2013 — 2017 |
Pan, Fan |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Metabolic Regulation of T Cell Fate and Tumor Immunity @ Johns Hopkins University
DESCRIPTION (provided by applicant): Immunotherapy, which focuses on augmenting host immunity against tumor-associated antigens, represents an important means to treat cancer that is yielding clinical success. Successful manipulation of T cell responses requires understanding how particular T cell subsets influence cancer development and growth. For example, Th1 and Th17 cells can augment tumorigenesis. Treg cells can block anti-tumor immune responses and thus represents one of the main obstacles to successful tumor immunotherapy. While Tregs are recognized as tumor supporting cells, the relationship between Th17 cells and tumor immunity has been controversial. A major unappreciated element in T cell fate decisions is the metabolic environment. As part of an effort to study the metabolic regulation of T cell differentiation decisions, we have discovered that hypoxia inducible factor 1 (HIF-1) plays a critical role in driving the Th17 response. Further preliminary results suggest that lack of this molecule results in reduced tumor initiation and progression. In this proposal, we aim to: (1) further dissect the role of HIF-1 in Th17 development. We will address the breadth, and particular facets of HIF-1's contribution to the Th17 lineage. We will also touch on the suitability of HIF-1 as a therapeutic target in humans; (2) we will explore the role of HIF-1 in regulating the Th17 and Treg responses in inflammation-induced carcinogenesis and cancer progression; (3) we will subsequently use these in vivo cancer models to test the therapeutic potential of HIF-1 targeting. In these studies mice will be treated with the HIF-1 inhibitors, Digoxin and Acriflavine and we will evaluate the ability of these compounds to impede tumor growth either alone or in concert with Treg depletion. Such a strategy is expected to have potent anti-tumor effects as it should, given our preliminary data and past results, simultaneously sabotage two major tumor- promoting immune cell populations
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2018 — 2019 |
Pan, Fan |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
E3 Ligase Mediated Control of Foxp3 Expression and Immune Suppression-Mechanisms and Potential as Immunotherapeutic Target @ Johns Hopkins University
Project Summary Tumor cells exploit mechanisms of immune regulation to evade detection and eradication by host defenses. Foxp3+CD4+CD25+ regulatory T cell (Treg)-mediated immune suppression is crucial for immune evasion by tumor cells and an obstacle for successful tumor immunotherapy. Hence, the ability to disrupt Treg function is of major therapeutic significance. Recent work by us and others revealed that the key Treg transcription factor, Foxp3 is subject to polyubiquitination-dependent posttranslational regulation. Particularly, we found the E3 ubiquitin ligase Stub1, which is induced in response to a range of stress signals, facilitates the degradation of Foxp3 providing a potential target for dynamic modulation of Treg suppression. In the current proposal, we are seeking to: 1) Dissect molecular signaling pathways involved in Stub1 expression and its post-translational modification; 2) Understand the consequences of physiological Stub1 induction and genetic deletion for Treg cell homeostasis, differentiation and function; and 3) Test pharmacological activators of Foxp3 ubquitination as novel immunotherapic strategies to undermine immune suppression in the cancer setting. These studies will expand our understanding of the mechanisms behind posttranslational Foxp3 regulation. Specifically, we will further explore pathways determining Stub1 activity and expression, including the previously unappreciated phosphorylation of the ligase by the kinase GS3K?. To this end, we will utilize biochemical approaches and well-characterized models of in vitro and in vivo Treg function to establish the consequences of ablating these pathways. Furthermore, pharmacological modifiers of the Stub1/Ubiquitin-dependent pathway for Foxp3 degradation (identified in a drug screen and previous studies) will be tested for efficacy as breakers of immune suppression - a major obstacle for anti-cancer immunotherapy. This vetting will be carried out in an aggressive murine melanoma model (in vivo) as well as in ex vivo studies of human leukocytes obtained from healthy donors and advanced cancer patients. In so doing we will determine the potential therapeutic application of modulating Stub1 activity to boost anti-tumor immunity. Our experiments may reveal novel modes of regulating Stub1 activity and Foxp3 protein downregulation. Detailed assessment of physiological Stub1 induction and its impact on Foxp3 and Treg function is predicted to demonstrate a potent therapeutic application. Use of Stub1- activators in combination with proven checkpoint targeting agents may yield even better anti-tumor efficacy.
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2019 |
Pan, Fan |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Role of Yap in Treg Function and Yap Targeting For Cancer Immunotherapy @ Johns Hopkins University
Background: Foxp3+CD4+CD25+ regulatory T cells (Treg)-mediated immune suppression is crucial for immune evasion by tumor cells and an obstacle for successful tumor immunotherapy. Hence, the ability to disrupt Treg function is of major therapeutic significance. Although Foxp3 is a master regulator of Treg, Foxp3 expression is not sufficient to account for the suppressive capacity of Tregs. It has been suggested that Foxp3 needs to associate with other co-factors in order to suppress non-Treg (T effector) genes and enforce Treg associated gene expression and function. Recently, we found that Yes-associated protein (YAP), a downstream co-activator of the Hippo pathway, is highly expressed by Tregs and is critical for Foxp3-mediated suppressive activity. Furthermore, T cell specific YAP knockout mice mount superior immune responses to implanted B16 melanomas. We hypothesize that YAP is an attractive target for immunotherapeutic strategies aimed at breaking tolerance and enhancing anti-tumor immunity in the cancer setting. Specific Aims: In the current proposal, we are seeking to: 1) Further dissect the molecular mechanisms by which YAP facilitates Foxp3+ Treg function; 2) Understand the consequences of YAP deletion for Treg cell differentiation and function; and 3) Explore the anti-tumor efficacy of YAP inhibitor(s) alone or in combination with immune checkpoint blockade. Objectives & Significance: These studies will expand our understanding of the mechanisms behind YAP facilitates Foxp3 regulation and Treg function. In so doing we will further dissect the molecular mechanism by which YAP facilitates Foxp3-mediated Treg function. Furthermore, we will explore Yap as a potential novel therapeutic target by pharmacologically manipulating YAP activity, and testing various inhibitors for efficacy as breakers of immune tolerance, which is a major obstacle for anti-cancer immunotherapy. The use of such Yap inhibitors in combination with other immune modulators such as anti-PD-1 is expected to improve the effectiveness of immunotherapy, and boost anti-tumor immunity and patient survival. Methodology: In these studies we will deploy biochemical, molecular biology, genetic and bioinformatic approaches to further dissect the role of YAP in Treg cell biology, and attempt to discover known and novel inhibitors of Yap that are effective alone and synergistic with immunotherapies in reducing tumor burden. Both novel and known YAP inhibitors will be tested for their capacity to undermine Treg function and break immune tolerance in vitro and in vivo. Expected Results & Implications: Our experiments will reveal a novel role of YAP in Treg cell function. We predict that a detailed understanding of the physiological role of YAP induction and its impact on Foxp3 and Treg function will provide insight into therapeutic targeting of this pathway. The use of YAP inhibitors in combination with proven checkpoint targeting agents may yield even better anti-tumor efficacy.
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