Browsing by Subject "Natural Killer Cell"

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    Epigenetic regulation of killer immunoglobulin-like receptor Gene expression in developing human natural killer cells.
    (2010-05) Cichocki, Frank M.
    The immune system is our primary defense against infection and disease. Immune cells need to recognize and efficiently destroy invasive pathogens while, at the same time, exercising tolerance towards normal cells and tissues within the body. Because pathogenic organisms are constantly evolving to evade detection, the immune system must employ multiple recognition strategies to keep pace. Natural killer (NK) cells have evolved a self versus non-self recognition strategy known as “missing self” that is based upon the recognition of self major histocompatibility complex (MHC) molecules by stochastically expressed inhibitory receptors on the surface of NK cells. When MHC expression is downregulated by a virus or cellular transformation event, the dampening signals that balance against NK cell activation are lost due to a lack of inhibitory receptor engagement. This lack of inhibitory signaling, along with the engagement of activating receptors, leads to the elimination of the distressed cell through targeted NK cell-mediated cytotoxicity. The work presented in this manuscript focuses on the transcriptional regulation of a critically important family of human NK cell inhibitory receptors known as killer immunoglobulin-like receptors (KIR). The KIR genes are present within the leukocyte receptor complex on chromosome 19 and are expressed in a variegated, clonally restricted pattern on fully differentiated NK cells. How this pattern of gene expression is regulated during NK cell development is not well understood despite the demonstrated clinical relevance of KIR during hematopoietic cell transplantation to treat patients with leukemia, the influence of the KIR repertoire on the progression of HIV to AIDS, and the importance of KIR during pregnancy. Progress in the elucidation of how KIR genes are regulated has been slow due to the complexity of the KIR locus and the lack of KIR genes in mice, which are much more amenable to genetic manipulation. We have shown that the 5’ upstream regulatory region of each KIR gene contains a previously uncharacterized distal promoter with a functional c-Myc binding site. Stimulation of primary peripheral blood NK cells with IL-15 induces c-Myc binding at the distal promoter, which acts to promote KIR transcription. We also found that the overexpression of c-Myc protein in the NK92 cell line, which lacks surface KIR due to dense methylation of CpG dinucleotides proximal to the transcriptional start site, causes de novo surface KIR expression. Taken together, these results suggest that IL-15 directly promotes KIR transcription by inducing the binding of c-Myc to the distal promoter. We hypothesize that the recruitment of c-Myc and the initiation of active transcription from the distal promoter may also be key steps in the removal of repressive epigenetic marks within KIR promoters during human NK cell development to allow for stable gene expression. In addition to identifying a novel distal promoter, our group has found that the conventional proximal KIR promoter exhibits bi-directional transcriptional activity, meaning that transcription can initiate in either the sense or antisense orientation. We observed a strong inverse correlation between the expression of KIR antisense transcripts and receptor expression on the cell surface, leading to the hypothesis that antisense transcripts directly participate in RNA-mediated transcriptional repression of individual KIR genes. We found that over-expressing full-length antisense transcripts during NK cell development led to an approximately 70% reduction in KIR expression compared to controls. Furthermore, we determined that full-length antisense transcripts are processed into a 28 base RNA with biochemical properties similar to those attributed to members of the PIWI family of small RNAs. We also demonstrate that the 28 base sequence is necessary for antisense transcript-mediated repression of KIR gene expression. This work establishes a direct association between KIR antisense transcription and the initiation of DNA methylation within the KIR promoter. Further elucidation of the mechanisms that regulate KIR expression during NK cell development may provide a basis for new strategies in the design of NK cell-based therapies
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    Targeting the Tumor Stroma Using a Monoclonal Antibody Platform Technology
    (2021-04) Hintz, Hallie
    1 in 9 men will be diagnosed with prostate cancer during their lifetime and it remains the second leading cause of cancer death among American men. Men who fail standard-of-care androgen deprivation therapy (ADT) and progress to metastatic castration resistant prostate cancer (mCRPC) are left with few therapeutic options. Current second line therapies only provide a small survival benefit and there is a critical unmet need for new and innovative approaches to treat mCRPC. Imaging is a crucial aspect of mCRPC clinical management used for the detection of recurrent or distant disease. The development of new therapies is also dependent on accurate imaging modalities for patient staging and evaluating treatment response. Our research shows fibroblast activation protein alpha (FAP) is a relevant target for imaging and treating mCRPC. FAP is emerging as the next pan-cancer target given its upregulated expression in cancer associated fibroblasts (CAFs) and localization to the tumor microenvironment. Here we document the discovery and validation of a monoclonal antibody that selectively binds to FAP. The lead antibody, B12, was identified from a naïve murine single-chain variable fragment antibody phage display library screened against recombinant human FAP. The heavy and light chains of B12 were cloned into full-length human immunoglobulin 1 vectors and expressed as a chimeric monoclonal antibody (B12 mAb). B12 mAb was shown to detect FAP expression in cell lines and was rapidly internalized by FAP-expressing cells in vitro. B12 mAb demonstrated cross-reactivity with murine FAP, but not with the highly homologous protease human dipeptidyl peptidase IV. PET/CT imaging with [89Zr]Zr-B12 mAb demonstrated high tumor uptake and long-term retention of the probe in several preclinical animal models. Furthermore, we show its superiority to other clinically investigated imaging probes which suggests clinical translation of B12 mAb as a non-invasive mCRPC imaging probe. Next, we evaluated the therapeutic potential of B12 mAb as an antibody-dependent cell-mediated cytotoxicity (ADCC) inducing agent in combination with an engineered NK-92MI CD64 cell therapy. The immunotherapy demonstrated selective cytotoxicity in vitro and treatment effectively controlled tumor growth in an animal model. Furthermore, we engineered B12 mAb as an antibody-drug conjugate (ADC) and showed cytotoxic effect in several in vitro and in vivo solid tumor models. Overall, this research represents a platform technology for the development of theranostics targeting FAP that could provide urgently needed therapies and imaging probes for mCRPC patients.