Cross-talk between miRNA and Notch signaling pathways in tumor development and progression

Gamma secretase inhibitor impairs epithelial-to-mesenchymal transition induced by TGF-β in ovarian tumor cell lines

Ovarian cancer is characterized by being highly metastatic, a feature that represents the main cause of failure of the treatment. This study investigated the effects of γ-secretase inhibition on the TGF-β-induced epithelial-mesenchymal transition (EMT) process in ovarian cancer cell lines. SKOV3 cells incubated in the presence of TGF-β showed morphological and biochemical changes related to EMT, which were blocked by co-stimulation with TGF-β and the γ-secretase inhibitor DAPT. In SKOV3 and IGROV1 cells, the co-stimulation blocked the cadherin switch and the increase in the transcription factors Snail, Slug, Twist and Zeb1 induced by TGF-β. DAPT impaired the translocation of phospho-β-catenin to the inner cell compartment observed in TGF-β-treated cells, but was not able to block the induction at protein level induced by TGF-β. Moreover, the inhibitor blocked the increased cell migration and invasiveness ability of both cell lines induced by TGF-β. Notch target genes (Hes1 and Hey1) were induced by TGF-β, decreased by DAPT treatment and remained low in the presence of both stimuli. However, DAPT alone caused no effects on most of the parameters analyzed. These results demonstrate that the γ-secretase inhibitor used in this study exerted a blockade on TGF-β-induced EMT in ovarian cancer cells.

NOTCH receptors in gastric and other gastrointestinal cancers: oncogenes or tumor suppressors?

Gastric cancer (GC) ranks the most common cancer types and is one of the leading causes of cancer-related death. Due to delayed diagnosis and high metastatic frequency, 5-year survival rate of GC is rather low. It is a complex disease resulting from the interaction between environmental factors and host genetic alterations that deregulate multiple signaling pathways. The Notch signaling pathway, a highly conserved system in the regulation of the fate in several cell types, plays a pivotal role in cell differentiation, survival and proliferation. Notch is also one of the most commonly activated signaling pathways in tumors and its aberrant activation plays a key role in cancer advancement. Whether Notch cascade exerts oncogenic or tumor suppressive function in different cancer types depends on the cellular context. Mammals have four NOTCH receptors that modulate Notch pathway activity. In this review, we provide a comprehensive summary on the functional role of NOTCH receptors in gastric and other gastrointestinal cancers. Increasing knowledge of NOTCH receptors in gastrointestinal cancers will help us recognize the underlying mechanisms of Notch signaling and develop novel therapeutic strategies for GC.

Niclosamide inhibits colon cancer progression through downregulation of the Notch pathway and upregulation of the tumor suppressor miR-200 family

Colorectal cancer (CRC) is among the most frequent causes of cancer-related deaths worldwide. Thus, there is a need for the development of new therapeutic approaches for the treatment of CRC. Accumulating evidence has revealed that niclosamide, an anthelminthic drug, exerts antitumor activity in several types of cancer, including colon cancer. However, the underlying molecular mechanisms responsible for the effects of this drug remain elusive. Previous studies have shown that the aberrant Notch signaling pathway contributes to the carcinogenesis of colon cancer. Herein, we examined the effects of niclosamide on the growth, migration and apoptosis of colon cancer cells, and the role of the Notch signaling pathway. By performing MTT, wound-healing and Transwell migration assays, we observed that niclosamide suppressed the growth and migration of colon cancer cells, and flow cytometry demonstrated that cell apoptosis was induced. This was associated with the decreased protein expression of Notch1, Notch2, Notch3 and Hey1, and the increased expression of the tumor suppressor microRNA (miR or miRNA)-200 family members (miR-200a, miR-200b, miR-200c, miR-141 and miR-429) that are typically downregulated in colon cancer. Collectively, these findings demonstrate that niclosamide potentially inhibits the progression of colon cancer by downregulating Notch signaling and by upregulating the miR-200 family members.

Notch Signaling Mediates Skeletal Muscle Atrophy in Cancer Cachexia Caused by Osteosarcoma

Skeletal muscle atrophy in cancer cachexia is mediated by the interaction between muscle stem cells and various tumor factors. Although Notch signaling has been known as a key regulator of both cancer development and muscle stem cell activity, the potential involvement of Notch signaling in cancer cachexia and concomitant muscle atrophy has yet to be elucidated. The murine K7M2 osteosarcoma cell line was used to generate an orthotopic model of sarcoma-associated cachexia, and the role of Notch signaling was evaluated. Skeletal muscle atrophy was observed in the sarcoma-bearing mice, and Notch signaling was highly active in both tumor tissues and the atrophic skeletal muscles. Systemic inhibition of Notch signaling reduced muscle atrophy. In vitro coculture of osteosarcoma cells with muscle-derived stem cells (MDSCs) isolated from normal mice resulted in decreased myogenic potential of MDSCs, while the application of Notch inhibitor was able to rescue this repressed myogenic potential. We further observed that Notch-activating factors reside in the exosomes of osteosarcoma cells, which activate Notch signaling in MDSCs and subsequently repress myogenesis. Our results revealed that signaling between tumor and muscle via the Notch pathway may play an important role in mediating the skeletal muscle atrophy seen in cancer cachexia.

The reciprocal regulation loop of Notch2 pathway and miR-23b in controlling gastric carcinogenesis

Gastric carcinoma is one of the most common malignancies and the third highest cause of global cancer-related death. Notch2 receptor intracellular domain (N2IC), the activated form of Notch2 receptor, enhances gastric carcinogenesis. MicroRNAs (miRNAs) act as either oncogenes or tumor suppressors in tumorigenesis and cross-talk with Notch pathways. Herein, microRNA-23b (miR-23b) was identified as a Notch2 receptor-related miRNA and its role in gastric carcinogenesis was investigated. Levels of miR-23b in stomach adenocarcinoma samples were down-regulated, whereas those of Notch2 receptor, v-ets erythroblastosis virus E26 oncogene homolog 1 (Ets1), and E2F1 transcripts were up-regulated. Results also showed that N2IC down-regulated miR-23b expression in gastric cancer cells through up-regulating E2F1. The miR-23b inhibited gastric tumorigenesis including growth, viability, epithelial-mesenchymal transition, and abilities of colony formation, migration, invasion, and tumorsphere formation. Mechanistically, miR-23b suppressed tumor progression and pluripotency gene expression and affected tumorsphere ultra-structure in gastric cancer cells via targeting Notch2 receptor or Ets1. Furthermore, miR-23b diminished the xenografted tumor growth and lung metastasis of SC-M1 gastric cancer cells through Notch2 pathway. Our results suggest that Notch2 pathway and miR-23b interplay in a reciprocal regulation loop in gastric cancer cells and this axis plays an important role in gastric carcinogenesis.

Chicken gga-miR-103-3p Targets CCNE1 and TFDP2 and Inhibits MDCC-MSB1 Cell Migration

Marek’s disease (MD) is a highly contagious viral neoplastic disease caused by Marek’s disease virus (MDV), which can lead to huge economic losses in the poultry industry. Recently, microRNAs (miRNAs) have been found in various cancers and tumors. In recent years, 994 mature miRNAs have been identified through deep sequencing in chickens, but only a few miRNAs have been investigated further in terms of their function. Previously, gga-miR-103-3p was found downregulated in MDV-infected samples by using Solexa deep sequencing. In this study, we further verified the expression of gga-miR-103-3p among MDV-infected spleen, MD lymphoma from liver, noninfected spleen, and noninfected liver, by qPCR. The results showed that the expression of gga-miR-103-3p was decreased in MDV-infected tissues, which was consistent with our previous study. Furthermore, two target genes of gga-miR-103-3p, cyclin E1 (CCNE1) and transcription factor Dp-2 (E2F dimerization partner 2) (TFDP2), were predicted and validated by luciferase reporter assay, qPCR, and western blot analysis. The results suggested that CCNE1 and TFDP2 are direct targets of gga-miR-103-3p in chickens. Subsequent cell proliferation and migration assay showed that gga-miR-103-3p suppressed MDCC-MSB1 migration, but did not obviously modulate MDCC-MSB1 cell proliferation. In conclusion, gga-miR-103-3p targets the CCNE1 and TFDP2 genes, and suppresses cell migration, which indicates that it might play an important role in MD tumor transformation.

microRNA and Bone Cancer

MicroRNA molecules have a variety of roles in cellular development and proliferation processes, including normal osteogenesis. These effects are exerted through post-translational inhibition of target genes. Altered miRNA expression has been demonstrated in several cancers, both in the tumor tissue and in the peripheral circulation. This may influence carcinogenesis if the specific miRNA targets are encoded by tumor suppressor genes or oncogenes. To date, most research investigating the role of microRNAs and primary bone tumors has focused on osteosarcoma and Ewing sarcoma. Several microRNAs including the miR-34 family have been implicated in osteosarcoma tumorigenesis via effects on the Notch signaling pathway. Progression, invasion, and metastasis of osteosarcoma tumor cells is also influenced by microRNA expression. In addition, microRNA expression may affect the response to chemotherapy in osteosarcoma and thus hold potential for future use as either a prognostic indicator or a therapeutic target. The EWS-FLI1 fusion protein produced in Ewing sarcoma has been shown to induce changes in miRNA expression. MicroRNA expression profiling may have some potential for prediction of disease progression and survival in Ewing sarcoma. There is limited evidence to support a role for microRNAs in other primary bone tumors, either malignant or benign; however, early work is suggestive of involvement in chondrosarcoma, multiple osteochondromatosis, and giant cell tumors of bone.

Control of Neural Daughter Cell Proliferation by Multi-level Notch/Su(H)/E(spl)-HLH Signaling

The Notch pathway controls proliferation during development and in adulthood, and is frequently affected in many disorders. However, the genetic sensitivity and multi-layered transcriptional properties of the Notch pathway has made its molecular decoding challenging. Here, we address the complexity of Notch signaling with respect to proliferation, using the developing Drosophila CNS as model. We find that a Notch/Su(H)/E(spl)-HLH cascade specifically controls daughter, but not progenitor proliferation. Additionally, we find that different E(spl)-HLH genes are required in different neuroblast lineages. The Notch/Su(H)/E(spl)-HLH cascade alters daughter proliferation by regulating four key cell cycle factors: Cyclin E, String/Cdc25, E2f and Dacapo (mammalian p21CIP1/p27KIP1/p57Kip2). ChIP and DamID analysis of Su(H) and E(spl)-HLH indicates direct transcriptional regulation of the cell cycle genes, and of the Notch pathway itself. These results point to a multi-level signaling model and may help shed light on the dichotomous proliferative role of Notch signaling in many other systems.

Cripto-1 as a novel therapeutic target for triple negative breast cancer

Triple-negative breast cancer (TNBC) presents the poorest prognosis among the breast cancer subtypes and no current standard therapy. Here, we performed an in-depth molecular analysis of a mouse model that establishes spontaneous lung metastasis from JygMC(A) cells. These primary tumors resembled the triple-negative breast cancer (TNBC) both phenotypically and molecularly. Morphologically, primary tumors presented both epithelial and spindle-like cells but displayed only adenocarcinoma-like features in lung parenchyma. The use of laser-capture microdissection combined with Nanostring mRNA and microRNA analysis revealed overexpression of either epithelial and miRNA-200 family or mesenchymal markers in adenocarcinoma and mesenchymal regions, respectively. Cripto-1, an embryonic stem cell marker, was present in spindle-like areas and its promoter showed activity in primary tumors. Cripto-1 knockout by the CRISPR-Cas9 system inhibited tumor growth and pulmonary metastasis. Our findings show characterization of a novel mouse model that mimics the TNBC and reveal Cripto-1 as a TNBC target hence may offer alternative treatment strategies for TNBC.

Non-coding RNAs in Mammary Gland Development and Disease

Non-coding RNAs (ncRNAs) are untranslated RNA molecules that function to regulate the expression of numerous genes and associated biochemical pathways and cellular functions. NcRNAs include small interfering RNAs (siRNAs), microRNAs (miRNAs), PIWI-interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs) and long non-coding RNAs (lncRNAs). They participate in the regulation of all developmental processes and are frequently aberrantly expressed or functionally defective in disease. This Chapter will focus on the role of ncRNAs, in particular miRNAs and lncRNAs, in mammary gland development and disease.

Deregulation of miR-21 and miR-155 and their putative targets after silibinin treatment in T47D breast cancer cells

OBJECTIVES

MicroRNAs (miRNAs) are a class of short RNAs that control the biological processes including cell proliferation, apoptosis and development. Aberrant expression of miRNAs was determined in the different stages of tumor development and metastasis. To study the effect of silibinin on miRNAs expression, we evaluated quantitative expression of miR-21 and miR-155 as two oncomiRs and several potential targets in silibinin-treated T47D cells.

MATERIALS AND METHODS

The rate of proliferation and apoptosis was measured in silibinin-treated and untreated cells. The expression levels of miR-21 and miR-155 were evaluated in T47D cells treated with silibinin (100 µg/ml). Also, their putative targets were predicted in apoptotic pathways using multiple algorithms; as a confirmation, the transcription level of APAF-1, CASP-9 and BID was evaluated.

RESULTS

In silibinin-treated cells, death was occurred in a dose and time-dependent manner. miR-21 and miR-155 was downregulated in cells treated with silibinin (100 µg/ml). It is noticeable that the expression of their potential targets including CASP-9 and APAF-1 was increased in silibinin-treated cells after 48 hr.

CONCLUSION

Our findings showed a correlation between the expression of miR-21 and miR-155 and apoptosis in silibinin treated T47D cells. It seems that miRNAs such as miR-21 and miR-155 were regulated by silibinin. Also, increase in the transcript level of APAF-1 and CASP-9 after downregulation of miR-21 and miR-155 might indicate that these genes were targeted by aforementioned miRNAs in T47D cells.

miR-124 interacts with the Notch1 signalling pathway and has therapeutic potential against gastric cancer

Aberrant Notch signalling plays an important role in cancer progression. However, little is known about the interaction between miRNA and the Notch signalling pathway and its role in gastric cancer (GC). In this study, we found that miR‐124 was down‐regulated in GC compared with adjacent normal tissue. Forced expression of miR‐124 inhibited GC cell growth, migration and invasion, and induced cell cycle arrest. miR‐124 negatively regulated Notch1 signalling by targeting JAG1. miR‐124 levels were also shown to be inversely correlated with JAG1 expression in GC. Furthermore, we found that the overexpression of the intracellular domain of Notch1 repressed miR‐124 expression, promoted GC cell growth, migration and invasion. Conversely, blocking Notch1 using a γ‐secretase inhibitor up‐regulated miR‐124 expression, inhibited GC cell growth, migration and invasion. In conclusion, our data demonstrates a regulatory feedback loop between miR‐124 and Notch1 signalling in GC cells, suggesting that the miR‐124/Notch axis may be a potential therapeutic target against GC.

Down-regulation of miR-135b in colon adenocarcinoma induced by a TGF-β receptor I kinase inhibitor (SD-208)

OBJECTIVES

Transforming growth factor-β (TGF-β) is involved in colorectal cancer (CRC). The SD-208 acts as an anti-cancer agent in different malignancies via TGF-β signaling. This work aims to show the effect of manipulation of TGF-β signaling on some miRNAs implicated in CRC.

MATERIALS AND METHODS

We investigated the effects of SD-208 on SW-48, a colon adenocarcinoma cell line. The cell line was treated with 0.5, 1 and 2 μM concentrations of SD-208. Then, the xenograft model of colon cancer was established by subcutaneous inoculation of SW-48 cell line into the nude mice. The animals were treated with SD-208 for three weeks. A quantitative real-time PCR was carried out for expression level analysis of selected oncogenic (miR-21, 31, 20a and 135b) and suppressor-miRNAs (let7-g, miR-133b, 145 and 200c). Data were analyzed using the 2-∆∆CT method through student's t-test via the GraphPad Prism software.

RESULTS

Our results revealed that SD-208 could significantly down-regulate the expression of one key onco-miRNA, miR-135b, in either SW-48 colon cells (P=0.006) or tumors orthotopically implanted in nude mice (P=0.018). Our in silico study also predicted that SD-208 could modulate the expression of potential downstream tumor suppressor targets of the miR135b.

CONCLUSION

Our data provide novel evidence that anticancer effects of SD-208 (and likely other TGF-β inhibitors) may be owing to their ability to regulate miRNAs expression.

MicroRNA-224: as a potential target for miR-based therapy of cancer

MicroRNAs (miRNAs) are small noncoding RNA molecules which regulate the target gene expression posttranscriptionally. Increasing studies have shown that microRNAs play important roles in multiple biological pathways. For instance, aberrant expression of microRNA-224 (miR-224) plays a vital role in tumor biology in various types of human cancer. Here, we aim to summarize the molecular mechanisms that lead to the overexpression of miR-224 in cancers, analyze the effect of miR-224 on tumor biology, and reveal the clinical significance of miR-224. MiR-224 regulates its targets by modulating messenger RNA (mRNA) stability and/or protein translation, and it would provide new insight into molecular targeting cancer treatment.

Integrative Analysis with Monte Carlo Cross-Validation Reveals miRNAs Regulating Pathways Cross-Talk in Aggressive Breast Cancer

In this work an integrated approach was used to identify functional miRNAs regulating gene pathway cross-talk in breast cancer (BC). We first integrated gene expression profiles and biological pathway information to explore the underlying associations between genes differently expressed among normal and BC samples and pathways enriched from these genes. For each pair of pathways, a score was derived from the distribution of gene expression levels by quantifying their pathway cross-talk. Random forest classification allowed the identification of pairs of pathways with high cross-talk. We assessed miRNAs regulating the identified gene pathways by a mutual information analysis. A Fisher test was applied to demonstrate their significance in the regulated pathways. Our results suggest interesting networks of pathways that could be key regulatory of target genes in BC, including stem cell pluripotency, coagulation, and hypoxia pathways and miRNAs that control these networks could be potential biomarkers for diagnostic, prognostic, and therapeutic development in BC. This work shows that standard methods of predicting normal and tumor classes such as differentially expressed miRNAs or transcription factors could lose intrinsic features; instead our approach revealed the responsible molecules of the disease.

Novel strategies targeting cancer stem cells through phytochemicals and their analogs

Cancer stem cells (CSCs) are cells that exist within a tumor with a capacity of self-renewal and an ability to differentiate, giving rise to heterogeneous populations of cancer cells. These cells are increasingly being implicated in resistance to conventional therapeutics and have also been implicated in tumor recurrence. Several cellular signaling pathways including Notch, Wnt, phosphoinositide-3-kinase-Akt-mammalian target of rapamycin pathways, and known markers such as CD44, CD133, CD166, ALDH, etc. have been associated with CSCs. Here, we have reviewed our current understanding of self-renewal pathways and factors that help in the survival of CSCs with special emphasis on those that have been documented to be modulated by well characterized natural agents such as curcumin, sulforaphane, resveratrol, genistein, and epigallocatechin gallate. With the inclusion of a novel derivative of curcumin, CDF, we showcase how natural agents can be effectively modified to increase their efficacy, particularly against CSCs. We hope that this article will generate interest among researchers for further mechanistic and clinical studies exploiting the cancer preventive and therapeutic role of nutraceuticals by targeted elimination of CSCs.

The role of epigenetic mechanisms in Notch signaling during development

The Notch pathway is a highly conserved cell-cell communication pathway in metazoan involved in numerous processes during embryogenesis, development, and adult organisms. Ligand-receptor interaction of Notch components on adjacent cells facilitates controlled sequential proteolytic cleavage resulting in the nuclear translocation of the intracellular domain of Notch (NICD). There it binds to the Notch effector protein RBP-J, displaces a corepressor complex and enables the induction of target genes by recruitment of coactivators in a cell-context dependent manner. Both, the gene-specific repression and the context dependent activation require an intense communication with the underlying chromatin of the regulatory regions. Since the epigenetic landscape determines the function of the genome, processes like cell fate decision, differentiation, and self-renewal depend on chromatin structure and its remodeling during development. In this review, structural features enabling the Notch pathway to read these epigenetic marks by proteins interacting with RBP-J/Notch will be discussed. Furthermore, mechanisms of the Notch pathway to write and erase chromatin marks like histone acetylation and methylation are depicted as well as ATP-dependent chromatin remodeling during the activation of target genes. An additional fine-tuning of transcriptional regulation upon Notch activation seems to be controlled by the commitment of miRNAs. Since cells within an organism have to react to environmental changes, and developmental and differentiation cues in a proper manner, different signaling pathways have to crosstalk to each other. The chromatin status may represent one major platform to integrate these different pathways including the canonical Notch signaling.

miR-340 inhibits glioblastoma cell proliferation by suppressing CDK6, cyclin-D1 and cyclin-D2

Glioblastoma development is often associated with alteration in the activity and expression of cell cycle regulators, such as cyclin-dependent kinases (CKDs) and cyclins, resulting in aberrant cell proliferation. Recent studies have highlighted the pivotal roles of miRNAs in controlling the development and growth of glioblastoma. Here, we provide evidence for a function of miR-340 in the inhibition of glioblastoma cell proliferation. We found that miR-340 is downregulated in human glioblastoma tissue samples and several established glioblastoma cell lines. Proliferation and neurosphere formation assays revealed that miR-340 plays an oncosuppressive role in glioblastoma, and that its ectopic expression causes significant defect in glioblastoma cell growth. Further, using bioinformatics, luciferase assay and western blot, we found that miR-340 specifically targets the 3'UTRs of CDK6, cyclin-D1 and cyclin-D2, leading to the arrest of glioblastoma cells in the G0/G1 cell cycle phase. Confirming these results, we found that re-introducing CDK6, cyclin-D1 or cyclin-D2 expression partially, but significantly, rescues cells from the suppression of cell proliferation and cell cycle arrest mediated by miR-340. Collectively, our results demonstrate that miR-340 plays a tumor-suppressive role in glioblastoma and may be useful as a diagnostic biomarker and/or a therapeutic avenue for glioblastoma.

Regulation of breast cancer stem cell features

Cancer stem cells (CSCs) are rare, tumour-initiating cells that exhibit stem cell properties: capacity of self-renewal, pluripotency, highly tumorigenic potential, and resistance to therapy. Cancer stem cells have been characterised and isolated from many cancers, including breast cancer. Developmental pathways, such as the Wnt/β-catenin, Notch/γ-secretase/Jagged, Shh (sonic hedgehog), and BMP signalling pathways, which direct proliferation and differentiation of normal stem cells, have emerged as major signalling pathways that contribute to the self-renewal of stem and/or progenitor cells in a variety of organs and cancers. Deregulation of these signalling pathways is frequently linked to an epithelial-mesenchymal transition (EMT), and breast CSCs often possess properties of cells that have undergone the EMT process. Signalling networks mediated by microRNAs and EMT-inducing transcription factors tie the EMT process to regulatory networks that maintain "stemness". Recent studies have elucidated epigenetic mechanisms that control pluripotency and stemness, which allows an assessment on how embryonic and normal tissue stem cells are deregulated during cancerogenesis to give rise to CSCs. Epigenetic-based mechanisms are reversible, and the possibility of "resetting" the abnormal cancer epigenome by applying pharmacological compounds targeting epigenetic enzymes is a promising new therapeutic strategy. Chemoresistance of CSCs is frequently driven by various mechanisms, including aberrant expression/activity of ABC transporters, aldehyde dehydrogenase and anti-oncogenic proteins (i.e. BCL2, B-cell lymphoma-2), enhanced DNA damage response, activation of pro-survival signalling pathways, and epigenetic deregulations. Despite controversy surrounding the CSC hypothesis, there is substantial evidence for their role in cancer, and a number of drugs intended to specifically target CSCs have entered clinical trials.

miR-34a-5p suppresses colorectal cancer metastasis and predicts recurrence in patients with stage II/III colorectal cancer

Although surgery remains the mainstay of curative treatment for colorectal cancer (CRC), many patients still have high chance to experience disease relapse. It is therefore imperative to identify prognostic markers that can help predict the clinical outcomes of CRC. Aberrant microRNA expression holds great potential as diagnostic and prognostic biomarker for CRC. Here we aimed to investigate clinical potential of miR-34a-5p as a prognostic marker for CRC recurrence and its functional significance. First, we validated that miR-34a-5p was downregulated in CRC tumour tissues (P<0.05). The expression level of tissue miR-34a-5p was then evaluated in two independent cohorts of 268 CRC patients. miR-34a-5p expression was positively correlated with disease-free survival in two independent cohorts (cohort I: n=205, P<0.001; cohort II: n=63, P=0.006). Moreover, the expression of miR-34a-5p was an independent prognostic factor for CRC recurrence by multivariate analysis (P<0.001 for cohort I, P=0.007 for cohort II). Ectopic expression of miR-34a-5p in p53 wild-type colon cancer cell HCT116 significantly inhibited cell growth, migration, invasion and metastasis. miR-34a-5p induced cell apoptosis, cell cycle arrest at G1 phase and p53 transcription activity in HCT116 cells, but not in the HCT116 p53 knockout (p53(-/-)) cells. miR-34a-5p significantly suppressed the HCT116 growth in vivo, whereas it showed no effect on the HCT116 p53(-/-) xenograft, indicating that the growth-inhibiting effect by miR-34a-5p was dependent on p53. In addition, the expression level of miR-34a-5p in patients with p53-positive expression was higher than that in patients with p53-negative expression (P<0.01). In conclusion, miR-34a-5p inhibits recurrence of CRC through inhibiting cell growth, migration and invasion, inducing cell apoptosis and cell cycle arrest in a p53-dependent manner.

miR-34a-5p suppresses colorectal cancer metastasis and predicts recurrence in patients with stage II/III colorectal cancer

Although surgery remains the mainstay of curative treatment for colorectal cancer (CRC), many patients still have high chance to experience disease relapse. It is therefore imperative to identify prognostic markers that can help predict the clinical outcomes of CRC. Aberrant microRNA expression holds great potential as diagnostic and prognostic biomarker for CRC. Here we aimed to investigate clinical potential of miR-34a-5p as a prognostic marker for CRC recurrence and its functional significance. First, we validated that miR-34a-5p was downregulated in CRC tumour tissues (P<0.05). The expression level of tissue miR-34a-5p was then evaluated in two independent cohorts of 268 CRC patients. miR-34a-5p expression was positively correlated with disease-free survival in two independent cohorts (cohort I: n=205, P<0.001; cohort II: n=63, P=0.006). Moreover, the expression of miR-34a-5p was an independent prognostic factor for CRC recurrence by multivariate analysis (P<0.001 for cohort I, P=0.007 for cohort II). Ectopic expression of miR-34a-5p in p53 wild-type colon cancer cell HCT116 significantly inhibited cell growth, migration, invasion and metastasis. miR-34a-5p induced cell apoptosis, cell cycle arrest at G1 phase and p53 transcription activity in HCT116 cells, but not in the HCT116 p53 knockout (p53(-/-)) cells. miR-34a-5p significantly suppressed the HCT116 growth in vivo, whereas it showed no effect on the HCT116 p53(-/-) xenograft, indicating that the growth-inhibiting effect by miR-34a-5p was dependent on p53. In addition, the expression level of miR-34a-5p in patients with p53-positive expression was higher than that in patients with p53-negative expression (P<0.01). In conclusion, miR-34a-5p inhibits recurrence of CRC through inhibiting cell growth, migration and invasion, inducing cell apoptosis and cell cycle arrest in a p53-dependent manner.

AKT family and miRNAs expression in IL-2 induced CD4(+)T cells

OBJECTIVES

Study of non-coding RNAs is considerable to elucidate principal biological questions or design new therapeutic strategies. miRNAs are a group of non-coding RNAs that their functions in PI3K/AKT signaling and apoptosis pathways after T cell activation is not entirely clear. Herein, miRNAs expression and their putative targets in the mentioned pathways were studied in the activated CD4(+)T cells.

MATERIALS AND METHODS

Herein, proliferation rate and IL-2 secretion were measured in treated and untreated cells by IL-2. Putative targets of up-regulated miRNAs were predicted by bioinformatics approaches in the apoptotic and PI3K/AKT signaling pathways. Then the expression of two putative targets was evaluated by quantitative RT-PCR.

RESULTS

Proliferation rate of treated cells by IL-2 increased in a dose- and time- dependent manner. Naive and activated CD4(+)T cells induced by different dose of IL-2 secreted abundant amounts of IL-2. Also, in IL-2 un-induced cells (IL-2 depleted cells) after 3 days, decrease of proliferation has been shown. In silico analysis predicted putative targets of up-regulated miRNAs such as AKT1, AKT3 and apoptotic genes in the activated cells induced or un-induced by IL-2. Decrease of AKT3 was shown by Q-RT-PCR as a potential target of miRNAs overexpressed in IL-2 depleted cells. But there was no significant difference in AKT1 expression in two cell groups.

CONCLUSION

Our analysis suggests that decrease of AKT3 was likely controlled via up-regulation of specific miRNAs in IL-2 depleted cells. Also it seems that miRNAs play role in induction of different apoptosis pathways in IL-2 induced and un-induced cells.

Crosstalk between miR-34a and Notch Signaling Promotes Differentiation in Apical Papilla Stem Cells (SCAPs)

Stem cells from the apical papilla (SCAPs) are important for the formation and regeneration of root dentin. Here, we examined the expression of Notch signaling components in SCAPs and investigated crosstalk between microRNA miR-34aand Notch signaling during cell differentiation. We found that human SCAPs express NOTCH2, NOTCH3, JAG2, DLL3, and HES1, and we tested the relationship between Notch signaling and both cell differentiation and miR-34a expression. NOTCH activation in SCAPs inhibited cell differentiation and up-regulated the expression of miR-34a, whereas miR-34a inhibited Notch signaling in SCAPs by directly targeting the 3'UTR of NOTCH2 and HES1 mRNA and suppressing the expression of NOTCH2, N2ICD, and HES1. DSPP, RUNX2, OSX, and OCN expression was consequently up-regulated. Thus, Notch signaling in human SCAPs plays a vital role in maintenance of these cells. miR-34a interacts with Notch signaling and promotes both odontogenic and osteogenic differentiation of SCAPs.

Correlation of over-expressions of miR-21 and Notch-1 in human colorectal cancer with clinical stages

AIM

The aim of the study was to identify expressions of Notch-1, microRNA-21 (miR-21), and phosphatase and tensin homolog (PTEN) in colorectal cancer (CRC), and to explore their relationship with clinical stages and metastatic status of CRC.

MAIN METHODS

102 CRC patients were enrolled and clinical data were analyzed. Expressions of Notch-1 and miR-21 in CRC and adjacent non-tumor tissues of these patients were measured by real time-PCR. Protein expressions of Notch-1 and PTEN of 12 paired tissues were determined by Western blot and immunohistochemistry. The correlations between gene expressions in different clinical stages as well as metastatic status were evaluated by linear regression.

KEY FINDINGS

Notch-1 was over-expressed in 86.27% (88/102) CRC tissues, particularly in advanced stages, while miR-21 expression was increased to 74.51% (76/102) in CRC tissues compared with matched adjacent non-tumor tissues. The expressions of Notch-1 and miR-21 were positively correlated with CRC development, especially in advanced-stages (r(2)=0.3839, p<0.01). Expressions of PTEN were significantly down-regulated in CRC tissues and negatively correlated with expressions of Notch-1 (r(2)=0.5207, p<0.01) and miR-21 (r(2)=0.6996, p<0.01).

SIGNIFICANCE

These data indicate that the crosstalk between Notch-1 and miR-21 is involved in CRC development through degradation of PTEN.

Notch and NF-kB signaling pathways regulate miR-223/FBXW7 axis in T-cell acute lymphoblastic leukemia

Notch signaling deregulation is linked to the onset of several tumors including T-cell acute lymphoblastic leukemia (T-ALL). Deregulated microRNA (miRNA) expression is also associated with several cancers, including leukemias. However, the transcriptional regulators of miRNAs, as well as the relationships between Notch signaling and miRNA deregulation, are poorly understood. To identify miRNAs regulated by Notch pathway, we performed microarray-based miRNA profiling of several Notch-expressing T-ALL models. Among seven miRNAs, consistently regulated by overexpressing or silencing Notch3, we focused our attention on miR-223, whose putative promoter analysis revealed a conserved RBPjk binding site, which was nested to an NF-kB consensus. Luciferase and chromatin immunoprecipitation assays on the promoter region of miR-223 show that both Notch and NF-kB are novel coregulatory signals of miR-223 expression, being able to activate cooperatively the transcriptional activity of miR-223 promoter. Notably, the Notch-mediated activation of miR-223 represses the tumor suppressor FBXW7 in T-ALL cell lines. Moreover, we observed the inverse correlation of miR-223 and FBXW7 expression in a panel of T-ALL patient-derived xenografts. Finally, we show that miR-223 inhibition prevents T-ALL resistance to γ-secretase inhibitor (GSI) treatment, suggesting that miR-223 could be involved in GSI sensitivity and its inhibition may be exploited in target therapy protocols.

MicroRNA function and dysregulation in bone tumors: the evidence to date

Micro ribonucleic acids (miRNAs) are small non-coding RNA segments that have a role in the regulation of normal cellular development and proliferation including normal osteogenesis. They exert their effects through inhibition of specific target genes at the post-transcriptional level. Many miRNAs have altered expression levels in cancer (either increased or decreased depending on the specific miRNA). Altered miRNA expression profiles have been identified in several malignancies including primary bone tumors such as osteosarcoma and Ewing’s sarcoma. It is thought that they may function as tumor suppressor genes or oncogenes and hence when dysregulated contribute to the initiation and progression of malignancy. miRNAs are also thought to have a role in the development of bone metastases in other malignancies. In addition, evidence increasingly suggests that miRNAs may play a part in determining the response to chemotherapy in the treatment of osteosarcoma. These molecules are readily detectable in tissues, both fresh and formalin fixed paraffin embedded and, more recently, in blood. Although there are fewer published studies regarding circulating miRNA profiles, they appear to reflect changes in tissue expression. Thus miRNAs may serve as potential indicators of disease presence but more importantly, may have a role in disease characterization or as potential therapeutic targets. This review gives a brief overview of miRNA biochemistry and explores the evidence to date implicating these small molecules in the pathogenesis of bone tumors.

Anti-cancer Therapies in High Grade Gliomas

High grade gliomas represent one of the most aggressive and treatment-resistant types of human cancer, with only 1–2 years median survival rate for patients with grade IV glioma. The treatment of glioblastoma is a considerable therapeutic challenge; combination therapy targeting multiple pathways is becoming a fast growing area of research. This review offers an up-to-date perspective of the literature about current molecular therapy targets in high grade glioma, that include angiogenic signals, tyrosine kinase receptors, nodal signaling proteins and cancer stem cells related approaches. Simultaneous identification of proteomic signatures could provide biomarker panels for diagnostic and personalized treatment of different subsets of glioblastoma. Personalized medicine is starting to gain importance in clinical care, already having recorded a series of successes in several types of cancer; nonetheless, in brain tumors it is still at an early stage.

Identification of male gametogenesis expressed genes from the scallop Nodipecten subnodosus by suppressive subtraction hybridization and pyrosequencing

Despite the great advances in sequencing technologies, genomic and transcriptomic information for marine non-model species with ecological, evolutionary, and economical interest is still scarce. In this work we aimed to identify genes expressed during spermatogenesis in the functional hermaphrodite scallop Nodipecten subnodosus (Mollusca: Bivalvia: Pectinidae), with the purpose of obtaining a panel of genes that would allow for the study of differentially transcribed genes between diploid and triploid scallops in the context of meiotic arrest and reproductive sterility. Because our aim was to isolate genes involved in meiosis and other testis maturation-related processes, we generated suppressive subtractive hybridization libraries of testis vs. inactive gonad. We obtained 352 and 177 ESTs by clone sequencing, and using pyrosequencing (454-Roche) we maximized the identified ESTs to 34,276 reads. A total of 1,153 genes from the testis library had a blastx hit and GO annotation, including genes specific for meiosis, spermatogenesis, sex-differentiation, and transposable elements. Some of the identified meiosis genes function in chromosome pairing (scp2, scp3), recombination and DNA repair (dmc1, rad51, ccnb1ip1/hei10), and meiotic checkpoints (rad1, hormad1, dtl/cdt2). Gene expression analyses in different gametogenic stages in both sexual regions of the gonad of meiosis genes confirmed that the expression was specific or increased towards the maturing testis. Spermatogenesis genes included known testis-specific ones (kelch-10, shippo1, adad1), with some of these known to be associated to sterility. Sex differentiation genes included one of the most conserved genes at the bottom of the sex-determination cascade (dmrt1). Transcript from transposable elements, reverse transcriptase, and transposases in this library evidenced that transposition is an active process during spermatogenesis in N. subnodosus. In relation to the inactive library, we identified 833 transcripts with functional annotation related to activation of the transcription and translation machinery, as well as to germline control and maintenance.

Notch signaling: targeting cancer stem cells and epithelial-to-mesenchymal transition

Notch signaling is an evolutionarily conserved pathway involved in cell fate control during development, stem cell self-renewal, and postnatal tissue differentiation. Roles for Notch in carcinogenesis, the biology of cancer stem cells, tumor angiogenesis, and epithelial-to-mesenchymal transition (EMT) have been reported. This review describes the role of Notch in the "stemness" program in cancer cells and in metastases, together with a brief update on the Notch inhibitors currently under investigation in oncology. These agents may be useful in targeting cancer stem cells and to reverse the EMT process.

Pathway crosstalk analysis based on protein-protein network analysis in ovarian cancer

Ovarian cancer is the fifth leading cause of cancer death in women aged 35 to 74 years. Although there are several popular hypothesis of ovarian cancer pathogenesis, the genetic mechanisms are far from being clear. Recently, systems biology approaches such as network-based methods have been successfully applied to elucidate the mechanisms of diseases. In this study, we constructed a crosstalk network among ovarian cancer related pathways by integrating protein-protein interactions and KEGG pathway information. Several significant pathways were identified to crosstalk with each other in ovarian cancer, such as the chemokine, Notch, Wnt and NOD-like receptor signaling pathways. Results from these studies will provide the groundwork for a combination therapy approach targeting multiple pathways which will likely be more effective than targeting one pathway alone.

MicroRNA-215 inhibits relapse of colorectal cancer patients following radical surgery

To investigate the role of miR-215 in the relapse following radical surgery of colorectal cancer patients. The clinical data and surgical frozen tumor tissues were retrospectively collected from 125 stage II/III colorectal cancer patients, which contained 60 patients who relapsed and 65 patients who did not relapse within 3 years after surgery. The expression of miR-215 was determined by real-time PCR, and the relationship between miR-215 expression and the relapse was analyzed statistically. miR-215 was downregulated in relapsed patients compared to nonrelapsed patients (P = 0.001). The low expression of miR-215 was significantly correlated with a high probability of 3-year relapse (P = 0.001), which was more obvious in stage III patients (P < 0.001). The multivariate analysis showed that miR-215 expression could function as an independent predictive marker for relapse. It seemed that patients with high expressions of miR-215 could benefit from 5-fluorouracil-containing adjuvant chemotherapy without significant difference, whereas this phenomenon was reverse in patients with low expressions of miR-215. Our study highlighted for the first time that miR-215 could function as a potential predictive marker for relapse following radical surgery of colorectal cancer, and the possible correlation between miR-215 and 5-fluorouracil-containing adjuvant chemotherapy would be validated in the future.

Role of Notch signaling pathway in gastric cancer pathogenesis

Notch signaling pathway is activated dynamically during evolution playing significant role in cell fate determination and differentiation. It has been known that alterations of this pathway may lead to human malignancies, including gastric cancer. Despite a decline in the overall incidence, this disease still remains an important global health problem. Therefore, a better understanding of the molecular alterations underlying gastric cancer may contribute to the development of rationally designed molecular targeted therapies. It has been reported that Notch1 receptor could become a prognostic marker of gastric cancer and novel target for gastric cancer therapy. Among the novel and targeted approaches for the treatment of gastric cancer is also the process of Notch receptors regulation by specific microRNA. γ-secretase inhibitors are also taken into consideration.

Diallyl trisulfide inhibits proliferation, invasion and angiogenesis of osteosarcoma cells by switching on suppressor microRNAs and inactivating of Notch-1 signaling

Notch signaling pathway plays critical roles in human cancers, including osteosarcoma, suggesting that the discovery of specific agents targeting Notch would be extremely valuable for osteosarcoma. Our previous studies have shown that diallyl trisulfide (DATS) inhibits proliferation of osteosarcoma cells by triggering cell cycle arrest and apoptosis in vitro. However, the underlying mechanism is still unclear. In this study, we found that DATS suppressed cell survival, wound-healing capacity, invasion and angiogenesis in osteosarcoma cells. These effects were associated with decreased expression of Notch-1 and its downstream genes, such as vascular endothelial growth factor and matrix metalloproteinases, as well as increased expression of a panel of tumor-suppressive microRNAs (miRNAs), including miR-34a, miR-143, miR-145 and miR-200b/c that are typically lost in osteosarcoma. We also found that reexpression of miR-34a and miR-200b by transfection led to reduced expression of Notch-1, resulting in the inhibition of osteosarcoma cell proliferation, invasion and angiogenesis. These results clearly suggest that DATS inhibited osteosarcoma growth and aggressiveness via a novel mechanism targeting a Notch-miRNA regulatory circuit. Our data provide the first evidence that the downregulation of Notch-1 and reexpression of miRNAs by DATS may be an effective approach for the treatment of osteosarcoma.

Differential combinatorial regulatory network analysis related to venous metastasis of hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is one of the most fatal cancers in the world, and metastasis is a significant cause to the high mortality in patients with HCC. However, the molecular mechanism behind HCC metastasis is not fully understood. Study of regulatory networks may help investigate HCC metastasis in the way of systems biology profiling.

Methods

By utilizing both sequence information and parallel microRNA(miRNA) and mRNA expression data on the same cohort of HBV related HCC patients without or with venous metastasis, we constructed combinatorial regulatory networks of non-metastatic and metastatic HCC which contain transcription factor(TF) regulation and miRNA regulation. Differential regulation patterns, classifying marker modules, and key regulatory miRNAs were analyzed by comparing non-metastatic and metastatic networks.

Results

Globally TFs accounted for the main part of regulation while miRNAs for the minor part of regulation. However miRNAs displayed a more active role in the metastatic network than in the non-metastatic one. Seventeen differential regulatory modules discriminative of the metastatic status were identified as cumulative-module classifier, which could also distinguish survival time. MiR-16, miR-30a, Let-7e and miR-204 were identified as key miRNA regulators contributed to HCC metastasis.

Conclusion

In this work we demonstrated an integrative approach to conduct differential combinatorial regulatory network analysis in the specific context venous metastasis of HBV-HCC. Our results proposed possible transcriptional regulatory patterns underlying the different metastatic subgroups of HCC. The workflow in this study can be applied in similar context of cancer research and could also be extended to other clinical topics.

Epigenetic silencing of Notch signaling in gastrointestinal cancers

The Notch signaling pathway drives proliferation, differentiation, apoptosis, cell fate choices and maintenance of stem cells during embryogenesis and in self-renewing tissues of the adult. In addition, aberrant Notch signaling has been implicated in several tumors, where Notch can function both as an oncogene or a tumor-suppressor gene, depending on the context.   This Extra View aims to review what is currently known about Notch signaling, in particular in gastrointestinal tumors, providing a summary of our data on Notch1 signaling in gastric cancer with results obtained in colorectal cancer (CRC). We have already reported that the epigenetic regulation of the Notch ligand DLL1 controls Notch1 signaling activation in gastric cancer, and that Notch1 inhibition is associated with the diffuse type of gastric cancer. Here, we describe additional data showing that in CRC cell lines, unlike gastric cancer, DLL1 expression is not regulated by promoter methylation. Moreover, in CRC, Notch1 receptor is not affected by any mutation. These data suggest a different regulation of Notch1 signaling between gastric cancer and CRC.

The microRNA-30 family targets DLL4 to modulate endothelial cell behavior during angiogenesis

Delta-like 4 (DLL4), a membrane-bound ligand belonging to the Notch signaling family, plays a fundamental role in vascular development and angiogenesis. We identified a conserved microRNA family, miR-30, which targets DLL4. Overexpression of miR-30b in endothelial cells led to increased vessel number and length in an in vitro model of sprouting angiogenesis. Microinjection of miR-30 mimics into zebrafish embryos resulted in suppression of dll4 and subsequent excessive sprouting of intersegmental vessels and reduction in dorsal aorta diameter. Use of a target protector against the miR-30 site within the dll4 3'UTR up-regulated dll4 and synergized with Vegfa signaling knockdown to inhibit angiogenesis. Furthermore, restoration of miR-30b or miR-30c expression during Kaposi sarcoma herpesvirus (KSHV) infection attenuated viral induction of DLL4. Together these results demonstrate that the highly conserved molecular targeting of DLL4 by the miR-30 family regulates angiogenesis.

The Notch signalling system: recent insights into the complexity of a conserved pathway

Notch signalling links the fate of one cell to that of an immediate neighbour and consequently controls differentiation, proliferation and apoptotic events in multiple metazoan tissues. Perturbations in this pathway activity have been linked to several human genetic disorders and cancers. Recent genome-scale studies in Drosophila melanogaster have revealed an extraordinarily complex network of genes that can affect Notch activity. This highly interconnected network contrasts our traditional view of the Notch pathway as a simple linear sequence of events. Although we now have an unprecedented insight into the way in which such a fundamental signalling mechanism is controlled by the genome, we are faced with serious challenges in analysing the underlying molecular mechanisms of Notch signal control.

miRNA-34c regulates Notch signaling during bone development

During bone homeostasis, osteoblast and osteoclast differentiation is coupled and regulated by multiple signaling pathways and their downstream transcription factors. Here, we show that microRNA 34 (miR-34) is significantly induced by BMP2 during osteoblast differentiation. In vivo, osteoblast-specific gain of miR-34c in mice leads to an age-dependent osteoporosis due to the defective mineralization and proliferation of osteoblasts and increased osteoclastogenesis. In osteoblasts, miR-34c targets multiple components of the Notch signaling pathway, including Notch1, Notch2 and Jag1 in a direct manner, and influences osteoclast differentiation in a non-cell-autonomous fashion. Taken together, our results demonstrate that miR-34c is critical during osteoblastogenesis in part by regulating Notch signaling in bone homeostasis. Furthermore, miR-34c-mediated post-transcriptional regulation of Notch signaling in osteoblasts is one possible mechanism to modulate the proliferative effect of Notch in the committed osteoblast progenitors which may be important in the pathogenesis of osteosarcomas. Therefore, understanding the functional interaction of miR-34 and Notch signaling in normal bone development and in bone cancer could potentially lead to therapies modulating miR-34 signaling.

Curcumin induces cell death in esophageal cancer cells through modulating Notch signaling

Background

Curcumin inhibits the growth of esophageal cancer cell lines; however, the mechanism of action is not well understood. It is becoming increasingly clear that aberrant activation of Notch signaling has been associated with the development of esophageal cancer. Here, we have determined that curcumin inhibits esophageal cancer growth via a mechanism mediated through the Notch signaling pathway.

Methodology/Principal Findings

In this study, we show that curcumin treatment resulted in a dose and time dependent inhibition of proliferation and colony formation in esophageal cancer cell lines. Furthermore, curcumin treatment induced apoptosis through caspase 3 activation, confirmed by an increase in the ratio of Bax to Bcl2. Cell cycle analysis demonstrated that curcumin treatment induced cell death and down regulated cyclin D1 levels. Curcumin treatment also resulted in reduced number and size of esophagospheres. Furthermore, curcumin treatment led to reduced Notch-1 activation, expression of Jagged-1 and its downstream target Hes-1. This reduction in Notch-1 activation was determined to be due to the down-regulation of critical components of the γ-secretase complex proteins such as Presenilin 1 and Nicastrin. The combination of a known γ-secretase inhibitor DAPT and curcumin further decreased proliferation and induced apoptosis in esophageal cancer cells. Finally, curcumin treatment down-regulate the expressions of Notch-1 specific microRNAs miR-21 and miR-34a, and upregulated tumor suppressor let-7a miRNA.

Conclusion/Significance

Curcumin is a potent inhibitor of esophageal cancer growth that targets the Notch-1 activating γ-secretase complex proteins. These data suggest that Notch signaling inhibition is a novel mechanism of action for curcumin during therapeutic intervention in esophageal cancers.

Over-expression of FoxM1 leads to epithelial-mesenchymal transition and cancer stem cell phenotype in pancreatic cancer cells

FoxM1 is known to play important role in the development and progression of many malignancies including pancreatic cancer. Studies have shown that the acquisition of epithelial-to-mesenchymal transition (EMT) phenotype and induction of cancer stem cell (CSC) or cancer stem-like cell phenotypes are highly inter-related, and contributes to drug resistance, tumor recurrence, and metastasis. The molecular mechanism(s) by which FoxM1 contributes to the acquisition of EMT phenotype and induction of CSC self-renewal capacity is poorly understood. Therefore, we established FoxM1 over-expressing pancreatic cancer (AsPC-1) cells, which showed increased cell growth, clonogenicity, and cell migration. Moreover, over-expression of FoxM1 led to the acquisition of EMT phenotype by activation of mesenchymal cell markers, ZEB1, ZEB2, Snail2, E-cadherin, and vimentin, which is consistent with increased sphere-forming (pancreatospheres) capacity and expression of CSC surface markers (CD44 and EpCAM). We also found that over-expression of FoxM1 led to decreased expression of miRNAs (let-7a, let-7b, let-7c, miR-200b, and miR-200c); however, re-expression of miR-200b inhibited the expression of ZEB1, ZEB2, vimentin as well as FoxM1, and induced the expression of E-cadherin, leading to the reversal of EMT phenotype. Finally, we found that genistein, a natural chemo-preventive agent, inhibited cell growth, clonogenicity, cell migration and invasion, EMT phenotype, and formation of pancreatospheres consistent with reduced expression of CD44 and EpCAM. These results suggest, for the first time, that FoxM1 over-expression is responsible for the acquisition of EMT and CSC phenotype, which is in part mediated through the regulation of miR-200b and these processes, could be easily attenuated by genistein.

Over-expression of FoxM1 leads to epithelial-mesenchymal transition and cancer stem cell phenotype in pancreatic cancer cells

FoxM1 is known to play important role in the development and progression of many malignancies including pancreatic cancer. Studies have shown that the acquisition of epithelial-to-mesenchymal transition (EMT) phenotype and induction of cancer stem cell (CSC) or cancer stem-like cell phenotypes are highly inter-related, and contributes to drug resistance, tumor recurrence, and metastasis. The molecular mechanism(s) by which FoxM1 contributes to the acquisition of EMT phenotype and induction of CSC self-renewal capacity is poorly understood. Therefore, we established FoxM1 over-expressing pancreatic cancer (AsPC-1) cells, which showed increased cell growth, clonogenicity, and cell migration. Moreover, over-expression of FoxM1 led to the acquisition of EMT phenotype by activation of mesenchymal cell markers, ZEB1, ZEB2, Snail2, E-cadherin, and vimentin, which is consistent with increased sphere-forming (pancreatospheres) capacity and expression of CSC surface markers (CD44 and EpCAM). We also found that over-expression of FoxM1 led to decreased expression of miRNAs (let-7a, let-7b, let-7c, miR-200b, and miR-200c); however, re-expression of miR-200b inhibited the expression of ZEB1, ZEB2, vimentin as well as FoxM1, and induced the expression of E-cadherin, leading to the reversal of EMT phenotype. Finally, we found that genistein, a natural chemo-preventive agent, inhibited cell growth, clonogenicity, cell migration and invasion, EMT phenotype, and formation of pancreatospheres consistent with reduced expression of CD44 and EpCAM. These results suggest, for the first time, that FoxM1 over-expression is responsible for the acquisition of EMT and CSC phenotype, which is in part mediated through the regulation of miR-200b and these processes, could be easily attenuated by genistein.

γ-secretase inhibition combined with cisplatin enhances apoptosis of nasopharyngeal carcinoma cells

The Notch signaling pathway plays an important role in the proliferation and differentiation of cells. Although recent studies have shown that Notch plays a role in the mechanisms of cisplatin resistance, the mechanism by which Notch plays roles in intrinsic or acquired cisplatin resistance remains unclear. In the present study, poorly differentiated nasopharyngeal carcinoma cells were treated with a γ-secretase inhibitor (DAPT), which led to a decrease in the Notch intracellular domain and inhibition of Notch signaling. Treatment was not sufficient to induce pronounced apoptosis of CNE-2 cells, but did result in the down-regulation of the P-glycoprotein and ERCC1 protein. In contrast, the combined treatment of DAPT and cisplatin induced substantial cell apoptosis compared to cisplatin treatment alone.