Side population cells as prototype of chemoresistant, tumor-initiating cells

Trophoblast Side-Population Markers are Dysregulated in Preeclampsia and Fetal Growth Restriction

Dysregulated progenitor cell populations may contribute to poor placental development and placental insufficiency pathogenesis. Side-population cells possess progenitor properties. Recent human trophoblast side-population isolation identified enrichment of 8 specific genes (CXCL8, ELL2, GATA6, HK2, HLA-DPB1, INTS6, SERPINE3 and UPP1) (Gamage et al. 2020, Stem Cell Rev Rep). We characterised these trophoblast side-population markers in human placenta and in placental insufficiency disorders: preeclampsia and fetal growth restriction (FGR). Trophoblast side-population markers localised to mononuclear trophoblasts lining the placental villous basement membrane in preterm control, preeclamptic and FGR placental sections (n = 3, panel of 3 markers/serial section). Analysis of single-cell transcriptomics of an organoid human trophoblast stem cell (hTSC) to extravillous trophoblast (EVT) differentiation model (Shannon et al. 2022, Development) identified that all side-population genes were enriched in mononuclear trophoblast and trophoblasts committed to differentiation under hTSC culture conditions. In vitro validation via 96 h time course hTSC differentiation to EVTs or syncytiotrophoblasts (n = 5) demonstrated ELL2 and HK2 increased with differentiation (p < 0.0024, p < 0.0039 respectively). CXCL8 and HLA-DPB1 were downregulated (p < 0.030, p < 0.011 respectively). GATA6 and INTS6 increased with EVT differentiation only, and UPP1 reduced with syncytialisation. SERPINE3 was undetectable. Trophoblast side-population marker mRNA was measured in human placentas (< 34-weeks' gestation; n = 78 preeclampsia, n = 30 FGR, and n = 18 gestation-matched controls). ELL2, HK2 and CXCL8 were elevated in preeclamptic (p = 0.0006, p < 0.0001, p = 0.0335 respectively) and FGR placentas (p = 0.0065, p < 0.0001, p = 0.0001 respectively) versus controls. Placental GATA6 was reduced in pregnancies with preeclampsia and FGR (p = 0.0014, p = 0.0146 respectively). Placental INTS6 was reduced with FGR only (p < 0.0001). This study identified the localisation of a unique trophoblast subset enriched for side-population markers. Aberrant expression of some side-population markers may indicate disruptions to unique trophoblast subtypes in placental insufficiency.

The most recent progress of baicalein in its anti-neoplastic effects and mechanisms

Problems, such as toxic side effects and drug resistance of chemoradiotherapy, target therapy and immunotherapy accompanying the current anti-cancer treatments, have become bottlenecks limiting the clinical benefit for patients. Therefore, it is urgent to find promising anti-cancer strategies with higher efficacy and lesser side effects. Baicalein, a flavonoid component derived from the Chinese medicine scutellaria baicalensis, has been widely studied for its remarkable anti-cancer activity in multiple types of malignancies both at the molecular and cellular levels. Baicalein exerts its anti-tumor effects by inhibiting angiogenesis, invasion and migration, inducing cell apoptosis and cell cycle arrest, as well as regulating cell autophagy, metabolism, the tumor microenvironment and cancer stem cells with no obvious toxic side effects. The role of classic signaling pathways, such as PI3K/AKT/mTOR, MAPK, AMPK, Wnt/β-catenin, JAK/STAT3, MMP-2/-9, have been highlighted as the major targets for baicalein exerting its anti-malignant potential. Besides, baicalein can regulate the relevant non-coding RNAs, such as lncRNAs, miRNAs and circ-RNAs, to inhibit tumorigenesis and progression. In addition to the mentioned commonalities, baicalein shows some specific anti-tumor characteristics in some specific cancer types. Moreover, the preclinical studies of the combination of baicalein and chemoradiotherapy pave the way ahead for developing baicalein as an adjunct treatment with chemoradiotherapy. Our aim is to summary the role of baicalein in different types of cancer with its mechanisms based on in vitro and in vivo experiments, hoping providing proof for baicalein serving as an effective and safe compound for cancer treatment in clinic in the future.

Interventing mitochondrial PD-L1 suppressed IFN-γ-induced cancer stemness in hepatocellular carcinoma by sensitizing sorafenib-induced ferroptosis

Evidence recently showed that pleiotropic cytokine interferon-gamma (IFN-γ) in the tumor microenvironment (TME) plays a positive role in hepatocellular carcinoma (HCC) progression through the regulation of liver cancer stem cells (LCSCs) in HCC. The present study explored the role and potential mechanism of mitochondrial programmed cell death-ligand 1 (PD-L1) and its regulation of ferroptosis in modulating the cancer stemness of LCSCs. It was shown that mimicking TME IFN-γ exposure increased the LCSCs ratio and cancer stemness phenotypes in HCC cells. IFN-γ exposure inhibited sorafenib (Sora)-induced ferroptosis by enhancing glutathione peroxidase 4 (GPX4) expression as well reactive oxygen species (ROS) and lipid peroxidation (LPO) generation in LCSCs. Furthermore, IFN-γ exposure upregulated PD-L1 expression and its mitochondrial translocation, inducing dynamin-related protein 1 (Drp1)-dependent mitochondrial fission and correlating with glycolytic metabolism reprogramming in LCSCs. The genetic intervention of PD-L1 promoted ferroptosis-dependent anti-tumor effects of Sora, reduced glycolytic metabolism reprogramming, and inhibited cancer stemness of HCC in vitro and in vivo. Our results revealed a novel mechanism that IFN-γ exposure-induced mitochondrial translocation of PD-L1 enhanced glycolytic reprogramming to mediate the GPX4-dependent ferroptosis resistance and cancer stemness in LCSCs. This study provided new insights into the role of mitochondrial PD-L1-Drp1-GPX4 signal axis in regulating IFN-γ exposure-associated cancer stemness in LCSCs and verified that PD-L1-targeted intervention in combination with Sora might achieve promising synergistic anti-HCC effects.

The role of LOXL2 induced by glucose metabolism-activated NF-κB in maintaining drug resistance through EMT and cancer stemness in gemcitabine-resistant PDAC

Gemcitabine is considered a standard treatment for pancreatic cancer, but developing drug resistance greatly limits the effectiveness of chemotherapy and increases the rate of recurrence. Lysyl oxide-like 2 (LOXL2) is highly expressed in pancreatic cancer and is involved in carcinogenesis and EMT regulation. However, studies on the role of LOXL2 in drug resistance are limited. Here, we investigated the mechanism of LOXL2 induction and the effect of LOXL2 on EMT and CSC in gemcitabine-resistant pancreatic cancer. Glucose metabolism was activated in gemcitabine-resistant pancreatic cancer cells, and NF-κB signaling was regulated accordingly. Activated NF-κB directly induces transcription by binding to the promoters of LOXL2 and ZEB1. The EMT process was significantly inhibited by the coregulation of ZEB1 and LOXL2. In addition, LOXL2 inhibition reduced the expression of cancer stemness markers and stemness by regulating MAPK signaling activity. LOXL2 inhibits tumor growth of gemcitabine-resistant pancreatic cancer cells and increases the sensitivity to gemcitabine in mouse models. KEY MESSAGES: We identified a specific mechanism for inducing LOXL2 overexpression in gemcitabine-resistant pancreatic cancer. Taken together, our results suggest LOXL2 has an important regulatory role in maintaining gemcitabine resistance and may be an effective therapeutic target to treat pancreatic cancer.

The CD44std and CD44v9 subpopulations in non-tumorigenic invasive SNU-423 cells present different features of cancer stem cells

Hepatocellular carcinoma (HCC) is a type of liver cancer, in which CD44 isoforms have been proposed as markers to identify cancer stem cells (CSCs). However, it is unclear what characteristics are associated with CSCs that exclusively express CD44 isoforms. The objective of the present study was to determine the expression of CD44 isoforms and their properties in CSCs. Analysis of transcriptomic data from HCC patient samples identified CD44v8-10 as a potential marker in HCC. In SNU-423 cells, CD44 expression was detected in over 99% of cells, and two CD44 isoforms, namely, CD44std and CD44v9, were identified in this cell line. CD44 subpopulations, including both CD44v9+ (CD44v9) and CD44v9- (CD44std) cells, were obtained by purification using a magnetic cell separation kit for human CD44v9+ cancer stem cells. CD44v9 cells showed greater potential for colony and spheroid formation, whereas CD44std cells demonstrated significant migration and invasion capabilities. These findings suggested that CD44std and CD44v9 may be used to identify features in CSC populations and provide insights into their roles in HCC.

Impact of Non-Coding RNAs on Chemotherapeutic Resistance in Oral Cancer

Drug resistance in oral cancer is one of the major problems in oral cancer therapy because therapeutic failure directly results in tumor recurrence and eventually in metastasis. Accumulating evidence has demonstrated the involvement of non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in processes related to the development of drug resistance. A number of studies have shown that ncRNAs modulate gene expression at the transcriptional or translational level and regulate biological processes, such as epithelial-to-mesenchymal transition, apoptosis, DNA repair and drug efflux, which are tightly associated with drug resistance acquisition in many types of cancer. Interestingly, these ncRNAs are commonly detected in extracellular vesicles (EVs) and are known to be delivered into surrounding cells. This intercellular communication via EVs is currently considered to be important for acquired drug resistance. Here, we review the recent advances in the study of drug resistance in oral cancer by mainly focusing on the function of ncRNAs, since an increasing number of studies have suggested that ncRNAs could be therapeutic targets as well as biomarkers for cancer diagnosis.

EBV LMP1-activated mTORC1 and mTORC2 Coordinately Promote Nasopharyngeal Cancer Stem Cell Properties

Epstein-Barr Virus (EBV) is associated with several malignant diseases, including Burkitt's lymphoma, nasopharyngeal carcinoma (NPC), certain types of lymphomas, and a portion of gastric cancers. Virus-encoded oncoprotein LMP1 induces the epithelial-to-mesenchymal transition (EMT), leading to cancer stem cell formation. In the current study, we investigated how LMP1 contributes to cancer stem cell development in NPC. We found that LMP1 plays an essential role in acquiring CSC characteristics, including tumor initiation, metastasis, and therapeutic resistance by activating the PI3K/mTOR/Akt signaling pathway. We dissected the functions of distinct signaling (mTORC1 and mTORC2) in the acquisition of different CSC characteristics. Side population (SP) formation, which represents the chemotherapy resistance feature of CSC, requires mTORC1 signaling. Tumor initiation capability is mainly attributed to mTORC2, which confers on NPC the capabilities of proliferation and survival by activating mTORC2 downstream genes c-Myc. Both mTORC1 and mTORC2 enhance cell migration and invasion of NPC cells, suggesting that mTORC1/2 co-regulate metastasis of NPC. The revelation of the roles of the mTOR signaling pathways in distinct tumorigenic features provides a guideline for designing efficient therapies by choosing specific mTOR inhibitors targeting mTORC1, mTORC2, or both to achieve durable remission of NPC in patients. Importance LMP1 endows NPC to gain cancer stem cell characteristics through activating mTORC1 and mTORC2 pathways. The different mTOR pathways are responsible for distinct tumorigenic features. Rapamycin-insensitive mTORC1 is essential for CSC drug resistance. NPC tumor initiation capacity is mainly attributed to mTORC2 signaling. mTORC1 and mTORC2 co-regulate NPC cell migration and invasion. The revelation of the roles of mTOR signaling in NPC CSC establishment has implications for novel therapeutic strategies to treat relapsed and metastatic NPC and achieve durable remission.

MiR-199 Reverses the Resistance to Gemcitabine in Pancreatic Cancer by Suppressing Stemness through Regulating the Epithelial-Mesenchymal Transition

PURPOSE

the present study aims to investigate the function of miR-199 on gemcitabine (GEM)-resistance in pancreatic cancer, as well as the underlying mechanism.

METHODS

the GEM-resistant SW1990 cell line (SW1990/SZ) was established. The CCK-8 assay was used to detect the cell viability. The self-renewal of SW1990/SZ cells was evaluated by sphere formation and the colony formation assay. The apoptosis was detected by flow cytometry and the migration ability was measured by the transwell assay. The dual-luciferase gene reporter assay was utilized to confirm the binding between miR-199 and Snail. The expression level of CD44, ALDH1, Nanog, E-cadherin, Vimentin, β-catenin, and Snail was determined by the Western blotting assay.

RESULTS

the cell sphere formation rate, number of spheres, and expression level of CD44, ALDH1, and Nanog in GEM-treated SW1990/SZ cells were significantly suppressed by miR-199, accompanied by declined proliferation ability, an increased apoptotic rate, inhibited migration ability, and suppressed EMT progression. The binding site between miR-199 and 3'-UTR of Snail was predicted and confirmed. The inhibitory effect of miR-199 on self-renewal of SW1990/GZ cells and the faciliating property of miR-199 on the inhibitory effect of GEM against the proliferation ability, migration ability, and EMT progression were abolished by overexpressing Snail.

CONCLUSION

MiR-199 reversed the resistance to GEM in pancreatic cancer by suppressing stemness through regulating the EMT.

The plasticity of pancreatic cancer stem cells: implications in therapeutic resistance

The ever-growing perception of cancer stem cells (CSCs) as a plastic state rather than a hardwired defined entity has evolved our understanding of the functional and biological plasticity of these elusive components in malignancies. Pancreatic cancer (PC), based on its biological features and clinical evolution, is a prototypical example of a CSC-driven disease. Since the discovery of pancreatic CSCs (PCSCs) in 2007, evidence has unraveled their control over many facets of the natural history of PC, including primary tumor growth, metastatic progression, disease recurrence, and acquired drug resistance. Consequently, the current near-ubiquitous treatment regimens for PC using aggressive cytotoxic agents, aimed at ‘‘tumor debulking’’ rather than eradication of CSCs, have proven ineffective in providing clinically convincing improvements in patients with this dreadful disease. Herein, we review the key hallmarks as well as the intrinsic and extrinsic resistance mechanisms of CSCs that mediate treatment failure in PC and enlist the potential CSC-targeting ‘natural agents’ that are gaining popularity in recent years. A better understanding of the molecular and functional landscape of PCSC-intrinsic evasion of chemotherapeutic drugs offers a facile opportunity for treating PC, an intractable cancer with a grim prognosis and in dire need of effective therapeutic advances.

[Identification of the side population associated with ATP-binding cassette transporters activity using imaging flow cytometry]

DyeCycle Violet efflux, caused by ATP-binding cassette transporters activity, was analyzed in human colorectal adenocarcinoma cell lines SW480, HT-29, Caco-2 by neans of FACSAria III flow cytometer and ImageStreamX Mk II imaging flow cytometer. Along with similarity of cytometry data obtained on the two instruments, the use of imaging flow cytometry made it possible to characterize the morphology of side population cells, as well as morphology of other cell populations differing in the degree of dye accumulation. The population of cells, which are smaller than the side population cells and practically do not take the dye, is of the special interest. Probably, this population may contribute to the tumor resistance to chemotherapy.

Homoharringtonine synergizes with quizartinib in FLT3-ITD acute myeloid leukemia by targeting FLT3-AKT-c-Myc pathway

Acute myeloid leukemia (AML) with FLT3 internal tandem duplication (FLT3-ITD) has a dismal prognosis. FLT3 inhibitors have been developed to treat patients with FLT3-ITD AML; however, when used alone, their efficacy is insufficient. FLT3 inhibitors combined with chemotherapy may be a promising treatment for FLT3-ITD AML. Homoharringtonine (HHT) is a classical anti-leukaemia drug with high sensitivity to FLT3-ITD AML cells. Here, we showed that HHT synergizes with a selective next-generation FLT3 inhibitor, quizartinib, to inhibit cell growth/viability and induce cell-cycle arrest and apoptosis in FLT3-ITD AML cells in vitro, significantly inhibit acute myeloid leukemia progression in vivo, and substantially prolong survival of mice-bearing human FLT3-ITD AML. Mechanistically, HHT and quizartinib cooperatively inhibit FLT3-AKT and its downstream targets GSK3β, c-Myc, and cyclin D1, cooperatively up-regulate the pro-apoptosis proteins Bim and Bax, and down-regulate the anti-apoptosis protein Mcl1. Most strikingly, HHT and quizartinib cooperatively reduce the numbers of side-population (SP) and aldehyde dehydrogenase (ALDH)-positive cells, which reportedly are rich in LSCs. In conclusion, HHT combined with quizartinib may be a promising treatment strategy for patients with FLT3-ITD AML.

Association of ALDH1A1-NEK-2 axis in cisplatin resistance in ovarian cancer cells

Development of acquired resistance to cisplatin (CDDP) is a major obstacle in the treatment of ovarian cancer patients. According to the cancer stem cell (CSC) hypothesis, the recurrence and chemoresistance are presumed to be linked to cancer stem/progenitor cells. Here, we investigated the CSC-like phenotypes and mechanism of chemoresistance in CDDP resistant ovarian cancer cells. A well-established CDDP sensitive ovarian cancer cell line A2780 and its resistant population A2780-Cp were used. We also developed a supra resistant population (SKOV3-Cp) from a naturally CDDP resistant cell line SKOV3. Both resistant/supra resistant cell lines showed significantly higher self-renewal capability than their parental counterparts. They also showed significant resistance to apoptosis and sub-G1 arrest by CDDP treatment. Stem cell marker ALDH1 positivity rates were higher both in A2780-Cp and SKOV3-Cp cell lines than in their counterparts, quantified by Aldefluor assay kit. Hoechst 33342 dye effluxing side populations were increased up to about five folds in A2780-Cp cells and two folds in SKOV3-Cp cells compared to A2780 and SKOV3 cells, respectively. Among major stemness related genes (POU5F1/OCT4, SOX2, NANOG, NES, BMI1, KLF4 and ALDH1A1), ALDH1A1 and KLF4 were significantly overexpressed in both resistant/supra resistant cells. Silencing ALDH1A1 in A2780 and A2780-Cp cells using siRNA greatly reduced the stem cell population and sensitized cells to CDDP. Moreover, silencing of ALDH1A1 reduced the transcript and protein level of its downstream target NEK-2. We also observed the downregulation of ABC transporters (ABCB1/MDR1, ABCG2 and ABCC1/MRP1) either by ALDH1A1 or NEK-2 silencing and upreguation of ABCB1/MDR1 due to the overexpression of NEK-2. Taken together, the present study suggests that stemness gene ALDH1A1 can be involved in CDDP resistance through the upregulation of NEK-2 in ovarian cancer.

Cancer Stem Cell Markers in Relation to Patient Survival Outcomes: Lessons for Integrative Diagnostics and Next-Generation Anticancer Drug Development

Solid tumors display a complex biology that requires a multipronged treatment strategy. Most anticancer interventions, including chemotherapy, are currently unable to prevent treatment resistance and relapse. In general, therapeutics target cancer cells and overlook the tumor microenvironment (TME) and the presence of cancer stem cells (CSCs) with self-renewal and tumorigenic abilities. CSCs have been postulated to play key roles in tumor initiation, progression, therapy resistance, and metastasis. Hence, CSC markers have been suggested as diagnostics to forecast cancer prognosis as well as molecular targets for new-generation cancer treatments, especially in resistant disease. We report here original findings on expression and prognostic significance of CSC markers in several cancers. We examined and compared the transcriptional expression of CSC markers (ABCB1, ABCG2, ALDH1A1, CD24, CD44, CD90, CD133, CXCR4, EPCAM, ICAM1, and NES) in tumor tissues versus the adjacent normal tissues using publicly available databases, The Cancer Genome Atlas and Gene Expression Profiling Interactive Analysis. We found that CSC transcriptional markers were, to a large extent, expressed in higher abundance in solid tumors such as colon, lung, pancreatic, and esophageal cancers. On the other hand, no CSC marker in our analysis was expressed in the same pattern in all cancers, while individual CSC marker expression, alone, was not significantly associated with overall patient survival. Innovation in next-generation cancer therapeutics and diagnostics ought to combine CSC markers as well as integrative diagnostics that pool knowledge from CSCs and other TME components and cancer cells.

Kv7 Channels in Lung Diseases

Lung diseases constitute a global health concern causing disability. According to WHO in 2016, respiratory diseases accounted for 24% of world population mortality, the second cause of death after cardiovascular diseases. The Kv7 channels family is a group of voltage-dependent K⁺ channels (Kv) encoded by KCNQ genes that are involved in various physiological functions in numerous cell types, especially, cardiac myocytes, smooth muscle cells, neurons, and epithelial cells. Kv7 channel α-subunits are regulated by KCNE1–5 ancillary β-subunits, which modulate several characteristics of Kv7 channels such as biophysical properties, cell-location, channel trafficking, and pharmacological sensitivity. Kv7 channels are mainly expressed in two large groups of lung tissues: pulmonary arteries (PAs) and bronchial tubes. In PA, Kv7 channels are expressed in pulmonary artery smooth muscle cells (PASMCs); while in the airway (trachea, bronchus, and bronchioles), Kv7 channels are expressed in airway smooth muscle cells (ASMCs), airway epithelial cells (AEPs), and vagal airway C-fibers (VACFs). The functional role of Kv7 channels may vary depending on the cell type. Several studies have demonstrated that the impairment of Kv7 channel has a strong impact on pulmonary physiology contributing to the pathophysiology of different respiratory diseases such as cystic fibrosis, asthma, chronic obstructive pulmonary disease, chronic coughing, lung cancer, and pulmonary hypertension. Kv7 channels are now recognized as playing relevant physiological roles in many tissues, which have encouraged the search for Kv7 channel modulators with potential therapeutic use in many diseases including those affecting the lung. Modulation of Kv7 channels has been proposed to provide beneficial effects in a number of lung conditions. Therefore, Kv7 channel openers/enhancers or drugs acting partly through these channels have been proposed as bronchodilators, expectorants, antitussives, chemotherapeutics and pulmonary vasodilators.

Highly expressed STAT1 contributes to the suppression of stemness properties in human paclitaxel-resistant ovarian cancer cells

Signal transducer and activator of transcription-1 (STAT1) is an important factor in various cellular processes. The cancer stem cell (CSC) is considered as a tumor-initiating cell that drives the inner hierarchy in many cancers including epithelial ovarian cancer (EOC). Here, we explored for the first time the regulation of STAT1 on stemness properties in chemoresistant EOC cells. The paclitaxel (PTX)-resistant EOC cell line (OV3R-PTX) was derived from PTX-sensitive OVCAR-3 cells treated by the PTX regimen. A single cell clone OV3R-PTX-B4 was selected by fluorescence-activated cell sorting. PTX-resistant cells grew slowly in conventional 2D and 3D cultures, but tumor xenograft with PTX-resistant cells grew fast in nude mice. Interestingly, OV3R-PTX-B4 cells shared the characteristics of CSCs and stemness properties were found to be increased in the non-adherent spheroid culture system. The PTX-resistant cells had a high expression of CSC-related markers and low expression of STAT1 that had a high methylation level of CpG in its promoter region. Overexpressed STAT1 suppressed stemness properties, cell proliferation, and colony formation and favored the overall survival of patients with EOC. In summary, these data indicate a regulatory mechanism of STAT1 underlying drug resistance and provide a potential therapeutic application for EOC patients with PTX resistance.

The heparan sulfate proteoglycan syndecan-1 regulates colon cancer stem cell function via a focal adhesion kinase-Wnt signaling axis

In colon cancer, downregulation of the transmembrane heparan sulfate proteoglycan syndecan-1 (Sdc-1) is associated with increased invasiveness, metastasis, and dedifferentiation. As Sdc-1 modulates signaling pathways relevant to stem cell function, we tested the hypothesis that it may regulate a tumor-initiating cell phenotype. Sdc-1 small-interfering RNA knockdown in the human colon cancer cell lines Caco2 and HT-29 resulted in an increased side population (SP), enhanced aldehyde dehydrogenase 1 activity, and higher expression of CD133, LGR5, EPCAM, NANOG, SRY (sex-determining region Y)-box 2, KLF2, and TCF4/TCF7L2. Sdc-1 knockdown enhanced sphere formation, cell viability, Matrigel invasiveness, and epithelial-to-mesenchymal transition-related gene expression. Sdc-1-depleted HT-29 xenograft growth was increased compared to controls. Decreased Sdc-1 expression was associated with an increased activation of β1-integrins, focal adhesion kinase (FAK), and wingless-type (Wnt) signaling. Pharmacological FAK and Wnt inhibition blocked the enhanced stem cell phenotype and invasive growth. Sequential flow cytometric SP enrichment substantially enhanced the stem cell phenotype of Sdc-1-depleted cells, which showed increased resistance to doxorubicin chemotherapy and irradiation. In conclusion, Sdc-1 depletion cooperatively enhances activation of integrins and FAK, which then generates signals for increased invasiveness and cancer stem cell properties. Our findings may provide a novel concept to target a stemness-associated signaling axis as a therapeutic strategy to reduce metastatic spread and cancer recurrence. DATABASES: The GEO accession number of the Affymetrix transcriptomic screening is GSE58751.

Syndecan-1-Dependent Regulation of Heparanase Affects Invasiveness, Stem Cell Properties, and Therapeutic Resistance of Caco2 Colon Cancer Cells

The heparan sulfate proteoglycan Syndecan-1 binds cytokines, morphogens and extracellular matrix components, regulating cancer stem cell properties and invasiveness. Syndecan-1 is modulated by the heparan sulfate-degrading enzyme heparanase, but the underlying regulatory mechanisms are only poorly understood. In colon cancer pathogenesis, complex changes occur in the expression pattern of Syndecan-1 and heparanase during progression from well-differentiated to undifferentiated tumors. Loss of Syndecan-1 and increased expression of heparanase are associated with a change in phenotypic plasticity and an increase in invasiveness, metastasis and dedifferentiation. Here we investigated the regulatory and functional interplay of Syndecan-1 and heparanase employing siRNA-mediated silencing and plasmid-based overexpression approaches in the human colon cancer cell line Caco2. Heparanase expression and activity were upregulated in Syndecan-1 depleted cells. This increase was linked to an upregulation of the transcription factor Egr1, which regulates heparanase at the promoter level. Inhibitor experiments demonstrated an impact of focal adhesion kinase, Wnt and ROCK-dependent signaling on this process. siRNA-depletion of Syndecan-1, and upregulation of heparanase increased the colon cancer stem cell phenotype based on sphere formation assays and phenotypic marker analysis (Side-population, NANOG, KLF4, NOTCH, Wnt, and TCF4 expression). Syndecan-1 depletion increased invasiveness of Caco2 cells in vitro in a heparanase-dependent manner. Finally, upregulated expression of heparanase resulted in increased resistance to radiotherapy, whereas high expression of enzymatically inactive heparanase promoted chemoresistance to paclitaxel and cisplatin. Our findings provide a new avenue to target a stemness-associated signaling axis as a therapeutic strategy to reduce metastatic spread and cancer recurrence.

SOX2 upregulates side population cells and enhances their chemoresistant ability by transactivating ABCC1 expression contributing to intrinsic resistance to paclitaxel in melanoma

Paclitaxel is the last choice for the treatment of advanced melanoma as a second-line chemotherapeutic agent, but there are still many cases of intrinsic resistance to paclitaxel in melanoma and the reasons that cause paclitaxel resistance remain unclear. Here, we identified that high expression of SRY-box transcription factor 2 (SOX2) and high ratio of side population (SP) cells reduced the sensitivity to paclitaxel in melanoma cells. The knockout and the induction of SOX2 completely depleted and significantly upregulated the ratios of melanoma SP cells, respectively. These data suggest that SOX2, a pluripotent transcription factor for inducing cancer stem cells in melanoma, is also sufficient and necessary for the induction of melanoma SP cells. ATP-binding cassette (ABC) subfamily C member 1 (ABCC1) is one of ABC transporters which causes SP cells to be resistance to chemotherapeutic agents by efficiently pumping drugs out of cells. The knockout and the induction of ABCC1 significantly increased and decreased the sensitivity of melanoma cells to paclitaxel. High expression of ABCC1 was identified in melanoma cell lines with high expression of SOX2 and in their SP cells. SOX2 was identified to induce ABCC1 transcription. Taken together, SOX2 upregulates SP cells and enhances their chemoresistant ability by increasing ABCC1 expression, which contributes to intrinsic resistance to paclitaxel in melanoma. Our findings will lead to new insights into melanoma biology and therapy resistance, and eventually to new therapeutic targets.

Highly versatile cancer photoimmunotherapy using photosensitizer-conjugated avidin and biotin-conjugated targeting antibodies

Background

Photoimmunotherapy (PIT) employing antibody-photosensitizer conjugates is a promising treatment for cancer. However, the fixed antigen specificity severely limits the efficacy and the applicability. Here we describe a universal strategy for PIT of cancer by using a near-infrared (NIR) photosensitizer IRDye700DX-conjugated NeutrAvidin, designated as AvIR, together with various biotinylated antibodies (BioAbs) for cellular targeting.

Methods

Cytotoxicity of AvIR-mediated PIT was evaluated by fluorescence imaging and cell viability assay. Phototoxic effect on tumorigenicity was assessed by tumorsphere-formation assay and Matrigel invasion assay. Cancer stem cell-like side-population (SP) cells were identified by flow cytometry.

Results

CHO cells stably expressing carcinoembryonic antigen or EpCAM were pre-labeled with each BioAb for the corresponding antigen, followed by AvIR administration. NIR light irradiation specifically killed the targeted cells, but not off-targets, demonstrating that the AvIR-mediated PIT does work as expected. CSC-like subpopulation of MCF-7 cells (CD24^low/CD44^high) and SP of HuH-7 cells (CD133⁺/EpCAM⁺) were effectively targeted and photokilled by AvIR-PIT with anti-CD44 BioAb or anti-CD133/anti-EpCAM BioAbs, respectively. As results, the neoplastic features of the cell lines were sufficiently suppressed. Cancer-associated fibroblast (CAF)-targeted AvIR-PIT by using anti-fibroblast activation protein BioAb showed an abolishment of CAF-enhanced clonogenicity of MCF-7 cells.

Conclusions

Collectively, our results demonstrate that AvIR-mediated PIT can greatly broaden the applicable range of target specificity, with feasibility of efficacious and integrative control of CSC and its microenvironment.

Cervical cancer stem cells and other leading factors associated with cervical cancer development

Cervical cancer (CC) is one of the leading causes of cancer-associated mortalities in women from developing countries. Similar to other types of cancer, CC is considered to be a multifactorial disease, involving socioeconomic, cultural, immunological and epigenetic factors, as well as persistent human papilloma virus (HPV) infection. It has been well established that cancer stem cells (CSCs) play an important role in defining tumor size, the speed of development and the level of regression following treatment; therefore, CSCs are associated with a poor prognosis. CSCs have been detected in many types of cancer, including leukemia, pancreatic, colon, esophagus, liver, prostate, breast, gastric and lung cancer. In cervical cancer, CSCs have been associated with resistance to normally used drugs such as cisplatin. The present review summarizes the strategies that high-risk HPV viruses (HPV-16 and HPV-18) have developed to transform normal epithelial cells into cancer cells, as well as the cellular pathways and studies associated with the identification of cervical cancer stem cell biomarkers. In this sense, the present review provides state of the art information regarding CC development.

Transition from mesenchymal to bleb-based motility is predominantly exhibited by CD133-positive subpopulation of fibrosarcoma cells

BACKGROUND INFORMATION

Metastatic disease is caused by the ability of cancer cells to reach distant organs and form secondary lesions at new locations. Dissemination of cancer cells depends on their migration plasticity - an ability to switch between motility modes driven by distinct molecular machineries. One of such switches is mesenchymal-to-amoeboid transition. Although mesenchymal migration of individual cells requires Arp2/3-dependent actin polymerisation, amoeboid migration is characterised by a high level of actomyosin contractility and often involves the formation of membrane blebs. The acquisition of amoeboid motility by mesenchymal cells is often associated with enhanced metastasis.

RESULTS

We studied the ability of mesenchymal HT1080 fibrosarcoma cells to switch to amoeboid motility. We induced the transition from lamellipodium-rich to blebbing phenotype either by down-regulating the Arp2/3 complex, pharmacologically or by RNAi, or by decreasing substrate adhesiveness. Each of these treatments induced blebbing in a subset of fibrosarcoma cells, but not in normal subcutaneous fibroblasts. A significant fraction of HT1080 cells that switched to blebbing behaviour exhibited stem cell-like features, such as expression of the stem cell marker CD133, an increased efflux of Hoechst-33342 and positive staining for Oct4, Sox2 and Nanog. Furthermore, the isolated CD133+ cells demonstrated an increased ability to switch to bleb-rich amoeboid phenotype both under inhibitor's treatment and in 3D collagen gels.

CONCLUSIONS

Together, our data show a significant correlation between the increased ability of cells to switch between migration modes and their stem-like features, suggesting that migration plasticity is an additional property of stem-like population of fibrosarcoma cells. This combination of features could facilitate both dissemination of these cells to distant locations, and their establishment self-renewal in a new microenvironment, as required for metastasis formation.

SIGNIFICANCE

These data suggest that migration plasticity is a new feature of cancer stem-like cells that can significantly facilitate their dissemination to a secondary location by allowing them to adapt quickly to challenging microenvironments. Moreover, it complements their resistance to apoptosis and self-renewal potential, thus enabling them not only to disseminate efficiently, but also to survive and colonise new niches.

Using CuO nanoparticles and hyperthermia in radiotherapy of MCF-7 cell line: synergistic effect in cancer therapy

The aim of this paper was examining the combined impacts of CuO nanoparticles (CuO NPs), hyperthermia (H), and irradiation (R) on an increment of MCF-7 cells. The MTT assay was employed to assess the antiproliferative effects of CuO NPs (25, 50, and 100 μg/ml), hyperthermia (41 °C for 1 h), and irradiation (200 cGy). Moreover, the perniciousness was estimated through the survival capability of cells, and apoptosis, ROS production, and levels of caspase-3, -8 and -9 proteins were determined. A significant (p < .01) decrease in proliferation index (0.124 ± 0.021), a significant (p < .01) increase in apoptosis (42% ± 1.54) of MCF7 cells, a significant (p < .03) increase in ROS formation (32.16 ± 1.9) and a significant (p < .01) increase in LDH release (33.28 ± 1.56) were recorded in the adjacency of MCF-7 cells by a combination of CuO NPs (100 µg/ml) and R + H compared to control and other treatments. The activities of caspase-3 (0.33 ± 0.014) and caspase-9 (0.389 ± 0.019) also increased significantly (p < .05). However, caspase-8 showed no significant changes in its activity (p = .065). Based on these observations, a combination of CuO NPs, hyperthermia, and irradiation could suppress the growth of MCF-7 cells and evoke cell apoptosis via mitochondrial membrane potential.

Voltage-dependent calcium channel α2δ1 subunit is a specific candidate marker for identifying gastric cancer stem cells

Purpose: Cancer stem cells (CSCs) are a subpopulation of cancer cells with self-renewal property and responsible for tumor malignancy, progression and drug resistance. Researches on CSC-specific markers in gastric cancer remain limited. Our current study explored the expression of voltage-dependent calcium channel α2δ1 subunit and the potential of using α2δ1 as a CSC marker in gastric cancer. We also compared the specificity of α2δ1 and CD44 in identifying gastric cancer stem cells (GCSCs).

Materials and methods: Expression of α2δ1 was analyzed in gastric cancer cell lines, patient-derived xenograft (PDX) models and clinical samples of malignant ascites of gastric cancer patients. α2δ1⁺ gastric cancer cells were isolated from gastric cancer cell lines. CSC properties of α2δ1⁺ gastric cancer cells were then verified by subsequent tests both in vitro and in vivo.

Results: The expression level of α2δ1 was found to differ drastically among gastric cancer cell lines, PDX models and clinical samples of malignant ascites. α2δ1⁺ gastric cancer cells sorted from HGC-27 and SGC-7901 cell lines demonstrated significant self-renewal properties, including tumorigenic capacity, sphere-formation capacity and asymmetric differentiation potential. Knockdown of α2δ1 in α2δ1⁺ HGC-27 significantly inhibited CSC properties and rendered HGC-27 more sensitive to chemotherapy. Flow cytometry showed that α2δ1⁺ gastric cancer cells accounted for a small fraction of CD44⁺ gastric cancer cells. Isolated CD44⁺α2δ1⁺ HGC-27 cells displayed more significant tumorigenic capacity and sphere-forming capacity compared with their CD44⁺α2δ1⁻ counterparts.

Conclusion: α2δ1⁺ gastric cancer cells possessed CSC properties. α2δ1 could be a proper marker in identifying GCSCs with superior specificity than CD44. The combination of α2δ1 and CD44 could be used to identify GCSCs with improved accuracy. Knockdown of α2δ1 combined with chemotherapy displayed higher therapeutic efficacy on gastric cancer cells, suggesting that α2δ1 could be a potential target for anticancer treatment.

Cytometry of Reaction Rate Constant: Measuring Reaction Rate Constant in Individual Cells To Facilitate Robust and Accurate Analysis of Cell-Population Heterogeneity

Robust and accurate analysis of cell-population heterogeneity is challenging but required in many areas of biology and medicine. In particular, it is pivotal to the development of reliable cancer biomarkers. Here, we prove that cytometry of reaction rate constant (CRRC) can facilitate such analysis when the kinetic mechanism of a reaction associated with the heterogeneity is known. In CRRC, the cells are loaded with a reaction substrate, and its conversion into a product is followed by time-lapse fluorescence microscopy at the single-cell level. A reaction rate constant is determined for every cell, and a kinetic histogram "number of cells versus the rate constant" is used to determine quantitative parameters of reaction-based cell-population heterogeneity. Such parameters include, for example, the number and sizes of subpopulations. In this work, we applied CRRC to a reaction of substrate extrusion from cells by ATP-binding cassette (ABC) transporters. This reaction is viewed as a potential basis for predictive biomarkers of chemoresistance in cancer. CRRC proved to be robust (insensitive to variations in experimental settings) and accurate for finding quantitative parameters of cell-population heterogeneity. In contrast, a typical nonkinetic analysis, performed on the same data sets, proved to be both nonrobust and inaccurate. Our results suggest that CRRC can potentially facilitate the development of reliable cancer biomarkers on the basis of quantitative parameters of cell-population heterogeneity. A plausible implementation scenario of CRRC-based development, validation, and clinical use of a predictor of ovarian cancer chemoresistance to its frontline therapy is presented.

Cancer stem cells in hepatocellular carcinoma: an overview and promising therapeutic strategies

The poor clinical outcome of hepatocellular carcinoma (HCC) patients is ascribed to the resistance of HCC cells to traditional treatments and tumor recurrence after curative therapies. Cancer stem cells (CSCs) have been identified as a small subset of cancer cells which have high capacity for self-renewal, differentiation and tumorigenesis. Recent advances in the field of liver CSCs (LCSCs) have enabled the identification of CSC surface markers and the isolation of CSC subpopulations from HCC cells. Given their central role in cancer initiation, metastasis, recurrence and therapeutic resistance, LCSCs constitute a therapeutic opportunity to achieve cure and prevent relapse of HCC. Thus, it is necessary to develop therapeutic strategies to selectively and efficiently target LCSCs. Small molecular inhibitors targeting the core stemness signaling pathways have been actively pursued and evaluated in preclinical and clinical studies. Other alternative therapeutic strategies include targeting LCSC surface markers, interrupting the CSC microenvironment, and altering the epigenetic state. In this review, we summarize the properties of CSCs in HCC and discuss novel therapeutic strategies that can be used to target LCSCs.

Genetic Models of Leukemia in Zebrafish

The zebrafish animal model is gaining increasing popularity as a tool for studying human disease. Over the past 15 years, many models of leukemia and other hematological malignancies have been developed in the zebrafish. These confer some significant advantages over similar models in other animals and systems, representing a powerful resource for investigation of the molecular basis of human leukemia. This review discusses the various zebrafish models of lymphoid and myeloid leukemia available, the major discoveries that have been made possible by them, and opportunities for future exploration.

Inhibition of pancreatic cancer stem cells by Rauwolfia vomitoria extract

The poor treatment outcomes of pancreatic cancer are linked to an enrichment of cancer stem cells (CSCs) in these tumors, which are resistant to chemotherapy and promote metastasis and tumor recurrence. The present study investigated an extract from the root of the medicinal plant Rauwolfia vomitoria (Rau) for its activity against pancreatic CSCs. In vitro tumor spheroid formation and CSC markers were tested, and in vivo tumorigenicity was evaluated in nude mice. Rau inhibited the overall proliferation of human pancreatic cancer cell lines with a 50% inhibitory concentration (IC₅₀) ranging between 125 and 325 µg/ml, and showed limited cytotoxicity towards normal epithelial cells. The pancreatic CSC population, identified using cell surface markers or a tumor spheroid formation assay, was significantly reduced, with an IC₅₀ value of ~100 µg/ml treatment for 48 h and ~27 µg/ml for long-term tumor spheroid formation. The levels of CSC-related gene Nanog and nuclear β-catenin were decreased, suggesting suppression of the Wnt/β-catenin signaling pathway. In vivo, 20 mg/kg of Rau administered five times per week by oral gavage significantly reduced the tumorigenicity of PANC-1 cells in immunocompromised mice. Taken together, these data showed that Rau preferentially inhibited pancreatic cancer stem cells. Further investigation is warranted to examine the potential of Rau as a novel treatment for pancreatic cancer.

Relationship between CD44high/CD133high/CD117high cancer stem cells phenotype and Cetuximab and Paclitaxel treatment response in head and neck cancer cell lines

Recent evidence suggests that cancer stem cells (CSCs), a small population of cancer cells that are highly tumourigenic, capable of self-renewal and have the ability to differentiate into cells that constitute the tumor, are the "drivers" of local recurrence and metastatic spread and may be associated with resistant to conventional therapy. The objectives of the study are to identify and characterize two head and neck cancer cell lines with regard CD44high/CD133high/CD117high profile (CSCs) and CD44low/CD133low/CD117low profile (Non-CSCs); to investigate the influence of chemotherapy treatment in CSCs and compare with Non-CSCs; to evaluate CD44 and EGFR gene expression in CSCs. Fluorescent-activated cell sorting (FACS) using specific cell surface marker combination (CD44, CD117 and CD133) was performed to isolate CSCs of Non-CSCs from cell lines. The Wound Healing assay was performed to confirm the presence of CSCs. After, the CSCs subpopulation and Non-CSCs were cultured and exposed for 24 h to Cetuximab and Paclitaxel treatment, separately. Cell proliferation was determined by MTS assay. CD44 and EGFR gene expression was quantified by quantitative real time PCR (qPCR) using TaqMan® Assay in both subpopulations. CSCs subpopulation untreated were considered as relative expression control. We firstly characterized CSCs in HN13 and HEP-2 cell lines with CD44, CD133 and CD117 biomarkers. We treated CSCs and Non-CSCs subpopulations with Cetuximab and Paclitaxel treatment and found that CSCs subpopulations demonstrated more resistance to Paclitaxel chemoterapy, when compared with Non-CSCs subpopulations of oral cancer cell line. These CSCs subpopulations presented up-regulation of CD44 gene and down-regulation of EGFR gene in oral cancer cell line, and down-regulation of CD44 gene and up-regulation of EGFR gene in laryngeal cancer cell line when compared with Non-CSCs subpopulations. We conclude that the combination of CD44, CD133 and CD117 biomarkers have stem cell properties in both cell lines. CSCs has ability to resist to Paclitaxel treatment in oral cancer cell line. CSCs present high expression of CD44 gene and down expression of EGFR gene in oral cancer cell line. CSCs in laryngeal cell line present down expression of CD44 gene and high expression of EGFR gene when compared with cells without characteristics of cancer stem cells.

Extract of the Medicinal Plant Pao Pereira Inhibits Pancreatic Cancer Stem-Like Cell In Vitro and In Vivo

Pancreatic cancers are enriched with cancer stem-like cells (CSCs), which are resistant to chemotherapies, and responsible for tumor metastasis and recurrence. Here, we investigated the extract of a medicinal plant Pao Pereira (Pao) for its activity against pancreatic CSCs. Pao inhibited overall proliferation of human pancreatic cancer cell lines with IC₅₀ ranging from 125 to 325 μg/mL and had limited cytotoxicity to normal epithelial cells. Pancreatic CSC population, identified using surface markers CD24+ CD44+ EpCam+ or tumor spheroid formation assay, was significantly reduced, with IC₅₀s of ~100 μg/mL for 48 hours treatment, and ~27 μg/mL for long-term treatment. Nuclear β-catenin levels were decreased, suggesting suppression of Wnt/β-catenin signaling pathway. In vivo, Pao at 20 mg/kg, 5 times/week gavage, significantly reduced tumorigenicity of PANC-1 cells in immunocompromised mice, indicating inhibition of CSCs in vivo. Further investigation is warranted in using Pao as a novel treatment targeting pancreatic CSCs.

Role of EZH2 in cancer stem cells: from biological insight to a therapeutic target

Epigenetic modifications in cancer stem cells largely result in phenotypic and functional heterogeneity in many solid tumors. Increasing evidence indicates that enhancer of zeste homolog 2 (EZH2), the catalytic subunit of Polycomb repressor complex 2, is highly expressed in cancer stem cells of numerous malignant tumors and has a critical function in cancer stem cell expansion and maintenance. Here, we review up-to-date information regarding EZH2 expression patterns, functions, and molecular mechanisms in cancer stem cells in various malignant tumors and discuss the therapeutic potential of targeting EZH2 in tumors.

Effects of increased accumulation of doxorubicin due to emodin on efflux transporter and LRP1 expression in lung adenocarcinoma and colorectal carcinoma cells

Treatment with doxorubicin (dox) and emodin, separately and together, under normoxic and hypoxia-like conditions induced by CoCl₂, led to greater intracellular compound accumulation over 10 h post-addition in the presence of CoCl₂ in lung adenocarcinoma (A549) and colorectal carcinoma (HCT-15) cell lines. Confocal microscopy revealed that emodin, by itself, showed high cytosolic distribution in both cell lines, at 40 min post-addition but had entered the nuclei by 2 h, while dox entered the nuclei by 40 min. Both compounds modulated the expression of the efflux transporters (PgP, ABCG2, or MRP1-4) and the endocytic receptor, low-density lipoprotein receptor-related protein 1 (LRP1), to different extents under the study conditions. Efflux transporter upregulation was linked to lower intracellular compound levels due to greater efflux. Increased dox accumulation was accompanied by unaltered expression or upregulation of LRP1 in A549 cells. In both cell lines, increased accumulation of dox and emodin was observed whenever LRP1 and the efflux transporters known to transport dox and emodin were all up- or downregulated concomitantly. Increased growth inhibition was linked to co-treatment with dox and emodin and with increased ligand accumulation. The results presented in this study raise the hypothesis that higher production of LRP1 protein may be associated with higher endocytosis of upregulated transporter proteins at the cell surface, and hence, increased dox and emodin accumulation and growth inhibition. If so, elevation of LRP1 expression may be a useful target for interventions to promote the efficacy of these and other anticancer drugs.

FH535, a β-catenin pathway inhibitor, represses pancreatic cancer xenograft growth and angiogenesis

The WNT/β-catenin pathway plays an important role in pancreatic cancer carcinogenesis. We evaluated the correlation between aberrant β-catenin pathway activation and the prognosis pancreatic cancer, and the potential of applying the β-catenin pathway inhibitor FH535 to pancreatic cancer treatment. Meta-analysis and immunohistochemistry showed that abnormal β-catenin pathway activation was associated with unfavorable outcome. FH535 repressed pancreatic cancer xenograft growth in vivo. Gene Ontology (GO) analysis of microarray data indicated that target genes responding to FH535 participated in stemness maintenance. Real-time PCR and flow cytometry confirmed that FH535 downregulated CD24 and CD44, pancreatic cancer stem cell (CSC) markers, suggesting FH535 impairs pancreatic CSC stemness. GO analysis of β-catenin chromatin immunoprecipitation sequencing data identified angiogenesis-related gene regulation. Immunohistochemistry showed that higher microvessel density correlated with elevated nuclear β-catenin expression and unfavorable outcome. FH535 repressed the secretion of the proangiogenic cytokines vascular endothelial growth factor (VEGF), interleukin (IL)-6, IL-8, and tumor necrosis factor-α, and also inhibited angiogenesis in vitro and in vivo. Protein and mRNA microarrays revealed that FH535 downregulated the proangiogenic genes ANGPT2, VEGFR3, IFN-γ, PLAUR, THPO, TIMP1, and VEGF. FH535 not only represses pancreatic CSC stemness in vitro, but also remodels the tumor microenvironment by repressing angiogenesis, warranting further clinical investigation.

Targeting cancer stem cells in the clinic: Current status and perspectives

Resistance to chemotherapy and cancer relapse are major clinical challenges attributed to a sub population of cancer stem cells (CSCs). The concept of CSCs has been the subject of intense research by the oncology community since evidence for their existence was first published over twenty years ago. Emerging data indicates that they are also able to evade novel therapies such as targeted agents, immunotherapies and anti-angiogenics. The inability to appropriately identify and isolate CSCs is a major hindrance to the field and novel technologies are now being utilized. Agents that target CSC-associated cell surface receptors and signaling pathways have generated promising pre-clinical results and are now entering clinical trial. Here we discuss and evaluate current therapeutic strategies to target CSCs.

Current diagnostics and treatment of fibrosarcoma -perspectives for future therapeutic targets and strategies

Adult-type fibrosarcoma is a rare and highly aggressive subtype of soft tissue sarcomas. Due to the existence of other spindle-cell shaped sarcomas, its diagnosis is always one of exclusion. The likelihood of misdiagnoses between similar tumour entities is high, and often leads to inappropriate tumour treatment. We summarize here the main features of fibrosarcoma. When fibrosarcoma is appropriately diagnosed, the patient`s overall prognosis is generally quite poor. Fibrosarcoma is characterized by its low sensitivity towards radio- and chemotherapy as well as by its high rate of tumour recurrences. Thus it is important to identify new methods to improve treatment of this tumour entity. We discuss some promising new directions in fibrosarcoma research, specifically focusing on more effective targeting of the tumour microenvironment. Communication between tumour cells and their surrounding stromal tissue play a crucial role in cancer progression, invasion, metastasis and chemosensitivity. The therapeutic potential of targeting the tumour microenvironment is addressed.

Role of Pericellular Matrix in the Regulation of Cancer Stemness

Cancer stem cells (CSC) are a prominent component of the tumor bulk and extensive research has now identified them as the subpopulation responsible for tumor relapse and resistance to anti-cancer treatments. Surrounding the bulk formed of tumor cells, an extracellular matrix contributes to cancer growth; the main component of the tumor micro-environment is hyaluronan, a large disaccharide forming a molecular network surrounding the cells. The hyaluronan-dependent coat can regulate cell division and motility in cancer progression and metastasis. One of the receptors of hyaluronan is CD44, a surface protein frequently used as a CSC marker. Indeed, tumor cells with high levels of CD44 appear to exhibit CSC properties and are characterized by elevated relapse rate. The CD44-hyaluronan-dependent interactions are Janus-faced: on one side, they have been shown to be crucial in both malignancy and resistance to therapy; on the other, they represent a potential value for future therapies, as disturbing the CD44-hyaluronan axis would not only impair the pericellular matrix but also the subpopulation of self-renewing oncogenic cells. Here, we will review the key roles of HA and CD44 in CSC maintenance and propagation and will show that CSC-like spheroids from a rabdhomyosarcoma cell line, namely RD, have a prominent pericellular coat necessary for sphere formation and for elevated migration. Thus, a better understanding of the hyaluronan-CD44 interactions holds the potential for ameliorating current cancer therapies and eradicating CSC.

Evidence for circulating cancer stem-like cells and epithelial-mesenchymal transition phenotype in the pleurospheres derived from lung adenocarcinoma using liquid biopsy

Lung cancer stem cells are supposed to be the main drivers of tumor initiation, maintenance, drug resistance, and relapse of the disease. Hence, identification of the cellular and molecular aspects of these cells is a prerequisite for targeted therapy of lung cancer. Currently, analysis of circulating tumor cells has the potential to become the main diagnostic technique to monitor disease progression or therapeutic response as it is non-invasive. However, accurate detection of circulating tumor cells has remained a challenge, as epithelial cell markers used so far are not always trustworthy for detecting circulating tumor cells, especially during epithelial-mesenchymal transition. As cancer stem cells are the only culprit to initiate metastatic tumors, our aim was to isolate and characterize circulating tumor stem cells rather than circulating tumor cells from the peripheral blood of NSCLC adenocarcinoma as limited data are available addressing the gene expression profiling of lung cancer stem cells. Here, we reveal that CD44(+)/CD24(-) population in circulation not only exhibit stem cell-related genes but also possess epithelial-mesenchymal transition characteristics. In conclusion, the use of one or more cancer stem cell markers along with epithelial, mesenchymal and epithelial mesenchymal transition markers will prospectively provide the most precise assessment of the threat for recurrence and metastatic disease and has a great potential for forthcoming applications in harvesting circulating tumor stem cells and their downstream applications. Our results will aid in developing diagnostic and prognostic modalities and personalized treatment regimens like dendritic cell-based immunotherapy that can be utilized for targeting and eliminating circulating tumor stem cells, to significantly reduce the possibility of relapse and improve clinical outcomes.

Leukemic stem cells: identification and clinical application

Leukemic stem cells (LSCs) in acute myeloid leukemia (AML) represent a low-frequency subpopulation of leukemia cells that possess stem cell properties distinct from the bulk leukemia cells, including self-renewal capacity and drug resistance. Due to these properties, LSCs are supposed to facilitate the development of relapse. The existence of LSCs is demonstrated by the ability to engraft and initiate human AML in immune-compromised mouse models. Although several lines of evidence suggest the complex heterogeneity of phenotypes displayed by LSC, many studies consider the CD34+/CD38- compartment as the most relevant. To increase the understanding of the true LSC, techniques such as multicolor flow cytometry, side-population assay and ALDH assay are utilized in many laboratories and could aid in this. A better understanding of different LSC phenotypes is necessary to enhance risk group classification, guide clinical decision-making and to identify new therapeutic targets. These efforts to eliminate LSC should ultimately improve the dismal AML outcome by preventing relapse development.

Regulation of voltage-gated potassium channels attenuates resistance of side-population cells to gefitinib in the human lung cancer cell line NCI-H460

BACKGROUND

Side-population (SP) cells that exclude anti-cancer drugs have been found in various tumor cell lines. Moreover, SP cells have a higher proliferative potential and drug resistance than main population cells (Non-SP cells). Also, several ion channels are responsible for the drug resistance and proliferation of SP cells in cancer.

METHODS

To confirm the expression and function of voltage-gated potassium (Kv) channels of SP cells, these cells, as well as highly expressed ATP-binding cassette (ABC) transporters and stemness genes, were isolated from a gefitinib-resistant human lung adenocarcinoma cell line (NCI-H460), using Hoechst 33342 efflux.

RESULTS

In the present study, we found that mRNA expression of Kv channels in SP cells was different compared to Non-SP cells, and the resistance of SP cells to gefitinib was weakened with a combination treatment of gefitinib and Kv channel blockers or a Kv7 opener, compared to single-treatment gefitinib, through inhibition of the Ras-Raf signaling pathway.

CONCLUSIONS

The findings indicate that Kv channels in SP cells could be new targets for reducing the resistance to gefitinib.

E-Cadherin repression increases amount of cancer stem cells in human A549 lung adenocarcinoma and stimulates tumor growth

Here we show that cancer stem cells amount in human lung adenocarcinoma cell line A549 depends on E-cadherin expression. In fact, downregulation of E-cadherin expression enhanced expression of pluripotent genes (c-MYC, NESTIN, OCT3/4 and SOX2) and enriched cell population with the cells possessing the properties of so-called 'cancer stem cells' via activation of Wnt/β-catenin signaling. Repression of E-cadherin also stimulated cell proliferation and migration in vitro, decreased cell amount essential for xenografts formation in nude mice, increased tumors vascularization and growth. On the other hand, E-cadherin upregulation caused opposite effects i.e. diminished the number of cancer stem cells, decreased xenograft vascularization and decelerated tumor growth. Therefore, agents restoring E-cadherin expression may be useful in anticancer therapy.

Kinetic Modeling of ABCG2 Transporter Heterogeneity: A Quantitative, Single-Cell Analysis of the Side Population Assay

The side population (SP) assay, a technique used in cancer and stem cell research, assesses the activity of ABC transporters on Hoechst staining in the presence and absence of transporter inhibition, identifying SP and non-SP cell (NSP) subpopulations by differential staining intensity. The interpretation of the assay is complicated because the transporter-mediated mechanisms fail to account for cell-to-cell variability within a population or adequately control the direct role of transporter activity on staining intensity. We hypothesized that differences in dye kinetics at the single-cell level, such as ABCG2 transporter-mediated efflux and DNA binding, are responsible for the differential cell staining that demarcates SP/NSP identity. We report changes in A549 phenotype during time in culture and with TGFβ treatment that correlate with SP size. Clonal expansion of individually sorted cells re-established both SP and NSPs, indicating that SP membership is dynamic. To assess the validity of a purely kinetics-based interpretation of SP/NSP identity, we developed a computational approach that simulated cell staining within a heterogeneous cell population; this exercise allowed for the direct inference of the role of transporter activity and inhibition on cell staining. Our simulated SP assay yielded appropriate SP responses for kinetic scenarios in which high transporter activity existed in a portion of the cells and little differential staining occurred in the majority of the population. With our approach for single-cell analysis, we observed SP and NSP cells at both ends of a transporter activity continuum, demonstrating that features of transporter activity as well as DNA content are determinants of SP/NSP identity.

Downregulated expression of miRNA-149 promotes apoptosis in side population cells sorted from the TSU prostate cancer cell line

The objective of the present study was to identify prostate cancer stem cells and determine the effects of modulating specific miRNAs on prostate CSC proliferation and apoptosis. We applied flow cytometry sorting of side population cells to cultures of prostate cancer cell lines (TSU, DU145, PC-3 and LNCaP). The proportion of SP cells in the TSU line was 1.60±0.40% (mean ± SD), while that of the DU145, PC-3 and LNCaP lines was 0.60±0.05, 0.80±0.05 and 0.60±0.20%, respectively. Because the proportion of SP cells derived from TSU cells is greater, these cells were selected to sort side population cells and non-side population cells. The stem-like properties of SP cells had been identified by in vivo and in vitro experiments, and the related study was published. RNA was extracted from the SP cells and non-SP cells and analyzed using miRNA microarray technology. Fifty-three miRNAs with significant differences in their expression were detected in total. Furthermore, 20 of these miRNAs were validated by qPCR. We found that hsa-miR‑149 expression in SP cells and non-SP cells was significantly different; hsa-miR-149 was significantly upregulated in SP cells. By constructing a vector for lentiviral infection, we found that the downregulation of hsa-miR-149 leads to a reduction in proliferation, an increase in apoptosis, and a significant reduction in the colony formation potential, thus, inhibiting tumor growth in vivo of SP cells from the TSU cell line. The present study will provide new avenues toward understanding the function of prostate cancer stem cells (PCSCs) in tumorigenicity and metastasis.

Current evidence for cancer stem cells in gastrointestinal tumors and future research perspectives

Cancer stem cells (CSCs) are a very heterogeneous subpopulation of "stem-like" cancer cells that have been identified in many cancers, including leukemias and solid tumors. It is believed that CSCs drive tumor growth, malignant behavior and are responsible for the initiation of metastatic spread. In addition, CSCs have been implicated in chemotherapy and radiotherapy resistance. Current evidence supports the theory that CSCs share at least two main features of normal stem cells: self-renewal and differentiation, properties that contribute to tumor survival even in the presence of aggressive chemotherapy; however, the mechanism(s) governing the unique biology of CSCs remain unclear. In the field of gastrointestinal cancer, where we face very low survival rates across different tumor types, unraveling the role of CSCs in gastrointestinal tumors should improve our knowledge of cancer biology and chemoresistance, ultimately benefiting patient survival. Towards this end, much effort is being invested in the characterization of CSCs as a means of overcoming drug resistance and controlling metastatic spread. In this review we will cover the concept of CSCs, the current evidence for CSCs in gastrointestinal tumors and future research directions.

Induction of artificial cancer stem cells from tongue cancer cells by defined reprogramming factors

Background

The cancer stem cells (CSCs), a small subpopulation of cells in tumor are responsible for the tumor initiation, growth, recurrence and metastasis of cancer, as well as resistance of cancers to drugs or radiotherapy. CSCs are an important target for the development of novel strategies in cancer treatment. However, CSCs-targeted new anti-cancer drug discovery is currently hindered by the lack of easy and reliable methods for isolating, collecting and maintaining sufficient number of CSCs. Here, we examined whether introduction of defined reprogramming factors (Oct4, shp53, Sox2, Klf4, l-Myc and Lin28) into HSC2 tongue cancer cells could transform the HSC2 into HSC2 with CSCs properties.

Methods

We introduced the defined reprogramming factors into HSC2 tongue cancer cells via episomal vectors by electroporation method to generate transfectant cells. We investigated the malignant properties of the transfectant cells by cell proliferation assay, migration assay, wound healing assay, sphere formation assay, chemosensitivity and radiosensitivity assay in vitro; and also examined the tumorigenic potential of the transfectants in vivo.

Results

The transfectant cells (HSC2/hOCT3/4-shp53-F, HSC2/hSK, HSC2/hUL, HSC2/hOCT3/4-shp53-F + hSK, HSC2/hOCT3/4-shp53-F + hUL, HSC2/hSK + hUL, HSC2/hOCT3/4-shp53-F + hSK + hUL) displayed a malignant phenotype in culture and form tumors on the back of nude mice more efficiently than parental HSC2 and control HSC2/EGFP transfectant cells. They exhibited increased resistance to chemotherapeutic agents; 5-fluorouracil, cisplatin, docetaxel, trifluorothymidine, zoledronic acid, cetuximab, bortezomib and radiation when compared with HSC2 and HSC2/EGFP. Among all the transfected cells, HSC2/hOCT3/4-shp53-F + hSK + hUL cell containing all of the reprogramming factors showed the most aggressive and malignant properties and presented the highest number of spheres in the culture medium containing human recombinant fibroblast Growth Factor-2 (FGF-2) and epidermal Growth Factor (EGF).

Conclusion

These findings suggest that artificial cancer stem cells obtained by the induction of cellular reprogramming may be useful for investigating the acquisition of potential malignancy as well as screening the CSCs-targeting drugs.

Cancer Stem Cell Quiescence and Plasticity as Major Challenges in Cancer Therapy

Cells with stem-like properties, tumorigenic potential, and treatment-resistant phenotypes have been identified in many human malignancies. Based on the properties they share with nonneoplastic stem cells or their ability to initiate and propagate tumors in vivo, such cells were designated as cancer stem (stem-like) or tumor initiating/propagating cells. Owing to their implication in treatment resistance, cancer stem cells (CSCs) have been the subject of intense investigation in past years. Comprehension of CSCs' intrinsic properties and mechanisms they develop to survive and even enhance their aggressive phenotype within the hostile conditions of the tumor microenvironment has reoriented therapeutic strategies to fight cancer. This report provides selected examples of malignancies in which the presence of CSCs has been evidenced and briefly discusses methods to identify, isolate, and functionally characterize the CSC subpopulation of cancer cells. Relevant biological targets in CSCs, their link to treatment resistance, proposed targeting strategies, and limitations of these approaches are presented. Two major aspects of CSC physiopathology, namely, relative in vivo quiescence and plasticity in response to microenvironmental cues or treatment, are highlighted. Implications of these findings in the context of the development of new therapies are discussed.