{
  "abstract": "Background In the hypoxic tumor microenvironment, ATP released by cancer cells is converted to adenosine by the CD39-CD73 axis. CD73 is overexpressed in several cancers, including multiple myeloma, where it increases adenosine levels, thereby enhancing tumor cell metabolism and suppressing antitumor immune responses. Specifically, adenosine binds to the A2AR receptor on natural killer (NK) cells and downregulates their proliferation and cytotoxic activity. We previously demonstrated that targeting CD73 in solid tumors through CD73-CAR-NK cells resulted in potent antitumor activity in vivo. 1 Multiple myeloma is a plasma cell cancer that develops in the bone marrow and remains incurable, as most patients relapse despite therapeutic advances. This study aims to evaluate the potential of targeting CD73 using engineered NK cells to induce effective NK cell antitumor activity against myeloma.Methods We validated the expression of CD73 on myeloma cells, including the myeloma cell line U266B1, by flow cytometry. Using a monoclonal antibody (mAb), we evaluated the effect of CD73 blockade on the cytotoxic activity and activation, via IFN-γ release, of human NK cells against myeloma. We further assembled a CD73 CAR, composed of neutralizing CD73 scFv and NK-specific transmembrane and intracellular signaling domains derived from FCγRIIIa (CD16), to generate CD73-CAR-NK cells. We are evaluating their efficacy against myeloma and their activation capacity upon CAR expression.Results Our results confirmed the expression of CD73 on U266B1 cells at high levels (>90%). Treatment with CD73 mAb had a significant cytotoxic effect against U266B1 cells in the absence of NK cells, suggesting that blocking this ectoenzyme has a direct metabolic effect that impairs cell viability. Cytotoxicity was further increased in co-culture with NK cells, indicating that there is a synergistic effect between the antitumoral activity of CD73 blockade and NK cells. Blocking CD73 did not affect IFN-γ release, which suggests that CD73 blockade enhances NK cell-mediated cytotoxicity through mechanisms independent of IFN-γ production. We have engineered NK cells to express a CD73 CAR and showed that this construct is effective in blocking CD73 activity and enhancing NK cell activity. CD73-CAR-NK cells are being evaluated against myeloma targets, with ongoing studies aimed at establishing toxicity, efficacy and sustained NK cell responses in myeloma in vitro and in vivo.Conclusions These results support CD73 as a therapeutic immunometabolic target against multiple myeloma to impair tumor cell metabolism and enhance NK cell-mediated cytotoxicity. Ongoing experiments are providing further insights into the potential of CD73-directed immunotherapeutic strategies for targeting multiple myeloma.Reference Chambers AM, Lupo KB, Wang J, Cao J, Utturkar S, Lanman N, Bernal-Crespo V, Jalal S, Pine SR, Torregrosa-Allen S, Elzey BD, Matosevic S. Engineered natural killer cells impede the immunometabolic CD73-adenosine axis in solid tumors. eLife. 2022;11:e73699",
  "authors": [
    {
      "affiliations": [
        "Purdue University, West Lafayette, IN, USA"
      ],
      "name": "Valentina Andrade Perez"
    },
    {
      "affiliations": [
        "Purdue University, West Lafayette, IN, USA"
      ],
      "name": "Shambhavi Borde"
    },
    {
      "affiliations": [
        "Purdue University, West Lafayette, IN, USA"
      ],
      "name": "Kumar Rishabh"
    },
    {
      "affiliations": [
        "Purdue University, West Lafayette, IN, USA",
        "Purdue Institute for Cancer Research, West Lafayette, IN, USA"
      ],
      "name": "Sandro Matosevic"
    }
  ],
  "title": "196 Targeting the CD73 immune checkpoint for NK cell-based therapy for myeloma",
  "uid": "9ec8648d-18b7-5266-9775-e6be9f4d0aff"
}