Hepatitis B virus PreS1 facilitates hepatocellular carcinoma development by promoting appearance and self-renewal of liver cancer stem cells

Hepatitis B virus (HBV) is a major etiologic agent of hepatocellular carcinoma (HCC). However, the molecular mechanism by which HBV infection contributes to HCC development is not fully understood. Here, we initially showed that HBV stimulates the production of cancer stem cells (CSCs)-related markers (CD133, CD117 and CD90) and CSCs-related genes (Klf4, Sox2, Nanog, c-Myc and Oct4) and facilitates the self-renewal of CSCs in human hepatoma cells. Cellular and clinical studies revealed that HBV facilitates hepatoma cell growth and migration, enhances white blood cell (WBC) production in the sera of patients, stimulates CD133 and CD117 expression in HCC tissues, and promotes the CSCs generation of human hepatoma cells and clinical cancer tissues. Detailed studies revealed that PreS1 protein of HBV is required for HBV-mediated CSCs generation. PreS1 activates CD133, CD117 and CD90 expression in normal hepatocyte derived cell line (L02) and human hepatoma cell line (HepG2 and Huh-7); facilitates L02 cells migration, growth and sphere formation; and finally enhances the abilities of L02 cells and HepG2 cells to induce tumorigeneses in nude mice. Thus, PreS1 acts as a new oncoprotein to play a key role in the appearance and self-renewal of CSCs during HCC development.

Zinc finger protein X-linked promotes expansion of EpCAM+ cancer stem-like cells in hepatocellular carcinoma

Zinc finger protein X‐linked (ZFX) is frequently upregulated in multiple human malignancies and also plays a critical role in the maintenance of self‐renewal in embryonic stem cells. However, the role of ZFX in liver cancer stem cells (CSCs) remains obscure. We observed that the elevated expression of both ZFX and epithelial cell adhesion molecule (EpCAM) was associated with aggressive clinicopathological features and indicated poor prognosis in patients with hepatocellular carcinoma (HCC). ZFX was commonly enriched in liver EpCAM⁺ CSCs. Knockdown of ZFX decreased the proportion of EpCAM⁺ CSCs in HCC cells and suppressed their expression of stemness‐related genes, self‐renewal capacity, chemoresistance, metastatic potential, and tumorigenicity. Conversely, upregulation of ZFX in CSCs rescued these inhibitory effects and enhanced stem‐like properties. Mechanistically, depletion of ZFX reduced nuclear translocation and transactivation of β‐catenin, thereby inhibiting the self‐renewal capacity of EpCAM⁺ CSCs. Moreover, knockdown of β‐catenin attenuated the self‐renewal of EpCAM⁺ HCC cells stably expressing ZFX, further indicating that β‐catenin is required for ZFX‐mediated expansion and maintenance of EpCAM⁺ CSCs. Taken together, our findings indicate that ZFX activates and maintains EpCAM⁺ liver CSCs by promoting nuclear translocation and transactivation of β‐catenin. Furthermore, combination of ZFX and EpCAM may serve as a significant indicator for prognosis of patients with HCC.

Dental Pulp Stem Cells: Current Advances in Isolation, Expansion and Preservation

Dental pulp stem cells (DPSCs) are mesenchymal stem cells with high self-renewal potential that have the ability to differentiate into several cell types. Thus, DPSCs have become a promising source of cells for several applications in regenerative medicine, tissue engineering, and stem cell therapy. Numerous methods have been reported for the isolation, expansion, and preservation of DPSCs. However, methods are diverse and do not follow specific rules or parameters, which can affect stem cell properties, adding more variation to experimental results. In this review, we compare and analyze current experimental evidence to propose some factors that can be useful to establish better methods or improved protocols to prolong the quality of DPSCs. In addition, we highlight other factors related to biological aspects of dental tissue source (e.g., age, genetic background) that should be considered before tooth selection. Although current methods have reached significant advances, optimization is still required to improve culture stability and its maintenance for an extended period without losing stem cell properties. In addition, there is still much that needs to be done toward clinical application due to the fact that most of DPSCs procedures are not currently following good manufacturing practices. The establishment of optimized general or tailored protocols will allow obtaining well-defined DPSCs cultures with specific properties, which enable more reproducible results that will be the basis to develop effective and safe therapies.

Resistin potentiates chemoresistance and stemness of breast cancer cells: Implications for racially disparate therapeutic outcomes

Breast cancer (BC) continues to be the most frequently diagnosed cancer in American women, which disproportionately affects women of African-American (AA) descent. Previously, we reported greater serum levels of resistin in AA BC patients relative to Caucasian-American (CA) patients, and established its role in growth and aggressiveness of breast tumor cells. Here we have investigated the role of resistin in BC-chemoresistance. MDA-MB-231 and MDA-MB-468 BC cells of CA and AA origin, respectively, were incubated with resistin prior to doxorubicin treatment. Our data suggest that resistin conferred chemoresistance to both BC cell lines; however, the effect on AA cells was more profound. Furthermore, the resistin-induced doxorubicin-resistance was shown to occur due to suppression of apoptosis. Resistin treatment also affected the stemness of BC cells, as suggested by reduced cell surface expression of CD24, induced expression of CD44 and ALDH1, and increased capability of cells to form mammospheres. Mechanistic studies revealed that resistin-induced chemoresistance, apoptosis and stemness of BC cells were mediated through STAT3 activation. Taken together, our findings provide novel insight into the role of resistin in BC biology, and strengthen its role in racially disparate clinical outcomes.

Linking of mPGES-1 and iNOS activates stem-like phenotype in EGFR-driven epithelial tumor cells

Inflammatory prostaglandin E-2 (PGE-2) favors cancer progression in epithelial tumors characterized by persistent oncogene input. However, its effects on tumor cell stemness are poorly understood at molecular level. Here we describe two epithelial tumor cells A431 and A459, originating from human lung and skin tumors, in which epithelial growth factor (EGF) induces sequential up-regulation of mPGES-1 and iNOS enzymes, producing an inflammatory intracellular milieu. We demonstrated that concerted action of EGF, mPGES-1 and iNOS causes sharp changes in cell phenotype demonstrated by acquisition of stem-cell features and activation of the epithelial-mesenchymal transition (EMT). When primed with EGF, epithelial tumor cells transfected with mPGES-1 or iNOS to ensure steady enzyme levels display major stem-like and EMT markers, such as reduction in E-cadherin with a concomitant rise in vimentin, ALDH-1, CD133 and ALDH activity. Tumorsphere studies with these cells show increased sphere number and size, enhanced migratory and clonogenic capacity and sharp changes in EMT markers, indicating activation of this process. The concerted action of the enzymes forms a well-orchestrated cascade where expression of iNOS depends on overexpression of mPGES-1. Indeed, we show that through its downstream effectors (PGE-2, PKA, PI3K/Akt), mPGES-1 recruits non-canonical transcription factors, thus facilitating iNOS production. In conclusion, we propose that the initial event leading to tumor stem-cell activation may be a leveraged intrinsic mechanism in which all players are either inherent constituents (EGF) or highly inducible proteins (mPGES-1, iNOS) of tumor cells. We suggest that incipient tumor aggressiveness may be moderated by reducing pivotal input of mPGES-1.

Ovatodiolide suppresses colon tumorigenesis and prevents polarization of M2 tumor-associated macrophages through YAP oncogenic pathways

Background

An increased expression of Yes-associated protein (YAP1) has been shown to promote tumorigenesis in many cancer types including colon. However, the role of YAP1 in promoting colon tumorigenesis remains unclear. Here, we demonstrate that YAP1 expression is associated with M2 tumor-associated macrophage polarization and the generation of colon cancer stem-like cells. YAP1 downregulation by gene silencing or a phytochemical, ovatodiolide, not only suppresses colon cancer tumorigenesis but also prevents M2 TAM polarization.

Methods

Human monocytic cells, THP-1, and colon cancer cell lines, HCT116 and DLD-1, were co-cultured to mimic the interactions between tumor and its microenvironment. M2 polarization of the THP-1 cells were examined using both flow cytometry and q-PCR technique. The inhibition of YAP1 signaling was achieved by gene-silencing technique or ovatodiolide. The molecular consequences of YAP1 inhibition was demonstrated via colony formation, migration, and colon-sphere formation assays. 5-FU and ovatodiolide were used in drug combination studies. Xenograft and syngeneic mouse models were used to investigate the role of YAP1 in colon tumorigenesis and TAM generation.

Results

An increased YAP1 expression was found to be associated with a poor prognosis in patients with colon cancer using bioinformatics approach. We showed an increased YAP1 expression in the colon spheres, and colon cancer cells co-cultured with M2 TAMs. YAP1-silencing led to the concomitant decreased expression of major oncogenic pathways including Kras, mTOR, β-catenin, and M2-promoting IL-4 and tumor-promoting IL-6 cytokines. TAM co-cultured colon spheres showed a significantly higher tumor-initiating ability in vivo. Ovatodiolide treatment alone and in combination with 5-FU significantly suppressed in vivo tumorigenesis and less TAM infiltration in CT26 syngeneic mouse model.

Conclusions

We have identified the dual function of YAP1 where its suppression not only inhibited tumorigenesis but also prevented the generation of cancer stem-like cells and M2 TAM polarization. Ovatodiolide treatment suppressed YAP1 oncogenic pathways to inhibit colon tumorigenesis and M2 TAM generation both in vitro and in vivo. Ovatodiolide should be considered for its potential for adjuvant therapeutic development.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-017-0421-3) contains supplementary material, which is available to authorized users.

Bone marrow mesenchymal stem cells regulate stemness of multiple myeloma cell lines via BTK signaling pathway

Bone marrow mesenchymal stem cells (BM-MSCs) are key components of bone marrow microenvironment. Although the importances of BM-MSCs activation in myeloma cells growth, development, progression, angiogenesis are well known, their role in the regulation of myeloma stemness is unclear. In this study, myeloma cell lines (LP-1, U266) were co-cultured with BM-MSCs, we found that BM-MSCs could up-regulate the expression of key stemness genes and proteins (OCT4, SOX2, NANOG) and increase clonogenicity. Similarly, the mechanisms underlying the BM-MSC activation of myeloma stemness remain unclear. Here, we found that PCI-32765, a Bruton tyrosine kinase (BTK) inhibitor, treatment significantly down- regulate expression of key stemness genes and proteins in vitro co-culture system. Together, our results revealed that BM-MSCs could increase myeloma stemness via activation of the BTK signal pathway.

Intra-tumor heterogeneity from a cancer stem cell perspective

Tumor heterogeneity represents an ongoing challenge in the field of cancer therapy. Heterogeneity is evident between cancers from different patients (inter-tumor heterogeneity) and within a single tumor (intra-tumor heterogeneity). The latter includes phenotypic diversity such as cell surface markers, (epi)genetic abnormality, growth rate, apoptosis and other hallmarks of cancer that eventually drive disease progression and treatment failure. Cancer stem cells (CSCs) have been put forward to be one of the determining factors that contribute to intra-tumor heterogeneity. However, recent findings have shown that the stem-like state in a given tumor cell is a plastic quality. A corollary to this view is that stemness traits can be acquired via (epi)genetic modification and/or interaction with the tumor microenvironment (TME). Here we discuss factors contributing to this CSC heterogeneity and the potential implications for cancer therapy.

Which has more stem-cell characteristics: Müller cells or Müller cells derived from in vivo culture in neurospheres?

OBJECTIVE

Müller cells can be acquired from in vitro culture or a neurosphere culture system. Both culture methods yield cells with progenitor-cell characteristics that can differentiate into mature nervous cells. We compared the progenitor-cell traits of Müller cells acquired from each method.

METHODS

Primary murine Müller cells were isolated in serum culture media and used to generate Müller cells derived from neurospheres in serum-free culture conditions. Gene expression of neural progenitor cell markers was examined by Q-PCR in the two groups. Expression of rhodopsin and the cone-rod homeobox protein CRX were assessed after induction with 1 μM all-trans retinoic acid (RA) for 7 days.

RESULTS

After more than four passages, many cells were large, flattened, and difficult to passage. A spontaneously immortalized Müller cell line was not established. Three-passage neurospheres yielded few new spheres. Genes coding for Nestin, Sox2, Chx10, and Vimentin were downregulated in cells derived from neurospheres compared to the cells from standard culture, while Pax6 was upregulated. Müller cells from both culture methods were induced into rod photoreceptors, but expression of rhodopsin and CRX was greater in the Müller cells from the standard culture.

CONCLUSION

Both culture methods yielded cells with stem-cell characteristics that can be induced into rod photoreceptor neurons by RA. Serum had no influence on the "stemness" of the cells. Cells from standard culture had greater "stemness" than cells derived from neurospheres. The standard Müller cells would seem to be the best choice for transplantation in cell replacement therapy for photoreceptor degeneration.

Proteasome activation enhances stemness and lifespan of human mesenchymal stem cells

The age-associated decline of adult stem cell function contributes to the physiological failure of homeostasis during aging. The proteasome plays a key role in the maintenance of proteostasis and its failure is associated with various biological phenomena including senescence and aging. Although stem cell biology has attracted intense attention, the role of proteasome in stemness and its age-dependent deterioration remains largely unclear. By employing both Wharton's-Jelly- and Adipose-derived human adult mesenchymal stem cells (hMSCs), we reveal a significant age-related decline in proteasome content and peptidase activities, accompanied by alterations of proteasomal complexes. Additionally, we show that senescence and the concomitant failure of proteostasis negatively affects stemness. Remarkably, the loss of proliferative capacity and stemness of hMSCs can be counteracted through proteasome activation. At the mechanistic level, we demonstrate for the first time that Oct4 binds at the promoter region of β2 and β5 proteasome subunits and thus possibly regulates their expression. A firm understanding of the mechanisms regulating proteostasis in stem cells will pave the way to innovative stem cell-based interventions to improve healthspan and lifespan.

TGF-β1-induced differentiation of SHED into functional smooth muscle cells

BACKGROUND

Adequate vascularization is crucial for supplying nutrition and discharging metabolic waste in freshly transplanted tissue-engineered constructs. Obtaining the appropriate building blocks for vascular tissue engineering (i.e. endothelial and mural cells) is a challenging task for tissue neovascularization. Hence, we investigated whether stem cells from human exfoliated deciduous teeth (SHED) could be induced to differentiate into functional vascular smooth muscle cells (vSMCs).

METHODS

We utilized two cytokines of the TGF-β family, transforming growth factor beta 1 (TGF-β1) and bone morphogenetic protein 4 (BMP4), to induce SHED differentiation into SMCs. Quantitative real-time polymerase chain reaction (RT-qPCR) was used to assess mRNA expression, and protein expression was analyzed using flow cytometry, western blot and immunostaining. Additionally, to examine whether these SHED-derived SMCs possess the same function as primary SMCs, in vitro Matrigel angiogenesis assay, fibrin gel bead assay, and functional contraction study were used here.

RESULTS

By analyzing the expression of specific markers of SMCs (α-SMA, SM22α, Calponin, and SM-MHC), we confirmed that TGF-β1, and not BMP4, could induce SHED differentiation into SMCs. The differentiation efficiency was relatively high (α-SMA+ 86.1%, SM22α+ 93.9%, Calponin+ 56.8%, and SM-MHC+ 88.2%) as assessed by flow cytometry. In vitro Matrigel angiogenesis assay showed that the vascular structures generated by SHED-derived SMCs and human umbilical vein endothelial cells (HUVECs) were comparable to primary SMCs and HUVECs in terms of vessel stability. Fibrin gel bead assay showed that SHED-derived SMCs had a stronger capacity for promoting vessel formation compared with primary SMCs. Further analyses of protein expression in fibrin gel showed that cultures containing SHED-derived SMCs exhibited higher expression levels of Fibronectin than the primary SMCs group. Additionally, it was also confirmed that SHED-derived SMCs exhibited functional contractility. When SB-431542, a specific inhibitor of ALK5 was administered, TGF-β1 stimulation could not induce SHED into SMCs, indicating that the differentiation of SHED into SMCs is somehow related to the TGF-β1-ALK5 signaling pathway.

CONCLUSIONS

SHED could be successfully induced into functional SMCs for vascular tissue engineering, and this course could be regulated through the ALK5 signaling pathway. Hence, SHED appear to be a promising candidate cell type for vascular tissue engineering.

Lovastatin Reduces Stemness via Epigenetic Reprograming of BMP2 and GATA2 in Human Endometrium and Endometriosis

OBJECTIVE

The stem cell theory in the endometriosis provides an advanced avenue of targeting these cells as a novel therapy to eliminate endometriosis. In this regard, studies showed that lovastatin alters the cells from a stem-like state to more differentiated condition and reduces stemness. The aim of this study was to investigate whether lovastatin treatment could influence expression and methylation patterns of genes regulating differentiation of endometrial mesenchymal stem cells (eMSCs) such as BMP2, GATA2 and RUNX2 as well as eMSCs markers.

MATERIALS AND METHODS

In this experimental investigation, MSCs were isolated from endometrial and endometriotic tissues and treated with lovastatin and decitabin. To investigate the osteogenic and adipogenic differentiation of eMSCs treated with the different concentration of lovastatin and decitabin, BMP2, RUNX2 and GATA2 expressions were measured by real-time polymerase chain reaction (PCR). To determine involvement of DNA methylation in BMP2 and GATA2 gene regulations of eMSCs, we used quantitative Methylation Specific PCR (qMSP) for evaluation of the BMP2 promoter status and differentially methylated region of GATA2 exon 4.

RESULTS

In the present study, treatment with lovastatin increased expression of BMP2 and RUNX2 and induced BMP2 promoter demethylation. We also demonstrated that lovastatin treatment down-regulated GATA2 expression via inducing methylation. In addition, the results indicated that CD146 cell marker was decreased to 53% in response to lovastatin treatment compared to untreated group.

CONCLUSION

These findings indicated that lovastatin treatment could increase the differentiation of eMSCs toward osteogenic and adiogenic lineages, while it decreased expression of eMSCs markers and subsequently reduced the stemness.

Stemness in Liver Cancer

Cancer cells possessing "stemness," or stem-cell properties, are referred to as cancer stem cells (CSC) or cancer-initiating cells. The concept that these cells rest at the apex of the cancer hierarchy is an evolving theme in cancer research. These cells are by definition primarily responsible for the initiation and propagation of tumors as well as relapse after therapy, and they are therefore of major scientific interest. Several studies indicate that hepatocellular carcinomas that harbor phenotypic features of stem cells and progenitor cells constitute a subclass of therapeutically challenging cancers that are associated with a particularly poor prognosis. We recently demonstrated that any cell type in the mouse hepatic lineage can undergo oncogenic reprogramming into a CSC by activating different cell type-specific pathways [<citeref rid="ref1">1</citeref>]. Identification of common and cell of origin-specific phenotypic and genetic changes could provide new therapeutic targets for liver cancer.

Pharmacological and immunological targeting of tumor mesenchymalization

Controlling the spread of carcinoma cells to distant organs is the foremost challenge in cancer treatment, as metastatic disease is generally resistant to therapy and is ultimately incurable for the majority of patients. The plasticity of tumor cell phenotype, in which the behaviors and functions of individual tumor cells differ markedly depending upon intrinsic and extrinsic factors, is now known to be a central mechanism in cancer progression. Our expanding knowledge of epithelial and mesenchymal phenotypic states in tumor cells, and the dynamic nature of the transitions between these phenotypes has created new opportunities to intervene to better control the behavior of tumor cells. There are now a variety of innovative pharmacological approaches to preferentially target tumor cells that have acquired mesenchymal features, including cytotoxic agents that directly kill these cells, and inhibitors that block or revert the process of mesenchymalization. Furthermore, novel immunological strategies have been developed to engage the immune system in seeking out and destroying mesenchymalized tumor cells. This review highlights the relevance of phenotypic plasticity in tumor biology, and discusses recently developed pharmacological and immunological means of targeting this phenomenon.

Crosstalk between SHH and stemness state signaling pathways in esophageal squamous cell carcinoma

The expression of GLI1 as a downstream gene of sonic hedgehog (Hh) pathway, studied in a variety of cancers including esophageal squamous cell carcinoma (ESCC). However, the interaction of Hh with other developmental pathways needs to be elucidated. In this study, we aimed to investigate the correlation of GLI1 expression with transcription factors (TFs) of stem cell signaling pathways, and their association with clinico-pathological data of ESCC. Using real-time PCR, we assessed the expression of GLI1 mRNA in 49 ESCC patients, and analyzed the correlation between GLI1 and selected TFs. The results showed overexpression of GLI1 in ESCC tissues in significant correlation with lymph node metastasis. The GLI1 up-regulation was also correlated to the SOX2 and SIZN1 (Smad-interacting zinc finger protein) expression. These correlations may confirmed the role of GLI1 in crosstalk among different cell signaling pathways in ESCC. To our knowledge, this is the first study to demonstrate the correlation of GLI1 expression with stemness marker and BMP signaling in ESCC.

Role of let-7 family microRNA in breast cancer

Metastasis and resistance to therapy significantly contribute to cancer-related deaths. Growing body of evidence suggest that altered expression of microRNAs (miRNAs) is one of the root cause of adverse clinical outcome. miRNAs such as let-7 are the new fine tuners of signaling cascade and cellular processes which regulates the genes in post-transcriptional manner. In this review, we described the regulation of let-7 expression and the involvement of molecular factors in this process. We discussed the mechanism by which let-7 alter the expression of genes involved in the process of tumorigenesis. Further, we listed the pathways targeted by let-7 to reduce the burden of the tumor. In addition, we described the role of let-7 in breast cancer metastasis and stemness properties. This article will provide the in-depth insight into the biology of let-7 miRNA and its role in the breast cancer progression.

Special AT-rich sequence-binding protein 2 acts as a negative regulator of stemness in colorectal cancer cells

AIM

To find the mechanisms by which special AT-rich sequence-binding protein 2 (SATB2) influences colorectal cancer (CRC) metastasis.

METHODS

Cell growth assay, colony-forming assay, cell adhesion assay and cell migration assay were used to evaluate the biological characteristics of CRC cells with gain or loss of SATB2. Sphere formation assay was used to detect the self-renewal ability of CRC cells. The mRNA expression of stem cell markers in CRC cells with upregulated or downregulated SATB2 expression was detected by quantitative real-time polymerase chain reaction. Chromatin immunoprecipitation (ChIP) was used to verify the binding loci of SATB2 on genomic sequences of stem cell markers. The Cancer Genome Atlas (TCGA) database and our clinical samples were analyzed to find the correlation between SATB2 and some key stem cell markers.

RESULTS

Downregulation of SATB2 led to an aggressive phenotype in SW480 and DLD-1 cells, which was characterized by increased migration and invasion abilities. Overexpression of SATB2 suppressed the migration and invasion abilities in SW480 and SW620 cells. Using sequential sphere formation assay to detect the self-renewal abilities of CRC cells, we found more secondary sphere formation but not primary sphere formation in SW480 and DLD-1 cells after SATB2 expression was knocked down. Moreover, most markers for stem cells such as CD133, CD44, AXIN2, MEIS2 and NANOG were increased in cells with SATB2 knockdown and decreased in cells with SATB2 overexpression. ChIP assay showed that SATB2 bound to regulatory elements of CD133, CD44, MEIS2 and AXIN2 genes. Using TCGA database and our clinical samples, we found that SATB2 was correlated with some key stem cell markers including CD44 and CD24 in clinical tissues of CRC patients.

CONCLUSION

SATB2 can directly bind to the regulatory elements in the genetic loci of several stem cell markers and consequently inhibit the progression of CRC by negatively regulating stemness of CRC cells.

Differential BMI1, TWIST1, SNAI2 mRNA expression pattern correlation with malignancy type in a spectrum of common cutaneous malignancies: basal cell carcinoma, squamous cell carcinoma, and melanoma

PURPOSE

Melanoma, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC) can be used as a unique model to identify molecular mechanisms to distinguish rarely metastatic (BCC), often metastatic (SCC) and most metastatic (melanoma) cancer. It is known that epithelial-mesenchymal transition and stemness transcription factors (TWIST1, SNAI2/SLUG, and BMI1) play an important role in metastasis and their dysregulation has been demonstrated in metastatic cancers. We hypothesized that this spectrum of cutaneous cancers (BCC, SCC, and melanoma) would be a unique cancer model system to elucidate steps toward cancer invasion and metastasis.

METHODS

We evaluated the mRNA expression level of BMI1, TWIST1, and SNAI2/SLUG and studied clinicopathological features in 170 skin cancers along with normal tissue samples.

RESULTS

We demonstrate downregulation of BMI1 mRNA expression in BCC samples compared with controls (p = 0.0001), SCC (p = 0.001), and melanoma (p = 0.0001) samples. Downregulation of TWIST1 mRNA expression is seen in only BCC samples compared with controls (p = 0.031). High SNAI2 mRNA expression is represented in melanoma samples compared with controls (p = 0.022) and SCC samples (p = 0.031). High mRNA expression of TWIST1 is seen in patients with positive history of cancers. Extremely low mRNA expression of BMI1 is detected in patients with positive history of cancers other than skin cancer.

CONCLUSIONS

These findings provide support for the hypothesis that the spectrum of cutaneous cancers could be better understood as a series of gene dosage-dependent entities with distinct molecular events. Oncogene-induced senescence, mechanism of which is still unclear, could be one explanation for these results.

Musashi 2 contributes to the stemness and chemoresistance of liver cancer stem cells via LIN28A activation

Accumulating evidence suggests that cancer stem cells (CSCs), a small subset of cancer cells, are responsible for tumor initiation, progression, relapse and metastasis. Musashi 2 (MSI2), a RNA-binding protein, was proposed to be a potent oncogene playing key roles in myeloid leukemia and gastrointestinal malignancies. However, it remains elusive how MSI2 regulates stem cell features in HCC. Herein, we demonstrated that MSI2 was highly expressed in liver CSCs. Overexpression or knockdown of MSI2 altered CSC-related gene expression, self-renewal as well as resistance to chemotherapy in HCC cell lines. In mouse xenograft models, MSI2 could markedly enhance tumorigenicity. Mechanistically, overexpression of MSI2 resulted in the upregulation of Lin28A. Stemness and chemotherapeutic drug resistance induced by MSI2 overexpression were dramatically reduced by Lin28A knockdown. Moreover, MSI2 and LIN28A levels positively correlated with the clinical severity and prognosis in HCC patients. In conclusion, MSI2 might play a crucial role in sustaining stemness and chemoresistance of liver CSCs via LIN28A-dependent manner in HCC. Our findings revealed that MSI2 and Lin28A might be used as potential therapeutic targets for eradicating liver CSCs.

High-fat diet feeding promotes stemness and precancerous changes in murine gastric mucosa mediated by leptin receptor signaling pathway

Obesity increases the risk for gastric cancers. However, the occurrence and mechanisms of precancerous atrophic gastritis induced by high-fat diet (HFD) remain unclear. Here, we show that HFD-associated lipotoxicity induces precancerous lesions that are accompanied by the disruption of organelle homeostasis, tissue integrity, and deregulated expression of stemness genes in the gastric epithelium mediated by leptin receptor (ObR) signaling. Following HFD feeding, ectopic fat accumulated and expression of LAMP2A in lysosome and COX IV in mitochondria increased in the gastric mucosa. HFD feeding also led to enhanced expression of activated-Notch1 and stem cell markers Lgr5, CD44, and EpCAM. In addition, HFD-fed mice showed intracellular β-catenin accumulation in the gastric mucosa with increased expression of its target genes, Nanog, Oct4, and c-Myc. These observations were abrogated in the leptin-deficient ob/ob mice and ObR-mutated db/db mice, indicating that these HFD-induced changes were responsible for effects downstream of the ObR. Consistent with this, the expression of the Class IA and III PI3Ks was increased following ObR activation in the gastric mucosa of HFD-fed mice. Together, these results suggest that HFD-induced lipotoxicity and deregulated organelle biosynthesis confer cancer stem cell-like properties to the gastric mucosa via signaling pathway mediated by leptin, PI3K and β-catenin.

ASPP2 suppresses stem cell-like characteristics and chemoresistance by inhibiting the Src/FAK/Snail axis in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the third leading cause of death in cancer patients worldwide. Understanding the molecular pathogenesis of HCC recurrence and chemoresistance is key to improving patients' prognosis. In this study, we report that downregulation of ASPP2, a member of the ankyrin-repeat-containing, SH3-domain-containing, and proline-rich-region-containing protein (ASPP) family, bestowed HCC cells with stem-like properties and resistance to chemotherapy, including the expansion of side population fractions, formation of hepatospheroids, expression of stem cell-associated genes, loss of chemosensitivity, and increased tumorigenicity in immunodeficient mice. An expression profiling assay revealed that ASPP2 specifically repressed focal adhesion kinase (FAK)/Src/extracellular signal regulated kinase (ERK) signaling. ASPP2 does this by physically interacting with C-terminal Src kinase (CSK) and stimulating its kinase activity, which eventually leads to activator protein 1 (AP1)-mediated downregulation of Snail expression. In addition, pharmacologic inhibition of Src attenuated the effects of ASPP2 deficiency. Our findings present functional and mechanistic insight into the critical role of ASPP2 in the inhibition of HCC stemness and drug resistance and may provide a new strategy for therapeutic combinations to treat HCC.

SOX-mediated molecular crosstalk during the progression of tumorigenesis

SOX family transcription factor has emerged as a double-edged sword relating to tumorigenesis and metastasis. Multiple studies have revealed different expression patterns and contradictory roles of SOX factors in the tumor initiation and progression. The aberrant expression of SOX factors is regulated by copy number alteration, methylation modulation, microRNAs, transcription factors and post-translational modification. This review summarizes the role of SOX factors in molecular interactions and signaling pathways during different steps of carcinogenesis, such as CSCs stemness maintenance, EMT occurrence, cell invasion, cell proliferation and apoptosis. The Wnt signaling pathway is also shown to provide vital intermediate signaling transduction. We believe that SOX family proteins may be used as prognostic markers for human clinical therapy, and novel therapy strategies targeting SOX factors should be explored in future clinical applications.

Long noncoding RNAs in normal and pathological pluripotency

The striking similarities between pluripotent and cancer cells, such as immortality and increased stress resistance, have long been acknowledged. Numerous studies searched for and successfully identified common molecular players and pathways, thus providing an entirely new challenge and potential therapeutic angle by targeting cancer cells or a specific stem population of the tumor via pluripotency associated processes. However, these strategies have until now mainly been restricted to proteins. Nonetheless, it has become clear over the past decade that the overwhelming majority of the genome produces noncoding transcripts, many of which have proven both functional and crucial for key cellular processes, including stemness maintenance. Moreover, numerous long noncoding RNAs are deregulated in cancer, but little is known concerning their functions and molecular mechanisms. Consequently, it seems essential to integrate the noncoding transcripts into the picture of the stemness-cancer connection. Whereas a number of studies have addressed the expression of lncRNAs in cancer stem cells, no systematic approach has yet been undertaken to identify lncRNAs implicated in the maintenance of the embryonic stemness state that is hijacked by cancer cells. The aim of this review is to highlight long noncoding RNAs with shared functions in stemness and cancer and to outline the current state of a field in its infancy, the search for long noncoding transcripts in cancer stem cells.

Inhibition of SALL4 reduces tumorigenicity involving epithelial-mesenchymal transition via Wnt/β-catenin pathway in esophageal squamous cell carcinoma

BACKGROUND

Growing evidence suggests that SALL4 plays a vital role in tumor progression and metastasis. However, the molecular mechanism of SALL4 promoting esophageal squamous cell carcinoma (ESCC) remains to be elucidated.

METHODS

The gene and protein expression profiles- were examined by using quantitative real-time PCR, immunohistochemistry and western blotting. Small hairpin RNA was used to evaluate the role of SALL4 both in cell lines and in animal models. Cell proliferation, apoptosis and invasion were assessed by CCK8, flow cytometry and transwell-matrigel assays. Sphere formation assay was used for cancer stem cell derivation and characterization.

RESULTS

Our study showed that the transcription factor SALL4 was overexpressed in a majority of human ESCC tissues and closely correlated with a poor outcome. We established the lentiviral system using short hairpin RNA to knockdown SALL4 in TE7 and EC109 cells. Silencing of SALL4 inhibited the cell proliferation, induced apoptosis and the G1 phase arrest in cell cycle, decreased the ability of migration/invasion, clonogenicity and stemness in vitro. Besides, down-regulation of SALL4 enhanced the ESCC cells' sensitivity to cisplatin. Xenograft tumor models showed that silencing of SALL4 decreased the ability to form tumors in vivo. Furthermore, our study demonstrated that SALL4 played a vital role in modulating the stemness of ESCC cells via Wnt/β-catenin signaling pathway and in epithelial-mesenchymal transition.

CONCLUSIONS

Our results revealed that SALL4 might serve as a functional marker for ESCC cancer stem cell, a crucial marker for prognosis and an attractive candidate for target therapy of ESCC.

Phosphodiesterase 5/protein kinase G signal governs stemness of prostate cancer stem cells through Hippo pathway

Cancer stem cells (CSC) are critical for initiation, metastasis, and relapse of cancers, however, the underlying mechanism governing stemness of CSC remains unknown. Herein, we have investigated the roles of phosphodiesterase 5 (PDE5) in stemness of prostate cancer cells. Both PDE5 and WW domain-containing transcription regulator protein-1 (TAZ), a core effector of Hippo pathway, are highly expressed in the PC3-derived cancer stem cells (PCSC). Either TAZ knockdown or inhibition of PDE5 activity attenuated colony formation, altered expression patterns of stem cell markers, and enhanced cisplatin cytotoxicity, resulting in attenuation of stemness in PCSC. In addition, inhibition of PDE5 activity by its specific inhibitors activates cGMP-dependent protein kinase G (PKG), which in turn induces MST/LATS kinases, resulting in cytosolic degradation of TAZ and activation of Hippo pathway. Accordingly, knockdown of TAZ almost completely abolished PDE5 inhibitor-induced attenuation in stemness in cultured PCSC, whereas knockdown of TAZ not only abolished PDE5 inhibitor-induced attenuation in stemness but also facilitated PDE5 inhibitor-induced trans-differentiation in PCSC xenografts. Together, the present study has uncovered that PDE/cGMP/PKG signal targets to Hippo/TAZ pathway in maintaining stemness of PCSC, and suggested that PDE5 inhibitors in combination with chemotherapeutic agents could effectively prevent initiation, metastasis, and relapse of prostate cancer.

Human Cartilage-Derived Progenitor Cells From Committed Chondrocytes for Efficient Cartilage Repair and Regeneration

Articular cartilage is not a physiologically self-renewing tissue. Injury of cartilage often progresses from the articular surface to the subchondral bone, leading to pathogenesis of tissue degenerative diseases, such as osteoarthritis. Therapies to treat cartilage defects using autologous chondrocyte-based tissue engineering have been developed and used for more than 20 years; however, the challenge of chondrocyte expansion in vitro remains. A promising cell source, cartilage stem/progenitor cells (CSPCs), has attracted recent attention. Because their origin and identity are still unclear, the application potential of CSPCs is under active investigation. Here we have captured the emergence of a group of stem/progenitor cells derived from adult human chondrocytes, highlighted by dynamic changes in expression of the mature chondrocyte marker, COL2, and mesenchymal stromal/stem cell (MSC) marker, CD146. These cells are termed chondrocyte-derived progenitor cells (CDPCs). The stem cell-like potency and differentiation status of CDPCs were determined by physical and biochemical cues during culture. A low-density, low-glucose 2-dimensional culture condition (2DLL) was critical for the emergence and proliferation enhancement of CDPCs. CDPCs showed similar phenotype as bone marrow mesenchymal stromal/stem cells but exhibited greater chondrogenic potential. Moreover, the 2DLL-cultured CDPCs proved efficient in cartilage formation both in vitro and in vivo and in repairing large knee cartilage defects (6-13 cm(2)) in 15 patients. These findings suggest a phenotype conversion between chondrocytes and CDPCs and provide conditions that promote the conversion. These insights expand our understanding of cartilage biology and may enhance the success of chondrocyte-based therapies.

SIGNIFICANCE

Injury of cartilage, a non-self-repairing tissue, often progresses to pathogenesis of degenerative joint diseases, such as osteoarthritis. Although tissue-derived stem cells have been shown to contribute to tissue renewal and homeostasis, the derivation, biological function, and application potential of stem/progenitor cells found in adult human articular cartilage are incompletely understood. This study reports the derivation of a population of cartilage stem/progenitor cells from fully differentiated chondrocytes under specific culture conditions, which have the potential to reassume their chondrocytic phenotype for efficient cartilage regeneration. These findings support the possibility of using in vitro amplified chondrocyte-derived progenitor cells for joint cartilage repair.

Hypoxia regulates stemness of breast cancer MDA-MB-231 cells

Human breast cancers include cancer stem cell populations as well as non-tumorigenic cancer cells. Breast cancer stem cells possess self-renewal capability and thus are the root cause of recurrence and metastasis of malignant tumors. Hypoxia is a fundamental pathological feature of solid tumor tissues and exerts a wide range of effects on the biological behavior of cancer cells. However, there is little information on the role of hypoxia in modulating the stemness of breast cancer cells. In the present study, we cultured MDA-MB-231 cells in a hypoxic gas mixture to simulate the hypoxic environment in tissues and to determine how hypoxia conditions could affect the cell proliferation, apoptosis, cytotoxicity, and colony-forming ability. Expression of the stem cell phenotype CD24(-)CD44(+)ESA(+) was analyzed to assess the effects of hypoxia on stemness transformation in MDA-MB-231 cells. Our results found that the cell toxicity of MDA-MB-231 cells was not affected by hypoxia. Hypoxia could slightly inhibit the growth of MDA-MB-231 cells, but the inhibitory effect is not significant when compared with normoxic control. Moreover, hypoxia significantly blocked the apoptosis in MDA-MB-231 cells (P < 0.05). The proportion of CD24(-)CD44(+)ESA(+) cells in MDA-MB-231 cells was increased greatly after they were treated with hypoxia, and cell colony-formation rate of MDA-MB-231 cells also increased significantly in hypoxia-treated cells. These results encourage the exploration of hypoxia as a mechanism which might not be underestimated in chemo-resistant breast cancer treatment.

Imatinib Inhibits the Renewal and Tumorigenicity of CT-26 Colon Cancer Cells after Cytoreductive Treatment with Doxorubicin

Conventional anti-cancer drugs preferentially eliminate differentiated cancer cells but those cells that are spared (i.e. cancer stem cells: CSC), initiate recurrence. We tested whether drugs that target receptor tyrosine kinases (RTKs) involved in developmental signaling cascades and activated in CSC, could be used to silence and/or to eliminate colorectal cancer cells refractory to conventional treatment with cytoreductive drugs. A sequential treatment model was thereby developed with doxorubicin (DOX) and imatinib. CT-26 mouse colon carcinoma cells were pre-treated with DOX to select DOX-refractory cells with CSC properties, which were then subsequently treated with RTK inhibitor imatinib, where their regrowth was found to be inhibited. Under both normoxic and hypoxic conditions, imatinib potently inhibited clonogenicity of DOX-refractory CT-26 cells. Treatment with DOX did not eliminate tumorigenic CT-26 cells, since CT-26 cells pre-exposed to DOX in vitro, when inoculated subcutaneously, induced tumors in 90 % of mice, as opposed to a 100 % rate in the case of chemonaive CT-26 cells. In mice inoculated with chemonaive CT-26 cells, tumor formation was not prevented by imatinib. However, imatinib prevented tumor formation in 50 % of mice inoculated with CT-26 cells pre-exposed to DOX in vitro, with the remaining 50 % mice showing delayed tumor formation. These results suggest that the sequential use of the drug imatinib, as a drug targeting cancer cells expressing stem cell features after conventional cytoreductive treatment, is a promising future strategy for preventing tumor recurrence.

Could drugs inhibiting the mevalonate pathway also target cancer stem cells?

Understanding the connection between metabolic pathways and cancer is very important for the development of new therapeutic approaches based on regulatory enzymes in pathways associated with tumorigenesis. The mevalonate cascade and its rate-liming enzyme HMG CoA-reductase has recently drawn the attention of cancer researchers because strong evidences arising mostly from epidemiologic studies, show that it could promote transformation. Hence, these studies pinpoint HMG CoA-reductase as a candidate proto-oncogene. Several recent epidemiological studies, in different populations, have proven that statins are beneficial for the treatment-outcome of various cancers, and may improve common cancer therapy strategies involving alkylating agents, and antimetabolites. Cancer stem cells/cancer initiating cells (CSC) are key to cancer progression and metastasis. Therefore, in the current review we address the different effects of statins on cancer stem cells. The mevalonate cascade is among the most pleiotropic, and highly interconnected signaling pathways. Through G-protein-coupled receptors (GRCP), it integrates extra-, and intracellular signals. The mevalonate pathway is implicated in cell stemness, cell proliferation, and organ size regulation through the Hippo pathway (e.g. Yap/Taz signaling axis). This pathway is a prime preventive target through the administration of statins for the prophylaxis of obesity-related cardiovascular diseases. Its prominent role in regulation of cell growth and stemness also invokes its role in cancer development and progression. The mevalonate pathway affects cancer metastasis in several ways by: (i) affecting epithelial-to-mesenchymal transition (EMT), (ii) affecting remodeling of the cytoskeleton as well as cell motility, (iii) affecting cell polarity (non-canonical Wnt/planar pathway), and (iv) modulation of mesenchymal-to-epithelial transition (MET). Herein we provide an overview of the mevalonate signaling network. We then briefly highlight diverse functions of various elements of this mevalonate pathway. We further discuss in detail the role of elements of the mevalonate cascade in stemness, carcinogenesis, cancer progression, metastasis and maintenance of cancer stem cells.

The Nuclear Receptor, RORγ, Regulates Pathways Necessary for Breast Cancer Metastasis

We have previously reported that RORγ expression was decreased in ER-ve breast cancer, and increased expression improves clinical outcomes. However, the underlying RORγ dependent mechanisms that repress breast carcinogenesis have not been elucidated. Here we report that RORγ negatively regulates the oncogenic TGF-β/EMT and mammary stem cell (MaSC) pathways, whereas RORγ positively regulates DNA-repair. We demonstrate that RORγ expression is: (i) decreased in basal-like subtype cancers, and (ii) inversely correlated with histological grade and drivers of carcinogenesis in breast cancer cohorts. Furthermore, integration of RNA-seq and ChIP-chip data reveals that RORγ regulates the expression of many genes involved in TGF-β/EMT-signaling, DNA-repair and MaSC pathways (including the non-coding RNA, LINC00511). In accordance, pharmacological studies demonstrate that an RORγ agonist suppresses breast cancer cell viability, migration, the EMT transition (microsphere outgrowth) and mammosphere-growth. In contrast, RNA-seq demonstrates an RORγ inverse agonist induces TGF-β/EMT-signaling. These findings suggest pharmacological modulation of RORγ activity may have utility in breast cancer.

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

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

Non-coding RNAs Functioning in Colorectal Cancer Stem Cells

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

Perspective: Cooperation of Nanog, NF-κΒ, and CXCR4 in a regulatory network for directed migration of cancer stem cells

Directed cell migration is a crucial mobility phase of cancer stem cells having stemness and tumorigenic characteristics. It is known that CXCR4 plays key roles in the perception of chemotactic gradients throughout the directed migration of CSCs. There are a number of complex signaling pathways and transcription factors that coordinate with CXCR4/CXCL12 axis during directed migration. In this review, we focus on some transcription factors such as Nanog, NF-κB, and Bmi-1 that cooperate with CXCR4/CXCL12 for the maintenance of stemness and induction of metastasis behavior in cancer stem cells.

Characterization of the expression of the pro-metastatic Mena(INV) isoform during breast tumor progression

Several functionally distinct isoforms of the actin regulatory Mena are produced by alternative splicing during tumor progression. Forced expression of the Mena(INV) isoform drives invasion, intravasation and metastasis. However, the abundance and distribution of endogenously expressed Mena(INV) within primary tumors during progression remain unknown, as most studies to date have only assessed relative mRNA levels from dissociated tumor samples. We have developed a Mena(INV) isoform-specific monoclonal antibody and used it to examine Mena(INV) expression patterns in mouse mammary and human breast tumors. Mena(INV) expression increases during tumor progression and to examine the relationship between Mena(INV) expression and markers for epithelial or mesenchymal status, stemness, stromal cell types and hypoxic regions. Further, while Mena(INV) robustly expressed in vascularized areas of the tumor, it is not confined to cells adjacent to blood vessels. Altogether, these data demonstrate the specificity and utility of the anti-Mena(INV)-isoform specific antibody, and provide the first description of endogenous Mena(INV) protein expression in mouse and human tumors.

Chemotherapy induces stemness in osteosarcoma cells through activation of Wnt/β-catenin signaling

Development of resistance represents a major drawback in osteosarcoma treatment, despite improvements in overall survival. Treatment failure and tumor progression have been attributed to pre-existing drug-resistant clones commonly assigned to a cancer stem-like phenotype. Evidence suggests that non stem-like cells, when submitted to certain microenvironmental stimuli, can acquire a stemness phenotype thereby strengthening their capacity to handle with stressful conditions. Here, using osteosarcoma cell lines and a mouse xenograft model, we show that exposure to conventional chemotherapeutics induces a phenotypic cell transition toward a stem-like phenotype. This associates with activation of Wnt/β-catenin signaling, up-regulation of pluripotency factors and detoxification systems (ABC transporters and Aldefluor activity) that ultimately leads to chemotherapy failure. Wnt/β-catenin inhibition combined with doxorubicin, in the MNNG-HOS cells, prevented the up-regulation of factors linked to transition into a stem-like state and can be envisaged as a way to overcome adaptive resistance. Finally, the analysis of the public R2 database, containing microarray data information from diverse osteosarcoma tissues, revealed a correlation between expression of stemness markers and a worse response to chemotherapy, which provides evidence for drug-induced phenotypic stem cell state transitions in osteosarcoma.

p-21 activated kinase 4 (PAK4) maintains stem cell-like phenotypes in pancreatic cancer cells through activation of STAT3 signaling

Pancreatic cancer (PC) remains a highly lethal malignancy due to its unusual chemoresistance and high aggressiveness. A subpopulation of pancreatic tumor cells, known as cancer stem cells (CSCs), is considered responsible not only for tumor-maintenance, but also for its widespread metastasis and therapeutic failure. Here we investigated the role of p-21 activated kinase 4 (PAK4) in driving PC stemness properties. Our data demonstrate that triple-positive (CD24⁺/CD44⁺/EpCAM⁺) subpopulation of pancreatic CSCs exhibits greater level of PAK4 as compared to triple-negative (CD24⁻/CD44⁻/EpCAM⁻) cells. Moreover, PAK4 silencing in PC cells leads to diminished fraction of CD24, CD44, and EpCAM positive cells. Furthermore, we show that PAK4-silenced PC cells exhibit decreased sphere-forming ability and increased chemo-sensitivity to gemcitabine toxicity. PAK4 expression is also associated with enhanced levels of stemness-associated transcription factors (Oct4/Nanog/Sox2 and KLF4). Furthermore, our data show decreased nuclear accumulation and transcriptional activity of STAT3 in PAK4-silenced PC cells and restitution of its activity leads to restoration of stem cell phenotypes. Together, our findings deliver first experimental evidence for the involvement of PAK4 in PC stemness and support its clinical utility as a novel therapeutic target in PC.

PKM2 promotes stemness of breast cancer cell by through Wnt/β-catenin pathway

Metastasis is one of the main causes of breast cancer (BCa)-related deaths in female. It has been reported that cancer stem cell played an important role in metastasis. Here we first revealed a specific role of pyruvate kinase isozymes M2 (PKM2) in the stemness of breast cancer cells. Breast cancer tissue analysis confirmed the upregulation of PKM2 in breast cancer, and high PKM2 levels were associated with poor prognosis of breast cancer patients. Holoclone assay and colony formation assay significantly elucidated the role of PKM2 in the self-renewal of breast cancer cells. Moreover, PKM2 elevated the proportion of stem cell and the ability of sphere formation in breast cancer cells. PKM2 played its functional role in stemness by regulating β-catenin. Collectively, we identified critical roles of PKM2 in the stemness of breast cancer cells which may elevate the therapeutic effect on breast cancer patients.

Establishment of a novel human medulloblastoma cell line characterized by highly aggressive stem-like cells

Medulloblastoma is a highly aggressive brain tumor and one of the leading causes of morbidity and mortality related to childhood cancer. These tumors display differential ability to metastasize and respond to treatment, which reflects their high degree of heterogeneity at the genetic and molecular levels. Such heterogeneity of medulloblastoma brings an additional challenge to the understanding of its physiopathology and impacts the development of new therapeutic strategies. This translational effort has been the focus of most pre-clinical studies which invariably employ experimental models using human tumor cell lines. Nonetheless, compared to other cancers, relatively few cell lines of human medulloblastoma are available in central repositories, partly due to the rarity of these tumors and to the intrinsic difficulties in establishing continuous cell lines from pediatric brain tumors. Here, we report the establishment of a new human medulloblastoma cell line which, in comparison with the commonly used and well-established cell line Daoy, is characterized by enhanced proliferation and invasion capabilities, stem cell properties, increased chemoresistance, tumorigenicity in an orthotopic metastatic model, replication of original medulloblastoma behavior in vivo, strong chromosome structural instability and deregulation of genes involved in neural development. These features are advantageous for designing biologically relevant experimental models in clinically oriented studies, making this novel cell line, named USP-13-Med, instrumental for the study of medulloblastoma biology and treatment.

NOTCH3 is expressed in human apical papilla and in subpopulations of stem cells isolated from the tissue

NOTCH plays a role in regulating stem cell function and fate decision. It is involved in tooth development and injury repair. Information regarding NOTCH expression in human dental root apical papilla (AP) and its residing stem cells (SCAP) is limited. Here we investigated the expression of NOTCH3, its ligand JAG1, and mesenchymal stem cell markers CD146 and STRO-1 in the AP or in the primary cultures of SCAP isolated from AP. Our in situ immunostaining showed that in the AP NOTCH3 and CD146 were co-expressed and associated with blood vessels having NOTCH3 located more peripherally. In cultured SCAP, NOTCH3 and JAG1 were co-expressed. Flow cytometry analysis showed that 7%, 16% and 98% of the isolated SCAP were positive for NOTCH3, STRO-1 and CD146, respectively with a rare 1.5% subpopulation of SCAP co-expressing all three markers. The expression level of NOTCH3 reduced when SCAP underwent osteogenic differentiation. Our findings are the first step towards defining the regulatory role of NOTCH3 in SCAP fate decision.

Concise Review: Human Dermis as an Autologous Source of Stem Cells for Tissue Engineering and Regenerative Medicine

The exciting potential for regenerating organs from autologous stem cells is on the near horizon, and adult dermis stem cells (DSCs) are particularly appealing because of the ease and relative minimal invasiveness of skin collection. A substantial number of reports have described DSCs and their potential for regenerating tissues from mesenchymal, ectodermal, and endodermal lineages; however, the exact niches of these stem cells in various skin types and their antigenic surface makeup are not yet clearly defined. The multilineage potential of DSCs appears to be similar, despite great variability in isolation and in vitro propagation methods. Despite this great potential, only limited amounts of tissues and clinical applications for organ regeneration have been developed from DSCs. This review summarizes the literature on DSCs regarding their niches and the specific markers they express. The concept of the niches and the differentiation capacity of cells residing in them along particular lineages is discussed. Furthermore, the advantages and disadvantages of widely used methods to demonstrate lineage differentiation are considered. In addition, safety considerations and the most recent advancements in the field of tissue engineering and regeneration using DSCs are discussed. This review concludes with thoughts on how to prospectively approach engineering of tissues and organ regeneration using DSCs. Our expectation is that implementation of the major points highlighted in this review will lead to major advancements in the fields of regenerative medicine and tissue engineering.

SIGNIFICANCE

Autologous dermis-derived stem cells are generating great excitement and efforts in the field of regenerative medicine and tissue engineering. The substantial impact of this review lies in its critical coverage of the available literature and in providing insight regarding niches, characteristics, and isolation methods of stem cells derived from the human dermis. Furthermore, it provides analysis of the current state-of-the-art regenerative approaches using human-derived dermal stem cells, with consideration of current guidelines, to assist translation toward therapeutic use.

Sensitivity of glioma initiating cells to a monoclonal anti-EGFR antibody therapy under hypoxia

AIMS

Glioma initiating cells (GICs) represent a subpopulation of tumor cells endowed with self-renewal and multilineage differentiation capacity but also with innate resistance to cytotoxic agents, a feature likely to pose major clinical challenges towards the complete eradication of minimal residual disease in glioma patients.

MATERIALS AND METHODS

In this work, GICs were obtained from two patient-derived high-grade gliomas xenograft model, expressing differently EGFR. GICs were exposed to anti-EGFR monoclonal antibody cetuximab during 48h in 1% or 21% oxygen tension. Cell viability and self-renewal capacity were then evaluated as well as their angiogenic properties.

KEY FINDINGS

GICs were sensitive to cetuximab only in normoxic condition whatever the EGFR status. Nevertheless, under hypoxia cetuximab was able to decrease the self-renewal capacity as well as the expression of CD133 while expression of GFAP increased. Moreover, cetuximab decreased the effect of GICs on endothelial cell migration under hypoxia.

SIGNIFICANCE

Consequently, anti-EGFR therapy can be envisaged to target specifically GICs in order to limit the tumor recurrence.

Elastic hydrogel substrate supports robust expansion of murine myoblasts and enhances their engraftment

The application of satellite cell-derived myoblasts in regenerative medicine has been restricted by the rapid loss of stemness during in vitro cell expansion using traditional culture systems. However, studies published in the past decade have highlighted the influence of substrate elasticity on stem cell fate and revealed that culture on a soft hydrogel substrate can promote self-renewal and prolong the regenerative potential of muscle stem cells. Whether hydrogel substrates have similar effects after long-term robust expansion remains to be determined. Herein we prepared an elastic chitosan/beta-glycerophosphate/collagen hydrogel mimicking the soft microenvironment of muscle tissues for use as the substrate for satellite cell culture and investigated its influence on long-term cell expansion. After 20 passages in culture, satellite cell-derived myoblasts cultured on our hydrogel substrate exhibited significant improvements in proliferation capability, cell viability, colony forming frequency, and potential for myogenic differentiation compared to those cultured on a routine rigid culture surface. Immunochemical staining and western blot analysis both confirmed that myoblasts cultured on the hydrogel substrate expressed higher levels of several differentiation-related markers, including Pax7, Pax3, and SSEA-1, and a lower level of MyoD compared to myoblasts cultured on rigid culture plates (all p<0.05). After transplantation into the tibialis anterior of nude mice, myoblasts that had been cultured on the hydrogel substrate demonstrated a significantly greater engraftment efficacy than those cultured on the traditional surface. Collectively, these results indicate that the elastic hydrogel substrate supported robust expansion of murine myoblasts and enhanced their engraftment in vivo.

Hypoxia inducible factor-1α: Its role in colorectal carcinogenesis and metastasis

Tumor growth creates a hypoxic microenvironment, which promotes angiogenesis and aggressive tumor growth and invasion. HIF1α is a central molecule involved in mediating these effects of hypoxia. In colorectal cancer (CRC), hypoxia stabilizes the transcription factor HIF1α, leading to the expression of genes that are involved in tumor vascularization, metastasis/migration, cell survival and chemo-resistance. Therefore, HIF1α is a rational target for the development of new therapeutics for CRC. This article reviews the central role of HIF1α in CRC angiogenesis, metastasis, and progression as well as the strategies to target HIF1α stabilization.

Depletion of B cell CLL/Lymphoma 11B Gene Expression Represses Glioma Cell Growth

B cell CLL/lymphoma 11B (Bcl11b), a C2H2 zinc finger transcription factor, not only serves as a critical regulator in development but also plays the controversial role in T cell acute lymphoblastic leukemia (T-ALL). We previously found that the enriched expression of Bcl11b was detected in high tumorigenic C6 glioma cells. However, the role of Bcl11b in glioma malignancy and its mechanisms remains to be uncovered. In this study, using the lentivirus-mediated knockdown (KD) approach, we found that Bcl11b KD in tumorigenic C6 cells reduced the cell proliferation, colony formation, and migratory ability. The results were further verified using two human malignant glioma cell lines, U87 and U251 cells. A cyclin-dependent kinase inhibitor p21, a known Bcl11b target, was significantly upregulated in tumorigenic C6, U87, and U251 cells after Bcl11b KD. Cellular senescence was observed by examination of the β-galactosidase activity in U87 and U251 cells with Bcl11b KD. Reduced expression of stemness gene Sox-2 and its downstream effector Bmi-1 was also observed in U87 and U251 cells with Bcl11b KD. These results suggest that the ablation of Bcl11b gene expression induced glioma cell senescence. Propidium iodide (PI) staining combined with flow cytometry analysis also showed that Bcl11b KD led to the cell cycle arrest of U87 and U251 cells at the G0/G1 or at the S phase, indicating that Bcl11b is required for glioma cell cycle progression. Together, this is the first study to show that the inhibition of Bcl11b suppresses glioma cell growth by regulating the expression of the cell cycle regulator p21 and stemness-associated genes (Sox-2/Bmi-1).

Glioblastoma stem cells (GSCs) epigenetic plasticity and interconversion between differentiated non-GSCs and GSCs

Cancer stem cells (CSCs) or cancer initiating cells (CICs) maintain self-renewal and multilineage differentiation properties of various tumors, as well as the cellular heterogeneity consisting of several subpopulations within tumors. CSCs display the malignant phenotype, self-renewal ability, altered genomic stability, specific epigenetic signature, and most of the time can be phenotyped by cell surface markers (e.g., CD133, CD24, and CD44). Numerous studies support the concept that non-stem cancer cells (non-CSCs) are sensitive to cancer therapy while CSCs are relatively resistant to treatment. In glioblastoma stem cells (GSCs), there is clonal heterogeneity at the genetic level with distinct tumorigenic potential, and defined GSC marker expression resulting from clonal evolution which is likely to influence disease progression and response to treatment. Another level of complexity in glioblastoma multiforme (GBM) tumors is the dynamic equilibrium between GSCs and differentiated non-GSCs, and the potential for non-GSCs to revert (dedifferentiate) to GSCs due to epigenetic alteration which confers phenotypic plasticity to the tumor cell population. Moreover, exposure of the differentiated GBM cells to therapeutic doses of temozolomide (TMZ) or ionizing radiation (IR) increases the GSC pool both in vitro and in vivo. This review describes various subtypes of GBM, discusses the evolution of CSC models and epigenetic plasticity, as well as interconversion between GSCs and differentiated non-GSCs, and offers strategies to potentially eliminate GSCs.

B-cell receptor-associated protein 31 regulates human embryonic stem cell adhesion, stemness, and survival via control of epithelial cell adhesion molecule

B-Cell receptor-associated protein 31 (BAP31) regulates the export of secreted membrane proteins from the endoplasmic reticulum (ER) to the downstream secretory pathway. Previously, we generated a monoclonal antibody 297-D4 against the surface molecule on undifferentiated human embryonic stem cells (hESCs). Here, we found that 297-D4 antigen was localized to pluripotent hESCs and downregulated during early differentiation of hESCs and identified that the antigen target of 297-D4 was BAP31 on the hESC-surface. To investigate the functional role of BAP31 in hESCs, BAP31 expression was knocked down by small interfering RNA. BAP31 depletion impaired hESC self-renewal and pluripotency and drove hESC differentiation into multicell lineages. BAP31 depletion hindered hESC proliferation by arresting cell cycle at G0/G1 phase and inducing caspase-independent cell death. Interestingly, BAP31 depletion reduced hESC adhesion to extracellular matrix (ECM). Analysis of cell surface molecules showed decreased expression of epithelial cell adhesion molecule (EpCAM) in BAP31-depleted hESCs, while ectopic expression of BAP31 elevated the expression of EpCAM. EpCAM depletion also reduced hESC adhesion to ECM, arrested cell cycle at G0/G1 phase and induced cell death, producing similar effects to those of BAP31 depletion. BAP31 and EpCAM were physically associated and colocalized at the ER and cell surface. Both BAP31 and EpCAM depletion decreased cyclin D1 and E expression and suppressed PI3K/Akt signaling, suggesting that BAP31 regulates hESC stemness and survival via control of EpCAM expression. These findings provide, for the first time, mechanistic insights into how BAP31 regulates hESC stemness and survival via control of EpCAM expression.

Profilin 2 promotes migration, invasion, and stemness of HT29 human colorectal cancer stem cells

We investigated the role of profilin 2 in the stemness, migration, and invasion of HT29 cancer stem cells (CSCs). Increased and decreased levels of profilin 2 significantly enhanced and suppressed the self-renewal, migration, and invasion ability of HT29 CSCs, respectively. Moreover, profilin 2 directly regulated the expression of stemness markers (CD133, SOX2, and β-catenin) and epithelial mesenchymal transition (EMT) markers (E-cadherin and snail). CD133 and β-catenin were up-regulated by overexpression of profilin 2 and down-regulated by depletion of profilin 2. SOX2 was decreased by profilin 2 depletion. E-cadherin was not influenced by profilin 2- overexpression but increased by profilin 2- knockdown. The expression of snail was suppressed by profilin 2- knockdown. We speculated that stemness and the EMT are closely linked through profilin 2-related pathways. Therefore, this study indicates that profilin 2 affects the metastatic potential and stemness of colorectal CSCs by regulating EMT- and stemness-related proteins.

Immune Targeting of Tumor Epithelial-Mesenchymal Transition via Brachyury-Based Vaccines

As a manifestation of their inherent plasticity, carcinoma cells undergo profound phenotypic changes during progression toward metastasis. One such phenotypic modulation is the epithelial-mesenchymal transition (EMT), an embryonically relevant process that can be reinstated by tumor cells, resulting in the acquisition of metastatic propensity, stem-like cell properties, and resistance to a variety of anticancer therapies, including chemotherapy, radiation, and some small-molecule targeted therapies. Targeting of the EMT is emerging as a novel intervention against tumor progression. This review focuses on the potential use of cancer vaccine strategies targeting tumor cells that exhibit mesenchymal-like features, with an emphasis on the current status of development of vaccine platforms directed against the T-box transcription factor brachyury, a novel cancer target involved in tumor EMT, stemness, and resistance to therapies. Also presented is a summary of potential mechanisms of resistance to immune-mediated attack driven by EMT and the development of novel combinatorial strategies based on the use of agents that alleviate tumor EMT for an optimized targeting of plastic tumor cells that are responsible for tumor recurrence and the establishment of therapeutic refractoriness.

The Rb-E2F transcriptional regulatory pathway in tumor angiogenesis and metastasis

The retinoblastoma tumor suppressor protein Rb plays a major role in regulating G1/S transition and is a critical regulator of cell proliferation. Rb protein exerts its growth regulatory properties mainly by physically interacting with the transcriptionally active members of the E2F transcription factor family, especially E2Fs 1, 2, and 3. Given its critical role in regulating cell proliferation, it is not surprising that Rb is inactivated in almost all tumors, either through the mutation of Rb gene itself or through the mutations of its upstream regulators including K-Ras and INK4. Recent studies have revealed a significant role for Rb and its downstream effectors, especially E2Fs, in regulating various aspects of tumor progression, angiogenesis, and metastasis. Thus, components of the Rb-E2F pathway have been shown to regulate the expression of genes involved in angiogenesis, including VEGF and VEGFR, genes involved in epithelial-mesenchymal transition including E-cadherin and ZEB proteins, and genes involved in invasion and migration like matrix metalloproteinases. Rb has also been shown to play a major role in the functioning of normal and cancer stem cells; further, Rb and E2F appear to play a regulatory role in the energy metabolism of cancer cells. These findings raise the possibility that mutational events that initiate tumorigenesis by inducing uncontrolled cell proliferation might also contribute to the progression and metastasis of cancers through the mediation of the Rb-E2F transcriptional regulatory pathway. This review highlights these recent studies on tumor promoting functions of the Rb-E2F pathway.