Self-renewal and solid tumor stem cells

TM4SF1 promotes the self-renewal of esophageal cancer stem-like cells and is regulated by miR-141

Cancer stem-like cells have been identified in primary human tumors and cancer cell lines. Previously we found TM4SF1 gene was highly expressed in side population (SP) cells from esophageal squamous cell carcinoma (ESCC) cell lines, but the role and underlying mechanism of TM4SF1 in ESCC remain unclear. In this study, we observed TM4SF1 was up-regulated but miR-141 was down-regulated in SP cells isolated from ESCC cell lines. TM4SF1 could stimulate the self-renewal ability and carcinogenicity of esophageal cancer stem-like cells, and promote cell invasion and migration. In miR-141 overexpression cells, the expression of TM4SF1 was significantly reduced. We also found that overexpression of miR-141 could abolish the self-renewal ability and carcinogenicity of esophageal cancer stem-like cells and decrease cell invasion and migration by suppressing TM4SF1. Consequently, TM4SF1 is a direct target gene of miR-141. The regulation of TM4SF1 by miR-141 may play an important role in controlling self-renewals of esophageal cancer stem-like cells. It may also promote the development of new therapeutic strategies and efficient drugs to target ESCC stem-like cells.

FGF1 and IGF1-conditioned 3D culture system promoted the amplification and cancer stemness of lung cancer cells

Lung cancer stem cells (LCSCs) are considered as the cellular origins of metastasis and relapse of lung cancer. However, routine two-dimensional culture system (2D-culture) hardly mimics the growth and functions of LCSCs in vivo and therefore significantly decreases the stemness activity of LCSCs. In this study, we constructed a special BME-based three-dimensional culture system (3D-culture) to amplify LCSCs in human lung adenocarcinoma cell line A549 cells and found 3D-culture promoted the enrichment and amplification of LCSCs in A549 cells displaying higher proliferation potential and invasion activity, but lower apoptosis. The expression and secretion levels of FGF1 and IGF1 were dramatically elevated in 3D-culture compared to 2D-culture. After growing in FGF1 and IGF1-conditioned 3D-culture, the proportion of LCSCs with specific stemness phenotypes in A549 cells significantly increased compared to that in conventional 3D suspension culture system. Further results indicated that FGF1 and IGF1 promoted the amplification and cancer stemness of LCSCs dependent on MAPK signaling pathway. Our data firstly established a growth factors-conditioned 3D-culture for LCSCs and demonstrated the effects of FGF1 and IGF1 in promoting the enrichment and amplification of LCSCs which might provide a feasible cell model in vitro for both mechanism study and translational research on lung cancer.

Combination therapy targeting both cancer stem-like cells and bulk tumor cells for improved efficacy of breast cancer treatment

Many types of tumors are organized in a hierarchy of heterogeneous cell populations. The cancer stem-like cells (CSCs) hypothesis suggests that tumor development and metastasis are driven by a minority population of cells, which are responsible for tumor initiation, growth and recurrences. The inability to efficiently eliminate CSCs during chemotherapy, together with CSCs being highly tumorigenic and invasive, may result in treatment failure due to cancer relapse and metastases. CSCs are emerging as a promising target for the development of translational cancer therapies. Ideal panacea for cancer would kill all malignant cells, including CSCs and bulk tumor cells. Since both chemotherapy and CSCs-specific therapy are insufficient to cure cancer, we propose combination therapy with CSCs-targeted agents and chemotherapeutics for improved breast cancer treatment. We generated in vitro mammosphere of 2 breast cancer cell lines, and demonstrated ability of mammospheres to grow and enrich cancer cells with stem-like properties, including self-renewal, multilineage differentiation and enrichment of cells expressing breast cancer stem-like cell biomarkers CD44(+)/CD24(-/low). The formation of mammospheres was significantly inhibited by salinomycin, validating its pharmacological role against the cancer stem-like cells. In contrast, paclitaxel showed a minimal effect on the proliferation and growth of breast cancer stem-like cells. While combination therapies of salinomycin with conventional chemotherapy (paclitaxel or lipodox) showed a potential to improve tumor cell killing, different subtypes of breast cancer cells showed different patterns in response to the combination therapies. While optimization of combination therapy is warranted, the design of combination therapy should consider phenotypic attributes of breast cancer types.

Radioresistance of the breast tumor is highly correlated to its level of cancer stem cell and its clinical implication for breast irradiation

BACKGROUND AND PURPOSE

Growing evidence suggested the coexistence of cancer stem cells (CSCs) within solid tumors. We aimed to study radiosensitivity parameters for the CSCs and differentiated tumor cells (TCs) and the correlation of the fractions of CSCs to the overall tumor radioresistance.

MATERIAL AND METHODS

Surviving fractions of breast cancer cell lines were analyzed using a dual-compartment Linear-quadratic model with independent fitting parameters: radiosensitive α_TC, β_TC, α_CSC, β_CSC, and fraction of CSCs f. The overall tumor radio-resistance, the biological effective doses and tumor control probability were estimated as a function of CSC fraction for different fractionation regimens. The pooled clinical outcome data were fitted to the single- and dual-compartment linear-quadric models.

RESULTS

CSCs were more radioresistant characterized by smaller α compared to TCs: α_TC=0.1±0.2, α_CSC=0.04±0.07 for MCF-7 (f=0.1%), α_TC=0.08±0.25, α_CSC=0.04±0.18 for SUM159PT (f=2.46%). Higher f values were correlated with increasing radioresistance in cell lines. Analysis of clinical outcome data is in accordance of a dual-compartment CSC model prediction. Higher percentage of BCSCs resulted in more overall tumor radioresistance and less biological effectiveness.

CONCLUSIONS

Percentage of CSCs strongly correlated to overall tumor radioresistance. This observation suggested potential individualized radiotherapy to account for heterogeneous population of CSCs and their distinct radiosensitivity for breast cancer.

1H-NMR-based metabolic profiling of a colorectal cancer CT-26 lung metastasis model in mice

Lung metastasis is an important cause for the low 5-year survival rate of colorectal cancer patients. Understanding the metabolic profile of lung metastasis of colorectal cancer is important for developing molecular diagnostic and therapeutic approaches. We carried out the metabonomic profiling of lung tissue samples on a mouse lung metastasis model of colorectal cancer using 1H-nuclear magnetic resonance (1H-NMR). The lung tissues of mice were collected at different intervals after marine colon cancer cell line CT-26 was intravenously injected into BALB/c mice. The distinguishing metabolites of lung tissue were investigated using 1H-NMR-based metabonomic assay, which is a highly sensitive and non-destructive method for biomarker identification. Principal component analysis (PCA), partial least squares discriminant analysis (PLS-DA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were applied to analyze 1H-NMR profiling data to seek potential biomarkers. All of the 3 analyses achieved excellent separations between the normal and metastasis groups. A total of 42 metabolites were identified, ~12 of which were closely correlated with the process of metastasis from colon to lung. These altered metabolites indicated the disturbance of metabolism in metastatic tumors including glycolysis, TCA cycle, glutaminolysis, choline metabolism and serine biosynthesis. Our findings firstly identified the distinguishing metabolites in mouse colorectal cancer lung metastasis models, and indicated that the metabolite disturbance may be associated with the progression of lung metastasis from colon cancer. The altered metabolites may be potential biomarkers that provide a promising molecular approach for clinical diagnosis and mechanistic study of colorectal cancer with lung metastasis.

Ribonucleic acid interference knockdown of IL-6 enhances the efficacy of cisplatin in laryngeal cancer stem cells by down-regulating the IL-6/STAT3/HIF1 pathway

Background

Cisplatin has been used in the treatment of many cancers, including laryngeal cancer; however, its efficacy can be reduced due to the development of drug resistance. This study aimed to investigate whether interleukin-6 (IL-6) knockdown may enhance the efficacy of cisplatin in laryngeal cancer stem cells (CSC) and the potential involvement of the signal transducer and activator of transcription 3 (STAT3) and hypoxia-inducible factor 1 (HIF1) in this effect.

Methods

The ALDH+ and CD44+ CSC in Hep2 human laryngeal squamous cancer cells were identified by the fluorescence-activated cell sorting technique. IL-6, STAT3 and HIF1 mRNA and protein expressions were examined with quantitative real-time polymerase chain reaction and Western blot, respectively. Cell proliferation was measured by MTT assay. Tumorigenicity was measured by a colony formation assay and invasion was determined by a cell invasion assay. Apoptotic cells were counted by flow cytometry. Immunohistochemistry was performed to detect immunoreactive IL-6, STAT3 and HIF1 cells in xenografts.

Results

The mRNA and protein levels of IL-6, STAT3 and HIF1 were significantly increased in Hep2-CSC as compared with those from Hep2 cells. Application of siRNA-IL-6 to knockdown IL-6 resulted in significantly decreased IL-6, STAT3 and HIF1 mRNA and protein levels. IL-6 knockdown reduced cell proliferation, tumorigenicity and invasion and increased apoptosis within CSC. Enhanced degrees of suppression in these parameters were observed when IL-6 knockdown was combined with cisplatin in these CSC. Results from the xenograft study showed that the combination of IL-6 knockdown and cisplatin further inhibited the growth of xenografts as compared with that obtained in the cisplatin-injected group alone. Immunoreactive IL-6, STAT3 and HIF1 cell numbers were markedly reduced in IL-6 knockdown tumor tissues. IL-6, STAT3 and HIF1 immunoreactive cell counts were further reduced in tissue where IL-6 knockdown was combined with cisplatin treatment as compared with tissue receiving cisplatin alone.

Conclusions

IL-6 knockdown can increase chemo-drug efficacy of cisplatin, inhibit tumor growth and reduce the potential for tumor recurrence and metastasis in laryngeal cancer. The IL-6/STAT3/HIF1 pathway may represent an important target for investigating therapeutic strategies for the treatment of laryngeal cancer.

Prognostic impact of CD133 expression in Endometrial Cancer Patients

To assess the impact of CD133 expression on the prognosis of endometrioid endometrial carcinoma (EEC). We retrospectively assessed CD133 expression in tissue microarray of 116 surgically treated FIGO I-III EEC. Tumors with ≥10% of CD133-expressing cells were considered CD133-positive (CD133+). On the basis of CD133 expression, clinical and pathological parameters, progression-free survival (PFS) and overall survival (OS) were evaluated. Of the EEC studied 85.2% showed CD133-expressing cells. Only 61% (n = 66) of EEC presented ≥10% of CD133 expressing cells and were considered CD133+. The mean OS for CD133+ tumour patients was 161 months (95% CI, 154–168) as compared with 146 months (95% CI, 123–160) for those with CD133- tumors (p = 0.012). The mean PFS for CD133+ tumour was 159 months (95% CI, 149–168) as compared with 147 months (95% CI, 132-161) in those with a CD133-tumour (p = 0.014). CD133+ tumours were less likely to have vascular invasion (p = 0.010) and more likely to be well differentiated (p = 0.034). C133+ tumours predicted favorable OS and PFS of EEC patients, with a Hazard Ratio 4.731 (95% CI, 1.251–17.89; p = 0.022). CD133+ tumor status correlates with favorable prognosis of EEC. Our findings are in agreement with studies addressing brain and colorectal tumours.

Reprogramming to developmental plasticity in cancer stem cells

During development and throughout adult life, sub-populations of cells exist that exhibit phenotypic plasticity - the ability to differentiate into multiple lineages. This behaviour is important in embryogenesis, is exhibited in a more limited context by adult stem cells, and can be re-activated in cancer cells to drive important processes underlying tumour progression. A well-studied mechanism of phenotypic plasticity is the epithelial-to-mesenchymal transition (EMT), a process which has been observed in both normal and cancerous cells. The epigenetic and metabolic modifications necessary to facilitate phenotypic plasticity are first seen in development and can be re-activated both in normal regeneration and in cancer. In cancer, the re-activation of these mechanisms enables tumour cells to acquire a cancer stem cell (CSC) phenotype with enhanced ability to survive in hostile environments, resist therapeutic interventions, and undergo metastasis. However, recent research has suggested that plasticity may also expose weaknesses in cancer cells that could be exploited for future therapeutic development. More research is needed to identify developmental mechanisms that are active in cancer, so that these may be targeted to reduce tumour growth and metastasis and overcome therapeutic resistance.

Harnessing the BMP signaling pathway to control the formation of cancer stem cells by effects on epithelial-to-mesenchymal transition

Cancer stem cells (CSCs) persist in tumors as a distinct population and may be causative in metastasis and relapse. CSC-rich tumors are associated with higher rates of metastasis and poor patient prognosis. Targeting CSCs therapeutically is challenging, since they seem to be resistant to standard chemotherapy. We have shown that a novel peptide agonist of bone morphogenetic protein (BMP) signaling, P123, is capable of inhibiting the growth of primary tumor cells by interacting with type I receptors selectively [activin receptor-like kinase 2 (ALK2) and ALK3, but not ALK6] and type II BMP receptors, activating SMAD 1/5/8 signaling and controlling the cell cycle pathway. Furthermore, the compound is capable of blocking transforming growth factor-β induced epithelial-to-mesenchymal transition (EMT) in primary tumor cells, a critical step for tumor progression and metastasis. In addition, we have investigated the effects of P123 on self-renewal, growth, differentiation (reversal of EMT) and apoptosis of isolated human breast CSCs. We have shown that P123 and BMP-7 reverse the EMT process in human breast CSCs, and inhibit self-renewal and growth. Moreover, compared with single treatment with paclitaxel, co-treatment with paclitaxel and P123 showed an increase in cell apoptosis. Together, these findings suggest that P123 has the therapeutic potential to suppress both bulk tumor cells and CSCs. We believe that P123 represents a new class of drugs that have the potential to eliminate the primary tumor, prevent reoccurrence and metastasis, and enhance the treatment of breast cancer.

Nestin and cluster of differentiation 146 expression in breast cancer: Predicting early recurrence by targeting metastasis?

The purpose of this study was to investigate the relationship between the expression of stem-cell markers nestin and cluster of differentiation 146 with clinicopathological characteristics in breast cancer and to determine whether a prognostic impact of nestin and CD146 expression exists regarding occurrence of disease relapse in breast cancer. A total of 141 patients who were histologically diagnosed with breast cancer and underwent radical operations from November 2006 to October 2013 in Laiko General Hospital, National and Kapodistrian University of Athens, were enrolled in the study. CD146 and nestin protein expression were evaluated using immunohistochemistry. Nestin expression was observed in 18.4% (26/141) of the cases, while CD146 expression was observed in 35.5% (50/141) of the cases. Nestin expression is significantly higher in younger patients with breast cancer. Nestin and CD146 expression were not correlated with the tumor size and the presence of lymph node metastasis. On the contrary, a significantly higher expression of nestin and CD146 was observed with triple-negative cancers (p < 0.0001 for both markers), low differentiated tumors (p = 0.021 for nestin and p = 0.008 for CD146), and increased Ki-67 expression (p = 0.007 for nestin and p < 0.0001 for CD146). The nestin-positive group of patients and the CD146-positive group of patients presented significantly higher rates of disease recurrence (log-rank test, p = 0.022 for nestin and p = 0.003 for CD146) with a distant metastasis, 30 months after the primary treatment. CD146 but not nestin, however, predicted independently (p = 0.047) disease recurrence. Nestin and CD146 are expressed in breast cancer cells with highly aggressive potency. They might contribute to disease relapse in breast cancer by activating the epithelial-mesenchymal transition pathway and assist tumor neovascularization.

MicroRNA-320a and microRNA-4496 attenuate Helicobacter pylori cytotoxin-associated gene A (CagA)-induced cancer-initiating potential and chemoresistance by targeting β-catenin and ATP-binding cassette, subfamily G, member 2

Infection with Helicobacter pylori is closely linked to an increased risk of gastric cancer. Although cytotoxin-associated gene A (CagA), a major virulence factor of H. pylori, is known to be a causal factor for gastric carcinogenesis, the molecular link between CagA and gastric cancer-initiating cell (CIC)-like properties remains elusive. Here, we demonstrate that CagA is required for increased expression of β-catenin and its target CIC markers via downregulation of microRNA (miR)-320a and miR-4496. CagA promoted gastric CIC properties and was responsible for chemoresistance. miR-320a and miR-4496 attenuated the in vitro self-renewal and tumour-initiating capacity of CagA-expressing CICs by targeting β-catenin. Moreover, miR-320a and miR-4496 decreased CagA-induced chemoresistance by targeting ATP-binding cassette, subfamily G, member 2 (ABCG2) at the transcriptional and post-transcriptional levels, respectively. Combination therapy with 5-fluorouracil and miR-320a/miR-4496 suppressed gastric tumourigenesis and metastatic potential in an orthotopic mouse model, probably via suppression of CagA-induced CIC properties and chemoresistance. Our results provide novel evidence that CIC properties, chemoresistance and tumourigenesis associated with H. pylori are linked to CagA-induced upregulation of β-catenin and ABCG2. These data provide novel insights into the molecular mechanisms of CagA-induced carcinogenisis and the therapeutic potential of of miR-320a and miR-4496. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Distinctive expression pattern of OCT4 variants in different types of breast cancer

BACKGROUND

OCT4 is a key regulator of self-renewal and pluripotency in embryonic stem cells which can potentially encode three spliced variants designated OCT4A, OCT4B and OCT4B1. Based on cancer stem cell concept, it is suggested that the stemness factors misexpressed in cancer cells and potentially is involved in tumorigenesis.

OBJECTIVE

Accordingly, in this study, we investigated the potential expression of OCT4 variants in breast cancer tissues.

METHODS

A total of 94 tumoral and peritumoral breast specimens were evaluated with respect to the expression of OCT4 variants using quantitative RT-PCR and immunohistochemical (IHC) analysis.

RESULTS

We detected the expression of OCT4 variants in breast tumor tissues with no or very low levels of expression in peritumoral samples of the same patients. While OCT4B was highly expressed in lobular type of breast cancer, OCT4A and OCTB1 variants are highly expressed in low grade (I and II) ductal tumors. Furthermore, the results of this study revealed a considerable association between the expression level of OCT4 variants and the expression of ER, PR, Her2 and P53 factors.

CONCLUSIONS

All data demonstrated a distinctive expression pattern of OCT4 spliced variants in different types of breast cancer and provide further evidence for the involvement of embryonic genes in carcinogenesis.

Isolation, identification, and characterization of cancer stem cells: A review

Cancer stem cells (CSCs) or tumor-initiating cells (TICs) as a small subset of neoplastic cells are able to produce a tumor (tumorigenesis), maintain the population of tumorigenic cells (self-renewal), and generate the heterogeneous cells constructing the entire tumor (pluripotency). The research on stationary and circulating CSCs due to resistance to conventional therapies and inability in complete eradication of cancer is critical for developing novel therapeutic strategies for a more effective reduction in the risk of tumor metastasis and cancer recurrence. This review compiles information about different methods of detection and dissociation, side population, cellular markers, and establishment culture of CSCs, as well as characteristics of CSCs such as tumorigenicity, and signaling pathways associated with self-renewal and the capability of the same histological tumor regeneration in various cancers.

Screening of breast cancer stem cell inhibitors using a protein kinase inhibitor library

BACKGROUND

Cancer stem cells (CSCs), a subpopulation in tumors, are known to cause drug resistance, tumor recurrence and metastasis. Based on the characteristic formation of mammospheres in in vitro conditions, the mammosphere formation assay has become an essential tool for quantifying CSC activity in breast cancer research. However, manual counting of mammospheres is a time-consuming process that is not amenable to high-throughput screening, and there are occasional inaccuracies in the process of determining the mammosphere diameter. In this study, we proposed a novel automated counting method of mammosphere using the National Institute of Standards and Technology (NIST)'s Integrated Colony Enumerator (NICE) with a screening of protein kinase library.

METHODS

Human breast cancer cell line MCF-7 was used for evaluation of tumor sphere efficiency, migration, and phenotype transition. Cell viability was assessed using MTT assay, and CSCs were identified by an analysis of CD44 expression and ALDEFLUOR assay using flow cytometry. Automated counting of mammosphere using NICE program was performed with a comparison to the result of manual counting. After identification of inhibitors to ameliorate CSC formation by screening a library of 79 protein kinase inhibitors using automated counting in primary, secondary and tertiary mammosphere assay, the effect of selected kinase inhibitors on migration, colony formation and epithelial-to-mesenchymal transition (EMT) of MCF-7 cells was investigated.

RESULTS

Automated counting of mammosphere using NICE program was an easy and less time-consuming process (<1 min for reading 6-well plate) which provided a comparable result with manual counting. Inhibition of calcium/calmodulin-dependent protein kinase II (CaMKII), Janus kinase-3 (JAK-3), and IκB kinase (IKK) were identified to decrease the formation of MCF-7-derived CSCs in primary, secondary and tertiary mammosphere assay. These protein kinase inhibitors alleviated TGF-β1-induced migration, colony formation and EMT of MCF-7 cells.

CONCLUSIONS

We have developed a novel automated cell-based screening method which provided an easy, accurate and reproducible way for mammosphere quantification. This study is the first to show the efficacy of an automated medium-throughput mammosphere-counting method in CSC-related research with an identification of protein kinase inhibitors to ameliorate CSC formation.

BRCA1-IRIS overexpression promotes and maintains the tumor initiating phenotype: implications for triple negative breast cancer early lesions

Tumor-initiating cells (TICs) are cancer cells endowed with self-renewal, multi-lineage differentiation, increased chemo-resistance, and in breast cancers the CD44+/CD24-/ALDH1+ phenotype. Triple negative breast cancers show lack of BRCA1 expression in addition to enhanced basal, epithelial-to-mesenchymal transition (EMT), and TIC phenotypes. BRCA1-IRIS (hereafter IRIS) is an oncogene produced by the alternative usage of the BRCA1 locus. IRIS is involved in induction of replication, transcription of selected oncogenes, and promoting breast cancer cells aggressiveness. Here, we demonstrate that IRIS overexpression (IRISOE) promotes TNBCs through suppressing BRCA1 expression, enhancing basal-biomarkers, EMT-inducers, and stemness-enforcers expression. IRISOE also activates the TIC phenotype in TNBC cells through elevating CD44 and ALDH1 expression/activity and preventing CD24 surface presentation by activating the internalization pathway EGFR→c-Src→cortactin. We show that the intrinsic sensitivity to an anti-CD24 cross-linking antibody-induced cell death in membranous CD24 expressing/luminal A cells could be acquired in cytoplasmic CD24 expressing IRISOE TNBC/TIC cells through IRIS silencing or inactivation. We show that fewer IRISOE TNBC/TICs cells form large tumors composed of TICs, resembling TNBCs early lesions in patients that contain metastatic precursors capable of disseminating and metastasizing at an early stage of the disease. IRIS-inhibitory peptide killed these IRISOE TNBC/TICs, in vivo and prevented their dissemination and metastasis. We propose IRIS inactivation could be pursued to prevent dissemination and metastasis from early TNBC tumor lesions in patients.

Global expression profile of tumor stem-like cells isolated from MMQ rat prolactinoma cell

BACKGROUND

Cancer stem cells (CSCs), which have been isolated from various malignancies, were closely correlated with the occurrence, progression, metastasis and recurrence of the malignant cancer. Little is known about the tumor stem-like cells (TSLCs) isolated from benign tumors. Here we want to explore the global expression profile of RNA of tumor stem-like cells isolated from MMQ rat prolactinoma cells.

METHODS

In this study, total RNA was extracted from MMQ cells and MMQ tumor stem-like cells. RNA expression profiles were determined by Agilent Rat 8 × 60 K Microarray. Then we used the qRT-PCR to test the result of Microarray, and found VEGFA had a distinct pattern of expression in MMQ tumor stem-like cells. Then WB and ELISA were used to confirm the VEGFA protein level of tumor sphere cultured from both MMQ cell and human prolactinoma cell. Finally, CCK-8 was used to evaluate the reaction of MMQ tumor stem-like cells to small interfering RNAs intervention and bevacizumab treatment.

RESULT

The results of Microarray showed that 566 known RNA were over-expressed and 532 known RNA were low-expressed in the MMQ tumor stem-like cells. These genes were mainly involved in 15 different signaling pathways. In pathway in cancer and cell cycle, Bcl2, VEGFA, PTEN, Jun, Fos, APC2 were up-regulated and Ccna2, Cdc25a, Mcm3, Mcm6, Ccnb2, Mcm5, Cdk1, Gadd45a, Myc were down-regulated in the MMQ tumor stem-like cells. The expression of VEGFA were high in tumor spheres cultured from both MMQ cell and human prolactinomas. Down-regulation of VEGFA by small interfering RNAs partially decreased cell viability of MMQ tumor stem-like cells in vitro. Bevacizumab partially suppressed the proliferation of MMQ tumor stem-like cells.

CONCLUSIONS

Our findings characterize the pattern of RNA expression of tumor stem-like cells isolated from MMQ cells. VEGFA may act as a potential therapeutic target for tumor stem-like cells of prolactinomas.

Overexpression of Hiwi Inhibits the Growth and Migration of Chronic Myeloid Leukemia Cells

Chronic myeloid leukemia (CML) is a hematopoietic malignancy characterized by dysregulated growth and proliferation of hematopoietic stem/progenitor cells in bone marrow and excessive expansion of hematopoietic compartments in peripheral blood. Expression deletion of Hiwi, a human Piwi homolog, has been reported to be implicated in leukemogenesis. We here explored Hiwi's role in CML pathogenesis by determining how and whether its forced overexpression could affect CML cell growth and migration. The present results showed that lentivirus-mediated overexpression of Hiwi significantly suppressed cell proliferation and induced obvious apoptosis in K562 cells, a CML line cell line. Tumors in BALB/c nude mice generated by the K562 cells expressing Hiwi were much smaller than those formed by the control cells. Like in vitro, Hiwi upregulation induced cell apoptosis in the tumor tissues in vivo. Additionally, Hiwi elevation suppressed K562 cell migration and inhibited the activity and expression of matrix metalloproteinase-2 and -9. In summary, our study demonstrates that Hiwi overexpression inhibits CML cell growth and migration, providing insights into its role in CML pathogenesis.

EpCAM+ Liver Cancer Stem-Like Cells Exhibiting Autocrine Wnt Signaling Potentially Originate in Cirrhotic Patients

Hepatocellular carcinoma (HCC) is believed to originate from cancer stem cells (CSCs). While epithelial cell adhesion molecule (EpCAM) is a marker of normal hepatic stem cells (HSCs), EpCAM+ cells from HCC behave like CSCs. Since HCC mostly develops on a cirrhotic background, we sought to determine whether CSC‐like EpCAM+ cells exist in patients with advanced cirrhosis. Both flow cytometry and immunohistochemistry showed that frequency of EpCAM+ cells in advanced cirrhosis was increased as compared to control. To determine whether increased EpCAM population in advanced cirrhosis harbors any CSC‐like cells, we compared molecular and functional features of EpCAM+ cells from advanced cirrhosis (Ep+CIR; n = 20) with EpCAM+ cells from both HCC (Ep+HCC; n = 20) and noncancerous/noncirrhotic (control) (Ep+NSC; n = 7) liver tissues. Ep+CIRs displayed similarity with Ep+HCC cells including upregulated expression of stemness and Notch pathway genes, enhanced self‐renewal in serial spheroid assay and generation of subcutaneous tumors in nonobese diabetic/severe combined immunodeficiency mice. Moreover, transcriptome and miRNome of Ep+CIRs appeared closer to that of Ep+HCC cells than Ep+NSCs. Interestingly, more than 50% micro RNAs (miRNAs) and transcripts specifically expressed in Ep+HCCs were also expressed in Ep+CIRs. However, none of Ep+NSC specific miRNAs and only 7% Ep+NSC specific transcripts were expressed in Ep+CIRs. Further, according to gene expression and in vitro Wnt inhibition analysis, autocrine Wnt signaling appeared to be a distinct feature of Ep+CIR and Ep+HCC cells, which was absent from Ep+NSCs. EpCAM+ cells in advanced cirrhosis possibly include a population of CSC‐like cells which can be explored for early diagnosis of HCC development. Stem Cells Translational Medicine2017;6:807–818

Potential therapeutic effect of epigenetic therapy on treatment-induced neuroendocrine prostate cancer

Although adenocarcinomas of the prostate are relatively indolent, some patients with advanced adenocarcinomas show recurrence of treatment-induced neuroendocrine prostate cancer, which is highly aggressive and lethal. Detailed biological features of treatment-induced neuroendocrine prostate cancer have not been characterized owing to limited biopsies/resections and the lack of a cellular model. In this study, we used a unique cellular model (LNCaP/NE1.8) to investigate the potential role of cancer stem cells in treatment-induced neuroendocrine prostate cancer with acquired resistance to hormonal therapy and chemotherapy. We also studied the role of cancer stem cells in enhancing invasion in treatment-induced neuroendocrine prostate cancer cells that recurred after long-term androgen-ablation treatment. Using an in vitro system mimicking clinical androgen-ablation, our results showed that the neuroendocrine-like subclone NE1.8 cells were enriched with cancer stem cells. Compared to parental prostate adenocarcinoma LNCaP cells, NE1.8 cells are more resistant to androgen deprivation therapy and chemotherapeutic agents and show increased cancer cell invasiveness. Results from this study also suggest a potential epigenetic therapeutic strategy using suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, as a chemotherapeutic agent for therapy-resistant treatment-induced neuroendocrine prostate cancer cells to minimize the risk of prostate cancer recurrence and metastasis.

NF-kappaΒ-inducing kinase regulates stem cell phenotype in breast cancer

Breast cancer stem cells (BCSCs) overexpress components of the Nuclear factor-kappa B (NF-κB) signaling cascade and consequently display high NF-κB activity levels. Breast cancer cell lines with high proportion of CSCs exhibit high NF-κB-inducing kinase (NIK) expression. The role of NIK in the phenotype of cancer stem cell regulation is poorly understood. Expression of NIK was analyzed by quantitative RT-PCR in BCSCs. NIK levels were manipulated through transfection of specific shRNAs or an expression vector. The effect of NIK in the cancer stem cell properties was assessed by mammosphere formation, mice xenografts and stem markers expression. BCSCs expressed higher levels of NIK and its inhibition through small hairpin (shRNA), reduced the expression of CSC markers and impaired clonogenicity and tumorigenesis. Genome-wide expression analyses suggested that NIK acts on ERK1/2 pathway to exert its activity. In addition, forced expression of NIK increased the BCSC population and enhanced breast cancer cell tumorigenicity. The in vivo relevance of these results is further supported by a tissue microarray of breast cancer samples in which we observed correlated expression of Aldehyde dehydrogenase (ALDH) and NIK protein. Our results support the essential involvement of NIK in BCSC phenotypic regulation via ERK1/2 and NF-κB.

Chemotherapy curable malignancies and cancer stem cells: a biological review and hypothesis

Background

Cytotoxic chemotherapy brings routine cures to only a small select group of metastatic malignancies comprising gestational trophoblast tumours, germ cell tumours, acute leukemia, Hodgkin’s disease, high grade lymphomas and some of the rare childhood malignancies.

We have previously postulated that the extreme sensitivity to chemotherapy for these malignancies is linked to the on-going high levels of apoptotic sensitivity that is naturally linked with the unique genetic events of nuclear fusion, meiosis, VDJ recombination, somatic hypermutation, and gastrulation that have occurred within the cells of origin of these malignancies.

In this review we will examine the cancer stem cell/cancer cell relationship of each of the chemotherapy curable malignancies and how this relationship impacts on the resultant biology and pro-apoptotic sensitivity of the varying cancer cell types.

Discussion

In contrast to the common epithelial cancers, in each of the chemotherapy curable malignancies there are no conventional hierarchical cancer stem cells. However cells with cancer stem like qualities can arise stochastically from within the general tumour cell population. These stochastic stem cells acquire a degree of resistance to DNA damaging agents but also retain much of the key characteristics of the cancer cells from which they develop. We would argue that the balance between the acquired resistance of the stochastic cancer stem cell and the inherent chemotherapy sensitivity of parent tumour cell determines the overall chemotherapy curability of each diagnosis.

Summary

The cancer stem cells in the chemotherapy curable malignancies appear to have two key biological differences from those of the more common chemotherapy incurable malignancies. The first difference is that the conventional hierarchical pattern of cancer stem cells is absent in each of the chemotherapy curable malignancies.

The other key difference, we suggest, is that the stochastic stem cells in the chemotherapy curable malignancies take on a significant aspect of the biological characteristics of their parent cancer cells. This action includes for the chemotherapy curable malignancies the heightened pro-apoptotic sensitivity linked to their respective associated unique genetic events.

For the chemotherapy curable malignancies the combination of the relationship of their cancer stem cells combined with the extreme inherent sensitivity to induction of apoptosis from DNA damaging agents plays a key role in determining their overall curability with chemotherapy.

Cardamonin reduces chemotherapy-enriched breast cancer stem-like cells in vitro and in vivo

The failure of cytotoxic chemotherapy in breast cancers has been closely associated with the presence of drug resistant cancer stem cells (CSCs). Thus, screening for small molecules that selectively inhibit growth of CSCs may offer great promise for cancer control, particularly in combination with chemotherapy. In this report, we provide the first demonstration that cardamonin, a small molecule, selectively inhibits breast CSCs that have been enriched by chemotherapeutic drugs. In addition, cardamonin also sufficiently prevents the enrichment of CSCs when simultaneously used with chemotherapeutic drugs. Specifically, cardamonin effectively abolishes chemotherapeutic drug-induced up-regulation of IL-6, IL-8 and MCP-1 and activation of NF-κB/IKBα and Stat3. Furthermore, in a xenograft mouse model, co-administration of cardamonin and the chemotherapeutic drug doxorubicin significantly retards tumor growth and simultaneously decreases CSC pools in vivo. Since cardamonin has been found in some herbs, this work suggests a potential new approach for the effective treatment of breast CSCs by administration of cardamonin either concurrent with or after chemotherapeutic drugs.

Epigenetic therapy potential of suberoylanilide hydroxamic acid on invasive human non-small cell lung cancer cells

Metastasis is the reason for most cancer death, and a crucial primary step for cancer metastasis is invasion of the surrounding tissue, which may be initiated by some rare tumor cells that escape the heterogeneous primary tumor. In this study, we isolated invasive subpopulations of cancer cells from human non-small cell lung cancer (NSCLC) H460 and H1299 cell lines, and determined the gene expression profiles and the responses of these invasive cancer cells to treatments of ionizing radiation and chemotherapeutic agents. The subpopulation of highly invasive NSCLC cells showed epigenetic signatures of epithelial-mesenchymal transition, cancer cell stemness, increased DNA damage repair and cell survival signaling. We also investigated the epigenetic therapy potential of suberoylanilide hydroxamic acid (SAHA) on invasive cancer cells, and found that SAHA suppresses cancer cell invasiveness and sensitizes cancer cells to treatments of IR and chemotherapeutic agents. Our results provide guidelines for identification of metastatic predictors and for clinical management of NSCLC. This study also suggests a beneficial clinical potential of SAHA as a chemotherapeutic agent for NSCLC patients.

Heterogeneity of Cancer Stem Cells: Rationale for Targeting the Stem Cell Niche

Malignancy is fuelled by distinct subsets of stem-like cells which persist under treatment and provoke drug-resistant recurrence. Eradication of these cancer stem cells has therefore become a prime objective for the development and design of novel classes of anti-cancer therapeutics with improved clinical efficacy. Here, we portray potentially clinically-relevant hallmarks of cancer stem cells and focus on their recently appreciated properties of cell variability and plasticity, both of which make them elusive targets for cancer therapies. We reason that this 'disguise in heterogeneity' has fundamental implications for clinical management and elaborate on rational strategies to combat this diversity and target a broad range of tumorigenic cells. We propose exploitation of cancer stem cell niche dependence as a promising approach to interfere with various, rather than few, cancer stem cell subsets and suggest cancer-associated fibroblasts as a prime microenvironmental target for tumor stemness-depleting intervention.

Identification of High-Risk Aberrant Crypt Foci and Mucin-Depleted Foci in the Human Colon With Study of Colon Cancer Stem Cell Markers

BACKGROUND

During colonoscopic screening, only macroscopic lesions will be identified, and these are usually the result of multiple genetic abnormalities. Magnification endoscopic detection of aberrant crypt foci (ACF), long before they acquire complex genetic abnormalities, is promising. However, the features of high-risk ACF-like lesions need to be identified.

MATERIALS AND METHODS

In the present cross-sectional study, grossly visible normal mucosal flaps were shaved from 152 colectomies, including 96 colorectal cancer (CRC) cases and 56 controls (22 control specimens with disease with malignant potential and 34 without malignant potential). Methylene and Alcian blue stains were performed directly on the unfixed mucosal flaps to identify ACF and mucin-depleted foci (MDF). Detailed topographic analyses, with immunohistochemical staining for β-catenin and cancer stem cell (CSC) markers (CD44, CD24, and CD166) were performed.

RESULTS

ACF, MDF, and β-catenin-accumulated crypts were detected more in specimens with adjacent CRC. The left colon had ACF with a larger diameter and greater crypt multiplicity, density, and gyriform pit pattern and were considered the high-risk ACF group. MDF, more commonly associated with dysplasia, is also a marker of possible carcinogenesis. The CD44 CSC marker was significantly upregulated in ACF specimens compared with normal controls. Our 3-tier ACF-only pit pattern classification system showed better linearity with mucosal dysplasia than did the 6-tier Kudo classification.

CONCLUSION

High-risk ACF, when detected during chromoendoscopic screening, should be followed up. CSCs might play an important role in pathogenesis. Larger studies and genotypic risk stratification for definite identification of high-risk ACF are needed.

Targeting cancer stem cells and signaling pathways by phytochemicals: Novel approach for breast cancer therapy

Breast cancer is the most common form of cancer diagnosed in women worldwide and the second leading cause of cancer-related deaths in the USA. Despite the development of newer diagnostic methods, selective as well as targeted chemotherapies and their combinations, surgery, hormonal therapy, radiotherapy, breast cancer recurrence, metastasis and drug resistance are still the major problems for breast cancer. Emerging evidence suggest the existence of cancer stem cells (CSCs), a population of cells with the capacity to self-renew, differentiate and be capable of initiating and sustaining tumor growth. In addition, CSCs are believed to be responsible for cancer recurrence, anticancer drug resistance, and metastasis. Hence, compounds targeting breast CSCs may be better therapeutic agents for treating breast cancer and control recurrence and metastasis. Naturally occurring compounds, mainly phytochemicals have gained immense attention in recent times because of their wide safety profile, ability to target heterogeneous populations of cancer cells as well as CSCs, and their key signaling pathways. Therefore, in the present review article, we summarize our current understanding of breast CSCs and their signaling pathways, and the phytochemicals that affect these cells including curcumin, resveratrol, tea polyphenols (epigallocatechin-3-gallate, epigallocatechin), sulforaphane, genistein, indole-3-carbinol, 3, 3'-di-indolylmethane, vitamin E, retinoic acid, quercetin, parthenolide, triptolide, 6-shogaol, pterostilbene, isoliquiritigenin, celastrol, and koenimbin. These phytochemicals may serve as novel therapeutic agents for breast cancer treatment and future leads for drug development.

OCT4 spliced variants are highly expressed in brain cancer tissues and inhibition of OCT4B1 causes G2/M arrest in brain cancer cells

The new claim about the origin of cancer known as Cancer Stem Cell theory states that a somatic differentiated cell can dedifferentiated or reprogrammed for regaining the cancer cell features. It has been recently shown that expression of stemness factors such as Oct4, Sox2, Nanog and Klf4, in a variety of somatic cancers can leads to development of tumorogenesis. Here, the expression of Oct4 variants were evaluated in brain tumor tissues by quantitative RT-PCR and immunohistochemical (IHC) analysis. In next phase of our study, the expression of Oct4B1 was knock-down in brain cancer cell lines and its effect on cell cycle was assessed. Finally, in order to get insights into sequence-structure-function relationships of Oct4 isofroms, their sequences were analysed using bioinformatic tools. Our data revealed that all three variants of Oct4 are expressed in different types of brain cancer. The expression level of Oct4B1, in contast to Oct4B, was much higher in high-grade brain tumors compared with low-grade ones. In line with qPCR, the expression of Oct4A and B isofroms was confirmed with IHC in different types of brain tumors. Moreover, as a result of the suppression of Oct4B1 expression, the brain cancer cells were arrested in G2/M phase of cell cycle. Bioinfromatics data indicated that the predicted Oct4B1 protein have DNA binding properties. All together, our findings suggest that Oct4B1 has a potential role in tumorigenesis of brain cancer and can be considered as a new tumor marker with potential value in diagnosis and treatment of brain cancer.

Involvement of NRF2 Signaling in Doxorubicin Resistance of Cancer Stem Cell-Enriched Colonospheres

Cancer stem cells (CSCs) are a subset of tumor cells, which are characterized by resistance against chemotherapy and environmental stress, and are known to cause tumor relapse after therapy. A number of molecular mechanisms underlie the chemoresistance of CSCs, including high expression levels of drug efflux transporters. We investigated the role of the antioxidant transcription factor NF-E2-related factor 2 (NRF2) in chemoresistance development, using a CSC-enriched colonosphere system. HCT116 colonospheres were more resistant to doxorubicin-induced cell death and expressed higher levels of drug efflux transporters such as P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) compared to HCT116 monolayers. Notably, levels of NRF2 and expression of its target genes were substantially elevated in colonospheres, and these increases were linked to doxorubicin resistance. When NRF2 expression was silenced in colonospheres, Pgp and BCRP expression was downregulated, and doxorubicin resistance was diminished. Collectively, these results indicate that NRF2 activation contributes to chemoresistance acquisition in CSC-enriched colonospheres through the upregulation of drug efflux transporters.

Reflections on MUC1 glycoprotein: the hidden potential of isoforms in carcinogenesis

Mucin 1 (MUC1) has been described as the renaissance molecule due to the large set of functions it displays in both normal and neoplastic cells. This membrane-tethered glycoprotein is overexpressed and aberrantly glycosylated in most epithelial cancers, being involved in several processes related with malignant phenotype acquisition. With a highly polymorphic structure, both in the polypeptide and glycan counterparts, MUC1 variability has been associated with susceptibility to several diseases, including cancer. Biochemical features and biological functions have been characterized upon the full-length MUC1 protein, remaining to clarify the real impact on cell dynamics of the plethora of MUC1 isoforms. This review aims to encompass a detailed characterization of MUC1 role in carcinogenesis, highlighting recent findings in cell differentiation and uncovering new evidences of MUC1 isoforms involvement in malignant phenotype.

Aneuploidy in stem cells

Stem cells hold enormous promise for regenerative medicine as well as for engineering of model systems to study diseases and develop new drugs. The discovery of protocols that allow for generating induced pluripotent stem cells (IPSCs) from somatic cells has brought this promise steps closer to reality. However, as somatic cells might have accumulated various chromosomal abnormalities, including aneuploidies throughout their lives, the resulting IPSCs might no longer carry the perfect blueprint for the tissue to be generated, or worse, become at risk of adopting a malignant fate. In this review, we discuss the contribution of aneuploidy to healthy tissues and how aneuploidy can lead to disease. Furthermore, we review the differences between how somatic cells and stem cells respond to aneuploidy.

Enhanced inhibition of clonogenic survival of human medulloblastoma cells by multimodal treatment with ionizing irradiation, epigenetic modifiers, and differentiation-inducing drugs

Background

Medulloblastoma (MB) is the most common pediatric brain tumor. Current treatment regimes consisting of primary surgery followed by radio- and chemotherapy, achieve 5-year overall survival rates of only about 60 %. Therapy-induced endocrine and neurocognitive deficits are common late adverse effects. Thus, improved antitumor strategies are urgently needed. In this study, we combined irradiation (IR) together with epigenetic modifiers and differentiation inducers in a multimodal approach to enhance the efficiency of tumor therapy in MB and also assessed possible late adverse effects on neurogenesis.

Methods

In three human MB cell lines (DAOY, MEB-Med8a, D283-Med) short-time survival (trypan blue exclusion assay), apoptosis, autophagy, cell cycle distribution, formation of gH2AX foci, and long-term reproductive survival (clonogenic assay) were analyzed after treatment with 5-aza-2′-deoxycytidine (5-azadC), valproic acid (VPA), suberanilohydroxamic acid (SAHA), abacavir (ABC), all-trans retinoic acid (ATRA) and resveratrol (RES) alone or combined with 5-aza-dC and/or IR. Effects of combinatorial treatments on neurogenesis were evaluated in cultured murine hippocampal slices from transgenic nestin-CFPnuc C57BL/J6 mice. Life imaging of nestin-positive neural stem cells was conducted at distinct time points for up to 28 days after treatment start.

Results

All tested drugs showed a radiosynergistic action on overall clonogenic survival at least in two-outof-three MB cell lines. This effect was pronounced in multimodal treatments combining IR, 5-aza-dC and a second drug. Hereby, ABC and RES induced the strongest reduction of clongenic survival in all three MB cell lines and led to the induction of apoptosis (RES, ABC) and/or autophagy (ABC). Additionally, 5-aza-dC, RES, and ABC increased the S phase cell fraction and induced the formation of gH2AX foci at least in oneout-of-three cell lines. Thereby, the multimodal treatment with 5-aza-dC, IR, and RES or ABC did not change the number of normal neural progenitor cells in murine slice cultures.

Conclusion

In conclusion, the radiosensitizing capacities of epigenetic and differentiation-inducing drugs presented here suggest that their adjuvant administration might improve MB therapy. Thereby, the combination of 5-aza-dC/IR with ABC and RES seemed to be the most promising to enhance tumor control without affecting the normal neural precursor cells.

MiR-26a inhibits stem cell-like phenotype and tumor growth of osteosarcoma by targeting Jagged1

MicroRNAs (miRNAs) are important epigenetic regulators of gene expression. Although several miRNAs have been implicated in osteosarcoma, their role in regulation of osteosarcoma cancer stem cells (CSCs) remains unknown. Here we demonstrated that miR-26a is downregulated in osteosarcoma CSCs when derived by either sarcosphere generation, chemodrug or aldehyde dehydrogenase (ALDH) activity selection. Lentiviral overexpression of miR-26a in ZOS and 143B osteosarcoma cells decreases the expression of stem cell markers and suppresses sarcosphere formation, as well as ALDH activity. Moreover, miR-26a overexpression inhibits the tumor cell growth both in vitro and in vivo. We further demonstrate that miR-26a directly target Jagged1, one of the Notch ligand, and that its tumor suppressive effects are mediated through inhibition of Jagged1/Notch signaling. Importantly, reduced miR-26a expression, as determined by in situ hybridization in patient tumors (n=92), is associated with lung metastasis and poor overall survival of osteosarcoma patients. Together, these data suggest the essential role of miR-26a/Jagged1/Notch pathway in regulating the stem cell-like traits of osteosarcoma cells and provide a potential target for osteosarcoma therapy.

Verapamil inhibits tumor progression of chemotherapy-resistant pancreatic cancer side population cells

Tumor side population (SP) cells display stem-like properties that can be modulated by treatment with the calcium channel blocker verapamil. Verapamil can enhance the cytotoxic effects of chemotherapeutic drugs and multi-drug resistance by targeting the transport function of the P-glycoprotein (P-gp). This study focused on the therapeutic potential of verapamil on stem-like SP tumor cells, and further investigated its chemosensitizing effects using L3.6pl and AsPC-1 pancreatic carcinoma models. As compared to parental L3.6pl cells (0.9±0.22%), L3.6pl gemcitabine-resistant cells (L3.6pl_Gres) showed a significantly higher percentage of SP cells (5.38±0.99%) as detected by Hoechst 33342/FACS assays. The L3.6pl_Gres SP cells showed stable gemcitabine resistance, enhanced colony formation ability and increased tumorigenicity. Verapamil effectively inhibited L3.6pl_Gres and AsPC-1 SP cell proliferation in vitro. A pro-apoptotic effect of verapamil was observed in L3.6pl cells, but not in L3.6pl_Gres cells, which was linked to their differential expression of P-gp and equilibrative nucleoside transporter-1 (ENT-1). In an orthotopic pancreatic cancer mouse model, both low and high dose verapamil was shown to substantially reduce L3.6pl_Gres-SP cell tumor growth and metastasis, enhance tumor apoptosis, and reduce microvascular density.

Breast Cancer Stem Cell Culture and Enrichment Using Poly(ε-Caprolactone) Scaffolds

The cancer stem cell (CSC) population displays self-renewal capabilities, resistance to conventional therapies, and a tendency to post-treatment recurrence. Increasing knowledge about CSCs’ phenotype and functions is needed to investigate new therapeutic strategies against the CSC population. Here, poly(ε-caprolactone) (PCL), a biocompatible polymer free of toxic dye, has been used to fabricate scaffolds, solid structures suitable for 3D cancer cell culture. It has been reported that scaffold cell culture enhances the CSCs population. A RepRap BCN3D+ printer and 3 mm PCL wire were used to fabricate circular scaffolds. PCL design and fabrication parameters were first determined and then optimized considering several measurable variables of the resulting scaffolds. MCF7 breast carcinoma cell line was used to assess scaffolds adequacy for 3D cell culture. To evaluate CSC enrichment, the Mammosphere Forming Index (MFI) was performed in 2D and 3D MCF7 cultures. Results showed that the 60° scaffolds were more suitable for 3D culture than the 45° and 90° ones. Moreover, 3D culture experiments, in adherent and non-adherent conditions, showed a significant increase in MFI compared to 2D cultures (control). Thus, 3D cell culture with PCL scaffolds could be useful to improve cancer cell culture and enrich the CSCs population.

[Molecular mechanisms of niclosamide antitumor activity]

In this review the recent data regarding the antitumor activity of niclosamide and the molecular mechanisms of its antitumor activity are presented. Niclosamide has been used in the clinic for the treatment of intestinal parasite infections. In recent years in several screening investigations of various drugs and chemical compounds niclosamide was identified as a potential anticancer agent. Niclosamide not only inhibits the Wnt/β-catenin, mTORC1, STAT3, NF-κB and Notch signaling pathways, but also targets mitochondria in cancer cells to induce growth inhibition and apoptosis. A number of studies have established the anticancer activity of niclosamide in both in vitro and in vivo in xenotransplantation models using human tumors and immunodeficient mice. It is important that niclosamide is active not only against tumor cells but also cancer stem cells. Normal cells are resistant to niclosamide. The accumulated experimental data suggest niclosamide is a promising drug for the treatment of various types of cancer.

All-trans retinoic acids induce differentiation and sensitize a radioresistant breast cancer cells to chemotherapy

Background

Radiotherapy is of critical importance in the treatment of breast cancer. However, not all patients derive therapeutic benefit and some breast cancers are resistant to the treatment, and are thus evidenced with prospective distant metastatic spread and local recurrence. In this study, we investigated the potential therapeutic effects of all-trans retinoic acid (ATRA) on radiation-resistant breast cancer cells and the associated invasiveness.

Methods

The MCF7/C6 cells with gained radiation resistance after a long term treatment with fractionated ionizing radiation were derived from human breast cancer MCF7 cell line, and are enriched with cells expressing putative breast cancer stem cell biomarker CD44⁺/CD24^-/low/ALDH⁺. The enhanced invasiveness and the acquired resistances to chemotherapeutic treatments of MCF7/C6 cells were measured, and potential effects of all-trans retinoic acid (ATRA) on the induction of differentiation, invasion and migration, and on the sensitivities to chemotherapies in MCF7/C6 cells were investigated.

Results

MCF7/C6 cells are with enrichment of cancer stem-cell like cells with positive staining of CD44⁺/CD24^-/low, OCT3/4 and NANOG. MCF7/C6 cells showed an increased tumoregensis potential and enhanced aggressiveness of invasion and migration. Treatment with ATRA induces the differentiation in MCF7/C6 cells, resulting in reduced invasiveness and migration, and increased sensitivity to Epirubincin treatment.

Conclusion

Our study suggests a potential clinic impact for ATRA as a chemotherapeutic agent for treatment of therapy-resistant breast cancer especially for the metastatic lesions. The study also provides a rationale for ATRA as a sensitizer of Epirubincin, a first-line treatment option for breast cancer patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1088-y) contains supplementary material, which is available to authorized users.

Circulating Tumor Cells: A Window Into Tumor Development and Therapeutic Effectiveness

BACKGROUND

Circulating tumor cells (CTCs) are an important diagnostic tool for understanding the metastatic process and the development of cancer.

METHODS

This review covers the background, relevance, and potential limitations of CTCs as a measurement of cancer progression and how information derived from CTCs may affect treatment efficacy. It also highlights the difficulties of characterizing these rare cells due to the limited cell surface molecules unique to CTCs and each particular type of cancer.

RESULTS

The analysis of cancer in real time, through the measure of the number of CTCs in a " liquid" biopsy specimen, gives us the ability to monitor the therapeutic efficacy of treatments and possibly the metastatic potential of a tumor.

CONCLUSIONS

Through novel and innovative techniques yielding encouraging results, including microfluidic techniques, isolating and molecularly analyzing CTCs are becoming a reality. CTCs hold promise for understanding how tumors work and potentially aiding in their demise.

Low doses of PEG-coated gold nanoparticles sensitize solid tumors to cold plasma by blocking the PI3K/AKT-driven signaling axis to suppress cellular transformation by inhibiting growth and EMT

Metastasis, the primary cause of tumor cell transformation, is often activated during cancer invasion and progression and is associated with poor therapeutic outcomes. The effects of combined treatments that included PEG-coated gold nanoparticles (GNP) and cold plasma on epithelial-mesenchymal transition (EMT) and the maintenance of cancer stem cells (CSC) have not been described so far. Here, we report that co-treatment with GNP and cold plasma inhibited proliferation in cancer cells by abolishing the activation of the PI3K/AKT signaling axis. In addition, co-treatment reversed EMT in solid tumor cells by reducing the secretion of a number of proteins, resulting in the upregulation of epithelial markers such as E-cadherin along with down-regulation of N-Cadherin, Slug and Zeb-1. The inhibition of the PI3K/AKT pathway and the reversal of EMT by co-treatment prevented tumor cells growth in solid tumors. Furthermore, we show that GNP and plasma also suppresses tumor growth by decreasing mesenchymal markers in tumor xenograft mice models. Importantly, co-treatment resulted in a substantial decrease in sphere formation and the self-renewal capacity of glioma-like stem cells. Together, these results indicate a direct link between a decrease of EMT and an increase in cell death in solid tumors following co-treatment with cold plasma and GNP.

Mathematical modeling of bone marrow--peripheral blood dynamics in the disease state based on current emerging paradigms, part I

Stemming from current emerging paradigms related to the cancer stem cell hypothesis, an existing mathematical model is expanded and used to study cell interaction dynamics in the bone marrow and peripheral blood. The proposed mathematical model is described by a system of nonlinear differential equations with delay, to quantify the dynamics in abnormal hematopoiesis. The steady states of the model are analytically and numerically obtained. Some conditions for the local asymptotic stability of such states are investigated. Model analyses suggest that malignancy may be irreversible once it evolves from a nonmalignant state into a malignant one and no intervention takes place. This leads to the proposition that a great deal of emphasis be placed on cancer prevention. Nevertheless, should malignancy arise, treatment programs for its containment or curtailment may have to include a maximum and extensive level of effort to protect normal cells from eventual destruction. Further model analyses and simulations predict that in the untreated disease state, there is an evolution towards a situation in which malignant cells dominate the entire bone marrow - peripheral blood system. Arguments are then advanced regarding requirements for quantitatively understanding cancer stem cell behavior. Among the suggested requirements are, mathematical frameworks for describing the dynamics of cancer initiation and progression, the response to treatment, the evolution of resistance, and malignancy prevention dynamics within the bone marrow - peripheral blood architecture.

MiRNA Transcriptome Profiling of Spheroid-Enriched Cells with Cancer Stem Cell Properties in Human Breast MCF-7 Cell Line

Breast cancer is the second leading cause of cancer-related mortality worldwide as most patients often suffer cancer relapse. The reason is often attributed to the presence of cancer stem cells (CSCs). Recent studies revealed that dysregulation of microRNA (miRNA) are closely linked to breast cancer recurrence and metastasis. However, no specific study has comprehensively characterised the CSC characteristic and miRNA transcriptome in spheroid-enriched breast cells. This study described the generation of spheroid MCF-7 cell in serum-free condition and the comprehensive characterisation for their CSC properties. Subsequently, miRNA expression differences between the spheroid-enriched CSC cells and their parental cells were evaluated using next generation sequencing (NGS). Our results showed that the MCF-7 spheroid cells were enriched with CSCs properties, indicated by the ability to self-renew, increased expression of CSCs markers, and increased resistance to chemotherapeutic drugs. Additionally, spheroid-enriched CSCs possessed greater cell proliferation, migration, invasion, and wound healing ability. A total of 134 significantly (p<0.05) differentially expressed miRNAs were identified between spheroids and parental cells using miRNA-NGS. MiRNA-NGS analysis revealed 25 up-regulated and 109 down-regulated miRNAs which includes some miRNAs previously reported in the regulation of breast CSCs. A number of miRNAs (miR-4492, miR-4532, miR-381, miR-4508, miR-4448, miR-1296, and miR-365a) which have not been previously reported in breast cancer were found to show potential association with breast cancer chemoresistance and self-renewal capability. The gene ontology (GO) analysis showed that the predicted genes were enriched in the regulation of metabolic processes, gene expression, DNA binding, and hormone receptor binding. The corresponding pathway analyses inferred from the GO results were closely related to the function of signalling pathway, self-renewability, chemoresistance, tumorigenesis, cytoskeletal proteins, and metastasis in breast cancer. Based on these results, we proposed that certain miRNAs identified in this study could be used as new potential biomarkers for breast cancer stem cell diagnosis and targeted therapy.

VEGF-A acts via neuropilin-1 to enhance epidermal cancer stem cell survival and formation of aggressive and highly vascularized tumors

We identify a limited subpopulation of epidermal cancer stem cells (ECS cells), in squamous cell carcinoma, that form rapidly growing, invasive and highly vascularized tumors, as compared with non-stem cancer cells. These ECS cells grow as non-attached spheroids, and display enhanced migration and invasion. We show that ECS cell-produced vascular endothelial growth factor (VEGF)-A is required for the maintenance of this phenotype, as knockdown of VEGF-A gene expression or treatment with VEGF-A-inactivating antibody reduces these responses. In addition, treatment with bevacizumab reduces tumor vascularity and growth. Surprisingly, the classical mechanism of VEGF-A action via interaction with VEGF receptors does not mediate these events, as these cells lack VEGFR1 and VEGFR2. Instead, VEGF-A acts via the neuropilin-1 (NRP-1) co-receptor. Knockdown of NRP-1 inhibits ECS cell spheroid formation, invasion and migration, and attenuates tumor formation. These studies suggest that VEGF-A acts via interaction with NRP-1 to trigger intracellular events leading to ECS cell survival and formation of aggressive, invasive and highly vascularized tumors.

Non-coding RNAs Functioning in Colorectal Cancer Stem Cells

In recent years, the hypothesis of the presence of tumor-initiating cancer stem cells (CSCs) has received a considerable support. This model suggested the existence of CSCs which, thanks to their self-renewal properties, are able to drive the expansion and the maintenance of malignant cell populations with invasive and metastatic potential in cancer. Increasing evidence showed the ability of such cells to acquire self-renewal, multipotency, angiogenic potential, immune evasion, symmetrical and asymmetrical divisions which, along with the presence of several DNA repair mechanisms, further enhance their oncogenic potential making them highly resistant to common anticancer treatments. The main signaling pathways involved in the homeostasis of colorectal (CRC) stem cells are the Wnt, Notch, Sonic Hedgehog, and Bone Morfogenic Protein (BMP) pathways, which are mostly responsible for all the features that have been widely referred to stem cells. The same pathways have been identified in colorectal cancer stem cells (CRCSCs), conferring a more aggressive phenotype compared to non-stem CRC cells. Recently, several evidences suggested that non-coding RNAs (ncRNAs) may play a crucial role in the regulation of different biological mechanisms in CRC, by modulating the expression of critical stem cell transcription factors that have been found active in CSCs. In this chapter, we will discuss the involvement of ncRNAs, especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in stemness acquisition and maintenance by CRCSCs, through the regulation of pathways modulating the CSC phenotype and growth, carcinogenesis, differentiation, and epithelial to mesenchymal transition (EMT).

Effects of peritumoral nanoconjugated cisplatin on laryngeal cancer stem cells

OBJECTIVES/HYPOTHESIS

To evaluate the efficacy of peritumoral hyaluronic acid (HA)-cisplatin therapy in a murine model of laryngeal squamous cell carcinoma and to evaluate its effect on cancer stem cells (CSCs).

STUDY DESIGN

An orthotopic murine study utilizing University of Michigan squamous cell carcinoma-12 (UMSCC-12) laryngeal cancer cells was conducted in randomized controlled fashion with three treatment arms: saline, systemic cisplatin, and peritumoral HA-cisplatin.

METHODS

UMSCC-12 laryngeal cancer cells were inoculated into the buccal mucosa of athymic nude mice followed by weekly treatment with saline, systemic cisplatin, or peritumoral HA-cisplatin for 3 weeks. Tumor response and animal weight was monitored and change in CD44 proportion was analyzed ex vivo.

RESULTS

HA-cisplatin demonstrated superior antitumor efficacy and greater reduction in CD44 positivity on ex vivo analysis.

CONCLUSIONS

Peritumoral nanoconjugated HA-cisplatin provides superior antitumor efficacy compared to standard cisplatin therapy in an in vivo laryngeal cancer model. There was also selective targeting of CD44+ cancer cells with HA-cisplatin. This therapeutic strategy could represent the first selective laryngeal CSC-targeted therapy. Further preclinical investigation is warranted to evaluate its role for locally advanced head and neck cancer treatment.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:E184-E190, 2016.

MLL5 Orchestrates a Cancer Self-Renewal State by Repressing the Histone Variant H3.3 and Globally Reorganizing Chromatin

Mutations in the histone 3 variant H3.3 have been identified in one-third of pediatric glioblastomas (GBMs), but not in adult tumors. Here we show that H3.3 is a dynamic determinant of functional properties in adult GBM. H3.3 is repressed by mixed lineage leukemia 5 (MLL5) in self-renewing GBM cells. MLL5 is a global epigenetic repressor that orchestrates reorganization of chromatin structure by punctuating chromosomes with foci of compacted chromatin, favoring tumorigenic and self-renewing properties. Conversely, H3.3 antagonizes self-renewal and promotes differentiation. We exploited these epigenetic states to rationally identify two small molecules that effectively curb cancer stem cell properties in a preclinical model. Our work uncovers a role for MLL5 and H3.3 in maintaining self-renewal hierarchies in adult GBM.

Novel Small Molecule Inhibitors of Cancer Stem Cell Signaling Pathways

The main aim of oncologists worldwide is to understand and then intervene in the primary tumor initiation and propagation mechanisms. This is essential to allow targeted elimination of cancer cells without altering normal mitotic cells. Currently, there are two main rival theories describing the process of tumorigenesis. According to the Stochastic Model, potentially any cell, once defunct, is capable of initiating carcinogenesis. Alternatively the Cancer Stem Cell (CSC) Model posits that only a small fraction of undifferentiated tumor cells are capable of triggering carcinogenesis. Like healthy stem cells, CSCs are also characterized by a capacity for self-renewal and the ability to generate differentiated progeny, possibly mediating treatment resistance, thus leading to tumor recurrence and metastasis. Moreover, molecular signaling profiles are similar between CSCs and normal stem cells, including Wnt, Notch and Hedgehog pathways. Therefore, development of novel chemotherapeutic agents and proteins (e.g., enzymes and antibodies) specifically targeting CSCs are attractive pharmaceutical candidates. This article describes small molecule inhibitors of stem cell pathways Wnt, Notch and Hedgehog, and their recent chemotherapy clinical trials.