p53 and microRNA-34 are suppressors of canonical Wnt signaling

Noncoding RNAs in Tumor Epithelial-to-Mesenchymal Transition

Epithelial-derived tumor cells acquire the capacity for epithelial-to-mesenchymal transition (EMT), which enables them to invade adjacent tissues and/or metastasize to distant organs. Cancer metastasis is the main cause of cancer-related death. Molecular mechanisms involved in the switch from an epithelial phenotype to mesenchymal status are complicated and are controlled by a variety of signaling pathways. Recently, a set of noncoding RNAs (ncRNAs), including miRNAs and long noncoding RNAs (lncRNAs), were found to modulate gene expressions at either transcriptional or posttranscriptional levels. These ncRNAs are involved in EMT through their interplay with EMT-related transcription factors (EMT-TFs) and EMT-associated signaling. Reciprocal regulatory interactions between lncRNAs and miRNAs further increase the complexity of the regulation of gene expression and protein translation. In this review, we discuss recent findings regarding EMT-regulating ncRNAs and their associated signaling pathways involved in cancer progression.

MicroRNAs as growth regulators, their function and biomarker status in colorectal cancer

Gene expression is in part regulated by microRNAs (miRNAs). This review summarizes the current knowledge of miRNAs in colorectal cancer (CRC); their role as growth regulators, the mechanisms that regulate the miRNAs themselves and the potential of miRNAs as biomarkers. Although thousands of tissue samples and bodily fluids from CRC patients have been investigated for biomarker potential of miRNAs (>160 papers presented in a comprehensive tables), none single miRNA nor miRNA expression signatures are in clinical use for this disease. More than 500 miRNA-target pairs have been identified in CRC and we discuss how these regulatory nodes interconnect and affect signaling pathways in CRC progression.

MicroRNA-34a regulates WNT/TCF7 signaling and inhibits bone metastasis in Ras-activated prostate cancer

Aberrant activation of Ras and WNT signaling are key events that have been shown to be up-regulated in prostate cancer that has metastasized to the bone. However, the regulatory mechanism of combinatorial Ras and WNT signaling in advanced prostate cancer is still unclear. TCF7, a WNT signaling-related gene, has been implicated as a critical factor in bone metastasis, and here we show that TCF7 is a direct target of miR-34a. In samples of prostate cancer patients, miR-34a levels are inversely correlated with TCF7 expression and a WNT dependent gene signature. Ectopic miR-34a expression inhibited bone metastasis and reduced cancer cell proliferation in a Ras-dependent xenograft model. We demonstrate that miR-34a can directly interfere with the gene expression of the anti-proliferative BIRC5, by targeting BIRC5 3′UTR. Importantly, BIRC5 overexpression was sufficient to reconstitute anti-apoptotic signaling in cells expressing high levels of miR-34a. In prostate cancer patients, we found that BIRC5 levels were positively correlated with a Ras signaling signature expression. Our data show that the bone metastasis and anti-apoptotic effects found in Ras signaling-activated prostate cancer cells require miR-34a deficiency, which in turn aids in cell survival by activating the WNT and anti-apoptotic signaling pathways thereby inducing TCF7 and BIRC5 expressions.

Interrupted E2F1-miR-34c-SCF negative feedback loop by hyper-methylation promotes colorectal cancer cell proliferation

E2F1 promoted miR-34c transcription which reduced its target stem cell factor (SCF) and inhibited colorectal cancer (CRC) cell proliferation. While, SCF increased E2F1 production, suggesting an existence of E2F1-miR-34c-SCF negative feedback loop, which was interrupted by hyper-methylation of miR-34c promoter in CRC cells.

Tumour suppressor miR-34c deficiency resulted from hyper-methylation in its promoter is believed to be one of the main causes of colorectal cancer (CRC). Till date, miR-34c has been validated as a direct target of p53; but previous evidence suggested other transcription factor(s) must be involved in miR-34c transcription. In the present study, we in the first place identified a core promoter region (−1118 to −883 bp) of pre-miR-34c which was embedded within a hyper-methylated CpG island. Secondly, E2F1 promoted miR-34c transcription by physical interaction with the miR-34c promoter at site −897 to −889 bp. The transcriptional activating effect of E2F1 on miR-34c was in a p53 independent manner but profoundly promoted in the presence of p53 with exposure to 5-aza-2′-deoxycytidine (DAC). Thirdly, stem cell factor (SCF), a miR-34c target, was specifically reduced upon an introduction of E2F1 which lead to suppression of CRC cell proliferation. The E2F1-suppressed cell proliferation was partially abrogated by additional miR-34c inhibitor, indicating that the anti-proliferation effect of E2F1 was probably through activating miR-34c-SCF axis. Finally, SCF/KIT signalling increased E2F1 production by reducing its proteosomal degradation dependent on PI3K/Akt-GSK3β pathway. In conclusion, our results suggested the existence of E2F1-miR-34c-SCF negative feedback loop which was interrupted by the hyper-methylation of miR-34c promoter in CRC cells and increased cell proliferation.

Circulating microRNA signature of genotype-by-age interactions in the long-lived Ames dwarf mouse

Recent evidence demonstrates that serum levels of specific miRNAs significantly change with age. The ability of circulating sncRNAs to act as signaling molecules and regulate a broad spectrum of cellular functions implicates them as key players in the aging process. To discover circulating sncRNAs that impact aging in the long‐lived Ames dwarf mice, we conducted deep sequencing of small RNAs extracted from serum of young and old mice. Our analysis showed genotype‐specific changes in the circulating levels of 21 miRNAs during aging [genotype‐by‐age interaction (GbA)]. Genotype‐by‐age miRNAs showed four distinct expression patterns and significant overtargeting of transcripts involved in age‐related processes. Functional enrichment analysis of putative and validated miRNA targets highlighted cellular processes such as tumor suppression, anti‐inflammatory response, and modulation of Wnt, insulin, mTOR, and MAPK signaling pathways, among others. The comparative analysis of circulating GbA miRNAs in Ames mice with circulating miRNAs modulated by calorie restriction (CR) in another long‐lived mouse suggests CR‐like and CR‐independent mechanisms contributing to longevity in the Ames mouse. In conclusion, we showed for the first time a signature of circulating miRNAs modulated by age in the long‐lived Ames mouse.

p53 regulates cytoskeleton remodeling to suppress tumor progression

Cancer cells possess unique characteristics such as invasiveness, the ability to undergo epithelial-mesenchymal transition, and an inherent stemness. Cell morphology is altered during these processes and this is highly dependent on actin cytoskeleton remodeling. Regulation of the actin cytoskeleton is, therefore, important for determination of cell fate. Mutations within the TP53 (tumor suppressor p53) gene leading to loss or gain of function (GOF) of the protein are often observed in aggressive cancer cells. Here, we highlight the roles of p53 and its GOF mutants in cancer cell invasion from the perspective of the actin cytoskeleton; in particular its reorganization and regulation by cell adhesion molecules such as integrins and cadherins. We emphasize the multiple functions of p53 in the regulation of actin cytoskeleton remodeling in response to the extracellular microenvironment, and oncogene activation. Such an approach provides a new perspective in the consideration of novel targets for anti-cancer therapy.

Dynamics of p53 and Wnt cross talk

We present the mechanism of interaction of Wnt network module, which is responsible for periodic somitogenesis, with p53 regulatory network, which is one of the main regulators of various cellular functions, and switching of various oscillating states by investigating p53-Wnt model. The variation in Nutlin concentration in p53 regulating network drives the Wnt network module to different states, stabilized, damped and sustain oscillation states, and even to cycle arrest. Similarly, the change in Axin2 concentration in Wnt could able to modulate the p53 dynamics at these states. We then solve the set of coupled ordinary differential equations of the model using quasi steady state approximation. We, further, demonstrate the change of p53 and GSK3 interaction rate, due to hypothetical catalytic reaction or external stimuli, can able to regulate the dynamics of the two network modules, and even can control their dynamics to protect the system from cycle arrest (apoptosis).

FRA-1 as a driver of tumour heterogeneity: a nexus between oncogenes and embryonic signalling pathways in cancer

Tumour heterogeneity is a major factor undermining the success of therapies targeting metastatic cancer. Two major theories are thought to explain the phenomenon of heterogeneity in cancer--clonal evolution and cell plasticity. In this review, we examine a growing body of work implicating the transcription factor FOS-related antigen 1 (FRA-1) as a central node in tumour cell plasticity networks, and discuss mechanisms regulating its activity in cancer cells. We also discuss evidence from the FRA-1 perspective supporting the notion that clonal selection and cell plasticity represent two sides of the same coin. We propose that FRA-1-overexpressing clones featuring high plasticity undergo positive selection during consecutive stages of multistep tumour progression. This model underscores a potential mechanism through which tumour cells retaining elevated levels of plasticity acquire a selective advantage over other clonal populations within a tumour.

High Ki67 expression is an independent good prognostic marker in colorectal cancer

AIMS

To correlate Ki67 expression with outcome in colorectal cancer (CRC).

METHODS

Ki67 labelling index (Ki67LI) was analysed by immunohistochemistry on a tissue microarray containing 1800 CRCs. The results were compared with clinicopathological and molecular parameters.

RESULTS

Ki67LI was considered low in 26.3%, moderate in 56.7% and high in 17.0% of 1653 interpretable CRCs. High Ki67 expression was associated with low tumour stage (p<0.0001) and nodal status (p=0.0315), but not with tumour grade (p=0.8639), histological tumour type (p=0.1542) or tumour localisation, and was an independent prognosticator of favourable survival (p=0.0121). High Ki67 expression was also significantly associated with high-level nuclear β-catenin and p53 expression (p<0.0001 and p=0.0095, respectively).

CONCLUSIONS

In summary, our data show that high Ki67 expression in CRCs is associated with good clinical outcome. Ki67, p53 and β-catenin overexpression seem to be linked to CRC, and indicate a cellular state of high proliferative activity. Finally, our findings strongly argue for a clinical utility of Ki67 immunostaining as an independent prognostic biomarker in CRC.

Metabolic stress induces a Wnt-dependent cancer stem cell-like state transition

Reciprocal interactions between cancer cells and the tumor microenvironment drive multiple clinically significant behaviors including dormancy, invasion, and metastasis as well as therapy resistance. These microenvironment-dependent phenotypes share typical characteristics with cancer stem cells (CSC). However, it is poorly understood how metabolic stress in the confined tumor microenvironment contributes to the emergence and maintenance of CSC-like phenotypes. Here, we demonstrate that chronic metabolic stress (CMS) in a long-term nutrient deprivation induces a Wnt-dependent phenoconversion of non-stem cancer cells toward stem-like state and this is reflected in the transcriptome analysis. Addition of Wnt3a as well as transfection of dominant-negative Tcf4 establishes an obligatory role for the Wnt pathway in the acquisition of CSC-like characteristics in response to metabolic stress. Furthermore, systematic characterization for multiple single cell-derived clones and negative enrichment of CD44+/ESA+ stem-like cancer cells, all of which recapitulate stem-like cancer characteristics, suggest stochastic adaptation rather than selection of pre-existing subclones. Finally, CMS in the tumor microenvironment can drive a CSC-like phenoconversion of non-stem cancer cells through stochastic state transition dependent on the Wnt pathway. These findings contribute to an understanding of the metabolic stress-driven dynamic transition of non-stem cancer cells to a stem-like state in the tumor metabolic microenvironment.

microRNA regulation of Wnt signaling pathways in development and disease

Wnt signaling pathways and microRNAs (miRNAs) are critical regulators of development. Aberrant Wnt signaling pathways and miRNA levels lead to developmental defects and diverse human pathologies including but not limited to cancer. Wnt signaling pathways regulate a plethora of cellular processes during embryonic development and maintain homeostasis of adult tissues. A majority of Wnt signaling components are regulated by miRNAs which are small noncoding RNAs that are expressed in both animals and plants. In animal cells, miRNAs fine tune gene expression by pairing primarily to the 3'untranslated region of protein coding mRNAs to repress target mRNA translation and/or induce target degradation. miRNA-mediated regulation of signaling transduction pathways is important in modulating dose-sensitive response of cells to signaling molecules. This review discusses components of the Wnt signaling pathways that are regulated by miRNAs in the context of development and diseases. A fundamental understanding of miRNA functions in Wnt signaling transduction pathways may yield new insight into crosstalks of regulatory mechanisms essential for development and disease pathophysiology leading to novel therapeutics.

Dysregulation of miR-34a links neuronal development to genetic risk factors for bipolar disorder

Bipolar disorder (BD) is a heritable neuropsychiatric disorder with largely unknown pathogenesis. Given their prominent role in brain function and disease, we hypothesized that microRNAs (miRNAs) might be of importance for BD. Here we show that levels of miR-34a, which is predicted to target multiple genes implicated as genetic risk factors for BD, are increased in postmortem cerebellar tissue from BD patients, as well as in BD patient-derived neuronal cultures generated by reprogramming of human fibroblasts into induced neurons or into induced pluripotent stem cells (iPSCs) subsequently differentiated into neurons. Of the predicted miR-34a targets, we validated the BD risk genes ankyrin-3 (ANK3) and voltage-dependent L-type calcium channel subunit beta-3 (CACNB3) as direct miR-34a targets. Using human iPSC-derived neuronal progenitor cells, we further show that enhancement of miR-34a expression impairs neuronal differentiation, expression of synaptic proteins and neuronal morphology, whereas reducing endogenous miR-34a expression enhances dendritic elaboration. Taken together, we propose that miR-34a serves as a critical link between multiple etiological factors for BD and its pathogenesis through the regulation of a molecular network essential for neuronal development and synaptogenesis.

Pulmonary Proteome and Protein Networks in Response to the Herbicide Paraquat in Rats

Paraquat (PQ) has been one of the most widely used herbicides in the world. PQ, when ingested, is toxic to humans and may cause acute respiratory distress syndrome. To investigate molecular perturbation in lung tissues caused by PQ, Sprague Dawley male rats were fed with PQ at a dose of 25 mg/kg body weight for 20 times in four weeks. The effects of PQ on cellular processes and biological pathways were investigated by analyzing proteome in the lung tissues in comparison with the control. Among the detected proteins, 321 and 254 proteins were over-represented and under-represented, respectively, in the PQ-exposed rat lung tissues in comparison with the no PQ control. All over- and under-represented proteins were subjected to Ingenuity Pathway Analysis to create 25 biological networks and 38 pathways of interacting protein clusters. Over-represented proteins were involved in the C-jun-amino-terminal kinase pathway, caveolae-mediated endocytosis signaling, cardiovascular-cancer-respiratory pathway, regulation of clathrin-mediated endocytosis, non-small cell lung cancer signaling, pulmonary hypertension, glutamate receptor, immune response and angiogenesis. Under-represented proteins occurred in the p53 signaling pathway, mitogen-activated protein kinase signaling pathway, cartilage development and angiogenesis inhibition in the PQ-treated lungs. The results suggest that PQ may generate reactive oxygen species, impair the MAPK/p53 signaling pathway, activate angiogenesis and depress apoptosis in the lungs.

Tenovin-6-mediated inhibition of SIRT1/2 induces apoptosis in acute lymphoblastic leukemia (ALL) cells and eliminates ALL stem/progenitor cells

Background

Acute lymphoblastic leukemia (ALL) is a heterogeneous group of malignant disorders derived from B- or T-cell lymphoid progenitor cells. ALL often is refractory to or relapses after treatment; thus, novel targeted therapy for ALL is urgently needed. In the present study, we initially found that the level of SIRT1, a class III histone deacetylase, was higher in primary ALL cells from patients than in peripheral blood mononuclear cells from healthy individuals. But it is not clear whether inhibition of SIRT1 by its selective small molecule inhibitor Tenovin-6 is effective against ALL cells.

Methods

We tested the effect of Tenovin-6 on ALL cell lines (REH and NALM-6) and primary cells from 41 children with ALL and 2 adult patients with ALL. The effects of Tenovin-6 on cell viability were determined by MTS assay; colony-forming assays were determined by soft agar in ALL cell lines and methylcellulose medium in normal bone marrow cells and primary ALL blast cells; cell apoptosis and cell cycling were examined by flow cytometry; the signaling pathway was determined by Western blotting; ALL stem/progenitor cells were seperated by using MACS MicroBead kit.

Results

The results showed that Tenovin-6 treatment activated p53, potently inhibited the growth of pre-B ALL cells and primary ALL cells, and sensitized ALL cells to frontline chemotherapeutic agents etoposide and cytarabine. Tenovin-6 induced apoptosis in REH and NALM-6 cells and primary ALL cells and diminished expression of Mcl-1 and X-linked inhibitor of apoptosis protein (XIAP) in such cells. Furthermore, inhibition of SIRT1 by Tenovin-6 inhibited the Wnt/β-catenin signaling pathway and eliminated ALL stem/progenitor (CD133 + CD19-) cells.

Conclusion

Our results indicate that Tenovin-6 may be a promising targeted therapy for ALL and clinical trials are warranted to investigate its efficacy in ALL patients.

MicroRNAs as potential biomarkers in cancer: opportunities and challenges

MicroRNAs (miRNAs) are a group of small noncoding RNAs (ncRNAs) that posttranscriptionally regulate gene expression by targeting their corresponding messenger RNAs (mRNAs). Dysregulated miRNAs have been considered as a new type of ‘‘oncomiRs” or ‘‘tumor suppressors,” playing essential roles in cancer initiation and progression. Using genome-wide detection methods, ubiquitously aberrant expression profiles of miRNAs have been identified in a broad array of human cancers, showing great potential as novel diagnostic and prognostic biomarkers of cancer with high specificity and sensitivity. The detectable miRNAs in tissue, blood, and other body fluids with high stability provide an abundant source for miRNA-based biomarkers in human cancers. Despite the fact that an increasing number of potential miRNA biomarkers have been reported, the transition of miRNAs-based biomarkers from bench to bedside still necessitates addressing several challenges. In this review, we will summarize our current understanding of miRNAs as potential biomarkers in human cancers.

miR-34: from bench to bedside

The mir-34 family was originally cloned and characterized in 2007 as a p53 target gene. Almost immediately it became clear that its major role is as a master regulator of tumor suppression. Indeed, when overexpressed, it directly and indirectly represses several oncogenes, resulting in an increase of cancer cell death (including cancer stem cells), and in an inhibition of metastasis. Moreover, its expression is deregulated in several human cancers. In 2013, a miR-34 mimic has become the first microRNA to reach phase 1 clinical trials. Here we review the miR-34 family and their role in tumor biology, and discuss the potential therapeutic applications of miR-34a mimic.

Implications of epithelial-mesenchymal plasticity for heterogeneity in colorectal cancer

Colorectal cancer (CRC) is a genetically heterogeneous disease that develops and progresses through several distinct pathways characterized by genomic instability. In recent years, it has emerged that inherent plasticity in some populations of CRC cells can contribute to heterogeneity in differentiation state, metastatic potential, therapeutic response, and disease relapse. Such plasticity is thought to arise through interactions between aberrant signaling events, including persistent activation of the APC/β-catenin and KRAS/BRAF/ERK pathways, and the tumor microenvironment. Here, we highlight key concepts and evidence relating to the role of epithelial–mesenchymal plasticity as a driver of CRC progression and stratification of the disease into distinct molecular and clinicopathological subsets.

GSK-3 as potential target for therapeutic intervention in cancer

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) was initially identified and studied in the regulation of glycogen synthesis. GSK-3 functions in a wide range of cellular processes. Aberrant activity of GSK-3 has been implicated in many human pathologies including: bipolar depression, Alzheimer's disease, Parkinson's disease, cancer, non-insulin-dependent diabetes mellitus (NIDDM) and others. In some cases, suppression of GSK-3 activity by phosphorylation by Akt and other kinases has been associated with cancer progression. In these cases, GSK-3 has tumor suppressor functions. In other cases, GSK-3 has been associated with tumor progression by stabilizing components of the beta-catenin complex. In these situations, GSK-3 has oncogenic properties. While many inhibitors to GSK-3 have been developed, their use remains controversial because of the ambiguous role of GSK-3 in cancer development. In this review, we will focus on the diverse roles that GSK-3 plays in various human cancers, in particular in solid tumors. Recently, GSK-3 has also been implicated in the generation of cancer stem cells in various cell types. We will also discuss how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTORC1, Ras/Raf/MEK/ERK, Wnt/beta-catenin, Hedgehog, Notch and others.

Wnt activity and basal niche position sensitize intestinal stem and progenitor cells to DNA damage

Aging and carcinogenesis coincide with the accumulation of DNA damage and mutations in stem and progenitor cells. Molecular mechanisms that influence responses of stem and progenitor cells to DNA damage remain to be delineated. Here, we show that niche positioning and Wnt signaling activity modulate the sensitivity of intestinal stem and progenitor cells (ISPCs) to DNA damage. ISPCs at the crypt bottom with high Wnt/β-catenin activity are more sensitive to DNA damage compared to ISPCs in position 4 with low Wnt activity. These differences are not induced by differences in cell cycle activity but relate to DNA damage-dependent activation of Wnt signaling, which in turn amplifies DNA damage checkpoint activation. The study shows that instructed enhancement of Wnt signaling increases radio-sensitivity of ISPCs, while inhibition of Wnt signaling decreases it. These results provide a proof of concept that cell intrinsic levels of Wnt signaling modulate the sensitivity of ISPCs to DNA damage and heterogeneity in Wnt activation in the stem cell niche contributes to the selection of ISPCs in the context of DNA damage.

LEF1 Targeting EMT in Prostate Cancer Invasion Is Regulated by miR-34a

The microRNA-34a (miR-34a), a tumor-suppressive microRNA (miRNA), is implicated in epithelial-mesenchymal transition (EMT) and cancer stem cells. Lymphoid enhancer-binding factor-1 (LEF1) is a key transcription factor in the Wnt signaling pathway, and has been suggested to be involved in regulation of cell proliferation and invasion. Here, the molecular mechanism of miR-34a and LEF1 in cooperatively regulating prostate cancer cell invasion is described. Molecular profiling analysis of miRNA levels in prostate cancer cells revealed a negative correlation between miR-34a and LEF1 expression, and the downregulation of LEF1 by miR-34a was confirmed by luciferase assays. Furthermore, miR-34a specifically repressed LEF1 expression through direct binding to its 3'-untranslated regions (3'-UTR). miR-34a modulated the levels of LEF1 to regulate EMT in prostate cancer cells. Functionally, miR-34a negatively correlated with the migration and invasion of prostate cancer cells through LEF1. An analysis of miR-34a expression levels in matched human tumor and benign tissues demonstrated consistent and statistically significant downregulation of miR-34a in primary prostate cancer specimens. These data strongly suggest that miR-34a/LEF1 regulation of EMT plays an important role in prostate cancer migration and invasion.

IMPLICATIONS

The miR-34a-LEF1 axis represents a potential molecular target for novel therapeutic strategies in prostate cancer.

p53 mutations in colorectal cancer- molecular pathogenesis and pharmacological reactivation

Colorectal cancer (CRC) is one of the most common malignancies with high prevalence and low 5-year survival. CRC is a heterogeneous disease with a complex, genetic and biochemical background. It is now generally accepted that a few important intracellular signaling pathways, including Wnt/β-catenin signaling, Ras signaling, and p53 signaling are frequently dysregulated in CRC. Patients with mutant p53 gene are often resistant to current therapies, conferring poor prognosis. Tumor suppressor p53 protein is a transcription factor inducing cell cycle arrest, senescence, and apoptosis under cellular stress. Emerging evidence from laboratories and clinical trials shows that some small molecule inhibitors exert anti-cancer effect via reactivation and restoration of p53 function. In this review, we summarize the p53 function and characterize its mutations in CRC. The involvement of p53 mutations in pathogenesis of CRC and their clinical impacts will be highlighted. Moreover, we also describe the current achievements of using p53 modulators to reactivate this pathway in CRC, which may have great potential as novel anti-cancer therapy.

LGR5 expression in oral epithelial dysplasia and oral squamous cell carcinoma

OBJECTIVE

LGR5 is pivotal to oral cavity development and is implicated in epithelial malignancy whereby stimulation of LGR5 potentiates canonical Wnt signaling. This investigation tested our hypothesis of a correlation between LGR5 expression and the severity of oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC).

STUDY DESIGN

Immunoreactive LGR5 protein expression was quantified in 342 tissue samples ranging in disease severity from normal through mild and moderate or severe OED to OSCC.

RESULTS

LGR5 was restricted to the basal layers for normal tissues, projected to the stratum granulosum in severe dysplasia, intense in carcinoma nests of well-differentiated OSCC, but uniformly diffuse throughout poorly differentiated OSCC. Median LGR5 immunoreactivity index scores increased with disease severity: mild dysplasia = 1 < moderate or severe dysplasia = 2.5 < OSCC = 6.

CONCLUSIONS

Inclusion of LGR5 in a panel of immunohistochemical biomarkers may improve identification of increased potential for malignancy in OED.

Battle against cancer: an everlasting saga of p53

Cancer is one of the most life-threatening diseases characterized by uncontrolled growth and spread of malignant cells. The tumor suppressor p53 is the master regulator of tumor cell growth and proliferation. In response to various stress signals, p53 can be activated and transcriptionally induces a myriad of target genes, including both protein-encoding and non-coding genes, controlling cell cycle progression, DNA repair, senescence, apoptosis, autophagy and metabolism of tumor cells. However, around 50% of human cancers harbor mutant p53 and, in the majority of the remaining cancers, p53 is inactivated through multiple mechanisms. Herein, we review the recent progress in understanding the molecular basis of p53 signaling, particularly the newly identified ribosomal stress—p53 pathway, and the development of chemotherapeutics via activating wild-type p53 or restoring mutant p53 functions in cancer. A full understanding of p53 regulation will aid the development of effective cancer treatments.

The BMP pathway either enhances or inhibits the Wnt pathway depending on the SMAD4 and p53 status in CRC

BACKGROUND

Constitutive Wnt activation is essential for colorectal cancer (CRC) initiation but also underlies the cancer stem cell phenotype, metastasis and chemosensitivity. Importantly Wnt activity is still modulated as evidenced by higher Wnt activity at the invasive front of clonal tumours termed the β-catenin paradox. SMAD4 and p53 mutation status and the bone morphogenetic protein (BMP) pathway are known to affect Wnt activity. The combination of SMAD4 loss, p53 mutations and BMP signalling may integrate to influence Wnt signalling and explain the β-catenin paradox.

METHODS

We analysed the expression patterns of SMAD4, p53 and β-catenin at the invasive front of CRCs using immunohistochemistry. We activated BMP signalling in CRC cells in vitro and measured BMP/Wnt activity using luciferase reporters. MTT assays were performed to study the effect of BMP signalling on CRC chemosensitivity.

RESULTS

Eighty-four percent of CRCs with high nuclear β-catenin staining are SMAD4 negative and/or p53 aberrant. BMP signalling inhibits Wnt signalling in CRC only when p53 and SMAD4 are unaffected. In the absence of SMAD4, BMP signalling activates Wnt signalling. When p53 is lost or mutated, BMP signalling no longer influences Wnt signalling. The cytotoxic effects of 5-FU are influenced in a similar manner.

CONCLUSIONS

The BMP signalling pathway differentially modulates Wnt signalling dependent on the SMAD4 and p53 status. The use of BMPs in cancer therapy, as has been proposed by previous studies, should be targeted to individual cancers based on the mutational status of p53 and SMAD4.

Involvement of RARRES3 in the regulation of Wnt proteins acylation and signaling activities in human breast cancer cells

The Wnt/β-catenin signaling pathway has emerged as a key regulator of complex biological processes, such as embryonic development, cell proliferation, cell fate decision and tumorigenesis. Recent studies have shown that the deregulation of Wnt/β-catenin signaling is frequently observed and leads to abnormal cell growth in human breast cancer cells. In this study, we identified a novel regulatory mechanism of Wnt/β-catenin signaling through RARRES3 that targets and modulates the acylation status of Wnt proteins and co-receptor low-density lipoprotein receptor-related protein 6, resulting in the suppression of epithelial-mesenchymal transition and cancer stem cell properties. Mutation of the conserved active site residues of RARRES3 indicates that RARRES3 serves as an acyl protein thioesterase that tethers its target proteins and modulates their acylation status. Furthermore, the functions of p53 in cell proliferation and Wnt/β-catenin signaling are significantly associated with the induction of RARRES3. Thus our findings provide a new insight into the molecular link between p53, protein acylation and Wnt/β-catenin signaling whereby RARRES3 plays a pivotal role in modulating the acylation status of signaling proteins.

A platform technique for growth factor delivery with novel mode of action

Though growth factors allow tissue regeneration, the trade-off between their effectiveness and adverse effects limits clinical application. The key issues in current growth factor therapy largely derive from initial burst pharmacokinetics, rapid clearance, and proteolytic cleavage resulting in clinical ineffectiveness and diverse complications. While a number of studies have focused on the development of carriers, issues arising from soluble growth factor remain. In this study, we report a prodrug of growth factors constituting a novel mode of action (MoA). To mimic endogenous protein processing in cells, we developed a recombinant BMP-2 polypeptide based on a protein transduction domain (PTD) to transduce the protein into cells followed by furin-mediated protein cleavage and secretion of active growth factor. As proof of concept, a few micrograms scale of PTD-BMP-2 polypeptide sufficed to induce bone regeneration in vivo. As a simple platform, our technique can easily be extended to delivery of BMP-7 and DKK-1 as therapeutics for TGF-β and canonical Wnt signaling, respectively, to suppress the epithelial-mesenchymal transition (EMT), which constitutes a fundamental biological mechanism of many diseases. This technique largely overcomes the limitations of current soluble growth factors and opens the door to next generation growth factor therapeutics.

KITLG is a novel target of miR-34c that is associated with the inhibition of growth and invasion in colorectal cancer cells

MiR-34c is considered a potent tumour suppressor because of its negative regulation of multiple target mRNAs that are critically associated with tumorigenesis and metastasis. In the present study, we demonstrated a novel target of miR-34c, KITLG, which has been implicated in colorectal cancer (CRC). First, we found a significant negative relationship between miR-34c and KITLG mRNA expression levels in CRC cell lines, including HT-29, HCT-116, SW480 and SW620 CRC cell lines. In silico analysis predicted putative binding sites for miR-34c in the 3' untranslated region (3'UTR) of KITLG mRNA. A dual-luciferase reporter assay further confirmed that KITLG is a direct target of miR-34c. Then, the cell lines were infected with lentiviruses expressing miR-34c or a miR-34c specific inhibitor. Restoration of miR-34c dramatically reduced the expression of KITLG mRNA and protein, while silencing of endogenous miR-34c increased the expression of KITLG protein. The miR-34c-mediated down-regulation of KITLG was associated with the suppression on proliferation, cellular transformation, migration and invasion of CRC cells, as well as the promotion on apoptosis. Knockdown of KITLG by its specific siRNA confirmed a critical role of KITLG down-regulation for the tumour-suppressive effects of miR-34c in CRC cells. In conclusion, our results demonstrated that miR-34c might interfere with KITLG-related CRC and could be a novel molecular target for CRC patients.

Promoter polymorphisms of miR-34b/c are associated with risk of gastric cancer in a Chinese population

More and more evidence reveals that noncoding RNA miR-34b/c and tumor suppressor gene TP-53 independently, and/or jointly, play crucial roles in carcinogenesis. The purpose of the present hospital-based case-control study was to investigate the association between the miR-34b/c rs4938723 and TP53 Arg72Pro polymorphisms and the risk of gastric cancer. Two polymorphisms were genotyped in 419 gastric cancer patients and 402 age- and sex-matched cancer-free controls using polymerase chain reaction-restriction fragment length polymorphism analysis. The CC genotype and C allele of the miR-34b/c rs4938723 were associated with a significantly decreased risk of gastric cancer compared with the TT genotype and T allele (CC vs. TT: P = 0.006, adjusted odds ratio (OR) = 0.53, 95 % confidence interval (95 % CI) = 0.34-0.83; C vs. T: P = 0.005, adjusted OR = 0.75, 95 % CI = 0.61-0.92). Compared with individuals with the wild-type TT genotype, subjects with the variant genotypes (CT + CC) had a significantly decreased risk of gastric cancer (P = 0.047, adjusted OR = 0.75, 95 % CI = 0.57-0.99). Stratified analysis showed that the association between the risk of gastric cancer and the variant genotypes of miR-34b/c was more profound among men. However, no overall association was found between the TP53 Arg72Pro polymorphism and gastric cancer risk. In the combined analysis, no effects of the interaction of miR-34b/c rs4938723 and TP53Arg72Pro on gastric cancer risk were observed. Our findings indicate that the miR-34b/c rs4938723 CT/CC genotypes may be associated with a decreased risk of gastric cancer and the C allele may be a protective factor in gastric cancer.

Canonical Wnt signaling induces vascular endothelial dysfunction via p66Shc-regulated reactive oxygen species

OBJECTIVE

Reactive oxygen species regulate canonical Wnt signaling. However, the role of the redox regulatory protein p66(Shc) in the canonical Wnt pathway is not known. We investigated whether p66(Shc) is essential for canonical Wnt signaling in the endothelium and determined whether the canonical Wnt pathway induces vascular endothelial dysfunction via p66(Shc)-mediated oxidative stress.

APPROACH AND RESULTS

The canonical Wnt ligand Wnt3a induced phosphorylation (activation) of p66(Shc) in endothelial cells. Wnt3a-stimulated dephosphorylation of β-catenin, and β-catenin-dependent transcription, was inhibited by knockdown of p66(Shc). Exogenous H2O2-induced β-catenin dephosphorylation was also mediated by p66(Shc). Moreover, p66(Shc) overexpression dephosphorylated β-catenin and increased β-catenin-dependent transcription, independent of Wnt3a ligand. P66(Shc)-induced β-catenin dephosphorylation was inhibited by antioxidants N-acetyl cysteine and catalase. Wnt3a upregulated endothelial NADPH oxidase-4, and β-catenin dephosphorylation was suppressed by knocking down NADPH oxidase-4 and by antioxidants. Wnt3a increased H2O2 levels in endothelial cells and impaired endothelium-dependent vasorelaxation in mouse aortas, both of which were rescued by p66(Shc) knockdown. P66(Shc) knockdown also inhibited adhesion of monocytes to Wnt3a-stimulated endothelial cells. Furthermore, constitutively active β-catenin expression in the endothelium increased vascular reactive oxygen species and impaired endothelium-dependent vasorelaxation. In vivo, high-fat diet feeding-induced endothelial dysfunction in mice was associated with increased endothelial Wnt3a, dephosphorylated β-catenin, and phosphorylated p66(Shc). High-fat diet-induced dephosphorylation of endothelial β-catenin was diminished in mice in which p66(Shc) was knocked down.

CONCLUSIONS

p66(Shc) plays a vital part in canonical Wnt signaling in the endothelium and mediates Wnt3a-stimulated endothelial oxidative stress and dysfunction.

CSNK1E/CTNNB1 are synthetic lethal to TP53 in colorectal cancer and are markers for prognosis

Two genes are called synthetic lethal (SL) if their simultaneous mutations lead to cell death, but each individual mutation does not. Targeting SL partners of mutated cancer genes can kill cancer cells specifically, but leave normal cells intact. We present an integrated approach to uncovering SL pairs in colorectal cancer (CRC). Screening verified SL pairs using microarray gene expression data of cancerous and normal tissues, we first identified potential functionally relevant (simultaneously differentially expressed) gene pairs. From the top-ranked pairs, ~20 genes were chosen for immunohistochemistry (IHC) staining in 171 CRC patients. To find novel SL pairs, all 169 combined pairs from the individual IHC were synergistically correlated to five clinicopathological features, e.g. overall survival. Of the 11 predicted SL pairs, MSH2-POLB and CSNK1E-MYC were consistent with literature, and we validated the top two pairs, CSNK1E-TP53 and CTNNB1-TP53 using RNAi knockdown and small molecule inhibitors of CSNK1E in isogenic HCT-116 and RKO cells. Furthermore, synthetic lethality of CSNK1E and TP53 was verified in mouse model. Importantly, multivariate analysis revealed that CSNK1E-P53, CTNNB1-P53, MSH2-RB1, and BRCA1-WNT5A were independent prognosis markers from stage, with CSNK1E-P53 applicable to early-stage and the remaining three throughout all stages. Our findings suggest that CSNK1E is a promising target for TP53-mutant CRC patients which constitute ~40% to 50% of patients, while to date safety regarding inhibition of TP53 is controversial. Thus the integrated approach is useful in finding novel SL pairs for cancer therapeutics, and it is readily accessible and applicable to other cancers.

Wnt inhibitory factor 1 suppresses cancer stemness and induces cellular senescence

Hyperactivation of the Wingless-type (Wnt)/β-catenin pathway promotes tumor initiation, tumor growth and metastasis in various tissues. Although there is evidence for the involvement of Wnt/β-catenin pathway activation in salivary gland tumors, the precise mechanisms are unknown. Here we report for the first time that downregulation of the Wnt inhibitory factor 1 (WIF1) is a widespread event in salivary gland carcinoma ex-pleomorphic adenoma (CaExPA). We also show that WIF1 downregulation occurs in the CaExPA precursor lesion pleomorphic adenoma (PA) and indicates a higher risk of progression from benign to malignant tumor. Our results demonstrate that diverse mechanisms including WIF1 promoter hypermethylation and loss of heterozygosity contribute to WIF1 downregulation in human salivary gland tumors. In accordance with a crucial role in suppressing salivary gland tumor progression, WIF1 re-expression in salivary gland tumor cells inhibited cell proliferation, induced more differentiated phenotype and promoted cellular senescence, possibly through upregulation of tumor-suppressor genes, such as p53 and p21. Most importantly, WIF1 significantly diminished the number of salivary gland cancer stem cells and the anchorage-independent cell growth. Consistent with this observation, WIF1 caused a reduction in the expression of pluripotency and stemness markers (OCT4 and c-MYC), as well as adult stem cell self-renewal and multi-lineage differentiation markers, such as WNT3A, TCF4, c-KIT and MYB. Furthermore, WIF1 significantly increased the expression of microRNAs pri-let-7a and pri-miR-200c, negative regulators of stemness and cancer progression. In addition, we show that WIF1 functions as a positive regulator of miR-200c, leading to downregulation of BMI1, ZEB1 and ZEB2, with a consequent increase in downstream targets such as E-cadherin. Our study emphasizes the prognostic and therapeutic potential of WIF1 in human salivary gland CaExPA. Moreover, our findings demonstrate a novel mechanism by which WIF1 regulates cancer stemness and senescence, which might have major implications in the field of cancer biology.

Wnt/β-catenin signaling regulates the proliferation and differentiation of mesenchymal progenitor cells through the p53 pathway

Objective

Mesenchymal progenitor cells (MPCs) are found in articular cartilage from normal controls and patients with osteoarthritis (OA). Nevertheless, the molecular mechanisms of the proliferation and differentiation of these cells remain unclear. In this study, we aimed to determine the involvement of Wnt/β-catenin signaling in regulating the proliferation and differentiation of MPCs.

Methods

MPCs were isolated from the articular cartilage of normal and OA patients. Cells were sorted by immunomagnetic cell separation. Cell proliferation capacity was evaluated using the MTT assay. Toluidine blue staining and immunostaining with anti-collagen II or anti-aggrecan antibodies were used to determine the chondrogenic differentiation capabilities of MPCs. The mRNA and protein expression of target genes were examined by quantitative real-time polymerase chain reaction and Western blotting, respectively. Knock-down of p53 expression was achieved with RNA interference.

Results

Most cells isolated from the normal and OA patients were CD105⁺ and CD166⁺ positive (Normal subjects: CD105⁺/CD166⁺, 94.6%±1.1%; OA: CD105⁺/CD166⁺, 93.5%±1.1%). MPCs derived from OA subjects exhibited decreased differentiation capabilities and enhanced Wnt/β-catenin activity. Inhibition of Wnt/β-catenin signaling promoted proliferation and differentiation, whereas activation of this pathway by treatment with rWnt3a protein decreased the proliferation and differentiation of normal MPCs. Additionally, Wnt/β-catenin signaling positively regulated p53 expression, and silencing of p53 increased proliferation and differentiation of MPCs.

Conclusions

Wnt/β-catenin regulated the proliferation and differentiation of MPCs through the p53 pathway.

New insights into p53 functions through its target microRNAs

The tumor suppressor p53 pathway, whose alterations are highly associated with all types of human cancers, plays an essential role in preventing tumor development and progression mostly through its downstream target genes. Over the last decade, a growing list of p53 microRNA (miRNA) targets has been identified as additional downstream players of this pathway. Further studies of these miRNAs have revealed their more complicated regulations and functions in executing and/or regulating p53 activity. Here, we review the p53 miRNA targets identified thus far, and discuss how they fine-tune p53 stress responses, mediate the crosstalk between p53 and other signaling pathways, and expand the role of p53 in other human diseases in addition to cancers.

Cellular reprogramming in skin cancer

Early primitive stem cells have long been viewed as the cancer cells of origin (tumor initiating target cells) due to their intrinsic features of self-renewal and longevity. However, emerging evidence suggests a surprising capacity for normal committed cells to function as reserve stem cells upon reprogramming as a consequence of tissue damage resulting in inflammation and wound healing. This results in an alternative concept positing that tumors may originate from differentiated cells that can re-acquire stem cell properties due to genetic or epigenetic reprogramming. It is likely that both models are correct, and that a continuum of potential cells of origin exists, ranging from early primitive stem cells to committed progenitor or even terminally differentiated cells. A combination of the nature of the target cell and the specific types of gene mutations introduced determine tumor cell lineage, as well as potential for malignant conversion. Evidence from mouse skin models of carcinogenesis suggests that initiated cells at different stages within a stem cell hierarchy have varying degrees of requirement for reprogramming (e.g. inflammation stimuli), depending on their degree of differentiation. This article will present evidence in favor of these concepts that has been developed from studies of several mouse models of skin carcinogenesis.

p53 protein regulates Hsp90 ATPase activity and thereby Wnt signaling by modulating Aha1 expression

The p53 tumor suppressor gene encodes a homotetrameric transcription factor which is activated in response to a variety of cellular stressors, including DNA damage and oncogene activation. p53 mutations occur in >50% of human cancers. Although p53 has been shown to regulate Wnt signaling, the underlying mechanisms are not well understood. Here we show that silencing p53 in colon cancer cells led to increased expression of Aha1, a co-chaperone of Hsp90. Heat shock factor-1 was important for mediating the changes in Aha1 levels. Increased Aha1 levels were associated with enhanced interactions with Hsp90, resulting in increased Hsp90 ATPase activity. Moreover, increased Hsp90 ATPase activity resulted in increased phosphorylation of Akt and glycogen synthase kinase-3β (GSK3β), leading to enhanced expression of Wnt target genes. Significantly, levels of Aha1, Hsp90 ATPase activity, Akt, and GSK3β phosphorylation and expression of Wnt target genes were increased in the colons of p53-null as compared with p53 wild type mice. Using p53 heterozygous mutant epithelial cells from Li-Fraumeni syndrome patients, we show that a monoallelic mutation of p53 was sufficient to activate the Aha1/Hsp90 ATPase axis leading to stimulation of Wnt signaling and increased expression of Wnt target genes. Pharmacologic intervention with CP-31398, a p53 rescue agent, inhibited recruitment of Aha1 to Hsp90 and suppressed Wnt-mediated gene expression in colon cancer cells. Taken together, this study provides new insights into the mechanism by which p53 regulates Wnt signaling and raises the intriguing possibility that p53 status may affect the efficacy of anticancer therapies targeting Hsp90 ATPase.

Role of 3’-untranslated region translational control in cancer development, diagnostics and treatment

The messenger RNA 3’-untranslated region (3’UTR) plays an important role in regulation of gene expression on the posttranscriptional level. The 3’UTR controls gene expression via orchestrated interaction between the structural components of mRNAs (cis-element) and the specific trans-acting factors (RNA binding proteins and non-coding RNAs). The crosstalk of these factors is based on the binding sequences and/or direct protein-protein interaction, or just functional interaction. Much new evidence that has accumulated supports the idea that several RNA binding factors can bind to common mRNA targets: to the non-overlapping binding sites or to common sites in a competitive fashion. Various factors capable of binding to the same RNA can cooperate or be antagonistic in their actions. The outcome of the collective function of all factors bound to the same mRNA 3’UTR depends on many circumstances, such as their expression levels, affinity to the binding sites, and localization in the cell, which can be controlled by various physiological conditions. Moreover, the functional and/or physical interactions of the factors binding to 3’UTR can change the character of their actions. These interactions vary during the cell cycle and in response to changing physiological conditions. Abnormal functioning of the factors can lead to disease. In this review we will discuss how alterations of these factors or their interaction can affect cancer development and promote or enhance the malignant phenotype of cancer cells. Understanding these alterations and their impact on 3’UTR-directed posttranscriptional gene regulation will uncover promising new targets for therapeutic intervention and diagnostics. We will also discuss emerging new tools in cancer diagnostics and therapy based on 3’UTR binding factors and approaches to improve them.

MicroRNA regulation of T-lymphocyte immunity: modulation of molecular networks responsible for T-cell activation, differentiation, and development

MicroRNAs (miRNA) are a class of small non-coding RNAs that constitute an essential and evolutionarily conserved mechanism for post-transcriptional gene regulation. Multiple miRNAs have been described to play key roles in T-lymphocyte development, differentiation, and function. In this review, we highlight the current literature regarding the differential expression of miRNAs in various models of murine and human T-cell biology. We emphasize mechanistic understandings of miRNA regulation of thymocyte development, T-cell activation, and differentiation into effector and memory subsets. We describe the participation of miRNAs in complex regulatory circuits shaping T-cell proteomes in a context-dependent manner. It is striking that some miRNAs regulate multiple processes, while others only appear in limited functional contexts. It is also evident that the expression and function of specific miRNAs can differ between murine and human systems. Ultimately, it is not always correct to simplify the complex events of T-cell biology into a model driven by only one or two master regulator miRNAs. In reality, T-cell activation and differentiation involve the expression of multiple miRNAs with many mRNA targets; thus, the true extent of miRNA regulation of T-cell biology is likely far more vast than currently appreciated.

Comprehensive analysis of β-catenin target genes in colorectal carcinoma cell lines with deregulated Wnt/β-catenin signaling

Background

Deregulation of Wnt/β-catenin signaling is a hallmark of the majority of sporadic forms of colorectal cancer and results in increased stability of the protein β-catenin. β-catenin is then shuttled into the nucleus where it activates the transcription of its target genes, including the proto-oncogenes MYC and CCND1 as well as the genes encoding the basic helix-loop-helix (bHLH) proteins ASCL2 and ITF-2B. To identify genes commonly regulated by β-catenin in colorectal cancer cell lines, we analyzed β-catenin target gene expression in two non-isogenic cell lines, DLD1 and SW480, using DNA microarrays and compared these genes to β-catenin target genes published in the PubMed database and DNA microarray data presented in the Gene Expression Omnibus (GEO) database.

Results

Treatment of DLD1 and SW480 cells with β-catenin siRNA resulted in differential expression of 1501 and 2389 genes, respectively. 335 of these genes were regulated in the same direction in both cell lines. Comparison of these data with published β-catenin target genes for the colon carcinoma cell line LS174T revealed 193 genes that are regulated similarly in all three cell lines. The overlapping gene set includes confirmed β-catenin target genes like AXIN2, MYC, and ASCL2. We also identified 11 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that are regulated similarly in DLD1 and SW480 cells and one pathway – the steroid biosynthesis pathway – was regulated in all three cell lines.

Conclusions

Based on the large number of potential β-catenin target genes found to be similarly regulated in DLD1, SW480 and LS174T cells as well as the large overlap with confirmed β-catenin target genes, we conclude that DLD1 and SW480 colon carcinoma cell lines are suitable model systems to study Wnt/β-catenin signaling and associated colorectal carcinogenesis. Furthermore, the confirmed and the newly identified potential β-catenin target genes are useful starting points for further studies.

Current status of miRNA-targeting therapeutics and preclinical studies against gastroenterological carcinoma

Expanding knowledge about the crucial roles of microRNAs (miRNAs) in human diseases has led to the idea that miRNAs may be novel, promising therapeutic targets against various pathological conditions. The recent success of a human clinical trial using anti-miR-122 oligonucleotides against chronic hepatitis C virus has paved the way for this approach. In this review, we summarize briefly the current status of clinical trials of miRNA-targeting therapy and several representative preclinical trials against hepato-gastrointestinal carcinoma. In addition, we describe the currently available technologies for modification and delivery of oligonucleotides, which are essential in providing efficient, specific and safe approaches to targeting miRNAs.

Current status of miRNA-targeting therapeutics and preclinical studies against gastroenterological carcinoma

Expanding knowledge about the crucial roles of microRNAs (miRNAs) in human diseases has led to the idea that miRNAs may be novel, promising therapeutic targets against various pathological conditions. The recent success of a human clinical trial using anti-miR-122 oligonucleotides against chronic hepatitis C virus has paved the way for this approach. In this review, we summarize briefly the current status of clinical trials of miRNA-targeting therapy and several representative preclinical trials against hepato-gastrointestinal carcinoma. In addition, we describe the currently available technologies for modification and delivery of oligonucleotides, which are essential in providing efficient, specific and safe approaches to targeting miRNAs.

Changes in cell and tissue organization in cancer of the breast and colon

Most cancers arise in epithelia, the tissue type that lines all body cavities. The organization of epithelia enables them to act as a barrier and perform vectorial transport of molecules between body compartments. Crucial for their organization and function is a highly specialized network of cell adhesion and polarity proteins aligned along the apical-basal axis. Comparing breast and intestinal tissue as examples of common cancer sites, reveals an important contribution of polarity proteins to the initiation and progression of cancer. Defects in polarity are induced directly by mutations in polarity proteins, but also indirectly by changes in the expression of specific microRNAs and altered transcriptional programs that drive cellular differentiation from epithelial to more mesenchymal characteristics. The latter is particularly important in the metastatic process.

Hsa-miR-34b/c rs4938723 T>C and hsa-miR-423 rs6505162 C>A polymorphisms are associated with the risk of esophageal cancer in a Chinese population

Esophageal cancer is the eighth most common cancer and sixth leading cause of cancer associated death worldwide. Besides environmental risk factors, genetic factors might play an important role in the esophageal cancer carcinogenesis. We conducted a hospital based case–control study to evaluate the genetic susceptibility of functional single nucleotide polymorphisms (SNPs) in the microRNAs on the development of esophageal cancer. A total of 629 esophageal squamous cell carcinoma (ESCC) cases and 686 controls were recruited for this study. The hsa-miR-34b/c rs4938723 T>C, pri-miR-124-1 rs531564 C>G, pre-miR-125a rs12975333 G>T and hsa-miR-423 rs6505162 C>A genotypes were determined using Ligation Detection Reaction (LDR) method. Our results demonstrated that hsa-miR-34b/c rs4938723 CC genotype had a decreased risk of ESCC. The association was evident among patients who never drinking. Hsa-miR-423 rs6505162 C>A might associated with a significantly increased risk of ESCC in patients who smoking. These findings indicated that functional polymorphisms hsa-miR-34b/c rs4938723 T>C and hsa-miR-423 rs6505162 C>A might alter individual susceptibility to ESCC. However, our results were obtained with a limited sample size. Future larger studies with other ethnic populations are required to confirm current findings.

Impaired DICER1 function promotes stemness and metastasis in colon cancer

Disruption of microRNA (miRNA) expression patterns is now being recognized as a hallmark of human cancer. The causes of these altered profiles are diverse, and, among them, we found the existence of defects in the miRNA processing machinery. However, little is known about how these alterations affect the biology of the underlying tumors. Herein, we show that colorectal cancer cells with an impairment in DICER1, a major miRNA biogenesis gene, undergo enrichment of tumor stemness features and an epithelial-to-mesenchymal transition. These phenotypes are associated with the downregulation of miRNAs, such as miR-34a, miR-126 and those of the miR-200 family, that target critical coding genes in these pathways. Most importantly, DICER1 impairment also induces the acquisition of a greater capacity for tumor initiation and metastasis, two properties associated with cancer stem cells.

Canonical Wnt signaling activates miR-34 expression during osteoblastic differentiation

The canonical Wnt signaling pathway is crucial for the regulation of bone mass in humans and for the development of osteoblasts. MicroRNAs (miRs) represent a class of non‑coding RNAs, ~22 nucleotides in length, that regulate gene expression by targeting mRNAs for cleavage or translational repression. Several previous studies have demonstrated the involvement of miRNAs in modulating gene expression in osteoblasts and regulating osteoblast differentiation. In the present study, microRNA profiling was conducted using Wnt3a‑C2C12 cells; C2C12 cells were transfected with a Wnt3a expression plasmid to activate canonical Wnt signaling. miR‑34b‑5p and miR‑34c were identified to be upregulated by the activation of canonical Wnt signaling in C2C12 cells. Expression of mature miR‑34b/c increased from low levels at day 0 to maximum levels at day 28 of MC3T3‑E1 cell differentiation. To analyze the effects of these miRNAs on osteoblast differentiation, an antisense inhibitor was transfected into MC3T3‑E1 cells and osteoblast‑related gene expression was investigated. Knockdown of miR34b/c enhanced osteocalcin mRNA expression; however, alkaline phosphatase mRNA expression and activity were decreased by miR34b/c inhibition. These results indicated that miR‑34b/c regulates gene expression by targeting regulators of the osteogenic pathways and thereby contributes to osteoblast differentiation.

Alternative splicing targeting the hTAF4-TAFH domain of TAF4 represses proliferation and accelerates chondrogenic differentiation of human mesenchymal stem cells

Transcription factor IID (TFIID) activity can be regulated by cellular signals to specifically alter transcription of particular subsets of genes. Alternative splicing of TFIID subunits is often the result of external stimulation of upstream signaling pathways. We studied tissue distribution and cellular expression of different splice variants of TFIID subunit TAF4 mRNA and biochemical properties of its isoforms in human mesenchymal stem cells (hMSCs) to reveal the role of different isoforms of TAF4 in the regulation of proliferation and differentiation. Expression of TAF4 transcripts with exons VI or VII deleted, which results in a structurally modified hTAF4-TAFH domain, increases during early differentiation of hMSCs into osteoblasts, adipocytes and chondrocytes. Functional analysis data reveals that TAF4 isoforms with the deleted hTAF4-TAFH domain repress proliferation of hMSCs and preferentially promote chondrogenic differentiation at the expense of other developmental pathways. This study also provides initial data showing possible cross-talks between TAF4 and TP53 activity and switching between canonical and non-canonical WNT signaling in the processes of proliferation and differentiation of hMSCs. We propose that TAF4 isoforms generated by the alternative splicing participate in the conversion of the cellular transcriptional programs from the maintenance of stem cell state to differentiation, particularly differentiation along the chondrogenic pathway.

Physiological β-catenin signaling controls self-renewal networks and generation of stem-like cells from nasopharyngeal carcinoma

Background

A few reports suggested that low levels of Wnt signaling might drive cell reprogramming, but these studies could not establish a clear relationship between Wnt signaling and self-renewal networks. There are ongoing debates as to whether and how the Wnt/β-catenin signaling is involved in the control of pluripotency gene networks. Additionally, whether physiological β-catenin signaling generates stem-like cells through interactions with other pathways is as yet unclear. The nasopharyngeal carcinoma HONE1 cells have low expression of β-catenin and wild-type expression of p53, which provided a possibility to study regulatory mechanism of stemness networks induced by physiological levels of Wnt signaling in these cells.

Results

Introduction of increased β-catenin signaling, haploid expression of β-catenin under control by its natural regulators in transferred chromosome 3, resulted in activation of Wnt/β-catenin networks and dedifferentiation in HONE1 hybrid cell lines, but not in esophageal carcinoma SLMT1 hybrid cells that had high levels of endogenous β-catenin expression. HONE1 hybrid cells displayed stem cell-like properties, including enhancement of CD24⁺ and CD44⁺ populations and generation of spheres that were not observed in parental HONE1 cells. Signaling cascades were detected in HONE1 hybrid cells, including activation of p53- and RB1-mediated tumor suppressor pathways, up-regulation of Nanog-, Oct4-, Sox2-, and Klf4-mediated pluripotency networks, and altered E-cadherin expression in both in vitro and in vivo assays. qPCR array analyses further revealed interactions of physiological Wnt/β-catenin signaling with other pathways such as epithelial-mesenchymal transition, TGF-β, Activin, BMPR, FGFR2, and LIFR- and IL6ST-mediated cell self-renewal networks. Using β-catenin shRNA inhibitory assays, a dominant role for β-catenin in these cellular network activities was observed. The expression of cell surface markers such as CD9, CD24, CD44, CD90, and CD133 in generated spheres was progressively up-regulated compared to HONE1 hybrid cells. Thirty-four up-regulated components of the Wnt pathway were identified in these spheres.

Conclusions

Wnt/β-catenin signaling regulates self-renewal networks and plays a central role in the control of pluripotency genes, tumor suppressive pathways and expression of cancer stem cell markers. This current study provides a novel platform to investigate the interaction of physiological Wnt/β-catenin signaling with stemness transition networks.