Chrysin enhances sensitivity of BEL-7402/ADM cells to doxorubicin by suppressing PI3K/Akt/Nrf2 and ERK/Nrf2 pathway

Abstract

Nuclear factor-E2-related factor 2 (Nrf2) is an important cytoprotective transcription factor which plays a key role in antioxidant and detoxification processes. Recent studies have reported that development of chemoresistance is associated with the constitutive activation of the Nrf2-mediated signaling pathway in many types of cancer cells. Here, we investigated whether Nrf2 was associated with drug resistant in doxorubicin resistant BEL-7402 (BEL-7402/ADM) cells, and if chrysin could reverse drug resistance in BEL-7402/ADM cells. We found that remarkable higher level of Nrf2 and its target proteins in BEL-7402/ADM cells compared to BEL-7402 cells. Similarly, intracellular Nrf2 protein level was significantly decreased and ADM resistance was partially reversed by Nrf2 siRNA in BEL-7402/ADM cells. chrysin is a potent Nrf2 inhibitor which sensitizes BEL-7402/ADM cells to ADM and increases intracellular concentration of ADM. Mechanistically, chrysin significantly reduced Nrf2 expression at both the mRNA and protein levels through down-regulating PI3K-Akt and ERK pathway. Consequently, expression of Nrf2-downstream genes HO-1, AKR1B10, and MRP5 were reduced and the Nrf2-dependent chemoresistance was suppressed. In conclusion, these results clearly indicate that activation of Nrf2 is associated with drug resistance in BEL-7402/ADM cells and chrysin may be an effective adjuvant sensitizer to reduce anticancer drug resistance by down-regulating Nrf2 signaling pathway.

Keywords: 4′-6′-diamidino-2-phenylindole; ADM; AKR1B10; ATF3; Aldo–keto reductase 1B10; Chemoresistance; Chrysin; DAPI; EGCG; ERα; FCM; HCC; HO-1; Hepatocellular carcinoma; Keap1; MAPKs; MRP5; Nrf2; PI3K; PPAR; RARα; SFERRβ; activating transcription factor 3; doxorubicin; epigallocatechin 3-gallate; estrogenreceptor α; flow cytometry; heme oxygenase-1; hepatocellular carcinoma; kelch-like ECH-associated protein 1; mitogen-activated protein kinases; multidrug resistance-associated protein 5; nuclear factor erythroid 2-related factor 2; peroxisome proliferator-activated receptor; phosphatidylinositol-3 kinase; qRT-PCR; real-time quantitative PCR; retinoic acid receptor α; short-form estrogen-related receptor β.