Developing autologous organoid and humanized mouse models with thymic T cell education capacity to test head and neck cancer immunotherapy

About This Grant

SUMMARY. The programmed death receptor 1 (PD-1) drives immune escape in head and neck squamous cell cancer (HNSCC), whose incidence is rising due to human papillomavirus (HPV). PD-1 inhibitors (PD-1i) are in use in many cancers including both resectable HPV-neg and recurrent/metastatic (R/M) HPV-pos and -neg HSNCC, but most patients do not respond. Limitations in studying immunotherapy include the scarcity of models providing key aspects of human adaptive immunity, such as 1) systems where the tumor and immune system are partially or fully matched, and 2) thymic education necessary for T cell recognition to occur. In recently reported work we reprogrammed peripheral blood mononuclear cells (PBMCs) and cancer-associated fibroblasts (CAFs) from melanoma and HNSCC patients into induced pluripotent stem cells (iPSC). Next, we developed a novel protocol to differentiate patient iPSCs into functional isogenic multicellular stem cell derived thymic organoids (sTOs) by combining TEPs, mesenchymal cells and hematopoietic lymphoid progenitor cells generated from the same iPSC line. sTOs can educate developing T cells, both via positive and negative selection. The key advantage of sTOs is that they can be used both as organoids to generate T cells for testing in vitro and can also be implanted in humanized mice (HM) to test immunotherapies in vivo. The sTO produces T cells that are educated isogenically; after activation and exposure to PD-1i and other immune checkpoint inhibitors (ICI) these T cells can be co-cultured with autologous cancer cells to generate organoids (iSpheres). This cancer and T cell interaction tests immune-directed therapies in a patient specific manner, and by using controls that are not autologous (both cancer and T cells) the contribution of thymic education can be accurately dissected. Then we will produce cohorts of thymectomized HM, with HLA-matched cord blood derived HSCs, that will be transplanted with sTOs and patient-derived xenografts (PDX) from the same patient. This results in functional maturation of thymic tissue in vivo, education of developing T cells, peripheral migration, and tumor infiltration in an isogenic manner. We recently published results showing a delay in tumor growth in HM bearing sTO, but not in HM with mouse thymus, which we hypothesize is due to improved T cell education in matched thymi, a proof of principle observation. We have a large, developing collection of patient-matched PBMCs, CAFs, iPSC, cancer cell lines and PDX from HNSCC patients that will be used to develop a first set of ~10 in vitro and in vivo testing tools. We will then test this approach prospectively on models generated from ~10 patients receiving PD-1i. This plan has the potential of identify rational ICI selection strategy and allow testing the value of thymic education in cancer immunology. Neoantigen (neoAg) profiling of PD-1i-susceptible vs resistant cases to identify neoAg that are immunogenic adds a mechanistic layer. This project will focus on creating in vitro and in vivo patient-derived tools with T cell education to test mechanisms of therapy response in HNSCC, and will provide innovative mechanistic insights at the immunologic and molecular level of immune response.