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- All Subjects: Cellular Biology
- Creators: Wang, Xiao
- Creators: Jacobs, Bertram
Description
Cancer is one of the most serious global diseases. We have focused on cancer immunoprevention. My thesis projects include developing a prophylactic primary and metastatic cancer vaccines, early cancer detection and investigation of genes involved in tumor development. These studies were focused on frame-shift (FS) antigens. The FS antigens are generated by genomic mutations or abnormal RNA processing, which cause a portion of a normal protein to be translated out of frame. The concept of the prophylactic cancer vaccine is to develop a general cancer vaccine that could prevent healthy people from developing different types of cancer. We have discovered a set of cancer specific FS antigens. One of the FS candidates, structural maintenance of chromosomes protein 1A (SMC1A) FS, could start to accumulate at early stages of tumor and be specifically exposed to the immune system by tumor cells. Prophylactic immunization with SMC1A-FS could significantly inhibit primary tumor development in different murine tumor models and also has the potential to inhibit tumor metastasis. The SMC1A-FS transcript was detected in the plasma of the 4T1/BALB/c mouse tumor model. The tumor size was correlated with the transcript ratio of the SMC1A-FS verses the WT in plasma, which could be measured by regular RT-PCR. This unique cancer biomarker has a practical potential for a large population cancer screen, as well as clinical tumor monitoring. With a set of mimotope peptides, antibodies against SMC1A-FS peptide were detected in different cancer patients, including breast cancer, pancreas cancer and lung cancer with a 53.8%, 56.5% and 12.5% positive rate respectively. This suggested that the FS antibody could be a biomarker for early cancer detection. The characterization of SMC1A suggested that: First, the deficiency of the SMC1A is common in different tumors and able to promote tumor initiation and development; second, the FS truncated protein may have nucleolus function in normal cells. Mis-control of this protein may promote tumor development. In summary, we developed a systematic general cancer prevention strategy through the variety immunological and molecular methods. The results gathered suggest the SMC1A-FS may be useful for the detection and prevention of cancer.
ContributorsShen, Luhui (Author) / Johnston, Stephen Albert (Thesis advisor) / Chang, Yung (Committee member) / Miller, Laurence (Committee member) / Sykes, Kathryn (Committee member) / Jacobs, Bertram (Committee member) / Arizona State University (Publisher)
Created2012
Description
Currently in synthetic biology only the Las, Lux, and Rhl quorum sensing pathways have been adapted for broad engineering use. Quorum sensing allows a means of cell to cell communication in which a designated sender cell produces quorum sensing molecules that modify gene expression of a designated receiver cell. While useful, these three quorum sensing pathways exhibit a nontrivial level of crosstalk, hindering robust engineering and leading to unexpected effects in a given design. To address the lack of orthogonality among these three quorum sensing pathways, previous scientists have attempted to perform directed evolution on components of the quorum sensing pathway. While a powerful tool, directed evolution is limited by the subspace that is defined by the protein. For this reason, we take an evolutionary biology approach to identify new orthogonal quorum sensing networks and test these networks for cross-talk with currently-used networks. By charting characteristics of acyl homoserine lactone (AHL) molecules used across quorum sensing pathways in nature, we have identified favorable candidate pathways likely to display orthogonality. These include Aub, Bja, Bra, Cer, Esa, Las, Lux, Rhl, Rpa, and Sin, which we have begun constructing and testing. Our synthetic circuits express GFP in response to a quorum sensing molecule, allowing quantitative measurement of orthogonality between pairs. By determining orthogonal quorum sensing pairs, we hope to identify and adapt novel quorum sensing pathways for robust use in higher-order genetic circuits.
ContributorsMuller, Ryan (Author) / Haynes, Karmella (Thesis director) / Wang, Xiao (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Department of Chemistry and Biochemistry (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
Extrachromosomal circular DNA (eccDNA) has become an increasingly popular subject of study in eukaryotic cell biology due to its prevalence in human cancer. Though the literature reports a consensus regarding DNA break repair as a driver of eccDNA formation, there remains a lack of knowledge surrounding the exact mechanisms for eccDNA formation and the selective dynamics that promote their retainment in a cell or population. A central issue to studying eccDNA is the inability to distinguish between linear and circular DNA of homologous sequence. The work presented here describes an adapted eccDNA enrichment and detection assay, specifically for investigating the effects of manipulating a known eccDNA-forming locus in the budding yeast Saccharomyces cerevisiae. First, a galactose inducible GFP reporter was integrated within the copper inducible CUP1 tandem repeat locus of yeast cells. The eccDNA enrichment and detection assay was first applied to wildtype yeast to demonstrate the presence of CUP1 eccDNA in copper induced cells by qPCR. Although subsequent sequencing analysis failed to validate this result, it indicated the presence of various other known and previously un-reported eccDNA species. Finally, application of the enrichment protocol and qPCR detection assay to CUP1-GFP reporter cells yielded inconclusive results, suggesting the assay requires further optimization to sensitively detect eccDNA from this altered locus. While more work is necessary to draw conclusions regarding the limits of eccDNA production at a manipulated eccDNA-forming locus, this knowledge will lend to the potential for therapeutically targeting eccDNA at the point of de novo formation.
ContributorsKeal, Tula (Author) / Wang, Xiao (Thesis advisor) / Tian, Xiaojun (Committee member) / Plaisier, Christopher (Committee member) / Arizona State University (Publisher)
Created2022
Description
The portability of genetic tools from one organism to another is a cornerstone of synthetic biology. The shared biological language of DNA-to-RNA-to-protein allows for expression of polypeptide chains in phylogenetically distant organisms with little modification. The tools and contexts are diverse, ranging from catalytic RNAs in cell-free systems to bacterial proteins expressed in human cell lines, yet they exhibit an organizing principle: that genes and proteins may be treated as modular units that can be moved from their native organism to a novel one. However, protein behavior is always unpredictable; drop-in functionality is not guaranteed.
My work characterizes how two different classes of tools behave in new contexts and explores methods to improve their functionality: 1. CRISPR/Cas9 in human cells and 2. quorum sensing networks in Escherichia coli.
1. The genome-editing tool CRISPR/Cas9 has facilitated easily targeted, effective, high throughput genome editing. However, Cas9 is a bacterially derived protein and its behavior in the complex microenvironment of the eukaryotic nucleus is not well understood. Using transgenic human cell lines, I found that gene-silencing heterochromatin impacts Cas9’s ability to bind and cut DNA in a site-specific manner and I investigated ways to improve CRISPR/Cas9 function in heterochromatin.
2. Bacteria use quorum sensing to monitor population density and regulate group behaviors such as virulence, motility, and biofilm formation. Homoserine lactone (HSL) quorum sensing networks are of particular interest to synthetic biologists because they can function as “wires” to connect multiple genetic circuits. However, only four of these networks have been widely implemented in engineered systems. I selected ten quorum sensing networks based on their HSL production profiles and confirmed their functionality in E. coli, significantly expanding the quorum sensing toolset available to synthetic biologists.
My work characterizes how two different classes of tools behave in new contexts and explores methods to improve their functionality: 1. CRISPR/Cas9 in human cells and 2. quorum sensing networks in Escherichia coli.
1. The genome-editing tool CRISPR/Cas9 has facilitated easily targeted, effective, high throughput genome editing. However, Cas9 is a bacterially derived protein and its behavior in the complex microenvironment of the eukaryotic nucleus is not well understood. Using transgenic human cell lines, I found that gene-silencing heterochromatin impacts Cas9’s ability to bind and cut DNA in a site-specific manner and I investigated ways to improve CRISPR/Cas9 function in heterochromatin.
2. Bacteria use quorum sensing to monitor population density and regulate group behaviors such as virulence, motility, and biofilm formation. Homoserine lactone (HSL) quorum sensing networks are of particular interest to synthetic biologists because they can function as “wires” to connect multiple genetic circuits. However, only four of these networks have been widely implemented in engineered systems. I selected ten quorum sensing networks based on their HSL production profiles and confirmed their functionality in E. coli, significantly expanding the quorum sensing toolset available to synthetic biologists.
ContributorsDaer, René (Author) / Haynes, Karmella (Thesis advisor) / Brafman, David (Committee member) / Nielsen, David (Committee member) / Kiani, Samira (Committee member) / Arizona State University (Publisher)
Created2017
Description
Alzheimer’s disease (AD), despite over a century of research, does not have a clearly defined pathogenesis for the sporadic form that makes up the majority of disease incidence. A variety of correlative risk factors have been identified, including the three isoforms of apolipoprotein E (ApoE), a cholesterol transport protein in the central nervous system. ApoE ε3 is the wild-type variant with no effect on risk. ApoE ε2, the protective and most rare variant, reduces risk of developing AD by 40%. ApoE ε4, the risk variant, increases risk by 3.2-fold and 14.9-fold for heterozygous and homozygous representation respectively. Study of these isoforms has been historically complex, but the advent of human induced pluripotent stem cells (hiPSC) provides the means for highly controlled, longitudinal in vitro study. The effect of ApoE variants can be further elucidated using this platform by generating isogenic hiPSC lines through precise genetic modification, the objective of this research. As the difference between alleles is determined by two cytosine-thymine polymorphisms, a specialized CRISPR/Cas9 system for direct base conversion was able to be successfully employed. The base conversion method for transitioning from the ε3 to ε2 allele was first verified using the HEK293 cell line as a model with delivery via electroporation. Following this verification, the transfection method was optimized using two hiPSC lines derived from ε4/ε4 patients, with a lipofection technique ultimately resulting in successful base conversion at the same site verified in the HEK293 model. Additional research performed included characterization of the pre-modification genotype with respect to likely off-target sites and methods of isolating clonal variants.
ContributorsLakers, Mary Frances (Author) / Brafman, David (Thesis advisor) / Haynes, Karmella (Committee member) / Wang, Xiao (Committee member) / Arizona State University (Publisher)
Created2017
Description
Novel biological strategies for cancer therapy have recently been able to generate improved anti-tumor effects in the clinic. Of these new advancements, oncolytic virotherapy is a promising strategy through a dual mechanism of oncolysis and stimulation of tumor immunogenicity against the target cancer cells. Myxoma virus (MYXV) is an oncolytic poxvirus that has a natural tropism for Leporids, being nonpathogenic in humans and all other known vertebrates. MYXV is able to infect cancer cells due to mutations and defects in many innate signaling pathways, such as those involved in anti-viral responses. While MYXV alone infects and kills many classes of human cancer cells, recombinant techniques allow for the implementation of therapeutic transgenes, which have the potential of ‘arming’ the virus to enhance its potential as an oncolytic virus. The implementation of certain transgenes allows improved cancer cell killing and/or promotion of more robust anti-tumor immune responses. To investigate the potential of immune-inducing transgenes in MYXV, in vitro screening experiments were performed with several single transgene-armed recombinant MYXVs. As recent studies have shown the ability of MYXV to uniquely target malignant human hematopoietic stem cells, the potential of oncolytic MYXV armed with individual immune-enhancing transgenes was investigated through in vitro killing analysis using human acute myeloid leukemia (AML) and multiple myeloma (MM) cell lines. Additionally, in vitro experiments were performed using primary bone marrow (BM) cells obtained from human patients diagnosed with MM. Furthermore, the action of an engineered bispecific killer engager (huBIKE) was investigated through co-culture studies between the CD138 surface marker of target MM cells and the CD16 surface marker of primary effector peripheral blood mononuclear cells (PBMCs), particularly NK cells and neutrophils. In this study, several of the test armed MYXV-infected human AML and MM cell lines resulted in increased cell death compared to unarmed MYXV-infected cells. Additionally, increased killing of CD138+ MM cells from primary human BM samples was observed following infection with huBIKE-armed MYXV relative to infection with unarmed MYXV. Furthermore, analysis of co-culture studies performed suggests enhanced killing of target MM cells via engagement of NK cells with U266 MM cells by huBIKE.
ContributorsMamola, Joseph (Author) / McFadden, Grant (Thesis advisor) / Jacobs, Bertram (Committee member) / Blattman, Joseph (Committee member) / Arizona State University (Publisher)
Created2020
Description
Genome wide association studies (GWAS) have identified polymorphism in the Apolipoprotein E (APOE) gene to be the most prominent risk factor for Alzheimer’s disease (AD). Compared to individuals homozygous for the APOE3 variant, individuals with the APOE4 variant have a significantly elevated risk of AD. On the other hand, longitudinal studies have shown that the presence of the APOE2 variant reduces lifetime risk of developing AD by 40 percent. While there has been significant research that has identified the risk-inducing effects of APOE4, the underlying mechanisms by which APOE2 influences AD onset and progression have not been extensively explored. The hallmarks of AD pathology manifest in human neurons in the form of extracellular amyloid deposits and intracellular neurofibrillary tangles, whereas astrocytes are the primary source of the APOE protein in the brain. In this study, an isogenic human induced pluripotent stem cell (hiPSC)-based system is utilized to demonstrate that conversion of APOE3 to APOE2 greatly reduced the production of amyloid-beta (Aβ) peptides in hiPSC-derived neural cultures. Mechanistically, analysis of pure populations of neurons and astrocytes derived from these neural cultures revealed that mitigating effects of APOE2 is mediated by cell autonomous and non-autonomous effects. In particular, it was demonstrated the reduction in Aβ and pathogenic β-C-terminal fragments (APP-βCTF) is potentially driven by a mechanism related to non-amyloidogenic processing of amyloid precursor protein (APP), suggesting a gain of protective function of the APOE2 variant. Together, this study provides insights into the risk-modifying effects associated with the APOE2 allele and establishes a platform to probe the mechanisms by which APOE2 enhances neuroprotection against AD.
ContributorsRaman, Sreedevi (Author) / Brafman, David (Thesis advisor) / Smith, Barbara (Committee member) / Plaiser, Christopher (Committee member) / Wang, Xiao (Committee member) / Tian, Xiaojun (Committee member) / Arizona State University (Publisher)
Created2021
Description
Programmed cell death plays an important role in a variety of processes that promote the survival of the host organism. Necroptosis, a form of programmed cell death, occurs through a signaling pathway involving receptor-interacting serine-threonine protein kinase 3 (RIPK3). In response to vaccinia virus infection, necroptosis is induced through DNA-induced activator of interferon (DAI), which activates RIPK3, leading to death of the cell and thereby inhibiting further viral replication in host cells. DAI also localizes into stress granules, accumulations of mRNAs that have stalled in translation due to cellular stress. The toxin arsenite, a canonical inducer of stress granule formation, was used in this project to study necroptosis. By initiating necroptosis with arsenite and vaccinia virus, this research project investigated the roles of necroptosis proteins and their potential localization into stress granules. The two aims of this research project were to determine whether stress granules are important for arsenite- and virus-induced necroptosis, and whether the proteins DAI and RIPK3 localize into stress granules. The first aim was investigated by establishing a DAI and RIPK3 expression system in U2OS cells; arsenite treatment or vaccinia virus infection was then performed on the U2OS cells as well as on U2OSΔΔG3BP1/2 cells, which are not able to form stress granules. The second aim was carried out by designing fluorescent tagging for the necroptosis proteins in order to visualize protein localization with fluorescent microscopy. The results show that arsenite induces DAI-dependent necroptosis in U2OS cells and that this arsenite-induced necroptosis likely requires stress granules. In addition, the results show that vaccinia virus induces DAI-dependent necroptosis that also likely requires stress granules in U2OS cells. Furthermore, a fluorescent RIPK3 construct was created that will allowfor future studies on protein localization during necroptosis and can be used to answer questions regarding localization of necroptosis proteins into stress granules. This project therefore contributes to a greater understanding of the roles of DAI and RIPK3 in necroptosis, as well as the roles of stress granules in necroptosis, both of which are important in research regarding viral infection and cellular stress.
ContributorsGogerty, Carolina (Author) / Jacobs, Bertram (Thesis advisor) / Langland, Jeffrey (Committee member) / Jentarra, Garilyn (Committee member) / Arizona State University (Publisher)
Created2021