Colorectal cancer stem cell and chemoresistant colorectal cancer cell phenotypes and increased sensitivity to Notch pathway inhibitor

Uracil- and Pyridine-Containing HDAC Inhibitors Displayed Cytotoxicity in Colorectal and Glioblastoma Cancer Stem Cells

Cancer stem cells (CSCs) are a niche of highly tumorigenic cells featuring self-renewal, activation of pluripotency genes, multidrug resistance, and ability to cause cancer relapse. Seven HDACi (1-7), showing either hydroxamate or 2'-aminoanilide function, were tested in colorectal cancer (CRC) and glioblastoma multiforme (GBM) CSCs to determine their effects on cell proliferation, H3 acetylation levels and in-cell HDAC activity. Two uracil-based hydroxamates, 5 and 6, which differ in substitution at C5 and C6 positions of the pyrimidine ring, exhibited the greatest cytotoxicity in GBM (5) and CRC (6) CSCs, followed by the pyridine-hydroxamate 2, with 2- to 6-fold higher potency than the positive control SAHA. Finally, increased H3 acetylation as well as HDAC inhibition directly in cells by selected 2'-aminoanilide 4 and hydroxamate 5 confirmed target engagement. Further investigation will be conducted into the broad-spectrum anticancer properties of the most potent derivatives and their effects in combination with approved, conventional anticancer drugs.

Biofunctional study on chemoresistance in esophageal squamous carcinoma cells induced by missense mutation of NOTCH1 p.E450K

Background

Neoadjuvant chemotherapy (nCT) combined with surgery is one of the main strategies for the treatment of resectable locally advanced esophageal squamous cell carcinoma (ESCC). However, nearly 40% of patients did not benefit from nCT, and the detection rate of NOTCH1 missense mutation was significantly increased in patients who did not respond to chemotherapy, suggesting that the missense mutation may be related to tumor chemoresistance. We aim to explore the effect of a NOTCH1 missense mutation on cell phenotype, to interpret the biofunctional changes in cell lines with a NOTCH1 missense mutation and to analyze the effect of a NOTCH1 missense mutation on drug resistance in ESCC cell lines.

Methods

Sanger sequencing was used to evaluate the exon mutations in the NOTCH1 ligand binding region of candidate ESCC cell lines. After screening, KYSE450 and KYSE140 cells were selected as the research objects, and point mutation cell lines [KYSE140-mutant-type (MT) and KYSE450-MT] were constructed by CRISPR/Cas9 technology. Then, functional experiments were performed with the four cell lines [KYSE450-MT/wild-type (WT) and KYSE140-MT/WT]. The drug resistance of ESCC cell lines was assessed with a drug sensitivity test, and the proliferation, invasion and migration of ESCC lines were evaluated by proliferation test, scratch test and Transwell test. The cell cycle status of ESCC cells was assessed using flow cytometry.

Results

Drug sensitivity tests showed that the NOTCH1 p.E450K point mutation caused chemotherapy resistance in KYSE140 and KYSE450 ESCC cell lines. Cell proliferation, Wound scratch and Transwell assays showed that the NOTCH1 p.E450K point mutation enhanced the proliferation, invasion and migration abilities of KYSE140 and KYSE450 cells. Flow cytometry analysis showed that the NOTCH1 p.E450K point mutation caused an increase in KYSE140 and KYSE450 cells in S phase.

Conclusions

The NOTCH1 p.E450K point mutation causes chemotherapy resistance in KYSE140 and KYSE450 ESCC cells. Cell functional experiments showed that the NOTCH1 p.E450K point mutation enhanced the proliferation, migration and invasion abilities of KYSE140 and KYSE450 cells and increased the number of cells in S phase.

Potential markers of cancer stem-like cells in ESCC: a review of the current knowledge

In patients with esophageal squamous cell carcinoma (ESCC), the incidence and mortality rate of ESCC in our country are also higher than those in the rest of the world. Despite advances in the treatment department method, patient survival rates have not obviously improved, which often leads to treatment obstruction and cancer repeat. ESCC has special cells called cancer stem-like cells (CSLCs) with self-renewal and differentiation ability, which reflect the development process and prognosis of cancer. In this review, we evaluated CSLCs, which are identified from the expression of cell surface markers in ESCC. By inciting EMTs to participate in tumor migration and invasion, stem cells promote tumor redifferentiation. Some factors can inhibit the migration and invasion of ESCC via the EMT-related pathway. We here summarize the research progress on the surface markers of CSLCs, EMT pathway, and the microenvironment in the process of tumor growth. Thus, these data may be more valuable for clinical applications.

Application of exosomal miRNA mediated macrophage polarization in colorectal cancer: Current progress and challenges

Colorectal cancer (CRC) is a major global health problem with high morbidity and mortality rates. Surgical resection is the main treatment for early-stage CRC, but detecting it early is challenging. Therefore, effective therapeutic targets for advanced patients are still lacking. Exosomes, tiny vesicles in body fluids, play a crucial role in tumor metastasis, immune regulation, and drug resistance. Interestingly, they can even serve as a biomarker for cancer diagnosis and prognosis. Studies have shown that exosomes can carry miRNA, mediate the polarization of M1/M2 macrophages, promote the proliferation and metastasis of cancer cells, and affect the prognosis of CRC. Since the gastrointestinal tract has many macrophages, understanding the mechanism behind exosomal miRNA-mediated macrophage polarization in CRC treatment is crucial. This article summarizes recent advancements in the study of exosomal miRNAs in CRC and their potential as diagnostic and prognostic markers.

Notch receptor/ligand diversity: contribution to colorectal cancer stem cell heterogeneity

Cancer cell heterogeneity is a key contributor to therapeutic failure and post-treatment recurrence. Targeting cell subpopulations responsible for chemoresistance and recurrence seems to be an attractive approach to improve treatment outcome in cancer patients. However, this remains challenging due to the complexity and incomplete characterization of tumor cell subpopulations. The heterogeneity of cells exhibiting stemness-related features, such as self-renewal and chemoresistance, fuels this complexity. Notch signaling is a known regulator of cancer stem cell (CSC) features in colorectal cancer (CRC), though the effects of its heterogenous signaling on CRC cell stemness are only just emerging. In this review, we discuss how Notch ligand-receptor specificity contributes to regulating stemness, self-renewal, chemoresistance and cancer stem cells heterogeneity in CRC.

β-Lapachone Exerts Anticancer Effects by Downregulating p53, Lys-Acetylated Proteins, TrkA, p38 MAPK, SOD1, Caspase-2, CD44 and NPM in Oxaliplatin-Resistant HCT116 Colorectal Cancer Cells

β-lapachone (β-Lap), a topoisomerase inhibitor, is a naturally occurring ortho-naphthoquinone phytochemical and is involved in drug resistance mechanisms. Oxaliplatin (OxPt) is a commonly used chemotherapeutic drug for metastatic colorectal cancer, and OxPt-induced drug resistance remains to be solved to increase chances of successful therapy. To reveal the novel role of β-Lap associated with OxPt resistance, 5 μM OxPt-resistant HCT116 cells (HCT116-OxPt-R) were generated and characterized via hematoxylin staining, a CCK-8 assay and Western blot analysis. HCT116-OxPt-R cells were shown to have OxPt-specific resistance, increased aggresomes, upregulated p53 and downregulated caspase-9 and XIAP. Through signaling explorer antibody array, nucleophosmin (NPM), CD37, Nkx-2.5, SOD1, H2B, calreticulin, p38 MAPK, caspase-2, cadherin-9, MMP23B, ACOT2, Lys-acetylated proteins, COL3A1, TrkA, MPS-1, CD44, ITGA5, claudin-3, parkin and ACTG2 were identified as OxPt-R-related proteins due to a more than two-fold alteration in protein status. Gene ontology analysis suggested that TrkA, Nkx-2.5 and SOD1 were related to certain aggresomes produced in HCT116-OxPt-R cells. Moreover, β-Lap exerted more cytotoxicity and morphological changes in HCT116-OxPt-R cells than in HCT116 cells through the downregulation of p53, Lys-acetylated proteins, TrkA, p38 MAPK, SOD1, caspase-2, CD44 and NPM. Our results indicate that β-Lap could be used as an alternative drug to overcome the upregulated p53-containing OxPt-R caused by various OxPt-containing chemotherapies.

Cancer stem cells in colorectal cancer: Signaling pathways involved in stemness and therapy resistance

Colorectal cancer (CRC) is the third cause of cancer death worldwide. Although, in some cases, treatment can increase patient survival and reduce cancer recurrence, in many cases, tumors can develop resistance to therapy leading to recurrence. One of the main reasons for recurrence and therapy resistance is the presence of cancer stem cells (CSCs). CSCs possess a self-renewal ability, and their stemness properties lead to the avoidance of apoptosis, and allow a new clone of cancer cells to emerge. Numerous investigations inidicated the involvment of cellular signaling pathways in embryonic development, and growth, repair, and maintenance of tissue homeostasis, also participate in the generation and maintenance of stemness in colorectal CSCs. This review discusses the role of Wnt, NF-κB, PI3K/AKT/mTOR, Sonic hedgehog, and Notch signaling pathways in colorectal CSCs, and the possible modulating drugs that could be used in treatment for resistant CRC.

A potential requirement for Smad3 phosphorylation in Notch-mediated EMT in colon cancer

Colorectal cancer (CRC) remains a challenging disease to treat due to several factors including stemness and epithelial to mesenchymal transition (EMT). Dysfunctional signaling pathways such as Notch and TGF-β contribute to these phenomena. We previously found that cells expressing constitutively active Notch1 also had increased expression of Smad3, an important member of the TGF-β signaling pathway. We hypothesized that Smad3, mediates the Notch-induced stemness and EMT observed in CRC cells. The human colorectal carcinoma cell line HCT-116, stably transduced with constitutively active Notch-1 (ICN) or a GFP-vector control was treated with different combinations of TGF-β1, DAPT (a Notch inhibitor), or SIS3 (a Smad3 inhibitor). Western blot analysis was performed to determine the effects of Smad3 stimulation and inhibition on Notch and potential downstream EMT-related targets, CD44, Slug and Snail. Smad3 inhibition induced a decrease in Notch1 and Notch3 receptor expression and effectively inhibited CD44, Slug, and Snail expression. Colosphere forming ability was also reduced in cells with inhibited Smad3. These results indicate a key role of TGF-β signaling in Notch1-induced tumorigenesis, and suggest a potential use for Smad3 inhibitors in combination with Notch1 inhibitors that are already in use for CRC treatments.

Re-Sensitizing Cancer Stem Cells to Conventional Chemotherapy Agents

Cancer stem cells are found in many cancer types. They comprise a distinct subpopulation of cells within the tumor that exhibit properties of stem cells. They express a number of cell surface markers, such as CD133, CD44, ALDH, and EpCAM, as well as embryonic transcription factors Oct4, Nanog, and SOX2. CSCs are more resistant to conventional chemotherapy and can potentially drive tumor relapse. Therefore, it is essential to understand the molecular mechanisms that drive chemoresistance and to target them with specific therapy effectively. Highly conserved developmental signaling pathways such as Wnt, Hedgehog, and Notch are commonly reported to play a role in CSCs chemoresistance development. Studies show that particular pathway inhibitors combined with conventional therapy may re-establish sensitivity to the conventional therapy. Another significant contributor of chemoresistance is a specific tumor microenvironment. Surrounding stroma in the form of cancer-associated fibroblasts, macrophages, endothelial cells, and extracellular matrix components produce cytokines and other factors, thus creating a favorable environment and decreasing the cytotoxic effects of chemotherapy. Anti-stromal agents may potentially help to overcome these effects. Epigenetic changes and autophagy were also among the commonly reported mechanisms of chemoresistance. This review provides an overview of signaling pathway components involved in the development of chemoresistance of CSCs and gathers evidence from experimental studies in which CSCs can be re-sensitized to conventional chemotherapy agents across different cancer types.

GANT61 exerts anticancer cell and anticancer stem cell capacity in colorectal cancer by blocking the Wnt/β‑catenin and Notch signalling pathways

The present study aimed to assess the anticancer cell and anticancer stem cell (CSC) effects of GANT61, and its regulatory influence on the Wnt/β-catenin and Notch signalling pathways in colorectal cancer (CRC). HT-29 and HCT-116 cells were treated with 0, 2.5, 5, 10, 20 or 40 µM GANT61, after which relative cell viability and the expression of Gli1, β-catenin and Notch1, as well as the percentage of CD133⁺ cells, were detected. Subsequently, HT-29/HCT-116 cells and CSCs were treated with 20 µM GANT61, 10 mM of the Wnt/β-catenin pathway agonist HLY78, and 30 mM of the Notch pathway agonist JAG1 (alone or in combination), which was followed by the assessment of cell viability and apoptosis. In both cell lines, GANT61 reduced relative cell viability in a time- and dose-dependent manner, inhibited Gli1, β-catenin and Notch1 expression, and decreased the percentage of CD133⁺ cells in a dose-dependent manner. Furthermore, HLY78 and JAG1 were both found to improve the relative viability, while downregulating the apoptosis of untreated and GANT61-treated HT-29 and HCT-116 cells. Moreover, Wnt/β-catenin and Notch signalling pathway activity were upregulated in CSCs isolated from HT-29 and HCT-116 cells, compared with the associated control groups. GANT61 also reduced the viability of HT-29 and HCT-116 cells and increased apoptosis, whereas HLY78 and JAG1 treatment resulted in the opposite effect. Moreover, both HLY78 and JAG1 attenuated the effects of GANT61 on cellular viability and apoptosis. In conclusion, GANT61 was found to effectively eliminate cancer cells and CSCs by blocking the Wnt/β-catenin and Notch signalling pathways in CRC.

Suppressive effect of α-mangostin for cancer stem cells in colorectal cancer via the Notch pathway

Background

Since colon cancer stem cells (CSCs) play an important role in chemoresistance and in tumor recurrence and metastasis, targeting of CSCs has emerged as a sophisticated strategy for cancer therapy. α-mangostin (αM) has been confirmed to have antiproliferative and apoptotic effects on cancer cells. This study aimed to evaluate the selective inhibition of αM on CSCs in colorectal cancer (CRC) and the suppressive effect on 5-fluorouracil (5-FU)-induced CSCs.

Methods

The cell viability assay was performed to determine the optimal concentration of αM. A sphere forming assay and flow cytometry with CSC markers were carried out to evaluate the αM-mediated inhibition of CSCs. Western blot analysis and quantitative real-time PCR were performed to investigate the effects of αM on the Notch signaling pathway and colon CSCs. The in vivo anticancer efficacy of αM in combination with 5-FU was investigated using a xenograft mouse model.

Results

αM inhibited the cell viability and reduced the number of spheres in HT29 and SW620 cells. αM treatment decreased CSCs and suppressed the 5-FU-induced an increase in CSCs on flow cytometry. αM markedly suppressed Notch1, NICD1, and Hes1 in the Notch signaling pathway in a time- and dose-dependent manner. Moreover, αM attenuated CSC markers CD44 and CD133, in a manner similar to that upon DAPT treatment, in HT29 cells. In xenograft mice, the tumor and CSC makers were suppressed in the αM group and in the αM group with 5-FU treatment.

Conclusion

This study shows that low-dose αM inhibits CSCs in CRC and suppresses 5-FU–induced augmentation of CSCs via the Notch signaling pathway.

Comparison of Colorectal Cancer Stem Cells and Oxaliplatin-Resistant Cells Unveils Functional Similarities

Colorectal cancer is the second most common cancer in women, the third in men, and an important cause of cancer-related mortality. Recurrence and the development of chemotherapy resistance are major hindrances for patients’ treatment. The presence of cancer stem cells with chemotherapy resistance able to generate proliferating tumor cells contributes to tumor recurrence and resistance. In addition, tumor cells can develop chemoresistance through adaptation mechanisms. In this article, cancer stem cells were isolated from HT29 and SW620 colorectal cancer cell lines. Oxaliplatin resistance was induced by a single drug treatment simulating the usual guidelines of patient treatment. A comparison of these two populations showed similarities since cancer stem cells presented increased oxaliplatin resistance, and resistant cells contained an increased number of cancer stem cells. Cancer stem cells isolated from resistant cells showed increased oxaliplatin resistance. Cell invasion capacity and epithelial-mesenchymal transition were increased both in cancer stem cells and oxaliplatin-resistant cells. mRNA expression analysis showed that both cell types shared a significant proportion of commonly regulated genes. In summary, the data presented indicate that colorectal cancer stem cells and oxaliplatin-resistant cells are highly related cell populations that might have interesting implications in the development of tumor recurrence and resistance to chemotherapy.

Emerging agents that target signaling pathways to eradicate colorectal cancer stem cells

Colorectal cancer (CRC) represents the third most commonly diagnosed cancer and the second leading cause of cancer death worldwide. The modern concept of cancer biology indicates that cancer is formed of a small population of cells called cancer stem cells (CSCs), which present both pluripotency and self-renewal properties. These cells are considered responsible for the progression of the disease, recurrence and tumor resistance. Interestingly, some cell signaling pathways participate in CRC survival, proliferation, and self-renewal properties, and most of them are dysregulated in CSCs, including the Wingless (Wnt)/β-catenin, Notch, Hedgehog, nuclear factor kappa B (NF-κB), Janus kinase/signal transducer and activator of transcription (JAK/STAT), peroxisome proliferator-activated receptor (PPAR), phosphatidyl-inositol-3-kinase/Akt/mechanistic target of rapamycin (PI3K/Akt/mTOR), and transforming growth factor-β (TGF-β)/Smad pathways. In this review, we summarize the strategies for eradicating CRC stem cells by modulating these dysregulated pathways, which will contribute to the study of potential therapeutic schemes, combining conventional drugs with CSC-targeting drugs, and allowing better cure rates in anti-CRC therapy.

Targeting Notch to Maximize Chemotherapeutic Benefits: Rationale, Advanced Strategies, and Future Perspectives

Simple Summary

The Notch signaling pathway regulates cell proliferation, apoptosis, stem cell self-renewal, and differentiation in a context-dependent fashion both during embryonic development and in adult tissue homeostasis. Consistent with its pleiotropic physiological role, unproper activation of the signaling promotes or counteracts tumor pathogenesis and therapy response in distinct tissues. In the last twenty years, a wide number of studies have highlighted the anti-cancer potential of Notch-modulating agents as single treatment and in combination with the existent therapies. However, most of these strategies have failed in the clinical exploration due to dose-limiting toxicity and low efficacy, encouraging the development of novel agents and the design of more appropriate combinations between Notch signaling inhibitors and chemotherapeutic drugs with improved safety and effectiveness for distinct types of cancer.

Abstract

Notch signaling guides cell fate decisions by affecting proliferation, apoptosis, stem cell self-renewal, and differentiation depending on cell and tissue context. Given its multifaceted function during tissue development, both overactivation and loss of Notch signaling have been linked to tumorigenesis in ways that are either oncogenic or oncosuppressive, but always context-dependent. Notch signaling is critical for several mechanisms of chemoresistance including cancer stem cell maintenance, epithelial-mesenchymal transition, tumor-stroma interaction, and malignant neovascularization that makes its targeting an appealing strategy against tumor growth and recurrence. During the last decades, numerous Notch-interfering agents have been developed, and the abundant preclinical evidence has been transformed in orphan drug approval for few rare diseases. However, the majority of Notch-dependent malignancies remain untargeted, even if the application of Notch inhibitors alone or in combination with common chemotherapeutic drugs is being evaluated in clinical trials. The modest clinical success of current Notch-targeting strategies is mostly due to their limited efficacy and severe on-target toxicity in Notch-controlled healthy tissues. Here, we review the available preclinical and clinical evidence on combinatorial treatment between different Notch signaling inhibitors and existent chemotherapeutic drugs, providing a comprehensive picture of molecular mechanisms explaining the potential or lacking success of these combinations.

Nobiletin and Xanthohumol Sensitize Colorectal Cancer Stem Cells to Standard Chemotherapy

Simple Summary

Colorectal cancer stem cells (CR-CSCs) play a pivotal role in the therapy resistance and relapse of CRC patients. Herein we demonstrate that new treatment approaches comprising polymethoxyflavones and prenylflavonoids extracted from Citrus sinensis and Humulus lupulus, respectively, hamper the viability of CR-CSCs as well as synergizing with 5-fluorouracil and oxaliplatin (FOX)-based chemotherapy. Extract fractions containing Nobiletin and Xanthohumol, in combination with chemotherapy, decreased stemness properties of CR-CSCs and restrained the outgrowth of chemoresistant metastatic CR-CSCs. These data pinpoint Nobiletin and Xanthohumol as efficacious anti-cancer compounds in metastatic settings.

Abstract

Colorectal cancer (CRC) mortality is mainly caused by patient refractoriness to common anti-cancer therapies and consequent metastasis formation. Besides, the notorious toxic side effects of chemotherapy are a concurrent obstacle to be tackled. Thus, new treatment approaches are needed to effectively improve patient outcomes. Compelling evidence demonstrated that cancer stem cells (CSCs) are responsible for treatment failure and relapse. New natural treatment approaches showed capabilities to selectively target the CSC subpopulation by rendering them targetable by standard cytotoxic compounds. Herein we show the anti-cancer properties of the polymethoxyflavones and prenylflavonoids extracted from Citrus sinensis and Humulus lupulus, respectively. The natural biofunctional fractions, singularly and in combination, reduced the cell viability of CRC stem cells (CR-CSCs) and synergized with 5-fluorouracil and oxaliplatin (FOX) chemotherapy. These phenomena were accompanied by a reduced S and G2/M phase of the cell cycle and upregulation of cell death-related genes. Notably, both phytoextracts in combination with FOX thwarted stemness features in CR-CSCs as demonstrated by the impaired clonogenic potential and decreased Wnt pathway activation. Extracts lowered the expression of CD44v6 and affected the expansion of metastatic CR-CSCs in patients refractory to chemotherapy. Together, this study highlights the importance of polymethoxyflavones and prenylflavonoids as natural remedies to aid oncological therapies.

DYRK1A is required for maintenance of cancer stemness, contributing to tumorigenic potential in oral/oropharyngeal squamous cell carcinoma

DYRK1A, one of the dual-specificity tyrosine phosphorylation-regulated kinases (DYRKs), plays an important role in various biological processes by regulating downstream targets via kinase-dependent and independent mechanisms. Here, we report a novel role of DYRK1A in maintaining tumor growth and stemness of oral/oropharyngeal squamous cell carcinoma (OSCC) cells. Deletion of DYRK1A from OSCC cells abrogated their in vivo tumorigenicity and self-renewal capacity, the key features of cancer stem-like cells (CSCs; also referred to as tumor-initiating cells). The DYRK1A deletion also induced the suppression of CSC populations and properties, such as migration ability and chemoresistance. Conversely, ectopic expression of DYRK1A in OSCC cells augmented their CSC phenotype. Among five DYRK members (DYRK1A, 1B, 2, 3, and 4), DYRK1A is the most dominantly expressed kinase, and its expression is upregulated in OSCC compared to normal oral epithelial cells. More importantly, DYRK1A was highly enriched in various CSC-enriched OSCC populations compared to their corresponding non-CSC populations, indicating its pivotal role in cancer progression and stemness. Further, our study revealed that fibroblast growth factor 2 (FGF2) is a key regulator in the DYRK1A-mediated CSC regulation. Functional studies demonstrated that the loss of DYRK1A inhibits CSC phenotype via reduction of FGF2. Overexpression of DYRK1A promotes CSC phenotype via upregulation of FGF2. Our study delineates a novel mechanism of cancer stemness regulation by DYRK1A-FGF2 axis in OSCC. Thus, inhibition of DYRK1A would lead to a potential novel therapeutic option for targeting CSCs in OSCC.

Cancer stem cells in colorectal cancer and the association with chemotherapy resistance

The incidence and mortality of colorectal cancer (CRC) have always been among the highest in the world, although the diagnosis and treatment are becoming more and more advanced. At present, the main reason is that patients have acquired drug resistance after long-term conventional drug treatment. An increasing number of evidences confirm the existence of cancer stem cells (CSCs), which are a group of special cells in cancer, only a small part of cancer cells. These special cell populations are not eliminated by chemotherapeutic drugs and result in tumor recurrence and metastasis after drug treatment. CSCs have the ability of self-renewal and multidirectional differentiation, which is associated with the occurrence and development of cancer. CSCs can be screened and identified by related surface markers. In this paper, the characteristic surface markers of CSCs in CRC and the related mechanism of drug resistance will be discussed in detail. A better understanding of the mechanism of CSCs resistance to chemotherapy may lead to better targeted therapy.

Signaling pathways and microRNAs, the orchestrators of NANOG activity during cancer induction

Cancer stem cells (CSCs) are a small part of cancer cells inside the tumor that have similar characteristics to normal stem cells. CSCs stimulate tumor initiation and progression in a variety of cancers. Several transcription factors such as NANOG, SOX2, and OCT4 maintain the characteristics of CSCs and their upregulation is seen in many malignancies resulting in increased metastasis, invasion, and recurrence. Among these factors, NANOG plays an important role in regulating the self-renewal and pluripotency of CSCs and the clinical significance of NANOG has been suggested as a marker of CSCs in many cancers. The up and down-regulation of NANOG is associated with several important signaling pathways, including JAK/STAT, Wnt/β-catenin, Notch, TGF-β, Hedgehog, and several microRNAs (miRNAs). In this review, we will investigate the function of NANOG in CSCs and the molecular mechanism of its regulation by signaling pathways and miRNAs. We will also investigate targeting NANOG with different techniques, which is a promising treatment strategy for cancer treatment.

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

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

The Roles of Cancer Stem Cells and Therapy Resistance in Colorectal Carcinoma

Cancer stem cells (CSCs) are the main culprits involved in therapy resistance and disease recurrence in colorectal carcinoma (CRC). Results using cell culture, animal models and tissues from patients with CRC suggest the indispensable roles of colorectal CSCs in therapeutic failure. Conventional therapies target proliferating and mature cancer cells, while CSCs are mostly quiescent and poorly differentiated, thereby they can easily survive chemotherapeutic insults. The aberrant activation of Wnt/β-catenin, Notch, Hedgehog, Hippo/YAP (Yes-associated protein) and phosphatidylinositol 3-kinase/protein kinase B facilitates CSCs with excessive self-renewal and therapy resistance property in CRC. CSCs survive the chemo-radiotherapies by escaping therapy mediated DNA damage via altering the cell cycle checkpoints, increasing DNA damage repair capacity and by an efficient scavenging of reactive oxygen species. Furthermore, dysregulations of miRNAs e.g., miR-21, miR-93, miR-203, miR-215, miR-497 etc., modulate the therapeutic sensitivity of colorectal CSCs by regulating growth and survival signalling. In addition, a reversible quiescent G₀ state and the re-entering cell cycle capacity of colorectal CSCs can accelerate tumour regeneration after treatment. Moreover, switching to favourable metabolic signatures during a therapeutic regimen will add more complexity in therapeutic outcomes against CSCs. Therapeutic strategies targeting these underlying mechanisms of CSCs’ therapy resistance could provide a promising outcome, however, deep understanding and concerted research are necessary to design novel therapies targeting CSCs. To conclude, the understanding of these mechanisms of CSC in CRC could lead to the improved management of patients with CRC.

Extracellular Vesicle-derived circular RNAs confers chemoresistance in Colorectal cancer

Chemo-resistance is associated with poor prognosis in colorectal cancer (CRC), with the absence of early biomarker. Exosomes are microvesicles released by body cells for intercellular communication. Circular RNAs (circRNAs) are non-coding RNAs with covalently closed loops and enriched in exosomes. Crosstalk between circRNAs in exosomes and chemo-resistance in CRC remains unknown. This research aims to identify exosomal circRNAs associated with FOLFOX-resistance in CRC. FOLFOX-resistant HCT116 CRC cells (HCT116-R) were generated from parental HCT116 cells (HCT116-P) using periodic drug induction. Exosomes were characterized using transmission electron microscopy (TEM), Zetasizer and Western blot. Our exosomes were translucent cup-shaped structures under TEM with differential expression of TSG101, CD9, and CD63. We performed circRNAs microarray using exosomal RNAs from HCT116-R and HCT116-P cells. We validated our microarray data using serum samples. We performed drug sensitivity assay and cell cycle analysis to characterize selected circRNA after siRNA-knockdown. Using fold change >2 and p < 0.05, we identified 105 significantly upregulated and 34 downregulated circRNAs in HCT116-R exosomes. Knockdown of circ_0000338 improved the chemo-resistance of CRC cells. We have proposed that circ_0000338 may have dual regulatory roles in chemo-resistant CRC. Exosomal circ_0000338 could be a potential biomarker for further validation in CRC.

CD133: An emerging prognostic factor and therapeutic target in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of death worldwide. Recently, the role of cancer stem cells (CSCs) has been highlighted as a crucial emerging factor in chemoresistance, cancer relapse, and metastasis. CD133 is a surface marker of CSCs and has been argued to have prognostic and therapeutic values in CRC along with its related pathways such as Wnt, Notch, and hedgehog. Several studies have successfully applied targeted therapies against CD133 in CRC models namely bispecific antibodies (BiAbs) and anti-Wnt and notch pathways agents. These studies have yielded initial promising results in this regard. However, none of the therapeutics have been used in the clinical setting and their efficacy and adverse effects profile are yet to be elucidated. This review aims to gather the old and most recent data on the prognostic and therapeutic values of CD133 and CD133-targeted therapies in CRC.

Exosomal miRNA in chemoresistance, immune evasion, metastasis and progression of cancer

In the treatment of cancer, there are three significant limitations causing high mortality and recurrence rates among cancer patients. First, the escape of tumor cells from the immune system; second, the development of multi-drug resistance (MDR) to chemotherapeutic drugs; and, third, the noxious metastases of cancer cells. Exosomes are vesicular cargos involved in the transportation of miRNA, mRNA and proteins from one cell to another cell. This review details the current understanding of the exosomal transmission of miRNA and crosstalk with the downstream consequences, ultimately leading to the progression and metastasis of cancer. Further, this review also discusses how exosomal miRNA can provide promising novel targets for the treatment and detection of cancer.

Dipeptide γ-secretase inhibitor treatment enhances the anti-tumor effects of cisplatin against gastric cancer by suppressing cancer stem cell properties

The γ-secretase inhibitor blocks Notch activity by preventing its cleavage at the cell surface. In the present study, the effect of the γ-secretase inhibitor on the viability of gastric cancer cells when administered in combination with cisplatin was investigated, with particular focus on CD44^highLgr-5^high cancer cells. The four gastric cancer cell lines, MKN45, MKN74, SC-6-JCK and SH-10-TC, were used for the experiments. In the MTT assay, treatment with 25 µM dipeptide γ-secretase inhibitor (DAPT) alone did not affect cell proliferation in any of the four cell lines. Gastric cancer cells subjected to combination treatment with DAPT and cisplatin exhibited decreased viability when compared with those treated with cisplatin alone. Flow cytometry was performed to evaluate the expression of cluster of differentiation (CD)-44 and leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr-5), two cancer stem cell markers in gastric cancers. Treatment with cisplatin alone significantly increased the proportion of CD44^highLgr-5^high cells. However, the addition of DAPT to cisplatin reduced the CD44^highLgr-5^high fraction, suggesting that DAPT reduced the number of gastric cancer cells. In conclusion, the present study demonstrated the synergistic effects of DAPT in combination with cisplatin by decreasing the survival of gastric cancer cells. In addition, combination treatment with DAPT reduced the number of CD44^highLgr-5^high cells, which are thought to exhibit cancer stem cell properties. These results highlight the therapeutic potential of DAPT in gastric cancer treatment.

Acquired Resistance of ER-Positive Breast Cancer to Endocrine Treatment Confers an Adaptive Sensitivity to TRAIL through Posttranslational Downregulation of c-FLIP

Purpose: One third of ER-positive breast cancer patients who initially respond to endocrine therapy become resistant to treatment. Such treatment failure is associated with poor prognosis and remains an area of unmet clinical need. Here, we identify a specific posttranslational modification that occurs during endocrine resistance and which results in tumor susceptibility to the apoptosis-inducer TRAIL. This potentially offers a novel stratified approach to targeting endocrine-resistant breast cancer.Experimental Design: Cell line and primary-derived xenograft models of endocrine resistance were investigated for susceptibility to TRAIL. Tumor viability, cancer stem cell (CSC) viability (tumorspheres), tumor growth kinetics, and metastatic burden were assessed. Western blots for the TRAIL-pathway inhibitor, c-FLIP, and upstream regulators were performed. Results were confirmed in primary culture of 26 endocrine-resistant and endocrine-naïve breast tumors.Results: Breast cancer cell lines with acquired resistance to tamoxifen (TAMR) or faslodex were more sensitive to TRAIL than their endocrine-sensitive controls. Moreover, TRAIL eliminated CSC-like activity in TAMR cells, resulting in prolonged remission of xenografts in vivo In primary culture, TRAIL significantly depleted CSCs in 85% endocrine-resistant, compared with 8% endocrine-naïve, tumors, whereas systemic administration of TRAIL in endocrine-resistant patient-derived xenografts reduced tumor growth, CSC-like activity, and metastases. Acquired TRAIL sensitivity correlated with a reduction in intracellular levels of c-FLIP, and an increase in Jnk-mediated phosphorylation of E3-ligase, ITCH, which degrades c-FLIP.Conclusions: These results identify a novel mechanism of acquired vulnerability to an extrinsic cell death stimulus, in endocrine-resistant breast cancers, which has both therapeutic and prognostic potential. Clin Cancer Res; 24(10); 2452-63. ©2018 AACR.

In vitro characterization of spheres derived from colorectal cancer cell lines

Spherical cultures (SCs) can be regarded in cancer research as a link between in vitro investigations on cancer lines and in vivo studies of tumor development. SCs are believed to mimic tumor architecture and to be enriched in cancer stem cell-like cells (CSC-like cells). In the present study we characterized colonospheres derived from colorectal cancer (CRC) cell lines, and we confirmed the ability of HCT116 and HT29 cell lines to form spheres within serum-free medium, however, the detailed analysis presented the major differences concerning their characteristics including morphology, phenotype, proliferative potential, distribution in the cell cycle phases and spherogenicity. Moreover, after we magnetically separated CD133+ and CD133- cells we could conduct the analogical analysis as we performed for the original cells. We observed that all cellular fractions unveiled sphere formation capacity, even when cultured in limited number of cells per well and only SCs originated from CD133+ fraction resembled morphologically the parental spheres. Both CD133+ and CD133- subsets derived from HCT116 line were more enriched in cells in G0/G1 phase of the cell cycle in comparison to their HT29 analogues. Additionally, proliferative potential also varied amongst all studied fractions. Surprisingly, 3-D invasion assay revealed that only HCT116-derived populations were able to migrate into extended regions of Matrigel Matrix confirming their higher aggressiveness. Our results provided comprehensive characterization of CRC cell lines culture in adherent and spherical forms and, what seems to be the most advantageous, the comparison of two distinct fractions after magnetic separation. As we found the specific features of cells presented line- and expansion mode-dependency, thus, such complete description might appear crucial before CRC lines would be involved into sophisticated assays, especially focused on potentially novel therapeutic agents targeting CSC-like cells.

Therapeutic strategies against cancer stem cells in human colorectal cancer

Colorectal cancer (CRC) is the third most frequent malignancy and represents the fourth most common cause of cancer-associated mortalities in the world. Despite many advances in the treatment of CRC, the 5-year survival rate of patients with CRC remains unsatisfactory due to tumor recurrence and metastases. Recently, cancer stem cells (CSCs), have been suggested to be responsible for the initiation and relapse of the disease, and have been identified in CRC. Due to their basic biological features, which include self-renewal and pluripotency, CSCs may be novel therapeutic targets for CRC and other cancer types. Conventional therapeutics only act on proliferating and mature cancer cells, while quiescent CSCs survive and often become resistant to chemotherapy. In this review, markers of CRC-CSCs are evaluated and the recently introduced experimental therapies that specifically target these cells by inducing CSC proliferation, differentiation and sensitization to apoptotic signals via molecules including Dickkopf-1, bone morphogenetic protein 4, Kindlin-1, tankyrases, and p21-activated kinase 1, are discussed. In addition, novel strategies aimed at inhibiting some crucial processes engaged in cancer progression regulated by the Wnt, transforming growth factor β and Notch signaling pathways (pyrvinium pamoate, silibinin, PRI-724, P17, and P144 peptides) are also evaluated. Although the metabolic alterations in cancer were first described decades ago, it is only recently that the concept of targeting key regulatory molecules of cell metabolism, such as sirtuin 1 (miR-34a) and AMPK (metformin), has emerged. In conclusion, the discovery of CSCs has resulted in the definition of novel therapeutic targets and the development of novel experimental therapies for CRC. However, further investigations are required in order to apply these novel drugs in human CRC.

STROBE-compliant integrin through focal adhesion involve in cancer stem cell and multidrug resistance of ovarian cancer

Cancer stem cells (CSCs) are considered to be the root of carcinoma relapse and drug resistance in ovarian cancer. Hunting for the potential CSC genes and explain their functions would be a feasible strategy to meet the challenge of the drug resistance in ovarian cancer. In this study, we performed bioinformatic approaches such as biochip data extraction and pathway enrichment analyses to elucidate the mechanism of the CSC genes in regulation of drug resistance. Potential key genes, integrins, were identified to be related to CSC in addition to their associations with drug resistance and prognosis in ovarian cancer. A total of 36 ovarian CSC genes involved in regulation of drug resistance were summarized, and potential drug resistance-related CSC genes were identified based on 3 independent microarrays retrieved from the Gene Expression Omnibus (GEO) Profiles. Pathway enrichment of CSC genes associated with drug resistance in ovarian cancer indicated that focal adhesion signaling might play important roles in CSC genes-mediated drug resistance. Integrins are members of the adhesion molecules family, and integrin subunit alpha 1, integrin subunit alpha 5, and integrin subunit alpha 6 (ITGA6) were identified as central CSC genes and their expression in side population cells, cisplatin-resistant SKOV3 (SKOV3/DDP2) cells, and cisplatin-resistant A2780 (A2780/DDP) cells were dysregulated as measured by real-time quantitative polymerase chain reaction. The high expression of ITGA6 in 287 ovarian cancer patients of TCGA cohort was significantly associated with poorer progression-free survival. This study provide the basis for further understanding of CSC genes in regulation of drug resistance in ovarian cancer, and integrins could be a potential biomarker for prognosis of ovarian cancer.

Tumor-Initiating Cells: a criTICal review of isolation approaches and new challenges in targeting strategies

Most cancers contain a subpopulation of highly tumorigenic cells, known as cancer stem cells (CSCs) or tumor-initiating cells (TICs). Targeting TICs may be essential to achieve cure, because of their self-renewal and tumorigenic properties as well as their resistance to conventional therapies. Despite significant advances in TIC biology, their isolation and identification remain largely disputed and incompletely established. In this review, we discuss the latest developments in isolation and culturing approaches of TICs, with focus on colorectal cancer (CRC). We feature recent findings on TIC-relevant signaling pathways and the metabolic identity of TICs, as well as their current clinical implications. Lastly, we highlight the influence of inter- and intra-tumoral heterogeneity on TIC function and targeting approaches.

Acquisition of anticancer drug resistance is partially associated with cancer stemness in human colon cancer cells

Colorectal cancer (CRC) is one of the most aggressive cancers worldwide. Several anticancer agents are available to treat CRC, but eventually cancer relapse occurs. One major cause of chemotherapy failure is the emergence of drug-resistant tumor cells, suspected to originate from the stem cell compartment. The aim of this study was to ask whether drug resistance was associated with the acquisition of stem cell-like properties. We isolated drug-resistant derivatives of two human CRC cell lines, HT29 and HCT116, using two anticancer drugs with distinct modes of action, oxaliplatin and docetaxel. HT29 cells resistant to oxaliplatin and both HT29 and HCT116 cells resistant to docetaxel were characterized for their expression of genes potentially involved in drug resistance, cell growth and cell division, and by surveying stem cell-like phenotypic traits, including marker genes, the ability to repair cell-wound and to form colonospheres. Among the genes involved in platinum or taxane resistance (MDR1, ABCG2, MRP2 or ATP7B), MDR1 was uniquely overexpressed in all the resistant cells. An increase in the cyclin-dependent kinase inhibitor p21, in cyclin D1 and in CD26, CD166 cancer stem cell markers, was noted in the resistant cells, together with a higher ability to form larger and more abundant colonospheres. However, many phenotypic traits were selectively altered in either HT29- or in HCT116-resistant cells. Expression of EPHB2, ITGβ-1 or Myc was specifically increased in the HT29-resistant cells, whereas only HCT116-resistant cells efficiently repaired cell- wounds. Taken together, our results show that human CRC cells selected for their resistance to anticancer drugs displayed a few stem cell characteristics, a small fraction of which was shared between cell lines. The occurrence of marked phenotypic differences between HT29- and HCT116-drug resistant cells indicates that the acquired resistance depends mostly on the parental cell characteristics, rather than on the drug type used.

Cancer Stem Cells: Cellular Plasticity, Niche, and its Clinical Relevance

Cancer handles an estimated 7.6 million deaths worldwide per annum. A recent theory focuses on the role Cancer Stem Cells (CSCs) in driving tumorigenesis and disease progression. This theory hypothesizes that a population of the tumor cell with similar functional and phenotypic characteristics as normal tissue stem cells are responsible for formation and advancement of many human cancers. The CSCs subpopulation can differentiate into non-CSC tumor cells and promote phenotypic and functional heterogeneity within the tumor. The presence of CSCs has been reported in a number of human cancers including blood, breast, brain, colon, lung, pancreas prostate and liver. Although the origin of CSCs remains a mystery, recent reports suggest that the phenotypic characteristics of CSCs may be plastic and are influenced by the microenvironment specific for the individual tumor. Such factors unique to each tumor preserve the dynamic balance between CSCs to non-CSCs cell fate, as well as maintain the proper equilibrium. Alternating such equilibrium via dedifferentiation can result in aggressiveness, as CSCs are considered to be more resistant to the conventional cancer treatments of chemotherapy and radiation. Understanding how the tumoral microenvironment affects the plasticity driven CSC niche will be critical for developing a more effective treatment for cancer by eliminating its aggressive and recurring nature that now is believed to be perpetuated by CSCs.

Analysis of different components in the peritumoral tissue microenvironment of colorectal cancer: A potential prospect in tumorigenesis

The present study aimed to observe the varying expression of biomarkers in the microenvironment adjacent to colorectal cancer lesions to provide additional insight into the functions of microenvironment components in carcinogenesis and present a novel or improved indicator for early diagnosis of cancer. A total of 144 human samples from three different locations in 48 patients were collected, these locations were 10, 5 and 2 cm from the colorectal cancer lesion, respectively. The biomarkers analyzed included E‑cadherin, cytokeratin 18 (CK18), hyaluronidase‑1 (Hyal‑1), collagen type I (Col‑I), Crumbs3 (CRB3), vimentin, proteinase activated receptor 3 (PAR‑3), α‑smooth muscle actin (α‑SMA), cyclin D1 (CD1) and cluster of differentiation (CD)133. In addition, crypt architecture was observed. Related functional analysis of proteins was performed using hierarchical index cluster analysis. More severe destroyed crypt architecture closer to the cancer lesions was observed compared with the 10 cm sites, with certain crypts degraded entirely. Expression levels of E‑cadherin, CK18, CRB3 and PAR‑3 were lower in 2 cm sites compared with the 10 cm sites (all P<0.001), while the expression levels of the other biomarkers in the 2 cm sites were increased compared with 10 cm sites (all P<0.0001). Notably, the expression of CK18 in 2 cm sites was higher than in the 5 cm site (P<0.0001), which was different from the expression of E‑cadherin, CRB3 and PAR‑3. The expression levels of Hyal‑1 and Col‑I at the 2 cm sites were lower than that of the 5 cm sites (P>0.05 and P=0.0001, respectively), while the expression of vimentin, α‑SMA, CD1 and CD133 were not. Hyal‑1 and Col‑I may be independently important in cancer initiation in the tumor microenvironment. The results of the present study suggest that the biomarkers in the tissue microenvironment are associated with early tumorigenesis and may contribute to the development of carcinomas. These observations may be useful for early diagnosis of colorectal cancer.

In vivo relevant mixed urolithins and ellagic acid inhibit phenotypic and molecular colon cancer stem cell features: A new potentiality for ellagitannin metabolites against cancer

Colon cancer stem cells (CSCs) offer a novel paradigm for colorectal cancer (CRC) treatment and dietary polyphenols may contribute to battle these cells. Specifically, polyphenol-derived colon metabolites have the potential to interact with and affect colon CSCs. We herein report the effects against colon CSCs of two mixtures of ellagitannin (ET) metabolites, ellagic acid (EA) and the gut microbiota-derived urolithins (Uro) at concentrations detected in the human colon tissues following the intake of ET-containing products (pomegranate, walnuts). These mixtures reduce phenotypic and molecular features in two models of colon CSCs: Caco-2 cells and primary tumour cells from a patient with CRC. The mixture containing mostly Uro-A (85% Uro-A, 10% Uro-C, 5% EA) was most effective at inhibiting the number and size of colonospheres and aldehyde dehydrogenase activity (ALDH, a marker of chemoresistance) whereas the mixture containing less Uro-A but IsoUro-A and Uro-B (30% Uro-A, 50% IsoUro-A, 10% Uro-B, 5% Uro-C, 5% EA) had some effects on the number and size of colonospheres but not on ALDH. These data support a role for polyphenols metabolites in the control of colon cancer chemoresistance and relapse and encourage the research on the effects of polyphenols against CSCs.

Low temperature plasmas as emerging cancer therapeutics: the state of play and thoughts for the future

The field of plasma medicine has seen substantial advances over the last decade, with applications developed for bacterial sterilisation, wound healing and cancer treatment. Low temperature plasmas (LTPs) are particularly suited for medical purposes since they are operated in the laboratory at atmospheric pressure and room temperature, providing a rich source of reactive oxygen and nitrogen species (RONS). A great deal of research has been conducted into the role of reactive species in both the growth and treatment of cancer, where long-established radio- and chemo-therapies exploit their ability to induce potent cytopathic effects. In addition to producing a plethora of RONS, LTPs can also create strong electroporative fields. From an application perspective, it has been shown that LTPs can be applied precisely to a small target area. On this basis, LTPs have been proposed as a promising future strategy to accurately and effectively control and eradicate tumours. This review aims to evaluate the current state of the literature in the field of plasma oncology and highlight the potential for the use of LTPs in combination therapy. We also present novel data on the effect of LTPs on cancer stem cells, and speculatively outline how LTPs could circumvent treatment resistance encountered with existing therapeutics.

Advances and perspectives of colorectal cancer stem cell vaccine

Colorectal cancer is essentially an environmental and genetic disease featured by uncontrolled cell growth and the capability to invade other parts of the body by forming metastases, which inconvertibly cause great damage to tissues and organs. It has become one of the leading causes of cancer-related mortality in the developed countries such as United States, and approximately 1.2 million new cases are yearly diagnosed worldwide, with the death rate of more than 600,000 annually and incidence rates are increasing in most developing countries. Apart from the generally accepted theory that pathogenesis of colorectal cancer consists of genetic mutation of a certain target cell and diversifications in tumor microenvironment, the colorectal cancer stem cells (CCSCs) theory makes a different explanation, stating that among millions of colon cancer cells there is a specific and scanty cellular population which possess the capability of self-renewal, differentiation and strong oncogenicity, and is tightly responsible for drug resistance and tumor metastasis. Based on these characteristics, CCSCs are becoming a novel target cells both in the clinical and the basic studies, especially the study of CCSCs vaccines due to induced efficient immune response against CCSCs. This review provides an overview of CCSCs and preparation technics and targeting factors related to CCSCs vaccines in detail.