miRNAs expressed differently in cancer stem cells and cancer cells of human gastric cancer cell line MKN-45

Effect of Mir-4270 Inhibitor and Mimic on Viability and Stemness in Gastric Cancer Stem-Like Cells Derived from MKN-45 Cell Line

Background

MicroRNAs (miRNAs) are significant regulatory factors in stem cell proliferation, and change in miRNA expression influences the cancer stem cell viability and gene expression. Herein, we evaluated the effect of the hsa-miR-4270 inhibitor and its mimic on the expression of stem cell markers in gastric cancer (GC) stem-like cells.

Methods

GC stem-like cells were isolated from the MKN-45 cell line by a non-adherent surface system. The cells were confirmed by differentiation assays using dexamethasone and insulin as adipogenesis-inducing agents and also Staurosporine as a neural-inducing agent. Isolated GC stem-like cells were treated with different concentrations (0, 15, 20, 25, 30, 40, 50, and 60 nM) of hsa-miR-4270 inhibitor and its mimic. The quantity of cell viability was determined by trypan blue method. Transcription of the stem cell marker genes, including CD44, OCT3/4, SOX2, Nanog, and KLF4, was evaluated by real-time RT-PCR.

Results

The results showed that GC stem-like cells were differentiated into both adipose cells using dexamethasone and insulin and neural cells by Staurosporine. Treatment of GC stem-like cells with hsa-miR-4270 inhibitor decreased cell viability and downregulated OCT3/4, CD44, and Nanog to 86%, 79%, and 91% respectively. Also, SOX2 and KLF4 were overexpressed to 8.1- and 1.94-folds, respectively. However, hsa-miR-4270 mimic had opposite effects on the cell viability and gene expression of the stem cell markers.

Conclusion

The effect of hsa-miR-4270 inhibitor and its mimic on the expression of the stem cell markers in GCSCs indicated that hsa-miR-4270 stimulates the stemness property of GCSCs, likely through stimulating the development of gastric stem cells.

The metabolic addiction of cancer stem cells

Cancer stem cells (CSC) are the minor population of cancer originating cells that have the capacity of self-renewal, differentiation, and tumorigenicity (when transplanted into an immunocompromised animal). These low-copy number cell populations are believed to be resistant to conventional chemo and radiotherapy. It was reported that metabolic adaptation of these elusive cell populations is to a large extent responsible for their survival and distant metastasis. Warburg effect is a hallmark of most cancer in which the cancer cells prefer to metabolize glucose anaerobically, even under normoxic conditions. Warburg's aerobic glycolysis produces ATP efficiently promoting cell proliferation by reprogramming metabolism to increase glucose uptake and stimulating lactate production. This metabolic adaptation also seems to contribute to chemoresistance and immune evasion, a prerequisite for cancer cell survival and proliferation. Though we know a lot about metabolic fine-tuning in cancer, what is still in shadow is the identity of upstream regulators that orchestrates this process. Epigenetic modification of key metabolic enzymes seems to play a decisive role in this. By altering the metabolic flux, cancer cells polarize the biochemical reactions to selectively generate "onco-metabolites" that provide an added advantage for cell proliferation and survival. In this review, we explored the metabolic-epigenetic circuity in relation to cancer growth and proliferation and establish the fact how cancer cells may be addicted to specific metabolic pathways to meet their needs. Interestingly, even the immune system is re-calibrated to adapt to this altered scenario. Knowing the details is crucial for selective targeting of cancer stem cells by choking the rate-limiting stems and crucial branch points, preventing the formation of onco-metabolites.

Gastric Cancer Stem Cells: A Glimpse on Metabolic Reprogramming

Gastric cancer (GC) is one of the most widespread causes of cancer-related death worldwide. Recently, emerging implied that gastric cancer stem cells (GCSCs) play an important role in the initiation and progression of GC. This subpopulation comprises cells with several features, such as self-renewal capability, high proliferating rate, and ability to modify their metabolic program, which allow them to resist current anticancer therapies. Metabolic pathway intermediates play a pivotal role in regulating cell differentiation both in tumorigenesis and during normal development. Thus, the dysregulation of both anabolic and catabolic pathways constitutes a significant opportunity to target GCSCs in order to eradicate the tumor progression. In this review, we discuss the current knowledge about metabolic phenotype that supports GCSC proliferation and we overview the compounds that selectively target metabolic intermediates of CSCs that can be used as a strategy in cancer therapy.

The Effect of hsa-miR-451b Knockdown on Biological Functions of Gastric Cancer Stem-Like Cells

Numerous researches have extensively studied factors such as microRNAs that lead to cancer. Thus, the current study's purpose is to investigate the biological consequences of hsa-miR-451b inhibition on the properties and functions of gastric cancer stem-like cells. First, gastric cancer stem-like cells were transfected by hsa-miR-451b inhibitor then we used real-time RT-PCR to evaluate its effect on the expression of hsa-miR-451b and two of its direct target genes, Stemness markers such as KLF4, SOX2, CD44, OCT3/4 and NANOG genes and finally Akt, PI3K, Bcl-2, Bax, CASP3 and PCNA genes involved in apoptosis. Here, we conducted a DNA Laddering assay to investigate apoptosis. The level of the MMP-2 and -9 Activities and Migration were examined by Zymography and Transwell invasion assay. HUVEC cells were used to investigate angiogenesis. The outcomes revealed that the level of the MMP-2 and -9 Activities, migration and angiogenesis decreased, but apoptosis was induced by inhibiting hsa-miR-451b. Evaluating KREMEN1 and CASK expression showed that the former increased, and the latter dropped under hsa-miR-451b inhibition. Also, upregulation of the KLF4 and SOX2 and downregulation of the CD44, OCT3/4, and NANOG decreased Self-renewal ability of gastric cancer stem cells under hsa-miR-451b inhibition. Even, under hsa-miR-451b inhibition, downregulation of Akt, PI3K, Bcl-2 and PCNA as well as upregulation of Bax and CASP3 revealed a movement towards apoptosis in MKN-45 stem-like cells. In summary, hsa-miR-451b is an oncomir in the carcinogenesis of gastric cancer stem-like cells and may be suggested as an appropriate therapeutic target for future gastric cancer treatment.

An integrated analysis to predict micro-RNAs targeting both stemness and metastasis in human gastric cancer

BACKGROUND AND AIM

Cancer stem cells (CSCs), a subpopulation of tumor cells, assess the capacity of self-renewal, metastasis, and therapeutic resistance. Regulation of CSCs and their epithelial to mesenchymal transition (EMT) potential is one of the promising strategies to eliminate cancer or to inhibit metastasis. Micro-RNAs (miRNAs) as regulators of several cell properties, such as self-renewal, metastasis, and resistance to the drug, could be proper targets in cancer diagnosis and therapy. The aim of the present study is to select common miRNAs targeting both self-renewal and metastasis in gastric cancer.

METHODS

Stemness-related and EMT-related genes were selected by literature mining. The common miRNAs targeting genes were chosen using different databases and r programming language. The expression pattern of selected miRNAs and genes was evaluated in gastrospheres-as a gastric CSC model-and gastric tumor biopsies.

RESULTS

Based on the integrated analysis, six miRNAs common to both stemness and metastasis were identified. miR-200c-3p and miR-520c-3p overexpressed in MKN-45 gastrospheres and grade III tumors. In AGS spheres, however, miR-520c-3p and miR-200c-3p upregulation and miR-34a-5p downregulation were similar to grade II tumors. Interestingly, miR-200c-3p and miR-520c-3p indicated a positive correlation with OCT4 and NOTCH1 expression in grade III tumors and MKN-45 spheres. Protein-protein network revealed that the EMT acquisition can be induced by stemness activation through intermediated core-regulatory genes, including CTNNB1, CTNND1, MAML1, KAT2A, and MAML3.

CONCLUSION

The upregulation of mir-200c-3p and mir-520c-3p could effect on stemness and metastasis in gastric cancer as well as gastric CSCs. Therefore, they can be used as diagnosis and prognostic factors.

Dexmedetomidine Alleviates LPS-Induced Neuronal Dysfunction by Modulating the AKT/GSK-3β/CRMP-2 Pathway in Hippocampal Neurons

OBJECTIVE

Dexmedetomidine, an α2-adrenergic receptor agonist, mitigates cognitive dysfunction in elderly patients after surgery with general anesthesia. However, the underlying mechanism by which dexmedetomidine reduces cognitive dysfunction remains to be fully elucidated. The aim of this study was to investigate the effects of dexmedetomidine on lipopolysaccharide (LPS)-induced neuronal dysfunction in cultured hippocampal neurons.

METHODS

LPS, in the presence and absence of dexmedetomidine, was applied to cultured hippocampal neurons to mimic post-surgical inflammation. Neuronal morphology, including neurite outgrowth and synaptic transmission, was observed, and miniature excitatory postsynaptic currents were recorded by electrophysiological patch-clamp.

RESULTS

LPS significantly impaired neurite outgrowth in hippocampal neurons in a concentration- and time-dependent manner, which was reversed by dexmedetomidine treatment. Electrophysiological patch-clamp results showed that LPS induced synaptic transmission dysfunction, which was restored after dexmedetomidine addition. Furthermore, Western blotting assays showed that LPS suppressed the AKT/GSK-3β/CRMP-2 signaling pathway and dexmedetomidine countered the inhibitory effect of LPS by re-activating this pathway.

CONCLUSION

In general, dexmedetomidine protected against the effects of LPS-induced hippocampal neuron damage, including neurite outgrowth and synaptic transmission. Overall, dexmedetomidine modulated the AKT/GSK-3β/CRMP-2 signaling pathway to alleviate LPS-induced neurological dysfunction.

The positive feedback loop of RHPN1-AS1/miR-1299/ETS1 accelerates the deterioration of gastric cancer

Gastric cancer (GC) is the most prevailing malignant tumor of digestive tract and accounts for a considerable part of cancer-relevant deaths worldwide. An increasing number of literatures highlight the important role of lncRNAs in the occurrence and development of GC. Considering that the function of RHPN1-AS1 in GC remains to be fully inquired, we purposed to investigate the potential and mechanism of RHPN1-AS1 in GC. The expression of RHPN1-AS1 was significantly upregulated in GC samples and cells. High RHPN1-AS1 level was strongly correlated with advanced stages of GC and predicted poor outcomes of GC. Furthermore, depletion of RHPN1-AS1 inhibited cell proliferation and cell cycle whereas promoted cell apoptosis. Subcellular fractionation analysis expounded the main expression of RHPN1-AS1 in GC cell cytoplasm. Herein, we conjectured that RHPN1-AS1 might exert its performance in GC through the ceRNA network. Our findings demonstrated that RHPN1-AS1 enhanced ETS1 expression via sponging miR-1299. More importantly, the transcriptional activation of RHPN1-AS1 was mediated by ETS1. Results of recue assays validated that RHPN1-AS1/miR-1299/ETS1 positive feedback loop aggravated the malignant behaviors of GC, revealing RHPN1-AS1 as a latent effective target for the treatment of GC patients.

Proteome and miRNome profiling of microvesicles derived from medulloblastoma cell lines with stem-like properties reveals biomarkers of poor prognosis

Primary central nervous system (CNS) tumors are the most common deadly childhood cancer. Several patients with medulloblastoma experience local or metastatic recurrences after standard treatment, a condition associated with very poor prognosis. Current neuroimaging techniques do not accurately detect residual stem-like medulloblastoma cells promoting tumor relapses. In attempt to identify candidate tumor markers that could be circulating in blood or cerebrospinal (CSF) fluid of patients, we evaluated the proteome and miRNome content of extracellular microvesicles (MVs) released by highly-aggressive stem-like medulloblastoma cells overexpressing the pluripotent factor OCT4A. These cells display enhanced tumor initiating capability and resistance to chemotherapeutic agents. A common set of 464 proteins and 10 microRNAs were exclusively detected in MVs of OCT4A-overexpressing cells from four distinct medulloblastoma cell lines, DAOY, CHLA-01-MED, D283-MED, and USP13-MED. The interactome mapping of these exclusive proteins and miRNAs revealed ERK, PI3K/AKT/mTOR, EGF/EGFR, and stem cell self-renewal as the main oncogenic signaling pathways altered in these aggressive medulloblastoma cells. Of these MV cargos, four proteins (UBE2M, HNRNPCL2, HNRNPCL3, HNRNPCL4) and five miRNAs (miR-4449, miR-500b, miR-3648, miR-1291, miR-3607) have not been previously reported in MVs from normal tissues and in CSF. These proteins and miRNAs carried within MVs might serve as biomarkers of aggressive stem-like medulloblastoma cells to improve clinical benefit by helping refining diagnosis, patient stratification, and early detection of relapsed disease.

microRNAs Tune Oxidative Stress in Cancer Therapeutic Tolerance and Resistance

Relapsed disease following first-line therapy remains one of the central problems in cancer management, including chemotherapy, radiotherapy, growth factor receptor-based targeted therapy, and immune checkpoint-based immunotherapy. Cancer cells develop therapeutic resistance through both intrinsic and extrinsic mechanisms including cellular heterogeneity, drug tolerance, bypassing alternative signaling pathways, as well as the acquisition of new genetic mutations. Reactive oxygen species (ROSs) are byproducts originated from cellular oxidative metabolism. Recent discoveries have shown that a disabled antioxidant program leads to therapeutic resistance in several types of cancers. ROSs are finely tuned by dysregulated microRNAs, and vice versa. However, mechanisms of a crosstalk between ROSs and microRNAs in regulating therapeutic resistance are not clear. Here, we summarize how the microRNA-ROS network modulates cancer therapeutic tolerance and resistance and direct new vulnerable targets against drug tolerance and resistance for future applications.

Increased expression of miR-146a, miR-10b, and miR-21 in cancer stem-like gastro-spheres

BACKGROUND

Gastric cancer remains one of the leading causes of cancer-associated mortalities globally. Accumulating evidence support the presence of gastric cancer stem cells (CSCs) and their role in the pathogenesis and therapeutic challenges of gastric cancer. MicroRNAs (miRNAs) may be influenced by the cellular differentiative state and as critical regulators of the cellular fate in development and cancer, can modulate the behavior of CSCs too. Here, we aimed to investigate the expression relevance of three prognostic miRNAs (miR-21, miR-10b, and miR-146a) in CSCs of AGS and MKN-45 gastric cancer cell lines.

METHODS

Serial sphere-forming assay in serum-free culture medium was used to enrich the cellular population with stem-like properties. Gastro-spheres were characterized by evaluating the stemness gene expression, clonogenicity, and resistance to docetaxel and cisplatin in comparison with their parental cells. The expression level of miRNAs in gastro-spheres and their parental cells was measured using quantitative reverse transcription polymerase chain reaction.

RESULTS

Gastro-spheres from both cell lines exhibit stem-like properties: upregulated stemness associated genes (P < 0.05), more colonogenicity and more resistance to docetaxel (P < 0.05). MKN-45 gastro-spheres exhibited upregulated expression of miR-21 (1.8-folds), miR-10b (1.34-folds) and miR-146a (4.8-folds; P < 0.05) compared with the parental cells. AGS-derived gastro-spheres showed upregulation of miR-21 (4.7-folds; P < 0.01), miR-10b (15.2-folds; P < 0.001) and miR-146a (39.3-folds; P < 0.05).

CONCLUSION

Our data exhibited upregulation of miR-21, miR-10b, and miR-146a in the stem-like gastro-spheres; however; their function in gastric CSCs remains to be verified by further experiments.

MicroRNA-598 inhibits the growth and maintenance of gastric cancer stem-like cells by down-regulating RRS1

Emerging evidence has identified the critical role of microRNAs in gastric cancer (GC). Herein, this study intends to characterize the tumor suppressive role of microRNA-598 (miR-598) in GC stem-like cells, with the involvement of RRS1. The CD133+ GC stem-like cells were sorted by flow cytometry, after which immunofluorescence assay was used to determine the co-localization of CD133 and CD44v8-10. The miR-598 expression was examined in the CD133+ and CD133- cells. Subsequently, the CD133+ cells were subjected to miR-598 mimics, miR-598 inhibitors or RRS1 siRNA to validate the effect of miR-598 on GC stem-like cell proliferation, colony formation, apoptosis, migration and invasion capacities. Besides, the effect of miR-598 on the expression of key factors (OCT4, SOX2 and NANOG) associated with stem cell characteristics was measured. The obtained results indicated that the sphere forming capacity was higher in CD133+ cells. CD133+ MKN-45 cells expressed CD133 and CD44v8-10, and were expressed on the cell membrane. MiR-598 was poorly expressed in CD133+ cells. Notably, miR-598 negatively regulated RRS1. In response to miR-598 mimics and RRS1 siRNA, the MKN-45 cells displayed inhibited proliferation, colony formation, migration and invasion, accompanied by elevated apoptosis. Besides, the miR-598 inhibitors reversed the situation. This study highlights that miR-598 a tumor suppressor in GC stem-like cells by inhibiting RRS1, whereby miR-598 represses MKN-45 cell growth and invasion by attenuating self-renewal of GC stem-like cells.

The Role of MicroRNAs in the Regulation of Gastric Cancer Stem Cells: A Meta-Analysis of the Current Status

Gastric cancer (GC) remains one of the major causes of cancer-related mortality worldwide. As for other types of cancers, several limitations to the success of current therapeutic GC treatments may be due to cancer drug resistance that leads to tumor recurrence and metastasis. Increasing evidence suggests that cancer stem cells (CSCs) are among the major causative factors of cancer treatment failure. The research of molecular CSC mechanisms and the regulation of their properties have been intensively studied. To date, molecular gastric cancer stem cell (GCSC) characterization remains largely incomplete. Among the GCSC-targeting approaches to overcome tumor progression, recent studies have focused their attention on microRNA (miRNA). The miRNAs are short non-coding RNAs which play an important role in the regulation of numerous cellular processes through the modulation of their target gene expression. In this review, we summarize and discuss recent findings on the role of miRNAs in GCSC regulation. In addition, we perform a meta-analysis aimed to identify novel miRNAs involved in GCSC homeostasis.

Ibuprofen reduces cell proliferation through inhibiting Wnt/β catenin signaling pathway in gastric cancer stem cells

Nowadays, most studies focused on cancer stem cells (CSCs) through their abilities to cause tumorigenicity, drug resistance, and cancer recurrence. On the other side, nonsteroidal anti-inflammatory drugs (NSAIDs) have been taken into consideration because of cheapness and availability. For the reasons mentioned above, we have studied the effect of ibuprofen as an NSAID on CSCs derived from AGS and MKN-45 gastric cancer cell lines to perform effective cancer therapy. We evaluated cell viability, spheroid body formation, monolayer, and soft agar colony formation to express the anti-cancer effect of ibuprofen on CSCs. Also, real-time RT-PCR data of stemness markers and genes affected on, or downstream of Wnt signaling pathway were evaluated. Our findings suggest that ibuprofen at 1,000 μM for 48 h can reduce cell proliferation, stemness features in CSCs by changing the expression level of CD44, OCT3/4, SOX2, Nanog, and KLF4 as stemness markers. Furthermore, ibuprofen can have an inhibitory role in Wnt signaling pathway by changing the expression level of some genes, including CTNNB1, CTNNBIP1, SMARCD1, PYGO2, SUFU, CASK, and KREMEN1. According to our study, ibuprofen has an anti-proliferative effect on CSCs derived from AGS and MKN-45 cells.

MicroRNA-124 suppresses growth and aggressiveness of osteosarcoma and inhibits TGF-β-mediated AKT/GSK-3β/SNAIL-1 signaling

Osteosarcoma is one of the most common malignant tumors in adolescent populations and the prognosis remains incompletely understand. Previous reports have demonstrated that microRNA‑124 (miR‑124) has inhibitory effects on various human malignancies and is associated with tumor progression. However, the clinical significance and potential mechanisms of miR‑124 in the progression of osteosarcoma is not clearly understood. In this study, the potential molecular mechanism of miR‑124 in osteosarcoma tumorigenesis, growth and aggressiveness was investigated. The growth, proliferation, apoptosis, migration and invasion of osteosarcoma cells were investigated following miR‑124 transfection were determined by colony formation assay, western blotting, immunofluorescence, migration/invasion assays and reverse transcription‑quantitative polymerase chain reaction. In vivo anti‑cancer effects of miR‑124 were analyzed by a tumor growth assay, immunohistochemistry and survival rate observations. The results demonstrated that miR‑124 transfection significantly decreased integrin expression in osteosarcoma cells, and further inhibited growth, proliferation, migration and invasion of osteosarcoma cells. Flow cytometry assays indicated that miR‑124 transfection attenuated apoptosis resistance of osteosarcoma to tunicamycin, potentially via the downregulation of P53 and Bcl‑2 apoptosis regulator expression. Mechanistic assays demonstrated that miR‑124 transfection suppressed TGF‑β expression in osteosarcoma. An animal study revealed that tumor growth was reduced in tumor cells transfected with miR‑124 compared with control cells, and the survival rate was prolonged in mice with miR‑124 transfected xenografts compared with control tumors. In conclusion, these results indicate that miR‑124 transection inhibits the growth and aggressive of osteosarcoma, potentially via suppression of TGF‑β‑mediated AKT/GSK‑3β/snail family transcriptional repressor 1 (SNAIL‑1) signaling, suggesting miR‑124 may be a potential anti‑cancer agent/target for osteosarcoma therapy.

Identification and Isolation of Cancer Stem Cells Using NANOG-EGFP Reporter System

Cancer stem Cells or Cancer Stem-like Cells are thought to be associated with chemoresistance and recurrence in cancer patients following chemotherapy. Developing a method to study these malignant populations is the key to successful development of drug or immunotherapeutic assays. Here, we present a method of identification, isolation of Prostate Cancer Stem Cells (PCSCs) from the DU145 prostate cancer cell line using the NANOG-GFP expression system.

In vitro and in vivo effects of miRNA-19b/20a/92a on gastric cancer stem cells and the related mechanism

We aimed to analyze the in vitro and in vivo effects of miRNA-19b/20a/92a on gastric cancer stem cells (GCSCs) and the related mechanism. GCSCs were cultured until adherence and differentiation, and subjected to miRNA microarray analysis to find and to verify miRNA deletion. Cells stably expressing lentivirus carrying miRNA-19b/20a/92a were constructed by transfection. The relationship between miRNA-19b/20a/92a and renewal of GCSCs was studied by the tumor sphere assay, and that between miRNA-19b/20a/92a and their proliferation was explored with MTT and colony formation assays. Target genes of miRNA for promoting the proliferation and self-renewal of GCSCs were found by using bioinformatics database, and verified by the reporter gene assay and Western blot. The expressions of miRNA-19b/20a/92a gradually decreased during the adherence and differentiation of GCSCs. The expressions of lentivirus carrying miRNA-17-19 gene in MKN28 and CD44^-/EpCAM^- cells were increased significantly. Transient transfection with pre-miRNA-19b/20a/92a elevated miRNA expressions in CD44^-/EpCAM^- and MKN28 cells, whereas transfection with pre-miRNA-19b/20a/92a antagonists reduced the expressions in SGC7901 and CD44⁺/EpCAM⁺ cells. Overexpression of lenti-miRNA-19b/20a/92a significantly enhanced the capability of GCSCs to form tumor spheres. In the presence of chemotherapeutic agent, the survival of lenti-miRNA-19b/20a/92a-infected cells was prolonged. Transient transfection with pre-miRNA-19b/20a/92a significantly increased the number of CD44⁺/EpCAM⁺ cells, but transfection with antagonists had the opposite outcomes. The stable miRNA-19b/20a/92a expression groups proliferated faster than the control group did. The proliferation of cells transfected with pre-miRNA-19b/20a/92a was accelerated, whereas that of cells transfected with the antagonists was decelerated. Compared with the control group, the number of colonies in the former group was higher, but that in the latter group was lower. miRNA-19b and miRNA-92a could bind the 3' untranslated region of HIPK1, while miRNA-20a was able to bind that of E2F1. Expressions of miRNA-20a and miRNA-92a in gastric cancer samples were negatively correlated with the prognosis of patients. miRNA-19b/20a/92a facilitated the self-renewal of GCSCs by targeting E2F1 and HIPK1 on the post-transcriptional level and activating the β-catenin signal transduction pathway. miRNA-92a was an independent factor and index predicting the prognosis of gastric cancer.

Cancer stem cell research in Iran: potentials and challenges

Treatment modalities can reduce cancer-related mortality; however, a majority of patients develop drug resistance, metastasis and relapse. It has been proposed that tumorigenic characteristics of tumors are related to a proportion of cancer cells, termed cancer stem cells (CSCs). Following the first evidence regarding the existence of CSC population in acute myeloid leukemia in 1997, publications in CSCs field showed an explosive trend in all cancer types around the world. First research paper in the field of CSCs in Iran was published in 2004 on prostate cancer. Subsequently, an annual number of publications in the field of CSCs displayed a rapidly growing trend. Therefore, in the current review, we have presented a comprehensive evaluation of the CSCs research in Iran.

Silencing of ATM expression by siRNA technique contributes to glioma stem cell radiosensitivity in vitro and in vivo

Evidence has shown that both high expression of the ataxia-telangiectasia mutated (ATM) gene and glioma stem cells (GSCs) are responsible for radioresistance in glioma. Thus, we hypothesized that brain tumor radiosensitivity may be enhanced via silencing of the ATM gene in GSCs. In the present study we successfully induced GSCs from two cell lines and used CD133 and nestin to identify GSCs. A lentivirus was used to deliver siRNA-ATMPuro (A group) to GSCs prior to radiation, while siRNA-HKPuro (N group) and GSCs (C group) were used as negative and blank controls, respectively. RT-qPCR and western blotting were performed to verify the efficiency of the siRNA-ATM technique. The expression of the ATM gene and ATM protein were significantly downregulated post-transfection. Cell Counting Kit-8 (CCK-8) and colony formation assays revealed that the A group demonstrated weak cell proliferation and lower survival fractions post-irradiation compared to the C/N groups. Flow cytometry was used to examine the percentage of cell apoptosis and G2 phase arrest, which were both higher in the A group than in the C/N groups. We found that the comet tail percentage evaluated by comet assay was higher in the A group than in the C/N groups. After radiation treatment, three radiosensitive genes [p53, proliferating cell nuclear antigen (PCNA), survivin] exhibited a decreasing tendency as determined by RT-qPCR. Mice underwent subcutaneous implantation, followed by radiation, and the resulting necrosis and hemorrhage were more obvious in the A group than in the N groups. In conclusion, silencing of ATM via the siRNA technique improved radiosensitivity of GSCs both in vitro and in vivo.

MicroRNA-145 exerts tumor-suppressive and chemo-resistance lowering effects by targeting CD44 in gastric cancer

AIM

To determine the potential roles of CD4 and microRNA (miR)-145 in gastric cancer.

METHODS

The levels of CD44 and miR-145 were determined in gastric cancer cells. Quantitative real-time polymerase chain reaction was used to measure to the level of CD44 mRNA. A luciferase reporter assay and western blotting were performed to examine the effect of miR-145 on CD44 expression. Tumor sphere and MTT assays were carried out to evaluate the self-renewal and chemo-resistance properties of gastric cancer cells.

RESULTS

The expression of CD44 was greatly increased and miR-145 was decreased in gastric cancer cells that were highly enriched in cancer stem cells (CSCs). The results demonstrated that miR-145 regulated CD44 by targeting directly the CD44 3’-untranslated region (3’-UTR). In gastric cancer cells, overexpression of miR-145 repressed the activity of the CD44 3’-UTR, and disruption of miR-145/CD44 3’-UTR interactions abrogated the silencing effects. In addition, miR-145 inhibition stimulated CD44 3’-UTR activity and disruption of miR-145/CD44 3’-UTR interactions abrogated this stimulatory effect. Enforced CD44 expression greatly increased tumor sphere formation and chemo-resistance in gastric cancer cells. Furthermore, the inhibition of CSCs and the chemo-sensitivity of gastric cancer cells treated with miR-145 were significantly abrogated by overexpression of CD44.

CONCLUSION

miR-145 targeting of CD44 plays critical roles in the regulation of tumor growth and chemo-resistance in gastric cancer.

MicroRNA-520c enhances cell proliferation, migration, and invasion by suppressing IRF2 in gastric cancer

Dysregulation of microRNA (miRNA) is actively involved in the development and progression of gastric cancer (GC). MiR‐520c was previously found to be overexpressed in GC specimens and cells. However, the clinical significance of miR‐520c and its biological function in GC remain largely unknown. Here, we found that miR‐520c expression in GC tissues was significantly increased compared to normal adjacent gastric tissues. Its increased level was prominently correlated with poor clinical parameters and prognosis of GC patients. Accordingly, the expression of miR‐520c was obviously elevated in GC cell lines as compared with gastric epithelial cells. Overexpression of miR‐520c in N‐87 cells significantly increased the proliferative ability, migration, and invasion of cancer cells, while miR‐520c silencing suppressed MKN‐45 cell proliferation, migration, and invasion in vitro. Mechanically, miR‐520c inversely regulated interferon regulatory factor 2 (IRF2) abundance in GC cells. Herein, IRF2 was found to be a downstream target of miR‐520c in GC. Furthermore, IRF2 was down‐regulated in GC tissues compared to nontumor tissues. An inverse correlation between IRF2 and miR‐520c expression was observed in GC cases. Taken together, miR‐520c may serve as a prognostic predictor and a therapeutic target for GC patients.

PlGF Knockdown Decreases Tumorigenicity and Stemness Properties of Spheroid Body Cells Derived from Gastric Cancer Cells

Placental growth factor (PlGF) a member of the vascular endothelial growth factor family regulates some cell processes such as survival, growth of vascular endothelial cells, invasiveness, and also involves in pathological angiogenesis and metastasis in most cancers. Cancer stem cells are believed to be the main reason for the tumor relapse and resistance to therapy. These cells have various characteristics as same as normal tissue-specific adult stem cells including self-renewability and potent to differentiate into various cell types. However, the function of PlGF in gastric cancer stem cells is not well understood. We have investigated the effect of PlGF knockdown on the tumorigenicity and stem cell properties of spheroid body cells derived from two human gastric cancer cell lines. In this study, we isolated spheroid body cells which have stemness properties from MKN-45 and AGS without using growth factors. Validation of spheroid body cells was confirmed by various methods. Then the effects of PlGF knockdown were investigated on in vitro tumorigenicity, differentiation, migration, angiogenesis, and transcription levels of stemness markers of spheroid body cells. Our findings indicated that isolation of spheroid body cells from MKN-45 and AGS cells without using growth factors is an easy and inexpensive method to isolate cancer stem cells and knockdown of PlGF in spheroid body cells reduced in vitro tumorigenicity and stemness properties of spheroid body cells such as Self-renewal ability, colony forming, migratory, and MMPs activities and decreased ability to differentiation and angiogenesis. J. Cell. Biochem. 118: 851-859, 2017. © 2016 Wiley Periodicals, Inc.

Role of miRNAs and their potential to be useful as diagnostic and prognostic biomarkers in gastric cancer

Alterations in epigenetic control of gene expression play an important role in many diseases, including gastric cancer. Many studies have identified a large number of upregulated oncogenic miRNAs and downregulated tumour-suppressor miRNAs in this type of cancer. In this review, we provide an overview of the role of miRNAs, pointing to their potential to be useful as diagnostic and/or prognostic biomarkers in gastric cancer. Moreover, we discuss the influence of polymorphisms and epigenetic modifications on miRNA activity.

Bmi-1 regulates stem cell-like properties of gastric cancer cells via modulating miRNAs

Background

B cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) plays an important role in regulating stemness in some kinds of cancer. However, the mechanisms remain unclear. This study was to investigate whether and how Bmi-1 regulates stemness of gastric cancer.

Methods

We firstly explored the role of Bmi-1 in regulating stem cell-like features in gastric cancer. Secondly, we screened out its downstream miRNAs and clarified whether these miRNAs are involved in the regulation of stemness. Finally, we investigated the mechanisms how Bmi-1 regulates miRNAs.

Results

Bmi-1 positively regulates stem cell-like properties of gastric cancer and upregulates miR-21 and miR-34a. There was a positive correlation between Bmi-1 and miR-21 expression in gastric cancer tissues. MiR-21 mediated the function of Bmi-1 in regulating stem cell-like properties, while miR-34a negatively regulates stem cell-like characteristics via downregulating Bmi-1. Bmi-1 binds to PTEN promoter and directly inhibits PTEN and thereafter activates AKT. Bmi-1 also regulates p53 and PTEN via miR-21. Bmi-1 activated NF-kB via AKT and enhanced the binding of NF-kB to the promoter of miR-21 and miR-34a and increased their expression.

Conclusions

Bmi-1 positively regulates stem cell-like properties via upregulating miR-21, and miR-34a negatively regulates stem cell-like characteristics by negative feedback regulation of Bmi-1 in gastric cancer. Bmi-1 upregulates miR-21 and miR-34a by activating AKT-NF-kB pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0323-9) contains supplementary material, which is available to authorized users.

Role of miRNA dynamics and cytokine profile in governing CD44v6/Nanog/PTEN axis in oral cancer: modulating the master regulators

Late diagnosis, low therapeutic response, and metastasis are accountable for poor 5-year survival rate of OSCC. These failures are attributed to the existence of "cancer stem cell (CSC)" subpopulation. Hence, it is necessary to identify and understand the mechanism of CSCs in tumor development, metastasis, and chemotherapeutic response. Propelling evidences suggest that microRNA (miRNA)-mediated regulation and cytokines of tumor microenvironment have the ability to modulate CSC signalling pathway; however, their exact mechanism needs to be elucidated. Thus, in this study, we characterized CSC markers and highlighted the miRNA dynamics and cytokine profile regulating these CSCs in a pathway-dependent manner. Our results demonstrated CD44+ subpopulation as tumor-initiating cells with self-renewal capability, tumorigenic growth potential and intrinsic chemoresistance. These tumors exhibited increased expression of CSC markers (CD44v3, CD44v6, Nanog, and Bmi1) and significantly reduced expression of PTEN and ATM in OSCC patients. Pathway analysis of these CSC markers demonstrated a prospective pathway regulated by miRNA and cytokine network. On analyzing these modulators, we observed decreased expression of miRNA542-3p, miRNA34a and miRNA9, and significant upregulation of miRNA21, thus forming an unexplored axis. Cytokine profiling revealed significantly increased levels of IL-6 and IL-8 compared to normals and demonstrated their strong association with CD44v6. Collectively, this study indicates that miR5423p and miR34a targets the CD44v6-Nanog-PTEN axis, thus playing a vital role in regulating the CSC properties. Furthermore, we speculate an impinging role of cytokines IL-6 and IL-8 in regulating this CSC-mediated pathway which can have prognostic and therapeutic implications.

Deciphering the role of microRNA 21 in cancer stem cells (CSCs)

Irrespective of positive developments of cancer treatment, the mortality due to various cancers remains high and the mechanisms of cancer initiation and the development also remains mysterious. As we know that microRNAs are considered to be a short noncoding RNA molecules consisting of 21–25 nucleotides (nt) in length and they silence their target genes by inhibiting mRNA translation or degrading the mRNA molecules by binding to their 3′-untranslated (UTR) region and play a very important role in cancer biology. Recent evidences indicate that miR-21 is over expressed in cancer stem cells and plays a vital role in cell proliferation, apoptosis, and invasion. Even though an increased expression level of miR-21 has been observed in cancer stem cells, studies related to the role of miR-21 in cancer stem cells are limited. The main aim of this mini review is to explain the potency of miR-21 in various cancer stem cells (CSCs) and as a new target for therapeutic interventions of cancer progression.

STAT3 is Overactivated in Gastric Cancer Stem-Like Cells

Objective

Gastric cancer (GC) is widely associated with chronic inflammation. The pro inflammatory microenvironment provides conditions that disrupt stem/progenitor cell proliferation and differentiation. The signal transducer and activator of transcrip- tion-3 (STAT3) signaling pathway is involved in inflammation and also contributes to the maintenance of embryonic stem cell (ESCs) pluripotency. Here, we have investi- gated the activation status of STAT3 in GC stem-like cells (GCSLCs).

Materials and Methods

In this experimental research, CSLCs derived from the human GC cell line MKN-45 and patient specimens, through spheroid body formation, character- ized and then assayed for the STAT3 transcription factor expression in mRNA and protein level further to its activation.

Results

Spheroid cells showed higher potential for spheroid formation than the pa- rental cells. Furthemore, stemness genes NANOG, c-MYC and SOX-2 were over expressed in spheroids of MKN-45 and in patient samples. In MKN-45 spheroid cells, epithelial mesenchymal transition (EMT) related markers CDH2, SNAIL2, TWIST and VIMENTIN were upregulated (P<0.05), but we observed no change in expression of the E-cadherin epithelial marker. These cells exhibited more resistance to docetaxel (DTX) when compared with parental cells (P<0.05) according to the MTS assay. Al- though immunostaining and Western blotting showed expression of the STAT3 pro- tein in both spheroids and parents, the mRNA level of STAT3 in spheroids was higher than the parents. Nuclear translocation of STAT3 was accompanied by more intensive phospho-STAT3 (p-STAT3) in spheroid structures relative to the parent cells accord- ing to flow cytometry analysis (P<0.05).

Conclusion

The present findings point to STAT3 over activation in GCSLCs. Com- plementary experiments are required to extend the role of STAT3 in stemness fea- tures and invasion properties of GCSCs and to consider the STAT3 pathway for CSC targeted therapy.

Antioxidant Mechanisms and ROS-Related MicroRNAs in Cancer Stem Cells

Increasing evidence indicates that most of the tumors are sustained by a distinct population of cancer stem cells (CSCs), which are responsible for growth, metastasis, invasion, and recurrence. CSCs are typically characterized by self-renewal, the key biological process allowing continuous tumor proliferation, as well as by differentiation potential, which leads to the formation of the bulk of the tumor mass. CSCs have several advantages over the differentiated cancer cell populations, including the resistance to radio- and chemotherapy, and their gene-expression programs have been shown to correlate with poor clinical outcome, further supporting the relevance of stemness properties in cancer. The observation that CSCs possess enhanced mechanisms of protection from reactive oxygen species (ROS) induced stress and a different metabolism from the differentiated part of the tumor has paved the way to develop drugs targeting CSC specific signaling. In this review, we describe the role of ROS and of ROS-related microRNAs in the establishment and maintenance of self-renewal and differentiation capacities of CSCs.

Overexpression of microRNA-16 declines cellular growth, proliferation and induces apoptosis in human breast cancer cells

MicroRNAs (miRNA) are a large family of small single-stranded RNA molecules found in all multicellular organisms. Early studies have been shown that miRNA are involved in cancer development and progression, and this role can be done by working as an oncogenes and tumor suppressor genes, so manipulation of this molecules can be a promising approach in cancer therapy, and experimental results represented that the modification in breast cancer phenotype is possible by miRNA expression alteration. miR-16, which is located in 13q14 chromosome, plays critical roles as a tumor suppressor by targeting several oncogenes which regulate cell cycle and apoptosis. Hence, in the present study, we investigated whether miR-16 could decline growth and survival of MCF-7 cell line as model of human breast cancer. MCF-7 cell line was infected with lentiviruses containing miR-16 precursor sequence. The effects of ectopic expression of miR-16 on breast cancer phenotype were examined by cell cycle analysis and apoptosis assays. miR-16 cytotoxicity effect was measured by the MTT assay. We showed that the miR-16 overexpression reduces Cyclin D1 and BCL2 at messenger RNA (mRNA) and protein levels in MCF-7 cell line. In addition, this is found that enforced expression of miR-16 decreases cell growth and proliferation and induces apoptosis in MCF-7 cells. In conclusion, our results revealed that upregulation of miR-16 would be a potential approach for breast cancer therapy.

MicroRNA let-7a modifies the effect of self-renewal gene HIWI on patient survival of epithelial ovarian cancer

Aberrant expressions of self-renewal gene HIWI and microRNA (miRNA) let-7a are observed in epithelial ovarian cancer (EOC). A U-shape association between HIWI expression and overall survival is seen in several human cancers but unknown in EOC. HIWI directly and/or indirectly interacts with let-7a, but the clinical relevance of this interaction is yet to be addressed. Here, we analyzed HIWI and let-7a expressions in 211 primary EOC tissues using quantitative reverse-transcription PCR to investigate HIWI and its interaction with let-7a in the prognostic significance of EOC. Associations of HIWI and its interaction with miRNA let-7a with patient survival were analyzed using the Kaplan-Meier survival curves and Cox proportional hazard regression models. Kaplan-Meier survival curves showed that patients with medium HIWI had poorer overall survival than those with low or high HIWI. An 89% increased death risk (HR = 1.89, 95% CI: 1.29-2.98) was observed in the medium HIWI group in multivariate Cox proportional hazard regression analyses. Among patients with high let-7a expression, those with medium HIWI had an increased risk of death compared to those with low HIWI (HR = 2.62, 95% CI: 1.30-5.30), whereas among those with low let-7a, no significant association between HIWI expression and overall survival was observed (HR = 1.63, 95% CI: 0.86-3.08). Moreover, HIWI expression also affected chemotherapy response. The results suggested that miRNA let-7a could modify the effect of HIWI expression on patient survival of EOC, expanding our understanding of the clinical relevance of HIWI and let-7a interaction in EOC prognosis. © 2015 Wiley Periodicals, Inc.

Notch signaling pathway and gastric cancer

Gastric cancer is still the second leading cause of cancer-related death. Currently, all the available therapeutic methods in practice appear to be blunt for the majority of advanced-stage patients and their long time-survival rate is also still rather frustrating. The Notch signaling pathway is increasingly demonstrated to play an important role in controlling the fate of gastric cancer cells and gastric cancer stem cells, and some previous studies have indicated that different Notch receptors and ligands, such as Notch-1, 2, 3, Dll-1, 4 and Jag-1, 2, were highly expressed in gastric cancer tissues and were associated with various clinical parameters. More notably, these receptors and ligands were also found to be expressed in gastric cancer stem cells, which were CD44 positive, and could have a key role in regulating the fate of these cells. Taking into consideration the pivotal role of Notch signaling pathway in gastric cancer and cancer stem cells, it would be promising to predict that it could become therapeutic targets in the future.

Metformin may function as anti-cancer agent via targeting cancer stem cells: the potential biological significance of tumor-associated miRNAs in breast and pancreatic cancers

Metformin is one of the most used diabetic drugs for the management of type II diabetes mellitus (DM) in the world. Increased numbers of epidemiological and clinical studies have provided convincing evidence supporting the role of metformin in the development and progression of a variety of human tumors including breast and pancreatic cancer. Substantial pre-clinical evidence from in vitro and in vivo experimental studies strongly suggests that metformin has an anti-cancer activity mediated through the regulation of several cell signaling pathways including activation of AMP kinase (AMPK), and other direct and indirect mechanisms; however, the detailed mechanism(s) has not yet been fully understood. The concept of cancer stem cells (CSCs) has gained significant attention in recent years due its identification and defining its clinical implications in many different tumors including breast cancer and pancreatic cancer. In this review, we will discuss the protective role of metformin in the development of breast and pancreatic cancers. We will further discuss the role of metformin as an anti-cancer agent, which is in part mediated through targeting CSCs. Finally, we will discuss the potential role of metformin in the modulation of tumor-associated or CSC-associated microRNAs (miRNAs) as part of the novel mechanism of action of metformin in the development and progression of breast and pancreatic cancers.

Apoptotic death of cancer stem cells for cancer therapy

Cancer stem cells (CSCs) play crucial roles in tumor progression, chemo- and radiotherapy resistance, and recurrence. Recent studies on CSCs have advanced understanding of molecular oncology and development of novel therapeutic strategies. This review article updates the hypothesis and paradigm of CSCs with a focus on major signaling pathways and effectors that regulate CSC apoptosis. Selective CSC apoptotic inducers are introduced and their therapeutic potentials are discussed. These include synthetic and natural compounds, antibodies and recombinant proteins, and oligonucleotides.

Oncogenic micro-RNAs and Renal Cell Carcinoma

Tumor formation is a complex process that occurs in different steps and involves many cell types, including tumor cells, endothelial cells, and inflammatory cells, which interact to promote growth of the tumor mass and metastasization. Epigenetic alterations occurring in transformed cells result in de-regulation of miRNA expression (a class of small non-coding RNA that regulates multiple functions), which contributes to tumorigenesis. The specific miRNAs, which have an aberrant expression in tumors, are defined as oncomiRNAs, and may be either over- or under-expressed, but down-regulation is most commonly observed. Renal cell carcinoma (RCC) is a frequent form of urologic tumor, associated with an alteration of multiple signaling pathways. Many molecules involved in the progression of RCCs, such as HIF, VEGF, or mammalian target of rapamycin, are possible targets of de-regulated miRNAs. Within tumor mass, the cancer stem cell (CSC) population is a fundamental component that promotes tumor growth. The CSC hypothesis postulates that CSCs have the unique ability to self-renew and to maintain tumor growth and metastasis. CSCs present in RCC were shown to express the mesenchymal stem cell marker CD105 and to exhibit self-renewal and clonogenic properties, as well as the ability to generate serially transplantable tumors. The phenotype of CSC has been related to the potential to undergo the epithelial–mesenchymal transition, which has been linked to the expression pattern of tumorigenic miRNAs or down-regulation of anti-tumor miRNAs. In addition, the pattern of circulating miRNAs may allow discrimination between healthy and tumor patients. Therefore, a miRNA signature may be used as a tumor biomarker for cancer diagnosis, as well as to classify the risk of relapse and metastasis, and for a guide for therapy.

MicroRNAs: master regulators of drug resistance, stemness, and metastasis

MicroRNAs (miRNAs) are 20-22 nucleotides long small non-coding RNAs that regulate gene expression post-transcriptionally. Last decade has witnessed emerging evidences of active roles of miRNAs in tumor development, progression, metastasis, and drug resistance. Many factors contribute to their dysregulation in cancer, such as chromosomal aberrations, differential methylation of their own or host genes' promoters and alterations in miRNA biogenesis pathways. miRNAs have been shown to act as tumor suppressors or oncogenes depending on the targets they regulate and the tissue where they are expressed. Because miRNAs can regulate dozens of genes simultaneously and they can function as tumor suppressors or oncogenes, they have been proposed as promising targets for cancer therapy. In this review, we focus on the role of miRNAs in driving drug resistance and metastasis which are associated with stem cell properties of cancer cells. Furthermore, we discuss systems biology approaches to combine experimental and computational methods to study effects of miRNAs on gene or protein networks regulating these processes. Finally, we describe methods to target oncogenic or replace tumor suppressor miRNAs and current delivery strategies to sensitize refractory cells and to prevent metastasis. A holistic understanding of miRNAs' functions in drug resistance and metastasis, which are major causes of cancer-related deaths, and the development of novel strategies to target them efficiently will pave the way towards better translation of miRNAs into clinics and management of cancer therapy.

Emerging role of nanog in tumorigenesis and cancer stem cells

Nanog is a transcription factor that is well-established as a key regulator of embryonic stem cell (ESC) maintenance. Recent evidence demonstrates that Nanog is dysregulated and intimately involved in promoting tumorigenesis in part through regulation of the cancer stem cell (CSC) population. Elevated Nanog is associated with poorer outcome in numerous epithelial malignancies. Nanog is enriched in CSCs and ablation of Nanog is sufficient to reduce the CSC pool. Nanog has also been implicated to promote chemoresistance and epithelial-mesenchymal transition (EMT). Insight into the Nanog signaling cascade, upstream regulators and downstream effectors, is beginning to emerge but remains to be fully elucidated. This review highlights the current literature on the emerging role of Nanog in tumorigenesis and CSCs.

Targeting CSCs in tumor microenvironment: the potential role of ROS-associated miRNAs in tumor aggressiveness

Reactive oxygen species (ROS) have been widely considered as critical cellular signaling molecules involving in various biological processes such as cell growth, differentiation, proliferation, apoptosis, and angiogenesis. The homeostasis of ROS is critical to maintain normal biological processes. Increased production of ROS, namely oxidative stress, due to either endogenous or exogenous sources causes irreversible damage of bio-molecules such as DNA, proteins, lipids, and sugars, leading to genomic instability, genetic mutation, and altered gene expression, eventually contributing to tumorigenesis. A great amount of experimental studies in vitro and in vivo have produced solid evidence supporting that oxidative stress is strongly associated with increased tumor cell growth, treatment resistance, and metastasis, and all of which contribute to tumor aggressiveness. More recently, the data have indicated that altered production of ROS is also associated with cancer stem cells (CSCs), epithelial-to-mesenchymal transition (EMT), and hypoxia, the most common features or phenomena in tumorigenesis and tumor progression. However, the exact mechanism by which ROS is involved in the regulation of CSC and EMT characteristics as well as hypoxia- and, especially, HIF-mediated pathways is not well known. Emerging evidence suggests the role of miRNAs in tumorigenesis and progression of human tumors. Recently, the data have indicated that altered productions of ROS are associated with deregulated expression of miRNAs, suggesting their potential roles in the regulation of ROS production. Therefore, targeting ROS mediated through the deregulation of miRNAs by novel approaches or by naturally occurring anti-oxidant agents such as genistein could provide a new therapeutic approach for the prevention and/or treatment of human malignancies. In this article, we will discuss the potential role of miRNAs in the regulation of ROS production during tumorigenesis. Finally, we will discuss the role of genistein, as a potent anti-tumor agent in the regulation of ROS production during tumorigenesis and tumor development.

Overview of cancer stem cells (CSCs) and mechanisms of their regulation: implications for cancer therapy

The identification of small subpopulations of cancer stem cells (CSCs) from blood mononuclear cells in human acute myeloid leukemia (AML) in 1997 was a landmark observation that recognized the potential role of CSCs in tumor aggressiveness. Two critical properties contribute to the functional role of CSCs in the establishment and recurrence of cancerous tumors: their capacity for self-renewal and their potential to differentiate into unlimited heterogeneous populations of cancer cells. These findings suggest that CSCs may represent novel therapeutic targets for the treatment and/or prevention of tumor progression, since they appear to be involved in cell migration, invasion, metastasis, and treatment resistance-all of which lead to poor clinical outcomes. The identification of CSC-specific markers, the isolation and characterization of CSCs from malignant tissues, and targeting strategies for the destruction of CSCs provide a novel opportunity for cancer research. This overview describes the potential implications of several common CSC markers in the identification of CSC subpopulations that are restricted to common malignant diseases, e.g., leukemia, and breast, prostate, pancreatic, and lung cancers. The role of microRNAs (miRNAs) in the regulation of CSC function is also discussed, as are several methods commonly used in CSC research. The potential role of the antidiabetic drug metformin- which has been shown to have effects on CSCs, and is known to function as an antitumor agent-is discussed as an example of this new class of chemotherapeutics.

Targeting CSC-related miRNAs for cancer therapy by natural agents

The theory of cancer stem cells (CSCs) has provided evidence on fundamental clinical implications because of the involvement of CSCs in cell migration, invasion, metastasis, and treatment resistance, which leads to the poor clinical outcome of cancer patients. Therefore, targeting CSCs will provide a novel therapeutic strategy for the treatment and/or prevention of tumors. However, the regulation of CSCs and its signaling pathways during tumorigenesis are not well understood. MicroRNAs (miRNAs) have been proved to act as key regulators of the post-transcriptional regulation of genes, which involve in a wide array of biological processes including tumorigenesis. The altered expressions of miRNAs are associated with poor clinical outcome of patients diagnosed with a variety of tumors. Therefore, emerging evidence strongly suggest that miRMAs play critical roles in tumor development and progression. Emerging evidence also suggest that miRNAs participate in the regulation of tumor cell growth, migration, invasion, angiogenesis, drug resistance, and metastasis. Moreover, miRNAs such as let-7, miR-21, miR-22, miR-34, miR-101, miR-146a, and miR-200 have been found to be associated with CSC phenotype and function mediated through targeting oncogenic signaling pathways. In this article, we will discuss the role of miRNAs in the regulation of CSC phenotype and function during tumor development and progression. We will also discuss the potential role of naturally occurring agents (nutraceuticals) as potent anti-tumor agents that are believed to function by targeting CSC-related miRNAs.

Effect of shRNA-mediated inhibition of Nanog gene expression on the behavior of human gastric cancer cells

The aim of the present study was to employ RNA interference (RNAi) technology to construct and select shRNA-Nanog recombinant plasmids for the inhibition of Nanog gene expression and transfer these plasmids into the human gastric cancer cell line, SGC-7901, as well as to detect the expression of Nanog and the effects on the proliferation, migration, invasion, cell cycle and apoptosis of SGC-7901 cells. The pshRNA-Nanog interference plasmids were constructed and used to transfect SGC-7901 cells using lipofectamine. The expression of the Nanog gene was detected by fluorescence microscopy, RT-PCR and western blotting, and the most markedly inhibited group was identified. The SGC-7901 cells were transfected with recombinant shRNA-Nanog plasmids from the most markedly inhibited group using lipofectamine and the effect on proliferation was determined by CCK-8 assay. The migration and invasion of the SGC-7901 cells was determined by Transwell assays, while the cell cycle and apoptosis were analyzed by flow cytometry. The group with the highest inhibition rate was successfully constructed and identified. It was observed that the proliferation, invasion and migration capacity of the cells was reduced, that the cell cycle was arrested at the S phase and that apoptosis was significantly increased. The Nanog gene in gastric cancer cells is closely associated with cell proliferation, the cell cycle, apoptosis and migration and invasion abilities. The present study establishes the foundations for a novel approach for the genetic treatment of gastric cancer.

CpG island hypermethylation-associated silencing of microRNAs promotes human endometrial cancer

Background

Endometrial cancer (EC) is the most common gynecologic malignancy, but the molecular events involved in the development and progression of EC remain unclear. This study aimed to explore epigenetic modification of genes and miRNAs involved in EC development.

Methods

Ishikawa and AN3CA cells were treated with 5’-Aza-2-deoxycytidine or histone deacetylase inhibitor. The expression of miRNAs and related genes were detected by PCR and Western blot. Promoter methylation was detected by bisulfite specific PCR sequencing. The proliferation, colony formation, cell cycle progression, migration and invasion of EC cells were evaluated by MTT, soft agar assay, flow cytometry, wound healing and invasion assay, respectively.

Results

Aberrant expression of miRNAs including miR-200b, miR-130a/b, miR-625 and miR-222 was associated with tumorigenesis and metastasis in endometrial cancer. Silencing of miR-130b induced E-cadherin expression, while ectopic expression of miR-130b and knockdown of DICER1 increased the expression of Vimentin, zeb2, N-cadherin, Twist and Snail in EC cells. Furthermore, 5’-Aza-2-deoxycytidine and Histone deacetylase (HDAC) inhibitor inhibited the proliferation, colony formation, migration and invasion of EC cells, accompanied by reduced MMP secretion.

Conclusions

Our study provides the first description of epigenetic modification of epithelial mesenchymal transition associated genes and miRNAs in EC cells, which are extensively involved in the regulation of gene expression and subsequent accumulation of malignant features of EC cells.

The role of microRNAs in cancers of the upper gastrointestinal tract

Cancers of the oesophagus, gastro-oesophageal junction and stomach (upper gastrointestinal tract cancers; UGICs) pose a major health risk around the world. Collectively, the 5-year survival rate has remained <15%, and therapeutic improvements have been very slow and small. Novel molecules for early diagnosis, prognosis and therapy are, therefore, urgently needed. The role that microRNA (miRNA) molecules have in UGICs are worth pursuing to this end. miRNAs are small noncoding RNA molecules that regulate ∼60% of coding genes in humans and, therefore, are pivotal in mediating and regulating many physiologic processes. miRNAs are deregulated in many disease states, particularly in cancer, making them important targets. Here, we review the growing body of evidence regarding the alterations of miRNAs in UGICs. By suppressing translation and/or promoting degradation of mRNAs, miRNAs can contribute to carcinogenesis and progression of UGICs. In-depth studies of miRNAs in UGICs might yield novel insights and potential novel therapeutic strategies.

Inhibition of microRNA-302 (miR-302) by bone morphogenetic protein 4 (BMP4) facilitates the BMP signaling pathway

The signaling pathway mediated by BMPs plays an essential role during development as well as the maintenance of homeostasis in adult. Aberrant activation or inactivation of BMP signaling can lead to developmental defects and various human disorders. To fine-tune its activity, BMP signaling is regulated both positively and negatively by extrinsic and intrinsic regulatory factors that modulate binding of ligand to the receptors, and the activity of receptors and their dedicated signal transducers, the Smad proteins. Upon BMP binding to the receptor complex, Smad proteins translocate to the nucleus and modulate gene expression transcriptionally by directly associating with the promoter region of target genes, or post-transcriptionally through modulation of microRNA (miRNA) synthesis. In this study, we demonstrate that BMP signaling down-regulates transcription of the miRNA-302∼367 gene cluster. We show that the type II BMP receptor (BMPRII) is a novel target of miR-302. Upon overexpression, miR-302 targets a partially complementary sequence localized in the 3'-untranslated region (UTR) of BMPRII transcripts and leads to destabilization of the transcripts and down-regulation of BMP signaling. We propose that the negative regulatory loop of BMP4-miR-302-BMPRII is a potential mechanism for the maintenance and fine-tuning of the BMP signaling pathway in various systems.