Abstract：
Lynch syndrome (LS) is the most prevalent heritable form of colorectal cancer. Its early onset and high lifetime risk for colorectal cancer emphasize the necessity for effective chemoprevention. NFE2L2 (NRF2) is often considered a potential druggable target, and many chemopreventive compounds induce NRF2. However, although NRF2 counteracts oxidative stress, it is also overexpressed in colorectal cancer and may promote tumorigenesis. In this study, we evaluated the role of NRF2 in the prevention of LS-associated neoplasia. We found increased levels of NRF2 in intestinal epithelia of mice with intestinal epithelium-specific Msh2 deletion (MSH2ΔIEC) compared with C57BL/6 (wild-type) mice, as well as an increase in downstream NRF2 targets NAD(P)H dehydrogenase (quinone 1) and glutamate-cysteine ligase catalytic subunit. Likewise, NRF2 levels were increased in human MSH2-deficient LS tumors compared with healthy human controls. In silico analysis of a publicly accessible RNA sequencing LS dataset also found an increase in downstream NRF2 targets. Upon crossing MSH2ΔIEC with Nrf2null (MSH2ΔIECNrf2null) mice, we unexpectedly found reduced tumorigenesis in MSH2ΔIECNrf2null mice compared with MSH2ΔIEC mice after 40 weeks, which occurred despite an increase in oxidative damage in MSH2ΔIECNrf2null mice. The loss of NRF2 impaired proliferation as seen by Ki67 intestinal staining and in organoid cultures. This was accompanied by diminished WNT/β-catenin signaling, but apoptosis was unaffected. Microbial α-diversity increased over time with the loss of NRF2 based upon 16S rRNA gene amplicon sequencing of murine fecal samples. Altogether, we show that NRF2 protein levels are increased in MSH2 deficiency and associated neoplasia, but the loss of NRF2 attenuates tumorigenesis. Activation of NRF2 may not be a feasible strategy for chemoprevention in LS. Prevention Relevance: Patients with LS have an early onset and high lifetime risk for colorectal cancer. In this study, we show that NRF2 protein levels are increased in MSH2 deficiency and associated neoplasia, but the loss of NRF2 attenuates tumorigenesis. This suggests that NRF2 may not be a tumor suppressor in this specific context.
摘要：
Lynch综合征（LS）是结直肠癌（CRC）最常见的可遗传形式。它的早期发病和高终生CRC风险强调了有效化学预防的必要性。NFE2L2（NRF2）通常被认为是一个潜在的药物靶标，和许多化学预防化合物诱导NRF2。然而,而NRF2抵消氧化应激，它也在CRC中过度表达,并可能促进肿瘤发生。在这里，我们评估了NRF2在预防LS相关瘤形成中的作用.我们发现与C57BL/6（野生型）小鼠相比，具有肠上皮特异性Msh2缺失（MSH2ΔIEC）的小鼠肠上皮中NRF2的水平升高，以及下游NRF2靶标Nqo1和Gclc的增加。同样，与健康对照相比,NRF2水平在人MSH2缺陷型LS肿瘤中增加。对可公开获得的RNA测序LS数据集的计算机模拟分析也发现下游NRF2靶标的增加。在MSH2ΔIEC与Nrf2null小鼠(MSH2ΔIECNrf2null)杂交后,我们意外地发现，在40周后，与MSH2ΔIEC相比，MSH2ΔIECNrf2null的肿瘤发生减少。尽管MSH2ΔIECNrf2null小鼠的氧化损伤增加，但仍发生这种情况。如通过Ki67肠染色和类器官培养中所见，NRF2的丧失损害了增殖。这伴随着减少的WNT/β-连环蛋白信号传导。细胞凋亡未受影响。基于鼠粪便样品的16SrRNA基因扩增子测序，随着时间的推移，微生物α多样性随着NRF2的丧失而增加。总之,我们显示NRF2蛋白水平在MSH2缺乏和相关瘤形成中增加，但是NRF2的丢失会减弱肿瘤发生。NRF2的激活可能不是LS化学预防的可行策略。
