Anti-cancer stem cell activity of a hedgehog inhibitor GANT61 in estrogen receptor-positive breast cancer cells

GANT61 surmounts drug resistance of ADR by upregulating lysosome activities and reducing BCL2 expression in HL-60/ADR cells

BACKGROUND

Drug resistance remains a significant obstacle to Acute myeloid leukemia (AML) successful treatment, often leading to therapeutic failure. Our previous studies demonstrated that Glioma-associated oncogene-1 (GLI1) reduces chemotherapy sensitivity and promotes cell proliferation in AML cells. GANT61, an inhibitor of GLI1, emerges as a promising candidate in AML treatment. This study aims to explore the effects of the combination of GANT61 and Adriamycin (ADR) on AML cells resistance and elucidate the mechanisms through which GANT61 may potentiate the sensitivity of AML cells to ADR.

METHODS

AML cell lines and AML primary cells were studied to evaluate effects and mechanisms of GANT61. Flow cytometry assays were used to verify apoptosis. Cell Counting Kit-8 (CCK-8) and EDU+ staining were used to observe changes in cell viability and the cytotoxic effect to different drugs. The transcriptomic profiles of HL-60/ADR cells with or without GANT61 treatment were compared via RNA-Seq analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses and Gene Set Enrichment Analysis (GSEA) were performed for differentially expressed genes (DEGs) to reveal the underlying mechanisms of GANT61 in AML cells. GLI1, BCL2, Bax protein and mRNA expression levels were assessed by Western blot and Real-time polymerase chain reaction (RT-PCR).

RESULTS

Our studies found that the combination of GANT61 and ADR synergistically inhibits proliferation while enhancing apoptosis in HL-60/ADR cells, and does not significantly exacerbate myelosuppression. Mechanistically, GSEA revealed enrichment of the gene set associated with the KEGG term "Apoptosis" and "Lysosome" in GANT61 treated cells. Meanwhile, "Apoptosis" was identified as the third most relevant pathway enriched by lysosomal DEGs, and BCL2 expression showed a negative correlation with these lysosomal DEGs in AML patients. RT-PCR and Western blot analysis disclosed that GANT61 significantly restrained BCL2 expression in AML cells. Lastly, we proved that venetoclax, a BCL2 inhibitor, co-treatment with GANT61 improved ADR sensitivity in HL-60/ADR cells.

CONCLUSIONS

GANT61 effectively reversed ADR resistance in HL-60/ADR cells by upregulating lysosome activities and downgrading BCL2 expression, providing a new treatment strategy with acceptable toxicity for AML-resistant patients.

Primary cilia-associated signalling in squamous cell carcinoma of head and neck region

Squamous cell carcinoma (SCC) of the head and neck originates from the mucosal lining of the upper aerodigestive tract, including the lip, tongue, nasopharynx, oropharynx, larynx and hypopharynx. In this review, we summarise what is currently known about the potential function of primary cilia in the pathogenesis of this disease. As primary cilia represent a key cellular structure for signal transduction and are related to cell proliferation, an understanding of their role in carcinogenesis is necessary for the design of new treatment approaches. Here, we introduce cilia-related signalling in head and neck squamous cell carcinoma (HNSCC) and its possible association with HNSCC tumorigenesis. From this point of view, PDGF, EGF, Wnt and Hh signalling are discussed as all these pathways were found to be dysregulated in HNSCC. Moreover, we review the clinical potential of small molecules affecting primary cilia signalling to target squamous cell carcinoma of the head and neck area.

Breast Cancer Stem Cells and Tumor Heterogeneity: Characteristics and Therapeutic Strategies

Breast cancer is one of the most frequently detected malignancies worldwide. It is responsible for more than 15% of all death cases caused by cancer in women. Breast cancer is a heterogeneous disease representing various histological types, molecular characteristics, and clinical profiles. However, all breast cancers are organized in a hierarchy of heterogeneous cell populations, with a small proportion of cancer stem cells (breast cancer stem cells (BCSCs)) playing a putative role in cancer progression, and they are responsible for therapeutic failure. In different molecular subtypes of breast cancer, they present different characteristics, with specific marker profiles, prognoses, and treatments. Recent efforts have focused on tackling the Wnt, Notch, Hedgehog, PI3K/Akt/mTOR, and HER2 signaling pathways. Developing diagnostics and therapeutic strategies enables more efficient elimination of the tumor mass together with the stem cell population. Thus, the knowledge about appropriate therapeutic methods targeting both "normal" breast cancer cells and breast cancer stem cell subpopulations is crucial for success in cancer elimination.

Unravelling the Mysteries of the Sonic Hedgehog Pathway in Cancer Stem Cells: Activity, Crosstalk and Regulation

The Sonic Hedgehog (Shh) signalling pathway plays a critical role in normal development and tissue homeostasis, guiding cell differentiation, proliferation, and survival. Aberrant activation of this pathway, however, has been implicated in the pathogenesis of various cancers, largely due to its role in regulating cancer stem cells (CSCs). CSCs are a subpopulation of cancer cells with the ability to self-renew, differentiate, and initiate tumour growth, contributing significantly to tumorigenesis, recurrence, and resistance to therapy. This review focuses on the intricate activity of the Shh pathway within the context of CSCs, detailing the molecular mechanisms through which Shh signalling influences CSC properties, including self-renewal, differentiation, and survival. It further explores the regulatory crosstalk between the Shh pathway and other signalling pathways in CSCs, highlighting the complexity of this regulatory network. Here, we delve into the upstream regulators and downstream effectors that modulate Shh pathway activity in CSCs. This review aims to cast a specific focus on the role of the Shh pathway in CSCs, provide a detailed exploration of molecular mechanisms and regulatory crosstalk, and discuss current and developing inhibitors. By summarising key findings and insights gained, we wish to emphasise the importance of further elucidating the interplay between the Shh pathway and CSCs to develop more effective cancer therapies.

Signaling pathways governing the maintenance of breast cancer stem cells and their therapeutic implications

Breast cancer stem cells (BCSCs) represent a distinct subpopulation of cells with the ability to self-renewal and differentiate into phenotypically diverse tumor cells. The involvement of CSC in treatment resistance and cancer recurrence has been well established. Numerous studies have provided compelling evidence that the self-renewal ability of cancer stem cells is tightly regulated by specific signaling pathways, which exert critical roles to maintain an undifferentiated phenotype and prevent the differentiation of CSCs. Signaling pathways such as Wnt/β-catenin, NF-κB, Notch, Hedgehog, TGF-β, and Hippo have been implicated in the promotion of self-renewal of many normal and cancer stem cells. Given the pivotal role of BCSCs in driving breast cancer aggressiveness, targeting self-renewal signaling pathways holds promise as a viable therapeutic strategy for combating this disease. In this review, we will discuss the main signaling pathways involved in the maintenance of the self-renewal ability of BCSC, while also highlighting current strategies employed to disrupt the signaling molecules associated with stemness.

Awakening of Dormant Breast Cancer Cells in the Bone Marrow

Up to 40% of patients with breast cancer (BC) have metastatic cells in the bone marrow (BM) at the initial diagnosis of localized disease. Despite definitive systemic adjuvant therapy, these cells survive in the BM microenvironment, enter a dormant state and recur stochastically for more than 20 years. Once they begin to proliferate, recurrent macrometastases are not curable, and patients generally succumb to their disease. Many potential mechanisms for initiating recurrence have been proposed, but no definitive predictive data have been generated. This manuscript reviews the proposed mechanisms that maintain BC cell dormancy in the BM microenvironment and discusses the data supporting specific mechanisms for recurrence. It addresses the well-described mechanisms of secretory senescence, inflammation, aging, adipogenic BM conversion, autophagy, systemic effects of trauma and surgery, sympathetic signaling, transient angiogenic bursts, hypercoagulable states, osteoclast activation, and epigenetic modifications of dormant cells. This review addresses proposed approaches for either eliminating micrometastases or maintaining a dormant state.

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

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

GANT61 suppresses cell survival, invasion and epithelial-mesenchymal transition through inactivating AKT/mTOR and JAK/STAT3 pathways in anaplastic thyroid carcinoma

Glioma-associated oncogene (Gli) antagonist-61 (GANT61) not only suppresses the malignant behavior of several cancers but also presents synergistic effects with other anticancer agents on suppressing the progression of cancers, while relevant information is rare in anaplastic thyroid carcinoma (ATC). This study aimed to explore the therapeutic effect of GANT61 in ATC and its molecular mechanism. ATC cells (8505C and CAL-62) were treated with GANT61, followed by detection of cell proliferation, apoptosis, invasion and epithelial-mesenchymal transition (EMT) markers. Subsequently, RNA sequencing was performed to explore the potential downstream pathway. Following that, rescue experiments were conducted by SC79 (AKT activator) or colivelin (STAT3 activator) monotreatment or combined with GANT61 in ATC cells. GANT61 reduced Gli1 expression, suppressed proliferation at several time settings, promoted apoptosis, inhibited invasion and increased E-cadherin while decreased Vimentin and Snail expressions (EMT markers) in ATC cells. The subsequent RNA sequence identified 85 upregulated differentially expressed genes (DEGs) and 71 downregulated DEGs in GANT61-treated ATC cells, which were mainly enriched in PI3K/AKT, JAK/STAT, Hedgehog and mTOR pathways. Next, the inactivation of AKT/mTOR and JAK/STAT3 pathways by GANT61 treatment was verified by western blot. The following rescue experiments showed that SC79 or colivelin treatment promoted the malignant behaviors of ATC cells. More importantly, SC79 or colivelin treatment compensated the effect of GANT61 treatment on cell proliferation at several time settings and apoptosis, invasion, and part of that on EMT in ATC cells. GANT61 suppresses cell survival, invasion and EMT through inactivating AKT/mTOR or JAK/STAT3 pathways in ATC.

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.

GANT-61 Induces Autophagy and Apoptosis in Glioblastoma Cells despite their heterogeneity

Glioblastoma (GBM) is the most common adult primary tumor of the CNS characterized by rapid growth and diffuse invasiveness into the brain parenchyma. The GBM resistance to chemotherapeutic drugs may be due to the presence of cancer stem cells (CSCs). The CSCs activate the same molecular pathways as healthy stem cells such as WNT, Sonic hedgehog (SHH), and Notch. Mutations or deregulations of those pathways play a key role in the proliferation and differentiation of their surrounding environment, leading to tumorigenesis. Here we investigated the effect of SHH signaling pathway inhibition in human GBM cells by using GANT-61, considering stem cell phenotype, cell proliferation, and cell death. Our results demonstrated that GANT-61 induces apoptosis and autophagy in GBM cells, by increasing the expression of LC3 II and cleaved caspase 3 and 9. Moreover, we observed that SHH signaling plays a crucial role in CSC phenotype maintenance, being also involved in the epithelial-mesenchymal transition (EMT) phenotype. We also noted that SHH pathway modulation can regulate cell proliferation as revealed through the analysis of Ki-67 and c-MYC expressions. We concluded that SHH signaling pathway inhibition may be a promising therapeutic approach to treat patients suffering from GBM refractory to traditional treatments.

Hedgehog gene expression patterns among intrinsic subtypes of breast cancer: Prognostic relevance

PURPOSE

Hedgehog (Hh) signaling is a crucial developmental regulatory pathway recognized as a primary oncogenesis driver in various human cancers. However, its role in breast carcinoma (BC) has been underexplored.

METHODS

We analyzed the expression of several Hh associated genes in a clinical series and breast cancer cell lines. We included 193 BC stratified according to intrinsic immunophenotypes. Gene expression profiling ofBOC, PTCH, SMO, GLI1, GLI2, and GLI3 was performed by qRT-PCR. Results were correlated with clinical-pathological variables and outcome.

RESULTS

We observed expression ofGLI2 in triple-negative/basal-like (TN/BL) and GLI3 in luminal cells. In samples, BOC, GLI1, GLI2, and GLI3 expression correlated significantly with luminal tumors and good prognostic factors. In contrast, PTCH and SMO correlated with TN/BL phenotype and nodal involvement. Patients whose tumors expressed SMO had a poorer outcome, especially those with HER2 phenotype. Positive lymph-node status and high SMO remained independent poor prognostic factors.

CONCLUSION

Our results support a differential Hh pathway activation in BC phenotypes.SMO levels stratified patients at risk of recurrence and death in HER2 phenotype, and it showed an independent prognostic value. Therefore, SMO could be a potential therapeutic target for a subset of BC patients.

Nanosized Drug Delivery Systems for Breast Cancer Stem Cell Targeting

Breast cancer stem cells (BCSCs), also known as breast cancer initiating cells, are reported to be responsible for the initiation, progression, therapeutic resistance, and relapse of breast cancer. Conventional therapeutic agents mainly kill the bulk of breast tumor cells and fail to eliminate BCSCs, even enhancing the fraction of BCSCs in breast tumors sometimes. Therefore, it is essential to develop specific and effective methods of eliminating BCSCs that will enhance the efficacy of killing breast tumor cells and thereby, increase the survival rates and quality of life of breast cancer patients. Despite the availability of an increasing number of anti-BCSC agents, their clinical translations are hindered by many issues, such as instability, low bioavailability, and off-target effects. Nanosized drug delivery systems (NDDSs) have the potential to overcome the drawbacks of anti-BCSC agents by providing site-specific delivery and enhancing of the stability and bioavailability of the delivered agents. In this review, we first briefly introduce the strategies and agents used against BCSCs and then highlight the mechanism of action and therapeutic efficacy of several state-of-the-art NDDSs that can be used to treat breast cancer by eliminating BCSCs.

The Role of Smoothened in Cancer

Smoothened (SMO) belongs to the Hedgehog (HH) signaling pathway, which regulates cell growth, migration, invasion and stem cells in cancer. The HH signaling pathway includes both canonical and noncanonical pathways. The canonical HH pathway functions through major HH molecules such as HH ligands, PTCH, SMO and GLI, whereas the noncanonical HH pathway involves the activation of SMO or GLI through other pathways. The role of SMO has been discussed in different types of cancer, including breast, liver, pancreatic and colon cancers. SMO expression correlates with tumor size, invasiveness, metastasis and recurrence. In addition, SMO inhibitors can suppress cancer formation, reduce the proliferation of cancer cells, trigger apoptosis and suppress cancer stem cell activity. A better understanding of the role of SMO in cancer could contribute to the development of novel therapeutic approaches.

GANT61 Reduces Hedgehog Molecule (GLI1) Expression and Promotes Apoptosis in Metastatic Oral Squamous Cell Carcinoma Cells

Due to its importance in the pathogenesis of oral squamous cell carcinoma (OSCC), the Hedgehog (HH) pathway is considered a potential therapeutic target. We investigated the effects of GANT61, a GLI inhibitor, on HH gene expression, as well as on metastatic OSCC cell proliferation and death. Following culture in DMEM medium, cytotoxicity of GANT61 against different tumor and non-tumor cell types was assessed by alamarBlue assays. Cytotoxicity analysis revealed that the metastatic HSC3 cell line was the most sensitive (IC₅₀: 36 µM) to the tested compound. The compound’s effects on the expression of HH pathways components were analyzed by qPCR and Western blot; cell viability was analyzed by trypan blue assay and flow cytometry were used to investigate cell cycle phase, morphology, and death patterns in HSC3 cells. A significant reduction in mRNA levels of the GLI1 transcription factor was found after 12 h of treatment withGANT61. Protein expression levels of other HH pathway components (PTCH1, SHH, and Gli1) and HSC3 cell viability also decreased after 24 h of treatment. Cell cycle analysis and death pattern evaluations revealed significantly increased nuclear fragmentation in sub-G1 phase, as well as cell death due to apoptosis. In conclusion, the significantly reduced GLI1 gene expression seen in response to the GLI inhibitor indicates diminished downstream activation in HH pathway components. GANT61 significantly reduced cell viability in the metastatic cell line of OSCC and promoted a significant increase in nuclear fragmentation and cell death by apoptosis.

24-Dehydrocholesterol reductase promotes the growth of breast cancer stem-like cells through the Hedgehog pathway

Cholesterol is a risk factor for breast cancer. However, it is still unclear whether the cholesterol biosynthesis pathway plays any significant role in breast carcinogenesis. 24-Dehydrocholesterol reductase (DHCR24) is a key enzyme in the cholesterol synthesis pathway. Although DHCR24 is reported to have different functions in different cancers, it is not clear whether DHCR24 is involved in breast cancer. In this study, we found that DHCR24 expression was higher in breast cancer especially in luminal and HER2 positive breast cancer tissues compared with normal breast. Changes in DHCR24 expression altered cellular cholesterol content without affecting the adherent growth of breast cancer cells. However, DHCR24 knockdown reduced whereas DHCR24 overexpression enhanced breast cancer stem-like cell populations such as mammosphere and aldehyde dehydrogenase positive cell numbers. In addition, DHCR24 overexpression increased the expression of the Hedgehog pathway-regulated genes. Treating DHCR24 overexpressing breast cancer cell lines with the Hedgehog pathway inhibitor GANT61 blocked DHCR24-induced mammosphere growth and increased mRNA levels of the Hedgehog regulated genes. Furthermore, expression of a constitutively activated mutant of Smoothened, a key hedgehog signal transducer, rescued the decreases in mammosphere growth and Hedgehog regulated gene expression induced by knockdown of DHCR24. These results indicate that DHCR24 promotes the growth of breast cancer stem-like cells in part through enhancing the Hedgehog signaling pathway. Our data suggest that cholesterol contribute to breast carcinogenesis by enhancing Hedgehog signaling and cancer stem-like cell populations. Enzymes including DHCR24 involved in cholesterol biosynthesis should be considered as potential treatment targets for breast cancer.

A Gli inhibitor GANT61 suppresses cell proliferation, promotes cell apoptosis and induces G1/G0 cycle retardation with a dose- and time-dependent manner through inhibiting Notch pathway in multiple myeloma

PURPOSE

This study aimed to explore the effect of GANT61 on regulating cell proliferation, cell apoptosis and cell cycle, and to investigate whether GANT61 would function in multiple myeloma (MM) via inhibiting Notch pathway. Methods: RPMI-8226 and U266 cells were treated by GANT61 (0, 2.5, 5.0, 10.0, 20.0, 30.0, 40.0, 50.0 μmol/L) for 18, 24 and 36 hours (h), and cell proliferation was detected by Cell Counting Kit 8. Then these cells were treated by GANT61 at 0, 2.5, 5.0, 10.0 μmol/L for 24 h or treated by 10.0 μmol/L GANT61 for 0, 18, 24 and 36 h, and cell apoptosis rate, apoptosis markers and cell cycle were detected by AV/PI, Western blot, and PI staining. Notch1, Jagged1, Jagged2 and Hes1 expressions were detected by qPCR and Western blot. Further rescue experiments were conducted by upregulating Notch1. Results: In RPMI-8226 and U266 cells, GANT61 inhibited cell proliferation, increased cell apoptosis rate and cell percentage of G1/G0 phase while decreased cell percentage of S phase in a dose- and time-dependent manner. Besides, GANT61 inhibited Notch1, Jagged1, Jagged2 and Hes1 expressions in a dose- and time-dependent manner as well. In rescue experiments, Notch1 upregulation attenuated the inhibition of cell proliferation, promotion of cell apoptosis, induction of G1/G0 cycle retardation and repression of Notch signaling pathway induced by GANT61 treatment in RPMI-8226 and U266 cells. Conclusions: GANT61 suppresses cell proliferation, promotes cell apoptosis and induces G1/G0 cycle retardation with a dose- and time-dependent manner through inhibiting Notch pathway in MM.

ABBREVIATIONS

MM: Multiple myeloma; Hh: Hedgehog; EMT: epithelial mesenchymal transition; AML: acute myeloid leukemia; GANT61: GLI antagonist; DMSO: dimethyl sulfoxide; CCK-8: Cell Counting Kit 8; C-Caspase 3: Cleaved Caspase 3; Bcl-2: B-cell lymphoma-2; RT-qPCR: real-time quantitative polymerase chain reaction; OD: optical density; PTCH1: Patched1.

Dual or multiple drug loaded nanoparticles to target breast cancer stem cells

Breast cancer stem(-like) cells (BCSCs) have been found to be responsible for therapeutic resistance and disease relapse. BCSCs are difficult to eradicate due to their high resistance to conventional treatments and high plasticity. Functionalised nanoparticles have been investigated as smart vehicles to transport across various barriers and increase the interaction of therapeutic agents with cancer cells, as well as BCSCs. In this review, we discuss the different characteristics of BCSCs, and challenges to tackle BCSCs at cellular and molecular levels. The mechanisms of action and physicochemical properties of the current BCSC targeting agents are also covered. We will focus on the rational design and recent advances of "Nano + Nano" or single tumour targeting nanoparticle systems loaded with dual or multiple agents to kill all cancer cells including BCSCs. These cocktail therapies include the combination of a chemotherapy agent with a BCSC-specific inhibitor, a phytochemical agent or RNA based therapy. Given the heterogeneity of breast tumour tissue, targeting both BCSCs and bulk breast cancer cells simultaneously with multiple agents holds great promise in eliminating breast cancer. The future research needs to focus on overcoming various barriers in the 'clinical translation' of BCSC-targeting nanomedicines to cure breast cancer, which requires a significant multidisciplinary effort.

Bioinformatics Studies Provide Insight into Possible Target and Mechanisms of Action of Nobiletin against Cancer Stem Cells

OBJECTIVE

Nobiletin treatment on MDA-MB 231 cells reduces the expression of CXC chemokine receptor type 4 (CXCR4), which is highly expressed in cancer stem cell populations in tumor patients. However, the mechanisms of nobiletin in cancer stem cells (CSCs) remain elusive. This study was aimed to explore the potential target and mechanisms of nobiletin in cancer stem cells using bioinformatics approaches.

METHODS

Gene expression profiles by public COMPARE predicting the sensitivity of tumor cells to nobiletin. Functional annotations on gene lists are carried out with The Database for Annotation, Visualization and Integrated Discovery (DAVID) v6.8, and WEB-based GEne SeT Analysis Toolkit (WebGestalt). The protein-protein interaction (PPI) network was analyzed by STRING-DB and visualized by Cytoscape.

RESULTS

Microarray analyses reveal many genes involved in protein binding, transcriptional and translational activity. Pathway enrichment analysis revealed breast cancer regulation of estrogen signaling and Wnt/ß-catenin by nobiletin. Moreover, three hub genes, i.e. ESR1, NCOA3, and RPS6KB1 and one significant module were filtered out and selected from the PPI network.

CONCLUSION

Nobiletin might serve as a lead compound for the development of CSCs-targeted drugs by targeting estrogen and Wnt/ß-catenin signaling. Further studies are needed to explore the full therapeutic potential of nobiletin in cancer stem cells.
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Self-Renewal Signalling Pathway Inhibitors: Perspectives on Therapeutic Approaches for Cancer Stem Cells

The poor survival and prognosis of individuals with cancer are often attributed to tumour relapse and metastasis, which may be due to the presence of cancer stem cells (CSCs). CSCs have the characteristics of self-renewal, differentiation potential, high carcinogenicity, and drug resistance. In addition, CSCs exhibit many characteristics similar to those of embryonic or tissue stem cells while displaying persistent abnormal activation of self-renewal pathways associated with development and tissue homeostasis, including the Wnt, Notch, Hedgehog (Hh), TGF-β, JAK/STAT3, and NF-κB pathways. Therefore, we can eliminate CSCs by targeting these self-renewal pathways to constrain stem cell replication, survival and differentiation. At the same time, we cannot neglect the ping-pong effect of the tumour microenvironment, which releases cytokines and promotes self-renewal pathways in CSCs. Recently, meaningful progress has been made in the study of inhibitors of self-renewal pathways in tumours. This review primarily summarizes several representative and novel agents targeting these self-renewal signalling pathways and the tumour microenvironment and that represent a promising strategy for treating refractory and recurrent cancer.

Anti-cell growth and anti-cancer stem cell activity of the CDK4/6 inhibitor palbociclib in breast cancer cells

BACKGROUND

A cyclin-dependent kinase (CDK) 4/6 inhibitor, palbociclib, has been used to treat patients with estrogen receptor (ER)-positive (+) and human epidermal growth factor receptor (HER) 2-negative (-) advanced breast cancer. To investigate the mechanisms underlying the antitumor activity of palbociclib, we conducted a preclinical study on the anti-cell growth and anti-cancer stem cell (CSC) activity of palbociclib in breast cancer cells.

METHODS

The effects of palbociclib on Rb phosphorylation, cell growth, cell cycle progression, apoptosis, cell senescence and the proportion of CSCs were investigated in five human breast cancer cell lines of different subtypes. To investigate the mechanisms of the anti-CSC activity of palbociclib, small-interfering RNAs for CDK4 and/or CDK6 were used. Palbociclib dose-dependently reduced Rb phosphorylation and cell growth in association with G1-S cell cycle blockade and the induction of cell senescence, but without increased apoptosis, in all breast cancer cell lines.

RESULTS

The anti-cell growth activity of palbociclib widely differed among the cell lines. Palbociclib also dose-dependently reduced the CSC proportion measured by three different assays in four of five cell lines. The inhibition of CDK4 expression, but not CDK6 expression, reduced the increased proportion of putative CSCs induced by estradiol in ER (+)/HER2 (-) cell lines.

CONCLUSIONS

These results suggest that palbociclib exhibits significant anti-cell growth and anti-CSC activity in not only ER (+) breast cancer cell lines but also ER (-) cell lines. CDK4 inhibition induced by palbociclib may be responsible for its anti-CSC activity.

The role of hedgehog signaling in gastric cancer: molecular mechanisms, clinical potential, and perspective

Patients with advanced gastric cancer usually have a poor prognosis and limited therapeutic options. Overcoming this challenge requires novel targets and effective drugs. The Hedgehog (Hh) signaling pathway plays a crucial role in the development of the gastrointestinal tract and maintenance of the physiologic function of the stomach. Aberrantly activated Hh signaling is implicated in carcinogenesis as well as maintenance of cancer stem cells. Somatic mutations in the components of Hh signaling (PTCH1 and SMO) have been shown to be a major cause of basal cell carcinoma, and dozens of Hh inhibitors have been developed. To date, two inhibitors (GDC-0449 and LDE225) have been approved by the U.S. Food and Drug Administration to treat basal cell carcinoma and medulloblastoma. Here, we review the role of the Hh signaling in the carcinogenesis and progression of gastric cancer and summarize recent findings on Hh inhibitors in gastric cancer. Hedgehog signaling is often aberrantly activated and plays an important role during inflammation and carcinogenesis of gastric epithelial cells. Further study of the precise mechanisms of Hh signaling in this disease is needed for the validation of therapeutic targets and evaluation of the clinical utility of Hh inhibitors for gastric cancer.

The Roles of Hedgehog Signaling Pathway in Radioresistance of Cervical Cancer

Radiotherapy is an important treatment of cervical cancer, especially for advanced cervical cancer. According to research reports, Hedgehog signaling pathway plays an essential role in the growth, invasion, metastasis, recurrence, drug resistance, and radioresistance of cervical cancer. The components of Hedgehog signaling pathway could be biomarkers, related to progression and prognosis of cervical cancer. In addition, targeted therapy for Hedgehog signaling pathway is expected to become a new strategy for the treatment of radioresistant cervical cancer. This review summarizes the research status and progress of the relationship between radiation resistance and activation of Hedgehog signaling pathway in cervical cancer.

Characterization of the stemness potency of mammospheres isolated from the breast cancer cell lines

Stemness phenotype mammospheres established from cell lines and tissues taken from autopsy can be used to test and to identify the most sensitive drugs for chemotherapy. Therefore, the aim of the present study was isolation and characterization of cancer stem cells derived from MCF7, MDA-MB231, and SKBR3 breast cancer cell lines to demonstrate the stemness phenotypes of mammospheres generated for further their applications in therapeutic approaches. In this study, two luminal subtypes of cell lines, MCF7 and SKBR3 and a basal subtype cell line, MDA-MB-231, were chosen. Mammosphere culturing was implemented for breast cancer stem cells isolation and mammosphere formation efficiency. At the next step, CD44+/CD24– cell ratio, Oct4 and Nanog mRNA levels, proliferation rate, migration rate of mammospheres, and drug resistance (in third passage) were evaluated. In addition, tumorigenicity of mammospheres in the chick embryo model was evaluated and compared through the chick chorioallantoic membrane assay. Among mammospheres formed in all three cell lines, MCF7 had the highest mammosphere formation efficiency. CD24 marker (a differentiation marker for the breast cancer cells) was significantly reduced in the mammospheres generated from MCF7 and SKBR3, during three passages. Also, Oct4 and Nanog transcript levels were significantly higher in all three types of mammospheres, as compared with their cell lines. Proliferation, migration rate, and drug resistance of mammospheres generated from all three cell lines were found to be significantly higher. Tumorigenicity of MCF7 mammospheres was confirmed through tumor size measurement. Also, tumorigenicity of MCF7 and SKBR3 mammospheres was confirmed through more migration from ectoderm to mesoderm and endoderm. We succeeded to establish the technology that can be extended to tissue in the future. We have demonstrated a number of mammospheres can be generated from cell lines. Also, cells with different molecular features showed different stemness phenotypes.

Hedgehog pathway inhibition causes primary follicle atresia and decreases female germline stem cell proliferation capacity or stemness

Background

Follicle depletion is one of the causes of premature ovarian failure (POF) and primary ovarian insufficiency (POI). Hence, maintenance of a certain number of female germline stem cells (FGSCs) is optimal to produce oocytes and replenish the primordial follicle pool. The mechanism that regulates proliferation or stemness of FGSCs could contribute to restoring ovarian function, but it remains uncharacterized in postnatal mammalian ovaries. This study aims to investigate the mechanism by which inhibiting the activity of the hedgehog (Hh) signaling pathway regulates follicle development and FGSC proliferation.

Methods and results

To understand the role of the Hh pathway in ovarian aging, we measured Hh signaling activity at different reproductive ages and the correlation between them in physiological and pathological mice. Furthermore, we evaluated the follicle number and development and the changes in FGSC proliferation or stemness after blocking the Hh pathway in vitro and in vivo. In addition, we aimed to explain one of the mechanisms for the FGSC phenotype changes induced by treatment with the Hh pathway-specific inhibitor GANT61 via oxidative stress and apoptosis. The results show that the activity of Hh signaling is decreased in the ovaries in physiological aging and POF models, which is consistent with the trend of expression levels of the germline stem cell markers Mvh and Oct4. In vitro, blocking the Hh pathway causes follicular developmental disorders and depletes ovarian germ cells and FGSCs after treating ovaries with GANT61. The proliferation or stemness of cultured primary FGSCs is reduced when Hh activity is blocked. Our results show that the antioxidative enzyme level and the ratio of Bcl-2/Bax decrease, the expression level of caspase 3 increases, the mitochondrial membrane potential is abnormal, and ROS accumulate in this system.

Conclusions

We observed that the inhibition of the Hh signaling pathway with GANT61 could reduce primordial follicle number and decrease FGSC reproductive capacity or stemness through oxidative damage and apoptosis.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1299-5) contains supplementary material, which is available to authorized users.

Safety and Tolerability of Sonic Hedgehog Pathway Inhibitors in Cancer

The hedgehog pathway, for which sonic hedgehog (Shh) is the most prominent ligand, is highly conserved and is tightly associated with embryonic development in a number of species. This pathway is also tightly associated with the development of several types of cancer, including basal cell carcinoma (BCC) and acute promyelocytic leukemia, among many others. Inactivating mutations in Patched-1 (PTCH1), leading to ligand-independent pathway activation, are frequent in several cancer types, but most prominent in BCC. This has led to the development of several compounds targeting this pathway as a cancer therapeutic. These compounds target the inducers of this pathway in Smoothened (SMO) and the GLI transcription factors, although targeting SMO has had the most success. Despite the many attempts at targeting this pathway, only three US FDA-approved drugs for cancers affect the Shh pathway. Two of these compounds, vismodegib and sonidegib, target SMO to suppress signaling from either PTCH1 or SMO mutations that lead to upregulation of the pathway. The other approved compound is arsenic trioxide, which can suppress this pathway at the level of the GLI proteins, although current evidence suggests it also has other targets. This review focuses on the safety and tolerability of these clinically approved drugs targeting the Shh pathway, along with a discussion on other Shh pathway inhibitors being developed.

Carbonic anhydrase XII expression is linked to suppression of Sonic hedgehog ligand expression in triple negative breast cancer cells

Aberrant activity of the hedgehog (Hh) pathway is prevalent in pathologies such as cancer. Improved understanding of Hh activity in the aggressive tumor cell phenotype is being pursued for development of targeted therapies. Recently, we described a link between Hh activity and carbonic anhydrase XII (CAXII) expression. Extracellular facing CAs (IX/XII) are highly expressed in hypoxia, contribute to tumor pH regulation and are thus of clinical interest. Here we have extended the investigation of potential interactions between Hh activity and CAXII utilizing genomic disruption/knockout of either GLI1 (the main transcriptional factor induced with Hh activity) or CAXII in the triple negative breast cancer cell lines MDA-MB-231 and BT-549. Knockout of GLI1 and CAXII significantly decreased hallmarks of tumor aggressiveness including proliferation and migration. Most intriguingly, CAXII knockout caused a massive induction of the Sonic hedgehog (Shh) ligand expression (gene and protein). This novel finding indicates that CAXII plays a potential role in suppression of Shh and may act in a feedback loop to regulate overall Hh activity. Enhanced knowledge of these CA-Hh interactions in future studies may be of value in understanding this currently 'incurable' subclass of breast cancer.

Role of Hedgehog Signaling in Breast Cancer: Pathogenesis and Therapeutics

Breast cancer (BC) is the leading cause of cancer-related mortality in women, only followed by lung cancer. Given the importance of BC in public health, it is essential to identify biomarkers to predict prognosis, predetermine drug resistance and provide treatment guidelines that include personalized targeted therapies. The Hedgehog (Hh) signaling pathway plays an essential role in embryonic development, tissue regeneration, and stem cell renewal. Several lines of evidence endorse the important role of canonical and non-canonical Hh signaling in BC. In this comprehensive review we discuss the role of Hh signaling in breast development and homeostasis and its contribution to tumorigenesis and progression of different subtypes of BC. We also examine the efficacy of agents targeting different components of the Hh pathway both in preclinical models and in clinical trials. The contribution of the Hh pathway in BC tumorigenesis and progression, its prognostic role, and its value as a therapeutic target vary according to the molecular, clinical, and histopathological characteristics of the BC patients. The evidence presented here highlights the relevance of the Hh signaling in BC, and suggest that this pathway is key for BC progression and metastasis.

GANT61 alleviates arthritic symptoms by targeting fibroblast-like synoviocytes in CIA rats

BACKGROUND

Studies have identified that the fibroblast-like synoviocytes (FLS) exhibited tumor-like characteristics and was the key factor in the pathogenesis of Rheumatoid arthritis (RA). GANT61, an antagonist of the sonic hedgehog pathway, has been verified with inhibitory effect on many cancers. Here we investigated the effect of GANT61 on FLS and the development of collagen-induced arthritis (CIA).

METHODS

40 Sprague Dawley (SD) rats were randomly divided into four groups: normal, CIA, CIA+10 mg/kg GANT61 and CIA+20 mg/kg GANT61. CIA was induced in rat with collagen injecting. The GANT61 was administered by intraperitoneal injection every 2 days for 3 weeks. The CIA model was identified with the paw swelling, arthritis score and the pathologic changes in joint. The FLS of different group were primary cultured. The proliferative capacity of FLS was detecteded via Cell Counting Kit-8 (CCK-8) method, and the apoptosis was detecteded by flow cytometry. The Bcl-2, Bax, Caspases3 and cleaved Caspases3 in synovium and FLS were detecteded by Western Blot.

RESULTS

The 20 mg/kg GANT61 treatment reduced the incidence of CIA and relieved the arthritis symptoms in CIA rats. The Bcl-2 was upregulated and the Bax was downregulated in the CIA rats synovium. The 10 mg/kg and 20 mg/kg GANT61 diminished the Bcl-2 expression, 20 mg/kg GANT61 increased the Bax and activated the Caspases3 in the CIA synovium. The proliferation of CIA-FLS was significantly higher and the apoptosis of the CIA-FLS was lower than that of the control group. The 10 mg/kg and 20 mg/kg GANT61 treatment can reduce cell proliferation and induce apoptosis by diminishing Bcl-2 and increasing the Bax in CIA-FLS.

CONCLUSIONS

The GANT61 inhibit the proliferation of FLS and alleviated the arthritic symptoms in CIA rats, this implied the GANT61 may be recommended as a possible candidate for the therapy of RA.

M2 macrophage-derived IL6 mediates resistance of breast cancer cells to hedgehog inhibition

Hedgehog (Hh) pathway hyperactivation has been observed in various tumors, including breast cancer, and Hh pathway inhibitors have demonstrated antitumor activity in breast cancer. The tumor microenvironment (TME) has been shown to play an important role in modulating cancer cell drug sensitivity, but the TME response to Hh pathway inhibitors is unclear. In the current study, we observed increased TME infiltration of macrophages in breast cancer tissue, and specifically, M2 polarized macrophages after neoadjuvant chemotherapy. Furthermore, we observed an enhanced tolerance to Hh pathway inhibitors in MDA-MB-231 cells after co-culturing with M2 macrophages. In addition, we demonstrated that Hh pathway inhibition significantly induced IL6 expression, and validated that the tolerance to Hh pathway inhibitors was IL6-dependent. This study demonstrates a role of macrophages in Hh pathway inhibition resistance and a role of macrophage-derived IL6 in this resistance of breast cancer cells to Hh inhibition. These data indicate that antagonizing IL6 together with Hh pathway inhibitors may be a novel therapeutic strategy for breast cancer.

SOX2 regulates radioresistance in cervical cancer via the hedgehog signaling pathway

OBJECTIVE

Resistance to radiotherapy accounts for most treatment failures in cervical cancer patients who receive radical radiation therapy. To discover the possible mechanism of radioresistance and improve the 5-year survival rate, we focused on how sex-determining region Y-box 2 (SOX2) mediates radioresistance in cervical cancer as well as on the interaction between SOX2 and the hedgehog (Hh) signaling pathway in this study.

METHODS

We established the acquired radioresistant subclone cells Hela-RR and Siha-RR. RT-qPCR, Western blot analysis, IHC, clonogenic survival assay, CCK-8 assay, apoptosis analysis, cell cycle analysis and xenograft models were used to explore the relationship between SOX2 expression and radiation resistance and to determine how SOX2 mediates radioresistance in cervical cancer. Furthermore, luciferase reporter and ChIP-PCR assays were utilized to assess the interaction between SOX2 and the Hh signaling pathway.

RESULTS

Our research suggested that high expression of SOX2 was responsible for radioresistance in cervical cancer. SOX2 was observed to be closely related to irradiation-induced survival, proliferation, apoptosis, and cell cycle changes. The Hh signaling pathway was found to be activated in Hela-RR and Siha-RR, and the activation changed with SOX2 expression. IHC staining of SOX2 and Gli1 showed a close relationship between SOX2 and the Hh pathway. Luciferase reporter and ChIP-PCR assays demonstrated that SOX2 interacted with the Hh signaling pathway by occupying the HHAT promoter.

CONCLUSIONS

SOX2 is a potential therapeutic target of irradiation resistance in cervical cancer. It mediates radioresistance in cervical cancer via the Hh signaling pathway.

Role of GLI Transcription Factors in Pathogenesis and Their Potential as New Therapeutic Targets

GLI transcription factors have important roles in intracellular signaling cascade, acting as the main mediators of the HH-GLI signaling pathway. This is one of the major developmental pathways, regulated both canonically and non-canonically. Deregulation of the pathway during development leads to a number of developmental malformations, depending on the deregulated pathway component. The HH-GLI pathway is mostly inactive in the adult organism but retains its function in stem cells. Aberrant activation in adult cells leads to carcinogenesis through overactivation of several tightly regulated cellular processes such as proliferation, angiogenesis, EMT. Targeting GLI transcription factors has recently become a major focus of potential therapeutic protocols.

Comprehensive immunohistochemical analyses on expression levels of hedgehog signaling molecules in breast cancers

BACKGROUND

The hedgehog (Hh) signaling pathway plays important roles in cell proliferation, malignant progression, invasion and metastasis, and the expansion of cancer stem cells (CSCs). Comprehensive immunohistochemical (IHC) analyses have not yet been conducted on the expression levels of Hh signaling molecules in breast cancer tissues.

METHODS

A total of 204 patients with invasive breast cancer treated in our institute were study subjects. IHC analyses on the expression levels of the Hh signaling molecules, sonic Hh (SHH), PTCH1, GLI1, GLI2, and GLI3 and the CSC-related factor, SOX2, were investigated.

RESULTS

Positive correlations were observed among all of the Hh signaling molecules tested. SOX2 expression correlated with the expression levels of all Hh signaling molecules. SHH expression positively correlated with tumor size, the Ki-67 labeling index, histological grade, estrogen receptor negativity, progesterone receptor negativity, and HER2 positivity. GLI1 expression positively correlated with the histological grade. GLI2 expression positively correlated with the histological grade, Ki-67 labeling index, and HER2 positivity. Univariate analyses revealed that a younger age, larger tumor size, positive lymph node metastasis, higher histological grade, positive lymphatic invasion, and higher Ki-67 labeling index were related to poor relapse-free survival (RFS). The positivity of all Hh signaling molecules and SOX2 did not correlate with poor RFS. A multivariate analysis revealed that positive lymphatic invasion and a younger age were independent worse prognostic factors for RFS.

CONCLUSIONS

This comprehensive analysis demonstrated for the first time that SHH, GLI1, and GLI2 expression levels positively correlated with the malignant phenotypes of tumor cells.

Targeting Transcription Factors for Cancer Treatment

Transcription factors are involved in a large number of human diseases such as cancers for which they account for about 20% of all oncogenes identified so far. For long time, with the exception of ligand-inducible nuclear receptors, transcription factors were considered as “undruggable” targets. Advances knowledge of these transcription factors, in terms of structure, function (expression, degradation, interaction with co-factors and other proteins) and the dynamics of their mode of binding to DNA has changed this postulate and paved the way for new therapies targeted against transcription factors. Here, we discuss various ways to target transcription factors in cancer models: by modulating their expression or degradation, by blocking protein/protein interactions, by targeting the transcription factor itself to prevent its DNA binding either through a binding pocket or at the DNA-interacting site, some of these inhibitors being currently used or evaluated for cancer treatment. Such different targeting of transcription factors by small molecules is facilitated by modern chemistry developing a wide variety of original molecules designed to specifically abort transcription factor and by an increased knowledge of their pathological implication through the use of new technologies in order to make it possible to improve therapeutic control of transcription factor oncogenic functions.

Glioma-Associated Oncogene Homolog Inhibitors Have the Potential of Suppressing Cancer Stem Cells of Breast Cancer

Overexpression of Sonic Hedgehog signaling (Shh) pathway molecules is associated with invasiveness and recurrence in breast carcinoma. Therefore, inhibition of the Shh pathway downstream molecule Glioma-associated Oncogene Homolog (Gli) was investigated for its ability to reduce progression and invasiveness of patient-derived breast cancer cells and cell lines. Human primary breast cancer T2 cells with high expression of Shh signaling pathway molecules were compared with breast cancer line MDA-MB-231 cells. The therapeutic effects of Gli inhibitors were examined in terms of the cell proliferation, apoptosis, cancer stem cells, cell migration and gene expression. Blockade of the Shh signaling pathway could reduce cell proliferation and migration only in MDA-MB-231 cells. Hh pathway inhibitor-1 (HPI-1) increased the percentages of late apoptotic cells in MDA-MB-231 cells and early apoptotic cells in T2 cells. It reduced Bcl2 expression for cell proliferation and increased Bim expression for apoptosis. In addition, Gli inhibitor HPI-1 decreased significantly the percentages of cancer stem cells in T2 cells. HPI-1 worked more effectively than GANT-58 against breast carcinoma cells. In conclusion, HPI-1 could inhibit cell proliferation, reduce cell invasion and decrease cancer stem cell population in breast cancer cells. To target Gli-1 could be a potential strategy to suppress breast cancer stem cells.

NEAT1 acts as an inducer of cancer stem cell-like phenotypes in NSCLC by inhibiting EGCG-upregulated CTR1

Long non-coding RNAs (lncRNAs) play significant roles in the pathogenesis of various cancers, including lung cancer. In this study, we aimed to investigate the biological function of lncRNA nuclear enriched abundant transcript 1 (NEAT1) in cancer stem cells (CSCs). CSCs have been suggested as the main cause of tumor metastasis, tumor recurrence, and chemotherapy resistance. The copper transporter 1 (CTR1) has been the focus of many recent studies because of its correlation with cisplatin (CDDP) resistance. So far, the mechanism of how NEAT1 regulates CSCs in NSCLC remains unknown. In the current study, lung cancer stem cells were enriched from the parental NSCLC cells. We observed that NEAT1 was up-regulated while copper transporter 1 (CTR1) was down-regulated in the enriched NSCLC cancer stem cells. Knockdown of NEAT1 was able to decrease the CSC-like properties in NSCLC cells, while over-expression of NEAT1 could contribute to the stemness respectively. Meanwhile, appropriate doses of EGCG restrained the stemness triggered by over-expressing NEAT1 via inducing CTR1 expression. Wnt signal pathway and epithelial-to-mesenchymal transition (EMT) process were involved in NEAT1-induced CSCs in NSCLC. These findings may suggest a novel role of NEAT1 for NSCLC treatment.

Breast cancer lung metastasis: Molecular biology and therapeutic implications

Distant metastasis accounts for the vast majority of deaths in patients with cancer. Breast cancer exhibits a distinct metastatic pattern commonly involving bone, liver, lung, and brain. Breast cancer can be divided into different subtypes based on gene expression profiles, and different breast cancer subtypes show preference to distinct organ sites of metastasis. Luminal breast tumors tend to metastasize to bone while basal-like breast cancer (BLBC) displays a lung tropism of metastasis. However, the mechanisms underlying this organ-specific pattern of metastasis still remain to be elucidated. In this review, we will summarize the recent advances regarding the molecular signaling pathways as well as the therapeutic strategies for treating breast cancer lung metastasis.

Breast cancer stem cells as last soldiers eluding therapeutic burn: A hard nut to crack

Cancer stem cells (CSCs) are found in many cancer types, including breast carcinoma. Breast cancer stem cells (BCSCs) are considered as seed of cancer formation and they are associated with metastasis and genotoxic drug resistance. Several studies highlighted the presence of BCSCs in tumor microenvironment and they are accentuated with several carcinoma events including metastasis and resistance to genotoxic drugs and they also rebound after genotoxic burn. Stemness properties of a small population of cells in carcinoma have provided clues regarding the role of tumor microenvironment in tumor pathophysiology. Hence, insights in cancer stem cell biology with respect to molecular signaling, genetics and epigenetic behavior of CSCs have been used to modulate tumor drug resistance due to genotoxic drugs and signaling protein inhibitors. This review summarizes major scientific breakthroughs in understanding the contribution of BCSCs towards tumor's capability to endure destruction inflicted by molecular as well as genotoxic drugs.

Anti-cancer stem cell activity of a hedgehog inhibitor GANT61 in estrogen receptor-positive breast cancer cells

Estradiol (E2) increases not only the cell growth but also the cancer stem cell (CSC) proportion in estrogen receptor (ER)‐positive breast cancer cells. It has been suggested that the non‐canonical hedgehog (Hh) pathway activated by E2 plays an important role in the regulation of CSC proportion in ER‐positive breast cancer cells. We studied anti‐CSC activity of a non‐canonical Hh inhibitor GANT61 in ER‐positive breast cancer cells. Effects of GANT61 on the cell growth, cell cycle progression, apoptosis and CSC proportion were investigated in four ER‐positive breast cancer cell lines. CSC proportion was measured using either the mammosphere assay or CD44/CD24 assay. Expression levels of pivotal molecules in the Hh pathway were measured. Combined effects of GANT61 with antiestrogens on the anti‐cell growth and anti‐CSC activities were investigated. E2 significantly increased the cell growth and CSC proportion in all ER‐positive cell lines. E2 increased the expression levels of glioma‐associated oncogene (GLI) 1 and/or GLI2. GANT61 decreased the cell growth in association with a G1‐S cell cycle retardation and increased apoptosis. GANT61 decreased the E2‐induced CSC proportion measured by the mammosphere assay in all cell lines. Antiestrogens also decreased the E2‐induced cell growth and CSC proportion. Combined treatments of GANT61 with antiestrogens additively enhanced anti‐cell growth and/or anti‐CSC activities in some ER‐positive cell lines. In conclusion, the non‐canonical Hh inhibitor GANT61 inhibited not only the cell growth but also the CSC proportion increased by E2 in ER‐positive breast cancer cells. GANT61 enhanced anti‐cell growth and/or anti‐CSC activities of antiestrogens in ER‐positive cell lines.

Dialysis encephalopathy: precipitating factors and improvement in prognosis

Cancer stem cells (CSCs) contribute to the initiation, recurrence, and metastasis of cancer; however, there are still no drugs targeting CSCs in clinical application. There are several signaling pathways playing critical roles in CSC progression, such as the Wnt, Hedgehog, Notch, Hippo, and autophagy signaling pathways. Additionally, targeting the ferroptosis signaling pathway was recently shown to specifically kill CSCs. Therefore, targeting these pathways may suppress CSC progression. The structure of small-molecule drugs shows a good spatial dispersion, and its chemical properties determine its good druggability and pharmacokinetic properties. These characteristics make small-molecule drugs show a great advantage in drug development, which is increasingly popular in the market. Thus, in this review, we will summarize the current researches on the small-molecule compounds suppressing CSC progression, including inhibitors of Wnt, Notch, Hedgehog, and autophagy pathways, and activators of Hippo and ferroptosis pathways. These small-molecule compounds emphasize CSC importance in tumor progression and propose a new strategy to treat cancer in clinic via targeting CSCs.