Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (6 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2020)

Immunotherapies, such as “checkpoint blockade” have revolutionized modern cancer treatment, greatly increasing patient survival and leading to cures in a significant number of people. These groundbreaking drugs target inhibitory receptors on CD8 T cells, increasing T cell activation and promoting tumor destruction. However, tumors may evade such therapies via loss of MHC molecules or because they contain few/no neoantigens. Therefore, approaches to mobilize immune cells to kill CD8 T cell-resistant tumors are needed to combat these potential escape mechanisms. Natural killer (NK) cells recognize stress-induced ligands on tumor cells and do not require that tumors display neoantigens. CD4 T cells recognize epitopes presented by MHC II molecules that can serve as alternative targets for anti-tumor responses and are capable of activating other immune cells within the tumor microenvironment to kill tumor cells. Therefore, immunotherapies that mobilize NK cells or CD4 T cells have potential for targeting tumors resistant to CD8 T cells.

Cyclic-dinucleotides (CDNs) are a class of immunostimulatory molecules that bind to the STING protein and induce type I interferons (IFN) and other pro-inflammatory mediators. Recently, in mouse transplantable tumor models, it was shown that intratumoral CDN injections stimulate powerful CD8 T cell-mediated tumor rejection, often leading to long-lasting tumor regression and protection from rechallenge. Compounds that activate the STING pathway are currently being tested in clinical trials for treating cancer.

My thesis work examines the potential of CDNs to mobilize anti-tumor immune responses against MHC I-deficient tumors. The data show that CDNs trigger potent tumor rejection in several different tumor models, independent of CD8 T cells. The antitumor effects are dependent on NK and in some cases CD4 T cells, which can mediate rejection independently of each other. CDNs enhanced NK cell activation, cytotoxicity, and antitumor effects in part by inducing type I IFN (IFN). IFN acted in part directly on NK cells in vivo, and in part indirectly via dendritic cells. Upon applying CDNs in vivo, dendritic cells (DCs) upregulated IL-15R in an IFN-dependent manner, and IL-15 action was important for CDN-induced NK activation and tumor control. Mice lacking IFNAR specifically on DCs had reduced NK cell activation and tumor control.

CD4 T cells also mediate potent antitumor responses in some tumor models, independently of CD8 T cells and, in the primary response, independently of NK cells, B cells, and  T cells. CDN treatments led to increased tumor-specific priming of CD4 T cells and enhanced effector functions, such as production of IFN-, IL-2, and TNF. Tumor-specific CD4 T cells in tumors treated with CDNs had a less exhausted, Th1-like phenotype, with increased production of IFN-, which was necessary for the antitumor response. Mice that cleared their primary tumors exhibited a long-lasting antitumor memory response, which was dependent on CD4 T cells, IFN- and partially dependent on B cells, myeloid cells and, albeit to a minor extent, NK cells. Interestingly, the antitumor response did not rely on MHC II expression by the tumor cells, suggesting that CD4 T cells either initiate antitumor effects indirectly, without direct recognition of the tumor cell by CD4 T cells, or engage ligands other than conventional MHC II (and MHC I) on tumor cells.

In the final chapter of the thesis I described several genetic screens in cell lines aimed at identifying novel cellular ligands for NK cell activating receptors. The screens employed chimeric antigen receptor (CAR) T cells that incorporate NK cell activating receptors (NK CAR T cells) as selecting agents against human tumor cell lines mutagenized with a retroviral gene-trap or stably expressing CRISPR-Cas9 and a genome-wide gRNA library. I successfully generated multiple NK CAR T cells and performed several screens using NKp44 and NKp46 CAR T cells. These screens resulted in lists of genes, that when mutated, were enriched in the surviving cellular population. Future work will be needed to validate the hits from these screens and perform additional screens if necessary.

This thesis aims to identify mechanisms of immune cell activation induced by STING agonists as well as to unearth novel mechanisms of NK cell tumor recognition. This work is significant because it addresses CD8 T cell-independent immunological rejection of MHC-deficient tumors induced by CDNs and mediated by NK and CD4 T cells. A greater understanding of mechanisms leading to immunological clearance of MHC-deficient tumors will be necessary to develop approaches to overcome mechanisms tumors employ to escape CD8 T cell control and to design rational combination therapies with existing anti-cancer drugs. Therapeutics that activate NK cells and CD4 T cells may represent next-generation approaches to cancer immunotherapy.

    Cover page: Mechanisms of Clearance of MHC I-deficient Tumors Induced by STING Agonists
    • Article
    • Peer Reviewed
    UC Berkeley Previously Published Works (2022)
    Cyclic dinucleotides (CDN) and Toll-like receptor (TLR) ligands mobilize antitumor responses by natural killer (NK) cells and T cells, potentially serving as complementary therapies to immune checkpoint therapy. In the clinic thus far, however, CDN therapy targeting stimulator of interferon genes (STING) protein has yielded mixed results, perhaps because it initiates responses potently but does not provide signals to sustain activation and proliferation of activated cytotoxic lymphocytes. To improve efficacy, we combined CDN with a half life-extended interleukin-2 (IL-2) superkine, H9-MSA (mouse serum albumin). CDN/H9-MSA therapy induced dramatic long-term remissions of the most difficult to treat major histocompatibility complex class I (MHC I)–deficient and MHC I+ tumor transplant models. H9-MSA combined with CpG oligonucleotide also induced potent responses. Mechanistically, tumor elimination required CD8 T cells and not NK cells in the case of MHC I+ tumors and NK cells but not CD8 T cells in the case of MHC-deficient tumors. Furthermore, combination therapy resulted in more prolonged and more intense NK cell activation, cytotoxicity, and expression of cytotoxic effector molecules in comparison with monotherapy. Remarkably, in a primary autochthonous sarcoma model that is refractory to PD-1 checkpoint therapy, the combination of CDN/H9-MSA with checkpoint therapy yielded long-term remissions in the majority of the animals, mediated by T cells and NK cells. This combination therapy has the potential to activate responses in tumors resistant to current therapies and prevent MHC I loss accompanying acquired resistance of tumors to checkpoint therapy.
      Cover page: Synergy of a STING agonist and an IL-2 superkine in cancer immunotherapy against MHC I-deficient and MHC I+ tumors.
      • Article
      • Peer Reviewed
      UC Berkeley Previously Published Works (2021)
      Cancer patients often die from symptoms that manifest at a distance from any tumor. Mechanisms underlying these systemic physiological perturbations, called paraneoplastic syndromes, may benefit from investigation in non-mammalian systems. Using a non-metastatic Drosophila adult model, we find that malignant-tumor-produced cytokines drive widespread host activation of JAK-STAT signaling and cause premature lethality. STAT activity is particularly high in cells of the blood-brain barrier (BBB), where it induces aberrant BBB permeability. Remarkably, inhibiting STAT in the BBB not only rescues barrier function but also extends the lifespan of tumor-bearing hosts. We identify BBB damage in other pathological conditions that cause elevated inflammatory signaling, including obesity and infection, where BBB permeability also regulates host survival. IL-6-dependent BBB dysfunction is further seen in a mouse tumor model, and it again promotes host morbidity. Therefore, BBB alterations constitute a conserved lethal tumor-host interaction that also underlies other physiological morbidities.
        Cover page: Tumor-induced disruption of the blood-brain barrier promotes host deathCreative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UC Berkeley Previously Published Works (2020)
        Several immunotherapy approaches that mobilize CD8+ T cell responses stimulate tumor rejection, and some, such as checkpoint blockade, have been approved for several cancer indications and show impressive increases in patient survival. However, tumors may evade CD8+ T cell recognition via loss of MHC molecules or because they contain few or no neoantigens. Therefore, approaches are needed to combat CD8+ T cell-resistant cancers. STING-activating cyclic dinucleotides (CDNs) are a new class of immune-stimulating agents that elicit impressive CD8+ T cell-mediated tumor rejection in preclinical tumor models and are now being tested in clinical trials. Here, we demonstrate powerful CDN-induced, natural killer (NK) cell-mediated tumor rejection in numerous tumor models, independent of CD8+ T cells. CDNs enhanced NK cell activation, cytotoxicity, and antitumor effects in part by inducing type I interferon (IFN). IFN acted in part directly on NK cells in vivo and in part indirectly via the induction of IL-15 and IL-15 receptors, which were important for CDN-induced NK activation and tumor control. After in vivo administration of CDNs, dendritic cells (DCs) up-regulated IL-15Rα in an IFN-dependent manner. Mice lacking the type I IFN receptor specifically on DCs had reduced NK cell activation and tumor control. Therapeutics that activate NK cells, such as CDNs, checkpoint inhibitors, NK cell engagers, and cytokines, may represent next-generation approaches to cancer immunotherapy.
          Cover page: NK cells mediate clearance of CD8+ T cell–resistant tumors in response to STING agonists
          • Article
          • Peer Reviewed
          UC Berkeley Previously Published Works (2020)
          Thermography detects surface temperature and subsurface thermal activity of an object based on the Stefan-Boltzmann law. Impacts of the technology would be more far-reaching with finer thermal sensitivity, called noise-equivalent differential temperature (NEDT). Existing efforts to advance NEDT are all focused on improving registration of radiation signals with better cameras, driving the number close to the end of the roadmap at 20 to 40 mK. In this work, we take a distinct approach of sensitizing surface radiation against minute temperature variation of the object. The emissivity of the thermal imaging sensitizer (TIS) rises abruptly at a preprogrammed temperature, driven by a metal-insulator transition in cooperation with photonic resonance in the structure. The NEDT is refined by over 15 times with the TIS to achieve single-digit millikelvin resolution near room temperature, empowering ambient thermography for a broad range of applications such as in operando electronics analysis and early cancer screening.
            Cover page: Millikelvin-resolved ambient thermography
            • Article
            • Peer Reviewed
            UC Berkeley Previously Published Works (2017)
            All pathogens must acquire nutrients from their hosts. The intracellular bacterial pathogen Legionella pneumophila, the etiological agent of Legionnaires' disease, requires host amino acids for growth within cells. The mechanistic target of rapamycin complex 1 (mTORC1) is an evolutionarily conserved master regulator of host amino acid metabolism. Here, we identify two families of translocated L. pneumophila effector proteins that exhibit opposing effects on mTORC1 activity. The Legionella glucosyltransferase (Lgt) effector family activates mTORC1, through inhibition of host translation, whereas the SidE/SdeABC (SidE) effector family acts as mTORC1 inhibitors. We demonstrate that a common activity of both effector families is to inhibit host translation. We propose that the Lgt and SidE families of effectors work in concert to liberate host amino acids for consumption by L. pneumophila.
              Cover page: Positive and Negative Regulation of the Master Metabolic Regulator mTORC1 by Two Families of Legionella pneumophila Effectors
              Top