Mantle cell lymphoma is characterized by a genetic translocation results in aberrant overexpression of the CCND1 gene, which encodes cyclin D1. This protein functions as a regulator of the cell cycle ...progression, hence is considered to play an important role in the pathogenesis of the disease. In this study, we used RNA interference strategies to examine whether cyclin D1 might serve as a therapeutic target for mantle cell lymphoma. Knocking down cyclin D1 resulted in significant growth retardation, cell cycle arrest, and most importantly, induction of apoptosis. These results mark cyclin D1 as a target for mantle cell lymphoma and emphasize the therapeutic potential hidden in its silencing.
The transcription factor NFAT5/TonEBP, a member of the NFAT/Rel family of transcription factors, has been implicated in diverse cellular responses, including the response to osmotic stress, ...integrin-dependent cell migration, T cell activation, and the Ras pathway in Drosophila. To clarify the in vivo role of NFAT5, we generated NFAT5-null mice. Homozygous mutants were genetically underrepresented after embryonic day 14.5. Surviving mice manifested a progressive and profound atrophy of the kidney medulla with impaired activation of several osmoprotective genes, including those encoding aldose reductase, Na+/ Cl--coupled betaine/γ-aminobutyric acid transporter, and the Na+/myo-inositol cotransporter. The aldose reductase gene is controlled by a tonicity-responsive enhancer, which was refractory to hypertonic stress in fibroblasts lacking NFAT5, establishing this enhancer as a direct transcriptional target of NFAT5. Our findings demonstrate a central role for NFAT5 as a tonicity-responsive transcription factor required for kidney homeostasis and function.
The genes encoding the variable (V) region of the B-cell antigen receptor (BCR) are assembled from V, D (diversity), and J (joining) elements through a RAG-mediated recombination process that relies ...on the recognition of recombination signal sequences (RSSs) flanking the individual elements. Secondary V(D)J rearrangement modifies the original Ig rearrangement if a nonproductive original joint is formed, as a response to inappropriate signaling from a self-reactive BCR, or as part of a stochastic mechanism to further diversify the Ig repertoire. V H replacement represents a RAG-mediated secondary rearrangement in which an upstream V H element recombines with a rearranged V HD HJ H joint to generate a new BCR specificity. The rearrangement occurs between the cryptic RSS of the original V H element and the conventional RSS of the invading V H gene, leaving behind a footprint of up to five base pairs (bps) of the original V H gene that is often further obscured by exonuclease activity and N -nucleotide addition. We have previously demonstrated that V H replacement can efficiently rescue the development of B cells that have acquired two nonproductive heavy chain (IgH) rearrangements. Here we describe a novel knock-in mouse model in which the prerearranged IgH locus resembles an endogenously rearranged productive V HD HJ H allele. Using this mouse model, we characterized the role of V H replacement in the diversification of the primary Ig repertoire through the modification of productive V HD HJ H rearrangements. Our results indicate that V H replacement occurs before Ig light chain rearrangement and thus is not involved in the editing of self-reactive antibodies.
Significance The recombinatorial process of V(D)J rearrangement generates a vast antibody repertoire from a limited number of genes. The joints generated in the course of V(D)J recombination are imprecise thus yielding greater diversity but also resulting in frequent generation of nonproductive VDJ rearrangements. We have previously shown that B cells with two nonproductive IgH rearrangements can be efficiently rescued by a form of secondary V(D)J recombination called V H replacement. We now demonstrate that V H replacement also contributes to the diversity of the immune repertoire by modifying productive IgH rearrangements. Results presented herein suggest that V H replacement occurs exclusively during early stages of B-cell development and therefore does not contribute to the editing of self-reactive antibodies.
Effective clinical application of antiviral immunotherapies necessitates enhancing the functional state of natural killer (NK) and CD8+ T cells. An important mechanism for the establishment of viral ...persistence in the liver is the activation of the PD-1/PD-L1 inhibitory pathway. To examine the role of hepatic myeloid PD-L1 expression during viral infection, we determined the magnitude and quality of antiviral immune responses by administering PD-L1 short-interfering RNA (siRNA) encapsulated in lipidoid nanoparticles (LNP) in mice. Our studies indicate that Kupffer cells (KC) preferentially engulfed PD-L1 LNP within a short period of time and silenced Pdl1 during adenovirus and MCMV infection leading to enhanced NK and CD8+ T cell intrahepatic accumulation, effector function (interferon (IFN)-γ and granzyme B (GrB) production), CD8+ T cell–mediated viral clearance, and memory. Our results demonstrate that PD-L1 knockdown on KCs is central in determining the outcome of liver viral infections, and they represent a new class of gene therapy.
Abstract
The immune suppressive microenvironment is a major culprit for difficult-to-treat solid cancers. Particularly, inhibitory tumor-associated macrophages (TAM) define the resistant nature of ...the tumor milieu. To define tumor-enabling mechanisms of TAMs, we analyzed molecular clinical datasets correlating cell surface receptors with the TAM infiltrate. Though P-selectin glycoprotein ligand-1 (PSGL-1) is found on other immune cells and functions as an adhesion molecule, PSGL-1 is highly expressed on TAMs across multiple tumor types. siRNA-mediated knockdown and antibody-mediated inhibition revealed a role for PSGL-1 in maintaining an immune suppressed macrophage state. PSGL-1 knockdown or inhibition enhanced proinflammatory mediator release across assays and donors in vitro. In several syngeneic mouse models, PSGL-1 blockade alone and in combination with PD-1 blockade reduced tumor growth. Using a humanized tumor model, we observed the proinflammatory TAM switch following treatment with an anti-PSGL-1 antibody. In ex vivo patient-derived tumor cultures, a PSGL-1 blocking antibody increased expression of macrophage-derived proinflammatory cytokines, as well as IFNγ, indicative of T-cell activation. Our data demonstrate that PSGL-1 blockade reprograms TAMs, offering a new therapeutic avenue to patients not responding to T-cell immunotherapies, as well as patients with tumors devoid of T cells.
Significance:
This work is a significant and actionable advance, as it offers a novel approach to treating patients with cancer who do not respond to T-cell checkpoint inhibitors, as well as to patients with tumors lacking T-cell infiltration. We expect that this mechanism will be applicable in multiple indications characterized by infiltration of TAMs.
The immunoglobulin heavy chain repertoire is generated by somatic rearrangement of variable (V(H)), diversity (D(H)), and joining (J(H)) elements. It can be further diversified by V(H) replacement, ...where nonrearranged V(H) genes invade preexisting V(H)D(H)J(H) joints. To study the impact and mechanism of V(H) replacement, we generated mice in which antibody production depends on the replacement of a nonproductive V(H)D(H)J(H) rearrangement inserted into its physiological position in the immunoglobulin heavy chain locus. In these mice a highly diverse heavy chain repertoire resulted from V(H) replacement and a second process of noncanonical V(D)J recombination, direct V(H) to J(H) joining. V(H) replacement rarely generated detectable sequence duplications but often proceeded through recombination between the conserved homologous sequences at the 3' end of V(H). Thus, V(H) replacement is an efficient mechanism of antibody diversification, and its impact on the overall antibody repertoire could be greater than anticipated because it frequently leaves no molecular footprint.
Leukocytes are central regulators of inflammation and the target cells of therapies for key diseases, including autoimmune, cardiovascular, and malignant disorders. Efficient in vivo delivery of ...small interfering RNA (siRNA) to immune cells could thus enable novel treatment strategies with broad applicability. In this report, we develop systemic delivery methods of siRNA encapsulated in lipid nanoparticles (LNP) for durable and potent in vivo RNA interference (RNAi)-mediated silencing in myeloid cells. This work provides the first demonstration of siRNA-mediated silencing in myeloid cell types of nonhuman primates (NHPs) and establishes the feasibility of targeting multiple gene targets in rodent myeloid cells. The therapeutic potential of these formulations was demonstrated using siRNA targeting tumor necrosis factor-α (TNFα) which induced substantial attenuation of disease progression comparable to a potent antibody treatment in a mouse model of rheumatoid arthritis (RA). In summary, we demonstrate a broadly applicable and therapeutically relevant platform for silencing disease genes in immune cells.
Inflammation occurs in the context of integrin-mediated adhesive interactions of cells with their extracellular matrix environment. We investigated the role of the collagen binding integrin α1β1 in a ...model of colitis. α1β1 was expressed on lamina propria T cells and monocytes during disease. Both α1 deficiency and anti-α1 mAb treatment (prophylactic and therapeutic) protected against colitis. In vivo α1β1 blockade improved macroscopic and histologic scores, decreased inflammatory cytokine production, and profoundly affected the ability of lamina propria mononuclear cells to proliferate and produce IFN-γ in vitro. Development and α1-mediated inhibition of colitis can be lymphocyte independent, suggesting that activated monocytes also represent a key α1β1-expressing cell type involved in colitis. These results underscore the importance of innate immunity and, specifically, of leukocyte/matrix interactions in regulating local inflammatory responses.
Monoallelic demethylation and rearrangement control allelic exclusion of the immunoglobulin kappa-chain locus (Igk locus) in B cells. Here, through the introduction of pre-rearranged Igk genes into ...their physiological position, the critical rearrangement step was bypassed, thereby generating mice producing B cells simultaneously expressing two different immunoglobulin-kappa light chains. Such 'double-expressing' B cells still underwent monoallelic demethylation at the Igk locus, and the demethylated allele was the 'preferred' substrate for somatic hypermutation in each cell. However, methylation itself did not directly inhibit the activation-induced cytidine-deaminase reaction in vitro. Thus, it seems that the epigenetic mechanisms that initially bring about monoallelic variable-(diversity)-joining rearrangement continue to be involved in the control of antibody diversity at later stages of B cell development.
V(D)J recombination at the immunoglobulin heavy chain (IgH) locus follows the 12/23 rule to ensure the correct assembly of the variable region gene segments. Here, we report characterization of an in ...vivo model that allowed us to study recombination violating the 12/23 rule, namely a mouse strain lacking canonical D elements in its IgH locus. We demonstrate that VH to JH joining can support the generation of all B cell subsets. However, the process is inefficient in that B cells and antibodies derived from the DH-less allele are not detectable if the latter is combined with a wild-type IgH allele. There is no preferential usage of any particular VH gene family or JH element in VHJH junctions, indicating that 23/23-guided recombination is possible, but is a low frequency event at the IgH locus in vivo.
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