High cancer susceptibility and embryonic lethality associated with mutation of the PTEN tumor suppressor gene in mice

B Cell Aberrance in Lupus: the Ringleader and the Solution

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease with high heterogeneity but the common characterization of numerous autoantibodies and systemic inflammation which lead to the damage of multiple organs. Aberrance of B cells plays a pivotal role in the immunopathogenesis of SLE via both antibody-dependent and antibody-independent manners. Escape of autoreactive B cells from the central and peripheral tolerance checkpoints, over-activation of B cells and their excessive cytokines release which drive T cells and dendritic cells stimulation, and dysregulated surface molecules, as well as intracellular signal pathways involved in B cell biology, are all contributing to B cell aberrance and participating in the pathogenesis of SLE. Based on that rationale, targeting aberrance of B cells and relevant molecules and pathways is expected to be a promising strategy for lupus control. Multiple approaches targeting B cells through different mechanisms have been attempted, including B-cell depletion via monoclonal antibodies against B-cell-specific molecules, blockade of B-cell survival and activation factors, suppressing T-B crosstalk by interrupting costimulatory molecules and inhibiting intracellular activation signaling cascade by targeting pathway molecules in B cells. Though most attempts ended in failure, the efficacy of B-cell targeting has been encouraged by the FDA approval of belimumab that blocks B cell-activating factor (BAFF) and the recommended use of anti-CD20 as a remedial therapy in refractory lupus. Still, quantities of clinical trials targeting B cells or relevant molecules are ongoing and some of them have displayed promising preliminary results. Additionally, advances in multi-omics studies help deepen our understandings of B cell biology in lupus and may promote the discovery of novel potential therapeutic targets. The combination of real-world data with basic research achievements may pave the road to conquering lupus.

Targeting the Dysfunctional Placenta to Improve Pregnancy Outcomes Based on Lessons Learned in Cancer

In recent decades, our understanding of the disrupted mechanisms that contribute to major obstetrical diseases, including preeclampsia, fetal growth restriction, preterm birth, and gestational diabetes, has increased exponentially. Common to many of these obstetric diseases is placental maldevelopment and dysfunction; the placenta is a significant component of the maternal-fetal interface involved in coordinating, facilitating, and regulating maternal and fetal nutrient, oxygen and waste exchange, and hormone and cytokine production. Despite the advances in our understanding of placental development and function, there are currently no treatments for placental maldevelopment and dysfunction. However, given the transient nature and accessibility from the maternal circulation, the placenta offers a unique opportunity to develop targeted therapeutics for routine obstetric practices. Furthermore, given the similar developmental paradigms between the placenta and cancer, there is an opportunity to appropriate current knowledge from advances in targeted therapeutics in cancer treatments. In this review, we highlight the similarities between early placental development and cancer and introduce a number of targeted therapies currently being explored in cancer and pregnancy. We also propose a number of new effectors currently being targeted in cancer research that have the potential to be targeted in the development of treatments for pregnancy complications. Finally, we describe a method for targeting the placenta using nonviral polymers that are capable of delivering plasmids, small interfering RNA, and other effector nucleic acids, which could ultimately improve fetal and maternal outcomes from complicated pregnancies.

BAP1 suppresses prostate cancer progression by deubiquitinating and stabilizing PTEN

Deubiquitinase BAP1 is an important tumor suppressor in several malignancies, but its functions and critical substrates in prostate cancer (PCa) remain unclear. Here, we report that the mRNA and protein expression levels of BAP1 are downregulated in clinical PCa specimens. BAP1 can physically bind to and deubiquitinate PTEN, which inhibits the ubiquitination-mediated degradation of PTEN and thus stabilizes PTEN protein. Ectopically expressed BAP1 in PCa cells increases PTEN protein level and subsequently inhibits the AKT signaling pathway, thus suppressing PCa progression. Conversely, knockdown of BAP1 in PCa cells leads to the decrease in PTEN protein level and the activation of the Akt signaling pathway, therefore promoting malignant transformation and cancer metastasis. However, these can be reversed by the re-expression of PTEN. More importantly, we found that BAP1 protein level positively correlates with PTEN in a substantial fraction of human cancers. These findings demonstrate that BAP1 is an important deubiquitinase of PTEN for its stability and the BAP1-PTEN signaling axis plays a crucial role in tumor suppression.

Disorders Related to PI3Kδ Hyperactivation: Characterizing the Clinical and Immunological Features of Activated PI3-Kinase Delta Syndromes

Phosphoinositide-3-kinase δ (PI3Kδ) is found in immune cells and is part of the PI3K/AKT/mTOR/S6K signalling pathway essential to cell survival, growth and differentiation. Hyperactivation of PI3Kδ enzyme results in Activated PI3-kinase delta syndrome (APDS). This childhood onset, autosomal dominant, combined immunodeficiency, is caused by heterozygous gain of function (GOF) mutations in PIK3CD (encodes PI3Kδ catalytic subunit p110δ), mutations in PIK3R1 (encodes PI3Kδ regulatory subunit p85α) or LOF mutations in PTEN (terminates PI3Kδ signalling) leading to APDS1, APDS2 and APDS-Like (APDS-L), respectively. APDS was initially described in 2013 and over 285 cases have now been reported. Prompt diagnosis of APDS is beneficial as targeted pharmacological therapies such as sirolimus and potentially PI3Kδ inhibitors can be administered. In this review, we provide an update on the clinical and laboratory features of this primary immunodeficiency. We discuss the common manifestations such as sinopulmonary infections, bronchiectasis, lymphoproliferation, susceptibility to herpesvirus, malignancy, as well as more rare non-immune features such as short stature and neurodevelopmental abnormalities. Laboratory characteristics, such as antibody deficiency and B cell and T cell, phenotypes are also summarised.

PTEN and Other PtdIns(3,4,5)P3 Lipid Phosphatases in Breast Cancer

The phosphoinositide 3-kinase (PI3K)/AKT signalling pathway is hyperactivated in ~70% of breast cancers. Class I PI3K generates PtdIns(3,4,5)P₃ at the plasma membrane in response to growth factor stimulation, leading to AKT activation to drive cell proliferation, survival and migration. PTEN negatively regulates PI3K/AKT signalling by dephosphorylating PtdIns(3,4,5)P₃ to form PtdIns(4,5)P₂. PtdIns(3,4,5)P₃ can also be hydrolysed by the inositol polyphosphate 5-phosphatases (5-phosphatases) to produce PtdIns(3,4)P₂. Interestingly, while PTEN is a bona fide tumour suppressor and is frequently mutated/lost in breast cancer, 5-phosphatases such as PIPP, SHIP2 and SYNJ2, have demonstrated more diverse roles in regulating mammary tumourigenesis. Reduced PIPP expression is associated with triple negative breast cancers and reduced relapse-free and overall survival. Although PIPP depletion enhances AKT phosphorylation and supports tumour growth, this also inhibits cell migration and metastasis in vivo, in a breast cancer oncogene-driven murine model. Paradoxically, SHIP2 and SYNJ2 are increased in primary breast tumours, which correlates with invasive disease and reduced survival. SHIP2 or SYNJ2 overexpression promotes breast tumourigenesis via AKT-dependent and independent mechanisms. This review will discuss how PTEN, PIPP, SHIP2 and SYNJ2 distinctly regulate multiple functional targets, and the mechanisms by which dysregulation of these distinct phosphoinositide phosphatases differentially affect breast cancer progression.

Ras Pathways on Prox1 and Lymphangiogenesis: Insights for Therapeutics

Over the past couple of decades, lymphatics research has accelerated and gained a much-needed recognition in pathophysiology. As the lymphatic system plays heavy roles in interstitial fluid drainage, immune surveillance and lipid absorption, the ablation or excessive growth of this vasculature could be associated with many complications, from lymphedema to metastasis. Despite their growing importance in cancer, few anti-lymphangiogenic therapies exist today, as they have yet to pass phase 3 clinical trials and acquire FDA approval. As such, many studies are being done to better define the signaling pathways that govern lymphangiogenesis, in hopes of developing new therapeutic approaches to inhibit or stimulate this process. This review will cover our current understanding of the Ras signaling pathways and their interactions with Prox1, the master transcriptional switch involved in specifying lymphatic endothelial cell fate and lymphangiogenesis, in hopes of providing insights to lymphangiogenesis-based therapies.

Cellular and Molecular Progression of Prostate Cancer: Models for Basic and Preclinical Research

Simple Summary

The molecular progression of prostate cancer is complex and elusive. Biological research relies heavily on in vitro and in vivo models that can be used to examine gene functions and responses to the external agents in laboratory and preclinical settings. Over the years, several models have been developed and found to be very helpful in understanding the biology of prostate cancer. Here we describe these models in the context of available information on the cellular and molecular progression of prostate cancer to suggest their potential utility in basic and preclinical prostate cancer research. The information discussed herein should serve as a hands-on resource for scholars engaged in prostate cancer research or to those who are making a transition to explore the complex biology of prostate cancer.

Abstract

We have witnessed noteworthy progress in our understanding of prostate cancer over the past decades. This basic knowledge has been translated into efficient diagnostic and treatment approaches leading to the improvement in patient survival. However, the molecular pathogenesis of prostate cancer appears to be complex, and histological findings often do not provide an accurate assessment of disease aggressiveness and future course. Moreover, we also witness tremendous racial disparity in prostate cancer incidence and clinical outcomes necessitating a deeper understanding of molecular and mechanistic bases of prostate cancer. Biological research heavily relies on model systems that can be easily manipulated and tested under a controlled experimental environment. Over the years, several cancer cell lines have been developed representing diverse molecular subtypes of prostate cancer. In addition, several animal models have been developed to demonstrate the etiological molecular basis of the prostate cancer. In recent years, patient-derived xenograft and 3-D culture models have also been created and utilized in preclinical research. This review is an attempt to succinctly discuss existing information on the cellular and molecular progression of prostate cancer. We also discuss available model systems and their tested and potential utility in basic and preclinical prostate cancer research.

MicroRNA-23b-3p promotes pancreatic cancer cell tumorigenesis and metastasis via the JAK/PI3K and Akt/NF-κB signaling pathways

MicroRNA (miR)-23b-3p plays an important role in tumor growth, proliferation, invasion and migration in pancreatic cancer (PC). However, the function and mechanistic role of miR-23b-3p in the development of PC remains largely unknown. In the present study, the miR-23b-3p levels in the serum of patients with PC were found to be elevated, and the phosphorylation levels of Janus kinase (JAK)2, PI3K, Akt and NF-κВ were found to be upregulated. In addition, miR-23b-3p was induced in response to interleukin-6 (IL-6), which is known to be involved in the progression of PC. Overexpression of miR-23b-3p, on the other hand, activated the JAK/PI3K and Akt/NF-κB signaling pathways in PC cells, as evidenced by miR-23b-3p-induced upregulation of phosphorylated (p-)JAK2, p-PI3K, p-Akt and p-NF-κВ, as well as the downregulation of PTEN; and these effects were found to be reversible by miR-23b-3p inhibition. Furthermore, miR-23b-3p was found to downregulate PTEN by directly targeting the 3′-untranslated region of PTEN mRNA. Notably, in an in vivo xenograft mouse model, overexpression of miR-23b-3p accelerated PC cell-derived tumor growth, activated the JAK/Akt/NF-κВ signaling pathway and promoted liver metastasis. In contrast, knockdown of miR-23b-3p suppressed tumor growth and metastasis as well as JAK/Akt/NF-κВ signaling activity. In vivo imaging of the mice further confirmed the metastasis promoting role of miR-23b-3p in PC. These results suggested that miR-23b-3p enhances PC cell tumorigenesis and metastasis, at least, partially via the JAK/PI3K and Akt/NF-κB signaling pathways. Therefore, targeting miR-23b-3p or the JAK/PI3K and Akt/NF-κB signalings may be potential therapeutic strategy against PC.

Mechanism of PRL2 phosphatase-mediated PTEN degradation and tumorigenesis

Tumor suppressor PTEN (phosphatase and tensin homologue deleted on chromosome 10) levels are frequently found reduced in human cancers, but how PTEN is down-regulated is not fully understood. In addition, although a compelling connection exists between PRL (phosphatase of regenerating liver) 2 and cancer, how this phosphatase induces oncogenesis has been an enigma. Here, we discovered that PRL2 ablation inhibits PTEN heterozygosity-induced tumorigenesis. PRL2 deficiency elevates PTEN and attenuates AKT signaling, leading to decreased proliferation and increased apoptosis in tumors. We also found that high PRL2 expression is correlated with low PTEN level with reduced overall patient survival. Mechanistically, we identified PTEN as a putative PRL2 substrate and demonstrated that PRL2 down-regulates PTEN by dephosphorylating PTEN at Y336, thereby augmenting NEDD4-mediated PTEN ubiquitination and proteasomal degradation. Given the strong cancer susceptibility to subtle reductions in PTEN, the ability of PRL2 to down-regulate PTEN provides a biochemical basis for its oncogenic propensity. The results also suggest that pharmacological targeting of PRL2 could provide a novel therapeutic strategy to restore PTEN, thereby obliterating PTEN deficiency-induced malignancies.

Discovery of the PTEN Tumor Suppressor and Its Connection to the PI3K and AKT Oncogenes

PTEN (phosphatase and tensin homolog on chromosome 10) was discovered over 20 years ago in 1997 and linked to the phosphatidylinositol 3-kinase (PI3K) and AKT oncogenes the following year. The discovery of PTEN emerged from the linked concepts of oncogenes and tumor suppressor genes that cause and prevent cancer and the fields of tumor viruses and human cancer genetics from which these two concepts arose. While much has been learned since, the initial discovery and characterization, including the discovery that PTEN is a regulator of PI3K and AKT, provide the foundation on which we continue to build our knowledge. To provide the context in which these cancer genes were discovered, background information that led to their discovery will also be discussed, which will hopefully be a useful guide for readers seeking to build on the work of others.

Posttranslational Regulation and Conformational Plasticity of PTEN

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumor suppressor that is frequently down-modulated in human cancer. PTEN inhibits the phosphatidylinositol 3-phosphate kinase (PI3K)/AKT pathway through its lipid phosphatase activity. Multiple PI3K/AKT-independent actions of PTEN, protein-phosphatase activities and functions within the nucleus have also been described. PTEN, therefore, regulates many cellular processes including cell proliferation, survival, genomic integrity, polarity, migration, and invasion. Even a modest decrease in the functional dose of PTEN may promote cancer development. Understanding the molecular and cellular mechanisms that regulate PTEN protein levels and function, and how these may go awry in cancer contexts, is, therefore, key to fully understanding the role of PTEN in tumorigenesis. Here, we discuss current knowledge on posttranslational control and conformational plasticity of PTEN, as well as therapeutic possibilities toward reestablishment of PTEN tumor-suppressor activity in cancer.

Extracranial arteriovenous malformations: from bedside to bench

Arteriovenous malformation (AVM) is defined as a fast-flow vascular anomaly that shunts blood from arteries directly to veins. This short circuit of blood flow contributes to progressive expansion of draining veins, resulting in ischaemia, tissue deformation and in some severe cases, congestive heart failure. Various medical interventions have been employed to treat AVM, however, management of which remains a huge challenge because of its high recurrence rate and lethal complications. Thus, understanding the underlying mechanisms of AVM development and progression will help direct discovery and a potential cure. Here, we summarize current findings in the field of extracranial AVMs with the aim to provide insight into their aetiology and molecular influences, in the hope to pave the way for future treatment.

The Genetics and Mechanisms of T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy derived from early T-cell progenitors. The recognition of clinical, genetic, transcriptional, and biological heterogeneity in this disease has already translated into new prognostic biomarkers, improved leukemia animal models, and emerging targeted therapies. This work reviews our current understanding of the molecular mechanisms of T-ALL.

PTEN Mouse Models of Cancer Initiation and Progression

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is one of the most frequently mutated, deleted, and functionally inactivated tumor suppressor genes in human cancer. PTEN is found mutated both somatically and in the germline of patients with PTEN hamartoma tumor syndrome (PHTS). PTEN encodes a dual lipid and protein phosphatase that dephosphorylates the lipid phosphatidylinositol-3,4,5-trisphosphate (PIP₃), in turn negatively regulating the oncogenic PI3K-AKT pathway, a key proto-oncogenic player in cancer development and progression. Because of importance of PTEN in tumorigenesis, a large number of sophisticated genetically engineered mouse models (GEMMs) has been designed to elucidate the underlying mechanisms by which the "PTEN pathway" promotes tumorigenesis, while simultaneously providing a well-tailored system for the identification of novel therapies and offering platforms for new drug discoveries. This review summarizes the major cancer mouse models through which the PTEN pathway has been genetically deconstructed, and outlines the rapid development of GEMMs toward more detailed functional and tissue-specific analysis.

Loss of Ing3 Expression Results in Growth Retardation and Embryonic Death

The ING3 candidate tumour suppressor belongs to a family of histone modifying proteins involved in regulating cell proliferation, senescence, apoptosis, chromatin remodeling, and DNA repair. It is a stoichiometric member of the minimal NuA4 histone acetyl transferase (HAT) complex consisting of EAF6, EPC1, ING3, and TIP60. This complex is responsible for the transcription of an essential cascade of genes involved in embryonic development and in tumour suppression. ING3 has been linked to head and neck and hepatocellular cancers, although its status as a tumour suppressor has not been well established. Recent studies suggest a pro-metastasis role in prostate cancer progression. Here, we describe a transgenic mouse strain with insertional mutation of an UbC-mCherry expression cassette into the endogenous Ing3 locus, resulting in the disruption of ING3 protein expression. Homozygous mutants are embryonically lethal, display growth retardation, and severe developmental disorders. At embryonic day (E) 10.5, the last time point viable homozygous embryos were found, they were approximately half the size of heterozygous mice that develop normally. µCT analysis revealed a developmental defect in neural tube closure, resulting in the failure of formation of closed primary brain vesicles in homozygous mid-gestation embryos. This is consistent with high ING3 expression levels in the embryonic brains of heterozygous and wild type mice and its lack in homozygous mutant embryos that show a lack of ectodermal differentiation. Our data provide direct evidence that ING3 is an essential factor for normal embryonic development and that it plays a fundamental role in prenatal brain formation.

The Role of PTEN in Innate and Adaptive Immunity

The lipid and protein phosphatase and tensin homolog (PTEN) controls the differentiation and activation of multiple immune cells. PTEN acts downstream from T- and B-cell receptors, costimulatory molecules, cytokine receptors, integrins, and also growth factor receptors. Loss of PTEN activity in human and mice is associated with cellular and humoral immune dysfunction, lymphoid hyperplasia, and autoimmunity. Although most patients with PTEN hamartoma tumor syndrome (PHTS) have no immunological symptoms, a subclinical immune dysfunction is present in many, and clinical immunodeficiency in few. Comparison of the immune phenotype caused by PTEN haploinsufficiency in PHTS, phosphoinositide 3-kinase (PI3K) gain-of-function in activated PI3K syndrome, and mice with conditional biallelic Pten deletion suggests a threshold model in which coordinated activity of several phosphatases control the PI3K signaling in a cell-type-specific manner. Emerging evidence highlights the role of PTEN in polygenic autoimmune disorders, infection, and the immunological response to cancer. Targeting the PI3K axis is an emerging therapeutic avenue.

Revisiting PI3-kinase signalling in angiogenesis

PI3Ks belong to a family of lipid kinases that comprises eight isoforms. They phosphorylate the third position of the inositol ring present in phosphatidylinositol lipids and, in turn, activate a broad range of proteins. The PI3K pathway regulates primal cellular responses, including proliferation, migration, metabolism and vesicular traffic. These processes are fundamental for endothelial cell function during sprouting angiogenesis, the most common type of blood vessel formation. Research in animal models has revealed key functions of PI3K family members and downstream effectors in angiogenesis. In addition, perturbations in PI3K signalling have been associated with aberrant vascular growth including tumour angiogenesis and vascular malformations. Together, this highlights that endothelial cells are uniquely sensitive to fluctuations in PI3K signalling. Here, we aim to update the current view on this important signalling cue in physiological and pathological blood vessel growth.

Melatonin: A promising agent targeting leukemia

Leukemia or cancer of blood is a well-known cancer, which affects a range of people from newborns to the very old. It is a public health problem throughout the world. By way of treatment, due to the lack of specific anticancer therapies, common treatments of leukemia lead to severe side effects. Nonspecific anticancer drugs result in inhibition of normal cell growth and thereby their necrosis. Moreover, drug resistance is an additional problem, which stands in the way of leukemia treatment. Thus, finding new treatments for leukemia is essential. Melatonin, as a natural product, has been shown to be effective in a wide variety of diseases such as coronary heart disease, schizophrenia, chronic pain, and Alzheimer's disease. In addition, melatonin levels have been observed to be altered in different cancers, such as breast cancer, colorectal cancer endometrial cancer, and hematopoetical cancers. Anticancer features of melatonin such as pro-oxidation, apoptosis induction, antiangiogenesis property and metastasis and invasion inhibition suggest that this natural compound can be used as a potential agent in novel therapeutic strategies for cancers. Also, it has been reported that melatonin has positive and protective effects on different physiological reactions and in normal bone marrow cells suggesting effectiveness in leukemia therapy. Thus, the aim of our paper was to depict and summarize the main molecular targets of melatonin on leukemia models.

The Mechanisms Underlying PTEN Loss in Human Tumors Suggest Potential Therapeutic Opportunities

In this review, we will first briefly describe the diverse molecular mechanisms associated with PTEN loss of function in cancer. We will then proceed to discuss the molecular mechanisms linking PTEN loss to PI3K activation and demonstrate how these mechanisms suggest possible therapeutic approaches for patients with PTEN-null tumors.

Acylglycerol Kinase Maintains Metabolic State and Immune Responses of CD8+ T Cells

CD8⁺ T cell expansions and functions rely on glycolysis, but the mechanisms underlying CD8⁺ T cell glycolytic metabolism remain elusive. Here, we show that acylglycerol kinase (AGK) is required for the establishment and maintenance of CD8⁺ T cell metabolic and functional fitness. AGK deficiency dampens CD8⁺ T cell antitumor functions in vivo and perturbs CD8⁺ T cell proliferation in vitro. Activation of phosphatidylinositol-3-OH kinase (PI3K)-mammalian target of rapamycin (mTOR) signaling, which mediates elevated CD8⁺ T cell glycolysis, is tightly dependent on AGK kinase activity. Mechanistically, T cell antigen receptor (TCR)- and CD28-stimulated recruitment of PTEN to the plasma membrane facilitates AGK-PTEN interaction and AGK-triggered PTEN phosphorylation, thereby restricting PTEN phosphatase activity in CD8⁺ T cells. Collectively, these results demonstrate that AGK maintains CD8⁺ T cell metabolic and functional state by restraining PTEN activity and highlight a critical role for AGK in CD8⁺ T cell metabolic programming and effector function.

PTEN Tumor-Suppressor: The Dam of Stemness in Cancer

PTEN is one of the most frequently inactivated tumor suppressor genes in cancer. Loss or variation in PTEN gene/protein levels is commonly observed in a broad spectrum of human cancers, while germline PTEN mutations cause inherited syndromes that lead to increased risk of tumors. PTEN restrains tumorigenesis through different mechanisms ranging from phosphatase-dependent and independent activities, subcellular localization and protein interaction, modulating a broad array of cellular functions including growth, proliferation, survival, DNA repair, and cell motility. The main target of PTEN phosphatase activity is one of the most significant cell growth and pro-survival signaling pathway in cancer: PI3K/AKT/mTOR. Several shreds of evidence shed light on the critical role of PTEN in normal and cancer stem cells (CSCs) homeostasis, with its loss fostering the CSC compartment in both solid and hematologic malignancies. CSCs are responsible for tumor propagation, metastatic spread, resistance to therapy, and relapse. Thus, understanding how alterations of PTEN levels affect CSC hallmarks could be crucial for the development of successful therapeutic approaches. Here, we discuss the most significant findings on PTEN-mediated control of CSC state. We aim to unravel the role of PTEN in the regulation of key mechanisms specific for CSCs, such as self-renewal, quiescence/cell cycle, Epithelial-to-Mesenchymal-Transition (EMT), with a particular focus on PTEN-based therapy resistance mechanisms and their exploitation for novel therapeutic approaches in cancer treatment.

PTEN Methylation by NSD2 Controls Cellular Sensitivity to DNA Damage

The function of PTEN in the cytoplasm largely depends on its lipid-phosphatase activity, though which it antagonizes the PI3K-AKT oncogenic pathway. However, molecular mechanisms underlying the role of PTEN in the nucleus remain largely elusive. Here, we report that DNA double-strand breaks (DSB) promote PTEN interaction with MDC1 upon ATM-dependent phosphorylation of T/S398-PTEN. Importantly, DNA DSBs enhance NSD2 (MMSET/WHSC1)-mediated dimethylation of PTEN at K349, which is recognized by the tudor domain of 53BP1 to recruit PTEN to DNA-damage sites, governing efficient repair of DSBs partly through dephosphorylation of γH2AX. Of note, inhibiting NSD2-mediated methylation of PTEN, either through expressing methylation-deficient PTEN mutants or through inhibiting NSD2, sensitizes cancer cells to combinatorial treatment with a PI3K inhibitor and DNA-damaging agents in both cell culture and in vivo xenograft models. Therefore, our study provides a novel molecular mechanism for PTEN regulation of DSB repair in a methylation- and protein phosphatase-dependent manner. SIGNIFICANCE: NSD2-mediated dimethylation of PTEN is recognized by the 53BP1 tudor domain to facilitate PTEN recruitment into DNA-damage sites, governing efficient repair of DNA DSBs. Importantly, inhibiting PTEN methylation sensitizes cancer cells to combinatorial treatment with a PI3K inhibitor combined with DNA-damaging agents in both cell culture and in vivo xenograft models.This article is highlighted in the In This Issue feature, p. 1143.

Epigenetic Control of Gene Expression in the Normal and Malignant Human Prostate: A Rapid Response Which Promotes Therapeutic Resistance

A successful prostate cancer must be capable of changing its phenotype in response to a variety of microenvironmental influences, such as adaptation to treatment or successful proliferation at a particular metastatic site. New cell phenotypes emerge by selection from the large, genotypically heterogeneous pool of candidate cells present within any tumor mass, including a distinct stem cell-like population. In such a multicellular model of human prostate cancer, flexible responses are primarily governed not only by de novo mutations but appear to be dominated by a combination of epigenetic controls, whose application results in treatment resistance and tumor relapse. Detailed studies of these individual cell populations have resulted in an epigenetic model for epithelial cell differentiation, which is also instructive in explaining the reported high and inevitable relapse rates of human prostate cancers to a multitude of treatment types.

The PTEN⁻PI3K Axis in Cancer

The PI3K-AKT-mTOR signal transduction pathway regulates a variety of biological processes including cell growth, cell cycle progression and proliferation, cellular metabolism, and cytoskeleton reorganization. Fine-tuning of the phosphatidylinositol 3-kinase (PI3K) pathway signaling output is essential for the maintenance of tissue homeostasis and uncontrolled activation of this cascade leads to a number of human pathologies including cancer. Inactivation of the tumor suppressor phosphatase and tensin homologue deleted on Chromosome 10 (PTEN) and/or activating mutations in the proto-typical lipid kinase PI3K have emerged as some of the most frequent events associated with human cancer and as a result the PI3K pathway has become a highly sought-after target for cancer therapies. In this review we summarize the essential role of the PTEN-PI3K axis in controlling cellular behaviors by modulating activation of key proto-oncogenic molecular nodes and functional targets. Further, we highlight important functional redundancies and peculiarities of these two critical enzymes that over the last few decades have become a central part of the cancer research field and have instructed hundreds of pre-clinical and clinical trials to better cancer treatments.

PTEN arginine methylation by PRMT6 suppresses PI3K-AKT signaling and modulates pre-mRNA splicing

Arginine methylation is a ubiquitous posttranslational modification that regulates critical cellular processes including signal transduction and pre-mRNA splicing. Here, we report that the tumor-suppressor PTEN is methylated by protein arginine methyltransferase 6 (PRMT6). Mass-spectrometry analysis reveals that PTEN is dimethylated at arginine 159 (R159). We found that PTEN is mutated at R159 in cancers, and the PTEN mutant R159K loses its capability to inhibit the PI3K-AKT cascade. Furthermore, PRMT6 is physically associated with PTEN, promotes asymmetrical dimethylation of PTEN, and regulates the PI3K-AKT cascade through PTEN R159 methylation. In addition, using transcriptome analyses, we found that PTEN R159 methylation is involved in modulation of pre-mRNA alternative splicing. Our results demonstrate that PTEN is functionally regulated by arginine methylation. We propose that PTEN arginine methylation modulates pre-mRNA alternative splicing and influences diverse physiologic processes.

The Opposing Roles of PIK3R1/p85α and PIK3R2/p85β in Cancer

Dysregulation of the PI3K/PTEN pathway is a frequent event in cancer, and PIK3CA and PTEN are the most commonly mutated genes after TP53. PIK3R1 is the predominant regulatory isoform of PI3K. PIK3R2 is an ubiquitous isoform that has been so far overlooked, but data from The Cancer Genome Atlas shows that increased expression of PIK3R2 is also frequent in cancer. In contrast to PIK3R1, which is a tumor-suppressor gene, PIK3R2 is an oncogene. We review here the opposing roles of PIK3R1 and PIK3R2 in cancer, the regulatory mechanisms that control PIK3R2 expression, and emerging therapeutic approaches targeting PIK3R2.

MTA2-mediated inhibition of PTEN leads to pancreatic ductal adenocarcinoma carcinogenicity

Metastasis-associated protein 2 (MTA2) is a core subunit of the nucleosome remodeling and deacetylating (NuRD) complex and functions by mediating chromatin remodeling and gene silencing. However, its biological actions and clinical significance in pancreatic ductal adenocarcinoma (PDAC) remain elusive. The aim of this study was to explore the function and regulation mechanism of MTA2 in PDAC. As shown in GEO, ICGC, and TCGA databases, a higher expression of MTA2 was noticed in the PDAC tissues than in the normal pancreatic tissues. Moreover, a higher expression level of MTA2 was associated with a shorter overall survival time in these public PDAC databases. We further investigated the underlying mechanisms of these observations by using a chromatin immunoprecipitation (ChIP)-based deep sequencing, luciferase reporter, and quantitative ChIP assays. We identified the repressive binding of MTA2 to the promoter of phosphatase and tensin homolog (PTEN). We also found that Snail recruited MTA2 and HDAC1 to suppress PTEN expression. Ectopic expression and knockdown of MTA2 were performed to evaluate the effects of this gene on PDAC cell proliferation, migration, and invasion. Using CCK-8, colony formation and transwell assays, and a xenograft tumor model, we revealed that MTA2 promoted PDAC cell proliferation, migration, and invasion in vitro and PDAC tumor growth in vivo by downregulation of PTEN. In benzyl isothiocyanate (BITC)-treated MIA Paca-2 cells and PANC-1 cells, MTA2 level decreased in a dose- and time-dependent manner with concomitant upregulation of PTEN level and downregulation of phosphorylated PI3K and AKT levels, providing evidence of the involvement of MTA2 and PTEN in the regulation of the PI3K/AKT pathway in BITC-mediated PDAC suppression. Collectively, these findings uncover a novel role for MTA2 in the regulation of PDAC progression and help to elucidate the mechanisms involved in this process.

Tumor Suppressor PTEN Regulates Negatively Sertoli Cell Proliferation, Testis Size, and Sperm Production In Vivo

The IGFs are the major intratesticular factors regulating immature Sertoli cell proliferation and are, therefore, critical to establish the magnitude of sperm production. However, the intratesticular source of IGF production and the downstream signaling pathway mediating IGF-dependent Sertoli cell proliferation remain unclear. Single-cell RNA sequencing on mouse embryonic testis revealed a robust expression of Igf1 and Igf2 in interstitial steroidogenic progenitors, suggesting that IGFs exert paracrine actions on immature Sertoli cells. To elucidate the intracellular signaling mechanism that underlies the proliferative effects of IGFs on immature Sertoli cells, we have generated mice with Sertoli cell-specific deletion of the Pten gene, a negative regulator of the phosphatidylinositol-3 kinase (PI3K)/AKT pathway, alone or together with the insulin receptor (Insr) and the IGF1 receptor (Igf1r). Although ablation of Pten appears dispensable for Sertoli cell proliferation and spermatogenesis, inactivation of Pten in the absence of Insr and Igf1r rescued the Sertoli cell proliferation rate during late fetal development, testis size, and sperm production. Overall, these findings suggest that IGFs secreted by interstitial progenitor cells act in a paracrine fashion to promote the proliferation of immature Sertoli cells through the IGF/PTEN/PI3K pathway.

The Secret Life of Translation Initiation in Prostate Cancer

Prostate cancer (PCa) is the second most prevalent cancer in men worldwide. Despite the advances understanding the molecular processes driving the onset and progression of this disease, as well as the continued implementation of screening programs, PCa still remains a significant cause of morbidity and mortality, in particular in low-income countries. It is only recently that defects of the translation process, i.e., the synthesis of proteins by the ribosome using a messenger (m)RNA as a template, have begun to gain attention as an important cause of cancer development in different human tissues, including prostate. In particular, the initiation step of translation has been established to play a key role in tumorigenesis. In this review, we discuss the state-of-the-art of three key aspects of protein synthesis in PCa, namely, misexpression of translation initiation factors, dysregulation of the major signaling cascades regulating translation, and the therapeutic strategies based on pharmacological compounds targeting translation as a novel alternative to those based on hormones controlling the androgen receptor pathway.

PTEN-opathies: from biological insights to evidence-based precision medicine

The tumor suppressor phosphatase and tensin homolog (PTEN) classically counteracts the PI3K/AKT/mTOR signaling cascade. Germline pathogenic PTEN mutations cause PTEN hamartoma tumor syndrome (PHTS), featuring various benign and malignant tumors, as well as neurodevelopmental disorders such as autism spectrum disorder. Germline and somatic mosaic mutations in genes encoding components of the PI3K/AKT/mTOR pathway downstream of PTEN predispose to syndromes with partially overlapping clinical features, termed the "PTEN-opathies." Experimental models of PTEN pathway disruption uncover the molecular and cellular processes influencing clinical phenotypic manifestations. Such insights not only teach us about biological mechanisms in states of health and disease, but also enable more accurate gene-informed cancer risk assessment, medical management, and targeted therapeutics. Hence, the PTEN-opathies serve as a prototype for bedside to bench, and back to the bedside, practice of evidence-based precision medicine.

Restoration of tumour-growth suppression in vivo via systemic nanoparticle-mediated delivery of PTEN mRNA

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a well-characterized tumour-suppressor gene that is lost or mutated in about half of metastatic castration-resistant prostate cancers and in many other human cancers. The restoration of functional PTEN as a treatment for prostate cancer has, however, proven difficult. Here, we show that PTEN messenger RNA (mRNA) can be reintroduced into PTEN-null prostate cancer cells in vitro and in vivo via its encapsulation in polymer-lipid hybrid nanoparticles coated with a polyethylene glycol shell. The nanoparticles are stable in serum, elicit low toxicity and enable high PTEN mRNA transfection in prostate cancer cells. Moreover, significant inhibition of tumour growth is achieved when delivered systemically in multiple mouse models of prostate cancer. We also show that the restoration of PTEN function in PTEN-null prostate cancer cells inhibits the phosphatidylinositol 3-kinase (PI3K)-AKT pathway and enhances apoptosis. Our findings provide proof-of-principle evidence of the restoration of mRNA-based tumour suppression in vivo.

Hippocampal deficits in neurodevelopmental disorders

Neurodevelopmental disorders result from impaired development or maturation of the central nervous system. Both genetic and environmental factors can contribute to the pathogenesis of these disorders; however, the exact causes are frequently complex and unclear. Individuals with neurodevelopmental disorders may have deficits with diverse manifestations, including challenges with sensory function, motor function, learning, memory, executive function, emotion, anxiety, and social ability. Although these functions are mediated by multiple brain regions, many of them are dependent on the hippocampus. Extensive research supports important roles of the mammalian hippocampus in learning and cognition. In addition, with its high levels of activity-dependent synaptic plasticity and lifelong neurogenesis, the hippocampus is sensitive to experience and exposure and susceptible to disease and injury. In this review, we first summarize hippocampal deficits seen in several human neurodevelopmental disorders, and then discuss hippocampal impairment including hippocampus-dependent behavioral deficits found in animal models of these neurodevelopmental disorders.

TMPRSS2-ERG Controls Luminal Epithelial Lineage and Antiandrogen Sensitivity in PTEN and TP53-Mutated Prostate Cancer

Purpose: Deletions or mutations in PTEN and TP53 tumor suppressor genes have been linked to lineage plasticity in therapy-resistant prostate cancer. Fusion-driven overexpression of the oncogenic transcription factor ERG is observed in approximately 50% of all prostate cancers, many of which also harbor PTEN and TP53 alterations. However, the role of ERG in lineage plasticity of PTEN/TP53-altered tumors is unclear. Understanding the collective effect of multiple mutations within one tumor is essential to combat plasticity-driven therapy resistance.Experimental Design: We generated a Pten-negative/Trp53-mutated/ERG-overexpressing mouse model of prostate cancer and integrated RNA-sequencing with ERG chromatin immunoprecipitation-sequencing (ChIP-seq) to identify pathways regulated by ERG in the context of Pten/Trp53 alteration. We investigated ERG-dependent sensitivity to the antiandrogen enzalutamide and cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitor palbociclib in human prostate cancer cell lines, xenografts, and allografted mouse tumors. Trends were evaluated in TCGA, SU2C, and Beltran 2016 published patient cohorts and a human tissue microarray.Results: Transgenic ERG expression in mice blocked Pten/Trp53 alteration-induced decrease of AR expression and downstream luminal epithelial genes. ERG directly suppressed expression of cell cycle-related genes, which induced RB hypophosphorylation and repressed E2F1-mediated expression of mesenchymal lineage regulators, thereby restricting adenocarcinoma plasticity and maintaining antiandrogen sensitivity. In ERG-negative tumors, CDK4/6 inhibition delayed tumor growth.Conclusions: Our studies identify a previously undefined function of ERG to restrict lineage plasticity and maintain antiandrogen sensitivity in PTEN/TP53-altered prostate cancer. Our findings suggest ERG fusion as a biomarker to guide treatment of PTEN/TP53-altered, RB1-intact prostate cancer. Clin Cancer Res; 24(18); 4551-65. ©2018 AACR.

PTENα regulates mitophagy and maintains mitochondrial quality control

PTEN plays an important role in tumor suppression, and PTEN family members are involved in multiple biological processes in various subcellular locations. Here we report that PTENα, the first identified PTEN isoform, regulates mitophagy through promotion of PARK2 recruitment to damaged mitochondria. We show that PTENα-deficient mice exhibit accumulation of cardiac mitochondria with structural and functional abnormalities, and PTENα-deficient mouse hearts are more susceptible to injury induced by isoprenaline and ischemia-reperfusion. Mitochondrial clearance by mitophagy is also impaired in PTENα-deficient cardiomyocytes. In addition, we found PTENα physically interacts with the E3 ubiquitin ligase PRKN, which is an important mediator of mitophagy. PTENα binds PRKN through the membrane binding helix in its N-terminus, and promotes PRKN mitochondrial translocation through enhancing PRKN self-association in a phosphatase-independent manner. Loss of PTENα compromises mitochondrial translocation of PRKN and resultant mitophagy following mitochondrial depolarization. We propose that PTENα functions as a mitochondrial quality controller that maintains mitochondrial function and cardiac homeostasis.

ABBREVIATIONS

BECN1 beclin 1; CCCP carbonyl cyanide m-chlorophenylhydrazone; FBXO7 F-box protein 7; FS fraction shortening; HSPA1L heat shock protein family A (Hsp70) member 1 like; HW: BW heart weight:body weight ratio; I-R ischemia-reperfusion; ISO isoprenaline; MAP1LC3/LC3 microtubule associated protein 1 light chain 3; MBH membrane binding helix; MFN1 mitofusin 1; MFN2 mitofusin 2; Nam nicotinamide; TMRM tetramethylrhodamine ethyl ester; WGA wheat germ agglutinin.

Quantitative Evaluation of in Vivo Target Efficacy of Anti-tumor Agents via an Immunofluorescence and EdU Labeling Strategy

Current methods used to evaluate in vivo target efficacy of selected compound include western blot to semi-quantitatively analyze protein expression. However, problems arise as it is difficult to compare in vivo target efficacy of anti-tumor agents with the same mode of action. It is therefore desirable to develop a protocol that can quantitatively display in vivo target efficacy while also providing other useful information. In this study EdU labeling was used to mark out the proliferating area. The tumor tissue was accordingly divided into proliferating and non-proliferating areas. Fifteen tumor related proteins were stained by immunofluorescence and were found to express in either the proliferating or non-proliferating areas. This allows the quantitative analysis of protein expressions within the precise area. With simple image analysis, our method gave precise percent changes of protein expression and cell proliferation between the drugs treated group and the control group. Additional information, such as, the status of protein expression can also be obtained. This method exhibits high sensitivity, and provides a quantitative approach for in vivo evaluation of target efficacy.

Intermittent fasting uncovers and rescues cognitive phenotypes in PTEN neuronal haploinsufficient mice

Phosphatase and tensin homolog (PTEN) is an important protein with key modulatory functions in cell growth and survival. PTEN is crucial during embryogenesis and plays a key role in the central nervous system (CNS), where it directly modulates neuronal development and synaptic plasticity. Loss of PTEN signaling function is associated with cognitive deficits and synaptic plasticity impairment. Accordingly, Pten mutations have a strong link with autism spectrum disorder. In this study, neuronal Pten haploinsufficient male mice were subjected to a long-term environmental intervention – intermittent fasting (IF) – and then evaluated for alterations in exploratory, anxiety and learning and memory behaviors. Although no significant effects on spatial memory were observed, mutant mice showed impaired contextual fear memory in the passive avoidance test – an outcome that was effectively rescued by IF. In this study, we demonstrated that IF modulation, in addition to its rescue of the memory deficit, was also required to uncover behavioral phenotypes otherwise hidden in this neuronal Pten haploinsufficiency model.

Dysregulation of microRNA‑23b‑3p contributes to the development of intracranial aneurysms by targeting phosphatase and tensin homolog

MicroRNA‑23b‑3p (miR‑23b‑3p) has been reported to be involved in the pathogenesis of a number of diseases, including non‑small cell lung cancer and gastric cancer, by acting on different signaling pathways. The present study aimed to understand the association between the miR‑23b‑3p level of intracranial aneurysms (IAs) and the mechanism involved. Computational analysis was used to search for the target of miR‑23b‑3p, and luciferase assay was used to validate the miRNA/target association. Western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to determine the expression of miR‑23b‑3p and phosphatase and tensin homolog (PTEN), and their expression in smooth muscle cells (SMCs) treated with miRNA mimic or inhibitor. Firstly, an online miRNA database (www.mirdb.org) was searched using the 'seed sequence' located within the 3'‑untranslated region of the target gene, and then PTEN was validated as the direct target gene via a luciferase reporter assay system. The negative regulatory association between miR‑23b‑3p and PTEN was determined through the analysis of the relative luciferase activity. Additionally, RT-qPCR and western blot analysis was performed in order to assess the mRNA and protein expression levels of PTEN among IA (n=32) and control (n=17) groups or cells treated with scramble control, miR‑23b‑3p mimics, PTEN siRNA and miR‑23b‑3p inhibitors to verify the negative regulatory association between miR‑23b‑3p and PTEN. Experiments were then performed to investigate the effect of miR‑23b‑3p and PTEN on the viability and apoptosis of pulmonary artery SMCs (PASMCs). The results showed that cells transfected with miR‑23b‑3p inhibitors suppressed the viability of SMCs by promoting the apoptosis of the cells compared with that of the scramble controls, while cells transfected with miR‑23b‑3p mimics and PTEN siRNA enhanced the viability of VSMCs by inducing apoptosis. This indicated that miR‑23b‑3p negatively interfered with the viability of the cells, while PTEN positively interfered with the viability of the cells. In conclusion, PTEN was found to be a virtual target of miR‑23b‑3p, and a negative regulatory association existed between miR‑23b‑3p and PTEN. miR‑23b‑3p and PTEN interfered with the viability and apoptosis of SMCs.

"Immune TOR-opathies," a Novel Disease Entity in Clinical Immunology

Primary immunodeficiencies (PIDs) represent a group of mostly monogenic disorders caused by loss- or gain-of-function mutations in over 340 known genes that lead to abnormalities in the development and/or the function of the immune system. However, mutations in different genes can affect the same cell-signaling pathway and result in overlapping clinical phenotypes. In particular, mutations in the genes encoding for members of the phosphoinositide3-kinase (PI3K)/AKT/mTOR/S6 kinase (S6K) signaling cascade or for molecules interacting with this pathway have been associated with different PIDs that are often characterized by the coexistence of both immune deficiency and autoimmunity. The serine/threonine kinase mechanistic/mammalian target of rapamycin (mTOR), which acts downstream of PI3K and AKT, is emerging as a key regulator of immune responses. It integrates a variety of signals from the microenvironment to control cell growth, proliferation, and metabolism. mTOR plays therefore a central role in the regulation of immune cells’ differentiation and functions. Here, we review the different PIDs that share an impairment of the PI3K/AKT/mTOR/S6K pathway and we propose to name them “immune TOR-opathies” by analogy with a group of neurological disorders that has been originally defined by PB Crino and that are due to aberrant mTOR signaling (1). A better understanding of the role played by this complex intracellular cascade in the pathophysiology of “immune TOR-opathies” is crucial to develop targeted therapies.

Mutant and wild-type p53 form complexes with p73 upon phosphorylation by the kinase JNK

The transcription factors p53 and p73 are critical to the induction of apoptotic cell death, particularly in response to cell stress that activates c-Jun N-terminal kinase (JNK). Mutations in the DNA-binding domain of p53, which are commonly seen in cancers, result in conformational changes that enable p53 to interact with and inhibit p73, thereby suppressing apoptosis. In contrast, wild-type p53 reportedly does not interact with p73. We found that JNK-mediated phosphorylation of Thr⁸¹ in the proline-rich domain (PRD) of p53 enabled wild-type p53, as well as mutant p53, to form a complex with p73. Structural algorithms predicted that phosphorylation of Thr⁸¹ exposes the DNA-binding domain in p53 to enable its binding to p73. The dimerization of wild-type p53 with p73 facilitated the expression of apoptotic target genes [such as those encoding p53-up-regulated modulator of apoptosis (PUMA) and Bcl-2-associated X protein (BAX)] and, subsequently, the induction of apoptosis in response to JNK activation by cell stress in various cells. Thus, JNK phosphorylation of mutant and wild-type p53 promotes the formation of a p53/p73 complex that determines cell fate: apoptosis in the context of wild-type p53 or cell survival in the context of the mutant. These findings refine our current understanding of both the mechanistic links between p53 and p73 and the functional role for Thr⁸¹ phosphorylation.

Expression of inhibitor proteins that control primordial follicle reserve decreases in cryopreserved ovaries after autotransplantation

PURPOSE

Even with 86 live births reported globally so far, the mechanism of primordial follicle loss following autotransplantation of the frozen-thawed ovarian tissue needs further evaluation. Pten, Tsc1, p27, and Amh are the inhibitor proteins that play crucial roles in suppressing the transition from the primordial follicle to primary state, maintaining the primordial follicle reserve. In this study, we aimed to evaluate whether the expression patterns of these proteins change and it may be related to the global primordial follicle loss after autotransplantation of the frozen-thawed ovarian tissue.

METHODS

Four groups were established in rats: fresh-control, frozen/thawed, fresh-transplanted, and frozen/thawed and transplanted. After slow freezing and thawing process, two ovarian pieces were transplanted into the back muscle of the same rat. After 2 weeks, grafts were harvested, fixed, and embedded into the paraffin block. Normal and atretic primordial/growing follicle count was performed in all groups. Ovarian tissues were evaluated for the dynamic expressions of the Pten, Tsc1, p27, and Amh proteins using immunohistochemistry, and H-score analyses were done.

RESULTS

Ovarian tissue cryopreservation does not change the expression patterns of inhibitory proteins that control ovarian reserve. Both in fresh and frozen/thawed autotransplanted groups, the expression of inhibitory proteins and Amh decreased significantly in primordial follicles and in growing follicles, respectively. In control group and in frozen/thawed group, primordial follicle counts were similar but decreased by almost half in both fresh-transplanted and frozen/thawed and transplanted groups.

CONCLUSIONS

One of the causes of primordial follicle loss after transplantation of ovarian graft may be decreased expression of the inhibitory proteins that guard the ovarian reserve and transplantation itself seems to be the major cause for disruption of inhibitory molecular signaling. Our findings highlight important molecular aspects for future clinical applications for fertility preservation in humans.

Genetic Ablation of Rbm38 Promotes Lymphomagenesis in the Context of Mutant p53 by Downregulating PTEN

Mutant p53 exerts gain-of-function effects that drive metastatic progression and therapeutic resistance, but the basis for these effects remain obscure. The RNA binding protein RBM38 limits translation of mutant p53 and is often altered in tumors harboring it. Here we show how loss of Rbm38 significantly alters cancer susceptibility in mutant p53 knock-in mice by shortening lifespan, altering tumor incidence, and promoting T-cell lymphomagenesis. Loss of Rbm38 enhanced mutant p53 expression and decreased expression of the tumor suppressor Pten, a key regulator of T-cell development. Furthermore, Rbm38 was required for Pten expression via stabilization of Pten mRNA through an AU-rich element in its 3'UTR. Our results suggest that Rbm38 controls T-cell lymphomagenesis by jointly modulating mutant p53 and Pten, with possible therapeutic implications for treating T-cell malignancies.Significance: An RNA-binding protein controls T-cell lymphomagenesis by jointly modulating mutant p53 and PTEN, with possible therapeutic implications for treating T-cell malignancies. Cancer Res; 78(6); 1511-21. ©2018 AACR.

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.

Negative Regulation of Receptor Tyrosine Kinase (RTK) Signaling: A Developing Field

Trophic factors control cellular physiology by activating specific receptor tyrosine kinases (RTKs). While the over activation of RTK signaling pathways is associated with cell growth and cancer, recent findings support the concept that impaired down-regulation or deactivation of RTKs may also be a mechanism involved in tumor formation. Under this perspective, the molecular determinants of RTK signaling inhibition may act as tumor-suppressor genes and have a potential role as tumor markers to monitor and predict disease progression. Here, we review the current understanding of the physiological mechanisms that attenuate RTK signaling and discuss evidence that implicates deregulation of these events in cancer.

Recent advances in understanding the role of protein-tyrosine phosphatases in development and disease

Protein-tyrosine phosphatases (PTPs) remove phosphate groups from tyrosine residues, and thereby propagate or inhibit signal transduction, and hence influence cellular processes such as cell proliferation and differentiation. The importance of tightly controlled PTP activity is reflected by the numerous mechanisms employed by the cell to control PTP activity, including a variety of post-translational modifications, and restricted subcellular localization. This review highlights the strides made in the last decade and discusses the important role of PTPs in key aspects of embryonic development: the regulation of stem cell self-renewal and differentiation, gastrulation and somitogenesis during early embryonic development, osteogenesis, and angiogenesis. The tentative importance of PTPs in these processes is highlighted by the diseases that present upon aberrant activity.