Cancer stem cell definitions and terminology: the devil is in the details

Nano-Based Approved Pharmaceuticals for Cancer Treatment: Present and Future Challenges

Cancer is one of the main causes of death worldwide. To date, and despite the advances in conventional treatment options, therapy in cancer is still far from optimal due to the non-specific systemic biodistribution of antitumor agents. The inadequate drug concentrations at the tumor site led to an increased incidence of multiple drug resistance and the appearance of many severe undesirable side effects. Nanotechnology, through the development of nanoscale-based pharmaceuticals, has emerged to provide new and innovative drugs to overcome these limitations. In this review, we provide an overview of the approved nanomedicine for cancer treatment and the rationale behind their designs and applications. We also highlight the new approaches that are currently under investigation and the perspectives and challenges for nanopharmaceuticals, focusing on the tumor microenvironment and tumor disseminate cells as the most attractive and effective strategies for cancer treatments.

Sorafenib targets and inhibits the oncogenic properties of endometrial cancer stem cells via the RAF/ERK pathway

Background

Distinct subsets of cancer stem cells (CSCs) drive the initiation and progression of malignant tumors via enhanced self-renewal and development of treatment/apoptosis resistance. Endometrial CSC-selective drugs have not been successfully developed because most endometrial cell lines do not contain a sufficient proportion of stable CSCs. Here, we aimed to identify endometrial CSC-containing cell lines and to search for endometrial CSC-selective drugs.

Methods

We first assessed the presence of CSCs by identifying side populations (SPs) in several endometrial cancer cell lines. We then characterized cell viability, colony-formation, transwell invasion and xenotransplantion capability using the isolated SP cells. We also conducted real-time RT-PCR, immunoblot and immunofluorescence analyses of the cells’ expression of CSC-associated markers. Focusing on 14 putative CSC-selective drugs, we characterized their effects on the proliferation and apoptosis of endometrial cancer cell lines, examining cell viability and annexin V staining. We further examined the inhibitory effects of the selected drugs, focusing on proliferation, invasion, expression of CSC-associated markers and tumor formation.

Results

We focused on HHUA cells, an endometrial cancer cell line derived from a well-differentiated endometrial adenocarcinoma. HHUA cells contained a sufficient proportion of stable CSCs with an SP phenotype (HHUA-SP). HHUA-SP showed greater proliferation, colony-formation, and invasive capabilities compared with the main population of HHUA cells (HHUA-MP). HHUA-SP generated larger tumors with higher expression of proliferation-related markers, Ki67, c-MYC and phosphorylated ERK compared with HHUA-MP when transplanted into immunodeficient mice. Among the 14 candidate drugs, sorafenib, an inhibitor of RAF pathways and multiple kinase receptors, inhibited cell proliferation and invasion in both HHUA-SP and -MP, but more profoundly in HHUA-SP. In vivo treatment with sorafenib for 4 weeks reduced the weights of HHUA-SP-derived tumors and decreased the expression of Ki67, ZEB1, and RAF1.

Conclusions

Our results suggest that HHUA is a useful cell line for discovery and identification of endometrial CSC-selective drugs, and that sorafenib may be an effective anti-endometrial cancer drug targeting endometrial CSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02888-y.

Role of the Pro-Inflammatory Tumor Microenvironment in Extracellular Vesicle-Mediated Transfer of Therapy Resistance

Advances in our understanding of cancer biology have contributed to generating different treatments to improve the survival of cancer patients. However, although initially most of the therapies are effective, relapse and recurrence occur in a large percentage of these cases after the treatment, and patients then die subsequently due to the development of therapy resistance in residual cancer cells. A large spectrum of molecular and cellular mechanisms have been identified as important contributors to therapy resistance, and more recently the inflammatory tumor microenvironment (TME) has been ascribed an important function as a source of signals generated by the TME that modulate cellular processes in the tumor cells, such as to favor the acquisition of therapy resistance. Currently, extracellular vesicles (EVs) are considered one of the main means of communication between cells of the TME and have emerged as crucial modulators of cancer drug resistance. Important in this context is, also, the inflammatory TME that can be caused by several conditions, including hypoxia and following chemotherapy, among others. These inflammatory conditions modulate the release and composition of EVs within the TME, which in turn alters the responses of the tumor cells to cancer therapies. The TME has been ascribed an important function as a source of signals that modulate cellular processes in the tumor cells, such as to favor the acquisition of therapy resistance. Although generally the main cellular components considered to participate in generating a pro-inflammatory TME are from the immune system (for instance, macrophages), more recently other types of cells of the TME have also been shown to participate in this process, including adipocytes, cancer-associated fibroblasts, endothelial cells, cancer stem cells, as well as the tumor cells. In this review, we focus on summarizing available information relating to the impact of a pro-inflammatory tumor microenvironment on the release of EVs derived from both cancer cells and cells of the TME, and how these EVs contribute to resistance to cancer therapies.

Cancer Stem Cells and Their Possible Implications in Cervical Cancer: A Short Review

Cervical cancer (CC) is the fourth most common type of gynecological malignancy affecting females worldwide. Most CC cases are linked to infection with high-risk human papillomaviruses (HPV). There has been a significant decrease in the incidence and death rate of CC due to effective cervical Pap smear screening and administration of vaccines. However, this is not equally available throughout different societies. The prognosis of patients with advanced or recurrent CC is particularly poor, with a one-year relative survival rate of a maximum of 20%. Increasing evidence suggests that cancer stem cells (CSCs) may play an important role in CC tumorigenesis, metastasis, relapse, and chemo/radio-resistance, thus representing potential targets for a better therapeutic outcome. CSCs are a small subpopulation of tumor cells with self-renewing ability, which can differentiate into heterogeneous tumor cell types, thus creating a progeny of cells constituting the bulk of tumors. Since cervical CSCs (CCSC) are difficult to identify, this has led to the search for different markers (e.g., ABCG2, ITGA6 (CD49f), PROM1 (CD133), KRT17 (CK17), MSI1, POU5F1 (OCT4), and SOX2). Promising therapeutic strategies targeting CSC-signaling pathways and the CSC niche are currently under development. Here, we provide an overview of CC and CCSCs, describing the phenotypes of CCSCs and the potential of targeting CCSCs in the management of CC.

3D and organoid culture in research: physiology, hereditary genetic diseases and cancer

In nature, cells reside in tissues subject to complex cell–cell interactions, signals from extracellular molecules and niche soluble and mechanical signaling. These microenvironment interactions are responsible for cellular phenotypes and functions, especially in normal settings. However, in 2D cultures, where interactions are limited to the horizontal plane, cells are exposed uniformly to factors or drugs; therefore, this model does not reconstitute the interactions of a natural microenvironment. 3D culture systems more closely resemble the architectural and functional properties of in vivo tissues. In these 3D cultures, the cells are exposed to different concentrations of nutrients, growth factors, oxygen or cytotoxic agents depending on their localization and communication. The 3D architecture also differentially alters the physiological, biochemical, and biomechanical properties that can affect cell growth, cell survival, differentiation and morphogenesis, cell migration and EMT properties, mechanical responses and therapy resistance. This latter point may, in part, explain the failure of current therapies and affect drug discovery research. Organoids are a promising 3D culture system between 2D cultures and in vivo models that allow the manipulation of signaling pathways and genome editing of cells in a body-like environment but lack the many disadvantages of a living system. In this review, we will focus on the role of stem cells in the establishment of organoids and the possible therapeutic applications of this model, especially in the field of cancer research.

JAK-STAT core cancer pathway: An integrative cancer interactome analysis

Through a comprehensive review and in silico analysis of reported data on STAT-linked diseases, we analysed the communication pathways and interactome of the seven STATs in major cancer categories and proposed rational targeting approaches for therapeutic intervention to disrupt critical pathways and addictions to hyperactive JAK/STAT in neoplastic states. Although all STATs follow a similar molecular activation pathway, STAT1, STAT2, STAT4 and STAT6 exert specific biological profiles associated with a more restricted pattern of activation by cytokines. STAT3 and STAT5A as well as STAT5B have pleiotropic roles in the body and can act as critical oncogenes that promote many processes involved in cancer development. STAT1, STAT3 and STAT5 also possess tumour suppressive action in certain mutational and cancer type context. Here, we demonstrated member-specific STAT activity in major cancer types. Through systems biology approaches, we found surprising roles for EGFR family members, sex steroid hormone receptor ESR1 interplay with oncogenic STAT function and proposed new drug targeting approaches of oncogenic STAT pathway addiction.

Measures of Clonal Hematopoiesis: Are We Missing Something?

Clonal Hematopoiesis (CH) is a common, age-related phenomenon of growing scientific interest, due to its association with hematologic malignancy, cardiovascular disease and decreased overall survival. CH is commonly attributed to the preferential outgrowth of a mutant hematopoietic stem cell (HSC) with enhanced fitness, resulting in clonal imbalance. In-depth understanding of the relation between HSC clonal dynamics, CH and hematologic malignancy requires integration of fundamental lineage tracing studies with clinical data. However, this is hampered by lack of a uniform definition of CH and by inconsistency in the analytical methods used for its quantification. Here, we propose a conceptual and analytical framework for the definition and measurement of CH. First, we transformed the conceptual definition of CH into the CH index, which provides a quantitative measure of clone numbers and sizes. Next, we generated a set of synthetic data, based on the beta-distribution, to simulate clonal populations with different degrees of imbalance. Using these clonal distributions and the CH index as a reference, we tested several established indices of clonal diversity and (in-)equality for their ability to detect and quantify CH. We found that the CH index was distinct from any of the other tested indices. Nonetheless, the diversity indices (Shannon, Simpson) more closely resembled the CH index than the inequality indices (Gini, Pielou). Notably, whereas the inequality indices mainly responded to changes in clone sizes, the CH index and the tested diversity indices also responded to changes in the number of clones in a sample. Accordingly, these simulations indicate that CH can result not only by skewing clonal abundancies, but also by variation in their overall numbers. Altogether, our model-based approach illustrates how a formalized definition and quantification of CH can provide insights into its pathogenesis. In the future, use of the CH index or Shannon index to quantify clonal diversity in fundamental as well as clinical clone-tracing studies will promote cross-disciplinary discussion and progress in the field.

The Role of Tumor Stem Cell Exosomes in Cancer Invasion and Metastasis

Exosomes are lipid membrane bilayer-encapsulated vesicles secreted by cells into the extracellular space. They carry abundant inclusions (such as nucleic acids, proteins, and lipids) that play pivotal roles in intercellular communication. Tumor stem cells are capable of self-renewal and are crucial for survival, proliferation, drug resistance, metastasis, and recurrence of tumors. The miRNAs (microRNAs) in exosomes have various functions, such as participating in inflammatory response, cell migration, proliferation, apoptosis, autophagy, and epithelial-mesenchymal transition. Tumor stem cells secrete exosomes that act as important messengers involved in various tumor processes and several studies provide increasing evidence supporting the importance of these exosomes in tumor recurrence and metastasis. This review primarily focuses on the production and secretion of exosomes from tumors and tumor stem cells and their effects on cancer progression. Cancer stem cancer derived exosome play an important massager in the tumor microenvironment. It also emphasizes on the study of tumor stem cell exosomes in the light of cancer metastasis and recurrence aiming to provide valuable insights and novel perspectives, which could be beneficial for developing effective diagnostic and treatment strategies.

AC010973.2 promotes cell proliferation and is one of six stemness-related genes that predict overall survival of renal clear cell carcinoma

Extensive research indicates that tumor stemness promotes tumor progression. Nonetheless, the underlying roles of stemness-related genes in renal clear cell carcinoma (ccRCC) are unclear. Data used in bioinformatics analysis were downloaded from The Cancer Genome Atlas (TCGA) database. Moreover, the R software, SPSS, and GraphPad Prism 8 were used for mapping and statistical analysis. First, the stemness index of each patient was quantified using a machine learning algorithm. Subsequently, the differentially expressed genes between high and low stemness index were identified as stemness-related genes. Based on these genes, a stable and effective prognostic model was identified to predict the overall survival of patients using a random forest algorithm (Training cohort; 1-year AUC: 0.67; 3-year AUC: 0.79; 5-year AUC: 0.73; Validation cohort; 1-year AUC: 0.66; 3-year AUC: 0.71; 5-year AUC: 0.7). The model genes comprised AC010973.2, RNU6-125P, AP001209.2, Z98885.1, KDM5C-IT1, and AL021368.3. Due to its highest importance evaluated by randomforst analysis, the AC010973.2 gene was selected for further research. In vitro experiments demonstrated that AC010973.2 is highly expressed in ccRCC tissue and cell lines. Meanwhile, its knockdown could significantly inhibit the proliferation of ccRCC cells based on colony formation and CCK8 assays. In summary, our findings reveal that the stemness-related gene AC01097.3 is closely associated with the survival of patients. Besides, it remarkably promotes cell proliferation in ccRCC, hence a novel potential therapeutic target.

MicroRNAs and Corresponding Targets in Esophageal Cancer as Shown In Vitro and In Vivo in Preclinical Models

Squamous cell carcinoma of the esophagus is associated with a dismal prognosis. Therefore, identification of new targets and implementation of new treatment modalities are issues of paramount importance. Based on a survey of the literature, we identified microRNAs conferring antitumoral activity in preclinical in vivo experiments. In the category of miRs targeting secreted factors and transmembrane receptors, four miRs were up-regulated and 10 were down-regulated compared with five out of nine in the category transcription factors, and six miRs were down-regulated in the category enzymes, including metabolic enzymes. The down-regulated miRs have targets which can be inhibited by small molecules or antibody-related entities, or re-expressed by reconstitution therapy. Up-regulated miRs have targets which can be reconstituted with small molecules or inhibited with antagomirs.

ZNF32 promotes the self-renewal of colorectal cancer cells by regulating the LEPR-STAT3 signaling pathway

Due to the self-renewal characteristics and tumorigenic abilities of cancer stem cells (CSCs), CSCs have been demonstrated to play vital roles in carcinogenesis and antitumor therapy. Our previous report found that Krüppel-like family members (KLFs) and zinc finger protein 32 (ZNF32) play oncogenic roles in carcinogenesis. However, the roles and mechanism of ZNF32 in CSCs are still unknown. Our study demonstrated that ZNF32 was highly expressed in colorectal CSCs, which promoted their self-renewal capacity and tumorigenicity. Overexpression of ZNF32 in colorectal cancer (CRC) cells increased their self-renewal capacity. Furthermore, we identified the leptin receptor (LEPR) as the downstream target gene of ZNF32 and verified that the ZNF32-mediated regulation of CRC self-renewal is achieved via the LEPR- signal transducer and activator of transcription 3 (STAT3) pathway. Moreover, ZNF32 regulated the expression of SOX2, a core transcription factor in stem cells. Finally, we demonstrated that ZNF32 and LEPR were positively correlated in CRC tissues. ZNF32 expression was negatively correlated with the prognosis of CRC patients. Therefore, therapeutically targeting the ZNF32-LEPR-STAT3 pathway in the clinic is tempting.

Insights into the Role of Gremlin-1, a Bone Morphogenic Protein Antagonist, in Cancer Initiation and Progression

The bone morphogenic protein (BMP) antagonist Gremlin-1 is a biologically significant regulator known for its crucial role in tissue differentiation and embryonic development. Nevertheless, it has been reported that Gremlin-1 can exhibit its function through BMP dependent and independent pathways. Gremlin-1 has also been reported to be involved in organ fibrosis, which has been correlated to the development of other diseases, such as renal inflammation and diabetic nephropathy. Based on growing evidence, Gremlin-1 has recently been implicated in the initiation and progression of different types of cancers. Further, it contributes to the stemness state of cancer cells. Herein, we explore the recent findings on the role of Gremlin-1 in various cancer types, including breast, cervical, colorectal, and gastric cancers, as well as glioblastomas. Additionally, we highlighted the impact of Gremlin-1 on cellular processes and signaling pathways involved in carcinogenesis. Therefore, it was suggested that Gremlin-1 might be a promising prognostic biomarker and therapeutic target in cancers.

Integrated single-cell RNA sequencing analysis reveals distinct cellular and transcriptional modules associated with survival in lung cancer

Lung adenocarcinoma (LUAD) and squamous carcinoma (LUSC) are two major subtypes of non-small cell lung cancer with distinct pathologic features and treatment paradigms. The heterogeneity can be attributed to genetic, transcriptional, and epigenetic parameters. Here, we established a multi-omics atlas, integrating 52 single-cell RNA sequencing and 2342 public bulk RNA sequencing. We investigated their differences in genetic amplification, cellular compositions, and expression modules. We revealed that LUAD and LUSC contained amplifications occurring selectively in subclusters of AT2 and basal cells, and had distinct cellular composition modules associated with poor survival of lung cancer. Malignant and stage-specific gene analyses further uncovered critical transcription factors and genes in tumor progression. Moreover, we identified subclusters with proliferating and differentiating properties in AT2 and basal cells. Overexpression assays of ten genes, including sub-cluster markers AQP5 and KPNA2, further indicated their functional roles, providing potential targets for early diagnosis and treatment in lung cancer.

Interconnected high-dimensional landscapes of epithelial-mesenchymal plasticity and stemness in cancer

Establishing macrometastases at distant organs is a highly challenging process for cancer cells, with extremely high attrition rates. A very small percentage of disseminated cells have the ability to dynamically adapt to their changing micro-environments through reversibly switching to another phenotype, aiding metastasis. Such plasticity can be exhibited along one or more axes-epithelial-mesenchymal plasticity (EMP) and cancer stem cells (CSCs) being the two most studied, and often tacitly assumed to be synonymous. Here, we review the emerging concepts related to EMP and CSCs across multiple cancers. Both processes are multi-dimensional in nature; for instance, EMP can be defined on morphological, molecular and functional changes, which may or may not be synchronized. Similarly, self-renewal, multi-lineage potential, and resistance to anoikis and/or therapy may not all occur simultaneously in CSCs. Thus, understanding the complexity in defining EMP and CSCs is essential if we are to understand their contribution to cancer metastasis. This will require a more comprehensive understanding of the non-linearity of these processes. These processes are dynamic, reversible, and semi-independent in nature; cells traverse the inter-connected high-dimensional EMP and CSC landscapes in diverse paths, each of which may exhibit a distinct EMP-CSC coupling. Our proposed model offers a potential unifying framework for elucidating the coupled decision-making along these dimensions and highlights a key set of open questions to be answered.

Impact of Cancer Stem Cells and Cancer Stem Cell-Driven Drug Resiliency in Lung Tumor: Options in Sight

Causing a high mortality rate worldwide, lung cancer remains an incurable malignancy resistant to conventional therapy. Despite the discovery of specific molecular targets and new treatment strategies, there remains a pressing need to develop more efficient therapy to further improve the management of this disease. Cancer stem cells (CSCs) are considered the root of sustained tumor growth. This consensus corroborates the CSC model asserting that a distinct subpopulation of malignant cells within a tumor drives and maintains tumor progression with high heterogeneity. Besides being highly tumorigenic, CSCs are highly refractory to standard drugs; therefore, cancer treatment should be focused on eliminating these cells. Herein, we present the current knowledge of the existence of CSCs, CSC-associated mechanisms of chemoresistance, the ability of CSCs to evade immune surveillance, and potential CSC inhibitors in lung cancer, to provide a wider insight to drive a more efficient elimination of this pro-oncogenic and treatment-resistant cell fraction.

Bioactive Synthetic Polymers

Synthetic polymers are omnipresent in society as textiles and packaging materials, in construction and medicine, among many other important applications. Alternatively, natural polymers play a crucial role in sustaining life and allowing organisms to adapt to their environments by performing key biological functions such as molecular recognition and transmission of genetic information. In general, the synthetic and natural polymer worlds are completely separated due to the inability for synthetic polymers to perform specific biological functions; in some cases, synthetic polymers cause uncontrolled and unwanted biological responses. However, owing to the advancement of synthetic polymerization techniques in recent years, new synthetic polymers have emerged that provide specific biological functions such as targeted molecular recognition of peptides, or present antiviral, anticancer, and antimicrobial activities. In this review, the emergence of this generation of bioactive synthetic polymers and their bioapplications are summarized. Finally, the future opportunities in this area are discussed.

Tracing TET1 expression in prostate cancer: discovery of malignant cells with a distinct oncogenic signature

Background

Ten–eleven translocation methylcytosine dioxygenase 1 (TET1) is involved in DNA demethylation and transcriptional regulation, plays a key role in the maintenance of stem cell pluripotency, and is dysregulated in malignant cells. The identification of cancer stem cells (CSCs) driving tumor growth and metastasis is the primary objective of biomarker discovery in aggressive prostate cancer (PCa). In this context, we analyzed TET1 expression in PCa.

Methods

A large-scale immunohistochemical analysis of TET1 was performed in normal prostate (NOR) and PCa using conventional slides (50 PCa specimens) and tissue microarrays (669 NOR and 1371 PCa tissue cores from 371 PCa specimens). Western blotting, RT-qPCR, and 450 K methylation array analyses were performed on PCa cell lines. Genome-wide correlation, gene regulatory network, and functional genomics studies were performed using publicly available data sources and bioinformatics tools.

Results

In NOR, TET1 was exclusively expressed in normal cytokeratin 903 (CK903)–positive basal cells. In PCa, TET1 was frequently detected in alpha-methylacyl-CoA racemase (AMACR)–positive tumor cell clusters and was detectable at all tumor stages and Gleason scores. Pearson’s correlation analyses of PCa revealed 626 TET1-coactivated genes (r > 0.5) primarily encoding chromatin remodeling and mitotic factors. Moreover, signaling pathways regulating antiviral processes (62 zinc finger, ZNF, antiviral proteins) and the pluripotency of stem cells were activated. A significant proportion of detected genes exhibited TET1-correlated promoter hypomethylation. There were 161 genes encoding transcription factors (TFs), of which 133 were ZNF-TFs with promoter binding sites in TET1 and in the vast majority of TET1-coactivated genes.

Conclusions

TET1-expressing cells are an integral part of PCa and may represent CSCs with oncogenic potential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01201-7.

Celastrus orbiculatus Extract Reduces Stemness of Gastric Cancer Stem Cells by Targeting PDCD4 and EIF3H

BACKGROUND

Celastrus orbiculatus ethyl acetate extract (COE) has shown a strong anti-gastric cancer effect, but the understanding of its mechanism is still lacking. The results of previous studies indicated that COE may be able to inhibit the stemness of gastric cancer stem cells (GCSCs) by regulating PDCD4 and EIF3H expression.

AIMS

To explore if COE could inhibit the stemness of GCSCs by regulating PDCD4 and EIF3H expression in vitro and in vivo.

PROCEDURE

The GCSCs model was established by stem cell-conditioned culture. Spheroid formation and flow cytometry assays were used to detect the effect of COE on the spheroid formation ability of GCSCs and the percentage of CD44⁺/CD24⁺ and ALDH⁺ cell subpopulations. Western blot analysis was applied to measure the expression of GCSCs biomarkers (Nanog, Oct-4, and SOX-2), PDCD4, and EIF3H in GCSCs treated with COE; and RT-PCR was performed to investigate the effect of COE on PDCD4 mRNA expression in GCSCs. An in vivo tumorigenicity experiment was also conducted to evaluate the effect of COE on tumor-initiating ability of GCSCs in vivo; and the expression of PDCD4 and EIF3H in xenograft tissues was examined by immunohistochemistry (IHC) staining.

RESULTS

After culture in stem cell-conditioned medium, SGC7901 cells manifested significantly enhanced spheroid formation ability, upregulated Nanog, Oct-4, and SOX-2 expression and increased percentages of CD44⁺/CD24⁺ and ALDH⁺ cell subpopulations, indicating successful establishment of the GCSCs model. COE treatment significantly inhibited the spheroid formation ability of GCSCs and reduced the percentage of CD44⁺/CD24⁺ and ALDH⁺ cell subpopulations. The western blot analysis showed a significant decrease of Nanog, Oct-4, SOX-2, and EIF3H expression and an increase of PDCD4 expression in GCSCs after COE treatment in a concentration-dependent manner. COE treatment also significantly upregulated the mRNA expression of PDCD4 in GCSCs. In addition, COE displayed a strong inhibitory effect on the tumor-initiating ability of GCSCs in vivo and upregulated PDCD4 and downregulated EIF3H expression in xenograft tissues.

CONCLUSION

COE may be able to inhibit GC growth by suppressing the stemness of GCSCs via regulating PDCD4 and EIF3H expression.

LncRNA TCF7 Promotes Epithelial Ovarian Cancer Viability, Mobility and Stemness via Regulating ITGB8

This study aimed to investigate the carcinogenic role of long non-coding RNA T-cell factor 7 (lnc-TCF7) in epithelial ovarian cancer (EOC). Lnc-TCF7 overexpression and shRNA plasmids were transfected into SKOV3 and OVCAR3 cells, followed by measurement of cell proliferation, migration, invasion, apoptosis, stemness, and mRNA profile (via microarray). Besides, lnc-TCF7 expression was measured in tumor and adjacent tissues from 76 EOC patients. Lnc-TCF7 was upregulated in EOC cell lines; its overexpression increased cell proliferation, migration, invasion, but decreased apoptosis and promoted CD44, CD133 expressions, CD44+CD133+ cell proportion, spheres formation efficiency and drug resistance to cisplatin in SKOV3 and OVCAR3 cells. Besides, lnc-TCF7 ShRNA exhibited opposite effects comparing with its overexpression. Microarray analysis revealed 267 mRNAs were modulated by lnc-TCF7 dysregulation, among which ITGB8 was the most dysregulated one, which was validated by subsequent western blot and RT-qPCR. Furthermore, ITGB8 overexpression not only induced proliferation, migration, invasion and stemness, but also attenuated the effect of lnc-TCF7 ShRNA on these functions in SKOV3 and OVCAR3 cells. In addition, lnc-TCF7 was upregulated in tumor tissues and correlated with higher pathological grade, tumor size, International Federation of Gynecology and Obstetrics (FIGO) stage and worse overall survival in EOC patients. Conclusively, lnc-TCF7 regulates multiple oncogenic pathways, promotes proliferation, migration, invasion, stemness via upregulating ITGB8. It also correlates with advanced tumor features and poor prognosis in EOC, implying its potential as a target for EOC treatment.

Oncogene-Induced Reprogramming in Acute Lymphoblastic Leukemia: Towards Targeted Therapy of Leukemia-Initiating Cells

Simple Summary

Acute lymphoblastic leukemia is a heterogeneous disease characterized by a diversity of genetic alterations, following a sophisticated and controversial organization. In this review, we present and discuss the concepts exploring the cellular, molecular and functional heterogeneity of leukemic cells. We also review the emerging evidence indicating that cell plasticity and oncogene-induced reprogramming should be considered at the biological and clinical levels as critical mechanisms for identifying and targeting leukemia-initiating cells.

Abstract

Our understanding of the hierarchical structure of acute leukemia has yet to be fully translated into therapeutic approaches. Indeed, chemotherapy still has to take into account the possibility that leukemia-initiating cells may have a distinct chemosensitivity profile compared to the bulk of the tumor, and therefore are spared by the current treatment, causing the relapse of the disease. Therefore, the identification of the cell-of-origin of leukemia remains a longstanding question and an exciting challenge in cancer research of the last few decades. With a particular focus on acute lymphoblastic leukemia, we present in this review the previous and current concepts exploring the phenotypic, genetic and functional heterogeneity in patients. We also discuss the benefits of using engineered mouse models to explore the early steps of leukemia development and to identify the biological mechanisms driving the emergence of leukemia-initiating cells. Finally, we describe the major prospects for the discovery of new therapeutic strategies that specifically target their aberrant stem cell-like functions.

Carboplatin- and Etoposide-Loaded Lactoferrin Protein Nanoparticles for Targeting Cancer Stem Cells in Retinoblastoma In Vitro

Purpose

Cancer stem cells (CSCs) are known to contribute to tumor relapses by virtue of their chemoresistance. With the knowledge that nanoformulations can overcome drug resistance, we evaluated the efficacy and cytotoxicity of clinical-grade carboplatin (CPT)– and etoposide (ETP)–loaded lactoferrin nanoparticles (Lf-Nps) on total, CD133-enriched (non-CSC), and CD133-depleted (CSC) populations of retinoblastoma (Rb) Y79 cells.

Methods

Physicochemical properties of drug-loaded Lf-Nps were measured with transmission electron microscopy and attenuated total reflectance–Fourier transform infrared. The encapsulation efficiency, uptake, and release of drug-loaded Lf-Nps were measured using high-performance liquid chromatography and a UV-visible spectrophotometer. Cytotoxicity of the standard and drug-loaded Lf-Nps was evaluated by the MTT assay.

Results

The mean (SD) size and encapsulation efficiency of Lf-CPT and Lf-ETP were 61.2 (3.94) nm, 60% and 45.15 (5.85) nm, 38%, respectively, and the drug release efficiency was highest at pH 6. The increased drug uptake and lower release of drug-loaded Lf-Nps were observed in CSC and non-CSC populations compared to their standard forms. The relative increase of drug uptake and sustained intracellular retention of the drug-loaded Lf-Nps compared to standard drugs showed an enhanced cytotoxicity up to 50%, especially in Rb Y79 CSCs (IC₅₀: CPT, 230.3; Lf-CPT, 118.2; ETP, 198.1; and Lf-ETP, 129) compared to non-CSCs.

Conclusions

Our study documents an increase in drug uptake, retention, and cytotoxicity of Lf-CPT and Lf-ETP on Y79 CSCs and non-CSCs as compared to their standard drugs in vitro. The reversal of chemoresistance in the CSC population by nanoformulation appears promising with the potential to pave the way for improved targeted therapy and better clinical outcomes.

NR2F2 controls malignant squamous cell carcinoma state by promoting stemness and invasion and repressing differentiation

The nongenetic mechanisms required to sustain malignant tumor state are poorly understood. During the transition from benign tumors to malignant carcinoma, tumor cells need to repress differentiation and acquire invasive features. Using transcriptional profiling of cancer stem cells from benign tumors and malignant skin squamous cell carcinoma (SCC), we identified the nuclear receptor NR2F2 as uniquely expressed in malignant SCC. Using genetic gain of function and loss of function in vivo, we show that NR2F2 is essential for promoting the malignant tumor state by controlling tumor stemness and maintenance in mouse and human SCC. We demonstrate that NR2F2 promotes tumor cell proliferation, epithelial-mesenchymal transition and invasive features, while repressing tumor differentiation and immune cell infiltration by regulating a common transcriptional program in mouse and human SCCs. Altogether, we identify NR2F2 as a key regulator of malignant cancer stem cell functions that promotes tumor renewal and restricts differentiation to sustain a malignant tumor state.

CombiFlow: Combinatorial AML-specific plasma membrane expression profiles allow longitudinal tracking of clones

MRD detection with AML-specific PM markers predicts shorter relapse-free survival.

CombiFlow integrates expression data of multiple PM markers that allows longitudinal tracking of clonal evolution.

Acute myeloid leukemia (AML) often presents as an oligoclonal disease whereby multiple genetically distinct subclones can coexist within patients. Differences in signaling and drug sensitivity of such subclones complicate treatment and warrant tools to identify them and track disease progression. We previously identified >50 AML-specific plasma membrane (PM) proteins, and 7 of these (CD82, CD97, FLT3, IL1RAP, TIM3, CD25, and CD123) were implemented in routine diagnostics in patients with AML (n = 256) and myelodysplastic syndrome (n = 33). We developed a pipeline termed CombiFlow in which expression data of multiple PM markers is merged, allowing a principal component–based analysis to identify distinctive marker expression profiles and to generate single-cell t-distributed stochastic neighbor embedding landscapes to longitudinally track clonal evolution. Positivity for one or more of the markers after 2 courses of intensive chemotherapy predicted a shorter relapse-free survival, supporting a role for these markers in measurable residual disease (MRD) detection. CombiFlow also allowed the tracking of clonal evolution in paired diagnosis and relapse samples. Extending the panel to 36 AML-specific markers further refined the CombiFlow pipeline. In conclusion, CombiFlow provides a valuable tool in the diagnosis, MRD detection, clonal tracking, and understanding of clonal heterogeneity in AML.

RhoGTPase Signalling in Cancer Progression and Dissemination

Rho GTPases are a family of small G proteins that regulate a wide array of cellular processes related to their key roles controlling the cytoskeleton. On the other hand, cancer is a multi-step disease caused by the accumulation of genetic mutations and epigenetic alterations, from the initial stages of cancer development when cells in normal tissues undergo transformation, to the acquisition of invasive and metastatic traits, responsible for a large number of cancer related deaths. In this review, we discuss the role of Rho GTPase signalling in cancer in every step of disease progression. Rho GTPases contribute to tumour initiation and progression, by regulating proliferation and apoptosis, but also metabolism, senescence and cell stemness. Rho GTPases play a major role in cell migration, and in the metastatic process. They are also involved in interactions with the tumour microenvironment and regulate inflammation, contributing to cancer progression. After years of intensive research, we highlight the importance of relevant models in the Rho GTPase field, and we reflect on the therapeutic opportunities arising for cancer patients.

The Immune Privilege of Cancer Stem Cells: A Key to Understanding Tumor Immune Escape and Therapy Failure

Cancer stem cells (CSCs) are broadly considered immature, multipotent, tumorigenic cells within the tumor mass, endowed with the ability to self-renew and escape immune control. All these features contribute to place CSCs at the pinnacle of tumor aggressiveness and (immune) therapy resistance. The immune privileged status of CSCs is induced and preserved by various mechanisms that directly affect them (e.g., the downregulation of the major histocompatibility complex class I) and indirectly are induced in the host immune cells (e.g., activation of immune suppressive cells). Therefore, deeper insights into the immuno-biology of CSCs are essential in our pursuit to find new therapeutic opportunities that eradicate cancer (stem) cells. Here, we review and discuss the ability of CSCs to evade the innate and adaptive immune system, as we offer a view of the immunotherapeutic strategies adopted to potentiate and address specific subsets of (engineered) immune cells against CSCs.

Casein Kinase 1D Encodes a Novel Drug Target in Hedgehog-GLI-Driven Cancers and Tumor-Initiating Cells Resistant to SMO Inhibition

Simple Summary

Uncontrolled activation of hedgehog (HH)—GLI signaling contributes to the development of several human malignancies. Targeted inhibition of the HH—GLI signaling cascade with small-molecule inhibitors can reduce cancer growth, but patient relapse is very common due to the development of drug resistance. Therefore, a high unmet medical need exists for new drug targets and inhibitors to achieve efficient and durable responses. In the current study, we identified CSNK1D as a novel drug target in the HH—GLI signaling pathway. Genetic and pharmacological inhibition of CSNK1D activity leads to suppression of oncogenic HH—GLI signaling, even in cancer cells in which already approved HH inhibitors are no longer effective due to resistance mechanisms. Inhibition of CSNK1D function reduces the malignant properties of so-called tumor-initiating cells, thereby limiting cancer growth and presumably metastasis. The results of this study form the basis for the development of efficient CSNK1D inhibitors for the therapy of HH—GLI-associated cancers.

Abstract

(1) Background: Aberrant activation of the hedgehog (HH)—GLI pathway in stem-like tumor-initiating cells (TIC) is a frequent oncogenic driver signal in various human malignancies. Remarkable efficacy of anti-HH therapeutics led to the approval of HH inhibitors targeting the key pathway effector smoothened (SMO) in basal cell carcinoma and acute myeloid leukemia. However, frequent development of drug resistance and severe adverse effects of SMO inhibitors pose major challenges that require alternative treatment strategies targeting HH—GLI in TIC downstream of SMO. We therefore investigated members of the casein kinase 1 (CSNK1) family as novel drug targets in HH—GLI-driven malignancies. (2) Methods: We genetically and pharmacologically inhibited CSNK1D in HH-dependent cancer cells displaying either sensitivity or resistance to SMO inhibitors. To address the role of CSNK1D in oncogenic HH signaling and tumor growth and initiation, we quantitatively analyzed HH target gene expression, performed genetic and chemical perturbations of CSNK1D activity, and monitored the oncogenic transformation of TIC in vitro and in vivo using 3D clonogenic tumor spheroid assays and xenograft models. (3) Results: We show that CSNK1D plays a critical role in controlling oncogenic GLI activity downstream of SMO. We provide evidence that inhibition of CSNK1D interferes with oncogenic HH signaling in both SMO inhibitor-sensitive and -resistant tumor settings. Furthermore, genetic and pharmacologic perturbation of CSNK1D decreases the clonogenic growth of GLI-dependent TIC in vitro and in vivo. (4) Conclusions: Pharmacologic targeting of CSNK1D represents a novel therapeutic approach for the treatment of both SMO inhibitor-sensitive and -resistant tumors.

Adipose stem cell niche reprograms the colorectal cancer stem cell metastatic machinery

Obesity is a strong risk factor for cancer progression, posing obesity-related cancer as one of the leading causes of death. Nevertheless, the molecular mechanisms that endow cancer cells with metastatic properties in patients affected by obesity remain unexplored.

Here, we show that IL-6 and HGF, secreted by tumor neighboring visceral adipose stromal cells (V-ASCs), expand the metastatic colorectal (CR) cancer cell compartment (CD44v6 + ), which in turn secretes neurotrophins such as NGF and NT-3, and recruits adipose stem cells within tumor mass. Visceral adipose-derived factors promote vasculogenesis and the onset of metastatic dissemination by activation of STAT3, which inhibits miR-200a and enhances ZEB2 expression, effectively reprogramming CRC cells into a highly metastatic phenotype. Notably, obesity-associated tumor microenvironment provokes a transition in the transcriptomic expression profile of cells derived from the epithelial consensus molecular subtype (CMS2) CRC patients towards a mesenchymal subtype (CMS4). STAT3 pathway inhibition reduces ZEB2 expression and abrogates the metastatic growth sustained by adipose-released proteins. Together, our data suggest that targeting adipose factors in colorectal cancer patients with obesity may represent a therapeutic strategy for preventing metastatic disease.

Obesity is a major risk factor for cancer related death. Here, the authors show that visceral adipose-derived factors promote vasculogenesis and metastatic dissemination by activation of STAT3, which inhibits miR-200a and enhances ZEB2 expression, effectively reprogramming colorectal cancer cells into a highly metastatic phenotype.

A STAT5B-CD9 axis determines self-renewal in hematopoietic and leukemic stem cells

The transcription factors STAT5A and STAT5B are critical in hematopoiesis and leukemia. They are widely believed to have redundant functions but we describe a unique role for STAT5B in driving the self-renewal of hematopoietic and leukemic stem cells (HSCs/LSCs). We find STAT5B to be specifically activated in HSCs and LSCs, where it induces many genes associated with quiescence and self-renewal, including the surface marker CD9. Levels of CD9 represent a prognostic marker for patients with STAT5-driven leukemia and our findings suggest that anti-CD9 antibodies may be useful in their treatment to target and eliminate LSCs. We show that it is vital to consider STAT5A and STAT5B as distinct entities in normal and malignant hematopoiesis.

Proteases Regulate Cancer Stem Cell Properties and Remodel Their Microenvironment

Proteolytic activity is perturbed in tumors and their microenvironment, and proteases also affect cancer stem cells (CSCs). CSCs are the therapy-resistant subpopulation of cancer cells with tumor-initiating capacity that reside in specialized tumor microenvironment niches. In this review, we briefly summarize the significance of proteases in regulating CSC activities with a focus on brain tumor glioblastoma. A plethora of proteases and their inhibitors participate in CSC invasiveness and affect intercellular interactions, enhancing CSC immune, irradiation, and chemotherapy resilience. Apart from their role in degrading the extracellular matrix enabling CSC migration in and out of their niches, we review the ability of proteases to modulate CSC properties, which prevents their elimination. When designing protease-oriented therapies, the multifaceted roles of proteases should be thoroughly investigated.

Messing Up the Cancer Stem Cell Chemoresistance Mechanisms Supported by Tumor Microenvironment

Despite the recent advances in cancer patient management and in the development of targeted therapies, systemic chemotherapy is currently used as a first-line treatment for many cancer types. After an initial partial response, patients become refractory to standard therapy fostering rapid tumor progression. Compelling evidence highlights that the resistance to chemotherapeutic regimens is a peculiarity of a subpopulation of cancer cells within tumor mass, known as cancer stem cells (CSCs). This cellular compartment is endowed with tumor-initiating and metastasis formation capabilities. CSC chemoresistance is sustained by a plethora of grow factors and cytokines released by neighboring tumor microenvironment (TME), which is mainly composed by adipocytes, cancer-associated fibroblasts (CAFs), immune and endothelial cells. TME strengthens CSC refractoriness to standard and targeted therapies by enhancing survival signaling pathways, DNA repair machinery, expression of drug efflux transporters and anti-apoptotic proteins. In the last years many efforts have been made to understand CSC-TME crosstalk and develop therapeutic strategy halting this interplay. Here, we report the combinatorial approaches, which perturb the interaction network between CSCs and the different component of TME.

Biochemical Mechanisms Associating Alcohol Use Disorders with Cancers

Simple Summary

Of all yearly deaths attributable to alcohol consumption globally, approximately 12% are due to cancers, representing approximately 0.4 million deceased individuals. Ethanol metabolism disturbs cell biochemistry by targeting the structure and function of essential biomolecules (proteins, nucleic acids, and lipids) and by provoking alterations in cell programming that lead to cancer development and cancer malignancy. A better understanding of the metabolic and cell signaling realm affected by ethanol is paramount to designing effective treatments and preventive actions tailored to specific neoplasias.

Abstract

The World Health Organization identifies alcohol as a cause of several neoplasias of the oropharynx cavity, esophagus, gastrointestinal tract, larynx, liver, or female breast. We review ethanol’s nonoxidative and oxidative metabolism and one-carbon metabolism that encompasses both redox and transfer reactions that influence crucial cell proliferation machinery. Ethanol favors the uncontrolled production and action of free radicals, which interfere with the maintenance of essential cellular functions. We focus on the generation of protein, DNA, and lipid adducts that interfere with the cellular processes related to growth and differentiation. Ethanol’s effects on stem cells, which are responsible for building and repairing tissues, are reviewed. Cancer stem cells (CSCs) of different origins suffer disturbances related to the expression of cell surface markers, enzymes, and transcription factors after ethanol exposure with the consequent dysregulation of mechanisms related to cancer metastasis or resistance to treatments. Our analysis aims to underline and discuss potential targets that show more sensitivity to ethanol’s action and identify specific metabolic routes and metabolic realms that may be corrected to recover metabolic homeostasis after pharmacological intervention. Specifically, research should pay attention to re-establishing metabolic fluxes by fine-tuning the functioning of specific pathways related to one-carbon metabolism and antioxidant processes.

Identification and Characterization of Multiple Myeloma Stem Cell-Like Cells

Multiple myeloma (MM) is a B-cell tumor of the blood system with high incidence and poor prognosis. With a further understanding of the pathogenesis of MM and the bone marrow microenvironment, a variety of adjuvant cell therapies and new drugs have been developed. However, the drug resistance and high relapse rate of MM have not been fundamentally resolved. Studies have shown that, in patients with MM, there is a type of poorly differentiated progenitor cell (MM stem cell-like cells, MMSCs). Although there is no recognized standard for identification and classification, it is confirmed that they are closely related to the drug resistance and relapse of MM. This article therefore systematically summarizes the latest developments in MMSCs with possible markers of MMSCs, introduces the mechanism of how MMSCs work in MM resistance and recurrence, and discusses the active pathways that related to stemness of MM.

Transcending toward Advanced 3D-Cell Culture Modalities: A Review about an Emerging Paradigm in Translational Oncology

Cancer is a disorder characterized by an uncontrollable overgrowth and a fast-moving spread of cells from a localized tissue to multiple organs of the body, reaching a metastatic state. Throughout years, complexity of cancer progression and invasion, high prevalence and incidence, as well as the high rise in treatment failure cases leading to a poor patient prognosis accounted for continuous experimental investigations on animals and cellular models, mainly with 2D- and 3D-cell culture. Nowadays, these research models are considered a main asset to reflect the physiological events in many cancer types in terms of cellular characteristics and features, replication and metastatic mechanisms, metabolic pathways, biomarkers expression, and chemotherapeutic agent resistance. In practice, based on research perspective and hypothesis, scientists aim to choose the best model to approach their understanding and to prove their hypothesis. Recently, 3D-cell models are seen to be highly incorporated as a crucial tool for reflecting the true cancer cell microenvironment in pharmacokinetic and pharmacodynamics studies, in addition to the intensity of anticancer drug response in pharmacogenomics trials. Hence, in this review, we shed light on the unique characteristics of 3D cells favoring its promising usage through a comparative approach with other research models, specifically 2D-cell culture. Plus, we will discuss the importance of 3D models as a direct reflector of the intrinsic cancer cell environment with the newest multiple methods and types available for 3D-cells implementation.

Prognostic and predictive value of ALDH1, SOX2 and SSEA-4 in bladder cancer

Transurethral resection of bladder tumor (TUR-BT) and radical cystectomy (RC) are standard treatment options for bladder cancer (BC). Neoadjuvant chemotherapy (NAC) prior to RC improves outcome of some patients but currently there are no valid biomarkers to identify patients who benefit from NAC. Presence of cancer stem cells (CSC) has been associated with poor outcome and resistance to chemotherapy in various cancers. Here we studied the expression of stem cell markers ALDH1, SOX2 and SSEA-4 with immunohistochemistry in tissue microarray material consisting of 195 BC patients treated with RC and 74 patients treated with TUR-BT followed by NAC and RC. Post-operative follow-up data of up to 22 years was used. Negative to weak cytoplasmic SOX2 staining was associated with lymphovascular invasion and non-organ confined disease. It was also associated with shortened cancer-specific survival, but the finding was not statistically significant. Contrary to previous reports, none of the other tested biomarkers were associated with cancer-specific mortality or clinicopathological characteristics. Neither were they associated with response to NAC. Despite the promising results of previously published studies, our results suggest that CSC markers ALDH1, SOX2 and SSEA-4 have little if any prognostic or predictive value in BC treated with RC.

Mechanisms of cancer stem cell senescence: Current understanding and future perspectives

Cancer stem cells (CSCs) are a small population of heterogeneous tumor cells with the capacity of self-renewal and aberrant differentiation for immortality and divergent lineages of cancer cells. In contrast to bulky tumor cells, CSCs remain less differentiated and resistant to therapy even when targeted with tissue-specific antigenic markers. This makes CSCs responsible for not only tumor initiation, development, but also tumor recurrence. Emerging evidence suggests that CSCs can undergo cell senescence, a non-proliferative state of cells in response to stress. While cell senescence attenuates tumor cell proliferation, it is commonly regarded as a tumor suppressive mechanism. However, mounting research indicates that CSC senescence also provides these cells with the capacity to evade cytotoxic effects from cancer therapy, exacerbating cancer relapse and metastasis. Recent studies demonstrate that senescence drives reprogramming of cancer cell toward stemness and promotes CSC generation. In this review, we highlight the origin, heterogeneity and senescence regulatory mechanisms of CSCs, the complex relationship between CSC senescence and tumor therapy, and the recent beneficial effects of senotherapy on eliminating senescent tumor cells.

Angiogenesis-related non-coding RNAs and gastrointestinal cancer

Gastrointestinal (GI) cancers are among the main reasons for cancer death globally. The deadliest types of GI cancer include colon, stomach, and liver cancers. Multiple lines of evidence have shown that angiogenesis has a key role in the growth and metastasis of all GI tumors. Abnormal angiogenesis also has a critical role in many non-malignant diseases. Therefore, angiogenesis is considered to be an important target for improved cancer treatment. Despite much research, the mechanisms governing angiogenesis are not completely understood. Recently, it has been shown that angiogenesis-related non-coding RNAs (ncRNAs) could affect the development of angiogenesis in cancer cells and tumors. The broad family of ncRNAs, which include long non-coding RNAs, microRNAs, and circular RNAs, are related to the development, promotion, and metastasis of GI cancers, especially in angiogenesis. This review discusses the role of ncRNAs in mediating angiogenesis in various types of GI cancers and looks forward to the introduction of mimetics and antagonists as possible therapeutic agents.

Delineation of target expression profiles in CD34+/CD38- and CD34+/CD38+ stem and progenitor cells in AML and CML

In an attempt to identify novel markers and immunological targets in leukemic stem cells (LSCs) in acute myeloid leukemia (AML) and chronic myeloid leukemia (CML), we screened bone marrow (BM) samples from patients with AML (n = 274) or CML (n = 97) and controls (n = 288) for expression of cell membrane antigens on CD34+/CD38- and CD34+/CD38+ cells by multicolor flow cytometry. In addition, we established messenger RNA expression profiles in purified sorted CD34+/CD38- and CD34+/CD38+ cells using gene array and quantitative polymerase chain reaction. Aberrantly expressed markers were identified in all cohorts. In CML, CD34+/CD38- LSCs exhibited an almost invariable aberration profile, defined as CD25+/CD26+/CD56+/CD93+/IL-1RAP+. By contrast, in patients with AML, CD34+/CD38- cells variably expressed "aberrant" membrane antigens, including CD25 (48%), CD96 (40%), CD371 (CLL-1; 68%), and IL-1RAP (65%). With the exception of a subgroup of FLT3 internal tandem duplication-mutated patients, AML LSCs did not exhibit CD26. All other surface markers and target antigens detected on AML and/or CML LSCs, including CD33, CD44, CD47, CD52, CD105, CD114, CD117, CD133, CD135, CD184, and roundabout-4, were also found on normal BM stem cells. However, several of these surface targets, including CD25, CD33, and CD123, were expressed at higher levels on CD34+/CD38- LSCs compared with normal BM stem cells. Moreover, antibody-mediated immunological targeting through CD33 or CD52 resulted in LSC depletion in vitro and a substantially reduced LSC engraftment in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice. Together, we have established surface marker and target expression profiles of AML LSCs and CML LSCs, which should facilitate LSC enrichment, diagnostic LSC phenotyping, and development of LSC-eradicating immunotherapies.

Cervical Cancer Stem-Like Cell Transcriptome Profiles Predict Response to Chemoradiotherapy

Cervical cancer (CC) represents a major global health issue, particularly impacting women from resource constrained regions worldwide. Treatment refractoriness to standard chemoradiotheraphy has identified cancer stem cells as critical coordinators behind the biological mechanisms of resistance, contributing to CC recurrence. In this work, we evaluated differential gene expression in cervical cancer stem-like cells (CCSC) as biomarkers related to intrinsic chemoradioresistance in CC. A total of 31 patients with locally advanced CC and referred to Mário Penna Institute (Belo Horizonte, Brazil) from August 2017 to May 2018 were recruited for the study. Fluorescence-activated cell sorting was used to enrich CD34+/CD45- CCSC from tumor biopsies. Transcriptome was performed using ultra-low input RNA sequencing and differentially expressed genes (DEGs) using Log2 fold differences and adjusted p-value < 0.05 were determined. The analysis returned 1050 DEGs when comparing the Non-Responder (NR) (n=10) and Responder (R) (n=21) groups to chemoradiotherapy. These included a wide-ranging pattern of underexpressed coding genes in the NR vs. R patients and a panel of lncRNAs and miRNAs with implications for CC tumorigenesis. A panel of biomarkers was selected using the rank-based AUC (Area Under the ROC Curve) and pAUC (partial AUC) measurements for diagnostic sensitivity and specificity. Genes overlapping between the 21 highest AUC and pAUC loci revealed seven genes with a strong capacity for identifying NR vs. R patients (ILF2, RBM22P2, ACO16722.1, AL360175.1 and AC092354.1), of which four also returned significant survival Hazard Ratios. This study identifies DEG signatures that provide potential biomarkers in CC prognosis and treatment outcome, as well as identifies potential alternative targets for cancer therapy.

JNK in Tumor Microenvironment: Present Findings and Challenges in Clinical Translation

Simple Summary

Stress-activated c-Jun N-terminal kinases (JNKs) are members of mitogen-activated protein kinases (MAPKs). Apart from having both tumor promoting and tumor suppressing roles in cancers due to its impact on apoptosis and autophagy pathways, JNK also plays complex roles in the heterogeneous tumor microenvironment (TME) and is involved in different tumorigenesis pathways. The JNK pathway influences various stressful and chronic inflammatory conditions along with different cell populations in TME. In this review, we aim to present the current knowledge of JNK-mediated processes in TME and the challenges in clinical translation.

Abstract

The c-Jun N-terminal kinases (JNKs) are a group of mitogen-activated protein kinases (MAPKs). JNK is mainly activated under stressful conditions or by inflammatory cytokines and has multiple downstream targets for mediating cell proliferation, differentiation, survival, apoptosis, and immune responses. JNK has been demonstrated to have both tumor promoting and tumor suppressing roles in different cancers depending on the focused pathway in each study. JNK also plays complex roles in the heterogeneous tumor microenvironment (TME). JNK is involved in different tumorigenesis pathways. TME closely relates with tumor development and consists of various stressful and chronic inflammatory conditions along with different cell populations, in which the JNK pathway may have various mediating roles. In this review, we aim to summarize the present knowledge of JNK-mediated processes in TME, including hypoxia, reactive oxygen species, inflammation, immune responses, angiogenesis, as well as the regulation of various cell populations within TME. This review also suggests future research directions for translating JNK modulation in pre-clinical findings to clinical benefits.

Dichloroacetate attenuates the stemness of hepatocellular carcinoma cells via promoting nucleus-cytoplasm translocation of YAP

The antitumor effects of dichloroacetate (DCA) have been widely explored, however, its roles in hepatocellular carcinoma (HCC) progression are still unclear. In the current work, we found that DCA had little effects on HCC cell viability, but could attenuate the stemness of HCC cells, which is evident by decreasing the tumor sphere-formation ability, ALDH activity and the expression of stemness critical regulators. Mechanistic studies based on RNA-sequencing data showed that DCA activated the Hippo pathway. Furthermore, we indicated that DCA promoted the nucleus-cytoplasm translocation of YAP, but not TAZ, another critical executor of Hippo pathway. Moreover, suppressing of Hippo pathway using XMU-MP-1, an inhibitor of Hippo pathway, partially abrogated DCA-induced inhibitory effects on HCC cell stemness. This work suggests that DCA might be a potential inhibitor for HCC progression.

Schisandrin B inhibits epithelial‑mesenchymal transition and stemness of large‑cell lung cancer cells and tumorigenesis in xenografts via inhibiting the NF‑κB and p38 MAPK signaling pathways

Lung cancer is one of the most common types of cancer in the world, resulting in numerous cancer-associated deaths. The properties of cancer stem cells (CSCs) are important for the initiation and deterioration of lung cancer. Schisandrin B (SchB), an active compound extracted from Schisandra chinensis, exerts anticancer effects in various malignancies, including lung cancer. Nevertheless, the potential of SchB in epithelial-mesenchymal transition (EMT) and CSC features of large-cell lung cancer remains unclear. The present study established cancer stem-like cells derived from large-cell lung cancer cells, NCI-H460 and H661, and revealed that SchB inhibited the viability of cancer stem-like cells at concentrations of ≥40 µmol/l. Moreover, SchB prominently inhibited cell migration, invasion and EMT. Sphere-forming assays and western blotting demonstrated that the stemness of cancer stem-like cells was alleviated by SchB treatment. Mechanistically, the current findings revealed that SchB contributed to the suppression of the NF-κB and p38 MAPK signaling pathways. Notably, further results revealed that the malignant behaviors of NCI-H460-CSCs induced by the activation of the NF-κB and p38 MAPK signaling pathways were suppressed by SchB treatment. Consistently, the inhibitory role of SchB in EMT and CSC activities, as well as in the activation of the NF-κB and p38 MAPK signaling pathways, was confirmed in vivo. In conclusion, the present study demonstrated that SchB exerted inhibitory effects on large-cell lung cancer cells via targeting the NF-κB and p38 MAPK signaling pathways, suggesting that SchB may act as a potential therapeutic drug for large-cell lung cancer.

Nanog is a promising chemoresistant stemness marker and therapeutic target by iron chelators for esophageal cancer

Esophageal cancer is a disease showing poor prognosis. Although combination chemotherapy using cisplatin (CDDP) and 5-fluorouracil is standard for unresectable esophageal cancer, the response rate is 35%. Cancer stem cells (CSCs) and inflammation are reportedly responsible for the poor prognosis of esophageal cancer. However, comprehensive analyses have not been conducted and proposals for progress remain lacking. Iron is known to be a key factor in the stemness of CSCs. Our study focused on the therapeutic potential of iron control using iron chelators for CSCs in esophageal cancer. Among 134 immunohistochemically analyzed cases, Nanog expression was high in 98 cases and low in 36 cases. High Nanog expression correlated with low overall and disease-free survivals. The iron chelators deferasirox (DFX) and SP10 suppressed the proliferation and expression of stemness markers in TE8 and OE33 cells. DFX and SP10 did not induce compensatory interleukin (IL)-6 secretion, although CDDP did result in high induction. Moreover, BBI608 and SSZ, as other CSC-targeting drugs, could not suppress the expression of stemness markers. Overall, Nanog expression appears related to poor prognosis in esophageal cancer patients, and inhibition of stemness and compensatory IL-6 secretion by iron chelators may offer a novel therapeutic strategy for esophageal cancer.

Carboxy terminus of HSP70-interacting protein (CHIP) attenuates the stemness of thyroid cancer cells through decreasing OCT4 protein stability

Cancer cell stemness results in the occurrence and progression of tumors and Oct4 (octamer-binding transcription factor) has been confirmed to be a critical contributor and marker of cancer cell stemness. Here, we aimed to explore the underlying mechanisms contributing to Oct4 protein stability, which is necessary for thyroid cancer (TC) cell stemness. We indicated that carboxy terminus of HSP70-interacting protein (CHIP) protein was lowly expressed in TC tissues and cells, and positively correlated with the overall survival of TC patients. By analyzing the co-expression network in TC tissues, we found that CHIP and Oct4 expression exhibited a negative correlation. Functional experiments showed that CHIP knockdown promoted the stemness of TC cells, while CHIP overexpression reduced the stemness of TC spheroids formed by TC cells, in which CHIP expression was significantly decreased. Furthermore, CHIP had no effect on TC cell viability. Mechanistic studies revealed that CHIP directly interacted with Oct4 protein and induced Oct4 ubiquitination, whereas a catalytic CHIP mutant (H260Q) did not. And CHIP regulated the stemness of TC cells in an Oct4-dependent manner. Overall, this work indicates that the CHIP/Oct4 axis is essential for TC cell stemness.

Colorectal Cancer Stem Cell States Uncovered by Simultaneous Single-Cell Analysis of Transcriptome and Telomeres

Cancer stem cells (CSCs) presumably contribute to tumor progression and drug resistance, yet their definitive features have remained elusive. Here, simultaneous measurement of telomere length and transcriptome in the same cells enables systematic assessment of CSCs in primary colorectal cancer (CRC). The in-depth transcriptome profiled by SMART-seq2 is independently validated by high-throughput scRNA-seq using 10 × Genomics. It is found that rare CSCs exist in dormant state and display plasticity toward cancer epithelial cells (EPCs) that essentially are presumptive tumor-initiating cells (TICs), while both retaining the prominent signaling pathways including WNT, TGF-β, and HIPPO/YAP. Moreover, CSCs exhibit chromosome copy number variation (CNV) pattern resembling cancer EPCs but distinct from normal stem cells, suggesting the phylogenetic relationship between CSCs and cancer EPCs. Notably, CSCs maintain shorter telomeres and possess minimal telomerase activity consistent with their nonproliferative nature, unlike cancer EPCs. Additionally, the specific signature of CSCs particularly NOTUM, SMOC2, BAMBI, PHLDA1, and TNFRSF19 correlates with the prognosis of CRC. These findings characterize the heterogeneity of CSCs and their linkage to cancer EPCs/TICs, some of which are conventionally regarded as CSCs.

Artificial Tumor Microenvironments in Neuroblastoma

Simple Summary

Children with high-risk neuroblastoma have limited therapeutic options poor survival rates. The neuroblastoma tumor microenvironment contributes the lack of response to many interventions so innovative methods are needed to study the effects of the tumor microenvironment on new therapies. In this manuscript, we review the current literature related to the components of the tumor microenvironment and to the use of three-dimensional printing as modality to study cancer. This review highlights the potential for using three-dimensional printing to create an artificial tumor microenvironment in the presence of neuroblastoma to provide improved preclinical testing of novel therapies.

Abstract

In the quest to advance neuroblastoma therapeutics, there is a need to have a deeper understanding of the tumor microenvironment (TME). From extracellular matrix proteins to tumor associated macrophages, the TME is a robust and diverse network functioning in symbiosis with the solid tumor. Herein, we review the major components of the TME including the extracellular matrix, cytokines, immune cells, and vasculature that support a more aggressive neuroblastoma phenotype and encumber current therapeutic interventions. Contemporary treatments for neuroblastoma are the result of traditional two-dimensional culture studies and in vivo models that have been translated to clinical trials. These pre-clinical studies are costly, time consuming, and neglect the study of cofounding factors such as the contributions of the TME. Three-dimensional (3D) bioprinting has become a novel approach to studying adult cancers and is just now incorporating portions of the TME and advancing to study pediatric solid. We review the methods of 3D bioprinting, how researchers have included TME pieces into the prints, and highlight present studies using neuroblastoma. Ultimately, incorporating the elements of the TME that affect neuroblastoma responses to therapy will improve the development of innovative and novel treatments. The use of 3D bioprinting to achieve this aim will prove useful in developing optimal therapies for children with neuroblastoma.

Identification of a subpopulation of long-term tumor-initiating cells in colon cancer

Long-term tumor-initiating cells (LT-TICs) are viewed as a quantifiable target for colon cancer therapy owing to their extensive self-renewal and tumorigenic and metastatic capacities. However, it is unknown which subpopulation of colon cancer cells contains LT-TICs. Here, based on the methods for isolating and identifying cancer stem cells (CSCs) and the functional features of LT-TICs, we aimed to identify a subpopulation of LT-TICs. Among the six cell lines assessed, our results showed that CD133 and CD44 coexpression was only detected in HCT116 and HT29 cell lines. In HCT116 and HT29 cells, CD133⁺CD44⁺ cells not only shared the extensive tumorigenic potential of LT-TICs but also functionally reproduced the behaviors of LT-TICs that drive tumor metastasis (TM) formation, suggesting that CD133⁺CD44⁺ cells are a typical representation of LT-TICs in colon cancer. Mechanistically, the enhanced capacity of CD133⁺CD44⁺ cells to drive metastasis involves the up-regulated expression of Wnt-, epithelial–mesenchymal transition (EMT)-, and metastasis-related genes in these cells. Additionally, CD133⁺CD44⁺ cells presented significant chemoresistance compared with corresponding nontumorigenic CD133⁻CD44⁻ cells following exposure to oxaliplatin (OXLP) or 5-fluorouracil (5-FU). Accordingly, CD133⁺CD44⁺ cells contained lower reactive oxygen species (ROS) levels than CD1133⁻CD44⁻ cells, and the low ROS levels in CD133⁺CD44⁺ cells were related to the enhancement of antioxidant defense systems. More importantly, CD133⁺CD44⁺ cells developed less DNA damage after exposure to chemotherapeutics than CD133⁻CD44⁻ cells. In conclusion, we identified a subpopulation of LT-TICs in colon cancer.

FOSL1 promotes metastasis of head and neck squamous cell carcinoma through super-enhancer-driven transcription program

Previously, we discovered that FOSL1 facilitates the metastasis of head and neck squamous cell carcinoma (HNSCC) cancer stem cells in a spontaneous mouse model. However, the molecular mechanisms remained unclear. Here, we demonstrated that FOSL1 serves as the dominant activating protein 1 (AP1) family member and is significantly upregulated in HNSCC tumor tissues and correlated with metastasis of HNSCC. Mechanistically, FOSL1 exerts its function in promoting tumorigenicity and metastasis predominantly via selective association with Mediators to establish super-enhancers (SEs) at a cohort of cancer stemness and pro-metastatic genes, such as SNAI2 and FOSL1 itself. Depletion of FOSL1 led to disruption of SEs and expression inhibition of these key oncogenes, which resulted in the suppression of tumor initiation and metastasis. We also revealed that the abundance of FOSL1 is positively associated with the abundance of SNAI2 in HNSCC and the high expression levels of FOSL1 and SNAI2 are associated with short overall disease-free survival. Finally, the administration of the FOSL1 inhibitor SR11302 significantly suppressed tumor growth and lymph node metastasis of HNSCC in a patient-derived xenograft model. These findings indicate that FOSL1 is a master regulator that promotes the metastasis of HNSCC through a SE-driven transcription program that may represent an attractive target for therapeutic interventions.

The critical role of peroxiredoxin-2 in colon cancer stem cells

Colon cancer stem cells (CCSCs) play an important role in facilitating colon cancer occurrence, metastasis and drug resistance. The results of our previous studies confirmed that the well-studied antioxidant gene peroxiredoxin-2 (PRDX2) promotes colon cancer progression. However, the underlying function and mechanisms associated with PRDX2 remodeling in the context of CCSCs have remained poorly studied. In our present study, we demonstrated that PRDX2 is highly expressed in CD133/CD44-positive colon cancer tissues and spheroid CD133+CD44+ CCSCs. PRDX2 overexpression was shown to be closely correlated with CD133+CD44+ CCSCs in colon cancer. Furthermore, PRDX2 depletion markedly suppressed CD133+CD44+ CCSC stemness maintenance, tumor initiation, migration and invasion and liver metastasis. Furthermore, the expression of various EMT markers and Wnt/β-catenin signaling proteins was altered after PRDX2 inhibition. In addition, PRDX2 knockdown led to increased ROS production in CD133+CD44+ CCSCs, sensitizing CCSCs to oxidative stress and chemotherapy. These results suggest that PRDX2 could be a possible therapeutic target in CCSCs.

Tumor microenvironment in head and neck squamous cell carcinoma: Functions and regulatory mechanisms

The tumor microenvironment has been recently reported to play a pivotal role in sustaining tumor cells survival and protecting them from immunotherapy and chemotherapy-induced death. It remains largely unknown how the specific signaling pathway exerts the tumor microenvironment in head and neck squamous cell carcinoma though previous studies have elucidated the regulatory mechanisms involve in tumor immune microenvironment, stromal cells, tumor angiogenesis and cancer stem cell. These components are responsible for tumor progression as well as anti-cancer therapy resistance, leading to rapid tumor growth and treatment failure. In this review, we focus on discussing the interaction between tumor cells and the surrounding components for better understanding of anti-cancer treatment ineffectiveness and its underlying molecular mechanisms.

Shifting the Gears of Metabolic Plasticity to Drive Cell State Transitions in Cancer

Simple Summary

Metabolic adaptation by cancer cells is enabled through the rewiring of metabolic processes, thereby allowing them to survive and thrive in diverse tissue microenvironments. It is also exploited to maintain cancer stemness, drive epithelial–mesenchymal transition, and gain therapy resistance. These critical cellular events are pertinent to the various steps of cancer progression. Mechanistic insights into nutrient addiction arising from such metabolic rewiring have revealed therapeutic vulnerabilities that can be exploited as novel treatment modalities or for drug development. This review discusses concepts and principles of metabolic plasticity and highlights current preclinical and clinical strategies aimed at targeting these metabolic derangements.

Abstract

Cancer metabolism is a hallmark of cancer. Metabolic plasticity defines the ability of cancer cells to reprogram a plethora of metabolic pathways to meet unique energetic needs during the various steps of disease progression. Cell state transitions are phenotypic adaptations which confer distinct advantages that help cancer cells overcome progression hurdles, that include tumor initiation, expansive growth, resistance to therapy, metastasis, colonization, and relapse. It is increasingly appreciated that cancer cells need to appropriately reprogram their cellular metabolism in a timely manner to support the changes associated with new phenotypic cell states. We discuss metabolic alterations that may be adopted by cancer cells in relation to the maintenance of cancer stemness, activation of the epithelial–mesenchymal transition program for facilitating metastasis, and the acquisition of drug resistance. While such metabolic plasticity is harnessed by cancer cells for survival, their dependence and addiction towards certain metabolic pathways also present therapeutic opportunities that may be exploited.