| First Author | Zheng J | Year | 2023 |
| Journal | Free Radic Biol Med | Volume | 194 |
| Pages | 347-356 | PubMed ID | 36460215 |
| Mgi Jnum | J:332390 | Mgi Id | MGI:7424535 |
| Doi | 10.1016/j.freeradbiomed.2022.11.039 | Citation | Zheng J, et al. (2023) Overactivated NRF2 induces pseudohypoxia in hepatocellular carcinoma by stabilizing HIF-1alpha. Free Radic Biol Med 194:347-356 |
| abstractText | Hypoxia-inducible factor-1alpha (HIF-1alpha) is highly expressed/activated in most hypoxic tumors including hepatocellular carcinoma (HCC). Another key transcription factor, nuclear factor erythroid 2-related factor 2 (NRF2), is also constitutively overactivated in HCC. In an attempt to determine whether HIF-1alpha and NRF2 could play complementary roles in HCC growth and progression, we investigated the crosstalk between these two transcription factors and underlying molecular mechanisms in cultured HCC cells and experimentally induced hepatocarcinogenesis as well as clinical settings. While silencing of HIF-1alpha in HepG2 human hepatoma cells did not alter the protein expression of NRF2, NRF2 knockdown markedly reduced the nuclear accumulation of HIF-1alpha without influencing its mRNA expression. In diethylnitrosamine-induced hepatocarcinogenesis in wild type mice, there was elevated NRF2 expression with concomitant upregulation of HIF-1alpha. However, this was abolished in Nrf2 knockout mice. NRF2 and HIF-1alpha co-localized and physically interacted with each other as assessed by in situ proximity ligation and immunoprecipitation assays. In addition, the interaction between NRF2 and HIF-1alpha as well as their overexpression was found in tumor specimens obtained from HCC patients. In normoxia, HIF-1alpha undergoes hydroxylation by a specific HIF-prolyl hydroxylase domain protein (PHD), which facilitates ubiquitination and proteasomal degradation of HIF-1alpha. NRF2 contributes to pseudohypoxia, by directly binding to the oxygen-dependent degradation (ODD) domain of HIF-1alpha, which hampers the PHD2-mediated hydroxylation, concomitant recruitment of von-Hippel-Lindau and ubiquitination of HIF-1alpha. |
