Metabolic Engineering of Cancer for Selective Immunotargeting

描述(申请人提供)：针对选择性免疫靶向的代谢工程癌症是最常见和致命的疾病之一，一般来说，它很难治愈。在探索的不同癌症治疗策略中，使用癌症疫苗或癌症靶向抗体治疗癌症患者特别有吸引力，因为人类免疫系统可以非常有效和选择性地消除人体内的肿瘤。在用于患者免疫或抗体制备的癌症疫苗的开发中，癌细胞表达的异常糖链被称为肿瘤相关碳水化合物抗原(TACA)，因为它们在癌细胞表面丰富、暴露和保守，是有价值的分子靶点。然而，问题是TACA通常免疫原性差或患者的免疫系统耐受性差，这严重阻碍了基于TACA的功能性癌症疫苗或免疫疗法的交付。为了解决这一问题并开发有效的癌症治疗方法，提出了一种新的免疫治疗策略。首先，用非天然TACA衍生物制成的疫苗对动物(或患者)进行免疫，以引发特定的免疫反应。接下来，用类似的修饰的单糖处理动物，以使肿瘤细胞表达非天然的TACA衍生物(癌细胞糖工程)。然后，经过训练的免疫系统将专门识别和杀死糖工程肿瘤。新的免疫疗法也可以用TACA衍生物特异性抗体来实现，而不是用疫苗来治疗。要使该策略发挥作用，它必须满足两个条件，即可用于患者免疫或抗体制备的有效疫苗和用于癌细胞糖工程的有效方法。已有研究证明，后者可以利用灵活的生物合成途径来合成多聚糖。为了创造有效和可靠的基于TACA的疫苗，这里提出了一种新的疫苗策略，即将TACA与细菌单磷脂A(MPLA)相连。假设Mpla可以作为一种强大的疫苗载体和内置佐剂来研制完全合成的、自我佐剂的、结构明确的、易于复制的和强大的糖结合疫苗。这项建议旨在：(1)研究MPLA的构效关系，寻找新的、有效的疫苗载体和佐剂；(2)制备和研究TACA-MPLA结合物的免疫学性质，寻找合适的癌症免疫治疗疫苗；(3)通过上述治疗策略，将新的TACA-MPLA结合物用作主动和被动免疫治疗黑色素瘤和乳腺癌、结肠癌等癌症的疫苗。该项目的一个创新之处是将聚乳酸作为载体和佐剂用于全合成自佐剂碳水化合物疫苗的开发和相关研究。另一项创新是将MPLA结合疫苗与细胞糖工程相结合用于癌症治疗。这种结合将解决TACA的免疫耐受问题，这是癌症免疫学的核心问题，并有助于开发各种肿瘤的功能性治疗方法。新的疫苗策略也将适用于其他疫苗设计。因此，这两种策略都应该是广泛有用的，这一研究计划应该具有普遍意义，并对癌症研究产生广泛影响。

DESCRIPTION (provided by applicant): Metabolic Engineering of Cancer for Selective Immunotargeting Cancer is one of the most common and fatal diseases and, in general, it is difficult to cure. Among the different strategies probed for cancer therapy, treating cancer patients with cancer vaccines or cancer-targeting antibodies is especially attractive as the human immune system can be extremely effective and selective to eliminate tumors in the human body. In the development of cancer vaccines used for patient immunization or antibody preparation, the abnormal glycans expressed by cancer cells, called tumor-associated carbohydrate antigens (TACAs), are valuable molecular targets, as they are abundant, exposed, and conserved on the cancer cell surface. However, the problem is that TACAs are usually poorly immunogenic or tolerated by the patients' immune system, which has severely hindered the delivery of functional TACA-based cancer vaccines or immunotherapies. To address the problem and develop effective cancer cures, a new immunotherapeutic strategy was proposed. First, animals (or patients) are immunized with a vaccine made of an unnatural TACA derivative to elicit a specific immune response. Next, the animals are treated with a similarly modified monosaccharide to bioengineer tumor cell expression of the unnatural TACA derivative (cancer cell glycoengineering). Then, the trained immune system will specifically recognize and kill the glycoengineered tumors. The new immunotherapy can also be realized with a TACA derivative-specific antibody, instead of a vaccine, for the treatment. For the strategy to work, it has to mee two conditions, namely, a potent vaccine that can be used for patient immunization or antibody preparation and an effective method for cancer cell glycoengineering. It has been proved that the latter can exploit the flexible biosynthetic pathways for glycans. To create potent and reliabl TACA-based vaccines, a new vaccine strategy is proposed here, namely, to have TACAs linked to a bacterial monophosphoryl lipid A (MPLA). The hypothesis is that MPLA can act as a powerful vaccine carrier and built-in adjuvant to formulate fully synthetic, self-adjuvanting, structurally defined, readily reproducible, and robust glycoconjugate vaccines. This proposal aims to: (1) study the structure-activity relationship of MPLAs and identify new, potent vaccine carriers and adjuvants, (2) prepare and study the immunological properties of TACA-MPLA conjugates and identify the proper vaccines for cancer immunotherapy, and (3) use the new TACA-MPLA conjugates as vaccines for active and passive immunotherapy of cancer such as melanoma and breast or colon cancer by the above therapeutic strategy. One innovation of this project is the use of MPLA as a carrier and adjuvant for fully synthetic self-adjuvanting carbohydrate vaccine development and related studies. Another innovation is the combination MPLA conjugate vaccine with cell glycoengineering for cancer therapy. This combination will solve the immunotolerance problem of TACAs, a central issue in cancer immunology, and help develop functional cures for various tumors. The new vaccine strategy will be applicable to other vaccine design as well. Thus, both strategies should be widely useful, and this research program should be of general significance and have a broad impact on cancer research.