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Multiplexed activation of endogenous genes by CRISPRa elicits potent anti-tumor immunity

ABSTRACT: Immunotherapy has transformed cancer treatment. However, current immunotherapy modalities face many limitations. Here, we developed a new form of immunotherapy that elicits anti-tumor immunity through multiplexed activation of endogenous genes. We leveraged the CRISPR activation (CRISPRa) system to directly augment the in situ expression of endogenous genes, and thereby the presentation of tumor antigens, leading to dramatic anti-tumor immune responses. Deploying this as a cell-based vaccination strategy showed efficacy in both prophylactic and therapeutic settings. Intratumoral adeno-associated virus delivery of CRISPRa libraries elicited strong anti-tumor immunity across multiple cancer types. Precision targeting of mutated gene sets eradicated a large fraction of established tumors at both local and distant sites. This treatment modality led to alterations of the tumor microenvironment, marked by enhanced T cell infiltration and anti-tumor immune signatures. Multiplexed endogenous gene activation may serve as a versatile and highly scalable strategy to elicit potent immune responses against cancer.

ORGANISM(S): Mus musculus

PROVIDER: GSE133983 | GEO | 2020/04/14

REPOSITORIES: GEO

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Project description:Background: Dystrophic epidermolysis bullosa (DEB) is a skin blistering disease caused by mutations in COL7A1, which encodes type VII collagen (C7). There is no cure for DEB, but previous work has shown potential therapeutic benefit in increasing production of even partially functional C7. Genome-wide screens using CRISPR-Cas9 have enabled the identification of genes involved in cancer development, drug resistance, and other genetic diseases, suggesting that they could be used to identify novel drivers of C7 production. Methods: A keratinocyte C7 reporter cell line was created by integrating a tdTomato fluorescent marker into the last exon of the endogenous COL7A1 gene. A genome-wide CRISPR activation (CRISPRa) screen was performed with the C7_tdTomato reporter to identify genes and pathways that increase C7 expression. High tdTomato-expressing cells were sorted and sequenced to identify the single guide RNAs (sgRNAs) that became enriched relative to the starting material. Pathway analysis was performed on the corresponding genes to identify regulators and pathways that influence C7 expression. A targeted drug screen was performed in three different keratinocyte cell lines based on the CRISPRa screen results, and C7 upregulation was evaluated. Results: The C7_tdTomato cell line was validated as an effective reporter cell line for detection of C7 upregulation. The CRISPRa screen identified two genes, DENND4B and TYROBP as top hits based on enrichment in the high fluorescence population and representation with multiple sgRNAs. Pathway analysis of the CRISPRa screen showed enrichment of toll-like receptor and interferon-related upstream regulators and functions related to calcium uptake and immune signaling. Several compounds in the targeted drug screen increased C7 expression in at least one keratinocyte line, but only kaempferol, a plant flavonoid, significantly increased C7 mRNA and protein in a DEB patient line. Conclusions: The novel C7_tdTomato reporter cell line can be used to screen compounds for increased C7 expression. The CRISPRa screen combined with a fluorescent reporter cell line can be used to reveal mechanistic regulators of gene expression and therapeutic targets for rare genetic diseases. Kaempferol has shown promising results in increasing C7 production and should be further evaluated as a potential therapeutic for DEB patients.

Project description:The interaction of neoplastic cells with their tumor microenvironment (TME) is required for cancer progression. However, in vitro cancer models, including recent in vitro 3-dimensional (3D) organoid cultures of primary human tumors, are typically comprised exclusively of neoplastic epithelium, with stromal and/or immune interactions requiring artificial reconstitution. As relevant to cancer immunotherapy, the unified co-culture of primary tumor epithelia with their endogenous, syngeneic tumor-infiltrating lymphocytes (TILs) as a cohesive unit has remained particularly elusive. Here, we used a single 3D air-liquid interface (ALI) methodology to successfully propagate 3D Patient-Derived Tumor Organoids (PDOs) as primary tumor epithelia together with native immune and myofibroblast stromal compartments without reconstitution. Derived from >100 diverse human surgically resected tumor samples or from murine tumors in syngeneic immunocompetent mice, PDOs preserved cancer histologic subtypes and mutational spectrum with endogenous T, B, NK cells and macrophages integrally embedded amidst the tumor epithelium. PDO-based TILs accurately recapitulated the T cell receptor (TCR) spectrum of the original tumors, as determined by a robust droplet-based immune profiling solution that links gene expression and immune repertoire in single cells. Anti-PD-1 or anti-PD-L1 treatment of organoids from murine tumors from syngeneic immunocompetent hosts induced activation and cytolytic activity of tumor antigen-specific TILs, indicating successful PDO modeling of immune checkpoint blockade (ICB) and anti-tumor immunity. Crucially, the anti-PD-1 antibody nivolumab activated TILs in PDOs from human lung, renal and melanoma clinical tumor resections. The organoid-based propagation of primary tumor epithelium en bloc with its endogenous immune stroma should facilitate mechanistic investigation of TME-specific local tumor immunity, with applications for functional testing of individualized patient immunotherapy responses.

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Multiplexed activation of endogenous genes by CRISPRa elicits potent anti-tumor immunity

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