Potential Cancer Stem Cells Research Articles

P63 sustains self-renewal of mammary cancer stem cells through regulation of Sonic Hedgehog signaling

The predominant p63 isoform, ΔNp63, is a master regulator of normal epithelial stem cell (SC) maintenance. However, in vivo evidence of the regulation of cancer stem cell (CSC) properties by p63 is still limited. Here, we exploit the transgenic MMTV-ErbB2 (v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 2) mouse model of carcinogenesis to dissect the role of p63 in the regulation of mammary CSC self-renewal and breast tumorigenesis. ErbB2 tumor cells enriched for SC-like properties display increased levels of ΔNp63 expression compared with normal mammary progenitors. Down-regulation of p63 in ErbB2 mammospheres markedly restricts self-renewal and expansion of CSCs, and this action is fully independent of p53. Furthermore, transplantation of ErbB2 progenitors expressing shRNAs against p63 into the mammary fat pads of syngeneic mice delays tumor growth in vivo. p63 knockdown in ErbB2 progenitors diminishes the expression of genes encoding components of the Sonic Hedgehog (Hh) signaling pathway, a driver of mammary SC self-renewal. Remarkably, p63 regulates the expression of Sonic Hedgehog (Shh), GLI family zinc finger 2 (Gli2), and Patched1 (Ptch1) genes by directly binding to their gene regulatory regions, and eventually contributes to pathway activation. Collectively, these studies highlight the importance of p63 in maintaining the self-renewal potential of mammary CSCs via a positive modulation of the Hh signaling pathway.

The Hippo transducer TAZ promotes epithelial to mesenchymal transition and cancer stem cell maintenance in oral cancer

The Hippo pathway has emerged as a fundamental regulator in tissue growth, organ size and stem cell functions, and tumorigenesis when deregulated. However, its roles and associated molecular mechanisms underlying oral squamous cell carcinoma (OSCC) initiation and progression remain largely unknown. Here, we identified TAZ, the downstream effector of Hippo signaling, as a novel bona fide oncogene by promoting cell proliferation, migration/invasion and chemoresistance in OSCC. TAZ promoted epithelial-to-mesenchymal transition (EMT) and also was involved in TGF-β1-induced EMT in oral cancer cells. Furthermore, enriched TAZ sustained self-renewal, maintenance, tumor-seeding potential of oral cancer stem cells (CSCs). Remarkably, enforced TAZ overexpression conferred CSCs-like properties on differentiated non-CSCs and fueled phenotypic transition from non-CSCs to CSCs-like cells. Mechanistically, TAZ-TEADs binding and subsequent transcriptional activation of EMT mediators and pluripotency factors are presumably responsible for TAZ-mediated EMT and non-CSCs-to-CSCs conversion. Importantly, aberrant TAZ overexpression was found to be associated with tumor size, pathological grade and cervical lymph node metastasis, as well as unfavorable prognosis. Pharmacological repression of TAZ by simvastatin resulted in potent anti-cancer effects against OSCC. Taken together, our findings have revealed critical links between TAZ, EMT and CSCs in OSCC initiation and progression, and also established TAZ as a novel cancer biomarker and viable druggable target for OSCC therapeutics.

Metabolism in embryonic and cancer stemness.

Cells constantly adjust their metabolic state in response to extracellular signals and nutrient availability to meet their demand for energy and building blocks. Recently, there has been significant research into the metabolic aspects of embryonic stem cells/pluripotent stem cells (ESCs/PSCs) and cancer stem cells (CSCs), which has revealed the unique metabolic status of different stem cell lineages. While ESCs and CSCs were largely thought to harbor similar metabolic states, recent evidence demonstrates that their metabolic dependency is distinctly different. The glucose metabolism of ESCs largely depends on glycolysis, including a one-carbon pathway during differentiation. While proliferating cancer cells share the glycolytic phenotype of ESCs, the mitochondria-centric oxidative phosphorylation constitutes an important metabolic circuit of CSCs under metabolic stress, indicating the dynamic nature of metabolic plasticity. In this review, we catalogued metabolic signatures of cellular "stemness" to provide insights into the therapeutic potential of ESCs and CSCs.

Brefeldin A reduces anchorage-independent survival, cancer stem cell potential and migration of MDA-MB-231 human breast cancer cells.

Cancer stem cells (CSCs) are a subset of cancer cells in tumors or established cancer cell lines that can initiate and sustain the growth of tumors in vivo. Cancer stem cells can be enriched in serum-free, suspended cultures that allow the formation of tumorspheres over several days to weeks. Brefeldin A (BFA) is a mycotoxin that induces endoplasmic reticulum (ER) stress in eukaryotic cells. We found that BFA, at sub-microgram per milliliter concentrations, preferentially induced cell death in MDA-MB-231 suspension cultures (EC50: 0.016 µg/mL) compared to adhesion cultures. BFA also effectively inhibited clonogenic activity and the migration and matrix metalloproteinases-9 (MMP-9) activity of MDA-MB-231 cells. Western blotting analysis indicated that the effects of BFA may be mediated by the down-regulation of breast CSC marker CD44 and anti-apoptotic proteins Bcl-2 and Mcl-1, as well as the reversal of epithelial-mesenchymal transition. Furthermore, BFA also displayed selective cytotoxicity toward suspended MDA-MB-468 cells, and suppressed tumorsphere formation in T47D and MDA-MB-453 cells, suggesting that BFA may be effective against breast cancer cells of various phenotypes.

Epigenetic regulation of CD271, a potential cancer stem cell marker associated with chemoresistance and metastatic capacity.

Cancer stem cells (CSCs) are considered to be the cause of tumor initiation, metastasis and recurrence. Additionally, CSCs are responsible for the failure of chemotherapy and radiotherapy. The isolation and identification of CSCs is crucial for facilitating the monitoring, therapy or prevention of cancer. We aimed to identify esophageal squamous cell carcinoma (ESCC) stem-like cells, the epigenetic mechanism and identify novel biomarkers for targeting ESCC CSCs. Sixty-three paired ESCC tissues and adjacent non-cancerous tissues were included in this study. CD271, which was identified as the CSC marker for melanoma, was assessed using quantitative PCR (qPCR). Using flow cytometry, we isolated CD271+ cells comprising 7.5% of cancer cells from the KYSE70 cell line. Sphere formation and anchorage-independent growth were analyzed in CD271+ and CD271− cancer cells, respectively. qPCR was used to detect stem-related genes and CCK-8 was performed to analyze the sensitivity to chemotherapy in the two groups. Bisulfite genomic sequencing was used to analyze the methylation status. CD271 expression was significantly higher in ESCC tissues than in adjacent non-cancerous tissues. Compared with CD271− cancer cells, CD271+ cancer cells showed a higher ability of sphere and colony formation, a high level expression of stem-related gene, and resistance to chemotherapy. The expression of CD271 was induced by a demethylation agent. In conclusion, CD271+ ESCC cells possess stem-like properties. CD271 can potentially act as a prognostic marker for ESCC, whose expression is regulated epigenetically.

Impairment of Lysosomal Activity as a Therapeutic Modality Targeting Cancer Stem Cells of Embryonal Rhabdomyosarcoma Cell Line RD

Rhabdomyosarcoma is the most frequent soft tissue sarcoma in children and adolescents, with a high rate of relapse that dramatically affects the clinical outcome. Multiagent chemotherapy, in combination with surgery and/or radiation therapy, is the treatment of choice. However, the relapse rate is disappointingly high and identification of new therapeutic tools is urgently needed. Under this respect, the selective block of key features of cancer stem cells (CSC) appears particularly promising. In this study, we isolated rhabdomyosarcoma CSC with stem-like features (high expression of NANOG and OCT3/4, self-renewal ability, multipotency). Rhabdomyosarcoma CSC showed higher invasive ability and a reduced cytotoxicity to doxorubicin in comparison to native cells, through a mechanism unrelated to the classical multidrug resistance process. This was dependent on a high level of lysosome acidity mediated by a high expression of vacuolar ATPase (V-ATPase). Since it was not associated with other paediatric cancers, like Ewing’s sarcoma and neuroblastoma, V-ATPase higher expression in CSC was rhabdomyosarcoma specific. Inhibition of lysosomal acidification by the V-ATPase inhibitor omeprazole, or by specific siRNA silencing, significantly enhanced doxorubicin cytoxicity. Unexpectedly, lysosomal targeting also blocked cell growth and reduced the invasive potential of rhabdomyosarcoma CSC, even at very low doses of omeprazole (10 and 50 µM, respectively). Based on these observations, we propose lysosome acidity as a valuable target to enhance chemosensitivity of rhabdomyosarcoma CSC, and suggest the use of anti-V-ATPase agents in combination with standard regimens as a promising tool for the eradication of minimal residual disease or the prevention of metastatic disease.

Endothelial interleukin-6 defines the tumorigenic potential of primary human cancer stem cells.

Head and neck squamous cell carcinomas (HNSCC) contain a small subpopulation of stem cells endowed with unique capacity to generate tumors. These cancer stem cells (CSC) are localized in perivascular niches and rely on crosstalk with endothelial cells for survival and self-renewal, but the mechanisms involved are unknown. Here, we report that stromal interleukin (IL)-6 defines the tumorigenic capacity of CSC sorted from primary human HNSCC and transplanted into mice. In search for the cellular source of Interleukin-6 (IL-6), we observed a direct correlation between IL-6 levels in tumor-associated endothelial cells and the tumorigenicity of CSC. In vitro, endothelial cell-IL-6 enhanced orosphere formation, p-STAT3 activation, survival, and self-renewal of human CSC. Notably, a humanized anti-IL-6R antibody (tocilizumab) inhibited primary human CSC-mediated tumor initiation. Collectively, these data demonstrate that endothelial cell-secreted IL-6 defines the tumorigenic potential of CSC, and suggest that HNSCC patients might benefit from therapeutic inhibition of IL-6/IL-6R signaling.

Curcumin inhibits breast cancer stem cell migration by amplifying the E-cadherin/β-catenin negative feedback loop

IntroductionThe existence of cancer stem cells (CSCs) has been associated with tumor initiation, therapy resistance, tumor relapse, angiogenesis, and metastasis. Curcumin, a plant ployphenol, has several anti-tumor effects and has been shown to target CSCs. Here, we aimed at evaluating (i) the mechanisms underlying the aggravated migration potential of breast CSCs (bCSCs) and (ii) the effects of curcumin in modulating the same.MethodsThe migratory behavior of MCF-7 bCSCs was assessed by using cell adhesion, spreading, transwell migration, and three-dimensional invasion assays. Stem cell characteristics were studied by using flow cytometry. The effects of curcumin on bCSCs were deciphered by cell viability assay, Western blotting, confocal microscopy, and small interfering RNA (siRNA)-mediated gene silencing. Evaluations of samples of patients with breast cancer were performed by using immunohistochemistry and flow cytometry.ResultsHere, we report that bCSCs are endowed with aggravated migration property due to the inherent suppression of the tumor suppressor, E-cadherin, which is restored by curcumin. A search for the underlying mechanism revealed that, in bCSCs, higher nuclear translocation of beta-catenin (i) decreases E-cadherin/beta-catenin complex formation and membrane retention of beta-catenin, (ii) upregulates the expression of its epithelial-mesenchymal transition (EMT)-promoting target genes (including Slug), and thereby (iii) downregulates E-cadherin transcription to subsequently promote EMT and migration of these bCSCs. In contrast, curcumin inhibits beta-catenin nuclear translocation, thus impeding trans-activation of Slug. As a consequence, E-cadherin expression is restored, thereby increasing E-cadherin/beta-catenin complex formation and cytosolic retention of more beta-catenin to finally suppress EMT and migration of bCSCs.ConclusionsCumulatively, our findings disclose that curcumin inhibits bCSC migration by amplifying E-cadherin/beta-catenin negative feedback loop.Electronic supplementary materialThe online version of this article (doi:10.1186/scrt506) contains supplementary material, which is available to authorized users.

Tumorigenic potential of cancer stem cells (CSCs) isolated from human cholangiocarcinoma (CCA) subtypes in cirrhotic liver

Tumorigenic potential of cancer stem cells (CSCs) isolated from human cholangiocarcinoma (CCA) subtypes in cirrhotic liver

Abstract 3052: Genomic, transcriptomic, and epigenomic analyses of gastric cancer stem cells

Abstract Cancer stem cells are a small population of tumor cells with self-renewal and differentiation capacity, and have been isolated from many types of cancers including stomach. However, the molecular mechanisms underlying the self-renewal and tumorigenic potential of cancer stem cells are poorly understood. To understand the molecular characteristics of gastric cancer stem cells (GCSC), we performed five kinds of experiments including genomic (Exome-seq and Affymetrix SNP 6.0 array), transcriptomic (RNA-seq and small RNA-seq), and epigenomic (MBD-seq) analyses on GCSC, non-gastric cancer stem cells (non-GCSC), and normal tissues from three gastric cancer patients. Among the five data sets, miRNA changes were most significant between GCSC and non-GCSC showing that 39.4% of miRNAs were down-regulated and 1.25% of miRNAs were up-regulated in GCSC compared with non-GCSC. In RNA-seq, 217 (0.93%) genes were up-regulated while 470 (2.02%) genes were down-regulated. Gene-set analysis revealed that development-associated biological processes such as epidermis development and ectoderm development were most enriched terms. In MBD-seq, there were 2.80% of hypermethylated and 2.38% of hypomethylated genes in GCSC compared with non-GCSC. Detailed lists of genes, gene-sets and biological pathways that distinguish GCSC from non-GCSC will be presented and discussed. Citation Format: Seon-Young Kim, Su-Jin Baek, Myoung-Eun Han, Hee-Jin Kim, Jeong-Hwan Kim, Sae-Ock Oh. Genomic, transcriptomic, and epigenomic analyses of gastric cancer stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3052. doi:10.1158/1538-7445.AM2014-3052

Mitochondrial membrane potential and reactive oxygen species in cancer stem cells.

Cancer stem cells (CSCs) are believed as the initiators of the occurrence, development and recurrence of malignant tumors. Targeting this unique cell population would provide a less toxic approach than regular chemotherapeutic agents that kill bulk rapid proliferating tumor cells and also normal cells which divide rapidly. To date, major research effort has been aimed at identifying and eradicating CSC population. The metabolism heterogeneity of mitochondria in CSCs shows a big promise for cancer research. Of them, mitochondrial membrane potential (Δψm), reflecting the functional status of the mitochondrion is proved to be highly related to cancer malignancy. Reactive oxygen species, mainly produced from mitochondria, are also increased in many types of cancer cells. However, their statuses in CSCs remain poorly understood. Here we shall review the mitochondrial membrane potential and reactive oxygen species of CSCs and propose the novel potential targets for cancer therapy.

Abstract 1940: Short (S) isoform of cancer-stem-cell marker, DCLK1, is critically required to maintain proliferative/tumorigenic potential of colon cancer cells: identification of associated molecular pathways

Abstract DCLK1 (doublecortin-like-kinase-1) was recently identified as a specific marker for intestinal cancer-stem-cells (CSC) (Sureban et al, 2013; Nakanishi et al, 2013). Importantly, DCLK1 expression is significantly increased during colon-carcinogenesis (Gagliardi et al, 2012). We recently reported that 2 isoforms of DCLK1 (DCLK1-L/DCLK1-S) are transcribed by two different promoters (5′ and intron V), and that the L isoform (∼80KDa) is silenced by DNA methylation in human colon-adenocarcinomas, while the S-isoform (∼47KDa) is up-regulated by many fold in tumors; normal colonic cells mainly express the L-isoform (∼80KDa). Loss of DCLK1 expression in cancer cells/polyps was reported to result in loss of proliferation/polyp formation (Sureban et al 2011; Nakanishi et al, 2013). RNAi methods used so far, target both isoforms of DCLK1. In the current studies we used shRNA to specifically target S-isoform, in order to delineate biological role of cancer-specific S-isoform. Isogenic clones of colon cancer cells, expressing control shRNA (C-clones) or DCLK1-shRNA (KO clones), were generated. Western Blot analysis and RT-PCR analysis confirmed 80-90% knockdown compared to C-clones. Proliferation and Colonogenic/tumorigenic potential of KO clones was completely attenuated compared to C-clones, in vitro and in vivo. Our results confirmed that DCLK1-S is required for maintaining proliferative/tumorigenic potential of colon CSCs. Surprisingly, KO clones did not form spheroids in non-adherent cultures, while the C-clones formed spheroids within 4-6 days of seeding, suggesting DCLK1 may maintain stemness of colon cancer cells. To evaluate molecular pathways mediating effects of DCLK1-S, isogenic C and KO clones were subjected to next generation sequencing (RNAseq). 12 genes were up-regulated and 14 genes were down-regulated in KO vs C clones by >3fold; several others were changed by >1fold. Key genes involved in mitosis, EMT, cell adhesion, caspase-independent apoptosis, metabolism, and toll-like receptor signaling, were significantly down/up-regulated confirming that the S-isoform plays a critical role in CSC biology, by either directly or indirectly regulating several molecular pathways which likely support CSC phenotype. Conclusion. Our results show DCLK1-S is critically required for maintaining invasive/tumorigenic potential of colon cancer cells by directly or indirectly regulating several molecular pathways involved in maintaining non-differentiated/tumorigenic phenotype of CSCs. Thus DCLK1-S may serve as a diagnostic/prognostic marker and provide a useful cancer-specific target for eradicating colon CSCs. This work was supported by NIH Grants to PS (R01CA09795909 and R01CA09795909-S1) Citation Format: Malaney R. O'Connell, Shubhashish Sarkar, Pomila Singh. Short (S) isoform of cancer-stem-cell marker, DCLK1, is critically required to maintain proliferative/tumorigenic potential of colon cancer cells: identification of associated molecular pathways. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1940. doi:10.1158/1538-7445.AM2014-1940

Abstract 3476: Profiling CD antigens signature in human hepatocellular carcinoma (HCC) by cell-based high-throughput screening flow cytometry (HTS-FC)

Abstract Accumulating evidence supports the cancer stem cell (CSC) hypothesis, which posits that CSCs are the source of many solid tumor types including hepatocellular carcinoma (HCC). In HCC, CSCs have been identified by a variety of CD antigens, including CD133, CD326 (EpCAM), CD90, CD44, CD24, CD13, which could serve as potential therapeutic targets. However, due to the heterogeneity of HCC, these markers do not account for CSC activity in all tumors, and there is thus a need to identify novel HCC CSC markers. We have developed a cell-based high-throughput screening flow cytometry (HTS-FC) platform to robustly characterize expression profiles of CD antigens on primary human HCC cells. We titrated all commercial fluorescence conjugated CD antibodies (CD1 to CD363) into four 96-well microplates, isolated and stained HCC cells with CD45 antibody then divided and incubated these cells with different CD antibodies in microplates (1X10^5 cells/well) followed by a LIVE/DEAD® reactive dye treatment. Stained plates were fixed and subjected to BD™ LSR II flow cytometry using High Throughput Sampler Unit. Each CD antigen expression percentage was analyzed within the CD45 negative subpopulation by FlowJo software. After investigating 10 HCC tumors, we performed heat-map and cluster analysis using Multi Experiment Viewer software. Our analysis of primary human HCC cells demonstrated that previously identified index markers of HCC CSC are expressed on a highly variable fraction of tumor cells as follows: CD13 (76.10 ± 8.72%), CD24 (7.79 ± 5.33%), CD90 (5.29 ± 0.84%), EpCAM (0.50 ± 0.46%), CD44 (0.041 ± 0.019%) and CD133 (0.0051 ± 0.0034%). Based on the heat-map, we classified all CD markers into five groups: 20 CD13-like high expressions (30%∼100%), 12 median expressions (10%∼30%), 32 CD90-like low expressions (1.0%∼10%), 60 EpCAM-like rare expressions (0.03%∼1.0%) and 249 nonsense expressions. We focused on the CD90- and EpCAM-like groups (92 CD candidates) for novel potential CSC markers. Using quantitative real-time RT-PCR, we determined the mRNA level of 92 antigens in reference to the EpCAM+/CD133+ CSC subpopulations sorted from 4 human HCC cell lines (HepG2, Hep3B, PLC/PRF/5 and Huh7) and identified 20% of these 92 candidates with stem/progenitor mRNA phenotype. We then measured the mRNA level of these remaining candidates in 40 pairs of primary human HCC tumor/adjacent normal tissues and identified two novel CD antigens showing high tumor specificity. We are now purifying these cells from primary HCC tumors in order to determine whether these small populations identify cells with CSC activity in xenograft models and sphere-forming assays. These studies demonstrate that cell-based high-throughput screening flow cytometry screening can be used in combination with other cell/molecular biological techniques to identify novel populations of tumor cells with unique functional characteristics. Citation Format: Kui Chen, Laurie Ailles, John E. Dick, Anand Ghanekar. Profiling CD antigens signature in human hepatocellular carcinoma (HCC) by cell-based high-throughput screening flow cytometry (HTS-FC). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3476. doi:10.1158/1538-7445.AM2014-3476

MYC activates stem-like cell potential in hepatocarcinoma by a p53-dependent mechanism.

Activation of c-MYC is an oncogenic hallmark of many cancers, including liver cancer, and is associated with a variety of adverse prognostic characteristics. Despite a causative role during malignant transformation and progression in hepatocarcinogenesis, consequences of c-MYC activation for the biology of hepatic cancer stem cells (CSC) are undefined. Here, distinct levels of c-MYC overexpression were established by using two dose-dependent tetracycline-inducible systems in four hepatoma cell lines with different p53 mutational status. The CSCs were evaluated using side population (SP) approach as well as standard in vitro and in vivo assays. Functional repression of p53 was achieved by lentiviral shRNA transduction. The results show that c-MYC expression levels have a differential impact on liver CSC characteristics. At low levels, c-MYC activation led to increased proliferation and enhanced CSC properties including activation of reprogramming transcription factors and CSC marker expression (e.g., NANOG, OCT4, and EpCAM), expansion of SP, and acceleration of tumor growth upon subcutaneous transplantation into immunocompromised mice. However, when exceeding a threshold level, c-MYC induced a proapoptotic program and loss of CSC potential both in vitro and in vivo. Mechanistically, c-MYC-induced self-renewal capacity of liver cancer cells was exerted in a p53-dependent manner. Low c-MYC activation increased spheroid formation in p53-deficient tumor cells, whereas p53-dependent effects were blunted in the absence of c-MYC overexpression. Together, our results confirm the role of c-MYC as a master regulator during hepatocarcinogenesis and establish a new gatekeeper role for p53 in repressing c-MYC-induced CSC phenotype in liver cancer cells.

Chloroquine eliminates cancer stem cells through deregulation of Jak2 and DNMT1.

Triple negative breast cancer (TNBC) is known to contain a high percentage of CD44(+) /CD24(-/low) cancer stem cells (CSCs), corresponding with a poor prognosis despite systemic chemotherapy. Chloroquine (CQ), an antimalarial drug, is a lysotropic reagent which inhibits autophagy. CQ was identified as a potential CSC inhibitor through in silico gene expression signature analysis of the CD44(+) /CD24(-/low) CSC population. Autophagy plays a critical role in adaptation to stress conditions in cancer cells, and is related with drug resistance and CSC maintenance. Thus, the objectives of this study were to examine the potential enhanced efficacy arising from addition of CQ to standard chemotherapy (paclitaxel) in TNBC and to identify the mechanism by which CQ eliminates CSCs in TNBCs. Herein, we report that CQ sensitizes TNBC cells to paclitaxel through inhibition of autophagy and reduces the CD44(+) /CD24(-/low) CSC population in both preclinical and clinical settings. Also, we are the first to report a mechanism by which CQ regulates the CSCs in TNBC through inhibition of the Janus-activated kinase 2 (Jak2)-signal transducer and activator of transcription 3 signaling pathway by reducing the expression of Jak2 and DNA methyltransferase 1.

The prognostic value of CD133 expression in non-small cell lung cancer: a meta-analysis.

CD133 has been identified as a potential cancer stem cell (CSC) marker in non-small cell lung cancer (NSCLC). However, the clinical and prognostic significance of CD133 in NSCLC remains controversial. In this study, a meta-analysis with a total number of 13 studies was performed to clarify the association between CD133 expression and clinical outcomes in publications up to June 2013. Odds ratios (ORs) and their 95 % confidence intervals (CIs) were used to assess the association between CD133 expression and the clinicopathological characteristics of NSCLC. Hazard ratios (HRs) and their 95 % CI were used to quantify the predictive ability of CD133 on NSCLC prognosis. Analysis of these data showed that CD133 expression was not associated with any clinicopathological parameters except for histology (pooled OR = 1.35, 95%CI = 1.04-1.76, P = 0.024) and tumor differentiation (pooled OR = 3.19, 95%CI = 1.10-9.21, P = 0.032). Simultaneously, we also found that positive CD133 expression was not associated with disease-free survival (DFS) (pooled HR = 1.76, 95 % CI = 0.87-3.57, P = 0.114, random-effect) but was associated with overall survival (OS) (pooled HR = 2.06, 95 % CI = 1.08-3.91, P = 0.027, random-effect). Overall, it is appropriate to regard CD133 expression as a potential prognostic factor for the OS of NSCLC patients.

Combination of Sasa quelpaertensis Nakai leaf extract and cisplatin suppresses the cancer stemness and invasion of human lung cancer cells.

Lung cancer is the leading cause of cancer death worldwide, and most chemotherapeutic drugs have limited success in treating this disease. Furthermore, some drugs show undesirable side effects due to the enrichment of cancer stem cells (CSCs) that are present, leading to resistance to conventional chemotherapy and tumor relapse. CSCs possess self-renewal characteristics, aggressive tumor initiating activity, and ability to facilitate tumor metastasis. Therefore, development of nontoxic agents that can potentiate chemotherapy and eliminate CSCs would be highly desirable. In the present study, we investigated whether Sasa quelpaertensis leaf extracts (SQE) and cisplatin (CIS), individually or in combination, would exert anti-CSC and antimetastatic effect in H1299 and A549 human lung cancer cells. Following these treatments, cell growth, phosphorylation of phosphoinositide-3 kinase, and activation of the mammalian target of rapamycin were inhibited. Decreased serial sphere formation, clonogenicity, and expression of major stem cell markers, such as CD44 and SOX-2, in CD44(+) cancer stem cells were also observed. In addition, inhibition of cell migration and invasion in both cell lines as well as inhibition of matrix metalloproteinase-2 activity and expression were detected. Importantly, the anticancer stemness and antimetastasis effects in each of these assays were greater for the combined treatment with SQE and CIS than with each treatment individually. In conclusion, the data suggest that SQE alone, or in combination with CIS, represents a promising therapeutic strategy for eliminating cancer stemness and cell invasion potential of CSCs, thereby treating and preventing metastatic lung cancer cells.

Tumorigenic potential of cancer stem cells (CSCs) isolated from human cholangiocarcinoma (CCA) subtypes

Two different forms of CCA have been recently considered. A pure mucin-secreting form (Mucin-CCA) located either intra or extra-hepatically and a Mixed-CCA form with a peripheral location in the liver. We previously identified different subpopulations of CSCs in both Mucin- and Mixed-CCA, including epithelial (CD133+, LGR5+, EpCAM+), mesenchymal (CD90+) and quiescent (CD13+) CSCs. Aim: To evaluate the tumorigenic potential of different subpopulation of CSCs isolated from human Mucin- and Mixed-CCA. Methods: CSC subpopulations were immunoselected from human CCA samples (n = 18 surgically resected patients) and from primary cultures of human CCAs. The tumorigenic potential of CSC subpopulations was tested either in vitro (spheroid formation) or in vivo in xenographted tumors in mice after subcutaneous or intrahepatic injection in normal or cirrhotic (CCL4-induced) livers. In vitro, epithelial CSCs (CD133+, EpCAM+, LGR5+) formed a higher (p < 0.01) number of spheroids with respect to mesenchymal (CD90+) or quiescent (CD13+) CSCs. By comparing Mixed and Mucin-CCA, CD13+ cells immunoselected from IH-mixed and CD90+ or CD133+ cells from Mucin-CCA formed the highest number of spheroids. In subcutaneous tumor xenographts, cancers with a large predominance of stromal markers (desmin, vimentin and α-SMA) were formed by mesenchymal (CD90+), quiescent (CD13+) or epithelial (CD133+) CSCs, while EpCAM+ and LGR5+ only rarely formed tumor xenographts. In intrahepatic xenographts, in contrast, cancers with predominance of epithelial features were formed. Remarkably, injection of CD133+ cells in the cirrhotic liver reproduced the pure Mucin-CCA while CD90+ CSCs formed an undifferentiated CCA. In conclusion, heterogeneous CSC subpopulations were represented in human CCA. They generate different type of cancers depending from the type of CSC and the microenvironment. Remarkably, we identified a single CSC subpopulation capable to reproduce human Mucin-CCA (CD133+) or undifferentiated CCA (CD90+) when injected in the cirrhotic livers.

Highlights of This Issue

Inflammation has long been associated with cancer, and angiopoietin-like protein 2 (ANGPTL2) is known to facilitate inflammatory carcinogenesis and metastasis. In a transgenic mouse model, angptl2-associated inflammation was shown to promote production of reactive oxygen species (ROS), significantly accelerate methylation of the DNA mismatch repair enzyme Msh2 promoter, and decrease expression of Msh2 mRNA, resulting in impaired DNA repair mechanisms. Angptl2 accelerates susceptibility to both “preneoplastic change” and “malignant conversion” due to accumulation of oncogenic DNA mutations, activating chronic inflammation and oxidative stress in the premalignant tissue microenvironment. These findings suggest that Angptl2-induced inflammation increases susceptibility to microenvironmental changes, allowing accumulation of oncogenic DNA mutations.From the multitude of contributing factors implicated in prostate cancer, age and family history rank among the highest. However, despite a number of genetic loci linked to hereditary prostate cancer, no bona fide susceptibility gene has been identified. In the Rapid Impact article for this issue, Labbé and colleagues report on their study of the 20q13 chromosomal region, which had been previously identified as a hereditary prostate cancer susceptibility locus (HPC20) and is now shown in their study to be frequently coamplified with the androgen receptor (AR) in metastatic prostate cancer. High-resolution mapping uncovered AR recruitment hotspots in the 20q13 region. These findings reveal that AR, a primary driver of disease progression, is intimately involved in gene transcription of a known prostate susceptibility locus.The overexpression of miR-221 is a common event in human cancers, with growing evidence supporting its causative role. In this study, Fornari and colleagues identify for the first time the MDM2 oncogene as a direct target of an oncomicroRNA such as miR-221 in cancer tissue. A feed-forward loop sustaining miR-221 aberrant expression was revealed in which miR-221 activates the p53/MDM2 axis by inhibiting MDM2 and, in turn, p53 activation contributes to miR-221 enhanced expression. Moreover, by modulating p53 signaling, miR-221 affects cell-cycle progression and apoptotic response to doxorubicin in hepatocellular carcinoma (HCC)–derived cells, suggesting that miR-221 expression contributes to p53 context-specific response to doxorubicin treatment in HCC.Little is known about tumor initiating cells in oligodendrogliomas, impeding investigation of critical signaling pathways that could be exploited by targeted therapies. Srikanth and colleagues demonstrate that cells with stem-like characteristics are capable of propagating human oligodendrogliomas. Canonical bone morphogenetic protein (BMP) signaling is intact in these cells and potently diminishes their stemness by inducing astrocytic differentiation. Further analyses revealed sequestration of oligodendrocyte differentiation factors OLIG1/2 by BMP-induced ID proteins as a plausible mechanism. These findings elucidate the molecular pathways underlying the effects of BMP signaling on oligodendroglioma stem-like cells and suggest BMP activation as a potential cancer stem cell–targeted therapy in these tumors.

Implications of cancer stem cells in radiotherapy current understanding and future perspectives

Many theories were put forward about origin of cancer and immense research was carried out to understand the mechanisms involved in the origin and progression of the disease. The gain in scientific knowledge about cancer biology and technical advancement in treatment modalities resulted in improvement of clinical outcome in cancer therapy. However, recurrence and metastasis after therapy poses a major concern to clinicians. Resistant nature against therapeutic modalities and metastatic potential of cancer stem cells (CSCs), which even though form a fraction of tumor mass, result in failure of existing modalities of cancer treatment. The current article reviews the historical background of CSCs, involvement of various signaling pathways in the mechanism(s) of radioresistance and potential targets to be exploited in radiotherapy.