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Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2018)

Abstract

Role of Necroptosis in T Cell Activation

by

Zhanran Zhao

Doctor of Philosophy in Molecular and Cell Biology

University of California, Berkeley

Professor Astar Winoto, Chair

Necroptosis is a programmed cell death pathway characterized by a necrosis-like

morphology and mediated in part by the kinase activity of receptor-interacting protein kinase 3

(RIPK3) and, in most cases, its partner RIP1 as well. Necroptosis is a hidden cell death pathway,

as it was initially only described in cells deficient in FADD or caspase-8. Necroptosis has been

shown to play important roles in injury, disease models, and, more recently, in certain viral

infections. However, its role in a normal physiological setting is still not completely clear. Using

Nec-1, an inhibitor of RIP1 kinase activity, we have previously shown that a proportion of CD8

T cells can be rescued from cell death induced by TCR activation in vitro. This observation led

us to characterize the phenotype of T cells from mice deficient in RIP3 to examine the role

necroptosis plays in T cell activation. We found that inhibiting necroptosis can lead to increased

cell number and activity of cytotoxic T lymphocytes (CTLs). Furthermore, Rip3-/- mice showed

improved tumor responses compared to littermate controls, with decreased expression of

inhibitory markers on CTLs and reduced suppressive Treg populations in the tumor infiltrating

lymphocytes. Using adoptive transfer, we showed that this effect is primarily driven by Rip3-/- T

cells and that these T cells exhibit elevated activation activities and improved anti-tumor

function. Necroptosis thus helps to regulate T cell activation to maintain the delicate balance of

immune homeostasis.

    Cover page: Role of Necroptosis in T Cell Activation
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2020)

    Introduction

    Priming of tumor-specific T cells is a key to antitumor immune response and inflammation, in turn, is crucial for proper T-cell activation. As antigen-presenting cells can activate T cells, dendritic cells (DCs) loaded with tumor antigens have been used as immunotherapeutics against certain cancer in humans but their efficacy is modest. Necroptosis is a form of programmed cell death that results in the release of inflammatory contents. We previously generated mice with DC deficiency in a negative regulator of necroptosis, Fas-associated death domain (FADD), and found that these mice suffer from systemic inflammation due to necroptotic DCs. We hypothesize that FADD-deficient DCs could serve as a better vaccine than wild-type (WT) DCs against tumors.

    Materials and methods

    FADD-deficient and WT mouse DCs loaded with the relevant tumor peptide were injected onto mice before or after the syngeneic tumor challenge. DC vaccinations were repeated two more times and anti-PD-1 antibodies were coinjected in some experiments. Tumor sizes were measured by caliper, and the percentages of tumor-free mice or mice survived were examined over time. The cytometric analysis was carried out to analyze various immune populations.

    Results

    In two separate tumor models, we find that mice receiving FADD-deficient DCs as vaccine rejected tumors significantly better than those receiving a WT DC vaccine. Tumor growth was severely hampered, and survival extended in these mice. More activated CD8 T cells together with elevated cytokines were observed in mice receiving the FADD-deficient DC vaccine. Furthermore, we observed these effects were potent enough to protect against tumor challenge postinjection and can work in conjunction with anti-PD-1 antibodies to reduce the tumor growth.

    Conclusions

    Necroptotic-susceptible DCs are better antitumor vaccines than WT DCs in mice. Our findings suggest that necroptosis-driven inflammation by DCs may be a novel avenue to generating a strong adaptive antitumor response in the clinical setting.
      Cover page: Necroptotic‐susceptible dendritic cells exhibit enhanced antitumor activities in mice
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