PTEN, more than the AKT pathway

Progesterone receptor and PTEN expression predict survival in patients with low- and intermediate-grade pancreatic neuroendocrine tumors

CONTEXT

The PI3K-AKT-mTOR (phosphatidylinositol 3-kinase-AKT-mammalian target of rapamycin) pathway plays a crucial role in a subset of advanced pancreatic neuroendocrine tumors (PanNETs). In breast and endometrial carcinoma, activation of this pathway inhibits progesterone receptor (PR) expression.

OBJECTIVE

To determine whether combined low expression of PR and phosphatase and tensin homologue (PTEN), a negative regulator of the PI3K-AKT-mTOR pathway, is a prognostic factor.

DESIGN

A total of 160 resected PanNETs (89 low grade and 71 intermediate grade) were analyzed for PR and PTEN immunohistochemical positivity and staining was correlated with metastasis-free survival (MFS) and overall survival (OS). Progesterone receptor staining was scored as positive by using 1% or greater as cutoff. Weak/faint staining in greater than 90% of tumor cells was considered low PTEN positivity.

RESULTS

Most PanNETs (110 cases, 69%) were both PR and PTEN positive, 45 (28%) were either PR or PTEN positive, and only 5 (3%) had a PR-negative and PTEN-low profile. Combined PR-PTEN positivity was significantly associated with MFS in patients with stage I and II disease (P <.001) and OS in all patients (P < .001) and remained a significant predictor of survival after adjusting for other factors. Patients with PR-negative-PTEN-low PanNETs had the shortest median MFS and OS, compared to those with tumors that were either PR or PTEN positive and with tumors positive for both PR and PTEN (P ≤ .001).

CONCLUSION

Combined immunohistochemical assessment of PR and PTEN may help identify a small subset of PanNETs with more aggressive behavior and may aid in risk stratification.

Akt and p53R2, partners that dictate the progression and invasiveness of cancer

The serine/threonine kinase or the so-called "Akt" is a key regulatory molecule of signaling pathway that regulates various cellular processes. Many intracellular proteins are involved in the activation or inhibition of Akt signaling and the hyperactivation of Akt signaling pathway is found to be frequently involved in various types of human cancers. Furthermore, while p53R2, a p53-inducible peptide involved in the synthesis of dNTPs normally works toward suppression of cancer through elimination of reactive oxygen species (ROS), inhibition of MAPK/ERK pathway and providing dNTPs for DNA repair, the overexpression of p53R2 is reported to be associated with cancer progression and resistance to therapy. In this review article, we will discuss the situation in which cancer cells with hyperactive PI3K/Akt signaling can recruit p53R2 in favor of cancer progression and resistance to therapy. In the hyperactive state of PI3K/Akt signaling (which happens in the absence of deactivation or excess of activation), p53R2 can be used by cancer cells to promote proliferation. Therefore, the hyperactivity of PI3K/Akt pathway and elevated levels of p53R2 can give rise to highly invasive cancers.

Hesperidin induces apoptosis and triggers autophagic markers through inhibition of Aurora-A mediated phosphoinositide-3-kinase/Akt/mammalian target of rapamycin and glycogen synthase kinase-3 beta signalling cascades in experimental colon carcinogenesis

Abnormalities in the homeostasis mechanisms involved in cell survival and apoptosis are contributing factors for colon carcinogenesis. Interventions of these mechanisms by pharmacologically safer agents gain predominance in colon cancer prevention. We previously reported the chemopreventive efficacy of hesperidin against colon carcinogenesis. In the present study, we aimed at investigating the potential of hesperidin over the abrogated Aurora-A coupled pro-survival phosphoinositide-3-kinase (PI3K)/Akt signalling cascades. Further, the role of hesperidin over apoptosis and mammalian target of rapamycin (mTOR) mediated autophagic responses were studied. Azoxymethane (AOM) induced mouse model of colon carcinogenesis was involved in this study. Hesperidin treatment was provided either in initiation/post-initiation mode respectively. Hesperidin significantly altered AOM mediated anti-apoptotic scenario by modulating Bax/Bcl-2 ratio together with enhanced cytochrome-c release and caspase-3, 9 activations. In addition, hesperidin enhanced p53-p21 axis with concomitant decrease in cell cycle regulator. Hesperidin treatment caused significant up-regulation of tumour suppressor phosphatase and tensin homologue (PTEN) with a reduction in the expression of AOM mediated p-PI3K and p-Akt. Additionally, hesperidin administration exhibited inhibition against p-mTOR expression which in turn led to stimulation of autophagic markers Beclin-1 and LC3-II. Aurora-A an upstream regulator of PI3K/Akt pathway was significantly inhibited by hesperidin. Furthermore, hesperidin administration restored glycogen synthase kinase-3 beta (GSK-3β) activity which in turn prevented the accumulation of oncoproteins β-catenin, c-jun and c-myc. Taken together, hesperidin supplementation initiated apoptosis via targeted inhibition of constitutively activated Aurora-A mediated PI3K/Akt/GSK-3β and mTOR pathways coupled with autophagic stimulation against AOM induced colon carcinogenesis.

Adolescent mouse takes on an active transcriptomic expression during postnatal cerebral development

Postnatal cerebral development is a complicated biological process precisely controlled by multiple genes. To understand the molecular mechanism of cerebral development, we compared dynamics of mouse cerebrum transcriptome through three developmental stages using high-throughput RNA-seq technique. Three libraries were generated from the mouse cerebrum at infancy, adolescence and adulthood, respectively. Consequently, 44,557,729 (infancy), 59,257,530 (adolescence) and 72,729,636 (adulthood) reads were produced, which were assembled into 15,344, 16,048 and 15,775 genes, respectively. We found that the overall gene expression level increased from infancy to adolescence and decreased later on upon reaching adulthood. The adolescence cerebrum has the most active gene expression, with expression of a large number of regulatory genes up-regulated and some crucial pathways activated. Transcription factor (TF) analysis suggested the similar dynamics as expression profiling, especially those TFs functioning in neurogenesis differentiation, oligodendrocyte lineage determination and circadian rhythm regulation. Moreover, our data revealed a drastic increase in myelin basic protein (MBP)-coding gene expression in adolescence and adulthood, suggesting that the brain myelin may be generated since mouse adolescence. In addition, differential gene expression analysis indicated the activation of rhythmic pathway, suggesting the function of rhythmic movement since adolescence; Furthermore, during infancy and adolescence periods, gene expression related to axon repulsion and attraction showed the opposite trends, indicating that axon repulsion was activated after birth, while axon attraction might be activated at the embryonic stage and declined during the postnatal development. Our results from the present study may shed light on the molecular mechanism underlying the postnatal development of the mammalian cerebrum.

MicroRNA-382 induced by HIF-1α is an angiogenic miR targeting the tumor suppressor phosphatase and tensin homolog

Recent studies have revealed that microRNAs (miRs) play important roles in the regulation of angiogenesis. In this study, we have characterized miR-382 upregulation by hypoxia and the functional relevance of miR-382 in tumor angiogenesis. miRs induced by hypoxia in MKN1 human gastric cancer cells were investigated using miRNA microarrays. We selected miR-382 and found that the expression of miR-382 was regulated by HIF-1α. Conditioned media (CM) from MKN1 cells transfected with a miR-382 inhibitor (antagomiR-382) under hypoxic conditions significantly decreased vascular endothelial cell (EC) proliferation, migration and tube formation. Algorithmic programs (Target Scan, miRanda and cbio) predicted that phosphatase and tensin homolog (PTEN) is a target gene of miR-382. Deletion of miR382-binding sequences in the PTEN mRNA 3′-untranslated region (UTR) diminished the luciferase reporter activity. Subsequent study showed that the overexpression of miR-382 or antagomiR-382 down- or upregulated PTEN and its downstream target AKT/mTOR signaling pathway, indicating that PTEN is a functional target gene of miR-382. In addition, PTEN inhibited miR-382-induced in vitro and in vivo angiogenesis as well as VEGF secretion, and the inhibition of miR-382 expression reduced xenograft tumor growth and microvessel density in tumors. Taken together, these results suggest that miR-382 induced by hypoxia promotes angiogenesis and acts as an angiogenic oncogene by repressing PTEN.

Roles of deletion of Arid1a, a tumor suppressor, in mouse ovarian tumorigenesis

The chromatin remodeling gene, ARID1A, has been implied as a tumor suppressor, and its somatic inactivating mutations occur in a wide variety of human cancers, most frequently in ovarian and uterine endometrioid and ovarian clear cell carcinomas. Tumors with ARID1A mutations also frequently harbor PTEN or PIK3CA mutations, suggesting their collaboration in tumorigenesis. Here, we used a conditional knockout mouse model in which Arid1a and Pten were deleted either individually or in combination in the mouse ovarian surface epithelium. After 6 months, 59.1% of mice with Arid1a and Pten double knockout developed ovarian endometrioid or undifferentiated carcinoma, whereas the remaining mice showed hyperplasia of ovarian surface epithelium. In contrast, 52 mice with homozygous or heterozygous deletion in either Arid1a or Pten did not develop ovarian lesions. These results demonstrate that inactivation of Arid1a alone is insufficient for tumor initiation but it requires additional genetic alteration(s) such as Pten deletion to drive tumorigenesis.

MCT-1 expression and PTEN deficiency synergistically promote neoplastic multinucleation through the Src/p190B signaling activation

Multinucleation is associated with malignant neoplasms; however, the molecular mechanism underlying the nuclear abnormality remains unclear. Loss or mutation of PTEN promotes the development of malignant tumors. We now demonstrate that increased expression of the oncogene MCT-1 (multiple copies in T-cell malignancy 1) antagonizes PTEN gene presentation, PTEN protein stability and PTEN functional activity, thereby further promoting phosphoinositide 3 kinase/AKT signaling, survival rate and malignancies of the PTEN-deficient cells. In the PTEN-null cancer cells, MCT-1 interacts with p190B and Src in vivo, supporting that they are in proximity of the signaling complexes. MCT-1 overexpression and PTEN loss synergistically augments the Src/p190B signaling function that leads to inhibition of RhoA activity. Under such a condition, the incidence of mitotic catastrophes including spindle multipolarity and cytokinesis failure is enhanced, driving an Src/p190B/RhoA-dependent neoplastic multinucleation. Targeting MCT-1 by the short hairpin RNA markedly represses the Src/p190B function, improves nuclear structures and suppresses xenograft tumorigenicity of the PTEN-null breast cancer cells. Consistent with the oncogenic effects in vitro, clinical evidence has confirmed that MCT-1 gene stimulation is correlated with p190B gene promotion and PTEN gene suppression in human breast cancer. Accordingly, MCT-1 gene induction is recognized as a potential biomarker of breast tumor development. Abrogating MCT-1 function may be a promising stratagem for management of breast cancer involving Src hyperactivation and/or PTEN dysfunction.

Inhibition of phosphatase and tensin homologue (PTEN) in human ovary in vitro results in increased activation of primordial follicles but compromises development of growing follicles

In the mammalian ovary a small number of follicles are steadily recruited from the quiescent pool to undergo development. Follicle loss, maintenance and growth are strictly controlled by complex molecular interactions including the phosphoinositide 3-kinase (PI3K)-protein kinase B (Akt) signalling pathway. Stimulation of PI3K promotes phosphorylation of Akt resulting in follicle survival and activation of growth whereas this pathway is suppressed by the actions of the phosphatase and tensin homologue (PTEN). The aim of this study was to determine the effect of dipotassium bisperoxo(5-hydroxypyridine-2-carboxyl)oxovanadate (bpV), a reversible inhibitor of PTEN, on the activation, survival and development of human ovarian follicles in vitro. Biopsied ovarian tissue fragments were obtained from 17 women aged 23-46 years and exposed to 1 µM bpV(HOpic) (n = 146) or control medium (n = 128) for 24 h. Media were then replaced with control medium and all tissue incubated for a further 5 days. Ovarian tissue from each treatment group was fixed after the initial 24 h culture period and phosphorylated Akt was quantified by western blotting. After 6 days incubation all tissue fragments were inspected under light microscopy and any secondary follicles ≥100 µm isolated. Isolated follicles were cultured individually in control medium supplemented with 100 ng/ml recombinant human activin A. Tissue fragments without follicles suitable for isolation were fixed and processed for histological and immunohistochemical analysis. During 6 days culture, follicle activation occurred in tissue samples from both treatment groups but with significantly more follicles progressing to the secondary stage of development in the presence of 1 µM bpV(HOpic) compared with control (31 versus 16%; P < 0.05). Increased activation was associated with increased Akt phosphorylation and increased nuclear export of FOXO3. However isolated and cultured follicles that had been exposed to bpV(HOpic) showed limited growth and reduced survival compared with follicles from control fragments (P < 0.05). This study demonstrates that inhibition of PTEN with bpV(HOpic) affects human ovarian follicle development by promoting the initiation of follicle growth and development to the secondary stage, as in rodent species, but severely compromises the survival of isolated secondary follicles.

The PTEN Long N-tail is intrinsically disordered: increased viability for PTEN therapy

Aberrant activation of the PI3K/Akt/mTOR pathway is observed in several cancers and hyper proliferative disorders. PTEN, a tumor suppressor gene, negatively regulates the PI3K/Akt/mTOR pathway. Inhibitors of various components of this pathway are currently being used for cancer therapy. However, the use of these small molecule inhibitors remains limited due to the presence of compensatory feedback loops within the pathway such that inhibition of one oncogenic molecule often results in the activation of another oncogenic molecule resulting in the development of chemoresistance. One novel strategy that has emerged as a means to circumvent the problem of feedback signaling is by activating tumor suppressor genes that abrogate oncogenic pathways and regress tumor growth. In this regard, a newly identified isoform of the PTEN protein shows promise for use in tumors with elevated PI3K/Akt/mTOR signaling. This isoform is a translational variant of PTEN, termed as PTEN Long, and has additional 173 amino acids at its N-terminus (N-173) than normal PTEN. The N-173 region is required for PTEN secretion and transport across the body. Given the potential of this N-173 region to act as a drug delivery system for PTEN, we herein analyze the structural properties of this region. This N-173 tail has a large intrinsically disordered region (IDR) and is composed of highly charged basic residues. Further, the region is enriched in potential linear binding motifs, protein-binding sites and post-translational modifications (PTMs) indicating its probable role in PTEN function and transport across cells. An extensive analysis of this region is warranted to better exploit its structural and biophysical peculiarities to drug discovery and drug delivery applications.

Semaphorin 3A upregulates FOXO 3a-dependent MelCAM expression leading to attenuation of breast tumor growth and angiogenesis

Semaphorin 3A (Sema 3A), a member of semaphorin family, serves as a guidance clue during embryonic development and is known as a candidate tumor suppressor that attenuates breast tumor progression by binding with its co-receptor, neuropilin-1 (NRP-1). However, the underlying mechanism by which Sema 3A suppresses breast tumor growth is still unexplored. In this study, we report that Sema 3A regulates phosphorylation and nuclear translocation of phosphatase and tensin homolog (PTEN) and FOXO 3a. Moreover, Sema 3A controls NRP-1-mediated PTEN-dependent FOXO 3a activation. Overexpression of PTEN and FOXO 3a enhances Sema 3A-induced attenuation of breast cancer cell migration. Chromatin immunoprecipitation and electrophoretic mobility shift assay data revealed that FOXO 3a regulates MelCAM at the transcriptional level. Furthermore, Sema 3A induces NRP-1-mediated MelCAM expression through PTEN and FOXO 3a. The data also showed that vascular endothelial growth factor-induced angiogenesis is inhibited by Sema 3A. Loss of or gain in function study revealed that Sema 3A modulates phosphorylation of PTEN and FOXO 3a and expression of MelCAM, leading to suppression of tumor growth and angiogenesis using in vivo mice model. Clinical specimen analysis revealed that reduced expression of Sema 3A and p-PTEN are correlated with enhanced breast cancer progression, further strengthening our in vitro and in vivo findings. Correlation of relapse-free survival of breast cancer patients (n=2878) with expression levels of Sema 3A, NRP-1, FOXO 3a and MelCAM were studied by Kaplan-Meier analysis. Statistical analysis revealed a close association between reduced expression of Sema 3A and MelCAM with that of poor patient's survival. Our study demonstrated a novel mechanism of regulation of tumor suppression by Sema 3A in coordination with a chain of tumor-suppressor genes, which in turn inhibits breast cancer cell migration, tumor growth and angiogenesis.

Aberrant microRNA expression likely controls RAS oncogene activation during malignant transformation of human prostate epithelial and stem cells by arsenic

Inorganic arsenic (iAs), a human carcinogen, potentially targets the prostate. iAs malignantly transforms the RWPE-1 human prostate epithelial line to CAsE-PE cells, and a derivative normal stem cell (SC) line, WPE-stem, to As-Cancer SC (As-CSC) line. MicroRNAs (miRNA) are noncoding but exert negative control on expression by degradation or translational repression of target mRNAs. Aberrant miRNA expression is important in carcinogenesis. A miRNA array of CAsE-PE and As-CSC revealed common altered expression in both for pathways concerning oncogenesis, miRNA biogenesis, cell signaling, proliferation, and tumor metastasis and invasion. The KRAS oncogene is overexpressed in CAsE-PE cells but not by mutation or promoter hypomethylation, and is intensely overexpressed in As-CSC cells. In both transformants, decreased miRNAs targeting KRAS and RAS superfamily members occurred. Reduced miR-134, miR-373, miR-155, miR-138, miR-205, miR-181d, miR-181c, and let-7 in CAsE-PE cells correlated with increased target RAS oncogenes, RAN, RAB27A, RAB22A mRNAs, and KRAS protein. Reduced miR-143, miR-34c-5p, and miR-205 in As-CSC correlated with increased target RAN mRNA, and KRAS, NRAS, and RRAS proteins. The RAS/ERK and PI3K/PTEN/AKT pathways control cell survival, differentiation, and proliferation, and when dysregulated promote a cancer phenotype. iAs transformation increased expression of activated ERK kinase in both transformants and altered components of the PI3K/PTEN/AKT pathway including decreased PTEN and increases in BCL2, BCL-XL, and VEGF in the absence of AKT activation. Thus, dysregulated miRNA expression may be linked to RAS activation in both transformants.

Melanopsin ganglion cells are the most resistant retinal ganglion cell type to axonal injury in the rat retina

We report that the most common retinal ganglion cell type that remains after optic nerve transection is the M1 melanopsin ganglion cell. M1 ganglion cells are members of the intrinsically photosensitive retinal ganglion cell population that mediates non-image-forming vision, comprising ∼2.5% of all ganglion cells in the rat retina. In the present study, M1 ganglion cells comprised 1.7±1%, 28±14%, 55±13% and 82±8% of the surviving ganglion cells 7, 14, 21 and 60 days after optic nerve transection, respectively. Average M1 ganglion cell somal diameter and overall morphological appearance remained unchanged in non-injured and injured retinas, suggesting a lack of injury-induced degeneration. Average M1 dendritic field size increased at 7 and 60 days following optic nerve transection, while average dendritic field size remained similar in non-injured retinas and in retinas at 14 and 21 days after optic nerve transection. These findings demonstrate that M1 ganglion cells are more resistant to injury than other ganglion cell types following optic nerve injury, and provide an opportunity to develop pharmacological or genetic therapeutic approaches to mitigate ganglion cell death and save vision following optic nerve injury.

Kinetic analysis of mouse brain proteome alterations following Chikungunya virus infection before and after appearance of clinical symptoms

Recent outbreaks of Chikungunya virus (CHIKV) infection have been characterized by an increasing number of severe cases with atypical manifestations including neurological complications. In parallel, the risk map of CHIKV outbreaks has expanded because of improved vector competence. These features make CHIKV infection a major public health concern that requires a better understanding of the underlying physiopathological processes for the development of antiviral strategies to protect individuals from severe disease. To decipher the mechanisms of CHIKV infection in the nervous system, a kinetic analysis on the host proteome modifications in the brain of CHIKV-infected mice sampled before and after the onset of clinical symptoms was performed. The combination of 2D-DIGE and iTRAQ proteomic approaches, followed by mass spectrometry protein identification revealed 177 significantly differentially expressed proteins. This kinetic analysis revealed a dramatic down-regulation of proteins before the appearance of the clinical symptoms followed by the increased expression of most of these proteins in the acute symptomatic phase. Bioinformatic analyses of the protein datasets enabled the identification of the major biological processes that were altered during the time course of CHIKV infection, such as integrin signaling and cytoskeleton dynamics, endosome machinery and receptor recycling related to virus transport and synapse function, regulation of gene expression, and the ubiquitin-proteasome pathway. These results reveal the putative mechanisms associated with severe CHIKV infection-mediated neurological disease and highlight the potential markers or targets that can be used to develop diagnostic and/or antiviral tools.

Caffeine mediates sustained inactivation of breast cancer-associated myofibroblasts via up-regulation of tumor suppressor genes

Background

Active cancer-associated fibroblasts (CAFs) or myofibroblasts play important roles not only in the development and progression of breast carcinomas, but also in their prognosis and treatment. Therefore, targeting these cells through suppressing their supportive procarcinogenic paracrine effects is mandatory for improving the current therapies that are mainly targeting tumor cells. To this end, we investigated the effect of the natural and pharmacologically safe molecule, caffeine, on CAF cells and their various procarcinogenic effects.

Methodology/Principal Findings

We have shown here that caffeine up-regulates the tumor suppressor proteins p16, p21, p53 and Cav-1, and reduces the expression/secretion of various cytokines (IL-6, TGF-β, SDF-1 and MMP-2), and down-regulates α-SMA. Furthermore, caffeine suppressed the migratory/invasiveness abilities of CAF cells through PTEN-dependent Akt/Erk1/2 inactivation. Moreover, caffeine reduced the paracrine pro-invasion/−migration effects of CAF cells on breast cancer cells. These results indicate that caffeine can inactivate breast stromal myofibroblasts. This has been confirmed by showing that caffeine also suppresses the paracrine pro-angiogenic effect of CAF cells through down-regulating HIF-1αand its downstream effector VEGF-A. Interestingly, these effects were sustained in absence of caffeine.

Conclusion/Significance

The present findings provide a proof of principle that breast cancer myofibroblasts can be inactivated, and thereby caffeine may provide a safe and effective prevention against breast tumor growth/recurrence through inhibition of the procarcinogenic effects of active stromal fibroblasts.

Pathway modulations and epigenetic alterations in ovarian tumorbiogenesis

Cellular pathways are numerous and are highly integrated in function in the control of cellular systems. They collectively regulate cell division, proliferation, survival and apoptosis of cells and mutagenesis of key genes that control these pathways can initiate neoplastic transformations. Understanding these pathways is crucial to future therapeutic and preventive strategies of the disease. Ovarian cancers are of three major types; epithelial, germ-cell, and stromal. However, ovarian cancers of epithelial origin, arising from the mesothelium, are the predominant form. Of the subtypes of ovarian cancer, the high-grade serous tumors are fatal, with low survival rate due to late detection and poor response to treatments. Close examination of preserved ovarian tissues and in vitro studies have provided insights into the mechanistic changes occurring in cells mediated by a few key genes. This review will focus on pathways and key genes of the pathways that are mutated or have aberrant functions in the pathology of ovarian cancer. Non-genetic mechanisms that are gaining prominence in the pathology of ovarian cancer, miRNAs and epigenetics, will also be discussed in the review.

Bmi-1-shRNA inhibits the proliferation of lung adenocarcinoma cells by blocking the G1/S phase through decreasing cyclin D1 and increasing p21/p27 levels

B lymphoma Mo-MLV insertion region 1 (Bmi-1) is highly expressed in a variety of cancers and has been shown to regulate cell proliferation. The INK4a/ARF tumor suppressor gene locus is one of the major targets of Bmi-1. In the present study, we chose two lung adenocarcinoma cell lines, A549 cells (without INK4a locus) and SPC-A1 cells (with INK4a locus), to investigate if the small hairpin RNA-mediated knockdown of Bmi-1 could inhibit the proliferation of lung adenocarcinoma cells, and to delineate the possible mechanism underlying Bmi-1 modulation of cell proliferation. We also investigated the potential pathway underlying Bmi-1 regulation of lung adenocarcinoma cell proliferation in different genetic backgrounds. To this end, we used shRNA to knockdown Bmi-1 expression in lung adenocarcinoma cells, which led to inhibition of cell growth, colony formation in vitro, and tumorigenesis in vivo. In addition, phosphorylated Akt and cyclin D1 expression were downregulated, p21 and p27 levels were upregulated, and p16 expression remained unchanged in SPC-A1 cells. These data indicate that Bmi-1 might modulate the growth of lung adenocarcinoma cells in an INK4a-p16 independent pathway.

Enrichment of ovarian cancer stem-like cells is associated with epithelial to mesenchymal transition through an miRNA-activated AKT pathway

OBJECTIVES

Evidence has indicated that ovarian epithelial cancer-type cells under serum-free culture conditions can form spheroid cells and exhibit characteristics expected of cancer stem-like cells (CSCs). However, the mechanism by which differentiated ovarian cancer cells acquire stem-cell properties during CSC enrichment has needed to be elucidated. Recent studies have demonstrated that induction of epithelial to mesenchymal transition (EMT) can generate CSCs and be associated with tumour aggressiveness and metastasis.

MATERIALS AND METHODS

Ovarian epithelial cancer cell lines, SKOV3 and HO8920, were cultured for spheroid cells and adherent cells. CSC enrichment was investigated using MTT assay, flow cytometery and qRT-PCR and expression level of PI3K/AKT pathway components was analysed by western blotting.

RESULTS

Compared to adherent cells, the spheroid cells expressed mesenchymal markers highly and exhibited significantly more motility; we also observed increases in phosphate AKT1 levels in the spheroid cells. Moreover, transfection of miR-20a or miR-200c led to corresponding reduction in endogenous PTEN protein, while AKT1 and phosphate AKT1 levels were upregulated in miRNAs-transfected cells. Finally, PI3K/AKT pathway inhibitor LY294002 reduced expressions of mesenchymal markers and stem-cell gene activity in spheroid cells, enhancing sensitivity of spheroid cells to paclitaxel treatment.

CONCLUSIONS

Our findings demonstrate that EMT contributed to enrichment of ovarian CSCs in vitro, making EMT targeting in epithelial ovarian cancer a novel therapeutic option.

Rosiglitazone amplifies the sensitivity of docetaxel and reduces the expression of CD44v6

Breast cancer seriously impairs physical and mental health in females. Currently, with further investigation into drugs, a number of new pharmacological effects have been found that offer new methods for clinical application in the treatment of breast cancer. As a widely used antidiabetic drug, rosiglitazone (Ros) has become well known for its anticancer effects, mediated by the activation of peroxisome proliferator-activated receptor γ and downregulated expression of the associated invasion gene. The objective of the present study was to investigate the combination of Ros and docetaxel (DOC) and whether DOC has any effect on breast cancer cell lines. The results showed that the combination of Ros and DOC may cooperate to increase anti-growth efficacy. The additive inhibitory effects on cell proliferation were sequence-dependent and are not likely to be associated with cell cycle arrest. This suggested that the target activation of associated factors of the signaling pathway by Ros may be a compelling ally in cancer treatment. In addition, evidence was provided for a convergence of Ros and DOC to induce the reduced expression of CD44v6. Future studies are required to confirm which associated gene of Ros is significant in blocking the signaling pathway.

Targeting the nucleolus for cancer intervention

The contribution of the nucleolus to cancer is well established with respect to its traditional role in facilitating ribosome biogenesis and proliferative capacity. More contemporary studies however, infer that nucleoli contribute a much broader role in malignant transformation. Specifically, extra-ribosomal functions of the nucleolus position it as a central integrator of cellular proliferation and stress signaling, and are emerging as important mechanisms for modulating how oncogenes and tumor suppressors operate in normal and malignant cells. The dependence of certain tumor cells to co-opt nucleolar processes to maintain their cancer phenotypes has now clearly been demonstrated by the application of small molecule inhibitors of RNA Polymerase I to block ribosomal DNA transcription and disrupt nucleolar function (Bywater et al., 2012 [1]). These drugs, which selectively kill tumor cells in vivo while sparing normal cells, have now progressed to clinical trials. It is likely that we have only just begun to scratch the surface of the potential of the nucleolus as a new target for cancer therapy, with "suppression of nucleolar stress" representing an emerging "hallmark" of cancer. This article is part of a Special Issue entitled: Role of the Nucleolus in Human Disease.

Proteomic analysis of proton beam irradiated human melanoma cells

Proton beam irradiation is a form of advanced radiotherapy providing superior distributions of a low LET radiation dose relative to that of photon therapy for the treatment of cancer. Even though this clinical treatment has been developing for several decades, the proton radiobiology critical to the optimization of proton radiotherapy is far from being understood. Proteomic changes were analyzed in human melanoma cells treated with a sublethal dose (3 Gy) of proton beam irradiation. The results were compared with untreated cells. Two-dimensional electrophoresis was performed with mass spectrometry to identify the proteins. At the dose of 3 Gy a minimal slowdown in proliferation rate was seen, as well as some DNA damage. After allowing time for damage repair, the proteomic analysis was performed. In total 17 protein levels were found to significantly (more than 1.5 times) change: 4 downregulated and 13 upregulated. Functionally, they represent four categories: (i) DNA repair and RNA regulation (VCP, MVP, STRAP, FAB-2, Lamine A/C, GAPDH), (ii) cell survival and stress response (STRAP, MCM7, Annexin 7, MVP, Caprin-1, PDCD6, VCP, HSP70), (iii) cell metabolism (TIM, GAPDH, VCP), and (iv) cytoskeleton and motility (Moesin, Actinin 4, FAB-2, Vimentin, Annexin 7, Lamine A/C, Lamine B). A substantial decrease (2.3 x) was seen in the level of vimentin, a marker of epithelial to mesenchymal transition and the metastatic properties of melanoma.

Thioridazine induces apoptosis by targeting the PI3K/Akt/mTOR pathway in cervical and endometrial cancer cells

Recently, thioridazine (10-[2-(1-methyl-2-piperidyl) ethyl]-2-methylthiophenothiazine), a well-known anti-psychotic agent was found to have anti-cancer activity in cancer cells. However, the molecular mechanism of the agent in cellular signal pathways has not been well defined. Thioridazine significantly increased early- and late-stage apoptotic fraction in cervical and endometrial cancer cells, suggesting that suppression of cell growth by thioridazine was due to the induction of apoptosis. Cell cycle analysis indicated thioridazine induced the down-regulation of cyclin D1, cyclin A and CDK4, and the induction of p21 and p27, a cyclin-dependent kinase inhibitor. Additionally, we compared the influence of thioridazine with cisplatin used as a control, and similar patterns between the two drugs were observed in cervical and endometrial cancer cell lines. Furthermore, as expected, thioridazine successfully inhibited phosphorylation of Akt, phosphorylation of 4E-BP1 and phosphorylation of p70S6K, which is one of the best characterized targets of the mTOR complex cascade. These results suggest that thioridazine effectively suppresses tumor growth activity by targeting the PI3K/Akt/mTOR/p70S6K signaling pathway.

PTEN increases autophagy and inhibits the ubiquitin-proteasome pathway in glioma cells independently of its lipid phosphatase activity

Two major mechanisms of intracellular protein degradation, autophagy and the ubiquitin-proteasome pathway, operate in mammalian cells. PTEN, which is frequently mutated in glioblastomas, is a tumor suppressor gene that encodes a dual specificity phosphatase that antagonizes the phosphatidylinositol 3-kinase class I/AKT/mTOR pathway, which is a key regulator of autophagy. Here, we investigated in U87MG human glioma cells the role of PTEN in the regulation of autophagy and the ubiquitin-proteasome pathway, because both are functionally linked and are relevant in cancer progression. Since U87MG glioma cells lack a functional PTEN, we used stable clones that express, under the control of a tetracycline-inducible system (Tet-on), wild-type PTEN and two of its mutants, G129E-PTEN and C124S-PTEN, which, respectively, lack the lipid phosphatase activity only and both the lipid and the protein phosphatase activities of this protein. Expression of PTEN in U87MG glioma cells decreased proteasome activity and also reduced protein ubiquitination. On the contrary, expression of PTEN increased the autophagic flux and the lysosomal mass. Interestingly, and although PTEN negatively regulates the phosphatidylinositol 3-kinase class I/AKT/mTOR signaling pathway by its lipid phosphatase activity, both effects in U87MG cells were independent of this activity. These results suggest a new mTOR-independent signaling pathway by which PTEN can regulate in opposite directions the main mechanisms of intracellular protein degradation.

The microRNA networks of TGFβ signaling in cancer

In metazoans, the transforming growth factor β (TGFβ) signaling regulates a host of activities ranging from embryonic development to tissue homeostasis. The normal as well as tumor cells respond to this cytokine signaling pathway in a highly context-dependent manner. It acts as a potent tumor suppressor initially by inducing cell cycle arrest and apoptosis. But advanced tumors often misuse TGFβ signaling for tumor progression by selectively disabling the tumor suppressor arm and using other properties of TGFβ signaling such as induction of angiogenesis, epithelial to mesenchymal transition, and metastases. This dual role of TGFβ in cancer remained a mystery until recently. But recent advances in the field of microRNA provided a deeper understanding about this dual nature of TGFβ signaling in cancers. In the present review, we present an account of the role of microRNAs in deregulating TGFβ signaling and modulating cancer cell behavior during tumor initiation and cancer progression. This review also includes a discussion on the recent advances in the deregulation of TGFβ signaling in carcinogenesis.

Down-regulation of PTEN expression modulated by dysregulated miR-21 contributes to the progression of esophageal cancer

BACKGROUND AND AIM

miR-21, a putative tumor oncomiR, is a frequently overexpressed miRNA in a variety of tumors. Because it targets tumor-suppressor genes it has been linked to tumor progression. In this study we investigated the role of miR-21 in esophageal squamous cell carcinoma (ESCC), and its possible mechanism.

METHODS

Expression of miR-21 was detected by stem-loop RT-PCR in tissue from 76 invasive ESCC at stage I-IV and in their corresponding para-cancerous histological normal tissues (PCHNT). Thirty endoscopic esophageal mucosal biopsy specimens from non-tumor patients were used as controls. Expression of PTEN in 76 paired ESCC and PCHNT was investigated by real-time RT-PCR and an immunohistochemical method, respectively. Paired tumor and PCHNT specimens of 20 ESCC cases were randomly selected for western blot analysis. The effect of miR-21 on PTEN expression was assessed in the ESCC cell line with an miR-21 inhibitor to reduce miR-21 expression. Furthermore, the roles of miR-21 in cell biology were analyzed by use of miR-21 inhibitor-transfected cells.

RESULTS

Stem-loop RT-PCR revealed miR-21 was significantly overexpressed in ESCC tissues and cell lines. Overexpression of miR-21 correlated with tumor status, lymph node metastasis, and clinical stage. We demonstrated that knockdown of miR-21 significantly increased expression of PTEN protein. Consequent PTEN expression reduced cell proliferation, invasion, and migration.

CONCLUSIONS

Our findings suggest that miR-21 could be a potential oncomiR, probably by regulation of PTEN, and a novel prognostic factor for ESCC patients.

Decrease of apoptosis markers during adipogenic differentiation of mesenchymal stem cells from human adipose tissue

Although the proliferation and differentiation of mesenchymal stem cells (MSCs) from adipose tissue (AT) have been widely studied, relatively little information is available on the underlying mechanism of apoptosis during the adipogenic differentiation. Thus, the aim of this study was to analyze how the expression of some apoptotic markers is affected by in vitro expansion during adipogenic differentiation of AT-MSCs. The cultures incubated or not with adipogenic medium were investigated by Western blot at 7, 14, 21, and 28 days for the production of p53, AKT, pAKT, Bax, PDCD4 and PTEN. MSCs were recognized for their immunoreactivity to MSC-specific cell types markers by immunocytochemical procedure. The effectiveness of adipogenic differentiation was assessed by staining with Sudan III and examination of adipogenic markers expression, such as PPAR-γ and FABP, at different time points by Western blot. The adipogenic differentiation medium led to the appearance, after 7 days, of larger rounded cells presenting numerous vacuoles containing lipids in which it was evident a red-orange staining, that increased in size in a time-dependent manner, parallel to an increase of the levels of expression of PPAR-γ and FABP. More than 50 % of human MSCs were fully differentiated into adipocytes within the four-week induction period. The results showed that during adipogenic differentiation of AT-MSCs the PI3K/AKT signaling pathway is activated and that p53, PTEN, PDCD4, and Bax proteins are down-regulated in time-dependent manner. Our data provide new information on the behavior of some apoptotic markers during adipogenic differentiation of AT-MSCs to apply for tissues repair and regeneration.

p34 is a novel regulator of the oncogenic behavior of NEDD4-1 and PTEN

PTEN is one of the most frequently mutated or deleted tumor suppressors in human cancers. NEDD4-1 was recently identified as the E3 ubiquitin ligase for PTEN; however, a number of important questions remain regarding the role of ubiquitination in regulating PTEN function and the mechanisms by which PTEN ubiquitination is regulated. In the present study, we demonstrated that p34, which was identified as a binding partner of NEDD4-1, controls PTEN ubiquitination by regulating NEDD4-1 protein stability. p34 interacts with the WW1 domain of NEDD4-1, an interaction that enhances NEDD4-1 stability. Expression of p34 promotes PTEN poly-ubiquitination, leading to PTEN protein degradation, whereas p34 knockdown results in PTEN mono-ubiquitination. Notably, an inverse correlation between PTEN and p34/NEDD4-1 levels was confirmed in tumor samples from colon cancer patients. Thus, p34 acts as a key regulator of the oncogenic behavior of NEDD4-1 and PTEN.

Evaluation of expression of the PTEN gene, oestrogen and progesterone receptors as diagnostic and predictive factors in endometrial cancer

Endometrial cancer belongs to the commonest malignancy in females after breast cancer, malignant neoplasm of female genitals in Europe and North America but there is still not significant improvement as far as the curability of this neoplasm is concerned, especially its advanced forms. That is why there is need to define new factors that could be not only diagnostic but also predictve factors. In present study we analyzed the mRNA PTEN expression by quantitative real-time polymerase chain reaction (Q-PCR) in 123 women of endometrial carcinoma and 14 women of control group. Moreover we assessed oestrogen (ER) and progesterone receptors (PgR) in all cases. We defined the correlation between expression of PTEN gene and receptors and between PTEN expression and maturity grade of cancer. Neoplasm advancement grade G1 was diagnosed in 82.11 % of patients (n = 101), G2 in 9.76 % of patients (n = 12) and G3 in 8.13 % of patients (n = 10). Presence of ER and PgR and decreased expression of PTEN gene was found in majority of patients with endometrial cancer (79.12 % and 59.34 % respectively) and the most numerous group was with weak expression of ER and strong expression of PgR. There was no statistically significant difference in gene expression depending on receptors expression nor maturity grade of cancer (p > 0.05). Evaluation of expression of PTEN gene may turn out to be a very useful tool aimed at qualifying patients for different therapies of endometrial cancer and at searching of new diagnostic and therapeutic methods of this cancer independently on its receptor status nor maturity grade of cancer.

Towards the small and the beautiful: a small dibromotyrosine derivative from Pseudoceratina sp. sponge exhibits potent apoptotic effect through targeting IKK/NFκB signaling pathway

A dibromotyrosine derivative, (1'R,5'S,6'S)-2-(3',5'-dibromo-1',6'-dihydroxy-4'-oxocyclohex-2'-enyl) acetonitrile (DT), was isolated from the sponge Pseudoceratina sp., and was found to exhibit a significant cytotoxic activity against leukemia K562 cells. Despite the large number of the isolated bromotyrosine derivatives, studies focusing on their biological mechanism of action are scarce. In the current study we designed a set of experiments to reveal the underlying mechanism of DT cytotoxic activity against K562 cells. First, the results of MTT cytotoxic and the annexin V-FITC/PI apoptotic assays, indicated that the DT cytotoxic activity is mediated through induction of apoptosis. This effect was also supported by caspases-3 and -9 activation as well as PARP cleavage. DT induced generation of reactive oxygen species (ROS) and the disruption of mitochondrial membrane potential (MMP) as indicated by flow cytometric assay. The involvement of ROS generation in the apoptotic activity of DT was further corroborated by the pretreatment of K562 cells with N-acetyl-cysteine (NAC), a ROS scavenger, which prevented apoptosis and the disruption of MMP induced by DT. Results of cell-free system assay suggested that DT can act as a topoisomerase II catalytic inhibitor, unlike the clinical anticancer drug, etoposide, which acts as a topoisomerase poison. Additionally, we found that DT treatment can block IKK/NFκB pathway and activate PI3K/Akt pathway. These findings suggest that the cytotoxic effect of DT is associated with mitochondrial dysfunction-dependent apoptosis which is mediated through oxidative stress. Therefore, DT represents an interesting reference point for the development of new cytotoxic agent targeting IKK/NFκB pathway.

Attempted application of bioengineered/biosynthetic supporting matrices with phosphatidylinositol-trisphosphate-enhancing substances to organ culture of human primordial follicles

PURPOSE

To improve human primordial follicle culture.

METHODS

Thin or thick ovarian slices were cultured on alginate scaffolds or in PEG-fibrinogen hydrogels with or without bpV (pic), which prevents the conversion of phosphatidylinositol-trisphosphate (PIP3) to phosphatidylinositol-bisphosphate (PIP2) or 740Y-P which converts PIP2 to PIP3. Follicular growth was evaluated by follicular counts, Ki67 immunohistochemistry, and 17β-estradiol (E2) levels.

RESULTS

BpV (pic) had a destructive effect on cultured follicles. Thawed-uncultured samples had more primordial follicles than samples cultured in basic medium and fewer developing follicles than samples cultured in PEG-fibrinogen hydrogels with 740Y-P. There were more atretic follicles in samples cultured on alginate scaffolds than in PEG-fibrinogen hydrogels, and in samples cultured in PEG-fibrinogen hydrogels with 740Y-P than in PEG-fibrinogen hydrogels with basic medium. Ki67 staining was higher in PEG-fibrinogen hydrogels than on alginate scaffolds. E2 levels were higher in thick than in thin slices.

CONCLUSIONS

PEG-fibrinogen hydrogels appear to have an advantage over alginate scaffolds for culturing human primordial follicles. Folliculogenesis is not increased in the presence of substances that enhance PIP3 production or with thin rather than thick sectioning.

The anti-chemoresistant effect and mechanism of MUC1 aptamer-miR-29b chimera in ovarian cancer

OBJECTIVE

Currently, there are no effective therapies for advanced ovarian cancer. In this study, we aim to determine the anti-tumor effect of MUC1 aptamer-miR-29b chimera in xenograft ovarian cancer models and chemo-resistance tumor model and to further explore the associated mechanism.

METHODS

Xenograft ovarian cancer animal models were established using OVCAR-3, OVCA420, and OVCAR-3-Taxol cancer cells. The chimera (Chi-29b) was delivered through intraperitoneal injections. Tumor growth was evaluated. Gene expression and PTEN methylation were measured.

RESULTS

We demonstrated that intratumoral injection of Chi-29b chimera significantly inhibited the growth of xenograft OVCAR-3 tumors through downregulating PTEN methylation, subsequent PTEN expression, as well as downregulating MAPK 4 and IGF1 expressions. In contrast, Chi-29b inhibited tumor growth in OVCA420 tumors by downregulating MAPK 4 & 10 and IGF1 expression without affecting PTEN expression. Intraperitoneal injection of Chi-29b significantly increased apoptosis in paclitaxel-resistant OVCAR-3 cells and inhibited the growth of xenograft OVCAR-3-Taxol tumors. The anti-chemoresistant role of Chi-29b in OVCAR-3-Taxol tumors was associated with the activation of PTEN signaling and downregulation of MAPK 4 and 10 and IGF1 expression.

CONCLUSION

Our study indicated that Chi-29b chimera can effectively exert an anti-tumor effect in xenograft tumor models and an anti-chemoresistant role through inhibiting cancer stem cell activation.

PAS kinase as a nutrient sensor in neuroblastoma and hypothalamic cells required for the normal expression and activity of other cellular nutrient and energy sensors

PAS kinase (PASK) is a nutrient sensor that is highly conserved throughout evolution. PASK-deficient mice reveal a metabolic phenotype similar to that described in S6 kinase-1 S6K1-deficient mice that are protected against obesity. Hypothalamic metabolic sensors, such as AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR), play an important role in feeding behavior, the homeostasis of body weight, and energy balance. These sensors respond to changes in nutrient levels in the hypothalamic areas involved in feeding behavior and in neuroblastoma N2A cells, and we have recently reported that those effects are modulated by the anorexigenic peptide glucagon-like peptide-1 (GLP-1). Here, we identified PASK in both N2A cells and rat VMH and LH areas and found that its expression is regulated by glucose and GLP-1. High levels of glucose decreased Pask gene expression. Furthermore, PASK-silenced N2A cells record an impaired response by the AMPK and mTOR/S6K1 pathways to changes in glucose levels. Likewise, GLP-1 effect on the activity of AMPK, S6K1, and other intermediaries of both pathways and the regulatory role at the level of gene expression were also blocked in PASK-silenced cells. The absence of response to low glucose concentrations in PASK-silenced cells correlates with increased ATP content, low expression of mRNA coding for AMPK upstream kinase LKB1, and enhanced activation of S6K1. Our findings indicate that, at least in N2A cells, PASK is a key kinase in GLP-1 actions and exerts a coordinated response with the other metabolic sensors, suggesting that PASK might play an important role in feeding behavior.

MicroRNA-21 suppresses PTEN and hSulf-1 expression and promotes hepatocellular carcinoma progression through AKT/ERK pathways

MicroRNAs (miRNAs) have been believed to associate with malignant progression including cancer cell proliferation, apoptosis, differentiation, angiogenesis, invasion and metastasis. However, the functions of miRNAs are intricate, one miRNA can directly or indirectly target multiple genes and function as oncogene or tumor suppressor gene. In this study, we found that miR-21 inhibits PTEN and human sulfatase-1 (hSulf-1) expression in hepatocellular carcinoma (HCC) cells. The hSulf-1 is a heparin-degrading endosulfatase, which can inhibit the heparin binding growth factor-mediated signaling transduction into cells. Therefore, miR-21-mediated suppression of both hSulf-1 and PTEN led to activation of AKT/ERK pathways and epithelial-mesenchymal transition (EMT) in HCC cells, and finally enhance the activity of HCC cell proliferation and movement and promote HCC xenograft tumor growth in mouse models. These findings may provide candidate targets for prevention and treatment of HCC.

Monitoring the development of xenograft triple-negative breast cancer models using diffusion-weighted magnetic resonance imaging

Evaluations of tumor growth rates and molecular biomarkers are traditionally used to assess new mouse models of human breast cancers. This study investigated the utility of diffusion weighted (DW)-magnetic resonance imaging (MRI) for evaluating cellular proliferation of new tumor models of triple-negative breast cancer, which may augment traditional analysis methods. Eleven human breast cancer cell lines were used to develop xenograft tumors in severe combined immunodeficient mice, with two of these cell lines exhibiting sufficient growth to be serially passaged. DW-MRI was performed to measure the distributions of the apparent diffusion coefficient (ADC) in these two tumor xenograft models, which showed a correlation with tumor growth rates and doubling times during each passage. The distributions of the ADC values were also correlated with expression of Ki67, a biomarker of cell proliferation, and hypoxia inducible factor (HIF)-1α and vascular endothelial growth factor receptor-2 (VEGFR2), which are essential proteins involved in regulating aerobic glycolysis and angiogenesis that support tumor cell proliferation. Although phosphatase and tensin homolog (PTEN) levels were different between the two xenograft models, AKT levels did not differ nor did they correlate with tumor growth. This last result demonstrates the complexity of signaling protein pathways and the difficulty in interpreting the effects of protein expression on tumor cell proliferation. In contrast, DW-MRI may be a more direct assessment of tumor growth and cancer cell proliferation.

Inhibition of 72 kDa inositol polyphosphate 5-phosphatase E improves insulin signal transduction in diet-induced obesity

The 72 kDa inositol polyphosphate 5-phosphatase E (72k-5ptase) controls signal transduction through the catalytic dephosphorylation of the 5-position of membrane-bound phosphoinositides. The reduction of 72k-5ptase expression in the hypothalamus results in improved hypothalamic insulin signal transduction and reduction of food intake and body mass. Here, we evaluated the tissue distribution and the impact of obesity on the expression of 72k-5ptase in peripheral tissues of experimental animals. In addition, insulin signal transduction and action were determined in an animal model of obesity and insulin resistance treated with an antisense (AS) oligonucleotide that reduces 72k-5ptase expression. In lean Wistar rats, 72k-5ptase mRNA and protein are found in highest levels in heart, skeletal muscle, and white adipose tissue. In three distinct models of obesity, Wistar rats, Swiss mice fed on high-fat diet, and leptin-deficient ob/ob mice, the expression of 72k-5ptase is increased in skeletal muscle and adipose tissue. The treatment of obese Wistar rats with an anti-72k-5ptase AS oligonucleotide results in significant reduction of 72k-5ptase catalytic activity, which is accompanied by reduced food intake and body mass and improved insulin signal transduction and action as determined by immunoblotting and clamp studies respectively. 72k-5ptase expression is increased in obesity and its AS inhibition resulted in a significant improvement in insulin signal transduction and restoration of glucose homeostasis.

Genetic deregulation of the PIK3CA oncogene in oral cancer

The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway is one of the most commonly deregulated pathways in human cancers. PI3K comprises a catalytic (p110α) and regulatory subunit (p85), and p110α is encoded by the PIK3CA gene. Here, we summarize the known genetic alterations, including amplifications and mutations, of the PIK3CA oncogene in oral cancer. We discuss in detail PIK3CA mutations and their mutual exclusivity with pathway genes in addition to the incidence of PIK3CA mutations in relation to ethnicity. We describe the constitutive activation of PI3K signaling, oncogenicity, and the genetic deregulation of the PIK3CA gene and its association with oral cancer disease stage. We emphasize the importance of therapeutically targeting the genetically deregulated PIK3CA oncogene and its signaling. We also discuss the implications of targeting Akt and/or mTOR, which are the downstream effectors of PI3K that may possibly pave the way for molecular therapeutic targets for PIK3CA-driven oral carcinogenesis. Furthermore, this critical review provides a complete picture of the PIK3CA oncogene and its deregulation in oral cancer, which may facilitate early diagnosis and improve prognosis through personalized molecular targeted therapy in oral cancer.

PI3K/Akt and Stat3 signaling regulated by PTEN control of the cancer stem cell population, proliferation and senescence in a glioblastoma cell line

Malignant gliomas are the most common primary brain tumor in adults. A number of genes have been implicated in glioblastoma including mutation and deletion of PTEN. PTEN is a regulator of PI3K-mediated Akt signaling pathways and has been recognized as a therapeutic target in glioblastoma. To achieve potent therapeutic inhibition of the PI3K-Akt pathway in glioblastoma, it is essential to understand the interplay between the regulators of its activation. Here, ectopic expression of PTEN in the U-87MG human glioblastoma-astrocytoma cell line is shown to result in the depletion of glioblastoma stem cells (GSCs) and to cause growth retardation and senescence. These effects are likely to be associated with PTEN-mediated cooperative perturbation of Akt and Stat3 signals. Using an in vivo rat model of glioblastoma, we showed that PTEN-overexpressing U-87MG cells failed to induce tumor formation, while untreated U-87MG cells did so. Furthermore, cells expressing the phosphorylated form of Stat3 were completely absent from the brain of rats implanted with PTEN-overexpressing U-87MG cells. Based on these results, PTEN appears to function as a crucial inhibitor of GSCs and as an inducer of senescence, suggesting that functional enhancement of the PTEN pathway will be useful to provide a therapeutic strategy for targeting glioblastoma.

Redox-sensitive oxidation and phosphorylation of PTEN contribute to enhanced activation of PI3K/Akt signaling in rostral ventrolateral medulla and neurogenic hypertension in spontaneously hypertensive rats

AIMS

The activity of phosphoinositide 3-kinase (PI3K)/serine/threonine protein kinase (Akt) is enhanced under hypertension. The phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a negative regulator of PI3K signaling, and its activity is redox-sensitive. In the rostral ventrolateral medulla (RVLM), which is responsible for the maintenance of blood pressure, oxidative stress plays a pivotal role in neurogenic hypertension. The present study evaluated the hypothesis that redox-sensitive inactivation of PTEN results in enhanced PI3K/Akt signaling in RVLM, leading to neurogenic hypertension.

RESULTS

Compared to age-matched normotensive Wistar-Kyoto (WKY) rats, PTEN inactivation in the form of oxidation and phosphorylation were greater in RVLM of spontaneously hypertensive rats (SHR). PTEN inactivation was accompanied by augmented PI3K activity and PI3K/Akt signaling, as reflected by the increase in phosphorylation of Akt and mammalian target of rapamycin. Intracisternal infusion of tempol or microinjection into the bilateral RVLM of adenovirus encoding superoxide dismutase significantly antagonized the PTEN inactivation and blunted the enhanced PI3K/Akt signaling in SHR. Gene transfer of PTEN to RVLM in SHR also abrogated the enhanced Akt activation and promoted antihypertension. Silencing PTEN expression in RVLM with small-interfering RNA, on the other hand, augmented PI3K/Akt signaling and promoted long-term pressor response in normotensive WKY rats.

INNOVATION

The present study demonstrated for the first time that the redox-sensitive check-and-balance process between PTEN and PI3K/Akt signaling is engaged in the pathogenesis of hypertension.

CONCLUSION

We conclude that an aberrant interplay between the redox-sensitive PTEN and PI3k/Akt signaling in RVLM underpins neural mechanism of hypertension.

Altered Ca(2+) signaling in cancer cells: proto-oncogenes and tumor suppressors targeting IP3 receptors

Proto-oncogenes and tumor suppressors critically control cell-fate decisions like cell survival, adaptation and death. These processes are regulated by Ca(2+) signals arising from the endoplasmic reticulum, which at distinct sites is in close proximity to the mitochondria. These organelles are linked by different mechanisms, including Ca(2+)-transport mechanisms involving the inositol 1,4,5-trisphosphate receptor (IP3R) and the voltage-dependent anion channel (VDAC). The amount of Ca(2+) transfer from the endoplasmic reticulum to mitochondria determines the susceptibility of cells to apoptotic stimuli. Suppressing the transfer of Ca(2+) from the endoplasmic reticulum to the mitochondria increases the apoptotic resistance of cells and may decrease the cellular responsiveness to apoptotic signaling in response to cellular damage or alterations. This can result in the survival, growth and proliferation of cells with oncogenic features. Clearly, proper maintenance of endoplasmic reticulum Ca(2+) homeostasis and dynamics including its links with the mitochondrial network is essential to detect and eliminate altered cells with oncogenic features through the apoptotic pathway. Proto-oncogenes and tumor suppressors exploit the central role of Ca(2+) signaling by targeting the IP3R. There are an increasing number of reports showing that activation of proto-oncogenes or inactivation of tumor suppressors directly affects IP3R function and endoplasmic reticulum Ca(2+) homeostasis, thereby decreasing mitochondrial Ca(2+) uptake and mitochondrial outer membrane permeabilization. In this review, we provide an overview of the current knowledge on the proto-oncogenes and tumor suppressors identified as IP3R-regulatory proteins and how they affect endoplasmic reticulum Ca(2+) homeostasis and dynamics.

PTEN/Akt signaling controls mitochondrial respiratory capacity through 4E-BP1

Akt, a serine/threonine kinase has been shown to stimulate glycolysis in cancer cells but its role in mitochondrial respiration is unknown. Using PTEN-knockout mouse embryonic fibroblasts (MEF^PTEN−/−) with hyper-activated Akt as a cell model, we observed a higher respiratory capacity in MEF^PTEN−/− compared to the wildtype (MEF^WT). The respiratory phenotype observed in MEF^PTEN−/− was reproduced in MEF^WT by gene silencing of PTEN which substantiated its role in regulating mitochondrial function. The increased activities of the respiratory complexes (RCs) I, III and IV were retained in the same relative proportions as those present in MEF^WT, alluding to a possible co-ordinated regulation by PTEN/Akt. Using LY294002 (a PI3K inhibitor) and Akt inhibitor IV, we showed that the regulation of enzyme activities and protein expressions of the RCs was dependent on PI3K/Akt. There was insignificant difference in the protein expressions of mitochondrial transcription factor: peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and its downstream targets, the nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (mtTFA) between MEF^PTEN−/− and MEF^WT. Similarly, mRNA levels of the same subunits of the RCs detected in Western blots were not significantly different between MEF^PTEN−/− and MEF^WT suggesting that the regulation by Akt on mitochondrial function was probably not via gene transcription. On the other hand, a decrease of total 4E-BP1 with a higher expression of its phosphorylated form relative to total 4E-BP1 was found in MEF^PTEN−/−, which inferred that the regulation of mitochondrial respiratory activities by Akt was in part through this protein translation pathway. Notably, gene silencing of 4E-BP1 up-regulated the protein expressions of all RCs and the action of 4E-BP1 appeared to be specific to these mitochondrial proteins. In conclusion, PTEN inactivation bestowed a bioenergetic advantage to the cells by up-regulating mitochondrial respiratory capacity through the 4E-BP1-mediated protein translation pathway.

Loss of heterozygosity at tumor suppressor genes detectable on fractionated circulating cell-free tumor DNA as indicator of breast cancer progression

PURPOSE

LOH on circulating DNA may provide tumor-specific information on breast cancer. As identification of LOH on cell-free DNA is impeded by the prevalence of wild type DNA in blood of cancer patients, we fractionated plasma DNA, and determined the diagnostic and prognostic value of both fractions.

EXPERIMENTAL DESIGN

Our cohort of 388 patients with primary breast cancer before chemotherapy was selected from a multicenter study (SUCCESS). Postoperative plasma was fractionated in low- and high-molecular weight DNA by two different column systems. In both fractions, LOH was determined by a PCR-based microsatellite analysis using a panel of 8 polymorphic markers. Circulating tumor DNA in plasma from 30 patients after chemotherapy was additionally analyzed. The significance levels were adjusted for multiple comparisons.

RESULTS

More patients (38%) had LOH at all markers in the fraction containing short DNA fragments than in the fraction containing the long DNA molecules (28%, P = 0.0001). In both fractions 32.85% of LOH were concordant. LOH at the markers D3S1605, D10S1765, D12S1725, D13S218, and D17S855 significantly correlated with tumor stage, tumor size, and lymph node metastasis, positive progesterone, and HER2 receptor status. Most importantly, LOH at D12S1725 mapping to cyclin D2 correlated with shorter overall survival (P = 0.004).

CONCLUSIONS

The improved detection of LOH on cell-free DNA provides important information on DNA losses of tumor suppressor genes TIG1, PTEN, cyclin D2, RB1, and BRCA1 in breast cancer. In particular, loss of the cyclin D2 gene might become an important prognostic marker easily detectable in the peripheral blood.

miR-1297 mediates PTEN expression and contributes to cell progression in LSCC

MicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression after transcription, and are involved in cancer development. Laryngeal squamous cell carcinoma (LSCC) is one of the most common malignant neoplasms with increasing incidence in recent years. In this paper, we report the overexpression of miR-1297 in LSCC and Hep-2 cells. In addition, PTEN was identified to be directly regulated by miR-1297 through western blot and luciferase activity assay. Furthermore, downregulation of miR-1297 in Hep-2 cells was shown to inhibit cancer cell proliferation, migration, and tumor genesis. Our results document a new epigenetic mechanism for PTEN regulation in LSCC, which is crucial for the development of these tumors.

Phenotype selection reveals coevolution of muscle glycogen and protein and PTEN as a gate keeper for the accretion of muscle mass in adult female mice

We have investigated molecular mechanisms for muscle mass accretion in a non-inbred mouse model (DU6P mice) characterized by extreme muscle mass. This extreme muscle mass was developed during 138 generations of phenotype selection for high protein content. Due to the repeated trait selection a complex setting of different mechanisms was expected to be enriched during the selection experiment. In muscle from 29-week female DU6P mice we have identified robust increases of protein kinase B activation (AKT, Ser-473, up to 2-fold) if compared to 11- and 54-week DU6P mice or controls. While a number of accepted effectors of AKT activation, including IGF-I, IGF-II, insulin/IGF-receptor, myostatin or integrin-linked kinase (ILK), were not correlated with this increase, phosphatase and tensin homologue deleted on chromosome 10 (PTEN) was down-regulated in 29-week female DU6P mice. In addition, higher levels of PTEN phosphorylation were found identifying a second mechanism of PTEN inhibition. Inhibition of PTEN and activation of AKT correlated with specific activation of p70S6 kinase and ribosomal protein S6, reduced phosphorylation of eukaryotic initiation factor 2α (eIF2α) and higher rates of protein synthesis in 29-week female DU6P mice. On the other hand, AKT activation also translated into specific inactivation of glycogen synthase kinase 3ß (GSK3ß) and an increase of muscular glycogen. In muscles from 29-week female DU6P mice a significant increase of protein/DNA was identified, which was not due to a reduction of protein breakdown or to specific increases of translation initiation. Instead our data support the conclusion that a higher rate of protein translation is contributing to the higher muscle mass in mid-aged female DU6P mice. Our results further reveal coevolution of high protein and high glycogen content during the selection experiment and identify PTEN as gate keeper for muscle mass in mid-aged female DU6P mice.

Antagonism of miR-21 reverses epithelial-mesenchymal transition and cancer stem cell phenotype through AKT/ERK1/2 inactivation by targeting PTEN

Background

Accumulating evidence suggested that epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) characteristics, both of which contribute to tumor invasion and metastasis, are interrelated with miR-21. MiR-21 is one of the important microRNAs associated with tumor progression and metastasis, but the molecular mechanisms underlying EMT and CSC phenotype during miR-21 contributes to migration and invasion of breast cancer cells remain to be elucidated.

Methodology/Principal Findings

In this study, MDA-MB-231/anti-miR-21 cells were established by transfected hsa-miR-21 antagomir into breast cancer MDA-MB-231 cells. EMT was evaluated by the changes of mesenchymal cell markers (N-cadherin, Vimentin, and alpha-SMA), epithelial cell marker (E-cadherin), as well as capacities of cell migration and invasion; CSC phenotype was measured using the changes of CSC surface markers (ALDH1 and CD44), and the capacity of sphereforming (mammospheres). We found that antagonism of miR-21 reversed EMT and CSC phenotype, accompanied with PTEN up-regulation and AKT/ERK1/2 inactivation. Interestingly, down-regulation of PTEN by siPTEN suppressed the effects of miR-21 antagomir on EMT and CSC phenotype, confirming that PTEN is a target of miR-21 in reversing EMT and CSC phenotype. The inhibitors of PI3K-AKT and ERK1/2 pathways, LY294002 and U0126, both significantly suppressed EMT and CSC phenotype, indicating that AKT and ERK1/2 pathways are required for miR-21 mediating EMT and CSC phenotype.

Conclusions/Significance

In conclusion, our results demonstrated that antagonism of miR-21 reverses EMT and CSC phenotype through targeting PTEN, via inactivation of AKT and ERK1/2 pathways, and showed a novel mechanism of which might relieve the malignant biological behaviors of breast cancer.