TMI, an isoflavone from the fruits of Ficus altissima Blume, overcomes K562/ADR leukemia cells resistance by targeting Nrf2.

Chronic myeloid leukemia (CML) is a myeloproliferative tumor, which is prone to drug resistance during treatment. Previous studies have indicated that Ficus altissima Blume exhibits potential antitumor properties, with 5,7,2'-trihydroxy-4'-methoxy-6-(3-hydroxy-3-methylbutyl)-isoflavone (TMI) as its main active component. However, the antitumour activity of TMI and its underlying mechanisms remain unexplored. This study investigated the anti-proliferative effects of TMI on adriamycin (ADR)-resistant leukemia K562 cells (K562/ADR cells) and the mechanism of overcoming multidrug resistance (MDR). The findings demonstrated that TMI significantly downregulated P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) expression. It was confirmed that TMI triggered caspase-dependent apoptosis in K562/ADR and K562 cells. While reactive oxygen species accumulation and PI3K/AKT/mTOR mediated TMI's effect in K562 cells, these pathways were irrelevant to its apoptosis induction and MDR overcoming in K562/ADR cells. Further research found that the nuclear factor erythroid 2-related factor 2 (Nrf2) expression was significantly suppressed by TMI treatment. In contrast, exposure to the Nrf2 agonist tert-butylhydroquinone resulted in upregulation of P-gp and BCRP protein levels in K562/ADR cells. This suggests that TMI's overcoming of K562/ADR cell drug resistance is associated with Nrf2 degradation. Finally, molecular docking analysis and cellular thermal shift assay experiments showed that TMI exerted anti-drug resistance effect by directly binding to Nrf2 protein. Collectively, TMI overcomes K562/ADR cell resistance primarily through targeting and inhibiting Nrf2 protein and decreasing drug efflux protein expression, ultimately promoting cell death. These results highlight TMI's potential as a drug-resistant leukemia therapy, while also suggesting that developing Nrf2-targeted inhibitors may represent a novel strategy for overcoming tumor drug resistance.