The ERK1/2 pathway modulates nuclear PTEN-mediated cell cycle arrest by cyclin D1 transcriptional regulation

The oncogenic axis YAP/MYC/EZH2 impairs PTEN tumor suppression activity enhancing lung tumorigenicity

The tumor suppressor PTEN (phosphatase and tensin homolog deleted in chromosome 10) is genetically deleted or downregulated in many cancer types. Loss of PTEN protein expression is frequently found in lung cancer while genetic alterations are less abundant. PTEN expression is regulated at multiple genetic and epigenetic levels and even partial reduction of its expression increases cancer occurrence. We show that YAP and TAZ cooperate with EZH2, and MYC to transcriptionally repress onco-suppressor genes, including PTEN, in non-small cell lung cancer (NSCLC) cells. YAP/TAZ-EZH2-MYC transcriptional regulators form a nuclear complex that represses PTEN transcription, while their combinatorial targeting restores PTEN expression, attenuates NSCLC cell growth, and prevents compensatory responses induced by single treatments. Datasets analysis of NSCLC patients revealed that PTEN expression is negatively correlated to YAP/TAZ, EZH2 and MYC and that low expression of PTEN is predictive of poor prognosis, especially at earlier stages of the disease. These findings highlight the repressive role of the YAP/TAZ-EZH2-MYC axis on tumor-suppressor genes and offer a potential therapeutic strategy for lung cancer patients with low PTEN levels.

Elevated Notch-1 expression promotes the lymph node metastasis of gastric cancer and the Notch-1-PTEN-ERK1/2 signalling axis promotes the progression of gastric cancer

BACKGROUND

Gastric cancer (GC) is one of the most common malignant tumours and has a high fatality rate worldwide. This study investigated the role of the Notch-1 signalling pathway in the pathogenesis and progression of GC.

METHODS

A total of 64 patients with GC were included in this study. Immunohistochemistry staining was used to detect Notch-1 expression in tumour tissues and adjacent non-tumour tissues, and Notch-1 knockdown in GC cells was identified using short hairpin RNA. A cell scratch assay, transwell assay and flow cytometry analysis were used to analyse the effect of Notch-1 knockdown on cell proliferation, migration and cell cycle distribution. The expression of Notch-1, PTEN, Akt, ERK1/2, E-cadherin and other proteins was detected using Western blotting.

RESULTS

The expression level of Notch-1 in GC tissues was higher than that in adjacent non-tumour tissues (P < 0.05). High levels of Notch-1 were also found to be associated with sex (male) and lymph node metastasis (P < 0.05). Notch-1 knockdown in the AGS and BGC-823 GC cell lines inhibited the migration and proliferation of GC cells, and Notch-1 knockdown arrested the cell cycle in the G0/G1 phase. PTEN protein expression was elevated in the presence of Notch-1 knockdown, resulting in the inhibition of phosphorylated Akt protein expression. In addition, phosphorylated ERK protein levels decreased in the presence of Notch-1 knockdown. Further inhibition of ERK1/2 signalling by the MEK1/2 inhibitor U0126 decreased the proliferation of AGS cells. The results of in vivo experiments with xenotransplantation in nude mice are consistent with these results.

CONCLUSIONS

Notch-1 plays a key role in the development of GC and was found to promote the lymph node metastasis of GC. Notch-1 knockdown can effectively attenuate the progression of GC cells, which may function in part through the Notch-1-PTEN-ERK1/2 signalling axis.

Role of Tumor Suppressor PTEN and Its Regulation in Malignant Transformation of Endometrium

Tumor-suppressive effects of PTEN are well-known, but modern evidence suggest that they are not limited to its ability to inhibit pro-oncogenic PI3K/AKT signaling pathway. Features of PTEN structure facilitate its interaction with substrates of different nature and display its activity in various ways both in the cytoplasm and in cell nuclei, which makes it possible to take a broader look at its ability to suppress tumor growth. The possible mechanisms of the loss of PTEN effects are also diverse - PTEN can be regulated at many levels, leading to change in the protein activity or its amount in the cell, while their significance for the development of malignant tumors has yet to be studied. Here we summarize the current data on the PTEN structure, its functions and changes in its regulatory mechanisms during malignant transformation of the cells, focusing on one of the most sensitive to the loss of PTEN types of malignant tumors - endometrial cancer.

MAPK Signaling Pathway in Oral Squamous Cell Carcinoma: Biological Function and Targeted Therapy

Oral squamous cell carcinoma accounts for 95% of human head and neck squamous cell carcinoma cases. It is highly malignant and aggressive, with a poor prognosis and a 5-year survival rate of <50%. In recent years, basic and clinical studies have been performed on the role of the mitogen-activated protein kinase (MAPK) signaling pathway in oral cancer. The MAPK signaling pathway is activated in over 50% of human oral cancer cases. Herein, we review research progress on the MAPK signaling pathway and its potential therapeutic mechanisms and discuss its molecular targeting to explore its potential as a therapeutic strategy for oral squamous cell carcinoma.

Generating a new mouse model for nuclear PTEN deficiency by a single K13R mutation

Many human diseases, including cancer and neurological abnormalities, are linked to deficiencies of phosphatase and tensin homolog deleted on chromosome ten (PTEN), a dual phosphatase that dephosphorylates both lipids and proteins. PTEN functions in multiple intracellular locations, including the plasma membrane and nucleus. Therefore, a critical challenge to understand the pathogenesis of PTEN-associated diseases is to determine the specific role of PTEN at different locations. Toward this goal, the current study generated a mouse line in which lysine 13, which is critical for the nuclear localization of PTEN, is changed to arginine in the lipid-binding domain using the CRISPR-Ca9 gene-editing system. We found that PTEN_K13R mice show a strong decrease in the localization of PTEN in the nucleus without affecting the protein stability, phosphatase activity, and phosphorylation in the C-terminal tail region. PTEN_K13R mice are viable but produce smaller neurons and develop microcephaly. These data demonstrate that PTEN_K13R mice provide a useful animal model to study the role of PTEN in the nucleus in vivo.

RN181 regulates the biological behaviors of oral squamous cell carcinoma cells via mediating ERK/MAPK signaling pathway

OBJECTIVE

To explore the role of RN181 in the pathogenesis of oral squamous cell carcinoma (OSCC) cells via mediating ERK/MAPK signaling.

METHODS

The expression of RN181 was detected in OSCC tissues and cells. CAL27 and SCC-15 cells were divided into Control, Empty, RN181, si-RN181, U0126 (an inhibitor of ERK/MAPK pathway) and si-RN181 + U0126 groups. MTT was used to determine cell proliferation, flow cytometry to determine cell cycle and apoptosis, Transwell assay and wound healing test to determine cell invasion and migration, respectively. Western blotting was used to measure the protein expression. Furthermore, a xenograft tumor model was established to observe the effect of RN181 on the in vivo growth of OSCC cells.

RESULTS

RN181 was down-regulated in OSCC tissues and cells. As compared to the Control group, CAL27 and SCC-15 cells in the RN181 group and U0126 group presented with decreases in the proliferation, invasion and migration, but increases in the cell ratio at the G0/G1 phase and apoptosis, while the p-ERK 1/2/ERK 1/2 was down-regulated. Cells in the si-RN181 group manifested the opposite changes. U0126 could reverse the positive effect of si-RN181 on the growth of OSCC cells. In vivo experiment demonstrated that the tumor growth and weight were reduced in the RN181 group, with decreased Ki67 positive expression and elevated TUNEL positive cells.

CONCLUSION

RN181 was down-regulated in OSCC, and it could inhibit the proliferation, invasion and migration, cause the G0/G1 arrest, while promote the apoptosis of OSCC cells via inhibiting ERK/MAPK pathway.

The emerging roles of dual-specificity phosphatases and their specific characteristics in human cancer

Reversible phosphorylation of proteins, controlled by kinases and phosphatases, is involved in various cellular processes. Dual-specificity phosphatases (DUSPs) can dephosphorylate phosphorylated serine, threonine and tyrosine residues. This family consists of 61 members, 44 of which have been identified in human, and these 44 members are classified into six subgroups, the phosphatase and tensin homolog (PTEN) protein phosphatases (PTENs), mitogen-activated protein kinase phosphatases (MKPs), atypical DUSPs, cell division cycle 14 (CDC14) phosphatases (CDC14s), slingshot protein phosphatases (SSHs), and phosphatases of the regenerating liver (PRLs). Growing evidence has revealed dysregulation of DUSPs as one of the common phenomenons and highlighted their key roles in human cancers. Furthermore, their differential expression may be a potential biomarker for tumor prognosis. Despite this, there are still many unstudied members of DUSPs need to further explore their precise roles and mechanism in cancers. Most importantly, the systematic review is very limited on the functional/mechanistic characteristics and clinical application of DUSPs at present. In this review, the structures, functions and underlying mechanisms of DUSPs are systematically reviewed, and the molecular and functional characteristics of DUSPs in different tumor types according to the current researches are summarized. In addition, the potential roles of the unstudied members and the possible different mechanisms of DUSPs in cancer are discussed and classified based on homology alignment and structural domain analyses. Moreover, the specific characteristics of their expression and prognosis are further determined in more than 30 types of human cancers by using the online databases. Finally, their potential application in precise diagnosis, prognosis and treatment of different types of cancers, and the main possible problems for the clinical application at present are prospected.

Nuclear PTEN and p53 suppress stress-induced liver cancer through distinct mechanisms

PTEN and p53 are highly mutated in many cancers. These two tumor suppressors have critical functions in the nucleus, such as DNA repair, cell cycle progression, and genome maintenance. However, the in vivo functional relationship of nuclear PTEN and p53 is unknown. Here, we analyzed the liver of mice in which nuclear PTEN and p53 are individually or simultaneously depleted. We found that nuclear PTEN loss greatly upregulates p53 expression upon oxidative stress, while the loss of p53 potentiates stress-induced accumulation of PTEN in the nucleus. Next, we examined oxidative stress-induced DNA damage in hepatocytes, and found that nuclear PTEN loss aggravated the damage while p53 loss did not. Notably, mice lacking nuclear PTEN had increased hepatocellular carcinoma under oxidative stress, while mice lacking p53 in hepatocytes had accelerated hepatocellular carcinoma and intrahepatic cholangiocarcinoma. The formation of cholangiocarcinoma appears to involve the transformation of hepatocytes into cholangiocarcinoma. Simultaneous loss of nuclear PTEN and p53 exacerbated both types of liver cancers. These data suggest that nuclear PTEN and p53 suppress liver cancers through distinct mechanisms.

ATM Kinase Inhibition Preferentially Sensitises PTEN-Deficient Prostate Tumour Cells to Ionising Radiation

Simple Summary

Prostate cancer is the most frequently diagnosed cancer in men. Despite the importance of radical radiotherapy for the management of this disease, recurrence remains a challenge. PTEN is a tumour suppressor that is frequently inactivated in advanced prostate cancer and has been associated with relapse following radiotherapy. The present study shows that the role of PTEN in response to ionizing radiation is complex. Furthermore, it demonstrates that in the absence of PTEN, an increased response to combined treatment using radiotherapy and the ATM inhibitor KU-60019 can be observed. Our findings provide a strong rationale for evaluating loss of PTEN in prostate cancer as a therapeutic target for ATM inhibitor in combination with radiotherapy in the clinical setting.

Abstract

Radical radiotherapy, often in combination with hormone ablation, is a safe and effective treatment option for localised or locally-advanced prostate cancer. However, up to 30% of patients with locally advanced PCa will go on to develop biochemical failure, within 5 years, following initial radiotherapy. Improving radiotherapy response is clinically important since patients exhibiting biochemical failure develop castrate-resistant metastatic disease for which there is no curative therapy and median survival is 8–18 months. The aim of this research was to determine if loss of PTEN (highly prevalent in advanced prostate cancer) is a novel therapeutic target in the treatment of advanced prostate cancer. Previous work has demonstrated PTEN-deficient cells are sensitised to inhibitors of ATM, a key regulator in the response to DSBs. Here, we have shown the role of PTEN in cellular response to IR was both complex and context-dependent. Secondly, we have confirmed ATM inhibition in PTEN-depleted cell models, enhances ionising radiation-induced cell killing with minimal toxicity to normal prostate RWPE-1 cells. Furthermore, combined treatment significantly inhibited PTEN-deficient tumour growth compared to PTEN-expressing counterparts, with minimal toxicity observed. We have further shown PTEN loss is accompanied by increased endogenous levels of ROS and DNA damage. Taken together, these findings provide pre-clinical data for future clinical evaluation of ATM inhibitors as a neoadjuvant/adjuvant in combination with radiation therapy in prostate cancer patients harbouring PTEN mutations.

Linking Autism Risk Genes to Disruption of Cortical Development

Autism spectrum disorder (ASD) is a prevalent neurodevelopmental disorder characterized by impairments in social communication and social interaction, and the presence of repetitive behaviors and/or restricted interests. In the past few years, large-scale whole-exome sequencing and genome-wide association studies have made enormous progress in our understanding of the genetic risk architecture of ASD. While showing a complex and heterogeneous landscape, these studies have led to the identification of genetic loci associated with ASD risk. The intersection of genetic and transcriptomic analyses have also begun to shed light on functional convergences between risk genes, with the mid-fetal development of the cerebral cortex emerging as a critical nexus for ASD. In this review, we provide a concise summary of the latest genetic discoveries on ASD. We then discuss the studies in postmortem tissues, stem cell models, and rodent models that implicate recently identified ASD risk genes in cortical development.

Present and Future of Anti-Glioblastoma Therapies: A Deep Look into Molecular Dependencies/Features

Glioblastoma (GBM) is aggressive malignant tumor residing within the central nervous system. Although the standard treatment options, consisting of surgical resection followed by combined radiochemotherapy, have long been established for patients with GBM, the prognosis is still poor. Despite recent advances in diagnosis, surgical techniques, and therapeutic approaches, the increased patient survival after such interventions is still sub-optimal. The unique characteristics of GBM, including highly infiltrative nature, hard-to-access location (mainly due to the existence of the blood brain barrier), frequent and rapid recurrence, and multiple drug resistance mechanisms, pose challenges to the development of an effective treatment. To overcome current limitations on GBM therapy and devise ideal therapeutic strategies, efforts should focus on an improved molecular understanding of GBM pathogenesis. In this review, we summarize the molecular basis for the development and progression of GBM as well as some emerging therapeutic approaches.

The Loss of Nuclear PTEN Increases Tumorigenesis in a Preclinical Mouse Model for Hepatocellular Carcinoma

The PTEN gene is highly mutated in many cancers, including hepatocellular carcinoma. The PTEN protein is located at different subcellular regions-PTEN at the plasma membrane suppresses PI3-kinase signaling in cell growth, whereas PTEN in the nucleus maintains genome integrity. Here, using nuclear PTEN-deficient mice, we analyzed the role of PTEN in the nucleus in hepatocellular carcinoma that is induced by carcinogen and oxidative stress-producing hepatotoxin. Upon oxidative stress, PTEN was accumulated in the nucleus of the liver, and this accumulation promoted repair of DNA damage in wild-type mice. In contrast, nuclear PTEN-deficient mice had increased DNA damage and accelerated hepatocellular carcinoma formation. Both basal and oxidative stress-induced localization of PTEN in the nucleus require ubiquitination of lysine 13 in PTEN. Taken together, these data suggest the critical role of nuclear PTEN in the protection from DNA damage and tumorigenesis in vivo.

PTEN modulates gene transcription by redistributing genome-wide RNA polymerase II occupancy

Control of gene expression is one of the most complex yet continuous physiological processes impacting cellular homeostasis. RNA polymerase II (Pol II) transcription is tightly regulated at promoter-proximal regions by intricate dynamic processes including Pol II pausing, release into elongation and premature termination. Pol II pausing is a phenomenon where Pol II complex pauses within 30–60 nucleotides after initiating the transcription. Negative elongation factor (NELF) and DRB sensitivity inducing factor (DSIF) contribute in the establishment of Pol II pausing, and positive transcription elongation factor b releases (P-TEFb) paused complex after phosphorylating DSIF that leads to dissociation of NELF. Pol II pausing is observed in most expressed genes across the metazoan. The precise role of Pol II pausing is not well understood; however, it’s required for integration of signals for gene regulation. In the present study, we investigated the role of phosphatase and tensin homolog (PTEN) in genome-wide transcriptional regulation using PTEN overexpression and PTEN knock-down models. Here we identify that PTEN alters the expression of hundreds of genes, and its restoration establishes genome-wide Pol II promoter-proximal pausing in PTEN null cells. Furthermore, PTEN re-distributes Pol II occupancy across the genome and possibly impacts Pol II pause duration, release and elongation rate in order to enable precise gene regulation at the genome-wide scale. Our observations demonstrate an imperative role of PTEN in global transcriptional regulation that will provide a new direction to understand PTEN-associated pathologies and its management.

Experimental Study on the Effect of a Weifufang on Human Gastric Adenocarcinoma Cell Line BGC-823 Xenografts and PTEN Gene Expression in Nude Mice

Background: This study aims at investigating the effect of the Weifufang, an effective prescription for the treatment of gastric cancer developed by the Traditional Chinese Medicine (TCM)/Combination of TCM and Western Medicine Department of the Hunan Cancer Hospital, on gastric cancer xenografts in nude mice and its effect on the PTEN gene; it also aims at exploring the possible tumor suppression mechanism. Methods: Nude mice with xenografts were treated with different concentrations of the Weifufang for 2 weeks, and changes in tumor volume were observed. The histopathology of the tumor was detected by hematoxylin and eosin staining; PTEN gene expression in tumor tissues was detected by immunohistochemistry (IHC) and western blot. Results: After 2 weeks of treatment, tumor inhibition rates in the 5-flourouracil (5-FU) group, and in the Weifufang low-, middle-, and high-dose groups were 30.67%, 19%, 49.52%, and 29.36%, respectively. The IOD of the PTEN gene was detected by IHC. The values in the water group, the 5-FU group, and the Weifufang low-, middle-, and high-dose groups were 0.013 ± 0.004, 0.085 ± 0.062, 0.041 ± 0.024, 0.128 ± 0.032, and 0.061 ± 0.052, respectively. Except for the 5-FU group, the differences between the gastric compound middle dose-group and the other groups were statistically significant (p < 0.05). Results of PTEN expression detection by western blot: The expression levels in the water group, 5-FU group, and the Weifufang low-, middle-, and high-dose groups were 0.2240 ± 0.0172, 0.4200 ± 0.0228, 0.2760 ± 0.0163, 0.3840 ± 0.0133, and 0.3040 ± 0.0211, respectively. Except for the 5-FU group, differences between the Weifufang middle-dose group and the other groups were statistically significant (p < 0.05). Conclusion: The Weifufang may inhibit the growth of gastric cancer xenografts by upregulating PTEN gene expression. The middle-dose group had the best effect.

Dietary antioxidants remodel DNA methylation patterns in chronic disease

Chronic diseases account for over 60% of all deaths worldwide according to the World Health Organization reports. Majority of cases are triggered by environmental exposures that lead to aberrant changes in the epigenome, specifically, the DNA methylation patterns. These changes result in altered expression of gene networks and activity of signalling pathways. Dietary antioxidants, including catechins, flavonoids, anthocyanins, stilbenes and carotenoids, demonstrate benefits in the prevention and/or support of therapy in chronic diseases. This review provides a comprehensive discussion of potential epigenetic mechanisms of antioxidant compounds in reversing altered patterns of DNA methylation in chronic disease. Antioxidants remodel the DNA methylation patterns through multiple mechanisms, including regulation of epigenetic enzymes and chromatin remodelling complexes. These effects can further contribute to antioxidant properties of the compounds. On the other hand, decrease in oxidative stress itself can impact DNA methylation delivering additional link between antioxidant mechanisms and epigenetic effects of the compounds. LINKED ARTICLES: This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc.

Autism Spectrum Disorder Associated with Germline Heterozygous PTEN Mutations

This review examines our current understanding of autism spectrum disorder (ASD), its prevalence, impact, behavioral treatment, and outcomes. Building on this knowledge, ASD associated with PTEN mutations is introduced and recent human studies of neurobehavioral and neuroimaging findings in patients with PTEN mutations with and without ASD are reviewed. In doing so, we present evidence supporting a model of PTEN loss leading to neurobehavioral deficits, including ASD and intellectual disability. Next, we describe the neurobehavioral spectrum observed across PTEN mutation cases, adding specificity where possible, based on data from recent studies of child and adult PTEN patients. Finally, we end with a discussion of potential clinical recommendations for improving interventions and supports for people with PTEN-ASD and future research avenues for understanding and treating the functional and cognitive deficits in PTEN-ASD.

Phosphatidylinositol Kinases and Phosphatases in Entamoeba histolytica

Phosphatidylinositol (PtdIns) metabolism is indispensable in eukaryotes. Phosphoinositides (PIs) are phosphorylated derivatives of PtdIns and consist of seven species generated by reversible phosphorylation of the inositol moieties at the positions 3, 4, and 5. Each of the seven PIs has a unique subcellular and membrane domain distribution. In the enteric protozoan parasite Entamoeba histolytica, it has been previously shown that the PIs phosphatidylinositol 3-phosphate (PtdIns3P), PtdIns(4,5)P₂, and PtdIns(3,4,5)P₃ are localized to phagosomes/phagocytic cups, plasma membrane, and phagocytic cups, respectively. The localization of these PIs in E. histolytica is similar to that in mammalian cells, suggesting that PIs have orthologous functions in E. histolytica. In contrast, the conservation of the enzymes that metabolize PIs in this organism has not been well-documented. In this review, we summarized the full repertoire of the PI kinases and PI phosphatases found in E. histolytica via a genome-wide survey of the current genomic information. E. histolytica appears to have 10 PI kinases and 23 PI phosphatases. It has a panel of evolutionarily conserved enzymes that generate all the seven PI species. However, class II PI 3-kinases, type II PI 4-kinases, type III PI 5-phosphatases, and PI 4P-specific phosphatases are not present. Additionally, regulatory subunits of class I PI 3-kinases and type III PI 4-kinases have not been identified. Instead, homologs of class I PI 3-kinases and PTEN, a PI 3-phosphatase, exist as multiple isoforms, which likely reflects that elaborate signaling cascades mediated by PtdIns(3,4,5)P₃ are present in this organism. There are several enzymes that have the nuclear localization signal: one phosphatidylinositol phosphate (PIP) kinase, two PI 3-phosphatases, and one PI 5-phosphatase; this suggests that PI metabolism also has conserved roles related to nuclear functions in E. histolytica, as it does in model organisms.

Effects of Dietary Nutrients on Epigenetic Changes in Cancer

Gene-nutrient interactions are important contributors to health management and disease prevention. Nutrition can alter gene expression, as well as the susceptibility to disease, including cancer, through epigenetic changes. Nutrients can influence the epigenetic status through several mechanisms, such as DNA methylation, histone modifications, and miRNA-dependent gene silencing. These alterations were associated with either increased or decreased risk for cancer development. There is convincing evidence indicating that several foods have protective roles in cancer prevention, by inhibiting tumor progression directly or through modifying tumor's microenvironment that leads to hostile conditions favorable to tumor initiation or growth. While nutritional intakes from foods cannot be adequately controlled for dosage, the role of nutrients in the epigenetics of cancer has led to more research aimed at developing nutriceuticals and drugs as cancer therapies. Clinical studies are needed to evaluate the optimum doses of dietary compounds, the safety profile of dosages, to establish the most efficient way of administration, and bioavailability, in order to maximize the beneficial effects already discovered, and to ensure replicability. Thus, nutrition represents a promising tool to be used not only in cancer prevention, but hopefully also in cancer treatment.

Estrogen Receptor Beta (ERβ) Mediated-CyclinD1 Degradation via Autophagy Plays an Anti-Proliferation Role in Colon Cells

Dysfunction of autophagic degradation machinery causes tumorigenesis, including colorectal cancer (CRC). Overexpression of CyclinD1 in CRC has been reported. Recent evidence also suggests that ERβ deficiency is related to the pathogenesis of CRC. Very little is known, however, about the detailed molecular mechanisms underlying the relationship among ERβ, autophagy, and CyclinD1 in CRC. Here, results showed that ERβ played an anti-proliferation role in HCT116 through impairing cell cycle but not apoptosis. Additionally, CyclinD1 accumulation was increased in response to chloroquine (CQ) or in MEF Atg7 knockout cells. Further, ERβ could inhibit the mammalian target of rapamycin (mTOR) or activate Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) to promote autophagy in HCT116. In summary, these results indicate that ERβ-mediated CyclinD1 degradation can inhibit colon cancer cell growth via autophagy.

Novel Clofarabine-Based Combinations with Polyphenols Epigenetically Reactivate Retinoic Acid Receptor Beta, Inhibit Cell Growth, and Induce Apoptosis of Breast Cancer Cells

An epigenetic component, especially aberrant DNA methylation pattern, has been shown to be frequently involved in sporadic breast cancer development. A growing body of literature demonstrates that combination of agents, i.e. nucleoside analogues with dietary phytochemicals, may provide enhanced therapeutic effects in epigenetic reprogramming of cancer cells. Clofarabine (2-chloro-2′-fluoro-2′-deoxyarabinosyladenine, ClF), a second-generation 2′-deoxyadenosine analogue, has numerous anti-cancer effects, including potential capacity to regulate epigenetic processes. Our present study is the first to investigate the combinatorial effects of ClF (used at IC₅₀ concentration) with epigallocatechin-3-gallate (EGCG, tea catechin) or genistein (soy phytoestrogen), at physiological concentrations, on breast cancer cell growth, apoptosis, and epigenetic regulation of retinoic acid receptor beta (RARB) transcriptional activity. In MCF7 and MDA-MB-231 cells, RARB promoter methylation and expression of RARB, modifiers of DNA methylation reaction (DNMT1, CDKN1A, TP53), and potential regulator of RARB transcription, PTEN, were estimated using methylation-sensitive restriction analysis (MSRA) and quantitative real-time polymerase chain reaction (qPCR), respectively. The combinatorial exposures synergistically or additively inhibited the growth and induced apoptosis of breast cancer cells, followed by RARB hypomethylation with concomitant multiple increase in RARB, PTEN, and CDKN1A transcript levels. Taken together, our results demonstrate the ability of ClF-based combinations with polyphenols to promote cancer cell death and reactivate DNA methylation-silenced tumor suppressor genes in breast cancer cells with different invasive potential.

PTEN Physically Interacts with and Regulates E2F1-mediated Transcription in Lung Cancer

PTEN phosphorylation at its C-terminal (C-tail) serine/threonine cluster negatively regulates its tumor suppressor function. However, the consequence of such inhibition and its downstream effects in driving lung cancer remain unexplored. Herein, we ascertain the molecular mechanisms by which phosphorylation compromises PTEN function, contributing to lung cancer. Replacement of the serine/threonine residues with alanine generated PTEN-4A, a phosphorylation-deficient PTEN mutant, which suppressed lung cancer cell proliferation and migration. PTEN-4A preferentially localized to the nucleus where it suppressed E2F1-mediated transcription of cell cycle genes. PTEN-4A physically interacted with the transcription factor E2F1 and associated with chromatin at gene promoters with E2F1 DNA-binding sites, a likely mechanism for its transcriptional suppression function. Deletion analysis revealed that the C2 domain of PTEN was indispensable for suppression of E2F1-mediated transcription. Further, we uncovered cancer-associated C2 domain mutant proteins that had lost their ability to suppress E2F1-mediated transcription, supporting the concept that these mutations are oncogenic in patients. Consistent with these findings, we observed increased PTEN phosphorylation and reduced nuclear PTEN levels in lung cancer patient samples establishing phosphorylation as a bona fide inactivation mechanism for PTEN in lung cancer. Thus, use of small molecule inhibitors that hinder PTEN phosphorylation is a plausible approach to activate PTEN function in the treatment of lung cancer. Abbreviations AKT V-Akt Murine Thymoma Viral Oncogene CA Cancer adjacent CDK1 Cyclin dependent kinase 1 CENPC-C Centromere Protein C ChIP Chromatin Immunoprecipitation co-IP Co-immunoprecipitation COSMIC Catalog of Somatic Mutations In Cancer CREB cAMP Responsive Element Binding Protein C-tail Carboxy terminal tail E2F1 E2F Transcription Factor 1 ECIS Electric Cell-substrate Impedance Sensing EGFR Epidermal Growth Factor Receptor GSI Gamma Secretase Inhibitor HDAC1 Histone Deacetylase 1 HP1 Heterochromatin protein 1 KAP1/TRIM28 KRAB-Associated Protein 1/Tripartite Motif Containing 28 MAF1 Repressor of RNA polymerase III transcription MAF1 homolog MCM2 Minichromosome Maintenance Complex Component 2 miRNA micro RNA MTF1 Metal-Regulatory Transcription Factor 1 PARP Poly(ADP-Ribose) Polymerase PD-1 Programmed Cell Death 1 PD-L1 Programmed Cell Death 1 Ligand 1 PI3K Phosphatidylinositol-4,5-Bisphosphate 3-Kinase PLK Polo-like Kinase pPTEN Phosphorylated PTEN PTEN Phosphatase and Tensin Homolog deleted on chromosome ten PTM Post Translational Modification Rad51 RAD51 Recombinase Rad52 RAD52 Recombinase RPA1 Replication protein A SILAC Stable Isotope Labeling with Amino Acids in Cell Culture SRF Serum Response Factor TKI Tyrosine Kinase inhbitors TMA Tissue Microarray TOP2A DNA Topoisomerase 2A.

Notch-1-PTEN-ERK1/2 signaling axis promotes HER2+ breast cancer cell proliferation and stem cell survival

Trastuzumab targets the HER2 receptor on breast cancer cells to attenuate HER2-driven tumor growth. However, resistance to trastuzumab-based therapy remains a major clinical problem for women with HER2+ breast cancer. Breast cancer stem cells (BCSCs) are suggested to be responsible for drug resistance and tumor recurrence. Notch signaling has been shown to promote BCSC survival and self-renewal. Trastuzumab-resistant cells have increased Notch-1 expression. Notch signaling drives cell proliferation in vitro and is required for tumor recurrence in vivo. We demonstrate herein a mechanism by which Notch-1 is required for trastuzumab resistance by repressing PTEN expression to contribute to activation of ERK1/2 signaling. Furthermore, Notch-1-mediated inhibition of PTEN is necessary for BCSC survival in vitro and in vivo. Inhibition of MEK1/2-ERK1/2 signaling in trastuzumab-resistant breast cancer cells mimics effects of Notch-1 knockdown on bulk cell proliferation and BCSC survival. These findings suggest that Notch-1 contributes to trastuzumab resistance by repressing PTEN and this may lead to hyperactivation of ERK1/2 signaling. Furthermore, high Notch-1 and low PTEN mRNA expression may predict poorer overall survival in women with breast cancer. Notch-1 protein expression predicts poorer survival in women with HER2+ breast cancer. These results support a potential future clinical trial combining anti-Notch-1 and anti-MEK/ERK therapy for trastuzumab-resistant breast cancer.

Next Generation Sequencing of urine exfoliated cells: an approach of prostate cancer microRNAs research

There is emerging evidence that microRNAs (miRNAs) dysregulation is involved in the genesis and the progression of Prostate Cancer (PCa), thus potentially increasing their use in urological clinical practice. This is the first pilot study which utilizes Illumina Deep Sequencing to examine the entire miRNAs spectrum existent in urine exfoliated prostate cells (UEPCs) of PCa patients. A total of 11 male patients with histological diagnosis of PCa were enrolled in the present study. First-catch urine (30 mL) was collected following a prostate massage. Total RNA was extracted from urine and sequenced using an HiSeq2500 System (Illumina). QPCR assay was used to validate the highest NGS results in PCA patients and in age-matched, caucasian men. Remarkably, PCA let-7 family was down-regulated (P < 0.01), compared to the controls. The results of our study support the notion of a relatively high diagnostic value of miRNA family for PCa detection, especially in the let-7 family. The present research confirmed the potential use of miRNAs as non-invasive biomarkers in the diagnosis of PCa, potentially reducing the invasiveness of actual clinical strategy.

Nuclear PTEN deficiency causes microcephaly with decreased neuronal soma size and increased seizure susceptibility

Defects in phosphatase and tensin homolog (PTEN) are associated with neurological disorders and tumors. PTEN functions at two primary intracellular locations: the plasma membrane and the nucleus. At the membrane, PTEN functions as a phosphatidylinositol (3,4,5)-trisphosphate phosphatase and suppresses PI 3-kinase signaling that drives cell growth and tumorigenesis. However, the in vivo function of nuclear PTEN is unclear. Here, using CRISPR/Cas9, we generated a mouse model in which PTEN levels in the nucleus are decreased. Nuclear PTEN-deficient mice were born with microcephaly and maintained a small brain during adulthood. The size of neuronal soma was significantly smaller in the cerebellum, cerebral cortex, and hippocampus. Also, these mice were prone to seizure. No changes in PI 3-kinase signaling were observed. By contrast, the size of other organs was unaffected. Therefore, nuclear PTEN is essential for the health of the brain by promoting the growth of neuronal soma size during development.

Knockdown of Phospholipase Cε (PLCε) Inhibits Cell Proliferation via Phosphatase and Tensin Homolog Deleted on Chromosome 10 (PTEN)/AKT Signaling Pathway in Human Prostate Cancer

Background

Phospholipase Cɛ (PLCɛ), a member of the plc family, has been extensively studied to reveal its role in the regulation of different cell functions, but understanding of the underlying mechanisms remains limited. In the present study, we explored the effects of PLCɛ on PTEN (phosphatase and tensin homolog deleted on chromosome 10) in cell proliferation in prostate cancer cells.

Material/Methods

We assessed PLCɛ and PTEN expression in human benign prostate tissues compared to prostate cancer tissues by immunohistochemistry. Lentivirus-shPLCɛ (LV-shPLCɛ) was designed to silence PLCɛ expression in DU145 and PC3 cell lines, and the effectiveness was tested by qRT-PCR and Western blotting. MTT assay and colony formation assay were conducted to observe cell proliferation. Western blotting and immunofluorescence assays were used to detect changed PTEN expression in DU145.

Results

We observed that PLCɛ expression was reduced in human benign prostate tissues compared to prostate cancer tissues, while PTEN expression showed the opposite trend. Silencing of the PLCɛ gene significantly inhibited cell proliferation in DU145 and PC3 cell lines. DU145 is a PTEN-expressing cell, while PC3 is PTEN-deficient. After infection by LV-shPLCɛ, we noticed that PTEN expression was up-regulated in DU145 cells but not in PC3 cells. Furthermore, we found that PLCɛ gene knockdown decreased P-AKT protein levels, but AKT protein levels were not affected. Immunofluorescence assays showed that PTEN expression had an intracellular distribution change in the DU145 cell line, and Western blot analysis showed that PTEN was obviously up-regulated in cell nucleus and cytoplasm.

Conclusions

PLCɛ is an oncogene, and knockdown of expression of PLCɛ inhibits PCa cells proliferation via the PTEN/AKT signaling pathway.

PTEN: Tumor Suppressor and Metabolic Regulator

Phosphatase and Tensin Homolog deleted on Chromosome 10 (PTEN) is a dual phosphatase with both protein and lipid phosphatase activities. PTEN was first discovered as a tumor suppressor with growth and survival regulatory functions. In recent years, the function of PTEN as a metabolic regulator has attracted significant attention. As the lipid phosphatase that dephosphorylates phosphatidylinositol-3, 4, 5-phosphate (PIP₃), PTEN reduces the level of PIP₃, a critical 2nd messenger mediating the signal of not only growth factors but also insulin. In this review, we introduced the discovery of PTEN, the PTEN-regulated canonical and nuclear signals, and PTEN regulation. We then focused on the role of PTEN and PTEN-regulated signals in metabolic regulation. This included the role of PTEN in glycolysis, gluconeogenesis, glycogen synthesis, lipid metabolism as well as mitochondrial metabolism. We also included how PTEN and PTEN regulated metabolic functions may act paradoxically toward insulin sensitivity and tumor metabolism and growth. Further understanding of how PTEN regulates metabolism and how such regulations lead to different biological outcomes is necessary for interventions targeting at the PTEN-regulated signals in either cancer or diabetes treatment.

Phosphatase and tensin homologue: a therapeutic target for SMA

Spinal muscular atrophy (SMA) is one of the most common juvenile neurodegenerative diseases, which can be associated with child mortality. SMA is caused by a mutation of ubiquitously expressed gene, Survival Motor Neuron1 (SMN1), leading to reduced SMN protein and the motor neuron death. The disease is incurable and the only therapeutic strategy to follow is to improve the expression of SMN protein levels in motor neurons. Significant numbers of motor neurons in SMA mice and SMA cultures are caspase positive with condensed nuclei, suggesting that these cells are prone to a process of cell death called apoptosis. Searching for other potential molecules or signaling pathways that are neuroprotective for central nervous system (CNS) insults is essential for widening the scope of developmental medicine. PTEN, a Phosphatase and Tensin homologue, is a tumor suppressor, which is widely expressed in CNS. PTEN depletion activates anti-apoptotic factors and it is evident that the pathway plays an important protective role in many neurodegenerative disorders. It functions as a negative regulator of PIP3/AKT pathway and thereby modulates its downstream cellular functions through lipid phosphatase activity. Moreover, previous reports from our group demonstrated that, PTEN depletion using viral vector delivery system in SMN delta7 mice reduces disease pathology, with significant rescue on survival rate and the body weight of the SMA mice. Thus knockdown/depletion/mutation of PTEN and manipulation of PTEN medicated Akt/PKB signaling pathway may represent an important therapeutic strategy to promote motor neuron survival in SMA.

Characterization of cryptic splicing in germline PTEN intronic variants in Cowden syndrome

Germline mutations in the tumor‐suppressor gene PTEN predispose to subsets of Cowden syndrome (CS), Bannayan–Riley–Ruvalcaba syndrome, and autism. Evidence‐based classification of PTEN variants as either deleterious or benign is urgently needed for accurate molecular diagnosis and gene‐informed genetic counseling. We studied 34 different germline PTEN intronic variants from 61 CS patients, characterized their PTEN mRNA processing, and analyzed PTEN expression and downstream readouts of P‐AKT and P‐ERK1/2. While we found that many mutations near splice junctions result in exon skipping, we also identified the presence of cryptic splicing that resulted in premature termination or a shift in isoform usage. PTEN protein expression is significantly lower in the group with splicing changes while P‐AKT, but not P‐ERK1/2, is significantly increased. Our observations of these PTEN intronic variants should contribute to the determination of pathogenicity of PTEN intronic variants and aid in genetic counseling.

Estrogen receptor β regulates the tumoral suppressor PTEN to modulate pituitary cell growth

In this study, we focused on ERβ regulation in the adenohypophysis under different estrogenic milieu, by analyzing whether ER modulates the phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression and its subcellular localization on anterior pituitary glands from Wistar rats and GH3 lactosomatotroph cells that over-expressed ERβ. ERβ was regulated in a cyclic manner, and underwent dynamic changes throughout the estrous cycle, with decreased ERβ+ cells in estrus and under E2 treatment, but increased in ovariectomized rats. In addition, the ERα/β ratio increased in estrus and under E2 stimulation, but decreased in ovariectomized rats. Double immunofluorescence revealed that lactotroph and somatotroph ERβ+ were significantly decreased in estrus. Also, variations in the PTEN expression was observed, which was diminished with high E2 conditions but augmented with low E2 milieu. The subcellular localization of this phosphatase was cell cycle-dependent, with remarkable changes in the immunostaining pattern: nuclear in arrested pituitary cells but cytoplasmic in stimulated cells, and responding differently to ER agonists, with only DPN being able to increase PTEN expression and retaining it in the nucleus. Finally, ERβ over-expression increased PTEN with a noticeable subcellular redistribution, and with a significant nuclear signal increase in correlation with an increase of cells in G0/G1 phase. These results showed that E2 is able to inhibit ERβ expression and suggests that the tumoral suppressor PTEN might be one of the signaling proteins by which E2, through ERβ, acts to modulate pituitary cell proliferation, thereby adapting endocrine populations in relation with hormonal necessities.

Cell Cycle Control by PTEN

Continuous and error-free chromosome inheritance through the cell cycle is essential for genomic stability and tumor suppression. However, accumulation of aberrant genetic materials often causes the cell cycle to go awry, leading to malignant transformation. In response to genotoxic stress, cells employ diverse adaptive mechanisms to halt or exit the cell cycle temporarily or permanently. The intrinsic machinery of cycling, resting, and exiting shapes the cellular response to extrinsic stimuli, whereas prevalent disruption of the cell cycle machinery in tumor cells often confers resistance to anticancer therapy. Phosphatase and tensin homolog (PTEN) is a tumor suppressor and a guardian of the genome that is frequently mutated or deleted in human cancer. Moreover, it is increasingly evident that PTEN deficiency disrupts the fundamental processes of genetic transmission. Cells lacking PTEN exhibit cell cycle deregulation and cell fate reprogramming. Here, we review the role of PTEN in regulating the key processes in and out of cell cycle to optimize genomic integrity.

Antibody to human α-fetoprotein inhibits cell growth of human hepatocellular carcinoma cells by resuscitating the PTEN molecule: in vitro experiments

It has been proposed that α-fetoprotein (AFP) is a new member of the intracellular signaling molecule family of the phosphoinositide 3-kinase (PI3K)/AKT signaling pathway via interaction with the phosphatase and tensin homolog (PTEN). In this study, the effects of anti-human AFP antibody on the functions of PTEN were examined using an AFP-producing human hepatoma cell line. The antibody caused significant inhibition of cell growth, compared to a normal IgG control, with the accumulation of intracellular immune complexes followed by significant reduction of cytosolic functional AFP. Decrease in the amount of AKT phosphorylated on serine (S) 473 indicated that PI3K/AKT signaling was suppressed in the cells. S380-phosphorylated PTEN increased markedly by the second day after antibody treatment, with slight but significant increase in the PTEN protein level. Since phosphorylation at S380 is critical for PTEN stability, the increase in S380-phosphorylated PTEN indicated maintenance of the number of PTEN molecules and the related potential to control PI3K/AKT signaling. p53 protein (P53) significantly, but slightly increased during antibody treatment, because PTEN expression increased the stability and function of P53 via both molecular interactions. P53 phosphorylated at S20 or at S392 dramatically increased, suggesting an increase in the stability, accumulation and activation of P53. Glucose transporter 1 (GLUT1) increased immediately after antibody treatment, pointing to a deficiency of glucose in the cells. Immunofluorescence cytology revealed that antibody-treatment re-distributed GLUT1 molecules throughout the cytoplasm with a reduction of their patchy localization on the cell surface. This suggested that translocation of GLUT1 depends on the PI3K/AKT pathway, in particular on PTEN expression. Antibody therapy targeted at AFP-producing tumor cells showed an inhibitory effect on the PI3K/AKT pathway via the liberation, restoration and functional stabilization of PTEN. PTEN simultaneously induced both P53 activation and intracellular translocation of GLUT1, since these are closely associated with PTEN.

Oncogenic microRNA-4534 regulates PTEN pathway in prostate cancer

Prostate carcinogenesis involves alterations in several signaling pathways, the most prominent being the PI3K/AKT pathway. This pathway is constitutively active and drives prostate cancer (PCa) progression to advanced metastatic disease. PTEN, a critical tumor and metastasis suppressor gene negatively regulates cell survival, proliferation, migration and angiogenesis via the PI3K/Akt pathway. PTEN is mutated, downregulated/dysfunctional in many cancers and its dysregulation correlates with poor prognosis in PCa. Here, we demonstrate that microRNA-4534 (miR-4534) is overexpressed in PCa and show that miR-4534 is hypermethylated in normal tissues and cell lines compared to PCa tissues/cells. miR-4534 exerts its oncogenic effects partly by downregulating the tumor suppressor PTEN gene. Knockdown of miR-4534 impaired cell proliferation, migration/invasion and induced G0/G1 cell cycle arrest and apoptosis in PCa. Suppression of miR-4534 and its effects on tumor growth was confirmed in a xenograft mouse model. We performed parallel experiments in non-cancer RWPE1 cells by overexpessing miR-4534 followed by functional assays. Overexpression of miR-4534 induced pro-cancerous characteristics in this non-cancer cell line. Statistical analyses revealed that miR-4534 has potential to independently distinguish malignant from normal tissues and positively correlated with poor overall and PSA recurrence free survival. Taken together, our results show that depletion of miR-4534 in PCa induces a tumor suppressor phenotype partly through induction of PTEN. These results have important implications for identifying and defining the role of new PTEN regulators such as microRNAs in prostate tumorigenesis. Understanding aberrantly overexpressed miR-4534 and its downregulation of PTEN will provide mechanistic insight and therapeutic targets for PCa therapy.

Osteopontin expression is correlated with differentiation and good prognosis in medullary thyroid carcinoma

BACKGROUND

Osteopontin (OPN) or secreted phosphoprotein 1 (SPP1) is a matricellular glycoprotein whose expression is elevated in various types of cancer and has been shown to be involved in tumourigenesis and metastasis in many malignancies, including follicular cell-derived thyroid carcinomas. Its role in C-cell-derived thyroid lesions and tumours remains to be established.

OBJECTIVE

The objective of this study is to clarify the role of OPN expression in the development of medullary thyroid carcinoma (MTC).

METHODS

OPN expression was analysed in a series of 116 MTCs by immunohistochemistry and by qPCR mRNA quantification of the 3 OPN isoforms (OPNa, OPNb and OPNc) in six cases from which fresh frozen tissue was available. Statistical tests were used to evaluate the relationship of OPN expression and the clinicopathological and molecular characteristics of patients and tumours.

RESULTS

OPN expression was detected in 91 of 116 (78.4%) of the MTC. We also observed high OPN expression in C-cell hyperplasia as well as in C-cells scattered in the thyroid parenchyma adjacent to the tumours. OPN expression was significantly associated with smaller tumour size, PTEN nuclear expression and RAS status, and suggestively associated with non-invasive tumours. OPNa isoform was expressed significantly at higher levels in tumours than in non-tumour samples. OPNb and OPNc presented similar levels of expression in all samples. Furthermore, OPNa isoform overexpression was significantly associated with reduced growth and viability in the MTC-derived cell line (TT).

CONCLUSION

The expression of OPN in normal C-cells and C-cell hyperplasia suggests that OPN is a differentiation marker of C-cells, rather than a marker of biological aggressiveness in this setting. At variance with other cancers, OPN expression is associated with good prognostic features in MTC.

Regulatory Effects and Mechanism of Adenovirus-Mediated PTEN Gene on Hepatic Stellate Cells

BACKGROUND

Tension homology deleted on chromosome ten (PTEN) is important in liver fibrosis.

AIMS

The purpose of this study was to evaluate the PTEN gene effects and mechanism of action on hepatic stellate cells (HSCs).

METHODS

The rat primary HSCs and human LX-2 cells were transfected by an adenovirus containing cDNA constructs encoding the wild-type PTEN (Ad-PTEN), the PTEN mutant G129E gene (Ad-G129E) and RNA interference targeting the PTEN sequence PTEN short hairpin RNA (PTEN shRNA), to up-regulate and down-regulate PTEN expression, respectively. The HSCs were assayed with a fluorescent microscope, real time PCR, Western blot, MTT, flow cytometry and Terminal-deoxynucleoitidyl transferase mediated nick end labeling. In addition, the CCl4 induced rat hepatic fibrosis model was also established to check the in vivo effects of the recombinant adenovirus with various levels of PTEN expression.

RESULTS

The data have shown that the over-expressed PTEN gene led to reduced HSCs activation and viability, caspase-3 activity and cell cycle arrest in the G0/G1 and G2/M phases, as well as negative regulation of the PI3K/Akt and FAK/ERK signaling pathways in vitro. The over-expressed PTEN gene improved liver function, inhibited proliferation and promoted apoptosis of HSCs both in vitro and in vivo.

CONCLUSIONS

These data have shown that gene therapy using the recombinant adenovirus encoding wild-type PTEN inhibits proliferation and induces apoptosis of HSCs, which is a potential treatment option for hepatic fibrosis.

ATM-mediated PTEN phosphorylation promotes PTEN nuclear translocation and autophagy in response to DNA-damaging agents in cancer cells

PTEN (phosphatase and tensin homolog), a tumor suppressor frequently mutated in human cancer, has various cytoplasmic and nuclear functions. PTEN translocates to the nucleus from the cytoplasm in response to oxidative stress. However, the mechanism and function of the translocation are not completely understood. In this study, topotecan (TPT), a topoisomerase I inhibitor, and cisplatin (CDDP) were employed to induce DNA damage. The results indicate that TPT or CDDP activates ATM (ATM serine/threonine kinase), which phosphorylates PTEN at serine 113 and further regulates PTEN nuclear translocation in A549 and HeLa cells. After nuclear translocation, PTEN induces autophagy, in association with the activation of the p-JUN-SESN2/AMPK pathway, in response to TPT. These results identify PTEN phosphorylation by ATM as essential for PTEN nuclear translocation and the subsequent induction of autophagy in response to DNA damage.

Different effects of ZO-1, ZO-2 and ZO-3 silencing on kidney collecting duct principal cell proliferation and adhesion

Coordinated cell proliferation and ability to form intercellular seals are essential features of epithelial tissue function. Tight junctions (TJs) classically act as paracellular diffusion barriers. More recently, their role in regulating epithelial cell proliferation in conjunction with scaffolding zonula occludens (ZO) proteins has come to light. The kidney collecting duct (CD) is a model of tight epithelium that displays intense proliferation during embryogenesis followed by very low cell turnover in the adult kidney. Here, we examined the influence of each ZO protein (ZO-1, -2 and -3) on CD cell proliferation. We show that all 3 ZO proteins are strongly expressed in native CD and are present at both intercellular junctions and nuclei of cultured CD principal cells (mCCDcl1). Suppression of either ZO-1 or ZO-2 resulted in increased G0/G1 retention in mCCDcl1 cells. ZO-2 suppression decreased cyclin D1 abundance while ZO-1 suppression was accompanied by increased nuclear p21 localization, the depletion of which restored cell cycle progression. Contrary to ZO-1 and ZO-2, ZO-3 expression at intercellular junctions dramatically increased with cell density and relied on the presence of ZO-1. ZO-3 depletion did not affect cell cycle progression but increased cell detachment. This latter event partly relied on increased nuclear cyclin D1 abundance and was associated with altered β1-integrin subcellular distribution and decreased occludin expression at intercellular junctions. These data reveal diverging, but interconnected, roles for each ZO protein in mCCDcl1 proliferation. While ZO-1 and ZO-2 participate in cell cycle progression, ZO-3 is an important component of cell adhesion.

Association of CCND1 overexpression with KRAS and PTEN alterations in specific subtypes of non-small cell lung carcinoma and its influence on patients' outcome

Cyclin D1 is one of the major cellular oncogenes, overexpressed in number of human cancers, including non-small cell lung carcinoma (NSCLC). However, it does not exert tumorigenic activity by itself, but rather cooperates with other altered oncogenes and tumor suppressors. Therefore, in the present study, we have examined mutual role of cyclin D1, KRAS, and PTEN alterations in the pathogenesis of NSCLC and their potential to serve as multiple molecular markers for this disease. CCND1 gene amplification and gene expression were analyzed in relation to mutational status of KRAS gene as well as to PTEN alterations (loss of heterozygosity and promoter hypermethylation) in NSCLC patient samples. Moreover, the effect of these co-alterations on patient survival was examined. Amplified CCND1 gene was exclusively associated with increased gene expression. Statistical analyses also revealed significant association between CCND1 overexpression and KRAS mutations in the whole group and in the groups of patients with adenocarcinoma, grade 1/2, and stage I/II. In addition, CCND1 overexpression was significantly related to PTEN promoter hypermethylation in the whole group and in the group of patients with squamous cell carcinoma and lymph node invasion. These joint alterations also significantly shortened patients' survival and were shown to be an independent factor for adverse prognosis. Overall results point that cyclin D1 expression cooperates with KRAS and PTEN alterations in pathogenesis of NSCLC, and they could serve as potential multiple molecular markers for specific subgroups of NSCLC patients as well as prognostic markers for this type of cancer.

Connection between Tumor Suppressor BRCA1 and PTEN in Damaged DNA Repair

Genomic instability finally induces cell death or apoptosis. The tumor suppressor, phosphatase and tensin homolog on chromosome 10 (PTEN), is a dual-specificity phosphatase, which has protein phosphatase activity and lipid phosphatase activity that antagonizes PI3K activity. Cells that lack PTEN have constitutively higher levels of PIP3 and activated downstream PI3K/AKT targets. BRCA1, a well-known breast cancer tumor suppressor, is to associate with breast cancer risk and genetic susceptibility. Many studies have demonstrated that PTEN, as well as BRCA1, plays a critical role in DNA damage responses. The BRCA1 functionally cooperates with PTEN and might be an essential blockage in the development of several tumors. Actually, the PTEN and BRCA1 genes are recognized as one of the most frequently deleted and/or mutated in many human cancers. The PI3K/AKT pathway is constitutively active in BRCA1-defective human cancer cells. Loss or decrease of these PTEN or BRCA1 function, by either mutation or reduced expression, has a role in various tumor developments. This review summarizes recent findings of the function of BRCA1 and PTEN involved in genomic stability and cancer cell signaling.

PI3K/mTOR signaling in mesothelioma patients treated with induction chemotherapy followed by extrapleural pneumonectomy

INTRODUCTION

The prognostic significance of activity biomarkers within the phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling pathway was assessed in two independent cohorts of malignant pleural mesothelioma (MPM) patients uniformly treated with a multimodal approach. We specifically assessed expression signatures in a unique set of pre- and postchemotherapy tumor samples.

METHODS

Biomarker expression was assessed in samples of two independent cohorts of 107 (cohort 1) and 46 (cohort 2) MPM cases uniformly treated with platinum-based induction chemotherapy followed by extrapleural pneumonectomy from two different institutions, assembled on tissue microarrays. Expression levels of phosphatase and tensin homologue (PTEN), phospho-mTOR, and p-S6 in addition to marker of proliferation (Ki-67) and apoptosis (cleaved caspase-3) were evaluated by immunohistochemistry and correlated with overall survival (OAS) and progression-free survival (PFS). To assess PTEN genomic status, fluorescence in situ hybridization was performed.

RESULTS

Survival analysis showed that high p-S6 and Ki-67 expression in samples of treatment naïve patients of cohort 1 was associated with shorter PFS (p = 0.02 and p = 0.04, respectively). High Ki-67 expression after chemotherapy remained associated with shorter PFS (p = 0.03) and OAS (p = 0.02). Paired comparison of marker expression in samples before and after induction chemotherapy of cohort 1 revealed that decreased cytoplasmic PTEN and increased phospho-mTOR expression was associated with a worse OAS (p = 0.04 and p = 0.03, respectively).

CONCLUSIONS

These novel data reveal a prognostic significance of expression changes of PI3K/mTOR pathway components during induction chemotherapy if confirmed in other patient cohorts and support the growing evidence to target the PI3K/mTOR pathway in the treatment of MPM.

PTEN expression and function in adult cancer stem cells and prospects for therapeutic targeting

Phosphatase and tensin homolog deleted on chromosome ten (PTEN) is a non-redundant lipid phosphatase that restrains and fine tunes the phosphatidylinositol-3-kinase (PI3K) signaling pathway. PTEN is involved in inherited syndromes, which predispose to different types of cancers and is among the most frequently inactivated tumor suppressor genes in sporadic cancers. Indeed, loss of PTEN function occurs in a wide spectrum of human cancers through a variety of mechanisms, including mutations, deletions, transcriptional silencing, or protein instability. PTEN prevents tumorigenesis through multiple mechanisms and regulates a plethora of cellular processes, including survival, proliferation, energy metabolism and cellular architecture. Moreover, recent studies have demonstrated that PTEN is able to exit, exist, and function outside the cell, allowing for inhibition of the PI3K pathway in neighboring cells in a paracrine fashion. Most recently, studies have shown that PTEN is also critical for stem cell maintenance and that PTEN loss can lead to the emergence and proliferation of cancer stem cell (CSC) clones. Depending on the cellular and tissue context of origin, PTEN deletion may result in increased self-renewal capacity or normal stem cell exhaustion and PTEN-defìcient stem and progenitor cells have been reported in prostate, lung, intestinal, and pancreatic tissues before tumor formation; moreover, reversible or irreversible PTEN loss is frequently observed in CSC from a variety of solid and hematologic malignancies, where it may contribute to the functional phenotype of CSC. In this review, we will focus on the role of PTEN expression and function and downstream pathway activation in cancer stem cell biology and regulation of the tumorigenic potential; the emerging role of PTEN in mediating the crosstalk between the PI3K and MAPK pathways will also be discussed, together with prospects for the therapeutic targeting of tumors lacking PTEN expression.

Dysregulation of PTEN in cardiopulmonary vascular remodeling induced by pulmonary hypertension

Pulmonary hypertension (PH) is a disorder of lung vasculature characterized by arterial narrowing. Phosphatase-and-tensin homolog on chromosome 10 (PTEN), associated in the progression of multiple cancers, is implicated in arterial remodeling. However, the involvement of PTEN in PH remains unclear. The objective of the present study was to determine the role of PTEN in pulmonary vascular remodeling using established models of PH. The study used rat models of PH, induced by monocrotaline (MCT) administration (60 mg/kg) or continuous hypoxic exposure (10% oxygen) for 3 weeks. Pulmonary artery smooth muscle cells (SMCs) were used for in vitro confirmation. Development of PH was verified by hemodynamic, morphological and histopathology analyses. PTEN and key downstream proteins in pulmonary and cardiac tissues were analyzed by western blotting and RT-PCR. PTEN was significantly decreased (MCT, 53%; Hypoxia, 40%), pAkt was significantly increased (MCT, 42%; Hypoxia, 55%) in tissues of rats with PH. Similar results were observed in SMCs exposed to hypoxia (1% oxygen) for 48 h. Ubiquitination assay showed that PTEN degradation occurs via proteasomal degradation pathway. Western blotting demonstrated a significant downregulation of cell-cycle regulatory proteins p53 and p27, and upregulation of cyclin-D1 in the lungs of both models. The results showed that PTEN-mediated modulation of PI3K pathway was independent of the focal adhesion kinase and fatty acid synthase. The study, for the first time, established that PTEN plays a key role in the progression of pulmonary hypertension. The findings may have potential for the treatment of pulmonary hypertension using PTEN as a target.

DNA demethylation in the PTEN gene promoter induced by 5-azacytidine activates PTEN expression in the MG-63 human osteosarcoma cell line

This study used the MG-63 osteosarcoma cell line to investigate the demethylation of the phosphate and tension homolog (PTEN) gene promoter and the change in PTEN gene expression levels, which are caused by the methylation inhibitor 5-azacytidine (5-Zac), and the association between the two. Different concentrations of 5-Zac (0, 5 and 10 μmol/l) were added into the MG-63 cell culture medium and the cells were cultured for 72 h. The following techniques were performed on the cells: Western blot analysis to detect the PTEN protein; reverse transcription-polymerase chain reaction (PCR) to detect the mRNA transcription levels of the PTEN gene; flow cytometry to detect the cell apoptotic rate; and sodium bisulfate to deal with the DNA of each group. The genes of the PTEN promoter and the transcription factors specificity protein 1 (Sp1) and Myc were PCR amplified and transformed into Escherichia coli, then a number of clones were selected for sequencing and the methylation status of the amplified PTEN promoter fragment was detected. Following culture of the MG-63 cells with 5-Zac at concentrations of 0, 5 and 10 μmol/l for 72 h, the expression levels of PTEN protein in each group were gradually increased, presenting a concentration-dependent effect: Group 0 μmol/l compared with groups 5 and 10 μmol/l, P<0.05; and group 5 μmol/l compared with group 10 μmol/l, P=0.007. The mRNA expression levels of the PTEN gene significantly increased. The apoptotic rates of groups 0, 5 and 10 μmol/l were 0.69±0.42, 2.50±0.30 and 6.59±0.62%, and significant differences (P<0.01) were observed between every two groups. The bisulfate DNA sequencing results of three groups showed that, following the treatment with 5-Zac, the binding of the CG site to transcription factors was affected by demethylation. The average rate of demethylation indicated a statistical difference among the three groups. In conclusion, the methylation inhibitor 5-Zac leads to a significant increase in the expression levels of the tumor suppressor gene PTEN in the MG-63 osteosarcoma cell line in vitro. The expression levels of mRNA and the cellular apoptotic rate were also increased. The elevated activation and expression levels of the PTEN gene may be associated with the low methylation levels of the CG site that binds to the transcription factors Sp1 and Myc in the PTEN gene promoter, and they promote the combination of the transcription factors and the gene promoter.

PTEN, Longevity and Age-Related Diseases

Since the discovery of PTEN, this protein has been shown to be an effective suppressor of cancer and a contributor to longevity. This report will review, in depth, the associations between PTEN and other molecules, its mutations and regulations in order to present how PTEN can be used to increase longevity. This report will collect recent research of PTEN and use this to discuss PTEN’s role in caloric restriction, antioxidative defense of DNA-damage and the role it plays in suppressing tumors. The report will also discuss that variety of ways that PTEN can be compromised, through mutations, complete loss of alleles and its main antagonist, the PI3K/AKT pathway.

The function, mechanisms, and role of the genes PTEN and TP53 and the effects of asbestos in the development of malignant mesothelioma: a review focused on the genes' molecular mechanisms

The malignant mesothelioma is an aggressive form of cancer with a mean survival rate of less than a year. Moreover, environmental exposure to minerals is an important factor in the development of malignant mesothelioma (MM), especially the mineral asbestos, which has a well-documented role in MM, and more recently, the mineral erionite has been proven to be a strong carcinogenic inducer of MM. In addition, the virus simian virus 40 has been implicated as a co-carcinogenic player in MM. However, the molecular mechanisms involved in the pathogenesis of this cancer are still not fully understood. Indeed, it is known that several genes are altered or mutated in MM, among those are p16(INK4A), p14(ARF), and neurofibromatosis type II. Furthermore, TP53 has been reported to be mutated in the majority of the cancers; however, in MM, it is very uncommon mutations in this gene. Also, the PTEN gene has been shown to play an important role in endometrial cancer and glioblastoma, although the role of PTEN in MM has yet to be established. Taken altogether, this review focuses on the historical aspects, molecular mechanisms, interaction with other genes and proteins, and the role of these genes in MM. Lastly, this review questions the cancer theory of the two hits because the functions of both PTEN and TP53 are not fully explained by this theory.

Inhibition of PTEN expression and activity by angiotensin II induces proliferation and migration of vascular smooth muscle cells

PTEN (phosphatase and tensin homolog deleted on chromosome 10) is a tumor suppressor and has been suggested recently to be involved in the regulation of cardiovascular diseases. The molecular mechanisms of this regulation are however poorly understood. This study shows that down regulation of PTEN expression and activity by angiotensin II (Ang II) increased proliferation and migration of vascular smooth muscle cells (VSMCs). The presence of Ang II induced rapid PTEN phosphorylation and oxidation in accordance with increased AKT and FAK phosphorylation. The Ang II-mediated VSMC proliferation and migration was inhibited when cellular PTEN expression was increased by AT1 inhibitor losartan, PPARγ agonist rosiglitazone, NF-κB inhibitor BAY 11-7082. Over expression of PTEN in VSMCs by adenovirus transduction also resulted in inhibition of cell proliferation and migration in response to Ang II. These results suggest that PTEN down-regulation is involved in proliferation and migration of VSMCs induced by Ang II. This provides insight into the molecular regulation of PTEN in vascular smooth muscle cells and suggests that targeting the action of PTEN may represent an effective therapeutic approach for the treatment of cardiovascular diseases.

PTEN and melanomagenesis

The PI3K-PTEN-AKT signaling pathway is involved in various cellular activities, including proliferation, migration, cell growth, cell survival and differentiation during adult homeostasis as well as in tumorigenesis. It has been suggested that the constitutive activation of PI3K/AKT signaling with concurrent loss of function of the tumor suppressor molecule PTEN contributes to cancer formation. Members of the PI3K-PTEN-AKT pathway, including these proteins and mTOR, are altered in melanoma tumors and cell lines. A hallmark of activation of the pathway is the loss of function of PTEN. Indeed, loss of heterozygosity of PTEN has been observed in approximately 30% of human melanomas, implicating this signaling pathway in this cancer. PI3K signaling activation, via loss of PTEN function, can inhibit proapoptotic genes such as the FoxO family of transcription factors, while inducing cell growth- and cell survival-related elements such as p70S6K and AKT. Determining how the PI3K-PTEN-AKT signaling pathway, alone or in cooperation with other pathways, orchestrates the induction of target genes involved in a diverse range of activities is a major challenge in research into melanoma initiation and progression. Moreover, the acquisition of basic knowledge will help patient management with appropriate therapies that are already, or will shortly be, on the market.

Epigenetic mechanisms in anti-cancer actions of bioactive food components--the implications in cancer prevention

The hallmarks of carcinogenesis are aberrations in gene expression and protein function caused by both genetic and epigenetic modifications. Epigenetics refers to the changes in gene expression programming that alter the phenotype in the absence of a change in DNA sequence. Epigenetic modifications, which include amongst others DNA methylation, covalent modifications of histone tails and regulation by non-coding RNAs, play a significant role in normal development and genome stability. The changes are dynamic and serve as an adaptation mechanism to a wide variety of environmental and social factors including diet. A number of studies have provided evidence that some natural bioactive compounds found in food and herbs can modulate gene expression by targeting different elements of the epigenetic machinery. Nutrients that are components of one-carbon metabolism, such as folate, riboflavin, pyridoxine, cobalamin, choline, betaine and methionine, affect DNA methylation by regulating the levels of S-adenosyl-L-methionine, a methyl group donor, and S-adenosyl-L-homocysteine, which is an inhibitor of enzymes catalyzing the DNA methylation reaction. Other natural compounds target histone modifications and levels of non-coding RNAs such as vitamin D, which recruits histone acetylases, or resveratrol, which activates the deacetylase sirtuin and regulates oncogenic and tumour suppressor micro-RNAs. As epigenetic abnormalities have been shown to be both causative and contributing factors in different health conditions including cancer, natural compounds that are direct or indirect regulators of the epigenome constitute an excellent approach in cancer prevention and potentially in anti-cancer therapy.