{
  "abstract": "Background Non-small cell lung cancer (NSCLC) frequently evades immune surveillance through defective antigen presentation and a suppressive tumor microenvironment (TME), limiting the efficacy of immune checkpoint blockade (ICB). Conventional type 1 dendritic cells (cDC1s) are essential for initiating antitumor CD8 + T-cell responses; however, their abundance and function are often diminished in NSCLC, contributing to poor outcomes and resistance to immunotherapy. We hypothesized that in situ vaccination (ISV) using gene-modified cDC1s engineered to secrete FMS-like tyrosine kinase 3 ligand (FLT3L) would enhance cDC1 function within the TME, promote antitumor immunity, and improve responses to ICB.Methods Syngeneic murine models of NSCLC ( Kras G12D/P53-/-/Lkb1−/−; KrasG12D/P53-/- ; and KrasG12D ) with varying tumor mutational burden, along with the MC38 model, were used to assess the therapeutic efficacy of FLT3L-cDC1 ISV. Flow cytometry and multiplex immunofluorescence were used to evaluate immune mechanisms of response. To assess translational relevance, immune and tertiary lymphoid structure (TLS) signatures were analyzed in The Cancer Genome Atlas (TCGA) NSCLC datasets, with TLS signatures refined using a retrained xCell2 framework incorporating curated TLS and high endothelial venule (HEV) microdissection datasets.Results FLT3L-cDC1 ISV remodeled the TME across multiple NSCLC models, inducing T lymphocyte infiltration and expanding cytolytic CD8 + T cells. FLT3L-cDC1 ISV was associated with increased formation of immature TLS with primary follicle-like features within the TME. TCGA analyses revealed that FLT3L expression correlates with activated DC, T cell, and B cell signatures, as well as HEV-enriched TLS-associated programs. Combination with PD-1 blockade further enhanced the antitumor immunity of FLT3L-cDC1 ISV, resulting in robust local and systemic T-cell activation and the expansion of activated CCR7+PD-L1+ cDC1s and stem-like TCF1+PD-1+ CD8+ progenitors within the TME. In an LKB1-deficient NSCLC model, FLT3L-cDC1 ISV plus PD-1 blockade induced complete and durable regression in 85% of tumors, leading to long-lasting systemic tumor-specific immune memory, consistent with effective tumor vaccination.Conclusions FLT3L-cDC1 ISV represents a rational cytokine-enhanced cellular immunotherapy designed to overcome immunosuppression and restore DC function within the TME, thereby promoting tumor-specific adaptive immune responses and enhancing responsiveness to ICB.",
  "authors": [
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Jensen Abascal"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Camelia Dumitras"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA",
        "VA Greater Los Angeles Healthcare System, Los Angeles, California, USA"
      ],
      "name": "Linh M Tran"
    },
    {
      "affiliations": [
        "Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "William Crosson"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Bitta Kahangi"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA",
        "VA Greater Los Angeles Healthcare System, Los Angeles, California, USA"
      ],
      "name": "Michael Oh"
    },
    {
      "affiliations": [
        "Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Austin Rennels"
    },
    {
      "affiliations": [
        "Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Raymond J Lim"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Hong Jiang"
    },
    {
      "affiliations": [
        "UCLA, Los Angeles, California, USA"
      ],
      "name": "Diana Reyimjan"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Nalani J Coleman"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Edgar Perez-Reyes"
    },
    {
      "affiliations": [
        "Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Samantha Chin"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Kostyantyn Krysan"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA",
        "VA Greater Los Angeles Healthcare System, Los Angeles, California, USA",
        "Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Steven M Dubinett"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA"
      ],
      "name": "Bin Liu"
    },
    {
      "affiliations": [
        "Department of Medicine, David Geffen School of Medicine, Los Angeles, California, USA",
        "VA Greater Los Angeles Healthcare System, Los Angeles, California, USA"
      ],
      "name": "Ramin Salehi-Rad"
    }
  ],
  "title": "FLT3L-secreting cDC1 in situ vaccination enhances antitumor immunity and synergizes with PD-1 blockade in murine non-small cell lung cancer",
  "uid": "7254e255-27aa-50e0-973e-fa914aa48b73"
}