The adaptor protein VEPH1 interacts with the kinase domain of ERBB2 and impacts EGF signaling in ovarian cancer cells.

Upregulation of ERBB2 and activating mutations in downstream KRAS/BRAF and PIK3CA are found in several ovarian cancer histotypes. ERBB2 enhances signaling by the ERBB family of EGF receptors, and contains docking positions for proteins that transduce signaling through multiple pathways. We identified the adaptor protein ventricular zone-expressed pleckstrin homology domain-containing protein 1 (VEPH1) as a potential interacting partner of ERBB2 in a screen of proteins co-immunoprecipitated with VEPH1. In this study, we confirm a VEPH1 - ERBB2 interaction by co-immunoprecipitation and biotin proximity labelling and show that VEPH1 interacts with the juxtamembrane-kinase domain of ERBB2. In SKOV3 ovarian cancer cells, which bear a PIK3CA mutation and ERBB2 overexpression, ectopic VEPH1 expression enhanced EGF activation of ERK1/2, and mTORC2 activation of AKT. In contrast, in ES2 ovarian cancer cells, which bear a BRAFV600E mutation with VEPH1 amplification but low ERBB2 expression, loss of VEPH1 expression enabled further activation of ERK1/2 by EGF and enhanced EGF activation of AKT. VEPH1 expression in SKOV3 cells enhanced EGF-induced cell migration consistent with increased Snail2 and decreased E-cadherin levels. In comparison, loss of VEPH1 expression in ES2 cells led to decreased cell motility independent of EGF treatment despite higher levels of N-cadherin and Snail2. Importantly, we found that loss of VEPH1 expression rendered ES2 cells less sensitive to BRAF and MEK inhibition. This study extends the range of adaptor function of VEPH1 to ERBB2, and indicates VEPH1 has differential effects on EGF signaling in ovarian cancer cells that may be influenced by driver gene mutations.

The predicted collagen-binding domains of Drosophila SPARC are essential for survival and for collagen IV distribution and assembly into basement membranes.

The assembly of basement membranes (BMs) into tissue-specific morphoregulatory structures requires non-core BM components. Work in Drosophila indicates a principal role of collagen-binding matricellular glycoprotein SPARC (Secreted Protein, Acidic, Rich in Cysteine) in larval fat body BM assembly. We report that SPARC and collagen IV (Col(IV)) first colocalize in the trans-Golgi of hemocyte-like cell lines. Mutating the collagen-binding domains of Drosophila SPARC led to the loss of colocalization with Col(IV), a fibrotic-like BM, and 2nd instar larval lethality, indicating that SPARC binding to Col(IV) is essential for survival. Analysis of this mutant at 2nd instar reveals increased Col(IV) puncta within adipocytes, reflecting a disruption in the intracellular chaperone-like activity of SPARC. Removal of the disulfide bridge in the C-terminal EF-hand2 of SPARC, which is known to enhance Col(IV) binding, did not lead to larval lethality; however, a less intense fat body phenotype was observed. Additionally, both SPARC mutants exhibited altered fat body BM pore topography. Wing imaginal disc-derived SPARC did not localize within Col(IV)-rich matrices. This raises the possibility that SPARC interaction with Col(IV) requires initial intracellular interaction to colocalize at the BM or that wing-derived SPARC undergoes differential post-translational modifications that impacts its function. Collectively, these data provide evidence that the chaperone-like activity of SPARC on Col(IV) begins just prior to their co-secretion and demonstrate for the first time that the Col(IV) chaperone-like activity of SPARC is necessary for Drosophila development beyond the 2nd instar.

Increased androgen receptor levels and signaling in ovarian cancer cells by VEPH1 associated with suppression of SMAD3 and AKT activation.

Studies indicate androgens contribute to initiation or progression of epithelial ovarian cancer through poorly understood mechanisms. We provide evidence that the androgen receptor (AR) interacts in a ligand-independent manner with the putative armadillo repeat domain of ventricular zone expressed PH domain-containing 1 (VEPH1). This interaction was increased by mutation of the two nuclear receptor-interacting LxxLL motifs present within the VEPH1 armadillo repeat domain. Androgen treatment did not result in nuclear co-localization of VEPH1 with AR, suggesting that VEPH1 does not function as a nuclear co-regulatory protein. VEPH1 expression decreased SMAD3 and activated AKT levels in ovarian cancer cell lines and increased AR activity and protein levels, consistent with an impact on receptor stability. Treatment of cells with dihydrotestosterone (DHT) increased AR protein levels measured 24 h after treatment, an effect augmented in VEPH1-transfected cells, and inhibited by knock-down of endogenous VEPH1. SMAD3 overexpression decreased AR protein levels and prevented the VEPH1-dependent increase in AR; however, silencing of SMAD3 paradoxically also decreased AR levels. DHT treatment led to a rapid and sustained decrease in phosphorylated AKT (pAKT) levels that was enhanced by VEPH1 expression. Inhibition of PI3K resulted in increased AR protein levels. These studies indicate that VEPH1 acts to enhance AR activity in ovarian cancer cells by decreasing SMAD3 and pAKT levels, resulting in increased levels of AR protein.

Ventricular Zone Expressed PH Domain Containing 1 (VEPH1): an adaptor protein capable of modulating multiple signaling transduction pathways during normal and pathological development.

Ventricular Zone Expressed PH Domain-Containing 1 (VEPH1) is an 833-amino acid protein encoded by an evolutionarily conserved single-copy gene that emerged with pseudocoelomates. This gene has no paralog in any species identified to date and few studies have investigated the function of its encoded protein. Loss of expression of its ortholog, melted, in Drosophila results in a severe neural phenotype and impacts TOR, FoxO, and Hippo signaling. Studies in mammals indicate a role for VEPH1 in modulating TGFß signaling and AKT activation, while numerous studies indicate VEPH1 expression is altered in several pathological conditions, including cancer. Although often referred to as an uncharacterized protein, available evidence supports VEPH1 as an adaptor protein capable of modulating multiple signal transduction networks. Further studies are required to define these adaptor functions and the role of VEPH1 in development and disease progression.

Collagen IV trafficking: The inside-out and beyond story.

Collagen IV networks endow basement membranes (BMs) with remarkable tensile strength and function as morphoregulatory substrata for diverse tissue-specific developmental events. A complex repertoire of intracellular and extracellular molecular interactions are required for collagen IV secretion and supramolecular assembly into BMs. These include intracellular chaperones such as Heat shock protein 47 (Hsp47) and the chaperone-binding trafficking protein Transport and Golgi organization protein 1 (Tango1). Mutations in these proteins lead to compromised collagen IV protomer stability and secretion, leading to defective BM assembly and function. In addition to intracellular chaperones, a role for extracellular chaperones orchestrating the transport, supramolecular assembly, and architecture of collagen IV in BM is emerging. We present evidence derived from evolutionarily distant model organisms that supports an extracellular collagen IV chaperone-like activity for the matricellular protein SPARC (Secreted Protein, Acidic, Rich in Cysteine). Loss of SPARC disrupts BM homeostasis and compromises tissue biomechanics and physiological function. Thus, the combined contributions of intracellular and extracellular collagen IV-associated chaperones and chaperone-like proteins are critical to ensure proper secretion and stereotypic assembly of collagen IV networks in BMs.

VEPH1 expression decreases vascularisation in ovarian cancer xenografts and inhibits VEGFA and IL8 expression through inhibition of AKT activation.

BACKGROUND: VEPH1 is amplified in several cancers including ovarian but its impact on tumour progression is unknown. Previous work has shown that VEPH1 inhibits TGFß signalling while its Drosophila ortholog increases tissue growth, raising the possibility that VEPH1 could impact tumour growth or progression. METHODS: A CRISPR approach was used to disrupt VEPH1 expression in ovarian cancer ES-2 cells, while VEPH1-negative SKOV3 cells were stably transfected with VEPH1 cDNA. The impact of altered VEPH1 expression was assessed using in vitro and in vivo assays and mechanistic studies were performed in vitro. RESULTS: VEPH1 expression in SKOV3 cells resulted in a reduced tumour growth rate associated with increased necrotic area, and decreased microvessel density and VEGF-A levels relative to tumours formed by mock-transfected cells. VEPH1 expression also decreased VEGFA and IL8 expression in SKOV3 cells and was associated with decreased activated AKT levels. These effects were not observed in ES-2 cells, which bear a BRAFV600E activating mutation that leads to constitutively increased IL8 and VEGFA expression. CONCLUSIONS: VEPH1 expression in SKOV3 ovarian cancer cells inhibits AKT activation to decrease VEGFA and IL8 expression, which leads to decreased tumour vascularisation and progression.

Human ortholog of Drosophila Melted impedes SMAD2 release from TGF-ß receptor I to inhibit TGF-ß signaling.

Drosophila melted encodes a pleckstrin homology (PH) domain-containing protein that enables normal tissue growth, metabolism, and photoreceptor differentiation by modulating Forkhead box O (FOXO), target of rapamycin, and Hippo signaling pathways. Ventricular zone expressed PH domain-containing 1 (VEPH1) is the mammalian ortholog of melted, and although it exhibits tissue-restricted expression during mouse development and is potentially amplified in several human cancers, little is known of its function. Here we explore the impact of VEPH1 expression in ovarian cancer cells by gene-expression profiling. In cells with elevated VEPH1 expression, transcriptional programs associated with metabolism and FOXO and Hippo signaling were affected, analogous to what has been reported for Melted. We also observed altered regulation of multiple transforming growth factor-ß (TGF-ß) target genes. Global profiling revealed that elevated VEPH1 expression suppressed TGF-ß-induced transcriptional responses. This inhibitory effect was verified on selected TGF-ß target genes and by reporter gene assays in multiple cell lines. We further demonstrated that VEPH1 interacts with TGF-ß receptor I (TßRI) and inhibits nuclear accumulation of activated Sma- and Mad-related protein 2 (SMAD2). We identified two TßRI-interacting regions (TIRs) with opposing effects on TGF-ß signaling. TIR1, located at the N terminus, inhibits canonical TGF-ß signaling and promotes SMAD2 retention at TßRI, similar to full-length VEPH1. In contrast, TIR2, located at the C-terminal region encompassing the PH domain, decreases SMAD2 retention at TßRI and enhances TGF-ß signaling. Our studies indicate that VEPH1 inhibits TGF-ß signaling by impeding the release of activated SMAD2 from TßRI and may modulate TGF-ß signaling during development and cancer initiation or progression.

Slow binding kinetics of secreted protein, acidic, rich in cysteine-VEGF interaction limit VEGF activation of VEGF receptor 2 and attenuate angiogenesis.

VEGF-A (VEGF) drives angiogenesis through activation of downstream effectors to promote endothelial cell proliferation and migration. Although VEGF binds both VEGF receptor 1 (R1) and receptor 2 (R2), its proangiogenic effects are attributed to R2. Secreted protein, acidic, rich in cysteine (SPARC) is a matricellular glycoprotein thought to inhibit angiogenesis by preventing VEGF from activating R1, but not R2. Because R2 rather than R1 mediates proangiogenic activities of VEGF, the role of human SPARC in angiogenesis was reevaluated. We confirm that association of SPARC with VEGF inhibits VEGF-induced HUVEC adherence, motility, and proliferation in vitro and blocks VEGF-induced blood vessel formation ex vivo. SPARC decreases VEGF-induced phosphorylation of R2 and downstream effectors ERK, Akt, and p38 MAPK as shown by Western blot and/or phosphoflow analysis. Surface plasmon resonance indicates that SPARC binds slowly to VEGF (0.865 ± 0.02 × 10(4) M(-1) s(-1)) with a Kd of 150 nM, forming a stable complex that dissociates slowly (1.26 ± 0.003 × 10(-3) s(-1)). Only domain III of SPARC binds VEGF, exhibiting a 15-fold higher affinity than full-length SPARC. These findings support a model whereby SPARC regulates angiogenesis by sequestering VEGF, thus restricting the activation of R2 and the subsequent activation of downstream targets critical for endothelial cell functions.

Loss of SPARC dysregulates basal lamina assembly to disrupt larval fat body homeostasis in Drosophila melanogaster.

BACKGROUND: SPARC is a collagen-binding glycoprotein whose functions during early development are unknown. We previously reported that SPARC is expressed in Drosophila by hemocytes and the fat body (FB) and enriched in basal laminae (BL) surrounding tissues, including adipocytes. We sought to explore if SPARC is required for proper BL assembly in the FB. RESULTS: SPARC deficiency leads to larval lethality, associated with remodeling of the FB. In the absence of SPARC, FB polygonal adipocytes assume a spherical morphology. Loss-of-function clonal analyses revealed a cell-autonomous accumulation of BL components around mutant cells that include collagen IV (Col lV), Laminin, and Perlecan. Ultrastructural analyses indicate SPARC-deficient adipocytes are surrounded by an aberrant accumulation of a fibrous extracellular matrix. CONCLUSIONS: Our data indicate a critical requirement for SPARC for the proper BL assembly in Drosophila FB. Since Col IV within the BL is a prime determinant of cell shape, the rounded appearance of SPARC-deficient adipocytes is due to aberrant assembly of Col IV.

Cell-cell and cell-matrix dynamics in intraperitoneal cancer metastasis.

The peritoneal metastatic route of cancer dissemination is shared by cancers of the ovary and gastrointestinal tract. Once initiated, peritoneal metastasis typically proceeds rapidly in a feed-forward manner. Several factors contribute to this efficient progression. In peritoneal metastasis, cancer cells exfoliate into the peritoneal fluid and spread locally, transported by peritoneal fluid. Inflammatory cytokines released by tumor and immune cells compromise the protective, anti-adhesive mesothelial cell layer that lines the peritoneal cavity, exposing the underlying extracellular matrix to which cancer cells readily attach. The peritoneum is further rendered receptive to metastatic implantation and growth by myofibroblastic cell behaviors also stimulated by inflammatory cytokines. Individual cancer cells suspended in peritoneal fluid can aggregate to form multicellular spheroids. This cellular arrangement imparts resistance to anoikis, apoptosis, and chemotherapeutics. Emerging evidence indicates that compact spheroid formation is preferentially accomplished by cancer cells with high invasive capacity and contractile behaviors. This review focuses on the pathological alterations to the peritoneum and the properties of cancer cells that in combination drive peritoneal metastasis.

The impact of the ovarian microenvironment on the anti-tumor effect of SPARC on ovarian cancer.

A lack of host-derived SPARC promotes disease progression in an intraperitoneal (IP) ID8 mouse model of epithelial ovarian cancer (EOC). Since orthotopic injection (OT) of ID8 cells better recapitulates high-grade serous cancer, we examined the impact of host-derived SPARC following OT injection. Sparc(-/-) and wild-type (WT) mice were injected with ID8 cells either OT or IP and tumors were analyzed at the moribund stage. Sparc(-/-) mice had reduced survival and fewer well-defined abdominal lesions compared with WT controls after IP injection, whereas no differences were observed in survival or abdominal lesions between Sparc(-/-) and WT mice after OT injection. No differences in mass or collagen content were observed in ovarian tumors between OT-injected Sparc(-/-) and WT mice. The abdominal wall of the IP-injected Sparc(-/-) mice exhibited immature and less abundant collagen fibrils compared with WT mice both in injected and non-injected controls. In contrast to human EOC, SPARC was expressed by the tumor cells but was absent in reactive stroma of WT mice. Exposure to the ovarian microenvironment through OT injections alters the metastatic behaviour of ID8 cells, which is not affected by the absence of host-derived SPARC.

Dynamic distribution of nuclear coactivator 4 during mitosis: association with mitotic apparatus and midbodies.

The cytoplasmic localization of Nuclear Receptor Coactivator 4 (NcoA4), also referred to as androgen receptor associated protein 70 (ARA70), indicates it may possess activities in addition to its role within the nucleus as a transcriptional enhancer. Towards identifying novel functions of NcoA4, we performed an in silico analysis of its amino acid sequence to identify potential functional domains and related proteins, and examined its subcellular distribution throughout the cell cycle. NcoA4 has no known or predicted functional or structural domains with the exception of an LxxLL and FxxLF nuclear receptor interaction motif and an N-terminal putative coiled-coil domain. Phylogenetic analysis indicated that NcoA4 has no paralogs and that a region referred to as ARA70-I family domain, located within the N-terminus and overlapping with the coiled-coil domain, is evolutionarily conserved in metazoans ranging from cnidarians to mammals. An adjacent conserved region, designated ARA70-II family domain, with no significant sequence similarity to the ARA70-I domain, is restricted to vertebrates. We demonstrate NcoA4 co-localizes with microtubules and microtubule organizing centers during prophase. Strong NcoA4 accumulation at the centrosomes was detected during interphase and telophase, with decreased levels at metaphase and anaphase. NcoA4 co-localized with tubulin and acetylated tubulin to the mitotic spindles during metaphase and anaphase, and to midbodies during telophase. Consistent with these observations, we demonstrated an interaction between NcoA4 and α-tubulin. Co-localization was not observed with microfilaments. These findings indicate a dynamic distribution of NcoA4 with components of the mitotic apparatus that is consistent with a potential non-transcriptional regulatory function(s) during cell division, which may be evolutionarily conserved.

Shared antigenicity between the polar filaments of myxosporeans and other Cnidaria.

Nematocysts containing coiled polar filaments are a distinguishing feature of members of the phylum Cnidaria. As a first step to characterizing the molecular structure of polar filaments, a polyclonal antiserum was raised in rabbits against a cyanogen bromide-resistant protein extract of mature cysts containing spores of Myxobolus pendula. The antiserum reacted only with proteins associated with extruded polar filaments. Western blot and whole-mount immunohistochemical analyses indicated a conservation of polar filament epitopes between M. pendula and 2 related cnidarians, i.e., the anthozoan, Nematostella vectensis, and the hydrozoan, Hydra vulgaris. This conservation of polar filament epitopes lends further support to a shared affinity between Myxozoa and cnidarians.

Compact spheroid formation by ovarian cancer cells is associated with contractile behavior and an invasive phenotype.

Ovarian cancer cells are present in malignant ascites both as individual cells and as multicellular spheroid aggregates. Although spheroid formation affords protection of cancer cells against some chemotherapeutic agents, it has not been established whether a relationship exists between invasive behavior and predisposition to spheroid formation. Aspects of spheroid formation, including cell-matrix adhesion, remodeling and contractility are characteristic myofibroblast-like behaviors associated with fibrosis that contribute to tumor growth and dissemination. We explored the possibility that cell behaviors that promote spheroid formation also facilitate invasion. Our analysis of 6 human ovarian cancer cell lines indicated that ovarian cancer cells possessing myofibroblast-like properties formed compact spheroids and invaded 3D matrices. These cells readily contracted collagen I gels, possessed a spindle-like morphology, and had elevated expression of genes associated with the TGFbeta-mediated fibrotic response and/or beta1 integrin function, including fibronectin (FN), connective tissue growth factor (CTGF/CCN2), lysyl oxidase (LOX1), tissue transglutaminase 2 (TGM2) and urinary plasminogen activator receptor (uPAR). Whereas cell aggregation was induced by TGFbeta, and by beta1-integrin overexpression and activation, these treatments did not stimulate the contractile activity required for spheroid compaction. The positive relationship found between compact spheroid formation and invasive behavior implies a preferential survival of an invasive subpopulation of ovarian cancer cells, as cells in spheroids are more resistant to several chemotherapeutics. Preventing the formation of ovarian cancer spheroids may represent a novel strategy to improve the efficacy of existing therapeutics.

Collagen I but not Matrigel matrices provide an MMP-dependent barrier to ovarian cancer cell penetration.

BACKGROUND: The invasive potential of cancer cells is usually assessed in vitro using Matrigel as a surrogate basement membrane. Yet cancer cell interaction with collagen I matrices is critical, particularly for the peritoneal metastatic route undertaken by several cancer types including ovarian. Matrix metalloprotease (MMP) activity is important to enable cells to overcome the barrier constraints imposed by basement membranes and stromal matrices in vivo. Our objective was to compare matrices reconstituted from collagen I and Matrigel as representative barriers for ovarian cancer cell invasion. METHODS: The requirement of MMP activity for ovarian cancer cell penetration of Matrigel and collagen matrices was assessed in 2D transwell and 3D spheroid culture systems. RESULTS: The broad range MMP inhibitor GM6001 completely prevented cell perforation of polymerised collagen I-coated transwell membranes. In contrast, GM6001 decreased ES-2 cell penetration of Matrigel by only approximately 30% and had no effect on HEY cell Matrigel penetration. In 3D culture, ovarian cancer cells grown as spheroids also migrated into surrounding Matrigel matrices despite MMP blockade. In contrast, MMP activity was required for invasion into 3D matrices of collagen I reconstituted from acid-soluble rat-tail collagen I, but not from pepsin-extracted collagen I (Vitrogen/Purecol), which lacks telopeptide regions. CONCLUSION: Matrigel does not form representative barriers to ovarian cancer cells in either 2D or 3D culture systems. Our findings support the use of collagen I rather than Matrigel as a matrix barrier for invasion studies to better approximate critical interactions and events associated with peritoneal metastasis.

Identification of pathways associated with invasive behavior by ovarian cancer cells using multidimensional protein identification technology (MudPIT).

Proteomic profiling has emerged as a useful tool for identifying tissue alterations in disease states including malignant transformation. The aim of this study was to reveal expression profiles associated with the highly motile/invasive ovarian cancer cell phenotype. Six ovarian cancer cell lines were subjected to proteomic characterization using multidimensional protein identification technology (MudPIT), and evaluated for their motile/invasive behavior, so that these parameters could be compared. Within whole cell extracts of the ovarian cancer cells, MudPIT identified proteins that mapped to 2245 unique genes. Western blot analysis for selected proteins confirmed the expression profiles revealed by MudPIT, demonstrating the fidelity of this high-throughput analysis. Unsupervised cluster analysis partitioned the cell lines in a manner that reflected their motile/invasive capacity. A comparison of protein expression profiles between cell lines of high (group 1) versus low (group 2) motile/invasive capacity revealed 300 proteins that were differentially expressed, of which 196 proteins were significantly upregulated in group 1. Protein network and KEGG pathway analysis indicated a functional interplay between proteins up-regulated in group 1 cells, with increased expression of several key members of the actin cytoskeleton, extracellular matrix (ECM) and focal adhesion pathways. These proteomic expression profiles can be utilized to distinguish highly motile, aggressive ovarian cancer cells from lesser invasive ones, and could prove to be essential in the development of more effective strategies that target pivotal cell signaling pathways used by cancer cells during local invasion and distant metastasis.

Changes in host and parasite-derived cellular and extracellular matrix components in developing cysts of Myxobolus pendula (Myxozoa).

Cysts of Myxobolus pendula from the gill arch of creek chub (Semotilus atromaculatus) were examined at various stages of development using light and electron microscopy. The subepithelial host connective tissue underwent dramatic changes, including degradation and remodelling of collagen and vascularisation, in response to the infection. Inflammatory cells lay in a fluid-filled space beneath the host's connective tissue and surrounded a distinctive parasite-derived matrix, composed of collagen fibril bundles embedded in cellular processes of the underlying secretory cells. This collagen matrix was resistant to degradation and invasion by leukocytes. Secretion of a matrix by M. pendula as a structural support, and a protective barrier against the host inflammatory cells is a novel observation for cyst-forming Myxosporea.