Wnt is necessary for mesenchymal to epithelial transition in colorectal cancer cells.

BACKGROUND: Metastasis underlies most colorectal cancer mortality. Cancer cells spread through the body as single cells or small clusters of cells that have an invasive, mesenchymal, nonproliferative phenotype. At the secondary site, they revert to a proliferative "tumor constructing" epithelial phenotype to rebuild a tumor. We previously developed a unique in vitro three-dimensional model, called LIM1863-Mph, which faithfully recapitulates these reversible transitions that underpin colorectal cancer metastasis. Wnt signaling plays a key role in these transitions and is initiated by the coupling of extracellular Wnt to Frizzled (FZD). Using the LIM1863-Mph model system we demonstrated that the Wnt receptor FZD7 is necessary for mesenchymal to epithelial transition (MET). Here we investigate the role of Wnt in MET. RESULTS: Wnt secretion is dependent on palmitoylation by Porcupine (PORC). A PORC inhibitor (IWP2) that prevents Wnt secretion, blocked the epithelial transition of mesenchymal LIM1863-Mph cells. Wnt gene array analysis identified several Wnts that are upregulated in epithelial compared with mesenchymal LIM1863-Mph cells, suggesting these ligands in MET. Wnt2B was the most abundant differentially expressed Wnt gene. Indeed, recombinant Wnt2B could overcome the IWP2-mediated block in epithelial transition of mesenchymal LIM1863-Mph cells. CONCLUSIONS: Wnt2B co-operates with Frizzled7 to mediate MET in colorectal cancer. Developmental Dynamics 247:521-530, 2018. © 2017 Wiley Periodicals, Inc.

The Impact of BRCA1 Expression on Survival Status in Ovarian Serous Carcinoma of Egyptian Patients.

OBJECTIVES: The present study aimed to investigate the impact of BRCA1 protein expression on the patients' outcome of ovarian serous carcinoma, and its correlation with different clinicopathologic features. METHODS: Immunohistochemistry with BRCA1 was done for 80 cases of ovarian serous carcinoma that had a positive family history. Correlation with clinico-pathologic variables and patients' outcomes was investigated. RESULTS: BRCA1 expression was detected in 61.2% of the studied cases. A significant relation with patients' age, tumor grade and tumor stage was found (P<0.05). Also, there was a significant decrease in disease free survival (DFS) & overall survival (OS) in the positive BRCA1 group. Metastasis, recurrence, residual disease, and mortality rate showed significantly higher figures in patient with BRCA1 expression (P<0.05). CONCLUSION: Positive BRCA1 expression had proven to be associated with advanced stage & grade of tumors, as well as worsened prognostic survival parameters (metastasis, recurrence, residual disease, and mortality) in patients with ovarian serous carcinoma.

LKB1 regulates polarity remodeling and adherens junction formation in the Drosophila eye.

The serine-threonine kinase LKB1 regulates cell polarity from Caenorhabditis elegans to man. Loss of lkb1 leads to a cancer predisposition, known as Peutz-Jeghers Syndrome. Biochemical analysis indicates that LKB1 can phosphorylate and activate a family of AMPK- like kinases, however, the precise contribution of these kinases to the establishment and maintenance of cell polarity is still unclear. Recent studies propose that LKB1 acts primarily through the AMP kinase to establish and/or maintain cell polarity. To determine whether this simple model of how LKB1 regulates cell polarity has relevance to complex tissues, we examined lkb1 mutants in the Drosophila eye. We show that adherens junctions expand and apical, junctional, and basolateral domains mix in lkb1 mutants. Surprisingly, we find LKB1 does not act primarily through AMPK to regulate cell polarity in the retina. Unlike lkb1 mutants, ampk retinas do not show elongated rhabdomeres or expansion of apical and junctional markers into the basolateral domain. In addition, nutrient deprivation does not reveal a more dramatic polarity phenotype in lkb1 photoreceptors. These data suggest that AMPK is not the primary target of LKB1 during eye development. Instead, we find that a number of other AMPK-like kinase, such as SIK, NUAK, Par-1, KP78a, and KP78b show phenotypes similar to weak lkb1 loss of function in the eye. These data suggest that in complex tissues, LKB1 acts on an array of targets to regulate cell polarity.

Expression of PD-L1 in Early-Stage Invasive Breast Carcinoma and Its Relation to Tumor-Infiltrating Lymphocytes.

OBJECTIVES: Immunotherapeutic targets became one of the promising approaches in breast cancer (BC), especially in advanced stage triple-negative subtype (TNBC). However, the role of programmed cell death ligand 1 (PD-L1) targeting in other BC subtypes, especially in early-stage carcinoma is less explored. We aimed in this study to investigate the prevalence of PD-L1 in early-stage invasive BC of different molecular subtypes and to elucidate its relation to tumor-infiltrating lymphocytes (TILS) density (cytotoxic and regulatory T-cells), established clinicopathological factors and patients' outcome. MATERIAL AND METHODS: One hundred and nine cases of early-stage BC were enrolled in our study. Cases were classified into five molecular subtypes according to the Immunohistochemical data. PD-L1, FOXP3 and CD8 immunostaining were analyzed for all studied cases. PD-L1 expression was correlated with CD8+ cytotoxic T-cells, FOXP3+ regulatory T-cells, histopathologic parameters, BC molecular subtypes, 7-years disease-free survival (DFS) and overall survival (OS). RESULTS: PD-L1 was expressed in 11% of the studied early-stage BC cases. It showed a significant correlation with high tumor grade (p= <0.001), development of metastasis (p=0.037), high FOXP3+ T-cell density (p= <0.001) and low CD8+ T-cells density (p= <0.001). PD-L1 expression was higher in TNBC (16.1%), followed by HER2/neu-enriched group (14.3%). All luminal A cases showed negative PD-L1 expression. PD-L1 was found to be an independent prognostic factor for patients' survival (DFS; p=0.031 and OS: p=0.04). CONCLUSION: Although the impact of PD-L1 on early-stage BC outcomes had not been clearly established, our results indicated that PD-L1 is a negative prognostic marker in early settings. PD-L1 can serve as a new therapeutic target for patients with high-grade early-stage breast carcinoma.

Scribble mutants promote aPKC and JNK-dependent epithelial neoplasia independently of Crumbs.

BACKGROUND: Metastatic neoplasias are characterized by excessive cell proliferation and disruptions to apico-basal cell polarity and tissue architecture. Understanding how alterations in cell polarity can impact upon tumour development is, therefore, a central issue in cancer biology. The Drosophila gene scribble (scrib) encodes a PDZ-domain scaffolding protein that regulates cell polarity and acts as a tumour suppressor in flies. Increasing evidence also implicates the loss of human Scrib in cancer. In this report, we investigate how loss of Scrib promotes epithelial tumourigenesis in Drosophila, both alone and in cooperation with oncogenic mutations. RESULTS: We find that genetically distinct atypical protein kinase C (aPKC)-dependent and Jun N-terminal kinase (JNK)-dependent alterations in scrib mutants drive epithelial tumourigenesis. First, we show that over-expression of the apical cell polarity determinants Crumbs (Crb) or aPKC induces similar cell morphology defects and over-proliferation phenotypes as scrib loss-of-function. However, the morphological and proliferative defects in scrib mutants are independent of Crb function, and instead can be rescued by a dominant negative (kinase dead) aPKC transgene. Secondly, we demonstrate that loss of Scrib promotes oncogene-mediated transformation through both aPKC and JNK-dependent pathways. JNK normally promotes apoptosis of scrib mutant cells. However, in cooperation with oncogenic activated Ras or Notch signalling, JNK becomes an essential driver of tumour overgrowth and invasion. aPKC-dependent signalling in scrib mutants cooperates with JNK to significantly enhance oncogene-mediated tumour overgrowth. CONCLUSION: These results demonstrate distinct aPKC and JNK-dependent pathways through which loss of Scrib promotes tumourigenesis in Drosophila. This is likely to have a direct relevance to the way in which human Scrib can similarly restrain an oncogene-mediated transformation and, more generally, on how the outcome of oncogenic signalling can be profoundly perturbed by defects in apico-basal epithelial cell polarity.

Abnormalities in cell proliferation and apico-basal cell polarity are separable in Drosophila lgl mutant clones in the developing eye.

In homozygous mutants of Drosophila lethal-2-giant larvae (lgl), tissues lose apico-basal cell polarity and exhibit ectopic proliferation. Here, we use clonal analysis in the developing eye to investigate the effect of lgl null mutations in the context of surrounding wild-type tissue. lgl- clones in the larval eye disc exhibit ectopic expression of the G1-S regulator, Cyclin E, and ectopic proliferation, but do not lose apico-basal cell polarity. Decreasing the perdurance of Lgl protein in larval eye disc clones, by forcing extra proliferation of lgl- tissue (using a Minute background), leads to a loss in cell polarity and to more extreme ectopic cell proliferation. Later in development at the pupal stage, lgl mutant photoreceptor cells show aberrant apico-basal cell polarity, but this is not associated with ectopic proliferation, presumably because cells are differentiated. Thus in a clonal context, the ectopic proliferation and cell polarity defects of lgl- mutants are separable. Furthermore, lgl- mosaic eye discs have alterations in the normal patterns of apoptosis: in larval discs some lgl- and wild-type cells at the clonal boundary undergo apoptosis and are excluded from the epithelia, but apoptosis is decreased elsewhere in the disc, and in pupal retinas lgl- tissue shows less apoptosis.

A genetic screen for dominant modifiers of a cyclin E hypomorphic mutation identifies novel regulators of S-phase entry in Drosophila.

Cyclin E together with its kinase partner Cdk2 is a critical regulator of entry into S phase. To identify novel genes that regulate the G1- to S-phase transition within a whole animal we made use of a hypomorphic cyclin E mutation, DmcycEJP, which results in a rough eye phenotype. We screened the X and third chromosome deficiencies, tested candidate genes, and carried out a genetic screen of 55,000 EMS or X-ray-mutagenized flies for second or third chromosome mutations that dominantly modified the DmcycEJP rough eye phenotype. We have focused on the DmcycEJP suppressors, S(DmcycEJP), to identify novel negative regulators of S-phase entry. There are 18 suppressor gene groups with more than one allele and several genes that are represented by only a single allele. All S(DmcycEJP) tested suppress the DmcycEJP rough eye phenotype by increasing the number of S phases in the postmorphogenetic furrow S-phase band. By testing candidates we have identified several modifier genes from the mutagenic screen as well as from the deficiency screen. DmcycEJP suppressor genes fall into the classes of: (1) chromatin remodeling or transcription factors; (2) signaling pathways; and (3) cytoskeletal, (4) cell adhesion, and (5) cytoarchitectural tumor suppressors. The cytoarchitectural tumor suppressors include scribble, lethal-2-giant-larvae (lgl), and discs-large (dlg), loss of function of which leads to neoplastic tumors and disruption of apical-basal cell polarity. We further explored the genetic interactions of scribble with S(DmcycEJP) genes and show that hypomorphic scribble mutants exhibit genetic interactions with lgl, scab (alphaPS3-integrin--cell adhesion), phyllopod (signaling), dEB1 (microtubule-binding protein--cytoskeletal), and moira (chromatin remodeling). These interactions of the cytoarchitectural suppressor gene, scribble, with cell adhesion, signaling, cytoskeletal, and chromatin remodeling genes, suggest that these genes may act in a common pathway to negatively regulate cyclin E or S-phase entry.

Frizzled7 functions as a Wnt receptor in intestinal epithelial Lgr5(+) stem cells.

The mammalian adult small intestinal epithelium is a rapidly self-renewing tissue that is maintained by a pool of cycling stem cells intermingled with Paneth cells at the base of crypts. These crypt base stem cells exclusively express Lgr5 and require Wnt3 or, in its absence, Wnt2b. However, the Frizzled (Fzd) receptor that transmits these Wnt signals is unknown. We determined the expression profile of Fzd receptors in Lgr5(+) stem cells, their immediate daughter cells, and Paneth cells. Here we show Fzd7 is enriched in Lgr5(+) stem cells and binds Wnt3 and Wnt2b. Conditional deletion of the Fzd7 gene in adult intestinal epithelium leads to stem cell loss in vivo and organoid death in vitro. Crypts of conventional Fzd7 knockout mice show decreased basal Wnt signaling and impaired capacity to regenerate the epithelium following deleterious insult. These observations indicate that Fzd7 is required for robust Wnt-dependent processes in Lgr5(+) intestinal stem cells.

The Wnt signaling pathways and cell adhesion.

In multicellular organisms, the processes of tissue and organ formation are governed by morphogenetic signaling pathways. The Wnt pathways regulate morphogenesis by controlling cell adhesion and migration; processes that when corrupted, lead to tumorgenesis. It is well known that the Wnt signaling pathways affect adhesion and migration via downstream effectors. Canonical Wnt signaling regulates cell adhesion by regulating the stability of beta-Catenin, a component of the adherens junction. Whereas, non-canonical signaling modulates cytoskeletal dynamics by regulating the activity of downstream effectors that function to organize the cytoskeleton. Recent studies have uncovered a multitude of points of crosstalk between the Wnt pathways and the mechanisms that control cellular architecture, from the level of receptors to the level of transcription. At the same time, cellular mechanisms that are responsible for the regulation of adhesion and migration also function to modulate the activity of several Wnt pathway components. Uncovering these points of crosstalk may lead to better understanding and treatment of the processes that can lead to tumorgenesis.

The FERM-domain protein Expanded regulates Hippo pathway activity via direct interactions with the transcriptional activator Yorkie.

The Hippo kinase pathway plays a central role in growth regulation and tumor suppression from flies to man. The Hippo/Mst kinase phosphorylates and activates the NDR family kinase Warts/Lats, which phosphorylates and inhibits the transcriptional activator Yorkie/YAP. Current models place the FERM-domain protein Expanded upstream of Hippo kinase in growth control. To understand how Expanded regulates Hippo pathway activity, we used affinity chromatography and mass spectrometry to identify Expanded-binding proteins. Surprisingly we find that Yorkie is the major Expanded-binding protein in Drosophila S2 cells. Expanded binds Yorkie at endogenous levels via WW-domain-PPxY interactions, independently of Yorkie phosphorylation at S168, which is critical for 14-3-3 binding. Expanded relocalizes Yorkie from the nucleus, abrogating its nuclear activity, and it can regulate growth downstream of warts in vivo. These data lead to a new model whereby Expanded functions downstream of Warts, in concert with 14-3-3 proteins to sequester Yorkie in the cytoplasm, inhibiting growth activity of the Hippo pathway.