Pluripotency transcription factors and cancer stem cells: small genes make a big difference

Deciphering the Role of Cancer Stem Cells: Drivers of Tumor Evolution, Therapeutic Resistance, and Precision Medicine Strategies

Cancer stem cells (CSCs) play a central role in tumor progression, recurrence, and resistance to conventional therapies, making them a critical focus in oncology research. This review provides a comprehensive analysis of CSC biology, emphasizing their self-renewal, differentiation, and dynamic interactions with the tumor microenvironment (TME). Key signaling pathways, including Wnt, Notch, and Hedgehog, are discussed in detail to highlight their potential as therapeutic targets. Current methodologies for isolating CSCs are critically examined, addressing their advantages and limitations in advancing precision medicine. Emerging technologies, such as CRISPR/Cas9 and single-cell sequencing, are explored for their transformative potential in unraveling CSC heterogeneity and informing therapeutic strategies. The review also underscores the pivotal role of the TME in supporting CSC survival, promoting metastasis, and contributing to therapeutic resistance. Challenges arising from CSC-driven tumor heterogeneity and dormancy are analyzed, along with strategies to mitigate these barriers, including novel therapeutics and targeted approaches. Ethical considerations and the integration of artificial intelligence in designing CSC-specific therapies are discussed as essential elements of future research. The manuscript advocates for a multi-disciplinary approach that combines innovative technologies, advanced therapeutics, and collaborative research to address the complexities of CSCs. By bridging existing gaps in knowledge and fostering advancements in personalized medicine, this review aims to guide the development of more effective cancer treatment strategies, ultimately improving patient outcomes.

Dysregulation of the p53 pathway provides a therapeutic target in aggressive pediatric sarcomas with stem-like traits

PURPOSE

Pediatric sarcomas are bone and soft tissue tumors that often exhibit high metastatic potential and refractory stem-like phenotypes, resulting in poor outcomes. Aggressive sarcomas frequently harbor a disrupted p53 pathway. However, whether pediatric sarcoma stemness is associated with abrogated p53 function and might be attenuated via p53 reactivation remains unclear.

METHODS

We utilized a unique panel of pediatric sarcoma models and tumor tissue cohorts to investigate the correlation between the expression of stemness-related transcription factors, p53 pathway dysregulations, tumorigenicity in vivo, and clinicopathological features. TP53 mutation status was assessed by next-generation sequencing. Major findings were validated via shRNA-mediated silencing and functional assays. The p53 pathway-targeting drugs were used to explore the effects and selectivity of p53 reactivation against sarcoma cells with stem-like traits.

RESULTS

We found that highly tumorigenic stem-like sarcoma cells exhibit dysregulated p53, making them vulnerable to drugs that restore wild-type p53 activity. Immunohistochemistry of mouse xenografts and human tumor tissues revealed that p53 dysregulations, together with enhanced expression of the stemness-related transcription factors SOX2 or KLF4, are crucial features in pediatric osteosarcoma, rhabdomyosarcoma, and Ewing's sarcoma development. p53 dysregulation appears to be an important step for sarcoma cells to acquire a fully stem-like phenotype, and p53-positive pediatric sarcomas exhibit a high frequency of early metastasis. Importantly, reactivating p53 signaling via MDM2/MDMX inhibition selectively induces apoptosis in aggressive, stem-like Ewing's sarcoma cells while sparing healthy fibroblasts.

CONCLUSIONS

Our results indicate that restoring canonical p53 activity provides a promising strategy for developing improved therapies for pediatric sarcomas with unfavorable stem-like traits.

Prostate cancer stem cells: an updated mini-review

Prostate cancer is the most common malignant tumor in male genitourinary system. The incidence of prostate cancer ranks the first among all male malignant tumors worldwide, and the mortality rate ranks the second among all male malignant tumors. Prostate stem cells are heterogeneous subsets with the function of self-regeneration and proliferation in the prostate, which can produce all cell lineages that make up the prostate epithelium. At present, the pathogenesis of prostate cancer remains unclear. According to cancer stem cell hypothesis, prostate cancer may be a stem cell disease, which provides a new direction for revealing the pathogenesis of prostate cancer and developing treatment strategy for prostate cancer. In this mini-review, we highlight recent advances in our understanding of the origin, surface molecular markers, signaling pathway and the significance for clinical treatment of prostate cancer stem cells.

Reactive oxygen species from non-thermal gas plasma (CAP): implication for targeting cancer stem cells

Cancer remains a major global health challenge, with the persistence of cancer stem cells (CSCs) contributing to treatment resistance and relapse. Despite advancements in cancer therapy, targeting CSCs presents a significant hurdle. Non-thermal gas plasma, also known as CAP, represents an innovative cancer treatment. It has recently gained attention for its often found to be selective, immunogenic, and potent anti-cancer properties. CAP is composed of a collection of transient, high-energy, and physically and chemically active entities, such as reactive oxygen species (ROS). It is acknowledged that the latter are responsible for a major portion of biomedical CAP effects. The dynamic interplay of CAP-derived ROS and other components contributes to the unique and versatile properties of CAP, enabling it to interact with biological systems and elicit various therapeutic effects, including its potential in cancer treatment. While CAP has shown promise in various cancer types, its application against CSCs is relatively unexplored. This review assesses the potential of CAP as a therapeutic strategy for targeting CSCs, focusing on its ability to regulate cellular states and achieve redox homeostasis. This is done by providing an overview of CSC characteristics and demonstrating recent findings on CAP's efficacy in targeting these cells. By contributing insights into the unique attributes of CSCs and the potential of CAP, this work contributes to an advanced understanding of innovative oncology strategies.

Intricate relationship between cancer stemness, metastasis, and drug resistance

Cancer stem cells (CSCs) are widely acknowledged as the drivers of tumor initiation, epithelial-mesenchymal transition (EMT) progression, and metastasis. Originating from both hematologic and solid malignancies, CSCs exhibit quiescence, pluripotency, and self-renewal akin to normal stem cells, thus orchestrating tumor heterogeneity and growth. Through a dynamic interplay with the tumor microenvironment (TME) and intricate signaling cascades, CSCs undergo transitions from differentiated cancer cells, culminating in therapy resistance and disease recurrence. This review undertakes an in-depth analysis of the multifaceted mechanisms underlying cancer stemness and CSC-mediated resistance to therapy. Intrinsic factors encompassing the TME, hypoxic conditions, and oxidative stress, alongside extrinsic processes such as drug efflux mechanisms, collectively contribute to therapeutic resistance. An exploration into key signaling pathways, including JAK/STAT, WNT, NOTCH, and HEDGEHOG, sheds light on their pivotal roles in sustaining CSCs phenotypes. Insights gleaned from preclinical and clinical studies hold promise in refining drug discovery efforts and optimizing therapeutic interventions, especially chimeric antigen receptor (CAR)-T cell therapy, cytokine-induced killer (CIK) cell therapy, natural killer (NK) cell-mediated CSC-targeting and others. Ultimately use of cell sorting and single cell sequencing approaches for elucidating the fundamental characteristics and resistance mechanisms inherent in CSCs will enhance our comprehension of CSC and intratumor heterogeneity, which ultimately would inform about tailored and personalized interventions.

Cancer stem cells in meningiomas: novel insights and therapeutic implications

Meningiomas (MGs), which arise from meningothelial cells of the dura mater, represent a significant proportion of primary tumours of the central nervous system (CNS). Despite advances in treatment, the management of malignant meningioma (MMG) remains challenging due to diagnostic, surgical, and resection limitations. Cancer stem cells (CSCs), a subpopulation within tumours capable of self-renewal and differentiation, are highlighted as key markers of tumour growth, metastasis, and treatment resistance. Identifying additional CSC-related markers enhances the precision of malignancy evaluations, enabling advancements in personalised medicine. The review discusses key CSC biomarkers that are associated with high levels of expression, aggressive tumour behaviour, and poor outcomes. Recent molecular research has identified CSC-related biomarkers, including Oct-4, Sox2, NANOG, and CD133, which help maintain cellular renewal, proliferation, and drug resistance in MGs. This study highlights new therapeutic strategies that could improve patient prognosis with more durable tumour regression. The use of combination therapies, such as hydroxyurea alongside diltiazem, suggests more efficient and effective MG management compared to monotherapy. Signalling pathways such as NOTCH and hedgehog also offer additional avenues for therapeutic development. CRISPR/Cas9 technology has also been employed to create meningioma models, uncovering pathways related to cell growth and proliferation. Since the efficacy of traditional therapies is limited in most cases due to resistance mechanisms in CSCs, further studies on the biology of CSCs are warranted to develop therapeutic interventions that are likely to be effective in MG. Consequently, improved diagnostic approaches may lead to personalised treatment plans tailored to the specific needs of each patient.

Neutrophils exposed to a cholesterol metabolite secrete extracellular vesicles that promote epithelial-mesenchymal transition and stemness in breast cancer cells

Small extracellular vesicles (sEVs) are emerging as critical mediators of intercellular communication in the tumor microenvironment (TME). Here, we investigate the mechanisms by which sEVs derived from neutrophils treated with the cholesterol metabolite, 27-hydroxycholesterol (27HC), influence breast cancer progression. sEVs released from 27HC treated neutrophils enhance epithelial-mesenchymal transition (EMT) and stem-like properties in breast cancer cells, resulting in loss of adherence, increased migratory capacity and resistance to cytotoxic chemotherapy. Decreased microRNAs (miRs) within the sEVs resulted in activation of the WNT/β-catenin signaling pathway in recipient cells and suggest that this may be a predominant pathway for stem-like phenotype and EMT. Our findings underscore a novel mechanism by which 27HC-modulated neutrophils contribute to breast cancer pathophysiology through EV-mediated intercellular communication, suggesting potential therapeutic targets in cancer treatment.

The prognostic and immune significance of PLBD1 in pan-cancer and its roles in proliferation and invasion of glioma

Cancer is a destructive disease and is currently the leading cause of major threats to human health. PLBD1 is a transcription factor that regulates phospholipid metabolism, but its role in tumors is unknown. We assessed pan-cancer expression, methylation, and mutation data of PLBD1 by multiple databases to investigate its clinical prognostic value. In addition, we examined the pan-cancer immunological signature of PLBD1, particularly in gliomas. Furthermore, we assessed the impact of PLBD1 knockdown on the proliferation and invasive capacity of glioma cells by in vitro experiments. Our results suggest that PLBD1 is highly expressed in multiple types of cancers, and it can serve as an independent prognostic factor for gliomas. In addition, we found that the epigenetic alterations of PLBD1 were highly heterogeneous in a variety of cancers, including gliomas, and that its high methylation was associated with poor prognosis in a broad range of cancers. Immunological profiling demonstrated that PLBD1 was significantly associated with immune cell infiltration and multiple immune checkpoints in gliomas and is a potential biomarker for gliomas. Furthermore, cellular experiments showed that knockdown of PLBD1 significantly inhibited the proliferation and invasive ability of glioma cells. In conclusion, PLBD1 is a potential tumor prognostic biomarker and immunotherapeutic target that plays a crucial role in glioma cell proliferation, invasion and immunotherapy.

Role of circular RNAs in lung cancer

Lung cancer remains a global public health concern with significant research focus on developing better diagnosis/prognosis biomarkers and therapeutical targets. Circular RNAs (circRNAs) are a type of single-stranded RNA molecules that covalently closed and have ubiquitous expression. These molecules have been implicated in a variety of disease mechanisms, including lung cancer, as they exhibit oncogenic or tumor suppressor characteristics. Recent research has shown an important role that circRNAs play at different stages of lung cancer, particularly in lung adenocarcinoma. In this review, we summarize the latest research on circRNAs and their roles within lung cancer diagnosis, as well as on disease mechanisms. We also discuss the knowledge gaps on these topics and possible future research directions.

Cancer cell plasticity, stem cell factors, and therapy resistance: how are they linked?

Cellular plasticity can occur naturally in an organism and is considered an adapting mechanism during the developmental stage. However, abnormal cellular plasticity is observed in different diseased conditions, including cancer. Cancer cell plasticity triggers the stimuli of epithelial-mesenchymal transition (EMT), abnormal epigenetic changes, expression of stem cell factors and implicated signaling pathways, etc., and helps in the maintenance of CSC phenotype. Conversely, CSC maintains the cancer cell plasticity, EMT, and epigenetic plasticity. EMT contributes to increased cell migration and greater diversity within tumors, while epigenetic changes, stem cell factors (OCT4, NANOG, and SOX2), and various signaling pathways allow cancer cells to maintain various phenotypes, giving rise to intra- and inter-tumoral heterogeneity. The intricate relationships between cancer cell plasticity and stem cell factors help the tumor cells adopt drug-tolerant states, evade senescence, and successfully acquire drug resistance with treatment dismissal. Inhibiting molecules/signaling pathways involved in promoting CSCs, cellular plasticity, EMT, and epigenetic plasticity might be helpful for successful cancer therapy management. This review discussed the role of cellular plasticity, EMT, and stem cell factors in tumor initiation, progression, reprogramming, and therapy resistance. Finally, we discussed how the intervention in this axis will help better manage cancers and improve patient survivability.

Tumor Microenvironment: A Niche for Cancer Stem Cell Immunotherapy

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

Exploring the dynamic interplay between cancer stem cells and the tumor microenvironment: implications for novel therapeutic strategies

Cancer stem cells (CSCs) have emerged as key contributors to tumor initiation, growth, and metastasis. In addition, CSCs play a significant role in inducing immune evasion, thereby compromising the effectiveness of cancer treatments. The reciprocal communication between CSCs and the tumor microenvironment (TME) is observed, with the TME providing a supportive niche for CSC survival and self-renewal, while CSCs, in turn, influence the polarization and persistence of the TME, promoting an immunosuppressive state. Consequently, these interactions hinder the efficacy of current cancer therapies, necessitating the exploration of novel therapeutic approaches to modulate the TME and target CSCs. In this review, we highlight the intricate strategies employed by CSCs to evade immune surveillance and develop resistance to therapies. Furthermore, we examine the dynamic interplay between CSCs and the TME, shedding light on how this interaction impacts cancer progression. Moreover, we provide an overview of advanced therapeutic strategies that specifically target CSCs and the TME, which hold promise for future clinical and translational studies in cancer treatment.

Fibronectin promotes tumor progression through integrin αvβ3/PI3K/AKT/SOX2 signaling in non-small cell lung cancer

The tumor microenvironment, especially the extracellular matrix (ECM), is strongly associated with tumor cell proliferation and metastasis. Numerous studies have provided evidence suggesting that fibronectin (FN) in ECM supports cancer cell escape and contributes to cell migration, resulting in distant cancer metastasis and poor outcomes in patients. In our study, it was demonstrated that FN expression was elevated in tumor tissues from highly malignant NSCLC patients, compared to those with low malignancy (p = 0.0076). Importantly, FN promoted proliferative phenotypes and strengthened tumorigenesis capabilities in NSCLC cells, including A549 and Lewis cells, leading to sustained tumor growth in vivo. Mechanistically, it was identified that FN facilitated the activation of the integrin αvβ3/PI3K/AKT signaling pathway, which subsequently upregulated tumor stemness through the downstream transcription factor SOX2. Blockade of integrin αvβ3 signal efficiently suppressed NSCLC proliferation and tumorigenesis both in vitro and in vivo. In conclusion, our study demonstrated that extracellular FN could facilitate NSCLC development through the integrin αvβ3/PI3K/AKT/SOX2 signaling pathway. Blockade of integrin αvβ3 could efficiently enhance the anticancer effects of chemotherapy, offering an innovative approach for clinical NSCLC therapy.

Effect of microserum environment stimulation on extraction and biological function of colorectal cancer stem cells

BACKGROUND

3D cancer stem cell (CSC) cultures are widely used as in vitro tumor models. In this study, we determined the effects of enriching HCT116 tumor spheres initially cultured in serum-free medium with different concentrations of serum, focusing on the effect of microserum environment stimulation on extraction and biological function of colorectal cancer stem cells (CCSCs).

METHODS

CCSCs were enriched in standard serum-free medium and serum-free medium with different concentrations of serum for 1 week. The expression of CSC-associated markers in CCSCs, and the presence and relative proportion of CSCs (CD133/CD44 cell sorting) were then determined to elucidate the effect of the microserum environment on the preservation of CSC-related features. Further, the tumorigenic capacity of CCSCs was evaluated in an immunodeficiency mouse model.

RESULTS

Our data indicated that a significantly greater number of spheres with a greater size range and high viability without drastic alteration in biological and structural features, which maintained self-renewal potential after sequential passages were formed after serum supplementation. Real-time analysis showed that both serum spheres and serum-free spheres displayed similar expression patterns for key stemness genes. Serum spheres showed higher expression of the CSC surface markers CD133 and CD44 than did CSCs spheres cultured in serum-free medium. Adherent cultures in complete medium could adapt to the serum-containing microenvironment faster and showed higher proliferation ability. The addition of serum induced EMT and promoted the migration and invasion of serum globular cells. Compared with serum-free cells and adherent cells, serum spheres showed higher tumor initiation ability.

CONCLUSIONS

Microserum environment stimulation could be an effective strategy for reliable enrichment of intact CCSCs, and a more efficient CSC enrichment method.

The transposable element-derived transcript of LIN28B has a placental origin and is not specific to tumours

Transposable elements (TEs) are genetic elements that have evolved as crucial regulators of human development and cancer, functioning as both genes and regulatory elements. When TEs become dysregulated in cancer cells, they can serve as alternate promoters to activate oncogenes, a process known as onco-exaptation. This study aimed to explore the expression and epigenetic regulation of onco-exaptation events in early human developmental tissues. We discovered co-expression of some TEs and oncogenes in human embryonic stem cells and first trimester and term placental tissues. Previous studies identified onco-exaptation events in various cancer types, including an AluJb SINE element-LIN28B interaction in lung cancer cells, and showed that the TE-derived LIN28B transcript is associated with poor patient prognosis in hepatocellular carcinoma. This study further characterized the AluJb-LIN28B transcript and confirmed that its expression is restricted to the placenta. Targeted DNA methylation analysis revealed differential methylation of the two LIN28B promoters between placenta and healthy somatic tissues, indicating that some TE-oncogene interactions are not cancer-specific but arise from the epigenetic reactivation of developmental TE-derived regulatory events. In conclusion, our findings provide evidence that some TE-oncogene interactions are not limited to cancer and may originate from the epigenetic reactivation of TE-derived regulatory events that are involved in early development. These insights broaden our understanding of the role of TEs in gene regulation and suggest the potential importance of targeting TEs in cancer therapy beyond their conventional use as cancer-specific markers.

Zinc finger and SCAN domain-containing 18 suppresses the proliferation, self-renewal, and drug resistance of glioblastoma cells

Elucidation of cellular and molecular mechanisms key to glioblastoma growth, self-renewal, survival, and metastasis is important for developing novel therapeutic strategies. In this study, the expression and function of zinc finger and SCAN domain-containing 18 (ZSCAN18) in human glioblastoma cell lines were characterized. Compared with normal astrocytes, ZSCAN18 was significantly down-regulated in all tested glioblastoma cell lines, with the LN-229 cell line having the lowest ZSCAN18 expression. Lentivirus-mediated ZSCAN18 overexpression suppressed glioblastoma cell proliferation, sphere formation, and SOX2 and OCT4 expression, implying the negative role of ZSCAN18 in glioblastoma development. ZSCAN18 overexpression enhanced the sensitivity of glioblastoma cells to Temozolomide. The glioblastoma implantation model showed a consistent inhibitory effect of ZSCAN18 on the proliferation and self-renewal of glioblastoma cells in vivo. Notably, ZSCAN18 overexpression resulted in the down-regulation of glioma-associated oncogene homolog 1 (GLI1) which is the terminal component of the Hedgehog signaling. Lentivirus-mediated GLI1 overexpression restored the proliferation and promoted the resistance of glioblastoma cells to Temozolomide. However, GLI1 overexpression did not affect the self-renewal of ZSCAN18-overexpressing glioblastoma cells. Taken together, this research uncovers the role of ZSCAN18 in regulating glioblastoma cell growth and maintenance. ZSCAN18 could be a potential glioblastoma biomarker.

Significance of Oct-4 transcription factor as a pivotal therapeutic target for CD44+ /24- mammary tumor initiating cells: Aiming at the root of the recurrence

Breast cancer (BC) remains one of the deadliest and frequently diagnosed metastatic cancers worldwide. Cancer stem cells (CSCs) are the cell population within the tumor niche, having an epithelial to mesenchymal (EMT) transition phenotype, high self-renewal, vigorous metastatic capacity, drug resistance, and tumor relapse. Identification of targets for induction of apoptosis is essential to provide novel therapeutic approaches in BC. Our earlier studies showed that Vitamin C induces apoptotic cell death by losing redox balance in TNBC CSCs. In this study, we have attempted to identify previously unrecognized CSC survival factors that can be used as druggable targets for bCSCs apoptosis regulators isolated from the TNBC line, MDA MB 468. After a thorough literature review, Oct-4 was identified as the most promising marker for its unique abundance in cancer and absence in normal cells and the contribution of Oct-4 to the sustenance of cancer cells. We then validated a very high expression of Oct-4 in the MDA MB 468 bCSCs population using flow-cytometry. The loss of Oct-4 was carried out using small interfering RNA (siRNA)-mediated knockdown in the bCSCs, followed by assessing for cellular apoptosis. Our results indicated that Oct-4 knockdown induced cell death, changes in cellular morphology, inhibited mammosphere formation, and positive for Annexin-V expression, thereby indicating the role of Oct-4 in bCSC survival. Moreover, our findings also suggest the direct interaction between Oct-4 and Vitamin C using in silico docking. This data, hence, contributes towards novel information about Oct-4 highlighting this molecule as a novel survival factor in bCSCs.

Culture of Cancer Cells at Physiological Oxygen Levels Affects Gene Expression in a Cell-Type Specific Manner

Standard cell culture is routinely performed at supraphysiological oxygen levels (~18% O2). Conversely, O2 levels in most mammalian tissues range from 1-6% (physioxia). Such hyperoxic conditions in cell culture can alter reactive oxygen species (ROS) production, metabolism, mitochondrial networks, and response to drugs and hormones. The aim of this study was to investigate the transcriptional response to different O2 levels and determine whether it is similar across cell lines, or cell line-specific. Using RNA-seq, we performed differential gene expression and functional enrichment analyses in four human cancer cell lines, LNCaP, Huh-7, PC-3, and SH-SY5Y cultured at either 5% or 18% O2 for 14 days. We found that O2 levels affected transcript abundance of thousands of genes, with the affected genes having little overlap between cell lines. Functional enrichment analysis also revealed different processes and pathways being affected by O2 in each cell line. Interestingly, most of the top differentially expressed genes are involved in cancer biology, which highlights the importance of O2 levels in cancer cell research. Further, we observed several hypoxia-inducible factor (HIF) targets, HIF-2α targets particularly, upregulated at 5% O2, consistent with a role for HIFs in physioxia. O2 levels also differentially induced the transcription of mitochondria-encoded genes in most cell lines. Finally, by comparing our transcriptomic data from LNCaP and PC-3 with datasets from the Prostate Cancer Transcriptome Atlas, a correlation between genes upregulated at 5% O2 in LNCaP cells and the in vivo prostate cancer transcriptome was found. We conclude that the transcriptional response to O2 over the range from 5-18% is robust and highly cell-type specific. This latter finding indicates that the effects of O2 levels are difficult to predict and thus highlights the importance of regulating O2 in cell culture.

The Molecular and Cellular Strategies of Glioblastoma and Non-Small-Cell Lung Cancer Cells Conferring Radioresistance

Ionizing radiation (IR) has been shown to play a crucial role in the treatment of glioblastoma (GBM; grade IV) and non-small-cell lung cancer (NSCLC). Nevertheless, recent studies have indicated that radiotherapy can offer only palliation owing to the radioresistance of GBM and NSCLC. Therefore, delineating the major radioresistance mechanisms may provide novel therapeutic approaches to sensitize these diseases to IR and improve patient outcomes. This review provides insights into the molecular and cellular mechanisms underlying GBM and NSCLC radioresistance, where it sheds light on the role played by cancer stem cells (CSCs), as well as discusses comprehensively how the cellular dormancy/non-proliferating state and polyploidy impact on their survival and relapse post-IR exposure.

Regulation of Tumor and Metastasis Initiation by Chemokine Receptors

Tumor-initiating cells (TICs) are a rare sub-population of cells within the bulk of a tumor that are major contributors to tumor initiation, metastasis, and chemoresistance. TICs have a stem-cell-like phenotype that is dictated by the expression of master regulator transcription factors, including OCT4, NANOG, and SOX2. These transcription factors are expressed via activation of multiple signaling pathways that drive cancer initiation and progression. Importantly, these same signaling pathways can be activated by select chemokine receptors. Chemokine receptors are increasingly being revealed as major drivers of the TIC phenotype, as their signaling can lead to activation of stemness-controlling transcription factors. Additionally, the cell surface expression of chemokine receptors provides a unique therapeutic target to disrupt signaling pathways that control the expression of master regulator transcription factors and the TIC phenotype. This review summarizes the master regulator transcription factors known to dictate the TIC phenotype, along with the complex signaling pathways that can mediate their expression and the chemokine receptors that are most upstream of this phenotype.

Preventive cancer stem cell-based vaccination modulates tumor development in syngeneic colon adenocarcinoma murine model

BACKGROUND

Cancer stem cells (CSCs), a rare sub-fraction of tumor cells, with the capability of self-renewal and strong oncogenicity are tightly responsible for chemo and radio resistance and tumor metastasis in colorectal cancer. Hence, CSCs targeting would improve the efficacy of therapeutic strategies and clinical outcomes.

METHODS

Here, using three-dimensional CSC spheroids and syngeneic mice model, we evaluated the cancer preventive impact of CSCs-based vaccination. CSCs enrichment was performed via colonosphere formation from CT-26 cell line and CT-26-derived tumor biopsy and characterized by confirming high expression of key stemness genes (OCT4, SOX2, and NANOG) and CSC-related surface biomarkers (CD166, DCLK1, and CD133) via real-time PCR and flow cytometry, respectively. Then, the stemness phenotype and self-renewal in CSC-enriched spheroids were further confirmed by showing serial sphere formation capacity, clonogenicity potential, and enhanced in vivo tumorigenic capacity compared to their parental counterparts. CSCs lysates were used as vaccines in prophylactic settings compared to the parental cell lysate and PBS groups.

RESULT

Immunization of syngeneic mice with CSCs lysates was effective in the prevention of tumor establishment and significantly decreased tumor growth rate accompanied by an improvement in survival rate in tumor-bearing mice compared to groups subjected to parental cells lysate and PBS. These results, for the first time, showed that mice immunized with cell lysate from tumor biopsy-derived spheroids are resistant to tumor induction. Immunofluorescence staining indicated that only the serum antibodies from CSC-vaccinated mice reacted with colonospheres.

CONCLUSIONS

These findings represent CSCs lysate-based vaccination as a potential approach to hampering immunotherapy failure of colorectal cancer which along with other traditional therapies may effectively apply to prevent the establishment of aggressive tumors harboring stemness features.

Integrative Analysis of Bulk RNA-Seq and Single-Cell RNA-Seq Unveils the Characteristics of the Immune Microenvironment and Prognosis Signature in Prostate Cancer

The immune microenvironment is a culmination of the collaborative effort of immune cells and is important in cancer development. The underlying mechanisms of the tumor immune microenvironment in regulating prostate cancer (PRAD) are unclear. In the current study, 144 natural killer cell-related genes were identified using differential expression, single-sample gene set enrichment analysis, and weighted gene coexpression network analysis. Furthermore, VCL, ACTA2, MYL9, MYLK, MYH11, TPM1, ACTG2, TAGLN, and FLNC were selected as hub genes via the protein-protein interaction network. Based on the expression patterns of the hub genes, endothelial, epithelial, and tissue stem cells were identified as key cell subpopulations, which could regulate PRAD via immune response, extracellular signaling, and protein formation. Moreover, 27 genes were identified as prognostic signatures and used to construct the risk score model. Receiver operating characteristic curves revealed the good performance of the risk score model in both the training and testing datasets. Different chemotherapeutic responses were observed between the low- and high-risk groups. Additionally, a nomogram based on the risk score and other clinical features was established to predict the 1-, 3-, and 5-year progression-free interval of patients with PRAD. This study provides novel insights into the molecular mechanisms of the immune microenvironment and its role in the pathogenesis of PARD. The identification of key cell subpopulations has a potential therapeutic and prognostic use in PRAD.

Dehydroepiandrosterone (DHEA) Sensitizes Irinotecan to Suppress Head and Neck Cancer Stem-Like Cells by Downregulation of WNT Signaling

Purpose

Current treatment options for head and neck squamous cell carcinoma (HNSCC) are limited, especially for cases with cancer stem cell-induced chemoresistance and recurrence. The WNT signaling pathway contributes to maintenance of stemness via translocation of β-catenin into the nucleus, and represents a promising druggable target in HNSCC. Dehydroepiandrosterone (DHEA), a steroid hormone, has potential as an anticancer drug. However, the potential anticancer mechanisms of DHEA including inhibition of stemness, and its therapeutic applications in HNSCC remain unclear.

Methods

Firstly, SRB assay and sphere formation assay were used to examine cellular viability and cancer stem cell-like phenotype, respectively. The expressions of stemness related factors were measured by RT-qPCR and western blotting. The luciferase reporter assay was applied to evaluate transcriptional potential of stemness related pathways. The alternations of WNT signaling pathway were measured by nuclear translocation of β-catenin, RT-qPCR and western blotting. Furthermore, to investigate the effect of drugs in vivo, both HNSCC orthotopic and subcutaneous xenograft mouse models were applied.

Results

We found that DHEA reduced HNSCC cell viability, suppressed sphere formation, and inhibited the expression of cancer-stemness markers, such as BMI-1 and Nestin. Moreover, DHEA repressed the transcriptional activity of stemness-related pathways. In the WNT pathway, DHEA reduced the nuclear translocation of the active form of β-catenin and reduced the protein expression of the downstream targets, CCND1 and CD44. Furthermore, when combined with the chemotherapeutic drug, irinotecan (IRN), DHEA enhanced the sensitivity of HNSCC cells to IRN as revealed by reduced cell viability, sphere formation, expression of stemness markers, and activation of the WNT pathway. Additionally, this combination reduced in vivo tumor growth in both orthotopic and subcutaneous xenograft mouse models.

Conclusion

These findings indicate that DHEA has anti-stemness potential in HNSCC and serves as a promising anticancer agent. The combination of DHEA and IRN may provide a potential therapeutic strategy for patients with advanced HNSCC.

Evaluation of the Impact of Pregnancy-Associated Factors on the Quality of Wharton's Jelly-Derived Stem Cells Using SOX2 Gene Expression as a Marker

SOX2 is a recognized pluripotent transcription factor involved in stem cell homeostasis, self-renewal and reprogramming. It belongs to, one of the SRY-related HMG-box (SOX) family of transcription factors, taking part in the regulation of embryonic development and determination of cell fate. Among other functions, SOX2 promotes proliferation, survival, invasion, metastasis, cancer stemness, and drug resistance. SOX2 interacts with other transcription factors in multiple signaling pathways to control growth and survival. The aim of the study was to determine the effect of a parturient’s age, umbilical cord blood pH and length of pregnancy on the quality of stem cells derived from Wharton’s jelly (WJSC) by looking at birth weight and using SOX2 gene expression as a marker. Using qPCR the authors, evaluated the expression of SOX2 in WJSC acquired from the umbilical cords of 30 women right after the delivery. The results showed a significant correlation between the birth weight and the expression of SOX2 in WJSC in relation to maternal age, umbilical cord blood pH, and the length of pregnancy. The authors observed that the younger the woman and the lower the umbilical cord blood pH, the earlier the delivery occurs, the lower the birth weight and the higher SOX2 gene expression in WJSC. In research studies and clinical applications of regenerative medicine utilizing mesenchymal stem cells derived from Wharton’s Jelly of the umbilical cord, assessment of maternal and embryonic factors influencing the quality of cells is critical.

Ivermectin synergizes sorafenib in hepatocellular carcinoma via targeting multiple oncogenic pathways

Advanced hepatocellular carcinoma (HCC) results in generally poor clinical outcomes and necessitates better therapeutic strategies. Ivermectin, which is an existing anti‐parasitic drug, has been recently identified as a novel anti‐cancer drug. In line with previous efforts, this work demonstrates the translational potential of ivermectin to treat advanced HCC. We demonstrated that ivermectin at clinically relevant concentrations was active against growth and survival in multiple HCC cell lines. We showed that ivermectin had the potential to inhibit metastasis and target HCC stem cell functions. Mechanism studies correlated well with cellular phenotypes observed in ivermectin‐treated cells, and demonstrated inhibition of mTOR/STAT3 pathway, suppression of epithelial mesenchymal transition (EMT) and reduced expression of stem cell markers. We further demonstrated that ivermectin inhibited tumor formation and growth in HCC xenograft mouse model, without causing significant toxicity in the mice. Using combination index (CI), we showed that ivermectin and sorafenib were synergistic in HCC in vitro, and this was further confirmed in vivo. Our work demonstrates the potent anti‐HCC activities of ivermectin and its multiple targets on essential oncogenic pathways. Our findings provide preclinical evidence to initialize clinical trial using ivermectin and sorafenib for treating advanced HCC.

Tumour Stem Cells in Breast Cancer

Tumour stem cells (CSCs) are a self-renewing population that plays important roles in tumour initiation, recurrence, and metastasis. Although the medical literature is extensive, problems with CSC identification and cancer therapy remain. This review provides the main mechanisms of CSC action in breast cancer (BC): CSC markers and signalling pathways, heterogeneity, plasticity, and ecological behaviour. The dynamic heterogeneity of CSCs and the dynamic transitions of CSC⁻ non-CSCs and their significance for metastasis are considered.

β-elemene suppresses tumor metabolism and stem cell-like properties of non-small cell lung cancer cells by regulating PI3K/AKT/mTOR signaling

Multi-drug resistance remains a critical issue in cancer treatment that hinders the effective use of chemotherapeutic drugs. The active components of traditional Chinese medicine have been applied as adjuvants to accentuate the anticancer properties of conventional drugs such as cisplatin. However, their application requires further validation and optimization. This study explored the anticancer activity of β-elemene, a natural component of traditional Chinese medical formulations. The effect of β-elemene on the anticancer properties of cisplatin was evaluated in A549 and NCI-H1650 lung cancer cells. Cell apoptosis, stem-like properties, glucose metabolism, multi-drug resistance, and PI3K/AKT/mTOR activation were assessed via flow cytometry, tumorsphere formation, and western blotting. The target genes of β-elemene were predicted using bioinformatics tools and validated in both cell lines. A xenograft model of lung cancer was established in nude mice to evaluate the combined effects of β-elemene and cisplatin in vivo. We found that β-elemene acted synergistically with cisplatin against non-small cell lung cancer cells by promoting apoptosis and impairing glucose metabolism, multi-drug resistance, and stemness maintenance. These effects were mediated by the inhibition of PI3K/AKT/mTOR activation. Bioinformatics analysis revealed that RB1 and TP53 are common target genes associated with lung cancer and β-elemene. The anti-tumorigenic properties of β-elemene were confirmed in vivo, wherein β-elemene, along with cisplatin, significantly suppressed tumor growth in a mouse xenograft model of non-small cell lung cancer. As such, β-elemene acted as an inhibitor of PI3K/AKT/mTOR signaling and enhanced the anticancer effect of cisplatin by targeting tumor metabolism, chemoresistance, and stem-like behavior. Thus, β-elemene is an effective anticancer adjuvant agent with potential clinical applications.

5-O-(N-Boc-l-Alanine)-Renieramycin T Induces Cancer Stem Cell Apoptosis via Targeting Akt Signaling

Cancer stem cells (CSCs) drive aggressiveness and metastasis by utilizing stem cell-related signals. In this study, 5-O-(N-Boc-l-alanine)-renieramycin T (OBA-RT) was demonstrated to suppress CSC signals and induce apoptosis. OBA-RT exerted cytotoxic effects with a half-maximal inhibitory concentration of approximately 7 µM and mediated apoptosis as detected by annexin V/propidium iodide using flow cytometry and nuclear staining assays. Mechanistically, OBA-RT exerted dual roles, activating p53-dependent apoptosis and concomitantly suppressing CSC signals. A p53-dependent pathway was indicated by the induction of p53 and the depletion of anti-apoptotic Myeloid leukemia 1 (Mcl-1) and B-cell lymphoma 2 (Bcl-2) proteins. Cleaved poly (ADP-ribose) polymerase (Cleaved-PARP) was detected in OBA-RT-treated cells. Interestingly, OBA-RT exerted strong CSC-suppressing activity, reducing the ability to form tumor spheroids. In addition, OBA-RT could induce apoptosis in CSC-rich populations and tumor spheroid collapse. CSC markers, including prominin-1 (CD133), Octamer-binding transcription factor 4 (Oct4), and Nanog Homeobox (Nanog), were notably decreased after OBA-RT treatment. Upstream CSCs regulating active Akt and c-Myc were significantly decreased; indicating that Akt may be a potential target of action. Computational molecular modeling revealed a high-affinity interaction between OBA-RT and an Akt molecule. This study has revealed a novel CSC inhibitory effect of OBA-RT via Akt inhibition, which may improve cancer therapy.

Thymopentin-Mediated Inhibition of Cancer Stem Cell Stemness Enhances the Cytotoxic Effect of Oxaliplatin on Colon Cancer Cells

Thymopentin (TP5) is an immunomodulatory pentapeptide that has been widely used in malignancy patients with immunodeficiency due to radiotherapy and chemotherapy. Here, we propose that TP5 directly inhibits the stemness of colon cancer cells HCT116 and therefore enhances the cytotoxicity of oxaliplatin (OXA) in HCT116 cells. In the absence of serum, TP5 was able to induce cancer stemness reduction in cultured HCT116 cells and significantly reduced stemness-related signals, such as the expression of surface molecular markers (CD133, CD44 and CD24) and stemness-related genes (ALDH1, SOX2, Oct-4 and Nanog), and resulted in altered Wnt/β-catenin signaling. Acetylcholine receptors (AchRs) are implicated in this process. OXA is a common chemotherapeutic agent with therapeutic effects in various cancers. Although TP5 had no direct effect on the proliferation of HCT116, this pentapeptide significantly increased the sensitivity of HCT116 to OXA, where the effect of TP5 on the stemness of colon cancer cells through stimulation of AchRs may contribute to this process. Our results provide a promising strategy for increasing the sensitivity of colon cancer cells to chemotherapeutic agents by incorporating immunomodulatory peptides.

Subsets of cancer cells expressing CX3CR1 are endowed with metastasis-initiating properties and resistance to chemotherapy

Metastasis-initiating cells (MICs) display stem cell-like features, cause metastatic recurrences and defy chemotherapy, which leads to patients' demise. Here we show that prostate and breast cancer patients harbor contingents of tumor cells with high expression of CX3CR1, OCT4a (POU5F1), and NANOG. Impairing CX3CR1 expression or signaling hampered the formation of tumor spheroids by cell lines from which we isolated small subsets co-expressing CX3CR1 and stemness-related markers, similarly to patients' tumors. These rare CX3CR1High cells show transcriptomic profiles enriched in pathways that regulate pluripotency and endowed with metastasis-initiating behavior in murine models. Cancer cells lacking these features (CX3CR1Low) were capable of re-acquiring CX3CR1-associated features over time, implying that MICs can continuously emerge from non-stem cancer cells. CX3CR1 expression also conferred resistance to docetaxel, and prolonged treatment with docetaxel selected CX3CR1High phenotypes with de-enriched transcriptomic profiles for apoptotic pathways. These findings nominate CX3CR1 as a novel marker of stem-like tumor cells and provide conceptual ground for future development of approaches targeting CX3CR1 signaling and (re)expression as therapeutic means to prevent or contain metastasis initiation.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Emerging roles of epithelial-mesenchymal plasticity in invasion-metastasis cascade and therapy resistance

Strong association of cancer incidence and its progression with mortality highlights the need to decipher the cellular and molecular mechanisms that drive tumor cells to rapidly progress to metastatic disease and therapy resistance. Epithelial-mesenchymal plasticity (EMP) emerged as a key regulator of metastatic outgrowth. It allows neoplastic epithelial cells to delaminate from their neighbors either individually or collectively, traverse the extracellular matrix (ECM) barrier, enter into the circulation, and establish distal metastases. Plasticity between epithelial and mesenchymal states and the existence of hybrid epithelial/mesenchymal (E/M) phenotypes are increasingly being reported in different tumor contexts. Small subset of cancer cells with stemness called cancer stem cells (CSCs) exhibit plasticity, possess high tumorigenic potential, and contribute to high degree of tumoral heterogeneity. EMP characterized by the presence of dynamic intermediate states is reported to be influenced by (epi)genomic reprograming, growth factor signaling, inflammation, and low oxygen generated by tumor stromal microenvironment. EMP alters the genotypic and phenotypic characteristics of tumor cells/CSCs, disrupts tissue homeostasis, induces the reprogramming of angiogenic and immune recognition functions, and renders tumor cells to survive hostile microenvironments and resist therapy. The present review summarizes the roles of EMP in tumor invasion and metastasis and provides an update on therapeutic strategies to target the metastatic and refractory cancers.

Highly Valuable Polyunsaturated Fatty Acids from Microalgae: Strategies to Improve Their Yields and Their Potential Exploitation in Aquaculture

Microalgae have a great potential for the production of healthy food and feed supplements. Their ability to convert carbon into high-value compounds and to be cultured in large scale without interfering with crop cultivation makes these photosynthetic microorganisms promising for the sustainable production of lipids. In particular, microalgae represent an alternative source of polyunsaturated fatty acids (PUFAs), whose consumption is related to various health benefits for humans and animals. In recent years, several strategies to improve PUFAs' production in microalgae have been investigated. Such strategies include selecting the best performing species and strains and the optimization of culturing conditions, with special emphasis on the different cultivation systems and the effect of different abiotic factors on PUFAs' accumulation in microalgae. Moreover, developments and results obtained through the most modern genetic and metabolic engineering techniques are described, focusing on the strategies that lead to an increased lipid production or an altered PUFAs' profile. Additionally, we provide an overview of biotechnological applications of PUFAs derived from microalgae as safe and sustainable organisms, such as aquafeed and food ingredients, and of the main techniques (and their related issues) for PUFAs' extraction and purification from microalgal biomass.

THOC2 and THOC5 Regulate Stemness and Radioresistance in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer. Radioresistance and stemness are substantial obstacles to TNBC treatment. The THO complex (THOC) is a subunit of the TRanscription-EXport complex that functions in the coupling of transcription to nascent RNA splicing, elongation, and export. However, its role in regulating TNBC therapeutic resistance is not reported yet. In this study, the authors demonstrate that cancer stem cells are enriched in radioresistant TNBC cells and describe the role of the THOC in regulating TNBC radioresistance and stemness. The authors find that THOC2 and THOC5 are upregulated in radioresistant TNBC cells and associated with a poor prognosis in TNBC patients. Further investigation reveals that THOC2 promotes the stem-like properties and radioresistance of TNBC cells in a THOC5-dependent manner by facilitating the release of sex-determining region Y (SRY)-box transcription factor 2 (SOX2) and homeobox transcription factor (NANOG) transcripts from the nucleus. Silencing THOC2 or THOC5 expression decreases the protein expression of SOX2 and NANOG, depletes the stem-like properties, and causes radiosensitization in these TNBC cells. Moreover, THOC2 or THOC5 depletion blocks the xenograft tumorigenesis and growth of radioresistant TNBC in vivo. These findings uncover the novel correlations of THOC with TNBC stemness and therapeutic resistance, proposing alternative therapeutic strategies against relapsed TNBC.

Hydroquinone 5-O-Cinnamoyl Ester of Renieramycin M Suppresses Lung Cancer Stem Cells by Targeting Akt and Destabilizes c-Myc

Cancer stem cells (CSCs) are distinct cancer populations with tumorigenic and self-renewal abilities. CSCs are drivers of cancer initiation, progression, therapeutic failure, and disease recurrence. Thereby, novel compounds targeting CSCs offer a promising way to control cancer. In this study, the hydroquinone 5-O-cinnamoyl ester of renieramycin M (CIN-RM) was demonstrated to suppress lung cancer CSCs. CIN-RM was toxic to lung cancer cells with a half-maximal inhibitory concentration of around 15 µM. CIN-RM suppressed CSCs by inhibiting colony and tumor spheroid formation. In addition, the CSC population was isolated and treated and the CSCs were dispatched in response to CIN-RM within 24 h. CIN-RM was shown to abolish cellular c-Myc, a central survival and stem cell regulatory protein, with the depletion of CSC markers and stem cell transcription factors ALDH1A1, Oct4, Nanog, and Sox2. For up-stream regulation, we found that CIN-RM significantly inhibited Akt and consequently decreased the pluripotent transcription factors. CIN-RM also inhibited mTOR, while slightly decreasing p-GSK3β (Ser9) but rarely affected the protein kinase C (PKC) signal. Inhibiting Akt/mTOR induced ubiquitination of c-Myc and promoted degradation. The mechanism of how Akt regulates the stability of c-Myc was validated with the Akt inhibitor wortmannin. The computational analysis further confirmed the strong interaction between CIN-RM and the Akt protein with a binding affinity of −10.9 kcal/mol at its critical active site. Taken together, we utilized molecular experiments, the CSC phenotype, and molecular docking methods to reveal the novel suppressing the activity of this compound on CSCs to benefit CSC-targeted therapy for lung cancer treatment.

Pongol Methyl Ether Inhibits Akt and Suppresses Cancer Stem Cell Phenotypes in Lung Cancer Cells

Cancer stem cells (CSCs) are an important therapeutic target. The therapeutic agents targeting CSCs should lead to improved clinical outcomes. Here we have demonstrated the CSC-suppressing activity of pongol methyl ether (PME), a pure compound from Millettia erythrocalyx.

METHODS

CSC-suppressing effects were evaluated by spheroid formation assay and detection of CSC markers. The related CSC cell signals were evaluated by Western blot, immunofluorescence and molecular docking analysis. Proteins affected by PME treatment were subjected to bioinformatic analysis. Protein-protein interaction (PPI) networks were constructed by the Search Tool for Interactions of Chemicals (STITCH). The Kyoto Encyclopedia of Genes and Genomes (KEGG) mapper were used to confirm the underlying pathways.

RESULTS

PME (5-25 µM) significantly suppressed the ability of lung cancer cells to form colonies, grow in an anchorage-independent manner and generate tumour spheroids. PME at 25 µM significantly decreased the CSC markers (CD133 and ALDH1A1) and pluripotent transcription factors (Oct4 and Nanog). Akt, the key upstream signal of CSC control, was significantly decreased by the PME treatment. The molecular docking indicated that PME was bound to Akt-1 with a binding affinity of -9.2 kcal/mol greater than the Akt-1 inhibitor (reference compound; CQW). The STITCH network identified a total of 15 proteins interacted in PPI networks, and Akt-1 was identified as a central protein. The KEGG mapper indicated that the selected CSC markers were mostly involved in the 'signalling pathways regulating pluripotency of stem cells' pathway map and Akt, Oct4 and Nanog were the regulatory proteins in the dominant pathway. In addition, PME (10-25 µM) can suppress spheroid formation and reduce CSC-specific marker expression in patient-derived primary lung cancer cells.

CONCLUSIONS

Our study revealed a novel pharmacological effect and the underlying mechanism of PME that can attenuate CSC phenotypes in lung cancer cells and may be developed for lung cancer therapy.

SOX transcription factors and glioma stem cells: Choosing between stemness and differentiation

Glioblastoma (GBM) is the most common, most aggressive and deadliest brain tumor. Recently, remarkable progress has been made towards understanding the cellular and molecular biology of gliomas. GBM tumor initiation, progression and relapse as well as resistance to treatments are associated with glioma stem cells (GSCs). GSCs exhibit a high proliferation rate and self-renewal capacity and the ability to differentiate into diverse cell types, generating a range of distinct cell types within the tumor, leading to cellular heterogeneity. GBM tumors may contain different subsets of GSCs, and some of them may adopt a quiescent state that protects them against chemotherapy and radiotherapy. GSCs enriched in recurrent gliomas acquire more aggressive and therapy-resistant properties, making them more malignant, able to rapidly spread. The impact of SOX transcription factors (TFs) on brain tumors has been extensively studied in the last decade. Almost all SOX genes are expressed in GBM, and their expression levels are associated with patient prognosis and survival. Numerous SOX TFs are involved in the maintenance of the stemness of GSCs or play a role in the initiation of GSC differentiation. The fine-tuning of SOX gene expression levels controls the balance between cell stemness and differentiation. Therefore, innovative therapies targeting SOX TFs are emerging as promising tools for combatting GBM. Combatting GBM has been a demanding and challenging goal for decades. The current therapeutic strategies have not yet provided a cure for GBM and have only resulted in a slight improvement in patient survival. Novel approaches will require the fine adjustment of multimodal therapeutic strategies that simultaneously target numerous hallmarks of cancer cells to win the battle against GBM.

In silico identification of natural product inhibitors against Octamer-binding transcription factor 4 (Oct4) to impede the mechanism of glioma stem cells

Octamer-binding transcription factor 4 (Oct4) is a core regulator in the retention of stemness, invasive, and self-renewal properties in glioma initiating cells (GSCs) and its overexpression inhibits the differentiation of glioma cells promoting tumor cell proliferation. The Pit-Oct-Unc (POU) domain comprising POU-specific domain (POUS) and POU-type homeodomain (POUHD) subdomains is the most critical part of the Oct4 for the generation of induced pluripotent stem cells from somatic cells that lead to tumor initiation, invasion, posttreatment relapse, and therapeutic resistance. Therefore, the present investigation hunts for natural product inhibitors (NPIs) against the POUHD domain of Oct4 by employing receptor-based virtual screening (RBVS) followed by binding free energy calculation and molecular dynamics simulation (MDS). RBVS provided 13 compounds with acceptable ranges of pharmacokinetic properties and good docking scores having key interactions with the POUHD domain. More Specifically, conformational and interaction stability analysis of 13 compounds through MDS unveiled two compounds ZINC02145000 and ZINC32124203 which stabilized the backbone of protein even in the presence of linker and POUS domain. Additionally, ZINC02145000 and ZINC32124203 exhibited stable and strong interactions with key residues W277, R242, and R234 of the POUHD domain even in dynamic conditions. Interestingly, ZINC02145000 and ZINC32124203 established communication not only with the POUHD domain but also with the POUS domain indicating their incredible potency toward thwarting the function of Oct4. ZINC02145000 and ZINC32124203 also reduced the flexibility and escalated the correlations between the amino acid residues of Oct4 evidenced by PCA and DCCM analysis. Finally, our examination proposed two NPIs that can impede the Oct4 function and may help to improve overall survival, diminish tumor relapse, and achieve a cure not only in deadly disease GBM but also in other cancers with minimal side effects.

Immunohistochemical and molecular profiling of CD 117, Oct-4, and Sox-2 in canine cutaneous mast cell tumor of the crossbred dogs in Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand

BACKGROUND AND AIM

CD 117 (c-KIT) internal tandem duplication (ITD), octamer-binding transcription factor 4 (Oct-4), and sex-determining region Y-box 2 (Sox-2) may govern the oncogenicity and aggressiveness of canine cutaneous mast cell tumor (MCT) in the crossbred dogs. Thus, a comprehension of this matter may help us establishing a novel platform to treat the disease in those dogs. However, evidence has lacked so far. Thus, this study aimed to survey CD 117 ITD, Oct-4, and Sox-2 expressions and their relations to the 2-tier grading in a group of Thai crossbreed dogs. The study was done using polymerase chain reaction (PCR), Reverse transcription PCR (RT-PCR), and immunohistochemistry.

MATERIALS AND METHODS

Thirty-three MCT specimens graded by the 2-tier histopathology grading were collected from the crossbred and purebred dogs. CD 117 ITD was detected by conventional PCR and immunohistochemistry. While, Oct-4 and Sox-2 expression levels were determined at the protein and mRNA levels by immunohistochemistry and RT-PCR, respectively. The expression magnitude of each parameter was then related to the grades and breeds.

RESULTS

About 60.61% of specimens were low grade, while 39.39% were high grade. CD 117 ITD was not detected in all specimens. A significant increase of Oct-4 expression was found in the high-grade, crossbred dogs. Meanwhile, Sox-2 expressions were increased both in the purebred and crossbred dogs with high-grade MCT.

CONCLUSION

The study finding has indicated that the level of Sox-2 expression may be a useful tumorigenic and prognostic biomarker because it correlates to the 2-tier grades but not dog breeds.

Phytomedicines Targeting Cancer Stem Cells: Therapeutic Opportunities and Prospects for Pharmaceutical Development

The presence of small subpopulations of cells within tumor cells are known as cancer stem cells (CSCs). These cells have been the reason for metastasis, resistance with chemotherapy or radiotherapy, and tumor relapse in several types of cancers. CSCs underwent to epithelial–mesenchymal transition (EMT) and resulted in the development of aggressive tumors. CSCs have potential to modulate numerous signaling pathways including Wnt, Hh, and Notch, therefore increasing the stem-like characteristics of cancer cells. The raised expression of drug efflux pump and suppression of apoptosis has shown increased resistance with anti-cancer drugs. Among many agents which were shown to modulate these, the plant-derived bioactive agents appear to modulate these key regulators and were shown to remove CSCs. This review aims to comprehensively scrutinize the preclinical and clinical studies demonstrating the effects of phytocompounds on CSCs isolated from various tumors. Based on the available convincing literature from preclinical studies, with some clinical data, it is apparent that selective targeting of CSCs with plants, plant preparations, and plant-derived bioactive compounds, termed phytochemicals, may be a promising strategy for the treatment of relapsed cancers.

Impact of miRNAs expression modulation on the methylation status of breast cancer stem cell-related genes

PURPOSE

Altered miRNAs play a crucial role in the emergence of the breast cancer stem cell (BCSC) phenotype. The interplay between miRNAs and methylation enzymes has been documented. One of the most aggressive breast cancer cell lines, MDA-MB-231, has expressed much more DNMT3B than DNMT3A. This study aims to evaluate the ability of miR-203 restoration and miR-150 inhibition to regulate DNMT3B and DNMT3A to modify the methylation level of BCSC-associated genes.

METHODS

MDA-MB-231 cells were transfected with miR-203 mimic or miR-150 inhibitor or DNMT3B siRNA, and downstream analysis was performed by flow cytometry, real-time PCR and Western blotting.

RESULTS

DNMT3A and DNMT3B are regulated both by miR-203a-3p and miR-150-5p. Transfection with miR-203 mimic and miR-150 inhibitor significantly reduced the CD44+CD24- subpopulation and down-regulated the expression of CD44 mRNA by increasing promoter methylation levels. SiRNA knockdown of DNMT3B increased the CD44+CD24- subpopulation and the expression of CD44 and ALDH1A3 by decreasing methylation density. The inhibition of miR-150 down-regulated OCT3/4 and SOX2 expression without affecting methylation levels, while miR-203 restoration and miR-150 inhibition down-regulated NANOG expression by elevating the methylation level. A positive-feedback loop was found between miR-203 and its target DNMT3B, as restoring miR-203 suppressed DNMT3B, while knocking down DNMT3B up-regulated miR-203. The restoration of miR-203 and knockdown of DNMT3B decreased methylation levels and increased the expression of miR-141 and miR-200c.

CONCLUSIONS

The study concluded that miR-203 and miR-150 play a role in the regulation of genes involved in BCSC methylation, including other miRNAs, by targeting DNMT3B and DNMT3A.

Regulation of cancer stem cells in triple negative breast cancer

Triple Negative Breast Cancer (TNBC) is the most lethal subtype of breast cancer. Despite the successes of emerging targeted therapies, relapse, recurrence, and therapy failure rates in TNBC significantly outpace other subtypes of breast cancer. Mounting evidence suggests accumulation of therapy resistant Cancer Stem Cell (CSC) populations within TNBCs contributes to poor clinical outcomes. These CSCs are enriched in TNBC compared to non-TNBC breast cancers. The mechanisms underlying CSC accumulation have been well-characterized and discussed in other reviews. In this review, we focus on TNBC-specific mechanisms that allow the expansion and activity of self-renewing CSCs. We highlight cellular signaling pathways and transcription factors, specifically enriched in TNBC over non-TNBC breast cancer, contributing to stemness. We also analyze publicly available single-cell RNA-seq data from basal breast cancer tumors to highlight the potential of emerging bioinformatic approaches in identifying novel drivers of stemness in TNBC and other cancers.

Oct4-Mediated Inhibition of Lsd1 Activity Promotes the Active and Primed State of Pluripotency Enhancers

An aberrant increase in pluripotency gene (PpG) expression due to enhancer reactivation could induce stemness and enhance the tumorigenicity of cancer stem cells. Silencing of PpG enhancers (PpGe) during embryonic stem cell differentiation involves Lsd1-mediated H3K4me1 demethylation and DNA methylation. Here, we observed retention of H3K4me1 and DNA hypomethylation at PpGe associated with a partial repression of PpGs in F9 embryonal carcinoma cells (ECCs) post-differentiation. H3K4me1 demethylation in F9 ECCs could not be rescued by Lsd1 overexpression. Given our observation that H3K4me1 demethylation is accompanied by strong Oct4 repression in P19 ECCs, we tested if Oct4 interaction with Lsd1 affects its catalytic activity. Our data show a dose-dependent inhibition of Lsd1 activity by Oct4 and retention of H3K4me1 at PpGe in Oct4-overexpressing P19 ECCs. These data suggest that Lsd1-Oct4 interaction in cancer stem cells could establish a "primed" enhancer state that is susceptible to reactivation, leading to aberrant PpG expression.

Enhanced KRT13 gene expression bestows radiation resistance in squamous cell carcinoma cells

Cancer metastasis and recurrence are potentially lethal. A small number of cancer cell groups called cancer stem cells (CSCs) have both stem cell capacity and cancer-forming ability and are reported to play important roles in cancer metastasis and recurrence. These CSCs are considered to be radiation-resistant (RR). Therefore, understanding the biological effects of radiation on squamous cell carcinoma (SCC) cell lines in vitro and in vivo might be worthwhile to circumvent radiation resistance. Currently, there are no reports on the establishment of RR-SCC cells in serum-free defined culture, which mimics biological mechanisms and prevents instability of using serum in the culture medium. We isolated radiation-resistant strains, designated A431-LDR and A431-HDR, from A431 cells derived from vulval SCC and irradiated them with a total dose of 60 Gy at a low-dose rate (2.2 Gy/d) (RM1000) and a high-dose rate (5 Gy/5.75min) in serum-free defined culture. These cells exhibited high sphere-forming and migration ability in vitro and high tumor-forming ability in nude mice xenografts. Overexpression of KRT13 in A431-RR cells might play a role in its radiation-resistant characteristics. These cells might be useful not only to study cancer stem cells but also to study the circumvention of radiation resistance by novel cancer treatment modalities.

Cancer stem cells and macrophages: molecular connections and future perspectives against cancer

Cancer stem cells (CSCs) have been considered the key drivers of cancer initiation and progression due to their unlimited self-renewal capacity and their ability to induce tumor formation. Macrophages, particularly tumor-associated macrophages (TAMs), establish a tumor microenvironment to protect and induce CSCs development and dissemination. Many studies in the past decade have been performed to understand the molecular mediators of CSCs and TAMs, and several studies have elucidated the complex crosstalk that occurs between these two cell types. The aim of this review is to define the complex crosstalk between these two cell types and to highlight potential future anti-cancer strategies.

Kynurenine 3-monooxygenase upregulates pluripotent genes through β-catenin and promotes triple-negative breast cancer progression

Background

Triple-negative breast cancer (TNBC) is aggressive and has a poor prognosis. Kynurenine 3-monooxygenase (KMO), a crucial kynurenine metabolic enzyme, is involved in inflammation, immune response and tumorigenesis. We aimed to study the role of KMO in TNBC.

Methods

KMO alteration and expression data from public databases were analyzed. KMO expression levels in TNBC samples were analyzed using immunohistochemistry. Knockdown of KMO in TNBC cells was achieved by RNAi and CRISPR/Cas9. KMO functions were examined by MTT, colony-forming, transwell migration/invasion, and mammosphere assays. The molecular events were analyzed by cDNA microarrays, Western blot, quantitative real-time PCR and luciferase reporter assays. Tumor growth and metastasis were detected by orthotopic xenograft and tail vein metastasis mouse models, respectively.

Findings

KMO was amplified and associated with worse survival in breast cancer patients. KMO expression levels were higher in TNBC tumors compared to adjacent normal mammary tissues. In vitro ectopic KMO expression increased cell growth, colony and mammosphere formation, migration, invasion as well as mesenchymal marker expression levels in TNBC cells. In addition, KMO increased pluripotent gene expression levels and promoter activities in vitro. Mechanistically, KMO was associated with β-catenin and prevented β-catenin degradation, thereby enhancing the transcription of pluripotent genes. KMO knockdown suppressed tumor growth and the expression levels of β-catenin, CD44 and Nanog. Furthermore, mutant KMO (known with suppressed enzymatic activity) could still promote TNBC cell migration/invasion. Importantly, mice bearing CRISPR KMO-knockdown TNBC tumors showed decreased lung metastasis and prolonged survival.

Interpretation

KMO regulates pluripotent genes via β-catenin and plays an oncogenic role in TNBC progression.

Cancer Stem Cells and Nucleolin as Drivers of Carcinogenesis

Cancer, one of the most mortal diseases worldwide, is characterized by the gain of specific features and cellular heterogeneity. Clonal evolution is an established theory to explain heterogeneity, but the discovery of cancer stem cells expanded the concept to include the hierarchical growth and plasticity of cancer cells. The activation of epithelial-to-mesenchymal transition and its molecular players are widely correlated with the presence of cancer stem cells in tumors. Moreover, the acquisition of certain oncological features may be partially attributed to alterations in the levels, location or function of nucleolin, a multifunctional protein involved in several cellular processes. This review aims at integrating the established hallmarks of cancer with the plasticity of cancer cells as an emerging hallmark; responsible for tumor heterogeneity; therapy resistance and relapse. The discussion will contextualize the involvement of nucleolin in the establishment of cancer hallmarks and its application as a marker protein for targeted anticancer therapies

Effect of Menadione and Combination of Gemcitabine and Cisplatin on Cancer Stem Cells in Human Non-small Cell Lung Cancer (NSCLC) Cell Line A549

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Chemotherapy-induced adverse effects and resistance of NSCLC to conventional drugs reduce the efficacy of current therapies. Tumors contain a small population of cancer stem cells (CSCs) that play a critical role in tumor initiation, maintenance, and drug resistance that finally lead to cancer recurrence. Therefore, CSC-targeting therapies can offer the best hope for developing curative cancer therapies. Vitamins have a high potential for cancer prevention and treatment. Vitamins also ameliorate the side effects which occur in chemo-radio therapy. Menadione (2-methyl-1,4-naphthoquinone/vitamin-K3) is a synthetic form of vitamin K that indicated antitumor activities. The purpose of this study was to evaluate the anti-CSCs effect of menadione and combination of cisplatin and gemcitabine as a first-line treatment in patients with NSCLC on the NSCLC cell line A549. MTT results displayed decreased cell survival after treatment with cisplatin/gemcitabine for 48 h treatment (IC₅₀ values 0.25 µM for cisplatin and 5 µM for gemcitabine). Menadione also inhibited the cell growth in A549 cells (IC₅₀: 16 µM). Quantitative RT-PCR showed significant downregulation of CSC markers (Oct4, Nanog, Sox2, Aldh1, Abcb1, CD44, and CD133) and Snail, epithelial-mesenchymal transition marker, after treatment with menadione and cisplatin/gemcitabine. Flow cytometry showed CD44-positive cells that constitute a high percentage (70%) of A549 cells reduced significantly after treatment with cisplatin/gemcitabine or menadione. However, A549 cells did not show a significant population positive for CD133 and ABCB1 (less than 0.05%), and these fractions did not change after treatment with two agents.

Cancer Stem Cell (CSC) Inhibitors in Oncology-A Promise for a Better Therapeutic Outcome: State of the Art and Future Perspectives

Cancer stem cells (CSCs), a subpopulation of cancer cells endowed with self-renewal, tumorigenicity, pluripotency, chemoresistance, differentiation, invasive ability, and plasticity, reside in specialized tumor niches and are responsible for tumor maintenance, metastasis, therapy resistance, and tumor relapse. The new-age "hierarchical or CSC" model of tumor heterogeneity is based on the concept of eradicating CSCs to prevent tumor relapse and therapy resistance. Small-molecular entities and biologics acting on various stemness signaling pathways, surface markers, efflux transporters, or components of complex tumor microenvironment are under intense investigation as potential anti-CSC agents. In addition, smart nanotherapeutic tools have proved their utility in achieving CSC targeting. Several CSC inhibitors in clinical development have shown promise, either as mono- or combination therapy, in refractory and difficult-to-treat cancers. Clinical investigations with CSC marker follow-up as a measure of clinical efficacy are needed to turn the "hype" into the "hope" these new-age oncology therapeutics have to offer.