Self-sufficient primary natural killer cells to express a T cell receptor and interleukin-15 exhibit improved effector functions and prevent tumor immune evasion in Multiple Myeloma
TCR-engineered cells can be powerful tools in the treatment of malignancies. In contrast to CAR-engineered cells, TCR-engineered cells can recognize intracellular peptides presented in HLA-class I molecules, thereby broadening the potential tumor specific targets. One potential target candidate for TCR therapy in Multiple Myeloma is BOB1, a transcription factor highly expressed in all healthy and malignant B-cell lineages. Previous research showed that Multiple Myeloma cells cannot survive when BOB1 is not expressed, which prevents immune escape of the tumor cells by downregulating this target. However, tumor-resistance by HLA-class I downregulation can still negatively-impact the success of any TCR-mediated cell therapy. To overcome this, TCR therapy can be combined with NK therapy. Allogeneic NK-cells have demonstrated efficacy and safety against malignancies without inducing GvHD highlighting the feasibility for an “off the shelf” cellular therapeutic. They are capable of recognizing HLA-negative tumors, using a broad array of intrinsic activation mechanisms. However, expansion and survival of NK cells relies on the presence of cytokines, especially interleukin-15. This dependence on interleukin-15 may hamper NK cell persistence in vivo and consequently, the success of NK cell therapies. In here, we combined the anti-tumor effector functions of NK cells with TCR-engineering (NK:TCR), producing endogenous soluble interleukin-15, creating a novel therapeutic strategy to avoid TCR-associated immune resistance.
Expression of an HLA-B*07:02 restricted BOB1-specific TCR and the interleukin-15 gene in peripheral blood derived NK-cells was achieved following a 3-week retroviral transduction protocol. NK:BOB1-TCR/IL-15 cells were compared with control NK:BOB1-TCR and NK:CMV-TCR/IL-15 cells for effector function against HLA-B*07:02+ multiple myeloma and other malignant B-cell lines in vitro and in vivo.
Firstly, the TCR could be reproducibly expressed in NK-cells isolated from peripheral blood of multiple healthy donors generating pure NK:BOB1-TCR cell products. Secondly, NK:BOB1-TCR cells demonstrated antigen-specific effector functions against malignancies which were previously resistant to NK-mediated lysis and enhanced NK-efficacy in vivo using a preclinical xenograft model of multiple myeloma. Furthermore, in a model of HLA-class I loss, tumor cells with β-2-microglobulin knock-out were lysed by NK:BOB1-TCR in an NK-mediated manner while resistant to T-cell based killing. Viral incorporation of the interleukin-15 gene (NK:BOB1-TCR/IL-15) demonstrated a marked enhancement of TCR-mediated cytotoxicity as well as enhanced NK-mediated cytotoxicity resulting in improved persistence and performance of NK:BOB1-TCR/IL-15 compared to NK:BOB1-TCR in an orthotopic multiple myeloma mouse model.
NK:BOB1-TCR/IL-15 cell therapy enhances NK-cell efficacy and provides additional TCR-mediated lysis of Multiple Myeloma. Distinctively, the dual efficacy of NK:BOB1-TCR permits specific tumor targeting and the bypassing of TCR-associated immune-resistance, making NK:BOB1-TCR/15 cells a unique cellular therapeutic.