ABSTRACT Chibby (or PIGEA-14) is a novel antagonist of the Beta-catenin pathway in nucleus. However, the tumor-suppressing function of Chibby and the importance of nuclear targeting to the cellular functions of Chibby have not been validated. By fusion of Chibby cDNA with green fluorescent protein (GFP) or Flag-tag, it was found that exogenous Chibby expression was detected in the nucleus as well as cytoplasm of transfected HeLa cells, but with a preferential nuclear localization (more than 50% cells with nuclear Chibby expression). Chibby overexpression significantly abrogated the cellular Beta¡Vcatenin activities and induced apoptosis in HeLa cells. Moreover, Chibby gene delivery attenuated the proliferation, migration, and anchorage-independent growth of HeLa cells, supporting the tumor suppressor function of Chibby. Mutation or deletion of the predicted nuclear localization sequence (NLS), at residues 123-126, significantly promoted the cytoplasmic localization of Chibby, indicating residues 123-126 is the NLS domain of Chibby. Interestingly, ecotopic expression of Chibby NLS mutants remained capable of inducing apoptosis and inhibiting Beta¡Vcatenin activities in HeLa cells. Besides, overexpression Chibby NLS mutants effectively attenuated the viability, motility and colonies formation of HeLa cells. Expression analysis revealed that Chibby NLS mutants retained Beta-catenin in the cytoplasm and prevented its nuclear entry, thereby inhibiting the Beta-catenin transcriptional activities. In summary, Chibby shuttles between nucleus and cytoplasm, and possesses the functions of tumor suppressor and Beta-catenin antagonist.

The epidermal growth factor family of receptors is important in the development and progression of many types of cancers including, breast, lung, and glioblastoma. The family consists of 4 members (EGFR/erbB1, Her2/erbB2, erbB3, and erbB4). In all breast cancer cases, EGFR expression is deregulated 20 to 30% of the time; however in the most aggressive form of breast cancer (basal-like) EGFR expression is upregulated in 60% of cases. EGFR's expression and activity can be altered in transformed cells through a variety of mechanisms, such as novel protein-protein interactions, gene amplification, mutations, and loss of regulatory proteins. In this work we have examined the role of cancer specific protein interactions of EGFR with MUC1 and beta-catenin in the progression of breast cancer.Herein I report that the interaction of MUC1 and EGFR in breast cancer cells alters EGFR localization by promoting EGFR nuclear translocation. Importantly, I discovered that the presence of MUC1 mediates EGFR's interaction with chromatin. More specifically, I found that EGFR interacts with the cyclin D1 promoter region in a MUC1-dependent fashion which resulted in a significant increase in cyclin D1 protein expression. Nuclear EGFR localization has been shown to correlate with resistance to anti-EGFR therapies, which indicates that MUC1's interaction with EGFR could be a mechanism of resistance.MUC1's interaction with both EGFR and beta-catenin can promote transformation therefore a peptide therapy was developed, PMIP, which mimics the hypothesized interaction domains of MUC1's cytoplasmic tail. PMIP was designed to inhibit the interaction of MUC1/EGFR and MUC1/beta-catenin thereby regulating EGFR expression and promoting beta-catenin localization to adherens junctions. PMIP effectively enters the cytosol of cells and inhibits the target interactions. Importantly, PMIP inhibited invasion and proliferation of breast cancer cells and in mice significantly reduced the growth rate of breast cancer xenograft and genetically-driven tumors. This study demonstrated that the use of peptides to inhibit intracellular protein interactions is a viable option that would have limited toxic side-effects. Overall, this work reveals a new regulatory role of EGFR localization and activity by MUC1 and that this mechanism is viable therapeutic breast cancer target.Lastly, in a mouse model of breast cancer I examined the role of EGFR tyrosine kinase activity in beta-catenin dependent tumorigenesis. A transgenic mouse model of breast cancer, MMTV-Wnt-1, was bred onto an EGFR kinase deficient background. I discovered that the loss of EGFR kinase activity in this model resulted in a significant delay in tumor onset and inhibited tumor growth. These findings indicate a cooperation of EGFR and beta-catenin dependent signaling pathways, which promote transformation of glandular epithelial cells.

The USP4 is a deubiquitinating enzyme found elevated in certain human lung and adrenal tumours. USP4 has a very close relative, USP15, which has caused great difficulty in studying only one or the other. We have had generated two antibodies specific to USP4 and USP15, and have confirmed that the two do not cross react. Although there have been previous findings of interacting partners, possible substrates and pathways in which it is involved, the biological role of USP4 is mostly unknown. We have used these antibodies to determine that USP4 and USP15 expression differs across tissue and cell types, and that expression changes as the organism ages. We have shown that USP4 plays a role in canonical Wnt signaling, perhaps by stabilizing Beta-catenin, and identified GRK2 as a kinase, phosphorylating USP4. These data have provided enough information to form a hypothesis, implicating USP4 with the destruction complex in the Wnt signaling pathway.

The AC133 epitope of the pentaspan transmembrane glycoprotein CD133 has been used as a cell-surface marker for normal and cancer stem cells from a broad range of tissue types. Despite the utility of CD133 as a marker, little is known regarding its regulation and biological function. To study these poorly understood aspects of CD133, I took two main experimental approaches: RNA interference (RNAi) screening and affinity purification coupled with mass spectrometry (AP-MS) to identify CD133 regulatory genes and CD133 protein-protein interactions (PPIs), respectively. Both of these experimental approaches relied on a human embryonic kidney (HEK) 293 cell line that exogenously expresses affinity tagged CD133 (HEK293/AC133). This cell line allowed me to perform a large-scale RNAi screen to interrogate 11,248 genes for their involvement in cell-surface AC133 recognition. This resulted in the identification of the N-glycosylation pathway as a direct contributor to CD133 plasma membrane localization and cell-surface AC133 detection. I used the same RNAi screening approach on the colon adenocarcinoma cell line Caco-2, which express CD133 from its native promoter, to identify factors that regulate endogenous CD133 transcription. I was able to demonstrate that AF4 promotes CD133 transcription in a number of cancer cell lines. Furthermore, I showed that CD133 expression in an acute lymphoblastic leukemia (ALL) cell line SEM, which is dependent on the mixed-lineage leukemia (MLL)-AF4 gene fusion, is critical for the viability of these cells. To gain further insight into the function of CD133, I performed AP-MS using HEK293/AC133 cells to identify CD133 PPIs. I identified histone deacetylase 6 (HDAC6) as a CD133 protein interaction partner. I found that HDAC6 negatively regulates CD133 trafficking into the endosomal-lysosomal degradation pathway. CD133 binds HDAC6 to prevent inhibition of HDAC6 deacetylase activity by phosphorylation. Protection of HDAC6 from phosphorylation promotes HDAC6 deacetylation of β-catenin, which results in β-catenin dependent signalling and the suppression of cancer cell differentiation. My thesis provide functional roles for CD133 as a pro-proliferative protein and as a key signalling protein in certain cancer cell lines.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 133-173).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 44-52).

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2006. / Vita. Includes bibliographical references.

PART1, TITLE: A p53-inducible long non-coding RNA PICART1 mediating cancer cell proliferation and migration. Long non-coding RNAs (lncRNAs) function in the development and progression of cancer, but only a small portion of lncRNAs are characterized thus far. A novel lncRNA transcript with 2.53 kb in length was identified by a transcriptome sequencing analysis, named p53-inducible cancer-associated RNA transcript 1 (PICART1). This PICART1 is upregulated by p53 through a p53-binding site at -1808 to -1783bp. In breast and colorectal cancer cells and tissues, PICART1 expression was decreased. Ectopic expression of the PICART1 suppressed growth, proliferation, migration, and invasion of MCF7, MDA-MB-231 and HCT116 cells whereas silencing of PICART1 stimulated the cell growth and migration. In these cells, the expression of PICART1 lowered down the levels of p-AKT (Thr308 & Ser473) and p-GSK3β (Ser9), and accordingly, β-catenin, cyclin D1 and c-Myc expression were decreased, but p21cip1/Waf1 expression was increased. Together these data suggest that PICART1 is a novel p53-inducible tumor suppressor lncRNA, functioning through the AKT/GSK3β/β-catenin signaling cascade. PART2, TITLE: The novel long non-coding RNA PANCR is a tumor suppressor gene in breast cancer. Long non-coding RNAs (lncRNAs) function as oncogenes or tumor suppressors in development and progression of cancer. Chromosome 16q22.1 region is frequently deleted in breast cancer, which may contribute to breast carcinogenesis by inactivation of tumor suppressor genes. This study characterized a new lncRNA tumor suppressor, named p53 activating non-coding RNA (PANCR), located in this Chromosome 16q22.1 region. This PANCR lncRNA consists of 1.5kb in length. Our data showed that PANCR was downregulated in breast cancer tissues and cell lines. In the breast cancer cell lines, PANCR expression appeared reversely correlated with cell malignancy, and in breast cancer tissues, PANCR was downregulated over 2 times in 31 (62.0%) of 50 cases when compared to adjacent normal breast tissues. In breast cancer cells MCF7 cells, ectopic expression of PANCR suppressed cell proliferation in culture, but in contrast, shRNA–mediated silencing of PANCR promoted cell growth and proliferation.

Die Regulation des Wnt/β-catenin Signalwegs ist nicht nur entscheidend für alle Stadien der kardialen Entwicklung, sondern auch für die Homöostase im adulten Herzen. Tatsächlich ist die Aktivierung des Wnt/β-catenin Signalwegs mit dem pathologischen Herz-Remodeling assoziiert. Ein besseres Verständnis der Regulation des Wnt/β-catenin Signalwegs bei Herzinsuffizienz könnte die Identifikation potentieller Faktoren zum Blockieren des pathologischen Herz-Remodelings und/oder das Aktivieren der endogenen Regeneration ermöglichen. Diese Arbeit konzentriert sich auf die Identifikation von gewebespezifischen Regulatoren des Wnt/β-catenin Signalwegs im Herzen. Frühere Arbeiten unserer Gruppe identifizierten basic leucine zipper and W2 domains containing protein (BZW) 2 als einen kardialen Interaktionspartner von β-catenin und KLF15. Die Rolle von BZW2 im Wnt/β-catenin Signalweg bei der Kardiogenese und der Homöostase des adulten Herzens war das Thema dieser Studie. Eine Analyse des BZW2-Proteins zeigte, dass die mutmaßliche ZIP und bZIP umfassende Domäne wichtig für die nukleare Lokalisation ist. Die Expression von BZW2 hat sich als bedeutsam im adulten Herzen, aber auch während der embryonalen Kardiogenese erwiesen. Eine niedrige BZW2-Expression ist für die effektive Bildung des kardialen Mesoderms notwendig, denn es kam unter BZW2-Überexpression zu einem Abbruch der Kardiomyozytenbildung in einem Modell der in vitro Kardiogenese. Dennoch war die BZW2-Expression nicht entscheidend für die Embryogenese, was auf eine kompensatorische Funktion verwandter Proteine hindeuten könnte. Interessanterweise war BZW2 für den Erhalt der normalen Herzfunktion und während der Reaktion auf Stress notwendig. Obwohl BZW2 die Wnt-Transkriptionsaktivität in vitro nicht signifikant inhibiert hat, resultierte das Fehlen von BZW2 in de novo Synthese von β-catenin spezifisch im adulten Herzgewebe in vivo. Außerdem wurde BZW2 selbst durch den Wnt/β-catenin Signalweg reguliert, was auf seine Rolle als regulatorischer Rückkopplungsfaktor in vivo hindeutet. Zusammenfassend identifizierte diese Arbeit einen neuen herzgewebespezifischen Faktor des Wnt/β-catenin Signalwegs auf einer neuen Regulationsebene und demonstrierte seine Relevanz für die normale Herzhomöostase. Angesichts der ubiquitären Expression und der vielfältigen Funktionen von β-catenin könnte die gewebespezifische Modulation neue Therapieoptionen darstellen.

Note: Portions of this abstract have been previously published in the journal Blood, Basiorka et al. Blood. 2016 Oct 13, and has been reproduced in this manuscript with permission from the publisher. Myelodysplastic syndromes (MDS) are genetically diverse hematopoietic stem cell malignancies that share a common phenotype of cytological dysplasia, ineffective hematopoiesis and aberrant myeloid lineage maturation. Apoptotic cell death potentiated by inflammatory cytokines has been considered a fundamental feature of MDS for over two decades. However, this non-inflammatory form of cell death cannot account for the inflammatory nature of these disorders. We report that a hallmark of lower-risk (LR) MDS is activation of the NLRP3 inflammasome, which drives clonal expansion and pyroptosis, a caspase-1-dependent programmed cell death induced by danger-associated molecular pattern (DAMP) signals. Independent of genotype, MDS hematopoietic stem and progenitor cells (HSPC) overexpress pyroptosis-related transcripts, inflammasome proteins and manifest activated NLRP3 inflammasome complexes that direct caspase-1 activation, IL-1β and IL-18 maturation and pyroptotic cell death. Using the S100A9 transgenic (S100A9Tg) mouse model that phenocopies human MDS, we demonstrated that forced expression of S100A9 was sufficient to drive pyroptosis in vivo, implicating pyroptosis as the principal mechanism of HSPC cell death in S100A9Tg mice. The lytic cell death releases intraceullar contents that include alarmins and catalytically active ASC specks, which can propagate bystander inflammation. Notably, MDS mesenchymal stromal cells (MSC) and stromal-derived linages were found to predominantly undergo pyroptosis, with marked activation of caspase-1 and NLRP3 inflammasome complexes. These findings may account for the clusters of both HSPC and stromal cell death previously described in the bone marrows of patients with MDS. Mechanistically, pyroptosis is triggered by the alarmin S100A9 that is found in excess in MDS HSPC and bone marrow (BM) plasma. Further, both somatic gene mutations and S100A9-induced signaling activate NADPH oxidase (NOX), generating reactive oxygen species (ROS) that initiate cation influx, cell swelling and β-catenin activation. Accordingly, ROS and active β-catenin were significantly increased in MDS BM mononuclear cells (BM-MNC) and S100A9Tg mice compared to normal controls, as well as in human cell lines harboring gene mutations and in murine models of gene mutation knock-in or gene loss. ROS and β-catenin nuclear translocation were significantly reduced by NLRP3 or NOX inhibition, indicating that S100A9 and somatic gene mutations prime cells to undergo NOX1/4-dependent NLRP3 inflammasome assembly, pyroptosis and β-catenin activation. Together, these data explain the concurrent proliferation and inflammatory cell death characteristic of LR-MDS. Given that loss of a gene-rich area in del(5q) disease results in derepression of innate immune signaling, we hypothesized that this genetic deficit would trigger assembly of the NLRP3 inflammasome complex, akin to the pathobiological mechanism characteristic of non-del(5q) MDS. To this end, we utilized two distinct murine models of del(5q) disease, namely in the context of Rps14 haploinsufficiency and concurrent loss of mDia1 and microRNA (miR)-146a. In both models, pyroptosis was not evident in the HSPC compartment; however, early erythroid progenitors displayed high fractions of pyroptotic cells. This was associated with significant increases in caspase-1 and NLRP3 inflammasome activation, ROS and nuclear localization of β-catenin, which was extinguished by inflammasome or NOX complex inhibition. These data suggest that early activation of the inflammasome drives cell death and prevents terminal maturation of erythroid precursors, accounting for the progressive anemia characteristic of del(5q) disease, whereby hematopoietic defects are primarily restricted to the erythroid compartment. Importantly, these data implicate a similar pathobiological mechanism in del(5q) MDS as is observed in non-del(5q) patients. The identification of the NLRP3 inflammasome as a pathobiological driver of the LR non-del(5q) and del(5q) MDS phenotype allows for novel therapeutic agent development. Notably, knockdown of NLRP3 or caspase-1, neutralization of S100A9, and pharmacologic inhibition of NLRP3 or NOX suppresses pyroptosis, ROS generation and nuclear β-catenin in MDS, and are sufficient to restore effective hematopoiesis. In del(5q) murine models, inhibition of the NLRP3 inflammasome significantly improved erythroid colony forming capacity by a mechanism distinct from that of lenalidomide, highlighting the translational potential for targeting this innate immune complex in this subset of MDS. Thus, alarmins and founder gene mutations in MDS license a common redox-sensitive inflammasome circuit, which suggests new avenues for therapeutic intervention. Furthermore, aggregated clusters of the NLRP3 adaptor protein ASC [apoptosis-associated speck-like protein containing a caspase activation and recruitment domain (CARD)] are referred to as ASC specks. During pyroptosis, ASC specks are released from dying cells and function as DAMP signals that propagate inflammation. In this way, specks are a surrogate marker for NLRP3 inflammasome activation and pyroptotic cell death. Given that pyroptosis is the predominant mechanism of cell death in MDS and ASC specks are readily quantified by flow cytometry, we hypothesized that BM or peripheral blood (PB) plasma-derived ASC specks may be a biologically rational biomarker for the diagnosis of MDS. The percentage of ASC specks were significantly increased in MDS BM plasma compared to normal, healthy donors, which was validated by confocal microscopy. PB plasma-derived ASC specks were significantly greater in LR- versus HR-MDS, consistent with the greater extent of cell death and myeloid-derived suppressor cell (MDSC) expansion in LR disease. As hyperglycemia induces NLRP3 inflammasome activation, plasma glucose levels were measured to adjust for this confounding variable. Subsequently, the percentage of glucose-adjusted, PB plasma-derived ASC specks was measured in a panel of specimens of varied hematologic malignancies. The corrected percentage of ASC specks was significantly increased in MDS compared to normal donors and to each other malignancy investigated, including other myeloid and lymphoid leukemias, myeloproliferative neoplasms and overlap syndromes, like chronic myelomonocytic leukemia (CMML). These data indicate that the glucose-adjusted ASC speck percentage is MDS-specific and may be a valuable diagnostic biomarker. At a cutoff of 0.039, the biomarker minimizes misclassification error and achieves 95% sensitivity and 82% specificity in classifying MDS from normal donors, other hematologic malignancies and T2D. Lastly, the biomarker declined with treatment response to lenalidomide in LR-MDS patients, but not to erythropoietin stimulating agent (ESA) or hypomethylating agent (HMA) therapy. As such, the percentage of ASC specks represents the first biologically rational, diagnostic biomarker for MDS that can be implemented with current diagnostic practices to reduce diagnostic error.