Antigen-specific T cells engineered with nanoparticle photothermal therapy demonstrate antitumor efficacy in an immunocompetent murine model of ovarian cancer

Ovarian cancer (OC) is the most lethal gynecological malignancy with less than a 10% response rate to immune checkpoint blockade. Personalized vaccination with tumor lysate-pulsed dendritic cells amplifies T cell responses, including neoepitope-specific T cells, but is not curative. Thus, amplifying the pre-existing tumor-specific T cell response is insufficient. We developed a novel method to expand T cells ex vivo for OC specificity using Prussian Blue nanoparticle-photothermal therapy (PBNP-PTT), and verified in vivo efficacy using a syngeneic murine model. PBNP-PTT -generated ID8 OC cell lysate was used to stimulate bone marrow-derived dendritic cells (BMDCs) isolated from healthy female C57Bl6 mice. Autologous splenic CD3+ T cells were cocultured ex vivo with BMDCs and assessed in vitro for tumor-specific activation and killing using IFNy ELISpot and MTS cytotoxicity assays. Congenic mice bearing ID8B OC cells received either ex vivo expanded T cells or nonspecifically expanded T cells, and the accumulated ascites was profiled for cytokine composition. Adoptively transferred T cells were immunophenotyped with spectral flow cytometry.Ex vivo expansion of T cells with DCs primed using PBNP-PTT-generated OC cell lysate produced a pool of CD8+ T cells with enhanced IFNy and TNFa secretion in tumor coculture compared to nonspecifically expanded T cells. PBNP-PTT-expanded T cells exhibited greater tumor cell killing at increasing effector-to-target ratios and did not demonstrate off-target IFNy secretion. Tumor-bearing female C57Bl6 mice receiving OC-expanded T cells lived significantly longer and exhibited decreased tumor burden compared to mice receiving nonspecific T cells. Adoptively transferred T cells expanded with PBNP-PTT lysate also persisted longer in vivo with maintained activation in the ascites, and synergized with concurrent epigenetic therapy to further prolong survival. Ex vivo expansion methods using PBNP-PTT were also applied to healthy human blood donors to generate human T cells that demonstrate potent activation when challenged with human OC cell lines. In summary, we developed a novel method of engineering T cells ex vivo for specificity against ovarian cancer using nanoparticle photothermal therapy. This study is the first to harness PBNP-PTT ex vivo to demonstrate antitumor activity in vivo using an autologous mouse model of ovarian cancer.