Modulation of asparagine bioavailability and stress response signaling to enhance T cell robustness and maximize immunotherapy

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Summary: The exquisite specificity, amplitude, and quality of T cells govern tumor initiation, progression, and responses to therapy. Two of the most revolutionary and promising immunotherapies are the immune checkpoint blockade and the adoptive cell transfer, which are both dependent on the robust engagement of cytotoxic T effector (Teff) cells to control or eradicate cancer. A robust T cell-mediated anti-tumor response requires the coordination of nutrient and energy supplies with Teff cell expansion and function. However, the high metabolic demands of tumor cells compromise the function of Teff cells by competing for nutrients within the tumor micro-environment (TME). We propose that the critical barrier, which limits the patient’s response to immunotherapy, is the hostile metabolic microenvironment within tumors. We have previously shown that the transcription factors c-Myc and HIF1alpha are differentially required for driving the central carbon metabolic programs during T cell acti-vation and differentiation. We recently revealed that asparagine (Asn) is the most upregulated amino acid upon T cell activation, and its bioavailability represents a key metabolic node that governs the central carbon metab-olism and effector function in Teff cells. Some cancer cells solely rely on extracellular Asn to support growth and proliferation, representing a metabolic vulnerability of cancer. However, Teff cells can maintain an intracellular Asn pool for cell growth and function either through the uptake of extracellular Asn or through de novo biosyn-thesis of Asn, indicating a layer of metabolic plasticity of T cells. Enforced restriction of extracellular Asn rewires central carbon catabolic programs, leading to enhanced anti-tumor effector function in Teff cells. Moreover, these Teff cells are characterized by an enhanced ATF4 and Nrf2 signaling response. Hence, we hypothesize that modulation of Asn bioavailability can optimize carbon assimilation and integrate stress-response sig-naling pathways, enabling a robust anti-tumor response in metabolically restricted tumor microenviron-ments. To test our hypothesis, we propose to 1) decipher the reprogramming of central carbon metabolic path-ways and assess the impact of key metabolic steps on Teff cells in the context of Asn restriction; 2) determine the role of ATF4/Nrf2 axis in regulating the effector function of Teff cells; 3) target critical signaling and metabolic nodes to engineer central carbon catabolic programs, thus enhancing function and persistence of Teff cells, and 4) develop and test strategies to simultaneously exploit Asn dependence as a cancer cell metabolic vulnerability and maximize systemic anti-tumor immunity. Collectively, the completion of this project will reveal fundamental principles of the emerging connections between the tumor’s microenvironment, cell metabolism, and anti-tumor immunity. These studies are critical to developing novel approaches that improve clinical outcomes of cancer immunotherapy substantially.