Scribble regulates an EMT polarity pathway through modulation of MAPK-ERK signaling to mediate junction formation

The Scribble/SGEF/Dlg1 complex regulates the stability of apical junctions in epithelial cells

SGEF, a RhoG specific GEF, can form a ternary complex with the Scribble polarity complex proteins Scribble and Dlg1, which regulates the formation and maintenance of adherens junctions and barrier function of epithelial cells. Notably, silencing SGEF results in a dramatic downregulation of the expression of both E-cadherin and ZO-1. However, the molecular mechanisms involved in the regulation of this pathway are not known. Here, we describe a novel signaling pathway governed by the Scribble/SGEF/Dlg1 complex. Our results show that an intact ternary complex is required to maintain the stability of the apical junctions, the expression of ZO-1, and TJ permeability. In contrast, only SGEF is necessary to regulate E-cadherin expression. The absence of SGEF destabilizes the E-cadherin/catenin complex at the membrane, triggering a positive feedback loop that exacerbates the phenotype through the repression of E-cadherin transcription in a process that involves the internalization of E-cadherin by endocytosis, β-catenin signaling and the transcriptional repressor Slug.

Scribble, Lgl1, and myosin IIA interact with α-/β-catenin to maintain epithelial junction integrity

E-cadherin-catenin complex together with the cytoskeleton, builds the core of Adherens junctions (AJs). It has been reported that Scribble stabilizes the coupling of E-cadherin with catenins promoting epithelial cell adhesion, but the mechanism remains unknown. We show that Scribble, Lgl1, and NMII-A reside in a complex with E-cadherin-catenin complex. Depletion of either Scribble or Lgl1 disrupts the localization of E-cadherin-catenin complex to AJs. aPKCζ phosphorylation of Lgl1 regulates AJ localization of Lgl1 and E-cadherin-catenin complexes. Both Scribble and Lgl1 regulate the activation and recruitment of NMII-A at AJs. Finally, Scribble and Lgl1 are downregulated by TGFβ-induced EMT, and their re-expression during EMT impedes its progression. Our results provide insight into the mechanism regulating AJ integrity by Scribble, Lgl1, and NMII-A.

Defining bone fide effectors of RAS GTPases

RAS GTPases play essential roles in normal development and are direct drivers of human cancers. Three decades of study have failed to wholly characterize pathways stimulated by activated RAS, driven by engagement with 'effector' proteins that have RAS binding domains (RBDs). Bone fide effectors must bind directly to RAS GTPases in a nucleotide-dependent manner, and this interaction must impart a clear change in effector activity. Despite this, for most proteins currently deemed effectors there is little mechanistic understanding of how binding to the GTPase alters protein function. There has also been limited effort to comprehensively resolve the specificity of effector binding to the full array of RAS superfamily GTPase proteins. This review will summarize what is known about RAS-driven activation for an array of potential effector proteins, focusing on structural and mechanistic effects and highlighting how little is still known regarding this key paradigm of cellular signal transduction.

Scribble basal polarity acquisition in RPE cells and its mislocalization in a pathological AMD-like model

Apicobasal polarity is a hallmark of retinal pigment epithelium cells and is required to perform their functions; however, the precise roles of the different proteins that execute polarity are still poorly understood. Here, we have studied the expression and location of Scribble, the core member of the polarity basal protein complex in epithelial-derived cells, in human and mouse RPE cells in both control and pathological conditions. We found that Scribble specifically localizes at the basolateral membrane of mouse and human RPE cells. In addition, we observed an increase in the expression of Scribble during human RPE development in culture, while it acquires a well-defined basolateral pattern as this process is completed. Finally, the expression and location of Scribble were analyzed in human RPE cells in experimental conditions that mimic the toxic environment suffered by these cells during AMD development and found an increase in Scribble expression in cells that develop a pathological phenotype, suggesting that the protein could be altered in cells under stress conditions, as occurs in AMD. Together, our results demonstrate, for the first time, that Scribble is expressed in both human and mouse RPE and is localized at the basolateral membrane in mature cells. Furthermore, Scribble shows impaired expression and location in RPE cells in pathological conditions, suggesting a possible role for this protein in the development of pathologies, such as AMD.

Afadin couples RAS GTPases to the polarity rheostat Scribble

AFDN/Afadin is required for establishment and maintenance of cell-cell contacts and is a unique effector of RAS GTPases. The biological consequences of RAS complex with AFDN are unknown. We used proximity-based proteomics to generate an interaction map for two isoforms of AFDN, identifying the polarity protein SCRIB/Scribble as the top hit. We reveal that the first PDZ domain of SCRIB and the AFDN FHA domain mediate a direct but non-canonical interaction between these important adhesion and polarity proteins. Further, the dual RA domains of AFDN have broad specificity for RAS and RAP GTPases, and KRAS co-localizes with AFDN and promotes AFDN-SCRIB complex formation. Knockout of AFDN or SCRIB in epithelial cells disrupts MAPK and PI3K activation kinetics and inhibits motility in a growth factor-dependent manner. These data have important implications for understanding why cells with activated RAS have reduced cell contacts and polarity defects and implicate AFDN as a genuine RAS effector.

Goudreault et al. investigate the role of Afadin downstream of RAS GTPases, substantiating this cell adhesion protein as a true RAS effector that couples its activation to cell polarity through the Scribble protein.

Individual and Co-Expression Patterns of FAM83H and SCRIB at Diagnosis Are Associated with the Survival of Colorectal Carcinoma Patients

Background: FAM83H is important in teeth development; however, an increasing number of reports have indicated a role for it in human cancers. FAM83H is involved in cancer progression in association with various oncogenic molecules, including SCRIB. In the analysis of the public database, there was a significant association between FAM83H and SCRIB in colorectal carcinomas. However, studies evaluating the association of FAM83H and SCRIB in colorectal carcinoma have been limited. Methods: The clinicopathological significance of the immunohistochemical expression of FAM83H and SCRIB was evaluated in 222 colorectal carcinomas. Results: The expressions of FAM83H and SCRIB were significantly associated in colorectal carcinoma tissue. In univariate analysis, the nuclear expressions of FAM83H and SCRIB and the cytoplasmic expression of SCRIB were significantly associated with shorter survival of colorectal carcinomas. The nuclear expressions of FAM83H and SCRIB and the cytoplasmic expression of SCRIB were independent indicators of shorter cancer-specific survival in multivariate analysis. A co-expression pattern of nuclear FAM83H and cytoplasmic SCRIB predicted shorter cancer-specific survival (p < 0.001) and relapse-free survival (p = 0.032) in multivariate analysis. Conclusions: This study suggests that FAM83H and SCRIB might be used as prognostic markers of colorectal carcinomas and as potential therapeutic targets for colorectal carcinomas.

Infection by High-Risk Human Papillomaviruses, Epithelial-to-Mesenchymal Transition and Squamous Pre-Malignant or Malignant Lesions of the Uterine Cervix: A Series of Chained Events?

Wound healing requires static epithelial cells to gradually assume a mobile phenotype through a multi-step process termed epithelial-to-mesenchymal transition (EMT). Although it is inherently transient and reversible, EMT perdures and is abnormally activated when the epithelium is chronically exposed to pathogens: this event deeply alters the tissue and eventually contributes to the development of diseases. Among the many of them is uterine cervical squamous cell carcinoma (SCC), the most frequent malignancy of the female genital system. SCC, whose onset is associated with the persistent infection of the uterine cervix by high-risk human papillomaviruses (HR-HPVs), often relapses and/or metastasizes, being resistant to conventional chemo- or radiotherapy. Given that these fearsome clinical features may stem, at least in part, from the exacerbated and long-lasting EMT occurring in the HPV-infected cervix; here we have reviewed published studies concerning the impact that HPV oncoproteins, cellular tumor suppressors, regulators of gene expression, inflammatory cytokines or growth factors, and the interactions among these effectors have on EMT induction and cervical carcinogenesis. It is predictable and desirable that a broader comprehension of the role that EMT inducers play in SCC pathogenesis will provide indications to flourish new strategies directed against this aggressive tumor.

From Oncogenic Signaling Pathways to Single-Cell Sequencing of Immune Cells: Changing the Landscape of Cancer Immunotherapy

Over the past decade, there have been remarkable advances in understanding the signaling pathways involved in cancer development. It is well-established that cancer is caused by the dysregulation of cellular pathways involved in proliferation, cell cycle, apoptosis, cell metabolism, migration, cell polarity, and differentiation. Besides, growing evidence indicates that extracellular matrix signaling, cell surface proteoglycans, and angiogenesis can contribute to cancer development. Given the genetic instability and vast intra-tumoral heterogeneity revealed by the single-cell sequencing of tumoral cells, the current approaches cannot eliminate the mutating cancer cells. Besides, the polyclonal expansion of tumor-infiltrated lymphocytes in response to tumoral neoantigens cannot elicit anti-tumoral immune responses due to the immunosuppressive tumor microenvironment. Nevertheless, the data from the single-cell sequencing of immune cells can provide valuable insights regarding the expression of inhibitory immune checkpoints/related signaling factors in immune cells, which can be used to select immune checkpoint inhibitors and adjust their dosage. Indeed, the integration of the data obtained from the single-cell sequencing of immune cells with immune checkpoint inhibitors can increase the response rate of immune checkpoint inhibitors, decrease the immune-related adverse events, and facilitate tumoral cell elimination. This study aims to review key pathways involved in tumor development and shed light on single-cell sequencing. It also intends to address the shortcomings of immune checkpoint inhibitors, i.e., their varied response rates among cancer patients and increased risk of autoimmunity development, via applying the data from the single-cell sequencing of immune cells.

SCRIB Is Involved in the Progression of Ovarian Carcinomas in Association with the Factors Linked to Epithelial-to-Mesenchymal Transition and Predicts Shorter Survival of Diagnosed Patients

SCRIB is a polarity protein important in maintaining cell junctions. However, recent reports have raised the possibility that SCRIB might have a role in human cancers. Thus, this study evaluated the roles of SCRIB in ovarian cancers. In 102 human ovarian carcinomas, nuclear expression of SCRIB predicted shorter survival of ovarian carcinoma patients, especially in the patients who received post-operative chemotherapy. In SKOV3 and SNU119 ovarian cancer cells, overexpression of SCRIB stimulated the proliferation and invasion of cells. Knockout of SCRIB inhibited in vivo tumor growth of SKOV3 cells and overexpression of SCRIB promoted tumor growth. Overexpression of SCRIB stimulated epithelial-to-mesenchymal transition by increasing the expression of N-cadherin, snail, TGF-β1, and smad2/3, and decreasing the expression of E-cadherin; the converse was observed with inhibition of SCRIB. In conclusion, this study presents the nuclear expression of SCRIB as a prognostic marker of ovarian carcinomas and suggests that SCRIB is involved in the progression of ovarian carcinomas by stimulating proliferation and epithelial-to-mesenchymal transition-related invasiveness.

Nerve growth factor receptor increases the tumor growth and metastatic potential of triple-negative breast cancer cells

Cellular heterogeneity and the lack of metastatic biomarkers limit the diagnosis of and development of therapies for metastatic triple-negative breast cancer (TNBC). Thus, development of new clinically relevant markers is urgently needed. By using RNA-seq analysis, we found that nerve growth factor receptor (NGFR) was highly expressed in metastatic lung clones of MDA-MB-231 cells. This high level of NGFR expression was necessary for TNBC cells to grow into tumor spheres under nonadhesive conditions, resist anoikis, promote primary tumor growth and increase metastasis in mice. NGFR was also expressed at a high level in a greater number of TNBC patients (45%) than non-TNBC patients (23%), enriched in higher grade tumors, and negatively correlated with the overall survival of TNBC patients. Mechanistic analysis indicated that NGFR exerted its prometastatic effects by binding with neurotrophic receptor tyrosine kinase 3 (TrkC) mainly through a ligand-independent manner, which activated the MEK-ERK1-ZEB1 and PI3K-AKT signaling pathways, increased the level of fibronectin, and decreased the expression of PUMA. Notably, we observed that NGFR expression in TrkC-positive metastatic clones reduced cellular sensitivity to anti-Trk therapy. Moreover, WNT family member 5a (WNT5A) and TrkC activated NGFR transcription in a ZEB1-dependent manner. Taken together, this study identified NGFR as a novel driver for transforming TNBC into higher grade metastatic tumors. Our findings provide the basis for the future development of NGFR as a diagnostic and prognostic marker for determining the metastatic potential of TNBC and as a therapeutic target for treating TNBC patients.

Sprouty2 regulates positioning of retinal progenitors through suppressing the Ras/Raf/MAPK pathway

Sproutys are negative regulators of the Ras/Raf/MAPK signaling pathway and involved in regulation of organogenesis, differentiation, cell migration and proliferation. Although the function of Sproutys have been extensively studied during embryonic development, their role and mode of action during eye formation in vertebrate embryonic development is still unknown. Here we show that Xenopus sprouty2 is expressed in the optic vesicle at late neurula stage and knockdown of Sprouty2 prevents retinal progenitors from populating the retina, which in turn gives rise to small eyes. In the absence of Sprouty2, progenitor cell population of the retina can be restored by blocking the MAPK signaling pathway through overexpression of DN-Ras or DN-Raf. In contrast, activation of the MAPK pathway through overexpression of a constitutively active form of c-Raf (ca-Raf) inhibits progenitor population of the retina, similar to the Sprouty2 loss-of-function phenotype. Moreover, we present evidence that the retinal defect observed in Sprouty2 morphants is attributed to the failure of proper movement of retinal progenitors into the optic vesicle, rather than an effect on progenitor cell survival. These results suggest that Sprouty2 is required for the positioning of retinal progenitors within the optic vesicle through suppressing Ras/Raf/MAPK signaling pathway.

Scribble, Lgl1, and myosin II form a complex in vivo to promote directed cell migration

Scribble (Scrib) and Lethal giant larvae 1 (Lgl1) are conserved polarity proteins that play important roles in different forms of cell polarity. The roles of Scrib and Lgl1 in apical-basal cell polarity have been studied extensively, but little is known about their roles in the cell polarity of migrating cells. Furthermore, the effect of Scrib and Lgl1 interaction on cell polarity is largely unknown. In this study, we show that Scrib, through its leucine-rich repeat domain, forms a complex in vivo with Lgl1. Scrib also forms a complex with myosin II, and Scrib, Lgl1, and myosin II colocalize at the leading edge of migrating cells. The cellular localization and the cytoskeletal association of Scrib and Lgl1 are interdependent, as depletion of either protein affects its counterpart. In addition, depletion of either Scrib or Lgl1 disrupts the cellular localization of myosin II. We show that depletion of either Scrib or Lgl1 affects cell adhesion through the inhibition of focal adhesion disassembly. Finally, we show that Scrib and Lgl1 are required for proper cell polarity of migrating cells. These results provide new insights into the mechanism regulating the cell polarity of migrating cells by Scrib, Lgl1, and myosin II.

The polarity protein Scrib limits atherosclerosis development in mice

AIMS

The protein Scrib (Scribble 1) is known to control apico-basal polarity in epithelial cells. The role of polarity proteins in the vascular system remains poorly characterized; however, we previously reported that Scrib maintains the endothelial phenotype and directed migration. On this basis, we hypothesized that Scrib has anti-atherosclerotic functions.

METHODS AND RESULTS

Tamoxifen-induced Scrib-knockout mice were crossed with ApoE-/- knockout mice and spontaneous atherosclerosis under high-fat diet (HFD), as well as accelerated atherosclerosis in response to partial carotid artery ligation and HFD, was induced. Deletion of Scrib resulted in increased atherosclerosis development in both models. Mechanistically, flow- as well as acetylcholine-induced endothelium-dependent relaxation and AKT phosphorylation was reduced by deletion of Scrib, whereas vascular permeability and leucocyte extravasation were increased after Scrib knockout. Scrib immune pull down in primary carotid endothelial cells and mass spectrometry identified Arhgef7 (Rho Guanine Nucleotide Exchange Factor 7, βPix) as interaction partner. Scrib or Arhgef7 down-regulation by siRNA reduced the endothelial barrier function in human umbilical vein endothelial cells. Gene expression analysis from murine samples and from human biobank material of carotid endarterectomies indicated that loss of Scrib resulted in endothelial dedifferentiation with a decreased expression of endothelial signature genes.

CONCLUSIONS

By maintaining a quiescent endothelial phenotype, the polarity protein Scrib elicits anti-atherosclerotic functions.

FAM83H and SCRIB stabilize β-catenin and stimulate progression of gastric carcinoma

FAM83H primarily is known for its function in tooth development. Recently, a role for FAM83H in tumorigenesis, conjunction with MYC and β-catenin, has been suggested. Analysis of public data indicates that FAM83H expression is closely associated with SCRIB expression in human gastric cancers. Therefore, this study investigated the roles of FAM83H and SCRIB in 200 human gastric cancers and gastric cancer cells. In human gastric carcinomas, both the individual and combined expression patterns of the nuclear FAM83H and SCRIB were independent indicators of shorter survival of gastric carcinoma patients. In MKN-45 and NCI-N87 gastric cancer cells, the expression of FAM83H and SCRIB were associated with proliferation and invasiveness of cells. FAM83H-mediated in vivo tumor growth was attenuated with knock-down of SCRIB. Moreover, immunoprecipitation indicates that FAM83H, SCRIB, and β-catenin, form a complex, and knock-down of either FAM83H or SCRIB accelerated proteasomal degradation of β-catenin. In conclusion, this study has found that the individual and combined expression patterns of nuclear FAM83H and SCRIB are prognostic indicators of gastric carcinomas and further suggests that FAM83H and SCRIB are involved in the progression of gastric carcinomas by stabilizing β-catenin.

Overexpression of CSN6 promotes the epithelial-mesenchymal transition and predicts poor prognosis in hepatocellular carcinoma

BACKGROUND AND AIM

CSN6, as a critical subunit of the constitutive photomorphogenesis 9 (COP9) signalosome (CSN), has been previously reported to be increased in various cancers; however, its effect in hepatocellular carcinoma (HCC) remains unknown, which is the aim of present study, in terms of its explore the expression and role of CSN6 in HCC.

METHODS

QRT-PCR, Western blot and immunohistochemistry (IHC) were used to examine the expression of CSN6. Kaplan-Meier survival analysis and univariate and multivariate Cox analyses were used to investigate the clinical and prognostic significance of CSN6 expression in HCC patients. Furthermore, the biological function of CSN6 on HCC cell proliferation and migration was investigated through CCK-8, transwell migration and invasion assays. Besides, the associations between CSN6 and epithelial-mesenchymal transition (EMT) were determined.

RESULTS

CSN6 was increased in HCC tissues, and its overexpression was found to be associated with a poor prognoses for HCC patients. Overexpression of CSN6 promoted processes of HCC cell proliferation, migration, and invasion, while these processes were inhibited when CSN6 was silenced. Additionally, CSN6 was found to promote EMT by inhibiting E-cadherin, which were significantly mitigated via upregulation of Snail as a result of MEK/ERK pathway activation.

CONCLUSIONS

CSN6 up-regulation may play a contributory role in HCC metastasis and poor prognosis via activation of EMT, and may serve as an independent predictor for HCC prognosis.

Enteropathogenic Escherichia coli (EPEC) Recruitment of PAR Polarity Protein Atypical PKCζ to Pedestals and Cell-Cell Contacts Precedes Disruption of Tight Junctions in Intestinal Epithelial Cells

Enteropathogenic Escherichia coli (EPEC) uses a type three secretion system to inject effector proteins into host intestinal epithelial cells, causing diarrhea. EPEC induces the formation of pedestals underlying attached bacteria, disrupts tight junction (TJ) structure and function, and alters apico-basal polarity by redistributing the polarity proteins Crb3 and Pals1, although the mechanisms are unknown. Here we investigate the temporal relationship of PAR polarity complex and TJ disruption following EPEC infection. EPEC recruits active aPKCζ, a PAR polarity protein, to actin within pedestals and at the plasma membrane prior to disrupting TJ. The EPEC effector EspF binds the endocytic protein sorting nexin 9 (SNX9). This interaction impacts actin pedestal organization, recruitment of active aPKCζ to actin at cell–cell borders, endocytosis of JAM-A S285 and occludin, and TJ barrier function. Collectively, data presented herein support the hypothesis that EPEC-induced perturbation of TJ is a downstream effect of disruption of the PAR complex and that EspF binding to SNX9 contributes to this phenotype. aPKCζ phosphorylates polarity and TJ proteins and participates in actin dynamics. Therefore, the early recruitment of aPKCζ to EPEC pedestals and increased interaction with actin at the membrane may destabilize polarity complexes ultimately resulting in perturbation of TJ.

The Scribble family in cancer: twentieth anniversary

Among the more than 160 PDZ containing proteins described in humans, the cytoplasmic scaffold Scribble stands out because of its essential role in many steps of cancer development and dissemination. Its fame has somehow blurred the importance of homologous proteins, Erbin and Lano, all belonging to the LRR and PDZ (LAP) protein family first described twenty years ago. In this review, we will retrace the history of LAP family protein research and draw attention to their contribution in cancer by detailing the features of its members at the structural and functional levels, and highlighting their shared-but also different-implication in the tumoral process.

Scribble, Erbin, and Lano redundantly regulate epithelial polarity and apical adhesion complex

The basolateral protein Scribble (Scrib), a member of the LAP protein family, is essential for epithelial apicobasal polarity (ABP) in Drosophila However, a conserved function for this protein in mammals is unclear. Here we show that the crucial role for Scrib in ABP has remained obscure due to the compensatory function of two other LAP proteins, Erbin and Lano. A combined Scrib/Erbin/Lano knockout disorganizes the cell-cell junctions and the cytoskeleton. It also results in mislocalization of several apical (Par6, aPKC, and Pals1) and basolateral (Llgl1 and Llgl2) identity proteins. These defects can be rescued by the conserved "LU" region of these LAP proteins. Structure-function analysis of this region determined that the so-called LAPSDb domain is essential for basolateral targeting of these proteins, while the LAPSDa domain is essential for supporting the membrane basolateral identity and binding to Llgl. In contrast to the key role in Drosophila, mislocalization of Llgl proteins does not appear to be critical in the scrib ABP phenotype.

Extracellular-Signal Regulated Kinase: A Central Molecule Driving Epithelial-Mesenchymal Transition in Cancer

Epithelial-mesenchymal transition (EMT) is a reversible cellular process, characterized by changes in gene expression and activation of proteins, favoring the trans-differentiation of the epithelial phenotype to a mesenchymal phenotype. This process increases cell migration and invasion of tumor cells, progression of the cell cycle, and resistance to apoptosis and chemotherapy, all of which support tumor progression. One of the signaling pathways involved in tumor progression is the MAPK pathway. Within this family, the ERK subfamily of proteins is known for its contributions to EMT. The ERK subfamily is divided into typical (ERK 1/2/5), and atypical (ERK 3/4/7/8) members. These kinases are overexpressed and hyperactive in various types of cancer. They regulate diverse cellular processes such as proliferation, migration, metastasis, resistance to chemotherapy, and EMT. In this context, in vitro and in vivo assays, as well as studies in human patients, have shown that ERK favors the expression, function, and subcellular relocalization of various proteins that regulate EMT, thus promoting tumor progression. In this review, we discuss the mechanistic roles of the ERK subfamily members in EMT and tumor progression in diverse biological systems.

Pharmacological stimulation of G-protein coupled receptor 40 alleviates cytokine-induced epithelial barrier disruption in airway epithelial Calu-3 cells

Impairment of airway tight junctions induced by elevated levels of proinflammatory cytokines is implicated in the pathogenesis of inflammatory airway diseases. Pharmacological stimulation of G-protein coupled receptor (GPR) 40, a receptor of polyunsaturated fatty acids, have recently been shown to promote tight junction assembly in airway epithelial cells under non-inflammatory conditions. However, roles of GPR40 in regulating airway epithelial integrity in response to inflammatory insults are unknown. This study was aimed to investigate the effect of GPR40 stimulation on proinflammatory cytokine (TNFα and IL-1β)-induced tight junction disruption in human airway epithelial Calu-3 cells using GW9508, a GPR40 agonist. We found that stimulation of GPR40 by GW9508 attenuated the cytokine-induced airway epithelial barrier leakage as analyzed by measurements of transepithelial electrical resistance and transepithelial flux of fluorescently labeled dextran (molecular weight of 4 kDa). Furthermore, GW9508 prevented the cytokine-induced dislocalization of zonula occludens (ZO)-1, occludin and claudin-1. The barrier-protective effect of GW9508 was abolished by a GPR40 antagonist, but not a GPR120 antagonist. Immunofluorescence staining of NF-ĸB indicated that GW9508 had no effect on cytokine-induced NF-ĸB activation. Intriguingly, GW9508 inhibited cytokine-induced airway epithelial barrier disruption through suppression of extracellular signal-regulated kinase (ERK) phosphorylation in a phospholipase C (PLC) and calcium/calmodulin-dependent protein kinase kinase beta (CaMKKβ)-dependent manner. Collectively, this study uncovered the novel role of GPR40 in preventing cytokine-induced tight junction disruption in airway epithelial cells through mechanisms involving PLC-CaMKKβ-mediated suppression of ERK signaling. Pharmacological stimulation of GPR40 may be beneficial in the treatment of airway diseases.

Downregulation of NSD3 (WHSC1L1) inhibits cell proliferation and migration via ERK1/2 deactivation and decreasing CAPG expression in colorectal cancer cells

Purpose: NSD3 (WHSC1L1) is a protein lysine methyltransferase that is recurrently amplified (8p11.23) in several cancer types, and its upregulation is involved in tumor cell proliferation, metastasis, and epithelial-mesenchymal transition (EMT). We aimed to evaluate its potential function as an oncogenic force in colorectal cancer (CRC), and to elucidate relevant mechanisms of its oncogenic activity. Materials and methods: NSD3 levels were analyzed in human CRC and adjacent normal tissues or cells by Western blot analysis and RT-qPCR. Expression levels of the proteins were detected by Western blot analysis and RT-qPCR. Results: NSD3 was significantly upregulated in both CRC tissues and cell lines. Knockdown of NSD3 expression resulted in significant decreases in CRC cell proliferation, migration, and EMT process marker proteins vimentin, simultaneously reducing E-cadherin and N-cadherin expression. The opposite results were observed when NSD3 was overexpressed. Additionally, overexpressing of NSD3 dramatically activated the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway and enhanced actin-capping protein (CAPG) expression. Furthermore, the proliferation and migration abilities evidently facilitated by pcDNA3.1(+) expression vector containing full-length CDS of NSD3 (pcDNA3.1(+)-NSD3, or NSD3) were partially decreased after incubation with ERK1/2 signaling pathway inhibitor (PD98059) and/or specific siRNA against CAPG (siCAPG) in SW480 and HT-29 CRC cells. Conclusion: NSD3 overexpression stimulated CRC cell proliferation and migration through targeting the ERK1/2 signaling pathway and downstream CAPG. Thus, NSD3 could serve as a promising target for anticancer drug development for patients with CRC.

Decreased expression of cell polarity protein Scribble correlated with altered subcellular localization of the Crumbs homologue 3 protein in human adenomyotic endometrial cells

AIM

Previous studies have revealed that loss of cell apical-basal polarity contributed to the early stages of tumorigenesis. Adenomyosis involves a down-growth and aberrant implantation of the endometrial basalis into the myometrium. This study discovered aberrant expression of polarity protein Scribble (Scrib) and Crumbs homologue 3 protein (CRB3) in epithelial cells of diffuse adenomyosis.

METHODS

This was a case-controlled study, including 39 patients with histologic evidence of adenomyosis, and 48 patients with carcinoma in situ of the uterine cervix without adenomyosis or endometriosis as control. Adenomyotic foci, eutopic endometrium of adenomyotic patients as well as normal endometrium were collected. Reverse Transcription Polymerase Chain Reaction (RT-PCR), Immunoreactivity, confocal microscopy and immune electron microscopy were conducted to evaluate Scribble expression and localization of Scribble and CRB3.

RESULTS

Scrib was screen out as an abnormally expressed polarity protein in adenomyotic eutopic endometrium (ADM-EU) at messenger RNA (mRNA) level. The ADM-EU and adenomyotic ectopic endometrium showed a significantly decreased expression of Scrib compared with normal endometrium (all P-values <0.05). Scrib decreased significantly in ADM-EU than normal endometrium only in patients at proliferative phase and with severe dysmenorrhea (P-values <0.01, P-values <0.001 respectively). In ADM-EU, Scrib expression significantly lowered in patients with severe dysmenorrhea than mild dysmenorrhea (P-values <0.05). Aberrant redistribution of CRB3 from apical to basal lateral membrane portion was also detected in experiments by confocal microscopy immune electron microscopy (all P-values <0.01).

CONCLUSION

Basolateral polarity protein Scrib was found decreased significantly in endometrial cells of adenomyosis at mRNA and protein level, compared with normal endometrium. Menstrual phase and severity of dysmenorrhea has an impact on Scrib expression. Scrib decrease was accompanied by aberrant redistribution of CRB3 from apical to basal lateral membrane portion.

Paracrine Induction of Epithelial-Mesenchymal Transition Between Colorectal Cancer Cells and its Suppression by a p53/miR-192/215/NID1 Axis

BACKGROUND & AIMS

Intratumor heterogeneity is a common feature of colorectal cancer (CRC). Here, we analyzed whether mesenchymal-like CRC cells promote the progression of epithelial-like CRC cells via paracrine mechanisms.

METHODS

Six CRC cell lines that show an epithelial phenotype were treated with conditioned media (CM) from CRC cell lines that show a mesenchymal phenotype, and effects on epithelial-mesenchymal transition (EMT), migration, invasion, and chemoresistance were determined. Secreted factors potentially mediating these effects were identified by using cytokine arrays. Associations of these factors with tumor progression and patient survival were determined.

RESULTS

CM obtained from mesenchymal-like CRC cells induced EMT associated with increased migration, invasion, and chemoresistance in epithelial-like CRC cell lines. Notably, activation of p53 in mesenchymal-like CRC cells prevented these effects of CM. Increased concentrations of several cytokines were identified in CM from mesenchymal-like CRC cell lines and a subset of these cytokines showed repression by p53. The down-regulation of nidogen-1 (NID1) was particularly significant and was owing to p53-mediated induction of microRNA-192 and microRNA-215, which directly target the NID1 messenger RNA. NID1 was found to be required and sufficient for inducing EMT, invasion, and migration in epithelial-like CRC cells. In primary CRCs, increased NID1 expression was associated with p53 mutation and microRNA-192/215 down-regulation. Importantly, increased NID1 expression in CRCs correlated with enhanced tumor progression and poor patient survival.

CONCLUSIONS

Taken together, our results show that CRC cells promote tumor progression via secreting NID1, which induces EMT in neighboring tumor cells. Importantly, the interference of p53 with this paracrine signaling between tumor cells may critically contribute to tumor suppression.

MKK3 modulates JNK-dependent cell migration and invasion

The c-Jun N-terminal kinase (JNK) pathway plays essential roles in regulating a variety of physiological processes including cell migration and invasion. To identify critical factors that regulate JNK-dependent cell migration, we carried out a genetic screen in Drosophila based on the loss-of-cell polarity-triggered cell migration in the wing epithelia, and identified MKK3 licorne (lic) as an essential regulator of JNK-mediated cell migration and invasion. We found that loss of lic suppressed ptc > scrib-IR or ptc > Egr triggered cell migration in the wing epithelia, and Ras^v12/lgl^−/− induced tumor invasion in the eye discs. In addition, ectopic expression of Lic is sufficient to induce JNK-mediated but p38-independent cell migration, and cooperate with oncogenic Ras to promote tumor invasion. Consistently, Lic is able to activate JNK signaling by phosphorylating JNK, which up-regulates the matrix metalloproteinase MMP1 and integrin, characteristics of epithelial–mesenchymal transition (EMT). Moreover, lic is required for physiological JNK-mediate cell migration in thorax development. Finally, expression of human MKK3 in Drosophila is able to initiate JNK-mediated cell migration, cooperates with oncogenic Ras to trigger tumor invasion, and rescue loss-of-lic induced thorax closure defect. As previous studies suggest that MKK3 specifically phosphorylates and activates p38MAPK, our data provide the first in vivo evidence that MKK3 regulates JNK-dependent cell migration and invasion, a process evolutionarily conserved from flies to human.

Scribble: A master scaffold in polarity, adhesion, synaptogenesis, and proliferation

Key events ranging from cell polarity to proliferation regulation to neuronal signaling rely on the assembly of multiprotein adhesion or signaling complexes at particular subcellular sites. Multidomain scaffolding proteins nucleate assembly and direct localization of these complexes, and the protein Scribble and its relatives in the LAP protein family provide a paradigm for this. Scribble was originally identified because of its role in apical-basal polarity and epithelial integrity in Drosophila melanogaster It is now clear that Scribble acts to assemble and position diverse multiprotein complexes in processes ranging from planar polarity to adhesion to oriented cell division to synaptogenesis. Here, we explore what we have learned about the mechanisms of action of Scribble in the context of its multiple known interacting partners and discuss how this knowledge opens new questions about the full range of Scribble protein partners and their structural and signaling roles.

Keratin 80 promotes migration and invasion of colorectal carcinoma by interacting with PRKDC via activating the AKT pathway

Little is known about the function of Keratin 80 (KRT80), an epithelial keratin, in cancer. This study investigated the role of KRT80 in the prognosis of colorectal carcinoma (CRC) and the underlying mechanisms involved in CRC migration and invasion. We analyzed the expression of KRT80 using The Cancer Genome Atlas and Oncomine databases. Higher expression of KRT80 was found to be significantly associated with multiple pathological parameters, lower disease-free survival, and overall survival in CRC patients. Also, KRT80 was an independent prognostic indicator for CRC. Furthermore, altered KRT80 expression impacted migration and invasion of CRC cells, as well as the expression of epithelial–mesenchymal transition (EMT)-related markers and cell morphology via the AKT pathway. Inhibiting the expression of AKT could reverse these phenomena. Liquid Chromatograph Mass Spectrometer/Mass Spectromete, Co-immunoprecipitation, and laser scanning confocal microscopy techniques showed that KRT80 could interact with protein kinase, DNA-activated, catalytic polypeptide (PRKDC). Suppressing PRKDC could inhibit the expression of AKT and EMT, as well as the migration and invasion of CRC cells. Taken together, these results demonstrated that KRT80 was an independent prognostic biomarker for CRC and promoted CRC migration and invasion by interacting with PRKDC via activation of the AKT pathway.

Modeling Tissue Polarity in Context

Polarity is critical for development and tissue-specific function. However, the acquisition and maintenance of tissue polarity is context dependent. Thus, cell and tissue polarity depend on cell adhesion which is regulated by the cytoskeleton and influenced by the biochemical composition of the extracellular microenvironment and modified by biomechanical cues within the tissue. These biomechanical cues include fluid flow induced shear stresses, cell-density and confinement-mediated compression, and cellular actomyosin tension intrinsic to the tissue or induced in response to morphogens or extracellular matrix stiffness. Here, we discuss how extracellular matrix stiffness and fluid flow influence cell-cell and cell-extracellular matrix adhesion and alter cytoskeletal organization to modulate cell and tissue polarity. We describe model systems that when combined with state of the art molecular screens and high-resolution imaging can be used to investigate how force modulates cell and tissue polarity.

Bone morphogenetic protein and activin membrane-bound inhibitor overexpression inhibits gastric tumor cell invasion via the transforming growth factor-β/epithelial-mesenchymal transition signaling pathway

Gastric carcinoma is one of the most common human malignancies and remains the second leading cause of cancer-associated mortality worldwide. Gastric carcinoma is characterized by early-stage metastasis and is typically diagnosed in the advanced stage. Previous results have indicated that bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI) overexpression has been demonstrated to inhibit growth and metastasis of gastric cancer cells. However, the molecular mechanisms of the BAMBI-mediated signaling pathway in the progression of gastric cancer are poorly understood. In the present study, to assess whether BAMBI overexpression inhibited the growth and aggressiveness of gastric carcinoma cells through regulation of transforming growth factor (TGF)-β/epithelial-mesenchymal transition (EMT) signaling pathway, the growth and metastasis of gastric carcinoma cells were analyzed following BAMBI overexpression and knockdown in vitro and in vivo. Molecular changes in the TGF-β/EMT signaling pathway were studied in gastric carcinoma cells following BAMBI overexpression and knockdown. DNA methylation of the gene regions encoding the TGF-β/EMT signaling pathway was investigated in gastric carcinoma cells. Tumor growth in tumor-bearing mice was analyzed after mice were subjected to endogenous overexpression of BAMBI. Results indicated that BAMBI overexpression significantly inhibited gastric carcinoma cell growth and aggressiveness, whereas knockdown of BAMBI significantly promoted its growth and metastasis compared with the control (P<0.01). The TGF-β/EMT signaling pathway was downregulated in BAMBI-overexpressed gastric carcinoma cells; however, signaling was promoted following BAMBI knockdown. In addition, it was observed that BAMBI overexpression significantly downregulated the DNA methylation of the gene regions encoding the TGF-β/EMT signaling pathway (P<0.01). Furthermore, RNA interference-mediated BAMBI overexpression also promoted apoptosis in gastric cancer cells and significantly inhibited growth of gastric tumors in murine xenografts (P<0.01). In conclusion, the present findings suggest that BAMBI overexpression inhibited the TGF-β/EMT signaling pathway and suppressed the invasiveness of gastric tumors, suggesting BAMBI may be a potential target for the treatment of gastric carcinoma via regulation of the TGF-β/EMT signaling pathway.

Cytoplasmic localization of the cell polarity factor scribble supports liver tumor formation and tumor cell invasiveness

The loss of epithelial cell polarity plays an important role in the development and progression of liver cancer. However, the specific molecular mechanisms supporting tumor initiation and progression are poorly understood. In this study, transcriptome data and immunofluorescence stains of tissue samples derived from hepatocellular carcinoma (HCC) patients revealed that overexpression associated with cytoplasmic localization of the basolateral cell polarity complex protein scribble (Scrib) correlated with poor prognosis of HCC patients. In comparison with HCC cells stably expressing wild-type Scrib (Scrib^WT ), mutated Scrib with enforced cytoplasmic enrichment (Scrib^P305L ) induced AKT signaling through the destabilization of phosphatase and tensin homolog (PTEN) and PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1). Cytoplasmic Scrib^P305L stimulated a gene signature and a phenotype characteristic for epithelial to mesenchymal transition (EMT) and HCC cell invasiveness. Scrib^P305L -dependent invasion was mediated by the activator protein 1 (AP-1) constituents ATF2 and JunB through induction of paracrine-acting secreted protein acidic and cysteine-rich (SPARC). Coexpression of Scrib^P305L and the oncogene c-MYC through hydrodynamic gene delivery in mouse livers promoted tumor formation and increased abundance of pAKT, pATF2, and SPARC in comparison with controls. Finally, cytoplasmic Scrib localization correlated with AKT and ATF2 phosphorylation in human HCC tissues, and the Scrib^P305L -dependent gene signature was enriched in cancer patients with poor prognosis.

CONCLUSION

Perturbation of hepatocellular polarity due to overexpression and cytoplasmic enrichment of Scrib supports tumor initiation and HCC cell dissemination through specific molecular mechanisms. Biomarker signatures identified in this study can be used for the identification of HCC patients with higher risk for the development of metastasis. (Hepatology 2018;67:1842-1856).

Upsetting the Balance: When Viruses Manipulate Cell Polarity Control

The central importance of cell polarity control is emphasized by the frequency with which it is targeted by many diverse viruses. It is clear that in targeting key polarity control proteins, viruses affect not only host cell polarity, but also influence many cellular processes, including transcription, replication, and innate and acquired immunity. Examination of the interactions of different virus proteins with the cell and its polarity controls during the virus life cycles, and in virally‐induced cell transformation shows ever more clearly how intimately all cellular processes are linked to the control of cell polarity.

•

Multiple viruses target cell polarity.

•

Viral targeting of polarity frequently occurs through PDZ recognition.

•

Biological effects include immune-avoidance, cell proliferation and apoptosis inhibition.

The Scribble Cell Polarity Module in the Regulation of Cell Signaling in Tissue Development and Tumorigenesis

The Scribble cell polarity module, comprising Scribbled (Scrib), Discs-large (Dlg) and Lethal-2-giant larvae (Lgl), has a tumor suppressive role in mammalian epithelial cancers. The Scribble module proteins play key functions in the establishment and maintenance of different modes of cell polarity, as well as in the control of tissue growth, differentiation and directed cell migration, and therefore are major regulators of tissue development and homeostasis. Whilst molecular details are known regarding the roles of Scribble module proteins in cell polarity regulation, their precise mode of action in the regulation of other key cellular processes remains enigmatic. An accumulating body of evidence indicates that Scribble module proteins play scaffolding roles in the control of various signaling pathways, which are linked to the control of tissue growth, differentiation and cell migration. Multiple Scrib, Dlg and Lgl interacting proteins have been discovered, which are involved in diverse processes, however many function in the regulation of cellular signaling. Herein, we review the components of the Scrib, Dlg and Lgl protein interactomes, and focus on the mechanism by which they regulate cellular signaling pathways in metazoans, and how their disruption leads to cancer.

Iron modulation of erythropoiesis is associated with Scribble-mediated control of the erythropoietin receptor

Iron deficiency causes resistance in erythroid progenitors against proliferative but not survival signals of erythropoietin. Khalil et al. link this response to the down-regulation of Scribble, an orchestrator of receptor trafficking and signaling. With iron deprivation, transferrin receptor 2 drives Scribble degradation, reconfiguring erythropoietin receptor function.

Iron-restricted human anemias are associated with the acquisition of marrow resistance to the hematopoietic cytokine erythropoietin (Epo). Regulation of Epo responsiveness by iron availability serves as the basis for intravenous iron therapy in anemias of chronic disease. Epo engagement of its receptor normally promotes survival, proliferation, and differentiation of erythroid progenitors. However, Epo resistance caused by iron restriction selectively impairs proliferation and differentiation while preserving viability. Our results reveal that iron restriction limits surface display of Epo receptor in primary progenitors and that mice with enforced surface retention of the receptor fail to develop anemia with iron deprivation. A mechanistic pathway is identified in which erythroid iron restriction down-regulates a receptor control element, Scribble, through the mediation of the iron-sensing transferrin receptor 2. Scribble deficiency reduces surface expression of Epo receptor but selectively retains survival signaling via Akt. This mechanism integrates nutrient sensing with receptor function to permit modulation of progenitor expansion without compromising survival.

Regulation of cellular and PCP signalling by the Scribble polarity module

Since the first identification of the Scribble polarity module proteins as a new class of tumour suppressors that regulate both cell polarity and proliferation, an increasing amount of evidence has uncovered a broader role for Scribble, Dlg and Lgl in the control of fundamental cellular functions and their signalling pathways. Here, we review these findings as well as discuss more specifically the role of the Scribble module in PCP signalling.

CXC chemokine‑7 inhibits growth and migration of oral tongue squamous cell carcinoma cells, mediated by the epithelial‑mesenchymal transition signaling pathway

Oral tongue squamous cell carcinoma (OTSCC) is the most common oral malignancy with different histopathological symptoms and etiology of tumorigenesis. Migration and invasion is the most important characteristics of OTSCC, and limits tumor therapy in clinics. The epithelial‑to‑mesenchymal transition (EMT) signaling pathway is an important process in the progress of tumor cell migration and invasion. Previous studies have indicated that C‑X‑C chemokine receptor‑7 (CXCR‑7) promotes the progression and metastasis of tumor cells, presenting a potential target molecule for cancer therapy. The present study investigated the inhibitory effects of C‑X‑C chemokine‑7 (CXC‑7) on human OTSCC cells both in vitro and in vivo. The results demonstrated that the Tca8113 human OTSCC cell line expressed higher levels of CXC‑7 mRNA compared with the hNOE human normal oral epithelial cell line. MTT assays indicated that CXC‑7 suppressed Tca8113 cell growth, and the cytotoxicity of CXC‑7 was indicated as the cell survival of the negative control group was significantly decreased compared with the blank control and hNOE cells. Migration and invasion assays revealed that CXC‑7 inhibited Tca8113 cell local expansion and distant metastasis. In addition, the results demonstrated that the extracellular signal‑regulated kinase (ERK)/protein kinase B (AKT) signaling pathway was inhibited after CXC‑7 treatment in Tca8113 cells. N‑cadherin, E‑Cadherin, Snail and Slug expression levels in the ERK/AKT signaling pathway were inhibited in Tca8113 cells after treatment with CXC‑7. It was demonstrated that important extracellular matrix proteins involved in cell migration, including Slug, collagen type I and Vimentin, were significantly downregulated by CXC‑7 treatment. In conclusion, CXC‑7 inhibited growth and migration in OTSCC cells, mediated by the EMT signaling pathway. This suggests that CXC‑7 serves an inhibitory role in OTSCC migration, implicating CXCR‑7 as a promising biomarker for chemokine receptor‑based drug development.

MPA Modulates Tight Junctions' Permeability via Midkine/PI3K Pathway in Caco-2 Cells: A Possible Mechanism of Leak-Flux Diarrhea in Organ Transplanted Patients

Mycophenolic acid (MPA) is prescribed to prevent allograft rejection in organ transplanted patients. However, its use is sporadically linked to leak flux diarrhea and other gastrointestinal (GI) disturbances in around 75% of patients through yet unknown mechanisms. Recently, we identified Midkine as a modulator of tight junctions (TJs) permeability in MPA treated Caco-2 monolayer. In the present study, we investigated the possible involvement of Midkine dependent PI3K pathway in alteration of TJs under MPA treatment. Caco-2 cells were grown as monolayer to develop TJs and were treated for 72 h with DMSO (control) or MPA in presence and absence of Midkine inhibitor (iMDK) or PI3K inhibitors (LY/AMG). Caco-2 monolayer integrity was assessed by transepithelial electrical resistance (TEER) and FITC-dextran assays. Our functional assays showed that PI3K inhibitors (LY/AMG) can significantly inhibit the compromised TJs integrity of MPA-treated Caco-2 cells monolayer. Chromatin immunoprecipitation analyses showed a significant epigenetic activation of Midkine, PI3K, Cdx-2, and Cldn-2 genes and epigenetic repression of Cldn-1 gene after MPA treatment. The MPA-induced epigenetic alterations were further confirmed by mRNA and protein expression analysis. Collectively, our data shows that PI3K pathway as the downstream target of Midkine which in turn modulates p38MAPK and pAKT signaling to alter TJs permeability in Caco-2 cell monolayers treated with MPA. These results highlight the possible use of either Midkine or PI3K inhibitors as therapeutic agents to prevent MPA induced GI disturbances.

NUBPL, a novel metastasis-related gene, promotes colorectal carcinoma cell motility by inducing epithelial-mesenchymal transition

Nucleotide binding protein‐like, NUBPL, is an assembly factor for human mitochondrial complex I, which is the biggest member of the mitochondrial respiratory chain. However, the relationship between NUBPL and carcinoma progression remains unknown. In this study, NUBPL was characterized for its role in colorectal cancer (CRC) and the underlying molecular mechanisms. Data (n = 197) from the Oncomine database revealed that mRNA levels of NUBPL were remarkably overexpressed in CRC tissues compared with normal tissues. In addition, immunohistochemical analysis of 75 pairs of CRC and non‐tumor tissues showed that the expression level of NUBPL was significantly higher in CRC tissues, and its expression level was positively associated with lymph node metastasis (P = 0.028) and advanced staging (P = 0.030). Expression of NUBPL in metastatic lymph nodes of CRC patients was also detected by immunohistochemical staining and high expression levels of NUBPL were observed. Overexpression of NUBPL significantly promoted the migration and invasion ability of CRC cell lines SW480 and SW620, whereas knockdown of NUBPL lead to an opposite effect. Our further study found that NUBPL could induce epithelial–mesenchymal transition (EMT), characterized by downregulation of epithelial markers (E‐cadherin) and upregulation of mesenchymal markers (N‐cadherin and vimentin). Moreover, NUBPL was able to activate ERK, which is believed to promote EMT and tumor metastasis. Inhibition of ERK suppressed the NUBPL‐induced changes in EMT and cell motility. These data showed that NUBPL plays a vital role in CRC migration and invasion by inducing EMT and activating ERK. It might be a novel therapeutic target for CRC.

Systematic morphological profiling of human gene and allele function via Cell Painting

We hypothesized that human genes and disease-associated alleles might be systematically functionally annotated using morphological profiling of cDNA constructs, via a microscopy-based Cell Painting assay. Indeed, 50% of the 220 tested genes yielded detectable morphological profiles, which grouped into biologically meaningful gene clusters consistent with known functional annotation (e.g., the RAS-RAF-MEK-ERK cascade). We used novel subpopulation-based visualization methods to interpret the morphological changes for specific clusters. This unbiased morphologic map of gene function revealed TRAF2/c-REL negative regulation of YAP1/WWTR1-responsive pathways. We confirmed this discovery of functional connectivity between the NF-κB pathway and Hippo pathway effectors at the transcriptional level, thereby expanding knowledge of these two signaling pathways that critically regulate tumor initiation and progression. We make the images and raw data publicly available, providing an initial morphological map of major biological pathways for future study.

DOI:http://dx.doi.org/10.7554/eLife.24060.001

Many human diseases are caused by particular changes, called mutations, in patients’ DNA. A genome is the complete DNA set of an organism, which contains all the information to build the body and keep it working. This information is stored as a code made up of four chemicals called bases. Humans have about 30,000 genes built from DNA, which contain specific sequences of bases. Genome sequencing can determine the exact order of these bases, and has revealed a long list of mutations in genes that could cause particular diseases. However, over 30% of genes in the human body do not have a known role. Genes can serve multiple roles, some of which are not yet discovered, and even when a gene’s purpose is known, the impact of each particular mutation in a given gene is largely uncatalogued. Therefore, new methods need to be developed to identify the biological roles of both normal and abnormal gene sequences.

For hundreds of years, biologists have used microscopy to study how living cells work. Rohban et al. have now asked whether modern software that extracts data from microscopy images could create a fingerprint-like profile of a cell that would reflect how its genes affect its role and appearance. While some genes do not necessarily carry a code with instructions of what a cell should look like, they can indirectly modify the structure of the cell. The resulting changes in the shape of the cell can then be captured in images. The idea was that two cells with matching profiles would indicate that their combinations of genes had matching biological roles too.

Rohban et al. tested their approach with human cells grown in the laboratory. In each sample of cells, they ‘turned on’ one of a few hundred relatively well-known human genes, some of which were known to have similar roles. The cells were then stained via a technique called ‘Cell Painting’ to reveal eight specific components of each cell, including its DNA and its surface membrane. The stained cells were imaged under a microscope and the resulting microscopy images analyzed to create a profile of each type of cell. Rohban et al. confirmed that turning on genes known to perform similar biological roles lead to similar-looking cells. The analysis also revealed a previously unknown interaction between two major pathways in the cell that control how cancer starts and develops.

In the future, this approach could predict the biological roles of less-understood genes by looking for profiles that match those of well-known genes. Applying this strategy to every human gene, and mutations in genes that are linked to diseases, could help to answer many mysteries about how genes build the human body and keep it working.

DOI:http://dx.doi.org/10.7554/eLife.24060.002

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.

Preclinical Efficacy and Safety Assessment of Artemisinin-Chemotherapeutic Agent Conjugates for Ovarian Cancer

Artemisinin (ARS) and its derivatives, which are clinically used antimalarial agents, have shown antitumor activities. Their therapeutic potencies, however, are limited by their low solubility and poor bioavailability. Here, through a pharmacophore hybridization strategy, we synthesized ARS-drug conjugates, in which the marketed chemotherapeutic agents chlorambucil, melphalan, flutamide, aminoglutethimide, and doxifluridine, were separately bonded to Dihydroartemisinin (DHA) through various linkages. Of these, the artemisinin-melphalan conjugate, ARS4, exhibited most toxicity to human ovarian cancer cells but had low cytotoxicity to normal cells. ARS4 inhibited the growth and proliferation of ovarian cancer cells and resulted in S-phase arrest, apoptosis, and inhibition of migration; these effects were stronger than those of its parent drugs, DHA and melphalan. Furthermore, ARS4 modulated the expression of proteins involved in cell cycle progression, apoptosis, and the epithelial–mesenchymal transition (EMT). Moreover, in mice, ARS4 inhibited growth and intraperitoneal dissemination and metastasis of ovarian cancer cells without observable toxic effects. Our results provide a basis for development of the compound as a chemotherapeutic agent.

Research in context

Artemisinin compounds have recently received attention as anticancer agents because of their clinical safety profiles and broad efficacy. However, their therapeutic potencies are limited by low solubility and poor bioavailability. Here, we report that ARS4, an artemisinin-melphalan conjugate, possesses marked in-vitro and in-vivo antitumor activity against ovarian cancer, the effects of which are stronger than those for its parent drugs, Dihydroartemisinin and melphalan. In mice, ARS4 inhibits localized growth of ovarian cancer cells and intraperitoneal dissemination and metastasis without appreciable host toxicity. Thus, for patients with ovarian cancer, ARS4 is a promising chemotherapeutic agent.

•

Artemisinin-drug conjugates were designed via pharmacophore hybridization strategy

•

ARS4 induced apoptosis of ovarian cancer cells and cell cycle arrest and reversed the EMT polarity

•

In mice, ARS4 inhibited growth and intraperitoneal dissemination of ovarian cancer cells with no appreciable host toxicity

Expression and clinical significance of PcG-associated protein RYBP in hepatocellular carcinoma

Ring1 and YY1 binding protein (RYBP), a member of the polycomb group proteins, has been implicated in transcription repression and tumor cell-specific apoptosis. Previously, RYBP has been reported as a putative tumor suppressor in cancer tissues by regulating mouse double minute 2 homolog-p53 signaling. However, the exact role and underlying mechanisms of RYBP in cancer remain to be fully elucidated. The present study investigated the expression profile of RYBP in hepatocellular carcinoma (HCC) and examined the association between the expression of RYBP and metastasis of HCC. It was found that RYBP was downregulated in HCC tissues, compared with matched adjacent non-tumor tissues, as detected by reverse transcription-quantitative polymerase chain reaction and immunohistochemistry. In addition, Kaplan-Meier survival analysis showed that the negative expression of RYBP was associated with decreased overall survival rates in patients with HCC. It was also found that RYBP was associated with zinc finger E-box binding homeobox 1 and zinc finger E-box binding homeobox 2, which were overexpressed in HCC and correlated with epithelial-mesenchymal transition. The results of the present study suggested the importance of RYBP in HCC and its possible mechanism in the metastasis of HCC.

Crumbs 3b promotes tight junctions in an ezrin-dependent manner in mammalian cells

Crumbs 3 (CRB3) is a component of epithelial junctions, which has been implicated in apical-basal polarity, apical identity, apical stability, cell adhesion, and cell growth. CRB3 undergoes alternative splicing to yield two variants: CRB3a and CRB3b. Here, we describe novel data demonstrating that, as with previous studies on CRB3a, CRB3b also promotes the formation of tight junctions (TJs). However, significantly we demonstrate that the 4.1-ezrin-radixin-moesin-binding motif of CRB3b is required for CRB3b functionality and that ezrin binds to the FBM of CRB3b. Furthermore, we show that ezrin contributes to CRB3b functionality and the correct distribution of TJ proteins. We demonstrate that both CRB3 isoforms are required for the production of functionally mature TJs and also the localization of ezrin to the plasma membrane. Finally, we demonstrate that reduced CRB3b expression in head and neck squamous cell carcinoma (HNSCC) correlates with cytoplasmic ezrin, a biomarker for aggressive disease, and shows evidence that while CRB3a expression has no effect, low CRB3b and high cytoplasmic ezrin expression combined may be prognostic for HNSCC.

Analysis of different components in the peritumoral tissue microenvironment of colorectal cancer: A potential prospect in tumorigenesis

The present study aimed to observe the varying expression of biomarkers in the microenvironment adjacent to colorectal cancer lesions to provide additional insight into the functions of microenvironment components in carcinogenesis and present a novel or improved indicator for early diagnosis of cancer. A total of 144 human samples from three different locations in 48 patients were collected, these locations were 10, 5 and 2 cm from the colorectal cancer lesion, respectively. The biomarkers analyzed included E‑cadherin, cytokeratin 18 (CK18), hyaluronidase‑1 (Hyal‑1), collagen type I (Col‑I), Crumbs3 (CRB3), vimentin, proteinase activated receptor 3 (PAR‑3), α‑smooth muscle actin (α‑SMA), cyclin D1 (CD1) and cluster of differentiation (CD)133. In addition, crypt architecture was observed. Related functional analysis of proteins was performed using hierarchical index cluster analysis. More severe destroyed crypt architecture closer to the cancer lesions was observed compared with the 10 cm sites, with certain crypts degraded entirely. Expression levels of E‑cadherin, CK18, CRB3 and PAR‑3 were lower in 2 cm sites compared with the 10 cm sites (all P<0.001), while the expression levels of the other biomarkers in the 2 cm sites were increased compared with 10 cm sites (all P<0.0001). Notably, the expression of CK18 in 2 cm sites was higher than in the 5 cm site (P<0.0001), which was different from the expression of E‑cadherin, CRB3 and PAR‑3. The expression levels of Hyal‑1 and Col‑I at the 2 cm sites were lower than that of the 5 cm sites (P>0.05 and P=0.0001, respectively), while the expression of vimentin, α‑SMA, CD1 and CD133 were not. Hyal‑1 and Col‑I may be independently important in cancer initiation in the tumor microenvironment. The results of the present study suggest that the biomarkers in the tissue microenvironment are associated with early tumorigenesis and may contribute to the development of carcinomas. These observations may be useful for early diagnosis of colorectal cancer.

Identification of the interplay between SOX9 and S100P in the metastasis and invasion of colon carcinoma

Elevated expression of S100P has been detected in several tumor types and suggested to be responsible for tumor metastasis and invasion, but the upstream regulatory mechanisms promoting S100P overexpression are largely unknown. Here, we report that SOX9 was predicted and verified as a transcription factor of S100P. SOX9 and S100P were both overexpressed in colon cancer. SOX9 bound to and activated the S100P promoter. Knockdown of SOX9 expression down-regulated S100P expression, resulting in reduced invasiveness and metastasis of colon cancer cells by inhibiting the activation of receptor for advanced glycation end products (RAGE)/ERK signaling and epithelial-mesenchymal transition (EMT). Further, decreased expression of SOX9 dramatically inhibited the tumor growth and peritoneal metastasis in nude mice. More importantly, S100P was found to be critical for SOX9-mediated metastasis and invasion in colon cancer. Knockdown of S100P in SOX9-overexpressing colon cancer cells dramatically suppressed metastasis and invasion both in vitro and in mice. We also detected SOX9 and S100P expression in a tissue microarray with 90 colon cancer cases to provide their clinical relevance. There was a strong correlation between SOX9 and S100P expression in colon carcinomas. In conclusion, our results suggest that SOX9 promotes tumor metastasis and invasion through regulation of S100P expression.

ZDHHC7-mediated S-palmitoylation of Scribble regulates cell polarity

Scribble (SCRIB) is a tumor suppressor protein, playing critical roles in establishing and maintaining epithelial cell polarity. Paradoxically, SCRIB is frequently amplified in human cancers, however, fails to localize properly to cell-cell junctions, suggesting that mislocalization of SCRIB contributes to tumorigenesis. Using chemical reporters, here we showed that SCRIB localization is regulated by S-palmitoylation at conserved cysteine residues. The palmitoylation-deficient mutants of SCRIB are mislocalized, leading to disruption of cell polarity and loss of their tumor suppressive activities to oncogenic YAP, MAPK and PI3K/Akt pathways. We further found that ZDHHC7 is the major palmitoyl acyltransferase regulating SCRIB. Knockout of ZDHHC7 led to SCRIB mislocalization and YAP activation, and disruption of SCRIB’s suppressive activities in HRas^V12-induced cell invasion. In summary, we demonstrated that ZDHHC7-mediated SCRIB palmitoylation is critical for SCRIB membrane targeting, cell polarity, and tumor suppression, providing new mechanistic insights of how dynamic protein palmitoylation regulates cell polarity and tumorigenesis.

The function of Shoc2: A scaffold and beyond

The extracellular signal-regulated kinase (ERK1/2) cascade regulates a myriad of functions in multicellular organisms. Scaffold proteins provide critical spatial and temporal control over the specificity of signaling. Shoc2 is a scaffold that accelerates activity of the ERK1/2 pathway. Loss of Shoc2 expression in mice results in embryonic lethality, thus highlighting the essential role of Shoc2 in embryogenesis. In agreement, patients carrying mutated Shoc2 suffer from a wide spectrum of developmental deficiencies. Efforts to understand the mechanisms by which Shoc2 controls ERK1/2 activity revealed the intricate machinery that governs the ability of Shoc2 to transduce signals of the ERK1/2 pathway. Understanding the mechanisms by which Shoc2 contributes to a high degree of specificity of ERK1/2 signaling as well as deciphering the biological functions of Shoc2 in development and human disorders are major unresolved questions.

Multiple roles for keratin intermediate filaments in the regulation of epithelial barrier function and apico-basal polarity

As multicellular organisms evolved a family of cytoskeletal proteins, the keratins (types I and II) expressed in epithelial cells diversified in more than 20 genes in vertebrates. There is no question that keratin filaments confer mechanical stiffness to cells. However, such a number of genes can hardly be explained by evolutionary advantages in mechanical features. The use of transgenic mouse models has revealed unexpected functional relationships between keratin intermediate filaments and intracellular signaling. Accordingly, loss of keratins or mutations in keratins that cause or predispose to human diseases, result in increased sensitivity to apoptosis, regulation of innate immunity, permeabilization of tight junctions, and mistargeting of apical proteins in different epithelia. Precise mechanistic explanations for these phenomena are still lacking. However, immobilization of membrane or cytoplasmic proteins, including chaperones, on intermediate filaments (“scaffolding”) appear as common molecular mechanisms and may explain the need for so many different keratin genes in vertebrates.

The high-risk HPV E6 target scribble (hScrib) is required for HPV E6 expression in cervical tumour-derived cell lines

The ability of high-risk HPV E6 oncoproteins to target cellular proteins which harbor PDZ domains is believed to play an important role in the virus life cycle and to influence the ability of these viruses to bring about malignant transformation. Whilst many of these PDZ proteins are potential tumour suppressors, involved in the control of cell polarity and cell-contact, recent studies suggest that mislocalisation or overexpression might result in the emergence of oncogenic functions. This has been shown most clearly for two E6 targets, hDlg and hScrib. In this study we show that hScrib plays such a role in HeLa cells, where its expression is required for maintaining high levels of HPV-18 E6 protein. Loss of hScrib has no effect on E6 stability but results in lower levels of E6 transcription and a reduced rate of E6 translation. We further show that, in the context of cervical tumour-derived cell lines, both hScrib and E6 cooperate in the activation of the S6 kinase signaling pathway, and thereby contribute towards maintaining high rates of protein translation. These results indicate that the residual hScrib that is present within HPV transformed cells is pro-oncogenic, and highlights the dual functions of E6 cell polarity targets.

KITENIN promotes glioma invasiveness and progression, associated with the induction of EMT and stemness markers

KITENIN (KAI1 COOH-terminal interacting tetraspanin) promotes tumor invasion and metastasis in various cancers. This study assessed the association between KITENIN expression and advanced glioma grade in patients. In vitro assays revealed that KITENIN knockdown inhibited the invasion and migration of glioma cells, whereas KITENIN overexpression promoted their invasion and migration. In orthotopic mouse tumor models, mice transplanted with KITENIN-transfected glioma cells had significantly shorter survival than mice transplanted with mock-transfected cells. Patients with low KITENIN expression showed a significantly longer progression-free survival than patients with high KITENIN expression. KITENIN induced the expression of the epithelial-mesenchymal transition (EMT) markers (N-cadherin, ZEB1, ZEB2, SNAIL and SLUG) as well as the glioma stemness markers (CD133, ALDH1 and EPH-B1). Taken together, these findings showed that high levels of KITENIN increased glioma invasiveness and progression, associated with the up-regulation of EMT and stemness markers.

Analysis of the predictive efficiency of S100P on adverse prognosis and the pathogenesis of S100P-mediated invasion and metastasis of colon adenocarcinoma

Elevated expression of S100P has been detected in several tumor types. To analyze the potential use of S100P for the prediction of colorectal cancer (CRC) metastasis and prognosis, S100P expression was detected in 125 patients with colon adenocarcinoma by immunohistochemistry, followed by correlation and survival analysis. High S100P expression was correlated with metastasis, as demonstrated by clinically relevant data, and predicted poor survival more effectively than preoperative serum carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) levels in colon adenocarcinoma. Stable S100P knockdown CRC cell lines were established to elucidate the relationship between S100P expression and tumor progression in vitro and in vivo. S100P knockdown resulted in reductions in the invasiveness and metastasis of CRC cells. Xenograft growth in nude mice also demonstrated that down-regulated S100P dramatically inhibited peritoneal metastasis of CRC cells. S100P promoted the invasion and metastasis of CRC by activating RAGE/ERK signaling and promoting the epithelial-mesenchymal transition (EMT). RAGE was found to be crucial for S100P-mediated EMT in colon cancer. Knockdown of RAGE in S100P-overexpressing colon cancer cells dramatically suppressed EMT process. Our results indicate that overexpression of S100P is related with an invasive and metastatic phenotype of CRC which is EMT-involved and RAGE dependent.

MicroRNA Regulation of Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is a central regulatory program that is similar in many aspects to several steps of embryonic morphogenesis. In addition to its physiological role in tissue repair and wound healing, EMT contributes to chemo resistance, metastatic dissemination and fibrosis, amongst others. Classically, the morphological change from epithelial to mesenchymal phenotype is characterized by the appearance or loss of a group of proteins which have come to be recognized as markers of the EMT process. As with all proteins, these molecules are controlled at the transcriptional and translational level by transcription factors and microRNAs, respectively. A group of developmental transcription factors form the backbone of the EMT cascade and a large body of evidence shows that microRNAs are heavily involved in the successful coordination of mesenchymal transformation and vice versa, either by suppressing the expression of different groups of transcription factors, or otherwise acting as their functional mediators in orchestrating EMT. This article dissects the contribution of microRNAs to EMT and analyzes the molecular basis for their roles in this cellular process. Here, we emphasize their interaction with core transcription factors like the zinc finger enhancer (E)-box binding homeobox (ZEB), Snail and Twist families as well as some pluripotency transcription factors.