No abstract

Overcoming oxidative stress is a critical step for tumor growth and metastasis, however the underlying mechanisms in gastric cancer remain unclear. In this study, we found that overexpression of nicotinamide nucleotide transhydrogenase (NNT) was associated with shorter overall and disease free survival in gastric cancer. The NNT is considered a key antioxidative enzyme based on its ability to regenerate NADPH from NADH. Knockdown of NNT caused significantly NADPH reduction, induced high levels of ROS and significant cell apoptosis under oxidative stress conditions such as glucose deprival and anoikis. In vivo experiments showed that NNT promoted tumor growth, lung metastasis and peritoneal dissemination of gastric cancer. Moreover, intratumoral injection of NNT siRNA significantly suppressed gastric tumor growth in patient-derived xenograft (PDX) models. Overall, our study highlights the crucial functional roles of NNT in redox regulation and tumor progression and thus raises an important therapeutic hypothesis in gastric cancer.

TF IIB-related factor 1 (Brf1) is a key transcription factor of RNA polymerase III (Pol III) genes. Our early studies have demonstrated that Brf1 and Pol III genes are epigenetically modulated by histone H3 phosphorylation. Here, we have further investigated the relationship of the abnormal expression of Brf1 with a high level of phosphorylated AMPKα (pAMPKα) and explored the role and molecular mechanism of pAMPKα-mediated dysregulation of Brf1 and Pol III genes in lung cancer. Brf1 is significantly overexpressed in lung cancer cases. The cases with high Brf1 expression display short overall survival times. Elevation of Brf1 expression is accompanied by a high level of pAMPKα. Brf1 and pAMPKα colocalize in nuclei. Further analysis indicates that the carcinogen MNNG induces pAMPKα to upregulate Brf1 expression, resulting in the enhancement of Pol III transcription. In contrast, inhibiting pAMPKα decreases cellular levels of Brf1, resulting in the reduction of Pol III gene transcription to attenuate the rates of cell proliferation and colony formation of lung cancer cells. These outcomes demonstrate that high Brf1 expression reveals a worse prognosis in lung cancer patients. pAMPKα-mediated dysregulation of Brf1 and Pol III genes plays important roles in cell proliferation, colony formation, and tumor development of lung cancer. Brf1 may be a biomarker for establishing the prognosis of lung cancer. It is a new mechanism that pAMPKα mediates dysregulation of Brf1 and Pol III genes to promote lung cancer development.