Cancer Stem Cell-like Phenotype Research Articles

Ovatodiolide sensitizes aggressive breast cancer cells to doxorubicin, eliminates their cancer stem cell-like phenotype, and reduces doxorubicin-associated toxicity

Triple-negative breast cancer (TNBC) is chemotherapy–refractory and associated with poor clinical prognosis. Doxorubicin (Doxo), a class I anthracycline and first-line anticancer agent, effective against a wide spectrum of neoplasms including breast carcinoma, is associated with several cumulative dose-dependent adverse effects, including cardiomyopathy, typhilitis, and acute myelotoxicity. This study evaluated the usability of Ovatodiolide (Ova) in sensitizing TNBC cells to Doxo cytotoxicity, so as to reduce Doxo effective dose and consequently its adverse effects. TNBC cell lines MDA-MB-231 and HS578T were used. Pre-treatment of the TNBC cells with 10 µM Ova 24 h before Doxo administration increased the Doxo anticancer effect (IC50 1.4 µM) compared to simultaneous treatment with Doxo ( IC50 1.8 µM), or Doxo alone (IC50 9.2 µM). Intracellular accumulation of Doxo was lowest in Ova pre-treated cells at all Doxo concentrations, when compared with Doxo or simultaneously treated cells. In comparison to the Doxo-only group, cell cycle analysis of MDA-MB-231 cells treated concurrently with 2.5 µM Ova and 1.25 µM Doxo showed increased percentage of cells arrested at G0/G1; however, pre-treatment with the same concentration of Ova 24 h before Doxo showed greater tumor growth inhibition, with a 2.4-fold increased percentage of cells in G0/G1 arrest, greater Doxo-induced apoptosis, and significantly reduced intracellular Doxo accumulation. Additionally, Ova-sensitized TNBC cells also lost their cancer stem cell-like phenotype evidenced by significant dissolution, necrosis of formed mammospheres. Taken together, these findings indicate that Ova sensitizes TNBC cells to Doxo and potentiates doxorubicin-induced elimination of the TNBC cancer stem cell-like phenotype.

Abstract P2-07-07: Prostaglandin E receptor 2 (EP2) regulates breast cancer stem-cell like property and promotes epithelial-mesenchymal transition

Abstract Background: Presence of cancer stem-like cells (CSCs) is the main obstacle for poor treatment response and mortality in breast cancer patients. Prostaglandin E receptors have been reported to play a role in epithelial-mesenchymal transition (EMT) and metastasis, however, the contribution on cancer stem cell compartment remains unstudied. Methods: Human xenograft breast cancer model was used to study the expression of EP receptors during cancer development. Construction of stable EP2-expression cells was used to study tumorigenesis and characterization of EP2 receptor. Functional role of EP2 receptor on cell proliferation, flow cyometry, invasion and EMT gene expression array were performed in transfected cells. Expression of EP2 receptor was compared in primary tumor tissues by immunostaining and real-time PCR. Results: EP2 receptor was predominantly expressed in animal tissues during cancer development, as well as in human primary tumor tissues. In mouse xenograft model, MB-231-EP2 clone developed a more aggressive tumor with a larger tumor size and showed a significant increase in cancer stem cell marker aldehyde hydrogenase (ALDH1) expression. In vitro study, MB-231-EP2 clone increased colony formation capacity and S-phase entry by the regulation of E-cadherin, TWIST1 and ALDH1. Importantly, we found that Twist1 expression level was higher in breast cancer patients than healthy controls and was associated with ALDH1 expression. Conclusions: These findings implicated that EP2 receptor was crucial to nurture CSC phenotype and promote tumorigenesis in breast cancer. Blocking of EP2 might be a potential therapeutic strategy to improve treatment response for breast cancer patients. Citation Format: Vivian Y Shin, Man T Siu, John C Ho, Isabella Cheuk, Jiawei Chen, Ava Kwong. Prostaglandin E receptor 2 (EP2) regulates breast cancer stem-cell like property and promotes epithelial-mesenchymal transition [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-07-07.

MP19-01 FUNCTIONAL ANALYSIS OF CANCER STEM-LIKE CELLS BY A NOVEL HSP40 FAMILY MEMBER PROTEIN

INTRODUCTION AND OBJECTIVES: Cancer stem-like cells (CSCs) are small population of cancer cells with superior tumor initating, seilf-renewel, and differentiation properties. In the previous study, we found that HSP40 family member DNAJB8 contributes to the CSC phenotype in renal cell carcinoma(RCC). HSF1 has been described to induce heat shock proteins by heat shock stress and be related to initiation and progression of cancer. In this study, we investigated the relations of HSF1 and CSC phenotype including DNAJB8. METHODS: RCC cell lines ACHN was given heat shock by incubating in 45 degrees for 60 minutes. HSF1 and DNAJB8 expression was evaluated by RT-PCR and Western blot analysis. CSCs were isolated by side population method by flowcytometry. SP(side population) cells mean CSCs, MP(main population) cells mean non-CSCs. As an inhibitor of HSF1, temsirolimus (mTOR inhibitor) was used. The cell viability was assessed by MTT assay. RESULTS: Heat shock stress enhanced the expression of DNAJB8 as well as SOX2. The expression of these molecules reached maximum 24 hours after heat shock, and the SP population increased at the same time. When MP cells sorted by flowcytometry were stimulated by heat shock, SP population could be newly detected. This fact implies that heat shock stress could induce the reversion from MP cells to SP cells. Concerning the mechanism of the reversion from MP cells to SP cells by heat shock, HSF1 seems to play an important role. We found that the expression of phosphorylated HSF1 increased by heat shock, although the expression level of HSF1 itself did not change. Interestingly, when HSF1 was knocked down by siRNA, DNAJB8 could not be induced even after heat shock stress. This suggests that the stress-inducible expression of DNAJB8 is regulated by HSF1, which bind to the heat shock element(HSE) in the promoter of DNAJB8 gene and stimulate its transcription. Treatment with temsirolimus to ACHN cells could inhibit phosphorylation of HSF1, followed by down regulation of DNAJB8, resulting in the decrease of SP population. SP cells were more susceptible by temsilolimus treatment than MP cells. CONCLUSIONS: Stress including heat shock such as hyperthermia might induce DNAJB8 expression, which is related to CSC phenotype. Phosphorylation of HSF1 is required in this process. mTOR inhibitor could inhibit CSC specifically by inhibiting phosphorylation of HSF1.

Osteopontin promotes a cancer stem cell-like phenotype in hepatocellular carcinoma cells via an integrin-NF-κB-HIF-1α pathway.

There is increasing evidence to suggest that hepatocellular carcinomas (HCCs) are sustained by a distinct subpopulation of self-renewing cells known as cancer stem cells. However, the precise signals required for maintenance of stemness-like properties of these cells are yet to be elucidated. Here, we demonstrated that the level of oncoprotein osteopontin (OPN) in tumor cells of the edge of bulk tumors was significantly correlated with the clinical prognosis of patients with HCC. OPN was highly expressed in side population fractions of HCC cell lines, as well as in dormant cells, spheroids and chemo-resistant cancer cells, all of which are considered as having stemness-like cellular features. Depletion of OPN in HCC cell lines resulted in a reduction in the proportion of side population fractions, formation of hepato-spheroids, expression of stem-cell-associated genes and decreased tumorigenecity in immunodeficient mice. Mechanistically, OPN was demonstrated to bind to integrin αvβ3 and activate the transcription factor NF-κB, which resulted in upregulation of HIF-1α transcription and its downstream gene, BMI1, to mediate maintenance of the stemness-like phenotype. Suppression of the αvβ3-NF-κB-HIF-1α pathway decreased OPN-mediated self-renewal capabilities. Levels of OPN protein expression were significantly correlated with HIF-1α protein levels in HCC tumor tissue samples. OPN might promote a cancer stem cell-like phenotype via the αvβ3-NF-κB-HIF-1α pathway. Our findings offer strong support for OPN requirement in maintaining stem-like properties in HCC cells.

Cancer stem cell-like phenotype and survival are coordinately regulated by Akt/FoxO/Bim pathway.

Many solid tumors contain a subpopulation of cells with stem characteristics and these are known as cancer stem cells (CSCs) or tumor-initiating cells (TICs). These cells drive tumor growth and appear to be regulated by molecular pathway different from other cells in the tumor bulk. Here, we set out to determine whether elements of the PI3K-AKT pathway are necessary to maintain the CSC-like phenotype in breast tumor cells and for these cells to survive, bearing in mind that the identification of such elements is likely to be relevant to define future therapeutic targets. Our results demonstrate a close relationship between the maintenance of the CSC-like phenotype and the survival of these TICs. Inhibiting PI3K activity, or eliminating AKT activity, mostly that of the AKT1 isoform, produces a clear drop in TICs survival, and a reduction in the generation and growth of CD44(High) /CD24(Low) mammospheres. Surprisingly, the apoptosis of these TICs that is triggered by AKT1 deficiency is also associated with a loss of the stem cell/mesenchymal phenotype and a recovery of epithelial-like markers. Finally, we define downstream effectors that are responsible for controlling the CSC-phenotype, such as FoxO-Bim, and the death of these cells in the absence of AKT1. In summary, these data closely link the maintenance of the stem cell-like phenotype and the survival of these cells to the AKT-FoxO-Bim pathway.

Antithetical NFATc1-Sox2 and p53-miR200 signaling networks govern pancreatic cancer cell plasticity.

In adaptation to oncogenic signals, pancreatic ductal adenocarcinoma (PDAC) cells undergo epithelial-mesenchymal transition (EMT), a process combining tumor cell dedifferentiation with acquisition of stemness features. However, the mechanisms linking oncogene-induced signaling pathways with EMT and stemness remain largely elusive. Here, we uncover the inflammation-induced transcription factor NFATc1 as a central regulator of pancreatic cancer cell plasticity. In particular, we show that NFATc1 drives EMT reprogramming and maintains pancreatic cancer cells in a stem cell-like state through Sox2-dependent transcription of EMTand stemness factors. Intriguingly, NFATc1-Sox2 complex-mediated PDAC dedifferentiation and progression is opposed by antithetical p53-miR200c signaling, and inactivation of the tumor suppressor pathway is essential for tumor dedifferentiation and dissemination both in genetically engineered mouse models (GEMM) and human PDAC. Based on these findings, we propose the existence of a hierarchical signaling network regulating PDAC cell plasticity and suggest that the molecular decision between epithelial cell preservation and conversion into a dedifferentiated cancer stem cell-like phenotype depends on opposing levels of p53 and NFATc1 signaling activities.

Fucosylation is a common glycosylation type in pancreatic cancer stem cell-like phenotypes.

To evaluate/isolate cancer stem cells (CSCs) from tissue or cell lines according to various definitions and cell surface markers. Lectin microarray analysis was conducted on CSC-like fractions of the human pancreatic cancer cell line Panc1 by establishing anti-cancer drug-resistant cells. Changes in glycan structure of CSC-like cells were also investigated in sphere-forming cells as well as in CSC fractions obtained from overexpression of CD24 and CD44. Several types of fucosylation were increased under these conditions, and the expression of fucosylation regulatory genes such as fucosyltransferases, GDP-fucose synthetic enzymes, and GDP-fucose transporters were dramatically enhanced in CSC-like cells. These changes were significant in gemcitabine-resistant cells and sphere cells of a human pancreatic cancer cell line, Panc1. However, downregulation of cellular fucosylation by knockdown of the GDP-fucose transporter did not alter gemcitabine resistance, indicating that increased cellular fucosylation is a result of CSC-like transformation. Fucosylation might be a biomarker of CSC-like cells in pancreatic cancer.

Reduction of miR-29c enhances pancreatic cancer cell migration and stem cell-like phenotype.

The hallmarks of pancreatic cancer are limitless replicative potential as well as tissue invasion and metastasis, leading to an extremely aggressive disease with shockingly high lethality. However, the molecular mechanisms underlying these characteristics remain largely unclear. Herein, we report the results of a differential miRNA expression screen that compared pancreatic cancer tissues and normal pancreatic tissues, where the pancreatic cancer tissues had highly downregulated miR-29c with relative Wnt cascade hyperactivation. MiR-29c directly suppressed the following Wnt upstream regulators: frequently rearranged in advanced T-cell lymphomas 2 (FRAT2), low-density lipoprotein receptor-related protein 6 (LRP6), Frizzled-4 (FZD4) and Frizzled-5 (FZD5). Furthermore, transforming growth factor-β (TGF-β) inhibited miR-29c expression, leading to Wnt activation. Significantly, our results were consistent with an important correlation between miR-29c levels and TGF-β hyperactivation and the activated Wnt cascade in human pancreatic cancer specimens. These findings reveal a novel mechanism for Wnt hyperactivation in pancreatic cancer and may suggest a new target for clinical intervention in pancreatic cancer.

Divergent roles of CXCR3 isoforms in promoting cancer stem-like cell survival and metastasis.

There is growing evidence that several chemokine receptors including CXCR3 contribute to metastasis of breast and other cancers, however, in order to target CXCR3 effectively, it is critical to understand the relative contribution of each CXCR3 isoform. Furthermore, the possible contribution of either major CXCR3 isoform (CXCR3-A, CXCR3-B) to cancer stem cell behavior has not been reported. We employed primary invasive ductal carcinomas, a panel of breast cell lines, and a xenograft model of metastatic breast cancer to examine the role of CXCR3 isoforms in the behavior of breast cancer stem-like cells and the contribution of each isoform to metastasis. In primary human breast cancer specimens as well as established breast cancer cell lines, CXCR3-A is more highly expressed than CXCR3-B. Conversely, immortalized normal MCF10A cells express more CXCR3-B relative to CXCR3-A. Overexpression of CXCR3-B in MDA-MB-231 basal-like cells inhibits CXCR3 ligand-stimulated proliferation, which is accompanied by reduced ligand-mediated activation of ERK1/2 and p38 kinases. Likewise, metastatic capacity is reduced in vivo by higher levels of CXCR3-B, and migratory and invasive properties are inhibited in vitro; conversely, silencing of CXCR3-B enhances lung colonization. In contrast to the anti-metastatic and anti-proliferative roles of CXCR3-B in the non-stem cell population, this isoform supports a cancer stem-like cell phenotype. CXCR3-B is markedly elevated in mammosphere-forming parental cells and overexpressing CXCR3-B further enhances mammosphere-forming potential as well as growth in soft agar; stem-like behavior is inhibited in MDA-MB-231shCXCR3-B cells. Targeting of both CXCR3 isoforms may be important to block the stem cell-promoting actions of CXCR3-B, while inhibiting the pro-proliferative and metastasis-promoting functions of CXCR3-A.

Anchorage-dependent multicellular aggregate formation induces CD44 high cancer stem cell-like ATL cells in an NF-κB- and vimentin-dependent manner

Adult T-cell leukemia/lymphoma (ATL) is an intractable T-cell malignancy accompanied by massive invasion of lymphoma cells into various tissues. We demonstrate here that ATL cells cultured on a layer of epithelial-like feeder cells form anchorage-dependent multicellular aggregates (Ad-MCAs) and that a fraction of MCA-forming ATL cells acquire CD44 high cancer stem cell-like phenotypes. ATL cells forming Ad-MCAs displayed extracellular microvesicles with enhanced expression of CD44v9 at cell synapses, augmented expression of multidrug resistance protein 1, and increased NF-κB activity. Blockade of the NF-κB pathway dramatically reduced Ad-MCA formation by ATL cells and the emergence of CD44 high ATL cells, but left a considerable number of ATL cells adhering to the feeder layer. Disruption of vimentin cytoskeleton by treatment with withaferin A, a natural steroidal lactone, suppressed not only the adhesion of ATL cells to the feeder layer but also subsequent Ad-MCA formation by ATL cells, suggesting the involvement of vimentin in anchoring ATL cells to the feeder layer. Ad-MCA formation by ATL cells on a layer of epithelial-like feeder cells may mimic critical events that occur in metastatic colonization.

Nitric oxide induces cancer stem cell-like phenotypes in human lung cancer cells.

Even though tremendous advances have been made in the treatment of cancers during the past decades, the success rate among patients with cancer is still dismal, largely because of problems associated with chemo/radioresistance and relapse. Emerging evidence has indicated that cancer stem cells (CSCs) are behind the resistance and recurrence problems, but our understanding of their regulation is limited. Rapid reversible changes of CSC-like cells within tumors may result from the effect of biological mediators found in the tumor microenvironment. Here we show how nitric oxide (NO), a key cellular modulator whose level is elevated in many tumors, affects CSC-like phenotypes of human non-small cell lung carcinoma H292 and H460 cells. Exposure of NO gradually altered the cell morphology toward mesenchymal stem-like shape. NO exposure promoted CSC-like phenotype, indicated by increased expression of known CSC markers, CD133 and ALDH1A1, in the exposed cells. These effects of NO on stemness were reversible after cessation of the NO treatment for 7 days. Furthermore, such effect was reproducible using another NO donor, S-nitroso-N-acetylpenicillamine. Importantly, inhibition of NO by the known NO scavenger 2-(4-carboxy-phenyl)-4,4,5,5 tetramethylimidazoline-1-oxy-3-oxide strongly inhibited CSC-like aggressive cellular behavior and marker expression. Last, we unveiled the underlying mechanism of NO action through the activation of caveolin-1 (Cav-1), which is upregulated by NO and is responsible for the aggressive behavior of the cells, including anoikis resistance, anchorage-independent cell growth, and increased cell migration and invasion. These findings indicate a novel role of NO in CSC regulation and its importance in aggressive cancer behaviors through Cav-1 upregulation.

Ectopic expression of embryonic stem cell and other developmental genes in cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is a potentially devastating malignancy. The pathogenesis of this cancer remains poorly elucidated. Previous studies focused on analysis of expression and function of known oncogenes and tumor suppressor genes. However, emerging reports highlight that it is also important to analyze the expression of genes that are ectopically expressed in CTCL (e.g., embryonic stem cell genes (ESC), cancer testis (CT) genes, etc.). Currently, it is not known whether ESC genes are expressed in CTCL. In the current work, we analyze by RT-PCR the expression of 26 ESC genes, many of which are known to regulate pluripotency and promote cancer stem cell-like phenotype, in a historic cohort of 60 patients from Boston and in a panel of 11 patient-derived CTCL cell lines and compare such expression to benign inflammatory dermatoses that often clinically mimic CTCL. Our findings document that many critical ESC genes including NANOG, SOX2, OCT4 (POU5F1) and their upstream and downstream signaling members are expressed in CTCL. Similarly, polycomb repressive complex 2 (PRC2) genes (i.e., EZH2, EED, and SUZ12) are also expressed in CTCL lesional skin. Furthermore, select ESC genes (OCT4, EED, TCF3, THAP11, CHD7, TIP60, TRIM28) are preferentially expressed in CTCL samples when compared to benign skin biopsies. Our work suggests that ESC genes are ectopically expressed together with CT genes, thymocyte development genes and B cell-specific genes and may be working in concert to promote tumorigenesis. Specifically, while ESC genes may be promoting cancer stem cell-like phenotype, CT genes may be contributing to aneuploidy and genomic instability by producing aberrant chromosomal translocations. Further analysis of ESC expression and function in this cancer will greatly enhance our fundamental understanding of CTCL and will help us identify novel therapeutic targets.

Smad7 maintains epithelial phenotype of ovarian cancer stem-like cells and supports tumor colonization by mesenchymal-epithelial transition.

Epithelial ovarian carcinoma (EOC) is a lethal gynecological malignancy. Epithelial-mesenchymal transition (EMT) has an important role in the tumorigenesis and progression of EOC. During the process of EMT, the transforming growth factor-β (TGF-β)-Smad signaling pathway has been indicated to regulate cell motility and tumor development. Among numerous EMT-associated transcripts, Smad7 is considered to be an inhibitor, however its involvement together with TGF-β1 in the progression of ovarian cancer remains to be elucidated. The present study demonstrated that Smad7 was overexpressed in SK-OV-3 and stem-like side populations of EOC cells, both of which grow in an epithelial pattern. The transformation of cells from an epithelial to a mesenchymal phenotype was stimulated by TGF-β1 with a corresponding increase in Smad7 expression in SK-OV-3 cells. These results indicate that Smad7 is a regulator in the maintenance of the epithelial phenotype in EOC cells, and may serve as an inhibitory element which targets TGF-β-stimulated EMT. Furthermore, inhibition of Smad7 resulted in cellular mesenchymal transformation, with an increased expression of N-cadherin and a decreased expression of E-cadherin. The invasiveness and migratory capabilities of Smad7 small hairpin RNA transduced EOC cells was also reduced. The findings of the present study have identified Smad7 as a fundamental factor in the maintenance of epithelial growth of EOC cells. Reversal of EMT results in a mesenchymal-epithelial transition, which is necessary for EOC cell colonization at metastatic sites.

Abstract 3868: Six1 overexpression promotes malignant progression in models of cervical and colon cancer

Abstract The overexpression of Six1, a member of the Six family of homeodomain transcription factors, has been found in various human cancers, and is associated with increased tumor progression and metastasis. Previous studies in our laboratory discovered that the expression of Six1 mRNA increased during in vitro progression of human papillomavirus type 16 (HPV16) immortalized human keratinocytes (HKc/HPV16) toward a differentiation-resistant (HKc/DR) phenotype. The overexpression of Six1 induced Epithelial-Mesenchymal Transition (EMT) by the activation of p38 MAPK in HKc/DR. Although immortalized and resistant to serum and calcium-induced differentiation, HKc/DR are not tumorigenic. To further explore the role of Six1 in HPV16 immortalized cells we determined whether overexpression of Six1 in HKc/DR resulted in malignant conversion. We found that HKc/DR overexpressing Six1 (DR-Six1), but not HKc/DR controls (DR-Ctrl), formed squamous cell carcinomas in nude mice. Cancer stem cells are proposed to drive tumor initiation and progression; for this reason we analyzed cancer stem cell markers in DR-Ctrl and DR-Six1. We found that DR-Six1 had an increased CD24-/CD44+ population and increased aldehyde dehydrogenase 1 (ALDH1) expression as compared to DR-Ctrl, indicating a cancer stem cell-like phenotype in Six1 overexpressing cells. We then used the human cervical cancer cell line HeLa to further explore the enhanced tumorigenic and malignant properties associated with Six1 overexpression. We determined that overexpressing Six1 in HeLa increased their ability to form spheroids in vitro and increased tumor size in vivo. As an extension of this work, we investigated the role of Six1 on tumorigenesis and metastasis in colon cancer in vivo and in vitro by using the murine colon cancer cell line MC38. We found that Six1 promoted colon cancer tumorigenesis, progression and metastasis, and increased the population of cancer stem cell-like cells. Taken together, our studies demonstrate that Six1 overexpression increases the cancer stem cell-like cell population, and promotes malignant progression in models of cervical and colon cancer. Supported by grant P20MD001770 from the National Institute on Minority Health and Health Disparities. Citation Format: Hanwen Xu, Yu Zhang, Lucia Pirisi, Maria Marjorette Pena, Kim E. Creek. Six1 overexpression promotes malignant progression in models of cervical and colon cancer. [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 3868. doi:10.1158/1538-7445.AM2014-3868

Abstract 3534: Epigenetic control of the tumor suppressive microRNA miR-34a in bladder cancer

Abstract Bladder cancer is the sixth most common cancer in the world and the incidence is particularly high in southwestern Taiwan. One of the hypotheses suggests that cancers arise from cancer stem-like cell (CSC) with surface antigen CD44. MicroRNAs (miRNAs) are endogenous, non-protein-coding RNAs that can regulate the expression of their target mRNAs. Up to 90% of human genes can be regulated by this mechanism. However, the role of miRNAs in the regulation of CSC in bladder cancer is not fully explored. Bioinformatics prediction identified that miR-34a regulates the expression of CD44. In this study, we aimed to investigate how miR-34a are regulated in bladder cancer. Expression analysis showed that miR-34a was down-regulated in UMUC3 bladder cancer cells. COBRA assay and bisulphite pyrosequencing demonstrated extensive DNA methylation of miR-34a in this cell. Treatment of DNMT inhibitor, 5-aza restored miR-34a expression in UMUC3 cells thus suggesting that miR-34a is epigenetically silenced in UMUC3 cells. Over-expression of miR-34a resulted in a reduction of chemo-resistance to cisplatin in UMUC3 cells. This may be due to a down-regulation of CD44 and another predicted miR-34a target, c-myc in this cell. Recently, additional mechanism namely, competitive endogenous RNA (ceRNA) hypothesis in controlling the function of miRNAs are demonstrated. To test this hypothesis in bladder cancer, we overexpressed 3′UTR of CD44 in TSGH8301 bladder cancer cells which expressed miR-34a, and resulted in an up regulation of another target of miR-34a, c-myc in this cells. Since amplification of chromosome 8q24 where c-myc resides is frequently observed in bladder cancer, we investigated the relationship between expression of c-myc and CD44 in a publicly available expression array data set (GDS1479) using 60 bladder cancer patients. Interestingly, a positive correlation was found between the expression of c-myc and CD44 (P=0.0016) in this data set. In conclusion, aberrant promoter methylation and ceRNA mechanism may contribute to attenuate the function of miR-34a in bladder cancer. The tumor suppressive role of miR-34a in controlling CSC phenotype in bladder cancer deserves further investigation. Citation Format: Wen-Yu Huang, Pi-Che Chen, Chia-Ming Yeh, Frank H.C. Cheng, Hsiao-Yen Hsieh, Cheng-Huang Shen, Cheng-Da Hsu, Michael WY Chan. Epigenetic control of the tumor suppressive microRNA miR-34a in bladder cancer. [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 3534. doi:10.1158/1538-7445.AM2014-3534

Unsupervised analyses reveal molecular subtypes associated to prognosis and response to therapy in colorectal cancer

SUMMARY Colorectal cancer (CRC) tumors are highly heterogeneous at a molecular level. Recent studies have proposed molecular classifications of intrinsic CRC molecular subtypes identified after applying unsupervised clustering methods to genome-wide data. Those subtypes, characterized by their distinct clinical and biological features, provide new insight about the complexity of CRC. A common finding shared by almost all analyses was the identification of microsatellite instable tumors as an independent cluster, which is associated to better prognosis. Clusters of tumors characterized by a high stromal component exhibited a poor outcome. Moreover, some of the clusters were associated with response to standard chemotherapy or targeted agents. Regarding biological functions underlying tumor subtypes, recurrent ones across different studies were WNT pathway activation, epithelial-to-mesenchymal transition or cancer stem cell-like phenotype. Now, the challenge is to translate these findings into a comprehensive CRC classification and characterization helpful for patients’ stratification and better clinical management.

Identification of cancer stem cells and a strategy for their elimination

It has been established previously that up to 40% of mouse CD34+ hematopoietic stem cells are capable of internalizing exogenous dsDNA fragments both in vivo and ex vivo. Importantly, when mice are treated with a combination of cyclophosphamide and dsDNA, the repair of interstrand crosslinks in hematopoietic progenitors is attenuated, and their pluripotency is altered. Here we show for the first time that among various actively proliferating mammalian cell populations there are subpopulations capable of internalizing dsDNA fragments. In the context of cancer, such dsDNA-internalizing cell subpopulations display cancer stem cell-like phenotype. Furthermore, using Krebs-2 ascites cells as a model, we found that upon combined treatment with cyclophosphamide and dsDNA, engrafted material loses its tumor-initiating properties which we attribute to the elimination of tumor-initiating stem cell subpopulation or loss of its tumorigenic potential.

Delta-like homologue 1 and its role in the bone marrow niche and hematologic malignancies.

Delta-like homologue 1 (DLK1) is an imprinted gene, that acts as a Notch pathway antagonist. It is deregulated in solid and blood cancers, conferring malignant cells a cancer stem cell-like phenotype. DLK1 is important for normal hematopoiesis and for bone marrow homeostasis, because it directly affects the differentiation of mesenchymal stem cells into the nonhematopoietic components. It is possible that the resulting abnormal biology of mesenchymal stem cells promotes leukemic blasts survival providing also a sanctuary against chemotherapeutic agents. In this review, the effects of DLK1 on mesenchymal stem cells and the bone marrow microenvironment with perspectives are discussed.

Plastic induction of CD133AC133-positive cells in the microenvironment of glioblastoma spheroids.

Recent studies showed that the stemness of cancer stem cells is maintained under a hypoxic microenvironment. However, the relationship of the hypoxic microenvironment in a three-dimensional cell mass and the induction of cancer stem cell-like phenotype is not well known. We examined the relationship between CD133 expression and the hypoxic microenvironment using glioblastoma spheroids formed with the T98G cell line. CD133(AC133)- and HIF-1α-positive cells were observed in the marginal region of the central hypoxic area positive for HIF-1α 10 days after plating T98G cells. CD133(AC133)-positive cells were positive for nestin. Quantitative PCR analysis showed that the CD133 expression level is not different in spheroids during the tested period after spheroid formation, indicating that post-translational regulation of the CD133 protein mediates positivity to CD133(AC133). When spheroids were trypsinized and the dissociated cells were cultured under the adherent monolayer conditions, the CD133(AC133)-positive cells gradually disappeared. These results show that CD133(AC133)-positive cells, which may incline toward undifferentiated cells because of nestin positivity, are plastically induced under the different culture conditions, spheroid and monolayer. In this plasticity, HIF-1α is involved in the induction and maintenance of CD133(AC133)-positive cells. Spheroids as an in vitro tumor model are useful to study the dynamic changes in the tumor cell phenotype in the different cell microenvironments.

Downregulation of SCAI enhances glioma cell invasion and stem cell like phenotype by activating Wnt/β-catenin signaling

SCAI (suppressor of cancer cell invasion), has been recently characterized as a novel tumor suppressor that inhibits the invasive migration of several human tumor cells. However, the expression pattern, biological role and molecular mechanism of SCAI in human glioma remain unknown. In this study, we found that levels of SCAI protein and mRNA expression were significantly downregulated in glioma tissues and cell lines. Overexpression of SCAI inhibited, but silencing of SCAI robustly promoted the invasive and cancer stem cell-like phenotypes of glioma cells. Furthermore, we demonstrated that SCAI downregualtion activated the Wnt/β-catenin signaling, and blockade of the Wnt/β-catenin pathway abrogated the effects of SCAI downregulation on glioma cell aggressiveness. Taken together, our results provide the first demonstration of SCAI downregulation in glioma, and its downregulation contributes to increased glioma cell invasion and self-renewal by activating the Wnt/β-catenin pathway.