to S phase in renal CSCs. Finally, we demonstrated that the TS-induced effects in renal CSCs could be reversed through the downregulation of Nanog. Our results suggested that Nanog plays a role in mediating TS-induced renal CSC properties. This study may provide new insights into the molecular mechanism of TS-related renal tumorigenesis, which can contribute to the future development of therapeutics for renal cancer.

Hyaluronic acid-decorated liposomal nanoparticles for targeted delivery of 5-fluorouracil into HT-29 colorectal cancer cells

The use of liposomes as drug carriers improves the therapeutic efficacy of anticancer drugs, while at the same time reducing side effects. Hyaluronic acid (HA) is recognized by the CD44 receptor, which is overexpressed in many cancer cells. In this study, we developed HA-modified liposomes encapsulating 5-fluorouracil (5-FU) and tested them against a CD44 expressing colorectal cell line (HT29) and a non-CD44 expressing hepatoma cell line. The average size of 5-FU-lipo and 5-FU-lipo-HA nanoparticles were 112 ± 28 and 144 ± 77 nm, respectively. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium (MTT) assay showed selective cancer cell death depending on the CD44 expression in a time-dependent manner. Apoptosis assays and cell-cycle analysis indicated that G0/G1 arrest occurred. The colony formation study revealed that cells treated with 5-FU-lipo and 5-FU-lipo-HA had reduced colony formation. Quantitative reverse-transcription polymerase chain reaction study showed that the oncogenic messenger RNA and microRNA levels were significantly reduced in the 5-FU-lipo-HA-treated group, while tumor suppressors were increased in that group. We suggest that optimal targeted delivery and release of 5-FU into colorectal cancer cells, renders them susceptible to apoptosis, cell-cycle arrest, and decreased colony formation.

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.

ZIC2 promotes cancer stem cell traits via up-regulating OCT4 expression in lung adenocarcinoma cells

Background: Accumulating evidence has revealed the importance of cancer stem cells (CSCs) in self-renewal and chemoresistance. Previous studies reported high expression of ZIC2 was closely associated with tumorigenesis and CSC traits. However, the role of ZIC2 as a crucial factor for regulating CSC properties in lung adenocarcinoma (LAC) remains elusive. Methods: RT-PCR and WB assay were employed to assess ZIC2 expression in 20 LAC tumor tissues and the matched non-cancerous tissues. The role of ZIC2 in LAC CSC were analyzed by evaluation of CSC-related markers expression and spheroid formation in vitro. Cisplatin and paclitaxel resistance capacities were evaluated by CCK8 assay, colony formation assay, and flow cytometry analysis. Subcutaneous NOD/SCID mice models were generated to assess in vivo CSC features. Results: High expression of ZIC2 was found in LAC tumor tissues and indicated a poor overall survival in LAC patients. ZIC2 upregulated an array of CSCs-related genes, including EpCAM, OCT4, SOX2, NANOG, C-Myc and Bmi-1. Knockdown of ZIC2 inhibited sphere-forming capacity and decreased cisplatin and paclitaxel resistance. However, overexpression of ZIC2 achieved opposite effects. Mechanically, ZIC2 acts upstream of OCT4 to promote its expression, resulting in enhancement of CSC traits in LAC. Conclusion: Our results demonstrated that ZIC2 was crucial for promoting CSC traits in LAC cells, and served as a potential biomarker for predicting prognosis. The ZIC2-OCT4 network will facilitate the evaluation of the potential therapeutic efficacy of chemotherapy and predict patient sensitivity to treatment.

Cancer Stem Cells-Origins and Biomarkers: Perspectives for Targeted Personalized Therapies

The use of biomarkers in diagnosis, therapy and prognosis has gained increasing interest over the last decades. In particular, the analysis of biomarkers in cancer patients within the pre- and post-therapeutic period is required to identify several types of cells, which carry a risk for a disease progression and subsequent post-therapeutic relapse. Cancer stem cells (CSCs) are a subpopulation of tumor cells that can drive tumor initiation and can cause relapses. At the time point of tumor initiation, CSCs originate from either differentiated cells or adult tissue resident stem cells. Due to their importance, several biomarkers that characterize CSCs have been identified and correlated to diagnosis, therapy and prognosis. However, CSCs have been shown to display a high plasticity, which changes their phenotypic and functional appearance. Such changes are induced by chemo- and radiotherapeutics as well as senescent tumor cells, which cause alterations in the tumor microenvironment. Induction of senescence causes tumor shrinkage by modulating an anti-tumorigenic environment in which tumor cells undergo growth arrest and immune cells are attracted. Besides these positive effects after therapy, senescence can also have negative effects displayed post-therapeutically. These unfavorable effects can directly promote cancer stemness by increasing CSC plasticity phenotypes, by activating stemness pathways in non-CSCs, as well as by promoting senescence escape and subsequent activation of stemness pathways. At the end, all these effects can lead to tumor relapse and metastasis. This review provides an overview of the most frequently used CSC markers and their implementation as biomarkers by focussing on deadliest solid (lung, stomach, liver, breast and colorectal cancers) and hematological (acute myeloid leukemia, chronic myeloid leukemia) cancers. Furthermore, it gives examples on how the CSC markers might be influenced by therapeutics, such as chemo- and radiotherapy, and the tumor microenvironment. It points out, that it is crucial to identify and monitor residual CSCs, senescent tumor cells, and the pro-tumorigenic senescence-associated secretory phenotype in a therapy follow-up using specific biomarkers. As a future perspective, a targeted immune-mediated strategy using chimeric antigen receptor based approaches for the removal of remaining chemotherapy-resistant cells as well as CSCs in a personalized therapeutic approach are discussed.

The Relevance of Transcription Factors in Gastric and Colorectal Cancer Stem Cells Identification and Eradication

Gastric and colorectal cancers have a high incidence and mortality worldwide. The presence of cancer stem cells (CSCs) within the tumor mass has been indicated as the main reason for tumor relapse, metastasis and therapy resistance, leading to poor overall survival. Thus, the elimination of CSCs became a crucial goal for cancer treatment. The identification of these cells has been performed by using cell-surface markers, a reliable approach, however it lacks specificity and usually differs among tumor type and in some cases even within the same type. In theory, the ideal CSC markers are those that are required to maintain their stemness features. The knowledge that CSCs exhibit characteristics comparable to normal stem cells that could be associated with the expression of similar transcription factors (TFs) including SOX2, OCT4, NANOG, KLF4 and c-Myc, and signaling pathways such as the Wnt/β-catenin, Hedgehog (Hh), Notch and PI3K/AKT/mTOR directed the attention to the use of these similarities to identify and target CSCs in different tumor types. Several studies have demonstrated that the abnormal expression of some TFs and the dysregulation of signaling pathways are associated with tumorigenesis and CSC phenotype. The disclosure of common and appropriate biomarkers for CSCs will provide an incredible tool for cancer prognosis and treatment. Therefore, this review aims to gather the new insights in gastric and colorectal CSC identification specially by using TFs as biomarkers and divulge promising drugs that have been found and tested for targeting these cells.

Translational control of breast cancer plasticity

Plasticity of neoplasia, whereby cancer cells attain stem-cell-like properties, is required for disease progression and represents a major therapeutic challenge. We report that in breast cancer cells NANOG, SNAIL and NODAL transcripts manifest multiple isoforms characterized by different 5' Untranslated Regions (5'UTRs), whereby translation of a subset of these isoforms is stimulated under hypoxia. The accumulation of the corresponding proteins induces plasticity and "fate-switching" toward stem cell-like phenotypes. Mechanistically, we observe that mTOR inhibitors and chemotherapeutics induce translational activation of a subset of NANOG, SNAIL and NODAL mRNA isoforms akin to hypoxia, engendering stem-cell-like phenotypes. These effects are overcome with drugs that antagonize translational reprogramming caused by eIF2α phosphorylation (e.g. ISRIB), suggesting that the Integrated Stress Response drives breast cancer plasticity. Collectively, our findings reveal a mechanism of induction of plasticity of breast cancer cells and provide a molecular basis for therapeutic strategies aimed at overcoming drug resistance and abrogating metastasis.

Inhibition of Wnt/β-catenin pathway reverses multi-drug resistance and EMT in Oct4+/Nanog+ NSCLC cells

Cancer drug resistance and epithelial-mesenchymal transition (EMT), a critical process of cancer invasion and metastasis, have recently been associated with the existence of cancer stem cells (CSCs). However, there are no appropriate CSC-markers of non-small cell lung cancer (NSCLC)-associated drug resistance and EMT. It is unknown if and how the drug-resistant and EMT phenotypes in NSCLC cells link to specific stemness-related pathways. Here, we found a significant elevated expression of both Oct4 and Nanog in gefitinib-resistant NSCLC cells, which displayed multi-drug resistance (MDR) properties and exhibited EMT phenotype. Ectopic co-expression of Oct4/Nanog empowered NSCLC cells with cancer stem cell properties, including self-renewal, drug resistance, EMT and high tumorigenic capacity. Following molecular mechanism investigation indicated Oct4/Nanog-regulated drug resistance and EMT change through Wnt/β-catenin signaling activation. Moreover, silencing β-catenin abrogated Oct4/Nanog-mediated MDR and EMT process in NSCLC cells. Our findings propose Wnt/β-catenin pathway as a promising therapeutic target for the treatment of progression and metastasis of NSCLC with CSC-like signatures and epithelial-mesenchymal transition phenotype.

Novel Therapeutic Strategies for Ovarian Cancer Stem Cells

Ovarian cancer (OC) is one of the most lethal gynecologic malignancies. Due to the lack of specific symptoms and screening methods, this disease is usually diagnosed only at an advanced and metastatic stage. The gold-standard treatment for OC patients consists of debulking surgery followed by taxane combined with platinum-based chemotherapy. Most patients show complete clinical remission after first-line therapy, but the majority of them ultimately relapse, developing radio- and chemoresistant tumors. It is now proposed that the cause of recurrence and reduced therapy efficacy is the presence of small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and for this reason, effective targeted therapies for the complete eradication of CSCs are urgently needed. In this review article, we highlight the mechanisms of CSC therapy resistance, epithelial-to-mesenchymal transition, stemness, and novel therapeutic strategies for ovarian CSCs.

NANOG/NANOGP8 Localizes at the Centrosome and is Spatiotemporally Associated with Centriole Maturation

NANOG is a transcription factor involved in the regulation of pluripotency and stemness. The functional paralog of NANOG, NANOGP8, differs from NANOG in only three amino acids and exhibits similar reprogramming activity. Given the transcriptional regulatory role played by NANOG, the nuclear localization of NANOG/NANOGP8 has primarily been considered to date. In this study, we investigated the intriguing extranuclear localization of NANOG and demonstrated that a substantial pool of NANOG/NANOGP8 is localized at the centrosome. Using double immunofluorescence, the colocalization of NANOG protein with pericentrin was identified by two independent anti-NANOG antibodies among 11 tumor and non-tumor cell lines. The validity of these observations was confirmed by transient expression of GFP-tagged NANOG, which also colocalized with pericentrin. Mass spectrometry of the anti-NANOG immunoprecipitated samples verified the antibody specificity and revealed the expression of both NANOG and NANOGP8, which was further confirmed by real-time PCR. Using cell fractionation, we show that a considerable amount of NANOG protein is present in the cytoplasm of RD and NTERA-2 cells. Importantly, cytoplasmic NANOG was unevenly distributed at the centrosome pair during the cell cycle and colocalized with the distal region of the mother centriole, and its presence was markedly associated with centriole maturation. Along with the finding that the centrosomal localization of NANOG/NANOGP8 was detected in various tumor and non-tumor cell types, these results provide the first evidence suggesting a common centrosome-specific role of NANOG.

RNA N6-methyladenosine modification in solid tumors: new therapeutic frontiers

Epigenetic mRNA modification is an evolving field. N⁶-methyladenosine (m⁶A) is the most frequent internal transcriptional modification in eukaryotic messenger RNAs (mRNAs). This review will discuss the functions of the m⁶A mRNA machinery, including its "writers" that are components of the methyltransferase complex, its "readers" and its "erasers" (specifically FTO and ALKBH5) in cancer. The writers deposit the m⁶A and include METTL3, METTL14, WTAP, VIRMA, and RBM15. M⁶A methylation is removed by the m6A demethylases (FTO and ALKBH5). Lastly, the most diverse members are the readers that can contribute to mRNA splicing, stability, translation, and nuclear export. Many of these functions continue to be elucidated. The dysregulation of this machinery in various malignancies and the associated impact on tumorigenesis and drug response will be discussed herein with a focus on solid tumors. It is clear that, by contributing to either mRNA stability or translation, there are downstream targets that are impacted, contributing to cancer progression and the self-renewal ability of cancer stem cells.

Clinical Evolution of Epithelial-Mesenchymal Transition in Human Carcinomas

The significance of the phenotypic plasticity afforded by epithelial-mesenchymal transition (EMT) for cancer progression and drug resistance remains to be fully elucidated in the clinic. We evaluated epithelial-mesenchymal phenotypic characteristics across a range of tumor histologies using a validated, high-resolution digital microscopic immunofluorescence assay (IFA) that incorporates β-catenin detection and cellular morphology to delineate carcinoma cells from stromal fibroblasts and that quantitates the individual and colocalized expression of the epithelial marker E-cadherin (E) and the mesenchymal marker vimentin (V) at subcellular resolution ("EMT-IFA"). We report the discovery of β-catenin+ cancer cells that coexpress E-cadherin and vimentin in core-needle biopsies from patients with various advanced metastatic carcinomas, wherein these cells are transitioning between strongly epithelial and strongly mesenchymal-like phenotypes. Treatment of carcinoma models with anticancer drugs that differ in their mechanism of action (the tyrosine kinase inhibitor pazopanib in MKN45 gastric carcinoma xenografts and the combination of tubulin-targeting agent paclitaxel with the BCR-ABL inhibitor nilotinib in MDA-MB-468 breast cancer xenografts) caused changes in the tumor epithelial-mesenchymal character. Moreover, the appearance of partial EMT or mesenchymal-like carcinoma cells in MDA-MB-468 tumors treated with the paclitaxel-nilotinib combination resulted in upregulation of cancer stem cell (CSC) markers and susceptibility to FAK inhibitor. A metastatic prostate cancer patient treated with the PARP inhibitor talazoparib exhibited similar CSC marker upregulation. Therefore, the phenotypic plasticity conferred on carcinoma cells by EMT allows for rapid adaptation to cytotoxic or molecularly targeted therapy and could create a form of acquired drug resistance that is transient in nature. SIGNIFICANCE: Despite the role of EMT in metastasis and drug resistance, no standardized assessment of EMT phenotypic heterogeneity in human carcinomas exists; the EMT-IFA allows for clinical monitoring of tumor adaptation to therapy.

Regulation of N6-Methyladenosine in the Differentiation of Cancer Stem Cells and Their Fate

N6-methyladenosine (m6A) is one of the most common internal RNA modifications in eukaryotes. It is a dynamic and reversible process that requires an orchestrated participation of methyltransferase, demethylase, and methylated binding protein. m6A modification can affect RNA degradation, translation, and microRNA processing. m6A plays an important role in the regulation of various processes in living organisms. In addition to being involved in normal physiological processes such as sperm development, immunity, fat differentiation, cell development, and differentiation, it is also involved in tumor progression and stem cell differentiation. Curiously enough, cancer stem cells, a rare group of cells present in malignant tumors, retain the characteristics of stem cells and play an important role in the survival, proliferation, metastasis, and recurrence of cancers. Recently, studies demonstrated that m6A participates in the self-renewal and pluripotent regulation of these stem cells. However, considering that multiple targets of m6A are involved in different physiological processes, the exact role of m6A in cancer progression remains controversial. This article focuses on the mechanism of m6A and its effects on the differentiation of cancer stem cells, to provide a basis for elucidating the tumorigenesis mechanisms and exploring new potential therapeutic approaches.

SPOP suppresses pancreatic cancer progression by promoting the degradation of NANOG

Speckle-type POZ domain protein (SPOP), an adaptor in the E3 ubiquitin ligase complex, recognizes substrates and promotes protein degradation via the ubiquitin-proteasome system. It appears to help regulate progression of several cancers, and we show here that it acts as a tumor suppressor in pancreatic cancer. Our analysis of patient tissues showed decreased SPOP expression, which was associated with poor prognosis. SPOP knockdown in SW1990 (in vitro/vivo) and PANC-1 (in vitro) cells led to significantly greater proliferation, migration, and invasion. Co-immunoprecipitation experiments in SW1990 cells showed that SPOP interacted with the stem-cell marker NANOG, and this interaction has recently been shown to play a critical role in regulating progression of prostate cancer. We showed that, in one patient with pancreatic cancer, the expression of a truncated form of SPOP (p.Q360*) lacking the nuclear localization signal led to nuclear accumulation of NANOG, which promoted growth and metastasis of pancreatic cancer cells. Our results suggest that SPOP suppresses progression of pancreatic cancer by promoting the ubiquitination and subsequent degradation of NANOG. These results identify the SPOP-NANOG interaction as a potential therapeutic target against pancreatic cancer.

Metadherin Promotes Malignant Phenotypes And Induces Beta-Catenin Nuclear Translocation And Epithelial-Mesenchymal Transition In Gastric Cancer

Purpose

Metadherin (MTDH), as an oncogene, is associated with metastasis and poor prognosis. This study investigated MTDH expressions and development of gastric cancer (GC) cell phenotypes and the contribution of MTDH to epithelial–mesenchymal transition (EMT).

Patients and methods

MTDH expression was assayed in human GC cell lines and tumor tissue from 92 GC patients. Functional experiments were performed to characterize MTDH activity. Expressions of EMT-related proteins (vimentin and E-cadherin), phosphorylated β-catenin and β-catenin were assayed by immunohistochemistry, Western blotting, immunofluorescence, and co-immunoprecipitation, respectively.

Results

MTDH expressions were higher in GC tissue than that in gastric mucosa from the same patient. MTDH overexpression was correlated with metastasis and enhanced malignant GC phenotypes, i.e., proliferation, migration, invasiveness, and chemoresistance. MTDH overexpression was associated with expressions of vimentin, E-cadherin and cancer stem-cell biomarkers including CD44, CD133, and Oct4. MTDH complexed with β-catenin and decreased phosphorylated β-catenin levels to facilitate β-catenin translocation into the nucleus and expressions of downstream genes.

Conclusion

MTDH overexpression in GC cells is associated with EMT and development of cancer stem cell malignant phenotypes and affects the subcellular translocation of β-catenin. The results warrant investigation of the prognostic value of MTDH in GC and as a therapeutic target.

Emetine exhibits anticancer activity in breast cancer cells as an antagonist of Wnt/β‑catenin signaling

Emetine, an amoebicidal drug, exerts potent anticancer activity against various solid tumors, however, the underlying molecular mechanism remains unclear. In the present study, the effects of emetine were investigated on various proteins involved in the Wnt/β‑catenin signaling pathway, which has been linked to various human cancers. It was revealed that emetine blocked Wnt/β‑catenin signaling by targeting components of this pathway, including the low‑density lipoprotein‑receptor‑related protein 6 (LRP6) and disheveled (DVL). Moreover, nanomolar concentrations of emetine decreased phosphorylation of these proteins and suppressed the expression of Wnt target genes, including fibronectin, frizzled‑7 (Fzd7), c‑Myc, Nanog and CD133 in MDA‑MB‑231 and MDA‑MB‑468 breast cancer cells. Additionally, emetine treatment induced apoptosis and suppressed the viability, migration, invasion, and sphere formation of breast cancer cells. Collectively the present results indicated that emetine antagonizes Wnt/β‑catenin signaling, providing insight into the molecular mechanism underlying the anticancer activity of emetine.

Genetic variants in RUNX3, AMD1 and MSRA in the methionine metabolic pathway and survival in nonsmall cell lung cancer patients

Abnormal methionine dependence in cancer cells has led to methionine restriction as a potential therapeutic strategy. We hypothesized that genetic variants involved in methionine-metabolic genes are associated with survival in nonsmall cell lung cancer (NSCLC) patients. Therefore, we investigated associations of 16,378 common single-nucleotide polymorphisms (SNPs) in 97 methionine-metabolic pathway genes with overall survival (OS) in NSCLC patients using genotyping data from two published genome-wide association study (GWAS) datasets. In the single-locus analysis, 1,005 SNPs were significantly associated with NSCLC OS (p < 0.05 and false-positive report probability < 0.2) in the discovery dataset. Three SNPs (RUNX3 rs7553295 G > T, AMD1 rs1279590 G > A and MSRA rs73534533 C > A) were replicated in the validation dataset, and their meta-analysis showed an adjusted hazards ratio [HR] of 0.82 [95% confidence interval (CI) =0.75-0.89] and pmeta  = 2.86 × 10-6 , 0.81 (0.73-0.91) and pmeta  = 4.63 × 10-4 , and 0.77 (0.68-0.89) and pmeta  = 2.07 × 10-4 , respectively). A genetic score of protective genotypes of these three SNPs revealed an increased OS in a dose-response manner (ptrend  < 0.0001). Further expression quantitative trait loci (eQTL) analysis showed significant associations between these genotypes and mRNA expression levels. Moreover, differential expression analysis further supported a tumor-suppressive effect of MSRA, with lower mRNA levels in both lung squamous carcinoma and adenocarcinoma (p < 0.0001 and < 0.0001, respectively) than in adjacent normal tissues. Additionally, low mutation rates of these three genes indicated the critical roles of these functional SNPs in cancer progression. Taken together, these genetic variants of methionine-metabolic pathway genes may be promising predictors of survival in NSCLC patients.

Redox-Responsive Fluorescent Polycarbonates Based on Selenide for Chemotherapy of Triple-Negative Breast Cancer

Transient increase of reactive oxygen species (ROS) is vital for some physiological processes, whereas the chronic and sustained high ROS level is usually implicated in the inflammatory diseases and cancers. Herein, we report the innovative redox-responsive theranostic micellar nanoparticles that are able to load anticancer drugs through coordination and hydrophobic interaction and to fluorescently monitor the intracellular redox status. The nanoparticles were formed by the amphiphilic block copolymers composed of a PEG segment and a selenide-containing hydrophobic polycarbonate block with a small fraction of coumarin-based chromophore. Under the alternative redox stimulation that might be encountered in the physiological process of some healthy cells, these nanoparticles underwent the reversible changes in size, morphology, and fluorescence intensity. With the assistance of small model compounds, we clarified the chemistry behind these changes, that is, the redox triggered reversible transformation between selenide and selenoxide. Upon the monotonic oxidation similar to the sustained high ROS level of cancer cells, the nanoparticles could be disrupted completely, which was accompanied by the drastic decrease in fluorescence. Cisplatin and paclitaxel were simultaneously coloaded in the nanoparticles with a moderate efficacy, and the coordination between selenide and platinum improved the stability of the drug-loaded nanoparticles against dilution. The naked nanoparticles are cytocompatible, whereas the dual drug-loaded nanoparticles exhibited a concentration dependent and synergistic cytotoxicity to triple-negative breast cancer (TNBC) cells. Of importance, the drug-loaded nanoparticles are much more toxic to TNBC cells than to normal cells due in part to ROS overproduction in the former cell lines.

IDH1R132H Causes Resistance to HDAC Inhibitors by Increasing NANOG in Glioblastoma Cells

The R132H mutation in isocitrate dehydrogenase 1 (IDH1^R132H) is commonly observed and associated with better survival in glioblastoma multiforme (GBM), a malignant brain tumor. However, the functional role of IDH1^R132H as a molecular target for GBM treatment is not completely understood. In this study, we found that the overexpression of IDH1^R132H suppresses cell growth, cell cycle progression and motility in U87MG glioblastoma cells. Based on cell viability and apoptosis assays, we found that IDH1^R132H-overexpressing U87MG and U373MG cells are resistant to the anti-cancer effect of histone deacetylase inhibitors (HDACi), such as trichostatin A (TSA), vorinostat (SAHA), and valproic acid. Octyl-(R)-2-hydroxyglutarate (Octyl-2HG), which is a membrane-permeable precursor form of the oncometabolite (R)-2-hydroxyglutarate (R-2HG) produced in IDH1-mutant tumor cells, significantly increased HDACi resistance in glioblastoma cells. Mechanistically, IDH1^R132H and Octyl-2HG enhanced the promoter activation of NANOG via increased H3K4-3Me, consequently increasing NANOG mRNA and protein expression. Indeed, HDACi resistance was attenuated in IDH1^R132H-expressing glioblastoma cells by the suppression of NANOG using small interfering RNAs. Furthermore, we found that AGI-5198, a selective inhibitor of IDH1^R132H, significantly attenuates HDACi resistance and NANOG expression IDH1^R132H-expressing glioblastoma cells. These results suggested that IDH1^R132H is a potential molecular target for HDACi-based therapy for GBM.

Targeting AMP-activated kinase impacts hepatocellular cancer stem cells induced by long-term treatment with sorafenib

Hepatocellular carcinoma (HCC) is the third leading cause of cancer death worldwide. HCC treatment is hindered by the frequent emergence of chemoresistance to the multikinase inhibitor sorafenib, which has been related to the presence of cancer stem cells (CSCs) that self‐renew and often escape therapy. The key metabolic sensor AMP‐activated kinase (AMPK) has recently been recognized as a tumour growth regulator. In this study, we aimed to elucidate the role of AMPK in the development of a stem cell phenotype in HCC cells. To this end, we enriched the CSC population in HCC cell lines that showed increased expression of drug resistance (ALDH1A1, ABCB1A) and stem cell (CD133, Nanog, Oct4, alpha fetoprotein) markers and demonstrated their stemness phenotype. These cells were refractory to sorafenib‐induced cell death. We report that sorafenib‐resistant cells had lower levels of total and phosphorylated AMPK as well as its downstream substrate, ACC, compared with the parental cells. Interestingly, AMPK knockdown with siRNA or inhibition with dorsomorphin increased the expression of stem cell markers in parental cells and blocked sorafenib‐induced cell death. Conversely, the upregulation of AMPK, either by transfection or by pharmacological activation with A‐769662, decreased the expression of ALDH1A1, ABCB1A, CD133, Nanog, Oct4, and alpha fetoprotein, and restored sensitivity to sorafenib. Analysis of the underlying mechanism points to hypoxia‐inducible factor HIF‐1α as a regulator of stemness. In vivo studies in a xenograft mouse model demonstrated that stem‐like cells have greater tumourigenic capacity. AMPK activation reduced xenograft tumour growth and decreased the expression of stem cell markers. Taken together, these results indicate that AMPK may serve as a novel target to overcome chemoresistance in HCC.

Mechanisms of Anticancer Drug Resistance in Hepatoblastoma

The most frequent liver tumor in children is hepatoblastoma (HB), which derives from embryonic parenchymal liver cells or hepatoblasts. Hepatocellular carcinoma (HCC), which rarely affects young people, causes one fourth of deaths due to cancer in adults. In contrast, HB usually has better prognosis, but this is still poor in 20% of cases. Although more responsive to chemotherapy than HCC, the failure of pharmacological treatment used before and/or after surgical resection is an important limitation in the management of patients with HB. To advance in the implementation of personalized medicine it is important to select the best combination among available anti-HB drugs, such as platinum derivatives, anthracyclines, etoposide, tyrosine-kinase inhibitors, Vinca alkaloids, 5-fluorouracil, monoclonal antibodies, irinotecan and nitrogen mustards. This requires predicting the sensitivity to these drugs of each tumor at each time because, it should be kept in mind, that cancer chemoresistance is a dynamic process of Darwinian nature. For this goal it is necessary to improve our understanding of the mechanisms of chemoresistance involved in the refractoriness of HB against the pharmacological challenge and how they evolve during treatment. In this review we have summarized the current knowledge on the multifactorial and complex factors responsible for the lack of response of HB to chemotherapy.