增加的反应性氧/氮化物水平是慢性炎症的一个特征，有助于激活促炎症/增殖通路。在所分析的癌症中，四氢叶酸: 二氢叶酸比值低于相应的正常组织，导致不成对的一氧化氮合酶活性和增加的反应性氧/氮化物生成。我们先前证明了用高丝克皮喹治疗早期癌前病变小鼠和相关的大肠癌和醋酸氧甲烷诱导的大肠癌可以预防硫酸二戊糖钠引起的结肠炎。在此，我们报告了在结肠癌细胞株HCT116和HT29中增加四氢生物叶酸: 二氢生物叶酸比例并用高丝克皮喹重新耦合一氧化氮合酶，部分通过Akt/GSK-3β介导的β-连环蛋白下调抑制它们的增殖和增强细胞死亡。口服高丝克皮喹治疗醋酸氧甲烷/硫酸二戊糖钠诱导的大肠癌小鼠可以减少代谢性的【18F]-氟脱氧葡萄糖摄取并将这些肿瘤中的凋亡增加九倍。对小鼠和人组织的免疫组织化学分析表明在结肠癌肿瘤中四氢生物叶酸生物合成关键酶的表达降低了。人类1期结肠肿瘤表现出关键酶去磷酸齐喹啉还原酶的表达显著降低，这是涉及回收四氢生物叶酸的一种关键酶，表明了这些肿瘤中四氢生物叶酸: 二氢生物叶酸比例降低的潜在机制。总之，高丝克皮喹治疗可以增加结肠癌细胞的四氢生物叶酸: 二氢生物叶酸比例，重新耦合一氧化氮合酶并减少肿瘤生长。我们得出结论，一氧化氮合酶耦合可能为治疗结肠癌的患者提供一个有用的治疗靶点。版权所有©2023 Alam，Smith，Gobalakrishnan，McGinn，Yakovlev和Rabender。

Increased levels of reactive oxygen/nitrogen species are one hallmark of chronic inflammation contributing to the activation of pro-inflammatory/proliferative pathways. In the cancers analyzed, the tetrahydrobiopterin:dihydrobiopterin ratio is lower than that of the corresponding normal tissue, leading to an uncoupled nitric oxide synthase activity and increased generation of reactive oxygen/nitrogen species. Previously, we demonstrated that prophylactic treatment with sepiapterin, a salvage pathway precursor of tetrahydrobiopterin, prevents dextran sodium sulfate-induced colitis in mice and associated azoxymethane-induced colorectal cancer. Herein, we report that increasing the tetrahydrobiopterin:dihydrobiopterin ratio and recoupling nitric oxide synthase with sepiapterin in the colon cancer cell lines, HCT116 and HT29, inhibit their proliferation and enhance cell death, in part, by Akt/GSK-3β-mediated downregulation of β-catenin. Therapeutic oral gavage with sepiapterin of mice bearing azoxymethane/dextran sodium sulfate-induced colorectal cancer decreased metabolic uptake of [18F]-fluorodeoxyglucose and enhanced apoptosis nine-fold in these tumors. Immunohistochemical analysis of both mouse and human tissues indicated downregulated expression of key enzymes in tetrahydrobiopterin biosynthesis in the colorectal cancer tumors. Human stage 1 colon tumors exhibited a significant decrease in the expression of quinoid dihydropteridine reductase, a key enzyme involved in recycling tetrahydrobiopterin suggesting a potential mechanism for the reduced tetrahydrobiopterin:dihydrobiopterin ratio in these tumors. In summary, sepiapterin treatment of colorectal cancer cells increases the tetrahydrobiopterin:dihydrobiopterin ratio, recouples nitric oxide synthase, and reduces tumor growth. We conclude that nitric oxide synthase coupling may provide a useful therapeutic target for treating patients with colorectal cancer.Copyright © 2023 Alam, Smith, Gobalakrishnan, McGinn, Yakovlev and Rabender.