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

摘要：T细胞的高度特异性、幅度和质量决定了肿瘤的发生、发展和对治疗的反应。最具革命性和前景的两种免疫疗法是免疫检查点阻断和过继细胞转移，这两种疗法都依赖于细胞毒性T效应细胞(TJeff)的强大参与来控制或根除癌症。强大的T细胞介导的抗肿瘤反应需要营养和能量供应与Tef细胞的扩增和功能的协调。然而，肿瘤细胞的高代谢需求通过在肿瘤微环境(TME)内竞争营养物质来损害TJeff细胞的功能。我们认为，限制患者对免疫治疗反应的关键障碍是肿瘤内充满敌意的代谢微环境。我们以前已经证明，在T细胞激活和分化过程中，转录因子c-Myc和HIF1α是驱动中央碳代谢程序的不同需要。我们最近发现天冬酰胺(ASN)是T细胞激活时最上调的氨基酸，它的生物利用度代表着一个关键的代谢节点，它调控着TEF细胞的中心碳代谢和效应功能。一些癌细胞仅依靠细胞外ASN来支持生长和增殖，这代表了癌症的代谢脆弱性。然而，TJeff细胞可以通过摄取细胞外ASN或通过ASN的从头合成来维持细胞内ASN池的生长和功能，这表明T细胞具有一层代谢可塑性。对细胞外ASN的强制限制使中心碳分解代谢程序重新连接，从而增强了TJeff细胞的抗肿瘤效应功能。此外，这些TJeff细胞的特征是ATF4和Nrf2信号反应增强。因此，我们假设ASN生物利用度的调节可以优化碳同化和整合应激反应信号通路，从而在代谢受限的肿瘤微环境中实现强大的抗肿瘤反应。为了验证我们的假设，我们建议1)破译中央碳代谢途径的重新编程，并在ASN限制的背景下评估关键代谢步骤对TJeff细胞的影响；2)确定ATF4/Nrf2轴在调节TJeff细胞效应功能中的作用；3)针对关键信号和代谢节点来设计中央碳分解程序，从而增强TJeff细胞的功能和持久性；以及4)开发和测试策略，以同时利用ASN依赖作为癌细胞的代谢脆弱性，并最大限度地提高系统抗肿瘤免疫。总而言之，该项目的完成将揭示肿瘤微环境、细胞代谢和抗肿瘤免疫之间新出现的联系的基本原理。这些研究对于开发新的方法，大幅改善癌症免疫治疗的临床结果至关重要。

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.