Identifying Cell Death Pathways Activated by Myxoma virus in Melanoma

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Description
Melanoma is a type of skin cancer that can metastasize in advanced stages to other organs such as the brain, lymph nodes, lungs and liver. Current standard treatment options include surgery, radiation therapy, chemotherapy, and immunotherapy. More recently, oncolytic virotherapy…

Melanoma is a type of skin cancer that can metastasize in advanced stages to other organs such as the brain, lymph nodes, lungs and liver. Current standard treatment options include surgery, radiation therapy, chemotherapy, and immunotherapy. More recently, oncolytic virotherapy is being studied as a new strategy to fight cancer. Specifically, for melanoma, a herpes virus (T-VEC) was approved by the U.S Food and Drug Administration in 2015 to treat advanced disease. Oncolytic viruses have the capacity to replicate mostly in cancer cells while leaving healthy somatic cells free from infection. Additionally, most of these viruses have the ability to induce an immune response against the cancer as well. Myxoma virus (MYXV) causes myxomatosis in European rabbits but not in any other mammal. In humans, MYXV can infect and kill cancer cells acting as an oncolytic virus. However, the mechanisms behind how myxoma kills cancerous cells are not completely known. To investigate this, we treated melanoma murine cancer cells (B16F10) in vitro with different genetically modified myxoma virus mutants, as well as with a novel second mitochondria-derived activator of caspase mimicking drug SMAC-LCL161, to understand the mechanisms by which MYXV induces cell death. In parallel, B16F10 lacZ cells were subcutaneously injected into mice to engraft melanoma tumors. These tumors were treated with intratumoral injections of different viral mutants or armed viruses derived from MYXV along with SMAC-L61. After a period of treatment, the tumors were isolated. Cell death pathways in both cell culture and in tumors obtained from subcutaneous pathways were identified using different techniques. The study showed an increase in activated caspase 3 and cleaved PARP-1 activity in B16F10 lacZ cells from cell culture when compared to cells in vivo however the two apoptosis markers did not track with each other consistently.
Date Created
2019-12
Agent

Characterization of Necroptosis in Breast Cancer and Melanoma for Oncolytic Vaccinia Potential

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Description
With the advent of precision medicine, oncologists aim to target tumors that do not respond well to conventional treatment. One such therapy is oncolytic virotherapy, a treatment reliant on viral replication for tumor specific killing. Downregulation of the proteins RIP3…

With the advent of precision medicine, oncologists aim to target tumors that do not respond well to conventional treatment. One such therapy is oncolytic virotherapy, a treatment reliant on viral replication for tumor specific killing. Downregulation of the proteins RIP3 kinase, DAI or MLKL can result in a nonfunctional programmed necroptotic cell death pathway, common amongst breast cancer and melanoma. Vaccinia virus (VACV) mutants with a nonfunctional E3 protein are able to selectively replicate in necroptosis deficient cells but not in necroptosis competent cells, making them potential candidates for oncolytic virotherapy. In order to establish the efficacy and selectivity of this treatment, an accurate tumor model is required. Eight established breast adenocarcinomas and two established melanomas were selected as potential candidates, both human and murine. A pan screening method for necroptosis was established utilizing western blot analysis for expression of aforementioned proteins following various induction methods such as IFN α or VACV infection. In addition, live cell imaging after treatment with tumor necrosis factor (TNFα) and the pan-caspase inhibitor zVAD-fmk was used as a method to visualize necroptosis pathway functionality. Based on these results, cell lines will be selected and modified to create a breast cancer model with cells that are syngeneic, differing only in expression of either RIP3. VACV can be tested for tumor volume reduction in these models to ask if RIP3 expression affects efficacy of mutant VACV as an oncolytic virus.
Date Created
2019-05
Agent

Armed Oncolytic Myxoma Viruses to Eliminate Acute Myeloid Leukemia and Multiple Myeloma Cells

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Description
Novel biological strategies for cancer therapy have recently been able to generate antitumor effects in the clinic. Of these new advancements, oncolytic virotherapy seems to be a promising strategy through a dual mechanism of oncolysis and immunogenicity of the host…

Novel biological strategies for cancer therapy have recently been able to generate antitumor effects in the clinic. Of these new advancements, oncolytic virotherapy seems to be a promising strategy through a dual mechanism of oncolysis and immunogenicity of the host to the target cells. Myxoma virus (MYXV) is an oncolytic poxvirus that has a natural tropism for European rabbits, being nonpathogenic in humans and all other known vertebrates. MYXV is able to infect cancer cells which, due to mutations, have defects in many signaling pathways, notably pathways involved in antiviral responses. While MYXV alone elicits lysis of cancer cells, recombinant techniques allow for the implementation of transgenes, which have the potential of ‘arming’ the virus to enhance its potential as an oncolytic virus. The implementation of certain transgenes allow for the promotion of robust anti-tumor immune responses. To investigate the potential of immune-inducing transgenes in MYXV, in vitro experiments were performed with several armed recombinant MYXVs as well as unarmed wild-type and rabbit-attenuated MYXV. As recent studies have shown the ability of MYXV to uniquely target malignant human hematopoietic stem cells, the potential of oncolytic MYXV armed with immune-inducing transgenes was investigated through in vitro killing analysis using human acute myeloid leukemia (AML) and multiple myeloma (MM) cell lines. Furthermore, in vitro experiments were also performed using primary bone marrow (BM) cells obtained from human patients diagnosed with MM. In this study, armed MYXV-infected human AML and MM cells resulted in increased cell death relative to unarmed MYXV-infected cells, suggesting enhanced killing via induced mechanisms of cell death from the immune-inducing transgenes. Furthermore, increased killing of primary BM cells with multiple myeloma was seen in armed MYXV-infected primary cells relative to unarmed MYXV-infected primary cells.
Date Created
2019-05
Agent

Determining the oncolytic potential of Myxoma virus on triple negative breast cancer

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Description
Oncolytic virotherapy (OV) is the use of viruses that do not target normal human cells to infect and destroy cancer cells; some also stimulate the immune system against the tumors. Myxoma virus (VMYX) is a candidate for use as an…

Oncolytic virotherapy (OV) is the use of viruses that do not target normal human cells to infect and destroy cancer cells; some also stimulate the immune system against the tumors. Myxoma virus (VMYX) is a candidate for use as an oncolytic agent, as it is not pathogenic to humans and can infect a variety of human cancer cells. VMYX also can initiate immune responses against the virus-infected tumor. Thus, we investigated the oncolytic efficacy of a few recombinant constructs of VMYX on triple-negative breast cancer (TNBC), a highly aggressive subtype of breast cancer with limited treatment options. TNBC lacks an estrogen receptor, progesterone receptor, and HER2, which render hormone-based therapies useless. Further challenges of TNBC include early metastasis and recurrence, as well as poor prognosis due to a lack of molecular targets. Here, we utilized 4T1-Luc2 cells, an in vitro mouse model of TNBC, to examine the oncolytic potential of recombinant viral constructs of VMYX. Ability to infect was measured by fluorescence intensity, while ability to induce cytotoxicity was measured through MTS and SYTOX assays. Further characterization of cell death was performed using Caspase 3/7 activity assay, immunofluorescent staining and confocal microscopy to detect ecto-expression of calreticulin, and ATP release assays. We demonstrated the ability of recombinant VMYX constructs to infect and induce cell death in 4T1-Luc2 cells. VMYX-p14-FAST-GFP induced the most cell death, while VMYX-M011LKO-GFP best activated Caspase 3/7. Through ATP release assays and examination of ecto-expression of calreticulin, preliminary data indicated that VYX-135KO-GFP is unable to stimulate immunogenic cell death, a form of cell death that stimulates an adaptive immune response, in these cells. Future directions include further characterization of cell death in vitro, as well as in vivo studies.
Date Created
2019-05
Agent

Comparative Analysis of Immunosignatures and Serological Reactivity for Disease Profiling

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Description
Blood donations today undergo extensive screening for transfusion transmitted infections (TTI) since the discovery of the first infectious agent in the early 1900s. Nucleic Acid Testing (NAT) is a serological test used widely in disease detection. NAT is known to…

Blood donations today undergo extensive screening for transfusion transmitted infections (TTI) since the discovery of the first infectious agent in the early 1900s. Nucleic Acid Testing (NAT) is a serological test used widely in disease detection. NAT is known to rapidly and effectively detect pathogenic genomic material in blood by reducing the "window period" of infection. However, NAT produces false negative results for disease positive samples posing a risk of disease transmission. Therefore, NAT is used in conjunction with the Enzyme-Linked Immunosorbent Assay (ELISA) to mitigate these risks. However, the ELISA assay also poses the same risk as NAT. This study proposes immunosignaturing as an alternative serological test that may combat this risk and investigates whether it would be more effective than other standardized serological tests in disease detection. Immunosignaturing detects antibodies by utilizing a microarray of randomized peptide sequences. Immunosignaturing provides information about an individual's immune health from the pattern of reactivity of antibody-peptide binding. Unlike ELISA and NAT, immunosignaturing can be programmed to detect any disease and detect multiple diseases simultaneously. Using ELISA, NAT, and immunosignaturing, immune profiles of asymptomatic patients were constructed for 10 different classes of blood borne diseases. A pattern of infection was identified for each disease and the sensitivity and specificity of these assays were assessed relative to each other. Results indicate that immunosignaturing can be a viable diagnostic tool in blood testing. Immunosignatures demonstrated increased sensitivity and specificity compared to ELISA and NAT in discerning disease positive and negative samples within and across different classes of disease.
Date Created
2018-05
Agent

Use of large, immunosignature databases to pose new questions about infection and health status

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Description
Immunosignature is a technology that retrieves information from the immune system. The technology is based on microarrays with peptides chosen from random sequence space. My thesis focuses on improving the Immunosignature platform and using Immunosignatures to improve diagnosis for diseases.…

Immunosignature is a technology that retrieves information from the immune system. The technology is based on microarrays with peptides chosen from random sequence space. My thesis focuses on improving the Immunosignature platform and using Immunosignatures to improve diagnosis for diseases. I first contributed to the optimization of the immunosignature platform by introducing scoring metrics to select optimal parameters, considering performance as well as practicality. Next, I primarily worked on identifying a signature shared across various pathogens that can distinguish them from the healthy population. I further retrieved consensus epitopes from the disease common signature and proposed that most pathogens could share the signature by studying the enrichment of the common signature in the pathogen proteomes. Following this, I worked on studying cancer samples from different stages and correlated the immune response with whether the epitope presented by tumor is similar to the pathogen proteome. An effective immune response is defined as an antibody titer increasing followed by decrease, suggesting elimination of the epitope. I found that an effective immune response usually correlates with epitopes that are more similar to pathogens. This suggests that the immune system might occupy a limited space and can be effective against only certain epitopes that have similarity with pathogens. I then participated in the attempt to solve the antibiotic resistance problem by developing a classification algorithm that can distinguish bacterial versus viral infection. This algorithm outperforms other currently available classification methods. Finally, I worked on the concept of deriving a single number to represent all the data on the immunosignature platform. This is in resemblance to the concept of temperature, which is an approximate measurement of whether an individual is healthy. The measure of Immune Entropy was found to work best as a single measurement to describe the immune system information derived from the immunosignature. Entropy is relatively invariant in healthy population, but shows significant differences when comparing healthy donors with patients either infected with a pathogen or have cancer.
Date Created
2018
Agent

Identification of Host DEAD-Box RNA Helicases That Regulate Cellular Tropism of Oncolytic Myxoma Virus in Human Cancer Cells

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Description

Myxoma virus (MYXV), a Leporipoxvirus, is being developed as an oncolytic virotherapeutic for the treatment of a variety of human cancers. MYXV tropism for human cancer cells is largely mediated by intracellular signaling networks that regulate viral replication or innate…

Myxoma virus (MYXV), a Leporipoxvirus, is being developed as an oncolytic virotherapeutic for the treatment of a variety of human cancers. MYXV tropism for human cancer cells is largely mediated by intracellular signaling networks that regulate viral replication or innate antiviral response pathways. Thus, MYXV is fully or partially permissive for the majority of human cancer cells that harbor defects in antiviral signaling, but a minority are nonpermissive because the virus infection aborts before its completion. To identify host factors relevant for MYXV tropism in human cancer cells, we performed a small interfering RNA (siRNA) library screen targeting the 58 human DEAD-box RNA helicases in two permissive human cancer cells (HeLa and A549), one semi-permissive (786-0), and one nonpermissive cell line (PANC-1). Five host RNA helicases (DDX3X, DDX5, DHX9, DHX37, DDX52) were inhibitory for optimal replication and thus classified as anti-viral, while three other cellular RNA helicases (DHX29, DHX35, RIG-I) were identified as pro-viral or pro-cellular because knockdown consistently reduced MYXV replication and/or required metabolic functions of permissive cancer cells. These findings suggest that replication of MYXV, and likely all poxviruses, is dramatically regulated positively and negatively by multiple host DEAD-box RNA helicases.

Date Created
2017-11-16
Agent

Inhibition of PKR phosphorylation by Vaccinia Virus' E3 Protein

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Description
Vaccinia virus is a cytoplasmic, double-stranded DNA orthopoxvirus. Unlike mammalian cells, vaccinia virus produces double-stranded RNA (dsRNA) during its viral life cycle. The protein kinase R, PKR, is one of the principal host defense mechanisms against orthopoxvirus infection. PKR can…

Vaccinia virus is a cytoplasmic, double-stranded DNA orthopoxvirus. Unlike mammalian cells, vaccinia virus produces double-stranded RNA (dsRNA) during its viral life cycle. The protein kinase R, PKR, is one of the principal host defense mechanisms against orthopoxvirus infection. PKR can bind double-stranded RNA and phosphorylate eukaryotic translation initiation factor, eIF2α, shutting down protein synthesis and halting the viral life cycle. To combat host defenses, vaccinia virus encodes E3, a potent inhibitor of the cellular anti-viral eIF2α kinase, PKR. The E3 protein contains a C-terminal dsRNA-binding motif that sequesters dsRNA and inhibits PKR activation. We demonstrate that E3 also interacts with PKR by co-immunoprecipitation. This interaction is independent of the presence of dsRNA and dsRNA-binding by E3, indicating that the interaction is not due to dsRNA-bridging.
PKR interaction mapped to a region within the dsRNA-binding domain of E3 and overlapped with sequences in the C-terminus of this domain that are necessary for binding to dsRNA. Point mutants of E3 were generated and screened for PKR inhibition and direct interaction. Analysis of these mutants demonstrates that dsRNA-binding but not PKR interaction plays a critical role in the broad host range of VACV. Nonetheless, full inhibition of PKR in cells in culture requires both dsRNA-binding and PKR interaction. Because E3 is highly conserved among orthopoxviruses, understanding the mechanisms that E3 uses to inhibit PKR can give insight into host range pathogenesis of dsRNA producing viruses.
Date Created
2017-05
Agent

Myxoma Virus dsRNA Binding Protein M029 Inhibits the Type I IFN‐Induced Antiviral State in a Highly Species‐Specific Fashion

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Description

Myxoma virus (MYXV) is Leporipoxvirus that possesses a specific rabbit‐restricted host tropism but exhibits a much broader cellular host range in cultured cells. MYXV is able to efficiently block all aspects of the type I interferon (IFN)‐induced antiviral state in…

Myxoma virus (MYXV) is Leporipoxvirus that possesses a specific rabbit‐restricted host tropism but exhibits a much broader cellular host range in cultured cells. MYXV is able to efficiently block all aspects of the type I interferon (IFN)‐induced antiviral state in rabbit cells, partially in human cells and very poorly in mouse cells. The mechanism(s) of this species‐specific inhibition of type I IFN‐induced antiviral state is not well understood. Here we demonstrate that MYXV encoded protein M029, a truncated relative of the vaccinia virus (VACV) E3 double‐stranded RNA (dsRNA) binding protein that inhibits protein kinase R (PKR), can also antagonize the type I IFN‐induced antiviral state in a highly species‐specific manner. In cells pre‐treated with type I IFN prior to infection, MYXV exploits M029 to overcome the induced antiviral state completely in rabbit cells, partially in human cells, but not at all in mouse cells. However, in cells pre‐infected with MYXV, IFN‐induced signaling is fully inhibited even in the absence of M029 in cells from all three species, suggesting that other MYXV protein(s) apart from M029 block IFN signaling in a speciesindependent manner. We also show that the antiviral state induced in rabbit, human or mouse cells by type I IFN can inhibit M029‐knockout MYXV even when PKR is genetically knocked‐out, suggesting that M029 targets other host proteins for this antiviral state inhibition. Thus, the MYXV dsRNA binding protein M029 not only antagonizes PKR from multiple species but also blocks the type I IFN antiviral state independently of PKR in a highly species‐specific fashion.

Date Created
2017-02-02
Agent
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