Understanding methionine metabolism and its therapeutic potential in cancer

癌症与健康的癌症有不同的营养需求。在此， 靶向酶，从而靶向构成这些不同代谢网络的代谢网络， 需求吸引了许多药物开发工作。当靶向酶时， 癌症特异性代谢途径已经成功，代谢是否会受到影响 通过特定和受控的方式进行营养调控， 未知蛋氨酸的可用性影响一碳循环通量、DNA和组蛋白甲基化 以及表观遗传编程。饮食蛋氨酸限制（MR）也促进代谢 健康和延长昆虫和哺乳动物的寿命，两个抗癌功能。因此我们 假设饮食MR可以抑制肿瘤生长并增强抗癌治疗。我们 初步数据表明，饮食MR，一种成本效益的方法，改变血浆蛋氨酸， 在健康小鼠和人类中均有效。MR介导有希望的肿瘤结局：在两个 RAS驱动的结直肠癌（CRC）患者来源的异种移植物（PDX）模型，它延迟了肿瘤的生长， 生长并使肿瘤对5-氟尿嘧啶敏感，5-氟尿嘧啶是CRC的一线化疗; 在自体KRASG12D +/-; TP53-/-软组织肉瘤模型中，它达到了惊人的 与辐射协同作用。在这些模型中，半胱氨酸和甲硫氨酸代谢是 肿瘤和血浆中最受影响的代谢途径。然而，分子 饮食MR与代谢相互作用并最终介导肿瘤的机制 结果未知。为了探索机制，我建议关注CRC PDX模型 通过以下两个目标。在目标1中，我将首先采用最先进的代谢组学 在我们的实验室建立的方法来评估肿瘤和非肿瘤组织中的代谢改变， 通过饮食MR或MR和5-FU的组合治疗肿瘤组织。合并后， 研究结果在体外，我将通过补充半胱氨酸或甜菜碱进行饮食干预， 确定甲硫氨酸作为硫供体和一碳供体对肿瘤的贡献 CRC PDX模型的增长。在目标2中，我将首先描述表观遗传和 使用亚硫酸氢盐测序，ATAC- seq、ChIP-seq和RNA-seq。有了这些数据，我将构建一个代谢网络， 使用CRISPR/Cas9技术对代谢途径基因进行功能性筛选。成果 将揭示饮食MR介导的代谢，遗传和表观遗传机制 在CRC中单独和与5-FU佐剂的肿瘤抑制。预计还将提供目标 代谢物和基因用于未来的假设生成和靶向癌症的新疗法 新陈代谢.

Cancers have different nutritional requirements from their healthy counterparts. Herein, targeting the enzymes and thus the metabolic networks that constitute these different metabolic requirements is attracting numerous drug development efforts. While targeting enzymes in cancer-specific metabolic pathways has been successful, whether metabolism can be affected to similar extents by nutritional manipulation in specific and controlled manners is largely unknown. Methionine availability affects one-carbon cycle flux, DNA and histone methylation and thus epigenetic programming. Dietary methionine restriction (MR) also promotes metabolic health and extends insect and mammalian lifespan, two anti-cancer features. Thus, we hypothesize that dietary MR could inhibit tumor growth and enhance anti-cancer therapy. Our preliminary data show that dietary MR, a cost-effective approach, alters plasma methionine effectively in both healthy mice and humans. MR mediates promising tumor outcomes: in two RAS-driven colorectal cancer (CRC) patient-derived xenografts (PDX) models, it delays tumor growth and sensitizes tumor to 5-Fluorouracil, a frontline chemotherapy for CRC; and in an autochthonous KRASG12D+/-;TP53-/- soft tissue sarcoma model, it reaches a striking synergistic effect with radiation. In these models, cysteine and methionine metabolism is the most impacted metabolic pathway in the tumor and the plasma. However, the molecular mechanisms by which dietary MR interacts with metabolism and eventually mediates tumor outcome are unknown. To explore the mechanisms, I propose to focus on CRC PDX models through the following two aims. In Aim 1, I will first employ a state of the art metabolomics approach established in our laboratory to evaluate the metabolic alterations in tumor and non- tumor tissues by dietary MR or a combination of MR and 5-FU. Upon consolidation of the findings in vitro, I will conduct dietary interventions by supplementing cysteine or betaine to determine the contribution of methionine as a sulfur donor and a one-carbon donor to tumor growth in CRC PDX models, respectively. In Aim 2, I will first characterize the epigenetic and genetic adaptions to dietary MR in tumor and CRC cell linesusing bisulfite sequencing, ATAC- seq, ChIP-seq, and RNA-seq. With these data, I will construct a metabolic network and perform a functional screen of metabolic pathway genes using CRISPR/Cas9 technology. The outcome will reveal the metabolic, genetic, and epigenetic mechanisms underlying dietary MR-mediated tumor inhibition alone and in adjuvant with 5-FU in CRC. It is also anticipated to provide target metabolite and genes for future hypothesis generation and novel therapy targeting cancer metabolism.