Department of Biomedical Sciences, Unit of Oncology and Molecular Pathology, Cagliari, Italy.
Department of Biomedical Sciences, Unit of Biology and Genetics, University of Cagliari, Cagliari, Italy.
Cell Mol Gastroenterol Hepatol. 2022;13(1):113-127. doi: 10.1016/j.jcmgh.2021.08.011. Epub 2021 Sep 14.
BACKGROUND & AIMS: Activation of the kelch-like ECH-associated protein 1 (Keap1)-nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway has been associated with metabolic reprogramming in many tumors, including hepatocellular carcinoma (HCC). However, the contribution of Nrf2 mutations in this process remains elusive. Here, we investigated the occurrence of Nrf2 mutations in distinct models of mouse hepatocarcinogenesis.
HCCs were generated by experimental protocols consisting of the following: (1) a single dose of diethylnitrosamine (DEN), followed by repeated treatments with the nuclear-receptor agonist 1,4-bis-[2-(3,5-dichloropyridyloxy)]benzene; (2) repeated treatments with 1,4-bis-[2-(3,5-dichloropyridyloxy)]benzene alone; (3) a single dose of DEN followed by exposure to a choline-deficient L-amino acid-defined diet; and (4) a single dose of DEN with no further treatment. All of these protocols led to HCC development within 28-42 weeks. Activation of the Keap1-Nrf2 pathway was investigated by analyzing the presence of Nrf2 gene mutations, and the expression of Nrf2 target genes. Metabolic reprogramming was assessed by evaluating the expression of genes involved in glycolysis, the pentose phosphate pathway, and glutaminolysis.
No Nrf2 mutations were found in any of the models of hepatocarcinogenesis analyzed. Intriguingly, despite the described cooperation between β-catenin and the Nrf2 pathway, we found no evidence of Nrf2 activation in both early dysplastic nodules and HCCs, characterized by the presence of up to 80%-90% β-catenin mutations. No HCC metabolic reprogramming was observed either.
These results show that, unlike rat hepatocarcinogenesis, Nrf2 mutations do not occur in 4 distinct models of chemically induced mouse HCC. Interestingly, in the same models, metabolic reprogramming also was minimal or absent, supporting the concept that Nrf2 activation is critical for the switch from oxidative to glycolytic metabolism.
Kelch 样 ECH 相关蛋白 1（Keap1）-核因子（红系衍生 2）样 2（Nrf2）通路的激活与许多肿瘤（包括肝细胞癌（HCC））中的代谢重编程有关。然而，Nrf2 突变在此过程中的贡献仍不清楚。在这里，我们研究了 Nrf2 突变在不同的小鼠肝癌发生模型中的发生情况。
通过以下实验方案生成 HCC：（1）单次给予二乙基亚硝胺（DEN），然后用核受体激动剂 1,4-双-[2-（3,5-二氯吡啶氧基）]苯重复处理；（2）单独用 1,4-双-[2-（3,5-二氯吡啶氧基）]苯重复处理；（3）单次给予 DEN，然后暴露于胆碱缺乏的 L-氨基酸定义的饮食；和（4）单次给予 DEN，不再进一步处理。所有这些方案都在 28-42 周内导致 HCC 发展。通过分析 Nrf2 基因突变的存在以及 Nrf2 靶基因的表达来研究 Keap1-Nrf2 通路的激活情况。通过评估参与糖酵解、戊糖磷酸途径和谷氨酰胺分解的基因的表达来评估代谢重编程。
在分析的任何肝癌发生模型中均未发现 Nrf2 突变。有趣的是，尽管β-catenin 和 Nrf2 通路之间存在描述性的合作，但我们在早期发育不良结节和 HCC 中均未发现 Nrf2 激活的证据，这些结节和 HCC 的特征是高达 80%-90%的β-catenin 突变。也没有观察到 HCC 的代谢重编程。
这些结果表明，与大鼠肝癌发生不同，Nrf2 突变不会发生在 4 种不同的化学诱导的小鼠 HCC 模型中。有趣的是，在相同的模型中，代谢重编程也很少或不存在，这支持了 Nrf2 激活对于从氧化代谢到糖酵解代谢的转变至关重要的概念。
