Impact of Nuclear Factor Erythroid 2-Related Factor 2 in Hepatocellular Carcinoma: Cancer Metabolism and Immune Status

We examined phosphorylated nuclear factor erythroid 2-related factor 2 (P-NRF2) expression in surgically resected primary hepatocellular carcinoma (HCC) and investigated the association of P-NRF2 expression with clinicopathological features and patient outcome. We also evaluated the relationship among NRF2, cancer metabolism, and programmed death ligand 1 (PD-L1) expression. In this retrospective study, immunohistochemical staining of P-NRF2 was performed on the samples of 335 patients who underwent hepatic resection for HCC. Tomography/computed tomography using fluorine-18 fluorodeoxyglucose was performed, and HCC cell lines after NRF2 knockdown were analyzed by array. We also analyzed the expression of PD-L1 after hypoxia inducible factor 1 alpha (HIF1A) knockdown in NRF2-overexpressing HCC cell lines. Samples from 121 patients (36.1%) were positive for P-NRF2. Positive P-NRF2 expression was significantly associated with high alpha-fetoprotein (AFP) expression, a high rate of poor differentiation, and microscopic intrahepatic metastasis. In addition, positive P-NRF2 expression was an independent predictor for recurrence-free survival and overall survival. NRF2 regulated glucose transporter 1, hexokinase 2, pyruvate kinase isoenzymes L/R, and phosphoglycerate kinase 1 expression and was related to the maximum standardized uptake value. PD-L1 protein expression levels were increased through hypoxia-inducible factor 1 alpha after NRF2 overexpression in HCC cells. Conclusions: Our large cohort study revealed that P-NRF2 expression in cancer cells was associated with clinical outcome in HCC. Additionally, we found that NRF2 was located upstream of cancer metabolism and tumor immunity.