Notch Signaling in Cancer Stem Cells

Tissue-specific cancer stem/progenitor cells: Therapeutic implications

Surgical resection, chemotherapy, and radiation are the standard therapeutic modalities for treating cancer. These approaches are intended to target the more mature and rapidly dividing cancer cells. However, they spare the relatively quiescent and intrinsically resistant cancer stem cells (CSCs) subpopulation residing within the tumor tissue. Thus, a temporary eradication is achieved and the tumor bulk tends to revert supported by CSCs' resistant features. Based on their unique expression profile, the identification, isolation, and selective targeting of CSCs hold great promise for challenging treatment failure and reducing the risk of cancer recurrence. Yet, targeting CSCs is limited mainly by the irrelevance of the utilized cancer models. A new era of targeted and personalized anti-cancer therapies has been developed with cancer patient-derived organoids (PDOs) as a tool for establishing pre-clinical tumor models. Herein, we discuss the updated and presently available tissue-specific CSC markers in five highly occurring solid tumors. Additionally, we highlight the advantage and relevance of the three-dimensional PDOs culture model as a platform for modeling cancer, evaluating the efficacy of CSC-based therapeutics, and predicting drug response in cancer patients.

SERPINF1 Mediates Tumor Progression and Stemness in Glioma

Serpin family F member 1 (SERPINF1) reportedly plays multiple roles in various tumors; however, its clinical significance and molecular functions in glioma have been largely understudied. In the present study, we analyzed the prognostic value of SERPINF1 in three independent glioma datasets. Next, we explored the molecular functions and transcriptional regulation of SERPINF1 at the single-cell level. Moreover, in vitro experiments were conducted to evaluate the roles of SERPINF1 in the proliferation, invasion, migration, and stemness of glioma cells. Our results showed that a higher expression of SERPINF1 correlated with a poor overall survival rate in glioma patients (hazard ratio: 4.061 in TCGA, 2.017 in CGGA, and 1.675 in GSE16011, p < 0.001). Besides, SERPINF1 knockdown could suppress the proliferation, invasion, and migration of glioma cells in vitro. In addition, SERPINF1 expression was significantly upregulated in glioma stem cells (GSCs) compared to parental glioma cells. Knocking down SERPINF1 impaired the sphere formation of GSC-A172 and GSC-LN18. Bioinformatics analysis revealed that Notch signaling activation was closely associated with high SERPINF1 expression at the single-cell level. Furthermore, STAT1, CREM, and NR2F2 may participate in the transcriptional regulation of SERPINF1 in glioma. Overall, our results suggest that SERPINF1 may be a candidate prognostic predictor and potential therapeutic target for glioma.

RITA1 drives the growth of bladder cancer cells by recruiting TRIM25 to facilitate the proteasomal degradation of RBPJ

Bladder cancer (BC) is one of the most prevalent malignancies worldwide, but it lacks effective targeted therapy due to its elusive molecular mechanism. Therefore, it is important to further investigate the molecular mechanisms that mediate BC progression. By performing a tumor tissue–based gene microarray and shRNA library screening, we found that recombination signal binding protein for immunoglobulin kappa J region (RBPJ) interacting and tubulin associated 1 (RITA1) is crucial for the growth of BC cells. Moreover, RITA1 is aberrantly highly expressed in BC tissues and is also correlated with poor prognosis in patients with BC. Mechanistically, we determined that RITA1 recruits tripartite motif containing 25 (TRIM25) to ubiquitinate RBPJ to accelerate its degradation via proteasome, which leads to the transcriptional inhibition of Notch1 downstream targets. Our results suggest that aberrant high expression of RITA1 drives the growth of BC cells via the RITA1/TRIM25/RBPJ axis and RITA1 may serve as a promising therapeutic target for BC.

Lumiflavin Reduces Cisplatin Resistance in Cancer Stem-Like Cells of OVCAR-3 Cell Line by Inducing Differentiation

Ovarian cancer stem-like cells (CSCs) play a vital role in drug resistance and recurrence of ovarian cancer. Inducing phenotypic differentiation is an important strategy to enhance the effects of chemotherapy and reduce the drug resistance of CSCs. This study found that lumiflavin, a riboflavin decomposition product, reduced the development of CSC resistance and enhanced the chemotherapy effect of cisplatin (DDP) on CSCs in DDP-resistant ovarian cancer OVCAR-3 cell line (CSCs/DDP) and was related to the induction of CSC phenotypic differentiation. Results showed that the development of DDP-resistant OVCAR-3 cells was related to the increase in the proportion of CSCs/DDP, and the treatment with lumiflavin reduced the DDP-resistance levels of OVCAR-3 cells and proportion of CSCs/DDP. Further investigation found that lumiflavin synergistic with DDP increased apoptosis, decreased mitochondrial membrane potential, and inhibited the clonal formation of CSCs/DDP. Meanwhile, in vivo experiments showed that lumiflavin dose-dependently enhanced the chemotherapy effect of DDP on tumor-bearing nude mice inoculated by CSCs/DDP. Lumiflavin treatment also reduced the ratio of CD133+/CD177+ to CD44+/CD24 cells, which is the identification of CSCs, in CSCs/DDP. In addition, transcriptome sequencing results suggested that the role of lumiflavin was related to the notch and stem cell pathway, and Western blot analysis showed that lumiflavin inhibited the protein expression of notch signaling pathway in CSCs/DDP. In conclusion, lumiflavin reduces the development of the drug resistance of OVCAR-3 cell and increases the sensitivity of CSCs/DDP to DDP by inducing phenotypic differentiation, which may have a potential role in the chemotherapy treatment of ovarian cancer.

Metastasis and MAPK Pathways

Cancer is a leading cause of death worldwide. In many cases, the treatment of the disease is limited due to the metastasis of cells to distant locations of the body through the blood and lymphatic drainage. Most of the anticancer therapeutic options focus mainly on the inhibition of tumor cell growth or the induction of cell death, and do not consider the molecular basis of metastasis. The aim of this work is to provide a comprehensive review focusing on cancer metastasis and the mitogen-activated protein kinase (MAPK) pathway (ERK/JNK/P38 signaling) as a crucial modulator of this process.

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.

MicroRNAs as the critical regulators of tyrosine kinase inhibitors resistance in lung tumor cells

Lung cancer is the second most common and the leading cause of cancer related deaths globally. Tyrosine Kinase Inhibitors (TKIs) are among the common therapeutic strategies in lung cancer patients, however the treatment process fails in a wide range of patients due to TKIs resistance. Given that the use of anti-cancer drugs can always have side effects on normal tissues, predicting the TKI responses can provide an efficient therapeutic strategy. Therefore, it is required to clarify the molecular mechanisms of TKIs resistance in lung cancer patients. MicroRNAs (miRNAs) are involved in regulation of various pathophysiological cellular processes. In the present review, we discussed the miRNAs that have been associated with TKIs responses in lung cancer. MiRNAs mainly exert their role on TKIs response through regulation of Tyrosine Kinase Receptors (TKRs) and down-stream signaling pathways. This review paves the way for introducing a panel of miRNAs for the prediction of TKIs responses in lung cancer patients.

Radiation exposure elicits a neutrophil-driven response in healthy lung tissue that enhances metastatic colonization

Radiotherapy is one of the most effective approaches to achieve tumor control in cancer patients, although healthy tissue injury due to off-target radiation exposure can occur. In this study, we used a model of acute radiation injury to the lung, in the context of cancer metastasis, to understand the biological link between tissue damage and cancer progression. We exposed healthy mouse lung tissue to radiation before the induction of metastasis and observed a strong enhancement of cancer cell growth. We found that locally activated neutrophils were key drivers of the tumor-supportive preconditioning of the lung microenvironment, governed by enhanced regenerative Notch signaling. Importantly, these tissue perturbations endowed arriving cancer cells with an augmented stemness phenotype. By preventing neutrophil-dependent Notch activation, via blocking degranulation, we were able to significantly offset the radiation-enhanced metastases. This work highlights a pro-tumorigenic activity of neutrophils, which is likely linked to their tissue regenerative functions.

Live tumor imaging shows macrophage induction and TMEM-mediated enrichment of cancer stem cells during metastatic dissemination

Cancer stem cells (CSCs) play an important role during metastasis, but the dynamic behavior and induction mechanisms of CSCs are not well understood. Here, we employ high-resolution intravital microscopy using a CSC biosensor to directly observe CSCs in live mice with mammary tumors. CSCs display the slow-migratory, invadopod-rich phenotype that is the hallmark of disseminating tumor cells. CSCs are enriched near macrophages, particularly near macrophage-containing intravasation sites called Tumor Microenvironment of Metastasis (TMEM) doorways. Substantial enrichment of CSCs occurs on association with TMEM doorways, contributing to the finding that CSCs represent >60% of circulating tumor cells. Mechanistically, stemness is induced in non-stem cancer cells upon their direct contact with macrophages via Notch-Jagged signaling. In breast cancers from patients, the density of TMEM doorways correlates with the proportion of cancer cells expressing stem cell markers, indicating that in human breast cancer TMEM doorways are not only cancer cell intravasation portals but also CSC programming sites.

Gamma-Secretase Inhibitor (DAPT), a potential therapeutic target drug, caused neurotoxicity in planarian regeneration by inhibiting Notch signaling pathway

DAPT (N-[N-(3, 5-difluorophenacetyl)-l-alanyl]-s-phenylglycinet-butyl ester) is a γ-secretase inhibitor that indirectly blocks the activity of Notch pathway. It is a potential therapeutic target drug for many diseases, such as cancer, neurological, cardiovascular, and cerebrovascular diseases. However, the pharmacological action and specific mechanisms of DAPT are not clear. Planarians have strong regenerative capacity and can regenerate a new individual with a complete nervous system in one week. Thus, they are used as an ideal indicator of environmental toxicants and a novel model for studying neurodevelopmental toxicology. In this study, different concentrations and treatment times of DAPT are used to analyze the gene expression levels of major components in Notch pathway. The results show that the optimal concentration and exposure time of DAPT is 100 nM for 10 days in planarians and indicate that the inhibitory of DAPT treatment on Notch pathway is time- and concentration-dependent. The potential impact of DAPT is effectively analyzed by qPCR, WISH, and Immunofluorescence. The results indicate that DAPT exposure causes intact planarian wavy or swollen, and regenerative planarians asymmetric growth or muti-eye. Moreover, DAPT exposure increases cell proliferation and apoptosis, results in neurodevelopmental defects and dynamic changes of some marker genes. These results suggest that the balance of proliferation and apoptosis is disturbed, and then, affecting tissue homeostasis and differentiation. These findings demonstrate that DAPT has serious side effects in organisms and relies on Notch pathway to determine cell fate, it is cautious in the use of DAPT as a potential therapeutic approach for the disease in clinical trials.

Metastatic Pediatric Sclerosing Epithelioid Fibrosarcoma

Sclerosing epithelioid fibrosarcoma (SEF) is a rare and aggressive soft-tissue sarcoma thought to originate in fibroblasts of the tissues comprising tendons, ligaments, and muscles. Minimally responsive to conventional cytotoxic chemotherapies, >50% of SEF patients experience local recurrence and/or metastatic disease. SEF is most commonly discovered in middle-aged and elderly adults, but also rarely in children. A common gene fusion occurring between the EWSR1 and CREB3L1 genes has been observed in 80%–90% of SEF cases. We describe here the youngest SEF patient reported to date (a 3-yr-old Caucasian male) who presented with numerous bony and lung metastases. Additionally, we perform a comprehensive literature review of all SEF-related articles published since the disease was first characterized. Finally, we describe the generation of an SEF primary cell line, the first such culture to be reported. The patient described here experienced persistent disease progression despite aggressive treatment including multiple resections, radiotherapy, and numerous chemotherapies and targeted therapeutics. Untreated and locally recurrent tumor and metastatic tissue were sequenced by whole-genome, whole-exome, and deep-transcriptome next-generation sequencing with comparison to a patient-matched normal blood sample. Consistent across all sequencing analyses was the disease-defining EWSR1–CREB3L1 fusion as a single feature consensus. We provide an analysis of our genomic findings and discuss potential therapeutic strategies for SEF.

Overview and recent advances in the targeting of medulloblastoma cancer stem cells

Introduction: Medulloblastoma, an embryonal small round blue cell tumor primarily arising in the posterior fossa, is the most common malignancy of the central nervous system in children and requires intensive multi-modality therapy for cure. Overall 5-year survival is approximately 75% in children with primary disease, but outcomes for relapsed disease are very poor. Recent advances have identified molecular subgroups with excellent prognosis, with 5-year overall survival rates >90%, and subgroups with very poor prognosis with overall survival rates <50%. Molecular subtyping has allowed for more sophisticated risk stratification of patients, but new treatments for the highest risk patients have not yet improved outcomes. Targeting cancer stem cells may improve outcomes, and several candidate targets and novel drugs are under investigation.Areas covered: We discuss medulloblastoma epidemiology, biology, treatment modalities, risk stratification, and molecular subgroup analysis, links between subgroup and developmental biology, cancer stem cell biology in medulloblastoma including previously described cancer stem cell markers and proposed targeted treatments in the current literature.Expert opinion: The understanding of cancer stem cells in medulloblastoma will advance therapies targeting the most treatment-resistant cells within the tumor and therefore reduce the incidence of treatment refractory and relapsed disease.

Aquaporins implicated in the cell proliferation and the signaling pathways of cell stemness

Aquaporins (AQPs) are water channel proteins facilitating passive transport of water and other small molecules across biomembranes. Regulation of osmotic homeostasis via AQPs is accompanied by dynamic participation of various cellular signaling pathways. Recently emerging evidence reveals that functional roles of AQPs are further extended from the osmotic regulation via water permeation into the cell proliferation and differentiation. In particular, anomalous expression of AQPs has been demonstrated in various types of cancer cells and cancer stem-like cells and it has been proposed as markers for proliferation and progression of cancer cells. Thus, a more comprehensive view on AQPs could bring a great interest in the cell stemness accompanied by the expression of AQPs. AQPs are broadly expressed across tissues and cells in a cell type- and lineage-specific manner during development via spatiotemporal transcriptional regulation. Moreover, AQPs are expressed in various adult stem cells and cells associated with a stem cell niche as well as cancer stem-like cells. However, the expression and regulatory mechanisms of AQP expression in stem cells have not been well understood. This review highlighted the AQPs expression in stem cell niches/stem cells and the involvement of AQPs in the cell proliferation and signaling pathways associated with cell stemness.

In Vitro Evaluation of Notch Inhibition to Enhance Efficacy of Radiation Therapy in Melanoma

Purpose

The scope of radiation therapy is limited in melanoma. Using in vitro melanoma models, we investigated a Notch signaling inhibitor as a radiosensitizer to explore its potential to improve the efficacy of radiation therapy to widen the clinical application of radiation therapy in melanoma.

Methods and Materials

Melanoma cell lines A375, SKMEL28, and G361 were grown using standard tissue culture methods. Radiation was delivered with a clinical x-ray unit, and a gamma secretase inhibitor RO4929097 was used to inhibit Notch signaling. Cell viability signal was used to calculate Loewe's combination index to assess the interaction between radiation and RO4929097 and also the effect of scheduling of radiation and RO4929097 on synergy. Clonogenic assays were used to assess the clonogenic potential. An in vitro 3-dimensional culture model, γ-H2AX, and notch intracellular domain assays were used to interrogate potential underlying biological mechanisms of this approach. Scratch and transwell migration assays were used to assess cell migration.

Results

A375 and SKMEL28 cell lines showed consistent synergy for most single radiation doses examined, with a tendency for better synergy with the radiation-first schedule (irradiation performed 24 hours before RO4929097 exposure). Clonogenic assays showed dose-dependent reduction in colony numbers. Both radiation and RO4929097 reduced the size of melanospheres grown in 3-dimensional culture in vitro, where RO4929097 demonstrated a significant effect on the size of A375 and SKMEL28 melanospheres, indicating potential modulation of stem cell phenotype. Radiation induced γ-H2AX foci signal levels were reduced after exposure to RO4929097 with a tendency toward reduction in notch intracellular domain levels for all 3 cell lines. RO4929097 impaired both de novo and radiation-enhanced cell migration.

Conclusions

We demonstrate Notch signaling inhibition with RO4929097 as a promising strategy to potentially improve the efficacy of radiation therapy in melanoma. This strategy warrants further validation in vivo.

A Phase II and Pharmacodynamic Trial of RO4929097 for Patients With Recurrent/Progressive Glioblastoma

BACKGROUND

Cancer stem-like cells are a major cause of resistance to therapy in patients with glioblastoma (GBM) as well as other cancers. Tumor cells are maintained in a stem-like proliferative state in large part through the Notch signaling pathway. The function of this pathway in turn depends on gamma secretase activity. Inhibition of this enzyme therefore inhibits the Notch pathway and tumor growth as measured by a reduction in the formation of brain tumor neurospheres in murine models. RO4929097 is an oral gamma secretase inhibitor.

OBJECTIVE

To estimate the 6-mo progression-free survival rate (PFS6) in patients with progressive GBM and to inhibit by 50% the generation of neurospheres in fresh tissue resected from patients treated with RO4929097.

METHODS

In this phase II and pharmacodynamic study, patients with recurrent GBM received RO4929097 in a study of 2 groups. Group A patients had unresectable disease and received drug in a standard phase II design. Group B patients had resectable disease and received drug before and after surgical resection. Endpoints included PFS6 and the inhibition of neurosphere formation in the resected tumor samples.

RESULTS

A total of 47 patients received treatment, 7 of whom had tumor resection. The PFS6 was 4%, and the inhibition of neurosphere formation occurred in 1 of 7 patient samples.

CONCLUSION

RO4929097 was inactive in recurrent GBM patients and demonstrated minimal inhibition of neurosphere formation in fresh tissue samples.

RBPJ contributes to the malignancy of glioblastoma and induction of proneural-mesenchymal transition via IL-6-STAT3 pathway

Notch signaling plays a pivotal role in many cancers, including glioblastoma (GBM). Recombination signal binding protein for immunoglobulin kappa J region (RBPJ) is a key transcription factor of the Notch signaling pathway. Here, we interrogated the function of RBPJ in GBM. Firstly, RBPJ expression of GBM samples was examined. Then, we knocked down RBPJ expression in 2 GBM cell lines (U251 and T98) and 4 glioblastoma (GBM) stem-like cell lines derived from surgical samples of GBM (KGS01, KGS07, KGS10 and KGS15) to investigate the effect on cell proliferation, invasion, stemness, and tumor formation ability. Expression of possible downstream targets of RBPJ was also assessed. RBPJ was overexpressed in the GBM samples, downregulation of RBPJ reduced cell proliferation and the invasion ability of U251 and T98 cells and cell proliferation ability and stemness of glioblastoma stem-like cells (GSC) lines. These were accompanied by reduced IL-6 expression, reduced activation of STAT3, and inhibited proneural-mesenchymal transition (PMT). Tumor formation and PMT were also impaired by RBPJ knockdown in vivo. In conclusion, RBPJ promotes cell proliferation, invasion, stemness, and tumor initiation ability in GBM cells through enhanced activation of IL-6-STAT3 pathway and PMT, inhibition of RBPJ may constitute a prospective treatment for GBM.

COL2A1 Is a Novel Biomarker of Melanoma Tumor Repopulating Cells

Soft 3D-fibrin-gel selected tumor repopulating cells (TRCs) from the B16F1 melanoma cell line exhibit extraordinary self-renewal and tumor-regeneration capabilities. However, their biomarkers and gene regulatory features remain largely unknown. Here, we utilized the next-generation sequencing-based RNA sequencing (RNA-seq) technique to discover novel biomarkers and active gene regulatory features of TRCs. Systems biology analysis of RNA-seq data identified differentially expressed gene clusters, including the cell adhesion cluster, which subsequently identified highly specific and novel biomarkers, such as Col2a1, Ncam1, F11r, and Negr1. We validated the expression of these genes by real-time qPCR. The expression level of Col2a1 was found to be relatively low in TRCs but twenty-fold higher compared to the parental control cell line, thus making the biomarker very specific for TRCs. We validated the COL2A1 protein by immunofluorescence microscopy, showing a higher expression of COL2A1 in TRCs compared to parental control cells. KEGG pathway analysis showed the JAK/STAT, hypoxia, and Akt signaling pathways to be active in TRCs. Besides, the aerobic glycolysis pathway was found to be very active, indicating a typical Warburg Effect on highly tumorigenic cells. Together, our study revealed highly specific biomarkers and active cell signaling pathways of melanoma TRCs that can potentially target and neutralize TRCs.

Sustained activation of notch signaling maintains tumor-initiating cells in a murine model of liposarcoma

Cells in a tumor are heterogeneous, often including a small number of tumor-initiating cells (TICs) and the majority of cancerous and non-cancerous cells. We have previously reported that constitutive activation of Notch signaling in adipocytes of mice leads to dedifferentiated liposarcoma (DDLPS), an aggressive liposarcoma (LPS) with no effective treatment. Here, we explored the role of Notch signaling in cellular heterogeneity of LPS. We performed serial transplantations to enrich for TICs, and derived cells exhibiting sustained Notch activation (mLPS1 cells) and cells with normal Notch activity (mLPS2 cells). Both mLPS1 and mLPS2 cells proliferated rapidly, and neither exhibited contact inhibition. However, only the mLPS1 cells exhibited tumorigenicity and gave rise to LPS upon engraftment into mice. The mLPS1 cells also highly expressed markers of cancer stem cells (Cd133), mesenchymal stem cells (Cd73, Cd90, Cd105, Dlk1) and the long non-coding RNA Rian. By contrast, the mLPS2 cells accumulated lipid droplets and expressed mature adipocyte markers when induced to differentiate. Most importantly, CRISPR-mediated disruption of Notch abrogated the tumorigenic properties of mLPS1 cells. These results reveal a key role of Notch signaling in maintaining TICs in LPS.

Cancer Stem Cells, Quo Vadis? The Notch Signaling Pathway in Tumor Initiation and Progression

The Notch signaling pathway regulates cell proliferation, cytodifferentiation and cell fate decisions in both embryonic and adult life. Several aspects of stem cell maintenance are dependent from the functionality and fine tuning of the Notch pathway. In cancer, Notch is specifically involved in preserving self-renewal and amplification of cancer stem cells, supporting the formation, spread and recurrence of the tumor. As the function of Notch signaling is context dependent, we here provide an overview of its activity in a variety of tumors, focusing mostly on its role in the maintenance of the undifferentiated subset of cancer cells. Finally, we analyze the potential of molecules of the Notch pathway as diagnostic and therapeutic tools against the various cancers.

Knockdown of lncRNA BLACAT1 enhances radiosensitivity of head and neck squamous cell carcinoma cells by regulating PSEN1

OBJECTIVE

This work focused on the function role and underlying mechanism of BLACAT1 in regulating the radiosensitivity of head and neck squamous cell carcinoma (HNSCC) cells via PSEN1.

METHODS

BLACAT1 and PSEN1 expression in HNSCC tissues and cells were measured by qRT-PCR. Kaplan-Meier method and Spearman's correlation analysis determined the prognostic roles and association of BLCAT1 and PSEN1 in HNSCC. The impacts of BLACAT1 and PSEN1, alone and in combination, on radiosensitivity of HNSCC cells were separately assessed through CCK-8, colony formation, flow cytometry, western blot and γH2AX foci staining assays.

RESULTS

Our study disclosed that BLACAT1 and PSEN1 were both in association with poor prognosis and radioresistance of HNSCC cells. BLACAT1 knockdown improved the radiosensitivity of HNSCC cells by changing cellular activities containing repressed cell viability, accelerated cell apoptosis, induced cell cycle arrest, and stimulated DNA damage response. Further, we found that PSEN1 was positively correlated with BLACAT1. Rescue assays confirmed that BLACAT1 regulated the radiosensitivity of HNSCC cells by modulating PSEN1.

CONCLUSION

We revealed that BLACAT1 knockdown enhanced radioresistance of HNSCC cells via regulating PSEN1, exposing the probable target role of BLACAT1 in HNSCC.

ADVANCES IN KNOWLEDGE

This was the first time that the pivotal role of BLACAT1 was investigated in HNSCC, which provided a novel therapeutic direction for HNSCC patients.

Immunotherapy: Newer Therapeutic Armamentarium against Cancer Stem Cells

Mounting evidence from the literature suggests the existence of a subpopulation of cancer stem cells (CSCs) in almost all types of human cancers. These CSCs possessing a self-renewal capacity inhabit primary tumors and are more defiant to standard antimitotic and molecularly targeted therapies which are used for eliminating actively proliferating and differentiated cancer cells. Clinical relevance of CSCs emerges from the fact that they are the root cause of therapy resistance, relapse, and metastasis. Earlier, surgery, chemotherapy, and radiotherapy were established as cancer treatment modalities, but recently, immunotherapy is also gaining importance in the management of various cancer patients, mostly those of the advanced stage. This review abridges potential off-target effects of inhibiting CSC self-renewal pathways on immune cells and some recent immunological studies specifically targeting CSCs on the basis of their antigen expression profile, even though molecular markers or antigens that have been described till date as expressed by cancer stem cells are not specifically expressed by these cells which is a major limitation to target CSCs. We propose that owing to CSC stemness property to mediate immunotherapy response, we can apply a combination therapy approach by targeting CSCs and tumor microenvironment (TME) along with conventional treatment strategies as an effective means to eradicate cancer cells.

Exosomes as a storehouse of tissue remodeling proteases and mediators of cancer progression

Rapidly increasing scientific reports of exosomes and their biological effects have improved our understanding of their cellular sources and their cell-to-cell communication. These nano-sized vesicles act as potent carriers of regulatory bio-macromolecules and can induce regulatory functions by delivering them from its source to recipient cells. The details of their communication network are less understood. Recent studies have shown that apart from delivering its cargo to the cells, it can directly act on extracellular matrix (ECM) proteins and growth factors and can induce various remodeling events. More importantly, exosomes carry many surface-bound proteases, which can cleave different ECM proteins and carbohydrates and can shed cell surface receptors. These local extracellular events can modulate signaling cascades, which consequently influences the whole tissue and organ. This review aims to highlight the critical roles of exosomal proteases and their mechanistic insights within the cellular and extracellular environment.

HMGA Genes and Proteins in Development and Evolution

HMGA (high mobility group A) (HMGA1 and HMGA2) are small non-histone proteins that can bind DNA and modify chromatin state, thus modulating the accessibility of regulatory factors to the DNA and contributing to the overall panorama of gene expression tuning. In general, they are abundantly expressed during embryogenesis, but are downregulated in the adult differentiated tissues. In the present review, we summarize some aspects of their role during development, also dealing with relevant studies that have shed light on their functioning in cell biology and with emerging possible involvement of HMGA1 and HMGA2 in evolutionary biology.

Musashi2 contributes to the maintenance of CD44v6+ liver cancer stem cells via notch1 signaling pathway

BACKGROUND

Liver cancer stem cells (LCSCs) contribute to hepatocellular carcinoma (HCC) development, metastasis, and drug resistance. MSI2 and Notch1 signaling are involved in the maintenance of CSCs. However, it is unknown whether MSI2 and Notch1 are involved in the maintenance of CD44v6+ LCSCs. Therefore, we investigated the clinical significance and function of MSI2 and its relationship with Notch1 signaling in the maintenance of stemness properties in CD44v6+ LCSCs.

METHODS

The expression of MSI2 and CD44v6 were detected by fresh specimens and a HCC tissue microarray. The tissue microarray containing 82 HCC samples was used to analyze the correlation between CD44v6 and MSI2. CD44v6+/- cells were isolated using microbeads sorting. We explored the roles of MSI2 and Notch1 signaling in CD44v6+ LCSCs by sphere formation assay, transwell assay, clone formation assay in vitro, and xenograft tumor models in vivo. A Notch RT² PCR Array, Co-immunoprecipitation, and RNA-immunoprecipitation were used to further investigate the molecular mechanism of MSI2 in activating Notch1 signaling.

RESULTS

Here, we found MSI2 expression was positively correlated with high CD44v6 expression in HCC tissues, and further correlated with tumor differentiation. CD44v6+ cells isolated from HCC cell lines exhibited increased self-renewal, proliferation, migration and invasion, resistance to Sorafenib and tumorigenic capacity. Both MSI2 and Notch1 signaling were elevated in sorted CD44v6+ cells than CD44v6- cells and played essential roles in the maintenance of stemness of CD44v6+ LCSCs. Mechanically, MSI2 directly bound to Lunatic fringe (LFNG) mRNA and protein, resulting in Notch1 activation.

CONCLUSIONS

Our results demonstrated that MSI2 maintained the stemness of CD44v6+ LCSCs by activating Notch1 signaling through the interaction with LFNG, which could be a potential molecular target for stem cell-targeted therapy for liver cancer.

Analysis of the Differentially Expressed Genes Induced by Cisplatin Resistance in Oral Squamous Cell Carcinomas and Their Interaction

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a solid tumor, which originates from squamous epithelium, with about 400,000 new-cases/year worldwidely. Presently, chemoradiotherapy is the most important adjuvant treatment for OSCC, mostly in advanced tumors. However, clinical resistance to chemotherapy still leads to poor prognosis of OSCC patients. Via high-throughput analysis of gene expression database of OSCC, we investigated the molecular mechanisms underlying cisplatin resistance in OSCC, analyzing the differentially expressed genes (DEGs) and their regulatory relationship, to clarify the molecular basis of OSCC chemotherapy resistance and provide a theoretical foundation for the treatment of patients with OSCC and individualized therapeutic targets accurately.

METHODS

Datasets related to "OSCC" and "cisplatin resistance" (GSE111585 and GSE115119) were downloaded from the GEO database and analyzed by GEO2R. Venn diagram was used to obtain drug-resistance-related DEGs. Functional enrichment analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis were performed on DEGs using The Database for Annotation, Visualization and Integrated Discovery (DAVID) software. Protein-protein interaction (PPI) network was constructed by STRING (search tool for recurring instances of neighbouring genes) database. Potential target genes of miRNA were predicted via miRDB, and cBioportal was used to analyze the function and survival of the potential functional genes.

RESULTS

Forty-eight upregulated DEGs and 49 downregulated DEGs were obtained from the datasets, with cutoff as p < 0.01 and |log FC| > 1. The DEGs in OSCC mainly enriched in cell proliferation regulation, and chemokine activity. In PPI network with hub score > 300, the hub genes were identified as NOTCH1, JUN, CTNNB1, CEBPA, and ETS1. Among miRNA-mRNA targeting regulatory network, hsa-mir-200c-3p, hsa-mir-200b-3p, hsa-mir-429, and hsa-mir-139-5p were found to simultaneously regulate multiple hub genes. Survival analysis showed that patients with high CTNNB1 or low CEBPA expression had poor outcome.

CONCLUSIONS

In the OSCC cisplatin-resistant cell lines, NOTCH1, JUN, CTNNB1, CEBPA, and ETS1 were found as the hub genes involved in regulating the cisplatin resistance of OSCC. Members of the miR-200 family may reverse drug resistance of OSCC cells by regulating the hub genes, which can act as potential targets for the treatment of OSCC patients with cisplatin resistance.

[Medical treatment of small cell lung cancer: Can we leave the area of cisplatin-etoposide?]

Small cell lung cancer accounts for 14% of all lung cancers. It remains a major challenge for oncology as the progresses made in the past three decades are modest. After a rapid overview of current knowledge regarding somatic genomic alterations, this state-of-art addresses pathways to improve small-cell lung cancer outcome such as the targeting of DNA damage repair mechanisms firstly anti-PARPs, inhibitory molecules of EZH2, derepression of the NOTCH pathway, rovalbituzumab-tesirine, inhibition of serine/threonine Aurora A kinase, temozolomide and its dependence on methylation of the MGMT promoter. This first chapter suggests the beginning of precision medicine in small cell lung cancer. The last section focuses on the development of immuno-oncological agents and the information collected from phase 1 and 2 studies: the low intensity of PD-L1 tissue expression and the possible relationship of the activity of these agents as a function of tumor mutational burden are pointed out.

A multi-arm phase I dose escalating study of an oral NOTCH inhibitor BMS-986115 in patients with advanced solid tumours

Background Inhibiting Notch is a promising anti-cancer strategy as it plays a critical role in cancer stem cells maintenance and tumour angiogenesis. BMS-986115 is an orally active, selective inhibitor of gamma-secretase mediated Notch signalling. Method Two dose escalation schedules (Arm-A continuous daily schedule and Arm-B intermittent 2 times weekly schedule) of BMS-986115 were evaluated in advanced solid tumour patients. The primary objective was to establish the safety, tolerability and Maximum Tolerated Dose (MTD) of BMS-986115. Results Thirty six patients (24 in Arm A and 12 in Arm B) were treated. The most frequent treatment related adverse advents were diarrhoea (72%), hypophosphataemia (64%), and nausea (61%). The MTD was 1.5 mg daily in Arm A but not established in Arm B. Four patients in Arm A and 2 in Arm B experienced dose limiting toxicities (grade 3 nausea, diarrhoea, pruritus/urticaria and ileus). BMS-986115 showed dose related increase in exposure within the dose range tested. Target inhibition of Notch pathway related genes was observed. Three patients in Arm A and 2 in Arm B achieved stable disease for more than 6 months. Conclusion The daily oral dosing of BMS-986115 is safe and tolerable with biological activity demonstrated by continuous target engagement and Notch signalling inhibition.

Numb-like (NumbL) downregulation increases tumorigenicity, cancer stem cell-like properties and resistance to chemotherapy

NumbL, or Numb-like, is a close homologue of Numb, and is part of an evolutionary conserved protein family implicated in some important cellular processes. Numb is a protein involved in cell development, in cell adhesion and migration, in asymmetric cell division, and in targeting proteins for endocytosis and ubiquitination. NumbL exhibits some overlapping functions with Numb, but its role in tumorigenesis is not fully known. Here we showed that the downregulation of NumbL alone is sufficient to increase NICD nuclear translocation and induce Notch pathway activation. Furthermore, NumbL downregulation increases epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC)-related gene transcripts and CSC-like phenotypes, including an increase in the CSC-like pool. These data suggest that NumbL can act independently as a tumor suppressor gene. Furthermore, an absence of NumbL induces chemoresistance in tumor cells. An analysis of human tumors indicates that NumbL is downregulated in a variable percentage of human tumors, with lower levels of this gene correlated with worse prognosis in colon, breast and lung tumors. Therefore, NumbL can act as an independent tumor suppressor inhibiting the Notch pathway and regulating the cancer stem cell pool.

The FACT inhibitor CBL0137 Synergizes with Cisplatin in Small-Cell Lung Cancer by Increasing NOTCH1 Expression and Targeting Tumor-Initiating Cells

Traditional treatments of small-cell lung cancer (SCLC) with cisplatin, a standard-of-care therapy, spare the tumor-initiating cells (TIC) that mediate drug resistance. Here we report a novel therapeutic strategy that preferentially targets TICs in SCLC, in which cisplatin is combined with CBL0137, an inhibitor of the histone chaperone facilitates chromatin transcription (FACT), which is highly expressed in TICs. Combination of cisplatin and CBL0137 killed patient-derived and murine SCLC cell lines synergistically. In response to CBL0137 alone, TICs were more sensitive than non-TICs, in part, because CBL0137 increased expression of the tumor suppressor NOTCH1 by abrogating the binding of negative regulator SP3 to the NOTCH1 promoter, and in part because treatment decreased the high expression of stem cell transcription factors. The combination of cisplatin and CBL0137 greatly reduced the growth of a patient-derived xenograft in mice and also the growth of a syngeneic mouse SCLC tumor. Thus, CBL0137 can be a highly effective drug against SCLC, especially in combination with cisplatin.Significance: These findings reveal a novel therapeutic regimen for SCLC, combining cisplatin with an inhibitor that preferentially targets tumor-initiating cells. Cancer Res; 78(9); 2396-406. ©2018 AACR.

The Ever-Evolving Concept of the Cancer Stem Cell in Pancreatic Cancer

Pancreatic ductal adenocarcinoma (PDAC), the most common type of pancreatic cancer, is the 4th most frequent cause of cancer-related death worldwide, primarily due to the inherent chemoresistant nature and metastatic capacity of this tumor. The latter is believed to be mainly due to the existence of a subpopulation of highly plastic “stem”-like cells within the tumor, known as cancer stem cells (CSCs), which have been shown to have unique metabolic, autophagic, invasive, and chemoresistance properties that allow them to continuously self-renew and escape chemo-therapeutic elimination. As such, current treatments for the majority of PDAC patients are not effective and do not significantly impact overall patient survival (<7 months) as they do not affect the pancreatic CSC (PaCSC) population. In this context, it is important to highlight the need to better understand the characteristics of the PaCSC population in order to develop new therapies to target these cells. In this review, we will provide the latest updates and knowledge on the inherent characteristics of PaCSCs, particularly their unique biological properties including chemoresistance, epithelial to mesenchymal transition, plasticity, metabolism and autophagy.

Cancer stem cells as targets for immunotherapy

Current cancer therapies target the bulk of the tumour, while a population of highly resistant tumour cells may be able to repopulate the tumour and metastasize to new sites. Cancer cells with such stem cell-like characteristics can be identified based on their phenotypical and/or functional features which may open up ways for their targeted elimination. In this review we discuss potential off-target effects of inhibiting cancer stem-cell self-renewal pathways on immune cells, and summarize some recent immunological studies specifically targeting cancer stem cells based on their unique antigen expression.

Notch and its oncogenic activity in human malignancies

BACKGROUND

Increasing evidence has demonstrated that Notch signaling is deregulated in human hematological malignancies and solid tumors. This signaling has a protumorigenic effect but may also act as a tumor suppressor. How induction of a single pathway gives rise to the opposite effects in different cell types is still unknown.

METHODS

This review article includes available data from peer-reviewed publications associated with the role of Notch signaling during cancer pathogenesis.

RESULTS

Numerous reports have indicated that alterations in Notch signaling and its oncogenic activity were originally associated with the pathogenesis of T‑cell acute lymphoblastic leukemia/lymphoma (T-ALL), an aggressive hematologic tumor affecting children and adolescents. The possibility that Notch could play a significant role in human breast cancer development comes from studies on mouse mammary tumor virus-induced cancer. Numerous findings over the past several years have indicated that alterations in Notch signaling are also responsible for ovarian cancer development. Mention should also be made of the connection between expression of Notch 3 and increased resistance to chemotherapy, which remains a major obstacle to successful treatment. Notch as an oncogenic factor is also involved in the development of colon cancer, lung carcinoma and Kaposi's sarcoma.

CONCLUSION

Notch is a binary cell fate determinant and its overexpression has been described as oncogenic in a wide array of human malignancies. This finding led to interest in therapeutically targeting this pathway, especially by the use of gamma-secretase inhibitors (GSIs) blocking the cleavage of Notch receptors at the cell membrane by the inhibition of Notch intracellular domain (NICD) releasing. Preclinical cancer models have revealed that GSIs suppress the growth of cancers such as pancreatic, breast and lung cancer.

Roles of Long Noncoding RNAs in Recurrence and Metastasis of Radiotherapy-Resistant Cancer Stem Cells

Radiotherapy is a well-established therapeutic regimen applied to treat at least half of all cancer patients worldwide. Radioresistance of cancers or failure to treat certain tumor types with radiation is associated with enhanced local invasion, metastasis and poor prognosis. Elucidation of the biological characteristics underlying radioresistance is therefore critical to ensure the development of effective strategies to resolve this issue, which remains an urgent medical problem. Cancer stem cells (CSCs) comprise a small population of tumor cells that constitute the origin of most cancer cell types. CSCs are virtually resistant to radiotherapy, and consequently contribute to recurrence and disease progression. Metastasis is an increasing problem in resistance to cancer radiotherapy and closely associated with the morbidity and mortality rates of several cancer types. Accumulating evidence has demonstrated that radiation induces epithelial–mesenchymal transition (EMT) accompanied by increased cancer recurrence, metastasis and CSC generation. CSCs are believed to serve as the basis of metastasis. Previous studies indicate that CSCs contribute to the generation of metastasis, either in a direct or indirect manner. Moreover, the heterogeneity of CSCs may be responsible for organ specificity and considerable complexity of metastases. Long noncoding RNAs (lncRNAs) are a class of noncoding molecules over 200 nucleotides in length involved in the initiation and progression of several cancer types. Recently, lncRNAs have attracted considerable attention as novel critical regulators of cancer progression and metastasis. In the current review, we have discussed lncRNA-mediated regulation of CSCs following radiotherapy, their association with tumor metastasis and significance in radioresistance of cancer.

CBF1 is clinically prognostic and serves as a target to block cellular invasion and chemoresistance of EMT-like glioblastoma cells

BACKGROUND

Glioblastoma is the most common and most lethal primary brain cancer. CBF1 (also known as Recombination signal Binding Protein for immunoglobulin kappa J, RBPJ) is the cardinal transcriptional regulator of the Notch signalling network and has been shown to promote cancer stem-like cells (CSCs) in glioblastoma. Recent studies suggest that some of the malignant properties of CSCs are mediated through the activation of pro-invasive programme of epithelial-to-mesenchymal transition (EMT). Little is known whether CBF1 is involved in the EMT-like phenotype of glioma cells.

METHODS

In a collection of GBM neurosphere lines, we genetically inhibited CBF1 and investigated the consequences on EMT-related properties, including in vitro invasiveness by Boyden chambers assay, chemoresistance using a clinical drug library screen and glycolytic metabolism assessing live-cell extracellular acidification rate. We also compared CBF1 expression in cells exposed to low and high oxygen tension. In silico analysis in large-scale Western and Eastern patient cohorts investigated the clinical prognostic value of CBF1 expression in low- and high-grade glioma as well as medulloblastoma.

RESULTS

Mean CBF1 expression is significantly increased in isocitrate dehydrogenase 1 (IDH1) R132H mutant glioblastoma and serves as prognostic marker for prolonged overall survival in brain tumours, particularly after therapy with temozolomide. Hypoxic regions of glioblastoma have higher CBF1 activation and exposure to low oxygen can induce its expression in glioma cells in vitro. CBF1 inhibition blocks EMT activators such as zinc finger E-box-binding homeobox 1 (ZEB1) and significantly reduces cellular invasion and resistance to clinically approved anticancer drugs. Moreover, we indicate that CBF1 inhibition can impede cellular glycolysis.

CONCLUSIONS

Mean CBF1 activation in bulk tumour samples serves as a clinical predictive biomarker in brain cancers but its intratumoral and intertumoral expression is highly heterogeneous. Microenvironmental changes such as hypoxia can stimulate the activation of CBF1 in glioblastoma. CBF1 blockade can suppress glioblastoma invasion in vitro in particular in cells undergone EMT such as those found in the hypoxic niche. Targeting CBF1 can be an effective anti-EMT therapy to impede invasive properties and chemosensitivity in those cells.

Molecular Drivers of Pancreatic Cancer Pathogenesis: Looking Inward to Move Forward

Pancreatic cancer (PC) continues to rank among the most lethal cancers. The consistent increase in incidence and mortality has made it the seventh leading cause of cancer-associated deaths globally and the third in the United States. The biggest challenge in combating PC is our insufficient understanding of the molecular mechanism(s) underlying its complex biology. Studies during the last several years have helped identify several putative factors and events, both genetic and epigenetic, as well as some deregulated signaling pathways, with implications in PC onset and progression. In this review article, we make an effort to summarize our current understanding of molecular and cellular events involved in the pathogenesis of pancreatic malignancy. Specifically, we provide up-to-date information on the genetic and epigenetic changes that occur during the initiation and progression of PC and their functional involvement in the pathogenic processes. We also discuss the impact of the tumor microenvironment on the molecular landscape of PC and its role in aggressive disease progression. It is envisioned that a better understanding of these molecular factors and the mechanisms of their actions can help unravel novel diagnostic and prognostic biomarkers and can also be exploited for future targeted therapies.

H3 ubiquitination by NEDD4 regulates H3 acetylation and tumorigenesis

Dynamic changes in histone modifications under various physiological cues play important roles in gene transcription and cancer. Identification of new histone marks critical for cancer development is of particular importance. Here we show that, in a glucose-dependent manner, E3 ubiquitin ligase NEDD4 ubiquitinates histone H3 on lysine 23/36/37 residues, which specifically recruits histone acetyltransferase GCN5 for subsequent H3 acetylation. Genome-wide analysis of chromatin immunoprecipitation followed by sequencing reveals that NEDD4 regulates glucose-induced H3 K9 acetylation at transcription starting site and enhancer regions. Integrative analysis of ChIP-seq and microarray data sets also reveals a consistent role of NEDD4 in transcription activation and H3 K9 acetylation in response to glucose. Functionally, we show that NEDD4-mediated H3 ubiquitination, by transcriptionally activating IL1α, IL1β and GCLM, is important for tumour sphere formation. Together, our study reveals the mechanism for glucose-induced transcriptome reprograming and epigenetic regulation in cancer by inducing NEDD4-dependent H3 ubiquitination.

Histone modifications play important roles in gene transcription and cancer. Here the authors establish a role for the E3 ubiquitin ligase NEDD4 in modifying in a glucose-dependent manner the histone H3, thus regulating the expression of genes involved in tumorigenesis.

Notch signaling plays a crucial role in cancer stem-like cells maintaining stemness and mediating chemotaxis in renal cell carcinoma

Background

Cancer stem cells (CSCs) are correlated with the initiation, chemoresistance and relapse of tumors. Notch pathway has been reported to function in CSCs maintenance, but whether it is involved in renal cell carcinoma (RCC) CSCs maintaining stemness remain unclear. This study aims to explore the effect of Notch pathway on stemness of CSCs in RCC and the underlying mechanisms.

Methods

The CD133⁺/CD24⁺ cells were isolated from RCC ACHN and Caki-1 cell line using Magnetic-activated cell sorting and identified by Flow cytometry analysis. RT-PCR and immunoblot analyses were used for determining the stemness maker expression. The effect of Notch pathway on function of CSCs was assessed by self-renewal ability, chemosensitivity, invasive and migratory ability tumorigenicity in vivo using soft agar colony formation assay, sphere-forming assay, MTT assay, Transwell assay.

Results

Here, we found that the sorted CD133⁺/CD24⁺cells possessed elevated stemness maker CTR2, BCL-2, MDR1, OCT-4, KLF4, compared with parental cells, as well as enhanced self-renewal ability, stronger resistance to cisplatin and sorafenib, increased invasion and migration, and higher tumorigenesis in vivo, suggesting the CD133⁺/CD24⁺ cells have the stem-like characteristics of CSCs and thus identified as RCC CSCs. Then the enhanced notch1, notch2, Jagged1, Jagged2, DLL1 and DLL4 expression were detected in RCC CSCs and blockage of Notch1 or notch2 using pharmacological inhibitor MRK-003 or its endogenous inhibitor Numb resulted in loss of its stemness features: self-renewal, chemoresistance, invasive and migratory potential, and tumorigenesis in vivo. Moreover, it is confirmed that overexpression of notch1 up-regulated CXCR4 inRCC CSCs and augmented SDF-1-induced chemotaxis in RCC CSCs in vitro, which could be rescued when treatment of CXCR4 inhibitor, suggesting that notch signaling promotes the chemotaxis of RCC CSCs by SDF-1/CXCR4 axis.

Conclusions

Our results provide a new mechanism of RCC CSCs maintaining stemness via notch pathway as well as a potential therapeutic target in human RCC.

The epithelial to mesenchymal transition (EMT) and cancer stem cells: implication for treatment resistance in pancreatic cancer

The mechanical properties of epithelial to mesenchymal transition (EMT) and a pancreatic cancer subpopulation with stem cell properties have been increasingly recognized as potent modulators of the effective of therapy. In particular, pancreatic cancer stem cells (PCSCs) are functionally important during tumor relapse and therapy resistance. In this review we have surveyed recent advances in the role of EMT and PCSCs in tumor progression, metastasis and treatment resistance, and the mechanisms of integrated with biochemical signals and the underlying pathways involved in treatment resistance of pancreatic cancer. These findings highlight the importance of confirming stem-cells markers and complex molecular signaling pathways controlling EMT and cancer stem cells in pancreatic cancer during tumor formation, progression, and response to therapy.

Anti-Cancer Phytometabolites Targeting Cancer Stem Cells

Medicinal plants are a plentiful source of bioactive molecules with much structural diversity. In cancer treatment, molecules obtained from plants represent an attractive alternative to other treatments because several plant-derived compounds have exhibited lower toxicity and higher selectivity against cancer cells. In this review, we focus on the possible application of bioactive molecules obtained from plants against more primitive cell populations in cancers, cancer stem cells. Cancer stem cells are present in several kinds of tumors and are responsible for recurrences and metastases. Common anti-cancer drugs exhibit lower effectiveness against cancer stem cells because of their biological features. However, recently discovered natural phytometabolites exert cytotoxic effects on this rare population of cells in cancers. Therefore, this review presents the latest research on promising compounds from plants that can act as antitumor drugs and that mainly affect stem cell populations in cancers.

c-Jun N-terminal kinase promotes stem cell phenotype in triple-negative breast cancer through upregulation of Notch1 via activation of c-Jun

c-Jun N-terminal kinase (JNK) plays a vital role in malignant transformation of different cancers, and JNK is highly activated in basal-like triple-negative breast cancer (TNBC). However, the roles of JNK in regulating cancer stem-like cell (CSC) phenotype and tumorigenesis in TNBC are not well defined. JNK is known to mediate many cellular events via activating c-Jun. Here, we found that JNK regulated c-Jun activation in TNBC cells and that JNK activation correlated with c-Jun activation in TNBC tumors. Furthermore, the expression level of c-Jun was significantly higher in TNBC tumors than in non-TNBC tumors, and high c-Jun mRNA level was associated with shorter disease-free survival of patients with TNBC. Thus, we hypothesized that the JNK/c-Jun signaling pathway contributes to TNBC tumorigenesis. We found that knockdown of JNK1 or JNK2 or treatment with JNK-IN-8, an adenosine triphosphate-competitive irreversible pan-JNK inhibitor, significantly reduced cell proliferation, the ALDH1⁺ and CD44⁺/CD24^- CSC subpopulations, and mammosphere formation, indicating that JNK promotes CSC self-renewal and maintenance in TNBC. We further demonstrated that both JNK1 and JNK2 regulated Notch1 transcription via activation of c-Jun and that the JNK/c-Jun signaling pathway promoted CSC phenotype through Notch1 signaling in TNBC. In a TNBC xenograft mouse model, JNK-IN-8 significantly suppressed tumor growth in a dose-dependent manner by inhibiting acquisition of the CSC phenotype. Taken together, our data demonstrate that JNK regulates TNBC tumorigenesis by promoting CSC phenotype through Notch1 signaling via activation of c-Jun and indicate that JNK/c-Jun/Notch1 signaling is a potential therapeutic target for TNBC.

Notch pathway activation is essential for maintenance of stem-like cells in early tongue cancer

BACKGROUND

Notch pathway plays a complex role depending on cellular contexts: promotes stem cell maintenance or induces terminal differentiation in potential cancer-initiating cells; acts as an oncogene in lymphocytes and mammary tissue or plays a growth-suppressive role in leukemia, liver, skin, and head and neck cancer. Here, we present a novel clinical and functional significance of NOTCH1 alterations in early stage tongue squamous cell carcinoma (TSCC).

PATIENTS AND METHODS

We analyzed the Notch signaling pathway in 68 early stage TSCC primary tumor samples by whole exome and transcriptome sequencing, real-time PCR based copy number, expression, immuno-histochemical, followed by cell based biochemical and functional assays.

RESULTS

We show, unlike TCGA HNSCC data set, NOTCH1 harbors significantly lower frequency of inactivating mutations (4%); is somatically amplified; and, overexpressed in 31% and 37% of early stage TSCC patients, respectively. HNSCC cell lines over expressing NOTCH1, when plated in the absence of attachment, are enriched in stem cell markers and form spheroids. Furthermore, we show that inhibition of NOTCH activation by gamma secretase inhibitor or shRNA mediated knockdown of NOTCH1 inhibits spheroid forming capacity, transformation, survival and migration of the HNSCC cells suggesting an oncogenic role of NOTCH1 in TSCC. Clinically, Notch pathway activation is higher in tumors of non-smokers compared to smokers (50% Vs 18%, respectively, P=0.026) and is also associated with greater nodal positivity compared to its non-activation (93% Vs 64%, respectively, P=0.029).

CONCLUSION

We anticipate that these results could form the basis for therapeutic targeting of NOTCH1 in tongue cancer.

SYNJ2BP inhibits tumor growth and metastasis by activating DLL4 pathway in hepatocellular carcinoma

BACKGROUND

Synaptojanin 2 Binding Protein (SYNJ2BP) is essential to cell proliferation. Previous studies show that SYNJ2BP participates in sprouting angiogenesis, which plays an important part in several abnormal conditions including cancer. However, the activity of SYNJ2BP in hepatocellular carcinoma (HCC) has not been elucidated yet.

METHODS

Firstly, real-time PCR and western blotting (WB) were adopted to evaluate SYNJ2BP expressions in HCC tissues and HCC cell lines. Secondly, we did follow-up and prognostic study to explore the association of SYNJ2BP expression and HCC patients prognosis. Thirdly, we induced or silenced SYNJ2BP expression on selected HCC cell lines and explored the function of SYNJ2BP in vitro and in vivo. Lastly, we conducted Cignal Finder Cancer 10-Pathway Reporter Array in combination with loss- and gain-of-function assay to investigate potential mechanisms.

RESULTS

Through various techniques we found that SYNJ2BP was decreased in HCC tissues and HCC cell lines. The subsequent analysis showed that low expression of SYNJ2BP was associated with tumor size, tumor nodule number, vascular invasion, TNM stage and BCLC stage, and was an independent risk factor for survival of HCC. Later, the in vitro experiments demonstrated that SYNJ2BP inhibited HCC cells invasion, migration and proliferation, also the in vivo testing revealed that SYNJ2BP inhibited tumor growth and metastasis. Finally, we also uncovered that SYNJ2BP inhibited HCC growth and metastasis through activating DLL4-mediated Notch signaling pathway.

CONCLUSIONS

Collectively, our data provide evidence that SYNJ2BP may act as a tumor suppressor during HCC development and could serve as a potential therapeutic target.

Cancer of the Pancreas: Molecular Pathways and Current Advancement in Treatment

Pancreatic cancer is one of the most lethal cancers among all malignances, with a median overall survival of <1 year and a 5-year survival of ~5%. The dismal survival rate and prognosis are likely due to lack of early diagnosis, fulminant disease course, high metastasis rate, and disappointing treatment outcome. Pancreatic cancers harbor a variety of genetic alternations that render it difficult to treat even with targeted therapy. Recent studies revealed that pancreatic cancers are highly enriched with a cancer stem cell (CSC) population, which is resistant to chemotherapeutic drugs, and therefore escapes chemotherapy and promotes tumor recurrence. Cancer cell epithelial to mesenchymal transition (EMT) is highly associated with metastasis, generation of CSCs, and treatment resistance in pancreatic cancer. Reviewed here are the molecular biology of pancreatic cancer, the major signaling pathways regulating pancreatic cancer EMT and CSCs, and the advancement in current clinical and experimental treatments for pancreatic cancer.