PRICKLE1 Contributes to Cancer Cell Dissemination through Its Interaction with mTORC2

Overcoming Clinical Resistance to EZH2 Inhibition Using Rational Epigenetic Combination Therapy

Epigenetic dependencies have become evident in many cancers. On the basis of antagonism between BAF/SWI-SNF and PRC2 in SMARCB1-deficient sarcomas, we recently completed the clinical trial of the EZH2 inhibitor tazemetostat. However, the principles of tumor response to epigenetic therapy in general, and tazemetostat in particular, remain unknown. Using functional genomics and diverse experimental models, we define molecular mechanisms of tazemetostat resistance in SMARCB1-deficient tumors. We found distinct acquired mutations that converge on the RB1/E2F axis and decouple EZH2-dependent differentiation and cell-cycle control. This allows tumor cells to escape tazemetostat-induced G1 arrest, suggests a general mechanism for effective therapy, and provides prospective biomarkers for therapy stratification, including PRICKLE1. On the basis of this, we develop a combination strategy to circumvent tazemetostat resistance using bypass targeting of AURKB. This offers a paradigm for rational epigenetic combination therapy suitable for translation to clinical trials for epithelioid sarcomas, rhabdoid tumors, and other epigenetically dysregulated cancers.

SIGNIFICANCE

Genomic studies of patient epithelioid sarcomas and rhabdoid tumors identify mutations converging on a common pathway for response to EZH2 inhibition. Resistance mutations decouple drug-induced differentiation from cell-cycle control. We identify an epigenetic combination strategy to overcome resistance and improve durability of response, supporting its investigation in clinical trials. See related commentary by Paolini and Souroullas, p. 903. This article is featured in Selected Articles from This Issue, p. 897.

The role of prickle proteins in vertebrate development and pathology

Prickle is an evolutionarily conserved family of proteins exclusively associated with planar cell polarity (PCP) signalling. This signalling pathway provides directional and positional cues to eukaryotic cells along the plane of an epithelial sheet, orthogonal to both apicobasal and left-right axes. Through studies in the fruit fly Drosophila, we have learned that PCP signalling is manifested by the spatial segregation of two protein complexes, namely Prickle/Vangl and Frizzled/Dishevelled. While Vangl, Frizzled, and Dishevelled proteins have been extensively studied, Prickle has been largely neglected. This is likely because its role in vertebrate development and pathologies is still being explored and is not yet fully understood. The current review aims to address this gap by summarizing our current knowledge on vertebrate Prickle proteins and to cover their broad versatility. Accumulating evidence suggests that Prickle is involved in many developmental events, contributes to homeostasis, and can cause diseases when its expression and signalling properties are deregulated. This review highlights the importance of Prickle in vertebrate development, discusses the implications of Prickle-dependent signalling in pathology, and points out the blind spots or potential links regarding Prickle, which could be studied further.

Overcoming clinical resistance to EZH2 inhibition using rational epigenetic combination therapy

Essential epigenetic dependencies have become evident in many cancers. Based on the functional antagonism between BAF/SWI/SNF and PRC2 in SMARCB1-deficient sarcomas, we and colleagues recently completed the clinical trial of the EZH2 inhibitor tazemetostat. However, the principles of tumor response to epigenetic therapy in general, and tazemetostat in particular, remain unknown. Using functional genomics of patient tumors and diverse experimental models, we sought to define molecular mechanisms of tazemetostat resistance in SMARCB1-deficient sarcomas and rhabdoid tumors. We found distinct classes of acquired mutations that converge on the RB1/E2F axis and decouple EZH2-dependent differentiation and cell cycle control. This allows tumor cells to escape tazemetostat-induced G1 arrest despite EZH2 inhibition, and suggests a general mechanism for effective EZH2 therapy. This also enables us to develop combination strategies to circumvent tazemetostat resistance using cell cycle bypass targeting via AURKB, and synthetic lethal targeting of PGBD5-dependent DNA damage repair via ATR. This reveals prospective biomarkers for therapy stratification, including PRICKLE1 associated with tazemetostat resistance. In all, this work offers a paradigm for rational epigenetic combination therapy suitable for immediate translation to clinical trials for epithelioid sarcomas, rhabdoid tumors, and other epigenetically dysregulated cancers.

Using Drosophila melanogaster to Dissect the Roles of the mTOR Signaling Pathway in Cell Growth

The evolutionarily conserved target of rapamycin (TOR) serine/threonine kinase controls eukaryotic cell growth, metabolism and survival by integrating signals from the nutritional status and growth factors. TOR is the catalytic subunit of two distinct functional multiprotein complexes termed mTORC1 (mechanistic target of rapamycin complex 1) and mTORC2, which phosphorylate a different set of substrates and display different physiological functions. Dysregulation of TOR signaling has been involved in the development and progression of several disease states including cancer and diabetes. Here, we highlight how genetic and biochemical studies in the model system Drosophila melanogaster have been crucial to identify the mTORC1 and mTORC2 signaling components and to dissect their function in cellular growth, in strict coordination with insulin signaling. In addition, we review new findings that involve Drosophila Golgi phosphoprotein 3 in regulating organ growth via Rheb-mediated activation of mTORC1 in line with an emerging role for the Golgi as a major hub for mTORC1 signaling.

PRICKLE1 gene methylation and abnormal transcription in Chinese patients with ankylosing spondylitis

BACKGROUND

Ankylosing spondylitis (AS) is a common inflammatory arthritis without a reliable biomarker. The role of methylation and mRNA expression of PRICKLE1 promoter in the pathogenesis of ankylosing spondylitis remains unclear.

METHODS

A two-stage case-control design was used to detect the characteristics of methyl group and transcriptome of PRICKLE1 gene in Ankylosing spondylitis. The methylation degree of PRICKLE1 gene promoter region was tested by phosphate-sequencing, and further analyzed whether there was significant difference in methylation level of PRICKLE1 gene. The expression levels of PRICKLE1 mRNA in 50 AS patients and 50 healthy controls were detected by real-time quantitative PCR (RT-qPCR).

RESULTS

Compared with healthy control group, the intensity of methylation in 4 ponds of PRICKLE1 in patients with Ankylosing spondylitis was low, and the mRNA levels were overexpressed (P = 0.017). ROC results showed that the sensitivity of PRICKLE1 was 68.67% and specificity was 71.43%.

CONCLUSION

There is a significant change in the concentration of serum PRICKLE1 mRNA​in patients with Ankylosing spondylitis, and the degree of gene methylation is significantly reduced, suggesting that PRICKLE1 gene maybe involved in the pathogenesis of Ankylosing spondylitis, which may be useful for predicting the occurrence of AS and finding new early screening indicators.

Mapping the MOB proteins' proximity network reveals a unique interaction between human MOB3C and the RNase P complex

Distinct functions mediated by members of the monopolar spindle-one-binder (MOB) family of proteins remain elusive beyond the evolutionarily conserved and well-established roles of MOB1 (MOB1A/B) in regulating tissue homeostasis within the Hippo pathway. Since MOB proteins are adaptors, understanding how they engage in protein-protein interactions and help assemble complexes is essential to define the full scope of their biological functions. To address this, we undertook a proximity-dependent biotin identification approach to define the interactomes of all seven human MOB proteins in HeLa and human embryonic kidney 293 cell lines. We uncovered >200 interactions, of which at least 70% are unreported on BioGrid. The generated dataset reliably recalled the bona fide interactors of the well-studied MOBs. We further defined the common and differential interactome between different MOBs on a subfamily and an individual level. We discovered a unique association between MOB3C and 7 of 10 protein subunits of the RNase P complex, an endonuclease that catalyzes tRNA 5' maturation. As a proof of principle for the robustness of the generated dataset, we validated the specific interaction of MOB3C with catalytically active RNase P by using affinity purification-mass spectrometry and pre-tRNA cleavage assays of MOB3C pulldowns. In summary, our data provide novel insights into the biology of MOB proteins and reveal the first interactors of MOB3C, components of the RNase P complex, and hence an exciting nexus with RNA biology.

A complex of Wnt/planar cell polarity signaling components Vangl1 and Fzd7 drives glioblastoma multiforme malignant properties

Targeting common oncogenic drivers of glioblastoma multiforme (GBM) in patients has remained largely ineffective, raising the possibility that alternative pathways may contribute to tumor aggressiveness. Here we demonstrate that Vangl1 and Fzd7, components of the non-canonical Wnt planar cell polarity (Wnt/PCP) signaling pathway, promote GBM malignancy by driving cellular proliferation, migration, and invasiveness, and engage Rho GTPases to promote cytoskeletal rearrangements and actin dynamics in migrating GBM cells. Mechanistically, we uncover the existence of a novel Vangl1/Fzd7 complex at the leading edge of migrating GBM cells and propose that this complex is critical for the recruitment of downstream effectors to promote tumor progression. Moreover, we observe that depletion of FZD7 results in a striking suppression of tumor growth and latency and extends overall survival in an intracranial mouse xenograft model. Our observations support a novel mechanism by which Wnt/PCP components Vangl1 and Fzd7 form a complex at the leading edge of migratory GBM cells to engage downstream effectors that promote actin cytoskeletal rearrangements dynamics. Our findings suggest that interference with Wnt/PCP pathway function may offer a novel therapeutic strategy for patients diagnosed with GBM.

Expression of mTOR in normal and pathological conditions

The mechanistic/mammalian target of rapamycin (mTOR), a protein discovered in 1991, integrates a complex pathway with a key role in maintaining cellular homeostasis. By comprising two functionally distinct complexes, mTOR complex 1 (mTORC1) and mTORC2, it is a central cellular hub that integrates intra- and extracellular signals of energy, nutrient, and hormone availability, modulating the molecular responses to acquire a homeostatic state through the regulation of anabolic and catabolic processes. Accordingly, dysregulation of mTOR pathway has been implicated in a variety of human diseases. While major advances have been made regarding the regulators and effectors of mTOR signaling pathway, insights into the regulation of mTOR gene expression are beginning to emerge. Here, we present the current available data regarding the mTOR expression regulation at the level of transcription, translation and mRNA stability and systematize the current knowledge about the fluctuations of mTOR expression observed in several diseases, both cancerous and non-cancerous. In addition, we discuss whether mTOR expression changes can be used as a biomarker for diagnosis, disease progression, prognosis and/or response to therapeutics. We believe that our study will contribute for the implementation of new disease biomarkers based on mTOR as it gives an exhaustive perspective about the regulation of mTOR gene expression in both normal and pathological conditions.

Vangl-dependent Wnt/planar cell polarity signaling mediates collective breast carcinoma motility and distant metastasis

BACKGROUND

In light of the growing appreciation for the role of collective cell motility in metastasis, a deeper understanding of the underlying signaling pathways will be critical to translating these observations to the treatment of advanced cancers. Here, we examine the contribution of Wnt/planar cell polarity (Wnt/PCP), one of the non-canonical Wnt signaling pathways and defined by the involvement of the tetraspanin-like proteins Vangl1 and Vangl2, to breast tumor cell motility, collective cell invasiveness and mammary tumor metastasis.

METHODS

Vangl1 and Vangl2 knockdown and overexpression and Wnt5a stimulation were employed to manipulate Wnt/PCP signaling in a battery of breast cancer cell lines representing all breast cancer subtypes, and in tumor organoids from MMTV-PyMT mice. Cell migration was assessed by scratch and organoid invasion assays, Vangl protein subcellular localization was assessed by confocal fluorescence microscopy, and RhoA activation was assessed in real time by fluorescence imaging with an advanced FRET biosensor. The impact of Wnt/PCP suppression on mammary tumor growth and metastasis was assessed by determining the effect of conditional Vangl2 knockout on the MMTV-NDL mouse mammary tumor model.

RESULTS

We observed that Vangl2 knockdown suppresses the motility of all breast cancer cell lines examined, and overexpression drives the invasiveness of collectively migrating MMTV-PyMT organoids. Vangl2-dependent RhoA activity is localized in real time to a subpopulation of motile leader cells displaying a hyper-protrusive leading edge, Vangl protein is localized to leader cell protrusions within leader cells, and actin cytoskeletal regulator RhoA is preferentially activated in the leader cells of a migrating collective. Mammary gland-specific knockout of Vangl2 results in a striking decrease in lung metastases in MMTV-NDL mice, but does not impact primary tumor growth characteristics.

CONCLUSIONS

We conclude that Vangl-dependent Wnt/PCP signaling promotes breast cancer collective cell migration independent of breast tumor subtype and facilitates distant metastasis in a genetically engineered mouse model of breast cancer. Our observations are consistent with a model whereby Vangl proteins localized at the leading edge of leader cells in a migrating collective act through RhoA to mediate the cytoskeletal rearrangements required for pro-migratory protrusion formation.

Acidic Growth Conditions Promote Epithelial-to-Mesenchymal Transition to Select More Aggressive PDAC Cell Phenotypes In Vitro

Pancreatic Ductal Adenocarcinoma (PDAC) is characterized by an acidic microenvironment, which contributes to therapeutic failure. So far there is a lack of knowledge with respect to the role of the acidic microenvironment in the invasive process. This work aimed to study the phenotypic and genetic response of PDAC cells to acidic stress along the different stages of selection. To this end, we subjected the cells to short- and long-term acidic pressure and recovery to pH_e 7.4. This treatment aimed at mimicking PDAC edges and consequent cancer cell escape from the tumor. The impact of acidosis was assessed for cell morphology, proliferation, adhesion, migration, invasion, and epithelial-mesenchymal transition (EMT) via functional in vitro assays and RNA sequencing. Our results indicate that short acidic treatment limits growth, adhesion, invasion, and viability of PDAC cells. As the acid treatment progresses, it selects cancer cells with enhanced migration and invasion abilities induced by EMT, potentiating their metastatic potential when re-exposed to pH_e 7.4. The RNA-seq analysis of PANC-1 cells exposed to short-term acidosis and pH_e-selected recovered to pH_e 7.4 revealed distinct transcriptome rewiring. We describe an enrichment of genes relevant to proliferation, migration, EMT, and invasion in acid-selected cells. Our work clearly demonstrates that upon acidosis stress, PDAC cells acquire more invasive cell phenotypes by promoting EMT and thus paving the way for more aggressive cell phenotypes.

mTORC2 interactome and localization determine aggressiveness of high-grade glioma cells through association with gelsolin

mTOR complex 2 (mTORC2) has been implicated as a key regulator of glioblastoma cell migration. However, the roles of mTORC2 in the migrational control process have not been entirely elucidated. Here, we elaborate that active mTORC2 is crucial for GBM cell motility. Inhibition of mTORC2 impaired cell movement and negatively affected microfilament and microtubule functions. We also aimed to characterize important players involved in the regulation of cell migration and other mTORC2-mediated cellular processes in GBM cells. Therefore, we quantitatively characterized the alteration of the mTORC2 interactome under selective conditions using affinity purification-mass spectrometry in glioblastoma. We demonstrated that changes in cell migration ability specifically altered mTORC2-associated proteins. GSN was identified as one of the most dynamic proteins. The mTORC2-GSN linkage was mostly highlighted in high-grade glioma cells, connecting functional mTORC2 to multiple proteins responsible for directional cell movement in GBM. Loss of GSN disconnected mTORC2 from numerous cytoskeletal proteins and affected the membrane localization of mTORC2. In addition, we reported 86 stable mTORC2-interacting proteins involved in diverse molecular functions, predominantly cytoskeletal remodeling, in GBM. Our findings might help expand future opportunities for predicting the highly migratory phenotype of brain cancers in clinical investigations.

Novel Potential Markers of Myofibroblast Differentiation Revealed by Single-Cell RNA Sequencing Analysis of Mesenchymal Stromal Cells in Profibrotic and Adipogenic Conditions

Mesenchymal stromal cells (MSCs) are the key regulators of tissue homeostasis and repair after damage. Accumulating evidence indicates the dual contribution of MSCs into the development of fibrosis induced by chronic injury: these cells can suppress the fibrotic process due to paracrine activity, but their promoting role in fibrosis by differentiating into myofibroblasts has also been demonstrated. Many model systems reproducing fibrosis have shown the ability of peroxisome proliferator-activated receptor (PPAR) agonists to reverse myofibroblast differentiation. Thus, the differentiation of multipotent cells into myofibroblasts and adipocytes can be considered as processes that require the activation of opposite patterns of gene expression. To test this hypothesis, we analyzed single cell RNA-Seq transcriptome of human adipose tissue MSCs after stimulation of the myofibroblast or adipogenic differentiation and revealed several genes that changed their expression in a reciprocal manner upon these conditions. We validated the expression of selected genes by RT-PCR, and evaluated the upregulation of several relevant proteins using immunocytochemistry, refining the results obtained by RNA-Seq analysis. We have shown, for the first time, the expression of neurotrimin (NTM), previously studied mainly in the nervous tissue, in human adipose tissue MSCs, and demonstrated its increased gene expression and clustering of membrane receptors upon the stimulation of myofibroblast differentiation. We also showed an increased level of CHD3 (Chromodomain-Helicase-DNA-binding protein 3) in MSCs under profibrotic conditions, while retinol dehydrogenase-10 (RDH10) was detected only in MSCs after adipogenic induction, which contradicted the data of transcriptomic analysis and again highlights the need to validate the data obtained by omics methods. Our findings suggest the further analysis of the potential contribution of neurotrimin and CHD3 in the regulation of myofibroblast differentiation and the development of fibrosis.

Wnt signaling pathway-related gene PRICKLE1 is a prognostic biomarker for esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) has become a major health risk to human health. Although significant clinical progress has been made in the treatment of ESCC, the prognosis of patients still needs to be improved. Therefore, it is important to screen effective molecular indicators for the prognosis of ESCC. In this study, the intersection of up-regulated genes, down-regulated genes, and Wnt signaling pathway-related genes in ESCC was taken, and 47 overlapping genes were found. PRICKLE1 was determined to be an independent prognostic factor in ESCC based on univariate and multifactorial COX risk regression models. Kaplan-Meier survival curves showed that patients in the PRICKLE1 high expression group had significantly better overall survival. In addition, we performed various experiments to examine the effects of PRICKLE1 overexpression on proliferation, migration, and apoptosis of ESCC cells. The experimental results showed that the PRICKLE1-OE group had reduced cell viability, significantly lower migration ability and significantly higher apoptosis rate compared to the NC group.Therefore, we hypothesized that high PRICKLE1 expression could be used to predict the survival rate of ESCC patients, which could be used as an independent prognostic indicator for ESCC patients and provide potential applications for ESCC clinical treatment.

Ras-mediated activation of mTORC2 promotes breast epithelial cell migration and invasion

We previously identified the mechanistic target of rapamycin complex 2 (mTORC2) as an effector of Ras for the control of directed cell migration in Dictyostelium. Recently, the Ras-mediated regulation of mTORC2 was found to be conserved in mammalian cells, and mTORC2 was shown to be an effector of oncogenic Ras. Interestingly, mTORC2 has been linked to cancer cell migration, and particularly in breast cancer. Here, we investigated the role of Ras in promoting the migration and invasion of breast cancer cells through mTORC2. We observed that both Ras and mTORC2 promote the migration of different breast cancer cells and breast cancer cell models. Using HER2 and oncogenic Ras-transformed breast epithelial MCF10A cells, we found that both wild-type Ras and oncogenic Ras promote mTORC2 activation and an mTORC2-dependent migration and invasion in these breast cancer models. We further observed that, whereas oncogenic Ras-transformed MCF10A cells display uncontrolled cell proliferation and invasion, disruption of mTORC2 leads to loss of invasiveness only. Together, our findings suggest that, whereas the Ras-mediated activation of mTORC2 is expected to play a minor role in breast tumor formation, the Ras-mTORC2 pathway plays an important role in promoting the migration and invasion of breast cancer cells.

Transcriptome analysis of peripheral blood mononuclear cells in patients with type 1 diabetes mellitus

PURPOSE

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease characterized by the destruction of pancreatic β cells. The goal of this study was to explore potential biological biomarkers for T1DM.

METHODS

Two microarray datasets (GSE55098 and GSE156035) about human peripheral blood mononuclear cells (PBMCs) were systematically extracted from the Gene Expression Omnibus (GEO) database. Common genes were identified from the perspective of differentially expressed genes (DEGs) and weighted gene co-expression network analysis (WGCNA) respectively, and hub genes were identified by least absolute shrinkage and selection operator (LASSO) analysis. We also observed the expression of these hub genes in some common autoimmune diseases and predicted transcription factors (TFs) that might be associated with these genes.

RESULTS

Seven hub genes (DDIT4, ESCO2, SH3BP4, PRICKLE1, EPM2AIP1, KCNJ15 and GRM8) were finally identified. Receiver operating characteristic (ROC) analysis showed that the high expression of these genes could well predict the occurrence of T1DM. Gene set enrichment analysis (GSEA) suggested that most of these hub genes may be mainly involved in the changes of biological functions such as inflammation, infection, immunity, cancer, and apoptosis. Further, compared with the control group, the expression levels of these hub genes also changed in some other autoimmune diseases, such as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), primary biliary cholangitis (PBC), etc., indicating that they might be the common targets of these autoimmune diseases.

CONCLUSIONS

The present study identified novel genes associated with T1DM from the PBMCs perspective that might provide new ideas for the early diagnosis, monitoring, evaluation, and prediction of T1DM.

CRISPR-based kinome-screening revealed MINK1 as a druggable player to rewire 5FU-resistance in OSCC through AKT/MDM2/p53 axis

Cisplatin, 5FU and docetaxel (TPF) are the most common chemotherapy regimen used for advanced OSCC. However, many cancer patients experience relapse, continued tumor growth, and spread due to drug resistance, which leads to treatment failure and metastatic disease. Here, using a CRISPR/Cas9 based kinome knockout screening, Misshapen-like kinase 1 (MINK1) is identified as an important mediator of 5FU resistance in OSCC. Analysis of clinical samples demonstrated significantly higher MINK1 expression in the tumor tissues of chemotherapy non-responders as compared to chemotherapy responders. The nude mice and zebrafish xenograft experiments indicate that knocking out MINK1 restores 5FU mediated cell death in chemoresistant OSCC. An antibody based phosphorylation array screen revealed MINK1 as a negative regulator of p53. Mechanistically, MINK1 modulates AKT phosphorylation at Ser473, which enables p-MDM2 (Ser 166) mediated degradation of p53. We also identified lestaurtinib as a potent inhibitor of MINK1 kinase activity. The patient derived TPF resistant cell based xenograft data suggest that lestaurtinib restores 5FU sensitivity and facilitates a significant reduction of tumor burden. Overall, our study suggests that MINK1 is a major driver of 5FU resistance in OSCC. The novel combination of MINK1 inhibitor lestaurtinib and 5FU needs further clinical investigation in advanced OSCC.

The serine/threonine kinase MINK1 directly regulates the function of promigratory proteins

Upregulation of the developmental Wnt/planar cell polarity pathway is observed in many cancers and is associated with cancer development. We recently showed that PRICKLE1, a core Wnt/PCP component, is a poor-prognosis marker in triple negative breast cancer (TNBC). PRICKLE1 is phosphorylated by the serine/threonine kinase MINK1 and contributes to TNBC cell motility and invasiveness. However, the identity of MINK1 substrates and the role of MINK1 enzymatic activity in this process remain to be addressed. We performed a phosphoproteomic strategy and identified MINK1 substrates including LL5β. LL5β anchors microtubules at the cell cortex through its association with CLASPs to trigger focal adhesion disassembly. LL5β is phosphorylated by MINK1 promoting its interaction with CLASPs. Using a kinase inhibitor, we demonstrate that the enzymatic activity of MINK1 is involved in the protein complex assembly and localization, and cell migration. Analysis of gene expression data show that the concomitant up-regulation of PRICKLE1 and LL5β mRNA levels encoding MINK1 substrates is associated with a poor metastasis-free survival in TNBC patients. Altogether, our results suggest that MINK1 may represent a potential target in TNBC.

The Role of DACT Family Members in Tumorigenesis and Tumor Progression

Disheveled-associated antagonist of β-catenin (DACT), which ubiquitously expressed in human tissue, is critical for regulating cell proliferation and several developmental processes in different cellular contexts. In addition, DACT is essential for some other cellular processes, such as cell apoptosis, migration and differentiation. Given the importance of DACT in these cellular processes, many scientists are gradually interested in studying the role of DACT in tumorigenesis and cancer progression. This review article focuses on the latest research regarding the essential functions and potential DACT mechanisms in the occurrence and progression of tumors. Our study indicates that DACT may act as a tumor biomarker for cancer diagnosis and prognosis, as well as a promising therapeutic target in cancers.

Vangl as a Master Scaffold for Wnt/Planar Cell Polarity Signaling in Development and Disease

The establishment of polarity within tissues and dynamic cellular morphogenetic events are features common to both developing and adult tissues, and breakdown of these programs is associated with diverse human diseases. Wnt/Planar cell polarity (Wnt/PCP) signaling, a branch of non-canonical Wnt signaling, is critical to the establishment and maintenance of polarity in epithelial tissues as well as cell motility events critical to proper embryonic development. In epithelial tissues, Wnt/PCP-mediated planar polarity relies upon the asymmetric distribution of core proteins to establish polarity, but the requirement for this distribution in Wnt/PCP-mediated cell motility remains unclear. However, in both polarized tissues and migratory cells, the Wnt/PCP-specific transmembrane protein Vangl is required and appears to serve as a scaffold upon which the core pathway components as well as positive and negative regulators of Wnt/PCP signaling assemble. The current literature suggests that the multiple interaction domains of Vangl allow for the binding of diverse signaling partners for the establishment of context- and tissue-specific complexes. In this review we discuss the role of Vangl as a master scaffold for Wnt/PCP signaling in epithelial tissue polarity and cellular motility events in developing and adult tissues, and address how these programs are dysregulated in human disease.

Placental mammals acquired functional sequences in NRK for regulating the CK2-PTEN-AKT pathway and placental cell proliferation

The molecular evolution processes underlying the acquisition of the placenta in eutherian ancestors are not fully understood. Mouse NCK-interacting kinase (NIK)-related kinase (NRK) is expressed highly in the placenta and plays a role in preventing placental hyperplasia. Here, we show the molecular evolution of NRK, which confers its function for inhibiting placental cell proliferation. Comparative genome analysis identified NRK orthologs across vertebrates, which share the kinase and citron homology (CNH) domains. Evolutionary analysis revealed that NRK underwent extensive amino acid substitutions in the ancestor of placental mammals and has been since conserved. Biochemical analysis of mouse NRK revealed that the CNH domain binds to phospholipids, and a region in NRK binds to and inhibits casein kinase-2 (CK2), which we named the CK2-inhibitory region (CIR). Cell culture experiments suggest the following: 1) Mouse NRK is localized at the plasma membrane via the CNH domain, where the CIR inhibits CK2. 2) This mitigates CK2-dependent phosphorylation and inhibition of PTEN and 3) leads to the inhibition of AKT signaling and cell proliferation. Nrk deficiency increased phosphorylation levels of PTEN and AKT in mouse placenta, supporting our hypothesis. Unlike mouse NRK, chicken NRK did not bind to phospholipids and CK2, decrease phosphorylation of AKT, or inhibit cell proliferation. Both the CNH domain and CIR have evolved under purifying selection in placental mammals. Taken together, our study suggests that placental mammals acquired the phospholipid-binding CNH domain and CIR in NRK for regulating the CK2–PTEN–AKT pathway and placental cell proliferation.

Local Wnt signalling in the asymmetric migrating vertebrate cells

Wnt signalling is known to generate cellular asymmetry via Wnt/planar cell polarity pathway (Wnt/PCP). Wnt/PCP acts locally (i) to orient membrane polarity and asymmetric establishment of intercellular junctions via conserved set of PCP proteins most specifically represented by Vangl and Prickle, and (ii) to asymmetrically rearrange cytoskeletal structures via downstream effectors of Dishevelled (Dvl). This process is best described on stable phenotypes of epithelial cells. Here, however, we review the activity of Wnt signalling in migratory cells which experience the extensive rearrangements of cytoskeleton and consequently dynamic asymmetry, making the localised effects of Wnt signalling easier to distinguish. Firstly, we focused on migration of neuronal axons, which allows to study how the pre-existent cellular asymmetry can influence Wnt signalling outcome. Then, we reviewed the role of Wnt signalling in models of mesenchymal migration including neural crest, melanoma, and breast cancer cells. Last, we collected evidence for local Wnt signalling in amoeboid cells, especially lymphocytes. As the outcome of this review, we identify blank spots in our current understanding of this topic, propose models that synthesise the current observations and allow formulation of testable hypotheses for the future research.

Proliferation Cycle Transcriptomic Signatures are Strongly associated With Gastric Cancer Patient Survival

Gastric cancer is one of the most heterogeneous tumors with multi-level molecular disturbances. Sustaining proliferative signaling and evading growth suppressors are two important hallmarks that enable the cancer cells to become tumorigenic and ultimately malignant, which enable tumor growth. Discovering and understanding the difference in tumor proliferation cycle phenotypes can be used to better classify tumors, and provide classification schemes for disease diagnosis and treatment options, which are more in line with the requirements of today's precision medicine. We collected 691 eligible samples from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) database, combined with transcriptome data, to explore different heterogeneous proliferation cycle phenotypes, and further study the potential genomic changes that may lead to these different phenotypes in this study. Interestingly, two subtypes with different clinical and biological characteristics were identified through cluster analysis of gastric cancer transcriptome data. The repeatability of the classification was confirmed in an independent Gene Expression Omnibus validation cohort, and consistent phenotypes were observed. These two phenotypes showed different clinical outcomes, and tumor mutation burden. This classification helped us to better classify gastric cancer patients and provide targeted treatment based on specific transcriptome data.

Role of mammalian target of rapamycin complex 2 in primary and secondary liver cancer

The mammalian target of rapamycin (mTOR) acts in two structurally and functionally distinct protein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). Upon deregulation, activated mTOR signaling is associated with multiple processes involved in tumor growth and metastasis. Compared with mTORC1, much less is known about mTORC2 in cancer, mainly because of the unavailability of a selective inhibitor. However, existing data suggest that mTORC2 with its two distinct subunits Rictor and mSin1 might play a more important role than assumed so far. It is one of the key effectors of the PI3K/AKT/mTOR pathway and stimulates cell growth, cell survival, metabolism, and cytoskeletal organization. It is not only implicated in tumor progression, metastasis, and the tumor microenvironment but also in resistance to therapy. Rictor, the central subunit of mTORC2, was found to be upregulated in different kinds of cancers and is associated with advanced tumor stages and a bad prognosis. Moreover, AKT, the main downstream regulator of mTORC2/Rictor, is one of the most highly activated proteins in cancer. Primary and secondary liver cancer are major problems for current cancer therapy due to the lack of specific medical treatment, emphasizing the need for further therapeutic options. This review, therefore, summarizes the role of mTORC2/Rictor in cancer, with special focus on primary liver cancer but also on liver metastases.

Transcriptional Profiling of Tumorspheres Reveals TRPM4 as a Novel Stemness Regulator in Breast Cancer

Cancer stem cells (CSCs) have been implicated in the development of chemoresistance, tumor recurrence and metastasis in breast cancer, thus emerging as a promising target for novel therapies. To identify novel stemness regulators that could potentially be targeted in luminal ER⁺ tumors, we performed RNA-sequencing (RNA-seq) in MCF-7 adherent monolayer cells and tumorspheres enriched in breast CSCs (bCSCs). We identified 1421 differentially expressed genes (DEGs), with 923 of them being upregulated and 498 downregulated in tumorspheres. Gene ontology and pathway enrichment analyses revealed that distinct gene networks underlie the biology of the two cell systems. We selected the transient receptor potential cation channel subfamily M member 4 (TRPM4) gene that had not been associated with cancer stemness before for further investigation. We confirmed that TRPM4 was overexpressed in tumorspheres and showed that its knock-down affected the stemness properties of bCSCs in vitro. TRPM4 inhibition revealed potential anti-tumor effects by directly targeting the bCSC subpopulation. We suggest that TRPM4 plays a key role in stemness mediation, and its inhibition may represent a novel therapeutic modality against bCSCs contributing in the improvement of breast cancer treatments.

Cobalt-induced oxidative stress contributes to alveolar/bronchiolar carcinogenesis in B6C3F1/N mice

Rodent alveolar/bronchiolar carcinomas (ABC) that arise either spontaneously or due to chemical exposure are similar to a subtype of lung adenocarcinomas in humans. B6C3F1/N mice and F344/NTac rats exposed to cobalt metal dust (CMD) by inhalation developed ABCs in a dose dependent manner. In CMD-exposed mice, the incidence of Kras mutations in ABCs was 67% with 80% of those being G to T transversions on codon 12 suggesting a role of oxidative stress in the pathogenesis. In vitro studies, such as DMPO (5,5-dimethyl-1-pyrroline N-oxide) immune-spin trapping assay, and dihydroethidium (DHE) fluorescence assay on A549 and BEAS-2B cells demonstrated increased oxidative stress due to cobalt exposure. In addition, significantly increased 8-oxo-dG adducts were demonstrated by immunohistochemistry in lungs from mice exposed to CMD for 90 days. Furthermore, transcriptomic analysis on ABCs arising spontaneously or due to chronic CMD-exposure demonstrated significant alterations in canonical pathways related to MAPK signaling (IL-8, ErbB, Integrin, and PAK pathway) and oxidative stress (PI3K/AKT and Melatonin pathway) in ABCs from CMD-exposed mice. Oxidative stress can stimulate PI3K/AKT and MAPK signaling pathways. Nox4 was significantly upregulated only in CMD-exposed ABCs and NOX4 activation of PI3K/AKT can lead to increased ROS levels in human cancer cells. The gene encoding Ereg was markedly up-regulated in CMD-exposed mice. Oncogenic KRAS mutations have been shown to induce EREG overexpression. Collectively, all these data suggest that oxidative stress plays a significant role in CMD-induced pulmonary carcinogenesis in rodents and these findings may also be relevant in the context of human lung cancers.

mTOR Signaling in the Inner Ear as Potential Target to Treat Hearing Loss

Hearing loss affects many people worldwide and occurs often as a result of age, ototoxic drugs and/or excessive noise exposure. With a growing number of elderly people, the number of people suffering from hearing loss will also increase in the future. Despite the high number of affected people, for most patients there is no curative therapy for hearing loss and hearing aids or cochlea implants remain the only option. Important treatment approaches for hearing loss include the development of regenerative therapies or the inhibition of cell death/promotion of cell survival pathways. The mammalian target of rapamycin (mTOR) pathway is a central regulator of cell growth, is involved in cell survival, and has been shown to be implicated in many age-related diseases. In the inner ear, mTOR signaling has also started to gain attention recently. In this review, we will emphasize recent discoveries of mTOR signaling in the inner ear and discuss implications for possible treatments for hearing restoration.

PRICKLE1, a Wnt/PCP signaling component, is overexpressed and associated with inferior prognosis in acute myeloid leukemia

BACKGROUND

Prickle planar cell polarity protein 1 (PRICKLE1), a core component of the non-canonical Wnt/planar cell polarity (PCP) pathway, was recently reported to be upregulated and correlated with poor prognosis in solid cancers. However, the effect of PRICKLE1 on acute myeloid leukemia (AML) remains unknown. This study aims to characterize the prognostic significance of PRICKLE1 expression in patients with AML.

METHODS

RNA-seq was performed to compare mRNA expression profiles of AML patients and healthy controls. qRT-PCR and western blotting were used to analyze the expression of PRICKLE1 in AML patients and cell lines, and two independent datasets (TCGA-LAML and TARGET-AML) online were used to validate the expression results. The correlations between the expression of PRICKLE1 and clinical features were further analyzed.

RESULTS

Our data showed that PRICKLE1 expression levels were markedly high in AML patients at the time of diagnosis, decreased after complete remission and increased again at relapse. Of note, PRICKLE1 was highly expressed in drug resistant AML cells and monocytic-AML patients. High PRICKLE1 expression was found in FLT3/DNMT3A/IDH1/IDH2-mutant AML and associated with poor prognosis. Furthermore, high expression of PRICKLE1 may be correlated with migration and invasion components upregulation in AML patients.

CONCLUSIONS

These results indicated that high PRICKLE1 expression may be a poor prognostic biomarker and therapeutic target of AML.

Pan-cancer investigation reveals mechanistic insights of planar cell polarity gene Fuz in carcinogenesis

The fuzzy planar cell polarity protein (Fuz) is an effector component of the planar cell polarity (PCP) signaling. Together with other core and effector proteins, the PCP pathway controls polarized cell movements. Fuz was also reported as a negative regulator of cell survival. In this study, we performed a pan-cancer survey to demonstrate the role of Fuz in multiple types of cancer. In head-neck squamous cell carcinoma and lung adenocarcinoma tumor samples, a reduction of Fuz transcript expression was detected. This coincides with the poor overall survival probabilities of these patients. We further showed that Fuz promoter hypermethylation contributes to its transcriptional downregulation. Meanwhile, we also identified a relatively higher mutation frequency at the 404^th arginine amino acid residue in the coding sequence of Fuz locus, and further demonstrated that mutant Fuz proteins perturb the pro-apoptotic function of Fuz. In summary, our study unveiled an intriguing relationship between Fuz dysregulation and cancer prognosis, and further provides mechanistic insights of Fuz's involvement in carcinogenesis.

An Overview of Potential Therapeutic Agents Targeting WNT/PCP Signaling

Since the discovery of the proto-oncogene Wnt1 (Int1) in 1982, WNT signaling has been identified as one of the most important pathways that regulates a wide range of fundamental developmental and physiological processes in multicellular organisms. The canonical WNT signaling pathway depends on the stabilization and translocation of β-catenin and plays important roles in development and homeostasis. The WNT/planar cell polarity (WNT/PCP) signaling, also known as one of the β-catenin-independent WNT pathways, conveys directional information to coordinate polarized cell behaviors. Similar to WNT/β-catenin signaling, disruption or aberrant activation of WNT/PCP signaling also underlies a variety of developmental defects and cancers. However, the pharmacological targeting of WNT/PCP signaling for therapeutic purposes remains largely unexplored. In this review, we briefly discuss WNT/PCP signaling in development and disease and summarize the known drugs/inhibitors targeting this pathway.

Regulation of mTORC2 Signaling

Mammalian target of rapamycin (mTOR), a serine/threonine protein kinase and a master regulator of cell growth and metabolism, forms two structurally and functionally distinct complexes, mTOR complex 1 (mTORC1) and mTORC2. While mTORC1 signaling is well characterized, mTORC2 is relatively poorly understood. mTORC2 appears to exist in functionally distinct pools, but few mTORC2 effectors/substrates have been identified. Here, we review recent advances in our understanding of mTORC2 signaling, with particular emphasis on factors that control mTORC2 activity.

Enhancement of Breast Cancer Cell Aggressiveness by lncRNA H19 and its Mir-675 Derivative: Insight into Shared and Different Actions

Breast cancer is a major public health problem and the leading world cause of women death by cancer. Both the recurrence and mortality of breast cancer are mainly caused by the formation of metastasis. The long non-coding RNA H19, the precursor of miR-675, is involved in breast cancer development. The aim of this work was to determine the implication but, also, the relative contribution of H19 and miR-675 to the enhancement of breast cancer metastatic potential. We showed that both H19 and miR-675 increase the invasive capacities of breast cancer cells in xenografted transgenic zebrafish models. In vitro, H19 and miR-675 enhance the cell migration and invasion, as well as colony formation. H19 seems to induce the epithelial-to-mesenchymal transition (EMT), with a decreased expression of epithelial markers and an increased expression of mesenchymal markers. Interestingly, miR-675 simultaneously increases the expression of both epithelial and mesenchymal markers, suggesting the induction of a hybrid phenotype or mesenchymal-to-epithelial transition (MET). Finally, we demonstrated for the first time that miR-675, like its precursor H19, increases the stemness properties of breast cancer cells. Altogether, our data suggest that H19 and miR-675 could enhance the aggressiveness of breast cancer cells through both common and different mechanisms.

Identification of genes associated with gastric cancer survival and construction of a nomogram to improve risk stratification for patients with gastric cancer

The present study aimed to identify genes associated with gastric cancer survival and improve risk stratification for patients with gastric cancer. Transcriptomic and clinicopathological data from 443 gastric cancer samples were retrieved from The Cancer Genome Atlas database. The DESeq R package was applied to screen for differentially expressed genes between Tumor-Node-Metastasis (TNM) stage (I vs. IV) and histological grade (G3 vs. G1 and G2). A total of seven genes were common to both comparisons; spondin 1 (SPON1); thrombospondin 4 (THBS4); Sushi, Von Willebrand factor type A, EGF and pentraxin domain containing 1 (SVEP1); prickle planar cell polarity protein 1 (PRICKLE1); ATP binding cassette subfamily A member 8 (ABCA8); Slit guidance ligand 2 (SLIT2); and EGF containing fibulin extracellular matrix protein 1 (EFEMP1), were selected as candidate survival-associated genes for further analysis. The prognostic value of these genes was assessed according to a literature review and Kaplan-Meier survival analysis. In addition, a multivariate Cox regression analysis revealed PRICKLE1 expression to be an independent prognostic factor for patients with gastric cancer. Furthermore, a predictive nomogram was generated using PRICKLE1 expression, patient age and TNM stage to assess overall survival (OS) rate at 1, 3 and 5 years, with an internal concordance index of 0.65. External validation was conducted in an independent cohort of 59 patients with gastric cancer, and high consistency between the predicted and observed results for OS was exhibited. Overall, the current findings suggest that PRICKLE1 expression may serve as an independent prognostic factor that can be integrated with age and TNM stage in a nomogram able to predict OS rate in patients with gastric cancer.

Shear stimulation of FOXC1 and FOXC2 differentially regulates cytoskeletal activity during lymphatic valve maturation

Mutations in the transcription factor FOXC2 are predominately associated with lymphedema. Herein, we demonstrate a key role for related factor FOXC1, in addition to FOXC2, in regulating cytoskeletal activity in lymphatic valves. FOXC1 is induced by laminar, but not oscillatory, shear and inducible, endothelial-specific deletion impaired postnatal lymphatic valve maturation in mice. However, deletion of Foxc2 induced valve degeneration, which is exacerbated in Foxc1; Foxc2 mutants. FOXC1 knockdown (KD) in human lymphatic endothelial cells increased focal adhesions and actin stress fibers whereas FOXC2-KD increased focal adherens and disrupted cell junctions, mediated by increased ROCK activation. ROCK inhibition rescued cytoskeletal or junctional integrity changes induced by inactivation of FOXC1 and FOXC2 invitro and vivo respectively, but only ameliorated valve degeneration in Foxc2 mutants. These results identify both FOXC1 and FOXC2 as mediators of mechanotransduction in the postnatal lymphatic vasculature and posit cytoskeletal signaling as a therapeutic target in lymphatic pathologies.

Akt-targeted therapy as a promising strategy to overcome drug resistance in breast cancer - A comprehensive review from chemotherapy to immunotherapy

Breast cancer is the most frequently occurring cancer in women. Chemotherapy in combination with immunotherapy has been used to treat breast cancer. Atezolizumab targeting the protein programmed cell death-ligand (PD-L1) in combination with paclitaxel was recently approved by the Food and Drug Administration (FDA) for Triple-Negative Breast Cancer (TNBC), the most incurable type of breast cancer. However, the use of such drugs is restricted by genotype and is effective only for those TNBC patients expressing PD-L1. In addition, resistance to chemotherapy with drugs such as lapatinib, geftinib, and tamoxifen can develop. In this review, we address chemoresistance in breast cancer and discuss Akt as the master regulator of drug resistance and several oncogenic mechanisms in breast cancer. Akt not only directly interacts with the mitogen-activated protein (MAP) kinase signaling pathway to affect PD-L1 expression, but also has crosstalk with Notch and Wnt/β-catenin signaling pathways involved in cell migration and breast cancer stem cell integrity. In this review, we discuss the effects of tyrosine kinase inhibitors on Akt activation as well as the mechanism of Akt signaling in drug resistance. Akt also has a crucial role in mitochondrial metabolism and migrates into mitochondria to remodel breast cancer cell metabolism while also functioning in responses to hypoxic conditions. The Akt inhibitors ipatasertib, capivasertib, uprosertib, and MK-2206 not only suppress cancer cell proliferation and metastasis, but may also inhibit cytokine regulation and PD-L1 expression. Ipatasertib and uprosertib are undergoing clinical investigation to treat TNBC. Inhibition of Akt and its regulators can be used to control breast cancer progression and also immunosuppression, while discovery of additional compounds that target Akt and its modulators could provide solutions to resistance to chemotherapy and immunotherapy.

Whole Genome Messenger RNA Profiling Identifies a Novel Signature to Predict Gastric Cancer Survival

Molecular prognostic biomarkers for gastric cancer (GC) are still limited. We aimed to identify potential messenger RNAs (mRNAs) associated with GC prognosis and further establish an mRNA signature to predict the survival of GC based on the publicly accessible databases.

ECT2 associated to PRICKLE1 are poor-prognosis markers in triple-negative breast cancer

Background

Triple-negative breast cancers (TNBC) are poor-prognosis tumours candidate to chemotherapy as only systemic treatment. We previously found that PRICKLE1, a prometastatic protein involved in planar cell polarity, is upregulated in TNBC. We investigated the protein complex associated with PRICKLE1 in TNBC to identify proteins possibly involved in metastatic dissemination, which might provide new prognostic and/or therapeutic targets.

Methods

We used a proteomic approach to identify protein complexes associated with PRICKLE1. The mRNA expression levels of the corresponding genes were assessed in 8982 patients with invasive primary breast cancer. We then characterised the molecular interaction between PRICKLE1 and the guanine nucleotide exchange factor ECT2. Finally, experiments in Xenopus were carried out to determine their evolutionarily conserved interaction.

Results

Among the PRICKLE1 proteins network, we identified several small G-protein regulators. Combined analysis of the expression of PRICKLE1 and small G-protein regulators had a strong prognostic value in TNBC. Notably, the combined expression of ECT2 and PRICKLE1 provided a worst prognosis than PRICKLE1 expression alone in TNBC. PRICKLE1 regulated ECT2 activity and this interaction was evolutionary conserved.

Conclusions

This work supports the idea that an evolutionarily conserved signalling pathway required for embryogenesis and activated in cancer may represent a suitable therapeutic target.

Wnt/PCP Signaling Contribution to Carcinoma Collective Cell Migration and Metastasis

Our understanding of the cellular mechanisms governing carcinoma invasiveness and metastasis has evolved dramatically over the last several years. The previous emphasis on the epithelial-mesenchymal transition as a driver of the migratory properties of single cells has expanded with the observation that carcinoma cells often invade and migrate collectively as adherent groups. Moreover, recent analyses suggest that circulating tumor cells within the vasculature often exist as multicellular clusters and that clusters more efficiently seed metastatic lesions than single circulating tumor cells. While these observations point to a key role for collective cell migration in carcinoma metastasis, the molecular mechanisms driving collective tumor cell migration remain to be discerned. Wnt/PCP (planar cell polarity) signaling, one of the noncanonical Wnt signaling pathways, mediates collective migratory events such as convergent extension during developmental processes. Wnt/PCP signaling components are frequently dysregulated in solid tumors, and aberrant pathway activation contributes to tumor cell migratory properties. Here we summarize key studies that address the mechanisms by which Wnt/PCP signaling mediate collective cell migration in developmental and tumor contexts. We emphasize Wnt/PCP component localization within migrating cells and discuss how component asymmetry may govern the spatiotemporal control of downstream cytoskeletal effectors to promote collective cell motility.

DRUM: Inference of Disease-Associated m6A RNA Methylation Sites From a Multi-Layer Heterogeneous Network

Recent studies have revealed that the RNA N 6-methyladenosine (m6A) modification plays a critical role in a variety of biological processes and associated with multiple diseases including cancers. Till this day, transcriptome-wide m6A RNA methylation sites have been identified by high-throughput sequencing technique combined with computational methods, and the information is publicly available in a few bioinformatics databases; however, the association between individual m6A sites and various diseases are still largely unknown. There are yet computational approaches developed for investigating potential association between individual m6A sites and diseases, which represents a major challenge in the epitranscriptome analysis. Thus, to infer the disease-related m6A sites, we implemented a novel multi-layer heterogeneous network-based approach, which incorporates the associations among diseases, genes and m6A RNA methylation sites from gene expression, RNA methylation and disease similarities data with the Random Walk with Restart (RWR) algorithm. To evaluate the performance of the proposed approach, a ten-fold cross validation is performed, in which our approach achieved a reasonable good performance (overall AUC: 0.827, average AUC 0.867), higher than a hypergeometric test-based approach (overall AUC: 0.7333 and average AUC: 0.723) and a random predictor (overall AUC: 0.550 and average AUC: 0.486). Additionally, we show that a number of predicted cancer-associated m6A sites are supported by existing literatures, suggesting that the proposed approach can effectively uncover the underlying epitranscriptome circuits of disease mechanisms. An online database DRUM, which stands for disease-associated ribonucleic acid methylation, was built to support the query of disease-associated RNA m6A methylation sites, and is freely available at: www.xjtlu.edu.cn/biologicalsciences/drum.

Inhibition of mTORC2/RICTOR Impairs Melanoma Hepatic Metastasis

Mammalian target of rapamycin complex 2 (mTORC2) with its pivotal component rapamycin-insensitive companion of mTOR (RICTOR) is the major regulator of AKT phosphorylation and is increasingly implicated in tumor growth and progression. In cutaneous melanoma, an extremely aggressive and highly metastatic disease, RICTOR overexpression is involved in tumor development and invasiveness. Therefore, we investigated the impact of RICTOR inhibition in melanoma cells in vitro and in vivo with special emphasis on hepatic metastasis. Moreover, our study focused on the interaction of tumor cells and hepatic stellate cells (HSC) which play a crucial role in the hepatic microenvironment. In silico analysis revealed increased RICTOR expression in melanoma cells and tissues and indicated higher expression in advanced melanoma stages and metastases. In vitro, transient RICTOR knock-down via siRNA caused a significant reduction of tumor cell motility. Using a syngeneic murine splenic injection model, a significant decrease in liver metastasis burden was detected in vivo. Moreover, stimulation of melanoma cells with conditioned medium (CM) from activated HSC or hepatocyte growth factor (HGF) led to a significant induction of AKT phosphorylation and tumor cell motility. Blocking of RICTOR expression in cancer cells diminished constitutive and HGF-induced AKT phosphorylation as well as cell motility. Interestingly, RICTOR blockade also led to an abrogation of CM-induced effects on AKT phosphorylation and motility in melanoma cells. In conclusion, these results provide first evidence for a critical role of mTORC2/RICTOR in melanoma liver metastasis via cancer cell/HSC interactions.

Dendritic spine actin cytoskeleton in autism spectrum disorder

Dendritic spines are small actin-rich protrusions from neuronal dendrites that form the postsynaptic part of most excitatory synapses. Changes in the shape and size of dendritic spines correlate with the functional changes in excitatory synapses and are heavily dependent on the remodeling of the underlying actin cytoskeleton. Recent evidence implicates synapses at dendritic spines as important substrates of pathogenesis in neuropsychiatric disorders, including autism spectrum disorder (ASD). Although synaptic perturbations are not the only alterations relevant for these diseases, understanding the molecular underpinnings of the spine and synapse pathology may provide insight into their etiologies and could reveal new drug targets. In this review, we will discuss recent findings of defective actin regulation in dendritic spines associated with ASD.

Who does TORC2 talk to?

The target of rapamycin (TOR) is a protein kinase that, by forming complexes with partner proteins, governs diverse cellular signalling networks to regulate a wide range of processes. TOR thus plays central roles in maintaining normal cellular functions and, when dysregulated, in diverse diseases. TOR forms two distinct types of multiprotein complexes (TOR complexes 1 and 2, TORC1 and TORC2). TORC1 and TORC2 differ in their composition, their control and their substrates, so that they play quite distinct roles in cellular physiology. Much effort has been focused on deciphering the detailed regulatory links within the TOR pathways and the structure and control of TOR complexes. In this review, we summarize recent advances in understanding mammalian (m) TORC2, its structure, its regulation, and its substrates, which link TORC2 signalling to the control of cell functions. It is now clear that TORC2 regulates several aspects of cell metabolism, including lipogenesis and glucose transport. It also regulates gene transcription, the cytoskeleton, and the activity of a subset of other protein kinases.

The role of RICTOR downstream of receptor tyrosine kinase in cancers

The importance of the network defined by phosphatidylinositol-3-kinase (PI3K), AKT and mammalian target of rapamycin (mTOR) downstream of Receptor Tyrosine Kinase (RTK) has been known for many years but the central role of RICTOR (rapamycin-insensitive companion of mTOR) in this pathway is only starting to emerge. RICTOR is critical for mTORC2 (the mammalian target of rapamycin complex 2) kinase activity and as such plays a key role downstream of RTK. Alterations of RICTOR have been identified in a number of cancer cell types and its involvement in tumorigenesis has begun to be unraveled recently. Here, we summarize new research into the biology of RICTOR signaling in cancers focusing on tumors with altered RTK. We show that, as a key signaling node and critical effector of RTKs, RICTOR is becoming a valuable therapeutic target in cancer with altered RTK.

Selective mTORC2 Inhibitor Therapeutically Blocks Breast Cancer Cell Growth and Survival

Small-molecule inhibitors of the mTORC2 kinase (torkinibs) have shown efficacy in early clinical trials. However, the torkinibs under study also inhibit the other mTOR-containing complex mTORC1. While mTORC1/mTORC2 combined inhibition may be beneficial in cancer cells, recent reports describe compensatory cell survival upon mTORC1 inhibition due to loss of negative feedback on PI3K, increased autophagy, and increased macropinocytosis. Genetic models suggest that selective mTORC2 inhibition would be effective in breast cancers, but the lack of selective small-molecule inhibitors of mTORC2 have precluded testing of this hypothesis to date. Here we report the engineering of a nanoparticle-based RNAi therapeutic that can effectively silence the mTORC2 obligate cofactor Rictor. Nanoparticle-based Rictor ablation in HER2-amplified breast tumors was achieved following intratumoral and intravenous delivery, decreasing Akt phosphorylation and increasing tumor cell killing. Selective mTORC2 inhibition in vivo, combined with the HER2 inhibitor lapatinib, decreased the growth of HER2-amplified breast cancers to a greater extent than either agent alone, suggesting that mTORC2 promotes lapatinib resistance, but is overcome by mTORC2 inhibition. Importantly, selective mTORC2 inhibition was effective in a triple-negative breast cancer (TNBC) model, decreasing Akt phosphorylation and tumor growth, consistent with our findings that RICTOR mRNA correlates with worse outcome in patients with basal-like TNBC. Together, our results offer preclinical validation of a novel RNAi delivery platform for therapeutic gene ablation in breast cancer, and they show that mTORC2-selective targeting is feasible and efficacious in this disease setting.Significance: This study describes a nanomedicine to effectively inhibit the growth regulatory kinase mTORC2 in a preclinical model of breast cancer, targeting an important pathogenic enzyme in that setting that has been undruggable to date. Cancer Res; 78(7); 1845-58. ©2018 AACR.

From instruction to output: Wnt/PCP signaling in development and cancer

Planar cell polarity (PCP) provides positional information to direct tissue patterning and morphogenesis. While much of the molecular detail of the pathway has been delineated in Drosophila, ensuing studies have shown considerable conservation of both the components and mechanisms of signaling in vertebrates. A recognized feature of PCP is the asymmetric localization of components that translates a global directional cue into a polarized downstream output. Here we discuss recent advances in the PCP field, from the organization of these asymmetric complexes to their upstream directional regulation by Wnt ligands. We also discuss the impact of Wnt/PCP signaling in disease and more specifically an emerging role in cancer progression.

Molecular architecture of potassium chloride co-transporter KCC2

KCC2 is a neuron specific K⁺-Cl⁻ co-transporter that controls neuronal chloride homeostasis, and is critically involved in many neurological diseases including brain trauma, epilepsies, autism and schizophrenia. Despite significant accumulating data on the biology and electrophysiological properties of KCC2, structure-function relationships remain poorly understood. Here we used calixarene detergent to solubilize and purify wild-type non-aggregated and homogenous KCC2. Specific binding of inhibitor compound VU0463271 was demonstrated using surface plasmon resonance (SPR). Mass spectrometry revealed glycosylations and phosphorylations as expected from functional KCC2. We show by electron microscopy (EM) that KCC2 exists as monomers and dimers in solution. Monomers are organized into “head” and “core” domains connected by a flexible “linker”. Dimers are asymmetrical and display a bent “S-shape” architecture made of four distinct domains and a flexible dimerization interface. Chemical crosslinking in reducing conditions shows that disulfide bridges are involved in KCC2 dimerization. Moreover, we show that adding a tag to the C-terminus is detrimental to KCC2 function. We postulate that the conserved KCC2 C-ter may be at the interface of dimerization. Taken together, our findings highlight the flexible multi-domain structure of KCC2 with variable anchoring points at the dimerization interface and an important C-ter extremity providing the first in-depth functional architecture of KCC2.

Cellular and molecular mechanisms underlying planar cell polarity pathway contributions to cancer malignancy

While the mutational activation of oncogenes drives tumor initiation and growth by promoting cellular transformation and proliferation, increasing evidence suggests that the subsequent re-engagement of largely dormant developmental pathways contributes to cellular phenotypes associated with the malignancy of solid tumors. Genetic studies from a variety of model organisms have defined many of the components that maintain epithelial planar cell polarity (PCP), or cellular polarity in the axis orthogonal to the apical-basal axis. These same components comprise an arm of non-canonical Wnt signaling that mediates cell motility events such as convergent extension movements essential to proper development. In this review, we summarize the increasing evidence that the Wnt/PCP signaling pathway plays active roles in promoting the proliferative and migratory properties of tumor cells, emphasizing the importance of subcellular localization of PCP components and protein-protein interactions in regulating cellullar properties associated with malignancy. Specifically, we discuss the increased expression of Wnt/PCP pathway components in cancer and the functional consequences of aberrant pathway activation, focusing on Wnt ligands, Frizzled (Fzd) receptors, the tetraspanin-like proteins Vangl1 and Vangl2, and the Prickle1 (Pk1) scaffold protein. In addition, we discuss negative regulation of the Wnt/PCP pathway, with particular emphasis on the Nrdp1 E3 ubiquitin ligase. We hypothesize that engagement of the Wnt/PCP pathway after tumor initiation drives malignancy by promoting cellular proliferation and invasiveness, and that the ability of Wnt/PCP signaling to supplant oncogene addiction may contribute to tumor resistance to oncogenic pathway-directed therapeutic agents.

Two distinct mTORC2-dependent pathways converge on Rac1 to drive breast cancer metastasis

Background

The importance of the mTOR complex 2 (mTORC2) signaling complex in tumor progression is becoming increasingly recognized. HER2-amplified breast cancers use Rictor/mTORC2 signaling to drive tumor formation, tumor cell survival and resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapy. Cell motility, a key step in the metastatic process, can be activated by mTORC2 in luminal and triple negative breast cancer cell lines, but its role in promoting metastases from HER2-amplified breast cancers is not yet clear.

Methods

Because Rictor is an obligate cofactor of mTORC2, we genetically engineered Rictor ablation or overexpression in mouse and human HER2-amplified breast cancer models for modulation of mTORC2 activity. Signaling through mTORC2-dependent pathways was also manipulated using pharmacological inhibitors of mTOR, Akt, and Rac. Signaling was assessed by western analysis and biochemical pull-down assays specific for Rac-GTP and for active Rac guanine nucleotide exchange factors (GEFs). Metastases were assessed from spontaneous tumors and from intravenously delivered tumor cells. Motility and invasion of cells was assessed using Matrigel-coated transwell assays.

Results

We found that Rictor ablation potently impaired, while Rictor overexpression increased, metastasis in spontaneous and intravenously seeded models of HER2-overexpressing breast cancers. Additionally, migration and invasion of HER2-amplified human breast cancer cells was diminished in the absence of Rictor, or upon pharmacological mTOR kinase inhibition. Active Rac1 was required for Rictor-dependent invasion and motility, which rescued invasion/motility in Rictor depleted cells. Rictor/mTORC2-dependent dampening of the endogenous Rac1 inhibitor RhoGDI2, a factor that correlated directly with increased overall survival in HER2-amplified breast cancer patients, promoted Rac1 activity and tumor cell invasion/migration. The mTORC2 substrate Akt did not affect RhoGDI2 dampening, but partially increased Rac1 activity through the Rac-GEF Tiam1, thus partially rescuing cell invasion/motility. The mTORC2 effector protein kinase C (PKC)α did rescue Rictor-mediated RhoGDI2 downregulation, partially rescuing Rac-guanosine triphosphate (GTP) and migration/motility.

Conclusion

These findings suggest that mTORC2 uses two coordinated pathways to activate cell invasion/motility, both of which converge on Rac1. Akt signaling activates Rac1 through the Rac-GEF Tiam1, while PKC signaling dampens expression of the endogenous Rac1 inhibitor, RhoGDI2.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0868-8) contains supplementary material, which is available to authorized users.

Wnt/Planar Cell Polarity Signaling: New Opportunities for Cancer Treatment

Cancer cells are addicted to a large spectrum of extracellular cues implicated in initiation, stem cell renewal, tumor growth, dissemination in the body, and resistance to treatment. Wingless/Int-1 (Wnt) ligands and their associated signaling cascades contribute to most of these processes, paving the way for opportunities in therapeutic development. The developmental Wnt/planar cell polarity (PCP) pathway is the most recently described branch of Wnt signaling strongly implicated in cancer development at early and late stages. We describe here some of the latest knowledge accumulated on this pathway and the pending questions, present the most convincing findings about its role in cancer, and review the most promising strategies currently designed to target its components.