Self-renewal and solid tumor stem cells

Sugar symphony: glycosylation in cancer metabolism and stemness

Glycosylation is a complex co-translational and post-translational modification (PTM) in eukaryotes that utilizes glycosyltransferases to generate a vast array of glycoconjugate structures. Recent studies have highlighted the role of glycans in regulating essential molecular, cellular, tissue, organ, and systemic biological processes with significant implications for human diseases, particularly cancer. The metabolic reliance of cancer, spanning tumor initiation, disease progression, and resistance to therapy, necessitates a range of uniquely altered cellular metabolic pathways. In addition, the intricate interplay between cell-intrinsic and -extrinsic mechanisms is exemplified by the communication between cancer cells, cancer stem cells (CSCs), cancer-associated fibroblasts (CAFs), and immune cells within the tumor microenvironment (TME). In this review article, we explore how differential glycosylation in cancer influences the metabolism and stemness features alongside new avenues in glycobiology.

Extracellular vesicles in acute myeloid leukemia: The role in disease pathogenesis, potential biomarker, and application in clinical settings

Acute myeloid leukemia (AML), the most prevalent type of blood cancer, is initiated in the bone marrow and eventually migrates into the blood. It accounts for a 5-year overall survival rate of 29.8 %. AML results from the formation of immature white blood cells, also called AML blasts, from hematopoietic stem cells which eventually give rise to abnormal white blood cells, termed AML cells. The interaction of AML cells with their microenvironment appears to be significantly important in the pathogenesis of AML. A growing body of evidence identifies extracellular vesicles (EVs) to be a key component in intercellular communication via the transfer of biomolecules, such as DNA, RNAs, proteins, non-coding RNAs, lipids, metabolites etc. Although the role of EVs in various solid tumors is well-established, EVs' contribution to the pathogenesis of blood cancer, such as AML remains ill-defined. The present review highlights how EVs promote the progression of AML by influencing leukemogenesis, survival, angiogenesis, chemotherapeutic resistance, and immune evasion. A significant number of EVs are found in the biofluids of AML patients which are shown to carry signature cargo molecules, thereby rendering the EVs as predictive biomarkers for AML pathogenesis. EV-based clinical trials are mentioned in the later part of the review. Finally, EV-based therapeutics and their limitations are also briefly discussed in the context of AML.

Troxerutin suppresses the stemness of osteosarcoma via the CD155/SRC/β-catenin signaling axis

BACKGROUND

Osteosarcoma is the most prevalent primary malignant bone tumor affecting pediatric and adolescent individuals. However, despite the passage of three decades, there has been no notable enhancement in the overall survival rate of patients with osteosarcoma. In recent years, CD155 has been reported to exhibit abnormal amplification in a range of tumors, yet the precise underlying mechanism remains elusive. The objective of this study is to investigate the role of CD155 in osteosarcoma, and to identify drugs that specifically target this molecule, thereby offering a novel direction for the treatment of osteosarcoma.

METHODS

The prognosis of patients with osteosarcoma with high and low expression of CD155 was verified by immunohistochemistry. CCK-8 and colony formation assays were used to detect cell proliferation and drug resistance. Transwell experiments were used to detect cell migration and invasion. The sphere formation experiment was used to evaluate the stemness of tumor cells. Additionally, in vivo animal models were utilized to assess the functional role of CD155 in a biological context. RNA-seq and co-immunoprecipitation methods were used to search for downstream target molecules and signaling pathways of CD155. Finally, virtual screening was used to find drugs targeting CD155.

RESULTS

In this study, we have established the significant amplification of CD155 in osteosarcoma. Utilizing a comprehensive array of experimental methods, including CCK-8 assay, colony formation assay, Transwell assay, and in vivo animal models, we unequivocally demonstrate that CD155 significantly potentiates the malignancy of osteosarcoma both in vitro and in vivo. Additionally, our findings reveal that CD155 promotes osteosarcoma stemness by modulating the Wnt/β-catenin signaling pathway. Advanced molecular techniques, such as RNA sequencing and co-immunoprecipitation, have been instrumental in elucidating the mechanism of CD155 in activating the Wnt/β-catenin pathway via the SRC/AKT/GSK3β signaling axis, thereby enhancing the stem-cell-like properties of osteosarcoma cells. To explore targeted therapeutic options, we conducted virtual screening and identified troxerutin as a promising CD155 inhibitor.

CONCLUSIONS

Our findings reveal that troxerutin effectively inhibits CD155, attenuates the SRC/AKT/GSK3β signaling cascade, diminishes the nuclear localization of β-catenin, and consequently mitigates osteosarcoma stemness. These discoveries position troxerutin as a promising candidate for targeted osteosarcoma therapy.

Diversity of ER-positive and HER2-negative breast cancer stem cells attained using selective culture techniques

Breast cancer stem cells are a promising therapeutic target in cancer. We explored breast cancer stem cell diversity and establish a methodology for selectively culturing breast cancer stem cells. We collected breast cancer tissues from surgical samples of treatment-naïve patients with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Following isolation, cells were subjected to spheroid culture on non-adherent plates. Of the 57 cases, successful culture was achieved in 48 cases, among which the average ratio of CD44+/CD24- breast cancer cells increased from 13.8% in primary tumors to 61.6% in spheroids. A modest number of spheroid cells successfully engrafted in mice and subsequently re-differentiated within the murine environment, confirming their stemness. ER expression in spheroid cells exhibited negative conversion in 52.1% of cases. The proportion of Twist-, Snail-, and Vimentin-positive cells increased from 43.8%, 12.9%, and 7.7-75.0%, 58.1%, and 37.7%, respectively. ER-positive, HER2-negative breast cancer stem cells were classified into two groups using DNA microarrays. Gene Ontology analysis unveiled higher expression of immune response-related genes in one group and protein binding-associated genes in the other. We demonstrated stable and selective culture of breast cancer stem cells from patient-derived breast cancer tissue using spheroid cultures.

Cancer stem cells: Masters of all traits

Cancer is a heterogeneous disease, which contributes to its rapid progression and therapeutic failure. Besides interpatient tumor heterogeneity, tumors within a single patient can present with a heterogeneous mix of genetically and phenotypically distinct subclones. These unique subclones can significantly impact the traits of cancer. With the plasticity that intratumoral heterogeneity provides, cancers can easily adapt to changes in their microenvironment and therapeutic exposure. Indeed, tumor cells dynamically shift between a more differentiated, rapidly proliferating state with limited tumorigenic potential and a cancer stem cell (CSC)-like state that resembles undifferentiated cellular precursors and is associated with high tumorigenicity. In this context, CSCs are functionally located at the apex of the tumor hierarchy, contributing to the initiation, maintenance, and progression of tumors, as they also represent the subpopulation of tumor cells most resistant to conventional anti-cancer therapies. Although the CSC model is well established, it is constantly evolving and being reshaped by advancing knowledge on the roles of CSCs in different cancer types. Here, we review the current evidence of how CSCs play a pivotal role in providing the many traits of aggressive tumors while simultaneously evading immunosurveillance and anti-cancer therapy in several cancer types. We discuss the key traits and characteristics of CSCs to provide updated insights into CSC biology and highlight its implications for therapeutic development and improved treatment of aggressive cancers.

RANKL regulates differentially breast cancer stem cell properties through its RANK and LGR4 receptors

BACKGROUND

Breast cancer stem cells (BCSC) are a subpopulation responsible for cancer resistance and relapse. The receptor activator of nuclear factor kappa-Β ligand (RANKL) is a cytokine capable of activating RANK and LGR4 receptors. RANKL/RANK signaling maintains the self-renewal of BCSCs, however, the effect of RANKL via LGR4 remains unclear. Evidence from osteoclasts suggests that RANKL/LGR4 axis disrupts RANK signaling, leading to opposing cellular responses. Anti-RANKL inhibitors are potential agents for eradicating CSCs, but their effect on RANKL/LGR4 signal has not been demonstrated.

OBJECTIVE

This project aimed to elucidate the role of RANKL in regulating stemness depending on the expression of its receptors.

METHODS

We use in vitro and in vivo approaches to evaluate the effects of RANKL inhibition in stemness in low or high-LGR4 expressing cells. Furthermore, we analyze the effects of RANKL stimulation on the stemness of LGR4 or RANK overexpressing cells. Additionally, we evaluated the impact of RANKL/LGR4 signaling in the activity of Wnt/β-catenin and NF-κB signaling pathways.

RESULTS

Our findings indicated that elevated RANKL expression is related to a favorable prognosis in patients with high LGR4 levels. Furthermore, RANKL inhibition decreased BCSC properties in LGR4-low cell lines, while it promoted migration in LGR4-high cells. Additionally, the RANKL/RANK axis activated NF-κB signaling and enhanced BCSCs in RANK-overexpressing cells. In contrast, in LGR4-overexpressing cells, RANKL failed to activate NF-κB but instead inhibited the Wnt/β-catenin pathway, leading to a reduction in BCSCs.

CONCLUSION

Our findings suggest that RANKL exerts different responses according to the expression of its receptors.

Sertaconazole, an Imidazole Antifungal Agent, Suppresses the Stemness of Breast Cancer Cells by Inhibiting Stat3 Signaling

BACKGROUND/AIM

Breast cancer stem cells (BCSCs) are a subpopulation of tumor cells that play a role in therapeutic resistance. In this study, we demonstrated that sertaconazole, an antifungal agent, displayed a potent inhibition on cancer stem cells (CSCs) and investigated the mechanism of action involved in its anti-BCSC effect.

MATERIALS AND METHODS

The effect of sertaconazole on BCSCs was investigated using a mammosphere formation assay, a colony formation assay, and a cell migration assay. In addition, CD44high/CD24low and ALDEFLOR analyses, an apoptosis assay, quantitative real-time PCR, western blotting, an electrophoretic mobility shift assay, and a cytokine profiling assay were performed.

RESULTS

Sertaconazole inhibited cell proliferation, colony formation, cell migration, mammosphere formation, and mammosphere proliferation. It also induced apoptosis of breast cancer cells. It decreased the subpopulation of CD44high/CD24low and aldehyde dehydrogenase-expressing cells. It also reduced the DNA binding of Stat3 and nuclear protein expression levels of phosphorylated Stat3. Furthermore, it reduced the IL-8 mRNA levels of the mammosphere.

CONCLUSION

Sertaconazole can inhibit the Stat3 and IL-8 signaling pathways and induce CSC death. Thus, sertaconazole might be a potential inhibitor of BCSCs.

Identification of Crucial Cancer Stem Cell Genes Linked to Immune Cell Infiltration and Survival in Hepatocellular Carcinoma

Hepatocellular carcinoma is characterized by high recurrence rates and poor prognosis. Cancer stem cells contribute to tumor heterogeneity, treatment resistance, and recurrence. This study aims to identify key genes associated with stemness and immune cell infiltration in HCC. We analyzed RNA sequencing data from The Cancer Genome Atlas to calculate mRNA expression-based stemness index in HCC. A weighted gene co-expression network analysis was performed to identify stemness-related gene modules. A single-sample gene set enrichment analysis was used to evaluate immune cell infiltration. Key genes were validated using RT-qPCR. The mRNAsi was significantly higher in HCC tissues compared to adjacent normal tissues and correlated with poor overall survival. WGCNA and subsequent analyses identified 10 key genes, including minichromosome maintenance complex component 2, cell division cycle 6, forkhead box M1, NIMA-related kinase 2, Holliday junction recognition protein, DNA topoisomerase II alpha, denticleless E3 ubiquitin protein ligase homolog, maternal embryonic leucine zipper kinase, protein regulator of cytokinesis 1, and kinesin family member C1, associated with stemness and low immune cell infiltration. These genes were significantly upregulated in HCC tissues. A functional enrichment analysis revealed their involvement in cell cycle regulation. This study identified 10 key genes related to stemness and immune cell infiltration in HCC. These genes, primarily involved in cell cycle regulation, may serve as potential targets for developing more effective treatments to reduce HCC recurrence and improve patient outcomes.

Understanding, diagnosing, and treating pancreatic cancer from the perspective of telomeres and telomerase

Telomerase is associated with cellular aging, and its presence limits cellular lifespan. Telomerase by preventing telomere shortening can extend the number of cell divisions for cancer cells. In adult pancreatic cells, telomeres gradually shorten, while in precancerous lesions of cancer, telomeres in cells are usually significantly shortened. At this time, telomerase is still in an inactive state, and it is not until before and after the onset of cancer that telomerase is reactivated, causing cancer cells to proliferate. Methylation of the telomerase reverse transcriptase (TERT) promoter and regulation of telomerase by lactate dehydrogenase B (LDHB) is the mechanism of telomerase reactivation in pancreatic cancer. Understanding the role of telomeres and telomerase in pancreatic cancer will help to diagnose and initiate targeted therapy as early as possible. This article reviews the role of telomeres and telomerase as biomarkers in the development of pancreatic cancer and the progress of research on telomeres and telomerase as targets for therapeutic intervention.

The role of the miR-30a-5p/BCL2L11 pathway in rosmarinic acid-induced apoptosis in MDA-MB-231-derived breast cancer stem-like cells

Background

Rosmarinic acid (RA), a natural phenolic acid, exhibits promising anti-cancer properties. The abnormal expression of microRNA (miRNA) regulates the gene expression and plays a role as an oncogenic or tumor suppressor in TNBC. However, the biological role of RA in miR-30a-5p on BCL2L11 during MDA-MB-231 induced breast cancer stem-like cells (BCSCs) progression and its regulatory mechanism have not been elucidated.

Objective

To investigate whether RA inhibited the silencing effect of miR-30a-5p on the BCL2L11 gene and promoted apoptosis in BCSCs.

Materials and Methods

We assessed the migration, colony formation, proliferation, cell cycle, and apoptosis of BCSCs after RA treatment using the wound-healing assay, colony formation assay, CCK-8 assay, and flow cytometry, respectively. The expression of mRNA and protein levels of BCL-2, Bax, BCL2L11, and P53 genes in BCSCs after RA treatment was obtained by real-time polymerase chain reaction and Western blot. Differential miRNA expression in BCSCs was analyzed by high-throughput sequencing. Targetscan was utilized to predict the targets of miR-30a-5p. The dual luciferase reporter system was used for validation of the miR-30a-5p target.

Results

Wound-healing assay, colony formation assay, CCK-8 assay, and cell cycle assay results showed that RA inhibited migration, colony formation and viability of BCSCs, and cell cycle arrest in the G0-G1 phase. At the highest dose of RA, we noticed cell atrophy, while the arrest rate at 100 μg/mL RA surpassed that at 200 μg/mL RA. Apoptotic cells appeared early (Membrane Associated Protein V FITC+, PI-) or late (Membrane Associated Protein V FITC+, PI+) upon administration of 200 μg/mL RA, Using high-throughput sequencing to compare the differences in miRNA expression, we detected downregulation of miR-30a-5p expression, and the results of dual luciferase reporter gene analysis indicated that BCL2L11 was a direct target of miR-30a-5p.

Conclusion

RA inhibited the silencing effect of miR-30a-5p on the BCL2L11 gene and enhanced apoptosis in BCSCs.

PUM1-TRAF3 fusion protein activates non-canonical NF-κB signaling via rescued NIK in biliary tract cancer

Discovery and verification of diagnostic or therapeutic biomarkers for biliary tract cancer (BTC) is challenging owing to the low prevalence of the disease. Here, we identified and investigated the clinical impact of a fusion gene, Pumilio1-tumor necrosis factor receptor-associated factor 3 (PUM1-TRAF3), caused by 1;14 chromosomal translocation in BTC. PUM1-TRAF3 was initially identified in the RNA-sequencing of five BTC surgical tissues and confirmed by fluorescence in situ hybridization. Expression of the fusion gene was validated in an expanded cohort (5/55, 9.1%). Establishment and molecular assessment of PUM1-TRAF3 expressing BTC cells revealed that PUM1-TRAF3 activates non-canonical NF-κB signaling via NF-κB-inducing kinase (NIK). Abnormal TRAF3 activity, driven by competitive binding of PUM1-TRAF3 and TRAF3 to NIK, led to NIK rescue followed by P52/RelB nuclear translocation, all of which were reverted by an NIK inhibitor. The elevated expression of NIK and activated NF-κB signaling was observed in the PUM1-TRAF3-expressing regions of patient tissues. Expression of the PUM1-TRAF3 fusion was significantly correlated with strong NIK expression, which is associated with a poorer prognosis for patients with BTC. Overall, our study identifies a new fusion gene, PUM1-TRAF3, that activates NIK and non-canonical NF-κB signaling, which may be beneficial for developing precise treatment strategies for BTC.

CD57 defines a novel cancer stem cell that drive invasion of diffuse pediatric-type high grade gliomas

BACKGROUND

Diffuse invasion remains a primary cause of treatment failure in pediatric high-grade glioma (pHGG). Identifying cellular driver(s) of pHGG invasion is needed for anti-invasion therapies.

METHODS

Ten highly invasive patient-derived orthotopic xenograft (PDOX) models of pHGG were subjected to isolation of matching pairs of invasive (HGGINV) and tumor core (HGGTC) cells.

RESULTS

pHGGINV cells were intrinsically more invasive than their matching pHGGTC cells. CSC profiling revealed co-positivity of CD133 and CD57 and identified CD57+CD133- cells as the most abundant CSCs in the invasive front. In addition to discovering a new order of self-renewal capacities, i.e., CD57+CD133- > CD57+CD133+ > CD57-CD133+ > CD57-CD133- cells, we showed that CSC hierarchy was impacted by their spatial locations, and the highest self-renewal capacities were found in CD57+CD133- cells in the HGGINV front (HGGINV/CD57+CD133- cells) mediated by NANOG and SHH over-expression. Direct implantation of CD57+ (CD57+/CD133- and CD57+/CD133+) cells into mouse brains reconstituted diffusely invasion, while depleting CD57+ cells (i.e., CD57-CD133+) abrogated pHGG invasion.

CONCLUSION

We revealed significantly increased invasive capacities in HGGINV cells, confirmed CD57 as a novel glioma stem cell marker, identified CD57+CD133- and CD57+CD133+ cells as a new cellular driver of pHGG invasion and suggested a new dual-mode hierarchy of HGG stem cells.

Lipid metabolism dynamics in cancer stem cells: potential targets for cancers

Cancer stem cells (CSCs) represent a small subset of heterogeneous cells within tumors that possess the ability to self-renew and initiate tumorigenesis. They serve as potential drivers for tumor initiation, metastasis, recurrence, and drug resistance. Recent research has demonstrated that the stemness preservation of CSCs is heavily reliant on their unique lipid metabolism alterations, enabling them to maintain their own environmental homeostasis through various mechanisms. The primary objectives involve augmenting intracellular fatty acid (FA) content to bolster energy supply, promoting β-oxidation of FA to optimize energy utilization, and elevating the mevalonate (MVA) pathway for efficient cholesterol synthesis. Additionally, lipid droplets (LDs) can serve as alternative energy sources in the presence of glycolysis blockade in CSCs, thereby safeguarding FA from peroxidation. Furthermore, the interplay between autophagy and lipid metabolism facilitates rapid adaptation of CSCs to the harsh microenvironment induced by chemotherapy. In this review, we comprehensively review recent studies pertaining to lipid metabolism in CSCs and provide a concise overview of the indispensable role played by LDs, FA, cholesterol metabolism, and autophagy in maintaining the stemness of CSCs.

Epigenetic regulation of breast cancer metastasis

Breast cancer is the most frequently diagnosed malignancy and the second leading cause of cancer-related mortality among women worldwide. Recurrent metastasis is associated with poor patient outcomes and poses a significant challenge in breast cancer therapies. Cancer cells adapting to a new tissue microenvironment is the key event in distant metastasis development, where the disseminating tumor cells are likely to acquire genetic and epigenetic alterations during the process of metastatic colonization. Despite several decades of research in this field, the exact mechanisms governing metastasis are not fully understood. However, emerging body of evidence indicates that in addition to genetic changes, epigenetic reprogramming of cancer cells and the metastatic niche are paramount toward successful metastasis. Here, we review and discuss the latest knowledge about the salient attributes of metastasis and epigenetic regulation in breast cancer and crucial research domains that need further investigation.

Cancer stem cell hypothesis 2.0 in glioblastoma: Where are we now and where are we going?

Over the past 2 decades, the cancer stem cell (CSC) hypothesis has provided insight into many malignant tumors, including glioblastoma (GBM). Cancer stem cells have been identified in patient-derived tumors and in some mouse models, allowing for a deeper understanding of cellular and molecular mechanisms underlying GBM growth and therapeutic resistance. The CSC hypothesis has been the cornerstone of cellular heterogeneity, providing a conceptual and technical framework to explain this longstanding phenotype in GBM. This hypothesis has evolved to fit recent insights into how cellular plasticity drives tumor growth to suggest that CSCs do not represent a distinct population but rather a cellular state with substantial plasticity that can be achieved by non-CSCs under specific conditions. This has further been reinforced by advances in genomics, including single-cell approaches, that have used the CSC hypothesis to identify multiple putative CSC states with unique properties, including specific developmental and metabolic programs. In this review, we provide a historical perspective on the CSC hypothesis and its recent evolution, with a focus on key functional phenotypes, and provide an update on the definition for its use in future genomic studies.

Cold Atmospheric Plasma: An Emerging Immunomodulatory Therapy

Cold atmospheric plasma (CAP) is a novel technology that generates a unique combination of reactive oxygen and nitrogen species (ROS/RNS), electric fields, and UV radiation. CAP has shown promise in regulating the immune system and has potential clinical applications in wound healing, cancer treatment, and infection control. This review provides an overview of the immunological regulation activity of CAP, highlighting its substantial impact on cytokines production, immune cell phagocytosis, and immune cell proliferation. CAP has also been demonstrated to have potent therapeutic effect in anti‐inflammation, wound repair, viral and bacterial infections. Furthermore, CAP has been investigated as an adjuvant therapy for tumor treatment, eliciting a robust antitumor immune response and remarkable synergistic effects in diverse combination therapies. Further research is needed to fully understand the mechanisms underlying the effects of CAP on the immune system and to optimize its clinical application.

Evaluation of the Effects of Opium on the Expression of SOX2 and OCT4 in Wistar Rat Bladder

BACKGROUND

Bladder cancer is a malignancy greatly affected by behavioral habits. The aim of this study was to examine the effect of opium on changes in the expression of OCT4 and SOX2 in the bladder tissue of rats.

METHOD

Thirty six rats were divided into six groups: 24 rats in the addicted group received morphine and opium for 4 months with 12 rats in the control group. Blood testing was done for the evaluation of CBC, MDA, and TAC. The bladder tissue was removed and checked by histopathological examination. All total RNA was extracted, then cDNAs were synthesized and the OCT4 and SOX2 gene expressions were evaluated by Real-time PCR.

RESULTS

The OCT4 mRNA expression level in the opium group of rats was significantly increased compared to the control group (13.5 and 6.8 fold in males and females respectively). Also, in the morphine group, similar augmentation was detected (3.8 and 6.7 fold in males and females respectively). The SOX2 mRNA over-expression level was seen in the morphine group of both genders as compared to the control group (3.7 and 4.2 fold in male and female respectively) but in the opium group, enhancement of mRNA level was seen only in males (6.6 fold). Opium increases both OCT4 and SOX2 expression more than morphine in male rats, but in female rats, SOX2 is increased more by morphine.

CONCLUSION

Over expression of OCT4 and SOX2 was observed in rats treated with opium and morphine. Increased OCT4 and SOX2 expression was seen in opium-treated male rats, but in female rats, SOX2 was increased more by morphine.

Epithelial and Mesenchymal-like Pancreatic Cancer Cells Exhibit Different Stem Cell Phenotypes Associated with Different Metastatic Propensities

Pancreatic ductal adenocarcinoma (PDAC) is mostly diagnosed at advanced or even metastasized stages, limiting the prognoses of patients. Metastasis requires high tumor cell plasticity, implying phenotypic switching in response to changing environments. Here, epithelial-mesenchymal transition (EMT), being associated with an increase in cancer stem cell (CSC) properties, and its reversion are important. Since it is poorly understood whether different CSC phenotypes exist along the EMT axis and how these impact malignancy-associated properties, we aimed to characterize CSC populations of epithelial and mesenchymal-like PDAC cells. Single-cell cloning revealed CSC (Holoclone) and non-CSC (Paraclone) clones from the PDAC cell lines Panc1 and Panc89. The Panc1 Holoclone cells showed a mesenchymal-like phenotype, dominated by a high expression of the stemness marker Nestin, while the Panc89 Holoclone cells exhibited a SOX2-dominated epithelial phenotype. The Panc89 Holoclone cells showed enhanced cell growth and a self-renewal capacity but slow cluster-like invasion. Contrarily, the Panc1 Holoclone cells showed slower cell growth and self-renewal ability but were highly invasive. Moreover, cell variants differentially responded to chemotherapy. In vivo, the Panc1 and Panc89 cell variants significantly differed regarding the number and size of metastases, as well as organ manifestation, leading to different survival outcomes. Overall, these data support the existence of different CSC phenotypes along the EMT axis in PDAC, manifesting different metastatic propensities.

Aldehyde Dehydrogenase-1A1 (ALDH1A1): The Novel Regulator of Chemoresistance in Pancreatic Cancer Cells

Aldehyde dehydrogenase-1A1 (ALDH1A1), a member of a superfamily of 19 isozymes, exhibits various biological functions and is involved in several important physiological and pathological processes, including those associated with various diseases including cancers such as pancreatic cancer. Chemotherapy is one of the most important strategies for the treatment of pancreatic cancer; however, the chemoresistance exhibited by pancreatic cancer cells is a leading cause of chemotherapy failure. It has been reported that overexpression of ALDH1A1 significantly correlates with poor prognosis and tumor aggressiveness, and is clinically associated with chemoresistance. Additionally, ALDH1A1 may serve as a novel regulator for the diagnosis and prognosis of cancer resistance. In particular, ALDH1A1 can promote cancer progression by facilitating the manifestation of cancer stem cell properties. However, the molecular mechanism by which ALDH1A1 clinically regulates the development of chemoresistance, and its role in prognosis and cancer stem cells, including pancreatic cancer stem cells, remain unclear. Therefore, the current review aims to summarize the clinical functions of ALDH1A1 as a novel regulator of chemoresistance, prognosis, and cancer stem cell development in pancreatic cancer.

scMuffin: an R package to disentangle solid tumor heterogeneity by single-cell gene expression analysis

INTRODUCTION

Single-cell (SC) gene expression analysis is crucial to dissect the complex cellular heterogeneity of solid tumors, which is one of the main obstacles for the development of effective cancer treatments. Such tumors typically contain a mixture of cells with aberrant genomic and transcriptomic profiles affecting specific sub-populations that might have a pivotal role in cancer progression, whose identification eludes bulk RNA-sequencing approaches. We present scMuffin, an R package that enables the characterization of cell identity in solid tumors on the basis of a various and complementary analyses on SC gene expression data.

RESULTS

scMuffin provides a series of functions to calculate qualitative and quantitative scores, such as: expression of marker sets for normal and tumor conditions, pathway activity, cell state trajectories, Copy Number Variations, transcriptional complexity and proliferation state. Thus, scMuffin facilitates the combination of various evidences that can be used to distinguish normal and tumoral cells, define cell identities, cluster cells in different ways, link genomic aberrations to phenotypes and identify subtle differences between cell subtypes or cell states. We analysed public SC expression datasets of human high-grade gliomas as a proof-of-concept to show the value of scMuffin and illustrate its user interface. Nevertheless, these analyses lead to interesting findings, which suggest that some chromosomal amplifications might underlie the invasive tumor phenotype and the presence of cells that possess tumor initiating cells characteristics.

CONCLUSIONS

The analyses offered by scMuffin and the results achieved in the case study show that our tool helps addressing the main challenges in the bioinformatics analysis of SC expression data from solid tumors.

On-chip modeling of tumor evolution: Advances, challenges and opportunities

Tumor evolution is the accumulation of various tumor cell behaviors from tumorigenesis to tumor metastasis and is regulated by the tumor microenvironment (TME). However, the mechanism of solid tumor progression has not been completely elucidated, and thus, the development of tumor therapy is still limited. Recently, Tumor chips constructed by culturing tumor cells and stromal cells on microfluidic chips have demonstrated great potential in modeling solid tumors and visualizing tumor cell behaviors to exploit tumor progression. Herein, we review the methods of developing engineered solid tumors on microfluidic chips in terms of tumor types, cell resources and patterns, the extracellular matrix and the components of the TME, and summarize the recent advances of microfluidic chips in demonstrating tumor cell behaviors, including proliferation, epithelial-to-mesenchymal transition, migration, intravasation, extravasation and immune escape of tumor cells. We also outline the combination of tumor organoids and microfluidic chips to elaborate tumor organoid-on-a-chip platforms, as well as the practical limitations that must be overcome.

Single-Cell Transcriptomics for Unlocking Personalized Cancer Immunotherapy: Toward Targeting the Origin of Tumor Development Immunogenicity

Cancer immunotherapy is a promising approach for treating malignancies through the activation of anti-tumor immunity. However, the effectiveness and safety of immunotherapy can be limited by tumor complexity and heterogeneity, caused by the diverse molecular and cellular features of tumors and their microenvironments. Undifferentiated tumor cell niches, which we refer to as the "Origin of Tumor Development" (OTD) cellular population, are believed to be the source of these variations and cellular heterogeneity. From our perspective, the existence of distinct features within the OTD is expected to play a significant role in shaping the unique tumor characteristics observed in each patient. Single-cell transcriptomics is a high-resolution and high-throughput technique that provides insights into the genetic signatures of individual tumor cells, revealing mechanisms of tumor development, progression, and immune evasion. In this review, we explain how single-cell transcriptomics can be used to develop personalized cancer immunotherapy by identifying potential biomarkers and targets specific to each patient, such as immune checkpoint and tumor-infiltrating lymphocyte function, for targeting the OTD. Furthermore, in addition to offering a possible workflow, we discuss the future directions of, and perspectives on, single-cell transcriptomics, such as the development of powerful analytical tools and databases, that will aid in unlocking personalized cancer immunotherapy through the targeting of the patient's cellular OTD.

macroH2A2 antagonizes epigenetic programs of stemness in glioblastoma

Self-renewal is a crucial property of glioblastoma cells that is enabled by the choreographed functions of chromatin regulators and transcription factors. Identifying targetable epigenetic mechanisms of self-renewal could therefore represent an important step toward developing effective treatments for this universally lethal cancer. Here we uncover an epigenetic axis of self-renewal mediated by the histone variant macroH2A2. With omics and functional assays deploying patient-derived in vitro and in vivo models, we show that macroH2A2 shapes chromatin accessibility at enhancer elements to antagonize transcriptional programs of self-renewal. macroH2A2 also sensitizes cells to small molecule-mediated cell death via activation of a viral mimicry response. Consistent with these results, our analyses of clinical cohorts indicate that high transcriptional levels of this histone variant are associated with better prognosis of high-grade glioma patients. Our results reveal a targetable epigenetic mechanism of self-renewal controlled by macroH2A2 and suggest additional treatment approaches for glioblastoma patients.

Emerging Intrinsic Therapeutic Targets for Metastatic Breast Cancer

Breast cancer is now the most common cancer worldwide, and it is also the main cause of cancer-related death in women. Survival rates for female breast cancer have significantly improved due to early diagnosis and better treatment. Nevertheless, for patients with advanced or metastatic breast cancer, the survival rate is still low, reflecting a need for the development of new therapies. Mechanistic insights into metastatic breast cancer have provided excellent opportunities for developing novel therapeutic strategies. Although high-throughput approaches have identified several therapeutic targets in metastatic disease, some subtypes such as triple-negative breast cancer do not yet have an apparent tumor-specific receptor or pathway to target. Therefore, exploring new druggable targets in metastatic disease is a high clinical priority. In this review, we summarize the emerging intrinsic therapeutic targets for metastatic breast cancer, including cyclin D-dependent kinases CDK4 and CDK6, the PI3K/AKT/mTOR pathway, the insulin/IGF1R pathway, the EGFR/HER family, the JAK/STAT pathway, poly(ADP-ribose) polymerases (PARP), TROP-2, Src kinases, histone modification enzymes, activated growth factor receptors, androgen receptors, breast cancer stem cells, matrix metalloproteinases, and immune checkpoint proteins. We also review the latest development in breast cancer immunotherapy. Drugs that target these molecules/pathways are either already FDA-approved or currently being tested in clinical trials.

Identification and Clinical Significance of Pancreatic Cancer Stem Cells and Their Chemotherapeutic Drug Resistance

Pancreatic cancer ranks in the 10th-11th position among cancers affecting men in Taiwan, besides being a rather difficult-to-treat disease. The overall 5-year survival rate of pancreatic cancer is only 5-10%, while that of resectable pancreatic cancer is still approximately 15-20%. Cancer stem cells possess intrinsic detoxifying mechanisms that allow them to survive against conventional therapy by developing multidrug resistance. This study was conducted to investigate how to overcome chemoresistance and its mechanisms in pancreatic cancer stem cells (CSCs) using gemcitabine-resistant pancreatic cancer cell lines. Pancreatic CSCs were identified from human pancreatic cancer lines. To determine whether CSCs possess a chemoresistant phenotype, the sensitivity of unselected tumor cells, sorted CSCs, and tumor spheroid cells to fluorouracil (5-FU), gemcitabine (GEM), and cisplatin was analyzed under stem cell conditions or differentiating conditions. Although the mechanisms underlying multidrug resistance in CSCs are poorly understood, ABC transporters such as ABCG2, ABCB1, and ABCC1 are believed to be responsible. Therefore, we measured the mRNA expression levels of ABCG2, ABCB1, and ABCC1 by real-time RT-PCR. Our results showed that no significant differences were found in the effects of different concentrations of gemcitabine on CSCs CD44+/EpCAM+ of various PDAC cell line cultures (BxPC-3, Capan-1, and PANC-1). There was also no difference between CSCs and non-CSCs. Gemcitabine-resistant cells exhibited distinct morphological changes, including a spindle-shaped morphology, the appearance of pseudopodia, and reduced adhesion characteristics of transformed fibroblasts. These cells were found to be more invasive and migratory, and showed increased vimentin expression and decreased E-cadherin expression. Immunofluorescence and immunoblotting experiments demonstrated increased nuclear localization of total β-catenin. These alterations are hallmarks of epithelial-to-mesenchymal transition (EMT). Resistant cells showed activation of the receptor protein tyrosine kinase c-Met and increased expression of the stem cell marker cluster of differentiation (CD) 24, CD44, and epithelial specific antigen (ESA). We concluded that the expression of the ABCG2 transporter protein was significantly higher in CD44+ and EpCAM+ CSCs of PDAC cell lines. Cancer stem-like cells exhibited chemoresistance. Gemcitabine-resistant pancreatic tumor cells were associated with EMT, a more aggressive and invasive phenotype of numerous solid tumors. Increased phosphorylation of c-Met may also be related to chemoresistance, and EMT and could be used as an attractive adjunctive chemotherapeutic target in pancreatic cancer.

Can precancerous stem cells be risk markers for malignant transformation in the oral mucosa?

Accurate assessment of the carcinogenic potential of oral mucosal diseases can significantly reduce the prevalence of oral cancer. We speculate that precancerous stem cells (pCSCs) arise during the evolution of carcinomas based on long-term experimental findings, published literature, and the cancer stem cell (CSC) theory, wherein pCSCs exist in precancerous lesions and have characteristics of both CSCs and normal stem cells. This apparently contradictory feature may be the foundation of the reversible transformation of precancerous lesions. Predicting malignant transformation in potentially malignant oral illnesses would allow for focused treatment, prognosis, and secondary prevention. Currently available clinical assays for chromosomal instability and DNA aneuploidy have several deficiencies. We hope that our study will increase attention to pCSC research and lead to the development of novel strategies for the prevention and treatment of oral cancer by identifying pCSC markers.

In silico designing and expression of novel recombinant construct containing the variable part of CD44 extracellular domain for prediagnostic breast cancer

BACKGROUND

CD44, as a tumor-associated marker, can be used to detect stem cells in breast cancer. While CD44 is expressed in normal epithelial cells, carcinoma cells overexpress CD44.

AIMS

In the current study, we designed a recombinant protein that included the variable component of the CD44 (CD44v) extracellular domain to apply in clinical diagnosis of breast cancer.

METHODS

A total of 100 CD44v amino-acid residues were determined, and the structure was examined using bioinformatics tools. The construct was inserted into the PET28a vector and transformed in E. coli BL21(DE3). A nearly 12 kDa fusion protein was obtained by Ni-NTA affinity metal chromatography. Recombinant CD44v was examined by Western blotting, ELISA, and immunohistochemistry (IHC) assays.

RESULTS

The findings revealed that the structure of rCD44v was stable, and its antigenic domain was exposed. The recombinant CD44v was confirmed by western blotting, and the presence of antibodies against recombinant CD44v protein in the patient's serum was detected by the ELISA. Our data demonstrated a link between CD44v serum levels and the prevalence of breast cancer.

CONCLUSION

Assessments of antiCD44v antibodies with rCD44v could be a useful tool for identifying breast cancer in its early stages, which can lead to better outcomes.

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

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

Preclinical and Clinical Trials of New Treatment Strategies Targeting Cancer Stem Cells in Subtypes of Breast Cancer

Breast cancer (BC) can be classified into various histological subtypes, each associated with different prognoses and treatment options, including surgery, radiation, chemotherapy, and endocrine therapy. Despite advances in this area, many patients still face treatment failure, the risk of metastasis, and disease recurrence, which can ultimately lead to death. Mammary tumors, like other solid tumors, contain a population of small cells known as cancer stem-like cells (CSCs) that have high tumorigenic potential and are involved in cancer initiation, progression, metastasis, tumor recurrence, and resistance to therapy. Therefore, designing therapies specifically targeting at CSCs could help to control the growth of this cell population, leading to increased survival rates for BC patients. In this review, we discuss the characteristics of CSCs, their surface biomarkers, and the active signaling pathways associated with the acquisition of stemness in BC. We also cover preclinical and clinical studies that focus on evaluating new therapy systems targeted at CSCs in BC through various combinations of treatments, targeted delivery systems, and potential new drugs that inhibit the properties that allow these cells to survive and proliferate.

Notch signaling sculpts the stem cell niche

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

The Glycosylation of Immune Checkpoints and Their Applications in Oncology

Tumor therapies have entered the immunotherapy era. Immune checkpoint inhibitors have achieved tremendous success, with some patients achieving long-term tumor control. Tumors, on the other hand, can still accomplish immune evasion, which is aided by immune checkpoints. The majority of immune checkpoints are membrane glycoproteins, and abnormal tumor glycosylation may alter how the immune system perceives tumors, affecting the body's anti-tumor immunity. Furthermore, RNA can also be glycosylated, and GlycoRNA is important to the immune system. Glycosylation has emerged as a new hallmark of tumors, with glycosylation being considered a potential therapeutic approach. The glycosylation modification of immune checkpoints and the most recent advances in glycosylation-targeted immunotherapy are discussed in this review.

A systems biology investigation of curcumin potency against TGF-β-induced EMT signaling in lung cancer

Curcumin (diferuloylmethane) is bioactive phenolic compound which exerts diverse antimetastatic effect. Several studies have reported the antimetastatic effect of curcumin by its ability to modulate the epithelial-to-mesenchymal transition (EMT) process in different cancers, but underlying molecular mechanism is poorly understood. EMT is a highly conserved biological process in which epithelial cells acquire mesenchymal-like characteristics by losing their cell-cell junctions and polarity. As a consequence, deviation in cellular mechanism leads to cancer metastasis and thereby death. In this perspective, we explored the antimetastatic potential and mechanism of curcumin on the EMT process by establishing in vitro EMT model in lungs cancer (A549) cells induced by TGF-β1. Our results showed that curcumin mitigates EMT by regulating the expression of crucial mesenchymal markers such as MMP2, vimentin and N-cadherin. Besides, the transcriptional analysis revealed that the curcumin treatment differentially regulated the expression of 75 genes in NanoString nCounter platform. Further protein-protein interaction network and clusters analysis of differentially expressed genes revealed their involvement in essential biological processes that plays a key role during EMT transition. Altogether, the study provides a comprehensive overview of the antimetastatic potential of curcumin in TGF-β1-induced EMT in lung cancer cells.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03360-7.

Pleiotropic effects of DCLK1 in cancer and cancer stem cells

Doublecortin-like kinase 1 (DCLK1), a protein molecule, has been identified as a tumor stem cell marker in the cancer cells of gastrointestinal, pancreas, and human colon. DCLK1 expression in cancers, such as breast carcinoma, lung carcinoma, hepatic cell carcinoma, tuft cells, and human cholangiocarcinoma, has shown a way to target the DCLK1 gene and downregulate its expression. Several studies have discussed the inhibition of tumor cell proliferation along with neoplastic cell arrest when the DCLK1 gene, which is expressed in both cancer and normal cells, was targeted successfully. In addition, previous studies have shown that DCLK1 plays a vital role in various cancer metastases. The correlation of DCLK1 with numerous stem cell receptors, signaling pathways, and genes suggests its direct or an indirect role in promoting tumorigenesis. Moreover, the impact of DCLK1 was found to be related to the functioning of an oncogene. The downregulation of DCLK1 expression by using targeted strategies, such as embracing the use of siRNA, miRNA, CRISPR/Cas9 technology, nanomolecules, specific monoclonal antibodies, and silencing the pathways regulated by DCLK1, has shown promising results in both in vitro and in vivo studies on gastrointestinal (GI) cancers. In this review, we will discuss about the present understanding of DCLK1 and its role in the progression of GI cancer and metastasis.

Crosstalk between Ca2+ Signaling and Cancer Stemness: The Link to Cisplatin Resistance

In the fight against cancer, therapeutic strategies using cisplatin are severely limited by the appearance of a resistant phenotype. While cisplatin is usually efficient at the beginning of the treatment, several patients endure resistance to this agent and face relapse. One of the reasons for this resistant phenotype is the emergence of a cell subpopulation known as cancer stem cells (CSCs). Due to their quiescent phenotype and self-renewal abilities, these cells have recently been recognized as a crucial field of investigation in cancer and treatment resistance. Changes in intracellular calcium (Ca²⁺) through Ca²⁺ channel activity are essential for many cellular processes such as proliferation, migration, differentiation, and survival in various cell types. It is now proved that altered Ca²⁺ signaling is a hallmark of cancer, and several Ca²⁺ channels have been linked to CSC functions and therapy resistance. Moreover, cisplatin was shown to interfere with Ca²⁺ homeostasis; thus, it is considered likely that cisplatin-induced aberrant Ca²⁺ signaling is linked to CSCs biology and, therefore, therapy failure. The molecular signature defining the resistant phenotype varies between tumors, and the number of resistance mechanisms activated in response to a range of pressures dictates the global degree of cisplatin resistance. However, if we can understand the molecular mechanisms linking Ca²⁺ to cisplatin-induced resistance and CSC behaviors, alternative and novel therapeutic strategies could be considered. In this review, we examine how cisplatin interferes with Ca²⁺ homeostasis in tumor cells. We also summarize how cisplatin induces CSC markers in cancer. Finally, we highlight the role of Ca²⁺ in cancer stemness and focus on how they are involved in cisplatin-induced resistance through the increase of cancer stem cell populations and via specific pathways.

Lipocalin-2 inhibits pancreatic cancer stemness via the AKT/c-Jun pathway

Cancer stem cells (CSCs) are involved in cancer recurrence and metastasis owing to their self-renewal properties and drug-resistance capacity. Lipocalin-2 (Lcn2) of the lipocalin superfamily is highly expressed in pancreatic cancer. Nevertheless, reports on the involvement of Lcn2 in the regulation of pancreatic CSC properties are scant. This study is purposed to investigate whether Lcn2 plays a crucial role in CSC renewal and stemness maintenance in pancreatic carcinoma. Immunohistochemistry results of tumor tissue chips together with Gene Expression Omnibus sequencing files confirmed that Lcn2 is highly expressed in pancreatic carcinoma compared with that in normal tissues. The exogenous expression of Lcn2 attenuated CSC-associated SOX2, CD44, and EpCAM expression and suppressed sarcosphere formation and tumorigenesis in the pancreatic carcinoma cell line PANC-1, which showed low expression of Lcn2. However, Lcn2 knockout in BxPC-3 cell line, which presented high Lcn2 expression, promoted CSC stemness, further enhancing sarcosphere formation and tumorigenesis. Moreover, Lcn2 was found to regulate stemness in pancreatic cancer depending on the activation of AKT and c-Jun. Lcn2 suppresses stemness properties in pancreatic carcinoma by activating the AKT-c-Jun pathway, and thus, it may be a novel candidate to suppress the stemness of pancreatic cancer. This study provides a new insight into disease progression.

Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer

Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.

Evaluation of CD44+/CD24- and Aldehyde Dehydrogenase Enzyme Markers in Cancer Stem Cells as Prognostic Indicators for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) has been extensively studied not just for its aggressive behavior but also to understand its complex molecular nature. This type of heterogeneous tumor shows no expression of estrogen receptor (ER) or progesterone receptor (PR) and does not express the HER2 gene, and often these tumors are high grade with distinct histological groups. The basal-like subtype is most commonly related to the TNBC type of neoplasms; it can be further classified according to Lehmann and Burstein expert’s criteria. TNBC is related to breast stem cell markers such as CD44+/CD24- and high levels of enzyme aldehyde dehydrogenase (ALDH), which have been shown to possess stem cell features that are involved in differentiation, vascular invasion, tumorigenesis, and metastatic potential. CD44+/CD24- and high levels of ALDH have significance as markers as well as indicators of poor prognosis in TNBC. The databases used in this review are PMC, PubMed, and Google Scholar.

Survivin Inhibition by Piperine Sensitizes Glioblastoma Cancer Stem Cells and Leads to Better Drug Response

Glioblastoma multiforme (GBM) cancer stem cells (GSCs) are one of the strongest contributing factors to treatment resistance in GBM. Identification of biomarkers capable of directly affecting these cells within the bulk tumor is a major challenge associated with the development of new targeting strategies. In this study, we focus on understanding the potential of the multifunctional extraordinaire survivin as a biomarker for GSCs. We analyzed the expression profiles of this gene using various publicly available datasets to understand its importance in stemness and other cancer processes. The findings from these studies were further validated using human GSCs isolated from a GBM cell line. In these GSCs, survivin was inhibited using the dietary phytochemical piperine (PIP) and the subsequent effects on stemness, cancer processes and Temozolomide were investigated. In silico analysis identified survivin to be one of the most significant differentially regulated gene in GSCs, in comparison to common stemness markers. Further validation studies on the isolated GSCs showed the importance of survivin in stemness, cancer progression and therapy resistance. Taken together, our study identifies survivin as a more consistent GSC marker and also suggests the possibility of using survivin inhibitors along with standard of care drugs for better therapeutic outcomes.

Cancer Stem Cells: From an Insight into the Basics to Recent Advances and Therapeutic Targeting

Cancer is characterized by an abnormal growth of the cells in an uncontrolled manner. These cells have the potential to invade and can eventually turn into malignancy, leading to highly fatal forms of tumor. Small subpopulations of cancer cells that are long-lived with the potential of excessive self-renewal and tumor formation are called cancer stem cells (CSCs) or cancer-initiating cells or tumor stem cells. CSCs can be found in tissues, such as breast, brain, lung, liver, ovary, and testis; however, their origin is still a matter of debate. These cells can differentiate and possess self-renewal capacity maintained by numerous intracellular signal transduction pathways, such as the Wnt/β-catenin signaling, Notch signaling, transforming growth factor-β signaling, and Hedgehog signaling. They can also contribute to numerous malignancies and are an important reason for tumor recurrence and metastasis because they are resistant to the known therapeutic strategies that mainly target the bulk of the tumor cells. This review contains collected and compiled information after analyzing published works of the last three decades. The goal was to gather information of recent breakthroughs related to CSCs, strategies to target CSCs' niche (e.g., nanotechnology with tumor biology), and their signaling pathways for cancer therapy. Moreover, the role of metformin, an antidiabetic drug, acting as a chemotherapeutic agent on CSCs by inhibiting cellular transformation and its selective killing is also addressed.

Curcumin: reclaiming the lost ground against cancer resistance

Curcumin, a polyphenol, has a wide range of biological properties such as anticancer, antibacterial, antitubercular, cardioprotective and neuroprotective. Moreover, the anti-proliferative activities of Curcumin have been widely studied against several types of cancers due to its ability to target multiple pathways in cancer. Although Curcumin exhibited potent anticancer activity, its clinical use is limited due to its poor water solubility and faster metabolism. Hence, there is an immense interest among researchers to develop potent, water-soluble, and metabolically stable Curcumin analogs for cancer treatment. While drug resistance remains a major problem in cancer therapy that renders current chemotherapy ineffective, curcumin has shown promise to overcome the resistance and re-sensitize cancer to chemotherapeutic drugs in many studies. In the present review, we are summarizing the role of curcumin in controlling the proliferation of drug-resistant cancers and development of curcumin-based therapeutic applications from cell culture studies up to clinical trials.

Effects of noncoding RNAs in radiotherapy response in breast cancer: a systematic review

Radiotherapy has an essential role in breast cancer treatment. However, tumor cells may be resistant to radiotherapy. Noncoding RNAs are considered regulators of different pathways which modulate radiotherapy. This systematic review classifies long noncoding RNAs, and microRNAs precipitated in the radiation response of breast cancer patients. A total of 14 microRNAs and 8 long noncoding RNAs were studied in this review. MiR-22, miR-200 c, Let7, and LINP1 as tumor suppressors increase the effect of radiotherapy in BC. However, some noncoding RNAs such as HOTAIR, NEAT1, and miR-21 are precipitated in radio-resistance breast cancers. Significant changes in the pattern of noncoding RNAs expression before and after radiotherapy make them a good candidate for the prognosis and prediction of radiotherapy response. MiR-21 and miR-182 can promote radio-resistance via cancer stem cells. At last, the molecular mechanisms initiating radio-resistance were also examined to find the candidate noncoding RNAs for the development of radiation-sensitized agents.

Reactive oxygen species-inducing titanium peroxide nanoparticles as promising radiosensitizers for eliminating pancreatic cancer stem cells

BACKGROUND

Despite recent advances in radiotherapy, radioresistance in patients with pancreatic cancer remains a crucial dilemma for clinical treatment. Cancer stem cells (CSCs) represent a major factor in radioresistance. Developing a potent radiosensitizer may be a novel candidate for the eradication of pancreatic CSCs.

METHODS

CSCs were isolated from MIA PaCa-2 and PANC1 human pancreatic cancer cell lines. Titanium peroxide nanoparticles (TiOxNPs) were synthesized from titanium dioxide nanoparticles (TiO2NPs) and utilized as radiosensitizers when added one hour prior to radiation exposure. The antitumor activity of this novel therapeutic strategy was evaluated against well-established pancreatic CSCs model both in vitro and in vivo.

RESULTS

It is shown that TiOxNPs combined with ionizing radiation exhibit anti-cancer effects on radioresistant CSCs both in vitro and in vivo. TiOxNPs exhibited a synergistic effect with radiation on pancreatic CSC-enriched spheres by downregulating self-renewal regulatory factors and CSC surface markers. Moreover, combined treatment suppressed epithelial-mesenchymal transition, migration, and invasion properties in primary and aggressive pancreatic cancer cells by reducing the expression of proteins relevant to these processes. Notably, radiosensitizing TiOxNPs suppressed the growth of pancreatic xenografts following primary or dissociating sphere MIA PaCa-2 cell implantation. It is inferred that synergy is formed by generating intolerable levels of reactive oxygen species (ROS) and inactivating the AKT signaling pathway.

CONCLUSIONS

Our data suggested the use of TiOxNPs in combination with radiation may be considered an attractive therapeutic strategy to eliminate pancreatic CSCs.

Development of a Model System to Study Expression Profile of RAC2 Gene in Breast Cancer MDA-MB-231 Cell Line

The RAC2 gene encoding GTPases involve cellular signaling of actin polymerization, cell migration, and formation of the phagocytic NADPH oxidase complex. Oncogenic mutations in the RAC2 gene have been identified in various cancers, and extensive research is in progress to delineate its signaling pathways and identify potential therapeutic targets in breast cancers. This paper explored developing a bioinformatics model system to understand the RAC2 gene expression pattern concerning estrogenic receptor status in breast cancers. We have used the MDA-MB-231 breast cancer cell line to identify RAC2 gene expression. To simplify the development of model system with one dataset, we retrieved the microarray dataset GSE27515 from the Gene Expression Omnibus (GEO) for the differential gene expression analysis. Then, network analysis, pathway enrichment analysis, volcano plot, ORA, and the up/downregulated genes were used to highlight genes involved in signaling network pathways. We observed that the RAC2 gene is upregulated in the GSM679722, GSM676923, and GSM679724 downregulated in the samples GSM676925, GSM676926, and GSM676927 from the GEO dataset. Our observation found that the RAC2 gene is upregulated in the estrogen receptor (ER) negative breast cancers and downregulated in ER-positive breast cancer, involving pathways such as focal adhesion, MAPK signaling, axon guidance, and VEGF signaling pathway.

Endometrial Cancer Stem Cells: Where Do We Stand and Where Should We Go?

Endometrial cancer is one of the most common malignant diseases in women worldwide, with an incidence of 5.9%. Thus, it is the most frequent cancer of the female genital tract, with more than 34,000 women dying, in Europe and North America alone. Endometrial Cancer Stem Cells (CSC) might be drivers of carcinogenesis as well as metastatic and recurrent disease. Therefore, targeting CSCs is of high interest to improve prognosis of patients suffering of advanced or recurrent endometrial cancer. This review describes the current evidence of molecular mechanisms in endometrial CSCs with special emphasis on MYC and NF-κB signaling as well as mitochondrial metabolism. Furthermore, the current status of immunotherapy targeting PD-1 and PD-L1 in endometrial cancer cells and CSCs is elucidated. The outlined findings encourage novel therapies that target signaling pathways in endometrial CSCs as well as immunotherapy as a promising therapeutic approach in the treatment of endometrial cancer to impede cancer progression and prevent recurrence.

Understanding autophagy role in cancer stem cell development

Cancer stem cells (CSCs) are a small subpopulation of immature cells located in the tumor mass. These cells are responsible for tumor development, proliferation, resistance and spreading. CSCs are characterized by three unique features: the ability to self-renew, differentiation and tumor formation. CSCs are similar to stem cells, but they differ in the malignant phenotype. CSCs become immortal and survive harsh environmental conditions such as hypoxia, starvation and oxidative stress. However, this harsh tumor microenvironment induces the activation of autophagy, which further increases the CSCs stemness profile, and all these features further increase tumorigenicity and metastasis capacity. Autophagy is induced by the extracellular and cellular microenvironment. Hypoxia is one of the most common factors that highly increases the activity of autophagy in CSCs. Therefore, hypoxia-induced autophagy and CSCs proliferation should be elucidated in order to find a novel cure to defeat cancer cells (CSCs and non-CSCs). The remaining challenges to close the gap between the laboratory bench and the development of therapies, to use autophagy against CSCs in patients, could be addressed by adopting a 3D platform to better-mimic the natural environment in which these cells reside. Ultimately allowing to obtain the blueprints for bioprocess scaling up and to develop the production pipeline for safe and cost-effective autophagy-based novel biologics.

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

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

CRISPR System-Linked Self-Assembling Nanoplatforms for Inspection and Screening of Gastric Cancer Stem Cells

Cancer stem cells (CSCs) possess a high degree of plasticity, constituting a formidable challenge to identify and screen CSCs in situ with outstanding specificity and sensitivity. To overcome this limitation, a self-assembled heterodimer consisting of clustered regularly interspaced short palindromic repeats/Cas12a (named A-CCA) linkage is designed for in situ identification and screening of gastric CSCs (GCSCs) from gastric cancer cells (GCCs). In this system, the editable character of crRNA performs recognition of dual-targets in GCSCs, effectively boosting the specificity of identification, while the enzymatic reaction of Cas12a contributes meaningfully to the sensitivity of sensing, enabling in situ examination and screening of GCSCs. Specifically, the A-CCA nanoplatforms hybridized with ABCG 2 and ABCB 1 overexpress in GCSCs, which can generate heterodimers and simultaneously restore the function of trans-cleavage. At this time, the asymmetry of the heterodimer causes a circular dichroism signal, which together with the recovered fluorescence signal form a dual-signals output system that can further ensure the precision of screening GCSC. Therefore, fluorescence-enhanced GCSCs can be sorted out from GCCs by flow cytometry. Furthermore, GCSCs screened by this assay possess extremely aggressive tumorigenic efficiency, providing a fundamental research object for further developing CSC targeted drugs in vivo.

Estrogen receptor beta increases clear cell renal cell carcinoma stem cell phenotype via altering the circPHACTR4/miR-34b-5p/c-Myc signaling

Early clinical studies indicated that estrogen receptor beta (ERβ) might play key roles to impact the progression of clear cell renal cell carcinoma (ccRCC). The detailed molecular mechanisms, however, remain unclear. Here, we found ERβ could increase the cancer stem cell (CSC) population via altering the circPHACTR4/miR-34b-5p/c-Myc signaling. Mechanism dissection revealed that ERβ could suppress circular RNA PHACTR4 (circPHACTR4) expression via direct binding to the estrogen response elements (EREs) on the 5' promoter region of its host gene, phosphatase and actin regulator 4 (PHACTR4) to decrease miR-34b-5p expression. The decreased miRNA-34b-5p could then increase c-Myc mRNA translation via targeting its 3' untranslated region (3' UTR). The in vivo mouse model with subcutaneous xenografts of ccRCC cells also validated the in vitro data. Importantly, analysis results from ccRCC TCGA database and our clinical data further confirmed the above in vitro/in vivo data. Together, these results suggest that ERβ may increase CSC population in ccRCC via altering ERβ/circPHACTR4/miR-34b-5p/c-Myc signaling and that targeting this newly identified signal pathway may help physicians to better suppress ccRCC progression.

Utility of a Recombinant HSV-1 Vaccine Vector for Personalized Cancer Vaccines

Current approaches to cancer immunotherapy include immune checkpoint inhibitors, cancer vaccines, and adoptive cellular therapy. These therapies have produced significant clinical success for specific cancers, but their efficacy has been limited. Oncolytic virotherapy (OVT) has emerged as a promising immunotherapy for a variety of cancers. Furthermore, the unique characteristics of OVs make them a good choice for delivering tumor peptides/antigens to induce enhanced tumor-specific immune responses. The first oncolytic virus (OV) approved for human use is the attenuated herpes simplex virus type 1 (HSV-1), Talimogene laherparepvec (T-VEC) which has been FDA approved for the treatment of melanoma in humans. In this study, we engineered the recombinant oncolytic HSV-1 (oHSV) VC2-OVA expressing a fragment of ovalbumin (OVA) as a fusion protein with VP26 virion capsid protein. We tested the ability of VC2-OVA to act as a vector capable of stimulating strong, specific antitumor immunity in a syngeneic murine melanoma model. Therapeutic vaccination with VC2-OVA led to a significant reduction in colonization of tumor cells in the lungs of mice intravenously challenged B16cOVA cells. In addition, VC2-OVA induced a potent prophylactic antitumor response and extended survival of mice that were intradermally engrafted with B16cOVA tumors compared with mice immunized with control virus.