Nobiletin suppresses nasopharyngeal carcinoma by regulating the KEAP1/NRF2/ARE pathway

Nasopharyngeal carcinoma (NPC) ranks among the most prevalent malignancies, particularly in East Asia and Southeast Asia. Nobiletin (NOB), an exclusive polymethoxyflavonoid derived from citrus peel, exhibits diverse physiological properties, notably its potent anticancer activity. Kelch-like ECH-associated protein 1 (KEAP1), the repressor protein regulating the nuclear factor erythroid 2-related factor 2 (NRF2) transcription factor, has emerged as a promising strategy for addressing oxidative stress in various diseases. The KEAP1/NRF2/ARE signal is a fundamental pathway within the cellular homeostatic defense system. This study robustly demonstrates the chemopreventive potential of NOB through comprehensive in vitro and in vivo assessments using subcutaneous tumor mouse models. Furthermore, our groundbreaking findings reveal that NOB effectively hinders the migration and invasion capacities of CNE-2 and 5-8F (NPC) cells in a dose- and time-dependent manner. Mechanistically, NOB, a potent KEAP1 activator, significantly disrupts the NRF2/ARE signaling pathway by accelerating the proteasomal degradation of NRF2 and suppressing its nuclear translocation. Consequently, this cascade reduces the expressions of ARE-driven genes and antioxidant enzymes, thereby increasing intracellular reactive oxygen species (ROS) levels and increasing antitumor immunity. Moreover, the sensitivity induced by NOB is markedly diminished in CNE-2 cells following the gene silencing of KEAP1. These findings underscore the pivotal role of NOB in activating KEAP1. Overall, KEAP1 has emerged as a compelling target for potential malignancy treatment in nasopharyngeal carcinoma cell lines. Our results suggest the promising application of NOB as a natural sensitizer in chemotherapy, opening avenues for promising therapeutic interventions.