The processing of intracellular reactive oxygen species (ROS) by nuclear factor erythroid-derived 2-like 2 (Nrf2) and NADPH quinone oxidoreductase 1 (Nqo1) is important for tumor metastasis. However, the clinical and biological significance of Nrf2/Nqo1 expression in hepatocellular carcinoma (HCC) remains unclear. We aimed to clarify the clinical importance of Nrf2/Nqo1 expression in HCC and evaluate the association of Nrf2/Nqo1 expression with HCC metastasis. We also evaluated the impact of Nqo1 modulation on HCC metastatic potential. We used spheroids derived from HCC cell lines. In anchorage-independent culture, HCC cells showed increased ROS, leading to the upregulation of Nrf2/Nqo1. Futile stimulation of Nqo1 by β-lapachone induces excessive oxidative stress and dramatically increased anoikis sensitivity, finally diminishing the spheroid formation ability, which was far stronger than depletion of Nqo1. We analyzed 117 cases of primary HCC who underwent curative resection. Overexpression of Nrf2/Nqo1 in primary HCC was associated with tumor size, high α-fetoprotein, and des-γ-carboxy-prothrombin levels. Overexpression of Nrf2/Nqo1 was also associated with multiple intrahepatic recurrences (P = .0073) and was an independent risk factor for poor prognosis (P = .0031). NADPH quinone oxidoreductase 1 plays an important role in anchorage-independent survival, which is essential for survival for circulation and distant metastasis of HCC cells. These results suggest that targeting Nqo1 activity could be a potential strategy for HCC adjuvant therapy.
Keywords: Nqo1; Nrf2; hepatocellular carcinoma; metastasis; oxidative stress.
© 2020 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.