Nrf2 Mutations Are Frequent In Early Rat Preneoplastic Hepatic Lesions And In Human Hepatocellular Carcinomas Positive For The Stem/Progenitor Cell Marker Krt-19

Hepatocellular carcinoma (HCC) is a multistage process but the nature of the molecular changes associated to the different steps, particularly the very early steps, is largely unknown. Recently, we have shown that activation of the Keap-1-NRF2 pathway is a very early event in the Resistant-Hepatocyte (R-H) rat model of hepatocarcinogenesis, suggesting that dysregulation of this pathway may have a causal role in HCC development. The aim of the present study was to investigate by Sanger fluorescence-based sequence analysis whether and when NRF2 mutations could occur in this experimental model. The results showed that mutations of NRF2 are extremely frequent (17/19; 90%) in early preneoplastic lesions positive for the stem/progenitor cell marker KRT-19, which are considered to be the precursor cell population of HCC in this model. Notably, all the mutations were missense and involved the Keap1-NRF2 binding regions. Mutations of Keap-1 were more rare and were found only in preneoplastic lesions lacking NRF2 mutations (10%). KRT-19 positive HCCs arising 1 year later also showed a high percentage of NRF2 mutation (> 50%), suggesting that mutation of this gene provides a selective advantage towards progression to HCC. Finally, preliminary studies in a subset of KRT-19 positive human HCCs, which are known to exhibit the worse prognosis, showed the presence of NRF2 mutations in a very high percentage (55%) of tumors. On the opposite, no mutations were detected in KRT-19 negative human HCCs. Conclusion: Our results demonstrate that mutations of NRF2 are highly frequent in a subset of human HCCs (KRT-19+) characterized by poor prognosis. Moreover, the findings stemming from the multistage carcinogenic rat model demonstrate that NRF2 mutation is a very early event, suggesting that dysregulation of the NRF2-Keap1 pathway is likely essential for the clonal expansion of KRT-19+ preneoplastic hepatocytes to HCC. Citation Format: Patrizia Zavattari, Andrea Perra, Marta A. Kowalik, Maddalena M. Angioni, Silvia Menegon, Annalisa Petrelli, Luca Quagliata, Giovanna M. Ledda-Columbano, Luigi Terraciano, Silvia Giordano, Amedeo Columbano. NRF2 mutations are frequent in early rat preneoplastic hepatic lesions and in human hepatocellular carcinomas positive for the stem/progenitor cell marker KRT-19. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1399. doi:10.1158/1538-7445.AM2014-1399