The immune system has evolved to achieve a fine balance between recognizing and attacking foreign pathogens and preserving unresponsiveness to self-antigens. T cells that are unresponsive to self-antigens are called self-tolerant T cells and a hallmark of such tolerant T cells is their inability to attack cells expressing self-antigens in order to prevent autoimmunity. However, tolerance to these proteins impedes anti-tumor T cell immune responses because many cancer antigens that are targeted in immunotherapy are in fact self-antigens. Thus, a critical challenge in tumor immunology is to develop strategies that break T cell tolerance to tumor antigens without causing unacceptable autoimmune injury. It has been shown that tolerant T cells lack important proteins normally required for T cell effector functions, including two master transcription factors, Tbet and Eomes, which have been found to be critical for T cell function by repressing the expression of inhibitory molecules and mediating the expression of effector molecules. Therefore, the decreased expression of Tbet and Eomes in tolerant T cells might cause their functional unresponsiveness. Using a transgenic tumor mouse model, my research project investigates if enforced over-expression of Tbet and/or Eomes in tolerant tumor-specific T cells can re-program such tolerant T cells and restore effector functions, allowing re-programmed T cells to recognize and attack cancer cells. Tolerant T cells will be isolated from spleens of transgenic mice, retrovirally transduced in vitro to over-express Tbet and Eomes, and subsequently transferred into tumor-bearing mice. The main focus of my research will then be to analyze Tbet-, Eomes-, and/or control-transduced donor T cells for anti-tumor effector function in vivo to understand if and by what mechanism(s) T cells can be re-programmed via the over-expression of the master transcription factors and whether such re-programming could possibly become an effective strategy for the treatment of cancers in humans.