Reversing Exhaustion of Anti-Sarcoma T cells
SPECIFIC AIMS. Immunotherapy is a promising treatment approach, but at least two immunologic phenomena—antigen escape and T cell exhaustion—are emerging as key biologic obstacles to effective immunotherapy for most solid cancers. Antigen escape occurs when there is partial or complete loss of tumor antigen. One way to overcome antigen escape is to treat patients with a polyclonal repertoire of anti-tumor T cells procured from tumor itself. This approach—called TIL (tumor-infiltrating lymphocyte) therapy—involves surgically removing a tumor, isolating and growing T cells ex vivo, and re-infusing them back into the patient. Although TIL therapy can result in complete and durable responses in up to 20% of patients, most patients will ultimately progress and die of disease. In patients with a complete and durable response it has been shown that transfer of T cells with stem-like properties that can self-renew and persist is essential. Unfortunately, the majority of TIL isolated from the tumor microenvinment do not have stem-like features, but are dysfunctional or “exhausted”. Exhaustion is an epigenetically mediated cellular differentiation step wherein continued T cell receptor (TCR) signaling reshapes the chromatin landscape to constrain stemness, proliferation, and effector functions. Therefore, there is a critical need for strategies to promote stemness and overcome exhaustion to improve TIL therapy for sarcoma patients. Our long term goal is to improve the efficacy of T cell mediated therapy for patients with sarcoma. Our overall objective in this proposal is to develop an approach to reverse exhaustion and promote stemness in TIL. Our central hypothesis is that the epigenetic machinery enforcing exhaustion can be reset using transcription factor reprogramming and TIL can then be re-differentiated into mature stem-like T cells using an artificial thymic organoid (ATO). The rationale for this project is that these findings can be used to reverse exhaustion and improve efficacy of a polyclonal populations of anti-tumor T cells for patients with sarcoma. The two following specific aims are proposed: Aim 1: Evaluate the impact of transcription factor reprogramming and an artificial thymic organoid to transform TIL into tumor-specific naïve T cells. We hypothesize that the epigenome of terminally differentiated TIL can be reset through de-differentiation into induced pluripotent stem cells (iPSCs) using Yamanaka transcription factors and subsequently re-differentiated into mature naïve T cells with renewed stem-like capacity using our ATO. Aim 2: Assess the capacity of reprogrammed T cells to provide durable anti-tumor immunity. Polyclonal re-differentiated CD8 T cells with restored stemness and anti-tumor function will be adoptively transferred in a series of mouse models to test if this strategy improves tumor control in vivo and if reprogrammed CD8 T cells can establish long-lived memory for durable tumor control.