p53 inhibits tumor cell invasion via the degradation of snail protein in hepatocellular carcinoma

p53 inhibitor or antioxidants reduce the severity of ethmoid plate deformities in zebrafish Type 3 Treacher Collins syndrome model

Treacher Collins syndrome-3 (TCS-3) is a rare congenital craniofacial disorder attributed to variants in the RNA pol I subunit C (POLR1C). The pathogenesis of TCS-3 linked to polr1c involves the activation of apoptosis-dependent p53 pathways within neural crest cells (NCCs). This occurs due to disruptions in ribosome biogenesis, and the restoration of polr1c expression in early embryogenesis effectively rescues the observed craniofacial phenotype in polr1c-deficient zebrafish. Clinical variability in TCS patients suggests interactions between genes and factors like oxidative stress. Elevated production of reactive oxygen species (ROS) in epithelial cells may worsen phenotypic outcomes in TCS individuals. Our study confirmed excessive ROS production in facial regions, inducing apoptosis and altering p53 pathways. Deregulated cell-cycle and epithelial-to-mesenchymal transition (EMT) genes were also detected in the TCS-3 model. Utilizing p53 inhibitor (Pifithrin-α; PFT-α) or antioxidants (Glutathione; GSH and N-Acetyl-L-cysteine; NAC) effectively corrected migrated NCC distribution in the pharyngeal arch (PA), suppressed oxidative stress, prevented cell death, and modulated EMT inducers. Crucially, inhibiting p53 activation or applying antioxidants within a specific time window, notably within 30 h post-fertilization (hpf), successfully reversed phenotypic effects induced by polr1c MO.

Relationship between the Reduced Expression of Zinc Finger Protein 668 in Bladder Cancer and Its Invasiveness

The zinc finger protein 668 (ZNF668) gene encodes a Kruppel C2H2-type zinc-finger protein with 16 C2H2-type zinc fingers. The ZNF668 gene functions as a tumor suppressor gene in breast cancer. We histologically analyzed ZNF668 protein expression in bladder cancer and examined mutations of the ZNF668 gene in 68 cases of bladder cancer. In bladder cancer, the ZNF668 protein was expressed in the nuclei of cancer cells. In bladder cancer with submucosal and muscular infiltration, the expression of ZNF668 protein was significantly lower than that without submucosal and muscular infiltration. Eight heterozygous somatic mutations were detected in exon3 in five cases, and five of the mutations resulted in amino acid sequence mutations. Mutations resulting in amino acid sequence alterations also resulted in lower ZNF668 protein expression in bladder cancer cell nuclei, but no significant association with bladder cancer infiltration was detected. Decreased ZNF668 expression in bladder cancer was associated with submucosal and muscle invasion of cancer cells. Somatic mutations resulting in amino acid mutations in ZNF668 were found in 7.3% of the bladder cancer cases.

Functional role and epithelial to mesenchymal transition of the miR-590-3p/MDM2 axis in hepatocellular carcinoma

BACKGROUND

There is considerable evidence that microRNAs (miRNAs) regulate several key tumor-associated genes/pathways and may themselves have a dual regulatory function either as tumor suppressors or oncogenic miRNA, depending on the tumor type. MicroRNA-590-3p (miR-590-3p) is a small non-coding RNA involved in the initiation and progression of numerous tumors. However, its expression pattern and biological role in hepatocellular carcinoma (HCC) are controversial.

RESULTS

In the current work, computational and RT-qPCR analysis revealed that HCC tissues and cell lines exhibited miR-590-3p downregulation. Forced expression of miR-590-3p attenuated HepG2 cells proliferation, migration, and repressed EMT-related gene expression. Bioinformatic, RT-qPCR, and luciferase assays revealed that MDM2 is a direct functional target of miR-590-3p. Moreover, the knockdown of MDM2 mimicked the inhibitory effect of miR-590-3p in HepG2 cells.

CONCLUSION

We have identified not only novel targets for miR-590-3p in HCC, but also novel target genes for miR590-3p/MDM2 pathway in HCC like SNAIL, SLUG, ZEB1, ZEB2, and N-cadherin. Furthermore, these findings demonstrate a crucial role for MDM2 in the regulatory mechanism of EMT in HCC.

Helicobacter pylori promotes epithelial-to-mesenchymal transition by downregulating CK2β in gastric cancer cells

Strains of Helicobacter pylori that are positive for the oncoprotein CagA (cytotoxin-associated gene A) are associated with gastric cancer and might be related to the epithelial-to-mesenchymal transition (EMT). Casein kinase 2 (CK2) is a serine/threonine protein kinase that plays a major role in tumorigenesis through signaling pathways related to the EMT. However, the role played by the interaction between CagA and CK2 in gastric carcinogenesis is poorly understood. Although CK2α protein expression remained unchanged during H. pylori infection, we found that CK2α kinase activity was increased in gastric epithelial cells. We also found that the CK2β protein level decreased in H. pylori-infected gastric cancer cells in CagA-dependent manner and demonstrated that CagA induced CK2β degradation via HDM2 (human double minute 2; its murine equivalent is MDM2). We observed that CagA induced HDM2 protein phosphorylation and that p53 levels were decreased in H. pylori-infected gastric cancer cells. In addition, downregulation of CK2β induced AKT Ser473 phosphorylation and decreased the AKT Ser129 phosphorylation level in gastric cancer cells. We also found that the downregulation of CK2β triggered the upregulation of Snail levels in gastric cancer cells. Furthermore, our in vivo experiments and functional assays of migration and colony formation suggest that CK2β downregulation is a major factor responsible for the EMT in gastric cancer. Therefore, CK2 could be a key mediator of the EMT in H. pylori-infected gastric cancer and could serve as a molecular target for gastric cancer treatment.

Down-regulation of hepatic expression of GHR/STAT5/IGF-1 signaling pathway fosters development and aggressiveness of HCV-related hepatocellular carcinoma: Crosstalk with Snail-1 and type 2 transforming growth factor-beta receptor

Background and aims

So far, few clinical trials are available concerning the role of growth hormone receptor (GHR)/signal transducer and activator of transcription 5 (STAT5)/insulin like growth factor-1 (IGF-1) axis in hepatocarcinogenesis. The aim of this study was to evaluate the hepatic expression of GHR/STAT5/IGF-1 signaling pathway in hepatocellular carcinoma (HCC) patients and to correlate the results with the clinico-pathological features and disease outcome. The interaction between this signaling pathway and some inducers of epithelial-mesenchymal transition (EMT), namely Snail-1 and type 2 transforming growth factor-beta receptor (TGFBR2) was studied too.

Material and methods

A total of 40 patients with HCV-associated HCC were included in this study. They were compared to 40 patients with HCV-related cirrhosis without HCC, and 20 healthy controls. The hepatic expression of GHR, STAT5, IGF-1, Snail-1 and TGFBR2 proteins were assessed by immunohistochemistry.

Results

Compared with cirrhotic patients without HCC and healthy controls, cirrhotic patients with HCC had significantly lower hepatic expression of GHR, STAT5, and IGF-1proteins. They also displayed significantly lower hepatic expression of TGFBR2, but higher expression of Snail-1 versus the non-HCC cirrhotic patients and controls. Serum levels of alpha-fetoprotein (AFP) showed significant negative correlations with hepatic expression of GHR (r = -0.31; p = 0.029) and STAT5 (r = -0.29; p = 0.04). Hepatic expression of Snail-1 also showed negative correlations with GHR, STAT5, and IGF-1 expression (r = -0.55, p = 0.02; r = -0.472, p = 0.035, and r = -0.51, p = 0.009, respectively), whereas, hepatic expression of TGFBR2 was correlated positively with the expression of all these proteins (r = 0.47, p = 0.034; 0.49, p = 0.023, and r = 0.57, p<0.001, respectively). Moreover, we reported that decreased expression of GHR was significantly associated with serum AFP level>100 ng/ml (p = 0.048), increased tumor size (p = 0.02), vascular invasion (p = 0.002), and advanced pathological stage (p = 0.01). Similar significant associations were found between down-regulation of STAT5 expression and AFP level > 100 ng/ml (p = 0.006), vascular invasion (p = 0.009), and advanced tumor stage (p = 0.007). Also, attenuated expression of IGF-1 showed a significant association with vascular invasion (p < 0.001). Intriguingly, we detected that lower expression of GHR, STAT5 and IGF-1 were considered independent predictors for worse outcome in HCC.

Conclusion

Decreased expression of GHR/STAT5/IGF-1 signaling pathway may have a role in development, aggressiveness, and worse outcome of HCV-associated HCC irrespective of the liver functional status. Snail-1 and TGFBR2 as inducers of EMT may be key players. However, large prospective multicenter studies are needed to validate these results.

SNAIL driven by a feed forward loop motif promotes TGFβinduced epithelial to mesenchymal transition

Epithelial to Mesenchymal Transition (EMT) plays an important role in tissue regeneration, embryonic development, and cancer metastasis. Several signaling pathways are known to regulate EMT, among which the modulation of TGFβ(Transforming Growth Factor-β) induced EMT is crucial in several cancer types. Several mathematical models were built to explore the role of core regulatory circuit of ZEB/miR-200, SNAIL/miR-34 double negative feedback loops in modulating TGFβinduced EMT. Different emergent behavior including tristability, irreversible switching, existence of hybrid EMT states were inferred though these models. Some studies have explored the role of TGFβreceptor activation, SMADs nucleocytoplasmic shuttling and complex formation. Recent experiments have revealed that MDM2 along with SMAD complex regulates SNAIL expression driven EMT. Encouraged by this, in the present study we developed a mathematical model for p53/MDM2 dependent TGFβinduced EMT regulation. Inclusion of p53 brings in an additional mechanistic perspective in exploring the EM transition. The network formulated comprises a C1FFL moderating SNAIL expression involving MDM2 and SMAD complex, which functions as a noise filter and persistent detector. The C1FFL was also observed to operate as a coincidence detector driving the SNAIL dependent downstream signaling into phenotypic switching decision. Systems modelling and analysis of the devised network, displayed interesting dynamic behavior, systems response to various inputs stimulus, providing a better understanding of p53/MDM2 dependent TGF-βinduced Epithelial to Mesenchymal Transition.

Opposing Roles of Wild-type and Mutant p53 in the Process of Epithelial to Mesenchymal Transition

The central role of an aberrantly activated EMT program in defining the critical features of aggressive carcinomas is well documented and includes cell plasticity, metastatic dissemination, drug resistance, and cancer stem cell-like phenotypes. The p53 tumor suppressor is critical for leashing off all the features mentioned above. On the molecular level, the suppression of these effects is exerted by p53 via regulation of its target genes, whose products are involved in cell cycle, apoptosis, autophagy, DNA repair, and interactions with immune cells. Importantly, a set of specific mutations in the TP53 gene (named Gain-of-Function mutations) converts this tumor suppressor into an oncogene. In this review, we attempted to contrast different regulatory roles of wild-type and mutant p53 in the multi-faceted process of EMT.

Transcriptional and post-transcriptional control of epithelial-mesenchymal plasticity: why so many regulators?

The dynamic transition between epithelial-like and mesenchymal-like cell states has been a focus for extensive investigation for decades, reflective of the importance of Epithelial-Mesenchymal Transition (EMT) through development, in the adult, and the contributing role EMT has to pathologies including metastasis and fibrosis. Not surprisingly, regulation of the complex genetic networks that underlie EMT have been attributed to multiple transcription factors and microRNAs. What is surprising, however, are the sheer number of different regulators (hundreds of transcription factors and microRNAs) for which critical roles have been described. This review seeks not to collate these studies, but to provide a perspective on the fundamental question of whether it is really feasible that so many regulators play important roles and if so, what does this tell us about EMT and more generally, the genetic machinery that controls complex biological processes.

The p53 Protein Family in the Response of Tumor Cells to Ionizing Radiation: Problem Development

Survival mechanisms are activated in tumor cells in response to therapeutic ionizing radiation. This reduces a treatment's effectiveness. The p53, p63, and p73 proteins belonging to the family of proteins that regulate the numerous pathways of intracellular signal transduction play a key role in the development of radioresistance. This review analyzes the p53-dependent and p53-independent mechanisms involved in overcoming the resistance of tumor cells to radiation exposure.

Overexpression of NOP58 as a Prognostic Marker in Hepatocellular Carcinoma: A TCGA Data-Based Analysis

INTRODUCTION

NOP58 ribonucleoprotein, a core component of box C/D small nucleolar ribonucleoproteins, is involved in various cell physiological processes. However, its role in hepatocellular carcinoma (HCC) remains very unclear. We aim to investigate NOP58 expression and its probable prognostic value in patients with HCC based on The Cancer Genome Atlas (TCGA) database.

METHODS

RNA sequencing data and clinicopathological characteristics of patients with HCC were collected from TCGA database. Expression of NOP58 in HCC tissues and normal tissues was analyzed by Wilcoxon rank-sum test. Patients were divided into high and low subgroups according to median expression of NOP58. Logistic regression, gene set enrichment analysis (GSEA), and single-sample gene set enrichment analysis (ssGSEA) were conducted to annotate biological function and immune infiltration of NOP58.

RESULTS

NOP58 was significantly overexpressed in HCC tissues and correlated with significantly high tumor stage [odds ratio (OR) 10.01, 95% confidence interval (CI) 10.01-10.03; P = 0.003], advanced pathologic stage (OR 10.02, 95% CI 10.01-10.03; P < 0.001), advanced histologic stage (OR 10.03, 95% CI 10.02-10.04; P < 0.001), vascular invasion (OR 10.02, 95% CI 10.01-10.03; P = 0.003), poor performance status (OR 10.01, 95% CI 10.01-10.03; P = 0.003), and Mut-TP53 status (OR 10.02, 95% CI 10.01-10.03; P < 0.001). Elevated NOP58 expression had poor disease-specific survival (DSS; P < 0.001), progression-free interval (P = 0.006), and overall survival (OS; P < 0.001). NOP58 expression was independently correlated with OS (HR 1.731, 95% CI 10.037-2.890; P = 0.036). GSEA demonstrated that various cell cycle pathways along with RB-1 pathway, interleukin-10 signaling, regulation of TP53 activity, and P53 downstream pathway were differentially enriched in NOP58 high expression phenotype. NOP58 expression was positively correlated with infiltrating the levels of T helper type 2 (Th2) cells.

CONCLUSIONS

Overexpression of NOP58 is negatively correlated with overall survival in patients with HCC and might be a potential biomarker for prognosis of HCC.

Ethanol Extracts of Solanum lyratum Thunb Regulate Ovarian Cancer Cell Proliferation, Apoptosis, and Epithelial-to-Mesenchymal Transition (EMT) via the ROS-Mediated p53 Pathway

Ovarian cancer is a type of common gynecological tumors with high incidence and poor survival. The anticancer effects of the traditional Chinese medicine Solanum lyratum Thunb (SLT) have been intensively investigated in various cancers but in ovarian cancer is rare. The current study is aimed at investigating the effect of SLT on ovarian cancer cells. Lactate dehydrogenase (LDH) and MTT assays indicated that SLT concentrations of 0.25 and 0.5 μg/mL were not cytotoxic and had significant inhibitory effects on the cell viabilities of A2780 and SKOV3 cells, hence were used for subsequent experiments. Flow cytometric and western blot analysis revealed that SLT effectively suppressed ovarian cancer cell proliferation via inducing cell cycle arrest and increasing apoptosis. Cell cycle and apoptosis-related protein expressions were also regulated in SLT-treated cells. Moreover, DCFH-DA and western blot assays demonstrated that SLT enhanced ROS accumulation and subsequently activated the p53 signaling pathway. However, SLT-regulated ovarian cancer cell proliferation, apoptosis, migration, invasion, and EMT were significantly reversed by an ROS inhibitor (NAC, N-acetyl-L-cysteine). Furthermore, A2780 and SKOV3 cells cocultured with M0 macrophages showed that SLT activated the polarization of M0 macrophages to M1 macrophages and inhibited the polarization to M2 macrophages, with the increased percentage of CD86+ cells and decreased percentage of CD206+ cells were detected. In summary, this study illustrated the anticancer effects of SLT on ovarian cancer cells, suggesting that SLT may have the potential to provide basic evidence for the discovery of antiovarian cancer agents.

Urolithin A Inhibits Epithelial-Mesenchymal Transition in Lung Cancer Cells via P53-Mdm2-Snail Pathway

PURPOSE

The epithelial-to-mesenchymal transition (EMT) is a fundamental process in tumor progression that endows cancer cells with migratory and invasive potential. Snail, a zinc finger transcriptional repressor, plays an important role in the induction of EMT by directly repressing the key epithelial marker E-cadherin. Here, we assessed the effect of urolithin A, a major metabolite from pomegranate ellagitannins, on Snail expression and EMT process.

METHODS

The role of Snail in urolithin A-induced EMT inhibition in lung cancer cells was explored by wound healing assay and cell invasion assay. The qRT-PCR and CHX assay were performed to investigate how urolithin A regulates Snail expression. Immunoprecipitation assays were established to determine the effects of urolithin A in mdm2-Snail interaction. In addition, the expression of p53 was manipulated to explore its effect on the expression of mdm2 and Snail.

RESULTS

The urolithin A dose-dependently upregulated epithelial marker and decreased mesenchymal markers in lung cancer cells. In addition, exposure to urolithin A decreased cell migratory and invasive capacity. We have further demonstrated that urolithin A inhibits lung cancer cell EMT by decreasing Snail protein expression and activity. Mechanistically, urolithin A disrupts the interaction of p53 and mdm2 which leads Snail ubiquitination and degradation.

CONCLUSION

We conclude that urolithin A could inhibit EMT process by controlling mainly Snail expression. These results highlighted the role of pomegranate in regulation of EMT program in lung cancer.

Upregulation of fibronectin following loss of p53 function is a poor prognostic factor in ovarian carcinoma with a unique immunophenotype

Background

We previously demonstrated that ovarian high grade serous carcinomas (OHGSeCa) and ovarian clear cell carcinomas (OCCCa) with an HNF-1β+/p53+/ARID1A+ immunophenotype were associated with the worst unfavorable prognosis. To clarify the molecular mechanisms underlying this finding, we focused on alterations in the p53 signaling pathway in these tumors.

Methods

Changes in cell phenotype and function following knockdown of wild-type p53 (p53-KD) were assessed using OCCCa cells expressing endogenous HNF-1β and ARID1A. The prognostic significance of molecules that were deregulated following p53-KD was also examined using 129 OCCCa/OHGSeCa cases.

Results

p53-KD cells had increased expression of Snail, phospho-Akt (pAkt), and pGSK3β, and decreased E-cadherin expression, leading to epithelial-mesenchymal transition (EMT)/cancer stem cell (CSC) features. The cells also exhibited acceleration of cell motility and inhibition of cell proliferation and apoptosis. Next generation sequencing revealed that fibronectin (FN) expression was significantly increased in the p53 KD-cells, in line with our observation that wild-type p53 (but not mutant p53) repressed FN1 promoter activity. In addition, treatment of OCCCa cells with FN significantly increased cell migration capacity and decreased cell proliferation rate, independent of induction of EMT features. In clinical samples, FN/p53 scores were significantly higher in OCCCa/OHGSeCa with the HNF-1β+/p53+/ARID1A+ immunophenotype when compared to others. Moreover, high FN/high p53 expression was associated with the worst overall survival and progression-free survival in OCCCa/OHGSeCa patients.

Conclusion

These findings suggest that upregulation of FN following loss of p53 function may impact the biological behavior of OCCCa/OHGSeCa, particularly in tumors with an HNF-1β+/p53+/ARID1A+ immunophenotype, through alterations in cell mobility and cell proliferation. The accompanying induction of EMT/CSC properties and inhibition of apoptosis due to p53 abnormalities also contribute to the establishment and maintenance of tumor phenotypic characteristics.

Invaders Exposed: Understanding and Targeting Tumor Cell Invasion in Diffuse Intrinsic Pontine Glioma

Diffuse Intrinsic Pontine Glioma (DIPG) is a rare, highly aggressive pediatric brain tumor that originates in the pons. DIPG is untreatable and universally fatal, with a median life expectancy of less than a year. Resection is not an option, due to the anatomical location of the tumor, radiotherapy has limited effect and no chemotherapeutic or targeted treatment approach has proven to be successful. This poor prognosis is partly attributed to the tumor's highly infiltrative diffuse and invasive spread. Thus, targeting the invasive behavior of DIPG has the potential to be of therapeutic value. In order to target DIPG invasion successfully, detailed mechanistic knowledge on the underlying drivers is required. Here, we review both DIPG tumor cell's intrinsic molecular processes and extrinsic environmental factors contributing to DIPG invasion. Importantly, DIPG represents a heterogenous disease and through advances in whole-genome sequencing, different subtypes of disease based on underlying driver mutations are now being recognized. Recent evidence also demonstrates intra-tumor heterogeneity in terms of invasiveness and implies that highly infiltrative tumor subclones can enhance the migratory behavior of neighboring cells. This might partially be mediated by “tumor microtubes,” long membranous extensions through which tumor cells connect and communicate, as well as through the secretion of extracellular vesicles. Some of the described processes involved in invasion are already being targeted in clinical trials. However, more research into the mechanisms of DIPG invasion is urgently needed and might result in the development of an effective therapy for children suffering from this devastating disease. We discuss the implications of newly discovered invasive mechanisms for therapeutic targeting and the challenges therapy development face in light of disease in the developing brain.

p53 controls the switch between autophagy and apoptosis through regulation of PLSCR1 in sodium selenite-treated leukemia cells

Coordinated regulation of autophagy and apoptosis helps to enhance the antitumor effects of sodium selenite. However, the potential molecules that act as switch nodes in the crosstalk between autophagy and apoptosis is still elusive. Phospholipid scramblase 1 (PLSCR1) has been shown to regulate leukocyte differentiation, while its role in autophagy/apoptosis toggle switch remains unexplored. In this study, we showed that sodium selenite switched protective autophagy to apoptosis in p53-wild type NB4 cells without obvious caspase-8/apoptosis-inducing factor (AIF) axis activation, while induced autophagy-dependent caspase-8/AIF axis activation in p53-mutant Jurkat cells. Additionally, p53 was demonstrated as a positive regulator of PLSCR1. p53-dependent up-regulation of PLSCR1 accounted for the differential regulation of autophagy and apoptosis induced by sodium selenite. Furthermore, sodium selenite induced the release of AIF from mitochondria to cytosol with the facilitation of caspase-8 in Jurkat cells, while not in NB4 cells. The released AIF further enhanced autophagy flux through interacting with PLSCR1, which hereby resulting in the disassociation of PLSCR1 from Atg5-Atg12 complex. Our results indicate that PLSCR1 plays a critical role in p53-dependent regulation of autophagy and apoptosis in sodium selenite-treated leukemia cells. Manipulation of p53-PLSCR1 cascade might be beneficial to enhance the anti-tumor effects of sodium selenite.

p53-Mediated Tumor Suppression: DNA-Damage Response and Alternative Mechanisms

The tumor suppressor p53 regulates different cellular pathways involved in cell survival, DNA repair, apoptosis, and senescence. However, according to an increasing number of studies, the p53-mediated canonical DNA damage response is dispensable for tumor suppression. p53 is involved in mechanisms regulating many other cellular processes, including metabolism, autophagy, and cell migration and invasion, and these pathways might crucially contribute to its tumor suppressor function. In this review we summarize the canonical and non-canonical functions of p53 in an attempt to provide an overview of the potentially crucial aspects related to its tumor suppressor activity.

Jorunnamycin A from Xestospongia sp. Suppresses Epithelial to Mesenchymal Transition and Sensitizes Anoikis in Human Lung Cancer Cells

Metastasis is a key driving force behind the high mortality rate associated with lung cancer. Herein, we report the first study revealing the antimetastasis activity of jorunnamycin A, a bistetrahydroisoquinolinequinone isolated from a Thai blue sponge Xestospongia sp. evidenced by its inhibition of epithelial to mesenchymal transition (EMT), sensitization of anoikis, and suppression of anchorage-independent survival in human lung cancer cells. Treatment with jorunnamycin A (0.05-0.5 μM) altered the expression of p53 and Bcl-2 family proteins, particularly causing the down-regulation of antiapoptosis Bcl-2 and Mcl-1 proteins. Under detachment conditions for 12 h, jorunnamycin A-treated cells exhibited diminution of pro-survival proteins p-Akt and p-Erk as well as the survival-promoting factor caveolin-1. Corresponding with the inhibition on the Akt and Erk pathway as well as activation of p53, there was an increase in the epithelial marker E-cadherin and a remarkable decrease of EMT markers and associated proteins including vimentin, snail, and claudin-1. As the loss of anchorage dependence is an important barrier to metastasis, the observed inhibitory effects of jorunnamycin A on the coordinating networks of EMT and anchorage-independent growth emphasize the potential development of jorunnamycin A as an effective agent against lung cancer metastasis.

Alcohol-mediated calcium signals dysregulate pro-survival Snai2/PUMA/Bcl2 networks to promote p53-mediated apoptosis in avian neural crest progenitors

BACKGROUND

Prenatal alcohol exposure causes distinctive craniofacial anomalies that arise, in part, from the apoptotic elimination of neural crest (NC) progenitors that form the face. This vulnerability of NC to alcohol is puzzling as they normally express the transcriptional repressor Snail1/2 (in chick Snai2), which suppresses apoptosis and promotes their migration. Here, we investigate alcohol's impact upon Snai2 function.

METHODS

Chick cranial NC cells were treated with acute alcohol (52 mM, 2 hr). We evaluated NC migration, gene expression, proliferation, and apoptosis thereafter.

RESULTS

Transient alcohol exposure induced Snai2 (191% ± 23%; p = .003) and stimulated NC migration (p = .0092). An alcohol-induced calcium transient mediated this Snai2 induction, and BAPTA-AM blocked whereas ionomycin mimicked these pro-migratory effects. Alcohol suppressed CyclinD1 protein content (59.1 ± 12%, p = .007) and NC proliferation (19.7 ± 5.8%, p < .001), but these Snai2-enriched cells still apoptosed in response to alcohol. This was explained because alcohol induced p53 (198 ± 29%, p = .023), and the p53 antagonist pifithrin-α prevented their apoptosis. Moreover, alcohol counteracted Snai2's pro-survival signals, and Bcl2 was repressed (68.5 ± 6.0% of controls, p = .016) and PUMA was not induced, while ATM (1.32-fold, p = .01) and PTEN (1.30-fold, p = .028) were elevated.

CONCLUSIONS

Alcohol's calcium transient uncouples the Snai2/p53 regulatory loop that normally prevents apoptosis during EMT. This represents a novel pathway in alcohol's neurotoxicity, and complements demonstrations that alcohol suppresses PUMA in mouse NC. We propose that the NCs migratory behavior, and their requirement for Snai2/p53 co-expression, makes them vulnerable to stressors that dysregulate Snai2/p53 interactions, such as alcohol.

p73 induction by Abrus agglutinin facilitates Snail ubiquitination to inhibit epithelial to mesenchymal transition in oral cancer

BACKGROUND

Epithelial-to-mesenchymal transition (EMT), a key step in oral cancer progression, is associated with invasion, metastasis, and therapy resistance, thus targeting the EMT represents a critical therapeutic strategy for the treatment of oral cancer metastasis. Our previous study showed that Abrus agglutinin (AGG), a plant lectin, induces both intrinsic and extrinsic apoptosis to activate the tumor inhibitory mechanism.

OBJECTIVE

This study aimed to investigate the role of AGG in modulating invasiveness and stemness through EMT inhibition for the development of antineoplastic agents against oral cancer.

METHODS

The EMT- and stemness-related proteins were studied in oral cancer cells using Western blot analysis and fluorescence microscopy. The potential mechanisms of Snail downregulation through p73 activation in FaDu cells were evaluated using Western blot analysis, immunoprecipitation, confocal microscopy, and molecular docking analysis. Immunohistochemical staining of the tumor samples of AGG-treated FaDu-xenografted nude mice was performed.

RESULTS

At the molecular level, AGG-induced p73 suppressed Snail expression, leading to EMT inhibition in FaDu cells. Notably, AGG promoted the translocation of Snail from the nucleus to the cytoplasm in FaDu cells and triggered its degradation through ubiquitination. In this setting, AGG inhibited the interaction between Snail and p73 in FaDu cells, resulting in p73 activation and EMT inhibition. Moreover, in epidermal growth factor (EGF)-stimulated FaDu cells, AGG abolished the upregulation of extracellular signal-regulated kinase (ERK)1/2 that plays a pivotal role in the upregulation of Snail to regulate the EMT phenotypes. In immunohistochemistry analysis, FaDu xenografts from AGG-treated mice showed decreased expression of Snail, SOX2, and vimentin and increased expression of p73 and E-cadherin compared with the control group, confirming EMT inhibition as part of its anticancer efficacy against oral cancer.

CONCLUSION

In summary, AGG stimulates p73 in restricting EGF-induced EMT, invasiveness, and stemness by inhibiting the ERK/Snail pathway to facilitate the development of alternative therapeutics for oral cancer.

Phosphorylation of p53 Serine 15 Is a Predictor of Survival for Patients with Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant cancers with a poor prognosis. Several commonly investigated immunohistochemical markers in resected HCC have potential prognostic value, but the prognostic utility of p53 expression in HCC has remained elusive.

AIM

To evaluate the prognostic value of p53 and p53 phosphorylation at serine 15 (p53 Ser15-P) in patients with HCC.

METHODS

Surgically resected tumors from 199 HCC patients were analyzed for p21, p53, p53 Ser15-P, and proliferating cell nuclear antigen (PCNA) expression using immunohistochemistry.

RESULTS

Stratifying by the expression of p53 Ser15-P (P = 0.016), but not by p53 (P = 0.301), revealed significantly different survival outcomes in patients with HCC. Moreover, our analysis demonstrated that patients who were PCNA-positive and p53 Ser15-P-negative had significantly worse survival outcomes (P = 0.001) than patients who were PCNA-positive and p53 Ser15-P-positive.

CONCLUSIONS

P53 Ser15-P is associated with poor outcomes in patients with HCC, and this prognostic marker is useful for predicting the survival of patients with PCNA-positive HCC.

Non-redundant functions of EMT transcription factors

Epithelial-mesenchymal transition (EMT) is a crucial embryonic programme that is executed by various EMT transcription factors (EMT-TFs) and is aberrantly activated in cancer and other diseases. However, the causal role of EMT and EMT-TFs in different disease processes, especially cancer and metastasis, continues to be debated. In this Review, we identify and describe specific, non-redundant functions of the different EMT-TFs and discuss the reasons that may underlie disputes about EMT in cancer.

Group I Paks are essential for epithelial- mesenchymal transition in an Apc-driven model of colorectal cancer

p21-activated kinases (Paks) play an important role in oncogenic signaling pathways and have been considered as potential therapeutic targets in various cancers. Most studies of Pak function employ gene knock-out or knock-down methods, but these approaches result in loss of both enzymatic and scaffolding properties of these proteins, and thus may not reflect the effects of small molecule inhibitors. Here we use a transgenic mouse model in which a specific peptide inhibitor of Group I Paks is conditionally expressed in response to Cre recombinase. Using this model, we show that inhibition of endogenous Paks impedes the transition of adenoma to carcinoma in an Apc-driven mouse model of colorectal cancer. These effects are mediated by inhibition of Wnt signaling through reduced β-catenin activity as well as suppression of an epithelial-mesenchymal transition program mediated by miR-200 and Snai1. These results highlight the potential therapeutic role of Pak1 inhibitors in colorectal cancer.

p53-Pirh2 Complex Promotes Twist1 Degradation and Inhibits EMT

Epithelial-mesenchymal transition (EMT) is a critical process involved in cancer metastasis and chemoresistance. Twist1 is a key EMT-inducing transcription factor, which is upregulated in multiple types of cancers and has been shown to promote tumor cell invasiveness and support tumor progression. Conversely, p53 is a tumor suppressor gene that is frequently mutated in cancers. This study demonstrates the ability of wild-type (WT) p53 to promote the degradation of Twist1 protein. By forming a complex with Twist1 and the E3 ligase Pirh2, WT p53 promotes the ubiquitination and proteasomal degradation of Twist1, thus inhibiting EMT and maintaining the epithelial phenotype. The ability of p53 to induce Twist1 degradation is abrogated when p53 is mutated. Consequently, the loss of p53-induced Twist1 degradation leads to EMT and the acquisition of a more invasive cancer phenotype.Implication: These data provide new insight into the metastatic process at the molecular level and suggest a signaling pathway that can potentially be used to develop new prognostic markers and therapeutic targets to curtail cancer progression.

Epithelial mesenchymal transition Transcription Factor (TF): The structure, function and microRNA feedback loop

Epithelial to mesenchymal transition (EMT) is a phenomenon in which epithelial cells lose their cell to cell adhesion and detach from the base of the membrane. EMT is a fundamental process which occurs during tumor progression and metastasis. Cancer genomics is a complex network which involves a variety of factors such as transcription factors (TFs), coding genes and microRNAs (miRs). Both TFs and miRs are trans-regulatory elements that crosstalk. Due to a wide range of targets, TF-miR interaction provides a feedback or feedforward loop and cross-gene regulation consequently. In this review, we focused on the structure and function of two TF families involved in EMT, zinc finger and β helix loop helix and p53. Subsequently we analyzed recent findings on TF-miR interaction in EMT.

Overexpression of MCPH1 inhibits the migration and invasion of lung cancer cells

Background

The role of dysfunction of MCPH1, a recently identified tumor suppressor gene, has not yet been established in lung cancer. In our previous study, it was reported that MCPH1 expression is downregulated in lung cancer tissues and that MCPH1 overexpression inhibits the proliferation of non-small-cell lung cancer cells. The results can be found in the APJC and Oncology Letters journals.

Methods

Kaplan-Meier survival analysis was conducted to explore the prognostic significance of MCPH1. Cell experiments were performed to investigate the effects of MCPH1 on the biologic behaviors of lung cancer cells.

Results

In the current study, microarray analysis of MCPH1 revealed that lung cancer patients with high MCPH1 expression had longer relapse-free survival. Overexpression of MCPH1 in A549 lung carcinoma cells successfully inhibited cell migration and invasion. Moreover, overexpression of MCPH1 inhibited migration and invasion by regulating the activities of several proteins that control the epithelial–mesenchymal transition, such as Slug, Snail, E-cadherin, Mdm2, and p53.

Conclusion

Our results indicate that downregulation of MCPH1 correlates with tumor progression in lung cancer, and hence MCPH1 may be an important tumor suppressor gene and a novel candidate therapeutic target in lung cancer.

MDM2-p53 Interactions in Human Hepatocellular Carcinoma: What Is the Role of Nutlins and New Therapeutic Options?

Human hepatocellular carcinoma (HCC) is the fifth most common cancer and is associated with poor prognosis worldwide. The molecular mechanisms underlying the pathogenesis of HCC have been an area of continuing interest, and recent studies using next generation sequencing (NGS) have revealed much regarding previously unsettled issues. Molecular studies using HCC samples have been mainly targeted with the aim to identify the fundamental mechanisms contributing to HCC and identify more effective treatments. In response to cellular stresses (e.g., DNA damage or oncogenes), activated p53 elicits appropriate responses that aim at DNA repair, genetic stability, cell cycle arrest, and the deletion of DNA-damaged cells. On the other hand, the murine double minute 2 (MDM2) oncogene protein is an important cellular antagonist of p53. MDM2 negatively regulates p53 activity through the induction of p53 protein degradation. However, current research has shown that the mechanisms underlying MDM2-p53 interactions are more complex than previously thought. Microarray data have added new insight into the transcription changes in HCC. Recently, Nutlin-3 has shown potency against p53-MDM2 binding and the enhancement of p53 stabilization as well as an increment of p53 cellular accumulation with potential therapeutic effects. This review outlines the molecular mechanisms involved in the p53-MDM2 pathways, the biological factors influencing these pathways, and their roles in the pathogenesis of HCC. It also discusses the action of Nutlin-3 treatment in inducing growth arrest in HCC and elaborates on future directions in research in this area. More research on the biology of p53-MDM2 interactions may offer a better understanding of these mechanisms and discover new biomarkers, sensitive prognostic indicators as well as new therapeutic interventions in HCC.

Zinc finger protein 668 suppresses non-small cell lung cancer invasion and migration by downregulating Snail and upregulating E-cadherin and zonula occludens-1

Zinc finger protein 668 (ZNF668) is a recently discovered protein and its expression levels, as well as its involvement in the invasion and metastasis of non-small cell lung cancer (NSCLC), are largely unknown. In the present study, immunohistochemical analysis demonstrated that ZNF668 protein expression was decreased in lung tumors (51/167, 30.5%) compared with adjacent normal lung tissues (43/62, 69.4%; P<0.001). Subsequent statistical analysis revealed that ZNF668 expression was negatively associated with increased tumor-node-metastasis stage (P=0.019) and lymph node metastasis (P=0.002). Following ZNF668 downregulation by transfection of a ZNF668-expressing plasmid or small interfering RNA, it was demonstrated that ZNF668 inhibited the invasion and migration of NSCLC cells. Furthermore, restoration of ZNF668 expression downregulated the expression of Snail and increased the protein levels of epithelial (E-)cadherin and zonula occludens-1 (ZO-1). The results of the present study suggest that ZNF668 is downregulated in human NSCLC. Furthermore, restoration of ZNF668 expression was demonstrated to decrease the expression of Snail and increase the expression of E-cadherin and ZO-1, suppressing the invasion and migration of NSCLC cells.

The physical interaction of p53 and plakoglobin is necessary for their synergistic inhibition of migration and invasion

Plakoglobin (PG) is a paralog of β-catenin with similar adhesive, but contrasting signalling functions. Although β-catenin has well-known oncogenic function, PG generally acts as a tumor/metastasis suppressor by mechanisms that are just beginning to be deciphered. Previously, we showed that PG interacted with wild type (WT) and a number of mutant p53s, and that its tumor/metastasis suppressor activity may be mediated, at least partially, by this interaction. Here, carcinoma cell lines deficient in both p53 and PG (H1299), or expressing mutant p53 in the absence of PG (SCC9), were transfected with expression constructs encoding WT and different fragments and deletions of p53 and PG, individually or in pairs. Transfectants were characterized for their in vitro growth, migratory and invasive properties and for mapping the interacting domain of p53 and PG. We showed that when coexpressed, p53-WT and PG-WT cooperated to decrease growth, and acted synergistically to significantly reduce cell migration and invasion. The DNA-binding domain of p53 and C-terminal domain of PG mediated p53/PG interaction, and furthermore, the C-terminus of PG played a central role in the inhibition of invasion in association with p53.

p53 targets TSPAN8 to prevent invasion in melanoma cells

Cutaneous melanoma is a very deadly cancer because of its proclivity to metastasize. Despite the recent development of targeted and immune therapies, patient survival remains low. It is therefore crucial to enhance understanding of the molecular mechanisms underlying invasion. We previously identified tetraspanin 8 (TSPAN8) as an important modulator of melanoma invasiveness, and several of its transcriptional regulators, which affect TSPAN8 expression during melanoma progression toward an invasive stage. This study found that TSPAN8 promoter contains consensus-binding sites for p53 transcription factor. We demonstrated that p53 silencing was sufficient to turn on Tspan8 expression in non-invasive melanoma cells and that p53 acts as a direct transcriptional repressor of TSPAN8. We also showed that p53 modulated matrigel invasion in melanoma cells in a TSPAN8-dependent manner. In conclusion, this study reveals p53 as a negative regulator of Tspan8 expression. As TP53 gene is rarely mutated in melanoma, it was hitherto poorly studied but its role in apoptosis and growth suppression in melanoma is increasingly becoming clear. The study highlights the importance of p53 as a regulator of melanoma invasion and the concept that reactivating p53 could provide a strategy for modulating not only proliferative but also invasive capacity in melanoma treatment.

A Microfabricated 96-Well 3D Assay Enabling High-Throughput Quantification of Cellular Invasion Capabilities

This paper presents a 96-well microfabricated assay to study three-dimensional (3D) invasion of tumor cells. A 3D cluster of tumor cells was first generated within each well by seeding cells onto a micro-patterned surface consisting of a central fibronectin-coated area that promotes cellular attachment, surrounded by a poly ethylene glycol (PEG) coated area that is resistant to cellular attachment. Following the formation of the 3D cell clusters, a 3D collagen extracellular matrix was formed in each well by thermal-triggered gelation. Invasion of the tumor cells into the extracellular matrix was subsequently initiated and monitored. Two modes of cellular infiltration were observed: A549 cells invaded into the extracellular matrix following the surfaces previously coated with PEG molecules in a pseudo-2D manner, while H1299 cells invaded into the extracellular matrix in a truly 3D manner including multiple directions. Based on the processing of 2D microscopic images, a key parameter, namely, equivalent invasion distance (the area of invaded cells divided by the circumference of the initial cell cluster) was obtained to quantify migration capabilities of these two cell types. These results validate the feasibility of the proposed platform, which may function as a high-throughput 3D cellular invasion assay.

Allele-specific silencing of mutant p53 attenuates dominant-negative and gain-of-function activities

Many p53 hotspot mutants not only lose the transcriptional activity, but also show dominant-negative (DN) and oncogenic gain-of-function (GOF) activities. Increasing evidence indicates that knockdown of mutant p53 (mutp53) in cancer cells reduces their aggressive properties, suggesting that survival and proliferation of cancer cells are, at least partially, dependent on the presence of mutp53. However, these p53 siRNAs can downregulate both wild-type p53 (wtp53) and mutp53, which limits their therapeutic applications. In order to specifically deplete mutp53, we have developed allele-specific siRNAs against p53 hotspot mutants and validated their biological effects in the absence or presence of wtp53. First, the mutp53-specific siRNAs selectively reduced protein levels of matched p53 mutants with minimal reduction in wtp53 levels. Second, downregulation of mutp53 in cancer cells expressing a mutp53 alone (p53mut) resulted in significantly decreased cell proliferation and migration. Third, transfection of mutp53-specific siRNAs in cancer cells expressing both wtp53 and mutp53 also reduced cell proliferation and migration with increased transcripts of p53 downstream target genes, which became further profound when cells were treated with an MDM2 inhibitor Nutlin-3a or a chemotherapeutic agent doxorubicin. These results indicate that depletion of mutp53 by its specific siRNA restored endogenous wtp53 activity in cells expressing both wtp53 and mutp53. This is the first study demonstrating biological effects and therapeutic potential of allele-specific silencing of mutp53 by mutp53-specific siRNAs in cancer cells expressing both wtp53 and mutp53, thus providing a novel strategy towards targeted cancer therapies.

Attractor landscape analysis of colorectal tumorigenesis and its reversion

Background

Colorectal cancer arises from the accumulation of genetic mutations that induce dysfunction of intracellular signaling. However, the underlying mechanism of colorectal tumorigenesis driven by genetic mutations remains yet to be elucidated.

Results

To investigate colorectal tumorigenesis at a system-level, we have reconstructed a large-scale Boolean network model of the human signaling network by integrating previous experimental results on canonical signaling pathways related to proliferation, metastasis, and apoptosis. Throughout an extensive simulation analysis of the attractor landscape of the signaling network model, we found that the attractor landscape changes its shape by expanding the basin of attractors for abnormal proliferation and metastasis along with the accumulation of driver mutations. A further hypothetical study shows that restoration of a normal phenotype might be possible by reversely controlling the attractor landscape. Interestingly, the targets of approved anti-cancer drugs were highly enriched in the identified molecular targets for the reverse control.

Conclusions

Our results show that the dynamical analysis of a signaling network based on attractor landscape is useful in acquiring a system-level understanding of tumorigenesis and developing a new therapeutic strategy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-016-0341-9) contains supplementary material, which is available to authorized users.

Snail1-dependent p53 repression regulates expansion and activity of tumour-initiating cells in breast cancer

The zinc-finger transcription factor Snail1 is inappropriately expressed in breast cancer and associated with poor prognosis. While interrogating human databases, we uncovered marked decreases in relapse-free survival of breast cancer patients expressing high Snail1 levels in tandem with wild-type, but not mutant, p53. Using a Snail1 conditional knockout model of mouse breast cancer that maintains wild-type p53, we find that Snail1 plays an essential role in tumour progression by controlling the expansion and activity of tumour-initiating cells in preneoplastic glands and established tumours, whereas it is not required for normal mammary development. Growth and survival of preneoplastic as well as neoplastic mammary epithelial cells is dependent on the formation of a Snail1/HDAC1/p53 tri-molecular complex that deacetylates active p53, thereby promoting its proteasomal degradation. Our findings identify Snail1 as a molecular bypass that suppresses the anti-proliferative and pro-apoptotic effects exerted by wild-type p53 in breast cancer.

Guidelines for the selection of functional assays to evaluate the hallmarks of cancer

The hallmarks of cancer capture the most essential phenotypic characteristics of malignant transformation and progression. Although numerous factors involved in this multi-step process are still unknown to date, an ever-increasing number of mutated/altered candidate genes are being identified within large-scale cancer genomic projects. Therefore, investigators need to be aware of available and appropriate techniques capable of determining characteristic features of each hallmark. We review the methods tailored to experimental cancer researchers to evaluate cell proliferation, programmed cell death, replicative immortality, induction of angiogenesis, invasion and metastasis, genome instability, and reprogramming of energy metabolism. Selecting the ideal method is based on the investigator's goals, available equipment and also on financial constraints. Multiplexing strategies enable a more in-depth data collection from a single experiment - obtaining several results from a single procedure reduces variability and saves time and relative cost, leading to more robust conclusions compared to a single end point measurement. Each hallmark possesses characteristics that can be analyzed by immunoblot, RT-PCR, immunocytochemistry, immunoprecipitation, RNA microarray or RNA-seq. In general, flow cytometry, fluorescence microscopy, and multiwell readers are extremely versatile tools and, with proper sample preparation, allow the detection of a vast number of hallmark features. Finally, we also provide a list of hallmark-specific genes to be measured in transcriptome-level studies. Although our list is not exhaustive, we provide a snapshot of the most widely used methods, with an emphasis on methods enabling the simultaneous evaluation of multiple hallmark features.

miR-5003-3p promotes epithelial-mesenchymal transition in breast cancer cells through Snail stabilization and direct targeting of E-cadherin

One of the initial steps in metastatic dissemination is the epithelial-mesenchymal transition (EMT). Along this line, microRNAs (miRNAs) have been shown to function as important regulators of tumor progression at various stages. Therefore, we performed a functional screening for EMT-regulating miRNAs and identified several candidate miRNAs. Among these, we demonstrated that miR-5003-3p induces cellular features characteristic of EMT. miR-5003-3p induced upregulation of Snail, a key EMT-promoting transcription factor and transcriptional repressor of E-cadherin, through protein stabilization. MDM2 was identified as a direct target of miR-5003-3p, the downregulation of which induced Snail stabilization. E-cadherin was also demonstrated to be a direct target of miR-5003-3p, reinforcing the EMT-promoting function of miR-5003-3p. In situ hybridization and immunohistochemical analyses using tissue microarrays revealed that miR-5003-3p expression was higher in paired metastatic breast carcinoma tissues than in primary ductal carcinoma tissues, and was inversely correlated with the expression of MDM2 and E-cadherin. Furthermore, miR-5003-3p enhanced the formation of metastatic nodules in the lungs of mice in a tail vein injection experiment. Collectively, our results suggest that miR-5003-3p functions as a metastasis activator by promoting EMT through dual regulation of Snail stability and E-cadherin, and may therefore be a potential therapeutic target in metastatic cancers.

SLUG expression is an indicator of tumour recurrence in high-grade endometrial carcinomas

AIMS

To investigate how SNAIL and SLUG were involved in the nature of high-grade endometrial carcinomas (grade 3 endometrioid carcinoma, serous carcinoma and clear cell carcinoma), we analysed the correlation of their expression status with clinicopathological characteristics and evaluated their prognostic significance.

METHODS AND RESULTS

We performed immunohistochemical staining in 52 high-grade endometrial carcinomas. Expression status of SNAIL and SLUG was classified into a high expression (positive in more than 50% of the tumour cells) and a low expression. Thirteen cases (25%) showed a high expression of SLUG, whereas all 52 cases showed a low expression of SNAIL. High expression of SLUG was correlated significantly with tumour recurrence (P = 0.0203) and aberrant p53 expression (P = 0.000559). Overall survival was worse in patients with high SLUG expression at all stages (P = 0.0327) and in those who underwent adjuvant therapy (P = 0.00963). Among the patients with complete tumour resection, high SLUG expression was associated with worse recurrence-free survival (RFS) in the patients at all stages (P = 0.00264), at stages III/IV (P = 0.0146), and who underwent adjuvant therapy (P = 0.000743). SLUG expression was identified as an independent factor of RFS by multivariate analysis (hazard ratio 5.938, 95% confidence interval 1.251-28.18, P = 0.025).

CONCLUSIONS

SLUG expression could be correlated with TP53 mutational status and could be involved in therapeutic resistance resulting in tumour recurrence. A high expression level of SLUG can be an indicator of recurrence and a therapeutic target for long-term remission in high-grade endometrial carcinomas.

p53 directly activates cystatin D/CST5 to mediate mesenchymal-epithelial transition: a possible link to tumor suppression by vitamin D3

Cystatin D (CST5) encodes an inhibitor of cysteine proteases of the cathepsin family and is directly induced by the vitamin D receptor (VDR). Interestingly, vitamin D3 exerts tumor suppressive effects in a variety of tumor types. In colorectal cancer (CRC) cells CST5 was shown to mediate mesenchymal-epithelial transition (MET). Interestingly, vitamin D3 was shown to exert tumor suppressive effects in a variety of tumor types, including colorectal cancer (CRC). We recently performed an integrated genomic and proteomic screen to identify targets of the p53 tumor suppressor in CRC cells. Thereby, we identified CST5 as a putative p53 target gene. Here, we validated and characterized CST5 as a direct p53 target gene. After activation of a conditional p53 allele, CST5 was upregulated on mRNA and protein levels. Treatment with nutlin-3a or etoposide induced CST5 in a p53-dependent manner. These regulations were direct, since ectopic and endogenous p53 occupied a conserved binding site in the CST5 promoter region. In addition, treatment with calcitriol, the active vitamin D3 metabolite, and simultaneous activation of p53 resulted in enhanced CST5 induction and increased repression of SNAIL, an epithelial-mesenchymal transition (EMT) inducing transcription factor. Furthermore, CST5 inactivation decreased p53-induced mesenchymal-epithelial transition (MET) as evidenced by decreased inhibition of SNAIL and of migration by p53. Furthermore, CST5 expression was directly repressed by SNAIL. In summary, these results imply CST5 as an important mediator of tumor suppression by p53 in colorectal cancer. In addition, they suggest that a combined treatment activating p53 and the vitamin D3 pathway may function via induction of CST5.

Plakoglobin Reduces the in vitro Growth, Migration and Invasion of Ovarian Cancer Cells Expressing N-Cadherin and Mutant p53

Aberrant expression of cadherins and catenins plays pivotal roles in ovarian cancer development and progression. Plakoglobin (PG, γ-catenin) is a paralog of β-catenin with dual adhesive and signaling functions. While β-catenin has known oncogenic function, PG generally acts as a tumor/metastasis suppressor. We recently showed that PG interacted with p53 and that its growth/metastasis inhibitory function may be mediated by this interaction. Very little is known about the role of PG in ovarian cancer. Here, we investigated the in vitro tumor/metastasis suppressor effects of PG in ovarian cancer cell lines with mutant p53 expression and different cadherin profiles. We showed that the N-cadherin expressing and E-cadherin and PG deficient ES-2 cells were highly migratory and invasive, whereas OV-90 cells that express E-cadherin, PG and very little/no N-cadherin were not. Exogenous expression of PG or E-cadherin or N-cadherin knockdown in ES-2 cells (ES-2-E-cad, ES-2-PG and ES-2-shN-cad) significantly reduced their migration and invasion. Also, PG expression or N-cadherin knockdown significantly decreased ES-2 cells growth. Furthermore, PG interacted with both cadherins and with wild type and mutant p53 in normal ovarian and ES-2-PG cell lines, respectively.

miR-181b-3p promotes epithelial-mesenchymal transition in breast cancer cells through Snail stabilization by directly targeting YWHAG

Epithelial-mesenchymal transition (EMT) is essential for increased invasion and metastasis during cancer progression. Among the candidate EMT-regulating microRNAs that we previously identified, miR-181b-3p was found to induce EMT in MCF7 breast cancer cells, as indicated by an EMT-characteristic morphological change, increased invasiveness, and altered expression of an EMT marker. Transfection with a miR-181b-3p inhibitor reduced the expression of mesenchymal markers and the migration and invasion of highly invasive breast cancer cells. miR-181b-3p induced the upregulation of Snail, a master EMT inducer and transcriptional repressor of E-cadherin, through protein stabilization. YWHAG was identified as a direct target of miR-181b-3p, downregulation of which induced Snail stabilization and EMT phenotypes. Ectopic expression of YWHAG abrogated the effect of miR-181b-3p, including Snail stabilization and the promotion of invasion. In situ hybridization and immunohistochemical analyses indicated that YWHAG expression was inversely correlated with the expression of miR-181b-3p and Snail in human breast cancer tissues. Furthermore, transfection with miR-181b-3p increased the frequency of metastatic nodule formation in the lungs of mice in experimental metastasis assays using MDA-MB-231 cells. Taken together, our data suggest that miR-181b-3p functions as a metastasis activator by promoting Snail-induced EMT, and may therefore be a therapeutic target in metastatic cancers.

Snai2 and Snai3 transcriptionally regulate cellular fitness and functionality of T cell lineages through distinct gene programs

T lymphocytes are essential contributors to the adaptive immune system and consist of multiple lineages that serve various effector and regulatory roles. As such, precise control of gene expression is essential to the proper development and function of these cells. Previously, we identified Snai2 and Snai3 as being essential regulators of immune tolerance partly due to the impaired function of CD4(+) regulatory T cells in Snai2/3 conditional double knockout mice. Here we extend those previous findings using a bone marrow transplantation model to provide an environmentally unbiased view of the molecular changes imparted onto various T lymphocyte populations once Snai2 and Snai3 are deleted. The data presented here demonstrate that Snai2 and Snai3 transcriptionally regulate the cellular fitness and functionality of not only CD4(+) regulatory T cells but effector CD8(α+) and CD4(+) conventional T cells as well. This is achieved through the modulation of gene sets unique to each cell type and includes transcriptional targets relevant to the survival and function of each T cell lineage. As such, Snai2 and Snai3 are essential regulators of T cell immunobiology.

Reactivating p53 functions by suppressing its novel inhibitor iASPP: a potential therapeutic opportunity in p53 wild-type tumors

Although mutational inactivation of p53 is found in 50% of all human tumors, a subset of tumors display defective p53 function, but retain wild-type (WT) p53. Here, direct and indirect mechanisms leading to the loss of WT p53 activities are discussed. We summarize the oncogenic roles of iASPP, an inhibitor of WT p53, in promoting proliferation, invasion, drug or radiation-resistance and metastasis. From the therapeutic view, we highlight promising perspectives of microRNA-124, peptide and small molecules that reduce or block iASPP for the treatment of cancer. High iASPP expression enhances proliferation, aggressive behavior, the resistance to radiation/chemotherapy and correlates with poor prognosis in a range of human tumors. Overexpression of iASPP accelerates tumorigenesis and invasion through p53-dependent and p53-independent mechanisms. MicroRNA-124 directly targets iASPP and represses the growth and invasiveness of cancer cells. The disruption of iASPP-p53 interaction by a p53-derived peptide A34 restores p53 function in cancer cells. The inhibition of iASPP phosphorylation with small molecules induces p53-dependent apoptosis and growth suppression. The mechanisms underlying aberrant expression of iASPP in human tumors should be further investigated. Reactivating WT p53 functions by targeting its novel inhibitor iASPP holds promise for potential therapeutic interventions in the treatment of WT p53-containing tumors.

Curcumin Inhibits Invasiveness and Epithelial-Mesenchymal Transition in Oral Squamous Cell Carcinoma Through Reducing Matrix Metalloproteinase 2, 9 and Modulating p53-E-Cadherin Pathway

Hypotheses. Epithelial-mesenchymal transition (EMT) and invasion play a critical role in cancer progression and metastasis. We have shown that low E-cadherin and high Twist expression are significantly correlated with prognostic survival prediction in oral squamous cell carcinoma (OSCC). This study aimed to determine the anti-invasive effect of curcumin on the expression of matrix metalloproteinases (MMPs) and of EMT regulators in OSCC. Methods. SCC-25 cells were treated with curcumin, and cell proliferation, invasion, and expression of MMPs and EMT regulators were assessed for cell viability by trypan blue exclusion, for invasion by Matrigel invasion chamber, and for EMT regulators and MMP changes in the levels of proteins by immunoblotting. Results. Our data showed that curcumin treatment not only decreased the expression of MMP-2 and MMP-9 to inhibit invasiveness in oral cancer but also modulated the expression of EMT markers, such as Snail, Twist, and E-cadherin, and induced p53 expression that is crucial to EMT repression. Conclusion. Curcumin has the potential to become an adjunctive regimen for the prevention of cancer progression and metastasis in oral cancer.

Transcription factor snail regulates tumor necrosis factor α-mediated synovial fibroblast activation in the rheumatoid joint

OBJECTIVE

The transcription factor Snail is involved in various biologic functions. We hypothesized that this molecule regulates tumor necrosis factor α (TNFα)-mediated synovial fibroblast activation in the rheumatoid joint. The aim of this study was to examine the role of Snail in the expression of cadherin-11 (Cad-11) and myofibroblast markers, interleukin-6 (IL-6) production, and the invasive ability of cells.

METHODS

Synovium samples were obtained from patients with rheumatoid arthritis (RA) and from rats with collagen-induced arthritis (CIA). Synovial fibroblasts were treated with TNFα or a Wnt signaling inducer, and the joints of rats with CIA were injected with a TNFα antagonist. Modulation of Snail expression in the synovial fibroblasts and joints was performed by lentiviral vector-mediated transfer of complementary DNA or short hairpin RNA.

RESULTS

The expression of Snail and Cad-11 was higher in synovium and synovial fibroblasts from patients with RA compared with patients with osteoarthritis and was increased in rats with CIA. TNFα stimulation or activation of Wnt signaling up-regulated the expression of Snail, Cad-11, and α-smooth muscle actin (α-SMA) in synovial fibroblasts, and anti-TNFα therapy down-regulated the expression of Snail, Cad-11, and α-SMA in the joints of rats with CIA. Although synovial fibroblast transfectants in which Snail was overexpressed showed increased expression of Cad-11 and α-SMA and enhanced TNFα-mediated invasive capacity and IL-6 production, synovial fibroblast transfectants from rats with CIA in which Snail was silenced showed decreased expression and had the opposite effect on these functions. Normal joints in which Snail was overexpressed had hyperplastic synovium, with increased expression of Cad-11, α-SMA, and IL-6. Silencing Snail expression ameliorated arthritis, with reduced Cad-11 expression and reduced levels of extracellular matrix deposition in the joints of rats with CIA, whereas overexpression of Snail exacerbated arthritis, with increased Cad-11 expression and increased levels of extracellular matrix deposition.

CONCLUSION

Our results demonstrate that Snail regulates TNFα-mediated activation of synovial fibroblasts in the rheumatoid joint. These findings may contribute to the pharmacologic development of therapeutics targeting synovial fibroblasts in patients with RA.

Rap2a is a novel target gene of p53 and regulates cancer cell migration and invasion

The p53 transcription factor is a critical regulator of the cell cycle, DNA repair, and apoptosis. Recent evidences suggest that p53 may contribute to the regulation of cell invasion and migration. Rap2a, a member of the small GTPase superfamily, mediates diverse cellular events such as cell adhesion, migration and proliferation through various signaling pathways. In this study, we identify that Rap2a is a novel target of p53 and is induced upon DNA damage in a p53-dependent manner. Upon DNA damage, p53 directly binds to the promoter of Rap2a and activates its transcription. We show that Rap2a is significantly upregulated in many types of tumors. In addition, the ectopic expression of Rap2a enhances the migration and invasive ability of cancer cells and increases activities of matrix metalloproteinase MMP2 and MMP9. In contrast, the inactivation of Rap2a inhibits cell invasion and activities of MMP2 and MMP9. We also show that Rap2a regulates the phosphorylation level of Akt. Collectively, our results show that ectopic expression of Rap2a has a key role in enhancing migration, invasion and metastasis by upregulating p-Akt.

miR-1228 promotes the proliferation and metastasis of hepatoma cells through a p53 forward feedback loop

Background:

The effective mechanisms of microRNAs (miRNAs) functions as oncogenes or tumour suppressors in human hepatocellular carcinoma (HCC) are still obscure. Here, we investigated the function and expression of miR-1228 in HCC.

Methods:

The role of miR-1228 in HCC was determined by colony formation, transwell, and nude mice xenograft experiments. miR-1228 target gene were identified by EGFP reporter assays, real-time PCR, and western blot analysis. Dual-luciferase reporter assay and real-time PCR analysis are used to examine the regulation of p53.

Results:

miR-1228 promoted proliferation and metastasis, and facilitated the transition of cell cycle in hepatoma cells. miR-1228 downregulated p53 expression by binding to its 3′UTR. The ectopic expression of p53 abrogated the phenotypes induced by miR-1228. An inverse correlation existed between miR-1228 and p53 expression in hepatoma tissues compared with the adjacent tissues and three hepatoma cell lines. Moreover, we found that p53 suppressed the expression and promoter activity of miR-1228.

Conclusions:

miR-1228 functions as an oncogene by promoting cell cycle progression and cell mobility and negatively regulates the expression of p53. p53 downregulation in turn leads to an increase in miR-1228 expression, thereby forming a positive feedback loop that contributes to cancerogenesis in HCC.

An axis involving SNAI1, microRNA-128 and SP1 modulates glioma progression

BACKGROUND

Glioblastoma is an extraordinarily aggressive disease that requires more effective therapeutic options. Snail family zinc finger 1, dysregulated in many neoplasms, has been reported to be involved in gliomas. However, the biological mechanisms underlying SNAI1 function in gliomas need further investigation.

METHODS

Quantitative real-time PCR was used to measure microRNA-128 (miR-128) expression level and western blot was performed to detect protein expression in U87 and U251 cells and human brain tissues. Cell cycle, CCK-8, transwell and wound-healing assays were performed. Dual-luciferase reporter assay was used for identifying the mechanism of SNAI1 and miR-128b regulation. The mechanism of miR-128 targeting SP1 was also tested by luciferase reporter assay. Immunohistochemistry and in situ hybridisation staining were used for quantifying SNAI1, SP1 and miR-128 expression levels in human glioma samples.

RESULTS

The Chinese Glioma Genome Atlas (CGGA) data revealed that SNAI1 was up-regulated in glioma and we confirmed the findings in normal and glioma tissues. SNAI1 depletion by shRNA retarded the cell cycle and suppressed proliferation and invasion in glioma cell lines. The CGGA data showed that the Pearson correlation index between SNAI1 and miR-128 was negatively correlated. SNAI1 suppressed miR-128b expression by binding to the miR-128b specific promoter motif, and miR-128 targeted SP1 via binding to the 3'-untranslated region of SP1. Moreover, introduction of miR-128 anti-sense oligonucleotide alleviated the cell cycle retardation, proliferation and invasion inhibition induced by SNAI1 shRNA. Immunohistochemistry and in situ hybridisation analysis of SNAI1, SP1 and miR-128 unraveled their expression levels and correlations in glioma samples.

CONCLUSIONS

We propose that the SNAI1/miR-128/SP1 axis, which plays a vital role in glioma progression, may come to be a clinically relevant therapeutic target.