From adult stem cells to cancer stem cells: Oct-4 Gene, cell-cell communication, and hormones during tumor promotion

Multifaceted roles of OCT4 in tumor microenvironment: biology and therapeutic implications

OCT4 (Octamer-binding transcription factor 4, encoded by the POU5F1 gene) is a master transcription factor for maintaining the self-renewal and pluripotency of pluripotent stem cells, as well as a pioneer factor regulating epigenetics-driven cell reprogramming and cell fate conversion. It is also detected in a variety of cancer tissues and particularly in a small subpopulation of cancer cells known as cancer stem cells (CSCs). Accumulating evidence has revealed that CSCs are a dynamic population, exhibiting shift between multipotency and differentiation states, or quiescence and proliferation states. Such cellular plasticity of CSCs is profoundly influenced by dynamic interplay between CSCs and the tumor microenvironment (TME). Here, we review recent evidence showing that OCT4 expressed in CSCs plays a multifaceted role in shaping the TME by interacting with the cellular TME components, including cancer-associated fibroblasts, tumor endothelial cells, tumor-infiltrating immune cells, as well as the non-cellular TME components, such as extracellular matrix (ECM), metabolites, soluble factors (e.g., growth factors, cytokines and chemokines), and intra-tumoral microbiota. Together, OCT4 regulates crucial processes encompassing ECM remodeling, epithelial-mesenchymal transition, metabolic reprogramming, angiogenesis, and immune responses. The complex and bidirectional interactions between OCT4-expressing CSCs and the TME create a supportive niche for tumor growth, invasion, and resistance to therapy. Better understanding OCT4's roles in such interactions can provide deeper insights into potential therapeutic strategies and targets for disrupting the supportive environment of tumors. The emerging therapies targeting OCT4 in CSCs might hold promise to resensitize therapeutic-resistant cancer cells, and to eradicate all cancer cells when combined with other therapies targeting the bulk of differentiated cancer cells as well as the TME.

CD133-targeted multifunctional nanomicelles for dual-modality imaging and synergistic high-intensity focus ultrasound (HIFU) ablation on pancreatic cancer in nude mice

Pancreatic cancer is an aggressive and highly fatal malignant tumor. Recent studies have shown that cancer stem cells (CSCs) play an important role in resisting current therapeutic modalities. Furthermore, CD133 is highly expressed in CSCs. High-intensity focused ultrasound (HIFU) is a promising non-invasive therapeutic strategy for unresectable pancreatic cancers. In our study, we synthesized targeted CD133 organosilane nanomicelles by encapsulating perfluorohexane (PFH). The CD133 antibody on the surface could specifically bind to CD133-positive pancreatic cancer cells and selectively concentrate in pancreatic cancer tumor tissues. PFH was introduced to improve the ablation effect of HIFU due to its liquid-gas phase transition properties. By combining with the dorsal skinfold window chamber model (DSWC) of pancreatic cancer in nude mice, multiphoton fluorescence microscopy was used to evaluate the targeting effect of nanomicelles on pancreatic cancer tumor tissue. These multifunctional nanomicelles synergistically affected HIFU treatment of pancreatic cancer, providing an integrated research platform for diagnosing and treating pancreatic cancer with HIFU.

SIRT6 promotes metastasis and relapse in HER2-positive breast cancer

The histone deacetylase sirtuin 6 (SIRT6) has been endowed with anti-cancer capabilities in many tumor types. Here, we investigate the impact of SIRT6-overexpression (SIRT6-OE) in Delta16HER2 mice, which are a bona fide model of HER2-positive breast cancer. After an initial delay in the tumor onset, SIRT6-OE induces a more aggressive phenotype of Delta16HER2 tumors promoting the formation of higher number of tumor foci and metastases than controls. This phenotype of SIRT6-OE tumors is associated with cancer stem cell (CSC)-like features and tumor dormancy, and low senescence and oxidative DNA damage. Accordingly, a sub-set of HER2-positive breast cancer patients with concurrent SIRT6-OE has a significant poorer relapse-free survival (RFS) probability than patients with low expression of SIRT6. ChIP-seq, RNA-seq and RT-PCR experiments indicate that SIRT6-OE represses the expression of the T-box transcription factor 3 (Tbx3) by deacetylation of H3K9ac. Accordingly, loss-of-function mutations of TBX3 or low TBX3 expression levels are predictive of poor prognosis in HER2-positive breast cancer patients. Our work indicates that high levels of SIRT6 are indicative of poor prognosis and high risk of metastasis in HER2-positive breast cancer and suggests further investigation of TBX3 as a downstream target of SIRT6 and co-marker of poor-prognosis. Our results point to a breast cancer subtype-specific effect of SIRT6 and warrant future studies dissecting the mechanisms of SIRT6 regulation in different breast cancer subtypes.

CDC50A might be a novel biomarker of epithelial ovarian cancer-initiating cells

Background

The aim of this work was to screen and validate biomarkers of ovarian cancer-initiating cells to detect the mechanisms of recurrence of epithelial ovarian cancer (EOC).

Methods

Stably labelled the amino acid in side population (SP) cells of epithelial ovarian cancer which were rich in cancer-initiating cells and non-SP cells with isotope in culture and differentially expressed cellular membrane proteins in SP cells were identified through proteomics technology. The new candidate biomarker was screened and validated through RT-PCR and western blot. Both in cell lines and primary EOC, cancer-initiating biofunctions of CDC50A positive cells were validated. Moreover, the characteristics of mesenchymal transition (EMT) was also detected and the correlation between the biomarker and clinical prognosis was observed.

Results

Through proteomics technology, candidate protein CDC50A was screened, and its significantly differential expression in SP cells was validated. CDC50A-positive cells from cell lines and primary ovarian cancer tissues were validated to show characteristics of cancer-initiating cells both in vitro and in vivo, including sphere-forming, self-renewal, differentiation, tumor metastasis and tumorigenicity in mice. The relationship between CDC50A-positive cells from primary tissues and tumour metastasis was confirmed based on their mesenchymal transition characteristics. Among 16 high-grade ovarian serous cancer patients, a high ratio of CDC50A-positive cells in primary tumours was correlated with a shorter platinum-free interval (p = 0.031, HR 0.260, 95% CI 0.77 ~ 0.885).

Conclusion

CDC50A could be used to screen ovarian cancer-initiating cells and might be a new target to resolve tumour development in EOC patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09953-y.

Liquid-liquid phase separation in tumor biology

Liquid-liquid phase separation (LLPS) is a novel principle for explaining the precise spatial and temporal regulation in living cells. LLPS compartmentalizes proteins and nucleic acids into micron-scale, liquid-like, membraneless bodies with specific functions, which were recently termed biomolecular condensates. Biomolecular condensates are executors underlying the intracellular spatiotemporal coordination of various biological activities, including chromatin organization, genomic stability, DNA damage response and repair, transcription, and signal transduction. Dysregulation of these cellular processes is a key event in the initiation and/or evolution of cancer, and emerging evidence has linked the formation and regulation of LLPS to malignant transformations in tumor biology. In this review, we comprehensively summarize the detailed mechanisms of biomolecular condensate formation and biophysical function and review the recent major advances toward elucidating the multiple mechanisms involved in cancer cell pathology driven by aberrant LLPS. In addition, we discuss the therapeutic perspectives of LLPS in cancer research and the most recently developed drug candidates targeting LLPS modulation that can be used to combat tumorigenesis.

The safety of VASApos presumptive adult ovarian stem cells

Isolation and characterization of presumptive human adult ovarian stem cells (OSC) has broken the long standing dogma of the absence of postnatal neo-oogenesis. Human adult OSC have been immunosorted by antibodies reacting against the RNA helicase VASA and have been reported to engraft into appropriate stem cell niches to promote neo-oogenesis. Analysis of published research, however, questions some of the findings on isolation, characterization, in-vitro self-renewal and clinical safety of the presumptive human adult OSC. In the present study, human VASA^pos embryo-fetal primordial germ cells and presumptive adult OSC are shown to share several pluripotency and early germ cell markers not ascertained in the initial characterization of adult OSC. A new hypothesis is made that the restoration of fertility claimed to result from presumptive human adult OSC may be attributed instead to VASA^pos embryo-fetal primordial germ cell remnants in the adult ovary, or alternatively to earlier VASA^neg germ cells generated by in-vitro de-differentiation of the presumptive OSC. The suggested hypotheses have extensive implications for the practice and safety of adult OSC in the development of new treatments aimed at rescuing the ovarian reserve.

An Overview on the Complexity of OCT4: at the Level of DNA, RNA and Protein

OCT4 plays critical roles in self-renewal and pluripotency maintenance of embryonic stem cells, and is considered as one of the main stemness markers. It also has pivotal roles in early stages of embryonic development. Most studies on OCT4 have focused on the expression and function of OCT4A, which is the biggest isoform of OCT4 known so far. Recently, many studies have shown that OCT4 has various transcript variants, protein isoforms, as well as pseudogenes. Distinguishing the expression and function of these variants and isoforms is a big challenge in expression profiling studies of OCT4. Understanding how OCT4 is functioning in different contexts, depends on knowing of where and when each of OCT4 transcripts, isoforms and pseudogenes are expressed. Here, we review OCT4 known transcripts, isoforms and pseudogenes, as well as its interactions with other proteins, and emphasize the importance of discriminating each of them in order to understand the exact function of OCT4 in stem cells, normal development and development of diseases.

Connexins in Cancer: Jekyll or Hyde?

The expression, localization, and function of connexins, the protein subunits that comprise gap junctions, are often altered in cancer. In addition to cell-cell coupling through gap junction channels, connexins also form hemichannels that allow communication between the cell and the extracellular space and perform non-junctional intracellular activities. Historically, connexins have been considered tumor suppressors; however, they can also serve tumor-promoting functions in some contexts. Here, we review the literature surrounding connexins in cancer cells in terms of specific connexin functions and propose that connexins function upstream of most, if not all, of the hallmarks of cancer. The development of advanced connexin targeting approaches remains an opportunity for the field to further interrogate the role of connexins in cancer phenotypes, particularly through the use of in vivo models. More specific modulators of connexin function will both help elucidate the functions of connexins in cancer and advance connexin-specific therapies in the clinic.

Prognostic value of OCT4 in colorectal cancer: analysis using immunohistochemistry and bioinformatics validation

Aim: This study was first performed to investigate the role of octamer-binding transcription factor 4 (OCT4) in colorectal cancer (CRC). Methods: The electronic databases were searched for the eligible studies. Odds ratios and hazard ratios were calculated. Functional analysis of OCT4 was examined. Results: Eight studies with 1480 CRC cases were identified. OCT4 expression was correlated with advanced clinical stage, tumor grade, lymph node metastasis, lymphatic invasion, and distal metastasis. OCT4 was an independent prognostic biomarker for predicting worse disease-specific survival and overall survival in CRC. The functional analyses demonstrated that OCT4 was involved in multiple functions, such as cell adhesion, phosphoinositide 3-kinase/Akt signaling, and regulating pluripotency of stem cells. Conclusion: OCT4 may be correlated with disease progression and metastasis, and could predict prognosis in CRC.

Involvement of the Estrogen and Progesterone Axis in Cancer Stemness: Elucidating Molecular Mechanisms and Clinical Significance

Estrogen and progesterone regulate the growth and development of human tissues, including the reproductive system and breasts, through estrogen and progesterone receptors, respectively. These receptors are also important indicators for the clinical prognosis of breast cancer and various reproductive cancers. Many studies have reported that cancer stem cells (CSCs) play a key role in tumor initiation, progression, metastasis, and recurrence. Although the role of estrogen and progesterone in human organs and various cancers has been studied, the molecular mechanisms underlying the action of these hormones on CSCs remain unclear. Therefore, further elucidation of the effects of estrogen and progesterone on CSCs should provide a new direction for developing pertinent therapies. In this review, we summarize the current knowledge on the estrogen and progesterone axis involved in cancer stemness and discuss potential therapeutic strategies to inhibit CSCs by targeting relevant pathways.

What Can Chemical Carcinogenesis Shed Light on the LNT Hypothesis in Radiation Carcinogenesis?

To protect the public’s health from exposure to physical, chemical, and microbiological agents, it is important that any policy be based on rigorous scientifically based research. The concept of “linear no-threshold” (LNT) has been implemented to provide guideline exposures to these agents. The practical limitation to testing this hypothesis is to provide sufficient samples for experimental or epidemiological studies. While there is no universally accepted understanding of most human diseases, there seems to be better understanding of cancer that might help resolve the “LNT” model. The public’s concern, after being exposed to radiation, is the potential of producing cancer. The most rigorous hypothesis of human carcinogenesis is the “multistage, multimechanism” chemical carcinogenesis model. The radiation carcinogenesis LNT model, rarely, if ever, built it into their support. It will be argued that this multistage, multimechanism model of carcinogenesis, involving the “initiation” of a single cell by a mutagen event, followed by chronic exposure to threshold levels of epigenetic agents or conditions that stimulate the clonal expansion of the “initiated” cell, can convert these benign cells to become invasive and metastatic. This “promotion” process can be interrupted, thereby preventing these initiated cells from transitioning to the “progression” process of invasion and metastasis.

New oncogenic signalling pathway: EWS-Oct4 mediates bone and soft tissue tumourigenesis by activating fibroblast growth factor-4

Chromosomal translocations involving the interchange of parts between two non-homologous chromosomes can often lead to cancer by creating new fusion proteins. Here, Kim and co-workers show that a chimeric protein, EWS-Oct-4, transcriptionally activates fibroblast growth factor-4 (FGF-4) and triggers a downstream cascade of oncogenic signalling pathways, thereby facilitating the initiation of human bone and soft tissue tumour development. Comment on: https://doi.org/10.1111/febs.14946.

Down-regulation of DKK1 and Wnt1/β-catenin pathway by increased homeobox B7 resulted in cell differentiation suppression of intrauterine fetal growth retardation in human placenta

OBJECTIVE

This study aimed to test the influence of homeobox B7 (HoxB7) on the proliferation, invasion, and migration of human trophoblast cells and to reveal the down-regulation of HoxB7 on the transcriptional suppression of Dick Kopf-related protein1 (DKK1) and of Cysteine-rich glycosylated wingless protein 1 (Wnt1)/β-catenin in intrauterine fetal growth retardation (FGR).

METHODS

Quantitative measurement of HoxB7, DKK1, Wnt1, and β-catenin was performed in human placentas collected from normal pregnancies and from FGR with quantitative real time PCR (qRT-PCR). Cultured HTR-8/SVneo cells, transfected with a lentiviral plasmid that in-frame expresses human HoxB7 gene, were applied to functional assessment to study the biological impact of HoxB7 gene on DKK1, Wnt1, and β-catenin. Counting Kit-8, Transwell invasion assays, and flow cytometry were applied for the functional measurements.

RESULTS

The expression of HoxB7 was significantly increased, and of DKK1, Wnt1, and β-catenin was decreased, in FGR placenta tissues and in HTR-8/SVneo cells. Function studies revealed that overexpression of HoxB7 inhibited proliferation, migration, and invasion in HTR-8/SVneo cells. DKK1, Wnt1, and β-catenin were down-regulated in HTR-8/SVneo cells, inversely correlated with HoxB7 expression. Overexpression of HoxB7 showed a suppressive effect on proliferation, migration, and invasion in the HTR-8/SVneo cells.

CONCLUSIONS

Our results indicate that HoxB7 inhibited human trophoblast cell differentiation by down-regulating DKK1 expression and that it may affect transcription of Wnt1/β-catenin. The activation of HoxB7 might suppress the cell differentiation in HTR-8/SVneo cell cultures. The Wnt/β-catenin signaling pathway may play a significant role in the pathogenesis of FGR by regulating the invasion and proliferation of trophoblasts.

Differential gene expression induced by Verteporfin in endometrial cancer cells

Endometrial cancer (EMCA) is a clinically heterogeneous disease. Previously, we tested the efficacy of Verteporfin (VP) in EMCA cells and observed cytotoxic and anti-proliferative effects. In this study, we analyzed RNA sequencing data to investigate the comprehensive transcriptomic landscape of VP treated Type 1 EMCA cell lines, including HEC-1-A and HEC-1-B. There were 549 genes with differential expression of two-fold or greater and P < 0.05 after false discovery rate correction for the HEC-1-B cell line. Positive regulation of TGFβ1 production, regulation of lipoprotein metabolic process, cell adhesion, endodermal cell differentiation, formation and development, and integrin mediated signaling pathway were among the significantly associated terms. A functional enrichment analysis of differentially expressed genes after VP treatment revealed extracellular matrix organization Gene Ontology as the most significant. CDC23 and BUB1B, two genes crucially involved in mitotic checkpoint progression, were found to be the pair with the best association from STRING among differentially expressed genes in VP treated HEC-1-B cells. Our in vivo results indicate that subcutaneous tumors in mice were regressed after VP treatment by inhibiting cell cycle pathway proteins. The present study revealed multiple key genes of pathological significance in EMCA, thereby improving our understanding of molecular profiles of EMCA cells.

Cancer Prevention and Therapy of Two Types of Gap Junctional Intercellular Communication⁻Deficient "Cancer Stem Cell"

Early observations showed a lack of growth control and terminal differentiation with a lack of gap junctional intercellular communication (GJIC). Subsequent observations showed that epigenetic tumor promoters and activated oncogenes, which block gap junction function, provide insights into the multi-stage, multi-mechanism carcinogenic process. With the isolation of embryonic induced pluri-potent stem cells and organ-specific adult stem cells, gap junctions were linked to early development. While tumors and tumor cell lines are a heterogeneous mixture of "cancer stem cells" and "cancer non-stem cells", the cancer stem cells seem to be of two types, namely, they express (a) no connexin genes or (b) connexin genes, but do not have functional GJIC. These observations suggest that these "cancer stem cells" originate from normal adult stem cells or from the de-differentiation or re-programming of somatic differentiated cells. This "Concept Paper" provides a hypothesis that "cancer stem cells" either originate from (a) organ-specific adult stem cells before the expression of the connexin genes or (b) organ-specific adult stem cells that just express gap junction genes but that the connexin proteins are rendered dysfunctional by activated oncogenes. Therefore, cancer prevention and therapeutic strategies must account for these two different types of "cancer stem cell".

Clinical Efficacy of a Novel Therapeutic Principle, Anakoinosis

Classic tumor therapy, consisting of cytotoxic agents and/or targeted therapy, has not overcome therapeutic limitations like poor risk genetic parameters, genetic heterogeneity at different metastatic sites or the problem of undruggable targets. Here we summarize data and trials principally following a completely different treatment concept tackling systems biologic processes: the principle of communicative reprogramming of tumor tissues, i.e., anakoinosis (ancient greek for communication), aims at establishing novel communicative behavior of tumor tissue, the hosting organ and organism via re-modeling gene expression, thus recovering differentiation, and apoptosis competence leading to cancer control - in contrast to an immediate, "poisoning" with maximal tolerable doses of targeted or cytotoxic therapies. Therefore, we introduce the term "Master modulators" for drugs or drug combinations promoting evolutionary processes or regulating homeostatic pathways. These "master modulators" comprise a broad diversity of drugs, characterized by the capacity for reprogramming tumor tissues, i.e., transcriptional modulators, metronomic low-dose chemotherapy, epigenetically modifying agents, protein binding pro-anakoinotic drugs, such as COX-2 inhibitors, IMiDs etc., or for example differentiation inducing therapies. Data on 97 anakoinosis inducing schedules indicate a favorable toxicity profile: The combined administration of master modulators, frequently (with poor or no monoactivity) may even induce continuous complete remission in refractory metastatic neoplasia, irrespectively of the tumor type. That means recessive components of the tumor, successively developing during tumor ontogenesis, are accessible by regulatory active drug combinations in a therapeutically meaningful way. Drug selection is now dependent on situative systems characteristics, to less extent histology dependent. To sum up, anakoinosis represents a new substantive therapy principle besides novel targeted therapies.

Extra-virgin olive oil contains a metabolo-epigenetic inhibitor of cancer stem cells

Targeting tumor-initiating, drug-resistant populations of cancer stem cells (CSC) with phytochemicals is a novel paradigm for cancer prevention and treatment. We herein employed a phenotypic drug discovery approach coupled to mechanism-of-action profiling and target deconvolution to identify phenolic components of extra virgin olive oil (EVOO) capable of suppressing the functional traits of CSC in breast cancer (BC). In vitro screening revealed that the secoiridoid decarboxymethyl oleuropein aglycone (DOA) could selectively target subpopulations of epithelial-like, aldehyde dehydrogenase (ALDH)-positive and mesenchymal-like, CD44⁺CD24^−/low CSC. DOA could potently block the formation of multicellular tumorspheres generated from single-founder stem-like cells in a panel of genetically diverse BC models. Pretreatment of BC populations with noncytotoxic doses of DOA dramatically reduced subsequent tumor-forming capacity in vivo. Mice orthotopically injected with CSC-enriched BC-cell populations pretreated with DOA remained tumor-free for several months. Phenotype microarray-based screening pointed to a synergistic interaction of DOA with the mTOR inhibitor rapamycin and the DNA methyltransferase (DNMT) inhibitor 5-azacytidine. In silico computational studies indicated that DOA binds and inhibits the ATP-binding kinase domain site of mTOR and the S-adenosyl-l-methionine (SAM) cofactor-binding pocket of DNMTs. FRET-based Z-LYTE™ and AlphaScreen-based in vitro assays confirmed the ability of DOA to function as an ATP-competitive mTOR inhibitor and to block the SAM-dependent methylation activity of DNMTs. Our systematic in vitro, in vivo and in silico approaches establish the phenol-conjugated oleoside DOA as a dual mTOR/DNMT inhibitor naturally occurring in EVOO that functionally suppresses CSC-like states responsible for maintaining tumor-initiating cell properties within BC populations.

Nitric oxide promotes cancer cell dedifferentiation by disrupting an Oct4:caveolin-1 complex: A new regulatory mechanism for cancer stem cell formation

Cancer stem cells (CSCs) are unique populations of cells that can self-renew and generate different cancer cell lineages. Although CSCs are believed to be a promising target for novel therapies, the specific mechanisms by which these putative therapeutics could intervene are less clear. Nitric oxide (NO) is a biological mediator frequently up-regulated in tumors and has been linked to cancer aggressiveness. Here, we search for targets of NO that could explain its activity. We find that it directly affects the stability and function of octamer-binding transcription factor 4 (Oct4), known to drive the stemness of lung cancer cells. We demonstrated that NO promotes the CSC-regulatory activity of Oct4 through a mechanism that involves complex formation between Oct4 and the scaffolding protein caveolin-1 (Cav-1). In the absence of NO, Oct4 forms a molecular complex with Cav-1, which promotes the ubiquitin-mediated proteasomal degradation of Oct4. NO promotes Akt-dependent phosphorylation of Cav-1 at tyrosine 14, disrupting the Cav-1:Oct4 complex. Site-directed mutagenesis and computational modeling studies revealed that the hydroxyl moiety at tyrosine 14 of Cav-1 is crucial for its interaction with Oct4. Both removal of the hydroxyl via mutation to phenylalanine and phosphorylation lead to an increase in binding free energy (ΔG_bind) between Oct4 and Cav-1, destabilizing the complex. Together, these results unveiled a novel mechanism of CSC regulation through NO-mediated stabilization of Oct4, a key stem cell transcription factor, and point to new opportunities to design CSC-related therapeutics.

Endogenous authentic OCT4A proteins directly regulate FOS/AP-1 transcription in somatic cancer cells

OCT4A is well established as a master transcription factor for pluripotent stem cell (PSC) self-renewal and a pioneer factor for initiating somatic cell reprogramming, yet its presence and functionality in somatic cancer cells remain controversial and obscure. By combining the CRISPR-Cas9-based gene editing with highly specific PCR assays, highly sensitive immunoassays, and mass spectrometry, we provide unequivocal evidence here that full-length authentic OCT4A transcripts and proteins were both present in somatic cancer cells, and OCT4A proteins were heterogeneously expressed in the whole cell population and when expressed, they are predominantly localized in cell nucleus. Despite their extremely low abundance (approximately three orders of magnitude lower than in PSCs), OCT4A proteins bound to the promoter/enhancer regions of the AP-1 transcription factor subunit c-FOS gene and critically regulated its transcription. Knocking out OCT4A in somatic cancer cells led to dramatic reduction of the c-FOS protein level, aberrant AP-1 signaling, dampened self-renewal capacity, deficient cell migration that were associated with cell growth retardation in vitro and in vivo, and their enhanced sensitivity to anticancer drugs. Taken together, we resolve the long-standing controversy and uncertainty in the field, and reveal a fundamental role of OCT4A protein in regulating FOS/AP-1 signaling-centered genes that mediate the adhesion, migration, and propagation of somatic cancer cells.

Homeobox C10 inhibits the osteogenic differentiation potential of mesenchymal stem cells

PURPOSE

Mesenchymal stem cells (MSCs) are a reliable cell source for tissue regeneration. However, the molecular mechanisms underlying the directed differentiation of MSCs remain unclear which impedes potential clinical applications. Recent studies have discovered that Homeobox (HOX) genes are involved in the differentiation regulation of MSCs and bone formation. In this study, we investigate the HOXC10 function in the osteogenic differentiation potential of MSCs.

MATERIALS AND METHODS

Stem cells from apical papilla (SCAPs) and adipose-derived stem cells (ADSCs) were used in this study. Alkaline phosphatase (ALP) activity assays, ALP staining, Alizarin red staining, quantitative calcium analysis, osteogenesis-associated gene expression, and in vivo transplantation experiments were used to study osteogenic differentiation potential.

RESULTS

Our results showed that overexpression of HOXC10 in SCAPs inhibited ALP activity and mineralization in vitro and decreased the mRNA expression of collagen alpha-1 (I) chain, bone sialoprotein, osteocalcin, and a key transcription factor, runt-related transcription factor 2, in SCAPs. Depletion of HOXC10 promoted osteogenic differentiation in SCAPs in vitro. In addition, in vivo transplantation experiments in nude mice confirmed that SCAPs osteogenesis was triggered when HOXC10 was downregulated. Furthermore, depletion of HOXC10 also enhanced osteogenic differentiation in ADSCs.

CONCLUSIONS

Taken together, these results indicated that HOXC10 decreased the MSC osteogenic differentiation potential. Thus, inhibition of HOXC10 in MSCs might have the potential to improve tissue regeneration and provide insight into the mechanism underlying the directed differentiation of MSCs.

An Update on the Therapeutic Potential of Stem Cells

The seeming setbacks noted for stem cells underscore the need for experimental studies for safe and efficacious application to patients. Both clinical and experimental researchers have gained valuable knowledge on the characteristics of stem cells, and their behavior in different microenvironment. This introductory chapter focuses on adult mesenchymal stem cells (MSCs) based on the predominance in the clinic. MSCs can be influenced by inflammatory mediators to exert immune suppressive properties, commonly referred to as "licensing." Interestingly, while there are questions if other stem cells can be delivered across allogeneic barrier, there is no question on the ability of MSCs to provide this benefit. This property has been a great advantage since MSCs could be available for immediate application as "off-the-shelf" stem cells for several disorders, tissue repair and gene/drug delivery. Despite the benefit of MSCs, it is imperative that research continues with the various types of stem cells. The method needed to isolate these cells is outlined in this book. In parallel, safety studies are needed; particularly links to oncogenic event. In summary, this introductory chapter discusses several potential areas that need to be addressed for safe and efficient delivery of stem cells, and argue for the incorporation of microenvironmental factors in the studies. The method described in this chapter could be extrapolated to the field of chimeric antigen receptor T-cells (CAR-T). This will require application to stem cell hierarchy of memory T-cells.

Reflections on the use of 10 IARC carcinogenic characteristics for an objective approach to identifying and organizing results from certain mechanistic studies

To find a scientifically based method for evaluating mechanistic data related to risks to human beings, a new protocol for identifying, organizing, and summarizing mechanistic data for decision-making on cancer hazard identification was proposed by the International Agency for Research on Cancer and by an international working group of multidisciplinary experts. This Commentary examined the 10 key carcinogens’ characteristics proposed in the context of several paradigms assumed in the using of these 10 characteristics. These characteristics were assumed to represent a “carcinogen’s” mechanism of action but what was ignored were characteristics of the mechanisms of the “initiation,” “promotion,” and “progression” carcinogenic process. Challenges were made to the interpretation of genotoxicity data as well as from concepts and findings related to the promotion phase and the role of adult human stem cells. Reliance of interpretation of “genotoxicity” data (molecular-DNA lesions in DNA; induction of free radicals/oxidative stress markers; phenotypic surrogates of gene mutations), as well as from lesions in genomic versus mitochondrial DNA, or in the target cells for the carcinogenic process in either in vitro cultures or in vivo tissues, makes this “objective” use of the data questionable. A challenge to the “dedifferentiation” hypothesis of cancer was made. Because of an agent being misclassified as “genotoxic”—rather than an “epigenetic”—agent (which works by threshold levels; can be blocked; and must be present at critical times during development and at regular, sustained chronic exposures) could lead to unwise policy decisions.

DHFR and MDR1 upregulation is associated with chemoresistance in osteosarcoma stem-like cells

Tumor-initiating cells (TICs) are defined as a specialized subset of cells with tumor-initiating capacity that can initiate tumor growth, tumor relapse and metastasis. In the present study, osteosarcoma TICs (OS-TICs) were isolated and enriched from the osteosarcoma U2OS and MG-63 cell lines using sphere formation assays and serum-depleted media. These enriched OS-TICs showed the expression of several typical cancer stemness markers, including octamer-binding transcription factor 4, Nanog homeobox, cluster of differentiation (CD)117, Nestin and CD133, and the expression of ATP binding cassette subfamily G member 2, multidrug resistance protein 1 (MDR1) and dihydrofolate reductase (DHFR). Notably, in vitro and in vivo tumorigenic properties were enhanced in these OS-TICs. Additionally, methotrexate and doxorubicin are the most widely used anticancer agents against osteosarcoma, and the observed enhanced chemoresistance of OS-TICs to these two agents could be associated with the upregulation of DHFR and MDR1. These findings suggest that the upregulation of DHFR and MDR1 is associated with the development of chemoresistance of OS-TICs.

What roles do colon stem cells and gap junctions play in the left and right location of origin of colorectal cancers?

This "Commentary" examines an important clinical observation that right-sided colorectal cancers appear less treatable than the left-sided cancers. The concepts of (a) the "initiation/promotion/progression" process, (b) the stem cell hypothesis, (c) the role gap junctional intercellular communication, (d) cancer cells lacking GJIC either because of the non-expression of connexin genes or of non-functional gap junction proteins, and (e) the role of the microbiome in promoting initiated colon stem cells to divide symmetrically or asymmetrically are examined to find an explanation. It has been speculated that "embryonic-like" lesions in the ascending colon are initiated stem cells, promoted via symmetrical cell division, while the polyp-type lesions in the descending colon are initiated stem cells stimulated to divide asymmetrically. To test this hypothesis, experiments could be designed to examine if right-sided lesions might express Oct4A and ABCG2 genes but not any connexin genes, whereas the left-sided lesions might express a connexin gene, but not Oct4A or the ABCG2 genes. Treatment of the right sided lesions might include transcriptional regulators, whereas the left-sided lesions would need to restore the posttranslational status of the connexin proteins.

Long-term exposure of MCF-7 breast cancer cells to ethanol stimulates oncogenic features

Alcohol consumption is a risk factor for breast cancer. Little is known regarding the mechanism, although it is assumed that acetaldehyde or estrogen mediated pathways play a role. We previously showed that long-term exposure to 2.5 mM ethanol (blood alcohol ~0.012%) of MCF-12A, a human normal epithelial breast cell line, induced epithelial mesenchymal transition (EMT) and oncogenic transformation. In this study, we investigated in the human breast cancer cell line MCF-7, whether a similar exposure to ethanol at concentrations ranging up to peak blood levels in heavy drinkers would increase malignant progression. Short-term (1-week) incubation to ethanol at as low as 1-5 mM (corresponding to blood alcohol concentration of ~0.0048-0.024%) upregulated the stem cell related proteins Oct4 and Nanog, but they were reduced after exposure at 25 mM. Long-term (4-week) exposure to 25 mM ethanol upregulated the Oct4 and Nanog proteins, as well as the malignancy marker Ceacam6. DNA microarray analysis in cells exposed for 1 week showed upregulated expression of metallothionein genes, particularly MT1X. Long-term exposure upregulated expression of some malignancy related genes (STEAP4, SERPINA3, SAMD9, GDF15, KRT15, ITGB6, TP63, and PGR, as well as the CEACAM, interferon related, and HLA gene families). Some of these findings were validated by RT-PCR. A similar treatment also modulated numerous microRNAs (miRs) including one regulator of Oct4 as well as miRs involved in oncogenesis and/or malignancy, with only a few estrogen-induced miRs. Long-term 25 mM ethanol also induced a 5.6-fold upregulation of anchorage-independent growth, an indicator of malignant-like features. Exposure to acetaldehyde resulted in little or no effect comparable to that of ethanol. The previously shown alcohol induction of oncogenic transformation of normal breast cells is now complemented by the current results suggesting alcohol's potential involvement in malignant progression of breast cancer.

CD133+ cells in pulmonary arterial hypertension

Circulating mononuclear cells may play an important role for the vascular remodelling in pulmonary arterial hypertension (PAH), but studies addressing multiple progenitor populations are rare and inconsistent.

We used a comprehensive fluorescence-activated cell sorting analysis of circulating mononuclear cells in 20 PAH patients and 20 age- and sex-matched controls, and additionally analysed CD133+ cells in the lung tissue of five PAH transplant recipients and five healthy controls (donor lungs).

PAH patients were characterised by increased numbers of circulating CD133+ cells and lymphopenia as compared with control. In PAH, CD133+ subpopulations positive for CD117 or CD45 were significantly increased, whereas CD133+CD309+, CD133+CXCR2+ and CD133+CD31+ cells were decreased. In CD133+ cells, SOX2, Nanog, Ki67 and CXCR4 were not detected, but Oct3/4 mRNA was present in both PAH and controls. In the lung tissue, CD133+ cells included three main populations: type 2 pneumocytes, monocytes and undifferentiated cells without significant differences between PAH and controls.

In conclusion, circulating CD133+ progenitor cells are elevated in PAH and consist of phenotypically different subpopulations that may be up- or downregulated. This may explain the inconsistent results in the literature. CD133+ type 2 pneumocytes in the lung tissue are not associated with circulating CD133+ mononuclear cells.

Tryptophan derivatives regulate the transcription of Oct4 in stem-like cancer cells

The aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor that responds to environmental toxicants, is increasingly recognized as a key player in embryogenesis and tumorigenesis. Here we show that a variety of tryptophan derivatives that act as endogenous AhR ligands can affect the transcription level of the master pluripotency factor Oct4. Among them, ITE enhances the binding of the AhR to the promoter of Oct4 and suppresses its transcription. Reduction of endogenous ITE levels in cancer cells by tryptophan deprivation or hypoxia leads to Oct4 elevation, which can be reverted by administration with synthetic ITE. Consequently, synthetic ITE induces the differentiation of stem-like cancer cells and reduces their tumorigenic potential in both subcutaneous and orthotopic xenograft tumour models. Thus, our results reveal a role of tryptophan derivatives and the AhR signalling pathway in regulating cancer cell stemness and open a new therapeutic avenue to target stem-like cancer cells.

Inhibition of STAT3, FAK and Src mediated signaling reduces cancer stem cell load, tumorigenic potential and metastasis in breast cancer

Cancer stem cells (CSCs) are responsible for aggressive tumor growth, metastasis and therapy resistance. In this study, we evaluated the effects of Shikonin (Shk) on breast cancer and found its anti-CSC potential. Shk treatment decreased the expression of various epithelial to mesenchymal transition (EMT) and CSC associated markers. Kinase profiling array and western blot analysis indicated that Shk inhibits STAT3, FAK and Src activation. Inhibition of these signaling proteins using standard inhibitors revealed that STAT3 inhibition affected CSCs properties more significantly than FAK or Src inhibition. We observed a significant decrease in cell migration upon FAK and Src inhibition and decrease in invasion upon inhibition of STAT3, FAK and Src. Combined inhibition of STAT3 with Src or FAK reduced the mammosphere formation, migration and invasion more significantly than the individual inhibitions. These observations indicated that the anti-breast cancer properties of Shk are due to its potential to inhibit multiple signaling proteins. Shk also reduced the activation and expression of STAT3, FAK and Src in vivo and reduced tumorigenicity, growth and metastasis of 4T1 cells. Collectively, this study underscores the translational relevance of using a single inhibitor (Shk) for compromising multiple tumor-associated signaling pathways to check cancer metastasis and stem cell load.

Quantifying the Landscape for Development and Cancer from a Core Cancer Stem Cell Circuit

Cancer presents a serious threat to human health. The understanding of the cell fate determination during development and tumor-genesis remains challenging in current cancer biology. It was suggested that cancer stem cell (CSC) may arise from normal stem cells or be transformed from normal differentiated cells. This gives hints on the connection between cancer and development. However, the molecular mechanisms of these cell-type transitions and the CSC formation remain elusive. We quantified landscape, dominant paths, and switching rates between cell types from a core gene regulatory network for cancer and development. Stem cell, CSC, cancer, and normal cell types emerge as basins of attraction on associated landscape. The dominant paths quantify the transition processes among CSC, stem cell, normal cell, and cancer cell attractors. Transition actions of the dominant paths are shown to be closely related to switching rates between cell types, but not always to the barriers in between, because of the presence of the curl flux. During the process of P53 gene activation, landscape topography changes gradually from a CSC attractor to a normal cell attractor. This confirms the roles of P53 of preventing the formation of CSC through suppressing self-renewal and inducing differentiation. By global sensitivity analysis according to landscape topography and action, we identified key regulations determining cell-type switchings and suggested testable predictions. From landscape view, the emergence of the CSCs and the associated switching to other cell types are the results of underlying interactions among cancer and developmental marker genes. This indicates that the cancer and development are intimately connected. This landscape and flux theoretical framework provides a quantitative way to understand the underlying mechanisms of CSC formation and interplay between cancer and development.

Effects of the hippo signaling pathway in human gastric cancer

BACKGROUND/AIM

The Hippo signaling pathway is a newly discovered and conserved signaling cascade, which regulates organ size control by governing cell proliferation and apoptosis. This study aimed to investigate its effects in human gastric cancer.

METHODS

Tumor tissues (n=60), adjacent non-tumor tissues (n=60) and normal tissues (n=60) were obtained from the same patients with primary gastric cancer (GC). In addition, 70 samples of chronic atrophic gastritis (CAG) tissues were obtained from patients with intestinal metaplasia (IM) by endoscopic biopsy. Hippo signaling molecules, including Mst1, Lats1, YAP1, TAZ, TEAD1, Oct4 and CDX2, were determined by quantitative polymerase chain reaction (qPCR). Protein expression of Mst1, Lats1, YAP1, TEAD1 and CDX2 was assessed by immunohistochemistry and Western blotting.

RESULTS

Mst1, Lats1 and Oct4 mRNA expression showed an increasing tendency from GC tissues to normal gastric tissues, while the mRNA expression of YAP1, TAZ and TEAD1 was up-regulated (all P<0.01). Mst1 and Lats1 protein expression presented a similar trend with their mRNA expression. In addition, YAP1 and TEAD1 protein expression in GC was significantly higher than in the other groups (all P<0.01). CDX2 mRNA and protein expression in the CAG group were higher than in the other groups (all P<0.01). In GC, mRNA expression of Mst1, Lats1, Oct4, YAP1, TAZ, TEAD1 and CDX2 had a close correlation with lymphatic metastasis and tumor TNM stage (all P<0.01). Furthermore, protein expression of Mst1, Lats1 ,YAP1, TAZ, TEAD1 and CDX2 had a close correlation between each other (P<0.05).

CONCLUSION

The Hippo signaling pathway is involved in the development, progression and metastasis of human gastric cancer. Therefore, manipulation of Hippo signaling molecules may be a potential therapeutic strategy for gastric cancer.

Vitamin D3 regulates the formation and degradation of gap junctions in androgen-responsive human prostate cancer cells

1α-25(OH)2 vitamin D3 (1-25D), an active hormonal form of Vitamin D3, is a well-known chemopreventive and pro-differentiating agent. It has been shown to inhibit the growth of several prostate cancer cell lines. Gap junctions, formed of proteins called connexins (Cx), are ensembles of cell-cell channels, which permit the exchange of small growth regulatory molecules between adjoining cells. Cell-cell communication mediated by gap junctional channels is an important homeostatic control mechanism for regulating cell growth and differentiation. We have investigated the effect of 1-25D on the formation and degradation of gap junctions in an androgen-responsive prostate cancer cell line, LNCaP, which expresses retrovirally-introduced Cx32. Connexin32 is expressed by the luminal and well-differentiated cells of normal prostate and prostate tumors. Our results document that 1-25D enhances the expression of Cx32 and its subsequent assembly into gap junctions. Our results further show that 1-25D prevents androgen-regulated degradation of Cx32, post-translationally, independent of androgen receptor (AR)-mediated signaling. Finally, our findings document that formation of gap junctions sensitizes Cx32-expressing LNCaP cells to the growth inhibitory effects of 1-25D and alters their morphology. These findings suggest that the growth-inhibitory effects of 1-25D in LNCaP cells may be related to its ability to modulate the assembly of Cx32 into gap junctions.

The clinically used photosensitizer Verteporfin (VP) inhibits YAP-TEAD and human retinoblastoma cell growth in vitro without light activation

Verteporfin (VP), a benzoporphyrin derivative, is clinically used in photodynamic therapy for neovascular macular degeneration. Recent studies indicate that VP may inhibit growth of hepatoma cells without photoactivation through inhibition of YAP-TEAD complex. In this study, we examined the effects of VP without light activation on human retinoblastoma cell lines. Verteporfin but not vehicle control inhibited the growth, proliferation and viability of human retinoblastoma cell lines (Y79 and WERI) in a dose-dependent manner and was associated with downregulation of YAP-TEAD associated downstream proto-oncogenes such as c-myc, Axl, and surviving. In addition VP affected signals involved in cell migration and angiogenesis such as CTGF, cyr61, and VEGF-A but was not associated with significant effect on the mTOR/autophagy pathway. Of interest the pluripotency marker Oct4 were downregulated by Verteporfin treatment. Our results indicate that the clinically used photosensitizer VP is a potent inhibitor of cell growth in retinoblastoma cells, disrupting YAP-TEAD signaling and pluripotential marker OCT4. This study highlights for the first time the role of the YAP-TEAD pathway in Retinoblastoma and suggests that VP may be a useful adjuvant therapeutic tool in treating Rb patients.

A novel combination of homeobox genes is expressed in mesenchymal chorionic stem/stromal cells in first trimester and term pregnancies

Human chorionic mesenchymal stem/stromal cells (CMSCs) derived from the placenta are similar to adult tissue-derived MSCs. The aim of this study was to investigate the role of these cells in normal placental development. Transcription factors, particularly members of the homeobox gene family, play crucial roles in maintaining stem cell proliferation and lineage specification in embryonic tissues. In adult tissues and organs, stem cells proliferate at low levels in their niche until they receive cues from the microenvironment to differentiate. The homeobox genes that are expressed in the CMSC niche in placental tissues have not been identified. We used the novel strategy of laser capture microdissection to isolate the stromal component of first trimester villi and excluded the cytotrophoblast and syncytiotrophoblast layers that comprise the outer layer of the chorionic villi. Microarray analysis was then used to screen for homeobox genes in the microdissected tissue. Candidate homeobox genes were selected for further RNA analysis. Immunohistochemistry of candidate genes in first trimester placental villous stromal tissue revealed homeobox genes Meis1, myeloid ectropic viral integration site 1 homolog 2 (MEIS2), H2.0-like Drosophila (HLX), transforming growth factor β-induced factor (TGIF), and distal-less homeobox 5 (DLX5) were expressed in the vascular niche where CMSCs have been shown to reside. Expression of MEIS2, HLX, TGIF, and DLX5 was also detected in scattered stromal cells. Real-time polymerase chain reaction and immunocytochemistry verified expression of MEIS2, HLX, TGIF, and DLX5 homeobox genes in first trimester and term CMSCs. These data suggest a combination of regulatory homeobox genes is expressed in CMSCs from early placental development to term, which may be required for stem cell proliferation and differentiation.

Clonogenicity: holoclones and meroclones contain stem cells

When primary cultures of normal cells are cloned, three types of colony grow, called holoclones, meroclones and paraclones. These colonies are believed to be derived from stem cells, transit-amplifying cells and differentiated cells respectively. More recently, this approach has been extended to cancer cell lines. However, we observed that meroclones from the prostate cancer cell line DU145 produce holoclones, a paradoxical observation as meroclones are thought to be derived from transit-amplifying cells. The purpose of this study was to confirm this observation and determine if both holoclones and meroclones from cancer cell lines contain stem cells. We demonstrated that both holoclones and meroclones can be serially passaged indefinitely, are highly proliferative, can self-renew to form spheres, are serially tumorigenic and express stem cell markers. This study demonstrates that the major difference between holoclones and meroclones derived from a cancer cell line is the proportion of stem cells within each colony, not the presence or absence of stem cells. These findings may reflect the properties of cancer as opposed to normal cells, perhaps indicating that the hierarchy of stem cells is more extensive in cancer.

Induction of iPS cells and of cancer stem cells: the stem cell or reprogramming hypothesis of cancer?

This article as designed to examine whether the "stoichiometric" or "elite models" of the origin of the "induced pluripotent stem" (iPS) cells fits some experiment facts from the developmental biology of adult stem cells and from the field of cancer research. In brief, since the evidence presented to support the stoichiometric model failed to recognize the factual existence of adult organ specific stem cells, the model has not been rigorously tested. In addition, the demonstration of a subset of cells (MUSE cells) in normal primary in vitro cultures of human fibroblasts (the usual source of iPS cells) seems to be the origin of the iPS cells. Moreover, from the field of carcinogenesis, the "stem cell" versus "de-differentiation" or "reprogramming" hypotheses were examined. Again, using the role of glycolysis, known to be associated with the Warburg effect in cancer cells, a list of experiments showing that (a) normal stem cells, which have few mitochondria, metabolize via glycolysis; (b) the stem cells are targets for "initiation" or "immortalization" or the blockage of differentiation and apoptosis of the stem cells by "immortalizing viruses"; (c) Lactate dehydrogenase A (LDHA), when expressed, is associated with glycolysis and therefore, must be expressed in normal adult stem cells, as well as in cancer cells; and (d) p53, depleted or rendered dysfunctional by SV40 Large T antigen, is associated with the reduction of mitochondrial function and mass and is associated with the Warburg effect. Together, these observations from the iPS and "cancer stem cell" fields support the idea that both iPS cells and cancer stem cell are derived from adult organ-specific stem cells that do not restore or switch their metabolism of glucose from oxidative metabolism to glycolysis but, rather, in both cases, the adult stem cell, which metabolizes by glycolysis, is prevented from differentiation or from metabolizing by oxidative phosphorylation.

Clinicopathologic implication of hepatic progenitor cell marker expression in hepatoblastoma

Hepatic progenitor cells (HPCs) are thought to play a role in hepatoblastoma, as hepatoblastomas are characterized by an immature histology and a wide variety of cell lineages. We aimed to investigate the extent of expression of HPCs marker and its clinical implication in hepatoblastoma. We collected 61 hepatoblastomas and 9 childhood hepatocellular carcinomas (HCCs) and performed immunohistochemistry for HPC markers, including cytokeratin 19 (CK19), octamer-binding transcription factor 3/4 (Oct-3/4), epithelial cell adhesion molecule (EpCAM), and delta-like 1 homolog (DLK1). Of the hepatoblastoma samples, 27/61 (44.3%), 21/61 (34.4%), 51/61 (83.6%) and 56/61 (91.8%) exhibited positivity for CK19, Oct-3/4, EpCAM and DLK-1, respectively. For HCCs, the rates of expression were 22.2% (CK19), 77.8% (EpCAM) and 77.8% (DLK-1). Oct-3/4 was not expressed in HCC cells. Hepatoblastomas with a poorly differentiated epithelial component had a higher incidence of CK19 and Oct-3/4 expression than those with a well differentiated epithelial component (p=0.005 and 0.037, respectively). Higher disease stage of hepatoblastoma was correlated with CK19 expression (p=0.043). Oct-3/4-positive hepatoblastomas were associated with short disease-free survival (p=0.035). Both hepatoblastomas and childhood HCCs, therefore, exhibit characteristics of HPCs, and the poor prognosis of patients with Oct-3/4-positive hepatoblastoma suggests that stem-like properties affect hepatoblastoma pathogenicity.

Nicotine promotes acquisition of stem cell and epithelial-to-mesenchymal properties in head and neck squamous cell carcinoma

The ability of nicotine to enhance the malignancy of cancer cells is known; however, the possibility that nicotine could regulate a cancer stem cell phenotype remains to be well-established. In this study we sought to determine whether long-term exposure to nicotine could promote cancer stem cell-like properties in two head and neck squamous cell carcinoma cell lines, UMSCC-10B and HN-1. Nicotine treatment induced epithelial-to-mesenchymal transition (EMT) in both cell lines by repressing E-cadherin expression, and led to the induction of stem cell markers Oct-4, Nanog, CD44 and BMI-1, which was reversed upon ectopic re-expression of E-cadherin. Nicotine-treated cells formed spheres at a higher efficiency than non-treated cells, formed larger tumors when injected into mice, and formed tumors with 4-fold greater efficiency compared to control cells when injected at limiting doses. Consistent with previous literature, nicotine-treated cells demonstrated a greater capacity for survival and also a higher tendency to invade. Comparison of microRNA profiles between nicotine and control cells revealed the upregulation of miR-9, a repressor of E-cadherin, and the downregulation of miR-101, a repressor of EZH2. Taken together, these results suggest that nicotine may play a critical role in the development of tobacco-induced cancers by regulating cancer stem cell characteristics, and that these effects are likely mediated through EMT-promoting, microRNA-mediated pathways. Further characterization of such pathways remains a promising avenue for the understanding and treatment of tobacco-related cancers.

Nanog siRNA plus Cisplatin may enhance the sensitivity of chemotherapy in esophageal cancer

BACKGROUND

Cancer stem cells are regarded as the origin of tumors that can proliferate, relapse, and metastasize. Nanog, with its capacity to maintain the pluripotency and regulate proliferation and prevent differentiation, is one of the most important core markers of cancer stem cells. Studying the role of Nanog in esophageal squamous cell carcinoma (ESCC), therefore, has important implications.

METHODS

In the present study, we first detected the expression of Nanog in the ESCC and cell lines by RT-PCR, immunofluorescence, and immunohistochemisty. Then, we used small interfering RNA (siRNA) to block Nanog expression while evaluating the effect of Nanog siRNA on cell apoptosis and the combined effects with Cisplatin in ESCC cell lines.

RESULTS

The results showed that both mRNA and protein-level Nanog are overexpressed in ESCC tissues compared with their normal counterparts, and the increased occurrence of Nanog expression was positively correlated with TNM stages and histopathological differentiation of ESCC patients (p < 0.01). At the same time, Nanog siRNA efficiently decreased Nanog expression and induced cell apoptosis. Treatment with Nanog siRNA in combination with Cisplatin, therefore, enhanced chemosensitivity.

CONCLUSION

The present study's results suggest that detecting Nanog might be helpful for diagnosing ESCC, and Nanog siRNA combined with Cisplatin may be a feasible strategy to enhance the sensitivity of chemotherapy in patients with ESCC.

Stro-1(+) stromal cells have stem-like features in giant cell tumor of bone

BACKGROUND

Giant cell tumor of bone (GCTB) is an aggressive benign bone tumor with poor prognosis whose neoplastic component is stromal cells (SCs). Tumor stem-like cells (TSCs) have been demonstrated as precursors for tumor genesis and growth. The aim of this study is to identify TSCs in GCTB.

METHODS

Stro-1(+) and Stro-1(-) cells were isolated by fluorescence-activated cell sorting (FACS). Stem-like properties of both Stro-1(+) and Stro-1(-) subpopulations were assessed using MTT colorimetric assays, cell cycle analyses, sphere formation assays, and differentiation assays. Molecular profiles were analyzed by flow cytometry, immunofluorescence, and qRT-PCR.

RESULTS

The existence of rare Stro-1(+) cells was confirmed in vitro using FACS and in vivo by immunohistochemistry. These Stro-1(+) cells exhibited higher proliferative and cisplatin-resistant potentials than Stro-1(-) cells. In serum-free suspension cultures, Stro-1(+) SCs could form cell spheres and maintain self-renewal. Furthermore, Stro-1(+) SCs could differentiate into two mesenchymal lineage cells: osteoblasts and adipocytes. Cell surface markers CD44, CD117, and CD133 and stem cell-associated genes OCT3/4, NANOG, and ABCG2 were significantly higher in the Stro-1(+) subpopulation.

CONCLUSIONS

This study demonstrates that Stro-1(+) SCs in GCTB possess stem-like biological and molecular phenotypes, indicating that they are the TSCs of GCTB.

Muse cells and induced pluripotent stem cell: implication of the elite model

Induced pluripotent stem (iPS) cells have attracted a great deal attention as a new pluripotent stem cell type that can be generated from somatic cells, such as fibroblasts, by introducing the transcription factors Oct3/4, Sox2, Klf4, and c-Myc. The mechanism of generation, however, is not fully understood. Two mechanistic theories have been proposed; the stochastic model purports that every cell type has the potential to be reprogrammed to become an iPS cell and the elite model proposes that iPS cell generation occurs only from a subset of cells. Some reports have provided theoretical support for the stochastic model, but a recent publication demonstrated findings that support the elite model, and thus the mechanism of iPS cell generation remains under debate. To enhance our understanding of iPS cells, it is necessary to clarify the properties of the original cell source, i.e., the components of the original populations and the potential of each population to become iPS cells. In this review, we discuss the two theories and their implications in iPS cell research.

Why are epididymal tumours so rare?

Epididymal tumour incidence is at most 0.03% of all male cancers. It is an enigma why the human epididymis does not often succumb to cancer, when it expresses markers of stem and cancer cells, and constitutively expresses oncogenes, pro-proliferative and pro-angiogenic factors that allow tumour cells to escape immunosurveillance in cancer-prone tissues. The privileged position of the human epididymis in evading tumourigenicity is reflected in transgenic mouse models in which induction of tumours in other organs is not accompanied by epididymal neoplasia. The epididymis appears to: (i) prevent tumour initiation (it probably lacks stem cells and has strong anti-oxidative mechanisms, active tumour suppressors and inactive oncogene products); (ii) foster tumour monitoring and destruction (by strong immuno-surveillance and -eradication, and cellular senescence); (iii) avert proliferation and angiogenesis (with persistent tight junctions, the presence of anti-angiogenic factors and misplaced pro-angiogenic factors), which together (iv) promote dormancy and restrict dividing cells to hyperplasia. Epididymal cells may be rendered non-responsive to oncogenic stimuli by the constitutive expression of factors generally inducible in tumours, and resistant to the normal epididymal environment, which mimics that of a tumour niche promoting tumour growth. The threshold for tumour initiation may thus be higher in the epididymis than in other organs. Several anti-tumour mechanisms are those that maintain spermatozoa quiescent and immunologically silent, so the low incidence of cancer in the epididymis may be a consequence of its role in sperm maturation and storage. Understanding these mechanisms may throw light on cancer prevention and therapy in general.

Retinoids regulate the formation and degradation of gap junctions in androgen-responsive human prostate cancer cells

The retinoids, the natural or synthetic derivatives of Vitamin A (retinol), are essential for the normal development of prostate and have been shown to modulate prostate cancer progression in vivo as well as to modulate growth of several prostate cancer cell lines. 9-cis-retinoic acid and all-trans-retinoic acid are the two most important metabolites of retinol. Gap junctions, formed of proteins called connexins, are ensembles of intercellular channels that permit the exchange of small growth regulatory molecules between adjoining cells. Gap junctional communication is instrumental in the control of cell growth. We examined the effect of 9-cis-retinoic acid and all-trans retinoic acid on the formation and degradation of gap junctions as well as on junctional communication in an androgen-responsive prostate cancer cell line, LNCaP, which expressed retrovirally introduced connexin32, a connexin expressed by the luminal cells and well-differentiated cells of prostate tumors. Our results showed that 9-cis-retinoic acid and all-trans retinoic acid enhanced the assembly of connexin32 into gap junctions. Our results further showed that 9-cis-retinoic acid and all-trans-retinoic acid prevented androgen-regulated degradation of gap junctions, post-translationally, independent of androgen receptor mediated signaling. Finally, our findings showed that formation of gap junctions sensitized connexin32-expressing LNCaP cells to the growth modifying effects of 9-cis-retinoic acid, all-trans-retinoic acid and androgens. Thus, the effects of retinoids and androgens on growth and the formation and degradation of gap junctions and their function might be related to their ability to modulate prostate growth and cancer.

Recent advances in research of gastric cancer stem cells

Gastric cancer is a common malignancy of the digestive tract that has a high mortality and seriously affects people's health. At present, the pathogenesis of gastric cancer is still unclear. According to the cancer stem cell theory, cancer stem cells are malignant cells with the characteristics of normal stem cells, probably formed by the mutation of normal stem cells. Tumor stem cells have been identified in a variety of solid tumors. Recent studies have shown that the location of gastric cancer is consistent with the settlement area of stem cells, indicating that gastric cancer may be a kind of stem cells disease. In this article we will review the existence, origin, identification and separation of cancer stem cells.